JP2002303726A - Polarizing film, protective film for polarizer, method for manufacturing polarizing film, optical film and liquid crystal display device both using the polarizing film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing film solving a problem brought about by use of an adhesive. SOLUTION: The polarizing film has a protective film (B) arranged on at least one side surface of a polarizer (A) and is characterized by having the protective film (B) composed of a polymer film with two or more film layers and by having a softening point of a resin forming a film layer (b1 ) on the polarizer (A) side lower than that of a resin forming the outermost film layer (bX).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a polarizing film and a protective film for a polarizer. The present invention also relates to a method for producing a polarizing film, in which a protective film for a polarizer is heated and pressed on a polarizer. The polarizing film of the present invention can form a liquid crystal display device alone or as an optical film obtained by laminating the polarizing film.

[0002]

2. Description of the Related Art In a liquid crystal display device, it is indispensable to dispose polarizers on both sides of a glass substrate forming the outermost surface of a liquid crystal panel due to its image forming method.
BACKGROUND ART A polarizing film in which a protective film is bonded to a polarizer made of a dichroic substance such as a polyvinyl alcohol-based film and iodine is used.

Conventionally, the polarizing film has been manufactured by bonding a polarizer and a protective film with an adhesive. The adhesive is a compound or composition having a binding component, which is also used as a solution dissolved in water or an organic solvent or the like, and is cured by heating, light irradiation, a chemical reaction, or the like. Such an adhesive is poured between these layers immediately before laminating the polarizer and the protective film,
It is previously applied to either the polarizer or the protective film.

However, when an adhesive is used, it must go through a coating step, a laminating step, and a drying step, so that a large number of steps are required as a manufacturing process, and a large cost is required for production equipment. In addition, the protective film must be subjected to a saponification treatment, a corona treatment, a plasma treatment, a low-pressure UV treatment, a further undercoating treatment, etc. in order to increase the adhesion to the polarizer. As a result, the production cost of the obtained polarizing film becomes high. In addition, when the manufacturing process includes a large number of steps, there are many factors that cause defects in each of the steps.

Further, since a water-soluble adhesive such as an aqueous solution of polyvinyl alcohol is often used as the adhesive, the produced polarizing film has insufficient durability under heating and humidifying conditions. Therefore, the adhesive is easily affected by moisture, which is one of the causes of the early deterioration of the polarizing film.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polarizing film and a method for producing the same, which have solved the problems caused by using an adhesive. It is another object of the present invention to provide a polarizer protective film used for the polarizing film. Still another object is to provide an optical film and a liquid crystal display device in which the polarizing films are laminated.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, have found that the above-mentioned object can be achieved by the following polarizing film and the like, and have completed the present invention. .

[0008] That is, the present invention reduces the number of polarizers (A).
A protective film (B) is provided on one side.
A polarizing film, wherein the protective film (B) has two or more layers.
Polarized, consisting of a polymer film with an upper film layer
Film layer (b) on the child (A) side ₁ Softening of the resin forming
The point is the outermost film layer (b_X ) Of the resin forming
Polarizing film characterized by having a lower softening point
About.

The protective film (B) in the polarizing film is formed of two or more film layers, and further forms a film layer (b ₁ ) on the side of the protective film (B) which is brought into close contact with the polarizer (A). The softening point of the resulting resin is lower than the softening point of the outermost film layer (b _x ). By utilizing the difference in softening point between the film layers, the protective film (B) is heat-pressed to the polarizer (A) at a temperature at which only the film layer (b ₁ ) softens, thereby protecting the polarizer (A). The film (B) can be adhered without using an adhesive. As described above, since the polarizing film of the present invention adheres the polarizer (A) to the protective film (B) without using an adhesive, the polarizing film relates to a manufacturing problem due to the use of the adhesive and to the adhesive. There is no problem with the durability of the polarizing film.

In the above polarizing film, the softening point of the resin forming the film layer (b ₁ ) of the protective film (B) is preferably 80 ° C. or higher.

