JP2009229760A - Optical component, back light unit, and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology advantageous for achieving a thin display device allowing bright display on a screen while hardly producing a lamp image. <P>SOLUTION: An optical component 52 has a first main surface into which the light radiated by a light source 41 is made to come, and a second main surface for emitting diffused light when the light is made to come into the first main surface. The optical component 52 is provided with: a diffusion layer 26 including a transparent material and a plurality of regions that are distributed in the transparent material and have a refractive index different from that of the transparent material; an optical function layer 1 having, on the second main surface, a relief structure where one main surface constitutes the second main surface and that constitutes a plurality of optical elements each formed of a lens or a prism; and diffusion transmission layers 23 and 28 having, on the first main surface, a relief structure where one main surface constitutes the first main surface and the other main surface faces the optical function layer 1 on both sides of the diffusion layer 26 and that constitutes a plurality of optical elements each formed of a lens or a prism, where the surface area of the first main surface is smaller than that of the second main surface. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to display technology.

  Patent Document 1 describes an optical component used in a backlight unit of a liquid crystal display device. This optical component includes an optical functional layer having a plurality of convex portions each constituting a lens provided on the front surface, a diffusion layer facing the back surface, and a reflective layer interposed therebetween. . The reflection layer is provided with an opening at a position corresponding to the central portion of the lens.

  When the diffusion layer of this optical component is illuminated, the diffusion layer emits scattered light. Of this scattered light, light traveling toward the center of the lens is incident on the optical functional layer, and light traveling toward the peripheral edge of the lens is reflected by the reflective layer. The scattered light reflected by the reflective layer changes its traveling direction by being further scattered by the diffusion layer, and finally enters the optical functional layer. Scattered light that has entered the optical functional layer is emitted from the optical functional layer with a spreading angle controlled by a lens.

  As is clear from this, the reflective layer suppresses the incidence of scattered light on the periphery of the lens. Therefore, this optical component emits less light to the wide-angle side due to reflection at the interface between the peripheral edge of the lens and the air layer. Further, as described above, the light reflected by the reflective layer finally enters the central portion of the lens. Therefore, when this optical component is used, desired directivity and high light utilization efficiency can be achieved.

  By the way, many large liquid crystal display devices use a direct type backlight unit including a plurality of cold cathode tubes or LEDs (light-emitting diodes) as a light source. When a direct type backlight unit is used, a bright display is possible over the entire screen.

  When the direct type backlight unit is used, luminance unevenness corresponding to the arrangement of the light sources is likely to occur. That is, when a direct type backlight unit is used, a lamp image tends to appear on the screen. For this reason, the direct type backlight unit uses a diffusion layer having a higher diffusion capacity than that used in the edge type backlight unit.

  The diffusion layer is usually composed of a transparent material and a plurality of transparent particles distributed therein. Such a diffusion layer achieves a sufficient diffusion capacity for use in a direct type backlight unit, for example, by increasing the thickness.

  However, if this diffusion layer is thickened, the total light transmittance decreases. That is, it is difficult to perform bright display without generating a lamp image on the screen.

In addition, liquid crystal display devices tend to be thinner. Therefore, the backlight unit is required to reduce the thickness of the optical components used for the backlight unit and to shorten the distance between the components.
JP 2007-213035 A

  An object of the present invention is to provide a technique advantageous for realizing a thin display device capable of bright display with almost no lamp image on the screen.

  According to the first aspect of the present invention, the first main surface is used for diffusing the light emitted from the light source, and the diffused light is incident when the light is incident on the first main surface. An optical component having a second main surface to be emitted, the transparent layer, and a diffusion layer including a plurality of regions distributed in the transparent material and having a refractive index different from that of the transparent material, A relief structure is provided on the second principal surface, the principal surface constituting the second principal surface, the other principal surface facing the diffuse transmission layer, and constituting a plurality of optical elements each consisting of a lens or a prism. A plurality of optical functional layers, wherein one main surface constitutes the first main surface, the other main surface faces the optical functional layer with the diffusion layer interposed therebetween, and each includes a lens or a prism. A relief structure constituting an optical element is provided on the first main surface, First major surface optical component, characterized in that the surface area as compared to the second major surface is provided with a smaller diffuse transmission layer.

  According to a second aspect of the present invention, there is provided a backlight unit comprising the optical component according to the first aspect and a light source for illuminating the optical component from the diffuse transmission layer side.

  According to a third aspect of the present invention, there is provided a display device comprising the backlight unit according to the second aspect and a display panel facing the light source with the optical component interposed therebetween.

  According to the present invention, there is provided a technique advantageous for realizing a thin display device capable of bright display with almost no lamp image on the screen.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same referential mark is attached | subjected to the component which exhibits the same or similar function through all the drawings, and the overlapping description is abbreviate | omitted.

FIG. 1 is a cross-sectional view schematically showing a display device according to the first aspect of the present invention.
A display device 70 shown in FIG. 1 is a transmissive liquid crystal display device. The display device 70 includes a display panel 35 and a backlight unit 55. The display device 70 may further include other components such as a diffusion film, a prism sheet, and a polarization separation / reflection sheet.

  The display panel 35 includes a liquid crystal panel 32 and polarizing plates (polarizing films) 31 and 33. The liquid crystal panel 32 includes, for example, a pair of glass substrates and a liquid crystal layer sandwiched between them. The polarizing plates 31 and 33 are attached to the front surface and the back surface of the liquid crystal panel 32, respectively.

  The “front surface” is the surface on the observer side, and the “back surface” is the back surface. Further, “front” is a direction from the back side to the front side, and “rear” is a direction from the front side to the back side.

  The display panel 35 includes a plurality of pixels. The transmittance of each pixel changes according to the video signal written to it. For example, the display panel 35 displays an arbitrary image by controlling the transmittance of the pixels in a state where the back surface thereof is uniformly illuminated with white light.

  The display panel 35 is a transmissive display panel in this embodiment, but may be a transflective display panel. That is, the display device 70 may be a transflective liquid crystal display device.

