JPH09137138A - Production of tacky adhesive optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing a tacky adhesive optical film whereby an optical film can be coated easily, the production process can be simplified and shortened, and the optical film having a tacky adhesive layer excellent in heat resistance of adhesion can be obtd. SOLUTION: A tacky adhesive phase-contrast film is produced by compounding 100 pts.wt. monomer component comprising 70-100wt.% alkyl (meth)acrylate having a 1-12C alkyl group and 0-30wt.% polar vinyl monomer with 0.01-1 pt.wt. polyfunctional vinyl monomer and a photopolymn. initiator, applying the resultant photopolymerizable compsn. directly to one side of of a phase-contrast film, and exposing the coated side to light in an inert gas atmosphere to photopolymerize the applied compsn., thus forming a tacky adhesive layer on one side of the phasecontrast film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an optical film pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer provided on one surface of an optical film such as a retardation plate or a polarizing plate. The present invention relates to a method for producing an optical film pressure-sensitive adhesive sheet suitable for use.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been widely used as display devices for small TVs, portable personal computers, word processors, etc. in addition to simple display devices for digital watches and various electric appliances. , Higher resolution is required.

On the other hand, in a liquid crystal display device, a polarizing plate or a retardation plate is usually attached to the outer surface of a liquid crystal cell in which a liquid crystal polymer is sealed between a pair of glass substrates, that is, the outer surface of the glass plate. Have been combined. When laminating these optical films, the laminating is easy,
Adhesives are widely used. It is to be noted that this adhesive is strongly required to be resistant to peeling even under high temperature and high humidity conditions, that is, to have adhesive durability under high temperature and high humidity conditions.

Among the above optical films, the retardation plate of a liquid crystal display device is usually attached to the glass surface of a liquid crystal cell mainly by using a solvent type acrylic adhesive. In this case, in order to balance the foaming and peeling property of the pressure-sensitive adhesive layer due to the contraction of the retardation plate at high temperature, the pressure-sensitive adhesive layer had to have a high molecular weight. However, when the polymer has a high molecular weight, the solution viscosity increases, and thus the coatability of the pressure-sensitive adhesive decreases.

The retardation plate having the pressure-sensitive adhesive layer provided on one surface is usually obtained by forming the pressure-sensitive adhesive layer on a releasable support and transferring the pressure-sensitive adhesive layer to the retardation plate. Has been. Since the pressure-sensitive adhesive layer is transferred through the above steps, the adhesiveness of the pressure-sensitive adhesive layer to the retardation plate, that is, the anchoring property is low, and peeling occurs at the interface between the retardation plate and the pressure-sensitive adhesive layer (hereinafter referred to as anchor destruction). ) It tended to happen.

Further, in order to enhance the heat resistance of the above-mentioned pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer is usually cross-linked, but a sufficient curing time is required to completely finish gelation,
Therefore, there is also a problem that productivity is reduced.

In order to solve the above-mentioned various problems, various attempts have been made to improve the pressure-sensitive adhesive used in the optical film pressure-sensitive adhesive sheet. For example, a production method has been proposed in which an alcohol solution of a photopolymerizable monomer composition is directly applied to a retardation plate or a polarizing plate, and then photopolymerized (Japanese Patent Laid-Open No. HEI 2-
137922 publication).

However, the retardation plate pressure-sensitive adhesive sheet or the polarizing plate pressure-sensitive adhesive sheet obtained by the method described in the above prior art cannot sufficiently remove the residual solvent even if it is sufficiently heated at the final stage, Therefore, when it is stored or used under high temperature conditions, foaming may occur in the pressure-sensitive adhesive layer. As a matter of course, when foaming occurs in the pressure-sensitive adhesive layer of the optical film pressure-sensitive adhesive sheet, the quality of the displayed image is significantly reduced.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the various problems of the above-mentioned conventional optical film pressure-sensitive adhesive sheet, and its object is to coat the pressure-sensitive adhesive during the production. Excellent optical properties, sufficient anchor effect for the optical film of the pressure-sensitive adhesive layer, does not require curing time to crosslink the pressure-sensitive adhesive layer, and is less likely to cause foaming and peeling of the pressure-sensitive adhesive layer at high temperature. It is to provide a method for producing a film pressure-sensitive adhesive sheet.

