JP5936453B2 - Backlight device - Google Patents

Description

  The present invention relates to a backlight device and a liquid crystal display device used in a liquid crystal display device used as a display of a liquid crystal television, a liquid crystal monitor, and a personal computer.

  The liquid crystal display device is roughly divided into a backlight device that emits light and a liquid crystal cell device that displays an image using light emitted from the backlight device.

  When the image displayed on the liquid crystal display device is observed from an oblique direction rather than from a position perpendicular to the liquid crystal display device, the balance of red, green and blue light is lost, and a color different from the original color is observed. A phenomenon called color shift occurs.

  Conventionally, measures to reduce the color shift have been applied to a liquid crystal cell device that emits light to an observer. The chromatic dispersion characteristic of the in-plane retardation value of the film is “reverse chromatic dispersion” in which the retardation value decreases as the wavelength becomes shorter. The chromatic dispersion characteristic of the retardation value in the film thickness direction becomes the retardation as the wavelength becomes shorter. It has been proposed to dispose a special biaxial retardation compensation film having an increased value of “forward wavelength dispersion” on a polarizing plate included in a liquid crystal cell device (for example, see Patent Document 1).

JP-T-2006-515686

However, the biaxial retardation compensation film is a special sheet. Therefore, there has been a demand for a backlight device that can be configured more simply without using a biaxial retardation compensation film and that realizes a liquid crystal display device with a small color shift.
Therefore, a main object of the present invention is to provide a backlight device that can be simply configured and realizes a liquid crystal display device with a small color shift.

  The inventors of the present invention have studied a liquid crystal display device that can be simply configured and has a small color shift, and unlike the prior art, intend to take measures to reduce the color shift not in the liquid crystal cell device but in the backlight device. It came. In order to solve the above problems, the present inventors have intensively studied a backlight device. As a result, the present invention was completed.

  The backlight device according to the present invention is provided with a surface light emitting unit that emits planar light from a light emitting surface and a light emitting side on the surface light emitting unit, and light from which light from the light emitting surface is incident A deflection layer; and a light diffusion layer provided on the light exit side of the light deflection layer. The surface light emitting unit includes a light guide plate, a light source disposed on an end surface of the light guide plate, and a reflection plate disposed on the opposite side of the light deflection layer with respect to the light guide plate. A first azimuth angle, a second azimuth angle, a third azimuth angle, and a fourth azimuth angle in a plane orthogonal to the first direction, which is a direction from the surface light emitting portion toward the light deflection layer, Of light emitted from the light exit surface with respect to the first to fourth azimuth angles of 0 °, 45 °, 90 °, and 135 °, respectively, with respect to the second direction that is the direction from the light guide plate to the light guide plate, In the case where the luminance at a certain distance from the measurement target point on the light exit surface is measured in the viewing angle range of −40 ° to + 40 °, −60 ° to −74 °, and + 60 ° to + 74 ° with respect to the first direction. , In all the first to fourth azimuth angles, with respect to the maximum value in the luminance range of −60 ° to −74 ° and + 60 ° to + 74 ° in all the first to fourth azimuth angles. All the luminances in the viewing angle range of 40 ° to + 40 ° are 40% or less. The haze value of the light diffusion layer is 86% or less.

  In the backlight device according to the present invention, the first to fourth maximum brightness values in the range of viewing angles of −60 ° to −74 ° and + 60 ° to + 74 ° in all the first to fourth azimuth angles. 15% or less may be sufficient as all the brightness | luminances in the range of the viewing angle of -40 degrees-+40 degrees in all the 4th azimuth angles.

  In the backlight device according to the present invention, the light guide plate may be a plate having a trapezoidal cross section.

  In the backlight device according to the present invention, the light guide plate may have a shape in which two plates having a trapezoidal cross section are integrated so as to share and contact the upper base of the trapezoid.

  In the backlight device according to the present invention, the reflecting plate may be a mirror type.

  In the backlight device according to the present invention, the light deflection layer may be a prism sheet in which a plurality of first prism portions are provided on the incident surface side on which light from the light emitting surface is incident. Each of the plurality of first prism portions may extend in a third direction, which is a direction orthogonal to the first and second directions, and be arranged in parallel in the second direction.

  In the backlight device according to the present invention, the cross-sectional shape orthogonal to the third direction of each of the plurality of first prism portions is a triangle, and the apex of the triangle is the cross-sectional shape of each of the plurality of first prism portions. Are located on the surface light emitting part side, and the bases of the triangles, which are the cross-sectional shapes of the plurality of first prism parts, may be arranged in a straight line.

  In the backlight device according to the present invention, the light deflection layer is provided with a plurality of second prism portions on the side opposite to the incident surface side, and each of the plurality of second prism portions extends in the second direction. In addition, they may be arranged in parallel in the third direction.

The liquid crystal display device according to the present invention includes the backlight device described above and a liquid crystal cell device provided on the light emission surface side of the backlight device. The liquid crystal cell device includes a first polarizing plate, a liquid crystal cell in which a liquid crystal layer is provided between a pair of substrates, and a second polarizing plate. In the liquid crystal display device according to the present invention, the first polarizing plate, the liquid crystal cell, and the second polarizing plate are arranged in this order from the light emitting side of the backlight device. The transmission axes are arranged so as to be substantially perpendicular to each other.
In the liquid crystal display device according to the present invention, the liquid crystal cell device further includes an antiglare layer, and the first polarizing plate, the liquid crystal cell, the second polarizing plate, and the antiglare layer are provided from the light emitting side of the backlight device. They may be arranged in order.

  The present invention provides a backlight device that can be simply configured and realizes a liquid crystal display device with a small color shift.

