WO2014134887A1

WO2014134887A1 - Alignment film preparation method and system

Info

Publication number: WO2014134887A1
Application number: PCT/CN2013/077435
Authority: WO
Inventors: 惠大胜; 尹傛俊; 涂志中; 申莹; 郭磊
Original assignee: 合肥京东方光电科技有限公司; 京东方科技集团股份有限公司
Priority date: 2013-03-05
Filing date: 2013-06-19
Publication date: 2014-09-12
Also published as: CN103149739B; CN103149739A

Abstract

An alignment film preparation method and system, the alignment film preparation method comprising the steps of: coating the alignment film solution on a substrate; curing the coated alignment film solution; the alignment film solution is heated in the coating process thereof.

Description

Oriented film preparation method and system

Embodiments of the present invention relate to a method and system for preparing an oriented film. Background technique

In the manufacturing process of the liquid crystal display panel, it is necessary to form a uniform alignment film on the array substrate and the color filter substrate in order to arrange the liquid crystal molecules in a certain direction, thereby obtaining a liquid crystal with uniform brightness, high contrast and rapid response. Display panel. For example, the liquid crystal display panel as shown in FIG. 1 includes an array substrate 2 and a color filter substrate 3 disposed opposite to each other, and the liquid crystal cell formed by the array substrate 2 and the color filter substrate 3 is filled with liquid crystal, in order to make liquid crystal molecules of the display region The alignment film solution is applied to the array substrate 2 and the color filter substrate 3 to form an alignment film 1 , and the array substrate 2 and the color filter substrate 3 are connected and fixed by a sealant 6 .

The alignment film solution is composed of a solid (mainly polyimide, the content is generally 3% to 7%) and a solvent, and after the coating of the alignment film solution is completed (coating time is about 30 s), first at 100 ° C - 150 Pre-cure for about 1 min in a °C environment, and then main curing at 200 ° C - 250 ° C for about 20 min to remove the solvent to form an oriented film.

At present, there are mainly two ways to apply a more ortified coating film solution in the liquid crystal display panel manufacturing industry. One is to use an oriented film printing plate for transfer, and the printing plate transfer is usually to fix the printing plate. On a round roll, the alignment film solution is dropped into the groove on the printing plate, and the alignment film solution in the groove is transferred onto the substrate by the continuous rotation of the round roll, and during the transfer process, Use another round roller or squeegee to make the alignment film solution transfer uniformly; the other is inkjet printing. The inkjet printing method does not need to make a printing plate, and directly inputs the graphic into the computer through a set of nozzles. The alignment film solution is uniformly sprayed onto the substrate, which makes the equipment construction tube single, which greatly saves cost. Compared with the transfer method, the ink jet printing method has the advantages of not requiring the use of an alignment film printing plate, and the device has a small footprint, but the Halo (halo) region formed by the ink jet printing method is generally relatively wide. The mechanism by which the printing plate transfer method forms the Halo region is as shown in FIG. 2. From S11 to S14, the change of the alignment film solution coated on the surface of the substrate is shown as the time zone is extended, wherein the 1A region is the Halo region; The mechanism of forming the Halo zone by the printing method is shown in Figure 3. From S12 to S24, it is shown that the alignment film solution coated on the surface of the substrate changes over time, wherein the 1B region is the Halo region.

The main reason for the formation of the Halo region is: There is a surface tension between the liquid phase interface of the alignment film solution and the external gas phase interface. Under the action of the surface tension, the edge of the alignment film solution forms a curved surface, which causes the edge region to dry and solidify. The speed will be faster than the middle area; the drying and solidification speed of the edge area is fast, and the alignment film solution in the middle area continuously flows into the edge area, and the drying and solidification are continued, resulting in an uneven thickness region in the edge region of the alignment film, that is, Halo Area.

Since the viscosity of the liquid is inversely proportional to the surface tension, the smaller the viscosity of the liquid, the larger the surface tension, and the greater the difference in the drying and solidification speed of the alignment film solution between the edge region and the intermediate portion, and thus the larger the Halo region; and vice versa. In the ink jet printing method, due to the limitation of the head, only the alignment film solution having a relatively low viscosity (the solid content is generally less than 4%) can be used, and thus the Halo region formed is generally wide. In the prior art, the Halo zone formed by the transfer method is about 0.3 mm at the current general process level, and the Halo zone formed by the inkjet printing method is about 2 mm.

