JPH05333209A - Structure for fixing phase difference plate - Google Patents

Abstract

PURPOSE:To obtain the structure for fixing a phase difference plate using a tacky adhesive which does not foam and peel at and under a high temp. and high humidity. CONSTITUTION:This structure is constituted by successively providing the phase difference plate 3 and a polarizing plate 4 via a tacky adhesive layer 2 on one surface of an adherend 1. The acrylic tacky adhesive compsn. which is formed by copolymerizing a compd. consisting of 52 pts.wt. n-butyl acrylate, 40 pts.wt. ethyl acrylate, 3 pts.wt. acrylic acid, 5 pts.wt. N-vinyl pyrrolidone and 0.02 pt.wt. lauryl mercaptan and contains 100 pts.wt. acrylic copolymer having 700000 weight average mol.wt. and -10 deg.C glass transition temp. and 5 pts.wt. rosin modified phenolic resin is used as the tacky adhesive layer 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retardation plate fixing structure excellent in foaming resistance and peeling resistance under high temperature and high humidity.

[0002]

2. Description of the Related Art Conventionally, as a pressure-sensitive adhesive for forming an adhesive layer in a structure in which a retardation plate and a polarizing plate are sequentially provided on the surface of an adherend via an adhesive layer, an acrylic pressure-sensitive adhesive is usually used. Agent is used. However, when a general-purpose acrylic pressure-sensitive adhesive is used, a phenomenon of foaming or peeling occurs in the pressure-sensitive adhesive layer under high temperature and high humidity, and a retardation plate fixing structure of sufficient quality cannot be obtained.

[0003]

A retardation plate is a uniaxially stretched polymer film obtained by molding a polycarbonate resin as a main raw material by a T-die extrusion method and heat-stretching the birefringent liquid crystal display. It is used for prevention of coloration.

Polycarbonate, which is the main raw material of the retardation film, is a material that is difficult to adhere to and has a problem in terms of adhesion reliability. However, as a result of various studies, the present invention has been completed. ..

An object of the present invention is to provide a retardation plate fixing structure using an adhesive which does not cause foaming or peeling phenomenon under high temperature and high humidity.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a structure in which a retardation plate and a polarizing plate are sequentially provided on the surface of an adherend via an adhesive layer, and the adhesive layer comprises (A) (a) ) General formula CH
₂ = CR ¹ COOR ² (wherein R ¹ is hydrogen or a methyl group, R ² is an alkyl group having 1 to 18 carbon atoms) and at least one 70 to 97 parts by weight of an alkyl (meth) acrylate monomer , (B) an acrylic copolymer copolymerized with 1 to 10 parts by weight of acrylic acid or methacrylic acid as a main component, having a weight average molecular weight (Mw) of 500,000 or more and a glass transition temperature of -25 ° C. or more. 100 parts by weight, (B) 0.001 to 5 parts by weight of a polyfunctional organic compound or organometallic compound, and (C) a softening point of 150.
A retardation plate fixing structure using an acrylic pressure-sensitive adhesive composition containing 1 to 30 parts by weight of a tackifying resin containing 50% by weight or more of a high softening point tackifying resin at a temperature of not less than 0 ° C.

In the present invention, among the monomer components constituting the acrylic copolymer (A), the alkyl (meth) acrylate monomer (a) is, for example, n.
-Butyl acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, n-octyl (meth) acrylate, decyl (meth) acrylate, ethyl (meth) acrylate, methyl (meth) acrylate, etc. At least one of is used as the main monomer component.

The acrylic acid or methacrylic acid of (b) is used as a component whose carboxyl group reacts with a crosslinking agent described later to improve the cohesive force of the pressure-sensitive adhesive.

Further, in addition to the above-mentioned monomers, monomer components such as vinyl acetate, styrene, N-vinylpyrrolidone and acrylonitrile which increase the glass transition temperature and 2
—Hydroxyethyl (meth) acrylate, an —OH group-containing monomer component such as 2-hydroxypropyl (meth) acrylate, and a monomer component that lowers the glass transition temperature such as tetrafurfuryl acrylate and polyethylene glycol acrylate are appropriately used. However, if the content ratio of these monomer components is too large, the adhesive strength of the obtained copolymer may be decreased, or conversely, the heat resistance may be decreased. Limited.

