JP3653127B2 - Method for producing optical sheet having pressure-sensitive adhesive layer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an optical sheet having an adhesive layer.
[0002]
[Prior art]
The liquid crystal display element basically has a configuration in which polarizing plates are arranged on both sides of a liquid crystal cell, and a phase plate is often interposed between the polarizing plate on the incident light side and the liquid crystal cell. That is, the liquid crystal display element has a configuration of polarizing plate / liquid crystal cell / polarizing plate or polarizing plate / phase plate / liquid crystal cell / polarizing plate.
[0003]
When assembling a liquid crystal display element, prepare a sheet with a pressure-sensitive adhesive layer and release sheet on one side of a polarizing plate or phase plate in advance (usually purchased from a professional manufacturer), and peel off the release sheet. However, it is performed by adhering to the other party (liquid crystal cell or liquid crystal cell with phase plate).
[0004]
Now, to provide an adhesive layer and a release sheet on one side of a polarizing plate or a phase plate,
(i) after coating the solution of the pressure-sensitive adhesive composition on the releasable sheet side, removing the solvent by drying, and then sticking this to the polarizing plate or phase plate side,
(ii) a method of coating the solution of the pressure-sensitive adhesive composition on the side of the polarizing plate or the phase plate, removing the solvent by drying, and then covering the release sheet,
Any one of the above methods is employed, but industrially, in most cases, the former method (i) is employed which is less likely to damage the polarizing plate and the phase plate.
[0005]
[Problems to be solved by the invention]
However, the method (i) and the method (ii) described above involve the steps of coating with a solvent solution and then drying, and thus have the following problems.
(A) Since coating and drying are performed in an open state and take a long time, dust is likely to adhere to the coating surface, and the working environment is also deteriorated due to solvent evaporation during coating and drying.
(B) Since drying is required, it is disadvantageous in terms of utility, equipment cost and equipment occupation space, and is limited in line speed.
(C) During the drying process, it is likely to cause curling due to solvent volatilization.
(D) Film defects such as streaks, crushed skin, unevenness, and bubble entrapment are likely to occur in the coating film, and as a result, the adhesive strength, optical characteristics, and aesthetics may be deteriorated.
(E) Even when the adhesive composition solution is coated on the side of the releasable sheet as in (i) above, the other sheet may be affected by the residual solvent after drying.
[0006]
Under such a background, the present invention adopts a special film forming method using a pair of rolls, thereby causing various problems (dust adhesion, working environment) that have been a concern in the conventional coating method. Deterioration, utility disadvantage, equipment cost disadvantage, equipment occupancy space, line speed limitation, curling, film defects, damage to the other party's sheet) all at once, adhesive layer It is an object of the present invention to provide a method for producing an optical sheet having a favorable industrial advantage.
[0007]
[Means for Solving the Problems]
The method for producing an optical sheet having a pressure-sensitive adhesive layer according to the present invention comprises separating a base sheet (1), which is an optical sheet, on each of a pair of rolls arranged in parallel in a horizontal direction with a slight gap. Each of the moldable sheets (2) is supplied, and a fluid non-solvent type high-viscosity adhesive resin composition (a) for forming the adhesive layer (A) is discharged toward the gap between the rolls to discharge the composition. The high viscosity adhesive resin composition (a) is formed between the base sheet (1) and the release sheet (2) by rotating both rolls in the direction of biting each other while making a reservoir of the product (a). After being sandwiched, by taking a curing means for the highly viscous adhesive resin composition (a) in such a sandwiched state, the highly viscous adhesive resin composition (a) is entrained in bubbles. The pressure-sensitive adhesive layer (A) is not present.
[0008]
In this case, it is desirable that the non-solvent type high viscosity adhesive resin composition (a) contains a component that is cured by heating or irradiation with active energy rays.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below.