[0010]

Means for Solving the Problems The inventors of the present invention have made earnest studies to achieve the above-mentioned object, and as a result, the photopolymerizable composition was directly coated on one surface of the optical film and irradiated with light to thereby adhere the optical film. In the method of obtaining a sheet, it was found that an optical film pressure-sensitive adhesive sheet that can achieve the above objects can be obtained by using a specific photopolymerizable composition and irradiating with light under an inert gas atmosphere, and the present invention is made. Came to.

That is, in the method for producing an optical film pressure-sensitive adhesive sheet of the present invention, the number of carbon atoms in the (A) alkyl group is 1 to 1.
80% to 100% by weight of alkyl (meth) acrylate of 2
And 100 parts by weight of a monomer containing 0 to 20% by weight of a vinyl monomer having a polar group, (B) 0.01 to 1 part by weight of a polyfunctional vinyl monomer, and (C) a photopolymerization initiator. Apply the composition directly to one surface of the optical film,
It is characterized in that light irradiation is performed in an inert gas atmosphere.

Hereinafter, the present invention will be described in detail. Photopolymerizable composition In the present invention, a photopolymerizable composition containing the above-mentioned (A) monomer, (B) polyfunctional vinyl monomer, and (C) photopolymerization initiator is used.

The above-mentioned monomer (A) is an alkyl (meth) acrylate having from 1 to 12 carbon atoms in the alkyl group.
100% by weight and a polar group-containing vinyl monomer 0 to 3
Contains 0% by weight. That is, the vinyl monomer having a polar group may not be used, and even when it is used, it is used within the range of 30% by weight in the monomer (A).

Examples of the alkyl (meth) acrylate include ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec- Butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n- Nonyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, etc. can be mentioned. These acrylates may be used alone or in combination of two or more.

It is preferable to use a high boiling point monomer such as 2-ethylhexyl (meth) acrylate, rather than a low boiling point monomer such as ethyl (meth) acrylate or n-butyl (meth) acrylate.

Examples of the vinyl monomer having a polar group include (meth) acrylic acid, itaconic acid, crotonic acid, (anhydrous) maleic acid, (anhydrous) fumaric acid, and carboxyalkyl (meth) acrylates such as carboxyethyl acrylate. Vinyl monomers containing carboxy group such as 2-hydroxyethyl (meth) acrylate, 2
-Hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, caprolactone-modified (meth) acrylate, polyethylene glycol (meth) acrylate, polypropylene glycol (meth)
Vinyl monomers having hydroxyl groups such as acrylates;
(Meth) acrylonitrile, N-vinylpyrrolidone, N
-Vinylcaprolactam, N-vinyllaurylolactam, (meth) acryloylmorpholine, (meth) acrylamide, dimethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, dimethylamidopropyl (meth) ) Nitrogen-containing vinyl monomers such as acrylamide, dimethylaminomethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminoethyl (meth) acrylate and the like can be mentioned. These polar group-containing vinyl monomers may be used alone or in combination of two or more kinds. Preferably, it is desirable to use a high boiling monomer such as carboxyalkyl (meth) acrylate as compared to a low boiling monomer such as acrylic acid.

Vinyl monomers such as vinyl acetate, vinyl pivalate, vinyl propionate, styrene and isobornyl (meth) acrylate are added to the above-mentioned (A) monomer within a range not impairing the object of the present invention. Good.

