JP7334024B2 - Optical film and optical display panel - Google Patents

Description

The present invention relates to optical films and optical display panels.

There is a method of attaching a sheet-shaped polarizing film to an optical cell (hereinafter also referred to as a “sheet-to-panel method”) (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2006-039238 Japanese Patent Application Laid-Open No. 2009-062108

In recent years, as optical display panels have become thinner, polarizing films that are thinner than conventional ones (for example, with a thickness of 60 μm or less) are being developed. A polarizing film that is thinner than conventional films has a low stiffness (modulus of elasticity) and tends to be twisted and curled. Therefore, when the polarizing film is thin, technical improvements have been made over the years, but in the sheet-to-panel method, transportation of the polarizing film, peeling of the release film, and liquid crystal cell of the polarizing film piece It is difficult to handle such as bonding to the substrate, and there is concern that the yield may decrease.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a sheet-shaped optical film that enables the production of an optical display panel using a thin polarizing film even by the sheet-to-panel method. With the goal.

The present invention provides an optical film having a configuration in which a release film, an 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,
The thickness of the surface protective film satisfies the relational expression of 0.8≦(thickness of surface protective film)/(thickness of polarizing film).

According to this configuration, although the polarizing film is thin, the surface protective film is thick (specifically, 0.8 ≤ (thickness of surface protective film) / (thickness of polarizing film)), so the optical film The stiffness (modulus of elasticity) is strengthened, and the handleability of the polarizing film in the sheet-to-panel system can be improved. Therefore, by using the sheet-to-panel method, it is possible to suitably manufacture an optical display panel to which a thin polarizing film is bonded.

As one embodiment of the above invention, the thickness of the surface protective film satisfies (thickness of surface protective film)/(thickness of polarizing film)≦3.0. The surface protective film needs to be peeled off from the optical display panel in the next assembly process. “Trigger peeling”, which is the action of grasping and starting to peel, becomes heavy. As a result, when peeling the surface protective film from the optical display panel, delamination of the optical film (for example, peeling between the polarizer and the polarizer protective film, peeling between the adhesive layer and the polarizing film, adhesion delamination between the agent layer and the optical cell). Therefore, by controlling the thickness of the surface protective film so as to satisfy (thickness of the surface protective film) / (thickness of the polarizing film) ≤ 3.0, the trigger peelability of the surface protective film is improved, and the interlayer separation of the optical film is improved. Peeling can be suppressed.

As one embodiment of the above invention, the surface protective film is laminated on a polarizing film via a second pressure-sensitive adhesive layer. Moreover, as another embodiment, the protective film is a self-adhesive film.

As one embodiment of the invention, the polarizing film includes a polarizer having a thickness of 10 μm or less. A polarizing film containing such a polarizer having a thickness of 10 μm or less has a remarkably low stiffness (elastic modulus). As a result, there is a high possibility that twisting, curling, and the like will occur in the sheet-to-panel system. Therefore, the present invention is particularly suitable for the polarizing film.

As an embodiment of the above invention, the release film is peeled off, and the adhesive layer, the polarizing film, and the surface protective film are laminated in this order on one side of the optical cell for manufacturing an optical display panel. be done.

Another invention is an optical display panel having a configuration in which an adhesive layer, a polarizing film and a surface protective film are laminated in this order on one side of an optical cell,
The polarizing film has a thickness of 60 μm or less,
The surface protective film is an optical display panel having a thickness satisfying 0.8≦(thickness of surface protective film)/(thickness of polarizing film).

As one embodiment of the above invention, the thickness of the surface protective film satisfies (thickness of surface protective film)/(thickness of polarizing film)≦3.0.

As one embodiment of the above invention, the optical cell is a liquid crystal cell or an organic EL cell.

Cross-sectional schematic diagram of an optical film in a sheet state Schematic cross-sectional view of an optical film in a sheet state according to another embodiment Schematic perspective view of a sheet-fed optical film attached to an optical cell

The optical film 10 of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic cross-sectional view of an optical film 10. FIG. The optical film 10 has a configuration in which a release film 15, a first adhesive layer 11, a polarizing film 12, a second adhesive layer 13 and a surface protection film 14 are laminated in this order.

In another embodiment shown in FIG. 2, the surface protection film 14 is composed of a self-adhesive film and laminated on the polarizing film 12 without an adhesive layer interposed therebetween.