FIG. 1 is a schematic view showing a backlight device according to an embodiment of the present invention. FIG. 2 is a schematic view showing a liquid crystal display device using a backlight device according to an embodiment of the present invention. FIG. 3 is a diagram illustrating an angular distribution of luminance of light emitted from the light guide plate of the backlight device according to the embodiment of the present invention. FIG. 4 is a diagram illustrating a method for measuring the angular distribution of the luminance of light emitted from the light guide plate of the backlight device according to the embodiment of the present invention. FIG. 5 is a diagram illustrating a measurement result of an angular distribution of luminance of light emitted from the light guide plate in the backlight device of the first embodiment. FIG. 6 is a diagram illustrating a method for measuring chromaticity coordinates of light emitted from a liquid crystal display device including the backlight device according to the first embodiment.

  Hereinafter, the present invention will be described in detail. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. The dimensional ratios in the drawings do not necessarily match those described. Further, in the description, words indicating directions such as “up” and “down” are convenient words based on the state shown in the drawings.

  FIG. 1 shows a backlight device according to an embodiment of the present invention. The backlight device 11 according to an embodiment of the present invention includes a light deflection layer 16, a light source 13, a light guide plate 12, a reflection plate 14, and a light diffusion layer 9. The light source 13, the light guide plate 12, and the reflection plate 14 constitute a surface light emitting unit 15 that generates planar light. In the configuration shown in FIG. 1, the light emitting surface 12 a corresponds to the light emitting surface 15 a of the surface light emitting unit 15. The light guide plate 12 and the light deflection layer 16 are arranged along a predetermined direction so that planar light emitted from the light guide plate 12 enters the light deflection layer 16. The light deflection layer 16 and the light diffusion layer 9 are arranged along a predetermined direction so that planar light emitted from the light deflection layer 16 enters the light diffusion layer 9. For convenience of explanation, the “predetermined direction” is referred to as a Z-axis direction (first direction), and two directions orthogonal to the Z-axis direction are defined as an X-axis direction (second direction) and a Y-axis direction (third direction). Direction). The X-axis direction and the Y-axis direction are orthogonal to each other.

  The light guide plate 12 is made of a translucent material. Examples of the translucent material include methacrylic resin, polycarbonate resin, polyester resin, and cyclic polyolefin resin. In order to adjust the in-plane distribution of the amount of light emitted from the light exit surface 12a, dot printing, linear V-grooves, or the like may be formed on the surface of the light guide plate 12.

  The light source 13 is disposed on the end faces 12b and 12c of the light guide plate. The light source 13 may be a linear light source or a point light source. For example, a cold cathode tube or a light emitting diode (LED) can be used as the light source 13. When the LED is used as the light source 13, for example, it may be one white light emitting LED including three LED chips that emit red, blue, and green colors, or each of red, blue, and green. The LED which connected and integrated three LED which light-emits a color may be sufficient. Further, the LED may be an LED that emits white light by a combination of a blue light emitting LED chip or a near ultraviolet light emitting LED chip and a phosphor.

  The light deflection layer 16 is disposed on the light emitting surface 15 a side of the light guide plate 12. An example of the light deflection layer 16 is a prism sheet. The light deflection layer 16 serving as a prism sheet extends in a direction (Y-axis direction shown in FIG. 1) parallel to the side where the light source is arranged on the rectangular light emitting surface of the backlight device 11 and also in the extending direction. And a large number of prism parts (first prism parts) 16a arranged in parallel in a direction (X-axis direction shown in FIG. 1). The large number of prism portions 16a are light deflected on a surface (perpendicular to the extending direction (Y-axis direction) of the prism portion 16a) of the rectangular light emitting surface of the backlight device 11 that is perpendicular to the side where the light source is disposed. The cross section when the layer 16 is cut has a shape in which a plurality of triangles are connected. In other words, the cross-sectional shape of the prism portion 16a in the extending direction of the prism portion 16a is a triangle, and the plurality of prism portions 16a are continuous so that the bottoms of the cross-section are aligned on a straight line. The light deflection layer 16 as a prism sheet is disposed with the apex 16b not on the base of the triangle facing the light guide plate 12 in the cross section of the prism portion 16a orthogonal to the extending direction of the prism portion 16a.

  In the light deflection layer 16 as a prism sheet, a plurality of prism parts (second prism parts) may be formed on the surface 16c opposite to the light incident side on which the prism parts 16a are formed. The plurality of prism portions extend in a direction (X-axis direction shown in FIG. 1) perpendicular to the side where the light source 13 is arranged on the rectangular light emitting surface of the backlight device 11 and are orthogonal to the extending direction. It can arrange | position in parallel in the direction (Y-axis direction shown in FIG. 1) to do.

  In the backlight device 11, the surface light emitting unit 15 configured by the light guide plate 12, the light source 13, and the reflection plate 14 is a direction (X-axis direction) from the light source 13 toward the light guide plate 12 in a plane orthogonal to the Z-axis direction. For all four predetermined azimuth angles Ψ with respect to, when the light emitted from the light emitting surface 12a of the light guide plate 12 is measured, the luminance of the light emitted from the light guide plate 12 satisfies the predetermined condition Has been.

