(Meth)acrylic copolymer, adhesive composition and adhesive sheet containing same, and coating material and coated product using same

Abstract

A (meth)acrylic acid copolymer (A) having a weight average molecular weight of 1000 to 1,000,000, and in which when the half-width of the primary scatter peak when measured by small angle X-ray scattering is defined as X, 0.12<X, is used as an adhesive. The (meth)acrylic copolymer (A) is obtained by polymerizing a monomer mixture containing a macromonomer (a) having a number average molecular weight of 500-100,000, and a vinyl monomer (b). The adhesive has sufficient holding force and adhesive force, and the occurrence of adhesive deposit can be prevented when peeled off.

Claims

1. A (meth)acrylic copolymer (A) having a weight average molecular weight of 1,000 to 1,000,000, wherein the (meth)acrylic copolymer (A) satisfies 0.12<X, when X is defined as a half width of a primary scatter peak in small angle X-ray scattering measurement, wherein the (meth)acrylic copolymer (A) comprises a constituent unit derived from a macromonomer (a) having a number average molecular weight of 500 to 100,000 and a constituent unit derived from a vinyl monomer (b), wherein the macromonomer (a) is represented by Formula (1): ##STR00004## wherein in Formula (1): R is a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group, the alkyl group, cycloalkyl group, aryl group, or heterocyclic group may have a substituent; Z is an end group; and the symbol . . . represents a main chain moiety comprising two or more constituent units represented by Formula (a): ##STR00005## wherein in formula (a): P represents a hydrogen atom, a methyl group, or CH.sub.2OH: Q is selected from the group consisting of OR, O.sub.2CR, halogen, CO.sub.2H, COR, CO.sub.2R CN, CONH.sub.2, CONHR, CONR.sub.2, and R; R is selected from the group consisting of a hydrogen atom, substituted and unsubstituted alkyl, substituted and unsubstituted aryl, substituted and unsubstituted heteroaryl, substituted and unsubstituted aralkyl, substituted and unsubstituted alkaryl, and substituted and unsubstituted organosilyl; the substituents are the same as or different from each other, and are selected from the group consisting of carboxylic acid, carboxylic acid ester, epoxy, hydroxyl, alkoxy, primary amino, secondary amino, tertiary amino, isocyanato, sulfonic acid, and halogen; R is selected from the aromatic group consisting of substituted and unsubstituted aryl, substituted and unsubstituted heteroaryl; and the substituents are the same as or different from each other, and are selected from the group consisting of carboxylic acid, carboxylic acid ester, epoxy, hydroxyl, alkoxy, primary amino, secondary amino, tertiary amino, isocyanate, sulfonic acid, substituted and unsubstituted alkyl, substituted and unsubstituted aryl, substituted and unsubstituted olefins, and halogen.

2. The (meth)acrylic copolymer (A) according to claim 1, wherein the (meth)acrylic copolymer (A) has a relative dielectric constant of 3.5 or less at a frequency of 100 kHz.

3. The (meth)acrylic copolymer (A) according to claim 1, wherein the (meth)acrylic copolymer (A) is a polymerization product of a monomer mixture comprising the macromonomer (a) having a number average molecular weight of 500 to 100,000 and the vinyl monomer (b).

4. The (meth)acrylic copolymer (A) according to claim 1, wherein the (meth)acrylic copolymer (A) comprises a repeating unit derived from the macromonomer (a) in an amount of 7 to 40 mass %.

5. The (meth)acrylic copolymer (A) according to claim 1, wherein the macromonomer (a) has a glass transition temperature (Tga) of 0 C. to 150 C.

6. The (meth)acrylic copolymer (A) according to claim 1, wherein the macromonomer (a) comprises a monomer constituent unit having a (meth)acryloyl group in an amount of 80 mass % or more.

7. An adhesive composition, comprising the (meth)acrylic copolymer (A) according to claim 1.

8. An adhesive sheet, comprising the adhesive composition of claim 7.

9. A coating material, comprising the (meth)acrylic copolymer (A) according to claim 1.

10. A coated product, comprising the (meth)acrylic copolymer (A) according to claim 1.

Description

EXAMPLES

(1) Hereinafter, the adhesive resin composition of the invention will be described in more detail with reference to Examples and Comparative Examples. However, the invention is not limited thereto. The part in Examples means part by mass.