<Polarizing film>
In the present invention, a polarizing film having a thickness of 60 μm or less is used. The thickness of the polarizing film is preferably 55 μm or less, more preferably 50 μm or less, from the viewpoint of thinning. As the polarizing film, for example, (1) a configuration in which protective films are laminated on both sides of the polarizer in this order (both protective polarizing films), (2) a configuration in which a protective film is laminated only on one side of the polarizer ( single protective polarizing film) and the like.

(Polarizer)
A polarizer using a polyvinyl alcohol-based resin is used. As a polarizer, for example, hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films are coated with dichroic dyes such as iodine and dichroic dyes. Polyene-based oriented films such as those obtained by adsorbing a substance and uniaxially stretched, polyvinyl alcohol dehydrated products, polyvinyl chloride dehydrochlorinated products, and the like can be mentioned. Among these, a polarizer composed of a polyvinyl alcohol-based film and a dichroic substance such as iodine is suitable.

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 to 3 to 7 times its original length. If necessary, it may contain boric acid, zinc sulfate, zinc chloride, or the like, or it may be immersed in an aqueous solution of potassium iodide or the like. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed with water before dyeing. By washing the polyvinyl alcohol film with water, dirt and anti-blocking agents on the surface of the polyvinyl alcohol film can be washed away, and by swelling the polyvinyl alcohol film, uneven dyeing and other unevenness can be prevented. be. Stretching may be performed after dyeing with iodine, stretching may be performed while dyeing, or dyeing with iodine may be performed after stretching. It can also be stretched in an aqueous solution of 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 preferably 7 μm or less, 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 polarizer has little unevenness in thickness, is excellent in visibility, and has little dimensional change, so is excellent in durability against thermal shock.

On the other hand, a polarizing film containing a polarizer having a thickness of 10 μm or less has a remarkably low stiffness (elastic modulus), and therefore is highly likely to be twisted or curled in the sheet-to-panel system. Therefore, the present invention is particularly suitable for the polarizing film.

As a thin polarizer, typically,
Patent No. 4751486,
Patent No. 4751481 specification,
Patent No. 4815544 specification,
Patent No. 5048120,
WO 2014/077599 pamphlet,
International Publication No. 2014/077636,
and the like, or thin polarizers obtained from the production methods described therein.

The polarizer has optical characteristics represented by the single transmittance T and the degree of polarization P of the following formula: P>−(10 ^{0.929T−42.4} −1)×100 (where T<42.3), or
It is preferable to be configured to satisfy the condition of P≧99.9 (where 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 luminance is 500 cd/m ² or more. As another application, for example, it is attached to the viewing side of an organic EL cell.

As for the thin polarizer, among the production methods including the step of stretching and the step of dyeing in the state of a laminate, it is possible to stretch at a high magnification and improve the polarization performance. 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 preferred, particularly Japanese Patent No. 4751481 and Japanese Patent No. 4815544. It is preferably obtained by a manufacturing method including a step of auxiliary stretching in the air before stretching in a boric acid aqueous solution. These thin polarizers can be obtained by a manufacturing method including a step of stretching a polyvinyl alcohol-based resin (hereinafter also referred to as a PVA-based resin) layer and a stretching resin substrate in a laminate 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 substrate.

(Protective film)
As a material for forming the protective film, a material excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, etc. is 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 styrenes such as polystyrene and acrylonitrile-styrene copolymer (AS resin). type polymer, polycarbonate type polymer, and the like. In addition, polyethylene, polypropylene, polyolefins having a cyclo- or norbornene structure, polyolefin-based polymers such as ethylene/propylene copolymers, vinyl chloride-based polymers, amide-based polymers such as nylon and aromatic polyamides, imide-based polymers, and sulfone-based polymers , polyethersulfone-based polymer, polyetheretherketone-based polymer, polyphenylene sulfide-based polymer, vinyl alcohol-based polymer, vinylidene chloride-based polymer, vinyl butyral-based polymer, arylate-based polymer, polyoxymethylene-based polymer, epoxy-based polymer, or the above Blends of polymers are also examples of polymers that form the protective film.

In addition, one or more types of arbitrary appropriate additives may be contained in the protective film. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, and colorants. The content of the thermoplastic resin in the transparent 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. . If the content of the thermoplastic resin in the transparent 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 enhancement film, a diffusion film, or the like can be used.

The thickness of the protective film is preferably 5 to 50 μm or less, more preferably 5 to 45 μm, from the viewpoints of strength, workability such as handleability, and thinness.

