JP2011070012A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image device wherein a composite protective plate having a birefringent layer for improving visibility when a viewer views a screen with polarizing glasses is disposed at a viewer side, and which can be efficiently manufactured by using a composite protective plate that can be commonly used without depending on the design of a display device. <P>SOLUTION: The display device includes a composite protective plate wherein a birefringent layer, a pressure sensitive adhesive layer, and a protective plate are laminated in this order from a display device body side toward a viewer side. The composite protective plate is disposed on the viewer side of the display device with a space between itself and the display device body, and the slow axis of the birefringent layer is 45±10° or 135±10° to the screen of the display device. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a display device in which a composite protective plate is arranged on the viewer side.

  Polarized glasses have a polarizing film sandwiched between lenses, and the reflection of dazzling light can be cut by wearing polarized glasses. However, when viewing the screen of a liquid crystal display device or EL display device with polarized glasses, the screen becomes dark depending on the viewing angle. This is due to a decrease in transmittance due to a deviation between the direction of the polarization axis of the polarizing plate disposed on the viewer side of the display device and the direction of the polarization axis of the polarizing glasses in these display devices. This is a problem in car navigation, PND (Portable Navigation Device), aircraft cockpit, PDA (Personal Desital Assistant), mobile phone, fish finder, digital signage, etc. In view of this, for example, JP-A-10-10523 (Patent Document 1), JP-A-2005-352068 (Patent Document 2), JP-A-2008-83307 (Patent Document 3) and the like are visually recognized. It has been proposed to provide a birefringent layer such as a λ / 4 plate outside the viewer-side polarizing plate (viewer side).

Japanese Patent Laid-Open No. 10-10523 JP 2005-352068 A JP 2008-83307 A

  When the birefringent layer is provided on the viewer side of the display device, the slow axis of the birefringent layer is 45 ° or 135 ° with respect to the absorption axis of the polarizing plate on the outermost surface of the display device. Since it was designed individually, there was a problem that it was difficult to install later.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a composite having a birefringent layer for improving the visibility when viewing a screen with polarized glasses. It is an image device in which a protection plate is arranged on the viewer side, and it is an object of the present invention to provide an image device that can be efficiently manufactured using a composite protection plate that can be shared without depending on the design of the display device.

  The display device of the present invention is a display device comprising a composite protective plate in which a birefringent layer, a pressure sensitive adhesive layer and a protective plate are laminated in this order from the display device main body side toward the viewer side, The composite protection plate is disposed on the viewer side of the display device with a space from the display device body, and the slow axis of the birefringent layer is 45 ± 10 ° or 135 ± 10 ° with respect to the display device screen. It is characterized by being.

  In the display device according to the aspect of the invention, it is preferable that the composite protective plate further includes a transparent protective layer provided directly or via a pressure-sensitive adhesive layer on the display device body side of the birefringent layer.

  In the display device of the present invention, it is preferable that the birefringent layer of the composite protective plate satisfies the formulas (1) and (2).

Formula (1): 0.71 <R450 / R590 <0.82
Formula (2): 133 nm <R550 <143 nm
(In the above formula (1), R450 is the in-plane retardation value of the birefringent layer with respect to light having a wavelength of 450 nm, and R550 is the in-plane retardation value of the birefringent layer with respect to light having a wavelength of 550 nm. R590 is an in-plane retardation value of the birefringent layer with respect to light having a wavelength of 590 nm.
In the display device of the present invention, the birefringent layer of the composite protective plate may be composed of a plurality of layers.

  In the display device of the present invention, the birefringent layer of the composite protective plate has a polymer monomer unit having a positive refractive index anisotropy and a negative refractive index anisotropy having a larger wavelength dispersion than the polymer. An oriented film of a copolymer having a high molecular weight monomer unit is preferable because coloring and viewing angle dependency can be reduced.

  In the display device of the present invention, the protective plate of the composite protective plate may be a touch panel.

  According to the display device of the present invention, the visibility when the screen is viewed while wearing polarized glasses is improved by the composite protective plate arranged on the viewer side. In addition, there is an advantage that the composite protective plate can be shared without depending on the design of the display device.

It is sectional drawing which shows typically the display apparatus 1 of a preferable example of this invention. It is sectional drawing which shows typically the display apparatus 11 of another preferable example of this invention.

