JP2020190754A - Optical film, removal method and manufacturing method of optical display panel - Google Patents

Abstract

To provide an optical film being a sheet-like optical film with a release film, a first adhesive layer, a polarizing film and a surface protective film laminated in this order, allowing easy removal of the release film even if the polarizing film used is thin.SOLUTION: A sheet-like optical film includes a release film, a first adhesive layer, a polarizing film and a surface protective film laminated in this order. The polarizing film has thickness of 60 μm or less. If a virtual center face f is a plane direction of an intermediate position in total thickness of the optical film, a distance x(μm) between the virtual center face f and the surface protective film and a distance y(μm) between the virtual center face f and the release film have a relation of x-y>-20.SELECTED DRAWING: Figure 1

Description

The present invention relates to a sheet-fed optical film in which a release film, a first pressure-sensitive adhesive layer, a polarizing film, and a surface protective film are laminated in this order. The present invention also relates to a method for peeling a release film according to the optical film. Furthermore, the present invention relates to a method for manufacturing an optical display panel using the optical film.

Generally, the polarizing film is used as a polarizing film with an adhesive layer provided with an adhesive layer for sticking to an optical cell such as a liquid crystal cell on one side thereof. Usually, a release film is temporarily attached to the pressure-sensitive adhesive layer until it is applied for bonding. On the other hand, a surface protective film is temporarily attached to the other side of the polarizing film. Such a polarizing film with an adhesive layer having a release film and a surface protective film is applied to an optical display panel. At that time, first, the release film is peeled from the polarizing film with an adhesive layer. The exposed adhesive layer is attached to the optical cell. The surface protective film is directly bonded to the bonded polarizing film with the adhesive layer.

The bonding is performed by, for example, a method in which a polarizing film with an adhesive layer, which is unwound from a wound body and conveyed, is bonded to the surface of an optical cell via an exposed adhesive layer by peeling off a release film (hereinafter,). , Also referred to as "roll-to-panel method". Patent Document 1). Further, a method in which a polarizing film with an adhesive layer in a single-wafer state is attached to an optical cell via an exposed adhesive layer by peeling off a release film (hereinafter, also referred to as a "sheet-to-panel method"). ).

On the other hand, image display devices such as liquid crystal display devices are becoming thinner, and polarizing films are also required to be thinner. Therefore, thinning is also performed on the polarizer (Patent Document 2). Further, the thickness of the polarizing film can be reduced by using a single protective polarizing film in which a protective film is provided only on one side of the polarizer and no protective film is provided on the other side. Since the single protective polarizing film has one less protective film than the double protective polarizing film in which the protective films are provided on both sides of the polarizer, it can be thinned.

Japanese Patent No. 4406043 Japanese Patent No. 4751481

When the release film is peeled off from the release film and the polarizing film with an adhesive layer having the surface protective film, usually, the release film is fixed with the surface protective film side of the polarizing film with the adhesive layer fixed. Is peeled off. However, in recent years, there has been an increasing demand for a mode in which the surface protective film can be easily peeled off without adhesive residue, and the peeling force of the surface protective film is further reduced. Originally, from the viewpoint of the peeling order, the release film to be peeled first is designed so that the peeling force is sufficiently smaller (easier to peel) than the surface protective film to be peeled later. Is desirable. However, in recent years, polarizing films with an adhesive layer designed so that the peeling force of the surface protective film is not sufficiently large or the peeling force of the surface protective film is smaller than the peeling force of the release film. It was newly found that it was proposed. Therefore, when the release film is peeled off, there is a problem that peeling occurs not at the interface between the release film and the pressure-sensitive adhesive layer but at the interface between the polarizing film and the surface protective film. The problem can be solved, for example, by making the peeling force of the surface protective film and the peeling force of the release film substantially the same. However, since the release film is required to have a release force equal to or higher than a predetermined value in order to secure the adhesion between the polarizing film and the optical cell, the release force of the release film is designed to be substantially the same as the release force of the surface protective film. In this case, the adhesion between the polarizing film and the optical cell is reduced, or the demand for reducing the peeling force of the surface protective film cannot be met. In particular, the above problem becomes apparent in the sheet-to-panel method when the release film is peeled off from the polarizing film with a sheet-fed adhesive layer having a thin polarizing film having a predetermined thickness or less (for example, a thickness of 60 μm or less). It turned out to be.

The present invention is a single-wafer optical film in which a release film, a first pressure-sensitive adhesive layer, a polarizing film and a surface protective film are laminated in this order, and even when a thin polarizing film is used, the release film is released. An object of the present invention is to provide an optical film capable of easily peeling a mold film.

Another object of the present invention is to provide a method for peeling a release film related to the optical film, and further, the present invention is to provide a method for manufacturing an optical display panel using the optical film.

As a result of diligent studies, the inventors of the present application have found that the above problems can be solved by the following optical films and the like, and have reached the present invention.

That is, the present invention is a single-wafer optical film in which a release film, a first pressure-sensitive adhesive layer, a polarizing film, and a surface protective film are laminated in this order.
The polarizing film has a thickness of 60 μm or less and has a thickness of 60 μm or less.
When the plane direction of the intermediate position in the total thickness of the optical film is the virtual center plane f,
The distance x (μm) between the virtual center surface f and the surface protective film and the distance y (μm) between the virtual center surface f and the release film are characterized in that xy> -20. With respect to the optical film.

In the optical film, it is preferable that the distance x (μm) and the distance y have a relationship of xy> -10.

