JP2009176437A - Light source unit, backlight unit, and display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source unit, a backlight unit and a display, capable of more easily installing a reflecting plate, and aiming at uniformalization of luminance distribution and improvement of front luminance. <P>SOLUTION: The light source unit is provided with a light guide unit 12 made by arranging a plurality of light guides 8 equipped with a thick part 8c formed in the vicinity of the center part of a light emitting face 8a, a housing concave part 11 formed at the thick part 8c on a rear face, a thin end part 8e located at an end part of the light emitting face 8a, and a slanted rear face 8d slanted so as to be gradually thinned from the thick part 8c toward the thin end part 8e on a rear face, a light source 7 housed in a housing concave part 11 of each light guide 8 in the light guide unit 12, and a platy diffused light reflector 17 arranged in opposition on a rear face of the light guide unit 12. An air layer 31 is formed zoned between the slanted rear face 8d and the diffused light reflector 17. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light source unit including a plurality of light guides that diffuse light incident from a light source and emit uniform illumination light from an emission surface, and a backlight that illuminates a liquid crystal panel or the like from the back side using the light source unit. The present invention relates to a unit and a display device.

  In recent years, liquid crystal display devices (LCDs) using liquid crystal panels have been used in notebook personal computers, personal computer displays, image display means for information terminal equipment, image display means for information appliances such as large-screen TVs, mobile phones and personal use. 2. Description of the Related Art It has been used in various fields as an image display means of a personal digital assistant (PDA: Personal Digital Assistance). In a display device represented by a liquid crystal display device, a type having a built-in light source necessary for recognizing provided information is remarkably widespread.

  In such a display device, the demand for thinning has been increasing year by year, but as a conventional display device that has been thinned, for example, as described in Patent Documents 1 to 5, the back surface of a liquid crystal panel is used. Some surface light source devices that include a light source on the side, convert light from the light source into surface light emission via a light guide, and irradiate a liquid crystal panel include a so-called backlight unit.

  These backlight units, for example, on the light guide disposed between the light source and the image display unit, the transmittance adjustment for adjusting the luminance distribution of the planar light emitted from the exit surface of the light guide Body unit, a diffusion film that diffuses light that has passed through the transmittance adjusting body unit, and a plurality of prism sheets that condense the diffused light so as to be directed in a specific direction (for example, a normal direction to the image display unit) Has been.

  In particular, these light guides are concave portions extending in a substantially cylindrical shape for disposing a rod-shaped light source composed of a cold cathode ray tube on the back surface facing the light emitting surface in a thick portion provided at the substantially central portion of the light emitting surface. Is forming. And in the back surface of a light guide, it forms by providing a back inclined part toward the thin edge part of both sides from the thick part which formed the recessed part. In the backlight unit described in Patent Document 1, a light quantity correction surface that promotes the emission of illumination light is formed by forming a groove with a triangular cross section on the light emitting surface of the light guide except for the portion directly above the light source. ing. A light diffusing plate or a prism sheet is disposed on the light exit surface side of the light guide, thereby reducing the overall thickness and reducing unnatural luminance unevenness of the emitted light.

  Also, in the backlight units and liquid crystal display devices described in Patent Documents 2 to 5, a luminance adjusting unit is provided by providing a transmittance adjusting unit unit on the light exit surface side of the light guide, or providing a prism sheet, a diffusion sheet, or the like. The illumination light by the more uniform surface light emission is applied to the image display unit such as a liquid crystal panel.

  By the way, in the above-described conventional backlight unit and liquid crystal display device, in order to reduce luminance unevenness on a thin and large screen, a light guide according to the size of the large backlight unit and the image display unit. Need to be enlarged. Therefore, in the conventional backlight unit and liquid crystal display device described above, a light guide unit in which a plurality of light guides are integrally formed in the vertical and horizontal directions is formed.

In the light guide unit 1 configured as described above, for example, as shown in FIG. 20, the reflection plate 4 is attached so as to cover the back inclined portion 3 of each light guide 2, and the light source 5 further includes A reflector 7 is attached so as to close the recessed portion 6 accommodated therein. Thereby, the light leaking from each light guide 2 is reflected, and the utilization efficiency of light is improved.
Japanese Patent Laid-Open No. 9-304623 Japanese Patent Laid-Open No. 2005-23497 JP 2006-301518 A JP 2006-302687 A JP 2006-318754 A

However, in the backlight unit including the above-described light guide unit, the reflector is attached to the back inclined portion of each light guide constituting the light guide unit individually along the inclination of the back inclined portion. Manufacturing, it took a lot of time and effort to manufacture.
In addition, when the reflector is directly attached to the back inclined portion in this way, the light utilization efficiency can be increased, and the light emitted from the light exit surface of the light guide unit is somewhat Luminance unevenness occurred and there was still room for improvement. Furthermore, in the backlight unit, it is desired to further improve the front luminance.

  The present invention has been made in view of such a problem, and a light source unit and a back that can be provided with a simpler reflector, can achieve uniform luminance distribution, and improve front luminance. An object is to provide a light unit and a display device.

In order to solve the above problems, the present invention proposes the following means.
That is, the light source unit according to the present invention includes a light exit surface, a thick portion formed in the vicinity of the central portion of the exit surface, and an accommodation recess formed in the thick portion on the back surface facing the exit surface. And a light guide body including a thin end portion located at an end portion of the emission surface, and an inclined back surface inclined so that the thickness gradually decreases from the thick portion toward the thin end portion on the back surface. Are arranged opposite to the back surface of the light guide unit, a light source housed in a light receiving unit housing recess of each light guide body in the light guide unit, A substantially plate-like diffuse reflector, and an air layer is defined between the inclined back surface and the diffuse reflector.

