JP6502686B2 - Reflective liquid crystal display - Google Patents

Description

  The present invention relates to a reflective liquid crystal display device.

  A conventional reflective liquid crystal display device includes a reflective liquid crystal panel that performs light modulation for displaying an image, a light source that emits light to the reflective liquid crystal panel, and a polarizing plate that linearly polarizes light emitted from the light source. And a polarization separation means for reflecting light transmitted through the polarizing plate toward the reflective liquid crystal panel and selecting any polarization modulated by the reflective liquid crystal panel. As the polarization separation means, a film-like element such as a reflection type polarizing plate or a prism element such as a polarization beam splitter (PBS) is used.

  FIG. 4 is a schematic view showing a conventional reflective liquid crystal display device. FIG. 5 is a schematic view for explaining the uneven brightness distribution in the conventional reflective liquid crystal display device. A reflective liquid crystal panel 5 and a light source 1 are mounted on a substrate 8, and a reflector 2, a polarizing plate 3 as an optical member, and a polarization beam splitter 4 as a polarization separation means are disposed.

  The light emitted from the light source 1 is reflected and diffused by the reflection plate 2 and then transmitted through the polarizing plate 3 to be linearly polarized light p. Thereafter, the light is incident on the polarization beam splitter 4 and is reflected in the direction of the reflective liquid crystal panel 5. Here, the transmission axis of the polarization beam splitter 4 is set in the direction orthogonal to the transmission axis of the absorption type polarizing plate 3. The light incident on the reflective liquid crystal panel 5 is subjected to light modulation according to the driving state of the liquid crystal, and is reflected in the direction of the polarization beam splitter 4. The polarization beam splitter 4 can transmit only the polarization component s that has received the light modulation, and is separated as image light.

  In general, it is ideal that the shapes of the polarizing beam splitter 4 and the reflecting plate 2 are optimized so that the light irradiated to the reflective liquid crystal panel 5 is uniform on the surface, but the physical size is large. There is no choice but to compromise due to cost constraints. Therefore, as shown in FIG. 5B, the light irradiated to the reflective liquid crystal panel 5 has some unevenness. This unevenness is left even after the irradiation light is modulated by the reflective liquid crystal panel 5 and transmitted through the polarization beam splitter 4 as image light, so the observer visually recognizes the unevenness in brightness of the image light.

Patent No. 3539904 gazette JP, 2010-2503, A

  Various methods have been devised as a method of solving the above-mentioned uneven brightness on the image display. For example, in Patent Document 1, as shown in FIG. 6, a diffusion plate 6 is disposed between the polarizing plate 3 and the reflection plate 2, and the irradiation light from the light source 1 is made a uniform surface light source on the diffusion plate 6. Is described. On the other hand, Patent Document 2 mainly implements a method for detecting uneven brightness in a projection device such as a transmissive liquid crystal and a projector, and a video signal input to a reflective liquid crystal panel according to the degree and position of the detected unevenness. A method is described that corrects the brightness of the bright spot and increases the brightness of the dark spot unreasonably.

  Although the method of inserting the diffusion plate 6 can eliminate the light distribution unevenness in the light source or in the reflection plate 2, the light distribution unevenness in the polarization separation means such as the polarization beam splitter 4 is present as it is. On the other hand, the method of correcting the video signal requires a video signal processing circuit separately from the drive circuit of the panel. Alternatively, if it is performed by the existing video signal processing circuit, an extra burden is placed on the circuit. In addition, since the dynamic range of the original color gradation of the panel is narrowed by the amount of correction of the video signal, it is necessary to prepare a panel with a wide color range or multiple gradations in order to maintain the gradation characteristics. It will be expensive as a whole.

  The present invention has been made in view of the above problems, and it is an object of the present invention to provide a reflection type liquid crystal display device in which luminance unevenness of image light is eliminated.

A light source, a reflecting plate for reflecting and diffusing light emitted from the light source, a polarizing plate for linearly polarizing light incident from the reflecting plate, and a reflective liquid crystal panel for performing light modulation for displaying an optical image; In a reflection type liquid crystal display device comprising: a polarization separation means for reflecting linearly polarized light toward a reflection type liquid crystal panel and selecting arbitrary polarization modulated by the reflection type liquid crystal panel as an image light; A reflection type liquid crystal display device is provided that includes a brightness unevenness correction unit, and a diffusion plate between the brightness unevenness correction unit and the reflection plate.

The uneven brightness correction means may be a reflective liquid crystal display device which is a neutral density filter having different density distribution on the surface.

The uneven brightness correction means may be a reflection type liquid crystal display device which is a semi-transmissive reflection plate having a distribution of different reflectances on the surface.

