KR100242481B1 - Liquid crystal display device - Google Patents

Abstract

The present invention relates in particular to a liquid crystal light valve used in a projection type liquid crystal device, and an object thereof is to provide a projection type liquid crystal device which has improved display quality by improving display brightness and preventing nonuniformity or poor alignment of a spacer.

On the silicon substrate 2, a pixel array region 4 in which a display electrode composed of an aluminum (Al) thin film as a light reflection film is formed for each pixel is formed, and a counter electrode 16 is provided on a glass substrate 14, which is an opposing substrate. It is. The silicon substrate 2 and the glass substrate 4 face each other and are joined together by band-shaped spacers 6, 8, 10, 12 formed of an adhesive resin provided in parallel in a plurality around the outside of the pixel array region 4. have. The liquid crystal 18 is enclosed in the region between the pixel array region 4 and the counter electrode 16. The spacer is not formed on the pixel array region 4. The strip spacers 6 to 12 are configured to combine the upper and lower substrates around the pixel array region 4 and to make the thickness (cell gap) between the pixel array region 4 and the counter electrode 16 constant.

Description

Liquid crystal display

1 is a plan view of a reflective liquid crystal light valve according to an embodiment of the present invention.

2 is a cross-sectional view A-A of the reflective liquid crystal light valve according to the exemplary embodiment of the present invention.

3 is a cross-sectional view of a reflective liquid crystal light valve according to an embodiment of the present invention.

4 is a diagram showing a projection type liquid crystal device using a reflective liquid crystal light valve according to an embodiment of the present invention.

5 (a) and 5 (b) are micrographs showing a band-shaped spacer according to an embodiment of the present invention.

6 (a) and 6 (b) are micrographs showing a band-shaped spacer according to an embodiment of the present invention.

7 (a) and 7 (c) are micrographs showing a band-shaped spacer according to an embodiment of the present invention.

8 (a) and 8 (c) are micrographs showing the adhesion state of the spacer and the opposing glass substrate on the silicon substrate.

9 is a cross-sectional view of a conventional reflective liquid crystal light valve.

10 is a cross-sectional view of a conventional reflective liquid crystal light valve.

* Explanation of symbols for main parts of the drawings

2, 100: silicon substrate 4: pixel array region

6, 8, 10, 12: strip-shaped spacer 14: glass substrate

16: counter electrode 18: liquid crystal

20, 22, 24: liquid crystal injection port 30: sealant

32: spacer beads

34: Column spacer spacer

42 light source 44 polarizing beam splitter

46: color separation prism 48, 50, 52: reflective liquid crystal light valve

54: projection lens 56: screen

102 silicon oxide film 104 transistor

106: light absorbing layer 108: silicon nitride film

110 stud 112 light reflecting film

114: counter electrode 116: glass protective substrate

118 black matrix 120 liquid crystal layer

[Industrial use]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to liquid crystal displays, and more particularly to liquid crystal light valves used in projection type liquid crystal displays.

[Prior art]

In recent years, a projection type liquid crystal device that has the potential as an ultra-high definition display device replacing CRT has been in the spotlight. Projection type liquid crystal devices have already been used for display devices of HDTV and OHP.

The projection optical system of the projection liquid crystal device is formed of a light source, a light valve, a screen and an optical filter, a projection lens, and the like.

The light valve includes a projection type liquid crystal light valve in which a liquid crystal display panel is used and projects light from a light source to project an image onto a screen, and a reflection type liquid crystal light valve that reflects light from a light source to project an image onto a screen.

In general, the active matrix type liquid crystal display device is not limited to a projection type but includes an array substrate on which a switching element and a display electrode connected to the switching element are formed, and an opposite electrode disposed to face the array substrate through a predetermined gap (cell gap). It is formed of an opposing substrate, and liquid crystal is enclosed in an area between the array substrate and the opposing substrate.

Therefore, since the wavelength and birefringence of the light passing or reflecting the liquid crystal layer are determined by the cell gap, the degree of thickness thereof and the uniformity thereof in the plane are very important parameters that determine the performance of the liquid crystal display (LCD).

9 and 10 show the structure of a reflective liquid crystal light valve used in a conventional projection liquid crystal device. On the silicon substrate 2, a pixel array region 4 formed of an aluminum (A1) thin film and having a function as a light reflection film is formed for each pixel. As an example of the counter substrate, the counter electrode 16 is provided on the glass substrate 14.

The silicon substrate 2 and the glass substrate 14 are joined by the sealing material 30 at opposite sides, and the liquid crystal 18 is enclosed in the region between the pixel array region 4 and the counter electrode 16. Although not shown, the alignment film for orienting the liquid crystal 18 is formed on the pixel array region 4 and the side in contact with the liquid crystal on the counter electrode 16.

