JPH04130414A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To allow high-grade displaying by correcting the surface brightness of a back light source and a side light source if there is a fluctuation in transmissivity in a liquid crystal panel. CONSTITUTION:The fluctuation in brightness M in the brightness within the plane expressed by equation II is so determined as to satisfy the relation of equation III when the average brightness of the back light source is designated as Lav, the brightness at an arbitrary point (i) as Li, the average transmissivity of the liquid crystal cell on the back light source as Tav, the transmissivity at the arbitrary point (i) as Ti, the surface brightness of the liquid crystal display device at the arbitrary point (i) determined by the equation I as ai, and the average surface brightness as aav. The unequal display of the liquid crystal display device is prevented in this way and the liquid crystal display device having the high display grade is obtd.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a liquid crystal display device.

[Prior Art] In a conventional liquid crystal display device, column electrodes are inputted from both sides and divided in the center (hereinafter referred to as normal extraction), as shown in JP-A-59-121391, etc., as shown in FIG. A diffuser plate 41 was used on the back light source 40 so that a uniform light source spread over the liquid crystal cell 42.

[Problems to be Solved by the Invention] However, as liquid crystal display devices have recently become more precise and colored, the number of transparent electrodes has increased, and as a result, the signal input section has become more precise, and Even when connecting a board with a driver bonded onto a flexible tape using a flexible tape, the patterning accuracy of each connection part has become more precise and can be as small as 0. Since the thickness was less than 1 mm, there were restrictions on mounting, and the above-mentioned method of center division became impossible, and it became necessary to take out every other transparent electrode 44 vertically and alternately, as shown in FIG. (Hereinafter referred to as "alternate extraction") However, in the alternate extraction, the column electrodes 44 are longer than in the normal extraction, and pixels located far from the signal input section cannot obtain a sufficient effective voltage due to voltage drop. It is easily affected by its own resistance and wiring parts, and the resistance of each pixel becomes uneven, so variations in resistance cause differences in voltage drop levels, resulting in variations in effective voltage, which may affect the transmittance of the liquid crystal panel. Because of the non-uniformity within the screen,
When the brightness of the back light source is made uniform, such as in Japanese Patent Publication No. 91 and Japanese Unexamined Patent Publication No. 1-245220, there is a serious problem in that display unevenness occurs as a liquid crystal display device.

The present invention has been made to solve these problems, and its purpose is to prevent display unevenness in a liquid crystal display device and provide a liquid crystal display device with high display quality.

[Means for Solving the Problems] A liquid crystal display device of the present invention includes a liquid crystal cell having a liquid crystal sandwiched between a pair of transparent substrates disposed opposite to each other, and a back light source. Brightness to L
av, the brightness at any point i, T, v, the transmittance at any point i, T, the average transmittance of the liquid crystal cell on the backlight source, T; When the surface brightness of the liquid crystal display device is al and the average surface brightness is a av, L: *T: ”a: ......
・・・・・・・・・ ■a -11*1oo-1o
o=x-(p a V-15<M<15...
. . . ■02 It is characterized in that the in-plane brightness variation M expressed by the equation 0 satisfies the relationship expressed by the equation 0.

In liquid crystal display devices and electronic products, each transparent electrode substrate has a plurality of row electrodes or column electrodes so that driving signals are inputted alternately from the opposite side every other transparent electrode substrate.

A liquid crystal display device is characterized in that a color filter layer is formed under a row electrode or a column electrode of a liquid crystal cell.

A liquid crystal display device is characterized in that a color filter layer is formed under a row electrode or a column electrode of a liquid crystal cell with at least one protective film interposed therebetween.

A liquid crystal display device is characterized in that it has an optically anisotropic body on at least one of the top and bottom of the liquid crystal panel, or on both the top and bottom sides. show. In the figure, 1 is an upper polarizing plate, and 2 is a liquid crystal cell (hereinafter referred to as A) in which a liquid crystal as an optically anisotropic body is sandwiched between two substrates.
Note that the A cell may be in the form of a film as long as it is optically anisotropic. 3.4 is an upper transparent substrate and a lower transparent substrate of cell A, each of which is provided with an alignment film of 7.8 on the inner surface, subjected to an alignment process, and has a liquid crystal sandwiched therebetween to be used as an optically anisotropic body.