In the optical film, the present invention is suitable when the release force (1) of the release film is larger than the release force (2) of the surface protective film.

In the optical film, it is preferable that the virtual center surface f is on the first pressure-sensitive adhesive layer or the polarizing film.

In the optical film, it is preferable that the thickness of the release film is larger than the thickness of the surface protective film.

The optical film has a base film and a second pressure-sensitive adhesive layer as the surface protective film, and can be laminated on the polarizing film via the second pressure-sensitive adhesive layer. Further, as the surface protective film, a self-adhesive film can be used.

The optical film is preferably applied when the polarizing film has a polarizer having a thickness of 10 μm or less. Further, the optical film is preferably applied when the polarizing film is a single protective polarizing film having a protective film on only one side of the polarizer.

The present invention also relates to a method for peeling a release film, which comprises peeling a release film from the optical film.

Further, the present invention relates to the step of preparing the optical film (1).
The step (2) of peeling the release film from the optical film, and
The present invention relates to a method for manufacturing an optical display panel, which comprises a step (3) of bonding the side of the first pressure-sensitive adhesive layer of the optical film from which the release film has been peeled off to one surface of an optical cell.

In the method for manufacturing an optical display panel, a liquid crystal cell or an organic EL cell can be used as the optical cell.

In the optical film of the present invention (polarizing film with an adhesive layer having a release film and a surface protective film), as described above, the distance x between the virtual center surface f and the surface protection film and the release from the virtual center surface f. It is designed so that the distance y with the film has a relationship of xy> -20. With this design, when the release film is peeled off, a shearing force in the cross-sectional direction of the optical film is applied more to the interface between the release film and the first pressure-sensitive adhesive layer than to the interface between the polarizing film and the surface protection film. It is thought that it will be. As a result, even when the thickness of the polarizing film is 60 μm or less and the waist (elasticity) is weak (furthermore, when the peeling force of the surface protective film is smaller than the peeling force of the release film), the polarizing film The release film can be easily peeled from the single-wafer optical film in the sheet-to-panel method without causing peeling at the interface between the film and the surface protective film.

It is sectional drawing of the optical film in a single-wafer state. Schematic cross-sectional view of the single-wafer optical film of another embodiment It is a partially enlarged view of the sectional schematic view of the optical film of FIG. 1 or FIG.

The optical film F of the present invention will be described below with reference to the drawings. 1 to 3 are schematic cross-sectional views of the optical film F. The optical film F has a structure in which a release film 3, a first adhesive layer 2, a polarizing film 1, and a surface protective film 4 are laminated in this order.

FIG. 2 shows a case where the polarizing film 1 is a single protective polarizing film 1'having a protective film 1b only on one side of the polarizer 1a. In FIG. 2, the case where the one-sided protective polarizing film 1'has a first adhesive layer on the side of the polarizer 1a is exemplified, but the one-sided protective polarizing film 1'has a first one on the side of the protective film 1b. It can also be arranged to have a pressure-sensitive adhesive layer. Further, as the polarizing film 1, both protective polarizing films having protective films 1b on both sides of the polarizer 1a can be used.

Further, FIG. 2 shows a case where the surface protective film 4 has a base film 41 and a second pressure-sensitive adhesive layer 42. In FIG. 2, the second adhesive layer 42 side of the surface protective film 4 is bonded to the polarizing film 1. Note that FIGS. 1 and 3 show the case where the surface protection film 4 is a self-adhesive film.

Further, in FIGS. 1 to 3, the virtual center plane f related to the plane direction of the intermediate position in the total thickness of the optical film F is shown by a alternate long and short dash line. In FIGS. 1 to 3, the virtual center surface f is described within the thickness of the polarizing film 1, but the virtual center surface f may be within the thickness of the first pressure-sensitive adhesive layer 2 and may be released. It may be within the thickness of the mold film 3.

Further, FIG. 3 is a partially enlarged view of FIG. 1 or FIG. In FIG. 3, the distance x (μm) between the virtual center surface f and the surface protective film 4 and the distance y (μm) between the virtual center surface f and the release film 3 are shown. In FIG. 3, the virtual center surface f is described within the thickness of the polarizing film 1, but as described above, the virtual center surface f may be within the thickness of the first pressure-sensitive adhesive layer 2. Also, it may be within the thickness of the release film 3. In the optical film of the present invention, the thickness of each member is designed so that x and y have a relationship of xy> -20. It is preferable that x and y have a relationship of xy> -10. By increasing the thickness of the release film 3, the value of x becomes larger, which is relatively larger than the value of y, which is preferable in satisfying the relationship. When the virtual center surface f is within the thickness of the release film 3, the thickness of the release film 3 tends to be thick, which is not preferable in terms of cost and handling. As described above, the virtual center surface f is designed to be within the thickness of the polarizing film 1 or the first pressure-sensitive adhesive layer 2, and the x and y are satisfied with the relationship of xy> -20. By designing to do so, it is possible to ensure the ease of peeling of the release film while suppressing the thickness of the release film 3. The value of xy is an index indicating the positional relationship of the virtual center surface f on the optical film F, and when the virtual center surface f is inside the surface protective film 4, the distance x The value is calculated as a "-" number in the xy listing. When the virtual center surface f is inside the release film 3, the value of the distance y is calculated as a numerical value of “−” in the posting of xy.

