JP5706756B2 - Image display device - Google Patents

Description

  The present invention relates to an image display device including a front transparent plate on a viewing side surface of an image display panel.

  In the case of flat panel displays such as liquid crystal display devices, an acrylic plate or glass is placed closer to the viewing side than the image display panel in order to prevent the impact from being transmitted to the image display panel and being damaged when an impact is applied from the outer surface. A front transparent plate (also referred to as a “window layer” or the like) such as a plate may be provided. An image display device including a touch panel on the viewing side of the image display panel is also widely used, but such a touch panel also has a function as a front transparent plate for preventing an impact from being applied to the display panel.

  In an image display device having a front transparent plate, in addition to light (image) emitted from the image display panel and transmitted through the front transparent plate, external light reflected by the front and back surfaces of the front transparent plate, the surface of the image display panel, Since the reflected light of the external light reflected inside is visually recognized, there is a problem that the visibility of the image in a bright place such as outdoors is lowered.

  In order to reduce the visibility due to such reflection of external light, another polarizing plate (second polarizing plate) is provided on the viewing side further than the polarizing plate (first polarizing plate) on the surface of the image display panel. A method has been proposed in which two quarter-wave plates are provided between the two polarizing plates (for example, Patent Document 1). According to such a configuration, when the external light is incident from the second polarizing plate side, reflected on the image display panel side, and then reenters the second polarizing plate, The linearly polarized light vibrates in the direction orthogonal to the transmission axis direction. Therefore, the reflected light from the image display panel side is not visually recognized, and the deterioration of the visibility of the image in a bright place is suppressed. On the other hand, since the light (image) emitted from the image display cell to the viewer side through the first polarizing plate becomes linearly polarized light that vibrates in the transmission axis direction of the second polarizing plate, Even if the plate is provided, a decrease in luminance of the light (image) emitted from the panel is suppressed. Therefore, a decrease in visibility due to the reflected light of outside light is suppressed without significantly reducing the luminance of the image.

  According to the configuration disclosed in Patent Document 1, it is possible to suppress a decrease in visibility due to reflection of external light without reducing the luminance of an image with respect to light in a substantially front direction. However, when the image display device is viewed from an oblique direction, the apparent retardation of the two quarter-wave plates deviates from the quarter-wave, so that the image is colored or the reflected light is suppressed. Is insufficient, and there is a problem that visibility is lowered.

  In view of such a problem, in order to suppress coloring of an image when the image display device is viewed from an oblique direction, nx> nz> It has been proposed to use a film having ny three-dimensional refractive index characteristics (for example, Patent Document 2). Here, nx and ny are the refractive indexes in the slow axis direction and the fast axis direction in the film plane, respectively, and nz is the refractive index in the film normal direction. When the film satisfies the refractive index characteristic of nx> nz> ny, the Nz coefficient represented by (nz−nz) / (nx−ny) is more than 0 and less than 1, but Nz = 0.5 No change in retardation depending on the viewing direction. In general, a positive A plate having a three-dimensional refractive index of nx> ny≈1 (Nz≈1) is used as the quarter wavelength plate. However, in Patent Document 2, the Nz coefficient of two quarter wavelength plates is used. The total is 2. Therefore, even when the image display device is viewed from an oblique direction, the change in the apparent retardation of the quarter-wave plate is small, and the coloring of the image is suppressed.

Japanese Patent Laid-Open No. 5-281538 JP 2000-39611 A

  According to the configuration in which two quarter-wave plates having an Nz coefficient smaller than 1 are arranged between two polarizing plates as in Patent Document 2, coloring of an image in an oblique direction is reduced. The display characteristics in a dark place are good. However, when the total Nz of the two quarter-wave plates is smaller than 2, the reflected light suppression effect is not sufficient, and the visibility in a bright place is lowered. In view of such a problem, the present invention has an object of providing an image display device that includes a front transparent plate on the viewing-side surface of an image display panel and that suppresses a decrease in visibility due to reflected light even when viewed from an oblique direction. And