A functional layer such as a hard coat layer, an antireflection layer, an antisticking 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, antireflection layer, anti-sticking layer, diffusion layer, and antiglare layer can be provided on the transparent protective film itself, or can be provided separately from the transparent protective film. can also

(Intervening layer)
The protective film and the polarizer are laminated via an intervening layer such as an adhesive layer, pressure-sensitive adhesive layer, or undercoat layer (primer layer). At this time, it is desirable to laminate both without an air gap by an intervening layer.

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

Examples of water-based adhesives include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl-based latex-based adhesives, and water-based polyesters. A water-based adhesive is usually used as an adhesive consisting of an aqueous solution, and usually contains 0.5 to 60% by weight of solids.

Active energy ray-curable adhesives are adhesives that are cured by active energy rays such as electron beams and ultraviolet rays (radical curing type, cationic curing type). can be used. For 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 adhesive, the adhesive contains a radically polymerizable compound and a photopolymerization initiator.

In laminating the polarizer and the protective film, an easily adhesive layer can be provided between the transparent protective film and the adhesive layer. The easy-adhesion layer can be formed of various resins having, for example, a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a silicone system, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, or the like. These polymer resins can be used singly or in combination of two or more. Other additives may be added to form the easy-adhesion layer. More specifically, stabilizers such as tackifiers, ultraviolet absorbers, antioxidants, and heat stabilizers may be used.

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

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

<Surface protection film>
The surface protection film is provided on one side of the polarizing film (the side on which the pressure-sensitive adhesive layer is not laminated) in the optical film to protect the polarizing film. The thickness of the surface protective film satisfies 0.8≦(thickness of the surface protective film)/(thickness of the polarizing film), which can improve the handleability of the optical film in the sheet-to-panel system. The surface protective film preferably satisfies 1.0≦(thickness of surface protective film)/(thickness of polarizing film) from the viewpoint of increasing the stiffness (modulus of elasticity) of the entire optical film.
On the other hand, the thicker the surface protective film, the heavier the "trigger peeling" when peeling the surface protective film from the optical display panel (the peelability deteriorates), which may cause delamination of the optical film. The surface protective film preferably satisfies (thickness of protective film/thickness of polarizing film)≦3.0, and more preferably satisfies (thickness of protective film/thickness of polarizing film)≦2.5.

The surface protective film is laminated on the polarizing film via an adhesive layer, or is composed of a self-adhesive film and is laminated on the polarizing film without an adhesive layer, but protects the polarizing film. From the point of view, it is preferable to be laminated on the polarizing film via the pressure-sensitive adhesive layer (Fig. 1). As the surface protection film, an isotropic or nearly isotropic film material is selected from the viewpoint of inspection and management. Examples of film materials include polyester resins such as polyethylene terephthalate film, cellulose resins, acetate resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, and acrylic resins. Examples include transparent polymers such as resins. Among these, polyester-based resins are preferred. The surface protective film may be used as a laminate of one or more film materials, or may be a stretched product of the film. The thickness of the surface protective film is not particularly limited as long as 0.8≦(thickness of surface protective film)/(thickness of polarizing film) is satisfied. is preferably 100 μm or less.

Adhesives used for lamination of surface protective films include (meth)acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethers, and adhesives based on polymers such as fluorine-based and rubber-based polymers. can be selected and used. From the viewpoint of transparency, weather resistance, heat resistance, etc., an acrylic pressure-sensitive adhesive having an acrylic polymer as a base polymer is preferable. The thickness (dry film thickness) of the 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 protection film may be provided with a peeling treatment layer on the surface opposite to the surface on which the pressure-sensitive adhesive layer is provided, using a low-adhesion material such as silicone treatment, long-chain alkyl treatment, fluorine treatment, or the like.

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

Among these pressure-sensitive adhesives, those having excellent optical transparency, appropriate wettability, cohesiveness, and adhesion properties, and excellent weather resistance and heat resistance are preferably used. Acrylic pressure-sensitive adhesives are preferably used as those exhibiting such characteristics.