(2) <Synthesis of Macromonomer (a-1)>

(3) <Preparation of Dispersant 1>

(4) 900 Parts of deionized water, 60 parts of sodium 2-sulfoethyl methacrylate, 10 parts of potassium methacrylate, and 12 parts of methyl methacrylate (MMA) were put into a polymerization apparatus equipped with a stirrer, a cooling tube, and a thermometer, and stirred. The temperature of in the polymerization apparatus was raised to 50 C. while purging with nitrogen. During the process, 0.08 part of 2,2-azobis(2-methylpropionamidine) dihydrochloride was added as a polymerization initiator, and the temperature was further raised to 60 C. After raising the temperature, MMA was continuously dropped at a rate of 0.24 parts/min for 75 minutes using a dropping pump, so as to obtain a reaction solution. The reaction solution was kept at 60 C. for 6 hours, and then cooled to room temperature, so as to obtain dispersant 1 having a solid content of 10 mass % as a transparent aqueous solution.

(5) 145 Parts of deionized water, 0.1 part of sodium sulfate, and 0.25 parts of dispersant 1 (solid content 10 mass %) were put into a polymerization apparatus equipped with a stirrer, a cooling tube, and a thermometer, and stirred, so as to obtain a uniform aqueous solution. Next, 100 parts of MMA, 0.004 parts of bis[(difluoroboryl)diphenylglyoximate] cobalt (II) as a chain transfer agent, and 0.4 parts of PEROCTA O (registered trademark) (1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, manufactured by NOF Corporation) was added, so as to obtain an aqueous suspension.

(6) Next, the inside of the polymerization apparatus was purged with nitrogen, and heated to 80 C. to perform a reaction for 1 hour, and, in order to further increase a polymerization rate, the temperature in the polymerization apparatus was raised to 90 C. and kept for 1 hour. Thereafter, the reaction solution was cooled to 40 C. to obtain an aqueous suspension containing a macromonomer. This aqueous suspension was filtered, and the residue was washed with deionized water, dehydrated, and dried at 40 C. for 16 hours, so as to obtain macromonomer (a-1). The number average molecular weight of this macromonomer (a-1) was 2500, and the glass transition temperature thereof, measured by DSC, was 80 C.

(7) <Preparation of Macromonomers (a-2) to (a-4)>

(8) Macromonomers (a-2) to (a-4) were prepared in the same manner as the macromonomer 1, except that the amounts (parts) of the monomer added to the dispersant 1, the polymerization initiator, and the chain transfer agent were changed as given in Table 1. The number average molecular weight (Mn) and glass transition temperature (Tga) of the obtained macromonomer (a) are also given in Table 1.

(9) TABLE-US-00001 TABLE 1 Macromonomer (a) a-1 a-2 a-3 a-4 Monomer MMA 100 50 30 100 composition (Parts) IBXMA 50 70 (Parts) Polymerization (Parts) 0.4 0.5 0.5 0.8 initiator Chain transfer (Parts) 0.004 0.003 0.003 0.008 agent Physical Mn 2500 3000 2700 1400 properties Tga 80 100 115 60 ( C.)

(10) MMA: methyl methacrylate

(11) IBXMA: isobornyl methacrylate

(12) (Evaluation Method)

(13) Glass transition temperature (Tga) of macromonomer (a)

(14) The glass transition temperature (Tga) of macromonomer (a) was measured under a nitrogen atmosphere at a heating rate of 5 C./min using a differential scanning calorimeter (DSC Smart Roader manufactured by Rigaku Corporation).

(15) Molecular weights of macromonomer (a) and acrylic copolymer (A)

(16) Macromonomer (a)

(17) The molecular weight of macromonomer (a) was measured using Gel Permeation Chromatography (GPC) (HLC-8320 manufactured by Tosoh Corporation). After the content of a tetrahydrofuran solution of the macromonomer (a) was adjusted to 0.2 mass %, 10 L of the solution was injected into an apparatus equipped with columns (TSK gel Super HZM-MHZM-MHZ 2000, TSK guard column Super HZ-L), and the molecular weight of the macromonomer (a) was measured under conditions of flow rate: 0.35 mL/min, eluent: tetrahydrofuran (stabilizer BHT) and column temperature: 40 C., and converted to standard polystyrene equivalent to calculate a number average molecular weight (Mn).

(18) Acrylic Copolymer (A)

(19) The molecular weight of acrylic copolymer (A) was measured using Gel Permeation Chromatography (GPC) (HLC-8120 manufactured by Tosoh Corporation). After the content of a tetrahydrofuran solution of the acrylic copolymer (A) was adjusted to 0.3 mass %, 20 L of the solution was injected into an apparatus equipped with columns (TSK gel Super HM-H*4, TSK Guard column Super H-H), and the molecular weight of the acrylic copolymer (A) was measured under conditions of flow rate: 0.6 mL/min, eluent: tetrahydrofuran (stabilizer BHT) and column temperature: 40 C., and converted to standard polystyrene equivalent to calculate a weight average molecular weight (Mw).