When the content of the alkyl (meth) acrylate in the monomer (A) is too small, the tackiness becomes low. Therefore, the alkyl (meth) acrylate is
(A) so as to occupy 70 to 100% by weight in the monomer,
More preferably, it is used in an amount of 80% by weight or more.

The polar group-containing vinyl monomer is a component optionally used in the monomer (A). However, when the content of the polar group-containing vinyl monomer is too large, the cohesive force is increased and the sticking property is improved. Therefore, the vinyl monomer having a polar group is 3% of the total amount of the (A) monomer.
It is used in a proportion of 0% by weight or less. When other vinyl monomers such as vinyl acetate described above are used, the total amount of the other vinyl monomers in addition to the vinyl monomer having a polar group is 30% by weight based on the total weight of (A) monomers.
Used as follows:

The polyfunctional vinyl monomer (B) used in the present invention is ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate,
Polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, Neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate
Examples thereof include acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate and the like.

In the present invention, if the content of the polyfunctional vinyl monomer (B) in the photopolymerizable composition is too small, it becomes impossible to obtain sufficient cohesive force under high temperature conditions, and if it is too large. Since the crosslink density becomes high and peeling becomes easy, the (B) polyfunctional vinyl monomer is
0.01 to 5 relative to 100 parts by weight of the (A) monomer
It is used in parts by weight, preferably in the range of 0.03 to 1 part by weight.

As the above-mentioned (C) photopolymerization initiator, 4-
(Hydroxyethoxy) phenyl- (2-hydroxy-
2-propyl) ketone, α-hydroxy-α, α′-dimethyl-acetophenone, methoxyacetophenone,
Examples thereof include acetophenone-based initiators such as 2,2-dimethoxy-2-phenylacetophenone, ketal-based initiators such as benzyl ketal, halogenated ketones, acylphosphinoxides, and acylphosphonates.

The addition amount of the above-mentioned photopolymerization initiator is appropriately adjusted in consideration of the reactivity of the monomer components used and cannot be uniquely determined, but in general, the above-mentioned (A) monomer and (B) polyamine are added. It is added in the range of 0.01 to 1.0 parts by weight based on 100 parts by weight of the functional vinyl monomer in total. If the amount of the photopolymerization initiator added is less than 0.01 parts by weight, the photopolymerization may be insufficient and the proportion of unreacted substances may become too high. If the amount of the photopolymerization initiator added exceeds 1.0 part by weight, the amount of radicals generated becomes too large, and photopolymerization suddenly occurs to cause excessive heat generation, or the increase in molecular weight is hindered, resulting in a broad molecular weight distribution. This is because the above problem occurs.

The amount of radicals generated by the photopolymerization initiator varies depending on the type and intensity of light to be irradiated, time, the amount of dissolved oxygen in the monomer and solvent mixture, and the like. When the amount of dissolved oxygen is large, the amount of radicals generated is suppressed, polymerization may not proceed sufficiently, and unreacted substances may increase. Therefore, it is preferable to blow an inert gas such as nitrogen into the composition to replace oxygen with nitrogen before the light irradiation. The photopolymerizable composition before photopolymerization may be an oligomer composition in which the photopolymerization is partially advanced in advance to increase the viscosity.

Manufacturing Process The method for manufacturing an optical film pressure-sensitive adhesive sheet according to the present invention includes a step of coating the above-mentioned photopolymerizable composition on one surface of an optical film and irradiating with light in an inert gas atmosphere.

The above-mentioned optical film is not particularly limited, and various resin films forming a retardation plate or a polarizing plate can be used depending on the application. As such a resin film, a polycarbonate film,
Examples thereof include a polymethylmethacrylate film, a polystyrene film, a polysulfone film, or a stretched film of a resin modified with these.