Both the release film 3 and the surface protective film 4 are finally peeled off, and the release force (1) of the release film 3 and the peeling force (2) of the surface protective film 4 are different from each other. , It is preferable to design with a suitable peeling force. The peeling force (1) is the peeling force of the release film 3 against the first pressure-sensitive adhesive layer 2, and the peeling force (2) is the peeling force of the surface protective film 4 against the polarizing film 1.

The peeling force (1) is preferably 0.03 N / 25 mm or more from the viewpoint of preventing the edge from floating during processing. Further, it is preferably 0.05 to 0.5 N / 25 mm, and more preferably 0.1 to 0.3 N / 25 mm. Further, the peeling force (2) is preferably 0.2 N / 25 mm or less, more preferably 0.01 to 0.1 N / 25 mm, still more preferably 0.01, from the viewpoint of simple peeling. It is preferably ~ 0.05 N / 25 mm.

The optical film F of the present invention is suitably applied when the release force (1) of the release film 3 is larger than the release force (2) of the surface protective film 4. In the optical film F of the present invention, when the value of the peeling force (1) with respect to the peeling force (2) {peeling force (1) / peeling force (2)} is 1.1 times or more, further 1. It is suitable when it is 5 times or more.

<Polarizing film>
In the present invention, a polarizing film having a thickness (total thickness) of 60 μm or less is used. From the viewpoint of thinning, the polarizing film may have a thickness of 55 μm or less, more preferably 50 μm or less. In the sheet-to-panel method using the polarizing film, when the release film is peeled off, peeling is likely to occur not at the interface between the release film and the pressure-sensitive adhesive layer but at the interface between the polarizing film and the surface protective film. Application to the polarizing film is more suitable. The polarizing film is composed of, for example, (1) a structure in which protective films are laminated on both sides of the polarizer in this order (both protective polarizing films), and (2) a protective film is laminated only on one side of the polarizer. The configuration (single protective polarizing film) and the like can be mentioned.

≪Polarizer≫
As the polarizer, one using a polyvinyl alcohol-based resin is used. As the polarizer, for example, a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, an ethylene-vinyl acetate copolymerization system partially saponified film, and a bicolor property of iodine or a bicolor dye are used. Examples thereof include a uniaxially stretched film by adsorbing a substance, a polyene-based oriented film such as a dehydrated product of polyvinyl alcohol and a dehydrogenated product of polyvinyl chloride. Among these, a polarizer made of a polyvinyl alcohol-based film and a dichroic substance such as iodine is preferable.

A polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine and uniaxially stretching it can be produced, for example, by dyeing polyvinyl alcohol by immersing it in an aqueous solution of iodine and stretching it 3 to 7 times its original length. If necessary, boric acid, zinc sulfate, zinc chloride and the like may be contained, or the mixture may be immersed in an aqueous solution such as potassium iodide. Further, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed with water before dyeing. In addition to being able to clean the surface of the polyvinyl alcohol film and blocking inhibitors by washing the polyvinyl alcohol film with water, it also has the effect of preventing non-uniformity such as uneven dyeing by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, stretching while dyeing, or stretching and then dyeing with iodine. It can be stretched even in an aqueous solution such as boric acid or potassium iodide or in a water bath.

The thickness of the polarizer is preferably 10 μm or less, more preferably 8 μm or less, further 7 μm or less, and further preferably 6 μm or less from the viewpoint of thinning. On the other hand, the thickness of the polarizer is preferably 2 μm or more, more preferably 3 μm or more. Such a thin polarizing element has less uneven thickness, excellent visibility, and less dimensional change, so that it has excellent durability against thermal shock. On the other hand, in a polarizing film containing a polarizer having a thickness of 10 μm or less, the waist (elasticity) of the film is remarkably low. Therefore, in the sheet-to-panel method, when the release film is peeled off, the release film and the pressure-sensitive adhesive layer are used. The present invention is particularly suitable for the polarizing film because peeling is particularly likely to occur at the interface between the polarizing film and the surface protective film, not at the interface between the two.

As a thin polarizer, typically
Japanese Patent No. 4751486,
Japanese Patent No. 4751481
Patent No. 4815544,
Japanese Patent No. 5048120,
International Publication No. 2014/07759 Pamphlet,
International Publication No. 2014/077636 Pamphlet,
Etc., or the thin polarizing element obtained from the manufacturing method described in these.

The polarizer has optical characteristics represented by a simple substance transmittance T and a degree of polarization P of the following equation P> − (10 ^0.929 T ^-42.4 -1) × 100 (where T <42.3). Alternatively, it is preferably configured so as to satisfy the condition of P ≧ 99.9 (however, T ≧ 42.3). A polarizer configured to satisfy the above conditions primarily has the performance required for a display for a liquid crystal television using a large display element. Specifically, the contrast ratio is 1000: 1 or more and the maximum brightness is 500 cd / m ² or more. As another use, for example, it is attached to the visible side of an organic EL cell.

The thin polarizer is patented in Patent No. 4751486, in that it can be stretched at a high magnification and the polarization performance can be improved even in a manufacturing method including a step of stretching in a laminated state and a step of dyeing. Those obtained by a production method including a step of stretching in an aqueous boric acid solution as described in Japanese Patent No. 4751481 and Japanese Patent No. 4815544 are preferable, and particularly described in Japanese Patent No. 4751481 and Japanese Patent No. 4815544. It is preferably obtained by a production method including a step of auxiliary stretching in the air before stretching in a certain boric acid aqueous solution. These thin polarizers can be obtained by a production method including a step of stretching a polyvinyl alcohol-based resin (hereinafter, also referred to as PVA-based resin) layer and a resin base material for stretching in a laminated state and a step of dyeing. With this manufacturing method, even if the PVA-based resin layer is thin, it can be stretched without problems such as breakage due to stretching because it is supported by the stretching resin base material.

