Polarizing film and image display device
阅读说明：本技术 偏振膜及图像显示装置 (Polarizing film and image display device ) 是由 石原康隆 岸敦史 上野友德 于 2018-05-22 设计创作，主要内容包括：本发明涉及一种偏振膜,其具有起偏镜、并在所述起偏镜的两面具有第一透明层,其中,上述第一透明层的饱和水分率低于上述起偏镜的饱和水分率,上述第一透明层作为帮助上述起偏镜中的水分排出的浸透膜发挥功能。本发明的偏振膜即使在高温高湿环境中也可以抑制端部的偏振度的降低。(The present invention relates to a polarizing film having a polarizer and first transparent layers on both surfaces of the polarizer, wherein the first transparent layers have a saturated water content lower than that of the polarizer, and function as a permeable film that helps discharge of water in the polarizer. The polarizing film of the present invention can suppress a decrease in the degree of polarization at the end even in a high-temperature and high-humidity environment.)
1. A polarizing film having a polarizer and first transparent layers on both sides of the polarizer, wherein,
the saturated water content of the first transparent layer at 85 ℃ and 85% R.H. is lower than that of the polarizer at 85 ℃ and 85% R.H.,
the first transparent layer functions as a penetrating film that helps moisture in the polarizer to be discharged.
2. The polarizing film of claim 1,
the first transparent layer is formed directly on the polarizer.
3. The polarizing film according to claim 1 or 2,
the first transparent layer has a thickness of 3 μm or less.
4. The polarizing film according to any one of claims 1 to 3,
the first transparent layer is a cured product of a forming material containing a urethane prepolymer that is a reaction product of an isocyanate compound and a polyol.
5. The polarizing film of claim 4,
the isocyanate compound contains at least 1 selected from the group consisting of toluene diisocyanate and diphenylmethane diisocyanate.
6. The polarizing film according to any one of claims 1 to 5,
in the first transparent layer, the first transparent layer has a gradient distribution in which the saturated moisture concentration at 85 ℃ and 85% R.H. gradually decreases from the polarizer side toward the side opposite to the polarizer.
7. The polarizing film according to any one of claims 1 to 6,
the thickness of the polarizer is less than 10 μm.
8. The polarizing film according to any one of claims 1 to 7,
a second transparent layer is provided adjacent to at least one of the first transparent layers provided on both sides of the polarizer, on the side opposite to the side having the polarizer,
the saturated water content of the second transparent layer at 85 deg.C and 85% R.H. is lower than that of the first transparent layer at 85 deg.C and 85% R.H.,
the water in the polarizer permeates into the first transparent layer and the second transparent layer from the polarizer side in sequence.
9. The polarizing film according to claim 8 or 9,
the second transparent layer is an adhesive layer.
10. The polarizing film according to claim 8 or 9,
the second transparent layer is a protective film.
11. An image display device having the polarizing film according to any one of claims 1 to 10.
Technical Field
The present invention relates to a polarizing film. The polarizing film may be used alone or in combination with an optical film formed of the polarizing film to form an image display device such as a Liquid Crystal Display (LCD) or an organic EL display.
Background
In a liquid crystal display device, it is essential to dispose polarizing films on both sides of a glass substrate forming a surface of a liquid crystal panel in view of an image forming method. As the polarizing film, a polarizing film obtained by laminating a protective film on one surface or both surfaces of a polarizer made of a dichroic material such as a polyvinyl alcohol film and iodine with a polyvinyl alcohol adhesive or the like is generally used.
In addition, the polarizing film is exposed to a severe environment depending on its use and use state. Therefore, the polarizing film is required to have durability that can maintain optical characteristics even in a severe environment. For example, it has been proposed to provide a polyurethane resin having a predetermined storage modulus on at least one surface of a polarizer (
Disclosure of Invention
Problems to be solved by the invention
In addition, the polarizing film is sometimes used in a high-temperature and high-humidity environment, in addition to a high-temperature environment. In such a severe atmosphere, it is known that moisture in the atmosphere affects the optical characteristics of the polarizer, and the degree of polarization is greatly reduced at the end of the polarizing film. However, the polyurethane resins as in
The purpose of the present invention is to provide a polarizing film that can suppress a decrease in the degree of polarization at the ends even in a high-temperature, high-humidity environment.