In order to obtain the desired electro-optic properties of the liquid crystal material, it is necessary to obtain a predetermined cell gap uniformly over the entire display surface of the panel, so that a glass bead or a plastic sphere of several microns in diameter is used as a spacer bead. (32) is distributed in a large number between the pixel array region 4 and the counter electrode 16 to obtain a uniform cell gap (FIG. 9). However, the method of using the spacer sphere 32 has a process problem that it is very difficult to uniformly disperse the diameter of the spacer sphere 32 or to uniformly disperse the spacer sphere 32 in the panel. 4) It has a problem that orientation nonuniformity (display nonuniformity) and fall of brightness | luminance / aperture rate generate | occur | produce by the position of the said spacer sphere 32 above.

Instead of the method of dispersing the spacer sphere, a method of forming a pillar formed of an insulating film or the like in a cell gap and using it as a spacer has been proposed (Fig. 10). This mainly uses a photolithography process generally used in the manufacturing process of semiconductor devices, and uses a pillar of a silicon oxide film as a spacer (column spacer sphere 34) between the pixel array region 4 and the counter electrode 16. The cell gap is formed in a region so as to obtain a predetermined cell gap, and has the advantage that the position, number, and height of the spacer can be freely controlled as compared with the case of using a conventional spacer sphere.

[Inventions trying to solve]

However, in the reflective liquid crystal light valve shown in FIG. 10, the columnar spacers 34 are placed on adjacent pixel arrays to form a step (ditch), and thus reduce the light reflection area of the light reflecting film of Al. It is a factor for lowering the optical aperture of subpixels.

In addition, concave and convex portions are formed at the end of the column spacer 34 due to the step difference, and the load of the convex portion is easily concentrated during the cell process, so that the column of the column spacer 34 is damaged. easy.

In addition, since the spacer pillar is formed before the alignment treatment of the orientation film, the spacer pillar is mounted on rubbing and causes the alignment layer near the pillar not to be aligned.

Thus, since it is a spacer sphere or a spacer column, or because it is on the pixel array area which contributes to display, it distorts the liquid crystal orientation of the pixel of the part and becomes like a spacer when the LCD is driven. In a high-definition and large-screen projector, the larger the display screen is, the more the liquid crystal alignment is disturbed and is projected by the enlarged projection, and the display quality is deteriorated, which is a problem that must be solved.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device which improves display quality by improving display brightness and preventing nonuniformity or defects of alignment caused by spacers. Among them, display brightness is improved to prevent nonuniformity or defects caused by spacers. The present invention provides a projection type liquid crystal device with improved display quality.

[Means for solving the problem]

SUMMARY OF THE INVENTION An object of the present invention is to provide a substrate on which a pixel array region having a plurality of display electrodes is formed, an opposing transparent substrate on which a transparent electrode opposing the pixel array region is formed, and a substrate formed over a peripheral region of the pixel array region of the substrate and having a predetermined cell gap. And a spacer for bonding the opposing transparent substrate to each other.

Another object of the present invention is achieved by forming a plurality of spacers in parallel in a band shape in the outer peripheral region of the pixel array region.

Another object of the present invention is achieved by the outer spacer of the above-mentioned spacers also serving as a sealing material for enclosing the liquid crystal.

Still another object of the present invention is to provide a substrate having a plurality of display electrodes and having a pixel array region having a light shielding region therebetween, an opposing transparent substrate having a transparent electrode opposed to the pixel array region, and a light shielding region of the substrate, A width narrower than the width of the light shielding region is formed, and is achieved by a liquid crystal display device comprising a spacer for adhering the substrate and the opposing transparent substrate to a predetermined cell gap.

Another object of the present invention is achieved by forming a spacer with a photosensitive resin material having adhesiveness in the above-described liquid crystal display device.

Another object of the present invention is achieved by the substrate in the above-described liquid crystal display device being a silicon substrate and the plurality of display electrodes formed of a light reflecting material.

[Action]

According to the present invention, since a spacer is formed on the outer periphery of the pixel array region of the substrate to bond the substrate and the opposing transparent substrate to a predetermined cell gap, the display brightness of the liquid crystal display device is improved and the nonuniformity or defect of alignment caused by the spacer is prevented. This can improve display quality.

In addition, since spacers are formed in the light shielding area of the substrate to bond the substrate and the opposing transparent substrate with a predetermined cell gap that is narrower than the width of the light shielding area, the display brightness of the liquid crystal display device is improved and the nonuniformity or defect of the alignment by the spacer is prevented. The display quality can be improved.

