KR20060095396A - The fabrication method of liquid crystal display device - Google Patents

Abstract

The present invention relates to a method of manufacturing a liquid crystal display device capable of preventing the spacers from moving on the substrate after the module process, the method of manufacturing a liquid crystal display device according to the present invention comprises the steps of preparing a lower substrate; Preparing an upper substrate; Disposing a spacer on the lower substrate or the upper substrate; Performing a first curing process on the spacer disposed on the substrate; Bonding the lower substrate and the upper substrate; And performing a second curing process on the spacers to fix the spacers to both sides of the upper and lower substrates.

Liquid Crystal Display, Spacer, Inkjet, Adhesiveness, Secondary Curing

Description

Manufacturing method of liquid crystal display device {THE FABRICATION METHOD OF LIQUID CRYSTAL DISPLAY DEVICE}

1 is a cross-sectional view of a conventional liquid crystal display device.

2 is a flowchart illustrating a method of manufacturing a liquid crystal display device according to an exemplary embodiment of the present invention.

3 is a view showing a spacer forming method of the present invention.

4A to 4C are diagrams illustrating a substrate on which a spacer is applied during a manufacturing process of a conventional liquid crystal display device.

*** Description of the symbols for the main parts of the present invention ***

305: substrate 330: inkjet head

311, 311 ': Spacer 351: Shading area

The present invention relates to a method for manufacturing a liquid crystal display device, and more particularly, to a method for manufacturing a liquid crystal display device that can prevent the spacer from moving on the substrate after the module process.

Recently, with the development of various portable electronic devices such as mobile phones, PDAs, and notebook computers, there is a growing demand for flat panel display devices for light and thin applications. Such flat panel displays are being actively researched, such as LCD (Liquid Crystal Display), PDP (Plasma Display Panel), FED (Field Emission Display), VFD (Vacuum Fluorescent Display), but mass production technology, ease of driving means, Liquid crystal display devices (LCDs) are in the spotlight for reasons of implementation.

In general, a liquid crystal display device is a device for displaying information on a screen by using refractive index anisotropy of a liquid crystal. As shown in FIG. 1, a lower substrate 5, an upper substrate 3, and a lower substrate 5 and an upper portion are shown. It consists of the liquid crystal layer 7 formed between the board | substrates 3. As shown in FIG. The lower substrate 5 is a drive element array substrate. Although not shown in the drawing, a plurality of pixels are formed on the lower substrate 5, and a driving element such as a thin film transistor (hereinafter referred to as TFT) is formed in each pixel. The upper substrate 3 is a color filter substrate, and a color filter layer for real color is formed. In addition, a pixel electrode and a common electrode are formed on the lower substrate 5 and the upper substrate 3, respectively, and an alignment film for aligning liquid crystal molecules of the liquid crystal layer 7 is coated.

The lower substrate 5 and the upper substrate 3 are bonded by a sealant 9, and a liquid crystal layer 7 is formed therebetween to form a liquid crystal by a driving element formed on the lower substrate 5. The information is displayed by driving the molecules to control the amount of light passing through the liquid crystal layer. In addition, a spacer 11 is disposed between the lower substrate 5 and the upper substrate 3 to maintain a constant cell gap of the liquid crystal cell.

The spacers are formed to maintain cell gaps between the upper substrate and the lower substrate of the liquid crystal display, and may be classified into ball spacers and column spacers (or pattern spacers) according to their formation.

The ball spacer is formed by a scattering method on the upper substrate or the lower substrate in a fine ball shape, and the column spacer is a spacer for forming a photosensitive organic film using an exposure process.

The ball spacer forming method may be divided into a wet dispersion method in which a spacer is mixed with an alcohol and sprayed, and a dry dispersion method in which only a spacer is dispersed. In addition, the dry dispersion method includes the electrostatic dispersion method using static electricity and the electrostatic dispersion method using injection pressure of the body. The electrostatic dispersion method is mainly used for the liquid crystal display device which is vulnerable to static electricity.

The method of forming the ball spacer by the dispersion method has an advantage in that the spacer can be easily formed, but it is relatively difficult to form the spacer at a desired predetermined position because of the dispersion, and it is also difficult to uniform the dispersion density. Therefore, when the spacers are formed by the scattering method, the spacers are disposed in the openings of the unit pixels to reduce the aperture ratio, or the spacers to be scattered are entangled with each other, resulting in a defective screen.