Another object of the present invention is to provide an image display device having the polarizing film.
Means for solving the problems
The present inventors have conducted extensive studies and, as a result, have found that the above problems can be solved by the following polarizing film and the like, and have completed the present invention.
That is, the present invention relates to a polarizing film having a polarizer and first transparent layers on both sides of the polarizer, wherein,
the saturated water content of the first transparent layer at 85 deg.C and 85% R.H. is lower than that of the polarizer at 85 deg.C and 85% R.H.,
the first transparent layer functions as a permeable film that helps moisture in the polarizer to be discharged.
In the polarizing film, the first transparent layer is preferably formed directly on the polarizer.
In the polarizing film, the thickness of the first transparent layer is preferably 3 μm or less.
In the polarizing film, as the first transparent layer, a cured product of a forming material containing a urethane prepolymer which is a reaction product of an isocyanate compound and a polyol may be used. As the isocyanate compound, at least 1 selected from the group consisting of toluene diisocyanate and diphenylmethane diisocyanate is preferably used.
In the polarizing film, it is preferable that the first transparent layer has a gradient distribution in which a saturated moisture concentration of the first transparent layer at 85 ℃ and 85% r.h. gradually decreases from the polarizer side toward the opposite side to the polarizer.
In the polarizing film, the thickness of the polarizer is preferably 10 μm or less.
In the polarizing film, it is preferable that the first transparent layer on at least one of the first transparent layers provided on both surfaces of the polarizer has a second transparent layer adjacent to the side opposite to the side having the polarizer,
preferably, the saturated moisture content of the second transparent layer at 85 ℃ and 85% R.H. is lower than the saturated moisture content of the first transparent layer at 85 ℃ and 85% R.H.,
preferably, the water in the polarizer penetrates into the first transparent layer and the second transparent layer in this order from the polarizer side.
In the polarizing film, an adhesive layer may be used as the second transparent layer.
In the polarizing film, the second transparent layer may be a protective film.
In addition, the present invention relates to an image display device having the above polarizing film.
ADVANTAGEOUS EFFECTS OF INVENTION
Since the polarizer, which is a constituent element of the polarizing film, is formed of an aqueous material, moisture in the ambient atmosphere is easily introduced into the polarizer. Therefore, it is considered that when the polarizing film is kept in a high-temperature and high-humidity environment, the saturated moisture percentage under the polarizer is increased. As a result, the optical properties of the polarizing film tend to be lowered. In particular, in a high-temperature and high-humidity environment, since the amount of moisture entering the polarizer is large, the degree of polarization is greatly reduced at the ends of the polarizing film, and a phenomenon called end discoloration is considered to occur.
The polarizing film of the present invention has first transparent layers on both surfaces of a polarizer, which function as permeation films that help moisture in the polarizer to be discharged. Since the first transparent layer is designed to have a saturated moisture content lower than that of the polarizer in a high-temperature and high-humidity environment, even if moisture in the ambient atmosphere enters the polarizer, the moisture in the polarizer can be actively transmitted to the first transparent layer (permeable film) side having a saturated moisture content lower than that of the polarizer, and by this action, the moisture in the polarizer can be discharged to the outside of the polarizer. In this way, the polarizing film of the present invention, which has the first transparent layer, can suppress an increase in the saturated moisture percentage of the polarizer even in a high-temperature and high-humidity environment, and can suppress the amount of end discoloration of the polarizing film.
Drawings
Fig. 1 is an example of a schematic cross-sectional view of a polarizing film of the present invention.
Fig. 2 is an example of a schematic cross-sectional view of the polarizing film of the present invention.
Fig. 3 is an example of a schematic cross-sectional view of the polarizing film of the present invention.
Description of the symbols
P polarizer
1a first transparent layer
1b first transparent layer
2a second transparent layer (adhesive layer)
2b second clear layer (adhesive layer)
Detailed Description
Hereinafter, the polarizing film of the present invention will be described with reference to fig. 1 to 3.