EXAMPLE

A reflective liquid crystal light valve and a method for manufacturing the same according to an embodiment of the present invention will be described with reference to FIGS. 1 to 8 (c).

First, the structure of the reflective liquid crystal light valve of this embodiment will be described using FIG. 1 and FIG. 1 is a plan view of a reflective liquid crystal light valve of this embodiment. 2 is its A-A cross section.

For example, a pixel array region 4 in which a display electrode formed of an aluminum (Al) thin film is formed on each pixel is formed on a silicon (Si) substrate 2, and a glass substrate 14 is provided as an example of an opposing substrate. ), The counter electrode 16 is provided.

The silicon substrate 2 is opposed by the glass substrate 14 and is opposed by the band-shaped spacers 6, 8, 10, 12 formed of an adhesive resin provided in parallel in a plurality around the outside of the pixel array region 4. It is attached.

The liquid crystal 18 is enclosed in the region between the pixel array region 4 and the counter electrode 16. Although not shown, the alignment layer for orienting the liquid crystal 18 is formed on the pixel array region 4 and the side in contact with the liquid crystal 18 on the counter electrode 16. The spacer is not formed in the pixel array region 4.

A plurality of liquid crystal injection holes 20, 22, 24, and 25 are provided in the strip spacers 6-12 provided in parallel in the circumference of the pixel array area 4, respectively. Although not shown, a sealing material is provided on the outside of the columnar spacer to seal the liquid crystal. The strip-shaped spacers 6 to 12 of this embodiment face the upper and lower substrates around the pixel array region 4, and have a constant thickness (cell gap) between the pixel array region 4 and the counter electrode 16. To act.

Thus, since the columnar spacers made of resin parallel to the outer periphery of the pixel array region 4 are provided, a predetermined cell gap can be maintained even when the spacers are removed in the pixel array region 4, thereby improving display brightness and increasing the spacer. It is possible to realize a projection type liquid crystal device in which the display quality is improved by preventing the nonuniformity and the defect of the alignment caused by the PSA.

The dimension of the reflective liquid crystal light valve of this embodiment is that the distance A of the silicon substrate 2 is a square shape of about 20 to 35 mm in length and width, and the distance B of the pixel array region 4 is a substantially rectangular shape of about 15 to 30 mm. For example, pixels are formed in a matrix form of 1600 rows and 1280 columns. The thickness D, F and H of each strip | belt-shaped spacer is about 10 micrometers, their height I is about 3.2 micrometers, the space | intervals C, E, and G of the spacer are about 10 micrometers, and cell gap J is 3 micrometers.

The structure of one pixel of the reflective liquid crystal light valve of this embodiment will be described using FIG.

A transistor 104, not shown in detail, is formed on the silicon substrate 100. A silicon oxide film 102 having a thickness of about 2 μm is formed on the silicon substrate 100 and the transistor 104, and a light absorbing layer 106 is formed on the silicon oxide film 102. A 5000 nm thick silicon nitride film 108 is formed on the light absorption layer 100, and a 1500 nm thick light reflective film 112 is formed thereon.

The light reflecting film 112 is connected to a source electrode (not shown) of the transistor 104 by a stud 110 of tungsten (W) embedded in a through hole formed in the silicon oxide film 102 and the silicon nitride film 108. It also functions as a display electrode for driving the.

In one light reflection film 112, a subpixel of one display pixel is formed. The Al layer is not formed between the adjacent light reflecting films 112 (a distance of about 1.7 mu m), and thus the black matrix 118 is a light shielding region that does not reflect light.

The glass protection substrate 116 is formed as an opposing board | substrate, and the opposing electrode 114 is formed in the whole surface in the light reflection film side of the glass protection board 116. As shown in FIG. The light reflecting film 112 and the counter electrode 114 are maintained in a predetermined cell gap, and the liquid crystal is sealed therebetween to form the liquid crystal layer 120.

The transistor 104 is a FET (field effect transistor) in which a drain electrode connected to a data line and a gate electrode (not shown) are formed in addition to the source electrode, and is applied to the data line in the on state of the gate. It functions as a switching element which applies a voltage to the light reflection film 112 which is a display electrode.

Glass protection by changing the transmittance of light by changing the direction of the liquid crystal molecules 122 by the voltage applied between the light reflection film 112 and the counter electrode 114 which are display electrodes when the transistor 104 is on. The light incident on the substrate 116 is transmitted to the light reflection film 112 and reflected to display the light so as not to be re-emitted or transmitted from the glass protective substrate 116. Also in this figure, the alignment film is not shown.

