JP3395884B2 - Liquid crystal display panel and method of manufacturing the same - 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 an IPS (ion plane switching) type liquid crystal display panel for driving a liquid crystal by applying an electric field substantially parallel to a substrate surface, and a manufacturing method thereof.

[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 workstation is expected, and a demand for a screen size having a diagonal of 13 to 14 inches or more is increasing.

As the display mode of the TFT liquid crystal display, the twisted nematic (TN) mode is currently the mainstream, but for large screen display applications, Japanese Patent Laid-Open No. 6-160.
As described in Japanese Patent No. 878, an IPS mode one in which an electric field substantially parallel to the substrate surface is applied to move liquid crystal molecules in parallel to the substrate surface is expected due to its extremely wide viewing angle characteristic. Are gathering.

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 the pixel electrodes 3 and the common electrode 4 are provided on the vertically opposed substrates 1 and 2, and the polarizing plate 5 is provided outside each of the substrates 1 and 2. , 6 are installed, and as shown in FIG. 3A, by applying a power source voltage 7 to both electrodes 3 and 4, liquid crystal molecules 8 are generated by an electric field applied substantially parallel to the surfaces of the substrates 1 and 2. Direction is displaced to the state as shown in FIG. In the operation of the liquid crystal molecules 8 in this way,
It differs from the conventional TN mode in many respects.

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

[0007]

On the other hand, since the IPS system is a normally black (NB) mode in which black display is performed without applying an electric field, 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, which causes deterioration of contrast. Further, 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 a large number of beads per unit area as compared with the TN method. Such an increase in the bead dispersion density further increases the light leakage per unit area and becomes a factor of lowering the contrast.

In order to prevent such light leakage around the beads, it has been proposed to selectively form a spacer on the non-display portion, but since a spacer having a thickness of several μm exists, conventional rubbing is performed. In the alignment treatment by (1), there was a problem that alignment unevenness (rubbing stripe unevenness) caused by the step shape of the spacer was generated, and alignment uniformity could not be obtained.

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

[0010]

To achieve the above object, a liquid crystal display panel according to the present invention comprises a pair of substrates, at least one of which is transparent, and a dielectric anisotropy and a refractive index which are sandwiched between the substrates and oriented. A liquid crystal composition layer having anisotropy, a polarizing means, a plurality of pixels arranged in a matrix, a pixel electrode provided for each pixel, a signal wiring electrode, a thin film transistor element connected to a scanning wiring electrode, a common electrode, A liquid crystal display having 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 the 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 surface of the substrate on the side where the projection is present is irradiated with polarized ultraviolet light to perform liquid crystal alignment. Characterized in that subjected to a treatment, by this arrangement, in order to form a gap by the projections,
Since there is no light leakage around the beads as in the past, high contrast display is possible, and a uniaxially oriented alignment film is formed by irradiating polarized light to a photo-alignment material, resulting in a cell gap. Also, the uniformity of orientation becomes excellent.

Further, in the method for manufacturing a liquid crystal display panel according to the present invention, in order to manufacture the liquid crystal display panel, a step of forming a projection for forming a gap of a liquid crystal cell on at least one of the substrates by a photolithographic method, ,
At least the surface of the substrate on which the protrusions are present is irradiated with polarized ultraviolet light 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 substrates, at least one of which is transparent, and a dielectric anisotropy and a refractive index anisotropy which are sandwiched and oriented 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 that changes 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 are provided. In the liquid crystal display panel formed as described above, a protrusion 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 protrusion is present is subjected to polarized ultraviolet light irradiation for alignment treatment. It is characterized by being applied.

According to a second aspect of the invention, a pair of substrates, at least one of which is transparent, a liquid crystal composition layer having dielectric anisotropy and refractive index anisotropy sandwiched between the substrates and oriented, and 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, a voltage for changing the light transmittance or reflectance of the pixel A manufacturing method for manufacturing a liquid crystal display panel, comprising a means for applying a signal waveform, and a means for applying an electric field substantially parallel to a substrate surface between the pixel electrode and the common electrode. On the one hand, a step of forming a projection for forming a gap of the liquid crystal cell by a photolithography method, and irradiating polarized ultraviolet light to at least the substrate surface on the side where the projection is present. It characterized by having a step of performing an alignment process by.

