JP2002090751A - Liquid crystal display device and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the display quality without increasing the production cost. SOLUTION: The liquid crystal display device has a liquid crystal having negative dielectric anisotropy held between electrode substrates G1, G2. The electrode substrate G2 has an insulating structure 21 to control the tilt direction of the liquid crystal to divide each pixel into a plurality of domains and has a columnar spacer 22 to maintain the gap between the electrode substrates G1, G2. In particular, the insulating structure 21 is disposed in a recessed part formed on the electrode substrate G2 and made of the same material as that of the columnar spacer 22.

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 device in which liquid crystal is sandwiched between a pair of electrode substrates, and more particularly to a liquid crystal display device in which each pixel is divided into a plurality of mutually different domains in the tilt direction of liquid crystal molecules. And its manufacturing method.

[0002]

2. Description of the Related Art Liquid crystal display devices have been applied in various fields such as OA equipment, information terminals, watches, and televisions because of their characteristics of light weight, thinness, and low power consumption. In particular, active matrix type liquid crystal display devices use thin film transistors (Thin Fi
Since excellent responsiveness can be obtained by switching pixels using an lm transistor, it is used as a display monitor of a portable television or a computer in which a large amount of image information must be displayed.

[0003] In recent years, the improvement in definition and display speed of a liquid crystal display device has been demanded with an increase in the amount of information. The improvement in definition is achieved by making the TFT array structure finer and increasing the number of pixels. In this case, in order to transition the arrangement of the liquid crystal molecules within a shorter time with an increase in the number of pixels, a liquid crystal display mode capable of obtaining a response speed of the liquid crystal molecules of twice to several tens times the current one is necessary. Become.
As the liquid crystal display mode, for example, an OCB type, a VAN type, a HAN type, a π-alignment type using a nematic liquid crystal, and an interface stable ferroelectric liquid crystal (Surface S) using a smectic liquid crystal.
Tabilized Ferroelectric Liquid Crystal) type or antiferroelectric liquid crystal type can be used.

[0004] In particular, the VAN type alignment mode can obtain a faster response speed than the conventional twisted nematic type (TN) type alignment mode, and can perform the conventional rubbing alignment processing which causes defects such as electrostatic breakdown. In recent years, it has attracted attention because it can be made unnecessary by employing an alignment treatment. Further, in the VAN-type alignment mode, it is easy to design a compensation for a viewing angle, and a wide viewing angle can be obtained by adopting a multi-domain system in which pixels are divided into a plurality of domains in which tilt directions of liquid crystal molecules are different from each other.

For example, Japanese Patent No. 2565639 discloses a method in which a slit is provided as a part of or partially surrounding an electrode for applying an electric field to a liquid crystal layer, and the dielectric constant of the liquid crystal material varies due to fluctuation of the electric field on or near the slit. A technique for uniformly defining a tilt direction corresponding to anisotropy is disclosed. In this document, multiple domains are created by having a multi-directional component in the fluctuation of the electric field, thereby achieving a wide viewing angle.

At present, an initial tilt (pretilt) of liquid crystal molecules induced by a convex or concave insulating structure formed on an electrode or the periphery of the electrode and a fluctuation of an electric field corresponding to the dielectric property of the insulating structure. A technique for generating a plurality of domains to increase the viewing angle has also been proposed.

[0007]

By the way, in order to keep the gap (cell gap) between the pair of electrode substrates constant, the thickness of the liquid crystal layer protrudes from one of the electrode substrates to form a plurality of columnar supports for supporting the other electrode substrate. When defined by the spacer, the cell gap tends to be non-uniform due to the overlap of the columnar spacer and the insulating structure for dividing the domain. To prevent this, it is possible to form the columnar spacer by an independent process so as not to overlap the insulating structure for dividing the domain, but this complicates the manufacturing process and increases the manufacturing cost. Results.

