JPH11237635A - Liquid crystal display panel and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the leak of light around beads, to enable permit high- contrast display and to improve the uniformity of cell gaps and orientations by forming projections to form the gaps of liquid crystal cells, and performing liquid crystal orienting processing onto the surface of a substrate on the side where the projections exist by irradiating the surface with polarized ultraviolet rays. SOLUTION: Projections 18 composed of acrylic resin are formed on a storage capacitor 16 by photolithography. In this case, the height (thickness) of the projection 18 made of the acrylic resin is 3 μm but the height of the projection 18 can be adjusted corresponding to a required cell gap. Then, the lengthwise direction of pixel electrode wiring 14 and common electrode wiring 13 is irradiated with ultraviolet rays having a polarizing axis at 80 deg., for example, and a liquid crystal orienting processing is performed. Since a liquid crystal molecule is oriented while being deviated from the polarizing axis of the ultraviolet light at 90 deg. by this orienting processing, the long axis of the liquid crystal molecule is oriented while forming the angle of 10 deg. with the lengthwise direction of pixel electrode wiring 14 and common electrode wiring 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display panel of an IPS (ion plane switching) type which drives a liquid crystal by applying a substantially parallel electric field to a substrate surface, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, active matrix type liquid crystal displays using thin film transistors (TFTs) have been used in various fields such as displays for camcorders and displays for notebook computers.
It is forming a big market.

In particular, recently, application development as a monitor for a personal computer or a work station is expected, and a demand for a screen size of 13 to 14 inches or more on a diagonal is increasing.

At present, the twisted nematic (TN) mode is mainly used as the display mode of the TFT liquid crystal display.
As described in, for example, Japanese Patent Application Laid-Open No. 878, the IPS mode in which an electric field substantially parallel to the substrate surface is applied and liquid crystal molecules are moved in parallel to the substrate surface is expected due to its extremely wide viewing angle characteristics. Are gathering.

[0005] The movement of liquid crystal molecules in the IPS mode is
As schematically shown in FIG. 3, the configuration of the TFT liquid crystal display according to the IPS mode is such that a pixel electrode 3 and a common electrode 4 are provided on vertically opposed substrates 1 and 2, and a polarizing plate 5 is provided outside each of the substrates 1 and 2. As shown in FIG. 3 (a), when a power supply voltage 7 is applied to both electrodes 3 and 4, liquid crystal molecules 8 are applied by an electric field applied substantially parallel to the surfaces of substrates 1 and 2. Is displaced to a state as shown in FIG. When the liquid crystal molecules 8 operate as described above,
It differs from the conventional TN mode in many respects.

Conventionally, the formation of a gap in a liquid crystal panel has been performed by dispersing spherical spacer beads made of resin or glass having a diameter of several μm on a substrate and bonding them. Since the TN method is usually used in a normally white (NW) mode, light leakage around the beads during black display does not cause much problem. This is because the liquid crystal molecules around the beads also rise considerably during black display with the electric field applied. Further, the alignment treatment of the liquid crystal is performed by a rubbing treatment in which an alignment film such as polyimide is formed on the substrate surface and rubbed in one direction with a buff cloth.

[0007]

On the other hand, since the IPS mode is a normally black (NB) mode in which black display is performed without applying an electric field, the liquid crystal molecules around the beads are affected by the alignment regulating force on the bead surface. Directly received, relatively large light leakage occurs around the beads, causing a decrease in contrast. In addition, the IPS method requires more accurate gap control and gap uniformity than the TN method. In order to satisfy this requirement, it is necessary to disperse more beads per unit area than in the TN method. Such an increase in the bead dispersion density further increases light leakage per unit area and causes a reduction in contrast.

In order to prevent such light leakage around the beads, it has been proposed to selectively form a spacer in a non-display area. However, since a spacer having a thickness of several μm is present, a conventional rubbing method is used. In the alignment treatment by (1), alignment unevenness (rubbing stripe unevenness) due to the stepped shape of the spacer occurs, and there is a problem that alignment uniformity cannot be obtained.

An object of the present invention is to provide a liquid crystal display panel which does not leak light around the beads as in the prior art, enables high contrast display, and has excellent cell gap and uniformity of alignment, and a method of manufacturing the same. Is to do.