The acrylic copolymer (A) comprises 70 to 97 parts by weight of at least one kind of alkyl (meth) acrylate monomer of (a) and 1 to 10 parts by weight of one kind of acrylic acid or methacrylic acid of (b). And are copolymerized as main components in this proportion. The monomer component of (a) is 7
When the amount of the monomer component of (b) exceeds 10 parts by weight and the amount of the monomer component of (b) exceeds 10 parts by weight, the adhesive strength of the resulting copolymer decreases, and conversely, 97 parts by weight of the monomer component of (a). And the monomer component (b) is less than 1 part by weight, the heat resistance will decrease.

Further, the acrylic copolymer (A) must have a weight average molecular weight of 500,000 or more and a glass transition temperature of -25 ° C or more. When the weight average molecular weight is less than 500,000 or the glass transition temperature is less than -25 ° C, the storage elastic modulus and the loss elastic modulus under high temperature and high humidity are decreased, whereby the phase difference plate fixing structure is formed. The bubbles at the interface between the adherend, the retardation plate and the polarizing plate and the pressure-sensitive adhesive layer grow to cause a foaming phenomenon, or the pressure-sensitive adhesive layer easily flows and causes a peeling phenomenon between the layers.

The glass transition temperature (Tg) is the dynamic viscoelastic behavior of a polymer measured by a viscoelastic spectrometer at a frequency of 10 Hz, and is the ratio (tan δ) between the storage elastic modulus and the loss elastic modulus. It was measured by the method shown by the temperature indicated by the peak of a certain loss tangent curve.

Further, in order to adjust the molecular weight, a suitable chain transfer agent such as lauryl mercaptan may be contained.

The acrylic copolymer (A) may be copolymerized by any method, for example, solution polymerization, bulk polymerization, radical polymerization by emulsion polymerization, or the like. As the polymerization initiator, any conventionally known one such as a peroxide-based compound or an azo-based compound may be used, but it may be polymerized by irradiation with light or radiation.

In the acrylic pressure-sensitive adhesive composition of the present invention, in order to improve cohesive force and heat resistance, an organic compound or organic metal having a polyfunctional group as a crosslinking agent for the acrylic copolymer (A) is used. It contains the compound (B). Examples of such cross-linking agents include polyisocyanates, epoxy resins, melamine resins, polyvalent metal salts, metal chelates,
An aziridine compound or the like is used.

The content of the cross-linking agent is the acrylic copolymer 1
It is 0.001 to 5 parts by weight with respect to 00 parts by weight. When the content is less than 0.001, the cohesive force and heat resistance of the pressure-sensitive adhesive layer cannot be increased. On the contrary, when the content exceeds 5 parts by weight, they are sequentially provided on the adherend surface such as glass. Adhesion between the retardation plate and the polarizing plate deteriorates.

Further, the acrylic pressure-sensitive adhesive composition contains a tackifying resin (C) in order to enhance the tackiness.
Examples of such tackifying resins include rosin resins, xylene resins, phenol resins, C ₉ petroleum resins, and C ₅ and C ₉ copolymer petroleum resins, coumarone-indene resins, terpene resins and the like. The modified resin and the like are used.

The content of the tackifying resin is 1 to 30 parts by weight, preferably 3 parts by weight based on 100 parts by weight of the acrylic copolymer.
-20 parts by weight. If the content is less than 1 part by weight, the adhesiveness of the resulting acrylic pressure-sensitive adhesive is lowered,
When it exceeds the weight part, the heat resistance is lowered.

The tackifying resin has a softening point of 10
About 60 to 180 ° C. is preferably used centering on those around 0 ° C., but it is necessary to include 50% by weight or more of a high softening point tackifying resin having a softening point of 150 ° C. or higher. .. When the content is less than 50% by weight, heat resistance is poor.