An object of the present invention is to provide a liquid crystal display device capable of improving display quality without increasing the manufacturing cost, and a method of manufacturing the same.

[0009]

According to the present invention, a liquid crystal having a negative dielectric anisotropy is sandwiched between a pair of substrates, and each pixel is divided into a plurality of domains on one of the pair of substrates. To control the tilt direction of the liquid crystal, and a spacer for holding a gap between the pair of substrates, wherein the insulating structure is disposed in a recess formed in one of the substrates, and is made of the same material as the spacer. Liquid crystal display device is provided.

Further, according to the present invention, a liquid crystal having a negative dielectric anisotropy is sandwiched between a pair of substrates, and one of the substrates has a tilt direction of the liquid crystal to divide each pixel into a plurality of domains. Forming a base layer having a concave portion on one substrate in a method for manufacturing a liquid crystal display device including an insulating structure for controlling the thickness of the substrate and a spacer for holding a gap between the pair of substrates; And a step of arranging the insulating structure in the recess by patterning the insulating material to simultaneously form the insulating structure and the spacer.

In the liquid crystal display device and the method of manufacturing the same, the insulating structure is disposed in a recess formed in one of the substrates. In this case, even when the position of the insulating structure and the position of the spacer overlap, a spacer such as a columnar spacer can be formed by the same manufacturing process as that of the insulating structure using the difference in height of the base, so that manufacturing costs are reduced. The display quality can be improved without increasing. Further, when the concave portion is located around the pixel, the decrease in the contrast of the pixel can be alleviated even if the insulating structure is light-shielding to prevent light leakage. Further, in this case, since the insulating structure is prevented from largely entering the pixel region, the overlapping area with the electrode of the first electrode substrate can be sufficiently reduced, and the burning phenomenon due to the accumulated charge can be reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an active matrix type liquid crystal display device according to a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows a sectional structure of a liquid crystal display device, and FIG. 2 shows a plan structure of the liquid crystal display device. The liquid crystal display device operates in a multi-domain VAN type alignment mode, and includes electrode substrates G1 and G2, and a liquid crystal layer LQ sandwiched between the electrode substrates G1 and G2.
The liquid crystal layer LQ is composed of a liquid crystal material including a nematic liquid crystal having a negative dielectric anisotropy and a peripheral sealing material surrounding the liquid crystal material between the electrode substrates G1 and G2. The electrode substrates G1 and G2 are integrated with the liquid crystal layer LQ by being bonded by the peripheral sealing material.

The electrode substrate G1 is a light-transmitting insulating substrate 1 such as a glass plate, a plurality of pixel electrodes 2 arranged in a matrix and applying an electric field to the liquid crystal layer LQ for controlling the arrangement of liquid crystal molecules constituting pixels. A plurality of scanning lines 3 arranged along the rows of the pixel electrodes 2, a plurality of signal lines 4 arranged along the columns of the pixel electrodes 2, each near the intersection of the corresponding scanning line 3 and the corresponding signal line 4. The liquid crystal layer L formed so as to cover the plurality of pixel thin film transistors 5 arranged as switching elements and the plurality of pixel electrodes 2 and to be applied with no voltage is applied.
A vertical alignment film 6 for aligning the liquid crystal molecules of Q substantially perpendicular to the plane of the electrode substrate G1 is included. Thin film transistor 5 for each pixel
Denotes a gate electrode 5A connected to the corresponding scanning line 3 on the insulating substrate 1, and a gate insulating film 1 covering the gate electrode 5A.
A has a semiconductor layer 5B of amorphous silicon or polysilicon formed on A. The semiconductor layer 5B has a source region and a drain region arranged on both sides of the gate electrode 5A. The source region is connected to the corresponding pixel electrode 2,
The drain region is connected to the corresponding signal line 4. The plurality of scanning lines 3, the plurality of signal lines 4, and the plurality of thin film transistors 5 are covered with an insulating layer 7. The plurality of pixel electrodes 2 are formed on the insulating layer 7 and connected to the source region of the semiconductor layer 5B of the corresponding thin film transistor 5 via the contact holes 7A formed in the insulating layer 7. The electrode substrate G1 further includes a slit 20 formed in each pixel electrode 2. The slit 20 constitutes a tilt control unit that divides a pixel into a plurality of domains in an electric field applied to the liquid crystal layer LQ and makes the tilt direction of liquid crystal molecules different between these domains.

