JP2006017835A - Screen printing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To minimize an adverse effect of mesh marks of a screen mesh composed of metal wire rods on an alignment layer with an extremely simple method. <P>SOLUTION: In applying a peripheral sealing material 12 to a circumference of a panel substrate 10 for a liquid crystal display panel with a rubbing treated alignment layer 11 via the screen mesh 20 composed of the metal wire rods, the screen mesh 20 is calender treated. Representing an angle which the calender treating direction forms with a horizontal reference line H by Ca, and an angle of the rubbing direction R of the alignment layer 11 by Ru, Ca and Ru are fitted to each other in the identical direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a screen printing method in which a peripheral sealing material is applied around a panel substrate for a liquid crystal display panel having an alignment film using a screen mesh made of a metal wire, and more specifically, a screen mesh mesh for the alignment film. The present invention relates to a technique for minimizing the adverse effects of traces.

  Since the liquid crystal display panel is formed by bonding a pair of panel substrates via a peripheral sealing material, one of the manufacturing processes includes a step of applying the peripheral sealing material to the panel substrate. In this application process, in many cases, a screen printing method is employed from the viewpoint of productivity (for example, see Patent Document 1).

  Screen printing plates (screen meshes) are roughly classified into silk screen meshes, synthetic fiber meshes such as nylon and tetron, and stainless steel meshes. Of these, stainless steel meshes for precision printing are frequently used in the application process of peripheral sealing materials. .

  FIG. 9 shows a state in which the peripheral sealing material is applied to the panel substrate by the screen printing method, and FIG. 10 shows a plan view of the panel substrate to which the peripheral sealing material is applied. First, this will be described. A panel substrate 10 having an alignment film 11 that has been rubbed in the previous step is placed on the work table 1.

  A stainless mesh 20 stretched on the side frame F is disposed on the panel substrate 10. Note that the stainless mesh 20 has only an application portion of the peripheral sealing material 12 shown in FIG. 10 as an opening, and the other portion is covered with an emulsion (not shown).

  The peripheral sealing material liquid 12a such as epoxy resin is poured onto the stainless mesh 20 and moved while rubbing the squeegee S. As a result, the peripheral sealing material 12 is applied around the panel substrate 10 as shown in FIG. 10, but this has the following problems.

  That is, when the squeegee S is moved, tension is applied to the stainless steel mesh 20, and the stainless steel mesh 20 is in close contact with the surface of the alignment film 11, so that the mesh mark is transferred to the alignment film 11, which causes display defects. The generation of this mesh mark will be described with reference to FIGS.

  FIG. 11 is an enlarged view of a part of the stainless steel mesh 20 and shows the back side facing the panel substrate 10 side. In this example, the stainless steel mesh 20 is obtained by bias weaving (diagonal weaving) of warp yarns 21 and weft yarns 22 made of stainless wire. Here, the direction indicated by the white arrow of the warp yarn 21 is the bias direction B, and the horizontal reference line H An angle with respect to is a bias angle Bi.

  Also, since the warp yarn 21 and the weft yarn 22 are basically a plain weave and have a wave shape, a crest portion 21a from which the warp yarn 21 projects to the panel substrate 10 side and a crest portion 22a from which the weft yarn 22 projects to the panel substrate 10 side. Exist alternately.

  The stainless mesh 20 used in the peripheral sealing material application process is subjected to a calendar process for smoothing the crests 21a and 22a. This calendering process is performed using a rotating grindstone G as shown in FIG. 12. In this example, the rotating grindstone G is moved along the bias direction B of the warp 21 to smooth the crest portions 21a and 22a. Yes.

  FIG. 13 shows an enlarged view of the crest portions 21a and 22a in the chain line frame A1 of FIG. 6 after the calendar process. When the peak portions 21a and 22a are observed microscopically, both are finely scratched. Of the peak portions 21a and 22a, the peak portion 21a of the warp yarn 21 in the bias direction is the peak of the weft yarn 22. The cutting area is larger than that of the portion 22a.