The above problem is solved by controlling the three-dimensional refractive index of the two quarter-wave plates disposed between the two polarizing plates. The image display device of the present invention includes an image display panel including a first polarizing plate on a viewing side surface of an image display cell, and a front transparent plate on a viewing side of the image display panel. Between the front transparent plate, a first quarter-wave plate, a second quarter-wave plate, and a second polarizing plate are provided in this order from the first polarizing plate side. The first polarizing plate and the first quarter-wave plate constitute a first circular polarizing plate, and the second polarizing plate and the second quarter-wave plate are second circles. Construct a polarizing plate. The first circularly polarizing plate and the second circularly polarizing plate have the same polarity. In the present invention, the total Nz ₁ + Nz ₂ of the Nz coefficient Nz ₁ of the first quarter-wave plate and the Nz coefficient Nz ₂ of the second quarter-wave plate is 2.1 to 5.9. Is preferred. In one embodiment, the Nz coefficient Nz ₁ of the first quarter-wave plate and the Nz coefficient Nz ₂ of the second quarter-wave plate are both preferably greater than 1.

  The slow axis direction of the first first quarter wave plate and the slow axis direction of the second quarter wave plate are the first polarizing plate and the first quarter wave plate. So that the first circularly polarizing plate constituted by the second circularly polarizing plate constituted by the second circularly polarizing plate and the second quarterly polarizing plate are different polarities. It only has to be arranged. In one embodiment, it is preferable that the slow axis direction of the first first quarter-wave plate and the slow axis direction of the second quarter-wave plate are arranged so as to be orthogonal to each other.

  In one embodiment, the image display cell, the first polarizing plate, and the first quarter-wave plate are laminated without an air gap, and the front transparent plate, the second polarizing plate, It is preferable that the second quarter-wave plate is laminated without an air gap. The first quarter-wave plate and the second quarter-wave plate may be laminated without an air gap through an adhesive layer, an adhesive layer, or the like. From the viewpoint of preventing breakage, it is preferable that the quarter-wave plate and the second quarter-wave plate are not bonded together and an air layer is provided between them.

An embodiment of the present invention includes an organic EL display device in which the image display cell is an organic EL cell. In addition to the above-described configuration, the organic EL display device of the present invention further includes a third quarter-wave plate between the organic EL cell and the first polarizing plate, and the first quarter-wave plate. It is preferable that the slow axis direction and the slow axis direction of the third quarter-wave plate are orthogonal or parallel to each other. The Nz coefficient Nz ₃ of the third quarter-wave plate preferably satisfies 0 <Nz ₃ <1.5.

  In the image display device of the present invention, two polarizing plates and two quarter-wave plates are arranged between the image display cell and the front transparent plate so as to constitute a circularly polarizing plate, and Two quarter-wave plates have a predetermined three-dimensional refractive index characteristic. Therefore, a decrease in visibility due to the reflected light of the external light from the front direction and the oblique direction is suppressed without significantly reducing the luminance of the image.

It is sectional drawing which represents typically the image display apparatus by one Embodiment. It is sectional drawing which represents typically the image display apparatus (liquid crystal display device) by one Embodiment. It is sectional drawing which represents typically the image display apparatus (organic EL display apparatus) by one Embodiment of this invention. It is a perspective view which represents typically the arrangement | positioning relationship of a polarizing plate and a quarter wavelength plate in one Embodiment. It is a perspective view which represents typically the arrangement | positioning relationship of a polarizing plate and a quarter wavelength plate in one Embodiment. It is sectional drawing which represents typically one Embodiment of a laminated polarizing plate with an adhesive layer. It is sectional drawing which represents typically one Embodiment of a laminated polarizing plate with an adhesive layer.