  In an example of the luminance measurement method, the surface light emitting unit 15 is arranged so that the X-axis direction matches the vertical direction. For example, the surface light emitting unit 15 is arranged such that the direction from the end surface 12b toward the end surface 12c (in other words, the direction from the light source 13 on the end surface 12b side toward the light guide plate 12) is upward in the vertical direction. In this case, the four predetermined azimuth angles Ψ are the first azimuth angles that are 0 ° with respect to the upward direction when the upward direction in the vertical direction (X-axis direction) is 0 °. Ψ1, a second azimuth angle ψ2 that is 45 ° with the upward direction, a third azimuth angle ψ3 that is 90 ° with the upward direction, and an angle that is 135 ° with the upward direction. The azimuth angle of 4 is 4. When the X-axis direction is the vertical direction, the Z-axis direction is substantially the horizontal direction.

  In the measurement of the light emitted from the light guide plate 12, the light emitted from the light guide plate 12 with respect to all the first to fourth azimuth angles Ψ1 to ψ4 is a certain distance from the measurement target point in the light emission surface 12a. The luminance is measured in a range of viewing angles of −40 ° to + 40 ° with respect to the normal direction (Z-axis direction) of the light emitting surface 12a, and is −60 ° to −74 ° and + 60 ° to + 74 °. It is also measured in the range of viewing angles. The predetermined condition in the light guide plate 12 is the maximum value among the luminances in the range of viewing angles of −60 ° to −74 ° and + 60 ° to + 74 ° in all the first to fourth azimuth angles Ψ1 to Ψ4. Thus, all the luminances in the viewing angle range of −40 ° to + 40 ° in all the first to fourth azimuth angles ψ1 to ψ4 are 40% or less. Preferably, with respect to the maximum value among the luminances in the range of viewing angles of −60 ° to −74 ° and + 60 ° to + 74 ° in all of the first to fourth azimuth angles Ψ1 to Ψ4, the first to fourth All the luminances in the viewing angle range of −40 ° to + 40 ° in all the azimuth angles ψ1 to ψ4 are 15% or less.

FIG. 3 is an example of the angular distribution of the luminance of the emitted light from the light guide plate 12 that satisfies the predetermined condition. FIG. 3 shows the result of measuring the light emitted from the light guide plate 12 at the first to fourth azimuth angles ψ1 to ψ4. The horizontal axis in FIG. 3 is an angle (°) representing a viewing angle with respect to the normal direction (Z-axis direction) of the light emitting surface 12a, and the vertical axis is luminance (cd / m ² ). Of the curves indicating the measurement results of luminance, the solid line has an azimuth angle of 0 ° (the solid line partially overlaps the thick solid line and the dotted line on the left side of the graph of FIG. 3 when the azimuth is 45 ° and 90 °, respectively. The thick solid line has an azimuth angle of 45 ° (the thick solid line partially overlaps the solid line and the dotted line on the left side of the graph of FIG. 3 when the azimuth angle is 0 ° and 90 °, respectively). The dotted line has an azimuth angle of 90 ° (the dotted line partially overlaps the broken line indicating the case where the azimuth angle is 135 ° on the right side of the graph of FIG. 3, and the azimuth angle is 0 ° and 45 ° on the left side of the graph of FIG. (A part of the solid line and the thick solid line respectively indicate the case of °). The broken line is 135 ° in the azimuth angle (the broken line is on the right side of the graph of FIG. The measurement result in the part overlap.) Is shown. The rectangle drawn with the dashed-two dotted line described in the right-and-left end of FIG. 3 shows the range of the viewing angle of -60 degree--74 degree and +60 degree- + 74 degree. A rectangle drawn by a one-dot chain line near the lower center of FIG. 3 indicates a range of viewing angles from −40 ° to + 40 °.

In the luminance measurement results shown in FIG. 3, the maximum value of the luminance in the viewing angle range of −74 ° to −60 ° and + 60 ° to + 74 ° appears at the azimuth angle 0 ° (first azimuth angle ψ1). The maximum value is 1.4 × 10 ⁴ in the unit of the vertical axis in FIG. All the luminances in the viewing angle range of −40 ° to + 40 ° in all of the first to fourth azimuth angles Ψ1 to Ψ4 are 1.5 × 10 ³ or less in the unit of the vertical axis in FIG. Therefore, all the luminances in the viewing angle range of −40 ° to + 40 ° in all of the first to fourth azimuth angles Ψ1 to Ψ4 are 40% of the maximum value of 1.4 × 10 ⁴ (5.6 ×). 10 ³ ) or less, and 15% (2.1 × 10 ³ ) or less.

  A preferred embodiment of the light guide plate 12 is a light guide plate having a trapezoidal cross section. In the light guide plate 12 having a trapezoidal cross section, the end faces 12b and 12c are end faces corresponding to the upper base (shorter side) and the lower base (longer side) of the trapezoid, respectively. Accordingly, the thickness decreases from the end surface 12b toward the end surface 12c. In one embodiment, the light emission surface 12a and each of the end surfaces 12b and 12c are substantially orthogonal. The light guide plate 12 whose cross section is a trapezoidal plate, for example, adjusts the angle of intersection with the Z-axis direction of the surface on the opposite side of the light output surface 12a of the light guide plate 12 (surface on the reflecting plate 14 side), and / or Alternatively, as described above, it can be designed to satisfy the above conditions by forming printing dots, V-grooves, etc. on the surface of the light guide plate 12.