  Alternatively, instead of the display panel 35 including the liquid crystal panel 32, another display panel may be used. For example, a display panel that displays a still image with a light-transmitting colored pattern may be used.

  The backlight unit 55 is installed on the back side of the display panel 35. The backlight unit 55 includes a backlight body 45 and an optical component 52.

  The backlight main body 45 includes a plurality of light sources 41, a reflective layer 43, and a support (not shown). The light source 41 and the reflective layer 43 are supported by a support.

  As the light source 41, for example, a linear light source can be used. For example, a fluorescent lamp or a cold cathode fluorescent lamp (CCFL) can be used as the line light source. A point light source may be used as the light source 41. As the point light source, for example, an LED can be used.

  The reflective layer 43 faces the display panel 35 with the light source 41 interposed therebetween. Typically, the reflective layer 43 has a bowl shape. The reflective layer 43 is a light reflective film or sheet, for example, a white film or sheet. The reflective layer 43 may be a layer formed on a support such as a metal plate.

  In the backlight body 45, the light source 41 emits light in almost all directions. The reflection layer 43 reflects the light emitted backward from the light source 41 to the front F. When the reflective layer 43 has a bowl shape as shown in FIG. 1, the light emitted from the light source 41 to the side is reflected to the front F. Therefore, the backlight main body 45 advances almost all of the light emitted from the light source 41 to the front F.

  The optical component 52 is interposed between the light source 41 and the display panel 35. The optical component 52 includes the diffusion member 25, the mask layer 22, and the optical function layer 1. The diffusion member 25 and the optical function layer 1 are integrated with the mask layer 22 interposed therebetween.

The diffusion member 25 includes a diffusion transmission layer and a diffusion layer 26.
The diffuse transmission layer includes a light transmission layer 23 and a plurality of convex portions 28.

  The light transmission layer 23 faces the light source 41 with the convex portion 28 interposed therebetween. The light transmission layer 23 is a layer having light transparency.

  The light transmission layer 23 typically has a total light transmittance equal to or greater than the total light transmittance of the diffusion layer 26. The total light transmittance of the light transmission layer 23 is, for example, 80% or more. If the total light transmittance is sufficiently large, the luminance of light emitted from the light transmitting layer 23 to the front (observer side) F will not be insufficient. The total light transmittance is a measured value based on Japanese Industrial Standard JIS K7361-1.

  The light transmission layer 23 has a lower diffusivity than the diffusion layer 26. The haze value of the light transmission layer 23 is, for example, 95% or less. When the haze value is large, the light diffusion effect caused by the convex portion 28 is small. The haze value is a measured value based on Japanese Industrial Standard JIS K7136.

  As a material of the light transmission layer 23, for example, a transparent resin such as a thermoplastic resin can be used. As such resin, for example, polycarbonate resin, acrylic resin, fluorine acrylic resin, silicone acrylic resin, epoxy acrylate resin, polystyrene resin, cycloolefin polymer, methylstyrene resin, fluorene resin, polyethylene terephthalate or polypropylene are used. can do.

  The light transmission layer 23 may be non-stretched or may be stretched uniaxially or biaxially. The light transmission layer 23 may have a single layer structure or a multilayer structure.

  The light transmission layer 23 may further include light diffusion particles in addition to the resin. However, when the light transmissive layer 23 contains light diffusing particles, the light diffusing effect caused by the convex portions 28 is reduced. Therefore, typically, the light transmission layer 23 does not contain light diffusion particles.

  The convex portion 28 is supported by the light transmission layer 23. Specifically, the protrusions 28 are arranged on the back surface 23 a of the light transmission layer 23. Typically, the convex portions 28 are arranged at a constant pitch. The convex portion 28 forms a relief structure on the back surface of the diffuse transmission layer.

  Each of the convex portions 28 constitutes a lens or a prism as an optical element. The convex portions 28 may be arranged in one direction on the back surface 23a of the light transmission layer 23, or may be arranged in a plurality of directions. In the former case, each of the convex portions 28 is, for example, a lenticular, a cylindrical lens, or a triangular prism. In the latter case, each of the convex portions 28 is, for example, a lens or a pyramidal prism having an axis of symmetry perpendicular to the back surface 23a of the light transmission layer 23.

  These convex portions 28 form, for example, a lens array in which a plurality of lenses are arranged one-dimensionally or two-dimensionally. These convex portions 28 may form a prism array formed by arranging a plurality of prisms one-dimensionally or two-dimensionally.

  These convex portions 28 may have the same shape or different shapes. In the latter case, some of the convex portions 28 may be lenses, and the remaining convex portions 28 may be prisms. Alternatively, all the convex portions may be lenses, and the shape may be different between some of the convex portions and the remaining convex portions. Alternatively, all the convex portions may be prisms, and the shape may be different between some of the convex portions and the remaining convex portions. Here, as an example, it is assumed that the convex portions 28 are lenticulars having the same shape and are arranged one-dimensionally.

  The convex portion 28 is obtained, for example, by applying a radiation curable resin such as an ultraviolet curable resin on the back surface 23a of the light transmission layer 23 and irradiating the coating film with radiation such as ultraviolet rays while embossing. Alternatively, the convex portion 28 is formed by an injection molding method or a hot press molding method using a thermoplastic resin or a thermosetting resin such as polyethylene terephthalate, polycarbonate, polymethyl methacrylate, cycloolefin polymer, and acrylonitrile styrene copolymer. You can also. The material of the convex portion 28 may be the same as or different from the material of the light transmission layer 23.

  The diffusion layer 26 faces the light source 41 with the light transmission layer 23 and the convex portion 28 interposed therebetween. The back surface 26a of the diffusion layer 26 is joined to the front surface 23b of the light transmission layer 23 directly or via an adhesive layer or an adhesive layer (not shown).

  The diffusion layer 26 includes a transparent material and a plurality of regions distributed in the transparent material. These regions are distributed almost uniformly in the diffusion layer 26, for example.

