JP2002138260A - Optical film with pressure-sensitive adhesive layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare an optical film with a pressure-sensitive adhesive layer which does not much vary the adhesive force of a pressure-sensitive adhesive even under a moistening condition and excels in moistening durability without causing malfunctions such as peeling of the edge portion of the laminated surface of the optical film and a liquid crystal panel. SOLUTION: The optical film with a pressure-sensitive adhesive layer which is provided on one surface of an optical film to be applied to the glass substrate of a liquid crystal panel has a ratio (A/B) of the peeling force value (A) of the above pressure-sensitive adhesive in an atmosphere of 23 deg.C and 60% RH to the peeling force value (B) of that in an atmosphere of 75 deg.C and 95% RH, when the optical film with the pressure-sensitive adhesive layer applied to the glass substrate of the liquid crystal panel is peeled at a rate of 300 mm/min in the 90 deg. direction, of 1.0-2.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical film with a pressure-sensitive adhesive layer in which a pressure-sensitive adhesive layer for sticking to a glass substrate of a liquid crystal panel is provided on one side of an optical film.

[0002]

2. Description of the Related Art In a liquid crystal display, it is indispensable to arrange polarizing elements on both sides of a glass substrate forming the outermost surface of a liquid crystal panel in view of an image forming method. Affixed to the surface. In addition to the polarizing film on the outermost surface of the liquid crystal panel,
Various optical elements have been used to improve the display quality of a display. For example, a retardation film for preventing coloration, an optical compensation film for improving the viewing angle of a liquid crystal display, a brightness enhancement film for increasing the contrast of the display, an antiglare sheet, and the like are attached. These films are collectively called optical films.

[0003] When these optical films are attached to the outermost surface of a liquid crystal panel, an adhesive is usually used. Also,
Since the optical film can be instantly fixed to the outermost surface of the liquid crystal panel and has the advantage of not requiring a drying step to fix the optical film, the adhesive is
One side of the optical film is provided in advance as an adhesive layer. That is, an optical film with an adhesive layer is generally used for attaching the optical film to the outermost surface of the liquid crystal panel.

The required properties required of the pressure-sensitive adhesive include (1) re-bonding (rework) is possible;
(2) It has a stress relaxation property. (1)
Regarding, when bonding the optical film to the outermost surface of the liquid crystal panel, the bonding position is often wrong, and foreign matter often gets stuck on the bonding surface. This is a characteristic required to enable peeling and re-lamination. In this case, the liquid crystal panel is expensive and thus is reused, but the relatively inexpensive optical film is discarded. (2) is a characteristic required to prevent optical unevenness caused by a dimensional change of the optical film.

[0005] In addition to the above-mentioned properties, it is also essential that the pressure-sensitive adhesive does not cause any trouble in a durability test. However, conventional adhesives do not have sufficient humidification durability under humidification conditions (particularly at high temperatures), and the pressure-sensitive adhesive laminated on the optical film with the adhesive layer has the outermost surface of the liquid crystal panel (under humidification conditions). Adhesiveness to the glass substrate) was reduced, and a problem such as peeling off at the interface between the adhesive and the glass substrate occurred at the bonding end surface between the optical film and the liquid crystal panel.

[0006]

SUMMARY OF THE INVENTION The present invention relates to an optical film with an adhesive layer provided on one side of an optical film, wherein the adhesive layer is attached to a glass substrate of a liquid crystal panel. Even under the humidifying condition in which the optical film with the layer is adhered to the outermost surface (glass substrate) of the liquid crystal panel, the adhesive force of the adhesive does not largely change, and the end of the bonding surface between the optical film and the liquid crystal panel. An object of the present invention is to provide an optical film with a pressure-sensitive adhesive layer which is excellent in humidification durability and does not cause problems such as peeling.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on the physical properties of the pressure-sensitive adhesive of the optical film with a pressure-sensitive adhesive layer. As a result, the pressure-sensitive adhesive satisfies the following physical properties. It has been found that the above object can be achieved by using such a material, and the present invention has been completed.