≪Protective film≫
As the material constituting the protective film, those having excellent transparency, mechanical strength, thermal stability, moisture blocking property, isotropic property and the like are preferable. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, and styrene such as polystyrene and acrylonitrile-styrene copolymer (AS resin). Examples thereof include based polymers and polycarbonate polymers. In addition, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamides, imide polymers, and sulfone polymers. , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, allylate polymer, polyoxymethylene polymer, epoxy polymer, or the above. Polymer blends and the like are also examples of polymers that form the protective film. These protective films are usually attached to the polarizer by an adhesive layer.

In addition, one or more kinds of arbitrary suitable additives may be contained in a protective film. Examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a mold release agent, a color inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, a colorant and the like. The content of the thermoplastic resin in the protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. When the content of the thermoplastic resin in the protective film is 50% by weight or less, the high transparency inherent in the thermoplastic resin may not be sufficiently exhibited.

As the protective film, a retardation film, a brightness improving film, a diffusion film and the like can also be used.

The thickness of the protective film can be appropriately determined, but is generally preferably 5 to 50 μm, more preferably 5 to 45 μm, from the viewpoints of workability such as strength and handleability, and thin layer property. Is preferable.

A functional layer such as a hard coat layer, an antireflection layer, a sticking prevention layer, a diffusion layer or an antiglare layer can be provided on the surface of the protective film to which the polarizer is not adhered. The functional layers such as the hard coat layer, the antireflection layer, the sticking prevention layer, the diffusion layer and the antiglare layer can be provided on the protective film itself, or may be separately provided separately from the protective film. it can.

<Intervening layer>
The protective film and the polarizer are laminated via an intervening layer such as an adhesive layer, an adhesive layer, and an undercoat layer (primer layer). At this time, it is desirable that both are laminated without an air gap by an intervening layer. Note that also in FIG. 2, the intervening layer between the polarizer 1a and the protective film 1b is not shown.

The adhesive layer is formed by the adhesive. The type of adhesive is not particularly limited, and various adhesives can be used. The adhesive layer is not particularly limited as long as it is optically transparent, and various forms such as water-based, solvent-based, hot-melt-based, and active energy ray-curable type are used as the adhesive. Alternatively, an active energy ray-curable adhesive is suitable.

Examples of the water-based adhesive include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl-based latex-based adhesives, and water-based polyesters. The water-based adhesive is usually used as an adhesive composed of an aqueous solution, and usually contains 0.5 to 60% by weight of a solid content.

The active energy ray-curable adhesive is an adhesive whose curing proceeds by active energy rays such as electron beam and ultraviolet rays (radical curing type, cationic curing type). For example, in the form of electron beam curing type and ultraviolet curing type. Can be used. As the active energy ray-curable adhesive, for example, a photoradical curable adhesive can be used. When a photoradical-curable active energy ray-curable adhesive is used as an ultraviolet curable type, the adhesive contains a radical-polymerizable compound and a photopolymerization initiator.

The adhesive coating method is appropriately selected depending on the viscosity of the adhesive and the desired thickness. Examples of the coating method include a reverse coater, a gravure coater (direct, reverse and offset), a bar reverse coater, a roll coater, a die coater, a bar coater, a rod coater and the like. In addition, a method such as a dipping method can be appropriately used for coating.

Further, when an aqueous adhesive or the like is used, the coating of the adhesive is preferably performed so that the thickness of the finally formed adhesive layer is 30 to 300 nm. The thickness of the adhesive layer is more preferably 60 to 150 nm. On the other hand, when an active energy ray-curable adhesive is used, it is preferable that the thickness of the adhesive layer is 0.2 to 20 μm.

When laminating the polarizer and the protective film, an easy-adhesion layer can be provided between the protective film and the adhesive layer. The easy-adhesion layer can be formed of, for example, various resins having a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a silicone-based, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, and the like. These polymer resins may be used alone or in combination of two or more. Further, other additives may be added to form the easy-adhesion layer. Specifically, a tackifier, an ultraviolet absorber, an antioxidant, a stabilizer such as a heat-resistant stabilizer, or the like may be used.

The pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive. Various adhesives can be used as the adhesive, for example, rubber adhesive, acrylic adhesive, silicone adhesive, urethane adhesive, vinyl alkyl ether adhesive, polyvinylpyrrolidone adhesive, poly. Examples include acrylamide-based adhesives and cellulose-based adhesives. A sticky base polymer is selected according to the type of the pressure-sensitive adhesive. Among the above-mentioned pressure-sensitive adhesives, acrylic pressure-sensitive adhesives are preferably used because they are excellent in optical transparency, exhibit appropriate wettability, cohesiveness, and adhesiveness, and are excellent in weather resistance and heat resistance. To.

The undercoat layer (primer layer) is formed to improve the adhesion between the polarizer and the protective film. The material constituting the primer layer is not particularly limited as long as it is a material that exhibits a certain degree of strong adhesion to both the base film and the polyvinyl alcohol-based resin layer. For example, a thermoplastic resin having excellent transparency, thermal stability, stretchability, etc. is used. Examples of the thermoplastic resin include acrylic resins, polyolefin resins, polyester resins, polyvinyl alcohol resins, and mixtures thereof.