  The present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing an image display apparatus according to an embodiment of the present invention. The image display device 100 includes a front transparent plate 60 on the viewing side surface of the image display panel 50. The image display panel 50 includes a first polarizing plate 31 on the viewing side surface of the image display cell 10. A second polarizing plate 32 is disposed on the surface of the front transparent plate 60 facing the image display panel. Between the 1st polarizing plate 31 and the 2nd polarizing plate 32, the 1st 1/4 wavelength plate 41 and the 2nd 1/4 wavelength plate 42 are arrange | positioned from the 1st polarizing plate 31 side. Yes. Examples of such an image display device include a liquid crystal display device using a liquid crystal cell as an image display cell, and an organic EL display device (OLED) using an organic EL cell as an image display cell.

  FIG. 2 is a cross-sectional view schematically showing one embodiment of the liquid crystal display device according to the present invention. Examples of the liquid crystal cell 11 include a reflective liquid crystal cell that uses external light, a transmissive liquid crystal cell that uses light from a light source such as a backlight, and semi-transmissive and semi-reflective that uses both external light and light from the light source. Any type of liquid crystal cell may be used. In addition, as a driving method of the liquid crystal cell, for example, any type such as a VA mode, an IPS mode, a TN mode, an STN mode, or a bend alignment (π type) can be used.

  When a transmissive liquid crystal cell or a semi-transmissive / semi-reflective liquid crystal cell is employed as the liquid crystal cell 11, the liquid crystal panel 51 has a third side on the opposite side to the viewing side of the liquid crystal cell 11 as shown in FIG. The polarizing plate 33 is provided, and the liquid crystal display device 101 is provided with a light source 80.

  FIG. 3 is a cross-sectional view schematically showing one embodiment of the organic EL display device according to the present invention. As the organic EL cell 12, a light emitting body (organic electroluminescent light emitting body) is used in which a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate. Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Alternatively, a structure having various combinations such as a laminate of such a light-emitting layer and an electron injection layer made of a perylene derivative, or a stack of these hole injection layer, light-emitting layer, and electron injection layer is known. It has been. In the organic EL display device, as shown in FIG. 3, the organic EL panel 52 preferably includes a third quarter-wave plate 43 between the organic EL cell 12 and the first polarizing plate 31. If the 1st polarizing plate 31 and the 3rd quarter wavelength plate 43 are laminated | stacked so that a circularly-polarizing plate may be comprised, the external light mirror-reflected with the metal electrode of the organic EL cell 12 will be 1st. Since it is shielded by the polarizing plate 31, a decrease in the visibility of the image display device is suppressed.

  4A and 4B are diagrams showing the arrangement of the quarter-wave plates and the polarizing plates in the image display device of the present invention. The first polarizing plate 31 and the first quarter-wave plate 41 constitute a first circularly polarizing plate 91. That is, the angle formed by the transmission axis direction 31t of the first polarizing plate 31 and the slow axis direction 41s of the first quarter-wave plate 41 is about 45 °. Similarly, the second polarizing plate 32 and the second quarter-wave plate 42 constitute a second circularly polarizing plate 92. That is, the angle formed by the transmission axis direction 32t of the second polarizing plate 32 and the slow axis direction 42s of the second quarter-wave plate 42 is about 45 °. In addition, about 45 degrees refers to the range of about 35 degrees-55 degrees, Preferably it is 40-50 degrees, More preferably, it is 43 degrees-47 degrees, More preferably, it is 44 degrees-46 degrees. In this specification, unless otherwise specified, the sign of the angle (positive or negative) is not limited, and may be counterclockwise (+) or clockwise (−).

  The first circularly polarizing plate 91 and the second circularly polarizing plate 92 have the same polarity. That is, when the first circularly polarizing plate is a right circularly polarizing plate, the second circularly polarizing plate is also a right circularly polarizing plate, and when the second circularly polarizing plate is a left circularly polarizing plate, the second circularly polarizing plate is second. The circularly polarizing plate is also a left circularly polarizing plate. If the first polarizing plate 31, the first quarter-wave plate 41, the second quarter-wave plate 42, and the second polarizing plate 32 are arranged so as to satisfy the above relationship, an image is displayed. Vibration of light that exits from the cell 10, passes through the first polarizing plate 31, and reaches the second polarizing plate 32 through the first quarter-wave plate 41 and the second quarter-wave plate 42. The direction is equal to the transmission axis direction 32t of the second second polarizing plate. Therefore, the light (image) in the front direction emitted from the image display cell to the viewer side is emitted to the viewer side through the front transparent plate 60 without being almost absorbed by the second polarizing plate.

