JPH052235B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display with reduced viewing angle dependence.

[Conventional technology]

The use of liquid crystal displays as display elements that can be driven with low power consumption is increasing, and in recent years
Expectations for it as an alternative to CR displays and color TV picture tubes are growing, and many research results have been published. Currently, most liquid crystal displays use twisted nematic liquid crystals because of their fast response speed and high contrast ratio. FIG. 7 shows an example of the display principle of a transmissive twisted nematic liquid crystal display. A transmissive liquid crystal display is the smallest unit (hereinafter referred to as
This is called a pixel). A pixel consists of a transparent electrode 704 provided on two substrates 702 between two polarizing plates 703 facing each other so that the polarization axes are parallel to each other, and a twisted nematic liquid crystal 705 arranged in a twisted manner. provided and configured. In the ON state, a potential is applied to the transparent electrode 704 as shown in FIG. 7a, and the liquid crystal 705 stands up, allowing light from the light source 700 to pass therethrough. However, in the OFF state, the liquid crystal 705 is between the two transparent electrodes 704, as shown in (b) of the same figure.
The orientation is twisted by 90 degrees, and the polarization axis of the light from the light source 700 rotates by 90 degrees along the twisted liquid crystal molecules, so that it cannot pass through the other polarizing plate. A liquid crystal display constructs an image by combining a large number of pixels and controlling ON/OFF at each point.

[Problem that the invention seeks to solve]

The conventional liquid crystal display described above has a polarizing plate 7.
03 is used to control the transmission of light. However, a polarizing plate has a property that light incident obliquely on the polarization plane cannot be polarized well, and as shown in FIG.
The liquid crystal display 811 transmits light even in the OFF state, and therefore, the liquid crystal display 811 has a disadvantage in that the image quality, particularly the contrast, changes depending on the viewing angle of the viewing surface, which is highly dependent on the viewing angle.

Therefore, when viewed from an angle other than perpendicular to the viewing plane, the amount of transmitted light differs from the normal control amount, resulting in a problem of deteriorating image quality.

[Means for solving problems]

The conventional liquid crystal display described above does not have a structure that prevents light transmitted in an oblique direction, which causes a reduction in image quality (contrast) when viewed from an angle other than perpendicular to the viewing plane. In contrast, the present invention has a filter on the viewing surface of the liquid crystal display, and the inner wall surface of the filter or the hole itself is made of a material that has high absorption in the visible light range. A filter that is perpendicular to the viewing surface of the liquid crystal display, has a light scattering surface on the reflective side of the surface in contact with the viewing surface of the liquid crystal display, and has a thickness of 0.7 or more of the longest plane length of the hole. By providing it in contact with the viewing surface of the display, it absorbs the light that is transmitted in the oblique direction and scatters the light that is transmitted perpendicularly, so that it can be viewed with the same image quality from any direction.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows a schematic conceptual diagram showing the structure of a liquid crystal display with a filter according to an embodiment of the present invention. Two electrode substrates 1 are provided with transparent electrodes 104.
Twisted nematic liquid crystal 105 between 02
is filled, and polarizing plates 103 are provided on both sides. A light source 100 is provided on the side of one polarizing plate 103, and the other polarizing plate 103 serves as a viewing surface 114 of a liquid crystal display. A filter 101 in contact with this viewing surface 114 improves viewing angle dependence.
has been established.

Next, a filter 101 that improves viewing angle dependence
The detailed structure of will be explained with reference to FIG.

FIG. 2 is a schematic partially enlarged perspective view of a liquid crystal display with a filter, showing two electrode substrates 202.
The polarizing plates 203 provided in the two are arranged in parallel so that their polarization axes point in the same direction.

The transparent electrodes 204 are formed inside the polarizing plate 203 so as to face each other and have a size of amm×bmm. Twisted nematic liquid crystal 205 is sealed between polarizing plates 203, and by rubbing, the orientation of the crystal axis differs by 90 degrees between the polarizing plate surface on the viewing surface side and the polarizing plate surface on the reflection side, and the crystal axis is on the opposite side to the viewing surface. On the plane of the polarizing plate, the polarization axis and the crystal axis are oriented in the same direction.

When an electric field is applied to the transparent electrode 204, the molecules of the twisted nematic liquid crystal 205 stand up and transmit light. The transmitting part is considered to be approximately equal to the size of the transparent electrode 204, and the viewing surface has a size of amm×bmm.
A pixel 206 with a size of . In this embodiment, a filter 201 having holes corresponding to the pixels 206 on a one-to-one basis is provided in contact with the viewing surface of the liquid crystal display (the surface of the upper polarizing plate 203 in the figure). (Listed separately.) The filter 201 is the frame 207
and a scattering surface 209. The frame 207 is made of black ABS resin and molded into a plate shape with a thickness of hmm and has a vertical hole with an aperture diameter of amm×bmm corresponding to each pixel 206 on a one-to-one basis. Here, for a=b=0.5 (mm), h=1
(mm) 0.7 or more of the hole size of one hole. The scattering surface 209 provided on the surface 215
07 is filled with transparent resin 208 and then finished with a scattering surface. The transparent resin 208 only needs to fill at least the scattering surface 209, and does not need to fill the entire depth of the frame 207. Furthermore, the scattering surface 209 does not have to be a flat scattering surface. Also, the shape of the hole does not have to be square.

