CN1618602A - Method for stripping adhesive optical film - Google Patents

Abstract

The present invention provides a method of easily peeling an adhesive optical film from a substrate to which the adhesive optical film is adhered without damaging the substrate. In the method for peeling the adhesive optical film from the substrate with the optical film adhered to the adhesive optical film on the surface of the substrate, it is characterized in that a liquid is present in the adhesive The peeling method of the pressure-sensitive adhesive optical film that peels in the state of the peeling interface between the adhesive layer of the optical film and the substrate.

Description

Peeling method of adhesive optical film

technical field

The present invention relates to a peeling method of an adhesive optical film from a substrate with an optical film on which an adhesive optical film is adhered on the surface of a glass substrate or the like. Examples of the above-mentioned optical film include a polarizing plate, a retardation film, an optical compensation film, a brightness improvement film, and a laminated material of these, and the like.

Background technique

In liquid crystal displays, etc., it is essential to arrange polarizing elements on both sides of the liquid crystal cell due to the image forming method, but polarizing plates are usually pasted. In addition, in order to improve the display quality of the display, besides the polarizer, various optical elements can be used on the liquid crystal panel. For example, a phase difference plate for preventing coloration, a viewing angle expansion film for improving the viewing angle of a liquid crystal display, a brightness improving film for improving the contrast of a display, and the like can be used. These films are collectively referred to as optical films.

When affixing the above-mentioned optical film to a liquid crystal cell, an adhesive is usually used. In addition, in joining the optical film, the liquid crystal cell, and the optical film, the respective materials are usually bonded together with an adhesive in order to reduce light loss. In this case, due to the advantages of not needing to go through a drying process when the optical film is fixed, an adhesive type optical film in which an adhesive is previously provided on one side of the optical film as an adhesive layer is generally used. film.

Conventionally, when sticking the adhesive optical film on the surface of the liquid crystal cell, the sticking position may be dislocated, or the liquid crystal display may have problems when a foreign matter is brought in, so the sticky sticky optical film is peeled off. optical film, and again attach a new adhesive optical film to the surface of the liquid crystal cell. But, along with the enlargement of liquid crystal display and the thinning of liquid crystal unit, the peeling of adhesive optical film also becomes difficult gradually, especially when the cohesive force of adhesive layer is stronger, need bigger force in peeling off. Force, which will lead to poor operability, changes in the cell gap of the liquid crystal cell, resulting in a decrease in display quality and damage to the liquid crystal cell.

As a method to solve the above-mentioned problems, the following method has been proposed: a heated heating wire or a slicer (slicer) is inserted between the liquid crystal panel and the optical film, and the adhesive is softened or melted and peeled off (Patent Document 1, 2) A method of separating the optical film by forming a cut on the liquid crystal panel, and then peeling off the divided sheet (Patent Document 3). In addition, a method of peeling the transparent film and the adhesive from the display material after immersing a display material to which a transparent film is bonded via an adhesive in an alkaline solution has also been proposed (Patent Document 4).

However, the above-mentioned method requires difficult operations such as inserting a peeling jig between the liquid crystal panel and the optical film, or cutting only the optical film on the liquid crystal panel. In addition, there will be a large amount of paste residue on the liquid crystal panel, or the liquid crystal panel will be damaged by the alkaline solution.

Patent Document 1: Japanese Patent Application Laid-Open No. 11-95210;

Patent Document 2: JP-A-2002-350837 Gazette;

Patent Document 3: JP-A-2001-242448 Gazette;

Patent Document 4: Japanese Unexamined Patent Publication No. 2001-328849.

Contents of the invention

An object of the present invention is to provide a method for relatively easily peeling an adhesive optical film from a substrate to which the adhesive optical film is adhered without damaging the substrate.

The inventors of the present invention conducted intensive studies to solve the above-mentioned problems, and as a result, found that the above-mentioned object can be achieved by the following peeling method, and completed the present invention.

That is, the present invention relates to a peeling method of an adhesive optical film, which is a peeling method of an adhesive optical film that peels the adhesive optical film from a substrate with an optical film on which the adhesive optical film is adhered on the surface of a substrate , which is characterized in that the peeling is performed in a state where a liquid exists on the peeling interface between the adhesive layer of the adhesive optical film and the substrate.

When the adhesive optical film is peeled from the substrate with the optical film as described above, by making the liquid exist on the peeling interface between the adhesive layer of the adhesive optical film and the substrate, it is possible to remove the adhesive without damaging the substrate. The adhesive optical film is released from the substrate with good reactivity. Therefore, if the peeling method of the present invention is used, even when the size of the liquid crystal panel is large or the liquid crystal cell is thin, the reactivity is good. The reason why this effect can be exhibited is not clear, but it can be speculated as follows: the adhesive layer is swollen or softened by making the liquid contact the adhesive layer, or the liquid is soaked on the peeling interface to reduce the bonding area, Thereby substantially reducing the adhesive force.

