JP2013080054A - Display device and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device capable of reducing brightness unevenness on the display surface of a display panel.SOLUTION: The display device comprises: a liquid crystal panel unit 200; a frame member 204 for holding the liquid crystal panel unit 200; reflection type polarizing plates 202b and 202a provided on the rear face side of the frame member 204; and a plurality of light sources 301a to 301c which are provided on the rear face side of the frame member 204 with predetermined spaces therebetween, and irradiate the liquid crystal panel unit side with light through the frame member 204 and the reflection type polarizing plates 202b and 202a. The transmission axis of the reflection type polarizing plate 202b and the transmission axis of the reflection type polarizing plate 202a intersect with each other.

Description

  The present invention relates to a display device, and more particularly to a backlight device used for a rear liquid crystal of an imaging device and an imaging device including the backlight device.

  As a backlight device used in a liquid crystal display device, a direct type backlight device and an edge light type backlight device have been proposed. The direct type backlight device is a backlight device in which a plurality of light sources of the backlight are arranged directly below the liquid crystal display element. In the edge light type backlight device, the linear light source of the backlight is arranged at the edge portion of the liquid crystal display element, and the light is incident on the end face of the light guide plate, and the light is emitted to the rear surface side of the liquid crystal display element. It is a backlight device that performs display.

  Generally, the edge light type is more suitable for reducing the thickness of the backlight portion than the direct type. However, since the light source is disposed on the end face of the light guide plate, the edge light type has a large size in the width direction, which increases the cost of manufacturing the light guide plate.

  On the other hand, a direct type is used to increase the luminance of the light emitting surface. The direct type has higher utilization efficiency of the light beam emitted from the light source than the edge light type, and the brightness of the light irradiation surface can be easily increased. However, the direct type has a high luminance directly above the linear light source, which may cause a problem in luminance uniformity of the light emitting surface.

  Patent Document 1 discloses a direct type backlight device provided with a light diffusion plate, a reflective polarizing sheet, and a prism sheet in order from the light source side. This backlight device diffuses light from a light source by light diffusion, transmits / reflects the diffused light by a reflective polarizing sheet, and diffracts the transmitted light by a prism sheet so as to approach a direction perpendicular to the prism sheet. The light is condensed and emitted to the liquid crystal display panel.

JP 2005-302726 A

  The backlight device disclosed in Patent Document 1 collects light with a prism sheet and emits the light to a liquid crystal display panel. Therefore, the luminance in a predetermined viewing angle direction can be improved, but the luminance in the region immediately above the light source is high. May be too high. Therefore, depending on the display device including the backlight device disclosed in Patent Literature 1, luminance unevenness on the display surface of the liquid crystal display panel cannot be sufficiently reduced.

  An object of the present invention is to provide a display device capable of reducing luminance unevenness on a display surface of a display panel and an imaging device including the display device.

  A display device according to an embodiment of the present invention includes a display panel, a holding unit that holds the display panel, first and second polarizing plates provided on the back side of the display panel, and a back side of the holding unit. And a plurality of light sources that irradiate the display panel side with light through the holding means and the first and second polarizing plates. The first and second polarizing plates are arranged such that the transmission axis of the first polarizing plate intersects the transmission axis of the second polarizing plate.

  According to the display device and the imaging device including the display device of the present invention, it is possible to reduce luminance unevenness on the display surface of the liquid crystal display panel.

It is a figure which shows the structural example of the backlight apparatus of this embodiment. It is a figure explaining the directivity of the light source which a backlight apparatus has. It is a figure explaining the polarization | polarized-light characteristic of the reflective polarizing plate with which a backlight apparatus is provided. It is a figure explaining the polarization | polarized-light by the reflection type polarizing plate of the light which injected into the frame member from the light source.

  FIG. 1 is a diagram illustrating a configuration example of a backlight device according to the present embodiment. The display device of this embodiment includes a backlight device 100. In addition, the imaging apparatus of the present embodiment includes this display device. FIG. 1A is an example of an exploded perspective view of the backlight device 100. FIG. 1B is a cross-sectional view taken along the line AA in FIG. The backlight device 100 is a direct-type backlight device in which a plurality of light sources 301 a to 301 c are arranged on the back side of the liquid crystal panel unit 200. The light sources 301 a to 301 c are mounted on the substrate 203 and held by the frame member 204.