  Hereinafter, the present invention will be described in detail with appropriate reference to the accompanying drawings. It is sectional drawing which shows typically the display apparatus 1 of a preferable example of this invention. The upper direction (the direction A indicated by the arrow in the drawing) in FIG. 1 is the viewer side, and the lower direction is the display device main body side. As shown in FIG. 1, in the display device 1 of the present invention, a birefringent layer 4, a pressure-sensitive adhesive layer 5, and a protective plate 6 are laminated in this order from the display device body 3 side to the viewer side A. The composite protective plate 2 is provided. The composite protective plate 2 is arranged on the viewer side A of the display device with a space from the display device body 3.

  The display device 1 of the present invention is characterized in that the slow axis of the birefringent layer 4 is 45 ± 10 ° or 135 ± 10 ° with respect to the display device screen. Note that the angle formed by the slow axis of the birefringent layer and the display device screen refers to an angle defined with the long side of the screen as a reference, and counterclockwise as viewed from the front. As described above, in the image device of the present invention, the birefringent layer 4 having a slow axis of 45 ± 10 ° or 135 ± 10 ° with respect to the display device screen is interposed between the protective plate 6 and the pressure-sensitive adhesive layer 5. Are stacked. As a result, a birefringent layer is later installed for each display device so that the slow axis of the birefringent layer is 45 ° or 135 ° with respect to the absorption axis of the polarizing plate on the outermost surface of the display device as in the past. Unlike the case, there is provided an image device 1 that can be efficiently manufactured by using a common composite protective plate 2 without depending on the design of the display device.

  Examples of the polymer forming the birefringent layer 4 in the present invention include polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polyolefin such as polypropylene, polyarylate, polyamide, and cyclic olefin such as norbornene. And cyclic polyolefins having a monomer as a monomer. The stretched film may be processed by an appropriate method such as uniaxial or biaxial. A birefringent film in which the refractive index in the thickness direction of the film is controlled by applying a shrinkage force and / or stretching force under adhesion with the heat-shrinkable film can also be used.

  The birefringent layer 4 has a function of changing outgoing linearly polarized light into elliptically polarized light or changing outgoing linearly polarized light into circularly polarized light. In particular, as a birefringent layer that can convert linearly polarized light into circularly polarized light, a layer called a λ / 4 plate that exhibits a phase difference of ¼ wavelength with respect to the wavelength of light is used.

  The birefringent layer 4 is preferably a λ / 4 plate that converts linearly polarized light into circularly polarized light, and more preferably a broadband λ / 4 plate having a small wavelength dependency. Specifically, the birefringent layer 4 that satisfies the formulas (1) and (2) is preferable because coloring and viewing angle dependency can be reduced.

Formula (1): 0.71 <R450 / R590 <0.82
Formula (2): 133 nm <R550 <143 nm
In the above formula (1), R450 is the in-plane retardation value of the birefringent layer with respect to light having a wavelength of 450 nm, and R590 is the in-plane retardation value of the birefringent layer with respect to light having a wavelength of 590 nm. , R550 is an in-plane retardation value of the birefringent layer with respect to light having a wavelength of 550 nm.

  In the above formula (1), when R450 / R590 is 0.71 or less, the display through polarized sunglasses is strongly colored, and the same tendency is observed when R450 / R590 is 0.82 or more. It is in. Since coloring can be reduced, R450 / R590 = 0.7627 is optimal, and 0.71 <R450 / R590 <0.82.

  In the above formula (2), when R550 is 133 nm or less, the brightness tends to vary depending on the viewing direction when viewed through polarized sunglasses, and the same is true when R550 is 143 nm or more. Tend to. R550 = 138 nm is optimal because the brightness is uniform from any direction, and it is preferable that 133 nm <R550 <143 nm.

  The birefringent layer 4 in the present invention is composed of a blend polymer composed of a polymer having a positive refractive index anisotropy and a polymer having a negative refractive index anisotropy, or a positive refractive index anisotropy. It is preferably composed of a copolymer having a polymer monomer unit having a high molecular monomer unit having negative refractive index anisotropy. By forming the birefringent layer 4 with such a material, the above formula (1) can be satisfied with one layer. In addition, there is an advantage that the viewing angle dependency is small as compared with the case where a configuration satisfying the above formula (1) is satisfied with a plurality of layers. Among them, there is an oriented film of a copolymer having a polymer monomer unit having a positive refractive index anisotropy and a polymer monomer unit having a negative refractive index anisotropy having a larger wavelength dispersion than the polymer. Particularly preferably used. Specifically, Pure Ace WR (manufactured by Teijin Chemicals Ltd.), which is a commercial product, can be cited as a suitable example.