In the present invention, from the viewpoints of optical isotropy, heat resistance, and the like, it is preferable to form the above-mentioned pressure-sensitive adhesive layer using an acrylic pressure-sensitive adhesive.

In addition, in the present invention, the aforementioned liquid is preferably water and/or an organic solvent. A particularly good peeling effect can be obtained by using these liquids.

Description of drawings

Fig. 1 is a cross-sectional view of an example of an adhesive optical film.

FIG. 2 is a cross-sectional view of an example of a liquid crystal panel.

In the figure: 1-adhesive optical film, 2-optical film, 3-adhesive layer, 4-liquid crystal panel, 5-transparent substrate, 6-liquid crystal, 7-spacer.

Detailed ways

As shown in FIG. 1 , an adhesive optical film 1 has a structure in which an adhesive layer 3 is provided on an optical film 2 . Usually, the surface of the adhesive layer 3 is protected with a release film (not shown) in the stage before it is attached to the substrate, and when it is attached to the substrate, the adhesive layer 3 is bonded to on the substrate. In addition, as shown in FIG. 2 , in the liquid crystal panel 4 , two transparent substrates 5 such as glass substrates are fixed to face each other through spacers 7 , and liquid crystal 6 is injected into the gaps thereof to seal them. Then, the adhesive optical film 1 is adhered on both surfaces of the transparent substrate 5 .

The adhesive forming the adhesive layer 3 of the adhesive optical film 1 is not particularly limited, and various adhesives such as rubber adhesives, acrylic adhesives, and silicone adhesives can be used, but An acrylic pressure-sensitive adhesive that is colorless and transparent and has good adhesiveness to liquid crystal cells (glass substrates) and the like is preferable.

The acrylic adhesive is an acrylic polymer whose main skeleton is a monomer unit of an alkyl (meth)acrylate as a base polymer. In addition, (meth)acrylate means acrylate and/or methacrylate, and has the same meaning as (meth). The average carbon number of the alkyl group in the alkyl (meth)acrylate constituting the main skeleton of the acrylic polymer is 1-12, and specific examples of the alkyl (meth)acrylate include (methyl) Methyl acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc., these can be used alone or in combination. Among these compounds, an alkyl (meth)acrylate having an alkyl group having 1 to 7 carbon atoms is preferable.

The average molecular weight of the acrylic polymer is not particularly limited, but the weight average molecular weight (GPC) is preferably about 300,000 to 2.5 million. The above-mentioned acrylic polymer can be produced by various known methods, for example, radical polymerization methods such as bulk polymerization, solution polymerization, and suspension polymerization can be appropriately selected. Various well-known substances such as azos and peroxides can be used as the radical polymerization initiator. The reaction temperature is usually about 50-85° C., and the reaction time is about 1-8 hours. In addition, among the above-mentioned production methods, the solution polymerization method is preferable, and polar solvents such as ethyl acetate and toluene are usually used as solvents for acrylic polymers. The solution concentration is usually about 20-80% by weight.

As the base polymer of the rubber-based adhesive, for example, natural rubber, isoprene-based rubber, styrene-butadiene-based rubber, recycled rubber, polyisobutylene-based rubber, and styrene-isoprene-based ethylene-styrene rubber, and styrene-butadiene-styrene rubber.

Examples of the matrix polymer of the silicone-based adhesive include dimethylpolysiloxane, diphenylpolysiloxane, and methylphenylpolysiloxane.

A foaming agent may also be blended in the adhesive layer 3 . The foaming agent can lower the adhesive force of the adhesive layer 3 by utilizing expansion or foaming of the foaming agent caused by heat treatment. The foaming agent is not particularly limited, and various inorganic or organic foaming agents can be used.

In addition, the above-mentioned adhesive is preferably an adhesive composition containing a crosslinking agent. Examples of polyfunctional compounds that can be used in combination with adhesives include organic crosslinking agents and polyfunctional metal chelate compounds. As an organic type crosslinking agent, an epoxy type crosslinking agent, an isocyanate type crosslinking agent, an imine type crosslinking agent etc. are mentioned, for example. As the organic type crosslinking agent, an isocyanate type crosslinking agent is preferable. Multifunctional metal chelates are compounds in which polyvalent metals are bonded to organic compounds through covalent bonds or coordination bonds. Examples of polyvalent metal atoms include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, Ti wait. Examples of the atoms in the organic compound forming a covalent bond or a coordinate bond include an oxygen atom, and examples of the organic compound include alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, and ketone compounds.

There is no particular limitation on the mixing ratio of the base polymer such as acrylic polymer and the crosslinking agent, but usually the crosslinking agent (solid content) is preferably about 0.01 to 6 wt. parts, more preferably about 0.1-3 parts by weight.