When the production method of the present invention is applied to the production of a retardation plate pressure-sensitive adhesive sheet, the retardation plate pressure-sensitive adhesive sheet for a liquid crystal display device usually has a polarizing plate on the outer surface as another optical film. The films are laminated together. As a material for forming a polarizing plate film to be bonded to such a retardation plate adhesive sheet, hydrophilic materials such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene-vinyl acetate photopolymerization saponified film are used. Iodine and / or dichroic dye-based polarizing film in which iodine and / or dichroic dye is adsorbed and oriented on a polymer film; polyvinyl alcohol-based film is dehydrated to orient polyene and polyene-based polarizing film; An example is one in which a triacetyl cellulose film is laminated as a protective layer on both sides of a polyene-based polarizing film in which polyvinyl chloride is dehydrochlorinated and a polyene is oriented.

In the present invention, the method for coating the above-mentioned photopolymerizable composition on one surface of the optical film is not particularly limited, and a commonly used roll coater, die coater, knife coater or the like is used. Can be done by

In the present invention, the inert gas atmosphere at the time of photopolymerization means an atmosphere in which oxygen in the light irradiation zone is replaced with an inert gas such as nitrogen. When photopolymerization is carried out in such an inert gas atmosphere, oxygen in the light irradiation zone acts as a polymerization inhibitor,
This is because it affects the polymerization rate, molecular weight and molecular weight distribution of the obtained polymer. Therefore, it is desirable that oxygen is not present as much as possible in the inert gas atmosphere, and the oxygen concentration is preferably 5000 ppm or less.

Further, the dissolved oxygen in the photopolymerizable composition also acts as a polymerization inhibitor and affects the polymerization rate, molecular weight and molecular weight distribution of the obtained adhesive polymer, so that the dissolved oxygen should be removed beforehand by nitrogen substitution or the like. It is desirable to set it.

In the production method of the present invention, after the photopolymerizable composition is coated on one surface of the optical film, light irradiation is carried out in the inert gas atmosphere. In this case, examples of the light source used for light irradiation include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excited mercury lamp, and a metahalide lamp.

In photopolymerization, the type of light, the irradiation intensity,
The irradiation time affects the molecular weight and molecular weight distribution of the obtained polymer. It is necessary that the irradiation light has sufficient energy to excite the photopolymerizable initiator molecule. Therefore, an electromagnetic wave having a short wavelength or an electron beam is often used. Examples of short-wave electromagnetic waves include ultraviolet rays (UV) and γ-rays, but they are easy to generate, can downsize the device, and can be cross-linked by cutting molecules or extracting hydrogen from polymers. It is preferable to use ultraviolet rays that are less likely to cause.
When irradiating with ultraviolet rays, it is preferable to irradiate with ultraviolet rays using a lamp having a light emission distribution at a wavelength of 400 nm or less. This is because such a wavelength distribution is sufficient for decomposing the radical generator, the apparatus can be simplified, and the running cost is low.

The ultra-high pressure mercury lamp is particularly preferable because it emits light in the active wavelength region of the photopolymerizable initiator and does not reduce the tackiness of the resulting polymer. Further, when using an ultra-high pressure mercury lamp, the wavelength distribution of the irradiated light is sensitive and does not include light of a shorter wavelength, so that a cross-linking reaction between molecules that does not rely on a cross-linking agent is unlikely to occur The molecular weight and the amount of cross-linking of the polymer obtained can be easily controlled, and since it does not have long-wavelength light, it is difficult to evaporate the reaction composition by heating.

The light irradiation intensity upon light irradiation using the above-mentioned various lamps is appropriately determined according to the molecular weight and the molecular weight distribution of the target adhesive polymer, but in general, cleavage type photopolymerization initiation having an acetophenone group is initiated. When the agent is used, it is preferably in the range of 0.1 to 100 mW / cm ² . If the irradiation intensity is lower than 0.1 mW / cm ² , the reaction may not occur sufficiently and unreacted substances may increase. If the irradiation intensity exceeds 100 mW / cm ² , polymerization will occur rapidly, causing an explosion due to heat generation or runaway. This is because there is a danger such as.