If the Halo region is present in the display region of the liquid crystal display panel, the liquid crystal molecules in the Halo region cannot be properly oriented, which may affect the image quality of the liquid crystal panel. Therefore, it is necessary to ensure that the Halo area does not enter the effective display area, that is, the distance from the edge of the alignment film to the effective display area is usually larger than the width of the Halo area. Moreover, at present, both large-size LCD TVs and small-sized mobile handheld devices have their own size levels, maximizing the display area and reducing the need for non-display areas, commonly known as narrow bezel products. In order to reduce the non-display area of the liquid crystal display, one of the important efforts is to reduce the distance from the edge of the alignment film to the effective display area, that is, to reduce the width of the Halo region. Summary of the invention

Embodiments of the present invention provide a method and system for preparing an alignment film capable of reducing the width of a Halo region of an alignment film, thereby reducing a non-display area of the liquid crystal display panel, and providing technical support for production of a narrow bezel product.

The technical solution of the embodiment of the present invention is as follows:

A method for preparing an oriented film, comprising the steps of: coating an alignment film solution on a substrate; and curing the alignment film solution after the coating is completed;

The alignment film solution is heated during the application of the alignment film solution. In one embodiment, the alignment film solution is coated on the substrate by inkjet printing.

In one embodiment, the alignment film solution includes a mixed solvent, the temperature of heating the alignment film solution is higher than the boiling point of the solvent having the lowest boiling point in the mixed solvent, and is not higher than the highest boiling point of the mixed solvent. The boiling point of the solvent.

In one embodiment, the mixed solvent comprises N-methylpyrrolidone, γ-butyrolactone, butyl cellosolve, and dipropylene glycol methyl ether; the temperature of heating the alignment film solution is higher than the boiling point of butyl cellosolve, JM氐The boiling point of dipropylene glycol methyl ether.

In one embodiment, the temperature of the alignment film solution is heated from 175 °C to 185 °C. In one embodiment, the alignment film solution is heated by heating the substrate during the application of the alignment film solution.

In one embodiment, the alignment film solution is heated by heating the cavity of the alignment film preparation system during the application of the alignment film solution.

In one embodiment, the alignment film solution is heated under a vacuum negative pressure environment.

In one embodiment, the alignment film solution is heated by infrared heating, electric resistance heating or microwave heating.

The embodiment of the invention also provides an oriented film preparation system for implementing the above method:

An oriented film preparation system comprising: an inkjet printing mechanism and a heating mechanism; the inkjet printing mechanism for coating an alignment film solution on a substrate; the heating mechanism for coating an inkjet printing mechanism on a substrate The alignment film solution is heated during the alignment of the film solution.

In one embodiment, the alignment film preparation system further includes a vacuuming mechanism and a cavity for accommodating the substrate and the alignment film solution, the vacuuming mechanism for evacuating the cavity.

In the method for preparing an alignment film according to an embodiment of the present invention, since the alignment film solution is heated during the application of the alignment film solution, a part of the solvent in the alignment film solution is volatilized, and the viscosity of the alignment film solution is increased. The surface tension of the alignment film solution is reduced, so that the difference in the drying and curing speed of the alignment film solution between the edge region and the intermediate region is greatly reduced, and the formed alignment film is made as uniform as possible, thereby reducing the width of the Halo region. The alignment film preparation method of the present invention can reduce the non-display area of the liquid crystal display panel, and provides technical support for the design and production of the narrow frame product. DRAWINGS

1 is a schematic structural view of a liquid crystal display panel in the prior art; Figure 2 is a schematic view showing the mechanism of forming a Halo zone by a printing plate transfer method;

Figure 3 is a schematic view showing the mechanism of forming a Halo region by an ink jet printing method;

4 is a schematic structural view of an oriented film preparation system in the prior art;

Fig. 5 is a schematic structural view of an alignment film preparation system according to an embodiment of the present invention.