In addition, among the above-mentioned binders, if necessary, tackifiers, plasticizers, glass fibers, glass beads, metal powders, fillers composed of other inorganic powders, pigments, colorants, fillers, Various additives such as antioxidants, UV absorbers, silane coupling agents, etc. Moreover, you may contain the particle|grains, such as spherical shape and granular shape, and form it as the pressure-sensitive adhesive layer etc. which exhibit light-diffusion property.

Another adhesive layer or an adhesion-promoting layer may be interposed between the optical film 2 and the adhesive layer 3 for the purpose of strengthening the bonding between the two.

As the optical film 2, materials used in forming image display devices such as liquid crystal display devices can be used, and the type is not particularly limited. For example, a polarizing plate can be exemplified as an optical film. As a polarizing plate, a structure having a transparent protective film on one or both sides of a polarizer is generally used.

The polarizer is not particularly limited, and various polarizers can be used. As a polarizer, for example, on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene-vinyl acetate copolymer partially saponified films, iodine or Materials that are uniaxially stretched after dichroic substances such as dichroic dyes; polyolefin-based oriented films such as dehydration-treated products of polyvinyl alcohol or dehydrochloric acid-treated products of polyvinyl chloride, etc. Among them, a polarizer composed of a polyvinyl alcohol film and a dichroic substance such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is usually about 5 to 80 μm.

A polarizer obtained by uniaxially stretching a polyvinyl alcohol film dyed with iodine, for example, can be produced by dipping polyvinyl alcohol in an aqueous solution of iodine, dyeing it, and then stretching it to 3 to 7 times its original length. become. If necessary, it may be immersed in an aqueous solution of potassium iodide or the like which may contain boric acid, zinc sulfate, zinc chloride, or the like. In addition, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed with water before dyeing. Washing the polyvinyl alcohol film with water not only removes dirt and anti-blocking agents on the surface of the polyvinyl alcohol film, but also prevents unevenness such as staining by swelling the polyvinyl alcohol film. Stretching may be performed after dyeing with iodine, stretching may be performed while dyeing, or iodine dyeing may be performed after stretching. Stretching may also be performed in an aqueous solution of boric acid, potassium iodide, or the like, or in a water bath.

As a material for forming the transparent protective film provided on one or both sides of the above-mentioned polarizer, a material having excellent transparency, mechanical strength, thermal stability, moisture shielding property, isotropy, etc. is preferable. For example, polyester polymers such as polyethylene terephthalate or polyethylene naphthalate; cellulosic polymers such as cellulose diacetate or cellulose triacetate; polymethacrylic acid Acrylic polymers such as methyl ester; styrenic polymers such as polystyrene or acrylonitrile-styrene copolymer (AS resin); polycarbonate polymers, etc. In addition, as an example of the polymer forming the above-mentioned transparent protective film, for example, polyolefin-based polymers such as polyethylene, polypropylene, polyolefin having a cyclic or norbornene structure, and ethylene-propylene copolymer ; vinyl chloride polymers; amide polymers such as nylon or aromatic polyamide; imide polymers; sulfone polymers; polyethersulfone polymers; polyether-ether ketone polymers; polyphenylene sulfide Ether polymers; vinyl alcohol polymers; vinylidene chloride polymers; polyvinyl butyral polymers; arylate polymers; polyoxymethylene polymers; epoxy polymers; or the above A mixture of polymers. The transparent protective film can also be formed as a cured layer of thermosetting or ultraviolet curing resins such as acrylic, urethane, acrylic urethane, epoxy, and silicone.

In addition, for example, a polymer film described in JP-A-2001-343529 (WO01/37007) includes (A) a thermoplastic resin having a substituted and/or unsubstituted imino group in a side chain, and (B ) A resin composition of a thermoplastic resin having substituted and/or unsubstituted phenyl and nitrile groups in the side chain. As a specific example, a film of a resin composition containing an alternating copolymer of isobutylene and N-methylmaleic anhydride imide, and an acrylonitrile-styrene copolymer can be cited. As the film, a film composed of a mixed extrusion product of a resin composition or the like can be used.

The thickness of the protective film can be appropriately determined, but it is generally about 1 to 500 μm from the viewpoint of handling properties such as strength and handleability, and thin layer properties. It is particularly preferably 1-300 μm, more preferably 5-200 μm.

In addition, the protective film is best not to be colored. Therefore, it is preferable to use Rth=[(nx+ny)/2-nz] d (where nx and ny are the principal refractive indices in the plane of the film, nz is the refractive index in the film thickness direction, and d is the film thickness). The retardation value in the thickness direction of the film is -90nm ~ +75nm protective film. By using a protective film having a retardation value (Rth) in the thickness direction of -90 nm to +75 nm, coloring (optical coloring) of the polarizing plate due to the protective film can be substantially eliminated. The retardation value (Rth) in the thickness direction is more preferably -80 nm to +60 nm, particularly preferably -70 nm to +45 nm.