According to the light source unit having such a feature, the light emitted from the inclined rear surface of each light guide can be reincident on the light guide only by disposing the diffuse reflector on the back side of the light guide unit. Therefore, it is possible to easily configure the light source unit while maintaining high light use efficiency as in the conventional case.
In addition, since an air layer is formed between the diffuse reflector and the inclined back surface of the light guide, it can receive the contribution of the diffusion effect in the air layer, and the refraction of the air layer and the light guide. It is possible to effectively refract the light incident on the light guide using the rate difference and start up in the front direction.

 In the light source unit according to the present invention, the light source may be a point light source, and the light guide may be point-symmetric with respect to a central axis that includes the axis of the point light source of the housing recess and is perpendicular to the exit surface. .

  In the case of a point light source, the inclined back surface of each of the light guides may form a substantially conical surface. In this case, since the distance between the point light source and the inclined back surface becomes equal, the luminance distribution can be made more uniform.

In the light source unit according to the present invention, when the inclined back surface forms a substantially conical surface, the angle θ formed by the inclined back surface and the diffuse reflector is 19 ° ≦ θ ≦ 29 °, 31 ° ≦ It is characterized by being set within the ranges of θ ≦ 39 ° and 56 ° ≦ θ ≦ 72 °.
As a result, the light re-entering the light guide after leaking from the inclined back surface having a substantially conical surface can be narrowed to the optimum range, and the luminance distribution and the front luminance can be optimized.

  In the case of a point light source, the inclined back surface of each light guide may form a substantially quadrangular pyramid surface. In this case, since the manufacturing is easy, productivity can be improved.

  In the light source unit according to the present embodiment, the light source is a rod-shaped light source, and the light guide has a shape symmetrical to a plane that includes the axis of the rod-shaped light source of the housing recess and is orthogonal to the exit surface. It may be a thing.

  In the light source unit of the present embodiment, when the inclined surface is a substantially quadrangular pyramid surface and a rod-shaped light source, which is a point light source, the angle θ formed by the inclined back surface and the diffuse reflector is 28 °. ≦ θ ≦ 38 ° and 56 ° ≦ θ ≦ 73 ° are set. As a result, the light re-entering the light guide after leaking from the inclined back surface on the plane can be narrowed down to the optimum range, and the luminance distribution and the front luminance can be optimized.

In the light source unit according to the present invention, a diffuse reflection plate may be provided so as to surround an end portion in the surface direction of the light guide unit.
Thereby, since the light leaking from the thin end part of the light guide body arrange | positioned at the edge part of a light guide unit can be reflected in a light guide body, the utilization efficiency of light can be improved.

  In the light source unit according to the present invention, the light guide unit may be integrally formed.

A backlight unit according to the present invention includes any one of the light source units described above and an optical sheet that is disposed to face the light exit surface of the light guide unit and controls light emitted from the light exit surface. It is characterized by that.
According to such a backlight unit, the light emitted from the inclined back surface of each light guide can be re-entered into the light guide only by disposing the diffuse reflector on the back side of the light guide unit. Therefore, it is possible to easily configure the light source unit while maintaining high light utilization efficiency, and to receive the contribution of the diffusion effect in the air layer, and to use the difference in refractive index between the air layer and the light guide Then, the light incident on the light guide can be effectively refracted and raised in the front direction to improve the front luminance.

In addition, the backlight according to the present invention includes a translucent base material and a light reflection layer disposed on the incident surface side of the translucent base material between the light source unit and the light diffusion plate. The light reflecting layer includes an opening that transmits light and a light control sheet that includes a light reflecting portion that reflects light, and has high illuminance or luminance of light transmitted through the exit surface of the light guide. In the area, the area of the opening of the light control sheet is reduced, and in the area where the illuminance or luminance is low, the area of the opening is set large.
Thereby, the light emitted from the emission surface of each light guide of the light guide unit from each light source is transmitted as almost uniform illuminance or luminance by the light control unit, and light with a good balance of illuminance or luminance is emitted. Can do.
Instead of providing the light control sheet, the light from the light guide may be scattered by the diffusion plate, and substantially uniform light may be emitted toward the image display unit via the prism lens sheet or the lenticular lens sheet.

In the backlight unit according to the present invention, a transmittance adjustment pattern for adjusting the luminance distribution of the planar light emitted from the exit surface of the light guide is formed on the light incident surface of the light diffusion plate. It is characterized by having.
As in the above, this also reduces the uneven brightness of the light incident on the optical sheet from the light guide side even when the light from the light source leaks directly from the gap between the connecting portions of each light guide unit. be able to

Further, a display device according to the present invention is an image that is disposed on the light exit surface side of the backlight unit according to any one of the above and the optical sheet, and displays an image using light from the backlight unit as display light. It is characterized by comprising a display unit.
According to such a display device, the same effects as those of the light source unit and the backlight unit described above can be obtained.

According to the light source unit, the backlight unit, and the display device according to the present invention, the light emitted from the inclined rear surface of each light guide is guided only by disposing the diffuse reflector on the back side of the light guide unit. Therefore, it is possible to easily construct a light source unit having a reflection function.
Furthermore, by forming an air layer, it is possible to measure the uniformity of the luminance distribution due to the contribution of the diffusion effect in the air layer, and by utilizing the difference in refractive index between the air layer and the light guide. Front brightness can be improved by effectively refracting light incident on the light guide and raising it in the front direction.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
1 to 5 show a first embodiment of the present invention. FIG. 1 is a longitudinal sectional view of a main part of a display device, and FIGS. 3A and 3B are diagrams of a light guide using a point light source. FIG. 4 is a schematic view showing the arrangement of the respective light guides in the light guide unit, and FIG. 5 is a view showing the light traveling direction in the light source unit.
The light source unit and the backlight unit according to this embodiment will be described together with a display device using the light source unit and the backlight unit.

  In FIG. 1, the display device 1 according to the present embodiment is a liquid crystal display device configured by providing a liquid crystal display element (screen display unit) 3 above a backlight unit 2 that emits light upward. The liquid crystal display element 3 is configured by sandwiching a panel-like liquid crystal element 5 between a pair of polarizing plates 4 and 4. The liquid crystal display element 3 is connected to the drive unit M and is driven by the drive unit M.

