Baking device for liquid crystal alignment films

The present disclosure provides a baking device for liquid crystal alignment films, wherein the baking device includes a heating table with openings and lift pins extending and penetrating through the openings, and the lift pins can move between a retracting position and a stretching position to support a glass substrate coated with alignment films, wherein a blocking member is arranged on the lift pin in a surrounding manner to be tightly engaged thereon, so as to block the air stream flowing toward the glass substrate through the openings when the lift pins are situated in the retracting position. With the provision of the blocking members, the air streams flowing toward the glass substrate coated with alignment films can be resisted in the baking process, which prevents the air streams from affecting heat distribution and temperature distribution.

FIELD OF THE INVENTION

The present disclosure relates to the process for manufacturing liquid crystal display panels, and particularly relates to a baking device for liquid crystal alignment films.

BACKGROUND OF THE INVENTION

With its rapid development, the LCD technology has been widely used in all aspects of daily life. There have been considerable markets for LCD panels in information household appliances, such as liquid crystal screens, portable audio-video products of consumption type, mobile phones, liquid crystal televisions and the like, not to mention its traditional application to notebook computers (NB). Although the picture quality of LCD screens is closer to that of the completely developed cathode-ray tube (CRT) screens, there are still some problems of visual angle, contrast, display uniformity and the like in LCD screens, which need to be improved. Furthermore, in regard to the applications concerning high-density, highly refined and large-sized products, such as liquid crystal televisions, there are also problems desired to be solved with response speed and color reproducibility in LCD screens. The techniques concerning the control of liquid crystal alignment and the alignment films are closely related to the above-mentioned problems in liquid crystal panels. Therefore, manufacturing and controlling the alignment films are quite important.

FIG. 1shows a schematic diagram of a cross section of a liquid crystal display10in the prior art, wherein alignment films7are located between a liquid crystal6and transparent electrodes3and4. The importance of the alignment films7is due to the working principle of the liquid crystal display10. The liquid crystal6can be applied to a screen, as the dielectric constants of the liquid crystal6in the direction parallel with the molecules and those in the direction perpendicular to the molecules are different, whereby the liquid crystal can be driven through an electric field. On the other hand, the liquid crystal also has a refractive index varied according to the orientations of the molecules, i.e. exhibits a birefringence effect, which will change the polarizing direction of polarized light. A strong anchoring strength exists on the interfaces between the liquid crystal6and the alignment films7, and the liquid crystal6is restored to its original arrangement by means of elasticity, i.e. restoring force, after the electric field is turned off. Therefore, as is clearly evident, the liquid crystal6cannot function in the absence of the alignment films7.

The LCD panel manufacturing technology is becoming increasingly mature. With reference toFIG. 1, at present, an active TFT array substrate1with patterns and a color filter (CF) substrate2are generally first manufactured. An alignment film7is then coated on the inner surface of each of the active TFT array substrate1and the color filter substrate2. After heating and baking of the alignment films7, the TFT array substrate1and the color filter substrate2are adhered together with a sealant5, and liquid crystal6is filled into the space encompassed by the sealant5, the TFT array substrate1and the color filter substrate2. The alignment films7are used for the alignment of the liquid crystal6, thus if the alignment films7are not heated uniformly during the baking, the alignment of the liquid crystal6would be disrupted, which ultimately leads to a Mura phenomenon on display panels.

FIG. 2schematically shows a glass substrate11located in a baking device.FIG. 3shows a front view of a baking device20for liquid crystal alignment films in the prior art. With reference toFIG. 2andFIG. 3, a commonly-used prebake oven20performs heating with a heating table15provided with openings. Positions17on the treated glass substrate11, to which the openings of the heating table15correspond respectively, are indicated by circles inFIG. 2. Lift pins13pass through the openings, and the lift pins13can move between a stretching position and a retracting position to support the treated glass substrate11, which is coated with the alignment films. The glass substrate11is fetched and fed by a manipulator and is then processed with the ascending and descending of the lift pins13.

The lift pins13are situated in their retracting positions inFIG. 3. When the lift pins13are located at the retracting positions and the glass substrate11is being processed, due to the openings on the heating table15, air streams14can reach the bottom side surface of the glass substrate11, i.e. the side surface of the glass substrate11facing the heating table15, through the openings, which will cause temperature difference between the openings17and areas without such openings on the glass substrate11. Inevitably, most of the openings through which the lift pins13can pass may correspond to display areas12on the glass substrate11, which causes non-uniform heating of the alignment films and thus the Mura phenomenon on the whole display panel.