As the protective film, cellulose-based polymers such as cellulose triacetate are preferable from the viewpoint of polarization performance and durability. Particular preference is given to cellulose triacetate films. In addition, when protective films are provided on both sides of the polarizer, protective films made of the same polymer material or different polymer materials may be used on the front and back sides thereof. The aforementioned polarizer and protective film are usually bonded with a water-based adhesive or the like. Examples of the aqueous binder include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl latex, water-based polyurethane, and water-based polyester.

On the surface of the above-mentioned transparent protective film to which a polarizer is not bonded, a hard coat layer, antireflection treatment, antisticking treatment, treatment for the purpose of diffusion or antiglare may be applied.

The purpose of the hard coat treatment is to prevent damage to the surface of the polarizer, for example, by adding an appropriate UV-curable resin such as acrylic or silicone to the surface of the transparent protective film to improve the hardness, sliding properties, etc. The method of curing the film, etc. to form. The purpose of anti-reflection treatment is to prevent the reflection of external light on the surface of the polarizer, which can be accomplished by forming a conventional anti-reflection film or the like. In addition, the anti-sticking treatment is performed to prevent sticking with adjacent layers.

In addition, the purpose of implementing anti-glare treatment is to prevent external light from reflecting on the surface of the polarizer and interfering with the recognition of the light transmitted by the polarizer. In an appropriate method such as a method, the surface of the transparent protective film is provided with a fine concave-convex structure. As the fine particles contained in the formation of the above-mentioned surface fine uneven structure, for example, particles made of silicon dioxide, aluminum oxide, titanium oxide, zirconium oxide, tin oxide, indium oxide, cadmium oxide, Conductive inorganic particles composed of antimony, etc., and transparent particles such as organic particles composed of cross-linked or uncross-linked polymers. When forming the surface fine uneven structure, the amount of fine particles used is usually about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin for forming the surface fine uneven structure. The anti-glare layer may also serve as a diffusion layer for expanding the viewing angle by diffusing light transmitted through the polarizer (viewing angle widening function, etc.).

In addition, the above-mentioned anti-reflection layer, anti-adhesion layer, diffusion layer, anti-glare layer, etc. may be provided on the transparent protective film itself, and may also be provided as other optical layers arranged separately from the transparent protective film.

In addition, as the optical film of the present invention, for example, reflective plates or semi-transparent plates, retardation plates (including wavelength plates such as 1/2 and 1/4), viewing angle compensation films, brightness improvement films, etc. are used in liquid crystal displays. A thin film used as an optical layer that can be used in the formation of devices and the like. These can be used alone as the optical film of the present invention, or can be used by laminating one layer or two or more layers on the above-mentioned polarizing plate in actual use.

A particularly preferable polarizing plate is a reflective polarizing plate or a semi-transmitting polarizing plate in which a reflecting plate or a semi-transmitting reflecting plate is further laminated on the polarizing plate; A polarizing plate; a wide viewing angle polarizing plate formed by further laminating a viewing angle compensation film on the polarizing plate; or a polarizing plate formed by further laminating a brightness improving film on the polarizing plate.

A reflective polarizer is formed by providing a reflective layer on the polarizer, and can be used to form a type of liquid crystal display device that reflects incident light incident from the viewing side (display side) to display, and can omit a light source such as a built-in backlight , thus having advantages such as easy thinning of the liquid crystal display device. When forming a reflective polarizer, it can carry out by an appropriate method, such as the method of providing the reflective layer which consists of metal etc. on one side of a polarizer via a transparent protective layer etc. as needed.

Specific examples of reflective polarizers include reflective polarizers in which a reflective layer is formed by providing a foil or vapor-deposited film of a reflective metal such as aluminum on one surface of a matte-treated transparent protective film as needed. In addition, a reflective polarizer having a fine uneven structure on the surface is formed by adding fine particles to the protective film, and a reflective layer having a fine uneven structure thereon. The reflective layer with the above-mentioned fine concavo-convex structure diffuses incident light by diffuse reflection, thereby preventing orientation and appearance glare, and has the advantage of being able to suppress unevenness of light and shade. In addition, the transparent protective film containing fine particles also has the advantage of further suppressing unevenness in light and shade by diffusing light when incident light and reflected light pass through it. Reflecting the formation of the reflective layer of the micro-concave-convex structure of the surface micro-concave-convex structure of the transparent protective film, for example, it can be formed on the transparent protective film by appropriate methods such as evaporation methods such as vacuum evaporation methods, ion plating methods, and sputtering methods or plating methods. The method of attaching metal directly on the surface of the layer or the like.

Instead of attaching the reflecting plate directly to the transparent protective film of the above-mentioned polarizing plate, it is also possible to provide a reflecting layer on an appropriate film based on the transparent film to form a reflecting plate or the like. Also, since the reflective layer is usually made of metal, it is preferable to use a transparent protective film or A form in which the reflective surface is covered with a polarizer or the like.

