KR100859466B1 - Liquid crystal display device - Google Patents

Abstract

The present invention relates to a liquid crystal display device having a column spacer having a pattern for compensating a difference in volume expansion ratio with a liquid crystal. In particular, a thin film transistor and a pixel electrode are formed in each pixel to define a plurality of pixels. A first substrate; A second substrate facing the first substrate and provided with a color filter layer; A liquid crystal layer formed between the first and second substrates; And a column spacer formed on one of the first substrate and the second substrate and having a dot pattern for compensating a difference in volume expansion between liquid crystals.

Column Spacers, Dot Pattern

Description

Liquid crystal display device {LIQUID CRYSTAL DISPLAY DEVICE}

1A and 1B are a plan view and a cross-sectional view of a liquid crystal display device according to an embodiment of the prior art.

2A and 2B are a plan view and a cross-sectional view of a liquid crystal display device according to another embodiment of the prior art.

3A and 3B are a plan view and a cross-sectional view of a liquid crystal display device according to the present invention.

4A to 4C are cross-sectional views illustrating a process of forming a column spacer according to the present invention.

* Explanation of symbols on the main parts of the drawings

111 black matrix 112 color filter layer

113: common electrode 114: gate wiring

115: data wiring 116: column spacer

116a: photoresist 119: lower substrate

121: thin film transistor 122: pixel electrode

130: mask

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device (LCD), and more particularly to a liquid crystal display device including a spacer for maintaining a cell gap of a substrate.

BACKGROUND ART Liquid crystal display devices, which have recently been spotlighted as flat panel display devices, have been actively researched due to their high contrast ratio, suitable for gradation display or moving picture display, and low power consumption.

The liquid crystal display device is composed of two opposing substrates and a liquid crystal layer interposed therebetween, by applying a voltage to the electrodes formed on the substrate to rearrange the liquid crystal molecules of the liquid crystal layer to control the amount of light transmitted to display an image. Device.

At this time, if the gap between the two substrates is not constant, the transmittance of light passing through the portion is changed and brightness is uneven, so that the spacers are inserted between the two substrates to keep the substrate gap constant.

Hereinafter, a liquid crystal display device according to the related art will be described with reference to the accompanying drawings.

1A and 1B are a plan view and a cross-sectional view of a liquid crystal display device according to an exemplary embodiment of the prior art, and FIGS. 2A and 2B are a plan view and a cross-sectional view of a liquid crystal display device according to another embodiment of the prior art.

In general, as shown in FIGS. 1A and 1B, an LCD may include an upper substrate 18 having a color filter layer 12 for color implementation, and a lower substrate having a switching element capable of converting an arrangement direction of liquid crystal molecules. And a liquid crystal layer 20 formed between the upper and lower substrates 18 and 19.

In detail, the upper substrate 18 further includes a black matrix 11 that blocks light leakage in addition to the color filter layer 12, and a common electrode 13 that is a first electrode that applies a voltage to the liquid crystal layer 20. In addition, the lower substrate 19 receives a signal from the thin film transistor 21, which is the switching element, in addition to the gate line 14 and the data line 15 defining pixels by crossing vertically, and the thin film transistor 21. A pixel electrode 22 which is a second electrode that applies a voltage to the liquid crystal layer 20 is further formed.

In addition, a ball spacer 16 is inserted between the upper and lower substrates 18 and 19 to maintain a constant gap between the two substrates, and the liquid crystal is prevented from flowing to the outside of the substrate. Sealant (not shown) is formed.

At this time, the ball spacer 16 is uniformly distributed on the entire surface of the upper substrate or the lower substrate using a plastic ball or a glass ball having a desired aperture. The ball spacer has a dispersion density of 100 to 150ea / 1 mm 2.

The glass ball is generally made of a glass fiber made by spinning alkali-free glass in a suitable form, and mainly contains SiO ₂ . Such glass spacers have good heat resistance and chemical resistance, low reactivity with liquid crystals, and high hardness, and do not have deformation due to load.