  By the reflection type liquid crystal display device of the present invention, the brightness unevenness of the irradiation light is properly corrected, and uniform irradiation light is given to the reflection type liquid crystal panel. As a result, it is possible to provide a reflection type liquid crystal display device in which the luminance unevenness of the image light is eliminated.

Schematic view of a reflection type liquid crystal display device in the present invention It is the schematic of the brightness nonuniformity correction in this invention, (A) sectional drawing, (B) A-A 'sectional drawing Schematic view of a modification of the reflective liquid crystal display device in the present invention Schematic diagram of a conventional reflective liquid crystal display device It is the schematic explaining the brightness nonuniformity distribution in the conventional reflection type liquid crystal display device, (A) sectional view, (B) B-B 'sectional view Schematic diagram of a conventional reflective liquid crystal display device

  Hereinafter, an embodiment of the uneven brightness correction means of the reflective liquid crystal display device in the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a reflective liquid crystal display device in the present invention. FIG. 2 is a schematic view of luminance unevenness correction in the invention. FIG. 3 is a schematic view of a modification of the reflective liquid crystal display device in the present invention.

  FIG. 1 is a schematic block diagram of a reflection type liquid crystal display device showing an embodiment of the present invention, wherein an absorption type polarizing plate 3 and a brightness nonuniformity correction means are neutral between the polarization beam splitter 4 and the reflection plate 2. Density filter 7 is inserted. Here, as an example of the luminance unevenness, a case where the central area of the reflective liquid crystal display panel is brightest as shown in FIG.

  A neutral density filter 7 is disposed as the uneven brightness correction means, and the transmittance of the light transmitting position to the central portion of the reflective liquid crystal display panel 5 is decreased to reduce the light transmittance as shown in the cross section AA 'in FIG. The transmittance of the light transmitting position of the light reaching the panel periphery is set to be high to prevent light reduction. Thereby, it is possible to suppress the luminance unevenness of the image light of the reflective liquid crystal display device caused by the optical member including the polarization beam splitter 4. This embodiment mainly corrects the unevenness by reducing the brightness of the part that is too bright and balancing it with the dark part, so that it will be worse from the viewpoint of light utilization efficiency, but in recent years it has been LED etc. Since the improvement of the light emission efficiency of the above makes it possible to obtain a high enough brightness with lower power consumption, the practical power consumption demerit has no problem.

  In the present embodiment, it is desirable that the absorption type polarizing plate 3 and the neutral density filter 7 be bonded and laminated with an optical adhesive or a transparent adhesive. Thereby, the air layer between the optical members can be eliminated, and surface reflection between the members can be minimized.

  If the light diffusion effect of the reflection plate 2 is insufficient, a separate diffusion plate 6 may be inserted as shown in FIG. In that case, it is preferable to insert between the reflective plate 2 and the neutral density filter 7, and it is more preferable that the optical member including the neutral density filter 7 be laminated.

  In the present invention, as the characteristics required for the uneven brightness correction means, it is only necessary to be able to change the light transmittance distribution on the film surface. Therefore, the uneven brightness correction means includes the neutral density filter described above. As well as 7, it may be made of, for example, a semi-transmissive reflecting material such as a half mirror having a distribution of partially different reflectance. Similarly, the diffusivity on the surface of the diffusion plate 6 is partially different distribution, and the uneven brightness correction means is provided on the diffusion plate 6 to dim not only the too bright part but also to the too dark part. Can be distributed, which is preferable from the viewpoint of light utilization efficiency. The planar distribution of the luminance unevenness correction means may be appropriately adjusted according to the design requirements.

  In this embodiment, although the case where the uneven brightness occurs such that the central part of the reflection type liquid crystal display panel is the brightest and becomes darker as it goes to the outer peripheral side is taken as an example, it is not limited thereto. The present invention can be applied to various luminance unevenness caused by characteristics.

1 light source 2 reflector 3 polarizer 4 polarization beam splitter 5 reflective liquid crystal panel 6 diffuser 7 neutral density filter 8 substrate

Claims (3)

Light source,
A reflector that reflects and diffuses light emitted from the light source;
A polarizer that linearly polarizes light incident from the reflector;
A reflective liquid crystal panel that performs light modulation for displaying an optical image;
And a polarization separation unit configured to reflect the linearly polarized light toward the reflection type liquid crystal panel and sort any polarization modulated by the reflection type liquid crystal panel as an image light.
An uneven brightness correction means is provided between the polarizing plate and the reflecting plate,
A diffusion plate is provided between the uneven brightness correction means and the reflection plate,
A reflection type liquid crystal display device characterized by   2. The reflection type liquid crystal display device according to claim 1, wherein the luminance unevenness correction means is a neutral density filter having different density distribution on the surface. 2. The reflection type liquid crystal display device according to claim 1, wherein the brightness non-uniformity correction means is a semi-transmissive reflection plate having a distribution of different reflectances on the surface.

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