The electrode substrate G2 includes a light-transmitting insulating substrate 10 such as a glass plate, a color filter 11 formed on the insulating substrate 10, and a facing filter formed on the color filter 11 so as to face the plurality of pixel electrodes 2. An electrode 12 includes a vertical alignment film 13 formed over the counter electrode 12 to align liquid crystal molecules of the liquid crystal layer LQ substantially perpendicularly to the plane of the electrode substrate G2 when no voltage is applied. The color filter 11 is red (R),
It is composed of three colored layers of green (G) and blue (B). These coloring layers respectively face the plurality of pixel electrodes 2 and are separated from each other in accordance with the gap between the pixel electrodes 2. The electrode substrate G2 further includes an insulating structure 21 and a plurality of columnar spacers 22 formed on the counter electrode 12 and covered with the alignment film 13 in the gap between the colored layers.
The insulating structure 21 constitutes a tilt control unit that divides a pixel into a plurality of domains in an electric field applied to the liquid crystal layer LQ and makes the tilt direction of liquid crystal molecules different between these domains. Each columnar spacer 22 protrudes from the electrode substrate G2 to support the electrode substrate G1 in order to keep the gap (cell gap) between the electrode substrates G1 and G2 constant.

Here, a method for manufacturing the above-described liquid crystal display device will be described.

In the manufacturing process of the electrode substrate G1, film formation and patterning are performed according to a known manufacturing process.
The above is repeated, and the above-described scanning line 3, signal line 4, thin film transistor 5, and insulating layer 7 are formed. After the formation of the insulating layer 7, an ITO film having a thickness of 150 nm is deposited on the insulating layer 7 by a sputter deposition apparatus. This ITO film is patterned using a predetermined mask pattern, thereby forming a plurality of pixel electrodes 2 each having a missing portion forming a slit 20 having a width of 5 μm. Subsequently, the vertical alignment film 6 is formed by applying an alignment film material such as polyimide with a thickness of 70 nm and baking it at 180 ° C. so as to cover the plurality of pixel electrodes 2. Here, the slit 20 is formed at the boundary between the first and second regions obtained by bisecting the pixel electrode 2 in the row direction.

In the manufacturing process of the electrode substrate G2, a color filter 11 is formed on the insulating substrate 10 with a thickness of 3 μm,
An ITO film having a thickness of 150 nm is deposited on the colored layers of the color filter 11 and the insulating substrate 10 which is not masked by the colored layers by a sputter deposition apparatus. This ITO
The film is patterned using a predetermined mask pattern,
Thereby, the counter electrode 12 is formed. Thereafter, the counter electrode 12 is covered with a 4.8 μm thick black resist material obtained by mixing a phthalocyanine dye with an acrylic photosensitive resin, for example. This black resist material is patterned by a photoengraving process using a predetermined mask pattern, thereby forming an insulating structure 21 and a plurality of columnar spacers 22. The insulating structure 21 is disposed on the concave portion of the counter electrode 12 corresponding to the gap between the colored layers of the color filter 11, and is used as a grid-shaped light shielding layer surrounding each pixel as shown in FIG. The concave portion of the counter electrode 12 has a depth of 0.5d to 0.7d with respect to the cell gap value d of the electrode substrates G1 and G2. Each columnar spacer 22 is provided on the thin film transistor 5 of the electrode substrate G1.
Are arranged on the convex portion of the counter electrode 12 corresponding to the colored layer portion of the color filter 11 facing each other at a ratio of one for every several pixels, and the cell gap between the electrode substrate G1 and the electrode substrate G2 is regulated to a constant value d. Here, the insulating structure 21 and the plurality of columnar spacers 22 are formed at the same time by utilizing the height difference of the base. After this formation, an alignment film material such as polyimide is applied to a thickness of 70 nm so that the vertical alignment film 13 covers the counter electrode 12, the insulating structure 21, and the columnar spacer 22.
And fired at 180 ° C.