  Further, the light guide plate 12 of the preferred embodiment has a shape in which two plates 121, 121 having a trapezoidal cross section are in contact with each other so as to share the upper base (shorter bottom) of the trapezoid (FIG. 1). . In the light guide plate 12 having the shape in which the two plates 121 and 121 are integrated as described above, the light emission surface 12a is a plane corresponding to one side of the trapezoidal cross section of each of the plates 121 and 121. Composed. The end surfaces 12 b and 12 c of the light guide plate 12 are surfaces corresponding to the lower bases in the cross sections of the plates 121 and 121. Therefore, in the light guide plate 12 having the configuration in which the plates 121 and 121 are coupled, the thickness decreases from the end surfaces 12b and 12c toward the center as illustrated in FIG. Each of the two plates 121 and 121 is disposed such that the light emitting surface 12a of the light guide plate 12 and the z-axis direction are substantially orthogonal to each other. In the light guide plate 12 in which the plates 121 and 121 are combined, for example, the Z-axis direction of the surface (surface on the reflecting plate 14 side) on the opposite side to the light emitting surface 12a of each of the two plates 121 and 121 constituting the light guide plate 12 Can be designed to satisfy the above conditions by adjusting the angle of crossing with and / or forming printed dots, V-grooves, etc. on the surface of the light guide plate 12.

  Examples of the material of the light deflection layer 16 include polycarbonate resin, ABS resin, methacrylic resin, methyl methacrylate-styrene copolymer resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyolefin resin such as polyethylene and polypropylene. included. The prism film can be manufactured by a known method such as a profile extrusion method, a press molding method, an injection molding method, a roll transfer method, a laser ablation method, a mechanical cutting method, a mechanical polishing method, and a photopolymer process.

  When manufactured by a photopolymer process, what is called an ionizing radiation curable resin can be used as a material. Examples of ionizing radiation curable resins include those synthesized from polyfunctional acrylates such as acrylic acid or methacrylic acid esters of polyhydric alcohols, diisocyanates and polyhydric alcohols, and hydroxy esters of acrylic acid or methacrylic acid. Polyfunctional urethane acrylate and the like are included. These methods may be used alone, or two or more methods may be combined. The thickness of the light deflection layer 16 is usually 0.05 to 5 mm, preferably 0.1 to 2 mm. The distance L between the ridgelines of each prism part (first prism part) 16a is usually in the range of 10 to 500 μm, preferably in the range of 30 to 200 μm.

  The reflection plate 14 is installed on the lower surface 12d side of the light guide plate 12 (the side opposite to the emission surface). The reflecting plate 14 returns the light (leaked light) emitted from the lower surface of the light guide plate 12 to the light guide plate 12 side. As the reflecting plate 14, a white sheet or a mirror type sheet is used. The white sheet is a sheet that diffuses light by adding a filler to a resin film such as polyester or by providing a gap between the added filler and a base resin. The mirror type sheet is a sheet in which a specular reflection component is strengthened by depositing a metal such as aluminum or silver on the surface of a resin film such as polyester. The mirror type is preferable in that high front luminance can be obtained. Examples of the mirror-type sheet include a sheet having a smooth metal vapor-deposited surface in which reflected light does not have a diffuse reflection component and is only a regular reflection component and has no fine unevenness. An example of a mirror-type reflector is a sheet having a mirror-finished surface.

  The light diffusion layer 9 is a light diffusion layer having a haze value of 86% or less. In a liquid crystal display device using a backlight device including the light diffusion layer 9, even if the haze value of the light diffusion layer 9 is greater than 86%, the color shift does not decrease. Considering the effect of suppressing the color shift, the haze value of the light diffusion layer 9 is preferably 10% or more and 86% or less, more preferably 20% or more and 86% or less, and further preferably 30% or more and 86% or less.

  The light diffusion layer 9 is obtained, for example, by applying a coating material in which a diffusing agent is dispersed in a binder resin to a resin film serving as a base material. Examples of the material used as the base material of the light diffusion layer 9 include polycarbonate, methacrylic resin, methyl methacrylate-styrene copolymer resin, acrylonitrile-styrene copolymer resin, methacrylic acid-styrene copolymer resin, polystyrene, poly Examples thereof include polyolefins such as vinyl chloride, polypropylene, and polymethylpentene, cyclic polyolefins, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyamide resins, polyarylate, and polyimide.

  The binder resin may be any resin having a high light transmittance, and for example, an acrylic resin, a polyurethane resin, or an ionizing radiation curable resin is used. Examples of the diffusing agent mixed and dispersed in the binder resin include fine particles made of a substance having a refractive index different from that of the material serving as the binder resin. Specific examples of the diffusing agent include organic fine particles and inorganic fine particles of a type different from the binder resin material. Examples of the organic fine particles include acrylic resin, melamine resin, polyethylene, polystyrene, organic silicone resin, acrylic-styrene copolymer, and the like. Examples of the inorganic fine particles include calcium carbonate, silica, aluminum oxide, barium carbonate, barium sulfate, titanium oxide, and glass. One or more of the above diffusing agents are mixed and used. Organic polymer balloons and glass hollow beads can also be used as diffusing agents. The average particle diameter of the diffusing agent is preferably in the range of 0.5 μm to 30 μm. The shape of the diffusing agent may be not only spherical but also flat, plate-like and needle-like.

  The light diffusing layer 9 is blended with each constituent component and other components as necessary, and a coating solution prepared by dissolving or dispersing the component in an appropriate solvent is applied to a substrate and dried. It can be formed by curing using a necessary curing method as appropriate. The coating solution is applied to the substrate by a known method such as a roll coating method, a bar coating method, a spray coating method, or an air knife coating method. Alternatively, the diffusing agent may be directly dispersed in the base resin by melt kneading. The thickness of the light diffusion layer 9 may be any thickness that does not hinder the handling of the light diffusion layer 9 and is not particularly limited. The thickness of the light diffusion layer 9 is, for example, about 10 to 250 μm, preferably 12 to 100 μm.

  The haze value can be reduced to 86% or less by adjusting the kind of particles used as the diffusing agent, the amount added, the surface shape, and the like. The haze value can be measured using a haze computer (HZ-2 manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS-K-7136. As the light diffusion layer 9, commercially available ones such as “Opulse PBS-632L” (manufactured by Eiwa Co., Ltd.) and “LSE type” (manufactured by Kimoto Co., Ltd.) can be used.

  By combining a liquid crystal cell normally used in industrial production with the backlight device 11 including the light guide plate 12 and the light diffusion layer 9 that meet the above conditions when measuring the light emitted from the light guide plate 12, A liquid crystal display device 1 having a small color shift is provided.

  FIG. 2 is a diagram schematically illustrating a liquid crystal display device including a backlight device according to an embodiment of the present invention. The liquid crystal display device 1 includes a liquid crystal cell device 20 and a backlight device 11. The liquid crystal cell device 20 is disposed on the light incident side of the liquid crystal cell 21 with the liquid crystal layer 23 provided between the pair of transparent substrates 22a and 22b (the backlight device 11 and the liquid crystal cell 21 A first polarizing plate 41 and a second polarizing plate 52 disposed on the light emitting side of the liquid crystal cell 21. In the liquid crystal display device 1, the first polarizing plate 41, the liquid crystal cell 21, and the second polarizing plate 52 are arranged in order from the backlight device 11 side.

  A liquid crystal cell 21 used in a liquid crystal display device manufactured using a backlight device 11 according to an embodiment of the present invention includes a pair of transparent substrates 22a and 22b arranged to face each other at a predetermined distance, and the pair of transparent substrates 22a and 22b. And a liquid crystal layer 23 in which liquid crystal is sealed between the transparent substrates 22a and 22b. A transparent electrode and an alignment film are laminated on the pair of transparent substrates 22a and 22b, respectively, and a liquid crystal is aligned by applying a voltage based on display data between the transparent electrodes. As a display method of the liquid crystal cell 21, a display method such as a TN method, an IPS method, and a VA method can be adopted.

  As the 1st polarizing plate 41, what stuck the support film on both surfaces of the polarizer is used normally. Examples of polarizers include a dichroic dye or iodine adsorbed and oriented on a polarizer substrate such as a polyvinyl alcohol resin, a polyvinyl acetate resin, an ethylene / vinyl acetate (EVA) resin, a polyamide resin, or a polyester resin. And a polyvinyl alcohol / polyvinylene copolymer in which a molecular chain oriented of a dichroic dehydrated product of polyvinyl alcohol (polyvinylene) is contained in a molecularly oriented polyvinyl alcohol film. A polarizer having a dichroic dye or iodine adsorbed and oriented on a polarizer substrate of polyvinyl alcohol resin is preferably used as the polarizer. In general, the thickness of the polarizer is preferably 100 μm or less, more preferably in the range of 10 to 50 μm, and still more preferably in the range of 25 to 35 μm for the purpose of reducing the thickness of the polarizing plate.

  The support film for supporting and protecting the polarizer is preferably a film made of a polymer having low birefringence and excellent in transparency, mechanical strength, thermal stability, moisture shielding properties, and the like.

  Examples of such films include cellulose acetate resins such as TAC (triacetyl cellulose), acrylic resins, fluorine resins such as tetrafluoroethylene / hexafluoropropylene copolymers, polycarbonate resins, polyethylene Polyester resin such as terephthalate, polyimide resin, polysulfone resin, polyethersulfone resin, polystyrene resin, polyvinyl alcohol resin, polyvinyl chloride resin, polyolefin resin or polyamide resin, etc. are formed into a film. Includes processed products.

  Among these, a triacetyl cellulose film or a norbornene-based thermoplastic resin film whose surface is saponified with an alkali or the like can be preferably used from the viewpoints of polarization characteristics and durability. Since the norbornene-based thermoplastic resin film is a good barrier from heat and wet heat, the durability of the polarizing plate 41 is greatly improved, and the dimensional stability is greatly improved because of its low moisture absorption rate. Therefore, the norbornene-based thermoplastic resin film can be used particularly preferably.

  For forming into a film, a conventionally known method such as a casting method, a calendar method, or an extrusion method can be used. There is no limitation on the thickness of the support film. However, from the viewpoint of reducing the thickness of the polarizing plate 41, the thickness of the support film is preferably 500 μm or less, more preferably in the range of 5 to 300 μm, and still more preferably in the range of 5 to 150 μm.

  The second polarizing plate 52 is paired with the first polarizing plate 41 disposed on the back side of the liquid crystal cell 21. As the 2nd polarizing plate 52, what was illustrated by the 1st polarizing plate 41 may be used suitably here. However, the second polarizing plate 52 is disposed so that the polarization plane thereof is orthogonal to the polarization plane of the first polarizing plate 41.

  Applying a resin solution in which minute fillers are dispersed on the second polarizing plate 52, adjusting the coating film thickness so that the filler appears on the surface of the coating film, and forming fine irregularities on the surface of the substrate. Accordingly, the antiglare layer 53 may be provided on the second polarizing plate 52 (on the light emitting side of the second polarizing plate).

  The surface of the antiglare layer 53 usually has fine irregularities, but there may be no fine irregularities. Without using a fine filler, fine irregularities may be formed on the surface of the base film as the antiglare layer 53. In order to form fine irregularities on the surface of the substrate film, use a method of surface-treating the substrate film by sandblasting and embossing shaping, etc., or a mold or embossing roll having a mold surface with the irregularities reversed. A method of forming fine irregularities in the production process of the base film may be used.

  The antiglare layer 53 may have a light diffusing function only by internal diffusion (internal haze) or a light diffusing function by both internal diffusion (internal haze) and surface diffusion (external haze and unevenness). Alternatively, it may have a light diffusion function only by surface diffusion (external haze and unevenness).