As a method for forming the adhesive layer, for example, the adhesive is applied to a release film (separator or the like) that has been subjected to release treatment, and the polymerization solvent or the like is dried and removed to form an adhesive layer. In the embodiment of the polarizer (or the transparent protective film in the embodiment of FIG. 2 (B)), or the method of transferring to the polarizer in the embodiment of FIG. 2 (A) (or the transparent protective film in the embodiment of FIG. 2 (B)) It is prepared by a method of applying the above-mentioned adhesive, drying and removing the polymerization solvent, etc. to form an adhesive layer on the polarizer, etc. In addition, when applying the adhesive, one or more types of solvent other than the polymerization solvent may be used as appropriate. Fresh solvent may be added.

A silicone release liner is preferably used as the release-treated release film. 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 for drying the pressure-sensitive adhesive, an appropriate method can be appropriately adopted depending on the purpose. Preferably, a method of drying the coating film by heating is used. The drying temperature is preferably 40°C to 200°C, more preferably 50°C to 180°C, and particularly preferably 70°C to 170°C. A pressure-sensitive adhesive having excellent adhesive properties can be obtained by setting the heating temperature within the above range.

An appropriate drying time can be adopted as appropriate. The drying time is preferably 5 seconds to 2
0 minute, more preferably 5 seconds to 10 minutes, particularly preferably 10 seconds to 5 minutes.

Various methods are used as a method for forming the pressure-sensitive adhesive layer. Specifically, for example, roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, die coater, etc. A method such as an extrusion coating method can be used.

The thickness of the 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, even more preferably 5 to 35 μm.

<Release film>
The release film protects the pressure-sensitive adhesive layer until practical use. Materials constituting the release film include, for example, plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films, porous materials such as paper, cloth, and nonwoven fabric, nets, foam sheets, metal foils, laminates thereof, and the like. However, 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. Examples include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride Examples include polymer films, polyethylene terephthalate films, polybutylene terephthalate films, polyurethane films, ethylene-vinyl acetate copolymer films, and the like.

The thickness of the release film is usually 5 to 200 μm, preferably 5 to 100 μm, more preferably 5 to 50 μm. If necessary, the separator may be subjected to release and antifouling treatment using a silicone, fluorine, long-chain alkyl or fatty acid amide release agent, silica powder, etc.; It is also possible to perform antistatic treatment such as. In particular, by subjecting the surface of the release film to a release treatment such as silicone treatment, long-chain alkyl treatment, or fluorine treatment as appropriate, the releasability from the pressure-sensitive adhesive layer can be further enhanced.

The optical display panel of the present invention will be described below with reference to FIG. FIG. 3 is a schematic perspective view of the optical film 10 in a sheet state attached to the optical cell C. FIG. A sheet-shaped optical film 10 is provided on one main surface of the optical cell C. As shown in FIG. When the first side length of the main surface size of the optical cell C is x1 and the second side length y1 in the direction orthogonal to the first side, the sheet-shaped optical film 10 has the first side length x2 and the second side length is x2. When the length of the second side orthogonal to one side is y2, the relationships are x1>x2 and y1>y2. This relationship corresponds to the optical film corresponding to the main surface size of the optical cell of the present invention, but the relationship is not limited to this, and x1=x2 and y1=y2 may be satisfied. In FIG. 3, x1>y1, but this is not limited either, and x1=y2 or x1<y1 may be satisfied.

Even if the thickness of the polarizing film 12 is small, the thickness of the surface protective film 14 is made large. It can be pasted on the cell C.

That is, for manufacturing an optical display panel in which the first adhesive layer 11, the polarizing film 12, the second adhesive layer 13 and the surface protective film 14 are laminated in this order on one or both sides of the optical cell C, the present The sheet-shaped optical film 10 of the embodiment can be suitably used. The optical film 10 from which the release film 15 has been peeled off is attached to the optical cell C by a sheet-to-panel attachment device.

<Optical cell>
(liquid crystal cell, liquid crystal display panel)
The liquid crystal cell has a structure in which a liquid crystal layer is sealed between a pair of substrates (first substrate (visible side surface) Pa, second substrate (back surface) Pb) arranged opposite to each other. Although any type of liquid crystal cell can be used, it is preferable to use a vertical alignment (VA) mode or in-plane switching (IPS) mode liquid crystal cell in order to achieve high contrast. A liquid crystal display panel is obtained by bonding a polarizing film to one side or both sides of a liquid crystal cell, and a driving circuit is incorporated as necessary.

(Organic EL cell, Organic EL display panel)
An organic EL cell as another optical cell has a structure in which an electroluminescent layer is sandwiched between a pair of electrodes. Any type of organic EL cell can be used, for example, a top emission type, a bottom emission type, a double emission type, or the like. An organic EL display panel is obtained by bonding a polarizing film to one or both sides of an organic EL cell, and a driving circuit is incorporated as necessary.

