JP2002082338A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate securing of a liquid crystal injection space under the restriction accompanying the high definition. SOLUTION: A liquid crystal display element is provided with a pair of electrode substrates G1 and G2, a liquid crystal cell 10 interposed between the electrode substrates G1 and G2 and enclosing a liquid crystal composition LQ and plural columnar spacers 25 protruding from the electrode substrate G1 and supporting the electrode substrate G2. Especially, the columnar spacers 25 are formed on the electrode as the base G1 and are spread from the planarized parts of the base to the recessed parts of the substrate G1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display device in which a liquid crystal injection space is secured by a plurality of columnar spacers.

[0002]

2. Description of the Related Art Generally, a liquid crystal display device has a liquid crystal cell sandwiched between a pair of electrode substrates. The liquid crystal cell is constituted by a peripheral sealing material for connecting the electrode substrates and a liquid crystal composition surrounded by the peripheral sealing material between the electrode substrates. In manufacturing, a pair of electrode substrates is coated with a peripheral sealing material on one of the electrode substrates, leaving a liquid crystal injection port, and a granular spacer is scattered on a substrate region surrounded by the peripheral sealing material, and furthermore, on this electrode substrate. The peripheral electrode is cured by curing the peripheral sealing material in a state where the other electrode substrate is superimposed. The liquid crystal composition is injected into the liquid crystal cell from the liquid crystal injection port, and the liquid crystal injection port is sealed with an injection port sealing material that is filled and cured after the injection of the liquid crystal composition.

The granular spacer is made of, for example, plastic beads having a uniform particle size, and the gap between these electrode substrates is defined by the particle size of the beads to secure a liquid crystal injection space. However, the granular spacer disturbs the liquid crystal alignment around the spacer, which causes light leakage. When the granular spacers are scattered non-uniformly, there is a problem that a display failure occurs in which the contrast is remarkably reduced due to leaked light, and the yield of the liquid crystal display element is reduced.

In recent years, a technique for securing a liquid crystal injection space using a plurality of columnar spacers has been proposed to solve the above-mentioned problem. These columnar spacers protrude from one electrode substrate and support the other electrode substrate, thereby maintaining a uniform gap between the electrode substrates. In this case, alignment unevenness of about several μm occurs around the columnar spacer, but by arranging the columnar spacer in the light-shielding region, a decrease in contrast due to light leakage can be prevented. Such a columnar spacer is formed by depositing a spacer material layer over one electrode substrate and patterning the spacer material layer into a columnar shape.

[0005]

However, if the pixel electrode pitch becomes narrower with higher definition of the liquid crystal display element, it becomes impossible to secure a sufficiently wide and flat base for forming each columnar spacer, and the height of the columnar spacer is reduced. In addition, the contact area of the tip side substrate decreases with the variation of the formation position. Further, at the time of patterning, the columnar spacer has an inversely tapered shape having a base end narrower than the tip end due to the force of the developing solution hitting the spacer edge on the electrode substrate. That is, the strength of the columnar spacer is insufficient for the reasons described above, and the columnar spacer is likely to be dropped, and it is difficult to reliably support the other electrode substrate.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display element which can easily secure a liquid crystal injection space under the restrictions associated with high definition.

[0007]

According to the present invention, a pair of first and second substrates, a liquid crystal composition sandwiched between the first and second substrates, and a second substrate protruding from the first substrate are provided. And a plurality of columnar spacers supporting the first substrate, and the columnar spacers are formed by using the first substrate as a base and extending from a flat portion of the base to a concave portion.

In this liquid crystal display element, the columnar spacer is formed with the first substrate as a base and extending from a flat portion of the base to a recess. With this structure, even if the place where the columnar spacer is formed is restricted due to the high definition of the liquid crystal display element, select a flat base that can obtain the designed height and the contact area on the tip side substrate, and select the columnar spacer. It is possible to secure the base of the columnar spacer wider than when the spacer is formed. The tip of the columnar spacer contacts the second substrate in a region corresponding to the flat portion of the base, and the second end in a region corresponding to the concave portion of the base.
Although it does not come into contact with the substrate, even if the formation positions of the columnar spacers vary, the outermost contour of the columnar spacer on the tip side substrate contact surface can be made substantially coincident with the boundary between the flat portion and the concave portion of the base. That is, since no margin is required for the variation in the formation position of the columnar spacers, it is possible to prevent the height of the columnar spacers and the contact area of the front end substrate from being reduced. Further, since the columnar spacer also extends to the concave portion of the base, even if the columnar spacer is eroded by the force of the developing solution hitting the spacer edge during patterning, this erosion is prevented from proceeding beyond the boundary between the flat portion and the concave portion. Therefore,
A liquid crystal injection space can be secured by the columnar spacer having sufficient strength.