  The transparent material is a transparent resin such as a thermoplastic resin and a thermosetting resin. As this transparent resin, for example, polycarbonate resin, acrylic resin, fluorine acrylic resin, silicone acrylic resin, epoxy acrylate resin, acrylonitrile-styrene copolymer, polystyrene resin, cycloolefin polymer, methylstyrene resin, fluorene resin, Polyethylene terephthalate or polypropylene can be used.

  The plurality of regions distributed in the transparent material have a refractive index different from that of the transparent material. These regions are, for example, light diffusing particles or holes.

  As the light diffusing particles, for example, transparent particles made of an inorganic material or a resin can be used. As the transparent particles made of an inorganic material, for example, particles made of an oxide such as silica and alumina can be used. Transparent particles made of resin include acrylic resin, styrene resin, acrylic styrene resin, or a cross-linked product thereof; melamine formaldehyde resin; polytetrafluoroethylene, perfluoroalkoxy resin, tetrafluoroethylene-hexafluoropropylene copolymer, polyfluorovinylidene Fluorine resin such as ethylene-tetrafluoroethylene copolymer; or particles made of silicone resin can be used. As the light diffusion particles, one of these may be used alone, or two or more of these may be mixed and used. Further, the shape of the light diffusing particles is arbitrary.

  The material of the transparent material and the light diffusion particle may be different from that of the light transmission layer 23. Alternatively, the transparent material or the light diffusing particles may be the same material as the light transmission layer 23.

  The pores can be obtained, for example, by forming a layer containing a thermoplastic resin and particles dispersed therein and stretching the layer uniaxially or biaxially while heating the layer appropriately. That is, by stretching this layer while heating appropriately, a gap is formed between the thermoplastic resin and the particles, and this gap can be used as a void.

  Examples of the thermoplastic resin include polyethylene terephthalate, polyethylene-2,6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, cyclohexanedimethanol copolymer polyester resin, isophthalic acid copolymer polyester resin, spiroglycol copolymer polyester resin, and fluorene. Polyester resins such as copolyester resins, polyolefin resins such as polyethylene, polypropylene, polymethylpentene and alicyclic olefin copolymer resins, acrylic resins such as polymethyl methacrylate and acrylonitrile-styrene copolymers, polycarbonate, polystyrene, polyamide, Polyether, polyester amide, polyether ester, polyvinyl chloride, cycloolefin polymer These may be used a copolymer whose components, or mixtures of these resins.

  As particles dispersed in the thermoplastic resin, for example, inorganic particles such as titanium oxide and barium sulfate can be used. Alternatively, resin particles that are incompatible with the thermoplastic resin may be used as the particles to be dispersed in the thermoplastic resin as long as they are sufficiently hard as compared with the thermoplastic resin at the time of stretching.

  The total light transmittance of the diffusion layer 26 is, for example, in the range of 40% to 80%. If the total light transmittance is too small, light cannot be sufficiently emitted to the front F. If the total light transmittance is too large, sufficient diffusibility cannot be obtained, and therefore uniform in-plane brightness cannot be achieved.

  The haze value of the diffusion layer 26 is, for example, 98% or more. When the haze value is small, sufficient diffusibility cannot be obtained, and therefore uniform in-plane brightness cannot be achieved.

  When light diffusing particles are used as a plurality of regions distributed in the transparent material, the thickness of the diffusion layer 26 is, for example, in the range of 0.1 mm to 5 mm. When the diffusion layer 26 is too thin, sufficient diffusibility cannot be obtained. When the diffusion layer 26 is too thick, a sufficient total light transmittance cannot be obtained.

  When pores are used as the plurality of regions distributed in the transparent material, the thickness of the diffusion layer 26 is set in the range of, for example, 25 μm to 500 μm. When the diffusion layer 26 is too thin, the diffusion layer 26 is weak and easily wrinkles. When the diffusion layer 26 is too thick, a sufficient total light transmittance cannot be obtained.

Here, the diffusion member 25 will be described in more detail.
FIG. 2 is a cross-sectional view showing a light path in the diffusing member. In FIG. 2, reference numeral 28 a indicates the top of the convex portion 28, reference numeral 28 b indicates the side surface or the inclined surface 28 b of the convex portion 28, and reference numeral 28 c indicates the bottom surface of the convex portion 28. Reference numeral 30 indicates a joint position between the side surface 28 b and the bottom surface of the convex portion 28.

  As described above, the backlight body 45 causes almost all of the light emitted from the light source 41 to travel forward F. The light H traveling forward F enters the convex portion 28 constituting the lens. When the focal points of these lenses are located between the back surface 23a and the front surface 23b of the light transmission layer 23, the light incident on the lens is focused and diverged in the light transmission layer 23 as indicated by an arrow L in FIG. Then, the light enters the diffusion layer 26. Therefore, compared with the case where the light transmission layer 23 and the convex portion 28 are omitted, light can be incident on the diffusion layer 26 more uniformly and / or from various directions. Therefore, even when the diffusion layer 26 is thin, in-plane variations in light intensity are unlikely to occur, and the viewing angle dependency does not become excessively large. In particular, when a configuration described below using mathematical formulas is employed, it is possible to further reduce the in-plane variation of the light intensity and the increase in the observation angle dependency caused by making the diffusion layer 26 thinner.

That is, attention is paid to a cross section passing through the top portion 28 a of the convex portions 28 arranged in one direction and parallel to the arrangement direction of the convex portions 28 and the thickness direction of the light transmission layer 23. The cross section shown in FIG. 2 is one such cross section. In this section, the angle formed by each side surface 28b of the convex portion 28 with respect to the previous bottom surface at the joint position 30 with the bottom surface 28c, that is, the tangent l of the convex portion 28 at the joint position 30 is The angle formed with respect to the bottom surface 28c is θ, and the pitch of these convex portions is P. The convex portion 28 and the light transmission layer 23 are designed so that the angle θ and the pitch P and the thickness T and the refractive index n of the light transmission layer 23 satisfy the relationship shown in the following inequality.