  Referring to FIGS. 10 and 14, assuming that the angle of rubbing direction R indicated by the solid line arrow with respect to horizontal reference line H of alignment film 11 is Ru, conventionally, bias angle Bi of stainless steel mesh 20 and rubbing angle Ru of alignment film 11 are the same. The stainless mesh 20 is stretched and screen printing is performed without considering the relationship between the two.

  Therefore, for example, when the bias angle Bi and the rubbing angle Ru are substantially orthogonal to each other, as shown schematically in FIG. 14, particularly, the scratches attached to the crest portion 21a of the warp yarn 21 pass through the emulsion. This is transferred onto the alignment film 11 as a mesh mark intersecting with the rubbing direction R, and this causes the alignment film 11 to be partially disturbed. In a reflective color display liquid crystal display panel, there are streaks due to the mesh mark on the display. May occur.

  To prevent this, there are a method of using a non-deformable metal plate with an opening formed in a metal plate on a screen printing plate and a method of increasing the thickness of the emulsion. The cost is considerably higher than that. Further, the method of increasing the thickness of the emulsion is not a preferable method because the coating amount of the peripheral sealing material varies and the seal width may not be constant.

JP-A-7-137423

  Therefore, the object of the present invention is to minimize the adverse effect of the mesh marks on the screen mesh alignment film made of metal wire by a very simple method without introducing new equipment or drastically changing the existing coating conditions. There is to stop.

  In order to solve the above problems, the present invention is a screen printing method in which a peripheral sealing material is applied around a panel substrate for a liquid crystal display panel having an alignment film subjected to rubbing treatment via a screen mesh made of a metal wire. The screen mesh is calendered, the angle of the calendering direction with respect to a horizontal reference line is Ca, the angle of the rubbing direction of the alignment film is Ru, and the angle Ca of the calendering direction and the angle of the rubbing direction It is characterized by matching Ru with the same direction.

  In the present invention, when the angle Ca of the calendering direction and the angle Ru of the rubbing direction are matched in the same direction, the allowable range is relatively within 15 °. In addition, although the stainless mesh is typically mentioned as the screen mesh which consists of metal wires, the mesh of metal wires other than this may be used.

  According to the present invention, assuming that the screen mesh is calendered, the direction Ca of the calendering and the angle Ru of the rubbing direction are matched in the same direction, so that Since the rubbing direction is the same direction, even if the scratches are transferred to the alignment film, the alignment is hardly disturbed, and display defects due to mesh marks can be prevented.

  Next, an embodiment of the present invention will be described with reference to FIGS. 1 and 2, but the present invention is not limited to this. In the present invention, the screen printing apparatus and the screen printing plate can be used as they are in the above conventional example, and the configuration of the panel substrate to which the peripheral sealing material is applied may be the same as in the above conventional example.

  For this reason, FIG. 1A shows a panel substrate 10 which is the same substrate as FIG. 10 and FIG. 1B shows a partially enlarged view of a stainless mesh 20 as a screen printing plate similar to FIG. . Also in the present invention, the alignment film 11 subjected to the rubbing process is provided on the panel substrate 10, and the rubbing direction indicated by the solid line arrow is R, and the rubbing angle with respect to the horizontal reference line H is Ru.

  The stainless steel mesh 20 is formed by bias weaving warp yarns 21 and weft yarns 22 made of stainless steel wire. For example, a direction indicated by a white arrow of one warp yarn 21 is a bias direction B, and an angle with respect to the horizontal reference line H is a bias angle. Let it be Bi. The direction of the weft 22 may be the bias direction. That is, the bias direction may be referred to as a mesh direction. The stainless mesh 20 may be a plain weave.