In the figure: 1: alignment film; 2: array substrate; 3: color film substrate; 6: frame sealant; 7: inkjet printing mechanism; 8: force port thermal mechanism. detailed description

The specific embodiments of the invention are further described below in conjunction with the drawings and embodiments. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

Embodiment 1

Generally, the preparation process of the alignment film is as follows: First, an alignment film solution is applied on the surface of the substrate, and the coating time is about 30 s. After the coating is completed, pre-curing is performed for about 1 minute in an environment of 100 ° C - 150 ° C, and then Main curing is performed for about 20 minutes in an environment of 200 ° C to 250 ° C to remove the solvent in the alignment film solution to form an alignment film. The main improvement of the embodiment of the present invention is that in the process of coating the alignment film solution, the alignment film solution is heated to volatilize part of the solvent, thereby increasing the viscosity of the alignment film solution and reducing the surface of the alignment film solution. The tension causes the difference in the drying and curing speed of the alignment film solution in the edge region and the intermediate region to be greatly reduced, and the alignment film thus formed is more uniform, thereby reducing the width of the Halo region and reducing the width of the non-display region around the liquid crystal display panel. It is more conducive to the preparation of narrow frame products.

Wherein, the process of coating the alignment film solution on the substrate is generally a single layer coating, that is, coating once, or of course, multi-layer coating, depending on actual needs, while coating the entire alignment film solution In the process, it is necessary to continuously heat the alignment film solution, and the heating temperature is kept constant to ensure that the alignment film solution is uniformly heated, and the cured alignment film is of good quality.

In the present embodiment, the alignment film solution is coated on the substrate by inkjet printing as an example. The solvent in the alignment film solution in this embodiment mainly includes N-methylpyrrolidone (NMP) and γ-butyrolactone. (γ-BL), butyl cellosolve (BC) and dipropylene glycol methyl ether (DPM) have boiling points of 202 °C, 206 °C, 171 °C and 190 °C, respectively.

In order to accelerate the rate of solvent evaporation, the temperature of the heated alignment film solution is preferably higher than the boiling point of the solvent having the lowest boiling point in the mixed solvent, and at the same time, in order not to affect the subsequent curing effect, the heated alignment film is dissolved. The temperature of the liquid should not be higher than the boiling point of the solvent having the highest boiling point in the mixed solvent. In the present embodiment, the temperature of the heated alignment film solution is higher than the boiling point of butyl cellosolve (BC), that is, 171 ° C, which is lower than the boiling point of dipropylene glycol methyl ether (DPM), that is, 190 ° C. This is because N-methylpyrrolidone (NMP) can improve the linearity of printing and has the effect of further reducing the width of the Halo region, so the heating temperature is generally not higher than the boiling point of N-methylpyrrolidone (NMP). In actual operation, the temperature of the heated alignment film solution can be controlled at 175 ° C - 185 ° C, and can be temporarily controlled by a temperature control component such as a thermal switch. When the temperature is higher than 185 ° C, the heating is temporarily stopped, and the temperature is lower than 175. At °C, the heating efficiency is increased in such a manner that the temperature is kept constant within the range; the heating process is accompanied by the entire alignment film solution coating process to ensure the heating effect.

The above heating alignment film solution can be realized by heating the substrate or by heating the cavity of the alignment film preparation system. The cavity of the heated alignment film preparation system can make the heat distribution more uniform and the heating effect is better than that of the heating substrate, and the heating starts at the same time as the alignment film solution leaves the nozzle of the inkjet printing mechanism, however, The heat energy utilization rate is low, and the heat resistance requirement for the entire alignment film preparation system is also high. The heating film solution may be heated by infrared heating, electric resistance heating, microwave heating or any other effective heating method, and one of the heating methods may be used, or two or more heating methods may be simultaneously performed.

It is to be noted that the alignment film solution is heated to heat the substrate, for example, by resistance heating, and the heat energy utilization rate is high. The alignment film solution is heated in such a manner as to heat the cavity of the alignment film preparation system, for example, infrared heating and microwave heating, wherein the heater is placed, for example, inside the cavity of the alignment film preparation system to utilize the heat energy more efficiently.

In order to accelerate the evaporation of the solvent in the alignment film solution, for example, heating the alignment film solution under a vacuum negative pressure environment, the vacuum negative pressure environment can reduce the occurrence of defects such as bulging.

It should be noted that the above-mentioned alignment film preparation method can be applied not only to the ink jet printing method. When applied to the transfer mode, although the solid content of the alignment film solution is generally high, the above-described alignment film preparation method may not be as effective as reducing the width of the Halo region when applied to the ink jet printing method, However, the difference in the drying and curing speed of the alignment film solution in the edge region and the intermediate region can also be reduced, so that the accuracy of the Halo region width control can also be improved.