That is, the present invention relates to an optical film with an adhesive layer provided on one side of an optical film, wherein the adhesive layer is attached to a glass substrate of a liquid crystal panel. When the optical film with the pressure-sensitive adhesive layer is peeled in the direction of 90 ° at a speed of 300 mm / min, the peeling force value (A) of the pressure-sensitive adhesive in an atmosphere of 23 ° C. and 60% RH, 75 ° C., 95% % Of the pressure-sensitive adhesive in an atmosphere of% RH (A /
B) is 1.0 or more and 2.5 or less, It relates to the optical film with an adhesive layer characterized by the above-mentioned.

The ratio (A / B) of the peeling force value (A) of the adhesive measured under the above-mentioned peeling conditions in a normal atmosphere to the peeling force value (B) in a high-temperature and high-humidity atmosphere is 2.5. In the following, even under the humidifying condition, the adhesive force of the pressure-sensitive adhesive is hardly reduced, and the humidifying durability is excellent. The ratio (A /
B) is preferably as small as possible and preferably not more than 2.0. When the ratio (A / B) is 1.0, there is no decrease in the adhesive strength. On the other hand, when the ratio (A / B) exceeds 2.5, the humidification durability is poor, and problems such as peeling off on the back surface between the adhesive layer and the glass substrate occur.

[0010] The peeling force was measured by bonding an optical film with an adhesive having a size of 25 mm x 150 mm on an alkali-free glass plate # 1737 manufactured by Corning Co., Ltd.
After leaving for 15 minutes in an atmosphere of × 0.5 Mpa, the optical film was peeled at a peeling angle of 90 ° by a tensile tester at 300 mm /
Tensile strength measured at the peel rate per minute.

Usually, the peeling force value (A) is 1 to 20 (N /
About 25 mm), preferably 2 to 10 (N / 25 m
m), the peeling force value (B) is 0.4 to 20 (N / 25 m
m), preferably 1 to 10 (N / 25 mm), from the viewpoint of re-lamination property (reworkability) and humidification durability.

In the above optical film with an adhesive layer,
The saturated water absorption of the adhesive is 0.5% by weight or more and 2.5% by weight.
The following is preferred.

When the pressure-sensitive adhesive has a saturated water absorption within the above range, it absorbs water that tends to enter the interface between the pressure-sensitive adhesive layer and the glass substrate, and the adhesive strength of the optical film to the liquid crystal panel even under humidified conditions. It is considered that (peeling force) can be maintained to some extent, and as a result, good humidification durability is exhibited. If the saturated water absorption is less than 0.5% by weight,
Under the humidifying condition, the moisture penetrating into the interface between the pressure-sensitive adhesive layer and the glass substrate reduces the adhesive strength of the optical film with the pressure-sensitive adhesive layer to the liquid crystal panel where the pressure-sensitive adhesive layer is absorbed. From this viewpoint, the saturated water absorption of the pressure-sensitive adhesive is more preferably 1.1% by weight or more. On the other hand, when the saturated water absorption is increased, the water is absorbed too much under the humidifying condition, and the adhesive strength of the optical film with the adhesive layer to the liquid crystal panel is reduced. Therefore, the saturated water absorption of the adhesive is 2.5% by weight. And more preferably 1.8% by weight or less.

The saturated water absorption is calculated from the following formula based on the weight (a) of the solid content of the pressure-sensitive adhesive and the weight (b) of the pressure-sensitive adhesive after being left for 3 days in an atmosphere of 75 ° C. and 95% RH. (Ba)
/ A｝ × 100 (%).

In the above-mentioned optical film with a pressure-sensitive adhesive layer, examples of the optical film include a polarizing film, a retardation film, an optical compensation film, a brightness enhancement film and an antiglare sheet.

By suitably selecting these optical films having various functions and sticking them to the surface of a glass substrate of a liquid crystal panel, a good image formation of a liquid crystal display can be realized.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION An optical film with a pressure-sensitive adhesive layer according to the present invention, as shown in FIG.
Is provided. The release layer 3 is provided on the adhesive layer 2.
Can be provided.

As the optical film 1, a film used for forming a liquid crystal display device or the like can be used, and the type thereof is not particularly limited. For example, examples of the optical film include a polarizing film, a retardation film, an optical compensation film, a brightness enhancement film, an antiglare sheet, and the like.