In addition, in the above, the semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror that transmits light while reflecting light with the reflective layer. A transflective polarizer is usually provided on the back side of a liquid crystal cell, and can form a type of liquid crystal display device, etc., that is, when the liquid crystal display device is used in a relatively bright environment, the reflection is from the viewing side (display side) When used in a relatively dark environment, images are displayed using a built-in light source such as a backlight built into the back of the transflective polarizer. That is, the transflective polarizing plate is very useful in the formation of liquid crystal display devices of the type that can save the energy of using a light source such as a backlight in a bright environment, and can also use a built-in light source in a relatively dark environment. Useful in the formation of liquid crystal display devices of the type used.

Next, an elliptically polarizing plate or a circular polarizing plate formed by further laminating a retardation plate on a polarizing plate will be described. In the case of changing linearly polarized light into elliptically polarized light or circularly polarized light, or changing elliptically polarized light or circularly polarized light into linearly polarized light, or changing the polarization direction of linearly polarized light, a retardation plate or the like can be used. In particular, as a retardation plate that changes linearly polarized light into circularly polarized light or vice versa, a so-called 1/4 wavelength plate (also referred to as a λ/4 plate) can be used. A 1/2 wavelength plate (also called a λ/2 plate) is generally used in the case of changing the polarization direction of linearly polarized light.

The elliptically polarizing plate can be effectively used in the case of compensating (preventing) the coloring (blue or yellow) of a super-twisted nematic (STN) type liquid crystal display device due to the birefringence of the liquid crystal layer, thereby performing the non-coloring The situation of black and white display, etc. In addition, a polarizing plate that controls the three-dimensional refractive index can also compensate (prevent) coloring that occurs when viewing the screen of a liquid crystal display device from an oblique direction, and is therefore preferable. The circularly polarizing plate can be effectively used, for example, to adjust the color tone of an image of a reflective liquid crystal display device in which the image is displayed in color, and also has an antireflection function.

Examples of the retardation plate include a birefringent film formed by unidirectionally or biaxially stretching a polymer material, an alignment film of a liquid crystal polymer, a material supporting an alignment layer of a liquid crystal polymer, and the like. There is no particular limitation on the thickness of the retardation plate, and it is generally 20-150 μm.

Examples of the polymer material include polyvinyl alcohol, polyvinyl butyral, polymethyl vinyl ether, polyhydroxyethyl acrylate, hydroxyethyl cellulose, hydroxypropyl cellulose, and methyl cellulose. Polyethylene, polycarbonate, polyarylate, polysulfone, polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyphenylene sulfide, polyphenylene ether, polyallyl sulfone , polyvinyl alcohol, polyamide, polyimide, polyolefin, polyvinyl chloride, cellulosic polymers, norbornene resins, or their binary or ternary copolymers, grafted Copolymers, blends, etc. These polymer materials can be oriented by stretching or the like (stretched film).

Examples of liquid crystalline polymers include various polymers of the main chain type or side chain type in which a conjugated linear atomic group (mesogen) imparting liquid crystal orientation is introduced into the main chain or side chain of the polymer. Specific examples of main-chain liquid crystalline polymers include polymers having a structure in which the aforementioned linear atomic groups (mesogene) are bonded to spacers that impart flexibility, such as nematic-oriented polyester-based liquid crystalline polymers. polymers, disc-shaped polymers or cholesteric polymers, etc. Specific examples of side-chain type liquid crystalline polymers include compounds in which polysiloxane, polyacrylate, polymethacrylate, or polymalonate is the main chain skeleton, and the side chain A compound having the aforementioned linear mesogene portion composed of a para-substituted cyclic compound unit imparting nematic orientation via a spacer portion composed of a conjugated atomic group. These liquid crystalline polymers are treated by rubbing the surface of a film such as polyimide or polyvinyl alcohol formed on a glass plate, or by obliquely vapor-depositing silicon oxide. Heat treatment was carried out after spreading a liquid crystalline polymer solution on the orientation-treated surface.

The retardation plate may be a material having an appropriate retardation according to the purpose of use, such as various wavelength plates or materials for compensating for coloring or viewing angle caused by the birefringence of the liquid crystal layer, or two or more types may be laminated. A material that controls optical properties such as retardation.

In addition, the above-mentioned elliptically polarizing plate or reflective elliptically polarizing plate is formed by appropriately combining and laminating a polarizing plate or reflective polarizing plate and a retardation plate. Such elliptically polarizing plates and the like can also be formed by sequentially stacking (reflective) polarizing plates and retardation plates in sequence during the manufacture of liquid crystal display devices to form a combination of (reflective) polarizing plates and retardation plates, and as above As mentioned above, when preliminarily formed into an optical film such as an elliptically polarizing plate, it is excellent in quality stability and lamination workability, and thus has an advantage that the production efficiency of liquid crystal display devices and the like can be improved.

