Liquid crystal display device and method for manufacturing same
11079634 · 2021-08-03
Assignee
Inventors
Cpc classification
C09K2323/023
CHEMISTRY; METALLURGY
G02F1/133788
PHYSICS
International classification
Abstract
The present invention provides a liquid crystal display device that can sufficiently prevent crystallization of a liquid crystal material at low temperatures, and thereby has high response performance suitable for applications such as HMDs. The liquid crystal display device includes: paired substrates; a liquid crystal layer held between the substrates; and a photo-alignment film disposed on a surface facing the liquid crystal layer of at least one of the substrates, the liquid crystal layer containing a liquid crystal material that has a nematic-isotropic phase transition temperature of 75° C. or lower and a nematic phase temperature range narrower than 100° C., the photo-alignment film containing a polymer, the polymer and/or another component of the photo-alignment film containing a hydrophobic group.
Claims
1. A liquid crystal display device comprising: paired substrates; a liquid crystal layer held between the substrates; and a photo-alignment film disposed on a surface facing the liquid crystal layer of at least one of the substrates, the liquid crystal layer containing a liquid crystal material that has a nematic-isotropic phase transition temperature of 75° C. or lower and a nematic phase temperature range narrower than 100° C., the photo-alignment film containing a first polymer and a first compound each containing a hydrophobic group, wherein the first polymer includes a polyamic acid represented by the following formula (20): ##STR00031## and the first compound is represented by the following formula (21): ##STR00032##
2. A liquid crystal display device comprising: paired substrates; a liquid crystal layer held between the substrates; and a photo-alignment film disposed on a surface facing the liquid crystal layer of at least one of the substrates, the liquid crystal layer containing a liquid crystal material that has a nematic-isotropic phase transition temperature of 75° C. or lower and a nematic phase temperature range narrower than 100° C., the photo-alignment film containing a first polymer and a first compound each containing a hydrophobic group, wherein the first polymer includes a polyamic acid represented by the following formula (20): ##STR00033## and the first compound is represented by the following formula (22): ##STR00034##
3. A liquid crystal display device comprising: paired substrates; a liquid crystal layer held between the substrates; and a photo-alignment film disposed on a surface facing the liquid crystal layer of at least one of the substrates, the liquid crystal layer containing a liquid crystal material that has a nematic-isotropic phase transition temperature of 75° C. or lower and a nematic phase temperature range narrower than 100° C., the photo-alignment film containing a copolymer of a first monomer unit containing a photo-functional group and a second monomer unit containing a hydrophobic group, wherein the copolymer is represented by the following formula (19): ##STR00035##
4. The liquid crystal display device according to claim 3, wherein the photo-alignment film includes a polysiloxane with a photo-functional group and represented by the following formula (25): ##STR00036##
5. The liquid crystal display device according to claim 3, wherein the photo-alignment film further contains a second polymer, and the second polymer contains a hydrophobic group.
6. The liquid crystal display device according to claim 5, wherein the second polymer is represented by the following formula (14): ##STR00037## wherein H surrounded by a solid line represents a C4 or greater alkyl, alkenyl, or aralkyl group or a C4 or greater monovalent monocyclic or polycyclic hydrocarbon group; A represents a hydrogen atom, an OH group, a COOH group, or a NH.sub.2 group; a -Sp- group represents a —O— group, a —S— group, a —NH— group, a —CO— group, a —COO— group, a —OCO— group, a —NHCO— group, a —CONH— group, or a direct bond; Z represents a hydrogen atom, a CH.sub.3 group, or a C.sub.2H.sub.5 group; p shows the degree of polymerization and is an integer of 1 or greater; and n is any value falling within the range of 0 to 1.
7. The liquid crystal display device according to claim 6, wherein the second polymer is represented by the following formula (23) or (24): ##STR00038##
8. The liquid crystal display device according to claim 5, wherein the second polymer is a polymer containing a monomer unit derived from a monomer represented by the following formula (17): ##STR00039## wherein P's are the same as or different from each other and each represent an acryloyloxy group, a methacryloyloxy group, an acryloylamino group, or a methacryloylamino group; A3 represents a trivalent hydrocarbon group; A4 represents a phenylene group; a —CH.sub.2— group in each of A3 and A4 may be replaced by a —O— group or a —S— group unless the —CH.sub.2— group neighbors another one; a —CH═ group in each of A3 and A4 may be replaced by a —N═ group unless the —CH═ group neighbors another one; a hydrogen atom in each of A3 and A4 may be replaced by a fluorine atom, a chlorine atom, a —CN group, or a C1 to C12 alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, or alkylcarbonyloxy group, and at least one of their carbon atoms may be replaced by a silicon atom; the alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, or alkylcarbonyloxy group may be linear or branched; the —Z4— group and the —Z5— group are the same as or different from each other and each represent a —O— group, a —S— group, a —NH— group, a —CO— group, a —COO— group, a —OCO— group, a —NHCO— group, a —CONH— group, or a direct bond; L3 represents a C4 or greater alkyl, alkenyl, or aralkyl group or a C4 or greater monovalent monocyclic or polycyclic hydrocarbon group; the alkyl group and the alkenyl group may be linear or branched; at least one hydrogen atom in each of the aralkyl group and the monovalent monocyclic or polycyclic hydrocarbon group may be replaced by a C1 to C8 linear or branched alkyl or alkenyl group; a —CH.sub.2— group in each of the alkyl group, the alkenyl group, and the monovalent monocyclic or polycyclic hydrocarbon group may be replaced by a —O— group, a —CO— group, a —COO— group, or a —OCO— group unless oxygen atoms neighbor each other; and n3 is 0 or 1.
