WO2000073851A1

WO2000073851A1 - Printing plate with relief coating and method of making the same

Info

Publication number: WO2000073851A1
Application number: PCT/US2000/014132
Authority: WO
Inventors: Joseph A. Marcanio
Original assignee: Sony Electronics Inc.
Priority date: 1999-05-27
Filing date: 2000-05-23
Publication date: 2000-12-07
Also published as: AU5040100A

Abstract

An improved method of making a photo printing plate, which is used to transfer a pattern to a substrate (106) from which a shadow mask, printed circuit board or the like is made, includes exposing a layer of light-sensitive material on a transparent plate (200) through a mask, developing the exposed light-sensitive material and depositing a durable material (211) in the resulting recesses in the light-sensitive material. The durable material (211) is then cured or treated as necessary before the remaining light-sensitive material is removed. The resulting photo printing plate is durable, transfers an accurate, well-defined pattern to a substrate (106) being printed and allows easy and fast evacuation of air from between the printing plate and the substrate (106) being printed.

Description

PRINTING PLATE WITH RELIEF COATING AND METHOD OF MAKING THE SAME

FIELD OF THE INVENTION

The present invention relates to the field of photo printing plates that are used in a lithographic process for forming etching patterns on a substrate. More specifically, the present invention encompasses a method of making photo printing plates which have superior durability, air flow and pattern formation characteristics .

BACKGROUND OF THE INVENTION Photo printing plates may be used in a variety of applications to create an etching pattern on a substrate. One prominent application for such printing plates is the manufacture of shadow masks that are used in color television sets. Photo printing plates are also used in manufacturing printed circuit boards, aperture grilles and the like.

Fig. 1 illustrates an example of known photo printing plates and the method in which they are used. As shown in Fig. 1, a typical photo printing plate includes a transparent plate (101) with a pattern of opaque material (102) formed thereon.

To print with the photo printing plate (101, 102) shown in Fig. 1, the printing plate (101, 102) is positioned between a light source (not shown) and a substrate (106) to which the pattern (102) is to be transferred. Light (100) from the light source is then shown through the transparent plate (101) to the substrate (106) . Light (100) is not collimated due to the expense of collimating light over the large area required. Some of the light (100) is blocked by the opaque pattern (102) so that the shadow of the opaque pattern (102) appears on the substrate (106). The substrate (106) is coated with a light-sensitive material (105) frequently called photo-resist. The portions of the light-sensitive layer (105) which are exposed to light between the shadows of the opaque portions (102) will be physically altered. The substrate (106) is then "developed" meaning that the photo-resist is processed to remove only those portions which were or were not exposed to light. In this manner, the pattern of the opaque portions (102) is transferred, in either positive or negative, to the light-sensitive material

(105) on the substrate (106) . The substrate can then be etched so as to carve the pattern in the light-sensitive material (105) into the substrate (106).

Also as shown in Fig. 1, a second corresponding printing plate (108) may be used on the opposite side of the substrate (106) which is also coated with a layer of light-sensitive material (107). In this way, both sides of the substrate (106) may be printed simultaneously. The printing process described above is typically carried out after creating a vacuum between the printing plate (101, 102) and the substrate (106). This vacuum causes the printing plate (101, 102) to come into intimate contact with the substrate (106) during printing and prevents any unwanted variation, e.g., diffraction, in the transmission of the light (100) between the plate (101) and the substrate (106) . Air trapped between the plate (101) and the substrate (106) can cause the light (100) to diffract and blur the image being transferred to the substrate (106) . A traditional difficulty in this industry has been the time required to remove the air from between the plate (101) and the substrate (106). Particularly, if the opaque pattern (102) is a closed pattern and is pressed directly against the light-sensitive layer (105) on the substrate (106), it becomes difficult to evacuate the air between the plate (101) and the substrate (106).

To address this problem, several different types of "spacers" have been added to create gap between the opaque patter (102) and the substrate (106) and light- sensitive material (105) . For example, a clear spacer material (not shown) may be coated over the light- sensitive material (105) . Alternatively, as taught by U.S. Patent No. 5,149,608 to Deibler et al., spacers

(104) may be added to the printing plate (101) . These spacers (104) are transparent and are thicker than the opaque relief pattern (102) so as to separate the pattern (102) from the light-sensitive material (105).