[0010]
As the substrate sheet (1), an optical sheet or device such as a polarizing element film, a polarizing plate, a phase plate, a retardation element film, or a liquid crystal display element; a protective film that covers the surface of these optical sheet or device; Color filter; Film with transparent electrode; Single layer or multiple layers of various plastics films (including films having crosslinkable resin cured layer, organic gas-resistant layer, inorganic gas-resistant layer, etc.); Anti-glare film; scratch resistant film; optical sheet of the like.
[0011]
As the releasable sheet (2), a sheet having releasability on at least one side, for example, polycarbonate film, polyarylate film, polyethersulfone film, polysulfone film, polyester film, polystyrene film, polyolefin film, norbornene film, Single-layer or multi-layer plastics films such as phenoxy ether type polymer films, organic air-resistant films, sheets that have been subjected to releasability processing with silicone release agents, fluorine resin films, and certain types Examples of the film include a film having a releasability such as a polyolefin film, and a film formed by internally adding a release agent. The thickness of the releasable sheet (2) is not limited, but is usually 5 to 500 μm, preferably 10 to 100 μm in many cases.
[0012]
Release Sheet (2), when it may or may not be light isotropic in the case of using it to finally peeled off and removed, to the use to be used for light without peeling it it is required to be a light isotropic. However, when it is provided on the front surface of the polarizing plate on the incident light side, it does not have to be optically isotropic.
[0013]
As a fluid non-solvent type high viscosity adhesive resin composition (a) for forming an adhesive layer (A), a monomer component that gives a soft segment and a monomer component that gives a hard segment (and functional groups as needed) Those containing an adhesive grade acrylic polymer obtained by copolymerizing a monomer component or a polyfunctional (meth) acrylate component) as an essential component are preferably used.
[0014]
Here, as a monomer component which gives a soft segment when polymerized, an alkyl acrylate having 4 or more carbon atoms in the alkyl group (n-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, etc.), carbon number in the alkyl group 6 or more alkyl methacrylates (n-hexyl methacrylate, 2-ethylhexyl methacrylate, etc.) and the like. Monomer components that give hard segments include alkyl acrylates having 1 to 3 carbon atoms in the alkyl group (such as methyl acrylate), alkyl methacrylates having 1 to 5 carbon atoms in the alkyl group (such as methyl methacrylate), vinyl acetate, and styrene. Can be given. Examples of the functional group-containing monomer component include acrylic acid, methacrylic acid, crotonic acid, (anhydrous) itaconic acid, (anhydrous) maleic acid, fumaric acid, glycidyl (meth) acrylate, and N-methylolacrylamide. As polyfunctional (meth) acrylate components, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, butylene glycol, 1,6-hexanediol, neopentyl glycol And di-, tri- or poly (meth) acrylates of polyhydric alcohols such as trimethylolpropane, glycerin and pentaerythritol.
[0015]
The above adhesive-grade acrylic polymers usually lack fluidity even when heated, so the fluidity non-solvent type high viscosity for forming the adhesive layer (A). In order to obtain the adhesive resin composition (a), it is desirable to add a component that is cured by heating or irradiation with active energy rays. As the curing component, the monomer that gives the soft segment, the monomer that gives the hard segment, the functional group-containing monomer, and the polyfunctional (meth) acrylate described above are used in a monomer form. These monomers act as a plasticizer for the acrylic polymer during film formation to give fluidity, and then polymerize by taking a curing means. A relatively low molecular weight oligomer or a general plasticizer can be used together with or in place of such a monomer.
[0016]
As the high-viscosity adhesive resin composition (a), in addition to the above-mentioned acrylic polymer as an essential constituent element, a rubber-based, vinyl-based, silicone-based or other adhesive-grade resin composition may be used. it can.
[0017]
The viscosity of the fluid non-solvent type high viscosity adhesive resin composition (a) for forming the adhesive layer (A) is about 1000 to 100000 cps / 20 ° C, preferably 3000 to 80000 cps / 20 ° C, more preferably It is suitable to set it as 5000-50000 cps / 20 degreeC.