The softening point of the film layer (b ₁ ) is not particularly limited, but is preferably 80 ° C. or higher in consideration of the durability of the polarizing film. In particular, the softening point of the film layer (b ₁ )
It is preferred that the temperature is 90 ° C. or higher. On the other hand, if the softening point of the film layer (b ₁ ) is too high, the heating temperature becomes high, which may hinder the performance of the polarizer (A). Therefore, the softening point of the film layer (b ₁ ) is 280 ° C. or less. , And 2
50 ° C. or lower is preferred.

In the above polarizing film, the difference between the softening point of the resin forming the film layer (b ₁ ) and the softening point of the resin forming the film layer (b _X ) is preferably 5 ° C. or more. .

When the difference between the softening points of the resin forming the film layer (b ₁ ) and the resin forming the film layer (b _X ) is reduced, the lamination of the polarizer (A) and the protective film (B) by heat-pressing is difficult. Since the film layer (b _x ) also tends to be softened, and high-quality lamination tends to be difficult, the difference in the softening points is preferably 5 ° C. or more, more preferably 10 ° C. or more.

The present invention also relates to a polymer film having two or more film layers, wherein the resin forming the film layer (b ₁ ) adhered to the polarizer (A) has a softening point of the outermost film layer. (b _X) protective film (B) a protective film for a polarizer to be used as the polarizing film, characterized in that below the softening point of the resin forming the concerns.

The polarizing film of the present invention can be obtained by using such a protective film for a polarizer as the protective film (B) and laminating it with the polarizer (A). Incidentally, polarizing film layer of the photon protective film (b ₁₎ formed to the softening point of the resin is 80 ° C. or more, the film layer (b ₁₎ resin and film layer to form a (b _X) softening point of the resin forming the Is preferably 5 ° C. or more.

Further, the present invention is characterized in that the film layer (b ₁ ) of the protective film for a polarizer (B) is bonded to at least one surface of the polarizer (A), and is laminated by heating and pressing. And a method for producing a polarizing film.

[0017] By only film layer (b ₁₎ is heated crimping protective film for a polarizer at temperatures to soften the (B) to the polarizer (A), without using an adhesive, momentarily polarizer (A ) Can be adhered to the protective film (B).

The present invention also relates to an optical film in which at least one polarizing film is laminated, and a liquid crystal display device using the polarizing film or the optical film.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIG. 1, a polarizing film of the present invention has a protective film (B) directly provided on at least one surface of a polarizer (A). In FIG. 1, a protective film (B) is provided on one side of the polarizer (A). The protective film (B) may be provided on both sides of the polarizer (A).

The polarizer (A) is not particularly limited, and various types can be used. As the polarizer (A), for example,
Adsorb dichroic substances, such as iodine and dichroic dyes, to hydrophilic polymer films, such as polyvinyl alcohol-based films, partially formalized polyvinyl alcohol-based films, and ethylene / vinyl acetate copolymer-based partially saponified films, and uniaxially. Stretched products, polyene-based oriented films such as dehydration products of polyvinyl alcohol and dehydrochlorination products of polyvinyl chloride, and the like can be given. Among these, a polarizer composed of a polyvinyl alcohol-based film and a dichroic substance such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm.

A polarizer which is obtained by dyeing a polyvinyl alcohol-based film with iodine and uniaxially stretching is produced by, for example, dyeing polyvinyl alcohol by immersing it in an aqueous solution of iodine and stretching it to 3 to 7 times its original length. Can be. If necessary, it can be immersed in an aqueous solution of potassium iodide or the like which may contain boric acid, zinc sulfate, zinc chloride or the like. Further, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed with water before dyeing. By washing the polyvinyl alcohol-based film with water, dirt on the surface of the polyvinyl alcohol-based film and an anti-blocking agent can be washed, and by swelling the polyvinyl alcohol-based film, the effect of preventing unevenness such as uneven dyeing can be obtained. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be stretched and then dyed with iodine. Stretching can be performed in an aqueous solution of boric acid or potassium iodide or in a water bath.

As shown in FIG. 1, the protective film (B) provided on one or both sides of the polarizer (A) has a film layer (b ₁ ) in close contact with the polarizer (A) and an outermost film layer. It comprises a film layer having at least two layers of (b _x ). FIG. 1 illustrates a case in which, in addition to the film layer (b ₁ ) and the film layer (b _X ), a film layer is provided between them, but the intermediate layer is arbitrarily provided on the protective film.