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the examples shown below. All parts and percentages in each example are based on weight. All room temperature storage conditions not specified below are 23° C. and 65% RH.

<Polarizing film>
(Production of polarizer A0)
One surface of an amorphous isophthalic acid-copolymerized polyethylene terephthalate (IPA-copolymerized PET) film (thickness: 100 μm) substrate having a water absorption of 0.75% and a Tg of 75° C. was subjected to corona treatment. 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 at 25°C and dried to form a PVA-based resin layer having a thickness of 11 µm to prepare a laminate.
The resulting laminate was uniaxially stretched 2.0 times at free ends in the machine direction (longitudinal direction) between rolls with different peripheral speeds in an oven at 120° C. (in-air auxiliary stretching treatment).
Next, the laminate was immersed in an insolubilizing bath (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30° C. for 30 seconds (insolubilizing treatment).
Then, it was immersed in a dyeing bath at 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 blended with 100 parts by weight of water, and 1.0 parts by weight of potassium iodide was blended and immersed for 60 seconds in an iodine aqueous solution (dyeing treatment). .
Next, it was immersed for 30 seconds in a cross-linking bath at a liquid temperature of 30°C (an aqueous solution of boric acid 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). (crosslinking treatment).
After that, 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). Meanwhile, the film was uniaxially stretched in the machine direction (longitudinal direction) between rolls having different peripheral speeds so that the total draw ratio was 5.5 times (underwater stretching treatment).
After that, the laminate was immersed in a cleaning bath having a liquid temperature of 30° C. (aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).
As described above, an optical film laminate containing a polarizer having a thickness of 5 μm was obtained.

(Production of protective film)
Protective film: A (meth)acrylic resin film having a lactone ring structure with a thickness of 40 μm was used after corona treatment on the easy-adhesion-treated surface.

(Preparation of adhesive applied to protective film)
N-hydroxyethyl acrylamide (HEAA) 40 parts by weight and acryloylmorpholine (ACMO) 60 parts by weight and photoinitiator "IRGACURE 819" (manufactured by BASF) 3
Parts by weight were mixed to prepare an ultraviolet curable adhesive.

(Preparation of polarizing film A)
After laminating the protective film while applying the UV-curable adhesive to one surface of the polarizer A0 of the optical film laminate so that the thickness of the adhesive layer after curing is 0.5 μm. , UV rays were applied as active energy rays to cure the adhesive. Ultraviolet irradiation is performed using a gallium-encapsulated metal halide lamp, irradiation device: Light HAMMER10 manufactured by Fusion UV Systems, Inc., bulb: V bulb, peak illuminance: 1600 mW/cm2, integrated irradiation amount 1000/mJ/cm2 (wavelength 380 to 440 nm). UV irradiance was measured using a Solatell Sola-Check system. Next, the amorphous PET substrate was peeled off, and a polarizing film A using a thin polarizer was produced. The optical properties of the obtained polarizing film A were a single transmittance of 42.8% and a degree of polarization of 99.99%. The thickness of the polarizing film A is 45.5 μm.

(Preparation of polarizing film B)
In the same manner as in the case of the polarizing film A, the transparent protective films were attached to both surfaces of the polarizer A0 via the UV-curable adhesive. The optical properties of the obtained one-piece protective polarizing film B were a transmittance of 42.8% and a degree of polarization of 99.99%. The thickness of the polarizing film B is 86 μm.

<Formation of adhesive layer>
100 parts of butyl acrylate, 3 parts of acrylic acid, 0.1 part of 2-hydroxyethyl acrylate and 2,2'-azobisisobutyl are added to a reaction vessel equipped with a condenser, nitrogen inlet, thermometer and stirrer. A solution was prepared by adding 0.3 parts of lonitrile along with ethyl acetate. Next, this solution was stirred while nitrogen gas was blown thereinto, and reacted at 55° C. for 8 hours to obtain a solution containing an acrylic polymer having a weight average molecular weight of 2,200,000. Furthermore, ethyl acetate was added to the solution containing the acrylic polymer to obtain an acrylic polymer solution adjusted to a solid content concentration of 30%.