  When this design is adopted, the distance from the focal point of the lens to the back surface 23a of the light transmission layer 23 is shorter than the distance from the focal point of the lens to the front surface 23b of the light transmission layer 23. Therefore, for example, when the light H is irradiated as a parallel beam from the vertical direction toward the back surface 23 a of the light transmission layer 23, the light beam incident on each lens expands and enters the diffusion layer 26. As a result, the light beam transmitted through a certain lens and the light beam transmitted through the adjacent lens partially overlap on the back surface 26 a of the diffusion layer 26. Therefore, when this configuration is adopted, it is possible to further reduce the in-plane variation of the light intensity and the increase in the observation angle dependency caused by making the diffusion layer 26 thinner.

  As described above, when the convex portion 28 and the light transmission layer 23 are provided, even when the diffusion layer 26 is thinned, the in-plane variation of the light intensity and the dependence on the observation angle are sufficiently prevented from being excessively increased. it can. This effect can be obtained by adopting an appropriate design for the convex portion 28 and the light transmission layer 23 even when the diffusion transmission layer is thinned.

  Further, the diffuse transmission layer composed of the convex portion 28 and the light transmission layer 23 hardly affects the total light transmittance of the diffusion member 25. For example, the decrease in the total light transmittance of the diffusion member 25 due to the addition of the diffuse transmission layer is several percent. This value is small compared to the increase in the total light transmittance accompanying the thinning of the diffusion layer 26.

  In this diffusing member 25, the pitch P is arbitrary. However, if the pitch P is too large, the thickness T must be increased in order to satisfy the relationship shown in the above inequality. Considering production efficiency and production cost, it is not preferable that the thickness T is large. The pitch P is, for example, 0.5 mm or less, preferably 0.2 mm or less.

  The optical functional layer 1 faces the diffusion layer 26 with the mask layer 22 interposed therebetween. The optical function layer 1 includes a light transmission layer 17 and a plurality of convex portions 16.

  The light transmission layer 17 is a layer having a light transmission property. The back surface 17a and the front surface 17b of the light transmission layer 17 are substantially flat.

  As a material of the light transmission layer 17, for example, a thermoplastic resin or a thermosetting resin can be used. The material of the light transmission layer 17 may be the same as the material used for any of the layers included in the diffusion member 25. For example, the material of the light transmission layer 17 may be the same as the material of the light transmission layer 23. In this way, occurrence of warpage can be suppressed.

  The convex portion 16 is supported by the light transmission layer 17. Specifically, the protrusions 16 are arranged on the front surface 17 b of the light transmission layer 17. Typically, the convex portions 16 are arranged at a constant pitch. The convex portion 16 forms a relief structure on the front surface of the optical functional layer 1.

  Each of the convex portions 16 constitutes a lens or a prism as an optical element. The convex portions 16 may be arranged in one direction on the front surface 17b of the light transmission layer 17, or may be arranged in a plurality of directions. In the former case, each of the convex portions 16 is, for example, a lenticular, a cylindrical lens, or a triangular prism. In the latter case, each of the convex portions 16 is, for example, a lens or a pyramid-shaped prism having an axis of symmetry perpendicular to the front surface 17 b of the light transmission layer 17.

  These convex portions 16 form, for example, a lens array in which a plurality of lenses are arranged one-dimensionally or two-dimensionally. These convex portions 16 may form a prism array formed by arranging a plurality of prisms one-dimensionally or two-dimensionally.

  These convex portions 16 may have the same shape or different shapes. In the latter case, some of the convex portions 16 may be lenses, and the remaining convex portions 16 may be prisms. Alternatively, all the convex portions may be lenses, and the shape may be different between some of the convex portions and the remaining convex portions. Alternatively, all the convex portions may be prisms, and the shape may be different between some of the convex portions and the remaining convex portions. Here, as an example, it is assumed that the protrusions 16 are lenticulars having the same shape and are arranged one-dimensionally.

  The convex part 16 can be formed by the same method as described for the convex part 28, for example. The material of the convex portion 16 may be the same as or different from the material of the light transmission layer 17.

  The front surface of the optical functional layer 1 has a surface area different from that of the back surface of the diffuse transmission layer including the convex portion 28 and the light transmission layer 23. Specifically, the surface area S1 of the back surface of the diffuse transmission layer is smaller than the surface area S2 of the front surface of the optical functional layer 1. For example, the ratio S1 / S2 of the surface area S1 to the surface area S2 is in the range of about 0.8 to about 0.9.

  In order to make the ratio S1 / S2 less than 1, the convex portion 28 and the convex portion 16 may be different from each other in at least one of size and shape. For example, the width or diameter of the convex portion 28 may be larger than the width or diameter of the convex portion 16. Alternatively, the height of the convex portion 28 may be lower than the height of the convex portion 16. Alternatively, a one-dimensional array composed of a lenticular or cylindrical lens or a triangular prism may be formed on the convex portion 28, and a two-dimensional array composed of a lens or a prism may be formed on the convex portion 16. Alternatively, two or more of these structures may be combined.

  The mask layer 22 is interposed between the optical function layer 1 and the diffusion layer 16. The mask layer 22 is opened at a position corresponding to the top portion 16a of the convex portion 16 and a position corresponding to a region adjacent to the top portion 16a on the side surface of the convex portion 16 or the inclined surface 16b. The mask layer 22 transmits light that travels toward the top portion 16 a of the convex portion 16 and the vicinity thereof out of the light emitted from the diffusion member 25 forward, and travels toward the valley portion 13 between the convex portions 16. Is reflected or absorbed.

  As a material of the mask layer 22, for example, a light shielding material can be used. As the light shielding material, it is preferable to use a metal reflective material or a white material. In this way, the light reflected by the mask layer 22 is further scattered by the diffusion layer 26 and the like, so that its traveling direction is changed and finally enters the optical functional layer 1.