Use of a spacer or a spacer layer allows air to be evacuated under the opaque pattern (102). However, with a spacer (104) or a spacer layer, light (103) tends to diffract around the opaque pattern (102) in the space between the pattern (102) and the light-sensitive material (105) created by the presence of the spacer (104) . This diffraction blurs the edges of the pattern (102) as transferred to the light-sensitive material

(105) . Thus, in order to provide the sharpest, most defined pattern printed on the light-sensitive material (105), it is preferable to place the opaque pattern (102) in direct contact with the light-sensitive material (105). This, however, creates an additional problem. As taught by U.S. Patent No. 5,260,153 to Ohtake et al., opaque patterns are typically formed themselves by selectively exposing and developing a layer of light-sensitive material on a transparent plate.

Such an opaque pattern formed on a light-sensitive material generally has poor durability. Commonly used printing plates consist of a glass plate with a photographic emulsion or other organic coating from which the opaque pattern is formed. Due to the softness of these materials, as the printing plate is pressed against the substrate being printed, the opaque pattern on the printing plate becomes worn. This, again, reduces the definition of the pattern transferred. Moreover, any contamination between the plate and the substrate being printed will further erode the opaque pattern.

A previous solution to the durability problem has been to use as a printing plate, a glass plate coated with a very thin coating of chrome or iron oxide from which the desired opaque pattern is formed. The thin chrome or iron oxide coating is typically less than 1 micron in thickness. Such printing plates are very durable, but have no relief and, therefore, tend to trap air preventing the quick and effective formation of the necessary vacuum conditions between the printing plate and the substrate being printed.

Consequently, there is a need in the art for an improved photo printing plate and method of making the same that provides a printing plate which is durable, transfers a crisp, well defined image to the substrate being printed and has sufficient relief or air passages so as to allow the desired vacuum to be quickly achieved between the printing plate and the substrate being printed.

SUMMARY OF THE INVENTION

It is an object of the present invention to meet the above-described needs and others. Specifically, it is an object of the present invention to provide a method of making a photo printing plate that results in a plate that is durable, transfers a well defined image to the substrate being printed, and allows the necessary vacuum to be quickly achieved between the printing plate and the substrate being printed. It is a further object of the present invention to provide a photo printing plate with the advantages of durability, printing accuracy and sufficient air flow allowance to permit prompt evacuation. Additional objects, advantages and novel features of the invention will be set forth in the description which follows or may be learned by those skilled in the art through reading these materials or practicing the invention. The objects and advantages of the invention may be achieved through the means recited in the attached claims . To achieve these stated and other objects, the present invention may be embodied and described as a method of making a photo printing plate for transferring a pattern to a substrate being printed. The method includes depositing a first material in recesses of a developed light-sensitive material layer which is on a transparent plate. The recesses are formed to correspond to a pattern of opaque portions that are to be formed on the printing plate from the first material.

Preferably, this depositing of a first material in the recesses of the light-sensitive layer includes depositing, for example, a ceramic slurry such as a frit slurry, or depositing an alkoxysilane with a sol gel process. If a ceramic slurry is used, the method then continues by heat treating the ceramic slurry to form the pattern of opaque portions from hardened ceramic members which result from heat treating the ceramic slurry in the recesses .

However, a ceramic slurry or an alkoxysilane are not the only materials for practice of the present invention. Rather, any material which is viscous enough to conform to the recesses in the light-sensitive layer, but then hardens to hold the shape of the recess in which it was formed may be the hardening material deposited in accordance with the present invention. The method thus includes the step of hardening the deposited first material to form the pattern of opaque portions. After the deposited material is hardened, the method of the present invention includes removing the layer of light- sensitive material. Prior to depositing the first material, the method of the present invention includes depositing a layer of light-sensitive material on a transparent plate. Next the method includes exposing the light-sensitive material to light through a mask and developing the light- sensitive material to form the recesses in which the pattern of opaque portions will be formed. The thickness of the layer of light-sensitive material equals a desired relief of the opaque pattern, for example, 10 microns ± 5 microns .