  The liquid crystal display device manufactured with the backlight device 11 according to an embodiment of the present invention may have an optical functional film having other functions.

  Examples of such an optical functional film include a reflective polarizing film that transmits a certain kind of polarized light and reflects polarized light that shows the opposite property, a film with a diffusing function having a random uneven shape on the surface, And a film with a deflection function having a concavo-convex shape such as a prism portion or a lenticular lens on the surface. An example of a commercial product corresponding to a reflective polarizing film that transmits certain types of polarized light and reflects polarized light exhibiting the opposite properties is “DBEF” (available from 3M, Sumitomo 3M Limited in Japan) Can be included). Examples of commercially available products corresponding to a film with a diffusion function include “Opulse” (manufactured by Eiwa Co., Ltd.). Examples of commercially available products corresponding to a film with a deflection function include “BEF” (manufactured by 3M, available from Sumitomo 3M Limited in Japan).

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.

Example 1
The light guide plate built in the 16.4 type notebook PC VGN-FW73JGB made by SONY is used for the backlight unit used in the 32 inch type liquid crystal television KDL-32EX700 made by SONY and used in the 32 type liquid crystal television KDL-32EX700. The backlight device 11 of the present example was configured by replacing the light guide plate originally incorporated in the backlight device. The cross-sectional shape of the light guide plate incorporated in the 16.4 type notebook PC VGN-FW73JGB was trapezoidal.

  A method for manufacturing the backlight device 11 of this embodiment will be specifically described. The light guide plate 12 used in the backlight device 11 of Example 1 was produced as follows. That is, when the light guide plate incorporated in the 16.4 type notebook PC VGN-FW73JGB manufactured by SONY is referred to as the light guide plate 121, the two light guide plates 121 and 121 correspond to the upper side of the trapezoid in the cross-sectional shape. A so-called butterfly-shaped light guide plate 12 was produced by solvent-bonding the end faces of the light guide plates 121 and 121. The butterfly-shaped light guide plate 12 was replaced with the light guide plate originally incorporated in the backlight device used in the 32-inch liquid crystal television KDL-32EX700 manufactured by SONY, and the backlight device 11 of this embodiment was produced. . The reflection plate incorporated in the backlight device used in the 32-inch liquid crystal television KDL-32EX700 manufactured by SONY was a white diffusion type (white sheet) reflection sheet.

  A luminance measurement method will be described. FIG. 4 is a diagram showing a luminance measurement method in the present embodiment. In the luminance measurement, the luminance with the light deflection layer 16 and the light diffusion layer 9 removed was measured in order to measure the luminance of light from the surface light emitting unit 15. Therefore, in the luminance measurement, the light emitting surface of the backlight device 11 is the light emitting surface 15 a of the surface light emitting unit 15. The light emitting surface 15 a of the surface light emitting unit 15 corresponds to the light emitting surface 12 a of the light guide plate 12.

  As shown in FIG. 4, the backlight device 11 before incorporating the light deflection layer 16 and the light diffusion layer 9 (the backlight device 11 corresponding to the configuration in which the light deflection layer 16 and the light diffusion layer 9 are removed from the state of FIG. 1). The backlight device 11 (backlight module) was installed upright so that the light emitting surface of () was vertical. FIG. 4 shows a state before the light deflection layer 16 and the light diffusion layer 9 are incorporated in the backlight device 11. In other words, a state in which a unit in which the light source 13 is arranged with respect to the light guide plate 12 is incorporated in the housing is shown. An angle formed with the normal of the light emitting surface (angle formed with the z-axis direction) is θ, a luminance meter 70 is installed in a direction of a predetermined angle θ, and 1 cm from the center of the light emitting surface (position indicated by x in FIG. 4). The brightness of the upper part (measurement target point) was measured. The reason for removing the measurement point 1 cm above the center of the light emitting surface is to prevent an abnormal value that may occur when measuring at the center of the light emitting surface. At this time, the distance between the measurement point and the luminance meter 70 was set to 40 cm, and the luminance was measured in increments of 2 degrees with the measurement angle θ ranging from −74 ° to 74 °. In addition, TOP-7 company make BM-7 was used as the luminance meter 70, and the measurement angle of the luminance meter 70 was set to 1 degree.

  The azimuth angle Ψ was measured in four directions of 0 °, 45 °, 90 °, and 135 °, with the upper direction in FIG. 4 being 0 °.

FIG. 5 shows the angular distribution from the backlight device 11 measured as described above. The horizontal axis in FIG. 5 is the viewing angle with respect to the direction of the normal to the light emitting surface (z-axis direction), that is, the angle (°) representing the measurement angle θ, and the vertical axis is the luminance (cd / m ² ). Of the curves indicating the measurement results of luminance, the solid line represents an azimuth angle Ψ of 0 °, the thick solid line represents an azimuth angle Ψ of 45 ° (the thick solid line represents the case where the azimuth angle Ψ is 90 ° on the left side of the graph in FIG. 5). The dotted line partially overlaps with a broken line indicating that the azimuth angle Ψ is 135 ° on the right side of the graph of FIG. On the left side of the graph, the azimuth angle ψ is 135 ° (partially overlapped with a thick solid line indicating the case where the azimuth angle ψ is 45 °). The measurement result in partly overlapping with the dotted line indicating the case of 90 ° is shown. The maximum luminance value when the angle θ is −40 ° to 40 ° and the maximum luminance value when the angle θ is −74 ° to −60 ° and 60 ° to 74 ° are as follows.
Maximum luminance of −40 ° to 40 °; Max1 = 1479 cd / m ² (40 °)
Maximum luminance value at −74 ° to −60 ° and 60 ° to 74 °; Max2 = 13707 cd / m ² (−74 °)
as a result,
Max1 / Max2 = 11% <40%
Met.