In the step of bonding the electrode substrates G1 and G2, for example, a thermosetting acrylic or epoxy-based adhesive is printed on the alignment film 6 along the outer edge of the electrode substrate G1 so as to leave a liquid crystal injection port. Thereafter, the electrode substrates G1 and G2 are stacked with the alignment films 6 and 13 inside, and are heated to cure the adhesive as a peripheral sealing material. Subsequently, a liquid crystal material having a negative dielectric anisotropy is applied to the electrode substrate G.
The liquid crystal filling space is surrounded by a peripheral sealing material between 1 and G2, and is injected from the liquid crystal filling port by a normal method, and the liquid crystal filling port is sealed with an ultraviolet curable resin.
Thereafter, the polarizing films 15 and 16 are attached to the surfaces of the electrode substrates G1 and G2 on the opposite sides of the liquid crystal layer LQ with the polarization axes orthogonal to each other. Thus, the liquid crystal display device is completed.

In the liquid crystal display device of the first embodiment, when an electric field is applied to the liquid crystal layer LQ between the pixel electrode 2 and the counter electrode 12 by setting the potential of the pixel electrode 2 through the thin film transistor 5, the arrangement of the liquid crystal molecules is reduced. Are deformed from a state substantially perpendicular to each substrate plane to a state parallel thereto. At this time, the tilt direction of the liquid crystal molecules is reversed between the domains. Thereby, a good viewing angle can be obtained.

The insulating structure 21 is disposed as a light-shielding layer on the recess formed in the electrode substrate G2 around the pixel. In this case, a decrease in contrast can be reduced. In addition, since the insulating structure 21 is prevented from largely entering the pixel region, the overlapping area with the pixel electrode 2 can be sufficiently reduced, and the burning phenomenon caused by the accumulated charge can be reduced.
Furthermore, since the columnar spacers 22 are formed in the same process as the insulating structure 21, an increase in manufacturing cost can be prevented.

Hereinafter, an active matrix type liquid crystal display device according to a second embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. This liquid crystal display device is configured in the same manner as the liquid crystal display device of the first embodiment except that the columnar spacer 22 shown in FIG. 1 overlaps with the insulating structure 21 and is formed integrally from a low-resistance resist material. .

FIG. 3 shows a sectional structure of the liquid crystal display device, and FIG. 4 shows a plan structure of the liquid crystal display device. 3 and 4 denote the same parts as in the first embodiment, and a description thereof will be simplified or omitted.

Therefore, a method of manufacturing the liquid crystal display will be described. Incidentally, the manufacturing process of the electrode substrate G1 and the bonding process of the electrode substrates G1 and G2 are the same as in the first embodiment.

In the manufacturing process of the electrode substrate G2, a color filter is used.
A filter 11 is formed on the insulating substrate 10 with a thickness of 3 μm,
A 150 nm thick ITO film is covered with a sputter deposition device.
The coloring layers of the color filter 11 and the coloring layers
It is deposited on the insulating substrate 10 which is not to be screened. This ITO
The film is patterned using a predetermined mask pattern,
Thereby, the counter electrode 12 is formed. After this, the counter electrode
12 is, for example, carbon black on an acrylic photosensitive resin.
3.9 × 10 obtained by mixing 0.01 wt% ¹²Ω
4.8 μm thick low-resistance resist with a resistance value ρ of cm
Covered with material. As this low-resistance resist material,
Use common organic resist materials, inorganic metal oxides, etc.
However, basically, when the resistance value ρ is 10¹¹Ω ・ c
m <ρ <10¹⁴Processing less than 30μm in the range of Ωcm
It is preferable to use a material that causes an error. This resistance ρ
Range limits low resistance by mixing carbon black
Is important for.