Next, the outline of the projection type liquid crystal display device using the reflective liquid crystal light valve according to the present embodiment will be described using FIG.

The linearly polarized light emitted from the light source 42 is reflected by the polarization beam splitter 44 and incident on the color separation prism 46, where the three primary colors of red (R), green (G), and blue (B) are used. They are separated and incident on the reflective liquid crystal light valves 48, 50, and 52 for red (R), green (G), and blue (B), respectively. In each reflective liquid crystal light valve, the light subjected to the luminance modulation for each sub-pixel is reflected and incident on the color separation prism 46 again, shifted by 90 degrees from the circularly polarized light, and becomes linearly polarized light to the polarizing beam splitter 44. Incident.

Reflected light from the reflective liquid crystal light valves 48, 50, 52 passes through the polarizing beam splitter 44, enters the projection lens 54, is enlarged, and is projected onto the screen 56.

Next, the manufacturing method of the reflection type liquid crystal light valve of this Example is demonstrated using FIG. 5 (a)-FIG. 8 (c).

The reflective liquid crystal light valve of the present embodiment is characterized by the resin-shaped spacers 6-12 formed in the outer periphery of the pixel array region 4, and the other structure is, in principle, manufactured by a conventional manufacturing method. The manufacturing method of the spacers 6-12 is explained in full detail, and description of the manufacturing method of another part is abbreviate | omitted.

First, the forming material of the strip | belt-shaped spacers 6-12 is resin which has photosensitivity and adhesiveness. This resin with photosensitivity and adhesiveness uses what mixed the hardening | curing material in a fixed ratio with the nega type photoresist material. For example, but not limited to this, there is a resin obtained by Tokyo O. TPAR N-25 MB (topic) and TPAR-curing agent as a solvent at 30.6: 6 (Ref. K. Matsui, K.). Utsumi, H. Ohkubo and C. Sugitani, “Resin and Flexible Metal Bumps for Chip-On-Glass Technology,” 43rd Electronic Components and Technology Conference, pp. 205-210. Orlando, Florida, June, 1993). In the above-mentioned reference, a chip-on-glass (COG :) in which a resin having photosensitivity and adhesiveness directly connects a driving chip of a liquid crystal display device having an electrode gap of tens of macrons and a glass substrate of a liquid crystal display device wired with a transparent conductive film is used. Chip On Glass) technology and its excellent photosensitivity and adhesion.

In general, the photosensitive adhesive resin has an advantage that it can take a variety of conditions from the adhesive state to the complete adhesive curing state depending on the conditions of light irradiation or heating. Utilizing this feature, the bonding process can be divided into two stages: semi-cured precure bonding and fully cured postcure bonding, thereby enabling rework or repair. In the rework of the photosensitive film, only its thickness is controlled, but since the adhesiveness is variable, high precision cell gap control can be realized by utilizing rework / repair after temporary bonding.

Next, the process of forming the above-mentioned resin material on a silicon substrate and adhering to a glass substrate is demonstrated.

First, a crude liquid in which a main component and a hardening agent are mixed at a constant ratio (for example, Tokyo O is a resin obtained by mixing TPAR N-25 MB (topic) and TPAR-curing agent as a solvent at 30.6: 6). ) Is applied onto the silicon substrate at a film thickness of 3.0 mu m at 1500 revolutions per minute by the spinner method. Next, the silicon substrate is prebaked at 90 ° C. for 3 minutes on a hot plate, and then exposed to an exposure dose of 75 to 150 mJ / cm 2 by mirror projection. After exposure, the developer (5% triethanolamine) is developed at 25 ° C. by immersion and agitation for 50 seconds to pattern and form a desired spacer.

After heating at 80 ° C. for 2 minutes on a hot plate, the spacer formed on the silicon substrate and the glass substrate were press-bonded under conditions of 1 Kg and 30 minutes. Next, if necessary, the film is irradiated at a temperature of 150 ° C. for 30 minutes or in the case of ultraviolet (UV) irradiation at 2-3 J / cm 2, followed by post-baking.

The strip | belt-shaped spacer formed on the said process conditions is shown to FIG. 5 (a)-6 (c). The width | variety and space | interval (pitch) of the formed parallel spacer are 10 micrometers, and the spacer is 3 micrometers in thickness.

The inclination of the wall of the strip-shaped spacer can be changed by changing the exposure energy. FIG. 5 (a) is an electron micrograph (SEM) photograph of the spacer which exposed the exposure amount as 75 mJ / cm <2>, and FIG. 5 (b) is an enlarged photograph thereof. 6 (a) is an electron micrograph (SEM) photograph of the spacer which exposed the exposure amount as 100mJ / cm <2>, and FIG. 6 (b) is the enlarged photograph. Increasing such exposure amounts can make the inclination of the wall relatively rapid.