Description
BRIEF DESCRIPTION OF DRAWINGS
(1)
(2)
(3)
(4)
(5)
DESCRIPTION OF EMBODIMENTS
(6) The present invention is described in more detail below based on the following embodiment with reference to the drawings. The embodiment, however, is not intended to limit the scope of the present invention. The configurations of the embodiment may appropriately be combined or modified within the spirit of the present invention.
(7) Tni herein is determined by visually observing the liquid crystal state or the isotropic state while varying the temperature using a device such as one from Mettler.
(8) The nematic phase temperature range is measured in a similar manner by visually observing the liquid crystal state or the isotropic state while varying the temperature using a device such as one from Mettler.
(9) These temperatures can also be determined by a technique of determining the temperature at which phase transition occurs using a differential scanning calorimeter (DSC).
(10) The mode herein in which liquid crystal molecules are aligned in a direction substantially parallel to a main surface of a substrate with no voltage applied is also referred to as a horizontal alignment mode. The expression “substantially parallel” means that, for example, the pre-tilt angle of liquid crystal molecules is 0° or greater and 5° or smaller from the main surface of the substrate. The mode in which liquid crystal molecules are aligned in a direction substantially perpendicular to a main surface of a substrate with no voltage applied is also referred to as a vertical alignment mode. The expression “substantially perpendicular” means that, for example, the pre-tilt angle of liquid crystal molecules is 85° or greater and 90° or smaller from the main surface of the substrate. The room temperature is 15° C. or higher and 40° C. or lower, unless otherwise stated.
(11) The chemical bond as used herein usually means a covalent bond.
(12) The concept of the present invention is applicable to both horizontal alignment mode liquid crystal display devices and vertical alignment mode liquid crystal display devices, but is preferably applied to horizontal alignment mode liquid crystal display devices.
(13) A photo-alignment film containing a polymer whose main chain has a polyamic acid structure is also referred to as a polyamic acid-based photo-alignment film.
(14) Preferred examples of the polymer whose main chain has a polyamic acid structure include those having a polyamic acid structure represented by the following formula (1).
(15) ##STR00001##
(16) In the formula (1), p shows the degree of polymerization and is an integer of 1 or greater, preferably 10 or greater.
(17) In the formula (1), at least one of X, Y, and Side Chain contains a photo-functional group. In the case where X contains a photo-functional group, X is preferably a tetravalent group represented by any one of the following formulas (2-1) to (2-4), for example. These groups can be used for both horizontal photo-alignment films, which align liquid crystal molecules in a direction substantially parallel to the surfaces of the film, and vertical photo-alignment films, which align liquid crystal molecules in a direction substantially perpendicular to the surfaces of the film.
(18) ##STR00002##
(19) In the formula (1), in the case where X contains no photo-functional group, X may be a tetravalent group represented by any one of the following formulas (2-5) to (2-16). These groups can be used for both horizontal alignment films and vertical alignment films.
(20) ##STR00003##
(21) In the formula (1), in the case where Y contains a photo-functional group, Y is preferably a tetravalent group represented by any one of the following formulas (3-1) to (3-8), for example. These groups can be used for both horizontal photo-alignment films and vertical photo-alignment films.
(22) ##STR00004##
(23) In the formula (1), in the case where Y contains no photo-functional group, Y may be a trivalent group represented by any one of the following formulas (3-9) to (3-24). These groups can be used for both horizontal alignment films and vertical alignment films.
(24) ##STR00005## ##STR00006##
(25) In the formula (1), Side Chain is preferably a photo-functional group. Preferred examples of the photo-functional group include a monovalent group represented by any one of the following formulas (4-1) to (4-5). Groups represented by the formulas (4-1) and (4-2) are used for horizontal photo-alignment films. Groups represented by any of the formulas (4-3) to (4-5) are used for vertical photo-alignment films.
(26) ##STR00007##
(27) In the formula (1), Side Chain may contain a vertically or horizontally aligning functional group other than the photo-functional group, such as a monovalent group represented by any one of the following formulas (4-6) to (4-13). These groups are used for horizontal alignment films.
(28) ##STR00008##
(29) In the formula (1), Side Chain may be a monovalent group represented by any one of the following formulas (4-14) to (4-20). These groups are used for vertical alignment films.
(30) ##STR00009## ##STR00010##
(31) For a high contrast ratio, the alignment film is preferably a photo-alignment film. The alignment film is regarded as a photo-alignment film when at least one of X, Y, and Side Chain is a photo-functional group.
(32) Preferred examples of the polymer whose main chain has a polysiloxane structure include those having a structure represented by the following formula (5) or formula (6).
(33) ##STR00011##
(34) In the above formulas, p shows the degree of polymerization and is an integer of 1 or greater, preferably 10 or greater; Z represents a methyl, ethyl, methoxy, or ethoxy group; and Side Chain is the same as described above.
(35) The techniques (1) to (4) mentioned above are described below one by one.
(36) (1) Copolymer of Monomer Unit Containing Photo-Functional Group and Monomer Unit Containing Hydrophobic Group
(37) The copolymer is preferably, for example, one represented by the following formula (7), the following formula (8), or the following formula (9).