0.5 parts of a cross-linking agent based on a compound having an isocyanate group (manufactured by Nippon Polyurethane Co., Ltd., trade name "Coronate L") per 100 parts of the solid content of the acrylic polymer solution. and 0.075 parts of γ-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name “KMB-403”) as a silane coupling agent are blended in this order to form an adhesive solution. was prepared. The adhesive solution is applied to the surface of a release film (separator) made of a release-treated polyethylene terephthalate film (38 μm thick) so that the thickness after drying becomes 25 μm, dried, and the adhesive layer ( (corresponding to the first adhesive layer) was formed.

<Preparation of polarizing film A1 with adhesive layer>
Next, the pressure-sensitive adhesive layer formed on the release-treated surface of the release film (separator) was attached to the polarizer side of the polarizing film A to prepare a polarizing film with a pressure-sensitive adhesive layer. The thickness of the pressure-sensitive adhesive layer-attached polarizing film A1 was 45.5+25+38=108.5 μm.

<Lamination of surface protective film>
As the surface protection film, a polyester-based resin film of "Nitto Denko Corporation, product name RP301" was used. Substrates having different thicknesses of 25 μm, 38 μm, 50 μm, 75 μm, 100 μm and 150 μm were prepared. All the adhesive layers (corresponding to the second adhesive layer) have a thickness of 21 μm.

(Example 1)
The sheet-shaped optical film of Example 1 has a structure in which a surface protective film having a thickness of 38 μm is laminated on the pressure-sensitive adhesive layer-attached polarizing film A1.
(Thickness of surface protective film)/(Thickness of polarizing film) = 38/45.5 = 0.84 (rounded to the third decimal place, hereinafter the same.)
Trigger peel force = 0.3 [N/15mm]
The trigger peel force conforms to the following measurements. That is, the obtained sheet-shaped optical film was cut into pieces of 15 mm × 100 mm (50 mm in the absorption axis direction) and 100 mm × 15 mm (100 mm in the absorption axis direction), and each was laminated to an alkali-free glass having a thickness of 0.5 mm. Ta. A cellophane tape was attached to the short edge of the optical film bonded to the non-alkali glass, and the surface protective film was peeled off at a 180° peel speed of 0.3 m/min using Tensilon. The peak value of the peel force at that time was taken as the "trigger peel force". The trigger peel force was measured for each of 15 mm×100 mm (50 mm in the absorption axis direction) and 100 mm×15 mm (100 mm in the absorption axis direction), and the average value was adopted. The trigger release force is measured at room temperature.

(Example 2)
The sheet optical film of Example 2 has a structure in which a surface protective film having a thickness of 50 μm is laminated on the pressure-sensitive adhesive layer-attached polarizing film A1.
(Thickness of surface protective film)/(Thickness of polarizing film) = 50/45.5 = 1.10
Trigger peel force = 0.7 [N/15mm]

(Example 3)
The sheet optical film of Example 3 has a structure in which a surface protective film having a thickness of 75 μm is laminated on the pressure-sensitive adhesive layer-attached polarizing film A1.
(Thickness of surface protective film)/(Thickness of polarizing film) = 75/45.5 = 1.65
Trigger peel force = 1.5 [N/15mm]

(Example 4)
The sheet-shaped optical film of Example 4 has a structure in which a surface protective film having a thickness of 100 μm is laminated on the polarizing film A1 with an adhesive layer.
(Thickness of surface protective film)/(Thickness of polarizing film) = 100/45.5 = 2.20
Trigger peel force = 2.5 [N/15mm]

(Example 5)
The sheet-shaped optical film of Example 5 has a structure in which a surface protective film having a thickness of 150 μm is laminated on the pressure-sensitive adhesive layer-attached polarizing film A1.
(Thickness of surface protective film)/(Thickness of polarizing film) = 150/45.5 = 3.30
Trigger peel force = 5.0 [N/15mm]

(Comparative example 1)
The sheet-shaped optical film of Comparative Example 1 has a structure in which a surface protective film having a thickness of 25 μm is laminated on the polarizing film A1 with an adhesive layer.
(Thickness of surface protective film)/(Thickness of polarizing film) = 25/45.5 = 0.55
Trigger peel force = 0.2 [N/15mm]

<Production of pressure-sensitive adhesive layer-attached polarizing film B1>
Next, the pressure-sensitive adhesive layer formed on the release-treated surface of the release film (separator) was attached to the polarizer side of the polarizing film B to prepare a polarizing film with a pressure-sensitive adhesive layer. The thickness of the pressure-sensitive adhesive layer-attached polarizing film B1 was 86+25+38=149 μm.