The present invention also encompasses a photo printing plate for transferring a pattern to a substrate being printed. A printing plate according to the present invention includes a transparent plate and an opaque pattern on the transparent plate that is to be transferred to a substrate being printed. The opaque pattern is raised or in relief to the transparent plate and is formed of a ceramic or a hardened material. The printing plate of the present invention does not include spacer members apart from the opaque pattern itself. The members of the opaque pattern are arranged so as to define air passages therebetween through which air can be evacuated when the pattern on the plate is in contact with a substrate to be printed.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings illustrate the present invention and are a part of the specification.

Together with the following description, the drawings demonstrate and explain the principles of the present invention. Fig. 1 is an illustration of a conventional printing plate and photo printing process.

Figs. 2A to 2D illustrate a method of making an improved photo printing plate according to the present invention. Fig. 2E illustrates a photo printing plate according to the present invention. Fig. 3 illustrates the photo printing plate of Fig. 2E in use according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Using the drawings, the preferred embodiments of the present invention will now be explained.

Figs. 2A to 2D illustrate the various steps in the method of the present invention for forming an improved photo printing plate which is durable, allows easy evacuation of air and provides a precise pattern on the substrate being printed. Referring to Fig. 2A, a transparent plate (200), for example, a glass plate, is coated with a light-sensitive material (201) . The thickness of the light-sensitive material should be the same as the desired relief depth of the finished opaque pattern, for example, 10 microns ± 5 microns. A liquid photoresist, dry film photoresist or liquid UV curable resin may be used as the light-sensitive material (201) . The light-sensitive material (201) should be clean and uniformly coated on the plate (200) .

After the light-sensitive material (201) is deposited on the plate (200), the light-sensitive material (201) is selectively exposed to light. As shown in Fig. 2B, a mask (204) with opaque portions (205) is positioned a distance from the plate (200) . light (203) is then illuminated through the mask (204) to the light-sensitive material (201) on the plate (200). The shadows cast by the opaque portions (205) transfers the pattern of the opaque portions (205) to the light-sensitive material (201) by physically changing the potions of the light-sensitive material (201) exposed to the light (203) between the opaque portions (205) .

In the example shown in Fig. 2, the exposure to light hardens those potions of the light-sensitive material (201) exposed. Consequently, when the light- sensitive material (201) is developed, as shown in Fig. 2C, those sections of the light-sensitive material (201) shadowed by the opaque portions (205) which are not hardened are removed by the developing agent leaving openings (210) in the layer of light-sensitive material (201) . The developing agent used will be determined by and appropriate to the type of light- sensitive material used. Various light-sensitive materials and developing agents are known in the art. While the foregoing example illustrates a light- sensitive material hardened by exposure to light, an opposite arrangement may be used. Namely, the exposure to light may weaken the light-sensitive material on the plate (200) so that the exposed material is removed instead of the shaded material. With such an arrangement, the pattern of the opaque portions (205) of the mask (204) would be formed as a negative of the pattern desired on the plate (200) .

As shown in Fig. 2D, an opaque material (211) is the deposited in the openings (210) left by the removal of the shaded light-sensitive material. This opaque material (211) can be a liquid, a paste or a powder which is then hardened into a durable surface. The preferred opaque material (211) is a slurry of ceramic powder that will form a hard ceramic member if heat treated. Alternatively, an alkoxysilane deposited by a sol gel process can also be used as the opaque material (211) . In fact, any material with the proper viscosity to conform to the recesses formed in the light- sensitive material that can then be hardened to form a durable pattern could be used under the principles of the present invention.

Next, as shown in Fig. 2E, the remaining light- sensitive material (201) is removed by an appropriate solvent. The plate (200) is then subjected to a heat treatment to harden the material (211) into a durable surface, e.g., harden the ceramic slurry into a ceramic member. Preferably, the remaining light-sensitive material (201) is removed with an organic composition which then oxidizes or vaporized during the subsequent heat treatment of the ceramic material (211) .