The polarizing film of the present invention includes, for example, a polarizer P and first
As for the polarizing film of the present invention, for example, like the polarizing
In the
< polarizer >
The polarizer is not particularly limited, and various polarizers can be used. Examples of the polarizer include films obtained by uniaxially stretching hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene-vinyl acetate copolymer partially saponified films, and polyene oriented films such as polyvinyl alcohol dehydrated products and polyvinyl chloride desalted products, and the like. Among these, a polarizer made of a dichroic material such as a polyvinyl alcohol film and iodine is preferable. The thickness of these polarizers is not particularly limited, but is usually about 80 μm or less.
The polarizer obtained by uniaxially stretching a polyvinyl alcohol film dyed with iodine can be produced, for example, by dyeing a polyvinyl alcohol film by immersing the film in an aqueous iodine solution and stretching the film to 3 to 7 times the original length. If necessary, the substrate may be immersed in an aqueous solution of potassium iodide or the like optionally containing boric acid, zinc sulfate, zinc chloride or the like. Further, the polyvinyl alcohol film may be immersed in water and washed with water before dyeing, if necessary. By washing the polyvinyl alcohol film with water, dirt and an anti-blocking agent on the surface of the polyvinyl alcohol film can be washed off, and the polyvinyl alcohol film can be swollen to prevent unevenness such as uneven dyeing. The stretching may be performed after the dyeing with iodine, or may be performed while dyeing, or may be performed after the stretching with iodine. Stretching may be carried out in an aqueous solution or water bath of boric acid, potassium iodide, or the like.
In the present invention, a polarizer having a thickness of 10 μm or less can be used. From the viewpoint of reduction in thickness, the thickness of the polarizer is preferably 8 μm or less, more preferably 7 μm or less, and still more preferably 6 μm or less. On the other hand, the thickness of the polarizer is 2 μm or more, and more preferably 3 μm or more. Such a thin polarizer has excellent durability against thermal shock because of small thickness unevenness, excellent visibility, and small dimensional change.
Typical examples of the thin polarizers include thin polarizers described in japanese patent No. 4751486, japanese patent No. 4751481, japanese patent No. 4815544, japanese patent No. 5048120, international publication No. 2014/077599, and international publication No. 2014/077636, and thin polarizers obtained by the production methods described in these documents.
The polarizer is configured such that optical characteristics represented by a single transmittance T and a polarization degree P satisfy the following conditions:
P＞－(100.929T-42.4-1) x 100 (wherein T < 42.3), or
P is more than or equal to 99.9 (wherein, T is more than or equal to 42.3).
A polarizer configured to satisfy the above conditions has performance required for a display for a liquid crystal television using a large-sized display element. Specifically, the contrast ratio is 1000:1 or more and the maximum luminance is 500cd/m2The above. For another application, for example, the adhesive sheet can be bonded to the visible side of an organic EL display device.
As the thin polarizer, among the production methods including the step of stretching in a state of a laminate and the step of dyeing, from the viewpoint of being able to stretch to a high magnification to improve the polarizing performance, a thin polarizer obtained by a production method including the step of stretching in an aqueous boric acid solution as described in japanese patent No. 4751486, japanese patent No. 4751481, and japanese patent No. 4815544 is preferable, and a thin polarizer obtained by a production method including the step of stretching in an auxiliary gas atmosphere before stretching in an aqueous boric acid solution as described in japanese patent No. 4751481 and japanese patent No. 4815544 is particularly preferable. These thin polarizers can be obtained by a production method including a step of stretching a polyvinyl alcohol resin (hereinafter, also referred to as PVA-based resin) layer and a resin base material for stretching in a laminated state, and a step of dyeing. With this production method, even if the PVA-based resin layer is thin, it can be stretched without causing troubles such as breakage due to stretching by being supported by the stretching resin base material.