(38) ##STR00012##
(39) In the formulas, n is any value falling within the range of 0 to 1; the hydrophobic group H represents a C4 or greater alkyl, alkenyl, or aralkyl group or a C4 or greater monovalent monocyclic or polycyclic hydrocarbon group; the alkyl group and the alkenyl group may be linear or branched; at least one hydrogen atom in each of the aralkyl group and the monovalent monocyclic or polycyclic hydrocarbon group may be replaced by a C1 to C8 linear or branched alkyl or alkenyl group; and a —CH.sub.2— group in each of the alkyl group, the alkenyl group, or the monovalent monocyclic or polycyclic hydrocarbon group may be replaced by a —O— group, a —CO— group, a —COO— group, or a —OCO— group, unless oxygen atoms neighbor each other.
(40) The monomer unit containing a photo-functional group is represented by the formula (1), the formula (5), or the formula (6), and X, Y, Side Chain, and p are the same as described above. In formulas herein, H surrounded by a solid line represents a hydrophobic group, while H not surrounded by a solid line represents a hydrogen atom.
(41) (2) Introduction of Low-Molecular-Weight Additive (Compound) Containing Hydrophobic Group
(42) In the liquid crystal display device of the present invention, the photo-alignment film preferably contains a compound containing a hydrophobic group.
(43) The compound is preferably one represented by, for example, the following formula (10-1):
[Chem. 10-1]
S-A.sup.2-Z.sup.4-L.sup.3 (10-1)
wherein S is represented by any one of the following formulas (10-2) to (10-6); A.sup.2 represents a divalent hydrocarbon group or a direct bond; the —Z.sup.4— group represents a —O— group, a —S— group, a —NH— group, a —CO— group, a —COO— group, an —OCO— group, a —NHCO— group, a —CONH— group, or a direct bond; L.sup.3 represents a C4 or greater alkyl, alkenyl, or aralkyl group, or a C4 or greater monovalent monocyclic or polycyclic hydrocarbon group; the alkyl group and the alkenyl group may each be linear or branched; at least one hydrogen atom in each of the aralkyl group and the monovalent monocyclic or polycyclic hydrocarbon group may be replaced by a C1 to C8 linear or branched alkyl or alkenyl group; and a —CH.sub.2— group in each of the alkyl group, the alkenyl group, and the monovalent monocyclic or polycyclic hydrocarbon group may be replaced by a —O— group, a —CO— group, a —COO— group, or a —OCO— group unless oxygen atoms neighbor each other,
(44) ##STR00013##
wherein Me represents a methyl group and Et represents an ethyl group.
(45) The compound is preferably represented by, for example, the following formula (11-1):
(46) ##STR00014##
wherein S's are the same as or different from each other and each represented by any one of the following formulas (11-2) to (11-6); A.sup.3 represents a trivalent hydrocarbon group; A.sup.4 represents a phenylene group; a —CH.sub.2— group in each of A.sup.3 and A.sup.4 may be replaced by a —O— group or a —S— group unless the —CH.sub.2— group neighbors another one; a —CH═ group in each of A.sup.3 and A.sup.4 may be replaced by a —N═ group unless the —CH═ group neighbors another one; a hydrogen atom in each of A.sup.3 and A.sup.4 may be replaced by a fluorine atom, a chlorine atom, a —CN group, or a C1 to C12 alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, or alkylcarbonyloxy group, and at least one of their carbon atoms may be replaced by a silicon atom; the alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, or alkylcarbonyloxy group may be linear or branched; the —Z.sup.3— group and the —Z.sup.4— group are the same as or different from each other and each represent a —O— group, a —S— group, a —NH— group, a —CO— group, a —COO— group, a —OCO— group, a —NHCO— group, a —CONH— group, or a direct bond; L.sup.3 represents a C4 or greater alkyl, alkenyl, or aralkyl group or a C4 or greater monovalent monocyclic or polycyclic hydrocarbon group; the alkyl group and the alkenyl group may each be linear or branched; at least one hydrogen atom in each of the aralkyl group and the monovalent monocyclic or polycyclic hydrocarbon group may be replaced by a C1 to C8 linear or branched alkyl or alkenyl group; a —CH.sub.2— group in each of the alkyl group, the alkenyl group, and the monovalent monocyclic or polycyclic hydrocarbon group may be replaced by a —O— group, a —CO— group, a —COO— group, or a —OCO— group unless oxygen atoms neighbor each other; and n.sup.3 is 0 or 1,
(47) ##STR00015##
wherein Me represents a methyl group and Et represents an ethyl group.
(48) Examples of the compound include one represented by the following formula (12) or (13).
(49) ##STR00016##
(3) Blend of Polymer Containing Hydrophobic Group
(50) In the liquid crystal display device of the present invention, the photo-alignment film preferably further contains a polymeric material other than the above polymer, and the polymeric material preferably contains a hydrophobic group.
(51) The polymeric material other than the above polymer is preferably one whose main chain is a polyvinyl chain. Preferred examples thereof include one represented by the following formula (14):
(52) ##STR00017##
wherein the hydrophobic group H represents a C4 or greater alkyl, alkenyl, or aralkyl group or a C4 or greater monovalent monocyclic or polycyclic hydrocarbon group; A represents a hydrogen atom, an OH group, a COOH group, or a NH.sub.2 group; a -Sp- group represents a —O— group, a —S— group, a —NH— group, a —CO— group, a —COO— group, a —OCO— group, a —NHCO— group, a —CONH— group, or a direct bond; Z represents a hydrogen atom, a CH.sub.3 group, or a C.sub.2H.sub.5 group; p shows the degree of polymerization and is an integer of 1 or greater; and n is any value falling within the range of 0 to 1.