  The mask layer 22 can be formed on the optical function layer 1, for example. For example, when the convex portion 16 forms a lens, when the optical functional layer 1 is illuminated from the front side, a light intensity distribution corresponding to the arrangement of the convex portions 16 is generated on the back surface 17 a of the light transmission layer 17. For example, if this light intensity distribution is used for photolithography, the mask layer 22 can be formed without using a photomask.

  Note that the optical functional layer 1 and the diffusing member 25 can be integrated by, for example, bonding their edges together via a double-sided tape. Alternatively, the optical function layer 1 and the diffusing member 25 may be bonded using an adhesive.

  In this optical component 52, as described above, even when the diffusing member 25 is thin, it achieves high diffusing power and high total light transmittance. The optical functional layer 1 and the mask layer 22 further diffuse light and control the light spread angle without substantially affecting the total light transmittance of the optical component 52.

  Therefore, in the liquid crystal display device 70, the intensity distribution of the light K emitted from the optical component 52 toward the display panel 35 can be made uniform, and the spread angle can be optimized. Therefore, when the above-described technique is employed, it is possible to realize a thin display device capable of bright display with almost no lamp image on the screen.

  An optical component provided with a lens array or a prism array on both sides may generate moire interference fringes. However, in the optical component 52 described above, since the diffusion layer 26 is interposed between the front lens or prism and the rear lens or prism, no moire interference fringes are generated for the above reason.

  Further, as described above, with the thinning of the liquid crystal display device, the backlight unit is required to reduce the distance between components. Since the light source of the backlight unit is also a heat source, if the distance between the light source and the optical component installed in front of the light source is shortened, the temperature of the optical component when the light source is turned on may be higher.

  The multilayer structure may be warped with a temperature change due to a difference in linear expansion coefficient of the layers constituting the multilayer structure. When the previous optical component warps, the display performance as designed cannot be obtained, and in some cases, the warped optical component may destroy the display panel or the light source.

  In the optical component 52, the optical functional layer 1 and the diffuse transmission layer face each other with the diffusion layer 26 interposed therebetween. Since the optical functional layer 1 and the diffuse transmission layer have similar structures, the optical component 52 is less likely to be warped due to the difference in linear expansion coefficient compared to the structure in which the diffuse transmission layer is omitted. .

  In addition, in the optical component 52, as described above, the surface area S1 of the back surface of the diffuse transmission layer is smaller than the surface area S2 of the front surface of the optical function layer 1. When the surface area S1 is reduced, the absorption of infrared rays by the diffuse transmission layer is reduced, and therefore the temperature difference between the back surface and the front surface of the optical component 52 is reduced. Therefore, warpage due to this temperature difference can be suppressed.

  Thus, the optical component 52 is unlikely to warp even when the distance from the light source 41 is shortened. Therefore, the use of the optical component 52 is advantageous for reducing the thickness of the display device 70.

The backlight unit 55 included in the liquid crystal display device 70 may employ the following configuration.
FIG. 3 is a plan view schematically showing an example of a structure that can be employed in the backlight unit. In the backlight unit 55 shown in FIG. 3, a linear light source is used as the light source 41, and the convex portion 28 forms a lenticular. In FIG. 3, m indicates the length direction of the lenticular, and n indicates the length direction of the light source.

In the structure shown in FIG. 3, the length direction m of the lenticular is slightly inclined with respect to the length direction n of the light source 41. If the angle θ _{41 formed} by the direction m with respect to the direction n is excessively increased, the effect of suppressing the generation of the lamp image is reduced. The angle θ ₄₁ is set to 20 ° or less, for example.

If the angle θ ₄₁ is sufficiently small, the effect that the angle θ ₄₁ has on the effect of suppressing the generation of the lamp image is hardly present. That is, in reality, alignment between the light source 41 and the diffusing member 25 is not necessary. Therefore, when this optical component 52 is used, the manufacturing efficiency can be improved and the manufacturing cost can be reduced.

  The optical component 52 may not include the mask layer 22. Even when the mask layer 22 is omitted, although not as much as when the mask layer 22 is provided, the effect of further diffusing light and the effect of controlling the light spread angle can be obtained. In addition, as described above, the diffusing member 25 achieves high diffusivity and high total light transmittance even when it is thin. Therefore, also in this case, it is possible to realize a thin display device capable of bright display without generating a lamp image on the screen.

Next, the second aspect of the present invention will be described.
FIG. 4 is a cross-sectional view schematically showing a display device according to the second aspect of the present invention. FIG. 5 is a perspective view schematically showing an optical functional layer included in the display device shown in FIG.

  The display device 70 is the same as the display device 70 described with reference to FIGS. 1 and 2 except that the following configuration is adopted. That is, in this display device 70, the convex portion 16 constitutes a lenticular in which the V-shaped groove 4 is provided on the top portion 16a. In this display device 70, instead of providing the mask layer 22, the spacer 29 is interposed between the peripheral portions of the optical functional layer 1 and the diffusion layer 26, and the gap portion 14 is provided between them. A plurality of convex portions 19 are arranged on 26b. Each of the convex portions 16 may constitute a lens other than the lenticular, or may constitute a prism.

  The length direction of the V-shaped groove 4 is parallel to the length direction of the lenticular. When the convex portion 16 forms a two-dimensional array, at least one of the convex portions 16 may be provided with a plurality of V-shaped grooves 4 so as to intersect each other. Further, the groove provided in the convex portion 16 may not be the V-shaped groove 4. For example, the convex portion 16 may be provided with a U-shaped groove instead of the V-shaped groove.

  The spacer 29 plays a role of separating the optical functional layer 1 and the diffusion layer 26 from each other and forming the gap portion 14 therebetween. In addition, the spacer 29 serves as a component or a part thereof for fixing the optical functional layer 1 and the diffusion layer 26 to each other.