<First adhesive layer>
An appropriate pressure-sensitive adhesive can be used for forming the first pressure-sensitive adhesive layer, and the type thereof is not particularly limited. As adhesives, rubber adhesives, acrylic adhesives, silicone adhesives, urethane adhesives, vinyl alkyl ether adhesives, polyvinyl alcohol adhesives, polyvinylpyrrolidone adhesives, polyacrylamide adhesives, Examples include cellulose-based adhesives.

Among these adhesives, those having excellent optical transparency, exhibiting appropriate wettability, cohesiveness and adhesiveness, and excellent weather resistance and heat resistance are preferably used. Acrylic adhesives are preferably used to exhibit such characteristics.

As a method of forming the first pressure-sensitive adhesive layer, for example, the pressure-sensitive adhesive is applied to a release-treated film (separator or the like), and a polymerization solvent or the like is dried and removed to form a pressure-sensitive adhesive layer, and then a polarizing film is formed. It is produced by a method of transferring to a polarizing film, or a method of applying the pressure-sensitive adhesive to a polarizing film and drying and removing a polymerization solvent or the like to form a pressure-sensitive adhesive layer on the polarizing film. When applying the pressure-sensitive adhesive, one or more solvents other than the polymerization solvent may be newly added as appropriate.

A silicone release liner is preferably used as the release film that has been peeled off. In the step of applying the pressure-sensitive adhesive of the present invention on such a liner and drying it to form a pressure-sensitive adhesive layer, as a method of drying the pressure-sensitive adhesive, an appropriate method can be appropriately adopted depending on the purpose. Preferably, a method of overheating and drying the coating film is used. The heating and drying temperature is preferably 40 ° C. to 200 ° C., more preferably 50 ° C. to 180 ° C., and particularly preferably 70 ° C. to 170 ° C. By setting the heating temperature in the above range, a pressure-sensitive adhesive having excellent adhesive properties can be obtained.

As the drying time, an appropriate time can be adopted as appropriate. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, and particularly preferably 10 seconds to 5 minutes.

As a method for forming the pressure-sensitive adhesive layer, various methods are used. Specifically, for example, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, die coater, etc. Examples include a method such as an extrusion coating method.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and is, for example, about 1 to 100 μm. It is preferably 2 to 50 μm, more preferably 2 to 40 μm, and even more preferably 5 to 35 μm.

<Release film>
The release film protects the first pressure-sensitive adhesive layer until it is put into practical use. Examples of the constituent materials of the release film include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films, porous materials such as paper, cloth, and non-woven fabrics, nets, foam sheets, metal foils, and laminates thereof. An appropriate thin leaf body can be mentioned, but a plastic film is preferably used because of its excellent surface smoothness.

The plastic film is not particularly limited as long as it can protect the pressure-sensitive adhesive layer, and for example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, and vinyl chloride are all used. Examples thereof include polymer films, polyethylene terephthalate films, polybutylene terephthalate films, polyurethane films, and ethylene-vinyl acetate copolymer films.

The release film has
If necessary, mold release and antifouling treatment with silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based mold release agent, silica powder, etc., and antistatic treatment such as coating type, kneading type, vapor deposition type, etc. You can also do it. In particular, the peelability from the first pressure-sensitive adhesive layer can be further enhanced by appropriately performing a peeling treatment such as a silicone treatment, a long-chain alkyl treatment, or a fluorine treatment on the surface of the release film.

The thickness of the release film is usually preferably 5 to 200 μm, more preferably 5 to 100 μm, still more preferably 20 to 90 μm. As shown in FIG. 3, the thickness of the release film is such that the distance x between the virtual center surface f and the surface protective film and the distance y between the virtual center surface f and the release film are xy>-. It is preferable to design the thickness to be larger than the thickness of the surface protective film described later so that the relationship of 20 is obtained. When the thickness of the release film is larger than the thickness of the surface protective film, the difference between the thickness of the release film and the thickness of the surface protective film is preferably 5 to 70 μm, more preferably 7 to 65 μm. It is preferable, and more preferably 10 to 60 μm.

<Surface protection film>
The surface protective film is provided on one side of the polarizing film (the side on which the first pressure-sensitive adhesive layer is not laminated) in the optical film to protect the polarizing film.

As the base film of the surface protective film, a film material having isotropic or nearly isotropic is selected from the viewpoint of inspectability and controllability. Examples of the film material include polyester resins such as polyethylene terephthalate films, cellulose resins, acetate resins, polyether sulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, and acrylic resins. Examples include transparent polymers such as resins. Of these, polyester-based resins are preferable. The base film can be used as a laminate of one or more film materials, or a stretched product of the film can also be used. The thickness of the base film is designed to satisfy the above-mentioned xy> -20 relationship. The thickness of the base film is generally 10 to 150 μm, preferably 20 to 100 μm.

As the surface protective film, the base film can be used as a self-adhesive type film, and a film having the base film and the second pressure-sensitive adhesive layer can be used. From the viewpoint of protecting the polarizing film, it is preferable to use a surface protective film having a second pressure-sensitive adhesive layer.

The second pressure-sensitive adhesive layer used for laminating the surface protective film is based on, for example, a (meth) acrylic polymer, a silicone-based polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based polymer, or a rubber-based polymer. The pressure-sensitive adhesive can be appropriately selected and used. From the viewpoint of transparency, weather resistance, heat resistance and the like, an acrylic pressure-sensitive adhesive using an acrylic polymer as a base polymer is preferable. The thickness (dry film thickness) of the second pressure-sensitive adhesive layer is determined according to the required adhesive strength. It is usually about 1 to 100 μm, preferably 5 to 50 μm.