(53) Examples of the polymeric material other than the above polymer include one represented by the following formula (15) or (16).
(54) ##STR00018##
(4) Introduction and Polymerization of Monomer Containing Hydrophobic Group
(55) In the liquid crystal display device of the present invention, preferably, the photo-alignment film further contains a polymeric material other than the above polymer, the polymeric material contains a hydrophobic group, and the polymeric material is a polymer having a monomer unit derived from a monomer represented by the following formula (17):
(56) ##STR00019##
wherein P's are the same as or different from each other and each represent an acryloyloxy group, a methacryloyloxy group, an acryloylamino group, or a methacryloylamino group; A.sup.3 represents a trivalent hydrocarbon group; A.sup.4 represents a phenylene group; a —CH.sub.2— group in each of A.sup.3 and A.sup.4 may be replaced by a —O— group or a —S— group unless the —CH.sub.2— group neighbors another one; a —CH═ group in each of A.sup.3 and A.sup.4 may be replaced by a —N═ group unless the —CH═ group neighbors another one; a hydrogen atom in each of A.sup.3 and A.sup.4 may be replaced by a fluorine atom, a chlorine atom, a CN group, or a C1 to C12 alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, or alkylcarbonyloxy group, and at least one of their carbon atoms may be replaced by a silicon atom; the alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, or alkylcarbonyloxy group may be linear or branched; the —Z.sup.4— group and the —Z.sup.5— group are the same as or different from each other and each represent a —O— group, a —S— group, a —NH— group, a —CO— group, a —COO— group, a —OCO— group, a —NHCO— group, a —CONH— group, or a direct bond; L.sup.3 represents a C4 or greater alkyl, alkenyl, or aralkyl group or a C4 or greater monovalent monocyclic or polycyclic hydrocarbon group; the alkyl group and the alkenyl group may be linear or branched; at least one hydrogen atom in each of the aralkyl group and the monovalent monocyclic or polycyclic hydrocarbon group may be replaced by a C1 to C8 linear or branched alkyl or alkenyl group; a —CH.sub.2— group in each of the alkyl group, the alkenyl group, and the monovalent monocyclic or polycyclic hydrocarbon group may be replaced by a —O— group, a —CO— group, a —COO— group, or a —OCO— group unless oxygen atoms neighbor each other; and n.sup.3 is 0 or 1.
(Radical Polymerization Initiator Used in Polymerization)
(57) One aspect of the present invention may be a method for manufacturing the liquid crystal display device of the present invention, the method including: radically polymerizing the monomer using a radical polymerization initiator.
(58) The radical polymerization initiator is preferably an azo-based thermal radical polymerization initiator, more preferably one represented by, for example, the following formula (18).
(59) ##STR00020##
(60) The proportion of the monomer unit containing a hydrophobic group may fall within the range of 0.01 to 20 mass %, for example, of all polymers (100 mass %).
(61) Hereinafter, examples of the above embodiment are described.
Example 1 (Horizontal Photo-Alignment Film: Copolymer)
(62) (Production of Liquid Crystal Cell)
(63) A TFT substrate and a counter substrate with no electrode were prepared. To each of the substrates was applied a polyamic acid-based alignment film material that is represented by the following formula (19) and contains a copolymer containing azobenzene as a photo-functional group and an alkyl group as a hydrophobic group. The film material was pre-baked at 80° C. for two minutes, irradiated with linearly polarized light (including ultraviolet light having a wavelength of 310 to 370 nm) with an intensity of 2 J/cm.sup.2, and then post-baked at 110° C. for 20 minutes and then at 230° C. for 20 minutes, whereby photo-alignment films were formed. To one of the substrates was applied an ultraviolet-curable, thermosetting sealant (trade name: Photolec S, Sekisui Chemical Co., Ltd.) in a predetermined pattern using a dispenser. Onto the predetermined positions of the other substrate was dropped a positive liquid crystal material A (viscosity: 65 mPa.Math.s (20° C.), measured with a liquid crystal material characteristics measurement system from Toyo Corp.) having a Tni of 75° C. or lower and a liquid crystal phase temperature range narrower than 100° C. The substrates were bonded to each other in a vacuum, and the sealant was cured by ultraviolet light (including ultraviolet light having a wavelength of 300 to 400 nm). The substrates were further heated at 130° C. for 40 minutes to thermally cure the sealant, and subjected to realignment treatment such that the liquid crystal transformed into an isotropic phase. The substrates were cooled down to room temperature, and thereby an FFS-mode liquid crystal cell was obtained.
(64) ##STR00021##
(65) In the formula, n is 0.8 and p shows the degree of polymerization.
Comparative Example 1
(66) An FFS-mode liquid crystal cell of Comparative Example 1 was produced using a polyamic acid (containing only an azobenzene group and no alkyl group) represented by the following formula (20):
(67) ##STR00022##
wherein p shows the degree of polymerization.