The method for producing an optical film pressure-sensitive adhesive sheet of the present invention comprises a pressure-sensitive adhesive layer on an optical film including a retardation plate of a liquid crystal display device, a polarizing plate, a retardation plate other than the liquid crystal display device, and various polarizing plates. It can be applied to any method for producing an optical film pressure-sensitive adhesive sheet provided.

Action In the method for producing an optical film pressure-sensitive adhesive sheet of the present invention, the above-mentioned specific monomer composition is applied to one surface of the optical film, and then the monomer composition is polymerized by photopolymerization to form a pressure-sensitive adhesive layer. Since photopolymerization is used, by controlling the irradiation intensity and irradiation time of the light used, a pressure-sensitive adhesive layer of a high molecular weight substance can be easily formed, and since the gelation rate is saturated in the initial stage, No curing time required for cross-linking.

Moreover, since the above-mentioned monomer composition is applied prior to the polymerization, the coatability is excellent, and the applied monomer composition follows the minute irregularities on the surface of the optical film. It is surely applied to the surface. Therefore, since the monomer composition provided following the minute irregularities on the optical film surface is polymerized by photopolymerization, the anchor effect between the pressure-sensitive adhesive layer and the optical film is enhanced, and the optical film of the pressure-sensitive adhesive layer is formed. The adhesion to the surface is effectively enhanced, and thus the durable adhesion at high temperature is also enhanced.

[0038]

The present invention will be clarified by the following non-limiting examples and comparative examples.

Examples 1 to 4 (A) Monomer according to the formulation shown in Table 1 below,
The following components were added as (B) polyfunctional vinyl monomer and (C) photopolymerization initiator.

(A) Monomer: 2-ethylhexyl acrylate (hereinafter abbreviated as 2EHA), carboxyethyl acrylate (hereinafter abbreviated as CEA) as a vinyl monomer having a polar group, and vinylpyrrolidone (hereinafter abbreviated as Vp). ). (B) Polyfunctional vinyl monomer: 1,6-hexanediol diacrylate (hereinafter abbreviated as HDDA). (C) Photopolymerization initiator ... Benzyl dimethyl ketal (manufactured by Nippon Ciba Geigy, trade name: Irgacure 651, hereinafter abbreviated as I-651).

The above monomer components, photopolymerization initiator and Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd.) are shown in Table 1 below.
After adding to the container with the composition shown in (1), the mixture was stirred and uniformly mixed, and nitrogen substitution was performed with nitrogen gas for 30 minutes to remove dissolved oxygen in the system to obtain a photopolymerizable composition.

The above-mentioned photopolymerizable composition was directly applied to a 60 μm-thick stretched polycarbonate retardation plate, which was irradiated with an ultraviolet ray of 365 nm in an inert gas stream (residual oxygen concentration of 1000 ppm) at an irradiation intensity of 10 mW / cm ² . It was irradiated for minutes to obtain a retardation plate pressure-sensitive adhesive sheet having a 25 μm-thick pressure-sensitive adhesive layer formed on one surface.

Comparative Examples 1 to 5 2EHA was placed in a 5-neck separable flask equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen gas inlet tube and a dropping funnel according to the composition of the comparative example shown in Table 1 below. , Vp,
n-Dodecyl mercaptan (hereinafter abbreviated as DDM) and 100 parts by weight of ethyl acetate were added and mixed uniformly by stirring. Then, while raising the temperature of the system, the system was purged with nitrogen gas for 30 minutes to remove the dissolved oxygen in the system.

Next, with the system kept at 70 ° C., 0.
03 parts by weight of benzoyl peroxide (hereinafter referred to as BPO
Abbreviated. Was dissolved in 3 parts by weight of ethyl acetate, and the solution was added dropwise from a dropping funnel, and reacted for 10 hours in a nitrogen atmosphere (however, in Comparative Example 5, reacted for 20 hours) to perform gel permeation chromatography. (G
Polymerization was performed so that the weight average molecular weight (Mw) by PC) was the value shown in Table 1 below. After the reaction, the reaction mixture was diluted with ethyl acetate to obtain a solvent-type acrylic copolymer having a solid content of 40% by weight.