[0010]

In order to achieve the above object, a liquid crystal display panel according to the present invention comprises a pair of transparent substrates, at least one of which has a dielectric anisotropy and a refractive index sandwiched between the substrates. A liquid crystal composition layer having anisotropy, a polarizing means, a plurality of pixels arranged in a matrix, a thin film transistor element provided for each pixel and connected to a pixel electrode, a signal wiring electrode, a scanning wiring electrode, a common electrode, A liquid crystal display comprising: means for applying a voltage signal waveform that changes the light transmittance or reflectance of a pixel; and means for applying an electric field substantially parallel to a substrate surface between the pixel electrode and the common electrode. In the panel, a projection for forming a gap of a liquid crystal cell is formed on at least one of the pair of substrates, and at least the substrate surface on the side where the projection is present is irradiated with polarized ultraviolet light to form a liquid crystal display. Characterized in that subjected to a treatment, by this arrangement, in order to form a gap by the projections,
There is no light leakage around the beads as in the past, high-contrast display is possible, and a uniaxially oriented film is formed by irradiating polarized ultraviolet light to a photo-alignable material, which results in a cell gap. And it becomes what was excellent in the uniformity of orientation.

The method for manufacturing a liquid crystal display panel according to the present invention includes the steps of: forming a projection for forming a gap of a liquid crystal cell on at least one of the substrates by photolithography in order to manufacture the liquid crystal display panel; ,
The method includes a step of irradiating polarized ultraviolet light to at least the substrate surface on the side where the protrusions are present to perform an alignment treatment.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention has a pair of transparent substrates, at least one of which has a dielectric anisotropy and a refractive index anisotropy sandwiched between the substrates. A liquid crystal composition layer, a polarizing means, a plurality of pixels arranged in a matrix, a thin film transistor element provided for each pixel and connected to a pixel electrode, a signal wiring electrode, and a scanning wiring electrode;
A common electrode, means for applying a voltage signal waveform for changing the light transmittance or reflectance of the pixel, and means for applying an electric field substantially parallel to the substrate surface between the pixel electrode and the common electrode; In the liquid crystal display panel, a projection for forming a gap of a liquid crystal cell is formed on at least one of the pair of substrates, and at least the substrate surface on the side where the projection is present is irradiated with polarized ultraviolet light to perform an alignment process. It is characterized by having been performed.

According to a second aspect of the present invention, there is provided a liquid crystal composition layer having a dielectric anisotropy and a refractive index anisotropy which are sandwiched between at least one of the pair of substrates, and oriented between the substrates. A plurality of pixels arranged in a matrix, a thin film transistor element provided for each pixel and connected to the pixel electrode, the signal wiring electrode, and the scanning wiring electrode, a common electrode, and a voltage for changing the light transmittance or reflectance of the pixel A manufacturing method for manufacturing a liquid crystal display panel, comprising: means for applying a signal waveform; and means for applying an electric field substantially parallel to a substrate surface between the pixel electrode and the common electrode. On one side, a step of patterning projections for forming a gap of the liquid crystal cell by photolithography, and irradiating polarized ultraviolet light to at least the substrate surface on the side where the projections are present. It characterized by having a step of performing an alignment process by.

In the liquid crystal display panel and the method of manufacturing the same according to the present invention, the projection for forming the cell gap has a thickness of T.
It may be formed on the FT array substrate side, on the opposite substrate side, or on both sides of the substrate. However, in terms of process, it is more advantageous to form it on one of the substrates.

The projections are preferably arranged in the non-display area in consideration of the contrast and the light transmittance of the panel. That is, it is preferable that the TFT array substrate is arranged on a wiring, a storage capacitor, a transistor, or the like, or the counter substrate (generally, a color filter substrate) is arranged on a black matrix.

The protrusions may be formed by a printing method or the like, but are preferably formed by a photolithographic method in consideration of controlling the thickness, shape, and positional accuracy. The material of the projections may be inorganic or organic, but is preferably an insulator. In terms of process, it is easiest to use a photosensitive polymer such as an acrylic resin.

In general, a photoreactive material can be used as the alignment film. For example, a photodegradable polymer material or a photocrosslinkable polymer material is used. By irradiating the photoalignable material with polarized ultraviolet light, a selective photoreaction occurs in a portion having a transition moment in the polarization direction, and a uniaxial orientation is formed. In the present invention, the liquid crystal alignment treatment by polarized ultraviolet light may be performed on the substrates on both sides, or may be performed only on one substrate, but in the case of one side, it is performed on the substrate side on which the protrusions are formed. There is a need.

An embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, the screen has a diagonal of 15.2 inches, an aspect ratio of 16: 9, and a resolution of (vertical 768) .times.
An RGB IPS mode TFT liquid crystal panel under the conditions of (horizontal 1364) was manufactured as follows. FIG. 1 is a schematic diagram showing a planar structure of an array shape of a pixel portion of the panel in the present embodiment, and FIG. 2 is a schematic diagram showing a cross-sectional structure of the panel of FIG.