  The transmission axis direction 31t of the first polarizing plate 31 and the transmission axis direction 32t of the second polarizing plate 32 are preferably orthogonal (FIG. 4A) or parallel (FIG. 4B). More specifically, as shown in FIG. 4A, when the transmission axis direction 31t of the first first polarizing plate 31 and the transmission axis direction 32t of the second polarizing plate 32 are orthogonal to each other, the first The slow axis direction 41s of the ¼ wavelength plate and the slow axis direction 42s of the second ¼ wavelength plate are parallel to each other. 4B, when the transmission axis direction 31t of the first first polarizing plate 31 and the transmission axis direction 32t of the second polarizing plate 32 are parallel, the first 1 / The slow axis direction 41s of the four-wave plate and the slow axis direction 42s of the second quarter-wave plate are orthogonal to each other. The term “orthogonal” is not limited to the case where the angle is strictly 90 °, and the angle formed by both is generally in the range of 85 ° to 95 °, preferably 88 to 92 °, more preferably 89 °. ~ 91 °. “Parallel” is not limited to the case where the angle is strictly 0 °, and the angle formed by the two is generally in the range of 0 ± 5 °, preferably 0 ± 2 °, more preferably 0 ± 1. °.

  The first polarizing plate 31 and the second polarizing plate 32 are not particularly limited as long as they emit incident light having an arbitrary polarization state as linearly polarized light, and various types can be used. As such a polarizing plate, what laminated | stacked the transparent protective film as needed on one or both main surfaces of a polarizer is used, for example. Polarizers include hydrophilic polymers such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, ethylene / vinyl acetate copolymer partially saponified films, and dichroic substances such as iodine and dichroic dyes. And polyene-based oriented films such as a uniaxially stretched product and a dehydrated product of polyvinyl alcohol and a dehydrochlorinated product of polyvinyl chloride.

  As a transparent protective film laminated | stacked on the one or both main surfaces of a polarizer, what is excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropic property etc. is used suitably, for example. Moreover, the function as a polarizer protective film and the function as a quarter wavelength plate can also be combined by using a quarter wavelength plate as a transparent protective film arrange | positioned at one surface of a polarizer.

  The first quarter-wave plate 41 and the second quarter-wave plate have a front retardation of ¼ of the wavelength λ. The front retardation Re is the difference (nx−ny) between the refractive index nx in the slow axis direction and the refractive index ny in the fast axis direction in the plane of the quarter wavelength plate, and the thickness d of the quarter wavelength plate. It is represented by the product of In addition, it is not necessary that the retardation is “1/4 wavelength” or “λ / 4”, and the retardation is strictly ¼ times the wavelength λ, and linearly polarized light is converted into substantially circularly polarized light. Any range is acceptable. The “substantially circularly polarized light” may include not only perfect circularly polarized light but also elliptically polarized light that is close to perfect circularly polarized light, that is, whose ellipticity is close to 1. For example, those having a retardation Re in the range of 137.5 ± 30 nm at the wavelength λ = 550 nm are also included in the “¼ wavelength”. The retardation Re at the wavelength λ = 550 nm is preferably 137.5 ± 20 nm, more preferably 137.5 ± 10 nm.

Be the front retardation Re ₁ of the first quarter-wave plate and the front retardation Re ₂ of the second quarter-wave plate is substantially the same value, the coloring in the front direction of the image display device It is preferable in terms of prevention and contrast. The difference between Re ₁ and Re ₂ is most preferably 0, but practically, the difference between Re ₁ and Re ₂ may be within a range of ± 20 nm, preferably ± 10 nm. Further, from the viewpoint of preventing coloration and contrast in the front direction of the image display device, as shown in FIG. 4B, the slow axis direction 41s of the first quarter-wave plate 41 and the second quarter-wave plate It is preferable that the slow axis direction 42s of 42 is orthogonal.