  A chromaticity coordinate measurement method will be described. FIG. 2 is also a diagram showing the configuration of the liquid crystal display device of this embodiment. In this embodiment, the above-mentioned butterfly-type light guide plate is replaced with the light guide plate originally incorporated in the 32-inch liquid crystal television KDL-32EX700 in the backlight device used in the 32-inch liquid crystal television KDL-32EX700 manufactured by SONY. The surface light emitting part 15 was configured. The light deflecting layer 16, the light diffusing layer 9, and the liquid crystal cell device 20 of the liquid crystal television are arranged in this order from the surface light emitting unit 15 side on the light emitting surface 15a side of the surface light emitting unit 15. The liquid crystal display device 1 of the example was configured.

  The light deflection layer 16 of the backlight device 11 of Example 1 was a prism sheet. The cross-sectional shape of a large number of prism portions (first prism portions) 16a included in the light deflection layer 16 as a prism sheet was an isosceles triangle having an apex angle of 65 °. The distance L between the ridge lines of the adjacent prism portions 16a was 50 μm. The light diffusion layer 9 of the backlight device 11 of Example 1 was a diffusion sheet. The haze value of the light diffusion layer 9 as the diffusion sheet was 30.0%.

  As shown in FIG. 1, the light deflection layer 16 has the side on which the prism portion 16 a is formed facing the light source 13, and the ridge line of the prism portion 16 a is parallel to the end faces 12 b and 12 c on which the light source 13 is disposed. It was installed to become. In other words, the prism portion 16a extends in the Y-axis direction.

  In this liquid crystal display device, chromaticity coordinates u ′ and v ′ were measured. The measuring method of the chromaticity coordinates u 'and v' is the same as the measuring method of the brightness except for the following points. That is, in the measurement of luminance, as shown in FIG. 4, the backlight device 11 before incorporating the light deflection layer 16 and the light diffusion layer 9 (a configuration in which the light deflection layer 16 and the light diffusion layer 9 are removed from the state of FIG. 1). The backlight device 11 (backlight module) is installed upright so that the light emitting surface of the backlight device 11) corresponding to the above is vertical, whereas the measurement of the chromaticity coordinates u ′ and v ′ is shown in FIG. As shown, the liquid crystal display device 1 was placed upright so that the light emitting surface 1a of the liquid crystal display device 1 incorporating the light deflection layer 16 and the light diffusion layer 9 (the exit surface of the antiglare layer 53) was vertical. An angle formed with the normal of the light emitting surface (angle formed with the Z-axis direction) is θ, a color luminance meter 80 is installed in a direction of a predetermined angle θ, and a portion (measurement target point) 1 cm above the center of the light emitting surface. CIE1976 UCS chromaticity coordinates u ′ and v ′ in the black display state were measured. The reason why the measurement point is set 1 cm above the center of the light emitting surface is to prevent an abnormal value that may occur when measurement is performed at the center of the light emitting surface. At this time, the distance between the measurement point and the color luminance meter 80 was set to 40 cm, the measurement angle θ was in the range of −74 ° to 74 °, and the chromaticity coordinates u ′ and v ′ were measured in increments of 2 °. As the color luminance meter 80, BM-5AS manufactured by TOPCON was used, and the measurement angle of the color luminance meter 80 was set to 1 °.

  Further, the azimuth angle Ψ was measured in four directions of 0 °, 45 °, 90 °, and 135 °, with the upper direction in FIG. 6 being 0 °.

その結果、黒表示状態におけるカラーシフト（ΔＥ）は、０．０７３８１であった。 The distance between the farthest point (u′1, v′1) and the point (u′2, v′2) of the CIE 1976 UCS chromaticity coordinates u ′, v ′ measured above is expressed as a color shift (ΔE). did. The color shift (ΔE) is expressed by the following equation (1), and the smaller the value, the smaller the color shift.

As a result, the color shift (ΔE) in the black display state was 0.07341.

(Example 2)
In the liquid crystal display device 1, the color shift (ΔE) was determined in the same manner as in Example 1 except that a diffusion sheet having a haze value of 50.0% was used.
As a result, the color shift (ΔE) was 0.07703.

(Example 3)
In the liquid crystal display device 1, the color shift (ΔE) was determined in the same manner as in Example 1 except that a diffusion sheet having a haze value of 86.0% was used.
As a result, the color shift (ΔE) was 0.07622.

(Comparative Example 1)
In the liquid crystal display device 1, the color shift (ΔE) was determined in the same manner as in Example 1 except that a diffusion sheet having a haze value of 89.5% was used.
As a result, the color shift (ΔE) was 0.09033.

(Comparative Example 2)
Luminance and color shift (ΔE) were determined in the same manner as in Example 1 except that a commercially available SONY-made 32-type liquid crystal television “KDL-32EX700” was used as the backlight device and the liquid crystal display device.
The maximum values of −40 ° to 40 °, the maximum values of −60 ° to −74 °, and 60 ° to 74 ° are as follows.
Maximum value of −40 ° to 40 °; Max1 = 1963 cd / m ² (40 °)
Maximum value of −60 ° to −74 °, 60 ° to 74 °; Max2 = 2868 cd / m ² (−72 °)
as a result,
Max1 / Max2 = 68%> 40%.
The color shift (ΔE) was 0.10019.