[0018]
In order to produce an optical sheet having an adhesive layer according to the present invention, first, a base sheet (1) is placed on each of a pair of rolls arranged in parallel in the horizontal direction with a slight gap therebetween. ) And a releasable sheet (2) , respectively , and the fluid non-solvent type high viscosity adhesive resin composition (a) for forming the adhesive layer (A) is discharged toward the gap between the rolls. The high-viscosity adhesive resin composition (2) between the base sheet (1) and the release sheet (2) by rotating both rolls in the direction of biting each other while making a reservoir of the composition (a) After a) is sandwiched, the high-viscosity adhesive resin composition (a) is removed from the cells by taking a curing means for the high-viscosity adhesive resin composition (a) in such a state of being sandwiched . An adhesive layer (A) without biting is formed.
[0019]
The non-solvent type high viscosity adhesive resin composition (a) preferably contains a component that is cured by heating or irradiation with active energy rays. Examples of the curing means include heating and irradiation with active energy rays (ultraviolet rays, electron beams, and in some cases, visible rays). When curing is carried out by irradiation with ultraviolet rays or visible rays, it is usual to previously blend a high-viscosity adhesive resin composition (a) with a photopolymerization initiator in an amount of about 0.5 to 5% by weight based on the whole. In the case of irradiation with active energy rays, curing can be completed by performing heat treatment as necessary after irradiation.
[0020]
As a result, a target sheet having a layer structure of base sheet (1) / adhesive layer (A) / release sheet (2) is obtained. When the adhesive layer (A) is provided on both sides of the base sheet (1), the above base sheet (1) / adhesive layer (A) / release sheet (2) and release sheet (2 ) And the same operation as above may be repeated. The layer structure at this time is releasable sheet (2) / adhesive layer (A) / base sheet (1) / adhesive layer (A) / releasing sheet (2). The releasable sheet (2) may be peeled off at the time when the necessity arises, and may not be peeled off depending on the application.
[0021]
Next, the operation will be described. In the present invention, since a special film forming method using a pair of rolls arranged in parallel in the horizontal direction with a slight gap is adopted, various problems which have been a concern in the conventional coating method are adopted. (Dust adhesion, work environment deterioration, utility disadvantages, equipment cost disadvantages, equipment space disadvantages, line speed constraints, curls, film defects, counterpart sheet damage) It eliminates all at once, and an optical sheet having an adhesive layer can be advantageously produced industrially.
[0022]
【Example】
The following examples further illustrate the invention. Hereinafter, “parts” means parts by weight.
[0023]
Example 1
FIG. 1 is an explanatory view showing an example of the production method of the present invention.
[0024]
As an example of the base sheet (1), a phase plate having a total thickness of 208 μm in which both surfaces of a retardation film made of a uniaxially stretched polyvinyl alcohol film having a thickness of 42 μm were protected with a cellulose triacetate film was prepared. Further, as a releasable sheet (2), a polyester film (biaxially stretched polyethylene terephthalate film) having a thickness of 38 μm, which was subjected to a release treatment with a silicone release agent on one side, was prepared.
[0025]
Furthermore, as a fluid non-solvent type high viscosity adhesive resin composition (a) for forming an adhesive layer (A), 170 parts of a butyl acrylate-vinyl acetate (65:35 by weight ratio) copolymer, A resin solution having a viscosity of 11500 cps / 20 ° C. comprising 15 parts of butyl acrylate, 5 parts of vinyl acetate, 10 parts of acrylic acid and 2 parts of benzoin isobutyl ether (photopolymerization initiator) was prepared.