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

Further, 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 to arrange the TFT array substrate on the wiring, on the storage capacitor, on the transistor, or on the counter substrate (generally a color filter substrate) side on the black matrix.

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

As the alignment film, it is generally possible to use a photoreactive material. For example, it is a photodegradable polymer material or a photocrosslinkable polymer material. By irradiating a photo-alignment material with polarized ultraviolet light, a selective photoreaction of a portion having a transition moment in the polarization direction occurs, and uniaxial alignment is formed. In the present invention, the liquid crystal alignment treatment by polarized ultraviolet light may be performed on both sides of the substrate or only on one side of the substrate, but in the case of one side, it is performed on the side of the substrate on which the protrusion is 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 diagonal is 15.2 inches, the aspect ratio is 16: 9, and the resolution is (vertical 768) ×
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 an array-shaped planar structure 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.

In FIGS. 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 of a metal thin film containing aluminum as a main component. Then, the shape shown in the figure was formed on the same plane by the photolithography method. The metal material used is preferably a metal having a low wiring resistance, but it is not particularly limited to an aluminum-based metal, and may be a single layer film or a multilayer film. In this way, both electrode wirings 11, 1
3 is formed, an anodized layer of the aluminum film and silicon nitride (SiN _x ) are laminated as the insulating film 19, amorphous silicon is laminated as a semiconductor layer, and then the anodized layer and the silicon nitride on the common electrode wiring 13 are laminated. After removing a part of the layers, two layers of aluminum / titanium (Al / Ti) were deposited by the 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) which is 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, the 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 corresponding scanning electrode wiring 11 one line after or the common electrode wiring 13.

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

After that, the liquid crystal alignment treatment was performed by irradiating the pixel electrode wiring 14 and the common electrode wiring 13 with ultraviolet light having a polarization axis of 80 ° with respect to the longitudinal direction. The integrated energy of the irradiated ultraviolet light was 800 mJ as measured by an illuminometer having a central sensitivity at 254 nm. By this alignment treatment, the liquid crystal molecules are aligned by 90 ° with respect to the polarization axis of the ultraviolet light, so that the long axes of the liquid crystal molecules form an angle of 10 ° with the longitudinal directions of the pixel electrode wiring 14 and the common electrode wiring 13. It will be oriented.

Further, after that, T changed by irradiation with ultraviolet light.
In order to recover the FT characteristic, the array substrate 20 is set to 200
It heat-processed at 1 degreeC for 1 hour.

And a light shielding layer (black matrix)
And a color filter composed of R, G, and B color material layers are aligned by polarized ultraviolet light in the same manner as described above, a sealing resin is applied to the periphery, and the alignment direction of the liquid crystal is array substrate 20 and a counter substrate (not shown). ), So that they match,
The liquid crystal was vacuum injected. The liquid crystal used has a refractive index anisotropy Δn.
Was 0.090 and the dielectric anisotropy Δε was positive, and it was a 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 in the gap was ±.
The thickness was 0.05 μm or less, and it was possible to manufacture a panel having very good gap uniformity. Then, a pair of polarizing plates were attached above and below the substrate so that their polarization axes were orthogonal to each other and one polarization axis was aligned with the alignment direction of the liquid crystal, and a drive circuit was mounted on this panel to examine the display state. However, during black display, halftone display, and white display, no alignment unevenness like rubbing streaks was observed, and a very uniform display was obtained. Also, the contrast ratio could be realized over 300: 1 over the entire panel.