SUMMARY OF THE INVENTION

As mentioned above, there are certain defects in the prior art. For example, a baking device for alignment films is provided with openings through which lift pins pass, while air streams flow to the treated glass substrate through the openings during the baking of the alignment films, so that the alignment films are not heated uniformly, and temperature difference occurs between the positions corresponding to the openings and the other positions on the glass plate. This causes non-uniform properties of the alignment films, and thus color non-uniformity of a finished display panel. Aiming at these defects, the present disclosure provides a baking device for liquid crystal alignment films.

The present disclosure provides a baking device for liquid crystal alignment films. In a first embodiment, the baking device includes a heating table with openings and lift pins, each of which extends through a corresponding opening and thus can move between a retracting position and a stretching position to support a glass substrate coated with alignment films, wherein a blocking member is arranged on each lift pin in a surrounding manner to be tightly engaged thereon, so as to block the air stream flowing toward the glass substrate through the corresponding opening when said lift pin is situated in the retracting position. With the provision of the blocking members, the air streams flowing toward the glass substrate coated with alignment films can be resisted in the baking process, which prevents the air streams from affecting heat distribution and temperature distribution. Therefore, a balanced temperature can be maintained over the whole glass substrate in the baking process, which prevents the alignment films from being heated non-uniformly, i.e. solves the problem of color non-uniformity, which is to say that the finally obtained display panel possesses a uniform optical property and thus desired displayed pictures.

In a second embodiment improved based on the first embodiment, the blocking member is in contact with the surface of the heating table facing the glass substrate to block the corresponding opening when said lift pin is situated in the retracting position. At this moment, the blocking members can stop the air streams in order to avoid influence on temperature and heat distribution, and can also function as a limit simultaneously. The distance between the bottom surface of the blocking member and the top end of the respective lift pin equals exactly to the distance between the bottom surface of the glass substrate and the surface of the heating table in the baking process.

In a third embodiment improved based on the first or second embodiment, the blocking member includes a circular plate body. The circular plate bodies help to save materials, are easiest to manufacture, and can effectively function to achieve the objectives of the present disclosure, namely blocking the openings of the heating table and resisting the air streams flowing toward the treated glass substrate.

In a forth embodiment improved based on the first embodiment, the blocking member includes a truncated cone, the area of the surface of which facing the heating table is smaller than that of the surface of the same facing the glass substrate, and the area of the surface of the truncated cone facing the heating table is smaller than that of the cross section of the opening. At this moment, a portion of the truncated cone in contact with the heating table to block the opening lies on its lateral circumferential surface. In this embodiment, the blocking member shaped into a truncated cone is divided into two parts, with one above the surface of the heating table and the other inside the opening, which performs a double resisting of the air streams. This solution has relatively low requirement for process errors and better blocking effect.

In a fifth embodiment improved based on the forth embodiment, a guide angle is formed at the end of the opening facing the glass substrate, and the degree of the guide angle relative to the horizontal surface is equal to the degree of the slant angle of the side surface of the truncated cone relative to the horizontal surface. Thus, the side surfaces of the truncated cones can be jointed with the heating table in larger areas, which benefits the blocking of the openings, the locating of the truncated cones and the limiting of the lift pins.

In a sixth embodiment improved based on one of the first to fifth embodiments, the blocking member and the respective lift pin are connected with a threaded connection. Threaded connection structures are easy to manufacture and cost saving. Meanwhile, free assembly, expedient maintaining and batch production can be easily achieved.

In a seventh embodiment improved based on one of the first to fifth embodiments, the lift pin and the respective blocking member are formed as an integral through injection molding. Due to an integrated injection molding, the procedures are simplified, and the blocking members can be firmly fixed to the lift pins respectively without position deviations, regardless of the running-in problem during the mechanical process.

In an eighth embodiment improved based on one of the first to seventh embodiments, the blocking member is made of the same material as the heating table. Therefore, consistent thermal properties are ensured between the blocking members and the heating table, and thus temperature uniformity can be achieved between the positions corresponding to the openings and the other positions over the whole glass substrate.

In a ninth embodiment improved based on one of the first to eighth embodiments, the blocking member is made of a metal material. A metal material has good thermal conductivity, as a result of which heat energy can be transferred through it at a relatively high speed, and this further ensures temperature uniformity and effectively prevents color non-uniformity on the display panel. Moreover, due to the higher hardness of a metal material, the blocking members can also function as a stop limit. On account of good thermal property and physical property of the metal material, the blocking members can be appropriate for both the thermal design and the mechanical design of the baking device.

In a tenth embodiment improved based on the third embodiment, the radius of the circular plate body ranges from 1.2 to 1.5 times that of the respective opening. In this solution, the opening is advantageously blocked with the required blocking tightness and reduced raw materials or manufacturing procedures.

The above-mentioned technical features may be combined together in various appropriate manners or substituted by equivalent technical features, as long as the objectives of the present disclosure can be fulfilled.