[0009]

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 the accompanying drawings.

FIG. 1 schematically shows a plan structure of the liquid crystal display device, and FIG. 2 shows a sectional structure of the liquid crystal display device along the line II shown in FIG. The liquid crystal display element is a pair of electrode substrates G1
And G2, and a liquid crystal cell 10 sandwiched between these electrode substrates G1 and G2. The liquid crystal cell 10 is provided with a peripheral sealing material 10A connecting these electrode substrates G1 and G2.
And a liquid crystal composition LQ surrounded by a peripheral sealing material 10A between the electrode substrates G1 and G2. The liquid crystal cell 10 is formed by bonding the substrates G1 and G2 together with a peripheral sealing material 10A surrounding the liquid crystal composition LQ between the substrates G1 and G2. The display method of the liquid crystal cell 10 is, for example, TN type, ST type, GH type.
Shape, ECB type, or ferroelectric liquid crystal type.

The electrode substrate G1 is a light-transmitting insulating substrate 11, such as a glass plate, a plurality of pixel electrodes 12, which are arranged in a matrix on the insulating substrate 11, and is arranged on the insulating substrate 11 along rows of the pixel electrodes 12. Scanning lines 13, a plurality of signal lines 14 arranged on the insulating substrate 11 along the columns of the pixel electrodes 12, corresponding scanning lines 13 and corresponding signal lines 14, respectively.
A plurality of pixel thin film transistors 1 arranged on an insulating substrate 11 as switching elements in the vicinity of the intersection of
5 and a plurality of auxiliary capacitance lines 16 which are capacitively coupled to the pixel electrodes 12 of the corresponding row so as to form the auxiliary capacitances Cs and are arranged on the insulating substrate 11 so as to be substantially parallel to the scanning lines 13. Each auxiliary capacitance line 16 is electrically connected to the counter electrode 12 of the electrode substrate G2 via an electrode transfer material such as silver paste disposed at an end of the liquid crystal display element. The matrix array of the pixel electrodes 12 is, for example, 480 rows × 1920 columns = 921
It is composed of 600 pixels. Here, 1920 is the sum of 640 pixels × 3 colors (red, green, blue).

In the electrode substrate G1, each pixel thin film transistor 15 includes a polysilicon semiconductor layer formed on the insulating substrate 11, a gate electrode formed on a gate insulating film covering the semiconductor layer, amorphous silicon or polysilicon. A source electrode in contact with a source region formed in the semiconductor layer; and a drain electrode in contact with a drain region formed in the semiconductor layer.
The gate electrode is connected to one scanning line 13, the source electrode is connected to one pixel electrode 12 via the upper source electrode 19, and the drain electrode is connected to one signal line 14. The scanning lines 13 and the auxiliary capacitance lines 16 are formed on the gate insulating film, and are covered with the thin film transistor 15 by the interlayer insulating film 18. The upper source electrode 19 is connected to the signal line 1
4 together with the protective insulating film 20
Covered by The protective insulating film 20 further includes an insulating color filter 21 for filtering light transmitted through the pixel electrode 12.
Covered with. The color filter 21 is composed of red, green, and blue coloring layers R, G, and B that are formed as stripes that cover the columns of the pixel electrodes 12 respectively. The pixel electrode 12 contacts the upper source electrode 19 via the contact hole 22 formed in the color filter 21 above the auxiliary capacitance line 16. The electrode substrate G1 further includes an alignment film AL1 that covers the color filter 21 and the pixel electrode 12, and a polarizing plate PL1 that covers the insulating substrate 11 on the side opposite to the alignment film AL1.

The electrode substrate G2 includes a light-transmitting insulating substrate 23 such as a glass plate, a counter electrode 24 disposed on the insulating substrate 23 so as to face the plurality of pixel electrodes 12, an alignment film AL2 covering the counter electrode 24, On the side opposite to the alignment film AL2, a polarizing plate PL2 that covers the insulating substrate 23 is included.

The liquid crystal display element further includes an electrode substrate G1 for securing a liquid crystal injection space between the electrode substrates G1 and G2.
And a plurality of columnar spacers 25 projecting therefrom and supporting the electrode substrate G2. Each columnar spacer 25 is formed with the electrode substrate G1 as a base and extending from a flat portion of the base to a concave portion. Specifically, the color filter 21 is used as a flat portion, and the contact hole 22 formed in the color filter 21 is used as a concave portion. The pixel electrode 1
2 and the counter electrode 24 are light-transmitting,
The signal line 14 and the auxiliary capacitance line 16 are light-shielding.