In such an arrangement, the upper direction in FIG. 1 may be referred to as the display screen side, and the lower direction may be simply referred to as the back side or the light source side.
The display device 1 is a liquid crystal display device including the liquid crystal display element 3, but may be a projection screen device, a plasma display, an EL display, or the like as long as it includes at least the backlight unit 2. The type of the image display unit that displays the image by projecting the light from the light unit 2 as display light or projection light is not limited.

As shown in FIG. 1, the optical system in the backlight unit 2 includes a light guide unit 12, a diffuser plate 9, and an optical device that are connected to a light source 7 and a light guide 8 and are arranged on the display screen side of the light source 7. The seats 10 are sequentially arranged along the direction of the channel.
Further, a diffuse reflector 17 disposed on the back side and the side of the light guide unit 12 is provided, and the light source unit 30 is configured by the diffuse reflector 17, the light source 7, and the light guide unit 12. Yes.

The light source 7 is a point light source and is configured to emit light in all directions. As such a light source 7, a light emitting diode (LED) is preferable. As a light emitting diode, for example, a method of emitting white light by combining light emitting elements that emit light of a single color is well known. In mobile devices such as mobile phones, there is a white LED that emits pseudo white light by mounting a yellow phosphor on a light emitting element that emits blue light.
Note that the light source 7 that is a point light source is not limited to the above-described one, but, for example, is a device in which at least one other phosphor is mounted on one single-color light emitting element, such as that provided in a mobile device. Also good. Specifically, as shown in FIG. 2, for example, the light source 7 may be configured by covering a blue light emitting element 7B mounted on a substrate 7A with an LED lens 7D having a yellow light emitting phosphor 7C formed inside. .
The light source 7 is not limited to an LED as long as it is a point light source, and may be a normal fluorescent lamp, a halogen lamp, a semiconductor laser, or the like. Furthermore, the point light source is not limited to the above-described one, and it may be a single monochromatic LED element covered with at least one kind of phosphor.

  As shown in FIG. 3A, the light guide 8 is formed in a substantially square frustum shape having a rectangular shape such as a substantially square shape or a rectangular shape in a plan view by using a synthetic resin material having transparency. Then, one surface from which the light of the light guide 8 is emitted forms an emission surface 8a from which the light emitted from the light source 7 is emitted, and is formed in, for example, a rectangular flat shape.

  A concave portion 11 having a substantially U-shaped cross section is formed in the other surface of the light guide 8, that is, the central portion on the inclined rear surface 8 b side, and the light source 7 that is a point light source is accommodated in the concave portion 11. . The depth dimension and shape of the recess 11 are preferably formed so that the entire light source 7 can be accommodated therein, and the dimensions of the light source 7, the optical characteristics of the light guide 8, mechanical strength, aging, etc. are taken into consideration. Is preferably determined.

  Therefore, the inclined back surface 8b facing the light exit surface 8a of the light guide 8 is formed with a thick portion 8c having an accommodation recess 11 at the center, and from the thick portion 8c toward each side of the end of the light exit surface 8a. Four inclined surfaces 8d are formed as inclined portions. And the inclined surface 8d which goes to each edge | side of the output surface 8a becomes thin gradually with the output surface 8a, and makes the edge part of four sides into the flat thin edge part 8e, for example.

  In the present embodiment shown in FIG. 3A, the light guide 8 has a substantially regular quadrangular frustum shape in which the inclined back surface 8d forms a substantially quadrangular pyramid surface, but an appropriate polygonal frustum shape or FIG. ), The inclined back surface 8d may have a frustoconical shape having a substantially conical surface as a liquid.

As a material for forming the light guide 8, various materials can be used depending on applications as long as the material has heat resistance, mechanical strength, and solvent resistance to withstand manufacturing in addition to transparency. Specifically, for example, polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polyethylene terephthalate-isophthalate copolymer, terephthalic acid-cyclohexanedimethanol-ethylene glycol copolymer Polyester resins such as coextruded films of polyethylene terephthalate / polyethylene naphthalate, polyamide resins such as nylon 6, nylon 66 and nylon 610, polyolefin resins such as polyethylene, polypropylene (PP) and polymethylpentene, polyvinyl chloride Vinyl resin such as polyacrylate, polymethacrylate, acrylic resin such as polymethyl methacrylate (PMMA), polyimide, polyamideimide, polyetherimide, etc. Engineering resins such as imide resins, polyarylate, polysulfone, polyethersulfone, polyphenylene ether, polyphenylene sulfide (PPS), polyaramid, polyetherketone, polyethernitrile, polyetheretherketone, polyethersulfite, polycarbonate (PC), polystyrene, high impact polystyrene, acrylonitrile polystyrene copolymer, styrene resin such as ABS resin, cellulose film such as cellophane, cellulose triacetate, cellulose diacetate, and nitrocellulose.
And this light guide 8 is produced using, for example, a method of molding a heated raw material resin by extrusion molding or injection molding, a casting polymerization method of polymerizing and molding monomers, oligomers, etc. in a mold. Can do.

  As shown in FIG. 1, a plurality of light guides 8 are arranged in the vertical and horizontal directions so as to have substantially the same dimensions as the liquid crystal display element 3, the diffusion plate 9, and the optical sheet 10, and as shown in FIG. The thin end portions 8e, which are the end surfaces, are connected and fixed together by, for example, an adhesive. Therefore, the thin end 8e is preferably a flat surface that is substantially perpendicular to the emission surface 8a. Thus, a light guide unit 12 in which a plurality of light guides 8 are integrated is configured.

  Here, the adhesive is preferably the same material or the same refractive index as the material of the light guide 8 described above. In that case, since the refractive indexes of the light guide 8 and the adhesive are the same, the light transmitted through the light guide 8 passes through the adhesive linearly. Further, the adhesive does not necessarily have to be the same material as that of the light guide 8, and may not have the same refractive index.