(20) Holding Force Test Evaluation

(21) The resin solution prepared in Example was applied onto a 50 m release PET film using a 500 m applicator and dried at 90 C. for 90 minutes, and then the 50 m release PET film was attached to an adhesive surface to obtain an adhesive sheet of release PET-adhesive layer-release PET. According to JIS Z 0237, one of the release films of this adhesive sheet was peeled off, and, alternatively, a PET film was pressed by a 2 kg hand roller. This adhesive sheet was cut into strips of 20 mm100 mm, the other release film was peeled off, and the strips was attached to a SUS plate of 30 mm100 mm using a 2 kg hand roller such that the area of the attached surface is 20 mm25 mm. After curing at 70 C. for 30 minutes, a weight of 1 kg was attached to the end of the PET film, and holding time was measured in a constant-temperature zone at 70 C. Holding force was determined according to the following criteria.

(22) S: Holding time is 20 minutes or more

(23) A: Holding time is 5 minutes or more and less than 20 minutes

(24) C: Holding time is less than 5 minutes

(25) Adhesion Test

(26) One release film of the adhesive sheet of release PET-adhesive layer-release PET prepared in the holding force test was peeled off, and, alternatively, a 50 m PET film was attached thereto. This adhesive sheet was cut into strips having a width of 25 mm, and the peel strength (N/25 mm) of the strips to a glass substrate was measured under conditions of a peeling angle of 180 and a tension rate of 60 mm/min according to JIS Z 0237, so as to determine adhesive force. Further, the peeled glass substrate surface was visually observed to confirm the presence or absence of adhesive deposit. Adhesive deposit was determined according to the following criteria.

(27) A: No adhesive deposit

(28) B: Adhesive deposit somewhat exists, but there is no practical problem

(29) C: Adhesive deposit exists, and there is a practical problem

(30) Relative Dielectric Constant Measurement Method

(31) The release PET film on one side of the adhesive sheet of release PET-adhesive layer-release PET prepared in the holding force test was peeled off, a 125 m PET film was attached to one side of the adhesive sheet, and a 50 m PET film was attached to the other side of the adhesive sheet, so as to prepare a measurement sample.

(32) IMPEDANCE ANALYZER 4294 A manufactured by AGILENT Corporation was connected to 16451 B manufactured by the same company, and the electrostatic capacitance C.sub.B of the measurement sample at a frequency of 100 kHz was measured. The electrostatic capacitance C.sub.C of the 125 m PET film and the electrostatic capacitance C.sub.D of the 50 m PET film were also measured, and the electrostatic capacitance C.sub.A of the adhesive layer was calculated from Equation below.
(1/C.sub.B)=(1/C.sub.C)+(1/C.sub.A)+(1/C.sub.D)

(33) The relative dielectric constant .sub.r of the adhesive layer was calculated by applying the electrostatic capacitance C.sub.A of the adhesive layer calculated from Equation above to Equation below. Further, the thickness of the adhesive layer was measured by a micrometer.
C.sub.A=.sub.0.sub.r(L/2).sup.2/d

(34) .sub.0: Dielectric constant of vacuum=8.85410.sup.12

(35) L: Diameter of measurement electrode=38 mm

(36) d: Thickness of adhesive layer

(37) <Small Angle X-Ray Scattering Measurement>

(38) Small angle X-ray scattering measurement was carried out by BL03 XU of Spring-8 (Frontier Soft Matter Development and Industry Association Beam Line) which is a large synchrotron radiation facility.

(39) Only the adhesive layer, obtained by peeling the release PET from the sample sandwiched between both sides of the release PET prepared in the relative dielectric constant measurement, was provided on a jig for sample. The beam shape of X-ray was adjusted to 120 m in width and 120 m in length. The X-ray wavelength was set to 1 , and a CCD (Hamamatsu Photonics V 7739 P+ORCA R2) was used as a detector. The camera length was set to about 4 m, and correction was conducted using a standard sample (collagen). The kind, thickness and exposure time of an attenuator (attenuation plate) were adjusted, a detector was set so as not to be damaged by strong X-rays, and then the sample was irradiated with X-rays, so as to obtain a two-dimensional scattering image of the sample.

(40) Background correction was carried out from the two-dimensional scattering image of the sample obtained by the above procedure. Specifically, a two-dimensional scattering image of the background obtained by performing the same operation as the above procedure was acquired, and the two-dimensional scattering image of the background was subtracted from the two-dimensional scattering image of the sample using image processing software (Image-J), so as to obtain a two-dimensional scattering image for analysis. Ring-shaped scattering was confirmed in the two-dimensional scattering image for analysis.