The polarizer of the present invention can be used in a polarizer having a saturation moisture content of usually 10 to 40% by weight at 85 ℃ under 85% R.H. From the viewpoint of suppressing the discoloration of the end portions, the polarizer may have a saturated water content of 25 wt% or less, and more preferably 18 wt% or less. In the relationship between the polarizer and the first transparent layer, the saturation moisture percentage of the first transparent layer is not particularly limited as long as it is lower than the saturation moisture percentage of the polarizer.
The saturated water content of the polarizer of the present invention can be adjusted by any appropriate method. For example, a method of controlling the conditions of the drying step in the process of producing the polarizer by adjusting the conditions may be mentioned.
< first transparent layer >
The first transparent layer functions as a permeable film that helps moisture in the polarizer to be discharged, and a layer in which the saturation moisture percentage of the first transparent layer at 85 ℃ and 85% r.h. is set to be lower than the saturation moisture percentage of the polarizer can be used. The saturated moisture content of the first transparent layers on both sides may be the same, or may be different if the saturated moisture content is lower than that of the polarizer. The materials and thicknesses of the first transparent layers on both sides may be the same or different.
From the viewpoint of the function as a permeable film, the difference between the saturated moisture content of the polarizer and the saturated moisture content of the first transparent layer is preferably 1 to 20 wt%, and more preferably 3 to 15 wt%. On the other hand, if the difference in the saturated water content is too small, the water-permeable membrane does not function sufficiently, and therefore, it is preferable to control the water-permeable membrane within the above range. The saturated moisture content of the first transparent layer is preferably 1 to 10% by weight, and more preferably 3 to 8% by weight.
From the viewpoint of the function as a penetration film, reduction in thickness, and optical reliability, the thickness of the first transparent layer is preferably 3 μm or less, more preferably 2 μm or less, even more preferably 1.5 μm or less, and even more preferably 1 μm or less. If the first transparent layer is too thick, the first transparent layer may have a thickness that may adversely inhibit moisture discharge and may not function as a permeable film. On the other hand, from the viewpoint of ensuring the function as a penetration film, the thickness of the first transparent layer is preferably 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.3 μm or more.
As a material for forming the first transparent layer, a material having transparency and satisfying the saturation moisture percentage can be used. Examples of such a material include a material for forming a urethane prepolymer which is a reaction product of an isocyanate compound and a polyol.
The isocyanate compound is preferably a polyfunctional isocyanate compound, and specifically, a polyfunctional aromatic isocyanate compound, alicyclic isocyanate, aliphatic isocyanate compound, or a dimer thereof may be mentioned.
Examples of the polyfunctional aromatic isocyanate compound include: benzene diisocyanate, 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, 2 '-diphenylmethane diisocyanate, 4' -toluidine diisocyanate, 4 '-diphenyl ether diisocyanate, 4' -diphenyl diisocyanate, 1, 5-naphthalene diisocyanate, xylylene diisocyanate, methylenebis 4-phenylisocyanate, p-phenylene diisocyanate, and the like.
Examples of the polyfunctional alicyclic isocyanate compound include: 1, 3-cyclopentene diisocyanate, 1, 3-cyclohexane diisocyanate, 1, 4-cyclohexane diisocyanate, 1, 3-diisocyanate methylcyclohexane, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated tetramethylxylylene diisocyanate, and the like.
Examples of the polyfunctional aliphatic isocyanate compound include: trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1, 2-propylene diisocyanate, 1, 3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4, 4-trimethylhexamethylene diisocyanate, and the like.
The polyfunctional isocyanate compound includes a polyfunctional isocyanate compound having 3 or more isocyanate groups such as tris (6-isocyanatohexyl) isocyanurate.
Examples of the polyhydric alcohol include: ethylene glycol, diethylene glycol, 1, 3-butanediol, 1, 4-butanediol, neopentyl glycol, 3-methyl-1, 5-pentanediol, 2-butyl-2-ethyl-1, 3-propanediol, 2, 4-diethyl-1, 5-pentanediol, 1, 2-hexanediol, 1, 6-hexanediol, 1, 8-octanediol, 1, 9-nonanediol, 2-methyl-1, 8-octanediol, 1, 8-decanediol, octadecanediol, glycerol, trimethylolpropane, pentaerythritol, hexanetriol, polypropylene glycol, and the like.