Comparative Example 2
(68) In Comparative Example 2, the alignment film material contained a copolymer represented by the formula (19), and the liquid crystal material used was a positive liquid crystal material B (viscosity: 95 mPa.Math.s (20° C.), measured with a liquid crystal material characteristics measurement system from Toyo Corp.) having a Tni of 80° C. and a liquid crystal (nematic) phase temperature range of 100.5° C. or wider.
(69) (Electro-Optical Characteristics and Response Performance at 25° C.)
(70) The electro-optical characteristics (VT characteristics) and response performance of the liquid crystal cell were determined at a cell surface temperature of 25° C. using Photoal from Otsuka Electronics Co., Ltd.
(71) (Low-Temperature Storage Test)
(72) The liquid crystal cell was placed in a −20° C. thermostat bath and left to stand for 1000 hours to determine whether or not crystallization occurred.
(73)
(74) Table 1 shows the results of the response performance (sum of rise response τr and decay response τd) at 25° C. and crystallization during the −20° C. storage test (1000 hours).
(75) TABLE-US-00001 TABLE 1 Response performance Crystallization during τr + τd (ms) −20° C. storage test (25° C.) (1000 hours) Example 1 14.5 Not occurred Comparative Example 1 14.6 Occurred Comparative Example 2 22.3 Not occurred
(76) In Comparative Example 1, the response performance did not differ from that in Example 1 but crystallization occurred in the −20° C. storage test. The liquid crystal material crystallized presumably because the liquid crystal layer, containing no alkyl group (hydrophobic group) on its surface, was less likely to interact with liquid crystal molecules in the liquid crystal layer, and thus failed to weaken the strong p orbital electron interaction between the phenyl groups or the phenylene groups in the liquid crystal molecules.
(77) In Comparative Example 2, crystallization did not occur in the −20° C. storage test, but the response performance was degraded. Since the liquid crystal material B was used, the viscosity was high and the response performance was low.
(78) The results in Table 1 confirm that with a photo-alignment film polymer containing a hydrophobic group, excellent response performance was achieved using a liquid crystal material having a Tni of 75° C. or lower and a liquid crystal phase temperature range narrower than 100° C. while crystallization was reduced or avoided during low-temperature storage.
Example 2 (Introduction of Low-Molecular-Weight Additive Containing Hydrophobic Group into Horizontal Alignment Film)
(79) (Production of Liquid Crystal Cell)
(80) A TFT substrate and a counter substrate with no electrode were prepared. To each of the substrates was applied an alignment film material that contained a polyamic acid represented by the formula (20) and containing a photo-functional group (azobenzene) and a compound represented by the following formula (21) or a compound represented by the following formula (22). The film material was pre-baked at 80° C. for two minutes, irradiated with linearly polarized light (including ultraviolet light having a wavelength of 310 to 370 nm) with an intensity of 2 J/cm.sup.2, and then post-baked at 110° C. for 20 minutes and then at 230° C. for 20 minutes, whereby photo-alignment films were formed. The case of using an alignment film material containing a compound represented by the following formula (21) is Example 2-1, and the case of using an alignment film material containing a compound represented by the following formula (22) is Example 2-2. To one of the substrates was applied an ultraviolet-curable, thermosetting sealant (trade name: Photolec S, Sekisui Chemical Co., Ltd.) in a predetermined pattern using a dispenser. Onto the predetermined positions of the other substrate was dropped a positive liquid crystal material A having a Tni of 75° C. or lower and a liquid crystal phase temperature range narrower than 100° C. The substrates were bonded to each other in a vacuum, and the sealant was cured by ultraviolet light (including ultraviolet light having a wavelength of 300 to 400 nm). The substrates were further heated at 130° C. for 40 minutes to thermally cure the sealant, and subjected to realignment treatment such that the liquid crystal transformed into an isotropic phase. The substrates were cooled down to room temperature, and thereby an FFS-mode liquid crystal cell was obtained.
(81) ##STR00023##
(Electro-Optical Characteristics and Response Performance at 25° C.)
(82) Determination was conducted as in Example 1.
(83) (Low-Temperature Storage Test)
(84) Determination was conducted as in Example 1.
(85)
(86) Table 2 shows the results of the response performance (sum of rise response τr and decay response τd) at 25° C. and crystallization during the −20° C. storage test (1000 hours).
(87) TABLE-US-00002 TABLE 2 Response performance Crystallization during τr + τd (ms) −20° C. storage test (25° C.) (1000 hours) Example 2-1 14.5 Not occurred Example 2-2 14.5 Not occurred Comparative Example 1 14.6 Occurred
(88) The results in
Example 3 (Introduction of Polymeric Additive Containing Hydrophobic Group into Horizontal Alignment Film)
(89) (Production of Liquid Crystal Cell)
(90) A TFT substrate and a counter substrate with no electrode were prepared. To each of the substrates was applied an alignment film material that contained a polyamic acid containing a photo-functional group (azobenzene) and represented by the formula (20) and a polymeric additive represented by the following formula (23) or a polymeric additive represented by the following formula (24). The film material was pre-baked at 80° C. for two minutes, irradiated with linearly polarized light (including ultraviolet light having a wavelength of 310 to 370 nm) with an intensity of 2 J/cm.sup.2, and then post-baked at 110° C. for 20 minutes and then at 230° C. for 20 minutes, whereby photo-alignment films were formed. The case of using an alignment film material containing a polymeric additive represented by the following formula (23) is Example 3-1, and the case of using an alignment film material containing a polymeric additive represented by the following formula (24) is Example 3-2. To one of the substrates was applied an ultraviolet-curable, thermosetting sealant (trade name: Photolec S, Sekisui Chemical Co., Ltd.) in a predetermined pattern using a dispenser. Onto the predetermined positions of the other substrate was dropped a positive liquid crystal material A having a Tni of 75° C. or lower and a liquid crystal phase temperature range narrower than 100° C. The substrates were bonded to each other in a vacuum, and the sealant was cured by ultraviolet light (including ultraviolet light having a wavelength of 300 to 400 nm). The substrates were further heated at 130° C. for 40 minutes to thermally cure the sealant, and subjected to realignment treatment such that the liquid crystal transformed into an isotropic phase. The substrates were cooled down to room temperature, and thereby an FFS-mode liquid crystal cell was obtained.