  Further, as described above with reference to FIG. 12, the stainless mesh 20 has been subjected to calendar processing for smoothing the crest portion 21a of the warp yarn 21 and the crest portion 22a of the weft yarn 22, and FIG. The peak parts 21a and 22a in the chain line frame A2 of FIG. As can be seen from FIG. 2, in this example as well, the stainless steel mesh 20 is calendered along the bias direction B of the warp yarn 21. Here, since the calendar process is performed along the bias direction B, the direction of the calendar process is C, and the angle with respect to the horizontal reference line H is the calendar process angle Ca.

  The stainless steel mesh 20 is the same as the above-described conventional example in that only the portion where the peripheral sealing material 12 is applied to the panel substrate 10 is an opening, and other portions facing the alignment film 11 are covered with an emulsion.

  In applying the peripheral sealing material 12 to the panel substrate 10 using the stainless steel mesh 20, in the present invention, the calendering direction C of the stainless steel mesh 20 and the rubbing direction R of the alignment film 11 are matched to each other. That is, they are adjusted so as to be almost parallel.

  According to this, since the direction of the scratches shown in FIG. 2 by the calendar process and the rubbing direction R of the alignment film 11 shown in FIG. 1A substantially coincide with each other, the scratches mesh with the alignment film 11 during screen printing. Even if transferred as a trace, the orientation is hardly disturbed.

  In order to match the calendering direction C of the stainless steel mesh 20 and the rubbing direction R of the alignment film 11 to the same direction, the calendering direction C of the stainless steel mesh 20 is aligned with the rubbing direction R of the alignment film 11 as shown in FIG. However, since the rubbing direction R of the alignment film 11 varies depending on the type of the liquid crystal display panel, it is preferable to rotate the tension side in a plane parallel to the panel substrate 10. In some cases, the panel side may be rotated with the tension side fixed.

  It is most preferable that the angle Ca of the stainless steel mesh 20 in the calendering direction and the rubbing angle Ru of the alignment film 11 completely coincide with each other. However, various experiments have shown that the angle Ca in the calendering direction and the rubbing angle Ru are somewhat different. It has been found that even if they are shifted, display defects due to the mesh marks hardly occur. In the present invention, the allowable range of deviation between the angle Ca in the calendering direction and the rubbing angle Ru is relatively within 15 °.

  In the conventional example, the occurrence rate of display defects due to mesh marks was about 50%. However, according to the present invention, if the deviation including perfect coincidence is within 15 ° of the allowable range, the display based on mesh marks. The occurrence rate of defects can be reduced to almost 0%. In this embodiment, the calendar process is performed along the bias direction of the warp. However, the calendar process may be performed at a predetermined angle with respect to the bias direction or may be performed along the weft.

  A liquid crystal display panel was actually manufactured and its display state was observed. 3 to 5 show Examples 1 to 3 according to the present invention, and FIGS. 6 to 8 show Comparative Examples 1 to 3. FIG. In each figure, (a) is an explanatory diagram showing the relative relationship between the angle Ru in the rubbing direction (dashed double-lined double arrow) and the angle Ca in the calendar processing direction (black thick solid line arrow), and (b) is the liquid crystal. It is the elements on larger scale of the photograph which lighted the display panel and image | photographed the display screen. The white bright spots are due to in-plane spacers.

Example 1
As shown in FIG. 3A, when the angle Ca in the calendering direction was made to coincide with the angle Ru (upward 45 °) in the rubbing direction, no mesh mark was observed as shown in FIG. 3B. .
Example 2
As shown in FIG. 4 (a), the angle Ca in the calendering direction is shifted ± 6.5 ° with respect to the angle Ru in the rubbing direction (upward 45 °) to 38.5 ° and 51.5 °. Even in this case, no mesh mark was observed as shown in FIG.
Example 3
As shown in FIG. 5 (a), the angle Ca in the calendar processing direction is shifted by ± 15.0 ° with respect to the rubbing direction Ru (upward 45 °) to 30 ° and 60 °. As shown in FIG. 5B, no mesh mark was observed.

