JPH08306305A - Screen printing pattern forming method - Google Patents

Abstract

PURPOSE: To relieve viscosity control of ink, and improve printing accuracy when a transfer pattern is formed on a base board by screen printing. CONSTITUTION: First of all, a surface of a base board 1 being a printing object is arranged so as to turn to the under side. Next, a printing screen 2 having a prescribed pattern is arranged so as to be opposed to the surface of the base board 1 from the under side. Then, a squeegee 4 is abutted with an under surface of the printing screen 2, and an upper surface of the printing screen 2 is contacted with the surface of the base board 1, and a pattern of printing ink 3 is transferred to a base board surface. Afterwards, heat treatment of the base board 1 is performed, and a pattern 5 of the transferred printing ink is baked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for forming a pattern of an insulator or a conductor on a substrate by a screen printing method.

[0002]

2. Description of the Related Art FIG. 7 schematically shows a conventional screen printing pattern forming method. First, the surface of the substrate 1 to be printed is placed on a jig (not shown) with its surface facing upward. Next, the printing screen 2 having a predetermined pattern is arranged facing the surface of the substrate 1 from above. Then, the squeegee 4 is brought into contact with the upper surface of the printing screen 2, and the lower surface of the printing screen 2 is brought into contact with the surface of the substrate 1 to transfer the pattern of the printing ink 3 onto the surface of the substrate 1. After this, the substrate 1
Then, the pattern 5 of the transferred printing ink is fired. As a result, an insulator film or a conductor film having a desired pattern can be formed on the substrate 1.

[0003]

Conventionally, a substrate on which a striped pattern is printed and fired has been used as a component of a display. In this case, screen printing may be repeatedly performed to obtain a desired thickness. However, when the viscosity of the paste used as the printing ink 3 is low, the printed pattern sags and spreads in the horizontal direction, and the originally required pattern width cannot be obtained. Furthermore, this spread causes a problem that the number of times of screen printing increases when the patterns are piled up to a target thickness. On the contrary, when the viscosity of the paste is high, the printing ink 3 does not spread on the screen 2 and cannot be transferred onto the surface of the substrate 1 well. Since the transfer is insufficient, the thick film pattern printed and baked may be damaged. For these reasons, in the conventional screen printing method, the viscosity of the paste is very important, and when used in a mass production line, the viscosity of the paste must be controlled for a long period of time. However, it is extremely difficult to control the viscosity of the paste and keep it constant for a long time. This is a cause of reducing the yield of substrate manufacturing. As described above, it is necessary for the paste used for the printing ink 3 to satisfy the trade-off condition that the printing pattern does not drip and spread beyond the specified width and that the printing pattern spreads uniformly on the screen 2. However, it is practically difficult to maintain a stable paste viscosity under all environmental conditions such as temperature, humidity, and atmospheric pressure on a day.

[0004]

In view of the above-mentioned problems of the prior art, the present invention provides a method of forming a screen printing pattern which is capable of stably forming a desired thick film without being affected by a change in viscosity of printing ink. The purpose is to provide. The following measures have been taken in order to achieve this object. That is, the screen printing pattern forming method according to the present invention is performed by the following procedure. First, in the first procedure, the surface of the substrate to be printed is arranged so as to face downward. Then, in the second procedure, a printing screen having a predetermined pattern is arranged from the lower side so as to face the surface of the substrate. Then, a third procedure is performed to bring a squeegee into contact with the lower surface of the printing screen and bring the upper surface of the printing screen into contact with the surface of the substrate to transfer a pattern of printing ink to the surface. After that, the fourth procedure is performed to heat the substrate to burn the transferred pattern of the printing ink. Preferably, in the third procedure, the printing ink is supplied to the lower surface of the printing screen through a tube provided on the squeegee. Further, in a specific example, a printing screen having a striped pattern is arranged so as to face the surface of the substrate in the second procedure, and a striped pattern of printing ink made of an insulating material is repeatedly stacked in the third procedure. The striped pattern of the printing ink transferred and transferred in the fourth procedure is fired to form a ridge pattern.

[0005]

The present invention is characterized in that screen printing is carried out with the printer having an inverted structure. A screen is placed below the substrate, and printing ink is transferred from below with a squeegee. By adopting the reverse structure, gravity in the vertical direction acts on the printing ink, so that the printed pattern does not drip in the horizontal direction. As a result, the accuracy of the printing pattern can be significantly improved as compared with the conventional screen printing method. In particular, when a fine line pattern is required, it can be formed with extremely high precision. Even if the printing ink is dripping, the direction is vertical, so that the printing thickness per time can be increased, and when repeatedly forming a printing pattern having a desired thickness, it is necessary to reduce the number of repetitions. You can On the other hand, the viscosity of printing ink can be lowered to the extent that it does not drip from the surface of the substrate. Therefore,
The range of viscosity required for printing ink is relaxed, and quality control is facilitated.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is an explanatory view schematically showing a screen printing pattern forming method according to the present invention. As shown in the figure, in the screen printing pattern forming method according to the present invention, first, the surface of the substrate 1 to be printed is arranged so as to face downward in the direction of gravity. Next, the printing screen 2 having a predetermined pattern is arranged facing the surface of the substrate 1 from the lower side. Then, the squeegee 4 is brought into contact with the lower surface of the printing screen 2, the upper surface of the printing screen 2 is brought into contact with the surface of the substrate 1, and the pattern of the printing ink 3 is transferred to the surface of the substrate 1. After that, the substrate 1 is heated to burn the pattern 5 of the transferred printing ink. Thus, the present invention is characterized in that the screen printing mechanism is arranged upside down. The screen 2 is placed below the substrate 1, and the squeegee 4 transfers the ink 3 from under the screen 2. By arranging them in the opposite manner, the printed transfer pattern 5 is subjected to the action of gravity in the vertical direction, and the amount of lateral deflection is reduced accordingly. Therefore, the accuracy of the transfer pattern 5 can be significantly improved as compared with the conventional method. Further, since the sagging direction of the transfer pattern 5 is the vertical direction, it is possible to reduce the number of times of printing required to obtain a desired thickness when performing overprinting printing or the like. As a result, the printing process can be rationalized. On the other hand, the viscosity of the paste used as the printing ink 3 can be reduced to such an extent that the paste does not drop from the substrate 1 and the screen 2, so that the viscosity control condition of the paste can be relaxed.