(41) Next, the two-dimensional image for analysis was converted into a one-dimensional scattering spectrum. Specifically, the two-dimensional scattering image for analysis was read by X-ray data processing software (Fit 2d), and integrated over all the azimuth angles, thereby obtain a one-dimensional scattering spectrum in which horizontal axis is set to q (nm.sup.1) and vertical axis is set to scattering intensity. In the one-dimensional spectrum, a peak was found between q=0.2 and 0.4.

(42) From the obtained one-dimensional scattering spectrum, the half width X of a peak and the peak position Y are obtained. In the one-dimensional scattering spectrum, there are a case where scattering intensity increases toward the origin by taking a minimum value around q=0.1 and a case where scattering intensity decreases toward the origin after passing through an inflection point around q=0.1. In a case where scattering intensity increases toward the origin by taking a minimum value around q=0.1, an area larger than q of the minimum value was taken as an analysis target. Further, in a case where scattering intensity decreases toward the origin after passing through an inflection point around q=0.1, an area larger than q of the inflection point was taken as an analysis target. Next, as baseline correction, the minimum value of scattering intensity of a region to be analyzed was obtained, and the obtained minimum value was subtracted over the entire region to perform the baseline correction. The half width of the composite function obtained by fitting the obtained one-dimensional spectrum after correction with Gaussian function and Lorenz function was taken as X, and the peak position thereof was taken as Y. Waveform separation software (Fityk) was used in the fitting.

Preparation Example 1

(43) (Preparation of (meth)acrylic copolymer (A-1))

(44) 40 Parts of ethyl acetate as a main solvent, 8 parts of isopropyl alcohol, and 12.5 parts of macromonomer (a-2) were charged into a four-neck flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas inlet, and external temperature was raised to 85 C. under nitrogen gas flow aeration. After internal temperature was stabilized, a mixture including 20 parts of ethyl acetate, 74 parts of 2-ethylhexyl acrylate, 3.5 parts of acrylic acid, and 0.04 part of benzoyl peroxide was dropped over 4.5 hours. After the dropping, the mixture was kept for 1 hour, and then a mixture including 0.5 part of PEROCTA 0 and 10 parts of ethyl acetate was added over 1 hour. Then, after keeping for 2 hours, 0.5 part of IRGANOX 1010 (trade name, manufactured by BASF Corporation) as an antioxidant and 22 parts of ethyl acetate were added, and then cooled to room temperature, so as to obtain (meth)acrylic copolymer (A-1).

Preparation Examples 2 to 13

(45) (Preparation of (Meth)Acrylic Copolymers (A-2) to (A-13))

(46) (Meth)acrylic copolymers (A-2) to (A-13) were obtained in the same manner as Preparation Example 1, except that the composition of the used monomer mixture (macromonomer (a) and vinyl monomer (b)) and the kind of the solvent for initial charging were changed as given in Table 2.

(47) (Meth)acrylic copolymer (A-12) is an example in which the macromonomer (a) was not used.

(48) TABLE-US-00002 TABLE 2 Preparation Example 1 2 3 4 5 6 7 8 9 10 11 12 13 (Meth)acrylic copolymers (A) A-1 A-2 A-3 A-4 A-5 A-6 A-7 A-8 A-9 A-10 A-11 A-12 A-13 Monomer Macromonomer (a) a-1 12.5 13.5 11 11 mixture (parts) a-2 14.6 14.6 13.5 15 22 30 a-3 17 a-4 13.5 Vinyl monomer (b) MMA 11 (parts) 2-EHA 74 62.5 82.4 82.3 86 80.5 80 76 62.5 70 60 86 86 AA 3.5 4 3 3 3 3 3 4 3 3 3 3 MA 10 20 20 2-HPMA 6 6 2-HEMA 0.1 Initial charging solvent EtOAc 40 40 40 40 40 30 30 30 30 30 40 40 40 IPA 8 6 7 7 7 1 Polymerization initiator BMTK40 0.13 0.13 0.13 0.13 0.13 0.3 0.13 0.23 0.23 0.23 0.13 0.13 0.13 Dropping solvent EtOAc 20 20 0 0 20 0 0 5 20 10 20 Polymerization temperature C. 85 85 90 90 85 90 90 90 90 90 85 85 85 Weight average molecular Mw 10 14 25 25 8 14 31 27 33 27 10 15 18 weight 10.sup.4 10.sup.4 10.sup.4 10.sup.4 10.sup.4 10.sup.4 10.sup.4 10.sup.4 10.sup.4 10.sup.4 10.sup.4 10.sup.4 10.sup.4