Examples of the high softening point adhesive resin having a softening point of 150 ° C. or higher include rosin-modified phenol resin (for example, Arakawa Chemical Co., Ltd .: trade name “KP305”: softening point 180 ° C.), coumarone indene resin (for example, new Nittetsu Chemical Co., Ltd .: trade name "Esrigid A150": softening point 150 ° C) and the like are used.

In addition, if necessary, the acrylic pressure-sensitive adhesive composition may contain a commonly used compounding agent such as a filler such as a filler such as calcium carbonate and calcium oxide.

The retardation plate used in the present invention is not particularly limited. Examples of the adherend used in the present invention include transparent adherends such as glass, polyethylene terephthalate, and polyether sulfone.

[0023]

The retardation plate fixing structure of the present invention is an acrylic pressure-sensitive adhesive composition used for a pressure-sensitive adhesive layer in a structure in which a retardation plate and a polarizing plate are sequentially provided on the surface of an adherend via a pressure-sensitive adhesive layer. In the product, since the weight average molecular weight is 500,000 or more and the glass transition temperature contains an acrylic copolymer having a temperature of -25 ° C or more, a decrease in storage elastic modulus and loss elastic modulus under high temperature and high humidity can be suppressed, Thereby, the growth of bubbles at the interface between the adherend of the structure, the retardation plate and the polarizing plate, and the pressure-sensitive adhesive layer is prevented so that the foaming phenomenon does not occur, and the pressure-sensitive adhesive layer becomes difficult to flow. Since it contains the tackifying resin containing 50% by weight or more of the high softening point tackifying resin having a softening point of 150 ° C. or higher without causing a delamination phenomenon between layers, the tackiness under high temperature and high humidity is improved. Improved and excellent in peel resistance.

[0024]

EXAMPLES Examples of the present invention will be described below. Examples 1 to 5 and Comparative Examples 1 to 10 (1) Polymerization of acrylic pressure-sensitive adhesive composition In a flask equipped with a reflux condenser and a stirrer, a predetermined amount of n-butyl acrylate, ethyl acrylate, acrylic resin shown in Table 1 was used. Acid, N-vinylpyrrolidone, lauryl mercaptan and ethyl acetate were added and mixed uniformly, and then 0.03 parts by weight of benzoyl peroxide (based on 100 parts by weight of the monomer) was added as a polymerization initiator while stirring in a nitrogen stream. The mixture was added and copolymerized at 70 ° C. for 10 hours to obtain an acrylic copolymer solution.

(2) Preparation of acrylic pressure-sensitive adhesive composition This acrylic copolymer solution was diluted with ethyl acetate so that the solid content was 25% by weight, and the solid content of the copolymer was adjusted to 100 parts by weight. As a tackifying resin, a rosin-modified phenol resin (manufactured by Arakawa Chemical Co., Ltd .: trade name “KP305”: softening point 180 ° C.), coumarone indene resin (manufactured by Nippon Steel Chemical Co., Ltd .: trade name “ESRIGIT A150”: softening point 150)
℃), terpene phenol resin (Yasuhara Chemical Co., Ltd .: trade name “YS Polystar S145”: softening point 145
C.) and a disproportionated rosin ester (manufactured by Arakawa Chemical Co., Ltd .: trade name “Super Ester A115”: softening point 115 ° C.) in prescribed amounts shown in Table 1, and as a crosslinking agent, aziridine compound [N, N 0.15 parts by weight of'-hexamethylene-1,6-bis (1-aziridinecarboxamide)] was added and stirred to prepare an acrylic pressure-sensitive adhesive composition.

(3) Preparation of acrylic pressure-sensitive adhesive laminate The acrylic pressure-sensitive adhesive composition prepared in (2) was applied on a silicone-treated 38 μm thick polyester film with an applicator so that the glue thickness after drying would be 25 μm. After coating and drying in the oven for 4 minutes, each 15
A 0 μm-thick polarizing plate and a 85 μm-thick retardation plate were bonded together by a laminator to prepare an acrylic pressure-sensitive adhesive laminate.