Here, a method of 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 on the insulating substrate 1 according to a known manufacturing process.
1, the scanning line 13, the signal line 14, the thin film transistor 15, the auxiliary capacitance line 16, the interlayer insulating film 1
8, an upper source electrode 19, and a protective insulating film 20 are formed. After the formation of the protective insulating film 20, an ultraviolet curable acrylic resin resist in which a red pigment is dispersed is applied to the entire surface of the protective insulating film 20 by a spinner, and the wavelength is 365 nm and the energy density is 100 mJ / cm through a photomask.
The light is selectively exposed by irradiating the ^second light. After this exposure, the resin resist is developed with a 1% aqueous solution of KOH for 10 seconds, thereby forming a red colored layer R having a thickness of 3 μm corresponding to the exposed area to be developed. The contact hole 22 is 15 × 15 μm in the colored layer R.
Is formed so as to expose the upper source electrode 19. Here, the contact hole 22 is a recess having a depth of at least 3 μm. The green coloring layer G and the blue coloring layer B are formed in the same manner as the coloring layer R described above. The coloring layers R, G, and B are stripes each having a width of 40 μm and opposed to the columns of the pixel electrodes 12. The colored layer G is formed using an ultraviolet-curable acrylic resin resist in which a green pigment is dispersed, and the colored layer B is formed using an ultraviolet-curable acrylic resin resist in which a blue pigment is dispersed. After the color filter 21 is obtained by the coloring layers R, G, and B, an ITO film having a thickness of 1500 Å is deposited by a sputtering method, and the ITO film is patterned by a photolithography method to form a plurality of pixel electrodes 12. It is formed.

After the formation of the pixel electrode 12, a photosensitive transparent acrylic resin is applied to the entire surface of the color filter 21 and the pixel electrode 12 with a spinner, dried at 90 ° C. for 10 minutes, and then passed through a photomask at a wavelength of 365 nm and an energy density of It is selectively exposed by irradiating light of 300 mJ / cm ² . After this exposure, the acrylic resin has a pH of 1
Developed with 1.5 aqueous alkaline solution
It is baked at 60 ° C. for 60 minutes, thereby forming a plurality of columnar spacers 25 corresponding to the exposed regions to be developed. here,
Each columnar spacer 25 is provided at a rate of one for every seven pixels in the row direction, and is arranged at a location that is shielded from light by the auxiliary capacitance line 16 and avoids the opening of the pixel electrode 12. in this case,
The columnar spacer 25 has a width of 15 μm, a length of 40 μm, and a height of 5.5 μm, and is formed to extend from the flat portion to the recess with the color filter 21 as a flat portion and the contact hole 22 as a recess. Further, the shape of the columnar spacer 25 is a forward tapered shape having a base end wider than the front end. After the formation of the columnar spacer 25, the alignment film material is
1. The pixel electrode 12 and the columnar spacers are coated to a thickness of 500 Å to cover the entire surface, and further rubbed to form an alignment film AL1.
Incidentally, the lack of the columnar spacer 25 did not occur in the rubbing treatment.

In the manufacturing process of the electrode substrate G2, the counter electrode 2
4 is formed by depositing an ITO film having a thickness of 1500 angstroms on the insulating substrate 23 by a sputtering method.

Thereafter, an alignment film material is applied to a thickness of 500 angstroms so as to cover the entire surface of the counter electrode 24, and is further subjected to a rubbing process, thereby forming an alignment film AL2. The rubbing direction of the alignment film AL2 is set so as to be shifted by 90 degrees from the rubbing direction of the alignment film AL1.

In the step of bonding the electrode substrates G1 and G2, for example, a heat (or ultraviolet) curable acrylic or epoxy-based adhesive is used to leave the liquid crystal injection port.
1 is printed on the alignment film AL1 along the outer edge of the first electrode 1 and an electrode transfer material is formed on the transfer electrode connected to the auxiliary capacitance line 16 outside the adhesive. Thereafter, the electrode substrates G1 and G
2 are stacked with the alignment films AL1 and AL2 inside,
Heat treated. As a result, the adhesive becomes the peripheral sealing material 1
It is cured as OA. Subsequently, the liquid crystal composition is injected into the liquid crystal injection space surrounded by the peripheral sealing material 10A between the electrode substrates G1 and G2 and secured by the columnar spacer 25 from the liquid crystal injection port in a usual manner. It is sealed with an ultraviolet curing resin. The liquid crystal composition is constituted, for example, by adding 0.1 wt% of a chiral agent to a nematic liquid crystal. In the liquid crystal display device thus obtained, the gap between the electrode substrates G1 and G2 was 4.9 ± 0.2 μm.
m, having very high uniformity maintained in the range of m, and excellent display quality with a high contrast ratio can be obtained.
Also, no vacuum bubbles are generated in the low-temperature impact test.