As the material of the protective film (B), those having excellent transparency, mechanical strength, heat stability, moisture shielding property, isotropy and the like are preferable. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, and styrene such as polystyrene and acrylonitrile-styrene copolymer (AS resin). Polymers, polycarbonate polymers and the like. In addition, polyethylene, polypropylene, polyolefin having a cyclo- or norbornene structure, polyolefin polymers such as ethylene-propylene copolymer, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, and sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer,
Vinylidene chloride-based polymers, vinyl butyral-based polymers, arylate-based polymers, polyoxymethylene-based polymers, epoxy-based polymers, and blends of the above-mentioned polymers are also examples of the polymer forming the transparent protective film.

In the protective film (B) of the present invention, the softening point of the resin forming the film layer (b ₁ ) is
_X) to be lower than the softening point of the resin forming the, by selecting the material appropriately, prepared by forming two or more layers of the film layers. The resin forming the film layer (b ₁ ) and the resin forming the film layer (b _X ) may be of the same material or different materials as long as they have the above softening point difference. Materials are preferred. However, as the resin forming the film layer (b ₁ ), a thermoplastic resin which is softened by heating and pressing is used. The softening point is a value measured by the Vicat softening temperature test method of JIS K7206.

The thickness of the protective film (B) is generally 5
00 μm or less, preferably 1 to 300 μm. In particular, the thickness is preferably 5 to 200 μm. The thickness of the protective film (B) is particularly preferably 50 μm or less. In consideration of the heat-bondable film layer (b ₁₎ from 1 to 10
It is preferable that the thickness is about 0 μm and the film layer (b _x ) is about 10 to 450 μm.

[0026] The film layer (b _X), the hard coat layer or anti-reflection treatment, anti-sticking and may be one subjected to treatment for diffusion or antiglare. The anti-reflection layer, the anti-sticking layer,
The diffusion layer, the antiglare layer and the like can be provided on the protective film (B) itself, or can be provided as an optical layer separately from the protective film (B).

The polarizing film of the present invention is obtained by laminating at least one surface of the polarizer (A) on the side of the film layer (b ₁ ) of the protective film (B) and laminating by heating and pressing. can get.

Bonding of the polarizer (A) and the protective film (B) can be performed by passing through a roll. Heating is performed on the film layer (b ₁ ) and the film layer (b _X )
Film layer (b) in consideration of the softening point of the resin forming
₁ ) softens (melts) but does not soften the film layer (b _X ), that is, the softening point of the resin forming the film layer (b ₁ ) and the softening point of the resin forming the film layer (b _X ) It is preferable to set the temperature range in the middle of the above range. The heating is preferably performed from the side of the protective film (B) without damaging the polarizer (A). After thermocompression bonding,
By cooling, the film layer (b ₁ ) is cured, and the polarizer (A) and the protective film (B) adhere to each other.

The method of thermocompression bonding is not particularly limited, and a method of pressing simultaneously or sequentially with heating can be employed. As a heating method, for example, IR heater, hot air, high frequency,
A non-contact heating method using ultrasonic waves or the like, or a contact heating method based on heat conduction using a hot plate or a heat roll, and the like can be given. As the pressure bonding method, a method of pressing with a pinch roll or the like can be given. Pressurization can also be performed in a vacuum. When pressure is applied simultaneously with heating, a method of passing a pinch roll in a heated state can be employed.

The polarizing film of the present invention can be used as an optical film laminated with another optical layer in practical use. The optical layer is not particularly limited. For example, it is used for forming a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including a wavelength plate such as 1/2 or 1/4), and a viewing angle compensation film. One or more optical layers that may be used may be used. In particular, a reflective polarizing film or a transflective polarizing film in which a polarizing plate or a transflective reflecting plate is further laminated on the polarizing film of the present invention, an elliptically polarizing film or a circularly polarized light in which a retardation plate is further laminated on a polarizing film A wide viewing angle polarizing film in which a viewing angle compensation film is further laminated on a film or a polarizing film, or a polarizing film in which a brightness enhancement film is further laminated on a polarizing film is preferable.