(4) Measurement of Physical Properties Appearance Test of Foaming and Peeling After leaving the acrylic pressure-sensitive adhesive laminate prepared in (3) for one week, it was cut into a size of 75 × 150 mm and the silicone-treated polyester film was peeled off. As shown in FIG. 1, the retardation plate 3 and the polarizing plate 4 are attached to one surface of the adherend 1 made of a glass plate of 100 × 200 mm by a laminator so that air bubbles do not enter the adhesive surface. A test piece having a fixed structure was prepared.

For the evaluation of foaming, the test piece was placed on a glass stand and left in a thermostat at 80 ° C. for 500 hours, and then the change in appearance due to foaming was visually observed. For the evaluation of peeling, the test piece was tested at 60 ° C. × 90% R. H. After being left in the constant temperature bath for 500 hours, the appearance change due to peeling was visually observed.

The change in appearance due to foaming was evaluated according to the following evaluation criteria. No bubbles of 20 μm or more are recognized: Score 3 A small number of bubbles of 20 to 40 μm are recognized: Score 2 Many bubbles of 20 to 40 μm are recognized: Score 1

The change in appearance due to peeling was evaluated according to the following evaluation criteria. No peeling is observed: Score 3 Peeling of 0.5 mm or less is recognized: Score 2 Peeling exceeding 0.5 mm is recognized: Score 1 The results are also shown in Table 1.

80 ° C. constant load peeling test (against retardation plate) After leaving the acrylic pressure-sensitive adhesive laminate prepared in (3) for one week, it was cut into a size of 20 × 150 mm and the siliconized polyester film was peeled off. Then, the retardation plate was adhered to a glass plate fixed with a double-sided adhesive tape so that air bubbles did not enter, and a roller having a weight of 2 kg was reciprocated once to perform pressure bonding to obtain a test piece.

After leaving the test piece in a thermostat at 80 ° C. for 20 minutes or more, the acrylic pressure sensitive adhesive laminate was kept horizontal so that it was on the lower side, a load of 50 g was applied to one end of the test piece, and the peeling distance per unit time ( The peeling speed) was measured, and the results are also shown in Table 1.

[0033]

[Table 1]

As is clear from Table 1, in the cases of Examples 1 to 5 of the present invention, all have excellent foaming resistance, peeling resistance and constant load peeling force. In each of Comparative Examples 1 to 11, the foaming resistance was poor,
Moreover, the peeling resistance and the constant load peeling force are poor.

[0035]

Since the acrylic pressure-sensitive adhesive composition used in the retardation plate fixing structure of the present invention is constituted as described above, it has excellent foaming resistance and peeling resistance under high temperature and high humidity. It is a thing.

[0036]

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a retardation plate fixing structure of the present invention.

[Explanation of symbols]

 1 Adherent 2 Adhesive Layer 3 Phase Difference Plate 4 Polarizing Plate

Claims (1)

[Claims] 1. In a structure in which a retardation plate and a polarizing plate are sequentially provided on the surface of an adherend via an adhesive layer, (A) (a) the general formula CH ₂ = CR ^{1 is} added to the adhesive layer. COOR ² (In the formula, R ¹ is hydrogen or a methyl group, and R ² has 1 to 18 carbon atoms.
70 to 97 parts by weight of at least one kind of alkyl (meth) acrylate monomer represented by
(B) Acrylic copolymer 100 copolymerized with 1 to 10 parts by weight of acrylic acid or methacrylic acid as a main component, having a weight average molecular weight (Mw) of 500,000 or more and a glass transition temperature of -25 ° C or more. Adhesive containing 50 parts by weight or more of (B) 0.001 to 5 parts by weight of an organic compound or organometallic compound having a polyfunctional group (B) and (C) a high softening point tackifying resin having a softening point of 150 ° C. or higher. A retardation plate fixing structure, characterized in that an acrylic pressure-sensitive adhesive composition containing 1 to 30 parts by weight of an applied resin is used.