(49) MMA: methyl methacrylate

(50) 2-EHA: 2-ethylhexyl acrylate

(51) AA: acrylic acid

(52) MA: methacrylic acid

(53) 2-HEMA: 2-hydroxyethyl methacrylate

(54) EtOAc: ethyl acetate

(55) IPA: isopropyl alcohol

Examples 1 to 11, Comparative Examples 1 and 2

(56) The adhesive force, holding force, half width of primary scatter peak in small angle X-ray scattering measurement, and relative dielectric constant of the (meth)acrylic copolymer (A-1) prepared in Preparation Example 1 were measured, and the results thereof are given in Table 3. Similarly, those of the (meth)acrylic copolymers (A-2 to A-13) of Preparation Examples 2 to 13 were measured in the same manner (Table 3).

Example 12

(57) The (meth) acrylic copolymer (A-3) prepared in Preparation Example 3 was desolvated and formed into a sheet by hot melt, and the adhesive force, holding force, half width of primary scatter peak in small angle X-ray scattering measurement, and relative dielectric constant of the sheet were measured. Hot melt condition: heat press 0.2 MPa, 100 C., 10 min, film thickness 150 m.

(58) TABLE-US-00003 TABLE 3 Com- Com- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- parative parative ple 1 ple 2 ple 3 ple 4 ple 5 ple 6 ple 7 ple 8 ple 9 ple 10 ple 11 ple 12 Example 1 Example 2 Acrylic A-1 A-2 A-3 A-4 A-5 A-6 A-7 A-8 A-9 A-10 A-11 A-3 A-12 A-13 copolymer A Adhesive 5 7 5 5 4 3 6 7 13 4 3 5 3 1 force to glass [N/ 25 mm] Adhesive A A A A B A A A A A A A C A deposit Holding 27 54 40 45 7 30 40 >60 18 >60 >60 45 2 >60 force 70 C. Holding time (min) (1 kg) Deter- S S S S A S S S S S S S C S mination Half width 0.15 0.16 0.16 0.17 0.13 0.20 0.25 0.33 0.19 0.19 0.20 0.16 No peak 0.12 Relative 3.2 3.3 2.7 2.7 3.0 3.1 2.2 3.2 3.3 2.9 3.0 2.7 3.0 3.0 dielectric constant

(59) In Examples 1 to 12, good adhesive force and holding force are shown as adhesives. In particular, in Examples 1 to 4 and 6 to 12, there was no adhesive deposit, and excellent properties are shown.

(60) Meanwhile, Comparative Example 1 uses a (meth) acrylic copolymer (A-12) which does not use macromonomer (a). In Comparative Example 1, adhesive deposit was found. In Comparative Example 2, the half width of a primary scatter peak in small-angle X-ray scattering measurement was 0.12, which is outside the scope of the invention. In both cases, adhesive force and holding force were inferior to those of Examples.

Examples 13, 14 and 17

(61) The adhesive compositions of composition ratios given in Table 4 were cured or crosslinked after each test piece was prepared. Even in this case, these adhesive compositions had good holding force and adhesive force.

(62) [Curing Conditions]

(63) Apparatus: 2P curing apparatus, light source: high-pressure mercury lamp, irradiation intensity: 200 mW/cm.sup.2, irradiation amount: 1000 mJ/cm.sup.2

Examples 15 and 16

(64) The adhesive compositions of composition ratios given in Table 4 were cured or crosslinked after each test piece was prepared. Even in this case, these adhesive compositions had good holding force and adhesive force.

(65) [Curing Conditions]

(66) 100 C., 60 minutes

(67) TABLE-US-00004 TABLE 4 Example 13 Example 14 Example 15 Example 16 Example 17 Copolymer A (kind) A-3 A-3 A-4 A-4 4-3 Adhesive Copolymer A 200 200 200 200 200 composition solution (parts) PETA 10 10 INNA 200 UV3000B 10 BP 0.5 IRG184 0.5 7 PIC 0.5 Al(acac).sub.3 1.0 Glass adhesive force 4 5 5 5 7 [N/25 mm] Holding force >60 >60 >60 >60 >60 70 C. Holding time (min) (1 kg)

(68) PETA: pentaerythritol triacrylate

(69) INNA: isononyl acrylate

(70) UV 3000 B: urethane acrylate (trade name, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)

(71) BP: benzophenone

(72) IRG 184: IRGACURE 184 (trade name, manufactured BASF Corporation)

(73) PIC: polyisocyanate (CORONATE L, trade name, manufactured by Tosoh Corporation)

(74) Al(acac).sub.3: aluminum trisacetylacetonate