6 is a liquid crystal cell (hereinafter referred to as B cell) that performs display by applying voltage and has column electrodes or alternately taken out;
After forming the desired column electrodes 12 on the upper electrode substrate 7 of the B cell, an alignment film 14 is provided on the surface thereof and an alignment treatment is performed, and the column electrodes 1 are placed on the lower electrode substrate 10 of the B cell, which is the other transparent substrate.
After forming the desired row electrodes 13 so as to be perpendicular to the electrodes 2, an alignment film 15 is provided on the surface of the electrodes 13, and the liquid crystal 11 is sandwiched therebetween.

In addition, as shown in Fig. 2, the column electrodes are divided into
The transmittance of the liquid crystal panel was measured at the spot using a color computer TC-1800M manufactured by Tokyo Electric Power Co., Ltd. The results are shown in Table 1. (hereinafter X,
(The intersection point of Y is called A1, and the transmittance is called T.) By taking out data alternately as shown in Table 1,
It can be seen that the transmittance is uneven throughout the panel.

Table 1 To facilitate the explanation of the embodiment, the locations on the diffuser plate, lighting curtain, and light guide plate immediately below the divided areas A, , of the liquid crystal panel described above are set as B, 1, and the surface brightness is set as 1.
It is called.

[Example 1] FIG. 3 is a cross-sectional structural diagram of a liquid crystal display device showing an example of the present invention. In the figure, 17 is a liquid crystal panel with column electrodes taken out alternately in the left and right directions as viewed from the drawing, 18 is a diffuser plate made of acrylic or polycarbonate by a casting method, and 19 is a cold cathode tube with a tube brightness of 800 nits. , 20 is a reflector, b in the figure is the distance between the cold cathode tubes, and C is the effective display length of the liquid crystal panel 17. (In this example, c
= 120 mm) Under the above conditions, it is sufficient to set b = 50 mm to obtain a uniform amount of light on the diffuser plate 18, or to adjust the distance b to correct the difference in transmittance within the liquid crystal panel 17. 60 mm, and the shape of the reflection plate 20 was set so that more light would reach the lower transmittance of the liquid crystal cell 17.

Here, the screen as a liquid crystal display device is located at a certain location A1.
The transmittance of the panel at T, , and the surface brightness immediately below L1. Since it can be expressed as the product of , Table 2 is applied to this example.

As can be seen from Table 2, the luminance on the surface of the diffuser plate 18 is 80.5<a:<83.5. aav=8185, and the above-mentioned equations (1) and (2).

From (3), the brightness variation M is -1,65<M<2°02
As a result, it was possible to obtain a liquid crystal display device exhibiting a uniform and even luminance distribution.

Table 2 a*v=8 1. 8 5 (a;) may=83. 5 (a:), , =8o, 5 -1.65<M<2.02 For comparison in this example, the luminance L1. on the diffuser plate 18. Or the condition b=50 as mentioned above
mm, and the same evaluation as above was performed, the screen of the liquid crystal display device of the comparative example was as shown in Table 3, and the surface brightness was 72.2<a;<97°2, asv=81° 5
2, and the aforementioned equations (1), (2),
From (3), the brightness variation M is -11.43<M<19.
23, and it can be seen that quite severe display unevenness has occurred.

As can be seen from the above, for liquid crystal panels that have large variations in transmittance within the screen, such as those that are alternately taken out, by correcting the brightness distribution of the light source, it is possible to display uniformly and uniformly as a liquid crystal display device. Ta.

Table 3 aav=81. 52 (a:)lIax=97. 2 (a,) □, =72.2 -11.43<M<1 9° [Example 2] FIG. 4 is a liquid crystal display device showing an example of the present invention. In the figure, 17 is a liquid crystal panel taken out alternately in the DE direction, 21 is a light guide plate, 22 is a tubular light source, 23 is a reflective film, and 24 is a curved reflective plate. The tubular light sources 22 are disposed above and below the light guide plate 21, and the concave reflector 24 is disposed to guide light only in the direction of the light guide plate 21. The light guide plate 21 is made of silicon dioxide, which has a constant and high spectral reflectance in the visible light range, on the back side (the side opposite to the liquid crystal panel side).
A reflective film 23 made of magnesium oxide, phosphorus pentoxide, titanium white, zinc oxide, etc. was formed. Similar to Embodiment 1, the reflective film is arranged near the tubular light source 22 so that the surface roughness on the liquid crystal panel 17 is constant and to correct uneven transmittance of the liquid crystal panel 17 taken out alternately. When the density of the reflective film 23 was set to be as high as in Example 1, it was possible to obtain a uniform liquid crystal display device with no display unevenness, as in Example 1.