The total Nz ₁ + Nz ₂ of the Nz coefficient Nz ₁ of the first quarter-wave plate and the Nz coefficient Nz ₂ of the second quarter-wave plate is preferably 2.1 to 5.9. It is more preferably 5 to 5.5, further preferably 3 to 5, and particularly preferably 3.5 to 5.5. When the value of Nz ₁ + Nz ₂ is within the above range, a reduction in visibility due to reflection of external light when the image display device is viewed from an oblique direction is suppressed. Most preferably, Nz ₁ + Nz ₂ is 4.

If Nz ₁ + Nz ₂ is within the above range, the Nz coefficients of the first quarter-wave plate and the second quarter-wave plate are not particularly limited, but the first quarter-wave plate and the second quarter-wave plate are not limited. It is preferable that both of the ¼ wavelength plates satisfy Nz> 1, more preferably satisfy Nz> 1.2, and further preferably satisfy Nz> 1.5. Most preferred is the case of Nz ₁ = Nz ₂ = 2.

  Although the manufacturing method of the quarter wavelength plate with Nz larger than 1 is not specifically limited, For example, it obtains by extending | stretching the polymer film which has positive birefringence. Here, “having positive birefringence” means that when the polymer is oriented by stretching or the like, the refractive index in the orientation direction becomes relatively large, and many polymers correspond to this. Examples of the polymer having positive birefringence include polycarbonate resins, polyvinyl alcohol resins, cellulose fatty acid esters such as triacetyl cellulose, diacetyl cellulose, tripropionyl cellulose, and dipropionyl cellulose, and cellulose resins such as cellulose ether. Polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyarylate resins, polyimide resins, cyclic polyolefin (polynorbornene) resins, polysulfone resins, polyethersulfone resins, polyamide resins, polyethylene and polypropylene Examples include polyolefin resins.

  Preferable stretching methods for making the Nz coefficient larger than 1 include a transverse uniaxial stretching method, a longitudinal and transverse sequential biaxial stretching method, and a longitudinal and transverse simultaneous biaxial stretching method. As the stretching means, any appropriate stretching machine such as a roll stretching machine, a tenter stretching machine, a pantograph type or a linear motor type biaxial stretching machine can be used. A quarter-wave plate having an arbitrary Nz coefficient can be obtained by adjusting the longitudinal and lateral stretching ratios. Although a draw ratio can be suitably determined according to a film composition etc., it is about 1.05-5.00 times, for example.

  The front transparent plate 60 is provided from the viewpoint of preventing the image display panel from being damaged when an external force is applied from the viewing side surface (the upper side in the drawing) of the image display device. As the front transparent plate 60, a transparent plate having appropriate mechanical strength and thickness is used. As such a transparent plate, for example, a resin plate such as an acrylic resin or a polycarbonate resin, or a glass plate is used.

  A touch panel can also be used as the front transparent plate. In the display device of the present invention, the configuration of the touch panel used as the front transparent plate is not particularly limited, and a touch panel of an appropriate method such as an optical method, an ultrasonic method, a capacitance method, a resistance film method, or the like can be adopted.

  The formation method of the image display device is not particularly limited, and the image display cell 10, the first polarizing plate 31, the first quarter wavelength plate 41, the second quarter wavelength plate 42, and the second polarizing plate 32. , And the front transparent plate 60 may be laminated in this order and in the arrangement relationship as described above. Lamination of each member may be performed by simply superimposing the respective members as they are, or may be bonded through an appropriate adhesive layer or pressure-sensitive adhesive layer.