7 (a), 7 (b) and 7 (c) are examples of the band spacers formed on the silicon substrate. After forming these strip | belt-shaped spacers on a silicon substrate, the SEM photograph which bonded and bonded the strip | belt-shaped spacer and the opposing glass substrate by pressure is shown in FIG. The 8th (a), the 8th (b), and the 8th (c) figure are expanded and shown in order.

In this manner, a plurality of strip-shaped spacers can be provided in parallel around the outer periphery of the pixel array region 4. The desired pattern can be freely formed using photosensitivity and the spacer can be provided in any heat using adhesiveness, so that sufficient mechanical strength can be obtained. In the case of the band-shaped spacer described above, the adhesive strength of the spacer 1 row was 0.5 MPa (5 Kgf / cm 2). In addition, the in-plane dispersion of the formed cell gap was 9 µm ± 3% (900 µs), and the cell gap control was achieved with high accuracy by avoiding the slowing down of the glass depending on the thickness and the total area of the glass. .

The adhesive strength of the spacer is in the range of 0.1 to 1.5 MPa by changing the heating temperature in the range of 50 ° C. to 160 ° C., and by changing the pressurization pressure in the range of 0.4 Kg / cm 2 to 5.5 Kg / cm 2 or by irradiating ultraviolet rays at 2J / cm 2 or more. You can change from

In the above example, the pitch of the spacer is set to 10 µm, for example, but these values can be freely changed by changing the mask pattern.

As described above, according to the present embodiment, the resin thin film can be easily processed with high precision and its thickness and in-plane uniformity as in the processing of the photoresist, thereby making it possible to control the cell gap with extremely high precision.

Since the resin thin film has strong adhesiveness, the base material is not limited to an insulating film such as a silicon oxide film, but may be a metal, ITO (indium tin oxide) or glass used as a transparent electrode, and either the array substrate side or the opposite substrate side may be used. It can also be formed.

In addition, since the band spacers are provided in parallel around the outer side of the pixel array, sufficient mechanical strength is ensured, so that high-precision cell gap control is possible even without the spacers on the pixel array. Therefore, since the disturbance of the liquid-crystal orientation resulting from the spacer on a pixel can be eliminated, the problem resulting from the conventional columnar spacer can also be solved.

Summarizing the features of the manufacturing method of the strip-shaped spacer according to the present embodiment, the photolithography process holds a request that the processing and control cannot be performed with a processing precision of less than 1/10 of its width and thickness in the order of microns. This problem was solved by making the spacer adhesive. To this end, a resin having both photosensitivity and adhesiveness is employed as a spacer forming material, and in order to increase the adhesive strength, a plurality of spacers having a band-like pattern are provided in parallel around the pixel array region.

The present invention is not limited to the above embodiments, and various modifications are possible.

For example, in the above-described embodiment, the present invention is applied to the reflective liquid crystal light valve of Si-LCD used in the projection liquid crystal device, but other liquid crystal display devices such as the projection liquid crystal light valve or the pixel region are formed on the glass substrate. The present invention can of course also be applied to one liquid crystal display device.

In addition, a band-shaped spacer can be formed in a width narrower than the width of the black matrix on the area of the black matrix in the pixel array region 4 using the above-described spacer manufacturing method. In this case, the effect obtained in the above embodiment is reduced, but the display quality can be further improved as compared with the conventional spacer.

[Effects of the Invention]

As mentioned above, according to this invention, the liquid crystal display device which remarkably improved the cell gap precision and the uniformity between the board | substrate surfaces can be implement | achieved.

Moreover, the cell gap can be easily controlled by the manufacturing method of the semiconductor device of this invention.

Claims (4)

1. A liquid crystal display device comprising: a substrate having a plurality of display electrodes, a pixel array region having a light shielding region therebetween, an opposing transparent substrate having a transparent electrode opposed to the pixel array region, and And a spacer formed in the light shielding region of the substrate to have a width narrower than the width of the light shielding region and adhering the substrate and the opposing transparent substrate to a predetermined cell gap. The liquid crystal display of claim 1, wherein the spacer is formed of an adhesive photosensitive resin material. The liquid crystal display of claim 1, wherein the substrate is a silicon substrate, and the display electrode is formed of a light reflecting material. The liquid crystal display of claim 1, wherein the spacer is formed of a plurality of narrow walls in parallel.