The viewing angle compensating film is a film for widening the viewing angle to make the image appear clear even when the screen of the liquid crystal display device is viewed from a slightly oblique direction that is not perpendicular to the screen. Such a viewing angle compensation retardation plate is, for example, made of a retardation plate, an alignment film such as a liquid crystal polymer, or a material in which an alignment layer such as a liquid crystal polymer is supported on a transparent substrate. Generally, a polymer film that is uniaxially stretched along its surface direction and has birefringence is used as a retardation film, but as a retardation film used as a viewing angle compensation film, a polymer film that is birefringently stretched along its surface direction can be used. stretched and birefringent polymer films, birefringent polymers with controllable refractive index in the thickness direction that are uniaxially stretched in the plane direction and also stretched in the thickness direction, or bidirectionally stretched like obliquely oriented films. Stretch film, etc. As the oblique orientation film, for example, after bonding a heat-shrinkable film on the polymer film, under the action of the shrinkage force formed by heating, the polymer film has been stretched or/and shrunk. Materials obtained by oblique orientation of liquid crystal polymers, etc. As the raw material polymer of the phase difference plate, the same polymers as those described above for the phase difference plate can be used, and can be used to prevent coloring caused by changes in the recognition angle due to the phase difference caused by the liquid crystal cell, etc. Or a suitable polymer for the purpose of widening a viewing angle with good visibility.

In addition, from the viewpoint of realizing a wide viewing angle with good visibility, it is preferable to use a triacetate cellulose film to support an optically anisotropic layer composed of an alignment layer of a liquid crystal polymer, especially an oblique alignment layer of a discotic liquid crystal polymer. layers of optically compensated retardation plates.

A polarizing plate bonded together with a brightness improving film is usually provided on the rear side of a liquid crystal cell. The brightness improving film is a film that exhibits the property of reflecting linearly polarized light of a specific polarization axis or circularly polarized light of a specific direction when natural light enters due to the backlight of a liquid crystal display device or the like or reflection from the back side, etc., The polarizing plate formed by laminating the brightness improving film and the polarizing plate can allow the light from a light source such as a backlight to be incident to obtain transmitted light in a specific polarized state. At the same time, the specific polarized light Light outside the state cannot pass through and is reflected. The light reflected on the surface of the brightness-improving film is reversed again by means of a reflective layer or the like arranged on the rear side thereof, so that it is incident on the brightness-improving film again, and part or all of it is transmitted as light of a specific polarization state, thereby The light transmitted through the brightness improving film is increased while providing polarized light that is difficult to absorb to the polarizer, thereby increasing the amount of light that can be used in the display of liquid crystal display images, etc., and thereby the brightness can be improved. That is, in the case where light is incident through the polarizer from the back side of the liquid crystal cell with a backlight or the like without using the brightness improving film, light having a polarization direction that does not coincide with the polarization axis of the polarizer is basically received by the polarizer. Absorbs and therefore cannot pass through polarizers. That is, although it varies depending on the characteristics of the polarizer used, about 50% of the light is absorbed by the polarizer. Therefore, the amount of light that can be used in liquid crystal image displays, etc., decreases, resulting in darker images. Since the brightness improvement film repeatedly performs the following operations, that is, the light with a polarization direction that can be absorbed by the polarizer is not incident on the polarizer, but the light is reflected on the brightness improvement film, and then by means of the The reflective layer etc. on the side completes inversion, so that the light is incident on the brightness improving film again, so that the brightness improving film only changes the polarization direction of the light reflected and reversed between the two to pass through the polarizer. Since the polarized light in the polarization direction is transmitted and supplied to the polarizer, light such as a backlight can be effectively used in image display of a liquid crystal display device, and the screen can be brightened.

A diffusion plate may also be provided between the brightness improving film and the reflective layer or the like. The light in the polarized state reflected by the brightness improving film is directed toward the reflective layer and the like, and the diffuser is provided to uniformly diffuse the passing light while canceling the polarized state into a non-polarized state. That is, the diffuser returns the polarized light to its original natural light state. Repeatedly, the light in the unpolarized state, that is, the natural light state, is irradiated to the reflective layer or the like, reflected through the reflective layer or the like, and then passes through the diffusion plate again and enters the brightness improving film again. By providing a diffuser plate between the brightness improving film and the reflective layer, etc., which restores the polarized light to the original natural light state, it is possible to maintain the brightness of the display screen while reducing the unevenness of the brightness of the display screen, thereby providing uniformity. And a bright picture. By arranging the diffusion plate, the number of repeated reflections of the initial incident light can be appropriately increased, and a uniform and bright display image can be provided by utilizing the diffusion function of the diffusion plate.