Further, Comparative Examples 1 to 1 obtained as described above
For each 100 parts by weight of the solid content of each solvent-type acrylic copolymer of No. 5, N, N'-hexamethylene-1,6-bis (1
-Aziridinecarboxamide) (manufactured by Nippon Shokubai Co., Ltd., trade name: HDU) was added to obtain solvent-type acrylic pressure-sensitive adhesives 1 to 5.

The above-mentioned solvent-type acrylic pressure-sensitive adhesive was applied to a polyethylene terephthalate film having a thickness of 38 μm (hereinafter referred to as a release PET film) whose surface was release-treated, and then in an oven at 110 ° C. for 5 minutes. Dried, thickness 2
A 5 μm solvent-type acrylic pressure-sensitive adhesive film was obtained. Further, the solvent-based acrylic pressure-sensitive adhesive film, and a thickness of 60
A retardation plate pressure-sensitive adhesive sheet was obtained by laminating and transferring with a laminator a polycarbonate retardation plate of μm.

Production of Laminate for Liquid Crystal Display Each retardation plate pressure-sensitive adhesive sheet obtained in Examples 1 to 4 and Comparative Examples 1 to 5 and pressure-sensitive adhesive obtained by the same polymerization method as in Comparative Examples 1 to 5 above. A polarizing plate pressure-sensitive adhesive sheet having a layer on one surface was laminated with a laminator so as to prevent bubbles from entering between the pressure-sensitive adhesive layers on the polarizing plate sheet side. In this way, a retardation plate-polarizing plate laminate in which the pressure-sensitive adhesive layer of the retardation plate pressure-sensitive adhesive sheet is exposed is obtained, and this is 75 mm × 15.
It was cut to a size of 0 mm. Next, on the surface of the following glass plate, a laminator using the pressure-sensitive adhesive layer of the retardation plate of the above retardation plate-polarizing plate laminate and preventing bubbles from entering between the retardation plate and the glass plate. Then, they were laminated together to obtain a liquid crystal display laminate.

Glass plate used ... As the glass plate, a glass plate actually used in a glass cell for liquid crystal display (manufactured by Asahi Glass Co., Ltd., trade name: soda lime glass, 10
0 mm × 200 mm × thickness 2 mm) was used instead of the glass cell for liquid crystal display. The glass plate was washed by previously washing it in an aqueous solution of a surfactant, immersing it in pure water, and then heat-drying it in an oven at 110 ° C. for 10 minutes to remove water and wash it. .

Evaluation of Weight-Average Molecular Weight and Number-Average Molecular Weight The gel-permeation chromatography (GPC) was used to determine the polystyrene-converted weight-average molecular weight (Mw) of the acrylic pressure-sensitive adhesive. For the photopolymerization type pressure-sensitive adhesive, the Mw of the one obtained by photopolymerization of the HDDA-free product under the same conditions was used as a substitute, and for the solution polymerization type pressure-sensitive adhesive, the Mw before addition of the crosslinking agent was used. I asked. G used
The PC measuring device is a differential refractometer detector manufactured by Shimadzu Corporation.

Heat Resistant Adhesion Test Each liquid crystal display laminate obtained as described above was placed on a glass stand and allowed to stand in a thermostat at 105 ° C. for 500 hours, after which the appearance change due to foaming and peeling was observed with a microscope. . The meanings of the evaluation symbols for foaming and peeling are as follows.

Foaming: 1 ... When bubbles of 10 μm or more are not observed in the pressure-sensitive adhesive layer. 2 When a small amount of bubbles of 20 to 40 μm is observed in the adhesive layer. 3 ... When a large amount of bubbles of 20 to 40 μm are recognized.