Examples of the material for the adhesive include acrylic, urethane, rubber, and silicone adhesives. In order to improve resistance to stress such as warpage of the light guide 8, transparent fine particles such as beads may be mixed in the adhesive.

  When the thin end portions 8a and 8a of the light guides 8 and 8 are fixed and connected, an appropriate pressure-sensitive adhesive may be used instead of the adhesive, and the material of the pressure-sensitive adhesive is the same material as the above-described adhesive. The same material can be used, and transparent fine particles may be mixed. Furthermore, the light absorption of the adhesive or pressure-sensitive adhesive is preferably within 1%. If it exceeds 1%, the integrated light quantity emitted from the optical sheet 10 decreases, and the front luminance decreases. Or you may make it mutually adhere | attach by apply | coating oil.

Further, when the thin end portions 8a and 8a of the light guides 8 and 8 are connected to each other, the thin end portions 8a and 8a are welded to each other by a welder, for example, a laser welder 36, instead of an adhesive or an adhesive material. You may do it. In this case, since no other joining member such as an adhesive is interposed between the thin end portions 8a and 8a, the light transmission from the light source 7 is good.
Moreover, you may weld thin edge part 8a, 8a of the light guides 8 and 8 by plasma etc. using a plasma welding torch. Also, welding can be performed with ultrasonic waves, excimer laser, or the like.

  Further, instead of connecting the plurality of light guides 8 in this way, the light guide unit 12 may be integrally formed by extrusion molding or injection molding from the beginning.

As shown in FIG. 1, diffuse reflectors 17 (17 a, 17 b) are disposed on the back side and the side of the light guide unit 12 so as to surround the light guide unit 12.
The diffuse reflection plate 17a on the back side of the light guide unit 12 has a substantially plate shape having substantially the same dimensions as the light guide unit 12, and is parallel to the emission surface 8a of each light guide 8 and each light guide. It arrange | positions so that the opening edge part of the eight accommodating recessed parts 11 may be plugged up.
On the other hand, the diffuse reflection plate 17b on the side of the light guide unit 12 has a substantially plate shape as described above, and contacts the thin end portion on the outer side of the light guide 8 located on the outer periphery in the surface direction of the light guide unit 12. The light guides 8 are arranged so as to be in contact with each other and perpendicular to the emission surface 8a.

Such a diffuse reflection plate 17 is configured by forming a white layer or a metal layer on a plate-like substrate having a certain thickness. As a material for the white layer, for example, a composite material in which a white pigment made of an inorganic substance such as titanium dioxide, barium sulfate, and magnesium oxide is dispersed in a transparent resin can be used. As the metal layer, for example, a vapor deposition layer made of a material having high reflectivity and low light absorption such as silver and aluminum can be used.
The diffuse reflector 17 may be formed in a sheet shape and extremely thin.
Moreover, the diffuse reflection plate 17 is not limited to the above-described one, and may be formed of any material as long as the light from the light guide can be diffusely reflected. For example, a resin sheet in which a void is formed by kneading and stretching a filler or air in PET, PP (polypropylene) or the like to increase the reflectance may be used.

  Further, in the light source unit 30 of the present embodiment, the air layer 31 is provided between the diffuse reflector 17 and the inclined back surface 8d of each light guide 8 by disposing the diffuse reflector 17 as described above. Is partitioned.

  Therefore, the light emitted from the light source 7 enters the light guide 8 after being reflected directly or after being reflected by the diffuse reflection plate 17a that closes the opening edge of the housing recess 11. A part of the incident light passes through the inside of the light guide 8 and is directly emitted from the emission surface 8a of the light guide 8, and the other part is emitted from the emission surface 8a after being reflected by the inclined surface 8d. Further, some of the light passes through the inclined surface 8d, but the transmitted light is reflected by the diffuse reflector 17a through the air layer 31, and then enters the light guide 8 again and exits from the exit surface 8a. . In this way, the light guide 8 is configured to emit the light of the light source 7 from the entire emission surface 8a.

In the present embodiment, the angle θ formed between the diffuse reflector 17a on the back side of the light guide unit 12 and the inclined back surface 8d of each light guide 8 is substantially equal to that of the inclined back surface 8d shown in FIG. In the case of forming a quadrangular pyramid surface, it is set within the range of 28 ° ≦ θ ≦ 38 ° and 56 ° ≦ θ ≦ 73 °, and the inclined back surface 8d shown in FIG. Are set within the ranges of 19 ° ≦ θ ≦ 29 °, 31 ° ≦ θ ≦ 39 °, and 56 ° ≦ θ ≦ 72 °.
That is, the inclined back surface 8d forming a substantially quadrangular pyramid surface or a substantially conical surface in each light guide 8 is inclined so as to form the above-mentioned angle with the diffuse reflector 17a.

Further, the thickness of the light guide 8 and the ratio of the thickness between the central portion and the end in the surface direction of the light guide 8 are arbitrary depending on the dimensions of the light source 7, the light distribution on the exit surface 8a of the light guide 8, and the like. Can be changed.
In the light guide 8 configured as described above, the luminance distribution of light from the light source 7 on the emission surface 8a has the highest luminance at the central portion of the emission surface 8a, and goes toward the end of the emission surface 8a. The brightness decreases accordingly. That is, the region of the emission surface 8a that overlaps the light source 7 and the light guide 8 in the thickness direction is the illuminance or luminance peak region where the luminance of the light from the light source 7 is highest.

  As shown in FIG. 1, the light source unit 30 including the light guide unit 12, the light source 7, and the diffuse reflection plate 17 is housed in the housing 22, and the peripheral edge is held on the side surface of the housing 22. ing. In addition to the configuration shown in FIG. 1, the diffusion plate 9 and the optical sheet 10 in addition to the light guide unit 12 may be held substantially in parallel with each other by the side surface of the housing 22, Further, the liquid crystal display element 3 may be held.