[Example 3] As shown in FIG. 5 in the alternately extracted liquid crystal panel of Example 1, color filters 25 that mainly transmit red, green, and blue light are arranged on the lower transparent substrate 10 at the pitch of the column electrodes 12. After that, a protective film 26 is formed on the entire surface of the lower transparent substrate 10 or only on a desired area in order to improve chemical resistance, flatness, etc. Row electrodes 13 were laminated thereon so as to be perpendicular to the color filters 25, and an alignment film 15 was further provided to carry out an alignment treatment to sandwich the liquid crystal 11. In this example,
If a protective film is used, or if there are no problems with flatness or chemical resistance, there is no problem even without a protective film.In addition, the effects of this example are limited to the method of forming the color filter, the material of the protective film, etc. It is not something that will be done.

Liquid crystal panel 17 with color filters as described above
In addition, since the transmittance of the liquid crystal panel 17 is low due to the color filter 25, a light source with a brightness of 3000 nits was used as the back light source, and as in Example 1, a liquid crystal display with no display unevenness was obtained. I was able to obtain the device.

[Effects of the Invention] As described above, according to the present invention, when there are variations in transmittance in the liquid crystal panel, by correcting the surface brightness of the back light source and the side light source, a high quality display with no unevenness can be achieved. This has the effect of enabling display.

This is particularly effective in liquid crystal display devices having liquid crystal panels with uneven transmittance due to alternate extraction.

Furthermore, electronic products to which the liquid crystal display device of the present invention is applied as a man-machine interface have the effect of being able to provide high-quality products with uniform image quality and good visibility.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional structural diagram of a liquid crystal panel used in the present invention. FIG. 2 is a diagram showing division of column electrodes and row electrodes in the present invention. FIG. 3, FIG. 4, and FIG. 5 are diagrams showing a liquid crystal display device according to a third embodiment of the present invention. FIGS. 6 and 7 are diagrams showing conventional liquid crystal display devices. 1, 16 3, 4, 9, 1 5, 11 7, 8, 14. 12, 13 1 Full polarizing plate A cell Transparent substrate Liquid crystal B cell Alignment film Transparent electrode Alternate takeout Liquid crystal spring Diffuser plate Cold cathode tube reflector Light guide plate Tubular light source reflective film Curved reflector or above

Claims (5)

[Claims] (1) In a liquid crystal display device consisting of a liquid crystal cell in which a liquid crystal is sandwiched between a pair of transparent substrates disposed facing each other and a backlight source, the luminance at any point i of the backlight source is defined as L_i,
The transmittance at an arbitrary point i of the liquid crystal cell on the backlight source is T_i, and the arbitrary point i obtained by equation [1]
When the surface brightness of the liquid crystal display device is a_i and the average surface brightness is a_a_v, L_i*T_i=a_i......[1] |a_i/a_a_v-1|*100-100=M...[
2]-15<M<15......[3] The in-plane brightness variation M expressed by the formula [2] is [3]
A liquid crystal display device characterized by satisfying the following relationship. (2) At least one of the transparent electrode substrates has a plurality of row electrodes or column electrodes so that drive signals are alternately input from the opposite side to every other electrode.
The liquid crystal display device described. (3) The liquid crystal display device according to claim 1, wherein a color filter layer is formed under the row electrode or the column electrode of the liquid crystal cell. (4) The liquid crystal display device according to claim 1, wherein a color filter layer is formed under the row electrode or column electrode of the liquid crystal cell with at least one protective film interposed therebetween. (5) The liquid crystal display device according to claim 1, further comprising an optically anisotropic body on at least one of the upper and lower sides of the liquid crystal panel, or on both the upper and lower sides.