The surface protective film (the surface opposite to the second pressure-sensitive adhesive layer, if provided) is provided with a release-treated layer using a low-adhesive material such as a silicone treatment, a long-chain alkyl treatment, or a fluorine treatment. Can be done. The thickness of the surface protective film is the total thickness of the base film, the second pressure-sensitive adhesive layer, and the peeling treatment layer.

<Release film release>
The optical film is prepared in a sheet-fed state having a predetermined shape (step (1)). Examples of the predetermined shape include a rectangular object. Next, the release film is peeled off from the optical film (step (2)). When peeling the release film, the surface protective film side of the optical film is fixed by, for example, adsorption, and the release film can be peeled off using a release roller or the like (for example, JP-A-9-). See 114384, etc.).

<Manufacturing of optical display panel>
The optical film (optical film with an adhesive layer having a surface protective film) from which the release film has been peeled off by the above step (1) and then the step (2) is bonded to one surface of the optical cell by the step (3). .. In the step (3), the side of the first pressure-sensitive adhesive layer of the optical film is bonded to the optical film to manufacture an optical display panel.

<Other optical layers>
The optical film of the present invention can be used by being laminated with another optical layer in practical use. The optical layer is not particularly limited, but for example, a liquid crystal display device such as a reflector, a semitransparent plate, a retardation plate (including a wave plate such as 1/2 or 1/4), a viewing angle compensation film, and a brightness improving film. One or two or more optical layers that may be used for forming the above can be used.

The optical film in which the above optical layers are laminated can also be formed by a method of sequentially and separately laminating them in the manufacturing process of a liquid crystal display device or the like, but those which are laminated in advance to form an optical film have high quality stability. It is excellent in assembly work and has the advantage of being able to improve the manufacturing process of liquid crystal display devices and the like. An appropriate adhesive means such as an adhesive layer can be used for laminating. When adhering the above-mentioned polarizing film with an adhesive layer or other optical film, the optical axes thereof can be arranged at an appropriate arrangement angle according to a target phase difference characteristic or the like.

<Optical cell>
(Liquid crystal cell, LCD display panel)
The liquid crystal cell has a configuration in which a liquid crystal layer is sealed between a pair of substrates (first substrate (visual side surface) Pa, second substrate (back surface) Pb) arranged to face each other. Any type of liquid crystal cell can be used, but in order to realize high contrast, it is preferable to use a liquid crystal cell in vertical orientation (VA) mode or in-plane switching (IPS) mode. The liquid crystal display panel is formed by laminating a polarizing film on one side or both sides of a liquid crystal cell, and a drive circuit is incorporated as needed.

An appropriate liquid crystal display device such as a liquid crystal display device in which optical films are arranged on one side or both sides of the liquid crystal cell, or a lighting system using a backlight or a reflector can be formed. In that case, the optical film of the present invention can be installed on one side or both sides of the liquid crystal cell. When the optical films of the present invention are provided on both sides, they may be the same or different. Further, when forming the liquid crystal display device, for example, an appropriate component such as a diffuser plate, an anti-glare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffuser plate, and a backlight is placed in one layer or at an appropriate position. Two or more layers can be arranged.

(Organic EL cell, organic EL display panel)
The organic EL cell as another optical cell has a configuration in which an electroluminescent layer is sandwiched between a pair of electrodes. As the organic EL cell, for example, any type such as a top emission method, a bottom emission method, and a double emission method can be used. In the organic EL display panel, the optical film (polarizing film) of the present invention is attached to the organic EL cell together with the retardation film, and a drive circuit is incorporated as needed.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to the examples shown below. In addition, each part and% in each example is based on weight. All the conditions for leaving at room temperature, which are not specified below, are 23 ° C. and 65% RH.

<Manufacturing of polarizing film>
(Making a polarizer)
Amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) having a water absorption rate of 0.75% and a Tg of 75 ° C. Corona treatment is applied to one side of the base material, and polyvinyl is applied to this corona treated surface. Alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (degree of polymerization 1200, degree of acetoacetyl modification 4.6%, degree of saponification 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd. , Trade name "Gosefimer Z200") at a ratio of 9: 1 was applied and dried at 25 ° C. to form a PVA-based resin layer having a thickness of 11 μm to prepare a laminate.
The obtained laminate was uniaxially stretched at the free end in the longitudinal direction (longitudinal direction) 2.0 times between rolls having different peripheral speeds in an oven at 120 ° C. (aerial auxiliary stretching treatment).
Next, the laminate was immersed in an insolubilizing bath at a liquid temperature of 30 ° C. (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Next, the polarizing plate was immersed in a dyeing bath having a liquid temperature of 30 ° C. while adjusting the iodine concentration and the immersion time so that the polarizing plate had a predetermined transmittance. In this example, 0.2 parts by weight of iodine was mixed with 100 parts by weight of water, and 1.0 part by weight of potassium iodide was mixed and immersed in the obtained iodine aqueous solution for 60 seconds (dyeing treatment). ..
Next, it was immersed in a cross-linked bath at a liquid temperature of 30 ° C. (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds. (Crossing treatment).
Then, the laminate is immersed in an aqueous solution of boric acid having a liquid temperature of 70 ° C. (an aqueous solution obtained by blending 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water). However, uniaxial stretching was performed between rolls having different peripheral speeds so that the total stretching ratio was 5.5 times in the longitudinal direction (longitudinal direction) (underwater stretching treatment).
Then, the laminate was immersed in a washing bath at a liquid temperature of 30 ° C. (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).
From the above, an optical film laminate containing a polarizer having a thickness of 5 μm was obtained.

