JPH0435860Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to a liquid crystal display device equipped with a Fresnel lens.

[Technical background of the invention and its problems]

2. Description of the Related Art Some liquid crystal display devices used in liquid crystal television receivers, liquid crystal projectors, and the like include a transmissive dot matrix liquid crystal display panel with a parallel Fresnel lens having a sawtooth cross section on the front or back side. This liquid crystal display device changes the direction of light that has passed through the liquid crystal display panel or the direction of light that enters the liquid crystal display panel from the back side by the light refraction effect of the Fresnel lens. According to a liquid crystal display device, even if the incident direction of the illumination light that illuminates the liquid crystal display panel from the back side is shifted from the viewing direction of the displayed image or the screen surface, the display image light can be directed toward the viewing direction or the screen image. You can do it.

However, in a liquid crystal display device equipped with this Fresnel lens, although the light passing through each slope of the Fresnel lens is refracted in a uniform direction by the slope, the boundary between the slopes of the Fresnel lens is Since the light passing through goes in another direction, the display dots in the area facing this boundary area become dark (the aperture ratio decreases), and for this reason, the liquid crystal display device equipped with the above-mentioned Fresnel lens has a problem in that the displayed image However, there have been problems in that striped patterns appear on the screen and the displayed image becomes dark overall.

[Purpose of invention]

This idea was made in view of the above-mentioned circumstances, and although its purpose was to change the direction of light using a Fresnel lens, it caused striped patterns to appear on the displayed image. To provide a liquid crystal display device capable of displaying a high-quality image while preventing the entire display image from becoming dark.

In particular, in a liquid crystal display device that refracts illumination light incident from an oblique direction on the back surface of the liquid crystal display panel in a direction perpendicular to the surface of the liquid crystal display panel, stripes may appear on the displayed image or the entire displayed image may become dark. The purpose is to prevent

[Summary of the idea]

In other words, the liquid crystal display device of this invention includes a dot matrix liquid crystal display panel, which is provided on the front side of the liquid crystal display panel, and which uses illumination light incident at an incident angle θ from an oblique direction on the back surface of the liquid crystal display panel to display the liquid crystal display panel. The Fresnel lens has a sawtooth cross section that refracts light in a direction perpendicular to the panel surface, and the pitch of the dots of the liquid crystal display panel and the pitch of the sloped portion of the Fresnel lens are approximately the same, and each of the Fresnel lenses It is characterized in that the position of the boundary part of the slope part is arranged so as to be shifted from the position between the dot rows of the liquid crystal display panel by approximately x tan θ (x is the distance between the liquid crystal layer of the liquid crystal display panel and the Fresnel lens). With this configuration, even if illumination light is incident from an oblique direction on the back surface of the liquid crystal display panel, substantially all display dots will face each slope of the Fresnel lens. In addition, since the boundary between the slopes of the Fresnel lens and the area between the rows of display dots on the LCD panel facing each other are areas where light does not originally pass through, according to this invention, it is possible to incorporate the display image into the display image on the LCD panel. A striped pattern may appear due to the light-opaque areas between the dot rows and the Fresnel lens boundary.
A high-quality image can be displayed while preventing the displayed image from becoming entirely dark.

[Example of idea]

below. An embodiment of this invention will be described with reference to the drawings. First, the principle of this invention will be explained using FIG.

In FIG. 1, 1 is a transmissive dot matrix liquid crystal display panel. As is well known, this dot matrix liquid crystal display panel 1 includes a transparent substrate 2a having a plurality of strip-shaped scanning electrodes (common side electrodes) 3 arranged in parallel on its inner surface, and a transparent substrate 2a formed on its inner surface in a direction perpendicular to the scanning electrodes 3. A nematic liquid crystal 5 having a positive dielectric anisotropy is placed between the transparent substrate 2b on which a large number of strip-shaped scanning electrodes (segment-side electrodes) 4, 4 are arranged in parallel, and the liquid crystal molecules are distributed between the substrates 2a, 2.
In addition, polarizing plates 6a and 6b are arranged on the outside of both substrates 2a and 2b so that their polarization axes are parallel to each other. When a voltage is applied between the scanning electrode 3 and the signal electrode 4, light is transmitted (opened) through the portion where the voltage-applied scanning electrode 3 and the signal electrode 4 face each other, and a dot is displayed. . In addition, 4a and 4a in the figure are the lead parts of each said signal electrode 4 and 4.

On the other hand, in FIG. 1, 7 is the liquid crystal display panel 1
This Fresnel lens 7 is a parallel Fresnel lens with a sawtooth cross section arranged on the front surface side (display surface side). It is provided along the length direction. This Fresnel lens 7 has one side of a transparent plate made of glass or acrylic resin formed into a serrated surface, each of which has sloped parts 7a,
The width of the slope portions 7a is slightly wider than the width of the display dots on the liquid crystal display panel 1 (the width of the signal electrodes 4, 4), and the pitch of the slope portions 7a, 7a is the same as the pitch of the display dot rows on the liquid crystal display panel 1. (Arrangement pitch of signal electrodes 4, 4). The Fresnel lens 7 is provided so that the boundary portions 7b, 7b between the slope portions 7a, 7a are opposed to each other between the display dot rows of the liquid crystal display panel 1 (between the signal electrodes 4, 4).