The ball spacer made of plastic is made of synthetic resin, and there are a thermoplastic type and a thermosetting type according to the type of resin. Compared to the glass ball, since the hardness is low and the deformation by the load is easy, the scattering density should be higher than that of the glass ball.

Methods of dispersing the ball spacers 16 include a wet dispersing method in which a spacer is mixed with a solvent and dispersed, and a dry dispersing method in which a space around a substrate is maintained while the spacers are charged and dispersed without aggregation.

On the other hand, in the case of a liquid crystal display device having a low cell gap and a large area, a column spacer 26 is used instead of the ball spacer 16 as shown in FIGS. 2A and 2B. This is because it is difficult to produce ball spacers of 4 to 5 μm or less and it is difficult to ensure uniformity of cell gap when applied to large areas.

The column spacer 26 is formed using a photolithography technique that removes unnecessary portions by an optical or chemical method in order to impart a predetermined pattern by an insulator.

That is, the photoresist is applied to the upper substrate 28 or the lower substrate 29 to a predetermined thickness, cured, exposed, chemically processed (developed), and the column spacers 26 are formed at arbitrary positions of the substrate. do.

In the photoresist exposure, the energy applied to the photoresist surface portion and the core portion is different so that the column spacer 26 has a larger area of the core portion than that of the surface portion. That is, the solid line representing the column spacer 26 of FIG. 2A represents the area of the surface of the column spacer, and the dotted line represents the area of the core portion of the column spacer.

However, the liquid crystal display device as described above has the following problems.

First, the column spacer and the liquid crystal region are separated by the difference in the volume expansion ratio of the column spacer and the liquid crystal due to the temperature change. At this time, the luminance difference occurs due to the gap difference of the liquid crystal cell, causing image unevenness.

When the liquid crystal display device is erected, a gravity failure occurs in which the upper liquid crystal is weighted downward through the gap by gravity.

Second, when the upper and lower substrates face each other, pressure is biased in a narrow contact area between the column spacer and the counter substrate, causing damage to the alignment layer of the counter substrate or impacting the pattern to cause image staining.

An object of the present invention is to provide a liquid crystal display device that compensates for the difference in volume expansion ratio between a column spacer and a liquid crystal by forming the surface of the column spacer in a dot pattern.

According to an aspect of the present invention, there is provided a liquid crystal display device including: a first substrate having a thin film transistor and a pixel electrode formed in a plurality of pixels; A second substrate facing the first substrate and provided with a color filter layer; A liquid crystal layer formed between the first and second substrates; And a column spacer formed on one of the first substrate and the second substrate and having a dot pattern for compensating a difference in volume expansion between liquid crystals.

That is, the surface of the column spacer is formed in a dot pattern to disperse the pressure caused by the contact between the column spacer and the counter substrate, and the liquid crystal is filled between the dot patterns of the column spacer, so that the volume of the portion where the liquid crystal and the column spacer are formed. To compensate for the expansion rate.

Hereinafter, a liquid crystal display according to the present invention will be described in detail with reference to the accompanying drawings.

3A and 3B are plan views and cross-sectional views of a liquid crystal display device according to the present invention, and FIGS. 4A to 4C are cross-sectional views illustrating a process of forming a column spacer according to the present invention.

As shown in FIG. 3B, the liquid crystal display according to the present invention includes a column spacer 116 for maintaining cell gaps between the upper and lower substrates 118 and 119, the upper and lower substrates 118 and 119, and the upper and lower substrates 118 and 119. The liquid crystal layer 120 encapsulated between the lower substrates is characterized in that the column spacer 116 has a dot pattern on a surface thereof in contact with the opposing substrate.

Accordingly, since the liquid crystal is filled between the dot patterns of the column spacer 116, the difference in volume expansion coefficient due to temperature change between the portion where the column spacer is formed and the portion where the liquid crystal layer is formed is compensated for.

