JP2005338367A - Polarizing plate and picture display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate in which curl can be suppressed even when a protecting layer, an optical layer, an adhesive layer, etc. are stuck to a polarizing plate and a picture display device in which the same is used. <P>SOLUTION: The polarizing plate is equipped with; the main body of a polarizing plate which is formed by bonding polarizer-protecting films to both surfaces of a polarizer; a protecting layer or an optical layer which is laminated on one surface of the main body of the polarizing plate; and an adhesive layer which is laminated on the other surface of the main body of the polarizing plate and the polarizing plate is characterized in that a ratio between the shear adhesive strength (F1) of the protective layer or the optical layer with respect to the main body of the polarizing plate and the shear adhesive strength (F2) of a separator through the adhesive layer with respect to the main body of the polarizing plate is within the range of 0.08≤F2/F1≤12.5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polarizing plate used in an image display device such as a liquid crystal display device (LCD) and an electroluminescence (EL) display device, and an image display device using the same.

  In the recent flat panel display (FPD) industry, LCDs have become very popular, especially mobile terminals that take advantage of the advantages of light weight, thinness, and power saving, but now they are not limited to large-scale computers and televisions. Many are used in displays. Various improvements have also been made on the polarizing plates used in these image display devices depending on the application (for example, Patent Documents 1 and 2).

The polarizing plate used for LCD, for example, first prepares a polarizer by drying a polyvinyl alcohol (PVA) film through a dyeing process, a crosslinking process, and a stretching process. On top of that, a polarizer protective film such as a triacetyl cellulose (TAC) film is bonded. Furthermore, a protective layer, an optical layer, an adhesive layer and the like for the purpose of protecting the polarizing plate, imparting functions, or convenience during lamination are appropriately laminated on both sides before shipment. In addition, each process, such as dyeing | staining, bridge | crosslinking, extending | stretching in the manufacturing process of a polarizer, does not need to be performed separately and may be performed simultaneously, The order can be changed arbitrarily.
JP 2002-265893 A JP 2003-50313 A

  However, when the protective layer, the optical layer, the adhesive layer, and the like are bonded to the polarizing plate bonded with such PVA and TAC, there are the following problems. FIG. 4 is a view showing a state in which a conventional polarizing plate is stored in a state where a protective layer, an adhesive layer, and a separator are bonded together. As shown in FIG. 4, when the protective layer 4, the adhesive layer 5 and the separator 6 are bonded to the polarizing plate body 3 in which PVA and TAC are bonded together, deviation occurs between the respective layers, and curling (warping) occurs. There was a problem that would occur. This is because the PVA and TAC of the polarizing plate main body 3 absorb moisture with time and expand, so that the tensile force F in the shear direction with respect to the protective layer 4, the adhesive layer 5, the separator 6 and the like has the respective shear adhesive force F1. , F2 worked, resulting in a shift.

  The present invention has been made to solve such problems of the prior art, and a polarizing plate that can suppress curling even when a protective layer, an optical layer, an adhesive layer, and the like are bonded to the polarizing plate, and a polarizing plate using the same. An object of the present invention is to provide an image display apparatus.

One embodiment of the polarizing plate according to the present invention is a polarizing plate body formed by bonding a polarizer protective film on both sides of a polarizer, a protective layer or an optical layer laminated on one surface of the polarizing plate body, A polarizing plate comprising an adhesive layer laminated on the other surface of the polarizing plate body, wherein the protective layer or the optical layer has a shear adhesive force (F1) to the polarizing plate body and the adhesive layer to the polarizing plate body. The ratio with the shearing adhesive force (F2) of the interposed separator is in the following range.
0.08 ≦ F2 / F1 ≦ 12.5

In another embodiment of the polarizing plate according to the present invention, a polarizing plate body formed by bonding a polarizer protective film on both sides of the polarizer, and a protective layer or an optical layer laminated on one surface of the polarizing plate body And a pressure-sensitive adhesive layer laminated on the other surface of the polarizing plate body, wherein the protective layer or the optical layer has a shear adhesive force (F1) to the polarizing plate body and the polarizing plate body The shear adhesive strength (F2) of the separator through the adhesive layer is both 15 N / 400 mm ² or more.

  Preferably, the polarizer has polyvinyl alcohol as a main component, and the polarizer protective film has triacetyl cellulose as a main component.

  Moreover, the liquid crystal panel according to the present invention is characterized in that the polarizing plate having the above-described configuration is attached to at least one surface of the liquid crystal cell in a state where the separator is peeled off.

  Furthermore, the image display device according to the present invention is manufactured using the polarizing plate having the above configuration or the liquid crystal panel having the above configuration.