1 and 2, reference numerals 11 and 13 denote a scanning electrode wiring and a common electrode wiring, respectively. In this embodiment, both electrode wirings 11 and 13 are formed by forming a metal thin film mainly composed of aluminum. Then, the shape shown in the figure was formed on the same plane by using a photolithographic method. The metal material to be used is desirably a metal having a low wiring resistance. However, it is not particularly limited to an aluminum-based metal, and may be a single-layer film or a multilayer film. Thus, both electrode wirings 11, 1
3 is formed, an anodic oxide layer of the aluminum film and silicon nitride (SiN _x ) are stacked as an insulating film 19, and amorphous silicon is stacked as a semiconductor layer. After removing a part of the layer, two layers of aluminum / titanium (Al / Ti) were deposited by a sputtering method, and the signal electrode wiring 12 and the pixel electrode wiring 14 were formed by dry etching.

Reference numeral 15 denotes a thin film transistor (TFT) as a switching element. In this embodiment, the line width of the pixel electrode wiring 14 is 5 μm, and the distance between the pixel electrode wiring 14 and the common electrode wiring 13 is 12 μm. Further, a storage capacitor 16 was formed between the pixel electrode wiring 14 and the scanning electrode wiring 11. In the present embodiment, the storage capacitor 16 is formed between the corresponding scanning electrode wiring 11 one line before, but may be formed between the scanning electrode wiring 11 or the common electrode wiring 13 one line later.

Further, as the insulating layer 17, silicon nitride (SiN
After the deposition of _x ), a projection 18 made of an acrylic resin was formed on the storage capacitor 16 by photolithography.
In the present embodiment, the height (film thickness) of the protrusion 18 of the acrylic resin is set to 3 μm, but the height of the protrusion 18 can be adjusted according to a required cell gap. A polyamic acid varnish composed mainly of cyclobutanetetracarboxylic acid and aromatic diamine was applied to this array substrate 20 by an offset printing method, and baked at 220 ° C. to form a polyimide film with a thickness of 80 nm.

Thereafter, ultraviolet light having a polarization axis at an angle of 80 ° with respect to the longitudinal direction of the pixel electrode wiring 14 and the common electrode wiring 13 was irradiated to perform a liquid crystal alignment treatment. The integrated energy of the irradiated ultraviolet light was measured by an illuminometer having a center sensitivity at 254 nm, and was set to 800 mJ. Since the liquid crystal molecules are aligned by 90 ° from the polarization axis of the ultraviolet light by this alignment treatment, the major axis of the liquid crystal molecules forms an angle of 10 ° with the longitudinal direction of the pixel electrode wiring 14 and the common electrode wiring 13. It will be oriented.

After that, T changed by irradiation with ultraviolet light.
To restore the FT characteristics, the array substrate 20 is
Heat-treated at 1 ° C. for 1 hour

Then, the light shielding layer (black matrix)
And a color filter composed of R, G, and B color material layers in the same manner as described above, using a polarized ultraviolet light, applying a sealing resin to the periphery thereof, and setting the alignment direction of the liquid crystal to the array substrate 20 and the counter substrate (not shown). )
Liquid crystal was injected under vacuum. The used liquid crystal has a refractive index anisotropy Δn
Was 0.090 and the dielectric anisotropy Δε was a positive perfluorinated mixed liquid crystal.

After injecting the liquid crystal, the gap of this liquid crystal panel was measured at 25 points over the entire surface of the panel. As a result, the average value of the gap was 3.2 μm and the variation of the gap was ±
The thickness was 0.05 μm or less, and a panel with very good gap uniformity could be manufactured. Then, a pair of polarizing plates were attached to the top and bottom of the substrate with their polarization axes orthogonal to each other, and one of the polarization axes was aligned with the alignment direction of the liquid crystal, and a driving circuit was mounted on this panel, and the display state was examined. However, at the time of black display, halftone display and white display, no alignment unevenness such as rubbing stripes was observed at all, and a very uniform display was obtained. Also, the contrast ratio was able to be realized at 300: 1 or more over the entire panel.

(Comparative Example 1) As Comparative Example 1, without forming a projection as in the present embodiment for forming a gap,
Except that the gap was formed by dispersing the beads as in the related art, and that the alignment treatment was performed by rubbing, a liquid crystal panel was manufactured in exactly the same manner as in the present embodiment, and the uniformity of the gap and the alignment unevenness were reduced. evaluated.

As beads for forming the gap, resin beads having an average particle diameter (diameter) of 3.0 μm were used, and the average dispersion density was 200 / mm ² . Further, on the alignment film, a polyamic acid varnish consisting of pyromellitic acid as an acid anhydride component as a main component and 4,4′-diaminodiphenylmethane as a diamine component is applied by offset printing,
Baking was performed at 220 ° C. for 1 hour to form a polyimide film having a thickness of 70 nm. The rubbing was performed using a rayon buff cloth at an angle of 10 ° with respect to the longitudinal direction, similarly to the pixel electrode wiring 14 and the common electrode wiring 13 in the present embodiment.