  From the viewpoint of suppressing reflection at the member interface, it is preferable to laminate the members without any air gaps by a method such as bonding each member through an appropriate adhesive layer or pressure-sensitive adhesive layer. On the other hand, when an impact is applied to the image display device from the outer surface, an air layer is provided between the front transparent plate 60 and the image display cell 10 from the viewpoint of preventing damage to the panel due to the impact. preferable. In particular, in the present invention, as shown in FIG. 1, it is preferable to have an air layer between the first quarter-wave plate 41 and the second quarter-wave plate 42. In this case, the first polarizing plate 31 and the first quarter wavelength plate 41 are laminated integrally with the image display cell via an adhesive layer or the like, and the second polarizing plate 32 and the second quarter wavelength are laminated. The plate 42 is laminated integrally with the front transparent plate 60 through an adhesive layer, and an air layer is employed between the first quarter-wave plate 41 and the second quarter-wave plate 42. obtain.

  In general, when an air layer is interposed between the front transparent plate and the image display cell, the reflectance at the air layer interface is high due to the difference in refractive index, and thus the visibility of the image display device tends to decrease. There is. In the present invention, the second polarizing plate 32 and the second quarter wavelength plate 42 are provided on the front transparent plate 60 side, and the first polarizing plate 31 and the first quarter are provided on the image display cell 10 side. By having the wave plate 41, re-emission of the reflected light on the air layer interface and the reflected light on the surface of the image display cell to the viewing side is suppressed, and therefore the degradation of the visibility due to the reflected light is small.

  When the image display device is an organic EL display device (OLED) using an organic EL cell as an image display cell, reflection at the metal electrode (cathode) of the organic EL cell 12 is large, and thus reflected light at the metal electrode. It is preferable to configure so that is not emitted to the viewing side. In order to suppress the emission of the reflected light from the metal electrode to the viewing side, a third quarter-wave plate 43 between the organic EL cell 12 and the first polarizing plate 31, as shown in FIG. It is preferable that the 1st polarizing plate 31 and the 3rd quarter wavelength plate 43 are laminated | stacked so that a circularly-polarizing plate may be comprised. That is, the angle formed by the transmission axis direction of the first polarizing plate 31 and the slow axis direction of the third quarter-wave plate 43 is preferably about 45 °. The slow axis direction of the first quarter-wave plate 41 and the slow axis direction of the third quarter-wave plate 43 may be either orthogonal or parallel.

In order to prevent light reflected by the metal electrode from the oblique direction in addition to the front direction from being emitted to the viewing side, the Nz coefficient Nz _{3 of} the third quarter-wave plate exceeds 0 and exceeds 1.5. It is preferable that it is less than. Nz ₃ is more preferably more than 0 and less than 1, more preferably 0.3 to 0.7, and still more preferably 0.4 to 0.6. Nz ₃ is ideally 0.5 from the viewpoint of suppressing a reduction in visibility due to obliquely reflected light.

  If the Nz coefficient of the third quarter-wave plate is in the above range, the change due to the apparent retardation angle with respect to the light propagating through the third quarter-wave plate in the oblique direction is small, and therefore the first The third circularly polarizing plate constituted by the polarizing plate 31 and the third quarter-wave plate 43 also acts as a circularly polarizing plate for light from an oblique direction. In this case, the oblique external light transmitted through the first polarizing plate to the organic EL cell 12 side is converted into circularly polarized light by the third quarter-wave plate and enters the organic EL cell 12, and the organic EL cell. After being reflected by the metal electrode, it is converted into linearly polarized light having a vibration direction in the absorption axis direction of the first polarizing plate by the third quarter-wave plate. Therefore, the reflected light from the metal electrode is absorbed by the first polarizing plate 31, and emission to the viewing side is suppressed.

  In the liquid crystal display device as shown in FIG. 2, for example, the second polarizing plate 32 and the second quarter-wave plate 42 are bonded to the front transparent plate 60 side, and the first polarizing plate is attached to the liquid crystal cell 11 side. 31 and the first quarter-wave plate 41 can be bonded together. Each of these layers can be bonded using an appropriate adhesive layer or pressure-sensitive adhesive layer (not shown). As described above, from the viewpoint of preventing damage to the panel due to an impact from the outer surface, an air layer is provided between the second quarter-wave plate 42 and the first quarter-wave plate. Although it is preferable, the second quarter-wave plate 42 and the first quarter-wave plate may be bonded together by an adhesive layer or a pressure-sensitive adhesive layer. In addition, the liquid crystal display device may include an optical element such as an optical compensation film between the liquid crystal cell 11 and the first polarizing plate 31.

  In the organic EL display device 102 as shown in FIG. 3, for example, the second polarizing plate 32 and the second quarter-wave plate 42 are bonded to the front transparent plate 60 side, and the third EL plate 12 side is connected to the third EL plate 12 side. The quarter-wave plate 43, the first polarizing plate 31, and the first quarter-wave plate 41 can be bonded together. As described above, from the viewpoint of preventing damage to the panel due to an impact from the outer surface, an air layer is provided between the second quarter-wave plate 42 and the first quarter-wave plate. preferable.

  There are no particular restrictions on the method of bonding the layers and the order of bonding. When the first polarizing plate 31 and the first quarter-wave plate 41 are bonded to the image display cell side, as shown in FIG. 5, the first polarizing plate 31 and the first quarter-wave plate 41 are bonded from the viewpoint of workability. It is preferable to create a laminated polarizing plate (circular polarizing plate) 91 to which the quarter wavelength plate 41 is bonded, and to bond the laminated polarizing plate and the image display cell. In the case of an organic EL display device, as shown in FIG. 6, a laminated polarizing plate 93 in which a third quarter-wave plate 43 is bonded to the polarizing plate 31 side of the circularly polarizing plate 91 is produced. This is preferably bonded to the organic EL cell 12.

  The laminated polarizing plate and the image display cell are preferably bonded together via an adhesive layer 71. The pressure-sensitive adhesive for laminating the laminated polarizing plates 91 and 93 and the image display cell is transparent, has no absorption in the visible light region, has a refractive index of 1/4 wavelength plate, and a member on the surface of the image display cell (generally Is preferably a small difference from the refractive index of the glass. As such an adhesive, an acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer can be appropriately selected and used. . In particular, an acrylic adhesive that is excellent in optical transparency, exhibits appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and is excellent in weather resistance, heat resistance, and the like is preferably used.

  The pressure-sensitive adhesive layer 71 is, for example, a natural or synthetic resin, in particular, a tackifier resin, a filler, a pigment, a colorant, an antioxidant made of glass fiber, glass beads, metal powder, or other inorganic powder. An additive to be added to the pressure-sensitive adhesive layer such as an agent may be contained. Moreover, the adhesive layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient. Although the thickness of an adhesive layer can be suitably determined according to a use purpose, adhesive force, etc., generally it is 1-500 micrometers, 2-200 micrometers is preferable, 3-100 micrometers is more preferable, and 4-50 micrometers is more preferable.

  Considering the workability of laminating the laminated polarizing plate and the image display cell, etc., as shown in FIGS. 5 and 6, with the adhesive layer provided with an adhesive layer on the side of the laminated polarizing plate to be adhered to the image display cell. It is preferable that the laminated polarizing plates 96 and 97 are produced and bonded to the image display cell. It is preferable that a separator is temporarily attached to the exposed surface of the pressure-sensitive adhesive layer 71 for the purpose of preventing contamination until it is put into practical use. Thereby, it can prevent contacting an adhesive layer in the usual handling state. As the separator, for example, an appropriate thin leaf body such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foamed sheet, metal foil, laminate thereof, or the like, silicone type, long chain alkyl type, fluorine type A suitable one according to the prior art, such as those coated with a suitable release agent such as molybdenum sulfide or molybdenum sulfide, is used.

  Even when the second polarizing plate 32 and the second quarter-wave plate 42 are bonded to the front transparent plate side, the laminated polarizing plate in which the second polarizing plate 32 and the second quarter-wave plate 42 are bonded together. A direction in which a plate (circular polarizing plate) 92 is prepared and the laminated polarizing plate and the front transparent plate are bonded to each other can be adopted. When the second quarter-wave plate 42 and the first quarter-wave plate are not bonded and an air layer is provided between them, each of the image display panel and the front transparent plate is made of an appropriate casing. It is preferably fixed.