  The birefringent layer 4 in the present invention may be composed of a plurality of layers. In this case, other optical functions such as an optical layer in which liquid crystal is applied, aligned and cured, and a wavelength selective absorption layer such as a UV cut are provided. You may make it have. When the birefringent layer 4 is composed of a plurality of layers, the birefringent layer 4 as a whole may be realized so as to satisfy the above formulas (1) and (2).

  The thickness of the birefringent layer 4 is not particularly limited, but is preferably in the range of 20 to 100 microns. When the thickness of the birefringent layer 4 is less than 20 microns, handling in the assembly process is preferable. When the thickness of the birefringent layer 4 exceeds 100 microns, it is not suitable for a thin and light mobile product.

  The viewer side A of the birefringent layer 4 is provided with a pressure-sensitive adhesive layer 5, and a separate film is disposed on the exposed surface of the pressure-sensitive adhesive layer 5 until it is bonded to the protective plate 6. It is customary to protect the surface temporarily.

  The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 5 disposed between the birefringent layer 4 and the protective plate 6 adheres to the surface of another substance simply by pressing, and pulls it from the adherend surface. In the case of peeling, it is a viscoelastic body that can be removed with almost no trace as long as the adherend has strength, and is also called an adhesive. The pressure-sensitive adhesive layer 5 can be formed on the basis of various pressure-sensitive adhesives conventionally used for image display devices. For example, there are acrylic, rubber, urethane, silicone, polyvinyl ether and the like. Moreover, an energy beam curing type, a thermosetting type, etc. may be sufficient. Among these, a pressure-sensitive adhesive using an acrylic resin having excellent transparency, weather resistance, heat resistance, and the like as a base polymer is preferable.

  The acrylic resin is not particularly limited, but (meth) such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Preferred are homopolymers of alkyl acrylates, copolymers of two or more alkyl (meth) acrylates, and copolymers of one or more alkyl (meth) acrylates with polar monomers. Used. Examples of polar monomers include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylamide, and 2-N, N-dimethylaminoethyl (meth). Mention may be made of monomers having a carboxy group, a hydroxyl group, an amide group, an amino group, an epoxy group and the like, such as acrylate and glycidyl (meth) acrylate.

  These acrylic resins can of course be used alone, but a crosslinking agent is usually used in combination. As the crosslinking agent, a divalent or polyvalent metal ion that forms a carboxylic acid metal salt with a carboxyl group, a polyamine compound that forms an amide bond with a carboxyl group, Examples thereof include polyepoxy compounds and polyol compounds that form an ester bond with a carboxyl group, and polyisocyanate compounds that form an amide bond with a carboxyl group. Of these, polyisocyanate compounds are widely used as organic crosslinking agents.

  The energy ray curable pressure sensitive adhesive has the property of being cured by irradiation of energy rays such as ultraviolet rays and electron beams, and has adhesiveness before the irradiation of energy rays and adheres to films and the like. It is a pressure-sensitive adhesive that has the property of adhering to the body and being cured by irradiation with energy rays to adjust the adhesion. As the energy ray curable pressure sensitive adhesive, it is particularly preferable to use an ultraviolet curable pressure sensitive adhesive. The energy beam curable pressure sensitive adhesive generally comprises an acrylic resin and an energy beam polymerizable compound as main components. Usually, a crosslinking agent is further blended, and a photoinitiator, a photosensitizer and the like can be blended as necessary.

  The pressure-sensitive adhesive used for forming the pressure-sensitive adhesive layer 5 includes, in addition to the base polymer and the crosslinking agent described above, the pressure-sensitive adhesive's adhesive force, cohesive force, viscosity, elastic modulus, In order to adjust the glass transition temperature, for example, natural or synthetic resins, tackifying resins, antioxidants, dyes, pigments, antifoaming agents, corrosives, photoinitiators, etc. An agent can also be blended. Furthermore, it can also be set as the pressure sensitive adhesive layer which contains a microparticle and shows light-scattering property.