As a polarizer constituting the polarizing film,
There is no particular limitation, and various types can be used. Examples of the polarizer include dichroic dyes such as iodine and dichroic dyes on hydrophilic polymer films such as polyvinyl alcohol-based films, partially formalized polyvinyl alcohol-based films, and ethylene / vinyl acetate copolymer-based partially saponified films. Examples thereof include a film obtained by adsorbing a substance and stretched, and a polyene-based oriented film such as a dehydrated product of polyvinyl alcohol and a dehydrochlorinated product of polyvinyl chloride. Although the thickness of the polarizer is not particularly limited, it is generally about 5 to 80 μm.

On one or both sides of the polarizer, a transparent protective layer may be provided as a coating layer of a polymer or a laminate layer of a film for the purpose of water resistance or the like. As the transparent polymer or film material for forming the transparent protective layer, an appropriate transparent material can be used, but a material having excellent transparency, mechanical strength, heat stability, moisture barrier property and the like is preferably used. Although the thickness of the transparent protective layer is not particularly limited, it is generally about 10 to 300 μm.

Materials for forming the transparent protective layer include:
For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as cellulose diacetate and cellulose triacetate, acrylic polymers such as polymethyl methacrylate, and styrene such as polystyrene and acrylonitrile-styrene copolymer (AS resin) Polymers, polycarbonate polymers and the like. In addition, polyethylene, polypropylene, polyolefin having a cyclo- or norbornene structure, polyolefin polymers such as ethylene-propylene copolymer, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, and sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Blends of polymers and the like are also examples of the polymer forming the transparent protective layer.

Examples of the retardation film include a birefringent film and a liquid crystal polymer film obtained by uniaxially or biaxially stretching a polymer material. Although the thickness of the retardation film is not particularly limited, it is generally about 20 to 150 μm. The retardation plate can be formed as a superimposed body of two or more stretched films to control the optical properties such as retardation, etc. It can also be used as an elliptically polarizing film laminated with a polarizing film to compensate for a phase difference or the like.

Examples of the polymer material include polyvinyl alcohol, polyvinyl butyral, polymethyl vinyl ether, polyhydroxyethyl acrylate, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, polycarbonate, polyarylate, polysulfone, polyethylene terephthalate, polyethylene naphthalate, and polyethylene naphthalate. Ether sulfone, polyphenylene sulfide, polyphenylene oxide,
Examples include polyallyl sulfone, polyvinyl alcohol, polyamide, polyimide, polyolefin, polyvinyl chloride, cellulose polymers, and various binary and ternary copolymers, graft copolymers, and blends thereof. These polymer materials become oriented products (stretched films) by stretching or the like.

Examples of the liquid crystalline polymer include various types of main chain type and side chain type in which a conjugated linear atomic group (mesogen) for imparting liquid crystal alignment is introduced into the main chain or side chain of the polymer. And so on. Specific examples of the main chain type liquid crystal polymer include a polyester liquid crystal polymer having a structure in which a mesogen group is bonded by a spacer portion imparting flexibility, such as a nematic alignment. Specific examples of the side-chain type liquid crystalline polymer include polysiloxane, polyacrylate, polymethacrylate or polymalonate having a main chain skeleton, and a paraffin-imparting paraffin having a conjugated atomic group as a side chain. And those having a mesogen moiety composed of a substituted cyclic compound unit. These liquid crystalline polymers are prepared, for example, by rubbing the surface of a thin film of polyimide or polyvinyl alcohol formed on a glass plate, or by applying a solution of the liquid crystalline polymer on an alignment-treated surface such as obliquely deposited silicon oxide. It is performed by developing and heat-treating.

The polarizing film and the retardation film can be laminated and used, and can be a reflection type polarizing film, a semi-transmissive layer type polarizing film, a polarized light separating polarizing film and the like. In addition, the above-described optical films can be used as optical compensation films and other various viewing angle widening films. Further, examples of the optical films include a brightness enhancement film and the like. Further, the polarizing film may be provided with a reflection layer having a fine uneven structure on the surface to form an antiglare sheet.

The pressure-sensitive adhesive used in the pressure-sensitive adhesive layer 2 constituting the optical film with a pressure-sensitive adhesive layer of the present invention has a ratio (A / B) of the peeling force value (A) to the peeling force value (B). Those in the range can be used without particular limitation.

Examples of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 2 include rubber-based pressure-sensitive adhesives, acrylic pressure-sensitive adhesives, and silicone-based pressure-sensitive adhesives. Of these, acrylic pressure-sensitive adhesives are preferable. The weight average molecular weight of the base polymer is preferably about 300,000 to 2.5 million.