(91) ##STR00024##
(92) In the formulas, p shows the degree of polymerization.
(93) (Electro-Optical Characteristics and Response Performance at 25° C.)
(94) Determination was conducted as in Example 1.
(95) (Low-Temperature Storage Test)
(96) Determination was conducted as in Example 1.
(97)
(98) Table 3 shows the results of the response performance (sum of rise response τr and decay response τd) at 25° C. and crystallization during the −20° C. storage test (1000 hours).
(99) TABLE-US-00003 TABLE 3 Response performance Crystallization during τr + τd (ms) −20° C. storage test (25° C.) (1000 hours) Example 3-1 14.6 Not occurred Example 3-2 14.7 Not occurred Comparative Example 1 14.6 Occurred
(100) The results in
Example 4 (Introduction of Polymer Containing Hydrophobic Group into Horizontal Alignment Film, Followed by Polymerization)
(101) A TFT substrate and a counter substrate with no electrode were prepared. To each of the substrates was applied an alignment film material containing a polysiloxane with a photo-functional group (cinnamate group) and represented by the following formula (25), a monomer containing a hydrophobic group and represented by the following formula (26) or a monomer containing a hydrophobic group and represented by the following formula (27), and a thermal polymerization initiator represented by the following formula (28). The film material was pre-baked at 60° C. for two minutes, and then thermally polymerized at 80° C. for 30 minutes. The case of using an alignment film material that contains a monomer containing a hydrophobic group and represented by the following formula (26) is Example 4-1, and the case of using an alignment film material that contains a monomer containing a hydrophobic group and represented by the following formula (27) is Example 4-2. The film material was irradiated with linearly polarized light (including ultraviolet light having a wavelength of 310 to 370 nm) with an intensity of 100 mJ/cm.sup.2, and then post-baked at 200° C. for 40 minutes, whereby photo-alignment films were formed. To one of the substrates was applied an ultraviolet-curable, thermosetting sealant (trade name: Photolec S, Sekisui Chemical Co., Ltd.) in a predetermined pattern using a dispenser. Onto the predetermined positions of the other substrate was dropped a positive liquid crystal material A having a Tni of 75° C. or lower and a liquid crystal phase temperature range narrower than 100° C. The substrates were bonded to each other in a vacuum, and the sealant was cured by ultraviolet light (including ultraviolet light having a wavelength of 300 to 400 nm). The substrates were further heated at 130° C. for 40 minutes to thermally cure the sealant, and subjected to realignment treatment such that the liquid crystal transformed into an isotropic phase. The substrates were cooled down to room temperature, and thereby an FFS-mode liquid crystal cell was obtained.
(102) ##STR00025##
Comparative Example 3
(103) In Comparative Example 3, an FFS-mode liquid crystal cell was obtained as in Example 4-1 (Example 4-2), except that an alignment film material containing only polysiloxane containing a photo-functional group and represented by the formula (25) was used.
(104) (Electro-Optical Characteristics and Response Performance at 25° C.)
(105) Determination was conducted as in Example 1.
(106) (Low-Temperature Storage Test)
(107) Determination was conducted as in Example 1.
(108)
(109) Table 4 shows the results of the response performance (sum of rise response τr and decay response τd) at 25° C. and crystallization during the −20° C. storage test (1000 hours).
(110) TABLE-US-00004 TABLE 4 Response performance Crystallization during τr + τd (ms) −20° C. storage test (25° C.) (1000 hours) Example 4-1 14.7 Not occurred Example 4-2 14.6 Not occurred Comparative Example 3 14.7 Occurred
(111) The results in
(112) The concept of the present invention is applicable to ECB-mode, TN-mode, or vertical alignment TN (VATN)-mode liquid crystal display devices, for example.
ADDITIONAL REMARKS
(113) Preferred aspects of the liquid crystal display device of the present invention and the method for manufacturing the liquid crystal display device. In other words, the preferred examples described below, as well as the preferred examples described above, are examples of preferred aspects of the present invention. These examples may appropriately be combined within the spirit of the present invention.
(114)
(115) The liquid crystal display device of the present invention also includes components such as thin-film transistor elements appropriately disposed on the lower glass substrate 11, which functions as a support substrate. The liquid crystal display device of the present invention includes, for example, pixel electrodes provided with slits on part of an insulating film that covers components such as thin-film transistor elements, and a common electrode disposed on the upper glass substrate 21, which functions as a support substrate. The material of the pixel electrode and the common electrode is preferably indium tin oxide (ITO) or indium zinc oxide (IZO). The liquid crystal display device of the present invention further includes a color filter layer (which may be disposed in the same layer as the black matrix) appropriately disposed on the upper glass substrate 21, for example. In this case, the paired substrate can be regarded as consisting of a TFT array substrate (TFT substrate) and a color filter substrate (counter substrate). Components such as a color filter layer may be disposed on the lower glass substrate 11, not on the upper glass substrate 21.
(116) One aspect of the present invention may be a liquid crystal display device including: paired substrates; a liquid crystal layer held between the substrates; and a photo-alignment film disposed on a surface facing the liquid crystal layer of at least one of the substrates, the liquid crystal layer containing a liquid crystal material that has a nematic-isotropic phase transition temperature of 75° C. or lower and a nematic phase temperature range narrower than 100° C., the photo-alignment film containing a polymer, the polymer and/or another component of the photo-alignment film containing a hydrophobic group. The hydrophobic group is a C1 or greater hydrocarbon group, and is preferably, for example, an aliphatic group such as an alkyl group or an alkylene group. The aliphatic group such as an alkyl group or an alkylene group is linear or cyclic. The aliphatic group is saturated or unsaturated.
(117) The hydrophobic group (preferably an aliphatic group) is preferably a C2 or greater one, more preferably a C5 or greater one, still more preferably a C8 or greater one, particularly preferably a C13 or greater one. There is no upper limit of the number of carbons, but the upper limit is preferably 30, for example.
(118) In the liquid crystal display device of the present invention, a main chain of the polymer preferably has a polyamic acid structure or a polysiloxane structure.
(119) In the liquid crystal display device of the present invention, the polymer preferably has an azobenzene structure or contains a cinnamate group.
(120) In the liquid crystal display device of the present invention, the polymer preferably contains a hydrophobic group. The expression “the polymer contains a hydrophobic group” means that a hydrophobic group has been introduced into the polymer by a chemical bond.
(121) The other components in the photo-alignment film may be any components such as a polymer other than the above polymer or a low-molecular-weight compound. For example, in the liquid crystal display device of the present invention, the photo-alignment film preferably contains a compound containing the hydrophobic group.
(122) In the liquid crystal display device of the present invention, the compound is preferably represented by, for example, the following formula (10-1):
[Chem. 29-1]
S-A.sup.2-Z.sup.4-L.sup.3 (10-1)
wherein S is represented by any one of the following formulas (10-2) to (10-6); A.sup.2 represents a divalent hydrocarbon group or a direct bond; the —Z.sup.4— group represents a —O— group, a —S— group, a —NH— group, a —CO— group, a —COO— group, a —OCO— group, a —NHCO— group, a —CONH— group, or a direct bond; L.sup.3 represents a C4 or greater alkyl, alkenyl, or aralkyl group, or a C4 or greater monovalent monocyclic or polycyclic hydrocarbon group; the alkyl group and the alkenyl group may each be linear or branched; at least one hydrogen atom in each of the aralkyl group and the monovalent monocyclic or polycyclic hydrocarbon group may be replaced by a C1 to C8 linear or branched alkyl or alkenyl group; a —CH.sub.2— group in each of the alkyl group, the alkenyl group, and the monovalent monocyclic or polycyclic hydrocarbon group may be replaced by a —O— group, a —CO— group, a —COO— group, or a —OCO— group unless oxygen atoms neighbor each other; and the divalent hydrocarbon group in A.sup.2 is, for example, an alicyclic hydrocarbon group, an aromatic monocyclic hydrocarbon group, or an aromatic condensed polycyclic hydrocarbon group,
(123) ##STR00026##
wherein Me represents a methyl group and Et represents an ethyl group.
(124) The compound is preferably represented by, for example, the following formula (11-1):
(125) ##STR00027##
wherein S's are the same as or different from each other and each represented by any one of the following formulas (11-2) to (11-6); A.sup.3 represents a trivalent hydrocarbon group; A.sup.4 represents a phenylene group; a —CH.sub.2— group in each of A.sup.3 and A.sup.4 may be replaced by a —O— group or a —S— group unless the —CH.sub.2— group neighbors another one; a —CH═ group in each of A.sup.3 and A.sup.4 may be replaced by a —N═ group unless the —CH═ group neighbors another one; a hydrogen atom in each of A.sup.3 and A.sup.4 may be replaced by a fluorine atom, a chlorine atom, a —CN group, or a C1 to C12 alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, or alkylcarbonyloxy group, and at least one of their carbon atoms may be replaced by a silicon atom; the alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, or alkylcarbonyloxy group may be linear or branched; the —Z.sup.3— group and the —Z.sup.4— group are the same as or different from each other and each represent a —O— group, a —S— group, a —NH— group, a —CO— group, a —COO— group, a —OCO— group, a —NHCO— group, a —CONH— group, or a direct bond; L.sup.3 represents a C4 or greater alkyl, alkenyl, or aralkyl group or a C4 or greater monovalent monocyclic or polycyclic hydrocarbon group; the alkyl group and the alkenyl group may each be linear or branched; at least one hydrogen atom in each of the aralkyl group and the monovalent monocyclic or polycyclic hydrocarbon group may be replaced by a C1 to C8 linear or branched alkyl or alkenyl group; a —CH.sub.2— group in each of the alkyl group, the alkenyl group, and the monovalent monocyclic or polycyclic hydrocarbon group may be replaced by a —O— group, a —CO— group, a —COO— group, or a —OCO— group unless oxygen atoms neighbor each other; n.sup.3 is 0 or 1; and the trivalent hydrocarbon group in A.sup.3 is, for example, an alicyclic hydrocarbon group, an aromatic monocyclic hydrocarbon group, or an aromatic condensed polycyclic hydrocarbon group,
(126) ##STR00028##
wherein Me represents a methyl group and Et represents an ethyl group.