<Comparative example 1>
As shown in FIG. 6 (a), when the angle Ca in the calendar processing direction is set to 45 ° to the right with respect to the angle Ru (45 ° to the right) in the rubbing direction, the angle Ru is approximately perpendicular to the angle Ru (45 ° to the right). Remarkably, mesh marks were recognized.
<Comparative example 2>
As shown in FIG. 7A, when the angle Ca in the calendering direction is set to 38.5 ° and 51.5 ° which are increased to the right with respect to the angle Ru (45 ° which is decreased to the right) in the rubbing direction, As shown in b), mesh marks were noticeable.
<Comparative Example 3>
As shown in FIG. 8 (a), when the angle Ca in the calendering direction is set to 30 ° and 60 ° ascending to the right relative to the angle Ru (downward 45 °) in the rubbing direction, it is shown in FIG. 8 (b). As can be seen, mesh marks were noticeable.

(A) The top view which showed the panel board | substrate which this invention prints, (b) The enlarged view which shows a part of stainless steel mesh in which the bias direction was set according to this invention. The enlarged view which shows A2 part of FIG.1 (b). Explanatory drawing which shows the relative relationship of the angle Ru of the rubbing direction and the angle Ca of a calendar process direction in Example 1. FIG. FIG. 3 is a partially enlarged view of a photograph taken of the display screen of the liquid crystal display panel in Example 1. Explanatory drawing which shows the relative relationship between the angle Ru of the rubbing direction and the angle Ca of a calendar process direction in Example 2. FIG. FIG. 6 is a partially enlarged view of a photograph taken of a display screen of a liquid crystal display panel in Example 2. Explanatory drawing which shows the relative relationship of the angle Ru of the rubbing direction and the angle Ca of a calendar process direction in Example 3. FIG. FIG. 6 is a partially enlarged view of a photograph of a display screen of a liquid crystal display panel in Example 3. Explanatory drawing which shows the relative relationship between the angle Ru of the rubbing direction in the comparative example 1, and the angle Ca of a calendar process direction. FIG. 4 is a partially enlarged view of a photograph of a display screen of a liquid crystal display panel in Comparative Example 1. Explanatory drawing which shows the relative relationship between the angle Ru of the rubbing direction in the comparative example 2, and the angle Ca of a calendar process direction. FIG. 10 is a partially enlarged view of a photograph of a display screen of a liquid crystal display panel in Comparative Example 2. Explanatory drawing which shows the relative relationship between the angle Ru of the rubbing direction in the comparative example 3, and the angle Ca of a calendar process direction. FIG. 10 is a partially enlarged view of a photograph of a display screen of a liquid crystal display panel in Comparative Example 3. The side view which shows typically the screen printing apparatus on which this invention is based. The same top view as FIG. 1A which showed the panel board | substrate which this invention prints. The enlarged view similar to FIG.1 (b) which shows a part of stainless steel mesh in which the bias direction was set according to the prior art example. The schematic diagram which shows the state which performs the calendar process to the said stainless steel mesh. The enlarged view which shows A1 part of FIG. The schematic diagram for demonstrating the problem of the said prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Panel board | substrate 11 Orientation film | membrane 12 Peripheral sealing material 20 Stainless steel mesh 21 Warp yarn 21a Warp thread peak part 22 Weft thread 22a Weft thread peak part R Rubbing direction Ru Rubbing angle B Bias direction Bi Bias angle C Calendar processing direction Ca Calendar processing angle

Claims (2)

A screen printing method in which a peripheral sealing material is applied to a periphery of a panel substrate for a liquid crystal display panel having an alignment film subjected to rubbing treatment through a screen mesh made of a metal wire,
Calendar the above screen mesh,
The angle of the calendering direction with respect to a horizontal reference line is Ca, the angle of the rubbing direction of the alignment film is Ru, and the calendering direction angle Ca and the rubbing direction angle Ru are matched in the same direction. Screen printing method.   2. The screen printing method according to claim 1, wherein when the angle Ca of the calendering direction and the angle Ru of the rubbing direction are matched in the same direction, an allowable range is relatively within 15 °.