Further, as shown in FIG. 1, a diffusion plate 9 that diffuses light emitted from the emission surface 8 a is disposed on the light emission direction front side of the light guide unit 12. The light diffusing plate 9 is configured by dispersing and mixing fine particles (light diffusing particles) for scattering light into a transparent resin material, and is disposed through a slight space from the emission surface 8a of the light guide 8. Has been. It is necessary to adopt fine particles having a refractive index different from that of the transparent resin material constituting the diffusion plate 9. As a result, the light incident on the diffusion plate 9 is refracted by the fine particles, sufficiently scattered, diffused substantially uniformly, and emitted toward the optical sheet 10. In place of the fine particles, fine cavities containing air may be dispersed and mixed.
Further, the emission surface 9 a of the diffusion plate 9 that emits light toward the optical sheet 10 is formed flat like the emission surface 8 a of the light guide 8.

  The optical sheet 10 is configured to transmit light emitted from the light exit surface 8 a of the light guide 8 and enter the light toward the liquid crystal display element 3. The optical sheet 10 is formed, for example, in a rectangular shape in plan view, and has a light-transmitting base material 19 and a prism lens arranged on the light-emitting surface of the light-transmitting base material 19 on the liquid crystal display element 3 side. Part 20.

  In the prism lens unit 20, for example, a plurality of unit prisms 20a having a triangular cross section and continuously extending in one direction (for example, a direction orthogonal to the paper surface in FIG. 1) are arranged in a direction orthogonal to the extending direction. The unit prism 20a has a pitch larger than the wavelength of the light, collects light in a direction away from the liquid crystal display element 3 incident through the diffusion plate 9, and passes the liquid crystal display element 3 on the axis toward the viewer. Turn around.

  In this way, when observing the liquid crystal display element 3, the prism lens unit 20 increases the on-axis luminance by reducing the off-axis luminance. The on-axis here is a direction that coincides with the visual direction of the viewer, and is generally a normal direction to the display screen.

  When the repetitive array structure of the prism lens unit 20 is arranged in only one direction, the direction change or recycling in the parallel direction is possible. In order to control the luminance of the display light in two directions orthogonal to each other in the horizontal plane, the two optical sheets 10 may be overlapped and combined so that the parallel directions of the unit prisms 20a group are substantially orthogonal to each other.

  The prism lens unit 20 is formed by a known extrusion molding method, injection molding method, or hot press molding method using, for example, PET, PC, PMMA, COP (cycloolefin polymer), acrylonitrile styrene copolymer, or the like. . In this case, the translucent base material 19 and the prism lens portion 20 may be made of different materials from different base materials, or may be integrally formed from one base material made of the same material. .

  In addition, instead of the prism lens unit 20 as the optical sheet 10, an approximately semi-cylindrical lenticular lens or a microlens array arranged on the translucent substrate 19 may be used as the lens sheet. These may have a lens shape with an asymmetric cross-sectional shape. For example, a cross-sectional shape in which one side is formed in a linear shape and the other is formed in a convex curved shape on the outside, and the above-described linear shape and the curved shape are rounded and connected at the lens apex portion.

  In the present embodiment, an air layer is formed by providing spaces among the light guide unit 12, the diffusion plate 9, and the optical sheet 10. By these air layers, the light emitted from the light guide unit 12, the diffusion plate 9, and the optical sheet 10 is collected, and the light that comes off the liquid crystal display element 3 can be further reduced.

Since the display device 1 according to the present embodiment has the above-described configuration, when the liquid crystal display element 3 is illuminated by the backlight unit 2, when the light source 7 of the light source unit 30 is turned on in the housing 22, the light source 7 The light emitted into the light guide 8 is emitted radially.
Then, a part of the light passes through the upper part of the recess 11 and reaches the emission surface 8a, and the other part of the light is reflected by the inclined back surface 8d and travels in the direction of the emission surface 8a. Furthermore, a part of the light is reflected by the diffuse reflection plate 17a that closes the opening edge of the housing recess 11, and then travels toward the emission surface 8a.

The light leaking from the inclined back surface 8d is refracted by the difference in refractive index between the light guide 8 and the air layer 31 at the boundary between the inclined surface 8d and the air layer 31, and when passing through the air layer 31, the air layer 31. It is diffused as needed by receiving the contribution of the diffusion effect.
Further, as shown in FIG. 5, such light is diffused to a certain range while being reflected by the diffusive reflecting plate 17, and then refracted again by the inclined back surface 8d to be guided to the range of the angle φ. Re-enters the light body 8 and travels toward the exit surface 8a.

    In this way, the light emitted from the light source 7 is dispersed and passes over the entire emission surface 8a, but the luminance directly above the light source 7 is the highest, and the luminance is slightly reduced toward the surrounding thin end 8e. Then, the light emitted from each emission surface 8a of the light guide unit 12 enters the diffusion plate 9, is refracted and scattered by the fine particles, and enters the optical sheet 10 in a substantially uniformly diffused state.

  In the optical sheet 10, the light is refracted and condensed by the unit prisms 20 a arranged in the prism lens unit 20, and enters the liquid crystal display element 3. Therefore, the light condensed by the liquid crystal display element 3 has high on-axis luminance, and the peak width of the luminance distribution curve is appropriately widened so that the liquid crystal image can be visually recognized by the observer.

  And in the light source unit 30 in such a display apparatus 1, only the plate-like diffuse reflection plates 17a and 17b are disposed on the back side and the side of the light guide unit 12, and the inclined back surfaces of the respective light guides 8 are arranged. Since the light emitted from 8d can reenter the light guides 8, the light source unit 30 can be easily configured while maintaining high light use efficiency.

  In addition, since the air layer 31 is formed between the diffuse reflector 17 and the inclined back surface 8d of each light guide 8, it is possible to receive the contribution of the diffusion effect in the air layer 31, and the air layer 31. By utilizing the refractive index of the light guide 8 and the light reflected by the diffuse reflector 17, the light re-entering the light guide 8 after being reflected by the diffuse reflector 17 can be appropriately refracted to rise in the front direction. Thereby, the luminance distribution emitted from the emission surface 8a can be made uniform, and the facet luminance can be improved.