The reflection type polarizing film is provided with a reflection layer on the polarizing film, and is used to form a liquid crystal display device or the like that reflects incident light from the viewing side (display side) to display. In addition, there is an advantage that the light source such as a backlight can be omitted and the liquid crystal display device can be easily made thinner. The reflective polarizing film can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is provided on one surface of the polarizing film via a transparent protective layer or the like as necessary.

Specific examples of the reflective polarizing film include a transparent protective film that has been matted as required, and a reflective layer formed by attaching a foil or a vapor-deposited film made of a reflective metal such as aluminum to one surface. can give. In addition, there may be mentioned, for example, a transparent protective film in which fine particles are contained to form a fine surface unevenness structure, and a reflective layer having a fine unevenness structure is formed thereon. The reflection layer having the fine uneven structure described above has an advantage of diffusing incident light by irregular reflection, preventing directivity and glare, and suppressing unevenness in brightness and darkness. Further, the transparent protective film containing fine particles also has an advantage that the incident light and the reflected light thereof are diffused when transmitting the light and the unevenness of brightness can be further suppressed. The formation of the reflective layer of the fine uneven structure reflecting the fine uneven structure on the surface of the transparent protective film is performed by, for example, making the metal transparent by an appropriate method such as an evaporation method such as a vacuum evaporation method, an ion plating method, or a sputtering method, or a plating method. It can be performed by a method of directly attaching to the surface of the protective layer.

The reflection plate may be used as a reflection sheet or the like in which a reflection layer is provided on an appropriate film according to the transparent film instead of the method of directly applying the reflection film to the transparent protective film. Since the reflective layer is usually made of a metal, the use form in which the reflective surface is covered with a transparent protective film, a polarizing film, or the like is intended to prevent a decrease in reflectance due to oxidation and, as a result, a long-lasting initial reflectance. It is more preferable to avoid separately providing a protective layer.

The transflective polarizing film can be obtained by forming a transflective reflective layer such as a half mirror that reflects and transmits light with the reflective layer. A transflective polarizing film is usually provided on the back side of a liquid crystal cell. When a liquid crystal display device or the like is used in a relatively bright atmosphere, an image is displayed by reflecting incident light from the viewing side (display side). In a relatively dark atmosphere, it is possible to form a liquid crystal display device of a type that displays an image using a built-in light source such as a backlight built in the back side of a transflective polarizing film. That is, the transflective polarizing film can save energy for use of a light source such as a backlight in a bright atmosphere, and is useful for forming a liquid crystal display device of a type that can be used with a built-in light source even in a relatively bright atmosphere. It is.

An elliptically polarizing film or a circularly polarizing film in which a retardation plate is further laminated on a polarizing film will be described. Change linearly polarized light to elliptically polarized light or circularly polarized light,
When changing elliptically polarized light or circularly polarized light to linearly polarized light or changing the polarization direction of linearly polarized light, a phase difference plate or the like is used. In particular, as a retardation plate for converting linearly polarized light to circularly polarized light or for converting circularly polarized light to linearly polarized light, a so-called 4 quarter wave plate
A wave plate (also called a λ / 4 plate) is used. A half-wave plate (also called a λ / 2 plate) is usually used to change the polarization direction of linearly polarized light.

The elliptically polarizing film compensates (prevents) the coloring (blue or yellow) caused by the birefringence of the liquid crystal layer of the liquid crystal display device of the Spartist Nematic (STN) type to provide a black-and-white display without the coloring. Used effectively. Further, the one in which the three-dimensional refractive index is controlled compensates (prevents) coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction.
It is preferred that The circularly polarizing film is effectively used, for example, when adjusting the color tone of an image of a reflection type liquid crystal display device that displays an image in color, and also has an antireflection function. As a specific example of the above-mentioned retardation plate,
Birefringent film, liquid crystal polymer alignment film, liquid crystal polymer alignment film obtained by stretching a film made of a suitable polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene and other polyolefins, polyarylate, and polyamide. One in which the layer is supported by a film is exemplified. The retardation plate may have an appropriate retardation according to the purpose of use such as, for example, various wavelength plates or those intended for compensation of a viewing angle or the like due to birefringence of a liquid crystal layer, and may have two or more types. A retardation plate may be laminated to control optical characteristics such as retardation.