This low-resistance resist material is patterned by a photoengraving process using a predetermined mask pattern, thereby forming an insulating structure 21 and a plurality of columnar spacers 22 at the same time. Insulating structure 2
Numeral 1 is disposed on the concave portion of the counter electrode 12 corresponding to the gap between the colored layers of the color filter 11, and is used as a grid-shaped light shielding layer surrounding each pixel as shown in FIG.
The concave portion of the counter electrode 12 has a depth of 0.5d to 0.7d with respect to the cell gap value d of the electrode substrates G1 and G2.
Each of the columnar spacers 22 overlaps with the insulating structure 21 on the convex portion of the counter electrode 12 corresponding to the colored layer portion of the color filter 11 facing the thin film transistor 5 of the electrode substrate G1. And the cell gap between the electrode substrate G1 and the electrode substrate G2 is defined as a constant value d. Here, the insulating structure 21 and the plurality of columnar spacers 22 are formed simultaneously and integrally using the difference in height of the base. After this formation, the vertical alignment film 13 is
2. It is formed by applying an alignment film material such as polyimide with a thickness of 70 nm and baking at 180 ° C. so as to cover the insulating structure 21 and the columnar spacers 22.

In the liquid crystal display device of the second embodiment, the same effect as that of the first embodiment can be obtained by allowing the position of the edge structure 21 and the position of the columnar spacer 22 to overlap.

FIG. 5 shows a sectional structure of a liquid crystal display device of a comparative example. In this liquid crystal display device, the counter electrode 31 is formed on the adjacent colored layer in the color filter 32 without providing any space therebetween. Insulating structure 33 for domain division
Is covered with a 1.5 μm thick black resist material obtained by mixing a phthalocyanine dye with an acrylic photosensitive resin, and the black resist material is patterned using a predetermined mask pattern to form a color filter. The colored layers are arranged at the boundaries between each other. The columnar spacer 34 is formed by covering the counter electrode 31 with an acrylic photosensitive resin having a thickness of 5.0 μm and patterning the photosensitive resin using a predetermined mask pattern. However, in this configuration, it is inevitable that a part of the insulating structure 31 largely enters the pixel region defined by each pixel electrode, so that the light transmittance of the pixel is reduced. Further, the insulating structure for dividing the domain and the columnar spacer require independent processes of film formation, exposure, and patterning.

Therefore, display unevenness such as light transmittance and image sticking of the liquid crystal display devices according to the first and second embodiments were compared with those of the liquid crystal display device of the comparative example shown in FIG. The light transmittance was evaluated by setting the aperture ratio of the pixel to 60%, and the display unevenness was evaluated by the presence or absence of an afterimage obtained after displaying a white window on a black background for 8 hours. According to this comparison result, the liquid crystal display device of the comparative example has a transmittance of 4% and causes display unevenness. In contrast, the liquid crystal display device according to the embodiment has a transmittance of 4.44% and can eliminate display unevenness.

The present invention is not limited to the above-described embodiment, and can be variously modified without departing from the gist thereof.

The columnar spacer 22 and the insulating structure 21 of each embodiment may be formed on either side of the electrode substrates G1 and G2. The columnar spacer 22 can be formed as a column or a prism, and preferably has a height of 3 μm to 5 μm. Further, the insulating structure 21 for domain division is formed by a concave portion obtained by partially thinning the color filter 11, a concave portion formed by an insulating layer covering the switching element 5, and formed by a contact hole penetrating to the switching element 5. It can be formed using a concave portion obtained as a gap between adjacent wirings and a concave portion for an insulating structure formed in advance on the electrode substrate G1 or G2. Here, the insulating layer covering the switching element 5 may be a color filter.