Peeling: 1 ... When peeling from glass is not observed. 2 ... When peeling of 0.5 mm or less is observed near the end. 3 ... When large peeling exceeding 0.5 mm is observed in the vicinity of the end. The evaluation results described above are also shown in Table 1 below.

Measurement of Anchor Force A 25 μm-primed polyethylene terephthalate film was attached to the pressure-sensitive adhesive layer side of the polarizing plate pressure-sensitive adhesive sheet obtained above and left in an atmosphere of 25 ° C. × 65% relative humidity for 1 day. After that, it was cut into a width of 25 mm, and the 180-degree peeling adhesive force was measured at a pulling speed of 300 mm / min.

[0054]

[Table 1]

The blending ratios in Table 1 are all parts by weight. As is clear from Table 1, in the solvent-type acrylic pressure-sensitive adhesives of Comparative Examples 1 to 4, foaming occurred in a considerable proportion when placed under high temperature. Further, in the solvent-type acrylic pressure-sensitive adhesives of Comparative Examples 1 to 3, relatively large peeling was observed at the end portions. Further, with the solvent-type acrylic pressure-sensitive adhesive of Comparative Example 4, although there was little foaming, when it was left at high temperature, large peeling was observed near the edges.

On the other hand, when the photopolymerizable pressure-sensitive adhesives of Examples 1 to 4 were used, almost no foaming was observed in the pressure-sensitive adhesive layer even at high temperature, and the edges were No peeling was observed near the part.

Furthermore, in Examples 1 to 4, the curing time was not required after the polymerization because the molecular weight was increased by photopolymerization, while in Comparative Examples 1 and 3 to 5, the curing time was as long as 7 days. Needed.

Further, in Comparative Examples 1 to 4, the adhesive force of the pressure-sensitive adhesive layer to the surface of the retardation plate was as low as 976 g or less, whereas in Examples 1 to 4, the anchoring force of the pressure-sensitive adhesive layer to the retardation plate was low. It can be seen that the value is very large at 2100 g or more. It is easy to apply a low-viscosity photopolymerizable composition onto the surface of the retardation plate, and the photopolymerizable composition was surely applied following the irregularities on the surface of the retardation plate. It is considered that this is because the polymer has a higher molecular weight.

[0059]

In the method for producing an optical film pressure-sensitive adhesive sheet of the present invention, after the above-mentioned specific photopolymerizable composition is directly applied to one surface of the optical film, the pressure-sensitive adhesive layer is directly applied to one surface of the optical film by photopolymerization. It is formed. Therefore, since the photopolymerizable composition has a low viscosity, it can be easily applied to the surface of the optical film, and adheres to the surface of the optical film while surely following the irregularities on the surface of the optical film. As a result, the pressure-sensitive adhesive layer formed by photopolymerization is firmly adhered to one surface of the optical film.

Further, since the pressure-sensitive adhesive layer is formed by photopolymerization, curing time for crosslinking is not required, so that the production process can be simplified and shortened. In addition, since the pressure-sensitive adhesive layer is formed by photopolymerization and the molecular weight can be easily increased by controlling the light irradiation conditions, it is difficult for foaming and peeling to occur at high temperatures, and it has excellent high-temperature durability adhesiveness. It becomes possible to easily provide the optical film pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer.

Claims (1)

[Claims] 1. The (A) alkyl group has 2 to 12 carbon atoms.
100 parts by weight of a monomer containing 70 to 100% by weight of alkyl (meth) acrylate and 0 to 30% by weight of a vinyl monomer having a polar group, and (B) 0.01 to 5 parts by weight of a polyfunctional vinyl monomer; ) A method for producing an optical film pressure-sensitive adhesive sheet, which comprises directly coating a photopolymerizable composition containing a photopolymerization initiator on one surface of an optical film and irradiating with light in an inert gas atmosphere.