  Here, although the spacer 29 consists only of a frame-shaped part, the spacer 29 may further include one or more columnar parts located in the frame-shaped part. Alternatively, a plurality of columnar portions may be used as the spacer 29. Alternatively, the spacer 29 may have a lattice shape.

  Each of the convex portions 19 constitutes a lens or a prism. Typically, the protrusions 19 are arranged at a constant pitch on the front surface 26 b of the diffusion layer 26.

  The convex portions 19 may be arranged in one direction on the front surface 26b of the diffusion layer 26, or may be arranged in a plurality of directions. In the former case, each of the convex portions 19 is, for example, a lenticular, a cylindrical lens, or a triangular prism. In the latter case, each of the convex portions 19 is, for example, a lens or a pyramidal prism having an axis of symmetry perpendicular to the front and back surfaces 26b of the diffusion layer 26.

  These convex portions 19 form, for example, a lens array in which a plurality of lenses are arranged one-dimensionally or two-dimensionally. These convex portions 19 may form a prism array formed by arranging a plurality of prisms one-dimensionally or two-dimensionally.

  These convex portions 19 may have the same shape or different shapes. In the latter case, some of the convex portions 19 may be lenses and the remaining convex portions 19 may be prisms. Alternatively, all the convex portions may be lenses, and the shape may be different between some of the convex portions and the remaining convex portions. Alternatively, all the convex portions may be prisms, and the shape may be different between some of the convex portions and the remaining convex portions. Here, as an example, it is assumed that the convex portions 19 are lenticulars having the same shape and are arranged one-dimensionally.

  In the display device 70, as described above, the groove 4 is provided in the top portion 16a of the convex portion 16. Therefore, total reflection occurs at the interface between the side wall of the groove 4 and the air layer, resulting in light recycling. Therefore, when the groove 4 is provided in this way, a higher luminance increase effect can be obtained as compared with the case where the groove 4 is omitted.

  When the groove 4 is provided in the top portion 16a of the convex portion 16, the side lobe of the light intensity spectrum is reduced. In addition, when the groove 4 is provided in the top portion 16a of the convex portion 16, it is possible to mitigate a sudden luminance drop (cut-off) that occurs when the observation direction is changed to the wide angle side.

  In the display device 70, as described above, the gap portion 14 is provided between the optical function layer 1 and the diffusion layer 26, and the convex portion 19 is disposed on the front surface 26 b of the diffusion layer 26. Since the convex portion 19 is adjacent to the gap portion 14 having a small refractive index, the degree of freedom in design regarding diffusion and light collection is large.

  Therefore, also in this aspect, the same effect as described in the first aspect can be obtained. Then, according to the optical component 52 included in the display device 70, for example, one or more optical gains can be achieved.

  The optical gain is one of indexes indicating the diffusibility of an object. The optical gain is a value expressed as a relative value when the luminance when the object is irradiated with specific light and the luminance when the previous light is irradiated on the diffuser that completely diffuses is 1. When the diffusivity of the measurement object has direction dependency, the diffusion characteristic of the object can be obtained by obtaining the optical gain for each direction. An optical gain in a certain direction being 1 or more means that the measurement object has an effect of collecting light in that direction, and the larger the value, the greater the light collection effect.

  Next, the third aspect of the present invention will be described. The third aspect is the same as the first and second aspects, except that the following structure is adopted for the diffuse transmission layer.

  FIG. 6 is a cross-sectional view schematically showing an example of a structure that can be employed in the diffuse transmission layer. The diffuse transmission layer shown in FIG. 6 is the same as the diffusion transmission layer of the optical component 52 described with reference to FIGS. 1 to 5 except that the light transmission layer 23 has a multilayer structure.

  The light transmission layer 23 includes a first light transmission layer 231, a second light transmission layer 232, and an intermediate layer 233 interposed therebetween. The first light transmission layer 231 and the second light transmission layer 232 may be made of different materials or the same material. The intermediate layer 233 is an adhesive layer or an adhesive layer, and joins the first light transmission layer 231 and the second light transmission layer 232 to each other.

  When this structure is adopted, the refractive index n and the linear expansion coefficient of the light transmission layer 23 can be changed according to the materials used for the first light transmission layer 231 and the second light transmission layer 232 and their thicknesses. it can. Therefore, when this structure is employed, it is easy to suppress warpage while achieving excellent optical performance.

  This effect is particularly great when the ratio S1 / S2 is within the above range, but can be obtained even when the ratio S1 / S2 is outside the above range. That is, when the configuration described here is employed, the ratio S1 / S2 is preferably within the above range, but may be outside the above range.

  When this structure is adopted, the material of the second light transmission layer 232 may be the same as or different from the material of the convex portion 28. Further, the intermediate layer 233 may be omitted.

  When the diffuse transmission layer has the structure shown in FIG. 6, the following design may be adopted for the optical component 52.

  For example, the optical component 52 is set so that the linear expansion coefficient α1 of the optical functional layer 1 and the linear expansion coefficient α2 of the laminate of the second light transmission layer 232 and the intermediate layer 233 satisfy the relationship represented by the following inequality (1). To design.

0.8 × α1 ≦ α2 ≦ 1.2 × α1 (1)
Alternatively, when the linear expansion coefficient α4 of the diffusion layer 26 is equal to or larger than the linear expansion coefficient α5 of the light transmission layer 231, a smaller value α3 of the linear expansion coefficients α1 and α2 and the linear expansion coefficients α4 and α5 The optical component 52 is designed so as to satisfy the relationship represented by the following inequality (2). Further, when the linear expansion coefficient α4 is smaller than the linear expansion coefficient α5, the optical component 52 is designed so that the linear expansion coefficient values α3 to α5 satisfy the relationship represented by the following inequality (3).

0.3 × α3 ≦ α4 ≦ 3.9 × α3 (2)
0.3 × α3 ≦ α5 ≦ 3.9 × α3 (3)
Alternatively, the optical component 52 is designed so that the thickness L of the optical functional layer 1 and the thickness M of the laminated body of the second light transmission layer 232 and the intermediate layer 233 satisfy the relationship represented by the following inequality (4). .