In the present invention, the urethane prepolymer is preferably a rigid structure having a large proportion of a cyclic structure (benzene ring, cyanurate ring, isocyanurate ring, etc.) in the structure of the molecule. For example, the polyfunctional isocyanate compounds can be used alone 1 or a combination of 2 or more, but from the point of the saturated water content adjustment, preferably aromatic isocyanate compounds. Other polyfunctional isocyanate compounds may be used in combination with the aromatic isocyanate compound. In particular, among the aromatic isocyanate compounds, at least 1 selected from the group consisting of toluene diisocyanate and diphenylmethane diisocyanate is preferably used as the isocyanate compound.
As the urethane prepolymer, trimethylolpropane-trimethylbenzene isocyanate or trimethylolpropane-tris (diphenylmethane diisocyanate) is preferably used.
In addition, a prepolymer having a protective group for a terminal isocyanate group may be used as the urethane prepolymer. As the protecting group, there are oxime, lactam and the like. The material having the blocked isocyanate group is heated to dissociate the blocking group from the isocyanate group, thereby reacting the isocyanate group.
In addition, a reaction catalyst may be used in order to increase the reactivity of the isocyanate group. The reaction catalyst is not particularly limited, and a tin-based catalyst or an amine-based catalyst is preferred. The reaction catalyst may be used in 1 or 2 or more species. The amount of the reaction catalyst used is usually 5 parts by weight or less based on 100 parts by weight of the urethane prepolymer. When the amount of the reaction catalyst is large, the crosslinking reaction speed becomes fast, causing foaming of the formed material. Even when the foamed forming material is used, sufficient adhesiveness cannot be obtained. In general, when the reaction catalyst is used, it is preferably 0.01 to 5 parts by weight, and more preferably 0.05 to 4 parts by weight.
The tin catalyst may be either an inorganic one or an organic one, but is preferably an organic one. Examples of the inorganic tin-based catalyst include: stannous chloride, stannic chloride, and the like. The organic tin catalyst is preferably one having a skeleton such as a methyl group, an ethyl group, an ether group, or an ester group and having at least 1 kind of organic group such as an aliphatic group or an alicyclic group. Examples thereof include: tetra-n-butyltin, tri-n-butyltin acetate, n-butyltin trichloride, trimethyltin hydroxide, dimethyltin dichloride, dibutyltin dilaurate, and the like.
The amine catalyst is not particularly limited. For example, a catalyst having at least 1 organic group such as an alicyclic group is preferable, such as quinacridone, amidine, diazabicycloundecene, etc. Further, as the amine catalyst, triethylamine and the like can be mentioned. Examples of the reaction catalyst other than the above include cobalt naphthenate and benzyltrimethylammonium hydroxide.
The above urethane prepolymer is generally used in the form of a solution. The solution may be solvent-based, or may be aqueous, such as an emulsion, a colloidal dispersion, or an aqueous solution. The organic solvent is not particularly limited as long as the components constituting the forming material can be uniformly dissolved. Examples of the organic solvent include: toluene, methyl ethyl ketone, ethyl acetate, and the like. When the aqueous dispersion is formed, alcohols such as n-butanol and isopropanol, and ketones such as acetone may be blended. When the urethane prepolymer is formed into an aqueous solution, the urethane prepolymer may be formed into an aqueous solution by using a dispersant or introducing a functional group having low reactivity with an isocyanate group such as a carboxylate, a sulfonate or a quaternary ammonium salt, or a water-dispersible component such as polyethylene glycol.
Examples of the material for forming the first transparent layer other than the urethane prepolymer include: cyanoacrylate-based forming materials, epoxy-based forming materials.
