JPS5957219A - Liquid crystal display element using plastic substrate - Google Patents

Abstract

PURPOSE:To suppress the generation of retardation by making the stretching axis direction of a pair of uniaxially stretched plastic film substrates which are placed to face to each other coincident and making the orientation direction roughtly perpendicular. CONSTITUTION:The stretching axes of the upper and lower substrates which are uniaxially stretched plastic films are made coincident in a Y direction, and the rubbing directions, that is, the horizontal orientation directions are intersected orthogonally with each other at the upper and lower substrates (the Y direction with the upper substrate and the X direction with the lower substrate) whereby the polarization axes of polarization plates are intersected orthogonally with the rubbing directions of the respective substrates. A liquid crystal display element is made strong to the change in temp. during manufacture or use by such disposition and the element having high reliability with difficulty in generating twist, camber, etc. is obtd. The uniaxially stretched films differ in the coefft. of expansion between the stretching axis and the other direction and therefore if the stretching axes at the upper and lower substrates are intersected orthogonally with each other, the substrates expand differently when the temp. changes, thus generating stress in a sealed part. On the other hand, if the stretching axis of the upper and lower substrates are coincident, the substrates expand and contract roughly equally when heated and cooled, thus obviating the generation of stress.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plastic liquid crystal display element using a -axis stretched plastic film substrate.

In recent years, progress has been made in the development of luxurious and flexible plastic film substrates for liquid crystal display devices. This was desired because plastic films are less likely to break even when they are thin, can be easily curved, and are inexpensive compared to glass; however, they are inferior to glass in heat resistance, There were various problems such as poor chemical properties, low visible light transmittance and darkness, poor flatness, and different optical rotation.

In the case of twisted nematic ('rN) type liquid crystal display elements using polarizing plates, the birefringence of the plastic film,
The uneven cape tends to cause color unevenness and retardation, and visibility tends to be lower than with glass.

Especially for versatility - biaxial stretching,...
Since the film exhibits refractive properties, it is necessary to make the crystal axis of the film parallel or direct to the polarization axis of the polarizing plate in order to prevent retardation when used as a substrate for an IN-type liquid crystal display element. . Furthermore, since nematic liquid crystals also have optical rotation, it is essential to eliminate the effect of birefringence by making the orientation direction parallel or perpendicular to the crystal axis direction of the film. However, the crystal axis structure 3B+ in a stretched plastic film is very complicated, and in order to prevent retardation due to the effect of birefringence, we tried changing the arrangement of the film and the polarizing plate many times, but the TN
The display surface of type liquid crystal display elements tends to be colored due to retardation, which is an effect of birefringence, reducing visibility. This is particularly likely to occur when a large-sized liquid crystal display element or a large number of liquid crystal display elements are manufactured simultaneously from a large-sized substrate.

In addition, in a biaxial diagonal stretched plastic film, even if the difference in anisotropy of the refractive index, which indicates the edge refraction rate, △n f is set as small as 0.003 or less, retardation will occur and crystals will It was found that the axis tends to have a complicated structure, and the crystal axis of the film and the polarization axis of the polarizing plate are adjusted so that the angle is < 1.
It was difficult to keep everything in order, which caused a drop in productivity.

On the other hand, -axis-stretched plastic films have a unidirectional stretching axis, which makes it easy to align the stretching axis of the film with the polarizing axis of the polarizing plate, and is less likely to cause retardation. Oh yeah.

The present invention aims to obtain a TN-type liquid crystal display device using a uniaxially stretched plastic film as a substrate that does not easily cause retardation. In a plastic substrate liquid crystal display element, a liquid crystal cell is made of a liquid crystal cell with polarizing plates provided on both sides of the liquid crystal cell, which is made of a liquid crystal cell whose periphery is sealed and whose interior is filled with a liquid crystal having a positive 19% anisotropy. This is a plastic substrate liquid crystal display device characterized in that the uniaxially stretched plastic film substrate is aligned in one direction and the orientation direction is substantially perpendicular.