(Comparative Example 1) As Comparative Example 1, without forming the protrusion as in the present embodiment for forming the gap,
Except that the gap was formed by dispersing beads as in the conventional method, and the alignment treatment was performed by rubbing, a liquid crystal panel was produced in exactly the same manner as in the present embodiment, and the uniformity of the gap and the alignment unevenness were obtained. 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 pieces / mm ² . The alignment film is coated with a polyamic acid varnish composed of pyromellitic acid as a main component of acid anhydride and 4,4′-diaminodiphenylmethane as a diamine component by offset printing.
A polyimide film having a film thickness of 70 nm that was baked at 220 ° C. for 1 hour was used. The rubbing was performed using rayon buff cloth at an angle of 10 ° with respect to the longitudinal direction, as in the case of the pixel electrode wiring 14 and the common electrode wiring 13 in the present embodiment.

The gap is 2 across the entire panel.
As a result of measuring at 5 points, the average value of the gap is 3.2.
It was found that the uniformity of the gap was inferior to that of the structure of the present embodiment, since the dispersion of the gap was ± 0.07 μm. The average contrast ratio is 18
Although it was 0: 1, there was also a region having a contrast ratio of about 100: 1 in a region where the dispersion density of beads was high. Furthermore, due to the aggregation of beads, bright spot-like display unevenness was also observed. The reason why the contrast ratio is lower than that in this embodiment is due to light leakage around the beads.

(Comparative Example 2) As Comparative Example 2, a liquid crystal panel was prepared in exactly the same manner as this embodiment except that the alignment treatment was performed by rubbing, and the uniformity of the gap and the alignment unevenness were evaluated. The protrusions for forming the gap were also manufactured in exactly the same manner as in this embodiment. The alignment film is formed by applying a polyamic acid varnish consisting of pyromellitic acid as a main component of acid anhydride and 4,4′-diaminodiphenylmethane as a diamine component by offset printing.
A polyimide film having a film thickness of 70 nm that was baked at 0 ° C. for 1 hour was used. The rubbing was performed with 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 2 across the entire panel.
As a result of measuring at 5 points, the average value of the gap is 3.2.
The variation in μm and gap was ± 0.05 μm or less, and the contrast ratio was 150: 1. However, in Comparative Example 2, since the protrusions for forming the gap were present, the alignment treatment by rubbing could not be performed uniformly, and the alignment unevenness caused by the rubbing treatment was observed on the entire panel, and the display quality was remarkably deteriorated. .

[0032]

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

[Brief description of drawings]

FIG. 1 is a schematic view showing a planar structure of an array shape in a liquid crystal display panel for explaining 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 method.

[Explanation of symbols]

11 Scan electrode wiring 12 signal electrode wiring 13 Common electrode wiring 14 Pixel electrode wiring 15 Thin film transistor 16 storage capacity 17,19 Insulation layer 18 protrusions 20 array substrate

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-217343 (JP, A) JP-A-9-197413 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02F 1/1337 G02F 1/1339 500 G02F 1/1368

Claims (2)

(57) [Claims] 1. A pair of substrates, at least one of which is transparent, a liquid crystal composition layer having dielectric anisotropy and refractive index anisotropy sandwiched between the substrates and oriented, polarizing means, and arranged in a matrix. A plurality of pixels, 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, and 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 the substrate surface between the pixel electrode and the common electrode, for forming a gap of a liquid crystal cell on at least one of the pair of substrates. And a liquid crystal alignment treatment is performed by irradiating polarized ultraviolet light on at least the surface of the substrate on which the projections are present. 2. A pair of substrates, at least one of which is transparent, a liquid crystal composition layer having dielectric anisotropy and refractive index anisotropy sandwiched between the substrates and oriented, polarizing means, and arranged in a matrix. A plurality of pixels, 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, and 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, comprising 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 provided on at least one of the substrates. A step of forming a pattern of projections for forming by a photolithographic method, and a liquid crystal alignment treatment by irradiating polarized ultraviolet light to at least the substrate surface on the side where the projections are present. Method of manufacturing a liquid crystal display panel comprising a step.