  The liquid crystal panel unit 200 functions as the liquid crystal display panel of this embodiment. The liquid crystal panel unit 200 includes a liquid crystal panel 191 and a pair of polarizing plates 190 and 192. The liquid crystal panel 191 includes a liquid crystal display element. The polarizing plate 190 is provided on the viewer side (display surface side) of the liquid crystal panel 191. The polarizing plate 191 is provided on the back side of the liquid crystal panel 191.

  The frame member 204 functions as a holding unit that holds the liquid crystal panel unit 200 at a predetermined distance from the plurality of light sources 301a to 301c. The light sources are arranged along the longitudinal direction of the liquid crystal display panel 200 at a predetermined interval from each other. The light source may be disposed along the short direction of the liquid crystal display panel 200. Further, the light source may be arranged along the longitudinal direction and the short direction of the liquid crystal display panel 200. In the present embodiment, the light source is a light emitting diode. The light source may be a laser or the like.

  The frame member 204 has a light reflecting surface 210 between the light source and the reflective polarizing plate 202b. Specifically, the inner wall of the frame member 204 forms the light reflecting surface 210. The inner wall shape of the frame member 204 that forms the light reflecting surface 210 is a slope shape that connects the outer periphery of the light sources 301a to 301c to the display range of the liquid crystal display panel 200. The light reflecting surface 210 reflects the light emitted from the light source and incident into the frame member 204 and guides it to the reflective polarizing plate 202b side.

  That is, between the light source and the liquid crystal panel unit 200, the light reflecting surface 210, the reflective polarizing plate 202b, the reflective polarizing plate 202a, and the diffusion sheet 201 of the frame member 204 are provided in this order from the light source side. The light source irradiates light on the liquid crystal display panel side (liquid crystal panel unit side) through the frame member 204, the reflective polarizing plate 202b, the reflective polarizing plate 202a, and the diffusion sheet 201.

  The reflective polarizing plate 202b is the first polarizing plate of this embodiment. The reflective polarizing plate 202a is the second polarizing plate of this embodiment. The reflection-type polarizing plates 202b and 202a are formed of reflection-type polarizing elements having the property of passing (polarizing) light in a certain arbitrary direction (transmission axis). That is, the reflective polarizing plates 202b and 202a polarize incident light. In the present embodiment, the transmission axis of the reflective polarizing plate 202b and the transmission axis of the reflective polarizing plate 202a intersect. The diffusion sheet 201 functions as a light diffusion member that diffuses the light transmitted through the reflective polarizing plate 202a. Thereby, luminance unevenness on the display surface of the liquid crystal panel unit 200 is reduced.

  As shown in FIG. 1B, the diffusion sheet 201, the reflective polarizing elements 202a and 202b, and the liquid crystal panel unit 200 are held in the recesses of the frame member 204. The substrate 203 is attached so that the light sources 301 a to 301 c are accommodated in the openings of the frame member 204.

  FIG. 2 is a graph illustrating the directivity of the light source included in the backlight device of the present embodiment. The vertical axis of the graph shown in FIG. 2 is the relative illuminance, and the horizontal axis is the radiation angle. As shown in the graph of FIG. 2, in the backlight device 100, the amount of light emitted from each light source (light sources 301 a to 301 c) is the maximum in the vertical direction. That is, the light source has the highest illuminance in the vertical direction of the light emitting surface, and has a tendency (directivity) that the illuminance decreases as the angle from the vertical direction increases.

  FIG. 3 is a diagram illustrating the polarization characteristics of the reflective polarizing plate provided in the backlight device of this embodiment. FIG. 3A is a diagram showing the transmission axis of the reflective polarizing plate 202a. FIG. 3B is a diagram showing the transmission axis of the reflective polarizing plate 202b.

  In general, light is divided into a longitudinal wave and a transverse wave, but the transmission axis 301 of the reflective polarizing plate 202a and the transmission axis 302 of the reflective polarizing plate 202b intersect substantially perpendicularly. In the backlight device according to the present embodiment, the display surface of the liquid crystal panel unit 200 is a rectangle having a different aspect ratio.