The first transparent layer may be formed as appropriate depending on the type of the forming material, and for example, the forming material may be applied to a polarizer, a resin film, or the like and then cured, and the transparent layer may be obtained as a coating layer. This is generally carried out by the following method: and drying the coating at about 30 to 100 ℃, preferably about 50 to 80 ℃ for about 0.5 to 15 minutes after the coating, thereby forming a cured layer. When the forming material contains an isocyanate component, the reaction may be accelerated by annealing at about 30 to 100 ℃, preferably at about 50 to 80 ℃ for about 0.5 to 24 hours.
The first transparent layer preferably has the following structure: the first transparent layer has a gradient distribution in which a saturated moisture concentration at 85 ℃ and 85% R.H. decreases gradually from the polarizer side toward the side opposite to the polarizer. With such a structure, the function as a permeable membrane can be more effectively exhibited.
< second transparent layer >
A second transparent layer may be further formed on the first transparent layer in the polarizing film of the present invention. Various layers can be formed as the second transparent layer, but from the viewpoint of further functioning as a permeable film, it is preferable to provide the second transparent layer having a saturated moisture percentage lower than that of the first transparent layer.
From the viewpoint of the function as a permeable film, the difference between the saturated moisture content of the first transparent layer and the saturated moisture content of the second transparent layer is preferably 0.1 to 8 wt%, and more preferably 0.5 to 5 wt%. It should be noted that, although there is no problem if the difference is too large, on the other hand, if it is too small, the function as a permeable membrane is not sufficiently exhibited, and therefore, it is preferable to perform control within the above range. The saturated moisture content of the second transparent layer is preferably in a range lower than the saturated moisture content of the first transparent layer, but a saturated moisture content of 0.1 to 8 wt% is generally preferable, and a saturated moisture content of 0.5 to 5 wt% is more preferable.
The second transparent layer has a thickness of about 1 to 100 μm from the viewpoint of a function as a penetration film. Preferably 2 to 50 μm, more preferably 2 to 40 μm, and further preferably 5 to 35 μm.
The second transparent layer may be formed of a resin film such as an adhesive layer, a hard coat layer, or a protective film. Among these, the adhesive layer is preferable from the viewpoint of suppressing the discoloration of the end portion of the polarizing film. When the second transparent layers are provided on both surfaces, the material and thickness of each second transparent layer may be the same or different.
Second transparent layer: adhesive layer
When the pressure-sensitive adhesive layer is formed, a suitable pressure-sensitive adhesive can be used, and the type thereof is not particularly limited. Examples of the binder include: rubber-based adhesives, acrylic adhesives, silicone-based adhesives, urethane-based adhesives, vinyl alkyl ether-based adhesives, and the like.
Among these pressure-sensitive adhesives, those excellent in optical transparency, exhibiting suitable adhesive properties such as wettability, cohesiveness and adhesiveness, and excellent in weather resistance, heat resistance and the like can be preferably used. As the adhesive exhibiting such characteristics, an acrylic adhesive can be preferably used.
As a method for forming the pressure-sensitive adhesive layer, the following method can be used: for example, a method in which the adhesive is applied to a separator or the like subjected to a peeling treatment, and then a polymerization solvent or the like is dried and removed to form an adhesive layer, followed by transfer to a first transparent layer; or a method of applying the adhesive to the first transparent layer, drying the first transparent layer to remove the polymerization solvent and the like, and forming an adhesive layer on the polarizer; and so on. In the case of applying the adhesive, one or more solvents other than the polymerization solvent may be added newly as appropriate.
As the separator subjected to the peeling treatment, a silicone release liner can be preferably used. In the step of forming the pressure-sensitive adhesive layer by applying the pressure-sensitive adhesive of the present invention to such a liner and drying the applied pressure-sensitive adhesive, a suitable method can be appropriately employed as a method for drying the pressure-sensitive adhesive according to the purpose. The method of drying the coating film by heating is preferably used. The heating and drying temperature is preferably 40 to 200 ℃, more preferably 50 to 180 ℃, and particularly preferably 70 to 170 ℃. By setting the heating temperature in the above range, an adhesive having excellent adhesive characteristics can be obtained.
The drying time may be suitably employed as appropriate. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, and particularly preferably 10 seconds to 5 minutes.