  Although the image display device of the present invention is used for any appropriate application, it has a front transparent plate and the reflection of light from an oblique direction is suppressed. Therefore, the image display device can be used outdoors such as a portable information terminal or a vehicle-mounted device. It is particularly suitable as a display device to be used.

  The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

  In each embodiment, using a quarter wave plate having various Nz coefficients, as shown in FIG. 4B, the slow axis direction 41 s of the first quarter wave plate 41 and the second quarter wave. An image display device arranged so that the slow axis direction of the wave plate 42 was orthogonal to each other was produced. The intensity of reflected light was visually confirmed when the image display device was viewed from an oblique direction outdoors on a clear day. The evaluation was performed in six stages of 1 to 6, where 1 is one in which reflected light is strongly observed and 6 is one in which reflected light is hardly confirmed. In addition, as a reference example, in FIG. 4B, a device in which the first quarter-wave plate 41 and the second quarter-wave plate 42 are omitted was produced, and the same evaluation was performed.

  Table 1 shows the Nz coefficient of the quarter-wave plate used in each example and reference example, and the evaluation results of reflected light in an oblique direction under external light.

  According to Table 1, it can be seen that the reflected light in the oblique direction is suppressed by adjusting the Nz coefficient of the first quarter wavelength plate and the second quarter wavelength plate.

DESCRIPTION OF SYMBOLS 10 Image display cell 50 Image display panel 100 Liquid crystal display device 11 Liquid crystal cell 51 Liquid crystal panel 80 Light source 101 Liquid crystal display device 12 Organic EL cell 51 Organic EL panel 102 Organic EL display device 60 Front transparent plate 31-33 Polarizing plates 31t and 32t Transmission Axial direction 41 to 43 1/4 wavelength plate 41s, 42s Slow axis direction 71 Adhesive layer 91, 92 Circularly polarizing plate (Laminated polarizing plate 93 Laminated polarizing plate 96, 97 Laminated polarizing plate with adhesive layer

Claims (6)

An image display panel comprising a first polarizing plate on the viewing side surface of the image display cell, and an image display device comprising a front transparent plate on the viewing side than the image display panel,
Between the first polarizing plate and the front transparent plate, in order from the first polarizing plate side, a first quarter-wave plate, a second quarter-wave plate, and a second polarizing plate In this order,
The first polarizing plate and the first quarter-wave plate constitute a first circular polarizing plate, and the second polarizing plate and the second quarter-wave plate are second circles. Configure the polarizing plate,
The first circularly polarizing plate and the second circularly polarizing plate are both right circularly polarizing plates or both left circularly polarizing plates,
The image display device, wherein a total Nz ₁ + Nz ₂ of the Nz coefficient Nz ₁ of the first quarter-wave plate and the Nz coefficient Nz ₂ of the second quarter-wave plate is 2.1 to 5.9. The first quarter Nz coefficient Nz ₂ wavelength plate Nz coefficient Nz ₁ and the second quarter-wave plate are both greater than 1, the image display apparatus according to claim 1.   3. The image display device according to claim 1, wherein a slow axis direction of the first first quarter-wave plate and a slow axis direction of the second quarter-wave plate are orthogonal to each other. The image display cell, the first polarizing plate, and the first quarter-wave plate are laminated without air gaps,
The front transparent plate, the second polarizing plate, and the second quarter-wave plate are laminated without air gaps,
4. The image display device according to claim 1, wherein an air layer exists between the first quarter-wave plate and the second quarter-wave plate. 5. The image display cell is an organic EL cell, and has a third quarter-wave plate between the organic EL cell and the first polarizing plate,
5. The slow axis direction of the first quarter wavelength plate and the slow axis direction of the third quarter wavelength plate are orthogonal or parallel to each other. Image display device. The image display device according to claim 5, wherein an Nz coefficient Nz _{3 of} the third quarter-wave plate is 0 <Nz ₃ <1.5.

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