  The thickness of the pressure sensitive adhesive layer 5 is preferably in the range of 1 to 40 μm. In order to obtain a thin composite protective plate, it is desirable to form the pressure-sensitive adhesive layer 5 as thin as possible within a range that does not impair properties such as workability and durability, and for example, within a range of 3 to 25 μm. It is suitable for suppressing the dimensional change of the polarizing film while maintaining good processability. Further, as will be described later, when the protective plate 6 is a touch panel and is bonded to the ITO layer, it is preferable that there are few acidic components such as carboxyl groups in consideration of the deterioration of the ITO.

  Here, FIG. 2 is a cross-sectional view schematically showing a display device 11 of another preferred example of the present invention. In the display device of the present invention, as in the example shown in FIG. 2, the composite protective plate 12 is provided on the display device body 5 side of the birefringent layer 4 directly or via a pressure-sensitive adhesive layer. 13 may be further provided. In the present invention, a surface treatment layer such as a hard coat layer, an antireflection layer, or an antiglare layer can be provided as the transparent protective layer 13 as necessary.

  The hard coat layer is formed to prevent the surface of the birefringent layer 4 from being scratched. The hard coat layer is mainly formed from an ultraviolet curable resin, for example, an acrylic or silicone resin, and the birefringent layer 4. Those having excellent adhesion and hardness are appropriately selected and can be formed on the surface of the birefringent layer 4.

  The antireflection layer is formed for the purpose of preventing reflection of external light on the surface of the birefringent layer 4 and preventing multiple reflection of display light, and can be formed by a known method.

  The antiglare layer is formed to prevent the surface of the birefringent layer 4 from coming into contact with the display device to generate Newton rings. For example, a roughening method such as a sandblasting method or an embossing method, In general, the surface of the birefringent layer 4 is formed to have a concavo-convex structure by, for example, a method of applying and curing a coating liquid in which transparent fine particles are mixed with an ultraviolet curable resin.

  The transparent protective layer 13 may be formed directly on the surface of the birefringent layer 4 or may be laminated via a pressure sensitive adhesive layer. As the transparent protective layer 13, a suitable transparent film can be used. Among these, a film made of a resin excellent in transparency, uniform optical properties, mechanical strength, thermal stability, etc. is preferably used. For example, cellulose resin films such as triacetyl cellulose and diacetyl cellulose, acrylic resin films such as polymethyl (meth) acrylate and polyethyl (meth) acrylate, polycarbonate resin films, polyethersulfone resin films, polysulfone resin films, Examples include, but are not limited to, a polyimide resin film, a polyolefin resin film, and a cyclic olefin resin film having a cyclic olefin as a monomer such as norbornene. An adhesive or a pressure sensitive adhesive can be used for bonding the transparent protective layer 13 and the birefringent layer 4.

  As the protective plate 6, the same material as that of the transparent protective layer 13 described above can be used. Further, similarly to the birefringent layer 4, a surface treatment layer such as a hard coat layer, an antireflection layer, or an antiglare layer may be provided on the surface on the viewer side A of the protective plate 6.

  Further, the protective plate 6 may have a touch panel function, and the touch panel method is not particularly limited to a resistive film type, a capacitance type, an electromagnetic induction type, an optical type, or the like.

  The display device body in the display device of the present invention includes, for example, a liquid crystal cell, and can be realized as a liquid crystal display device by installing the above-described composite protective plate on the viewer side of the liquid crystal cell. In this case, the liquid crystal cell used is arbitrary, and various liquid crystal cells such as an active matrix drive type represented by a thin film transistor type and a simple matrix drive type represented by a super twisted nematic type are used. Thus, a liquid crystal display device can be formed.

  Furthermore, the display device of the present invention can be realized so as to produce the same effect as an image display device that emits polarized light other than the liquid crystal display device, for example, an organic EL display device. Of course, the display device of the present invention is not limited to those exemplified here, and even if it is realized as a CRT or the like that does not emit polarized light, it does not harm the display.

  Hereinafter, the present invention will be described more specifically with reference to experimental examples and comparative experimental examples, but the present invention is not limited to these examples.