On the other hand, in the method of forming the column spacer by the photo process, since the spacer is formed by the photo process using a mask having a predetermined position for forming the spacer, the formation position of the spacer can be freely adjusted, and the density and shape of the spacer are formed. There is an advantage that can be adjusted freely. However, since the photo process is carried out, the use of the photoresist film discarded to form the spacer is excessive, causing cost increase and environmental pollution, and an expensive mask must be used for the photo process. It is quite economical to proceed with the process.

Accordingly, the present invention is to solve the problems as described above, and propose a spacer forming method that can be arranged in a fixed position while forming a spacer at a low cost. In addition, especially after the upper and lower substrates are bonded together in the module process of the liquid crystal display device, the secondary curing of the spacer is performed to improve adhesion between the spacer particles and the two substrates, thereby preventing the spacer from escaping from the top. The purpose is to provide a method of manufacturing.

In order to achieve the above object, a method of manufacturing a liquid crystal display device according to the present invention comprises the steps of preparing a lower substrate; Preparing an upper substrate; Disposing a spacer on the lower substrate or the upper substrate; Performing a first curing process on the spacer disposed on the substrate; Bonding the lower substrate and the upper substrate; And performing a second curing process on the spacers to fix the spacers to both sides of the upper and lower substrates.

That is, in the manufacture of the liquid crystal display device, the cell gap retention spacer particles are placed on the upper substrate or the lower substrate, and the curing process is performed twice before and after the two substrates are bonded to each other. The present invention provides a method for manufacturing a liquid crystal display device which improves fixing ability and thereby improves defects caused by movement of spacers.

In addition, in the arrangement of the vertices of the spacers, the spacers can be dropped in place, and the inkjet injection method is simple.

Hereinafter, a method of manufacturing a liquid crystal display device according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The manufacturing process of the liquid crystal display device may be classified into a driving device array process of forming a driving device on a lower substrate, a color filter process of forming a color filter on an upper substrate, and a cell process. The process of will be described with reference to FIG.

First, a plurality of gate lines and data lines are formed on the lower substrate by a driving element array process to define a unit pixel region, and the gate lines and the data lines are respectively formed in the pixel regions. A thin film transistor (TFT) which is a driving device to be connected is formed (S101). In addition, the pixel electrode is connected to the thin film transistor through the driving element array process to drive a liquid crystal layer as a signal is applied through the thin film transistor.

In addition, a color filter layer of R, G, and B and a common electrode are formed on the upper substrate by color filter process (S102).

On the other hand, the driving element array process and the color filter process for forming a color filter on the upper substrate are carried out collectively on a large area glass substrate in which a plurality of panel regions are formed, and the upper substrate and the lower substrate It can be formed in a continuous process or in a separate process.

Subsequently, a protective film for protecting an electrode pattern and an alignment film for liquid crystal alignment are sequentially stacked on the upper substrate and the lower substrate, respectively (S103). In addition, after applying the alignment layer, the alignment layer is rubbed to provide alignment control force or surface fixation force (ie, pretilt angel and alignment direction) to the liquid crystal molecules of the liquid crystal layer formed between the upper substrate and the lower substrate. (Rubbing) (S103).

Subsequently, in order to maintain a constant cell gap on the lower substrate, a spherical spacer is coated (S104), and first curing is performed (S105). The spherical spacer is prepared in the form of a spacer particle dispersion, and is vertex-positioned on the light shielding region of the liquid crystal display element by an inkjet printing method. This method is distinguished from the scattering method of randomly and uniformly dispersing spacer particles on a substrate on which a pixel electrode is formed, and has an advantage in that spacers can be applied in an arbitrary pattern on an arbitrary position on the substrate. In other words, spacer particles can be selectively disposed only in portions other than the pixel region serving as the opening, that is, the light shielding region. In addition, the inkjet printing method is very effective because the spacer can be arranged in any pattern at any position without directly contacting the substrate.

3 is a view showing a method of forming a spacer at a predetermined position on a substrate by an inkjet printing method according to the present invention. As shown in the drawing, the head 330 of the inkjet printing apparatus is formed on the substrate 305. They are spaced apart with regular intervals between them.