As the monomer used for the acrylic polymer which is the base polymer of the acrylic pressure-sensitive adhesive, various alkyl (meth) acrylate / (meth) acrylate means acrylate and / or methacrylate. Has the same meaning. You can use｝. Specific examples of such an alkyl (meth) acrylate include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate,
Examples thereof include 2-ethylhexyl (meth) acrylate, which can be used alone or in combination.

Among these, those using butyl acrylate in an amount of 30% by weight or more as the monomer unit of the base polymer can be set so that the base polymer exhibits tackiness by adjusting the relaxation modulus of the base polymer. preferable.

It is preferable to use a small amount of (meth) acrylic acid instead of part of the alkyl (meth) acrylate in order to impart polarity to the obtained acrylic polymer. Further, glycidyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, N-methylol (meth) acrylamide, or the like may be used in combination as a crosslinkable monomer. Further, if desired, other copolymerizable monomers such as vinyl acetate and styrene can be used together to the extent that the adhesive properties of the acrylic polymer are not impaired.

As the base polymer of the rubber-based pressure-sensitive adhesive,
For example, natural rubber, isoprene rubber, styrene-butadiene rubber, recycled rubber, polyisobutylene rubber,
Further, styrene-isoprene-styrene-based rubber, styrene-butadiene-styrene-based rubber and the like can be mentioned. Examples of the base polymer of the silicone-based pressure-sensitive adhesive include dimethylpolysiloxane and diphenylpolysiloxane.

The pressure-sensitive adhesive preferably contains a crosslinking agent. Examples of the crosslinking agent include a polyisocyanate compound, a polyamine compound, a melamine resin, a urea resin, and an epoxy resin. Further, the pressure-sensitive adhesive, if necessary, a tackifier, a plasticizer, a filler, an antioxidant, an ultraviolet absorber, and the like, and each may be appropriately used without departing from the object of the present invention. it can.

The formation of the pressure-sensitive adhesive layer 2 is performed on one side of the optical film 1 to be adhered to a glass substrate of a liquid crystal panel. The forming method is not particularly limited, and examples thereof include a method of applying a pressure-sensitive adhesive (solution) to the optical film 1 and drying the same, and a method of transferring the film using a release sheet 3 provided with a pressure-sensitive adhesive layer 2. The thickness of the pressure-sensitive adhesive layer 2 (dry film thickness) is not particularly limited.
It is preferably about 40 μm.

The constituent material of the release sheet 3 is as follows.
Examples thereof include paper, synthetic resin films such as polyethylene, polypropylene, and polyethylene terephthalate. The surface of the release sheet 3 may be subjected to a release treatment such as a silicone treatment, a long-chain alkyl treatment, or a fluorine treatment as needed in order to enhance the releasability from the pressure-sensitive adhesive layer 2.

[0035]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the invention thereto. In each example, parts are parts by weight.

Example 1 (Preparation of adhesive solution) 100 parts of butyl acrylate, 4 parts of acrylic acid, and 0.2 part of 2-hydroxyethyl acrylate
6 parts, 0.4 parts of azobisisobutyronitrile and 220 parts of ethyl acetate were reacted at about 60 ° C. while stirring to obtain a polymer solution. Solid content of the polymer solution 1
For 00 parts, Coronate L (made by Nippon Polyurethane)
An adhesive solution was prepared by adding 0.5 part.

(Preparation of Polarizing Film with Pressure-Sensitive Adhesive Layer) The pressure-sensitive adhesive solution prepared above was coated on release paper having a thickness of 35 μm so that the thickness after drying was 25 μm.
This was laminated on a polarizing film to produce a polarizing film with an adhesive layer.

Example 2 80 parts of butyl acrylate, 20 of methyl acrylate
Part, acrylic acid 3 parts, azobisisobutyronitrile 0.1 part.
The reaction was carried out at about 60 ° C. while stirring 4 parts and 220 parts of ethyl acetate to obtain a polymer solution. 0.5 part of Coronate L (manufactured by Nippon Polyurethane) was added to 100 parts of the solid content of the polymer solution to prepare an adhesive solution.
Further, a polarizing film with a pressure-sensitive adhesive layer was produced in the same manner as in Example 1.