0.3 ≦ M / L ≦ 2.9 (4)
Alternatively, combine two or more of these designs. For example, the linear expansion coefficients α1 to α5 satisfy the relationships shown in the inequalities (1) and (2) or the relationships shown in the inequalities (1) and (3), and the thicknesses L and M are inequalities ( The optical component 52 is designed so as to satisfy the relationship shown in 4).

  The optical component 52 employing such a design hardly warps even when heated to a high temperature from the diffuse transmission layer side, for example, when heated to about 80 ° C.

<Example 1>
In this example, the influence of the diffuse transmission layer on the diffusion performance of the optical component 52 was examined.
First, the optical component 52 shown in FIG. 1 was manufactured. Here, the following configuration is adopted for the optical component 52.

As the light transmission layer 17, a polyethylene terephthalate film having a thickness of 75 μm was used. Urethane acrylate was used as the material of the convex portion 16, and each was a cylindrical lens. Each cylindrical lens had a width of 90 μm and a height of 45 μm. The linear expansion coefficient of the optical functional layer 1 was 6 × 10 ⁻⁵ cm / cm / ° C.

  As a material for the mask layer 22, a mixture of urethane resin and titanium oxide particles was used. The thickness of the mask layer 22 was 20 μm. The mask layer 22 was provided with a slit having a width of 70 μm corresponding to the top portion 16 a of the convex portion 16.

As the diffusion layer 26, a sheet made of a mixture of polystyrene resin and acrylic particles was used. The thickness of the diffusion layer 26 was 2 mm, and the linear expansion coefficient was 7 × 10 ⁻⁵ cm / cm / ° C.

As the light transmission layer 23, a polycarbonate film having a thickness of 0.5 mm was used. Urethane acrylate was used as the material of the convex portion 128, and each was a cylindrical lens. Each cylindrical lens had a width of 100 μm and a height of 60 μm. The linear expansion coefficient of the diffuse transmission layer was 1.3 × 10 ⁻⁴ cm / cm / ° C. The refractive index n of polycarbonate is 1.59.

  Next, the diffusion ability of the optical component 52 was examined. Specifically, first, the display device 70 shown in FIG. 1 was manufactured using the optical component 52. Here, five cold cathode tubes were used as the light source 41.

Next, a white image was displayed on the display device 70, and the luminance in the vertical direction was measured over the entire area of the screen while keeping the driving conditions constant. Then, from the luminance distribution data thus obtained, the average luminance in the region corresponding to the cold cathode tube in the screen was calculated, and the luminance variance σ ² with respect to this average luminance was obtained. As a result, the standard deviation σ was 1% or less.

  Moreover, the optical component similar to the above was manufactured except that the light transmission layer 23 and the convex portion 28 were omitted. And also about this optical component, the diffusivity was investigated by the method similar to the above-mentioned. As a result, the standard deviation σ was about 6%.

Next, the several display apparatus 70 from which the thickness T of the light transmissive layer 23 differs was manufactured. These display devices 70 have the same configuration as the display device 70 described above except that the thickness T is different. And about these display apparatuses 70, the diffusivity was investigated by the method similar to the above-mentioned. The results are summarized in Table 1 below.

  As shown in Table 1, the standard deviation σ could be less than 6% by making the thickness T larger than 200 μm. And the standard deviation (sigma) was able to be 1% or less by making thickness T into 260 micrometers or more.

<Example 2>
In this example, the influence of the ratio S1 / S2 between the surface area S1 of the back surface of the diffuse transmission layer and the surface area S2 of the front surface of the optical functional layer 1 on the warp was examined.

  First, a plurality of optical components 52 shown in FIG. 1 were manufactured. These optical components 52 have different ratios S1 / S2 by making the dimensions of the convex portions 28 different. Each optical component 52 has the same configuration as that described in Example 1 except for the size of the convex portion 28.

Next, each of these optical components 52 was placed on a support including a plurality of pins each extending in the vertical direction. Each optical component 52 was installed horizontally such that the diffuse transmission layer faced downward. Next, each of the optical components 52 was heated to 80 ° C. by illuminating with five cold cathode tubes from the lower side. After 500 hours from the start of heating, the distance from the plane defined by the tip of the pin was measured for each of the four corners of the optical component 52. And the value obtained by dividing those averages by the length of the short side of the optical component 52 was made into curvature amount. Further, an optical component similar to the above was manufactured except that the light transmission layer 23 and the convex portion 28 were omitted, and the warpage amount of this optical component was also measured by the same method. The results are summarized in Table 2 below.

  As shown in Table 2, the amount of warpage of the optical component 52 including the light transmission layer 23 and the convex portion 28 was smaller than that of the optical component in which the light transmission layer 23 and the convex portion 28 were omitted. Moreover, when the light transmission layer 23 and the convex part 28 were provided, the amount of warpage decreased as the ratio S1 / S2 was decreased.

<Example 3>
In this example, in the optical component 52 employing the structure shown in FIG. 6, the linear expansion coefficient α1 of the optical functional layer 1 and the linear expansion coefficient α2 of the laminate of the second light transmission layer 232 and the intermediate layer 233 are warped. The effects on the

  First, a plurality of optical components 52 shown in FIG. 1 were manufactured. Here, the structure shown in FIG. 6 is adopted for the diffuse transmission layer of each optical component 52. These optical components 52 differed in the ratio α2 / α1 of the linear expansion coefficient α2 to the linear expansion coefficient α1 by changing the combination of materials used for the light transmission layers 17 and 232. Except for this, each optical component 52 has the same configuration as that described in Example 1.

Next, the warpage amount of each of these optical components 52 was measured by the same method as described in Example 2. The results are summarized in Table 3 below.

  As is clear from Tables 2 and 3, the optical component 52 including the light transmission layer 23 and the convex portion 28 has a warpage amount as compared with the optical component in which the light transmission layer 23 and the convex portion 28 are omitted. It was small. Further, as shown in Table 3, the amount of warpage showed a high correlation with the ratio α2 / α1.