In the liquid crystal display element of the present invention, since the stretching direction of the stretched glass film substrate is the same for the upper and lower substrates, the upper and lower substrates expand in the same direction during heating and cooling during manufacturing.
Do not shrink or cause stress to the seal.
, twisting and warping, and reliability is improved. Of course, reliability is improved because stress on the seal part is less likely to occur due to temperature changes not only during manufacturing but also during use.

In addition, the liquid crystal display element of the present invention has good contrast, is less likely to cause color unevenness, is thin, has a scratch length of plastic film, and is 4! Advantages such as quantity, resistance to breakage, ability to curve, etc.
It should be kept as is.

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

FIG. 1 is a cross-sectional view of an example of a liquid crystal element of the present invention. Two uniaxially stretched plastic film substrates (IA), (I
B) The inner surface has transparent % poles of the desired shape (2A), (2B)
%, then overcoat (3A), (3B) for orientation such as SiOx, PVA, etc. is formed, and a sealing material (
4) is sealed and filled with liquid crystal (5) to form a liquid crystal cell, and on both sides there are polarizing plates (6A), (
6B) is arranged, and a reflector plate (7B) is arranged on the back side.
) are arranged.

This overcoat for orientation may be formed by rubbing or by oblique vapor deposition after overcoating with the super fat.

The liquid crystal display element in this example shows a typical liquid crystal display element, and includes the use of 810x, TiOx, etc. (7) 77 tercoat, multilayer electrode, in-plane spacer, in-plane seal, fixed display, color polarizing film, For the use of a transflective plate, light source, light guide plate, conductive connection with the outside, multilayer cell formation, surface printing, non-glare treatment, curved surface, etc., any of the conventionally known glazed paulownia structures can be used.

Uniaxially stretched plastic films used in the present invention include acrylic film, polyester film, polycarbonate film, polypropylene film, polyvinyl chloride film, polystyrene film, polyvinylidene chloride film, polyethylene film, polyvinylidene film, polystyrene film, Transparent films such as Sansugi Cellulose Film Gin can be used, and may be appropriately selected and used in consideration of the manufacturing process, usage conditions, and the like.

Among them, uniaxially stretched polyester film has excellent durability.
This is preferable because it is easy to manufacture by a process similar to the manufacturing process of conventional liquid crystal display elements using glass substrates.

In addition, any nematic liquid crystal having positive frost induction and anisotropy can be used as the liquid crystal, and if necessary, chiral nematic liquid crystal, cholesteric liquid crystal, dichroic dye, dielectric substance,
Optically active substance 5, etc. may be added.

Figures 2 and 3 show the polarization axis of the polarizing plate of the liquid crystal display element of the present invention, the longitudinal stretching direction of the -axially stretched plastic film, and
FIG. 1 is an explanatory diagram showing the direction of the ram alignment direction.

Figures 2 and 3 show the stretching axis (broken line arrow) and rubbing direction (double line arrow) of the uniaxially stretched plastic film (IA) (IB) of the liquid crystal display element of this item t13)I.
It is an explanatory view showing the relationship between the electrode and the polarization axis direction (arrow) of the polarizing plate (6A) + (6B). 1. Large crystals, sealing materials, etc. are omitted from the illustration. For convenience of explaining the direction,
The direction parallel to the bottom side of the figure is the X direction, and the direction parallel to the right side is the Y direction.
direction.

In Figure 2, the stretching axes of the upper and lower substrates of the -axis stretched plastic film are aligned in the Y direction, and the rubbing direction, that is, the direction of lateral alignment treatment, is orthogonal to the upper and lower substrates (in the upper substrate, the stretching axes of the upper and lower substrates are aligned in the Y direction).
The figure shows a liquid crystal display element in which the polarizing axis of the polarizing plate is aligned directly with the rubbing direction of each substrate (in the case of the lower substrate, the X direction).