[0032]

As described above, according to the present invention, it is possible to provide a liquid crystal display device capable of improving display quality without increasing the manufacturing cost, and a method of manufacturing the same.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a cross-sectional structure of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a planar structure of the liquid crystal display device shown in FIG.

FIG. 3 is a diagram illustrating a cross-sectional structure of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a planar structure of the liquid crystal display device shown in FIG.

FIG. 5 is a diagram illustrating a cross-sectional structure of a liquid crystal display device of a comparative example.

[Explanation of symbols]

 2: Pixel electrode 12: Counter electrode 6, 13: Vertical alignment film 20: Slit 21: Insulating structure 22: Columnar spacer LQ: Liquid crystal layer G1, G2: Electrode substrate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) G09F 9/30 320 G09F 9/30 349C 5G435 349 349Z 349A G02F 1/136 500 (72) Inventor Takeshi Yamaguchi Saitama Saitama 1-9-9, Hara-cho, Fukaya-shi, Japan Inside the Toshiba Fukaya plant (72) Inventor Atsushi Manabe 1-9-2, Hara-cho, Fukaya-shi, Saitama F-term in the Toshiba Fukaya plant (reference) 2H089 LA09 MA04X MA05X NA14 NA15 NA17 NA55 QA05 QA14 TA12 TA15 2H090 HB08Y HC12 LA04 LA09 LA15 MA01 MA10 MB14 2H091 FA08X FA08Z FA35Y FB04 FC12 FC26 GA06 GA08 GA13 LA03 LA12 LA15 2H092 GA13 HA04 JA24 PA03 PA03 PA05 PA03 PA03 PA03 PA05 PA04 BA43 CA19 DA15 EA04 EA07 EC03 FB15 5G435 AA17 BB12 CC09 FF13 GG12 HH14

Claims (8)

[Claims] 1. A liquid crystal having a negative dielectric anisotropy is sandwiched between a pair of substrates, and one of the pair of substrates has an insulating layer for controlling a tilt direction of the liquid crystal to divide each pixel into a plurality of domains. An insulating structure, and a spacer that holds a gap between the pair of substrates, wherein the insulating structure is disposed in a recess formed in the one substrate, and is made of the same material as the spacer. Liquid crystal display device. 2. The liquid crystal display device according to claim 1, wherein the insulating structure has a light shielding property. 3. The insulating structure according to claim 1, wherein the insulating structure has a resistance of 10 ¹¹ Ω · cm <.
The liquid crystal display device according to claim 1, wherein the liquid crystal display device has a resistance value ρ of ρ <10 ¹⁴ Ω · cm. 4. The liquid crystal display device according to claim 1, wherein the insulating structure is formed around each of the pixels. 5. The liquid crystal display device according to claim 1, wherein the recess is formed by a color filter formed on the one substrate. 6. The semiconductor device according to claim 6, wherein the switching element and an insulating layer covering the switching element are formed on the one substrate, and the recess is formed by a contact hole penetrating to the switching element formed in the insulating layer. The liquid crystal display device according to claim 1, wherein: 7. The liquid crystal display device according to claim 6, wherein the insulating layer is a color filter. 8. A liquid crystal having a negative dielectric anisotropy is sandwiched between a pair of substrates, and one of the pair of substrates has an insulating layer for controlling a tilt direction of the liquid crystal to divide each pixel into a plurality of domains. A method of manufacturing a liquid crystal display device including a conductive structure and a spacer that holds a gap between the pair of substrates, wherein a step of forming a base layer having a recess on the one substrate;
Forming an insulating material on the base layer, and arranging the insulating structure in the concave portion by patterning the insulating material to simultaneously form the insulating structure and the spacer. A method for manufacturing a liquid crystal display device, comprising: