Method of manufacturing double-sided polarizing plate and double-sided polarizing plate manufactured using the same

Abstract

A method of manufacturing a double-sided polarizing plate and a double-sided polarizing plate manufactured using the same are provided. The method of manufacturing a double-sided polarizing plate includes attaching transparent films to both surfaces of a polarizer by means of adhesive layers, irradiating the adhesive layers with active energy rays emitted by an energy source disposed in a single direction with respect to the polarizer, and thermally treating a surface of the transparent film disposed opposite to the energy source at a temperature of 25° C. to 65° C.

Claims

1. A method of manufacturing a double-sided polarizing plate, comprising: attaching transparent films to both surfaces of a polarizer by means of adhesive layers; irradiating the adhesive layers with active energy rays emitted by an energy source disposed in a single direction with respect to the polarizer; and thermally treating a surface of the transparent film disposed opposite to the energy source at a temperature of 30° C. to 50° C., wherein the thermal treatment is performed in a drum, wherein the irradiation with the active energy rays is performed simultaneously with the thermal treatment, wherein the adhesive layers are formed using a cationic adhesive, wherein the cationic adhesive includes (1) 5 to 90 parts by weight of an epoxy compound having at least two epoxy groups in a molecule; (2) 5 to 90 parts by weight of an oxetane compound having at least one oxetanyl group in the molecule; and (3) 0.5 to 20 parts by weight of an optical cationic photopolymerization initiator, based on a total of 100 parts by weight of an adhesive composition, wherein the epoxy compound is a combination of a first epoxy compound containing one or more epoxidized alicyclic groups and a second epoxy compound containing one or more glycidyl ether groups, and wherein the first epoxy compound and the second epoxy compound are mixed at a weight ratio of 1:1 to 3:1.

2. The method of claim 1, further comprising simultaneously curing the adhesive layers formed on both surfaces of the polarizer by once irradiation with the active energy rays.

3. The method of claim 1, wherein the adhesive layer formed on the transparent film having the energy source disposed therein has a thickness of 0.1 μm to 10 μm.

4. The method of claim 1, wherein the adhesive layer formed on the transparent film disposed opposite to the energy source has a thickness of 0.1 μm to 3 μm.

5. The method of claim 1, wherein the cationic adhesive further comprises at least one selected from the group consisting of a silane coupling agent, a vinyl-based compound, and a radical polymerizable monomer.

6. The method of claim 1, wherein at least one of the transparent films formed on both surfaces of the polarizer is an acrylic film.

7. The method of claim 1, further comprising forming a primer layer between at least one surface of the adhesive layer and at least one surface of the transparent film.

8. The method of claim 7, wherein the primer layer has a thickness of 100 nm to 1 μm.

9. The method of claim 7, wherein the primer layer is formed of a primer composition comprising 1 to 50 parts by weight of a urethane polymer; 0.1 to 10 parts by weight of water-dispersible fine particles; and the balance of water, based on a total of 100 parts by weight of the primer composition.

10. The method of claim 9, wherein the primer composition further comprises a cross-linking agent.

Description

MODE FOR INVENTION

Preparative Example 1

Preparation of Acrylic Film

(1) A resin composition in which a poly(N-cyclohexylmaleimide-co-methyl methacrylate) resin, a styrene-anhydrous maleic acid copolymeric resin and a phenoxy-based resin were uniformly mixed at a weight ratio of 100:2.5:5 was fed to a 24φ extruder in which a space spanning from a feed hopper to an extruder was replaced with nitrogen, and melted at 250° C. to prepare a feed pellet.

(2) PKFE (Mw=60,000, Mn=16,000, Tg=95° C.; commercially available from InChemRez®) was used as the phenoxy-based resin, Dylaeck 332 including styrene at 85% by weight and anhydrous maleic acid at 15% by weight was used as the styrene-anhydrous maleic acid copolymeric resin, and the poly(N-cyclohexylmaleimide-co-methyl methacrylate) resin was analyzed through NMR. As a result, the content of N-cyclohexylmaleimide was 6.5% by weight.

(3) The resulting feed pellet was dried under a vacuum, melted at 260° C. in an extruder, and passed through a coat hanger-type T-die, followed by a chromium-plated casting roll and a drying roll, thereby manufacturing a film having a thickness of 150 μm. The film was elongated at 125° C. in an MD direction using Pilot Elongation equipment to manufacture an acrylic film. In this case, the film was elongated at a percentage of 170% using a difference in speeds of rolls.

(4) The acrylic film manufactured thus was treated with corona, and one surface of the acrylic film was coated with a primer composition, in which 20 parts by weight of an oxazoline cross-linking agent (WS700, commercially available from Nippon Shokubai) was added to a primer composition having a solid content of 10% by weight prepared by diluting CK-PUD-F (a urethane dispersion commercially available from Chokwang Paint Ltd.) with pure water, using a #7 bar, and elongated at 130° C. in a TD direction to a percentage of 190% using a tender to manufacture an acrylic film including a primer layer having a thickness of 400 nm.

Preparative Example 2

Preparation of Adhesive Composition

(5) (1) Adhesive Composition A

(6) Five parts by weight of a cationic initiator, CPI 100P (commercially available from Sanapro), was added to 100 parts by weight of a resin composition prepared by adding 25% by weight of 3,4-epoxycyclohexylmethyl-3,4′-epoxycyclohexanecarboxylate (Celloxide 2021P commercially available from Dicel), 25% by weight of 1,4-cyclohexane dimethanol diglycidyl ether, 35% by weight of 3-ethyl-3-[(3-ethyloxetan-3-yl)methoxymethyl]oxetane (Toa Gosei Aaron Oxetane DOX221), and 15% by weight of 3-ethyl-3-hydroxymethyloxetane (Toa Gosei Aaron Oxetane OXA) to prepare an adhesive composition A for polarizing plates.

(7) (2) Adhesive Composition B

(8) Five parts by weight of a cationic initiator, CPI 100P (commercially available from Sanapro), and 5 parts by weight of vinyltriethylsilane were added to 100 parts by weight of a resin composition prepared by adding 25% by weight of 3,4-epoxycyclohexylmethyl-3,4′-epoxycyclohexanecarboxylate (Celloxide 2021P commercially available from Dicel), 25% by weight of 1,4-cyclohexane dimethanol diglycidyl ether, and 50% by weight of 3-ethyl-3-[(3-ethyloxetan-3-yl)methoxymethyl]oxetane (Toa Gosei Aaron Oxetane DOX221) to prepare an adhesive composition B for polarizing plates.

(9) (3) Adhesive Composition C

(10) Five parts by weight of a cationic initiator, CPI 100P (commercially available from Sanapro), and 5 parts by weight of vinyl acetate were added to 100 parts by weight of a resin composition prepared by adding 25% by weight of 3,4-epoxycyclohexylmethyl-3,4′-epoxycyclohexanecarboxylate (Celloxide 2021P commercially available from Dicel), 25% by weight of 1,4-cyclohexane dimethanol diglycidyl ether, and 50% by weight of 3-ethyl-3-[(3-ethyloxetan-3-yl)methoxymethyl]oxetane (Toa Gosei Aaron oxetane DOX221) to prepare an adhesive composition C for polarizing plates.

Example 1

(11) Primer layers of the two acrylic films prepared in Preparative Example 1 were coated with adhesive composition A, using a microgravure coater, so that the final thickness of each of adhesive layers amounted to 1 μm. Thereafter, the two acrylic films coated with the adhesive composition were laminated on both surfaces of a PVA element. Then, one surface of the PVA element was unidirectionally irradiated with UV rays with a quantity of light of 900 mJ/cm.sup.2 using a UV irradiation system (a fusion lamp, D bulb), and a surface of the acrylic film disposed opposite to the UV irradiation system was closely adhered to a drum at the same time. The temperature of the drum was adjusted to 25° C. to manufacture a polarizing plate.

Example 2

(12) A polarizing plate was manufactured in the same manner as in Example 1, except that the adhesive composition B was used as the adhesive composition.

Example 3

(13) A polarizing plate was manufactured in the same manner as in Example 1, except that the adhesive composition C was used as the adhesive composition.

Example 4

(14) A polarizing plate was manufactured in the same manner as in Example 1, except that the temperature of the drum was set to 30° C.

Example 5

(15) A polarizing plate was manufactured in the same manner as in Example 1, except that the temperature of the drum was set to 40° C.

Example 6

(16) A polarizing plate was manufactured in the same manner as in Example 1, except that the temperature of the drum was set to 60° C.

Example 7

(17) Primer layers of the two acrylic films prepared in Preparative Example 1 were coated with adhesive composition A, using a microgravure coater, so that the final thickness of each of adhesive layers amounted to 1 μm. Thereafter, the two acrylic films coated with the adhesive composition were laminated on both surfaces of a PVA element. Then, one surface of the PVA element was unidirectionally irradiated with UV rays with a quantity of light of 900 mJ/cm.sup.2 using a UV irradiation system (a fusion lamp, D bulb), and a surface of the acrylic film disposed opposite to the UV irradiation system was then passed through an oven whose temperature was set to 30° C., thereby manufacturing a polarizing plate.

Example 8

(18) A polarizing plate was manufactured in the same manner as in Example 7, except that the temperature of the oven was set to 40° C.

