JPS628129A - liquid crystal display device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal display device that is thin, uniform, and has high contrast.

Figure 2 is a diagram when observing a conventional liquid crystal display device.
4 indicates the liquid crystal display panel, and 4 indicates the location where the panel is observed. As is clear from the figure, as the display area of the liquid crystal display panel 1 increases, the difference between the viewing angles 2 and S increases. 12
For a panel size comparable to an inch ORT, the viewing angle difference reaches 15° to 30°. Figure 1 is a graph of driving voltage (horizontal axis) to reflection intensity (vertical axis) when viewing angles are changed.Curve 5 is a curve when viewed from the direction perpendicular to the panel surface, and curve 6 is a curve perpendicular to the above. Curve 7 is a curve when viewed from a direction deviated by 15 degrees from the direction, and curve 7 is a curve when viewed from a direction also deviated by 50 degrees. As is clear from FIG. 1, even when the same driving voltage VoN is applied, the display density differs in A, B, and C depending on the viewing angle direction. In addition, the display density of the non-lit parts is different as shown in A/, Bl, (31), which means that when observing the display, the display gradually becomes darker (or darker) from the top to the bottom of the screen. This shows that large dot displays have the disadvantage that a uniform display appearance cannot be obtained over the entire display surface.

Furthermore, the contrast ratio between the lit portion and the non-lit portion also differs depending on the viewing angle direction. In Figure 1, 8 is the contrast when viewed from a direction perpendicular to the display surface, 9 is the contrast when viewed from a 15° direction to the vertical axis, and 10 is the contrast when viewed from a 30° direction to the vertical axis. Show contrast. As is clear from the figure, as the angle becomes larger, the steepness of the curve between driving voltage and reflected intensity increases, and the load resistance improves.

As described above, in conventional liquid crystal display devices, differences in display density and contrast occur due to differences in the location of the display surface, which has become a major problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device that eliminates the density unevenness in the lit and non-lit areas of the display surface and has a uniform display appearance over the entire surface.

Another object of the present invention is to provide a liquid crystal display device that eliminates the contrast difference due to the difference in viewing angle direction mentioned above and can uniformly obtain good display contrast over the entire surface.

In the present invention, a Fresnel lens having a sawtooth cross section is superimposed on a liquid crystal display panel to refract the optical path, and the sawtooth angle is continuously changed, so that the refraction angle is continuously changed on the display surface. It is characterized by the fact that uniform contrast 1 and optical density can be obtained no matter where the display surface is measured from.

FIG. 4 is a cross-sectional view of the Fresnel lens 11 according to the present invention superimposed on the liquid crystal display panel 12. After the emitted light 15 from the backlight passes through the liquid crystal display panel 12,
It is refracted by the Fresnel lens 11 and enters the observer's eye. Now angle 15 is #, 16 is 04.17 is 03.18
is θ, 19 is 01 (angle made with the line perpendicular to the panel)
, and if the sawtooth angle is set as ψ as shown in the figure, θ1,000ψ−θ, (1) iθ, =%・5iflθ, (2) (% is the refractive index of the Fresnel lens 11 with respect to air, and in the present invention Using acrylic resin, the following equation (4) holds: θS; ψ−84 (8) % sin θ4 ms θm.

Here, for each case where the sawtooth angle ψ is changed, the incident angle 08 to the observer with respect to the incident angle θ6 is expressed as (1) to (4).
) and the results are shown in Figure 5.

Here, as shown in FIG. 3, in order to install the Fresnel lens 27 so that only light entering at a constant angle of incidence 20 enters the observer's eye 2a over the entire display surface, point 24 is required.
The sawtooth angle at θ, (2°) = 5o', θ1(2
It can be seen from the above equation and FIG. 5 that the sawtooth angle ψ should be approximately 37.8' so as to satisfy 2)=10'. Similarly, at point 25, the incident angle θ, (20) = -50'
, θ1 (22)=25°, the sawtooth angle ψ should be approximately 9°.

As mentioned above, the sawtooth angle ψ of the Fresnel lens is set to point 24.
If the incident light angle from the backlight is continuously changed from 9° to 57°86 from point 25, the incident light angle n from the backlight will always be
Only the light that has passed through the liquid crystal panel from the o″′ direction enters the observer's eye 23.As a result, as shown in FIG. Therefore, the contrast is 10.
can be obtained uniformly over the entire surface, and chondratic differences depending on the location of the display surface and uneven display shading can be prevented.