The printing plate, comprising the transparent plate (200) and the opaque pattern portions (211), is then ready for use. To print the pattern of the opaque pattern (211) on a substrate, the substrate (106) is covered with a layer of light-sensitive material (105) . The printing plate (200, 211) is then brought into contact with the light-sensitive material (105).

The air is evacuated from between the plate (200) and the substrate (106) . Due to the relief of the opaque pattern (211), air passages between the pattern (211) are formed through which air can be easily and rapidly evacuated.

With the opaque pattern members (211) in direct contact with the light-sensitive material (105), light (203) is able to expose portions of the light-sensitive material (105) between opaque pattern members (211) without diffraction causing any blurring of the pattern as transferred to the light-sensitive material (105). Moreover, with the opaque pattern members (211) being formed of a hardened material, such as ceramic, the pattern (211) is extremely durable. For purposes of this document, a hardened material is a material which was once viscous so as to conform to the shape of the recesses in the developed light-sensitive material, but has since lost that viscosity and now holds the shape of the recess in which it was formed.

The preceding description has been presented only to illustrate and describe the invention. It is not intended to be exhaustive or to limit the invention to any precise form disclosed. Many modifications and variations are possible in light of the above teaching. The preferred embodiment was chosen and described in order to best explain the principles of the invention and its practical application. The preceding description is intended to enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims.

Claims

WHAT IS CLAIMED IS:

1. A method of making a photo printing plate for transferring a pattern to a substrate being printed, the method comprising depositing a first material in recesses of a developed light-sensitive material layer on a transparent plate, said recesses corresponding to a pattern of opaque portions to be formed on said printing plate from said first material.

2. The method of claim 1, wherein said depositing a first material comprises depositing a ceramic slurry in said recesses.

3. The method of claim 2, further comprising heat treating said ceramic slurry to form said pattern of opaque portions from hardened ceramic members which result from heat treating said ceramic slurry in said recesses.

4. The method of claim 1, wherein said depositing a first material comprises depositing an alkoxysilane by sol gel processing.

5. The method of claim 1, further comprising hardening said first material.

6. The method of claim 1, further comprising removing said layer of light-sensitive material.

7. The method of claim 1, further comprising exposing said light-sensitive material to light through a mask and developing said light-sensitive material to form said recesses prior to said depositing said first material .

8. The method of claim 1, further comprising depositing said layer of light-sensitive material on said transparent plate prior to said depositing said first material, wherein a thickness of said layer of light-sensitive material equals a desired relief of said opaque pattern.

9. The method of claim 8, wherein said thickness is 10 microns ± 5 mircrons .

10. A photo printing plate for transferring a pattern to a substrate being printed comprising: a transparent plate; and an opaque pattern to be transferred to a substrate being printed disposed on said transparent plate; wherein said opaque pattern is in relief to said substrate and is formed of a ceramic material.

11. The plate of claim 10, wherein said printing plate does not include spacer members.

12. The plate of claim 10, wherein members of said pattern formed of a ceramic material are arranged so as to define air passages therebetween through which air can be evacuated when said pattern on said plate is in contact with a substrate to be printed.

13. The plate of claim 10, wherein said relief of said opaque pattern is 10 microns ± 5 microns.

14. A photo printing plate for transferring a pattern to a substrate being printed comprising: a transparent plate; and an opaque pattern to be transferred to a substrate being printed disposed on said transparent plate; wherein said opaque pattern is in relief to said substrate and is formed of an alkoxysilane material.

15. The plate of claim 14, wherein said printing plate does not include spacer members.

16. The plate of claim 14, wherein members of said pattern are arranged so as to define air passages therebetween through which air can be evacuated when said pattern on said plate is in contact with a substrate to be printed.

17. A photo printing plate for transferring a pattern to a substrate being printed comprising: a transparent plate; and an opaque pattern to be transferred to a substrate being printed disposed on said transparent plate; wherein said opaque pattern is in relief to said substrate and is formed of a hardened material.

18. The plate of claim 17, wherein said printing plate does not include spacer members.

19. The plate of claim 17, wherein members of said pattern are arranged so as to define air passages therebetween through which air can be evacuated when said pattern on said plate is in contact with a substrate to be printed.