Example 9

(19) A polarizing plate was manufactured in the same manner as in Example 7, except that the temperature of the oven was set to 60° C.

Comparative Example1

(20) A polarizing plate was manufactured in the same manner as in Example 1, except that the temperature of the drum was set to 15° C.

Comparative Example 2

(21) A polarizing plate was manufactured in the same manner as in Example 1, except that the temperature of the drum was set to 70° C.

Comparative Example3

(22) A polarizing plate was manufactured in the same manner as in Example 7, except that the temperature of the oven was set to 70° C.

Comparative Example 4

(23) Adhesive composition A was pre-heated at 60° C., and primer layers of the two acrylic films prepared in Preparative Example 1 were coated with the heated adhesive composition A, using a microgravure coater, so that the final thickness of each of adhesive layers amounted to 1 μm. Thereafter, the two acrylic films coated with the adhesive composition were laminated on both surfaces of a PVA element. Then, one surface of the PVA element was unidirectionally irradiated with UV rays with a quantity of light of 900 mJ/cm.sup.2 using a UV irradiation system (a fusion lamp, D bulb), thereby manufacturing a polarizing plate.

Experimental Example 1

Evaluation of Peel Strength of Polarizing Plates

(24) The peel strengths of the adhesive layers formed on surfaces which were directly irradiated with active energy rays and not irradiated with the active energy rays with respect to the polarizing plates manufactured in Examples 1 to 9 and Comparative Examples 1 to 4 were measured. The peel strength of a polarizing plate having a width of 20 mm and a length of 100 mm was measured by peeling a surface of the acrylic film, which was not irradiated with UV rays, from a PVA element at a rate of 300 mm/min and an angle of 90°. The results are listed in the following Table 1. The peel strength is indicated by OK when the peel strength is greater than or equal to 2 N, and indicated by NG when the peel strength is less than 2 N.

Experimental Example 2

Evaluation of Appearance of Polarizing Plates

(25) The appearance of each of the polarizing plates manufactured in Examples 1 to 9 and Comparative Examples 1 to 4 was observed with the naked eye to determine whether wrinkles occurred and whether curling was observed in MD and TD directions. The results are listed in the following Table 1. OK: No wrinkles and curls in MD and TD directions, and NG: There are wrinkles and curls in MD and/or TD directions.

(26) TABLE-US-00001 TABLE 1 Thermal Peel treatment Thermal Peel strength system treatment strength of Primer for temperature Thickness of non- Non- Non- of of UV- light- UV- light - light - Non- Adhesive irradiated irradiated Evaluation irradiated irradiated irradiated irradiated layer surface surface of Items surface surface surface surface Adhesive (μm) measured measured appearance Ex. 1 CkPUD CkPUD Drum 25 A 1 OK OK OK F + WS700 F + WS700 20 20 parts parts by by weight weight Ex. 2 CkPUD CkPUD Drum 25 B 1 OK OK OK F + WS700 F + WS700 20 20 parts parts by by weight weight Ex. 3 CkPUD CkPUD Drum 25 C 1 OK OK OK F + WS700 F + WS700 20 20 parts parts by by weight weight Ex. 4 CkPUD CkPUD Drum 30 A 1 OK OK OK F + WS700 F + WS700 20 20 parts by parts by weight weight Ex. 5 CkPUD CkPUD Drum 40 A 1 OK OK OK F + WS700 F + WS700 20 20 parts parts by by weight weight Ex. 6 CkPUD CkPUD Drum 60 A 1 OK OK OK F + WS700 F + WS700 20 20 parts parts by by weight weight Ex. 7 CkPUD CkPUD Oven 30 A 1 OK OK OK F + WS700 F + WS700 20 20 parts parts by by weight weight Ex. 8 CkPUD CkPUD Oven 40 A 1 OK OK OK F + WS700 F + WS700 20 20 parts parts by by weight weight Ex. 9 CkPUD CkPUD Oven 60 A 1 OK OK OK F + WS700 F + WS700 20 20 parts parts by by weight weight Com. CkPUD CkPUD Drum 15 A 1 OK NG OK Ex. 1 F + WS700 F + WS700 20 20 parts parts by by weight weight Com. CkPUD CkPUD Drum 70 A 1 OK OK NG Ex. 2 F + WS700 F + WS700 20 20 parts parts by by weight weight Com. CkPUD CkPUD Oven 70 A 1 OK OK NG Ex. 3 F + WS700 F + WS700 20 20 parts parts by by weight weight Com. CkPUD CkPUD Adhesive A 1 OK NG NG Ex. 4 F + WS700 F + WS700 composition 20 20 heated at parts parts 60° C. before by by curing (No weight weight separate thermal treatment on non-light- irradiated surface)

(27) The present invention has been described in detail. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art from this detailed description.