Then, the gap is set to 2 over the entire surface of the panel.
As a result of measurement at 5 points, the average value of the gap was 3.2.
μm and the variation of the gap was ± 0.07 μm, and it was found that the uniformity of the gap was worse than that of the configuration of the present embodiment. The average contrast ratio is 18
Although the ratio was 0: 1, in a region where the dispersion density of beads was high, there was a region where the contrast ratio was about 100: 1. Further, due to the aggregation of the beads, bright spot-like display unevenness was also observed. The reason why the contrast ratio is lower than that in the present embodiment is due to light leakage around the beads.

Comparative Example 2 As Comparative Example 2, a liquid crystal panel was produced in exactly the same manner as in the present embodiment except that the alignment treatment was performed by rubbing, and the uniformity of the gap and the uneven alignment were evaluated. Protrusions for forming a gap were produced in exactly the same manner as in the present embodiment. The alignment film is formed by applying a polyamic acid varnish composed of pyromellitic acid as an acid anhydride component as a main component and 4,4′-diaminodiphenylmethane as a diamine component by an offset printing method.
Baking was performed at 0 ° C. for 1 hour to obtain a polyimide film having a thickness of 70 nm. The rubbing was performed using a rayon buff cloth at an angle of 10 ° with respect to the longitudinal direction, similarly to the pixel electrode wiring 14 and the common electrode wiring 13 in the present embodiment.

The gap is set to 2 over the entire panel.
As a result of measurement at 5 points, the average value of the gap was 3.2.
μm, the variation of the gap was ± 0.05 μm or less, and the contrast ratio was 150: 1. However, in Comparative Example 2, since the projections for gap formation were present, the alignment treatment by rubbing could not be performed uniformly, and the alignment unevenness caused by the rubbing treatment was recognized on the entire panel, and the display quality was significantly lowered. .

[0032]

As described above, according to the liquid crystal display panel and the method of manufacturing the same according to the present invention, it is possible to eliminate a decrease in contrast due to the conventional spacer beads for forming a gap, thereby achieving a high contrast display. This makes it possible to easily realize a practical and high-quality IPS type liquid crystal display panel having excellent cell gap uniformity, eliminating alignment unevenness due to rubbing treatment, and also having excellent alignment uniformity. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a planar structure of an array in a liquid crystal display panel for describing an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a cross-sectional structure of the liquid crystal display panel of FIG.

FIG. 3 is a schematic diagram for explaining movement of liquid crystal molecules in the IPS mode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Scan electrode wiring 12 Signal electrode wiring 13 Common electrode wiring 14 Pixel electrode wiring 15 Thin film transistor 16 Storage capacitance 17, 19 Insulating layer 18 Projection 20 Array substrate

Claims (2)

[Claims] 1. A liquid crystal composition layer having at least one of a pair of transparent substrates, a liquid crystal composition having dielectric anisotropy and refractive index anisotropy sandwiched and aligned between the substrates, polarizing means, and a matrix arranged in a matrix. A plurality of pixels, a thin film transistor element provided for each pixel, connected to the pixel electrode, the signal wiring electrode, and the scanning wiring electrode, a common electrode, and a means for applying a voltage signal waveform for changing the light transmittance or reflectance of the pixel. A liquid crystal display panel having means for applying an electric field substantially parallel to a substrate surface between the pixel electrode and the common electrode, wherein a liquid crystal cell gap is formed on at least one of the pair of substrates. A liquid crystal display panel, comprising: forming a projection; and irradiating polarized ultraviolet light to at least the surface of the substrate on which the projection is present to perform a liquid crystal alignment process. 2. A liquid crystal composition layer having at least one pair of transparent substrates, a liquid crystal composition layer having a dielectric anisotropy and a refractive index anisotropy sandwiched and aligned between the substrates, polarizing means, and a matrix. A plurality of pixels, a thin film transistor element provided for each pixel, connected to the pixel electrode, the signal wiring electrode, and the scanning wiring electrode, a common electrode, and a means for applying a voltage signal waveform for changing the light transmittance or reflectance of the pixel. A manufacturing method for manufacturing a liquid crystal display panel having a means for applying an electric field substantially parallel to a substrate surface between the pixel electrode and the common electrode, wherein a gap of a liquid crystal cell is formed on at least one of the substrates. A step of patterning projections to be formed by a photolithographic method, and irradiating polarized ultraviolet light to at least the substrate surface on the side where the projections are present to perform a liquid crystal alignment process. Method of manufacturing a liquid crystal display panel comprising a step.