In the liquid crystal display element of the present embodiment, the columnar spacer 25 is formed so as to extend from the flat portion of the base to the recess with the base of the electrode substrate G1. With this structure,
Even if the place where the columnar spacer 25 is formed is restricted due to the high definition of the liquid crystal display element, as shown in FIG. 4, a flat base that can obtain the designed height and the contact area on the front end side substrate is selected. The base of the columnar spacer 25 that is wider than when the columnar spacer 25 is formed can be secured.
Although the tip of the columnar spacer 25 contacts the electrode substrate G2 in a region corresponding to the flat portion of the base and does not contact the electrode substrate G2 in a region corresponding to the concave portion of the base, the position where the columnar spacer 25 is formed varies. Even, the columnar spacer 25
The outermost contour of the front-end-side substrate contact surface can substantially match the boundary between the flat portion and the concave portion of the base. That is, since a margin for the variation in the formation position of the columnar spacer 25 is not required, it is possible to prevent the height of the columnar spacer 25 and the contact area of the tip-side substrate from being reduced. Further, since the columnar spacers 25 also extend to the concave portions on the base, even if the columnar spacers 25 are eroded by the force of the developing solution that strikes the spacer edges during patterning, the erosion is prevented from proceeding beyond the boundary between the flat portions and the concave portions. Therefore, a liquid crystal injection space can be secured by the columnar spacer 25 having sufficient strength.

Hereinafter, an active matrix type liquid crystal display device according to a second embodiment of the present invention will be described with reference to the accompanying drawings. This liquid crystal display element is the same as the liquid crystal display device except that the insulating layer 30 serves as a base of the columnar spacer 25 instead of the color filter 21 shown in FIG. 1, and the color filter 21 is formed between the insulating substrate 23 of the electrode substrate G2 and the counter electrode 24. The configuration is the same as that of the liquid crystal display device of the first embodiment. For this reason, the liquid crystal display device of the second embodiment has a planar structure similar to that of FIG.

FIG. 3 shows a cross-sectional structure of the liquid crystal display device of the second embodiment along the line II shown in FIG. In FIG. 3, the same parts as those in the first embodiment are denoted by the same reference numerals,
The description is simplified or omitted.

Therefore, a method of 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.
1, the scanning line 13, the signal line 14, the thin film transistor 15, the auxiliary capacitance line 16, the interlayer insulating film 1
8, an upper source electrode 19, and a protective insulating film 20 are formed. After the formation of the protective insulating film 20, a photosensitive acrylic transparent resin is applied to the entire surface of the protective insulating film 20 with a spinner,
After drying at 90 ° C. for 10 minutes, a wavelength of 365 nm and an energy density of 300 mJ / cm ² are passed through a photomask.
The light is selectively exposed by irradiating the light. After this exposure, the acrylic resin is developed with an alkaline aqueous solution having a pH of 11.5, and further baked at 200 ° C. for 60 minutes, thereby forming an insulating layer 30 having a thickness of 3 μm corresponding to the exposed region to be developed. The contact hole 22 is an insulating layer 30
Is formed to expose the upper source electrode 19 in a size of 15 × 15 μm. Here, the contact hole 22 is a concave portion having a depth of at least 3 μm. Thereafter, an ITO film having a thickness of 1500 angstroms is deposited by a sputtering method, and the ITO film is patterned by a photolithography method to form a plurality of pixel electrodes 1.
2 are formed.

After the formation of the pixel electrode 12, a photosensitive transparent acrylic resin is applied to the entire surface of the color filter 21 and the pixel electrode 12 with a spinner, dried at 90 ° C. for 10 minutes, and then passed through a photomask at a wavelength of 365 nm and energy density. It is selectively exposed by irradiating light of 300 mJ / cm ² . After this exposure, the acrylic resin has a pH of 1
Developed with 1.5 aqueous alkaline solution
It is baked at 60 ° C. for 60 minutes, thereby forming a plurality of columnar spacers 25 corresponding to the exposed regions to be developed. here,
Each columnar spacer 25 is provided at a rate of one for every seven pixels in the row direction, and is arranged at a location that is shielded from light by the auxiliary capacitance line 16 and avoids the opening of the pixel electrode 12. in this case,
The columnar spacer 25 has a width of 15 μm, a length of 40 μm, and a height of 5.5 μm, and is formed to extend from the flat portion to the recess with the insulating layer 30 as a flat portion and the contact hole 22 as a recess. Further, the shape of the columnar spacer 25 is a forward tapered shape having a base end wider than the front end. This columnar spacer 2
After the formation of 5, an alignment film material is applied to a thickness of 500 angstroms so as to cover the entire surface of the color filter 21, the pixel electrode 12, and the columnar spacer, and is further subjected to a rubbing process, thereby forming an alignment film AL1. Incidentally, the lack of the columnar spacer 25 did not occur in the rubbing treatment.