Furthermore, if this stiff Fresnel lens is used, the uniformity of the display surface can be ensured even if the viewing direction is changed to 26 as shown in FIG.

In the above-described embodiment, the concave-convex surface of the Fresnel lens 33 is placed on the viewer side, but the same effect can be ensured even if the concave-convex surface of the Fresnel lens 33 is placed on the panel side. #I6 diagram shows the case where the 7-renel uneven surface is facing the panel 54 side, and the angles are 28.29, 30, 31.
52Tt θ, respectively.

0! , θS*'4*'l, and the sawtooth angle of the Fresnel lens is 9, the following equation holds true.

su #1 = s ・5in01 (1) 0, = θ,
+ψ (2) Calculation・3-01=siaθ, (8) θ, 20, −ψ (4) Here, at various sawtooth angles ψ, the angle of incidence of light on the panel θ, to the observer The relationship of the emission angle θ1 of is (1)
FIG. 7 is a diagram obtained by using equations (4) and graphed. As is clear from the figure, in order to ensure that only the light whose incident light θ6 to the panel is always 30° enters the observer's eyes, the sawtooth angle (ψ) of the Fresnel lens 33 is continuously set in the range of 06 to 40°. It turns out that it would be better to change it.

In addition, it is important to prevent moiré fringes that the concave-convex pitch of the Fresnel lens is as fine as possible by an integer fraction of the dot pitch of the liquid crystal display, and that the concave-convex line of the 7-resnel lens coincides with the direction of the dot line of the liquid crystal display. Furthermore, if the pitch of the concave and convex portions of the Fresnel lens is not made uniform but is randomly selected, it is possible to make the remote moiré fringes less noticeable.

As explained above, in the present invention, a Fresnel lens is inserted between the liquid crystal display panel and the viewer, and the sawtooth angle of the Fresnel lens is changed depending on the location. A liquid crystal display device with contrast can be obtained.

(2) A liquid crystal display device with uniform display density over the entire liquid crystal display surface can be provided.

(8) If the Fresnel lens angle is adjusted so that the light from the oblique direction behind the liquid crystal display surface enters the viewer's eyes, the liquid crystal display device can have a good fundus-to-last ratio even for viewers looking directly in front of it. can be provided.

(4) By adjusting the concavo-convex pitch and the display dot pitch of the Fresnel lens, or by setting them at random pitches, a good liquid crystal display without the occurrence of moiré fringes can be obtained.

[Brief explanation of drawings]

Figure 1 is a graph of electro-optical characteristics of a typical liquid crystal display. 5 is an electro-optical characteristic curve viewed from a direction perpendicular to the display surface. 6 is also 15" from the vertical direction, 7 is also 50"
Electro-optical characteristic curve viewed from the ° direction. FIG. 2 is a diagram illustrating the difference in viewing angle in a conventional liquid crystal display. 1...Liquid crystal panel Fig. 5 is an explanatory diagram 27 based on the embodiment of the present invention...
・The Fresnel lens according to the present invention in FIG. 4 is an explanatory diagram 11 of the first embodiment of the present invention...Fresnel lens 12...The liquid crystal display panel FIG. 3 is a graph showing the relationship between the angle of light incidence on the liquid crystal panel and the angle of light exit from the Fresnel lens when the sawtooth angle of the Fresnel lens is changed based on the example. FIG. 6 is an explanatory diagram of a second embodiment of the present invention. BB-... Fresnel lens 34 based on the present invention
・・・・・・Liquid crystal panel FIG. 7 shows the relationship between the Fresnel lens sawtooth angle, the angle of light incidence on the liquid crystal panel, and the angle of light incidence on the observer, which is also based on the second embodiment of the present invention. More than just a graph

Claims (2)

[Claims] (1) In a liquid crystal display device comprising at least a liquid crystal display panel and a Fresnel lens having a sawtooth cross-sectional shape arranged on the liquid crystal display panel, the sawtooth angle (ψ
) is changed almost continuously in one direction to compensate for changes in viewing angle of an observer on the surface of a liquid crystal display panel. (2) Claim 1 characterized in that the sawtooth angle (ψ) is continuously changed within a range of 0° to 50°.
The liquid crystal display device described in Section 1.