<Example 4>
In this example, in the optical component 52 adopting the structure shown in FIG. 6, the smaller value α3 of the linear expansion coefficients α1 and α2, the linear expansion coefficient α4 of the diffusion layer 26, and the linear expansion coefficient α5 of the light transmission layer 231 are obtained. The effect on warpage was investigated.

  First, a plurality of optical components 52 shown in FIG. 1 were manufactured. Here, the structure shown in FIG. 6 is adopted for the diffuse transmission layer of each optical component 52. The optical component 52 has a ratio α5 / ratio of the linear expansion coefficient α5 to the linear expansion coefficient α3 by changing the combination of the material used for the light transmission layers 17, 231 and 232 and the material used for the diffusion layer 26. The combination of α3 and the ratio α4 / α3 of the linear expansion coefficient α4 to the linear expansion coefficient α3 was varied. Except for this, each optical component 52 has the same configuration as that described in Example 1.

Next, the warpage amount of each of these optical components 52 was measured by the same method as described in Example 2. The results are summarized in Table 4 below.

  As apparent from Tables 2 and 4, the optical component 52 including the light transmission layer 23 and the convex portion 28 has a warpage amount as compared with the optical component in which the light transmission layer 23 and the convex portion 28 are omitted. It was small. Further, as shown in Table 4, the warpage amount showed a high correlation with the ratio α5 / α3 and the ratio α4 / α3.

<Example 5>
In this example, in the optical component 52 adopting the structure shown in FIG. 6, the thickness L of the optical functional layer 1 and the thickness M of the laminated body of the second light transmission layer 232 and the intermediate layer 233 affect the warpage. I investigated.

  First, a plurality of optical components 52 shown in FIG. 1 were manufactured. Here, the structure shown in FIG. 6 is adopted for the diffuse transmission layer of each optical component 52. And these optical components 52 changed ratio M / L of thickness M to thickness L by changing thickness L and M. Except for this, each optical component 52 has the same configuration as that described in Example 1.

Next, the warpage amount of each of these optical components 52 was measured by the same method as described in Example 2. The results are summarized in Table 5 below.

  As is apparent from Tables 2 and 5, the optical component 52 including the light transmission layer 23 and the convex portion 28 has a warpage amount as compared with the optical component in which the light transmission layer 23 and the convex portion 28 are omitted. It was small. Moreover, as shown in Table 5, the amount of warpage showed a high correlation with the ratio M / L.

Sectional drawing which shows schematically the display apparatus which concerns on the 1st aspect of this invention. Sectional drawing which shows the path | route of the light in a diffusion member. The top view which shows roughly an example of the structure employable as a backlight unit. Sectional drawing which shows schematically the display apparatus which concerns on the 2nd aspect of this invention. FIG. 5 is a perspective view schematically showing an optical function layer included in the display device shown in FIG. 4. Sectional drawing which shows schematically an example of the structure employable as a diffuse transmission layer.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Optical functional layer, 4 ... Groove, 13 ... Valley part, 14 ... Space | gap part, 16 ... Convex part, 16a ... Top part, 16b ... Inclined surface, 17 ... Light transmission layer, 17a ... Back surface, 17b ... Front surface, 19 ... Convex part, 22 ... Mask layer, 23 ... Light transmission layer, 23a ... Back face, 23b ... Front face, 25 ... Diffusion member, 26 ... Diffusion layer, 26a ... Back face, 26b ... Front face, 28 ... Convex part, 28a ... Top part, 28b ... inclined surface, 28c ... bottom face, 29 ... spacer, 30 ... bonding position, 31 ... polarizing plate, 32 ... liquid crystal panel, 33 ... polarizing plate, 35 ... display panel, 41 ... light source, 43 ... reflective layer, 45 ... backlight Main body 52... Optical component 55. Backlight unit 70. Display device 231 Light transmission layer 232 Light transmission layer 233 Intermediate layer

Claims (6)

A first main surface that is used for diffusing light emitted by a light source and that makes the light incident thereon, and a second main surface that emits diffused light when the light is incident on the first main surface. Optical components,
A diffusion layer including a transparent material and a plurality of regions distributed in the transparent material and having a refractive index different from that of the transparent material;
An optical functional layer provided on the second main surface with a relief structure in which one main surface constitutes the second main surface and each of which constitutes a plurality of optical elements composed of lenses or prisms;
One principal surface constitutes the first principal surface, the other principal surface faces the optical functional layer with the diffusion layer interposed therebetween, and constitutes a plurality of optical elements each composed of a lens or a prism. An optical component, wherein a relief structure is provided on the first main surface, and the first main surface comprises a diffuse transmission layer having a smaller surface area than the second main surface. The diffusion transmission layer includes a light transmission layer and a plurality of convex portions arranged on the light transmission layer, and passes through a top of the plurality of convex portions arranged in one direction, and the arrangement direction of the convex portions and the light transmission In a cross section parallel to the thickness direction of the layer, the angle θ formed by each side surface of the convex portion with respect to the bottom surface at the joining position with the bottom surface, the pitch P of the convex portions, and the thickness of the light transmitting layer The optical component according to claim 1, wherein the thickness T and the refractive index n satisfy a relationship represented by the following inequality.

  The optical component according to claim 1, further comprising a mask layer interposed between the diffusion layer and the optical functional layer and provided with a plurality of openings. A spacer which is interposed between the diffusion layer and the optical functional layer and forms a gap between them;
The optical system according to claim 1, further comprising a plurality of convex portions that are supported by a main surface of the diffusion layer facing the optical functional layer and each constitute a lens or a prism. parts. The optical component according to any one of claims 1 to 4,
A backlight unit comprising: a light source that illuminates the optical component from the diffuse transmission layer side.   6. A display device comprising: the backlight unit according to claim 5; and a display panel facing the light source with the optical component interposed therebetween.

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