The column spacer 116 is formed inside one of the upper and lower substrates 118 and 119. The column spacer 116 is formed using a photolithography technique after applying a photoresist.                     

In general, the column spacer 116 may be easily formed on the upper substrate 118. This is because a lot of fine patterns are formed on the lower substrate 119, which may cause a defect in spacer patterning.

At this time, the pattern of the lower substrate 119 perpendicularly intersects the data line 115 and the gate line 114, which define pixels, and is formed at the intersections of the two lines to determine the on / off of each pixel. 121 and a pixel electrode 122 opposed to the common electrode to apply a voltage for driving the liquid crystal.

In addition, the column spacer 116 may be formed per pixel, per pixel, or per pixel, and the array form may be arranged in a stripe structure or a diagonal structure. In this case, as shown in FIG. 3A, the column spacer 116 is arranged in a stripe structure, and one column spacer 116 is formed per three pixels.

In addition, although the column spacer 116 is formed on the gate wiring 114 in the drawing, the column spacer 116 may be formed on the intersection of the gate wiring 114 and the data wiring 115 or on the data wiring 115.

Specifically, referring to the formation process of the column spacer 116 according to the present invention, first, as shown in FIG. 4A, the black matrix 111 for preventing RGB mixing and the color filter layer 112 for RGB for expressing color. And a photoresist 116a is applied to the entire surface of the upper substrate 118 where the common electrode 113 for applying a voltage to the liquid crystal is applied, and the photoresist is cured by applying heat.

As the photoresist material, a polymer material such as photo acryl resin having photosensitive properties is used. For example, a polymer material having no photosensitive property may be used. An organic insulating material such as BCB (Benzocyclobutene) or silicon nitride (SiNx) may be used. The column spacer may be formed using a polymer material such as an inorganic insulating material such as silicon oxide (SiOx).

Next, as shown in FIG. 4B, after aligning the mask 130 on the upper substrate 118, the photoresist 116a is exposed by irradiating UV rays through the light transmitting portion of the mask 130.

Finally, as shown in FIG. 4C, the exposed photoresist is removed by chemical treatment (development) to complete the column spacer 116 having the surface of the dot pattern by the plurality of protrusion patterns. The surface of the column spacer 116 is smaller than the surface area fixed to the upper substrate 118 to be in contact with the opposing substrate, because more energy is applied to the surface than the photoresist core portion during exposure.

The solid line of FIG. 3A shows the area of the column spacer surface in contact with the opposing substrate, and the dotted line shows the area of the column spacer core.

In this case, the column spacer 116 may have a dot pattern only in an area in contact with the opposing substrate as shown in FIG. 3A or a dot pattern as shown in FIG. 3B, depending on the degree of exposure.

Since the column spacer formed as described above has a dot pattern on the surface in contact with the opposing substrate, the pressure due to the bonding of the substrate is dispersed to prevent the image stain due to the pressing.

 The liquid crystal display of the present invention as described above has the following effects.

First, the liquid crystal is present between the column spacer dot patterns through surface modification of the column spacer to compensate for the difference in volume expansion rate between the column spacer and the liquid crystal. As a result, the gravity failure due to the difference in volume expansion rate is improved, and eventually, image staining is prevented.

Second, by dispersing the contact area of the surface of the column spacer with the opposing substrate in contact with the column spacer, the pressure applied to the opposing substrate by the column spacer is dispersed. Therefore, it is possible to improve the crushing stain caused by the pressure.

Claims (3)

A first substrate defined by a plurality of pixels and having a thin film transistor and a pixel electrode formed in each pixel; A second substrate facing the first substrate and provided with a color filter layer; A liquid crystal layer formed between the first and second substrates; And Liquid crystals comprising one column spacer per three pixels formed on the gate line or data line of the first substrate and having a plurality of protrusion patterns to have a dot pattern for compensating the difference in volume expansion coefficient between liquid crystals. Display element. delete The method of claim 1, And a liquid crystal filling the protrusion pattern of the column spacer.

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