  In the light source unit 31 according to the present embodiment, the angle θ formed between the inclined back surface 8d of the light guide 8 and the diffuse reflector 17a is such that the inclined back surface 8d shown in FIG. 3A forms a substantially quadrangular pyramid surface. In this case, they are set within the ranges of 28 ° ≦ θ ≦ 38 ° and 56 ° ≦ θ ≦ 73 °, and the inclined back surface 8d shown in FIG. 3B forms a substantially conical surface. Is set within the ranges of 19 ° ≦ θ ≦ 29 °, 31 ° ≦ θ ≦ 39 °, and 56 ° ≦ θ ≦ 72 °, so that the light guide is described in detail in the examples below. Thus, the light re-entering the light guide 8 after leaking from the inclined back surface 8d can be narrowed down to an optimum range, and the luminance distribution and the front luminance can be optimized.

The present invention is not limited to the light source unit 30, the backlight unit 2, and the display device 1 according to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.
Other embodiments and modifications of the present invention will be described below, but the same or similar parts and members as those of the light source unit 30, the backlight unit 2, and the display device 1 according to the first embodiment described above are the same. This will be described using reference numerals.

  For example, the concave portion 11 of the light guide 8 is not limited to a substantially U-shaped cross section, and various modifications are possible. The inner surface of the concave portion 11 may be an appropriate inner surface such as a substantially U-shaped or V-shaped cross section. What has a shape is employable. FIG. 6 illustrates the recess 11 of the light guide 8 according to the first modification.

In FIG. 6A, the upper surface of the recess 11 on the exit surface 8a side may be a flat surface. In this case, the central portion of the exit surface 8a of the light guide 8 can be further brightened.
Further, for example, as shown in FIGS. 6B to 6F, the upper surface of the recess 11 may be formed in a tapered shape. In this case, the luminance of the region immediately above the light source 7 on the emission surface 8a is relatively low. be able to. In the case of a tapered shape, a V-shape as shown in FIG. 6B, a curved shape that swells inside the recess 11 as shown in FIG. 6C, and an outer side of the recess 11 as shown in FIG. 6D. It is good also as the curved surface shape which swells.

  Moreover, it is good also as a shape which combined several flat surfaces and curved surfaces like FIG.6 (e), (f), In this case, the freedom degree of the light distribution distribution in the output surface 8a of the light guide 8 improves. To do. Furthermore, the recess 11 may adopt a shape obtained by appropriately combining, for example, the shapes shown in FIGS.

  As a second modification, a rod-like light source such as a cold cathode tube may be adopted as the light source 24 instead of the point light source as the light source 7 of the light guide 8. That is, the light guide 25 shown in FIG. 7 has a substantially U-shaped receiving recess 26 in the thick portion 25c of the back surface 25b facing the light exit surface 25a, as in the light guide 8 according to the first embodiment. Is formed. A light source 24 such as a cold cathode tube is accommodated in the recess 26. Therefore, the concave portion 26 has a substantially U-shaped cross section extending in a tunnel shape along the extending direction of the light source 24.

  Further, on the back surface 25b, inclined surfaces 25d are provided from the thick portion 25c toward both sides of the light source 24 and are connected to the thin end portion 25e. Therefore, the light guide 8 is formed so as to be substantially line symmetrical with respect to a plane perpendicular to the emission surface 25 a including the light source 24.

  In addition to the cold cathode tube, the light source 24 includes, for example, a normal fluorescent tube, a hot cathode tube, an external electrode tube, LEDs and semiconductor lasers arranged in a row, and in particular, a cold cathode tube, an external electrode, and the like. It is preferable to use LEDs arranged in tubes or rows.

  Furthermore, as a third modification, the light guide 27 may be provided with a flat surface 27 f parallel to the emission surface 8 a around the opening edge of the housing recess 11 of the light guide 8. Thereby, since a contact area with the diffuse reflection board 17 can be ensured, it becomes possible to improve the adhesion degree and installation balance between the light guide 8 and the diffuse reflection board 17.

  Next, a display device 40 according to a second embodiment of the present invention will be described with reference to FIG. A display device 40 shown in FIG. 11 has substantially the same configuration as the display device 1 including the backlight unit 2 according to the first embodiment. As a difference, the light control sheet 41 is disposed between the light guide unit 12 configured by connecting the light guides 8 and 8 and the diffusion plate 9.

  In the display device 40 according to the second embodiment, with respect to the plurality of light guides 8 constituting the light guide unit 12, the light guides 8 and 8 are connected to the thin end portions 8e and 8e as in the first embodiment. Has been. In addition, the diffuse reflector 17 surrounding the light guide 8 from the back side and the side is also integrally connected.

  Next, the light control sheet 41 will be described. The light control sheet 41 is formed in a rectangular shape in plan view, and has a light-transmitting base 42 and a light exit surface 8 a of each light guide 8 on the light incident surface side of the light-transmitting base 42. And a light reflecting layer 43 provided so as to face each other. Normally, the illuminance or luminance distribution of the light emitted from the light source 7 from the light exit surface 8a of the light guide 8 is highest in the region directly above the light source 7, and the illuminance or luminance increases from the region directly above to the thin edge 8e side of the periphery. Tend to decrease gradually. In order to equalize the illuminance or luminance distribution for each light guide 8 to a more uniform distribution, the light reflecting layer 43 is provided in the second embodiment.

  That is, in the light control sheet 41, the light reflection layer 43 partially reflects the light from the light exit surface 8 a of each light guide 8 toward the translucent substrate 42, so that the liquid crystal display element 3 side from the light control sheet 41. Is controlled so as to make the luminance distribution or illuminance distribution of the emitted light more uniform.

  The light reflection layer 43 includes light reflection portions 44 that reflect light incident on the light control sheet 41 and openings 45 that are provided between adjacent light reflection portions 44 and 44 and transmit light alternately. A plurality are formed.