(Protective film A)
Protective film A: A (meth) acrylic resin film having a lactone ring structure having a thickness of 40 μm was used after being subjected to corona treatment on the easily adhesive-treated surface.

(Protective film B)
Protective film B: A (meth) acrylic resin film having a lactone ring structure having a thickness of 20 μm was used after being subjected to corona treatment on the easily adhesive-treated surface.

(Adhesive applied to protective films A and B)
An ultraviolet curable adhesive was prepared by mixing 40 parts by weight of N-hydroxyethylacrylamide (HEAA), 60 parts by weight of acryloyl morpholine (ACMO), and 3 parts by weight of the photoinitiator "IRGACURE 819" (manufactured by BASF).

<Manufacturing of single protective polarizing film A>
After applying the ultraviolet curable adhesive to the surface of the polarizer of the optical film laminate so that the thickness of the adhesive layer after curing is 1 μm, the protective film A is attached.
The adhesive was cured by irradiating it with ultraviolet rays as active energy rays. For ultraviolet irradiation, gallium-filled metal halide lamp, irradiation device: Fusion UV Systems, Light HAMMER10 manufactured by Inc., valve: V valve, peak illuminance: 1600 mW / cm ² , cumulative irradiation amount 1000 / mJ / cm ² (wavelength 380 to 440 nm). ), And the illuminance of ultraviolet rays was measured using a Solar-Check system manufactured by Solartell. Next, the amorphous PET substrate was peeled off to prepare a single-protective polarizing film A using a thin polarizing element. The optical characteristics of the obtained single-protection polarizing film A were a simple substance transmittance of 42.8% and a degree of polarization of 99.99%. The thickness of the obtained single-protective polarizing film is 46 μm.

<Making a single protective polarizing film B>
In the production of the single protective polarizing film A, a single protective polarizing film B was obtained except that the protective film B was used instead of the protective film A for the polarizer (the side from which the amorphous PET substrate was peeled off). It was. The optical characteristics of the obtained single-protection polarizing film B were a simple substance transmittance of 42.8% and a degree of polarization of 99.99%. The thickness of the obtained single-protective polarizing film is 26 μm.

<Making both protective polarizing films C>
The protective film A was attached to the polarizer of the single protective polarizing film A (the side from which the amorphous PET substrate was peeled off) via an ultraviolet curable adhesive in the same manner as described above. The optical characteristics of the obtained both protective polarizing films C were a transmittance of 42.8% and a degree of polarization of 99.99%. The thickness of the polarizing film C is 87 μm.

<Preparation of adhesive>
100 parts of butyl acrylate, 3 parts of acrylate, 0.1 part of 2-hydroxyethyl acrylate and 2,2'-azobisisobuty in a reaction vessel equipped with a cooling tube, nitrogen introduction tube, thermometer and stirrer. 0.3 part of ronitrile was added together with ethyl acetate to prepare a solution. Next, the solution was stirred while blowing nitrogen gas and reacted at 55 ° C. for 8 hours to obtain a solution containing an acrylic polymer having a weight average molecular weight of 2.2 million. Further, ethyl acetate was added to the solution containing the acrylic polymer to obtain an acrylic polymer solution having a solid content concentration adjusted to 30%.

A cross-linking agent containing 0.5 part of a compound having an isocyanate group as a main component with respect to 100 parts of the solid content of the acrylic polymer solution (manufactured by Nippon Polyurethane Co., Ltd., trade name "Coronate L"). And 0.075 parts of γ-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Industry Co., Ltd., trade name “KMB-403”) are blended in this order as a silane coupling agent to prepare an adhesive solution. Was prepared.

Example 1
<Lamination of surface protection film>
A surface protective film was provided on the protective film side of the single protective polarizing film A. As the surface protective film, a polyester resin film (base film) having a thickness of 38 μm and having a product name of RP207 manufactured by Nitto Denko Corporation was used. The surface protective film has a pressure-sensitive adhesive layer (corresponding to a second pressure-sensitive adhesive layer) having a thickness of 15 μm.

<Formation of adhesive layer with release film>
The above pressure-sensitive adhesive solution is applied to the surface of a release film (separator) made of a stripped polyethylene terephthalate film (thickness 38 μm) so that the thickness after drying is 20 μm, dried, and the pressure-sensitive adhesive layer (thickness 38 μm) is applied. (Corresponding to the first pressure-sensitive adhesive layer) was formed. Next, the pressure-sensitive adhesive layer is attached to the side of the polarizer of the one-side protection polarizing film A having a surface protection film, and the optical film of the present invention (polarizing film with a pressure-sensitive adhesive layer having a release film and a surface protection film). Was produced.

Examples 2-5, Comparative Examples 1-7, Reference Examples 1 and 2
In Example 1, the release film was obtained in the same manner as in Example 1 except that the type of the polarizing film, the thickness of the base film of the surface protective film, and the thickness of the release film were changed as shown in Table 1. And a polarizing film with an adhesive layer having a surface protective film was prepared.

The polarizing film with an adhesive layer having the release film and the surface protective film obtained in the above Examples, Comparative Examples and Reference Examples was evaluated as follows. The results are shown in Table 1.