In this embodiment, the thickness of the filter 201 is set to be 0.7 or more of the long side of each hole (the diameter in the case of a circular hole), so it absorbs the light that passes through the liquid crystal display in an oblique direction, and absorbs only the light that passes almost vertically. By scattering it on a scattering surface, it can be seen in the same way from any direction.

Further, in this embodiment, since the holes correspond to the pixels 206 on a one-to-one basis, there is an advantage that the resolution does not deteriorate.

FIG. 3 is a cross-sectional view of a main part showing another embodiment of the present invention. In this embodiment, similarly to the embodiment shown in FIGS. 1 and 2, a liquid crystal display section 317 includes a polarizing plate 303,
It is composed of an electrode substrate 302, a transparent electrode 304, and a twisted nematic liquid crystal 305. The filter section 318 includes the frame 307 and the scattering surface 30.
9 and an absorption layer 310. The material of the frame 307 does not have to be black resin or the like, and may be other resins or metals. Absorbent layer 31
0 is a hole surrounded by a frame 307 whose inner wall is coated with a substance such as black paint that has high absorption in the visible light range. The scattering surface 309 is made by finishing the surface of the transparent resin 308 filled in the frame 307 into a scattering surface, but it does not have to be flat. In addition, the holes 319 provided in the film shape of the scattering surface 309 may remain hollow.

In this example, since the number of holes is greater than the number of pixels,
Several holes 3 are formed on the transparent electrode 304 corresponding to one pixel.
It has 19. For this purpose, the filter section 318
Even if the thickness of the absorbing layer 3 is made thinner, the light that passes obliquely can be absorbed.
10, and only the light that is transmitted almost perpendicularly is scattered by the scattering surface, so that it can be seen in the same way from any direction. Furthermore, in this embodiment, metal can also be used as the frame material, which has the advantage of increasing strength.

〔Effect of the invention〕

Next, the effects of the present invention will be explained. As shown in FIG. 4, the filter has a frame 407 having vertical holes in a polarizing plate 403 (upper side) on the viewing surface, and an inner wall layer made of a material having high absorption in the visible light range. By providing such a filter in contact with the viewing surface of the liquid crystal display (on the upper polarizing plate 403), the light source 1 that passes through the polarizing plate 403 obliquely can be prevented.
Can absorb light from 00. Furthermore, a scattering surface 409 is provided on the surface opposite to the surface in contact with the viewing surface of the filter.
By providing this, it is possible to scatter the light received at an angle perpendicular to or close to the polarizing plate on the viewing plane that is selectively transmitted through the holes in the filter. For example, the size of the light angle selected here can be determined by the thickness of the filter and the size of the hole. FIG. 5 shows the relationship between the maximum transmission angle θmax and the hole diameter/filter thickness when the hole is circular. Because it scatters only the almost perpendicular transmitted light controlled by the liquid crystal display,
You can see almost the same amount of light no matter what angle you look at, and you can get almost the same contrast no matter what angle you look at.

In other words, the present invention attenuates light that obliquely transmits through the polarizing plate on the viewing plane and disturbs the brightness of the pixel and causes a decrease in contrast ratio. By scattering light, it becomes possible to see it the same way from any angle,
As shown in FIG. 6, this has the effect of improving the viewing angle dependence of contrast.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the structure of a liquid crystal display with a filter according to an embodiment of the present invention. FIG. 2 is a schematic partially enlarged perspective view for explaining a filter used in an embodiment of the present invention. FIG. 3 is a schematic partially enlarged perspective view for explaining a filter used in another embodiment of the present invention. FIG. 4 is a schematic perspective view for explaining the effect of the filtered liquid crystal display of the present invention. FIG. 5 is a graph for explaining the structure and function of the filter used in the present invention. 6th
The figure is a graph showing the viewing angle characteristics of the filtered liquid crystal display of the present invention. Figure 7 shows a and b.
2A and 2B are schematic cross-sectional views showing the structure of a conventional liquid crystal display, in which FIG. 1A shows the display in the ON state and FIG. FIG. 8 is a schematic diagram for explaining the visual dependence of a conventional liquid crystal display. 100,400,700,800...light source, 1
01,201...Filter, 102,202,
302, 402, 702...electrode substrate, 103,
203,303,403,703...Polarizing plate, 1
04,204,304,404,704...transparent electrode, 105,205,305,405,705
...Twisted nematic liquid crystal, 206,
806...Pixel, 207,307,407...Frame, 208,308,408...Transparent resin,
209, 309, 409... scattering surface, 310...
Absorption layer, 811...Liquid crystal display, 812...
... Oblique incident light, 813 ... Viewpoint when viewed from an angle, 114 ... Viewing plane, 215 ... Surface, 216
...Back side, 317...Display section, 318...
...Filter section, 319...hole.

Claims (1)

[Scope of Claims] 1. A liquid crystal display device, and a filter provided on a viewing surface of the liquid crystal display device, the filter having holes corresponding to the pixels of the liquid crystal display, and the filter having holes corresponding to the pixels of the liquid crystal display. 1. A liquid crystal display with a filter, wherein the inner wall surface is made of a material having a large absorption rate in the visible light region, and has a scattering surface on a surface opposite to the side that contacts the viewing surface of the hole. 2. The liquid crystal display with a filter according to claim 1, wherein the hole of the filter is smaller in area than each pixel of the display. 3. A display with a filter according to claim 1 or 2, wherein the thickness of the hole in the filter is 0.7 or more of the longest plane length of the hole.