According to one mode of the polarizing plate according to the present invention, the shear adhesive forces F1 and F2 acting on both surfaces of the expanding polarizing plate main body maintain a predetermined balance, so that the polarizing plate curls on either side. Can be prevented.
Moreover, according to the other form of the polarizing plate according to the present invention, any of the protective layer, the optical layer, the adhesive layer, and the separator has a shear adhesive force F1, F2 that is greater than or equal to a predetermined value from the tensile force due to the expansion of the polarizing plate body. Since each works, the polarizing plate can be prevented from curling on either side.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. In addition, the polarizing plate of this embodiment shows an example, and is not limited to this. FIG. 1 is a view showing a polarizing plate according to an embodiment of the present invention.

As shown in FIG. 1, the polarizing plate according to the present embodiment includes a polarizing plate body 3 formed by bonding a polarizer protective film 2 on both sides of a polarizer 1, and a laminate on one surface of the polarizing plate body 3. A polarizing plate 7 having a protective layer 4 formed thereon, an adhesive layer 5 and a separator 6 laminated on the other surface of the polarizing plate body 3, and a shear adhesive force of the protective layer 4 to the polarizing plate body 3 The ratio of (F1) to the shearing adhesive force (F2) of the separator 6 through the adhesive layer 5 with respect to the polarizing plate body 3 is in the following range.
0.08 ≦ F2 / F1 ≦ 12.5

  When the polarizing plate body 3 expands due to a change with time, a force that the polarizing plate body 3 tries to shear by pulling the protective layer 4 parallel to the contact surface works, and shear adhesive force that suppresses shear as a reaction thereof (F1) works. Similarly, the polarizing body 3 pulls the separator 6 in parallel to the contact surface via the adhesive layer 5 to exert a shearing force, and the reaction acts as a shearing adhesive force (F2) that suppresses shearing.

  When the shear adhesive forces F1 and F2 acting on the separator 6 through the protective layer 4 and the adhesive layer 5 with respect to the polarizing plate body 3 are in the above range, the shear adhesive forces F1 and F2 acting on both surfaces of the polarizing plate body 3 are substantially Since they are the same, it is possible to prevent the polarizing plate from curling on either side. Further, the present invention provides that the shear adhesive force F1 of the protective layer 4 and the polarizing plate body 3, the adhesive layer 5, the separator 6, and the shearing adhesive force F2 of the polarizing plate body 3 even if the shear adhesive forces F1 and F2 are not completely the same. It was found that if the ratio F2 / F1 is within the above range, even if curling occurs, the curling amount can be suppressed to 3.0% or less with respect to the length of the short side of the polarizing plate 7. It is.

  In addition, the measuring method (regulation method) of the shear adhesive force is based on a tensile shear test. In this tensile shear test, a polarizing plate body 3 constituted by attaching a polarizer protective film 2 to both surfaces of a polarizer 1 and a protective layer 4 or an adhesive layer 5 and a separator 6 are bonded together in a shear direction ( A tensile test is performed in parallel to the bonding surface and in opposite directions. In addition, the adhesion surface of the polarizing plate body 3 and the protective layer 4 or the adhesive layer 5 and the separator 6 is a square 20 mm in length and width, and the pulling speed is 50 μm / min. The maximum load when such a tensile shear test is performed is the shear adhesive force F1, F2.

  If the ratio F2 / F1 of the shear adhesive force is 0.08 or more and 12.5 or less, the effect of the present invention for suppressing curling can be obtained, but the shear adhesive forces F1 and F2 have the same adhesive force, that is, the ratio F2. Since / F1 is desirably close to 1, it is preferably 0.2 or more and 2.8 or less, more preferably 0.3 or more and 1.4 or less, and most preferably F2 / F1 = 1. This range was found for the following reason. First, when the ratio F2 / F1 is less than 0.08, the shear adhesive force F2 is too small as compared with the shear adhesive force F1, and thus the minimum adhesive force necessary for the shear adhesive force cannot be obtained. This is because it is easy to peel off. Further, when the ratio F2 / F1 exceeds 12.5, the shear adhesive force F2 is too large compared to the shear adhesive force F1, so that the peelability of the separator 6 is deteriorated or the protective layer 4 is peeled off in the process. Because it ends up.

That is, if the shearing adhesive force F2 itself is too small, the separator 6 is peeled off during the manufacturing process, and if the shearing adhesive force F2 itself is too large, the peelability of the separator 6 is lowered and workability is deteriorated. . The same can be said for the shear adhesive force F1, and if the shear adhesive force F1 is too small, the protective layer 4 is peeled off during the manufacturing process. Therefore, when the ratio F2 / F1 is in the range of 0.08 or more and 12.5 or less as described above, the separator 6 and the protective layer 4 or the optical layer have a shear adhesive strength that does not peel off during the manufacturing process. It only has to be. Specifically, sufficient if the respective shear adhesive strength (F1, F2) is 0.5 N / 400 mm ² or more, preferably in 3.0 N / 400 mm ² or more, more that there 6.0 N / 400 mm ² or more preferable.