The inkjet head 330 has a bar shape, and a plurality of jetting nozzles are arranged at a predetermined interval on a rear surface of the inkjet head 330 opposite to the substrate 305. At this time, the supply amount and the dropping position of the spacer 311 applied to the substrate 330 is adjusted by opening and closing the nozzle. In addition, the inkjet printing process time may be adjusted by adjusting the number of the inkjet head 330 and the nozzles.

Inkjet printing is performed while the stage (not shown) on which the substrate 305 is disposed or the inkjet head 330 moves, and the pixel region 350 on the substrate 305 along the scanning direction ↗ of the inkjet head 305 is moved. The spacer 311 ′ is selectively printed on the light shielding area 351 except for the above.

On the surface of the spacer particles coated in this way, a sticking material that is cured by light or heat is formed, and the spacer having undergone the primary curing process is fixed on the substrate. In this case, a heat source such as a UV / VIS light source or a thermal head such as a laser beam, a xenon lamp, a halogen lamp, or the like may be used as an energy source for the primary curing process, depending on the type of adhesive material of the spacer.

In addition, a sealant for bonding the substrate is applied to the edge region of the upper substrate on which the color filter is formed (S105), and the sealant usually has a predetermined width at a predetermined position on the resin layer cured by heat or light (UV). It is formed by coating by dispensing or screen printing.

Subsequently, the sealant is cured and pressure-bonded to the upper substrate and the lower substrate (S106), and then secondary curing of the spacer is performed to increase adhesion of the spacer (S107). This is to fix the spacer, which is first cured and fixed on the lower substrate, to the upper substrate. By applying light or heat on the upper substrate, a secondary curing process is performed on the adhesive material of the spacer in contact with the upper substrate. The spacer is more securely fixed between the alignment layers of the upper and lower substrates. This is to further improve the apex fixation of the spacers than to cure only one substrate constituting the conventional liquid crystal panel, and to perform the secondary curing of the spacers before the module process step.

Substantially, in the conventional manufacturing process of the liquid crystal display device, even if the spacer is positioned at a desired position using an inkjet printing method, due to excessive pressure in the process of pressing and attaching the polarizing plate to the upper and lower portions of the liquid crystal panel during the module process. A problem arises in that the spacer moves away from the initial injection position along the pressing direction of the polarizer to the opening region of the pixel.

4A and 4C illustrate such a problem, and show a substrate coated with a spacer by conventional inkjet printing. First, FIG. 4A shows a substrate immediately after spacer printing, FIG. 4B shows a substrate after liquid crystal injection, and FIG. 4C shows a state of the substrate after the polarizer is attached. As shown in the figure, the spacers do not deviate from the vertices disposed on the substrate from the printing step to the step of injecting and encapsulating the liquid crystal into the cell gap of the liquid crystal panel so that the same number of spacers are formed at the same position immediately after printing and after the liquid crystal injection. Found. However, it was confirmed that the spacers deviated from the vertices according to the direction of the pressure applied in the process of the module, and mostly moved to other positions, that is, the opening regions of the liquid crystal display.

Since the spacer particles are generally made of synthetic resin, glass, or the like, when the spacer is disposed on the pixel electrode, a polarization is disturbed to cause a so-called small piece phenomenon in which the polarization is lost. Disruption of light may occur, resulting in a decrease in contrast ratio or color tone, resulting in deterioration of display quality.

In addition, when the adhesion between the spacer and the substrate is not sufficient, when the impact from the outside is applied on the liquid crystal panel, the spacer may break out of the peak and damage the alignment layer, or may damage the thin film transistor element. When a pressure is applied to the display area of R, a ripple phenomenon may occur in which the display area becomes dark due to the movement of the spacer.

Therefore, in order to solve this problem, the present invention performs aging for secondary curing of the spacer fixing component after the upper and lower plates are bonded, thereby preventing the spacer from moving, thereby preventing defects due to non-fixing of the spacer. It is.