  When the right side of the long side of the liquid crystal panel unit 200 when viewed from the observer side of the backlight device is 0 degree, the transmission axis direction α of the reflective polarizing plate 202a is approximately 45 degrees. The transmission axis direction β of the reflective polarizing plate 202b is approximately 135 degrees. The transmission axis direction α may be approximately 135 degrees and the transmission axis direction β may be approximately 45 degrees. The term “substantially” mentioned here means that a deviation of about ± 10 degrees from the above-mentioned angle is allowed, but the deviation is preferably within ± 5 °, and more preferably within ± 2 degrees.

  The reflective polarizers 202a, 202b reflect diffusely, such as, for example, multilayer optical film (MOF) reflective polarizers, continuous / dispersive polarizers, wire grid reflective polarizers, or cholesteric reflective polarizers. It is a polarizing film (DRPF). Both MOFs and continuous / dispersed phase reflective polarizers selectively transmit light in one polarization state while transmitting light in an orthogonal polarization state, so that at least two materials, usually a polymeric material, are used. Depends on the difference in refractive index.

  Examples of the MOF reflective polarizer include Vikuiti (registered trademark) including a diffusing surface, a multilayer reflective polarizer DBEF-D2, and a thin APF-D220 manufactured by 3M Company.

  FIG. 4 is a diagram for explaining the polarization of light incident from the light source into the frame member by the reflective polarizing plate. Generally, when two polarizing plates are arranged substantially vertically, light does not pass. However, it actually has a certain angular width. Therefore, the reflective polarizing plate 202b that recycles light by multiple reflection transmits light (252) in the transmission axis direction β out of the light incident on the reflective polarizing plate 202b. The light transmitted through the reflective polarizing plate 202 is reflected by the reflective polarizing plate 202a having a transmission axis in the α direction. An inverted arrow 253 indicates the reflected light.

  On the other hand, the light (251) in the α direction orthogonal to the transmission axis direction β is reflected by the reflective polarizing plate 202b. However, since the transmission axis direction β has a certain width, a part of the light (251) in the α direction is transmitted without being reflected by the reflective polarizing plate 202b.

  The light reflected without vertically passing through the reflective polarizing plates 202b and 202a is reflected by the light reflecting surface 210 of the frame member 204 and is incident on the reflective polarizing plate 202b again. By repeating the transmission and reflection described above, the amount of light transmitted through the reflective polarizing plates 202a and 202b is reduced. Further, the light transmitted through the reflective polarizing plate 202 a is diffused by the diffusion sheet 201 and enters the display surface of the liquid crystal panel unit 200.

  According to the back panel device of the present embodiment described above, the light from the light source is repeatedly reflected and diffused by the plurality of reflection type polarizing plates whose transmission axes intersect with each other, and the light passes through the plurality of reflection type polarizing plates vertically. The amount of permeation can be reduced. Therefore, according to the back panel device of the present embodiment, it is possible to reduce the luminance in the region immediately above the light source. Thereby, luminance unevenness on the display surface of the liquid crystal panel unit 200 can be reduced.

200 Liquid crystal display panel 204 Frame member 301a, 301b, 301c Light source

Claims (6)

A display panel;
Holding means for holding the display panel;
First and second polarizing plates provided on the back side of the display panel;
A plurality of light sources provided on the back side of the holding means at predetermined intervals, and irradiating the display panel side with light through the holding means and the first and second polarizing plates; ,
A display device, wherein a transmission axis of the first polarizing plate intersects a transmission axis of the second polarizing plate. The display device according to claim 1, wherein a transmission axis of the first polarizing plate and a transmission axis of the second polarizing plate are orthogonal to each other. When the display panel is viewed from the viewer side of the display device when the right direction of the long side of the display panel is 0 degree, the transmission axis direction of the first polarizing plate is 45 degrees, The display device according to claim 1, wherein the transmission axis direction of the polarizing plate is 135 degrees. The display device according to any one of claims 1 to 3, wherein a light diffusion member is provided between the display panel and the first and second polarizing plates. The display device according to claim 1, wherein the holding unit includes a light reflecting surface that reflects light incident from the plurality of light sources.   An imaging device comprising the display device according to any one of claims 1 to 5.

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