In Table 1, the distances x and y shown in FIG. 3 were calculated from the total thickness of the polarizing film with the pressure-sensitive adhesive layer having the release film and the surface protective film and the thickness of each member. For the virtual center surface f, a value that is half of the total thickness is described.

<Elemental transmittance T and degree of polarization P of the polarizer>
The single transmittance T and the degree of polarization P of the obtained polarizing film were measured using a spectral transmittance measuring device with an integrating sphere (Dot-3c of Murakami Color Technology Laboratory).
The degree of polarization P is the transmittance (parallel transmittance: Tp) when two identical polarizing films are overlapped so that their transmission axes are parallel, and the two transmission axes are overlapped so as to be orthogonal to each other. It is obtained by applying the combined transmittance (orthogonal transmittance: Tc) to the following equation. Polarization degree P (%) = {(Tp-Tc) / (Tp + Tc)} ^1/2 × 100
Each transmittance is shown by a Y value whose luminosity factor is corrected by a 2 degree field of view (C light source) of JIS Z8701 with 100% of completely polarized light obtained through a Granteller prism polarizer.

<Measurement of peeling force>

Regarding the polarizing film with an adhesive layer having the release film and the surface protective film obtained in Examples, Comparative Examples and Reference Examples, 25 mm × 100 mm (absorption axis direction is 25 mm) and 100 mm × 25 mm (absorption axis direction is 100 mm). After peeling off the release film and the surface protection film on the side where the peeling force is not measured, use double-sided tape (Nitto Denko Co., Ltd., double-sided tape No. 511) to make each 0.5 mm thick non-alkali It was pasted on the glass. A cellophane tape is attached to the short side edge of the polarizing film with an adhesive layer attached to non-alkali glass, and only the start part is peeled off in advance, and then the release film or surface protection film is peeled 180 ° using Tencilon. The film was peeled parallel to the long side of the film at a speed of 0.3 m / min. The peeling force was measured at each of 15 mm × 100 mm (absorption axis direction is 10 mm) and 100 mm × 15 mm (absorption axis direction is 100 mm), and the average value was adopted.
The release force of the release film was 0.16 N / 25 mm in each case.
The peeling force of the surface protective film was 0.09 N / 25 mm in each case.

<Peeling test>
The polarizing film with an adhesive layer having the release film and the surface protective film obtained in Examples, Comparative Examples and Reference Examples was cut into 5 mm × 15 mm to obtain a single-wafered state (sample).
The surface protective film side of the sample was fixed on the glass with double-sided tape (double-sided tape No. 511 manufactured by Nitto Denko KK) with the release film side of the sample on the upper side and the surface protective film side on the lower side. .. Next, the release film was peeled off from the edge edge in parallel with the diagonal direction of the sample by hand peeling at an angle of 90 ° using a pickup tape (manufactured by Nitto Denko KK, masking tape No. 720), and according to the following criteria. evaluated.
〇: Only the release film was peeled off.
X: Peeled off at the interface between the surface protective film and the polarizing film.
The peeling was performed 5 times, and the number of times of ◯ was shown as the number of times / n5.

In Comparative Example 7, since the virtual center surface f is inside the surface protective film, the value of the distance x is described as “−”.

F Single-wafered optical film 1, 1'Polarizing film 1a Polarizer 1b Protective film 2 First adhesive layer 3 Release film 4, 4'Surface protective film 41 Base film 42 Second adhesive layer

Claims (12)

A single-wafer optical film in which a release film, a first pressure-sensitive adhesive layer, a polarizing film, and a surface protective film are laminated in this order.
The polarizing film has a thickness of 60 μm or less and has a thickness of 60 μm or less.
When the plane direction of the intermediate position in the total thickness of the optical film is the virtual center plane f,
The distance x (μm) between the virtual center surface f and the surface protective film and the distance y (μm) between the virtual center surface f and the release film are characterized in that xy> -20. Optical film. The optical film according to claim 1, wherein the distance x (μm) and the distance y have a relationship of xy> -10. The optical film according to claim 1 or 2, wherein the release force (1) of the release film is larger than the release force (2) of the surface protective film. The optical film according to any one of claims 1 to 3, wherein the virtual central surface f is on the first pressure-sensitive adhesive layer or a polarizing film. The optical film according to any one of claims 1 to 4, wherein the thickness of the release film is larger than the thickness of the surface protective film. The invention according to any one of claims 1 to 5, wherein the surface protective film has a base film and a second pressure-sensitive adhesive layer, and is laminated on the polarizing film via the second pressure-sensitive adhesive layer. Optical film. The optical film according to any one of claims 1 to 5, wherein the surface protective film is a self-adhesive film. The optical film according to any one of claims 1 to 7, wherein the polarizing film has a polarizing element having a thickness of 10 μm or less. The optical film according to any one of claims 1 to 8, wherein the polarizing film is a single protective polarizing film having a protective film on only one side of the polarizer. A method for peeling a release film, which comprises peeling the release film from the optical film according to any one of claims 1 to 9. The step (1) of preparing the optical film according to any one of claims 1 to 9.
The step (2) of peeling the release film from the optical film, and
A method for manufacturing an optical display panel, comprising a step (3) of bonding the side of the first pressure-sensitive adhesive layer of the optical film from which the release film has been peeled off to one surface of an optical cell. The method for manufacturing an optical display panel according to claim 11, wherein the optical cell is a liquid crystal cell or an organic EL cell.