JP2012048914A - Lighting device and liquid crystal display using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fix intensity and a light-distribution angle of emitted light of a lighting device irrespective of distances from a light source.SOLUTION: Reflecting prisms 9 for deflecting light from the light source 1 in an emitting surface direction by reflecting the light and diffusion prisms 10 for deflecting the light in the emitting surface direction by diffusing the light are arranged on at least either of an emitting surface and an opposite surface of a light guide plate 2 in order to control a vertical component and a diffusion component of the emitted light.

Description

  The present invention relates to an illumination device having a flat light emitting surface and a liquid crystal display device using the same.

  Liquid crystal display devices are widely used in portable devices such as notebook personal computers, mobile phones, PDAs, and electronic dictionaries. Since the liquid crystal display device is not a self-luminous display device, it is necessary to incorporate a flat illumination device on the back of the liquid crystal display panel. Since lighting devices for portable devices are required to be thin, it is not possible to use a thick light-emitting source on the back surface of the liquid crystal display panel. On the other hand, this type of display device needs to increase the intensity of illumination light so that it can be seen outdoors during the day. In addition, uniform light emission without uneven brightness is desired for the displayed image. Therefore, a sidelight type lighting device has been studied. In the sidelight type lighting device, since the light source can be installed on the side of the light emitting surface, the entire thickness can be reduced.

  Conventionally, in order to achieve both high intensity of illumination light and uniform light emission, the concave / convex prism is formed so as to be orthogonal to the light emitted radially from the point light source. A light guide plate for controlling the thickness has been proposed (see Patent Document 1). FIG. 11A is a top view showing a diffusion pattern formed on the lower surface of the light guide plate of the illumination device 3 described in Patent Document 1. FIG. The light source 30 is attached to the light guide plate 22 with its exit surface in contact with the incident surface 26 of the light guide plate 22. Light incident from the light source 30 is introduced into the light guide plate 22 and propagates through the light guide plate 22 by total reflection while spreading radially around the light source 30. The diffusion pattern 24 formed on the light guide plate 22 includes a large number of diffusion pattern elements 24a, and these diffusion pattern elements 24a are arranged concentrically around the light source 30 corresponding to the guided light propagating while spreading radially. Has been.

International Publication No. 98/19105

  However, in the illumination device described in Patent Document 1, since the diffusion pattern 24a formed by the concave and convex prisms on the light guide plate is formed at an angle orthogonal to the light source, the distribution of the emitted light depends on the distance from the light source. The light angle changes. FIG. 1B is a schematic longitudinal sectional view of a conventional lighting device 3. The arrows in the drawing indicate the light distribution characteristics of the emitted light. As illustrated, in the light guide plate 22, the light distribution angle of the emitted light is large at a position where the distance from the point light source 30 is short, and the light distribution angle of the emitted light is small at a position where the distance from the point light source 30 is long. That is, as the distance from the light source 30 becomes longer, the light emitted from the light guide plate 22 has more light components perpendicular to the light guide plate 22, and light components having various angles with respect to the light guide plate 22. It will decrease. This is because, in general, in sidelight type lighting devices, there are various angles of light inside the light guide plate at positions where the distance from the light source is short, but at positions where the distance from the light source is long, there is an angle. This is because light is reduced and much light parallel to the light guide plate remains. For this reason, in the vicinity of the light source 30, light of various angles hits the diffusion pattern element 24 a, and light having a higher diffusibility than the position away from the light source 30 is emitted. On the other hand, at a position away from the light source 30, light parallel to the light guide plate hits the diffusion pattern element 24 a, and light having higher directivity in the vertical direction than the vicinity of the light source 1 is emitted. Thus, in the conventional illumination device, the light distribution angle of the emitted light changes according to the distance from the light source 1.

  FIG. 1C is a schematic longitudinal sectional view of a liquid crystal display device 4 in which a liquid crystal display panel 5 is mounted on a conventional illumination device 3. In the illumination device 3, the intensity C1 is set to be equal so that uniform light emission is obtained. However, as described above, the light distribution angle of the emitted light changes according to the distance from the light source 30. When transmitting through a medium having a low transmittance such as the liquid crystal display panel 5, the intensity of the emitted light having a small light distribution angle is larger than that of the output light having a large light distribution angle. For this reason, in the liquid crystal display device 4 in which the liquid crystal display panel 5 is mounted on the conventional illumination device 3, a difference occurs in the intensity C <b> 2 according to the distance from the point light source 30, and uniform light emission cannot be obtained. Accordingly, the unevenness of the liquid crystal display device is increased.

  In order to solve the above problem, a first light deflecting light from a light source in a direction perpendicular to the exit surface is provided on at least one of the exit surface and the opposite surface (surface opposite to the exit surface) of the light guide plate of the lighting device. And a second prism for diffusing light from the light source. Thereby, the vertical component and the diffusion component of the emitted light can be controlled, and the intensity and the light distribution angle of the emitted light can be made constant regardless of the distance from the light source.

  The first prism is provided with a planar reflecting surface, and the light from the light source is reflected by this reflecting surface and deflected in the direction perpendicular to the emitting surface. The second prism is provided with a curved diffusion surface, and light from the light source is diffused by this diffusion surface. The first prism and the second prism may be formed in a concave shape on the opposing surface of the light guide plate.

  Alternatively, a prism sheet may be provided on the exit surface of the light guide plate, and the first prism and the second prism may be formed on at least one of the front surface and the back surface of the prism sheet. The first prism is provided with a planar refracting surface, and the light from the light source is refracted by this refracting surface and deflected in a direction perpendicular to the emitting surface. The second prism is provided with a curved diffusion surface, and light from the light source is diffused by this diffusion surface.

Furthermore, the first prism and the second prism may be formed so that the density changes according to the distance from the light source.
Alternatively, the first prism and the second prism may be formed so that the size changes according to the distance from the light source.

Alternatively, the shape of the first prism may be changed to the shape of the second prism according to the distance from the light source.
In the liquid crystal display device of the present invention, a liquid crystal display panel is disposed on the exit surface of the above-described illumination device.

  The intensity of light emitted from the illumination device can be improved, and the light distribution angle can be made constant regardless of the distance from the light source. In addition, when the liquid crystal display element is mounted on the lighting device, a liquid crystal display device without unevenness can be realized.

It is a top view which shows typically the structure of the illuminating device of this invention. It is a perspective view which shows typically the structure of the illuminating device of this invention. It is a perspective view which shows the example of a shape of the reflective prism of this invention, and a diffusion prism. It is sectional drawing which shows the structure of the illuminating device of this invention typically. It is a perspective view which shows typically the structure of the illuminating device of this invention. It is a perspective view which shows typically the structure of the illuminating device of this invention. It is a top view which shows the example of a shape of the prism of the illuminating device of this invention. It is sectional drawing which shows the structure of the illuminating device of this invention typically. It is sectional drawing which shows typically the structure of the liquid crystal display device of this invention. It is sectional drawing which shows typically the structure of the liquid crystal display device of this invention. It is a figure which shows typically the structure of the conventional illuminating device and a liquid crystal display device.

  The illumination device of the present invention includes a first prism that deflects light from a light source in a direction perpendicular to the emission surface, and at least one of an exit surface of the light guide plate and an opposite surface opposite to the exit surface; A second prism for diffusing light is provided. That is, the light from the light source is converted into a light component in the direction perpendicular to the emission surface (hereinafter referred to as the vertical component) by the first prism, and the light from the light source is varied with respect to the emission surface by the second prism. It is converted into a light component having a certain angle (hereinafter referred to as a diffusion component). The vertical component and the diffusion component of the emitted light are controlled by these patterns, and the illuminating device can make the intensity and the light distribution angle of the emitted light constant regardless of the distance from the light source.

  The first prism is provided with a planar reflecting surface, and the light from the light source is reflected by this reflecting surface and deflected in a direction perpendicular to the emitting surface. The second prism is provided with a curved diffusion surface, and diffuses light from the light source through this diffusion surface. These prisms may be formed in a concave shape on the opposing surface of the light guide plate.

  Alternatively, a prism sheet may be provided on the exit surface of the light guide plate, and the first prism and the second prism may be formed on at least one of the front surface and the back surface of the prism sheet. In this case, the first prism is provided with a planar refracting surface, and the light from the light source is refracted by this refracting surface and deflected in a direction perpendicular to the emitting surface. The second prism is provided with a curved diffusion surface, and diffuses light from the light source by the diffusion surface.

  Further, the first prism and the second prism may be formed so that the density and the size change according to the distance from the light source in order to control the vertical component and the diffusion component of the emitted light. The first prism and the second prism respectively form an arc-shaped first prism line and a second prism line centered on the light source, and the first prism line and the second prism line are alternately arranged. May be.

Alternatively, the vertical component and the diffusion component of the emitted light can also be controlled by forming the first prism so that its shape changes to the second prism according to the distance from the light source.
In the liquid crystal display device of the present invention, a liquid crystal display panel is disposed on the exit surface of the illumination device having the above-described configuration.
Hereinafter, the present invention will be specifically described with reference to the drawings.

  1 and 2 are a top view and a perspective view of the illumination device 11 of the present embodiment. As shown in the drawing, a light source 1 is disposed on the side of the light guide plate 2. A reflecting prism 9 and a diffusing prism 10 are formed on the entire lower surface of the light guide plate 2, that is, on the opposite surface opposite to the exit surface. The reflecting prism 9 and the diffusing prism 10 are arranged in an arc shape with the light source 1 as the center, and the arc-shaped reflecting prism line and the diffusing prism line are alternately arranged. In this embodiment, the reflecting prism 9 has a shape obtained by rolling over a triangular prism having a triangular cross section, and the diffusion prism 10 has a conical shape.

  FIG. 3 is a perspective view showing an example of the shape of the reflecting prism 9 and the diffusing prism 10 used in this embodiment. FIG. 3A to FIG. 3C are examples of the shape of the reflecting prism 9. 3A shows a quadrangular pyramid shape, FIG. 3B shows a shape obtained by overturning a right triangular prism, and FIG. 3C shows a shape obtained by overturning an isosceles triangular prism. Each shape has a flat surface 9a facing the light source 1, and this flat surface 9a serves as a reflecting surface, reflects light from the light source, and changes the direction in a direction perpendicular to the emitting surface. FIG. 3D to FIG. 3F are examples of the shape of the diffusion prism 10. 3D shows a conical shape, FIG. 3E shows a truncated cone shape, and FIG. 3F shows a hemispherical shape. Each of the shapes has a curved surface 10a facing the light source 1, and the curved surface 10a reflects and diffuses light from the light source and emits it from the emitting surface. The shapes of the reflecting prism 9 and the diffusing prism 10 are not limited to these examples as long as they have the functions described above. In other words, the reflection prism 9 may have a shape having a plane that deflects light from the light source in a direction perpendicular to the emission surface. In addition, the diffusion prism 10 may have a curved surface facing the light source 1.

  Next, the light distribution characteristic of the emitted light of the illuminating device of a present Example is demonstrated using FIG. FIG. 4 is a longitudinal sectional view schematically showing the configuration of the illumination device 11 of this embodiment. Also, the circle including the arrow and the three arrows in FIG. 4 schematically shows the light distribution characteristics of the emitted light. The light guide plate 2 has a flat plate shape and has an exit surface 7 and an opposing surface 8. A light source 1 is disposed on the side of the light guide plate 2. A reflection prism 9 and a diffusion prism 10 are formed in a concave shape on the facing surface 8 of the light guide plate 2. The reflecting prism 9 reflects the light from the light source 1 and converts it into a light component (vertical component) perpendicular to the exit surface 7. The diffusion prism 10 converts light from the light source 1 into light components (diffusion components) having various angles with respect to the emission surface. The vertical and diffuse components of the emitted light are controlled by the reflecting prism 9 and the diffusing prism 10. Therefore, as illustrated, in the illumination device 11, the intensity of the emitted light and the light distribution angle are constant regardless of the distance from the light source 1.

  FIG. 5 is a perspective view schematically showing the lighting apparatus according to the present embodiment. The present embodiment is different from the first embodiment in that the diffusion prism 10 is formed so that the density changes according to the distance from the light source 1. Since other configurations are the same as those of the first embodiment, description thereof is omitted. In this embodiment, the density of the diffusion prism 10 is low at a position where the distance from the light source 1 is short, and the density of the diffusion prism 10 is high at a position where the distance from the light source 1 is long. Therefore, the diffusion component can be further increased at a position away from the light source 1, and the intensity of the emitted light and the light distribution angle are constant regardless of the distance from the light source 1. In FIG. 5, the configuration in which the density of the diffusing prism 10 changes according to the distance from the light source 1 has been described. However, the configuration in which the density of the reflection pattern 9 changes according to the distance from the light source 1 may be used. A configuration in which the densities of both the prism 9 and the diffusing prism 10 change according to the distance from the light source 1 may be adopted.

  FIG. 6 is a perspective view schematically showing the lighting apparatus according to the present embodiment. The present embodiment is different from the first embodiment in that the diffusing prism 10 is formed so that the size changes according to the distance from the light source 1. Since other configurations are the same as those of the first embodiment, description thereof is omitted. In this embodiment, the size of the diffusion prism 10 is small at a position where the distance from the light source 1 is short, and the size of the diffusion prism 10 is large at a position where the distance from the light source 1 is long. Therefore, the diffusion component can be further increased at a position away from the light source 1, and the intensity of the emitted light and the light distribution angle are constant regardless of the distance from the light source 1. In FIG. 6, the configuration in which the size of the diffusing prism 10 changes according to the distance from the light source 1 has been described, but the configuration in which the size of the reflective pattern 9 changes according to the distance from the light source 1 may be used. The size of both the prism 9 and the diffusion prism 10 may be changed according to the distance from the light source 1. It is desirable that the sizes of the reflecting prism 9 and the diffusing prism 10 change in a similar shape.

  In Examples 1 to 3 described above, two types of patterns of the reflecting prism 9 and the diffusing prism 10 are alternately arranged. In this embodiment, the shape of the reflecting prism 9 is changed to the shape of the diffusing prism 10 according to the distance from the light source.

  7A to 7D are top views showing changes in the shape of the reflecting prism 9 of this embodiment. The reflecting prism 9 has a plane facing the light source 1 like a quadrangular pyramid shape in FIG. 7A at a position where the distance from the light source 1 is short. As the distance from the light source 1 is increased, the square pyramid-shaped corners of FIGS. 7B and 7C are removed, the plane facing the light source 1 is reduced, and the curved surface facing the light source 1 is increased. A position having a sufficiently long distance from the light source 1 has a curved surface facing the light source 1 as shown in FIG. That is, as the reflecting prism 9 is moved away from the light source, its shape and function are changed to become the diffusing prism 10.

  In this way, by changing the shape of the reflecting prism 9 according to the distance from the light source 1, the intensity of the emitted light and the light distribution angle of the illumination device can be made constant regardless of the distance from the light source 1.

  FIG. 8 is a longitudinal sectional view schematically showing the illumination device according to the present embodiment. A light source 1 is disposed on the side of the flat light guide plate 2. The light guide plate 2 receives light from the light source 1 and exits from the exit surface 7. A prism sheet 13 is disposed above the light guide plate 2 so as to face the emission surface 7. On the back surface of the prism sheet 13, a deflection prism 14 that refracts the light emitted from the emission surface 7 and changes the direction in a direction perpendicular to the emission surface 7, and a diffusion prism that diffuses the light emitted from the emission surface 7. 15 is formed. The embodiment shown in FIGS. 7A to 7C can be used as the shape of the deflecting prism 14. In this case, the plane 9 a becomes a refracting surface, and light from the light source is refracted by the plane 9 a and redirected in a direction perpendicular to the emission surface 7.

  In this embodiment, the light guide plate 2 is not formed with a reflecting prism or a diffusing prism. Therefore, as shown in the drawing, the intensity C1 of the light emitted from the light guide plate 2 is constant regardless of the distance from the light source 1, but the light distribution angle changes according to the distance from the light source 1. That is, the diffusion component of the emitted light decreases as the distance from the light source increases. By using the prism sheet 13, the vertical component and the diffusion component of the light emitted from the prism sheet 13 are controlled, and the intensity C 2 and the light distribution angle of the emitted light from the illumination device 16 are constant regardless of the distance from the light source 1. .

  The deflecting prism 14 and the diffusing prism 15 may be formed on the back surface of the prism sheet 13, may be formed on the front surface, or may be formed on both surfaces. Further, as described in the second and third embodiments, the deflecting prism 14 and the diffusing prism 15 may be formed so that the density changes according to the distance from the light source 1, and the size changes. May be formed. Further, as described in the fourth embodiment, the deflection prism 14 may be formed so that its shape changes to the shape of the diffusion prism 15 according to the distance from the light source 1.

  FIG. 9 is a diagram schematically showing the liquid crystal display device of this example. The liquid crystal display device 12 includes the illumination device 11 having the structure of the above-described first to fifth embodiments and the liquid crystal display panel 5 installed on the upper surface thereof. In the liquid crystal display panel 5, two glass substrates are bonded to each other with a gap provided by a sealing material, a liquid crystal panel 19 having a liquid crystal layer (not shown) formed in the gap, and a polarizing plate 20 bonded to the upper and lower surfaces thereof. Formed from. An illuminating device 11 is installed on the back surface of the liquid crystal display panel 5 and irradiates illumination light from the back surface of the liquid crystal display panel 5. The illumination device 11 includes a light guide plate 2 and a light source 1 installed on a side surface thereof. A reflection sheet 17 is disposed on the back surface of the light guide plate 2. A diffusion sheet 18 is disposed between the light guide plate 2 and the liquid crystal display panel 5.

  When a structure using a prism sheet is used for the illumination device 11, the prism sheet is disposed between the liquid crystal display panel 5 and the diffusion sheet 18.

  Next, the light distribution characteristics of the liquid crystal display device of this embodiment will be described. FIG. 10 is a longitudinal sectional view schematically showing the configuration of the liquid crystal display device 12 of the present embodiment. In the liquid crystal display device 12, the liquid crystal display panel 5 is disposed above the emission surface 7 of the light guide plate 2. Since the intensity C1 of light emitted from the illumination device 11 and the light distribution angle are constant regardless of the distance from the light source 1, the intensity C2 of light emitted from the liquid crystal display panel 5 is also independent of the distance from the light source 1. It becomes constant. Therefore, the liquid crystal display device 12 without unevenness can be realized.

  In each of the embodiments described above, an LED can be used as the light source 1. The light guide plate 2 may be made of a translucent plastic material such as acrylic (PMMA), polycarbonate (PC), or cycloolefin polymer (COP), or glass. The reflecting prism 9 and the diffusing prism 10 can be simultaneously formed by injection molding in the process of creating the light guide plate 2. The light guide plate 2, the reflecting prism 9, and the diffusing prism 10 can be formed of the same material.

  Since the illumination device and the liquid crystal display device have a small intensity distribution, they can be applied to a transmissive display device.

DESCRIPTION OF SYMBOLS 1,30 Light source 2,22 Light-guide plate 3,11,16 Illuminating device 4,12 Liquid crystal display device 5 Liquid crystal display panel 7 Output surface 8 Opposite surface 9 Reflective prism 10,15 Diffusion prism 13 Prism sheet 14 Deflection prism 17 Reflective sheet 18 Diffusion sheet 19 Liquid crystal panel 20 Polarizing plate 24 Diffusion pattern 24a Diffusion pattern element 26 Incident surface

Claims (7)

In a lighting device comprising a light source and a light guide plate arranged on the side of the light source,
A first prism for deflecting light from the light source in a direction perpendicular to the emission surface, at least one of an emission surface of the light guide plate and an opposite surface opposite to the emission surface; A lighting device, wherein a second prism for diffusing light is provided. The first prism and the second prism are formed in a concave shape on the facing surface,
The first prism has a planar reflecting surface that reflects light from the light source and deflects it in a direction perpendicular to the exit surface, and the second prism has a curved surface shape that diffuses light from the light source. The illuminating device according to claim 1, further comprising a diffusion surface. A prism sheet is provided on the emission surface,
The first prism and the second prism are formed on at least one of the front surface and the back surface of the prism sheet,
The first prism has a planar refracting surface that refracts light from the light source and deflects it in a direction perpendicular to the exit surface, and the second prism has a curved surface shape that diffuses light from the light source. The illuminating device according to claim 1, further comprising a diffusion surface.   At least one of said 1st prism and said 2nd prism is formed so that a density may change according to the distance from the said light source, The any one of Claims 1-3 characterized by the above-mentioned. The lighting device described.   At least one of said 1st prism and said 2nd prism is formed so that a size may change corresponding to the distance from the said light source, The Claim 1 characterized by the above-mentioned. The lighting device described.   4. The illumination device according to claim 2, wherein the first prism is formed so that the shape thereof changes to the second prism as the distance from the light source increases. 5. In a liquid crystal display device comprising a light source, a light guide plate disposed on the side of the light source, and a liquid crystal display element disposed above the light guide plate,
A first prism for converting light from the light source into a light component in a direction perpendicular to the emission surface on at least one of an emission surface of the light guide plate and an opposite surface opposite to the emission surface; and the light source A liquid crystal display device comprising: a second prism that converts light from the light into light components having various angles with respect to the emission surface.

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