Further, in the present embodiment, each of the shear adhesive strength F1, F2 are both 15N / 400 mm ² or more, preferably 25 N / 400 mm ² or more, more preferably by a 40N / 400 mm ² or more, it found that can suppress curl ing. In this case, the effect of the present invention can be obtained even if the ratio F2 / F1 is outside the range of 0.08 to 12.5, but it is more preferable that the ratio is within the range of the ratio. However, when the polarizing plate according to the present invention is used, generally, the protective layer 4 or the separator 6 is appropriately peeled and used. In order to prevent this peeling from becoming difficult, the shear adhesive strength is 55 N. / 400 mm ² or less is preferable. However, it is not limited to this when the protective layer 4 is used without being peeled off, or when an optical layer is laminated instead of the protective layer 4 and peeling is not required.

In the present embodiment, the polarizing plate 7 that satisfies both the condition that F2 / F1 is 0.08 or more and 12.5 or less and the condition that the respective shear adhesive forces F1 and F2 are 15 N / 400 mm ² or more are satisfied. However, as described above, the effect of the present invention can be obtained if at least one of the conditions is satisfied. That is, when only the conditions for setting the respective shear adhesive strengths F1 and F2 to 15 N / 400 mm ² or more are satisfied, any of the protective layer, the optical layer, the adhesive layer, and the separator is determined by the tensile force due to expansion of the polarizing plate body. Since the shear adhesive strengths F1 and F2 that are greater than or equal to each value work, it is possible to prevent the polarizing plate from curling to either side.

  As a structural example of the polarizing plate body 3 of the present embodiment, an appropriate adhesive made of a vinyl alcohol polymer or the like is interposed on both surfaces of a polarizer 1 made of a film containing polyvinyl alcohol containing a dichroic substance as a main component. Then, the polarizer protective film 2 is adhered.

  This will be described more specifically. The polarizer 1 is, for example, a film mainly composed of appropriate polyvinyl alcohol such as polyvinyl alcohol or partially formalized polyvinyl alcohol, dyeing treatment with a dichroic substance containing iodine or a dichroic dye, stretching treatment, cross-linking Appropriate processing such as processing is performed in a predetermined order and method, and a material that transmits linearly polarized light when natural light is incident is used. In particular, those excellent in light transmittance and polarization degree are preferable. The thickness of the polarizer 1 is generally about 5 to 40 μm.

  The material of the polarizer protective film 2 provided on both surfaces of the polarizer 1 is a predetermined transparent film, for example, a polyester-based polymer such as polyethylene terephthalate or polyethylene naphthalate, or a cellulose-based material such as diacetylcellulose or triacetylcellulose. Examples thereof include acrylic polymers such as polymers and polymethyl methacrylate, styrene polymers such as polystyrene and acrylonitrile / styrene copolymers (AS resin), polycarbonate polymers, and the like. Also, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Polymer blends and the like can also be mentioned, but are not limited thereto. Preferably, a film mainly composed of an acetate-based resin such as triacetyl cellulose, more preferably, triacetyl cellulose whose surface is saponified with an alkali or the like from the viewpoint of polarization characteristics or durability. A film can be used. The thickness of the polarizer protective film 2 is not particularly limited, but is generally 500 μm or less, and preferably 5 to 300 μm.

  The polarizer protective film 2 may be subjected to a hard coat process, an antireflection process, a process for preventing sticking, diffusion or anti-glare, and the like without departing from the spirit of the present invention. The hard coat treatment is performed for the purpose of preventing scratches on the polarizing plate surface. For example, it can be formed by applying a cured film excellent in hardness, slipperiness, etc. with an appropriate ultraviolet curable resin such as a silicone-based resin to the surface of the transparent polarizer protective film. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate. For example, it can be realized by forming an existing antireflection film or the like. Further, the treatment for preventing sticking is performed for the purpose of preventing adhesion with an adjacent layer. The anti-glare treatment is performed for the purpose of preventing external light from being reflected on the surface of the polarizing plate and hindering viewing of the light transmitted through the polarizing plate. For example, it can be realized by forming a fine concavo-convex structure on the surface of the polarizer protective film 2 using a roughening method such as a sandblasting method or an embossing method, a blending method of transparent fine particles, or the like. Examples of the transparent fine particles include silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, and antimony oxide having an average particle size of 0.5 to 20 μm. In addition, inorganic fine particles having conductivity may be used, and organic fine particles composed of crosslinked or uncrosslinked polymer particles may be used. The usage-amount of transparent fine particles is 2-70 mass parts per 100 mass parts of transparent resin, and 5-50 mass parts is especially used suitably. Furthermore, the antiglare layer containing transparent fine particles can be provided as the polarizer protective film 2 itself or as a coating layer on the surface of the polarizer protective film 2. The antiglare layer may also serve as a diffusion layer (viewing angle compensation function) for diffusing the light transmitted through the polarizing plate to expand the viewing angle. The antireflection layer, the antisticking layer, the diffusion layer, the antiglare layer, and the like described above can be provided separately from the polarizer protective film 2 as an optical layer composed of a sheet provided with these layers.

  The adhesion treatment between the polarizer 1 and the polarizer protective film 2 is not particularly limited. For example, an adhesive mainly composed of polyvinyl alcohol, boric acid, borax, glutaraldehyde, melamine, or An adhesive or the like using at least one of a water-soluble crosslinking agent of vinyl alcohol polymer such as acid is used. Such an adhesive can be formed as a water-soluble coating / drying layer or the like. However, when preparing the aqueous solution, other additives and catalysts such as acids may be blended as necessary.

  The polarizing plate body 3 is used as a protective layer 4 that protects the polarizing plate body 3 from scratches or the like until it is attached to another member, or another optical layer (not shown) for adding further optical characteristics to the polarizing plate body 3. It is used by laminating or laminating other optical layers. Here, the protective layer 4 is obtained by laminating an adhesive layer made of various adhesives or pressure-sensitive adhesives on a film formed of the same material as the polarizer protective film 2, and the protective layer 4 and the polarizing plate main body. 3 is peeled off at the interface between the polarizing plate body 3 and the adhesive layer (the protective layer 4 together with the adhesive layer). As such a protective layer 4, a layer in which a part of the adhesive layer does not remain on the polarizing plate body 3 (no adhesive residue) is preferably used. For example, an SPV series manufactured by Nitto Denko Corporation can be used. Also, the optical layer is not particularly limited. For example, a reflection plate, a transflective plate, a retardation plate (including a λ plate such as a half-wave plate and a quarter-wave plate), a viewing angle One or two or more predetermined optical layers that can be used for forming a liquid crystal display device, such as a compensation film and a brightness enhancement film, can be used. In particular, the polarizing plate 3 described above is a reflective polarizing plate or a semi-transmissive polarizing plate in which a reflecting plate or a semi-transmissive reflecting plate is laminated, an elliptical polarizing plate or a circular polarizing plate in which a retardation plate is laminated, and viewing angle compensation. A polarizing plate in which a film is laminated or a polarizing plate in which a brightness enhancement film is laminated is preferable.

  The said reflecting plate is demonstrated. The reflector is usually provided on the back side of the liquid crystal cell, and is used for a liquid crystal display device or the like that reflects incident light from the viewing side (display side), so that installation of a light source such as a backlight can be omitted. Therefore, it is possible to easily reduce the thickness of the liquid crystal display device.

  Formation of the reflective polarizing plate can be realized by attaching a reflective layer made of metal or the like to one side of the polarizing plate via the polarizer protective film 2 described above as necessary. Specific examples thereof include those in which a reflective layer is formed by attaching a foil or a vapor deposition film made of a reflective metal such as aluminum on one surface of the polarizer protective film 2 that is matted as necessary. Moreover, the reflective polarizing plate etc. which have the reflection layer which reflected the said fine concavo-convex structure on the surface of the polarizer protective film 2 which contained microparticles | fine-particles and made the surface a fine concavo-convex structure are mentioned. The reflective layer having the surface fine uneven structure can diffuse incident light by irregular reflection to prevent directivity and glare, and to suppress uneven brightness. The reflective layer of the fine concavo-convex structure reflecting the surface fine concavo-convex structure of the polarizer protective film 2 can be used to protect the metal by various vapor deposition / plating methods such as vacuum vapor deposition, ion plating and sputtering. It can be performed by a method of attaching directly to the surface of the film 2 or the like. Moreover, it is good also as using a reflective sheet etc. which provided the reflecting layer in the predetermined film according to the said polarizer protective film 2 instead of the system directly attached to the polarizer protective film 2 for a reflecting plate. Since the reflective layer of the reflector is usually made of metal, it can be used in a state where the reflective surface is covered with a film, a polarizing plate, etc., to prevent a decrease in reflectance due to oxidation, and thus to maintain and protect the initial reflectance for a long period of time. It is preferable from the viewpoint of avoiding additional attachment of layers.

  A transflective polarizing plate will be described. The semi-transmissive layer is a semi-transmissive reflective layer such as a half mirror that reflects and transmits light, which is used instead of the reflective layer. The transflective polarizing plate is usually provided on the back side of the liquid crystal cell, and displays an image by reflecting incident light from the viewing side (display side) when the liquid crystal display device is used in a relatively bright atmosphere. When using in a relatively dark atmosphere, use a built-in light source such as a backlight built in on the back side (opposite to the viewing side with a transflective polarizing plate in between). A liquid crystal display device that displays an image (by transmission) can be obtained. According to such a liquid crystal display device, energy can be saved by using a light source such as a backlight in a relatively bright atmosphere, and the built-in light source can be used efficiently in a relatively dark atmosphere.

  Subsequently, the elliptically polarizing plate and the circularly polarizing plate will be described. A phase difference plate or the like is used when linearly polarized light is polarized into elliptically or circularly polarized light, elliptically polarized light or circularly polarized light is polarized into linearly polarized light, or the polarization direction of linearly polarized light is changed. In particular, a so-called quarter-wave plate (also referred to as a λ / 4 plate) is used as a retardation plate that polarizes linearly polarized light into elliptically polarized light or circularly polarized light, or polarizes elliptically polarized light or circularly polarized light into linearly polarized light. A half-wave plate (also referred to as a λ / 2 plate) is used to change the polarization direction of linearly polarized light. The elliptically polarizing plate compensates (prevents) coloring (blue or yellow) caused by birefringence of the liquid crystal layer of a super twist nematic (STN) type liquid crystal display device, and makes such a monochrome display without coloring. It is effective for. Furthermore, the one in which the three-dimensional refractive index is controlled is preferable because it can also compensate for coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction. The circularly polarizing plate is effective, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which the image is displayed in color, and has a function of preventing reflection.

  Specific examples of such a retardation plate include a birefringent film obtained by stretching a film made of a predetermined polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, polyolefin, polyarylate, polyamide, and a liquid crystal polymer. And a film in which an alignment layer of a liquid crystal polymer is supported by a film. In addition, as the tilted alignment film, for example, a heat-shrinkable film bonded to the polymer film is heated and shrunk, and the polymer film is stretched and / or shrunk in the direction in which the shrinkage force works, or a liquid crystal polymer. And the like that are obliquely oriented.

  Subsequently, a polarizing plate in which a viewing angle compensation film is laminated on the polarizing plate body 3 will be described. The viewing angle compensation film is provided to widen the viewing angle so that the image can be seen relatively clearly even when the image of the liquid crystal display device is viewed from a slightly oblique direction rather than from the vertical direction. As such a viewing angle compensation film, a triacetyl cellulose film or the like coated with a discotic liquid crystal or a retardation plate is used. A normal retardation film uses a birefringent polymer film uniaxially stretched in a predetermined plane direction, whereas a retardation film used as a viewing angle compensation film biaxially stretches in a predetermined plane direction. Such as a birefringent polymer film, a uniaxially stretched film in a predetermined plane direction, and a tilted polymer film that is also stretched in the thickness direction (controlling the refractive index in the thickness direction). Often used. As described above, the tilt-oriented polymer film is heated and shrunk, for example, with the heat-shrinkable film adhered to the polymer film, and the polymer film is stretched and / or shrunk in the direction in which the shrinkage force works. And those obtained by obliquely aligning a liquid crystal polymer. The raw material polymer for the retardation plate here is the same as that of the above-described retardation plate.

  Furthermore, the polarizing plate which bonded the brightness enhancement film to the polarizing plate main body 3 is demonstrated. Such a polarizing plate is provided on the back side of the liquid crystal cell. When only light is incident on the polarizing plate from the back side of the liquid crystal cell using a backlight or the like without using a brightness enhancement film, most of the light having a polarization direction that does not coincide with the polarization axis of the polarizer 1 is absorbed by the polarizer 1. As a result, the light does not pass through the polarizer 1. Accordingly, approximately 50% of the incident light from the light source (which varies depending on the characteristics of the polarizer) is absorbed by the polarizer 1, and accordingly, the amount of light that can be used for image display is reduced and the image becomes dark. . On the other hand, when a polarizing plate having a brightness enhancement film is used, if natural light is incident on the polarizing plate due to reflection from the backlight or the back side of the liquid crystal display device, linearly polarized light or circularly polarized light having a predetermined polarization axis is reflected. It has the characteristic of transmitting the light. Accordingly, light from a light source such as a backlight is incident to transmit predetermined polarized light, and light other than polarized light is reflected. The light reflected on the surface of the brightness enhancement film is further reflected by a reflective layer or the like provided on the rear side thereof and reenters the brightness enhancement film, and part or all of the light is transmitted as predetermined polarized light. It is possible to increase the amount of light transmitted through the enhancement film and supply polarized light that is not easily absorbed by the polarizer 1 to increase the amount of light available to the liquid crystal display device, thereby improving the brightness of the liquid crystal display device.

  Such brightness enhancement films, for example, transmit linearly polarized light with a predetermined polarization axis and reflect other light, such as a multilayer thin film of dielectrics or a multilayer laminate of thin film films having different refractive index anisotropies. Such as cholesteric liquid crystal layers, especially cholesteric liquid crystal polymer alignment films and those that support the alignment liquid crystal layer on a film substrate, reflect either left-handed or right-handed circularly polarized light. , Or the like exhibiting the property of transmitting the other circularly polarized light, etc., are used as appropriate.

  In a brightness enhancement film having a characteristic of transmitting linearly polarized light having a predetermined polarization axis, the transmitted light is allowed to pass through the polarizer 1 with the polarization axis aligned and efficiently transmitted while suppressing absorption loss due to the polarizing plate. Can do. On the other hand, in a brightness enhancement film having a property of transmitting circularly polarized light, it may be incident on the polarizer 1 as it is. However, in order to suppress absorption loss, the transmitted circularly polarized light is linearly polarized through a phase plate and polarized. It is preferable to make it enter into a child.

  A quarter wave plate is used as the retardation plate at this time. As a retardation plate that functions as a quarter-wave plate in a wide wavelength range such as the visible light region, for example, a retardation layer that functions as a quarter-wave plate for monochromatic light with a wavelength of 550 nm and other retardation characteristics For example, a phase difference layer functioning as a half-wave plate, and the like. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or more retardation plates.

  The cholesteric liquid crystal layer also has a structure in which two or more layers having different reflection wavelengths are combined and overlapped to provide circularly polarized reflection in a wide wavelength range such as the visible light region. Thus, it is possible to obtain transmitted circularly polarized light in a wide wavelength range.

  Further, the polarizing plate may be configured by laminating a polarizing plate and two or more optical layers as in the above-described polarization separation type polarizing plate. Therefore, it may be a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the reflective polarizing plate or semi-transmissive polarizing plate and a retardation plate are combined. Optical members in which two or three or more optical layers are laminated may be sequentially laminated separately in the manufacturing process of the liquid crystal display device. However, it is better to use those laminated in advance as optical members for stable quality and assembly. It is preferable because it is excellent in workability and the like and can improve the manufacturing efficiency of a liquid crystal display device or the like.

  The polarizing plate body 3 is provided with an adhesive layer 5 for bonding with other members such as a liquid crystal cell. The pressure-sensitive adhesive layer 5 can be formed by laminating various pressure-sensitive adhesives such as acrylic, synthetic rubber, and rubber. In particular, the moisture absorption rate is low from the viewpoints of preventing foaming and peeling phenomena due to moisture absorption, reducing optical characteristics due to thermal expansion differences, preventing warping of liquid crystal cells, and forming liquid crystal display devices with high quality and durability. The pressure-sensitive adhesive layer 5 is preferably formed of a pressure-sensitive adhesive having excellent heat resistance. Moreover, you may form the adhesion layer 5 which contains microparticles | fine-particles and shows light diffusibility.

  Furthermore, a separator 6 is provided in order to prevent contamination of the adhesive layer 5 until the adhesive layer 5 provided on the polarizing plate body 3 is actually attached to another member. Here, the separator 6 is an interface between the pressure-sensitive adhesive layer 5 and the separator 6 while maintaining the pressure-sensitive adhesive force of the pressure-sensitive adhesive layer 5 even after being bonded via the polarizing plate body 3 and the pressure-sensitive adhesive layer 5, for example. It can be peeled (only the separator 6). Examples of the constituent material for the separator 6 include synthetic resin films such as paper, polyethylene, polypropylene, and polyethylene terephthalate. As long as the conditions of the present invention are satisfied, the surface of the separator 6 (the surface in contact with the adhesive layer 5) has a silicone-based, long-chain alkyl-based, fluorine-based, if necessary, in order to improve the peelability from the adhesive layer 5. Alternatively, the release treatment may be performed by providing a release coat with a release agent such as molybdenum sulfide. The same applies to the surface of the protective layer 4 (the surface in contact with the polarizing plate body 3). However, when the protective layer 4 was used without being peeled off, or when an optical layer was laminated instead of the protective layer 4 and was not peeled off, the protective layer 4 was used for the adhesive treatment between the polarizer 1 and the polarizer protective film 2. It is good also as adhering with the same adhesive agent etc. and not performing a mold release process.

  In addition, each layer which comprises the said polarizing plate 7 is an ultraviolet absorption function by processing with ultraviolet absorbers, such as a salicylic acid ester type compound, a benzophenone type compound, a benzotriazole type compound, a cyanoacrylate type compound, a nickel complex salt type compound etc., for example. It may be a thing given.

  The polarizing plate 7 as described above can be preferably used for forming various devices such as a liquid crystal display device. The liquid crystal display device can be a transmissive type, a reflective type, or a transmissive / reflective liquid crystal display device by disposing the polarizing plate 7 on one side or both sides of the liquid crystal cell. The liquid crystal cell used in this liquid crystal display device is not limited. For example, there are various types such as an active matrix drive type typified by a thin film transistor type, a simple matrix drive type typified by a twist nematic type and a super twist nematic type, etc. The liquid crystal cell can be applied.

  Further, when the polarizing plate 7 and the optical member are provided on both sides of the liquid crystal cell, the same member may be provided or different members may be provided. Furthermore, when forming the liquid crystal display device, for example, predetermined components such as a prism array sheet, a lens array sheet, a light diffusion plate, and a backlight can be arranged in one or more layers at predetermined positions.

  Examples of the present invention and comparative examples are shown below. The shear adhesive strengths F1 and F2 and the curl amount of the polarizing plate 7 according to the present invention and the conventional polarizing plate were measured and compared. The present invention is not limited to these embodiments.

<Measurement method of shear adhesive strength>
When measuring the shear adhesive strengths F1 and F2, the polarizing plate 7 was cut to a size of 100 mm × 20 mm. When measuring the shearing adhesive force F2, as shown in FIG. 2, the adhesive layer 5 (that is, the contact portion between the polarizing plate body 3, the adhesive layer 5 and the separator 6) is half left with the bonded portion of 20 mm × 20 mm. The cut one was used as a sample. Further, when measuring the shear adhesive force F1, as shown in FIG. 3, the protective layer 4 (that is, the contact portion between the polarizing plate body 3 and the protective layer 4) is half-cut leaving a bonded portion of 20 mm × 20 mm. The sample was used as a sample. Each of the samples was attached to a tensile tester (manufactured by Shimadzu Corporation: AG-20kNG), and pulled at a pulling speed of 50 μm / min to perform measurement. The maximum loads at this time were defined as shear adhesive forces F1 and F2, respectively.

<Measurement method of curl amount>
In the measurement of the curl amount, the polarizing plate 7 was cut to a size of 297 mm × 226 mm, and left for 6 hours at a temperature of 25 ° C. and a humidity of 90% RH. Thereafter, the amount of the polarizing plate placed on the flat surface lifted from the surface was measured. At this time, the values at the four corners were measured, and the maximum value at this time was adopted. Further, the ratio between this value and the length of the short side of the polarizing plate (226 mm) was compared as the curl amount (%).

<Preparation of polarizing plate body>
A polarizing plate main body is obtained by laminating a polarizer protective film 2 made of a TAC film having a thickness of 40 μm on both sides of a polarizer 1 having a thickness of 30 μm prepared by dyeing a PVA film with iodine using a PVA adhesive. 3 was produced.

<Lamination of adhesive layer and separator>
A separator 6 made of a polyethylene terephthalate (PET) film having a thickness of 38 μm obtained by laminating an adhesive layer 5 made of an acrylic pressure-sensitive adhesive layer 5 on one surface of the polarizing plate main body 3 was bonded. The adhesive layer 5 was prepared by adding 100 parts of ethyl acetate to 100 parts of butyl acrylate, 1 part of ethyl hydroxyacrylate, and 0.3 part of azobisisobutylnitrile, and reacting at 60 ° C. for 5 hours to obtain a polymer solution. 0.2 parts of an isocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Co., Ltd., trade name: Coronate L) is blended per 100 parts of the polymer solution.

<Lamination of protective layer>
A protective sheet 4 having a total thickness of 61 μm (manufactured by Nitto Denko Corporation, PPF-100T) having an adhesive layer thickness of 23 μm is bonded to the other surface of the produced polarizing plate body 3 as an asymmetric polarizing plate 7. Got.

  In the preparation of the adhesive layer 5 of Example 1 <Lamination of Adhesive Layer and Separator>, 5 parts of acrylic acid was added instead of 1 part of ethyl hydroxyacrylate. Other conditions are the same as in the first embodiment.