(Reference example 1)
The sheet optical film of Reference Example 1 has a structure in which a surface protective film having a thickness of 38 μm is laminated on the pressure-sensitive adhesive layer-attached polarizing film B1.
(Thickness of surface protective film)/(Thickness of polarizing film) = 38/86 = 0.44
Trigger peel force = 0.3 [N/15mm]

(Reference example 2)
The sheet optical film of Reference Example 2 has a structure in which a surface protective film having a thickness of 200 μm is laminated on the pressure-sensitive adhesive layer-attached polarizing film B1.
(Thickness of surface protective film)/(Thickness of polarizing film) = 200/86 = 2.33
Trigger peel force = 5.0 [N/15mm]

Using a sheet-to-panel system, the optical films of Examples 1 to 5, Comparative Examples 1, and Reference Examples 1 and 2 were separated from the release films, and then the glass plates (optical cell replacement) (n=100 times). As a result, the sheet-shaped optical films of Examples 1 to 5 could be suitably bonded to the optical cell without any trouble in handling. However, in Example 5, when the surface protective film was peeled off from the optical film bonded to the glass plate, the trigger peeling was heavy, and delamination of the polarizing film occurred. Moreover, in Reference Examples 1 and 2, the thickness of the polarizing film was increased as a whole. On the other hand, the single wafer optical films of Comparative Examples 1 and 2 had difficulty in handling and could not be adhered to the optical cell with high accuracy, and as a result of the inspection, 30% of the films were judged to be defective.

10 optical film in sheet state 11 first adhesive layer 12 polarizing film 13 second adhesive layer 14 surface protective film 15 release film C optical cell

Claims (5)

A sheet-shaped optical film having a configuration 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 surface protective film having one substrate is laminated to the polarizing film via a second adhesive layer , or laminated to the polarizing film with a self-adhesive film,
The polarizing film has a polarizer and a protective film provided only on one side of the polarizer, and the thickness of the polarizing film is 60 μm or less, provided that from the structure of the polarizing film The brightness enhancement film is removed,
The surface protective film satisfies the relational expression of 0.8 ≤ (thickness of surface protective film) / (thickness of polarizing film) ≤ 1.65,
The optical film in a sheet state was cut into 15 mm × 100 mm (50 mm in the absorption axis direction) and 100 mm × 15 mm (100 mm in the absorption axis direction) pieces, each of which was attached to an alkali-free glass having a thickness of 0.5 mm, and a cellophane tape was applied. The peak value of the peel force when the surface protective film is peeled off at a 180° peel speed of 0.3 m/min using Tensilon after being attached to the short side edge of the optical film laminated to non-alkali glass ( A sheet-shaped optical film having a trigger peel force) of 0.3 to 5.0 [N/15 mm]. The sheet-shaped optical film according to claim 1, wherein the polarizing film includes a polarizer having a thickness of 10 µm or less. 2. Used for manufacturing an optical display panel having a configuration in which the release film is peeled off and an adhesive layer, a polarizing film, and a surface protection film are laminated in this order on one side of an optical cell. A sheet-shaped optical film according to . An optical display panel having a configuration in which a first adhesive layer, a polarizing film, and a surface protective film are laminated in this order on one surface of an optical cell,
The surface protective film having one substrate is laminated to the polarizing film via a second adhesive layer , or laminated to the polarizing film with a self-adhesive film,
The polarizing film has a polarizer and a protective film provided only on one side of the polarizer, and the thickness of the polarizing film is 60 μm or less, provided that from the structure of the polarizing film The brightness enhancement film is removed,
The surface protective film satisfies the relational expression of 0.8 ≤ (thickness of surface protective film) / (thickness of polarizing film) ≤ 1.65,
The optical film in a sheet state was cut into 15 mm × 100 mm (50 mm in the absorption axis direction) and 100 mm × 15 mm (100 mm in the absorption axis direction) pieces, each of which was attached to an alkali-free glass having a thickness of 0.5 mm, and a cellophane tape was applied. The peak value of the peel force when the surface protective film is peeled off at a 180° peel speed of 0.3 m/min using Tensilon after being attached to the short side edge of the optical film laminated to non-alkali glass ( An optical display panel having a trigger peel force) of 0.3 to 5.0 [N/15 mm]. 5. The optical display panel according to claim 4, wherein said optical cell is a liquid crystal cell or an organic EL cell.

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