The above-mentioned elliptically polarizing film or reflection type elliptically polarizing film is obtained by laminating a polarizing film or a reflection type polarizing film and a retardation plate in an appropriate combination. Such an elliptically polarizing film or the like can be formed by sequentially and separately laminating a (reflection type) polarizing film and a retardation plate in the manufacturing process of a liquid crystal display device so as to form a combination. An optical film such as a polarizing film has an advantage that the stability of quality and laminating workability are excellent and the production efficiency of a liquid crystal display device or the like can be improved.

The viewing angle compensation film is a film for widening the viewing angle so that an image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a direction not perpendicular to the screen but slightly oblique. Such a viewing angle compensating retardation plate includes, for example, a retardation film, an alignment film such as a liquid crystal polymer, and a transparent substrate on which an alignment layer such as a liquid crystal polymer is supported. A normal retardation plate is a polymer film having birefringence uniaxially stretched in the plane direction, whereas a retardation plate used as a viewing angle compensation film is biaxially stretched in the plane direction. Polymer films having birefringence, biaxially stretched films such as biaxially stretched films and polymers with birefringence in which the refractive index in the thickness direction, which is uniaxially stretched in the plane direction and also stretched in the thickness direction, is controlled. Used. Examples of the obliquely oriented film include a film obtained by bonding a heat shrinkable film to a polymer film and subjecting the polymer film to a stretching treatment and / or a shrinkage treatment under the action of the shrinkage force caused by heating, or a film obtained by obliquely orienting a liquid crystal polymer. No. As the raw material polymer of the retardation plate, the same polymer as that described in the above retardation plate is used. Prevention of coloring due to a change in the viewing angle based on the phase difference by the liquid crystal cell and expansion of the viewing angle for good visibility. Any suitable one for the purpose can be used.

In order to achieve a wide viewing angle with good visibility, an optically anisotropic layer composed of a liquid crystal polymer orientation layer, particularly a discotic liquid crystal polymer inclined orientation layer was supported by a triacetyl cellulose film. An optical compensation retardation plate can be preferably used.

A polarizing film obtained by laminating a polarizing film and a brightness enhancement film is usually used by being provided on the back side of a liquid crystal cell. The brightness enhancement film exhibits the property of reflecting linearly polarized light of a predetermined polarization axis or circularly polarized light of a predetermined direction when natural light is incident due to reflection from a backlight or a back side of a liquid crystal display device, and transmits other light. ,
The polarizing film obtained by laminating the brightness enhancement film and the polarizing film, while receiving light from a light source such as a backlight to obtain transmitted light in a predetermined polarization state, light other than the predetermined polarization state is reflected without transmitting. . The light reflected on the surface of the brightness enhancement film is further inverted through a reflection layer or the like provided on the rear side thereof and re-entered on the brightness enhancement film, and a part or all of the light is transmitted as light of a predetermined polarization state to achieve brightness. In addition to increasing the amount of light transmitted through the enhancement film, it is also possible to increase the amount of light that can be used for liquid crystal display and image display by supplying polarized light that is hardly absorbed by the polarizer, thereby improving the luminance. That is, when light is incident through a polarizer from the back side of a liquid crystal cell with a backlight or the like without using a brightness enhancement film, light having a polarization direction that does not match the polarization axis of the polarizer is almost completely polarized. Is absorbed by the polarizer and does not pass through the polarizer. That is, although it depends on the characteristics of the polarizer used, about 50% of the light is absorbed by the polarizer, and accordingly, the amount of light that can be used for displaying a liquid crystal image is reduced, and the image becomes dark. The brightness enhancement film is such that light having a polarization direction that is absorbed by the polarizer is once reflected by the brightness enhancement film without being incident on the polarizer, and then inverted through a reflection layer or the like provided behind the same. The light is repeatedly incident on the plate to improve the brightness, and only the polarized light whose polarization direction has been changed so that the polarization direction of the light reflected and inverted between the two can pass through the polarizer. Since the brightness enhancement film is transmitted and absorbed by the polarizer, light from a backlight or the like can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.