As a method for forming the adhesive layer, various methods can be employed. Specific examples thereof include: roll coating, roll and lick coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, blade coating, air knife coating, curtain coating, lip coating, extrusion coating using a die coater, and the like.
The thickness of the adhesive layer is not particularly limited, and is, for example, about 1 to 100 μm. Preferably 2 to 50 μm, more preferably 2 to 40 μm, and further preferably 5 to 35 μm.
When the pressure-sensitive adhesive layer is exposed, the pressure-sensitive adhesive layer can be protected with a sheet (separator) subjected to a peeling treatment until it is actually used.
Examples of the constituent material of the separator include: plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films, porous materials such as paper, cloth, and nonwoven fabrics, and suitable sheets such as nets, foamed sheets, metal foils, and laminates thereof, and the like.
The plastic film is not particularly limited as long as it can protect the pressure-sensitive adhesive layer, and examples thereof include: polyethylene films, polypropylene films, polybutylene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, vinyl chloride copolymer films, polyethylene terephthalate films, polybutylene terephthalate films, polyurethane films, ethylene-vinyl acetate copolymer films, and the like.
The thickness of the separator is usually 5 to 200 μm, preferably about 5 to 100 μm. The separator may be subjected to a mold release and antifouling treatment using a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based mold release agent, silica powder, or the like, or an antistatic treatment such as a coating-type, a mixing-type, or a vapor deposition-type treatment, as required. In particular, the surface of the separator may be appropriately subjected to a release treatment such as a silicone treatment, a long-chain alkyl treatment, or a fluorine treatment, thereby further improving the releasability from the pressure-sensitive adhesive layer.
Second transparent layer: protective film
The material constituting the protective film is preferably excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, and the like. Examples thereof include: polyester polymers such AS polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such AS cellulose diacetate and cellulose triacetate, acrylic polymers such AS polymethyl methacrylate, styrene polymers such AS polystyrene and acrylonitrile-styrene copolymer (AS resin), and polycarbonate polymers. Examples of the polymer forming the protective film include: examples of the polymer include polyolefin polymers such as polyethylene, polypropylene, cyclic polyolefins having a norbornene structure, and ethylene-propylene copolymers, amide polymers such as vinyl chloride polymers, nylon and aromatic polyamides, imide polymers, sulfone polymers, polyethersulfone polymers, polyetheretherketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, aromatic ester polymers, polyoxymethylene polymers, epoxy polymers, and blends of the above polymers.
The protective film may contain 1 or more kinds of any appropriate additives. Examples of additives include: ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, colorants, and the like. The content of the thermoplastic resin in the protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, even more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. When the content of the thermoplastic resin in the protective film is 50 wt% or less, there is a possibility that high transparency inherent in the thermoplastic resin cannot be sufficiently exhibited.
As the protective film, a retardation film, a brightness enhancement film, a diffusion film, or the like can be used. Examples of the retardation film include a retardation film having a front retardation of 40nm or more and/or a thickness direction retardation of 80nm or more. The front phase difference is usually controlled within a range of 40 to 200nm, and the thickness direction phase difference is usually controlled within a range of 80 to 300 nm. When the retardation film is used as the protective film, the retardation film also functions as a polarizer protective film, and therefore, the thickness can be reduced.
Examples of the retardation film include a birefringent film obtained by subjecting a thermoplastic resin film to a uniaxial stretching treatment or a biaxial stretching treatment. The temperature and stretch ratio of the stretching can be appropriately set depending on the retardation value, the material and thickness of the film.
The thickness of the protective film may be suitably determined, but is usually about 1 to 500 μm in view of strength, workability such as workability, and thin layer property. Particularly preferably 1 to 300 μm, more preferably 5 to 200 μm, further preferably 5 to 150 μm, and particularly preferably 20 to 100 μm.
A functional layer such as a hard coat layer, an antireflection layer, an adhesion prevention layer, a diffusion layer, or an antiglare layer may be provided on the surface of the protective film that is not bonded to the polarizer. The functional layers such as the hard coat layer, the antireflection layer, the adhesion prevention layer, the diffusion layer, and the antiglare layer may be provided as the protective film itself, or may be provided separately from the protective film.