On the other hand, the lower substrate and the upper substrate is composed of a large area transparent substrate. In other words, a plurality of panel regions are formed on a large transparent substrate, and a thin film transistor and a color filter layer, which are driving elements, are formed in each of the panel regions, so that the glass substrate is cut in order to manufacture a single liquid crystal panel. , Must be processed (S108). Thereafter, liquid crystal is injected into the individual liquid crystal panel processed as described above through the liquid crystal inlet, and the liquid crystal inlet is encapsulated to form a liquid crystal layer (S109), and then a polarizing plate is attached to the upper and lower portions of each liquid crystal panel (S110). By the inspection (S111), a liquid crystal display element is produced.

As described above, in the method of manufacturing the liquid crystal display device according to the embodiment of the present invention, after bonding the upper and lower substrates constituting the liquid crystal panel, the second component of the spacer is hardened, thereby fixing the fixing components of the spacer particles. Provided is a method for manufacturing a liquid crystal display device which can be adhered to a substrate to prevent deviation of the vertices of the spacer.

On the other hand, in recent years, a process method that enables the sealing of the upper and lower substrates to seal and liquid crystal injection end seal in one chamber has been attracting attention, and such a process is usually light (UV) curing. The liquid crystals are dropped in proportion to the area of the substrate before the substrate is bonded, and then vacuum (bubble in the liquid crystal) is bonded. At this time, when the substrate is pressed by a cell gap to bond, light UV is emitted to cure the seal material to encapsulate the liquid crystal. That is, the liquid crystals are first dropped before the bonding of the substrate, the pressure is applied in the state where the upper and lower substrates are aligned, and the liquid crystals 107 dropped by the application of the pressure at the same time as the bonding and the pressure are uniformly spread throughout the entire panel. Hardening of the sealant by exposure to heat or by thermal firing. This method is a process that has been widely considered as a candidate for the next generation line because it can reduce the number of equipment and significantly shorten the process time, the idea of the present invention can be applied to such a process, Secondary curing of the spacer can be carried out on the cured substrate.

In the spacer secondary curing process of the present embodiment, a heat source such as a UV / VIS light source or a thermal head such as a laser beam, a xenon lamp or a halogen lamp may be used as an energy source for curing.

Meanwhile, in the above specification, the spacer is applied to the lower substrate, for example, the sealant is applied to the upper substrate, but the spacer or the sealant may be applied to at least one of the upper substrate or the lower substrate.

As a result, the gist of the present invention is to improve the adhesion state of the spacer more than to cure only one substrate of the liquid crystal panel by performing the first curing after printing the spacer and the second curing after bonding the upper and lower plates. do.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

As described above, the manufacturing method of the liquid crystal display device according to the present invention, by spraying the spacer by the inkjet method, the process number is reduced compared to the conventional photolithography method, and after the upper and lower substrates are bonded, the spacer is second hardened By fixing between substrates, the vertex arrangement degree of a spacer improves. In addition, the alignment film damage, the light leakage, the contrast ratio and the lowering of the color tone caused by the spacer leaving the opening area can be improved, so that display quality can be improved and manufacturing cost can be expected.

Claims (12)

Preparing a lower substrate; Preparing an upper substrate; Disposing a spacer on the lower substrate or the upper substrate; Performing a first curing process on the spacer disposed on the substrate; Bonding the lower substrate and the upper substrate; And performing a second curing step on the spacers to fix the spacers to both sides of the upper and lower substrates. The method of claim 1, wherein the spacer is disposed by an inkjet printing method. The method of claim 1, wherein the spacer is formed of a fixing material whose surface is cured by light or heat. The method of claim 1, wherein the energy source used in the primary and secondary curing processes is a UV / VIS light source selected from the group consisting of a laser beam, a xenon lamp, and a halogen lamp. The method of claim 1, wherein the energy source used in the primary and secondary curing processes is a heat source selected from the group consisting of a thermal head. The method of claim 1, further comprising forming a common electrode on the lower substrate. The method of claim 1, further comprising forming a pixel electrode on the upper substrate. The method of claim 1, further comprising forming a thin film transistor on the lower substrate. The method of claim 1, further comprising forming a color filter on the upper substrate. The method of claim 1, further comprising forming a sealant on the upper substrate. The method of claim 1, further comprising forming a protective film on the upper and lower substrates. The method of claim 1, further comprising forming an alignment layer on the upper and lower substrates.

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