As the above-mentioned brightness improving film, linearly polarized light having a predetermined polarization axis is transmitted and other light is reflected, such as a multilayer thin film of a dielectric or a multilayer laminate of thin films having different refractive index anisotropy. Such as those exhibiting the characteristic of having a cholesteric liquid crystal polymer oriented film or an oriented liquid crystal layer supported on a film substrate, reflecting either left-handed or right-handed circularly polarized light and transmitting other light. Appropriate materials such as those exhibiting characteristics can be used.

Accordingly, in the brightness enhancement film of the type that transmits linearly polarized light having a predetermined polarization axis, the transmitted light is incident on the polarization film with the polarization axis aligned as it is, thereby suppressing absorption loss by the polarization film. It can be transmitted efficiently. On the other hand, in a brightness enhancement film of a type that emits circularly polarized light such as a cholesteric liquid crystal layer, it can be directly incident on a polarizer,
From the viewpoint of suppressing the absorption loss, it is preferable that the circularly polarized light is linearly polarized through a phase difference plate and is incident on a polarizing film. By using a quarter-wave plate as the retardation plate, circularly polarized light can be converted to linearly polarized light.

A retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light region is, for example, a retardation layer that functions as a quarter-wave plate for light-color light having a wavelength of 550 nm and another retardation layer. It can be obtained by a method of superimposing a retardation layer exhibiting characteristics, for example, a retardation layer functioning as a half-wave plate. Therefore, the retardation plate disposed between the polarizing film and the brightness enhancement film may be composed of one or more retardation layers.

Note that the cholesteric liquid crystal layer also
Two layers or three layers in combination with different reflection wavelengths
By adopting an arrangement structure in which layers are superimposed, it is possible to obtain circularly polarized light in a wide wavelength range such as a visible light region, and to obtain transmitted circularly polarized light in a wide wavelength range based on the reflected light.

The polarizing film may be formed by laminating a polarizing film and two or three or more optical layers as in the above-mentioned polarized light separating type polarizing film. Therefore, a reflective elliptically polarizing film or a semi-transmissive elliptically polarizing film obtained by combining the above-mentioned reflective polarizing film or semi-transmissive polarizing film with a retardation plate may be used.

The optical film obtained by laminating the optical layer on a polarizing film can also be formed by a method of sequentially laminating the optical film in the process of manufacturing a liquid crystal display device or the like. Has an advantage that it is excellent in quality stability and assembling work, and can improve a manufacturing process of a liquid crystal display device or the like. Appropriate bonding means such as an adhesive layer can be used for lamination. When bonding the polarizing film and other optical films, their optical axes can be set at an appropriate arrangement angle according to the target retardation characteristics and the like.

The above-mentioned polarizing film or an optical film in which at least one polarizing film is laminated may be provided with an adhesive layer for bonding to another member such as a liquid crystal cell. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, for example, an acrylic polymer, a silicone-based polymer,
Polyesters, polyurethanes, polyamides, polyethers, fluorine-based or rubber-based polymers having a base polymer can be appropriately selected and used. In particular, an acrylic adhesive having excellent optical transparency, exhibiting appropriate wettability, cohesiveness and adhesive adhesive properties, and having excellent weather resistance and heat resistance can be preferably used.

In addition to the above, prevention of a foaming phenomenon and a peeling phenomenon due to moisture absorption, a decrease in optical characteristics due to a difference in thermal expansion, a prevention of warpage of a liquid crystal cell, and a formability of a liquid crystal display device having high quality and excellent durability. In view of the above, an adhesive layer having a low moisture absorption rate and excellent heat resistance is preferable.

The adhesive layer is made of, for example, a natural or synthetic resin, particularly a tackifying resin, a filler, a pigment, a coloring agent, a glass fiber, a glass bead, a metal powder, or another inorganic powder. It may contain an additive such as an inhibitor added to the adhesive layer. Further, an adhesive layer containing fine particles and exhibiting light diffusibility may be used.

The attachment of the adhesive layer to one or both sides of the polarizing film or the optical film can be performed by an appropriate method. As an example, an adhesive solution of about 10 to 40% by weight is prepared by dissolving or dispersing a base polymer or a composition thereof in a solvent composed of a single substance or a mixture of appropriate solvents such as toluene and ethyl acetate. A method of directly attaching it on a polarizing film or an optical film by an appropriate developing method such as a casting method or a coating method, or forming an adhesive layer on a separator according to the above and forming it on a polarizing film or an optical film. There is a method of transferring to the top.

The adhesive layer may be provided on one side or both sides of a polarizing film or an optical film as a superposed layer of different compositions or types. When provided on both surfaces, it is also possible to form an adhesive layer having a different composition, type and thickness on the front and back of the polarizing film or optical film. The thickness of the pressure-sensitive adhesive layer can be appropriately determined depending on the purpose of use and adhesive strength,
Generally, it is 1 to 500 µm, preferably 5 to 200 µm, particularly preferably 10 to 100 µm.

The exposed surface of the adhesive layer is temporarily covered with a separator for the purpose of preventing contamination and the like until it is practically used. Thus, it is possible to prevent the adhesive layer from coming into contact with the adhesive layer in a normal handling state. As a separator,
Except for the above thickness conditions, for example, a plastic film, a rubber sheet, paper, cloth, non-woven fabric, a net, a foamed sheet or a metal foil, a suitable thin leaf such as a laminate thereof, if necessary, a silicone-based or long mirror alkyl-based An appropriate material according to the related art, such as one coated with an appropriate release agent such as fluorine or molybdenum sulfide, may be used.

In the present invention, each layer such as a polarizer, a transparent protective film, an optical film, etc., which forms the above-mentioned polarizing film, and an adhesive layer, etc. may be provided, for example, with a salicylate compound, a benzophenol compound, a benzotriazole compound. And those having an ultraviolet absorbing ability by a method such as a method of treating with an ultraviolet absorber such as a cyanoacrylate compound, a nickel complex salt compound, or the like.

The polarizing film or optical film of the present invention can be preferably used for forming various devices such as a liquid crystal display device. The formation of the liquid crystal display device can be performed according to a conventional method. That is, a liquid crystal display device is generally formed by appropriately setting up components such as a liquid crystal cell and a polarizing film or an optical film, and an illumination system as necessary, and incorporating a drive circuit. There is no particular limitation except that the polarizing film or the optical film according to the present invention is used, and it can be in accordance with the conventional one. As for the liquid crystal cell, any type such as TN type, STN type and π type can be used.

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

[0056]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and the like specifically showing the configuration and effects of the present invention will be described below.

Example 1 (Protective Film) A protective film having a two-layer structure of a polypropylene film (15 μm) having a softening point of 120 ° C. and a polypropylene film (50 μm) having a softening point of 150 ° C. was used.

(Preparation of Polarizing Film) A roll laminator was applied at a temperature of 135 ° C. so that a film surface having a softening point of 120 ° C. was bonded to both surfaces of a 30 μm polarizer (polyvinyl alcohol film). And laminated by heating and pressing. In the obtained polarizing film, the polarizer and the protective film were in close contact with each other, and the appearance was not problematic.

[Brief description of the drawings]

FIG. 1 is a polarizing film of the present invention.

[Explanation of symbols]

 A Polarizer B Protective film

[Procedure amendment]

[Submission date] May 29, 2002 (2002.5.2)
9)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction contents]

The transflective polarizing film can be obtained by forming a transflective reflective layer such as a half mirror that reflects and transmits light with the reflective layer. A transflective polarizing film is usually provided on the back side of a liquid crystal cell. When a liquid crystal display device or the like is used in a relatively bright atmosphere, an image is displayed by reflecting incident light from the viewing side (display side). In a relatively dark atmosphere, it is possible to form a liquid crystal display device of a type that displays an image using a built-in light source such as a backlight built in the back side of a transflective polarizing film. That is, the transflective polarizing film can save energy for use of a light source such as a backlight in a bright atmosphere, and is useful for forming a liquid crystal display device of a type that can be used with a built-in light source even in a relatively dark atmosphere. It is.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0040

[Correction method] Change

[Correction contents]

A polarizing film obtained by laminating a polarizing film and a brightness enhancement film is usually used by being provided on the back side of a liquid crystal cell. The brightness enhancement film exhibits the property of reflecting linearly polarized light of a predetermined polarization axis or circularly polarized light of a predetermined direction when natural light is incident due to reflection from a backlight or a back side of a liquid crystal display device, and transmits other light. ,
The polarizing film obtained by laminating the brightness enhancement film and the polarizing film, while receiving light from a light source such as a backlight to obtain transmitted light in a predetermined polarization state, light other than the predetermined polarization state is reflected without transmitting. . The light reflected on the surface of the brightness enhancement film is further inverted through a reflection layer or the like provided on the rear side thereof and re-entered on the brightness enhancement film, and a part or all of the light is transmitted as light of a predetermined polarization state to achieve brightness. In addition to increasing the amount of light transmitted through the enhancement film, it is also possible to increase the amount of light that can be used for liquid crystal display and image display by supplying polarized light that is hardly absorbed by the polarizer, thereby improving the luminance. That is, when light is incident through a polarizer from the back side of a liquid crystal cell with a backlight or the like without using a brightness enhancement film, light having a polarization direction that does not match the polarization axis of the polarizer is almost completely polarized. Is absorbed by the polarizer and does not pass through the polarizer. That is, although it depends on the characteristics of the polarizer used, about 50% of the light is absorbed by the polarizer, and accordingly, the amount of light available for liquid crystal image display and the like is reduced, and the image becomes dark. The brightness enhancement film is such that light having a polarization direction that is absorbed by the polarizer is once reflected by the brightness enhancement film without being incident on the polarizer, and further inverted through a reflection layer or the like provided on the rear side thereof. The brightness enhancement film transmits only the polarized light whose polarization direction has been changed so that the polarization direction of the light reflected and inverted between the two can pass through the polarizer. Since light is supplied to the polarizer, light from a backlight or the like can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor: Masami Masada 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation F-term (reference) 2H049 BA02 BA03 BA04 BA07 BA27 BA43 BB03 BB16 BB22 BB43 BC03 BC14 BC22 2H091 FA08 FA08X FA08Z FA09 FA09X FA09Z FB02 FC08 FC09 FD06 FD16 FD17 GA16 LA02 LA06 LA12 LA30 4F100 AK01A AK01B AK01C AK07 AK21 AR00A AS00A BA02 BA03 BA10A BA10C EC032 GB41 JA04A JA04N

Claims (7)

[Claims] 1. A polarizer (A) having at least one surface,
A polarizing film protective film (B) is provided, a protective film (B) is comprised of a polymer film having two or more layers of the film layers, the polarizer (A) side of the film layer (b ₁₎ A softening point of the resin forming the outermost film layer (b _x ) is lower than the softening point of the resin forming the outermost film layer (b _x ). 2. The film layer (b) of the protective film (B)
_2. The polarizing film according to claim 1, wherein the softening point of the resin forming ₁ ) is 80 ° C. or higher. 3. The film layer (b) of the protective film (B)
3. The polarizing film according to claim 1, wherein the difference between the softening point of the resin forming ₁ ) and the softening point of the resin forming the film layer (b _X ) is 5 ° C. or more. 4. A softening point of a resin which forms a film layer (b ₁ ) which is made of a polymer film having two or more film layers and which is in close contact with the polarizer (A) is the outermost film layer (b _X The protective film for a polarizer used as the protective film (B) for a polarizing film according to any one of claims 1 to 3, which is lower than the softening point of the resin forming the polarizer. 5. At least one surface of the polarizer (A)
The film layer (b) of the protective film for a polarizer according to claim 4.
₁ ) A method for producing a polarizing film, comprising laminating and laminating by heating and pressing. 6. An optical film in which at least one polarizing film according to claim 1 is laminated. 7. A liquid crystal display device comprising the polarizing film according to claim 1 or the optical film according to claim 6.