This liquid crystal display device is used in liquid crystal television receivers, liquid crystal projectors, etc.
For example, if the viewing direction of the displayed image or the screen is diagonally above the surface of the liquid crystal display panel 1, illumination light that illuminates the liquid crystal display panel 1 from the back side (light from a light source lamp or light taken in from the outside) It is only necessary to make the external light (a) incident on the liquid crystal display panel 1 from a direction perpendicular to the back surface as shown in the figure.
Since the image light that has passed through the Fresnel lens 7 is redirected diagonally upward by the light refraction action of the slope portions 7a, 7a of the Fresnel lens 7, the image light can be directed toward the viewing direction or the screen surface.

In this liquid crystal display device, as described above, the pitch of the sloped portions 7a, 7a of the Fresnel lens 7 is adjusted to the pitch of the display dot rows of the liquid crystal display panel 1, and the Fresnel lens 7 is , 7a are provided so as to oppose each other between the rows of display dots on the liquid crystal display panel 1, so that all the display dots face the slopes 7a, 7a of the Fresnel lens 7. Therefore, the light transmitted through the liquid crystal display panel 1 does not pass through the boundary portions 7b, 7b between the slopes 7a, 7a of the Fresnel lens 7, and the display dots do not become dark. Part 7
Since the portion between the display dot rows of the liquid crystal display panel 1 that faces the boundary portions 7b and 7a between the dots a and 7a is originally a portion through which no light is transmitted, according to this liquid crystal display device, a striped pattern appears in the displayed image. It is possible to display high-quality images by preventing

An embodiment of the present invention to which the above principle is applied will be described below with reference to FIG. Note that the detailed operation is the same as the principle explained using FIG. 1 above, so a description thereof will be omitted. That is, FIG. 2 shows an embodiment of this invention. Even when the illumination light a is incident on the back surface of the liquid crystal display panel 1 from an oblique direction as in this embodiment, the Fresnel lens 7 is If the boundary portions 7b, 7b between the slope portions 7a, 7a are provided so as to face each other between the display dot rows of the liquid crystal display panel 1 on the optical axis of the light that obliquely passes through the liquid crystal display panel 1, To prevent striped patterns from appearing on a displayed image and to display a high-quality image.
In addition, in order to make the boundary portions 7b, 7b between the slope portions 7a, 7a of the Fresnel lens 7 face each other between the display dot rows of the liquid crystal display panel 1 on the oblique optical axis as in this embodiment, LCD display panel 1
Depending on the incident angle θ of the illumination light a with respect to the back surface of the LCD panel 1 and the distance x between the liquid crystal layer of the liquid crystal display panel 1 and the Fresnel lens 7, it is only necessary to provide the display panel 12 with a vertical shift in the figure by approximately x·tan θ. Also, in this example,
The liquid crystal display panel 1 used is one in which the display surface is on the substrate 2b side on which the signal electrodes 4, 4 are formed.
The display surface may be the substrate 2a side on which the scanning electrodes 3 are formed.

As shown in FIG. 3, the Fresnel lens 7 has a shape in which the width of the sloped portions 7a, 7a is the same as the width of the display dots on the liquid crystal display panel, and the portions that do not face the display dots are not sloped. Good too.

[Effect of idea]

As explained above, with the configuration of this invention, even if illumination light is incident from an oblique direction on the back surface of the liquid crystal display panel, substantially all display dots are opposed to each inclined surface of the Fresnel lens. In addition, since the boundary between the slopes of the Fresnel lens and the area between the rows of display dots on the liquid crystal display panel that are opposed to each other are areas where light does not originally pass through, the displayed image does not include the areas between the rows of display dots on the liquid crystal display panel. It is possible to display a high-quality image by preventing a striped pattern from being formed due to the light-impermeable portions on both sides of the Fresnel lens boundary and from making the displayed image dark as a whole.

[Brief explanation of the drawing]

Figure 1 is a diagram to explain the principle of this invention.
FIG. 2 is a sectional view of a portion of a liquid crystal display device showing an embodiment of this invention, and FIG. 3 is a sectional view showing a modified example of the Fresnel lens. DESCRIPTION OF SYMBOLS 1...Liquid crystal display panel, 7...Fresnel lens, 7a...Slope portion, 7b...Boundary portion.

Claims (1)

[Scope of Claim for Utility Model Registration] A dot matrix liquid crystal display panel, which is provided on the front side of this liquid crystal display panel, and which directs illumination light incident on the back surface of this liquid crystal display panel at an incident angle θ to the surface of this liquid crystal display panel. The Fresnel lens has a sawtooth cross section that refracts light in a direction perpendicular to the surface of the lens, and the pitch of the dots of the liquid crystal display panel and the pitch of the sloped portion of the Fresnel lens are approximately the same, and the pitch of each sloped portion of the Fresnel lens is made substantially the same. A liquid crystal characterized in that the position of the boundary portion is shifted from the position between the dot rows of the liquid crystal display panel by approximately x·tanθ (x is the distance between the liquid crystal layer of the liquid crystal display panel and the Fresnel lens). Display device.