In the manufacturing process of the electrode substrate G2, a black matrix of chromium is formed on the insulating substrate 23 corresponding to the matrix of the pixel electrodes 12, and an ultraviolet curable acrylic resin resist in which a red pigment is dispersed is insulated by a spinner. The wavelength 36 applied to the substrate 23 through a photomask
It is selectively exposed by irradiating light of 5 nm and energy density of 100 mJ / cm ² . After this exposure,
The resin resist is developed with a 1% aqueous solution of KOH for 10 seconds to form a red colored layer R having a thickness of 3 μm corresponding to the exposed area to be developed. Subsequently, the green coloring layer G and the blue coloring layer B are formed in the same manner as the above-described coloring layer R. The colored layers R, G, and B are the pixel electrodes 1
The stripes oppose each other in two rows. The colored layer G is formed using an ultraviolet-curable acrylic resin resist in which a green pigment is dispersed, and the colored layer B is formed using an ultraviolet-curable acrylic resin resist in which a blue pigment is dispersed.
After the color filter 21 is obtained from the colored layers R, G, and B, the counter electrode 24 is formed by depositing an 1500-Å-thick ITO film on the color filter 21 by a sputtering method. Thereafter, an alignment film material is applied to a thickness of 500 angstroms so as to cover the entire surface of the counter electrode 24, and is further rubbed, thereby forming an alignment film AL2. The rubbing direction of the alignment film AL2 is set so as to be shifted by 90 degrees from the rubbing direction of the alignment film AL1.

The step of bonding the electrode substrates G1 and G2 is performed in the same manner as in the first embodiment. The liquid crystal display device thus obtained has a very high uniformity in which the gap between the electrode substrates G1 and G2 is maintained in the range of 4.9 ± 0.2 μm, and obtains an excellent display quality with a high contrast ratio. Can be. Also, no vacuum bubbles are generated in the low-temperature impact test.

In the liquid crystal display device of the present embodiment, the columnar spacer 25 is formed so as to extend from the flat portion of the base to the recess with the base of the electrode substrate G1. Therefore, the same effect as in the first embodiment can be obtained.

[0030]

As described above, according to the present invention, it is possible to provide a liquid crystal display element in which a liquid crystal injection space can be easily secured under the restrictions associated with high definition.

[Brief description of the drawings]

FIG. 1 is a diagram showing a planar structure of an active matrix type liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a cross-sectional structure of the liquid crystal display element taken along line II shown in FIG.

FIG. 3 is a diagram showing a cross-sectional structure of an active matrix type liquid crystal display element according to a second embodiment of the present invention along the line II shown in FIG.

FIG. 4 is a diagram showing a conventional configuration in which a columnar spacer is formed by selecting a flat base, for comparison with the configuration of the present invention.

[Explanation of symbols]

 G1, G2: electrode substrate LQ: liquid crystal composition 10: liquid crystal cell 10A: peripheral sealing material 16: auxiliary capacitance line 21: color filter 22: contact hole 25: columnar spacer 30: insulating layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H089 LA09 LA16 LA19 LA20 NA14 NA17 NA24 NA25 NA33 NA39 NA45 NA55 NA60 PA08 QA12 QA14 QA15 TA04 TA09 TA12 TA13 2H090 JA03 JA05 JB02 JC12 JC17 LA02 LA04 LA05 LA15 MB02 MB03 2H091 FA02 FA02 FB13 FC10 FC26 FD04 FD12 FD22 FD24 GA13 LA03 LA11 LA15

Claims (3)

[Claims] A pair of first and second substrates;
A liquid crystal composition sandwiched between a first substrate and a second substrate;
A plurality of columnar spacers protruding from the substrate and supporting the second substrate, wherein the columnar spacers are formed by using the first substrate as a base and extending from a flat portion of the base to a recess. element. 2. The liquid crystal display device according to claim 1, wherein the first substrate includes an insulating layer having a contact hole formed as the recess. 3. The liquid crystal display device according to claim 2, wherein the insulating layer is a color filter.