<Reference example>
In Example 1 <Lamination of Adhesive Layer and Separator>, the same protective sheet (Nitto Denko Corporation: PPF-100T) as the one attached to the other surface in place of the adhesive layer 5 and the separator 6 was attached, A polarizing plate 7 in which protective layers 4 were laminated on both surfaces of the polarizing plate body 3 was produced. Other conditions are the same as in the first embodiment.

<Comparative example>
As a comparative example with the above example, a film having a thickness of 38 μm (Mitsubishi Chemical Polyester Film Co., Ltd .: MRF38) having a release treatment applied to the film surface was used as the separator 6. Other conditions are the same as in the first embodiment.

<Evaluation>
Table 1 shows the results of measuring the shear adhesive strengths F1 and F2 and the curl amount under the above conditions.

In the polarizing plate 7 of Example 1, the shear adhesive force F2 between the polarizing plate body 3 and the separator 6 via the adhesive layer 5 is 51 N / 400 mm ² , and the shear bonding between the polarizing plate body 3 and the protective layer 4 is performed. force F2 is because it was 42N / 400 mm ^2, the ratio F2 / F1 is 1.2, and the of 0.08 ≦ F2 / F1 ≦ 12.5 conditions and F1, F2 are both 15N / 400 mm ² or more conditions Both were satisfied.

In the polarizing plate 7 of Example 2, the shear adhesive force F2 between the polarizing plate body 3 and the separator 6 via the adhesive layer 5 is 15 N / 400 mm ² , and the shear bonding between the polarizing plate body 3 and the protective layer 4 is performed. Since the force F2 was 42 N / 400 mm ² , the ratio F2 / F1 was 0.36, which satisfied both the above two conditions.

In the polarizing plate 7 of the reference example, since the shear adhesive forces F1 and F2 were both 42 N / mm ² , the ratio F2 / F1 was 1.0, which satisfied both the above two conditions.

In the polarizing plate of the comparative example, the shear adhesive force F2 between the polarizing plate body 3 and the separator 6 via the adhesive layer 5 is 3.2 N / 400 mm ² , and the shear bonding between the polarizing plate body 3 and the protective layer 4 is performed. Since the force F2 was 42 N / 400 mm ² , the ratio F2 / F1 was 0.076, which did not satisfy any of the above two conditions.

  The curl amounts in Examples 1 and 2 and the reference example at this time were both less than 3.0% as shown in Table 1, whereas the curl amount in the comparative example was 3. It was more than 0%. When the curl amount exceeds 3.0%, problems such as bubble mixing and misalignment at the time of bonding are likely to occur when an image display device is formed. As described above, in Examples 1 and 2 and the reference example satisfying at least one of the above two conditions, the curl amount may be suppressed to less than 3.0%, which can be said to be practically not defective. It became clear.

It is a figure which shows the polarizing plate which concerns on one Embodiment of this invention. It is a figure which shows the sample used for the measurement of the shear adhesive force (F2) in the Example of this invention. It is a figure which shows the sample used for the measurement of the shear adhesive force (F1) in the Example of this invention. It is a figure which shows a state when it preserve | saves in the state which bonded together the protective layer, the adhesion layer, and the separator on the conventional polarizing plate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polarizer 2 Polarizer protective film 3 Polarizing plate main body 4 Protective layer 5 Adhesive layer 6 Separator 7 Polarizing plate

Claims (5)

A polarizing plate body formed by laminating a polarizer protective film on both sides of a polarizer, a protective layer or an optical layer laminated on one surface of the polarizing plate body, and an adhesive laminated on the other surface of the polarizing plate body A polarizing plate comprising a layer and a separator,
The ratio of the shear adhesive force (F1) of the protective layer or the optical layer to the polarizing plate body and the shear adhesive force (F2) of the separator through the adhesive layer to the polarizing plate body is in the following range. A polarizing plate.
0.08 ≦ F2 / F1 ≦ 12.5 A polarizing plate body formed by laminating a polarizer protective film on both sides of a polarizer, a protective layer or an optical layer laminated on one surface of the polarizing plate body, and an adhesive laminated on the other surface of the polarizing plate body A polarizing plate comprising a layer and a separator,
The shear adhesive force (F1) of the protective layer or optical layer to the polarizing plate body and the shear adhesive force (F2) of the separator through the adhesive layer to the polarizing plate body are both 15 N / 400 mm ² or more. A polarizing plate characterized by.   The polarizing plate according to claim 1 or 2, wherein the polarizer has polyvinyl alcohol as a main component, and the polarizer protective film has triacetyl cellulose as a main component.   A liquid crystal panel, wherein the polarizing plate according to claim 1 is attached to at least one surface of the liquid crystal cell in a state where the separator is peeled off.   An image display device manufactured using the polarizing plate according to claim 1 or the liquid crystal panel according to claim 4.

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