[Experimental Example 1]
An acrylic resin having a thickness of 2 mm is used for the protective plate 6, and an aromatic polycarbonate-based λ / 4 plate (Pure Ace WR (manufactured by Teijin Chemicals)) as a birefringent layer 4 on one side: R450 = 115 nm, R550 = 138 nm, R590 = 142 nm, R450 / R590 = 0.81), and a pressure sensitive adhesive so that the slow axis of the aromatic polycarbonate-based λ / 4 plate forms an angle of 45 ° with respect to the long side. A composite protective plate having the layer structure shown in 1 was obtained.

[Experiment 2]
Instead of Experimental Example 1, a polycarbonate λ / 4 plate (SEF440138 (manufactured by Sumitomo Chemical Co., Ltd.): R450 = 148 nm, R550 = 138 nm, R590 = 136 nm, R450 / R590 = 1.09) was used as the birefringent layer 4. Then, the laminate was laminated through a pressure-sensitive adhesive so that the slow axis of the λ / 4 plate forms an angle of 135 ° with respect to the long side to obtain a composite protective plate having a layer structure shown in FIG.

[Comparative Experiment Example 1]
The protective plate 6 and the birefringent layer 4 of Experimental Example 1 are bonded together so that the slow axis of the birefringent layer 4 forms an angle of 0 ° with respect to the long side, to obtain a composite protective plate having the layer configuration shown in FIG. It was.

[Comparative Experiment Example 2]
The protective plate 6 of Example 1 and the birefringent layer 4 were bonded together so that the slow axis of the birefringent layer 4 forms an angle of 30 ° with respect to the long side, to obtain a composite protective plate having the layer structure shown in FIG. .

[Reference Example 1]
Only the protective plate 6 of Experimental Example 1 was used as it was.

The composite protective plates obtained in each experimental example and comparative experimental example were replaced with protective plates or touch panels of the following 10 commercially available display devices, and the screen was observed through polarized glasses. The screen was implemented in portrait and landscape orientation as in actual use.
・ Commercial mobile phone 1: SH903i
・ Commercial mobile phone 2: F903i
-Commercial mobile phone 3: SO903i
-Commercial mobile phone 4: W61P
・ Commercial mobile phone 5: W53CA
・ Commercial mobile phone 6: W43S
・ Commercial mobile phone 7: iPhone
・ Commercial mobile phone 8: MEDIA SKIN
・ Commercial game machine 1: PSP3000
・ Commercial game machine 2: NINTENDO DSi
The results are shown in Tables 1 and 2. In Tables 1 and 2, “◯” represents an evaluation result, “Δ” is barely visible, and “X” is dark and cannot be seen well.

  The embodiments and experimental examples disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1,11 Display apparatus, 2,12 Composite protective board, 3 Display apparatus main body, 4 Birefringence layer, 5 Pressure sensitive adhesive layer, 6 Protection board, 13 Transparent protective layer.

Claims (6)

A birefringent layer, a pressure-sensitive adhesive layer, and a protective plate are a display device including a composite protective plate that is laminated in this order from the display device main body side toward the viewer side,
The composite protection plate is disposed on the viewer side of the display device with a space from the display device body, and the slow axis of the birefringent layer is 45 ± 10 ° or 135 ± 10 ° with respect to the display device screen. A display device characterized by being.   The display device according to claim 1, wherein the composite protective plate further includes a transparent protective layer provided directly or via a pressure-sensitive adhesive layer on the display device main body side of the birefringent layer. The display device according to claim 1, wherein the birefringent layer of the composite protective plate satisfies the formulas (1) and (2).
Formula (1): 0.71 <R450 / R590 <0.82
Formula (2): 133 nm <R550 <143 nm
(In the above formula (1), R450 is the in-plane retardation value of the birefringent layer with respect to light having a wavelength of 450 nm, and R550 is the in-plane retardation value of the birefringent layer with respect to light having a wavelength of 550 nm. R590 is an in-plane retardation value of the birefringent layer with respect to light having a wavelength of 590 nm.   The display device according to claim 1, wherein the birefringent layer of the composite protective plate is composed of a plurality of layers.   The birefringent layer of the composite protective plate comprises a polymer monomer unit having a positive refractive index anisotropy and a polymer monomer unit having a negative refractive index anisotropy having a larger wavelength dispersion than the polymer. The display apparatus in any one of Claims 1-4 comprised by the oriented film of the copolymer which has.   The display device according to claim 1, wherein the protective plate of the composite protective plate is a touch panel.

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