  The light reflecting portion 44 of the light reflecting layer 43 is formed of, for example, a white layer or a metal layer. As a material of the white layer, for example, a white pigment made of an inorganic material such as titanium dioxide, barium sulfate, and magnesium oxide is mixed in the transparent resin. The composite material made can be used. Moreover, as a metal layer, the vapor deposition layer which consists of a material with high reflectivity, such as silver and aluminum, and little light absorption can be used, for example.

  And although the light reflection layer 43 may be directly formed in the incident surface side of the translucent base material 42 by printing or vapor deposition, you may form by transfer, for example. When forming the light reflection layer 43 by transfer, for example, a photosensitive resin film is attached to the light incident surface of the translucent substrate 42, and the surface opposite to the photosensitive film with respect to the translucent substrate 42. A lens portion is provided on the photosensitive resin film, and the photosensitive resin film is exposed to ultraviolet rays through the translucent substrate 42. Thereby, the adhesive force of the photosensitive resin film is reduced only in the focal point of the lens unit and the region in the vicinity thereof due to the condensing action of the lens unit.

  Thereafter, the laminate of the translucent substrate 42 and the photosensitive resin film is pressed onto the release paper, and then the laminate is peeled from the release paper. In this way, the light reflecting layer 43 having the opening 45 in the focal point of the lens unit and the region in the vicinity thereof is obtained. Each opening 45 of the light reflecting layer 43 formed in this way is formed so that its central axis coincides with the optical axis of the corresponding lens part.

  Even when the printing method is used, for example, as described above, the light reflection layer 43 can be easily formed by printing by providing a step on the light incident surface when the light-transmitting substrate 42 is manufactured. . However, in order to make the central axis of each opening 45 of the light reflecting layer 43 coincide with the optical axis of the lens part, it is necessary to relatively align the lens part and the formation position of the step.

  As described above, in the backlight unit 2 according to the present embodiment, the opening formed at the position corresponding to the region where the luminance or illuminance of light from the light source 7 is highest in the emission surface 8a of the light guide 8. 45 is formed to be the smallest, and the opening 45 is formed to be larger in a region where the luminance of light on the light exit surface 8a of the light guide 8 is lower.

For this reason, the amount of light blocked in the light reflecting layer 43 can be increased as the luminance of light on the light exit surface 8a of the light guide 8 is increased. Therefore, even if the luminance distribution of light on the exit surface 8 a of the light guide 8 is nonuniform, the light emitted from the exit surface 8 a of the light guide 8 passes through each opening 45 of the light reflecting layer 43. In addition, it is possible to efficiently suppress luminance unevenness of light emitted from the emission surface of the translucent substrate 42.
Furthermore, since the diffusion plate 9 and the optical sheet 10 are provided on the light emission side of the light control sheet 41, the luminance unevenness and the illuminance unevenness of the light incident on the liquid crystal display element 3 from the light source 7 can be further reduced.

  In the third embodiment, the light control sheet 41 is provided separately from each light exit surface 8a of the light guide unit 12, but instead, the light reflecting layer 43 is brought into contact with each light exit surface 8a. You may make it suppress a deformation | transformation by pressing. Alternatively, a transparent flat sheet material is installed between the light control sheet 41 and each light exit surface 8a of the light guide unit 12, and the light reflection layer 43 of the light control sheet 41 is brought into contact with the sheet material. Thus, each emission surface 8a may be pressed flat. Alternatively, the diffusing plate 9 may be provided between the light guide unit 12 and the light control sheet 41 so as to be pressed against each emission surface 8a.

  In the light guide 8 shown in FIGS. 3A and 3B, the angle θ formed by the inclined back surface 8d and the diffuse reflector 17, that is, the inclination angle is changed from the exit surface of the light guide. A numerical simulation was performed to investigate the light intensity distribution of the emitted light.

  As conditions, the shape and size of the exit surface 8a of the light guide plate 8 is a square shape of 30 mm × 30 mm, the storage recess 11 is a cone shape having a diameter of 2 mm and a height of 2 mm, and the refractive index of the light guide 8 is 1. 52.

10 to 15 show the simulation results of the light intensity distribution on the exit surface 8a for the light guide 8 in which the inclined back surface 8d shown in FIG. 3B forms a conical surface. The horizontal axis is the emission angle, and the vertical axis is the relative light intensity. The relative light intensity is a value normalized with the light intensity at an emission angle of 0 ° as 1. In general, it is preferable that the light distribution is maximum at the front (an emission angle of 0 °) and that no sidelobe light is generated. Furthermore, experience has shown that when the relative light intensity is greater than 1.5, it is visually recognized as luminance unevenness.
Based on the above, when viewing FIG. 10 to FIG. 15, when θ <19 °, 29 ° <θ <31 °, and 39 <θ <56 °, the value of relative light intensity exceeds 1.5 depending on the emission angle. ing. In this case, it is not preferable because it is visually recognized as luminance unevenness at the observation angle.
Therefore, in the light guide 8 in which the inclined back surface 8d forms a conical surface, the angle θ formed by the inclined back surface 8d and the diffuse reflector 17 is 19 ° ≦ θ ≦ 29 °, 31 ° ≦ θ ≦ 39 °, 56 °. By setting within the range of ≦ θ ≦ 72 °, luminance unevenness can be suppressed.

16 to 19 show the simulation results of the light intensity distribution on the exit surface 8a for the light guide 8 in which the inclined back surface 8d shown in FIG. 3A forms a quadrangular pyramid surface.
As can be seen, when θ <28 ° and 38 ° <θ <56 °, the value of the relative light intensity exceeds 1.5 depending on the emission angle. In this case, it is not preferable because it is visually recognized as luminance unevenness at the observation angle.
Further, when 73 ° <θ, the half-value angle is smaller than 25 °, so that the brightness in the front direction increases and the brightness in the oblique direction decreases. It is known from experience that such a case is observed as luminance unevenness.
Therefore, in the light guide 8 in which the inclined back surface 8d forms a quadrangular pyramid surface, the angle θ formed by the inclined back surface 8d and the diffuse reflector 17 is in the range of 28 ° ≦ θ ≦ 38 ° and 56 ° ≦ θ ≦ 73 °. By setting the value within the range, luminance unevenness can be suppressed.

