JPS6340119A - Liquid crystal display body - Google Patents

Abstract

PURPOSE:To prevent generation of an area where a torsion angle of a liquid crystal in the vicinity of a seal is theta-pi, by making thickness of a liquid crystal layer of the outside of a display screen thicker than thickness of a liquid crystal layer of the inside of the display screen. CONSTITUTION:An area A and an area B show the outside of a display screen and the inside of the display screen, respectively, and due to existence of an insulator layer 7, thickness of a liquid crystal layer of the area A is thicker than thickness of a liquid crystal layer of the area B. Therefore, generation of an area where a torsion angle of a liquid crystal in the vicinity of a seal 6 is theta-pi can be prevented. That is to say, thickness of the liquid crystal layer in the vicinity of the seal of the outside of the display screen can be made thicker enough than thickness of the liquid crystal layer being a boundary in which the torsion angle of the liquid crystal is varied from theta to theta-pi, there fore, in that part, as for the torsion angle of the liquid crystal, theta becomes an absolutely stable value. In this way, an area where the torsion angle of the liquid crystals is theta-pi is not generated.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a liquid crystal display using a twisted nematic liquid crystal with a twist angle of more than 90 degrees ◇ [Prior Art] Twisted nematic liquid crystal with a twist angle of more than 90 degrees A liquid crystal display using liquid crystal is capable of multi-digit multiplex driving with a duty ratio of about 1/10, and is a liquid crystal display that is expected to develop in the future. As for literature, for example, JP-A-60-50511, JP-A-60-16222
There are 5 etc.

In such a liquid crystal display, in order to obtain a twist angle exceeding 90 degrees, a liquid crystal that spontaneously assumes a twisted helical structure by adding an optically active agent is used. Now, if the spontaneous twisting helical pitch of the liquid crystal is P, the twist angle of the liquid crystal in the liquid crystal cell is θ, and the thickness of the liquid crystal layer of the liquid crystal cell is d, then this king must satisfy the conditions. If the liquid crystal layer thickness d becomes smaller than the range of this condition, the twist angle of the liquid crystal in the liquid crystal cell becomes θ-π. On the other hand, if the liquid crystal layer thickness d becomes larger than the range of this condition, the twist angle of the liquid crystal in the liquid crystal cell becomes θ+π. We evaluated the display characteristics by varying the liquid crystal layer thickness d within the range of these conditions, and found that the smaller the liquid crystal layer thickness d within the range of these conditions, the better the display characteristics. In other words, in order to obtain good display characteristics, the thickness of the liquid crystal layer must be modified according to the conditional formula (1
) is required to be as small as possible within the range.

[Problem that the invention seeks to solve]

However, in the prior art described above, if the liquid crystal layer thickness is made as small as possible within the range of conditional expression (1) in order to improve display characteristics, the twist angle of the liquid crystal becomes θ−π due to unevenness in the layer thickness of the liquid crystal cell. Often certain areas arise. This area tends to occur near the seal that seals the liquid crystal. Therefore, even if this area initially appears only near the sticker outside the display screen, it tends to expand over time. As time passes, this area will expand to the inside of the display screen. What has been described above is a serious problem in the appearance quality and reliability of the prior art related to liquid crystal displays using twisted nematic liquid crystals with twist angles exceeding 90 degrees.

Therefore, the present invention solves the problem of the occurrence of a region where the twisting angular force of the liquid crystal is fθ-π near the seal by making the liquid crystal layer near the seal outside the display screen thicker than the liquid crystal layer inside the display screen. The object is to provide a liquid crystal display using twisted nematic liquid crystal with a twist angle of more than 90 degrees, which has high appearance quality and reliability.