The protective film (second transparent layer) may be directly attached to the 1 st transparent layer.
< surface protective film >
A surface protective film may be provided on the polarizing film of the present invention. The surface protective film generally has a base film and an adhesive layer, and protects the polarizer via the adhesive layer.
The base film of the surface protective film may be selected from materials having isotropy or near isotropy from the viewpoints of inspection property, manageability, and the like. Examples of the film material include: transparent polymers such as polyester resins such as polyethylene terephthalate films, cellulose resins, acetate resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, and acrylic resins. Of these, polyester-based resins are preferred. The substrate film may be a laminate of 1 or 2 or more kinds of film materials, or a stretched product of the above film. The thickness of the base film is usually 500 μm or less, preferably 10 to 200 μm.
As the pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer of the surface protective film, a pressure-sensitive adhesive containing a polymer such as a (meth) acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine polymer, or a rubber as a base polymer can be appropriately selected and used. From the viewpoint of transparency, weather resistance, heat resistance and the like, an acrylic adhesive containing an acrylic polymer as a base polymer is preferred. The thickness of the adhesive layer (dry film thickness) may be determined according to the desired adhesive force. Usually about 1 to 100 μm, preferably 5 to 50 μm.
In the surface protective film, a release treated layer may be provided on the surface of the base film opposite to the surface on which the pressure-sensitive adhesive layer is provided, using a low-adhesion material subjected to a silicone treatment, a long-chain alkyl treatment, a fluorine treatment, or the like.
< other optical layers >
The polarizing film of the present invention can be used as an optical film laminated with other optical layers in actual use. The optical layer is not particularly limited, and 1 or 2 or more layers of optical layers, which are used in the formation of liquid crystal display devices and the like, such as a reflective plate, a semi-transmissive plate, a retardation plate (including 1/2 wave plates, 1/4 wave plates, and the like), a viewing angle compensation film, and the like, may be used. In particular, a reflective polarizing film or a semi-transmissive polarizing film in which a reflective plate or a semi-transmissive reflective plate is further laminated on the polarizing film of the present invention, an elliptical polarizing film or a circular polarizing film in which a retardation plate is further laminated on the polarizing film, a wide-angle polarizing film in which a viewing angle compensation film is further laminated on the polarizing film, or a polarizing film in which a brightness enhancement film is further laminated on the polarizing film is preferable.
The optical film obtained by laminating the above optical layers on the polarizing film may be formed by sequentially laminating the respective layers in the manufacturing process of a liquid crystal display device or the like, but when the optical film is formed by laminating the layers in advance, there are advantages in that stability of quality, assembling work and the like are excellent, and the manufacturing process of the liquid crystal display device or the like can be improved. The lamination may be carried out by a suitable bonding method such as an adhesive layer. When the polarizing film and the other optical film are bonded to each other, the optical axes thereof may be set at an appropriate arrangement angle depending on the desired retardation characteristics and the like.
The polarizing film or the optical film of the present invention can be preferably used for formation of various image display devices such as a liquid crystal display device and an organic EL display device. The liquid crystal display device can be formed in a conventional manner. That is, the liquid crystal display device can be generally formed by appropriately assembling a liquid crystal cell, a polarizing film or an optical film, and components such as an illumination system used as needed, and introducing them into a driver circuit or the like. As the liquid crystal cell, any type of liquid crystal cell such as IPS type, VA type, etc. can be used, and IPS type is particularly preferable.
A suitable liquid crystal display device such as a liquid crystal display device in which a polarizing film or an optical film is disposed on one side or both sides of a liquid crystal cell, a liquid crystal display device using a backlight or a reflector in an illumination system, or the like can be formed. At this time, the polarizing film or the optical film of the present invention may be disposed on one side or both sides of the liquid crystal cell. In the case where the polarizing film or the optical film is provided on both sides, they may be the same material or different materials. Further, in forming a liquid crystal display device, appropriate members such as a diffusion plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, and a backlight may be disposed in appropriate positions in 1 layer or 2 layers or more.