Embodiment 2

The invention also provides an oriented film preparation system for realizing the method described in the first embodiment, as shown in FIG. 5; compared with the prior art alignment film preparation system (as shown in FIG. 4), including inkjet printing The mechanism 7 is configured to coat the alignment film solution on the substrate, and further comprises coating the alignment film in the inkjet printing mechanism During the course of the solution, the heating mechanism 8 of the alignment film solution is heated throughout. The heating mechanism 8 may be a device for heating the substrate or a device for heating the entire cavity of the alignment film preparation system. The heating mechanism 8 may be an infrared heating device, a resistance heating device, a microwave heating device or any other effective heating device, and may be a single heating device, or a combination of two or more heating devices, and may be in direct contact. The substrate is heated by heating the alignment film solution, such as resistance heating, or by placing it inside or outside the cavity of the alignment film preparation system. The selection of the above heating device and the selection of the position are not limited as long as the effect of heating the alignment film solution can be achieved. For example, the heating method is a method capable of achieving uniform heating. When the substrate is heated, it is necessary to uniformly heat the entire substrate, and it is possible to heat the resistor. When the cavity is heated, it is necessary to uniformly heat the entire cavity, for example, infrared heating and/or microwave heating.

In order to accelerate the volatilization of the solvent in the alignment film solution, the alignment film preparation system further includes a vacuuming mechanism and a cavity (not shown) for accommodating the substrate and the alignment film solution, and the vacuuming mechanism may be the cavity A portion of the interior, such as one or more vacuum pumps disposed at the top of the chamber, may also be a vacuuming mechanism connected to the exterior through one or more channels of the chamber. The vacuuming mechanism is configured to evacuate the cavity, and vacuum is used to form a vacuum negative pressure environment in the cavity for accommodating the substrate and the alignment film solution, thereby accelerating solvent evaporation and increasing the viscosity of the alignment film solution. Thereby, the unevenness in the curing process of the alignment film solution is lowered. The Halo region 1C formed by the alignment film preparation system of the embodiment of the present invention has a significantly reduced width compared to the Halo region 1B formed by the alignment film preparation system of the prior art, and the non-display region around the formed liquid crystal display panel is reduced. More conducive to the formation of narrow frame products.

The above embodiments are merely illustrative of the present invention and are not to be construed as limiting the scope of the invention, and various modifications and changes can be made without departing from the spirit and scope of the invention. Equivalent technical solutions are also within the scope of protection of the present invention.

Claims

claims

1. A method for preparing an alignment film, including the steps of: coating an alignment film solution on a substrate and curing the alignment film solution after the coating is completed;

Wherein, during the process of applying the alignment film solution, the alignment film solution is heated.

2. The alignment film preparation method according to claim 1, wherein the alignment film solution is coated on the substrate by inkjet printing.

3. The alignment film preparation method according to claim 1 or 2, wherein the alignment film solution includes a mixed solvent, and the temperature of heating the alignment film solution is higher than the boiling point of the solvent with the lowest boiling point in the mixed solvent, And not higher than the boiling point of the solvent with the highest boiling point in the mixed solvent.

4. The alignment film preparation method according to claim 3, wherein the mixed solvent includes N-methylpyrrolidone, γ-butyrolactone, butyl cellosolve and dipropylene glycol methyl ether; the temperature at which the alignment film solution is heated Higher than the boiling point of butyl cellosolve and lower than the boiling point of dipropylene glycol methyl ether.

5. The alignment film preparation method according to claim 4, wherein the temperature range for heating the alignment film solution is 175°C-185°C.

6. The alignment film preparation method according to claim 3, wherein in the process of coating the alignment film solution, the alignment film solution is heated by heating the substrate.

7. The alignment film preparation method according to claim 3, wherein in the process of coating the alignment film solution, the alignment film solution is heated by heating the cavity of the alignment film preparation system.

8. The alignment film preparation method according to claim 6 or 7, wherein the method of heating the alignment film solution is infrared heating, resistance heating or microwave heating.

9. The alignment film preparation method according to claim 8, wherein the alignment film solution is heated in a vacuum negative pressure environment.

10. An alignment film preparation system, including: an inkjet printing mechanism and a heating mechanism; the inkjet printing mechanism is used to coat the alignment film solution on the substrate; the heating mechanism is used to apply the inkjet printing mechanism on the substrate During the process of applying the alignment film solution, the alignment film solution is heated.

11. The alignment film preparation system according to claim 10, wherein the alignment film preparation system further includes a vacuuming mechanism and a cavity for accommodating the substrate and the alignment film solution, the vacuuming mechanism is used for The cavity is evacuated.