JPH0386579A - Method for taking in alignment mark - Google Patents

Abstract

PURPOSE:To sharply confirm an alignment mark up to the end part thereof by strong reflected light by forming the alignment mark to a transparent substrate and providing a reflecting surface to the transparent substrate under the alignment mark and observing the reflected light from the reflecting surface by a CCD camera. CONSTITUTION:Red image lines 5 and two alignment marks 4 are simultaneously printed on the surface part of a transparent substrate 1 in the first printing. When lights having proper intensity are emitted to the opposed alignment marks 4 on the respective sides of two CCD cameras 3, said lights are absorbed by red ink 6 at a place where the ink 6 is printed or the lights returned by the irregular reflection generated at the uneven parts of the surfaces of said marks are little and, therefore, an image becomes dark but, at the places of the alignment marks 4 where the red ink 6 is not printed, strong lights are reflected and returned from the reflecting surfaces under the alignment marks 4 and, therefore, the alignment marks 4 are sharply confirmed up to the boundary parts thereof. Therefore, when the observed images due to the CCD cameras are decomposed into fine pixels to be analyzed, the presice positions of said images can be grasped.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for capturing alignment marks in printing processes and the like.

[Conventional technology]

The color filters used in LCD color displays, etc. are placed on a transparent substrate made of glass or the like, with red, green, and blue areas! It is often manufactured by continuously forming a fine pattern consisting of the three primary colors wRGB by repeatedly forming fine lines on the order of microns. Intaglio printing or intaglio offset printing is often used as a means of forming images due to its high precision and cost, but when printing by replacing red, green, and blue inks, it is necessary to print with a predetermined size. (For example, 100 n
) It is necessary to print by accurately shifting the position. For this reason, so-called alignment marks for positioning are formed on both the printing plate and the substrate by appropriate means, and the positional relationship between the two alignment marks is observed and aligned.

[Problem to be solved by the invention]

An alignment mark, such as a cross, is formed on a transparent glass substrate using metal chromium or the like with high reflection efficiency, and when observed from above with a CCD camera, the alignment mark is much stronger than other parts. Since the light is reflected, the existence of the alignment mark can be easily confirmed. However, forming alignment marks using metal chromium or the like on the substrate in advance requires an extra vapor deposition and etching process, so it is only suitable for products that require particularly high precision due to manufacturing cost considerations. The problem is that it cannot be done. On the other hand,
There is also a method in which an alignment mark is simultaneously printed during the first printing of multi-step printing, and in the next printing, the substrate is moved a predetermined distance in a predetermined direction from the alignment mark. However, in this case, the difference in reflectance between the printed surface of the alignment mark and the surface of the transparent substrate is not as large as that of metallic chrome, so it is difficult to clearly recognize the boundary of the alignment mark. Therefore, there is a problem in that it is difficult to apply to precision printing which requires accurate positioning.

[Means to solve the problem]

The present invention has been made to solve the problems of the prior art described above, and includes forming an alignment mark on a transparent substrate, providing a reflective surface below the alignment mark on the transparent substrate, and reducing the amount of light reflected from the reflective surface. This is a method of capturing alignment marks characterized by observation using a CCD camera.

[Effect]

According to the present invention, a reflective surface is provided below the alignment mark, and since much stronger light is reflected from the reflective surface than the surrounding area, the CCD camera can clearly recognize the alignment mark. I can do it.

【Example】

Next, the present invention will be explained in detail based on an illustrated embodiment. In the figure, reference numeral 1 denotes a transparent substrate made of glass for printing and forming a fine pattern in the three primary colors of RGB, and is fixed onto a surface plate 2 by appropriate means (for example, by vacuum suction from the back side). Two CCD cameras 3 are installed above the transparent substrate 1 so that alignment marks 4 can be observed. A red line 5 with a width of 100 μm and two alignment marks 4 have already been simultaneously printed on the surface of the transparent substrate 1 during the first printing. In this case, a large number of red lines 5 forming a fine pattern are printed in parallel at a pitch of 300 μ+, and an alignment mark 4 is formed with red ink 6 in a cross-shaped hollow on the outer periphery of the pattern forming area. There is. The upper surface of the surface plate 2 facing the alignment mark 4 is processed into a mirror surface to form a reflective surface 21 that well reflects light from above. Therefore, when light of moderate intensity is emitted from each side of the two CCD cameras 3 toward the alignment mark 4 facing each other, the red ink 6 is absorbed by the ink 6 where it is printed, or the surface The image becomes darker because there is less light reflected back from the uneven surface of the red ink 6.
At the so-called alignment mark 4 where no mark is printed, strong light is reflected from the lower reflecting surface 21 and returned, so that the alignment mark 4 can be clearly recognized up to its boundary as shown in FIG. Therefore, if an image observed by a CCD camera is broken down into minute pixels and analyzed, its precise position can be determined. The distance between two adjacent red lines 6 is 200 each.
n, and in order to sequentially print 100n wide green lines and blue lines without overlapping or separating them, the surface plate 2 to which the substrate 1 is fixed must be accurately positioned. It is necessary to move the alignment mark 4 by 100 μm twice in either the left or right direction, but by observing the alignment marks 4 printed on the left and right sides of the transparent substrate 1 using the CCD camera 3 as described above, the position can be easily and accurately determined. Because I can,
If you move using an appropriate means such as a stepper,
A desired fine pattern can be easily printed. The reflective surface provided below the transparent substrate 1 may be formed by mirror-finishing the surface plate 2, by depositing metal chromium or the like and then polishing it, or by inserting aluminum foil or the like with excellent reflectivity. It doesn't matter if it's something you do. The shape of the alignment mark 4 is also not particularly limited, and may be appropriately selected from conventional shapes, or may be formed by printing on the transparent substrate 1 with ink 6 or the like as shown in FIG. It doesn't matter. Also, C
Only one CD camera 3 may be installed when the transparent substrate 1 is moved linearly in the horizontal direction, but if the installation orientation of the transparent substrate 1 is also a problem, rotation within the horizontal plane is supported. It is necessary to install at least two units.

【Effect of the invention】

As explained above, the alignment mark capturing method according to the present invention involves forming an alignment mark on a transparent substrate, providing a reflective surface below the alignment mark on the transparent substrate, and using a CCD camera to capture the reflected light from the reflective surface. Since this is an observation method, the alignment mark can be clearly recognized down to the edge using strong reflected light. Therefore, positioning can now be performed easily and with high precision, so it can be applied to, for example, the production of color filters that can be used in large-sized LCD displays, the demand of which has been rapidly increasing in recent years, and has a practical effect. be.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of one embodiment, Fig. 2 is an enlarged cross-sectional explanatory diagram of the main part thereof, Fig. 3 is an explanatory diagram of an observation image of an alignment mark, and Fig. 4 shows another method of forming an alignment mark. It is an explanatory diagram. ■...Transparent substrate, 2... Surface plate, 21... Reflective surface, 3... CCD camera, 4... Alignment mark, 5... Drawing line, 6... Ink.

Claims (1)

[Claims] A method for capturing an alignment mark, which comprises forming an alignment mark on a transparent substrate, providing a reflective surface below the alignment mark on the transparent substrate, and observing light reflected from the reflective surface with a CCD camera.