In the drawings, similar components are marked with similar reference signs. The accompanying drawings are not drawn to actual scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present disclosure will be introduced in detail below with reference to the accompanying drawings.

FIG. 4andFIG. 5show front views of a baking device30for liquid crystal alignment films according to the present disclosure. With reference toFIG. 4, the baking device30for liquid crystal alignment films according to the present disclosure includes a heating table35with openings37and lift pins33extending through the openings37, wherein the lift pins33can move between a retracting position (seeFIG. 4) and a stretching position (seeFIG. 5) to support a glass substrate31coated with the alignment films. A blocking member36is arranged on the lift pin33in a surrounding manner to be tightly engaged thereon, so as to resist the air stream34flowing toward the glass substrate31through the openings37when the lift pins33are situated in the retracting position.

With reference toFIG. 4, when the lift pins33are situated in the retracting position, the heating table35performs a baking process on the glass substrate31, and at this moment, the blocking member36is in contact with the surface of the heating table35facing the glass substrate31, in order to block the respective opening37. The blocking members36can also function as a stop limit. The distance between the bottom surface of the blocking member36and the top end of the respective lift pin33equals exactly to the distance between the bottom surface of the glass substrate31and the surface of the heating table35in the baking process. Meanwhile, with the blocking members36blocking the openings37, the air streams34from the lower portion can be obstructed before reaching the glass substrate31. Thus, the temperatures in the areas of the glass substrate31corresponding to the openings37of the heating table35are free from the disrupting influence of air streams34, and thus are kept consistent with those in other areas. Therefore, non-uniform processing, which leads to non-uniform properties of the glass substrate31, can be avoided, which helps to overcome the Mura phenomenon on the finally obtained display panels.

Preferably, the blocking members36are made of the same material as the heating table35. Therefore, consistent thermal properties are ensured between the blocking members36and the heating table35, and thus temperature uniformity can be achieved between the positions corresponding to the openings37and the other positions over the whole glass substrate.

The blocking members36are preferably made of a metal material. A metal material has good thermal conductivity, as a result of which heat energy can be transferred through it at a relatively high speed, and this further ensures temperature uniformity and effectively prevents color non-uniformity on the display panel. Moreover, due to the higher hardness of a metal material, the blocking members36can also function as a stop limit. On account of good thermal property and physical property of the metal material, the blocking members36can be appropriate for both the thermal design and the mechanical design of the baking device30.

With reference toFIG. 4andFIG. 5, the blocking member36can include a circular plate body. The circular plate body is perpendicular to the respective lift pin33, for example. The radius of the circular plate body can range from 1.2 to 1.5 times that of the opening37on the heating table35. In this case, the opening37can be better blocked.

In a further embodiment, the blocking member36includes a truncated cone, the longitudinal axis of which is parallel to the corresponding lift pin33, wherein the area of the surface of the truncated cone facing the heating table35is smaller than that of the surface of the truncated cone facing the glass substrate31. For example, the radius of the cross section of the truncated cone can be gradually reduced from top to bottom, and the area of the surface of the truncated cone facing the heating table35is smaller than that of the cross section of the respective opening37. Thus, when the lift pins33are situated in the retracting position, the side wall of the blocking member36, i.e. the truncated cone, abuts against the edge of the respective opening on the surface of the heating table35. In this embodiment, the blocking member36is divided into two parts, with one above the heating table35and the other inside the respective opening37, to realize a double resisting of the air stream34. This solution has relatively low requirement for process errors and better blocking effect.

Further, a guide angle is formed at the end of the opening37facing the glass substrate31, and the degree of the guide angle relative to the horizontal surface equals to the degree of the slant angle of the side surface of the truncated cone relative to the horizontal surface. Thus, the side surfaces of the truncated cones can be jointed with the heating table35in larger areas, which benefits the blocking of the openings37, the locating of the truncated cones and the limiting of the lift pins33.

The blocking member36and the respective lift pin33can be connected with a threaded connection. A threaded connection structure is easy in manufacture and low in cost. Meanwhile, free assembly, expedient maintaining and batch production can be easily achieved.

However, other connecting means may also be adopted between the blocking members36and the lift pins33. For example, the lift pin33can be provided with an annular groove on its outer surface, and the inner surface of the blocking member36can be embedded into the groove to form a tongue and groove connection.

The lift pin33and the respective blocking member36can also be formed as an integral through injection molding. In this way, procedures are reduced, and the blocking members36can be firmly fixed to the lift pins33without position deviations, regardless of the running-in problem during the mechanical process.

Although the present disclosure has been described with reference to the preferred examples, various modifications could be made to the present disclosure without departing from the scope of the present disclosure and components in the present disclosure could be substituted by equivalents. The present disclosure is not limited to the specific examples disclosed in the description, but includes all technical solutions falling into the scope of the claims.