As the brightness improving film, for example, a multilayer film of a dielectric or a multilayer laminate of films having different refractive index anisotropy, which have the property of transmitting linearly polarized light with a specific polarization axis and reflecting other light can be used. The thin film of the cholesteric liquid crystal polymer or the film supporting the alignment liquid crystal layer on the film substrate shows that any kind of circularly polarized light in left-handed or right-handed is reflected and other light is transmitted. Suitable films such as films with excellent properties.

Therefore, by using a brightness-improving film of the type that transmits linearly polarized light of a specific polarization axis, and making the transmitted light directly incident on the polarizer in a direction consistent with the polarization axis, absorption by the polarizer can be suppressed. While reducing the loss, the light can be effectively transmitted. On the other hand, using a brightness-improving film that transmits circularly polarized light, such as a cholesteric liquid crystal layer, can directly make light incident on a polarizer, but from the viewpoint of suppressing absorption loss, it is preferable to use a phase The circularly polarized light is linearly polarized by the difference plate, and then incident on the polarizer. Furthermore, by using a 1/4 wavelength plate as the retardation plate, it is possible to convert circularly polarized light into linearly polarized light.

A phase difference plate that can function as a 1/4 wavelength plate in a wide wavelength range such as the visible light region can be obtained, for example, by using a light-colored light with a wavelength of 550nm that can function as a 1/4 wavelength plate. The retardation layer and the retardation layer exhibiting other retardation characteristics, for example, a manner in which the retardation layer can function as a 1/2 wavelength plate overlaps, and the like. Therefore, the retardation plate disposed between the polarizing plate and the brightness improving film may be composed of one or more retardation layers.

In addition, as far as the cholesteric liquid crystal layer is concerned, it is also possible to combine materials with different reflection wavelengths to form a configuration structure in which two or more layers are overlapped, thereby obtaining reflection circular polarization in a wider wavelength range such as the visible light region. A component of light, so that a wider wavelength range of transmitted circularly polarized light can be obtained based on this.

In addition, the polarizing plate may be composed of a member in which a polarizing plate and two or more optical layers are laminated, like the above-mentioned polarized light separation type polarizing plate. Therefore, a reflection type elliptically polarizing plate or a semi-transmitting type elliptically polarizing plate obtained by combining the above-mentioned reflective polarizing plate or semi-transmitting type polarizing plate with a retardation plate may also be used.

An optical film in which the above-mentioned optical layers are laminated on a polarizer can be formed by sequentially laminating each other in the manufacturing process of a liquid crystal display device, etc. Since it is excellent in aspect, it has the advantage that the manufacturing process of a liquid crystal display device etc. can be improved. Appropriate bonding means, such as an adhesive layer, can be used for lamination. When bonding the polarizing plate and other optical layers, their optical axes can be arranged at an appropriate angle according to the target retardation characteristics and the like.

The method for forming the adhesive layer 3 on the above-mentioned optical film 2 is not particularly limited, and examples thereof include a method of applying an adhesive (solution) and drying it, using a release sheet provided with the adhesive layer 3, transfer method, etc. Examples of the constituent material of the release sheet include synthetic resin films such as paper, polyethylene, polypropylene, and polyethylene terephthalate; rubber sheets, paper, cloth, non-woven fabrics, nets, and foam sheets. And suitable sheet bodies, such as metal foil and these laminated bodies, etc. The surface of the release sheet may be subjected to a release treatment such as silicone treatment, long-chain alkyl treatment, or fluorine treatment, if necessary, in order to improve releasability from the pressure-sensitive adhesive layer 3 .

The thickness of the adhesive layer 3 (dry film thickness) is not particularly limited, but is preferably about 10 to 40 μm.

In addition, on each layer of the optical film or the adhesive layer of the adhesive optical film, for example, a salicylate compound, a benzophenol compound, a benzotriazole compound, or a cyanoacrylate compound can also be used. Compounds, nickel complex salt compounds and other ultraviolet absorbers are treated to make them have ultraviolet absorbing ability.

When bonding the above-mentioned adhesive optical film on the substrate of liquid crystal cell, etc., if the bonding position is misaligned or foreign matter is brought in, it will affect the liquid crystal display, etc., so it is necessary to peel off the adhesive optical film that has been bonded. film, and stick a new adhesive optical film on the surface of the liquid crystal cell, etc. again. However, when the adhesive force of the adhesive layer is strong, a large force is required for peeling, so the operability may deteriorate, or the gap of the liquid crystal cell may change, resulting in a decrease in display quality or damage to the liquid crystal cell, etc. .

The peeling method of the adhesive optical film of the present invention is characterized in that peeling is carried out in a state where a liquid exists on the peeling interface between the adhesive layer of the adhesive optical film and the substrate, and the adhesive can be released by this peeling method. The adhesion of the layers is reduced enough that the adhesive optical film can be peeled relatively easily without damaging the substrate. In addition, this peeling method can also suppress the residue of the paste on the surface of the substrate.