[0026]
The base sheet (1) and the release sheet (2) prepared above are respectively supplied to each of a pair of rolls arranged in parallel in the horizontal direction with a slight gap (release sheet (2 1), the release treatment surface was the upper surface), and the composition (a) was discharged toward the gap between the rolls to form a reservoir of the composition (a) as shown in FIG. The composition (a) was sandwiched between the base sheet (1) and the releasable sheet (2) by rotating them in the direction to bite each other. Next, in such a sandwiched state, the composition (a) was cured by irradiating with ultraviolet rays under the conditions of an output of 120 W / cm, a lamp distance of 150 mm, and an integrated light amount of 600 mJ / cm ² . As a result, a sheet having a layer structure of base sheet (1) / adhesive layer (A) / release sheet (2) was obtained. The thickness of the pressure-sensitive adhesive layer (A) was 30 μm , and no bubbles were observed.
[0027]
While the release sheet (2) was peeled and removed from this sheet, it was attached to the liquid crystal cell. The release sheet (2) was peeled off smoothly, and the adhesive layer (A) was a base sheet ( (Phase plate) (1) neatly transferred to the liquid crystal cell.
[0028]
Example 2
As an example of the substrate sheet (1), a polarizing plate having a total thickness of 205 μm in which both surfaces of a 35 μm-thick polyvinyl alcohol-iodine polarizing element film were protected with a cellulose triacetate film was prepared. Further, as a releasable sheet (2), a polyester film having a thickness of 25 μm (biaxially stretched polyethylene terephthalate film) having a release treatment with a silicone release agent on one side was prepared.
[0029]
Furthermore, as a fluid non-solvent type high viscosity adhesive resin composition (a) for forming an adhesive layer (A), 2-ethylhexyl acrylate-methyl methacrylate-acrylic acid (70:20:10 by weight) A resin solution having a viscosity of 5500 cps / 20 ° C. consisting of 20 parts of butyl acrylate, 10 parts of methyl methacrylate, 10 parts of acrylic acid and 3 parts of benzoin isobutyl ether (photopolymerization initiator) was prepared in 160 parts of the copolymer.
[0030]
Thereafter, in the same manner as in Example 1, a sheet having a layer structure of base sheet (1) / adhesive layer (A) / releasing sheet (2) was obtained. The thickness of the pressure-sensitive adhesive layer (A) was 25 μm , and no bubbles were observed.
[0031]
While the release sheet (2) was peeled and removed from this sheet, it was attached to the liquid crystal cell. The release sheet (2) was peeled off smoothly, and the adhesive layer (A) was a base sheet ( It was neatly transferred to the polarizing plate (1), and the sticking operation to the liquid crystal cell was smooth.
[0032]
【The invention's effect】
As described in the explanation of the operation, in the present invention, since a special film forming method using a pair of rolls arranged in parallel in the horizontal direction with a slight gap is adopted, the conventional coating is used. Various problems that have been addressed by law (dust adhesion, deterioration of work environment, utility disadvantage, equipment cost disadvantage, equipment occupation space disadvantage, line speed limitation, curl generation, membrane The occurrence of defects and the damage of the counterpart sheet) are eliminated at once, and an optical sheet having an adhesive layer can be produced industrially advantageously.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an example of a production method of the present invention.
[Explanation of symbols]
(1) ... base material sheet,
(2)… Releasable sheet,
(A) ... adhesive layer,
(a) ... high viscosity adhesive resin composition

Claims (2)

In each of a pair of rolls arranged in parallel horizontally spaced slightly the gap, an optical sheet with the substrate sheet (1) release sheet (2) is supplied, toward the gap between the rolls And discharging the fluid non-solvent type high-viscosity adhesive resin composition (a) for forming the pressure-sensitive adhesive layer (A) to make a reservoir of the composition (a), and biting both rolls together. The high-viscosity adhesive resin composition (a) is sandwiched between the base sheet (1) and the release sheet (2) by rotating in the direction, and in such a state A pressure-sensitive adhesive characterized in that the high-viscosity adhesive resin composition (a) becomes a pressure-sensitive adhesive layer (A) free from bubbles by taking a curing means for the high-viscosity adhesive resin composition (a). A method for producing an optical sheet having a layer.   The production method according to claim 1, wherein the non-solvent type high viscosity adhesive resin composition (a) contains a component which is cured by heating or irradiation with active energy rays.

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