[Means for solving problems]

The liquid crystal display of the present invention is a liquid crystal display using twisted nematic liquid crystal with a twist angle exceeding 90 degrees, and is characterized in that the thickness of the liquid crystal layer outside the display screen is thicker than the thickness of the liquid crystal layer inside the display screen. [Function] According to the above structure of the present invention, the thickness can be made sufficiently thicker than the area outside the display screen, so that the torsion angle of the liquid crystal in that part becomes an absolutely stable value θ, and the torsion angle of the liquid crystal is is θ
−π regions no longer occur.

〔Example〕

FIG. 1 is a cross-sectional view of main parts of a liquid crystal display according to a first embodiment of the present invention. body layer 7
, an upper polarizing plate 8 and a lower polarizing plate 9 ◎Furthermore, in FIG. 1, the area indicated by A means outside the display screen, and the area indicated by B means inside the display screen. As can be seen from Figure 1, due to the presence of the insulator layer 7, A
The liquid crystal layer thickness in the region indicated by is thicker than the liquid crystal layer thickness in the region indicated by B.

With the structure described above, it is possible to prevent the occurrence of a region where the twist angle of the liquid crystal is θ-π near the seal 6. To list the main values in this example, the twist angle θ=π of the liquid crystal, the spontaneous twist helical pitch P=
24μfn, liquid crystal layer thickness in the area indicated by A = 8μ, liquid crystal layer thickness in the area indicated by B ti B == 7μ
Since 0θ = π and P = 24μ, conditional expression (1) becomes 6μW < d < 18μ, but dA and (LB satisfy this condition ◇ Also, the liquid crystal outside the display screen Layer thickness dA and liquid crystal layer thickness within the display screen 1
The ratio of 1B, that is, the value of aA/cLB, is approximately 114.0 If this value is less than 11, the desired effect of the present invention cannot be obtained, and if it is more than 18, the color of the screen is There is a noticeable difference between the outside and the inside of the display screen, making it unsightly. Therefore, the appropriate value for aA/an is 1.8 from tl.

Now, the thickness of the insulator layer 7 is given as the difference between dA and di, which is 1μ. In this example, the insulator layer 7 is Si
It is formed by sputtering O□. In addition,
Other methods for forming the insulating layer include etching a portion of the lower or upper substrate other than the area indicated by B.

FIG. 2 is a sectional view of main parts of a liquid crystal display according to a second embodiment of the present invention, and the numbers in the figure correspond to the numbers in FIG. 1, respectively. The feature of this embodiment is that the insulator layer 7
is formed on both the upper substrate 1 and the lower substrate 2. Main numerical values θ in this example, P SA A %
d B are all the same as in the first embodiment, but the thickness of the insulating layer is 0.5 μm on each of the upper substrate side and the lower substrate side, and the sum of both is 1 μm. Effects] As described above, the present invention provides a liquid crystal display using twisted nematic liquid crystal with a twist angle of more than 90 degrees.
By making the thickness of the liquid crystal layer outside the display screen thicker than the thickness of the liquid crystal layer inside the display screen, it is possible to prevent the occurrence of a region where the twist angle of the liquid crystal is θ - π near the seal, improving the appearance quality and reliability. This has the effect of providing an excellent liquid crystal display.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of main parts of a liquid crystal display according to a first embodiment of the present invention. FIG. 2 is a sectional view of main parts of a liquid crystal display according to a second embodiment of the present invention. 1... Upper substrate 2... Lower substrate 3... Upper transparent electrode 4... Lower transparent electrode 5... Liquid crystal layer 6. ... Seal 7 ... Insulator layer 8 ... Upper polarizing plate 9 ... Lower polarizing plate and above

Claims (2)

[Claims] (1) A liquid crystal display using twisted nematic liquid crystal with a twist angle of more than 90 degrees, characterized in that the thickness of the liquid crystal layer outside the display screen is thicker than the thickness of the liquid crystal layer inside the display surface. (2) The liquid crystal display according to claim 1, wherein the thickness of the liquid crystal layer outside the display screen is 1.1 to 1.8 times the thickness of the liquid crystal layer inside the display screen.