With this arrangement, as described above, it is resistant to temperature changes during manufacture or use, and the liquid crystal display element is less likely to be twisted or warped, making it highly reliable. This is because the -axis stretched plastic film has a different expansion rate between the motion axis and the other directions.If the stretching axes of the upper and lower substrates are perpendicular to each other, different expansions occur when the temperature changes, and the seal part cause stress.

Moreover, if the seal is hardened by heating in the sealing process, stress is generated in the seal part due to contraction when the cell is cooled down to its original state, and the cell itself is likely to be twisted, warped, and warped.

In contrast, the present invention provides 1. Since the stretching axes of the upper and lower substrates are the same, even when heated and cooled, the expansion and contraction remain almost the same, and stress does not occur.

Also, the contrast and color unevenness are almost the same as with the glass substrate.
To some extent, l' production is also possible.

1.3 is another example of the present invention, and the difference from the case of FIG. 2 is that the rubbing direction and the 11/11 optical axis direction of the polarizing plate are made to match.

Comparing FIG. 2 and FIG. 3, the case in FIG. 2 is preferable and is less likely to cause retardation, but other features are the same.

In addition to these two types, negative display can be achieved by shifting the polarizing axis of one polarizing plate by 190', making the stretching axis and polarizing axis perpendicular to each other on one substrate, and making the stretching axis and polarizing axis parallel to each other on the other substrate. You can also do that.

However, among these embodiments of the present invention, the structure shown in FIG. 2 is preferable because it has no turchysion and has good visibility.

Also, in the above explanation, everything was explained in terms of perpendicular or parallel directions, but it is also possible to intentionally create a deviation of about ±10' to improve margins and improve multiplex performance, although some retardation will occur. .

Next, examples will be explained.

Uniaxially oriented polyester film base 8+, (1o.

Patterning μ thickness, 5ooΩ/[1] with transparent electrode,
A PTA overcoat was formed thereon by lath spin coating, and a substrate was produced by rubbing in the direction of the stretching axis, and a substrate was rubbed in a direction perpendicular to the stretching axis. The substrates are arranged so that the rubbing directions are perpendicular to each other, that is, the stretching axes are coincident, and the ilEkms face each other, and the periphery is sealed with a sealing material. Merck & Co. 1rf7J)e was injected, the injection port was sealed, and a liquid crystal cell was manufactured.

A liquid crystal display element was manufactured by arranging polarizing plates on both sides of this liquid crystal cell so that the polarization axes were perpendicular to the two pin directions.

The liquid crystal display element manufactured in this way has almost no deterioration in display quality due to birefringence, and has a display quality close to that of a liquid crystal display element using a conventional glass substrate.
No twisting or warping occurred, and the reliability against temperature changes was high.

As described above, although the present invention is a liquid crystal display element using a glass film substrate, it is possible to obtain a display quality close to that of a liquid crystal display element using a glass film substrate, and various applications are possible in the future. It is something.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal display element. 2 and 3 are explanatory diagrams of the structure of the liquid crystal display element of the present invention. IA, IB... - Axial stretched glass film substrate 2A, 2B... Transparent electrode fiA, 6B... Polarization, plate

Claims (2)

[Claims] (1) On both sides of a liquid crystal cell, uniaxially stretched plastic film substrates with transparent electrodes and laterally aligned are placed opposite each other, the periphery is sealed, and the inside is filled with liquid crystal having positive dielectric anisotropy. In a plastic substrate liquid crystal display element provided with a polarizing plate, the stretching axis directions of a pair of opposing nine-axis stretched plastic film substrates are aligned, and
A plastic substrate liquid crystal display element characterized in that the alignment direction is substantially perpendicular. (2) A feature characterized in that the polarizing plate is arranged substantially perpendicular to the orientation direction.
Geki's plastic substrate liquid crystal display element.