Further, if the luminance unevenness can be suppressed as in the above two cases, useless light emitted in the lateral direction can be reduced, so that an improvement in front luminance can be expected.
Furthermore, in this simulation, the case of a point light source was performed, but also in the case of a rod-shaped light source, by setting the angle of the inclined back surface as in the light guide shown in FIG. Improvements can be made.

It is a schematic sectional drawing which shows the display apparatus by 1st embodiment of this invention. It is a specific explanatory view of a point light source. It is a perspective view which shows the light source and light guide in the display apparatus shown in FIG. 1, (a) is the case where an inclined back surface forms a substantially quadrangular pyramid surface, (b) is an inclined back surface forming a substantially conical surface. This shows the case. It is a schematic diagram which shows the arrangement | sequence of each light guide of the light guide unit in the display apparatus shown in FIG. It is a figure which shows the advancing direction of the light in the light source unit in 1st embodiment. (A)-(f) is a figure which shows the modification of the shape of a light guide. It is a perspective view of the light guide by the modification using a rod-shaped light source. It is a perspective view of the light guide which has a flat surface around a storage recessed part. It is a schematic sectional drawing which shows the display apparatus by 2nd embodiment of this invention. This is a light distribution when the inclined rear surface of the light guide is a curved surface (substantially conical). This is a light distribution when the inclined rear surface of the light guide is a curved surface (substantially conical). This is a light distribution when the inclined rear surface of the light guide is a curved surface (substantially conical). This is a light distribution when the inclined rear surface of the light guide is a curved surface (substantially conical). This is a light distribution when the inclined rear surface of the light guide is a curved surface (substantially conical). This is a light distribution when the inclined rear surface of the light guide is a curved surface (substantially conical). It is a light distribution when the inclined back surface of the light guide is a flat surface (substantially a quadrangular pyramid shape). It is a light distribution when the inclined back surface of the light guide is a flat surface (substantially a quadrangular pyramid shape). It is a light distribution when the inclined back surface of the light guide is a flat surface (substantially a quadrangular pyramid shape). It is a light distribution when the inclined back surface of the light guide is a flat surface (substantially a quadrangular pyramid shape). It is a figure which shows the conventional light-guide unit.

Explanation of symbols

1, 40 Display device 2 Backlight unit 3 Liquid crystal display element (image display unit)
7, 24 Light source 8, 25 Light guide 8a, 25a Outgoing surface 8c, 25c Thick part 8e, 5e Thin end 9 Diffusion plate 10 Optical sheet 11, 26 Storage recess 12 Light guide unit 17 Diffusion reflector 41 Light control Sheet 43 Light reflection layer 44 Light reflection portion 45 Opening portion

Claims (13)

A light exit surface, a thick portion formed near the center of the exit surface, an accommodation recess formed in the thick portion on the back surface facing the exit surface, and an end of the exit surface A plurality of light guides arranged along the exit surface, and a thin-walled end portion and an inclined back surface inclined so that the thickness gradually decreases from the thick-walled portion toward the thin-walled end portion on the back surface. A light guide unit made of,
A light source accommodated in an accommodating recess of each light guide in the light guide unit;
A substantially plate-like diffuse reflector disposed opposite to the back surface of the light guide unit;
An air layer is defined between the inclined back surface and the diffuse reflector.   2. The light source according to claim 1, wherein the light source is a point light source, and the light guide is point-symmetric with respect to a central axis that includes an axis of the point light source of the housing recess and is perpendicular to the emission surface. unit.   The light source unit according to claim 2, wherein the inclined back surface of each light guide body forms a substantially conical surface.   The angle θ formed by the inclined back surface and the diffuse reflector is set in the range of 19 ° ≦ θ ≦ 29 °, 31 ° ≦ θ ≦ 39 °, and 56 ° ≦ θ ≦ 72 °. The light source unit according to claim 3.   The light source unit according to claim 2, wherein the inclined back surface of each light guide body forms a substantially quadrangular pyramid surface.   2. The light source unit according to claim 1, wherein the light source is a rod-shaped light source, and the light guide has a shape that is symmetrical with respect to a plane that includes an axis of the rod-shaped light source of the housing recess and is orthogonal to the emission surface.   The light source according to claim 5 or 6, wherein an angle θ formed by the inclined back surface and the diffuse reflector is set in a range of 28 ° ≦ θ ≦ 38 ° and 56 ° ≦ θ ≦ 73 °. unit.   The light source unit according to any one of claims 1 to 7, wherein a diffuse reflector is provided so as to surround an end portion in the surface direction of the light guide unit.   The light source unit according to any one of claims 1 to 8, wherein the light guide unit is integrally formed. The light source unit according to any one of claims 1 to 9,
A backlight unit comprising: an optical sheet that is disposed to face the emission surface of the light guide unit and that controls light emitted from the emission surface.   The backlight unit according to claim 10, wherein a light diffusion plate mixed with light diffusion particles is provided between the light source unit and the optical sheet. Between the light source unit and the light diffusion plate,
A light-transmitting substrate and a light-reflecting layer disposed on the incident surface side of the light-transmitting substrate, the light-reflecting layer having an opening that transmits light and a light-reflecting portion that reflects light And a light control sheet with
The area of the opening of the light control sheet is reduced in a region with high illuminance or brightness of light transmitted through the light exit surface of the light guide, and the area of the opening is set large in a region with low illuminance or brightness. The backlight unit according to claim 11.   The backlight unit according to any one of claims 10 to 12, and an image display unit that is disposed on an emission surface side of the optical sheet and displays an image using light from the backlight unit as display light. A display device characterized by comprising:

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