Comparative Example 1 100 parts of isooctyl acrylate, 0.6 part of 2-hydroxyethyl acrylate, 0.4 part of azobisisobutyronitrile and 220 parts of ethyl acetate were stirred while stirring.
The reaction was carried out at about 0 ° C. to obtain a polymer solution. 0.5 part of Coronate L (manufactured by Nippon Polyurethane) was added to 100 parts of the solid content of the polymer to prepare an adhesive solution. Further, a polarizing film with a pressure-sensitive adhesive layer was produced in the same manner as in Example 1.

The pressure-sensitive adhesive solution or the polarizing film with a pressure-sensitive adhesive layer obtained in each of Examples and Comparative Examples was subjected to the following evaluation. Table 1 shows the results.

(Measurement of Saturated Water Absorption of Pressure-Sensitive Adhesive) The pressure-sensitive adhesive solution prepared as described above was applied on release paper having a thickness of 35 μm so that the thickness after drying was 25 μm. About 1.0 g of the coated and dried adhesive was collected from the release paper,
The weight (a) was measured. 75 ° C, 95% R
The weight (b) was measured after being left for 3 days in an atmosphere of H. From the weight of both, the saturated water absorption of each adhesive ｛(b−
a) / a｝ × 100 (%) was calculated.

(Measurement of Peeling Force of Polarizing Film with Adhesive to Glass Substrate) The polarizing film with the adhesive prepared as described above was cut into a size of 25 mm × 150 mm.
It was stuck on a non-alkali glass plate # 1737 manufactured by Corning and left for 15 minutes in an atmosphere of 50 ° C. × 0.5 Mpa. This sample was peeled at 90 ° by a tensile tester,
Tensile at a peel rate of 300 mm / min, tensile strength (N /
25 mm). This peel force is 23 ° C., 65% R
Sample (A) left for 1 hour at 75 ° C, 95% R
The sample (B) left for 1 hour in H was measured, and the ratio (A / B) of the former peeling force value (A) to the latter peeling force value (B) was calculated.

(Humidation Durability Test) The polarizing film with an adhesive prepared as described above was cut into a size of 200 mm × 150 mm, and an alkali-free glass plate # manufactured by Corning Incorporated.
It was stuck on 1737 and left in an atmosphere of 50 ° C. × 0.5 Mpa for 15 minutes. This sample was taken at 75 ° C and 95% R
It was left under an atmosphere of H for 5 hours, and it was visually confirmed whether or not a problem such as peeling occurred at the pressure-sensitive adhesive layer / glass interface.
The test was performed on 100 sheets (denominator), and the number was expressed as the number (numerator) of no problem.

[0044]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an optical film with a pressure-sensitive adhesive layer of the present invention.

[Description of Signs] 1 Optical film 2 Adhesive layer 3 Release sheet

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuji Shiki 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Co., Ltd. No. 2 Nitto Denko Corporation F term (reference) 2H049 BA02 BA06 BB51 BC22 2H091 FA08X FA08Z FA11X FA11Z FA31X FA31Z FA37X FD15 GA17 LA02 LA06 4J004 AA05 AA10 AA11 AB01 CA03 CA04 CA05 CA06 CC02 CC03 CD03 CD05 CD06 FA02

Claims (3)

[Claims] 1. An optical film with an adhesive layer provided on one side of an optical film with an adhesive layer for attaching to a glass substrate of a liquid crystal panel, wherein the adhesive layer is attached to a glass substrate of the liquid crystal panel. The peeling force value (A) of the pressure-sensitive adhesive under an atmosphere of 23 ° C. and 60% RH when the optical film with the adhesive is peeled in a 90 ° direction at a speed of 300 mm / min, and an atmosphere of 75 ° C. and 95% RH The ratio (A) to the peeling force value (B) of the adhesive under
/ B) is 1.0 or more and 2.5 or less, The optical film with an adhesive layer characterized by the above-mentioned. 2. The optical film with an adhesive layer according to claim 1, wherein the saturated water absorption of the adhesive is 0.5% by weight or more and 2.5% by weight or less. 3. The optical film with a pressure-sensitive adhesive layer according to claim 1, wherein the optical film is a polarizing film, a retardation film, an optical compensation film, a brightness enhancement film, or an antiglare sheet.