(127) In the liquid crystal display device of the present invention, preferably, with the polymer taken as a first polymer, the photo-alignment film further contains a second polymer other than the first polymer, and the second polymer contains a hydrophobic group.
(128) In the liquid crystal display device of the present invention, the second polymer is preferably represented by the following formula (14):
(129) ##STR00029##
wherein H surrounded by a solid line represents a C4 or greater alkyl, alkenyl, or aralkyl group or a C4 or greater monovalent monocyclic or polycyclic hydrocarbon group; A represents a hydrogen atom, an OH group, a COOH group, or a NH.sub.2 group; a -Sp- group represents a —O— group, a —S— group, a —NH— group, a —CO— group, a —COO— group, a —OCO— group, a —NHCO— group, a —CONH— group, or a direct bond; Z represents a hydrogen atom, a CH.sub.3 group, or a C.sub.2H.sub.5 group; p shows the degree of polymerization and is an integer of 1 or greater; and n is any value falling within the range of 0 to 1.
(130) In the liquid crystal display device of the present invention, preferably, the second polymer is preferably a polymer containing a monomer unit derived from a monomer represented by the following formula (17):
(131) ##STR00030##
wherein P's are the same as or different from each other and each represent an acryloyloxy group, a methacryloyloxy group, an acryloylamino group, or a methacryloylamino group; A.sup.3 represents a trivalent hydrocarbon group; A.sup.4 represents a phenylene group; a —CH.sub.2— group in each of A.sup.3 and A.sup.4 may be replaced by a —O— group or a —S— group unless the —CH.sub.2— group neighbors another one; a —CH═ group in each of A.sup.3 and A.sup.4 may be replaced by a —N═ group unless the —CH═ group neighbors another one; a hydrogen atom in each of A.sup.3 and A.sup.4 may be replaced by a fluorine atom, a chlorine atom, a —CN group, or a C1 to C12 alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, or alkylcarbonyloxy group, and at least one of their carbon atoms may be replaced by a silicon atom; the alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, or alkylcarbonyloxy group may be linear or branched; the —Z.sup.4— group and the —Z.sup.5— group are the same as or different from each other and each represent a —O— group, a —S— group, a —NH— group, a —CO— group, a —COO— group, a —OCO— group, a —NHCO— group, a —CONH— group, or a direct bond; L.sup.3 represents a C4 or greater alkyl, alkenyl, or aralkyl group or a C4 or greater monovalent monocyclic or polycyclic hydrocarbon group; the alkyl group and the alkenyl group may be linear or branched; at least one hydrogen atom in each of the aralkyl group and the monovalent monocyclic or polycyclic hydrocarbon group may be replaced by a C1 to C8 linear or branched alkyl or alkenyl group; a —CH.sub.2— group in each of the alkyl group, the alkenyl group, and the monovalent monocyclic or polycyclic hydrocarbon group may be replaced by a —O— group, a —CO— group, a —COO— group, or a —OCO— group unless oxygen atoms neighbor each other; and n.sup.3 is 0 or 1.
(132) The trivalent hydrocarbon group in A.sup.3 is, for example, an alicyclic hydrocarbon group, an aromatic monocyclic hydrocarbon group, or an aromatic condensed polycyclic hydrocarbon group.
(133) Another aspect of the present invention may be a method for manufacturing the liquid crystal display device of the present invention, the method including: heating an alignment film material that contains an additive containing the hydrophobic group so as to produce the polymer containing the hydrophobic group.
(134) The heating temperature is preferably, for example, 100° C. or higher, more preferably 150° C. or higher. The upper limit of the heating temperature may be any temperature such as 300° C.
(135) The heating duration is, for example, preferably 10 minutes or longer, more preferably 20 minutes or longer. The upper limit of the heating duration may be any length such as 100 minutes.
(136) Pre-baking may be conducted before post-baking.
(137) Yet another aspect of the present invention may be a method for manufacturing the liquid crystal display device of the present invention, the method including: radically polymerizing the monomer using a radical polymerization initiator to produce the second polymer.
(138) In the method for manufacturing the liquid crystal display device of the present invention, the radical polymerization initiator is preferably an azo-based thermal radical polymerization initiator.
(139) The display mode of the liquid crystal display device of the present invention is preferably the twisted nematic (TN) mode, the electrically controlled birefringence (EBC) mode, the IPS mode, the FFS mode, the VA mode, or the VATN mode. The liquid crystal display device of the present invention may be a transmissive liquid crystal display device, a reflective liquid crystal display device, or a transflective liquid crystal display device. In the case where the liquid crystal display device of the present invention is a transmissive liquid crystal display device or a transflective liquid crystal display device, the liquid crystal display device of the present invention usually includes a backlight.
REFERENCE SIGNS LIST
(140) 11: Lower glass substrate 13, 23: Alignment film 21: Upper glass substrate 31: Liquid crystal layer 33: Seal 41: Backlight