As a liquid used for the peeling method of the pressure-sensitive adhesive optical film of this invention, water or an organic solvent is mentioned. Examples of organic solvents include aliphatic hydrocarbon solvents such as hexane and heptane, alicyclic hydrocarbon solvents such as cyclohexane and cycloheptane, aromatic hydrocarbon solvents such as toluene and xylene, methanol, ethanol, iso Alcohol solvents such as propanol, ketone solvents such as acetone and methyl ethyl ketone, ether solvents such as dimethyl ether and diethyl ether, ester solvents such as methyl acetate and ethyl acetate, etc. Organic solvents increase the peeling speed, so they are preferred when peeling adhesive optical films from large substrates.

Inorganic or organic additives may be added to the above-mentioned liquid within the range that does not impair the effect of the present invention. Among them, since there is a possibility of dissolving substrates such as glass, additives whose solutions are alkaline are not used.

As a method of making a liquid exist on the peeling interface between the pressure-sensitive adhesive layer of the adhesive optical film and the substrate, a method of dropping the liquid onto the peeling interface, showering, spraying, or the like can be exemplified. In addition, peeling may be performed in a state immersed in a liquid, or in vapor.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. Wherein, parts and % in each embodiment are based on weight.

Manufacturing example

(Production of adhesive optical film)

A polarizer was obtained by stretching an 80 μm thick polyvinyl alcohol film 5 times in an iodine aqueous solution at 40° C. and then drying it at 50° C. for 4 minutes. A cellulose triacetate film was bonded to both sides of the polarizer using a polyvinyl alcohol type adhesive to obtain a polarizer. An acrylic adhesive was applied to one side of the polarizer, and dried to form an adhesive layer (thickness: 25 μm), thereby producing an adhesive polarizer.

Example 1

(adhesion test)

The produced adhesive-type polarizing plate was cut into a size of 25 mm width. Then, on the surface of an alkali-free glass plate (manufactured by Corning Co., Corning 1737, thickness: 0.4 mm), the adhesive layer of the adhesive polarizer was bonded, and the Hold for 15 minutes. Then, using a tensile testing machine, under the conditions of a tensile speed of 300mm/min and a tensile angle of 90°, spray water at about 25°C on the peeling interface between the adhesive layer and the non-alkali glass plate. Peel off the bonded polarizer. Adhesive force (N/25mm) at the time of peeling is shown in Table 1.

(Peel operation experiment)

The produced adhesive type polarizing plate was cut into a size of 15 inches. Then, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive polarizing plate was attached to the surface of a glass liquid crystal cell having the same size, and kept in an autoclave (50° C., 0.5 MPa) for 15 minutes. Then, the adhesive polarizing plate was peeled from the corners while spraying water at about 25° C. on the peeling interface between the adhesive layer and the liquid crystal cell. This experiment was carried out 10 times, and the number of occurrences of defects such as cracks in the liquid crystal element or abnormal cell gaps was counted. Moreover, after peeling, it was confirmed whether the paste remained on the surface of the liquid crystal cell, and it evaluated by the following standard. The results are shown in Table 1.

○: No paste remains.

△: Some paste remains.

×: There are many paste residues.

Example 2

Adhesion force test and peeling operation test were performed in the same manner as in Example 1 except that toluene (about 25° C.) was used instead of water. The results are shown in Table 1.

Comparative example 1

The adhesion test and the peeling operation test were carried out in the same manner as in Example 1, except that water was not sprayed during peeling. The results are shown in Table 1.

Table 1 Adhesion (N/25mm) The number of occurrences of bad situations (times) paste residue Example 1 4.8 0 ○ Example 2 1.9 0 △ Comparative example 1 11.5 5 △

As can be seen from Table 1, when the adhesive optical film is peeled from the liquid crystal cell, by peeling off the adhesive layer of the adhesive optical film and the liquid crystal cell in a state where the liquid is present at the peeling interface, the adhesive can be removed. The adhesion of the agent layer is sufficiently low. For this reason, peeling does not cause trouble in the liquid crystal cell, and the adhesive optical film can be easily peeled off. In addition, the efficiency of the stripping operation can also be improved, so it contributes greatly to the improvement of the production efficiency of liquid crystal displays.

Claims (3)

1, a kind of stripping means of adhesive optical film, it is the stripping means of the adhesive optical film of release adhesive type optical thin film from the substrate of the band optical thin film that is stained with adhesive optical film at substrate surface, it is characterized in that, peel off the adhesive phase and the peeling off under the state that has liquid on the interface of substrate of adhesive optical film.

2, the stripping means of adhesive optical film according to claim 1 is characterized in that, described adhesive phase is formed by acrylic adhesives.

According to the stripping means of claim 1 or 2 described adhesive optical films, it is characterized in that 3, described liquid is water and/or organic solvent.

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