  The backlight device of the above embodiment and the above examples can be configured simply, and by using this backlight device, a liquid crystal display device having a small color shift and a small color shift depending on the viewing angle during black display. Can be manufactured. Therefore, the backlight device of this embodiment is extremely useful industrially. In addition, a liquid crystal display device using the backlight device of this embodiment is a display with high contrast and good visibility.

  As mentioned above, although one Embodiment and one Example of this invention were described, this invention is not limited to the said embodiment and Example, A various change is possible in the range which does not deviate from the meaning of invention. . For example, the surface light emitting unit may satisfy the predetermined condition described above at the four azimuth angles Ψ1 to Ψ4 as described above. The above conditions may be adjusted by the configuration of the light guide plate 12 or may be adjusted by the reflection state of the reflection plate 14. In the surface light emitting unit 15, at least one other optical sheet may be disposed on the light guide plate 12. In this case, the light emitting surface of the optical sheet closest to the light deflection layer 16 side among the other optical sheets on the light guide plate 12 is the light emitting surface of the backlight device at the time of luminance measurement described with reference to FIG. It is. Thus, when the surface light emission part 15 is provided with an optical sheet, the said predetermined conditions may be satisfy | filled using the optical characteristic in an optical sheet.

  DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device, 9 ... Light-diffusion layer, 11 ... Back light apparatus, 12 ... Light guide plate, 12a ... Light emission surface, 12b, 12c ... End surface, 12d ... Bottom surface, 13 ... Light source, 14 ... Reflection plate, 15 ... Surface light emitting part, 15a ... light emitting surface, 16 ... light deflection layer, 16a ... prism part (first prism part), 20 ... liquid crystal cell device, 21 ... liquid crystal cell, 22a, 22b ... transparent substrate, 23 ... liquid crystal layer, DESCRIPTION OF SYMBOLS 41 ... 1st polarizing plate, 52 ... 2nd polarizing plate, 53 ... Anti-glare layer, 70 ... Luminance meter, 80 ... Color luminance meter, 121 ... Light guide plate.

Claims (10)

A surface light emitting portion for emitting planar light from the light exit surface;
A light deflection layer provided on the light emitting side on the surface light emitting unit, and receiving light from the light emitting surface;
A light diffusion layer provided on the light exit side of the light deflection layer;
With
The surface light emitting unit is
A light guide plate;
A light source disposed on an end face of the light guide plate;
A reflector disposed on the opposite side of the light deflection layer with respect to the light guide plate;
Have
A first azimuth angle, a second azimuth angle, a third azimuth angle, and a fourth azimuth angle in a plane orthogonal to a first direction that is a direction from the surface light emitting portion toward the light deflection layer, The first to fourth azimuth angles that are 0 °, 45 °, 90 °, and 135 ° with respect to the second direction that is the direction from the light source toward the light guide plate are emitted from the light exit surface. The viewing angle of the light to be measured at a certain distance from the measurement target point on the light exit surface is −40 ° to + 40 °, −60 ° to −74 °, and + 60 ° to + 74 ° with respect to the first direction. When the measurement is performed in the range, the first to fourth azimuth angles with respect to the maximum value among the luminances in the range of viewing angles of −60 ° to −74 ° and + 60 ° to + 74 °. In the range of -40 ° to + 40 ° viewing angle in all fourth azimuth angles. All luminance is 40% or less,
The haze value of the light diffusion layer is 86% or less,
Backlight device. For all of the first to fourth azimuth angles, with respect to the maximum value in the luminance range of −60 ° to −74 ° and + 60 ° to + 74 ° in all the first to fourth azimuth angles. All the luminances in the viewing angle range of −40 ° to + 40 ° are 15% or less,
The backlight device according to claim 1. The light guide plate is a trapezoidal cross section;
The backlight device according to claim 1 or 2. The light guide plate is a light guide plate having a shape in which two plates having a trapezoidal cross section are in contact with each other so as to share the upper base of the trapezoid.
The backlight device according to claim 1 or 2. The reflector is a mirror type;
The backlight apparatus as described in any one of Claims 1-4. The light deflection layer is a prism sheet in which a plurality of first prism portions are provided on an incident surface side on which light from the light exit surface is incident,
Each of the plurality of first prism portions extends in a third direction which is a direction orthogonal to the first and second directions, and is arranged in parallel with the second direction.
The backlight apparatus as described in any one of Claims 1-5. The shape of the cross section perpendicular to the third direction of each of the plurality of first prism portions is a triangle,
The apex of the triangle that is the shape of the cross section of each of the plurality of first prism portions is located on the surface light emitting portion side,
The base of the triangle that is the shape of the cross section of each of the plurality of first prism portions is connected in a straight line.
The backlight device according to claim 6. The light deflection layer is provided with a plurality of second prism portions on the side opposite to the incident surface side,
Each of the plurality of second prism portions extends in the second direction and is arranged in parallel in the third direction.
The backlight device according to claim 6 or 7. The backlight device according to any one of claims 1 to 8,
A liquid crystal cell device provided on the light emitting surface side of the backlight device;
With
The liquid crystal cell device comprises:
A first polarizing plate, a liquid crystal cell in which a liquid crystal layer is provided between a pair of substrates, and a second polarizing plate,
From the light output side of the backlight device, the first polarizing plate, the liquid crystal cell, and the second polarizing plate are arranged in this order,
The liquid crystal display device, wherein the first polarizing plate and the second polarizing plate are arranged so that their transmission axes are substantially perpendicular to each other. The liquid crystal cell device further has an antiglare layer,
From the light output side of the backlight device, the first polarizing plate, the liquid crystal cell, the second polarizing plate, and the antiglare layer are arranged in this order.
The liquid crystal display device according to claim 9.

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