FIG. 2 is a schematic diagram showing an improved example of the screen printing pattern forming method shown in FIG. In this example,
The printing ink 3 is supplied to the lower surface of the screen 2 through a tube 6 provided on the squeegee 4. That is, a plurality of thin supply pipes 6 are passed inside the squeegee 4, and the printing ink 3 is pressure-fed thereto by the pressure feed pump 7. In the present invention, since the reverse structure is adopted, the printing ink cannot be placed on the screen as in the conventional case. In view of this point, in the example of FIG. 2, the amount of paste required for printing is pressure-fed at any time.

FIG. 3 shows an example of a printing apparatus suitable for carrying out the screen printing pattern forming method according to the present invention. As shown in the figure, the printing apparatus includes a screen 11 having a striped pattern. The screen 11 has a screen frame 12 with tension applied.
Pasted on. The screen frame 12 is fixed at a predetermined position in the printing device in an upside down posture. The printing apparatus is equipped with a supply means, and the screen 1
The substrate 13 is supplied so as to face the upper surface side of 1. In this example, this supply means is composed of the automatic alignment stage 14. The automatic alignment stage 14 includes a slide mechanism 16 for a ceiling portion via a stage up-and-down mechanism 15.
It is suspended from and can move to the left and right in the drawing. Below the automatic alignment stage 14, a pair of cameras 17 and 18 are provided. The pair of cameras 17 and 18 images the alignment marks formed in advance on the substrate 13. The imaged alignment marks are taken into the image processing monitors 19 and 20. A controller 21 is connected to the pair of image processing monitors 19 and 20, and drives and controls the automatic alignment stage 14 based on the position information of the imaged alignment mark.
The substrate 13 is automatically positioned. Therefore, the automatic alignment stage 14 is orthogonal to the horizontal plane.
It can move in any direction and can rotate horizontally. Further, the automatic alignment stage 14 can be vertically moved up and down by the stage up-and-down mechanism 15. The printing apparatus further includes a printing unit, and transfers the paste supplied to the lower surface side of the screen 11 to the upper surface of the substrate surface. In this example, the printing means is composed of a printing squeegee 22 and a drive mechanism 23 thereof. The printing squeegee 22 is connected to a drive mechanism 23 via a holder 24 and an arm 25, and is movable in the vertical and horizontal directions. A height adjusting gauge 26 of the printing squeegee 22 is attached to the bottom of the holder 24.

Next, the operation of the printing apparatus shown in FIG. 3 will be described in detail with reference to FIG. This figure shows the printing process. The substrate 13, which is positioned and arranged in advance on the bottom of the auto-alignment stage 14, is fed via the slide mechanism 16 directly above the upper surface of the screen 11 together with the stage 14. Subsequently, the substrate 13 is lowered by the stage up-and-down mechanism 15 and brought into close proximity to the upper surface side of the screen 11. on the other hand,
The paste is previously supplied to the lower surface side of the screen 11 having the stripe pattern. Since the paste has a certain degree of viscosity, it will not fall off the screen 11.
In this state, the printing squeegee 22 is raised via the drive mechanism 23 and brought into contact with the lower surface side of the screen 11. The contact amount is preset by the height gauge 26. Further, the printing squeegee 22 is moved in the direction parallel to the stripe pattern via the drive mechanism 23, and the paste is transferred to the substrate 13. The printing process is performed as described above. For example, the conductive material paste can be transferred to the substrate to print the striped electrodes. Alternatively, the insulating material paste can be repeatedly transferred to the substrate to print stripe-shaped ridges.

FIG. 5 is a perspective view showing an example of a striped pattern created by the printing apparatus shown in FIG.
Striped electrodes 32 are formed on the surface of the substrate 31. The electrodes 32 are formed by screen printing with the top and bottom reversed. The striped electrodes 32 are arranged at a predetermined pitch and have a predetermined electrode width. A ridge 33 is formed on the electrode 32.
The ridges 33 are formed with the same pitch by the upside down screen printing method. However, in order to obtain a desired height dimension, screen printing is repeatedly performed. That is, transfer and drying are alternately repeated. Each ridge 33 has a width smaller than that of the corresponding electrode 32. The ridge 33 is made of an insulating material and has a structural function such as a spacer. The substrate 31 having such a configuration is used as a component of a plasma addressed liquid crystal display panel, for example.

FIG. 6 is a schematic cross-sectional view showing an example of a plasma addressed liquid crystal display panel assembled using the substrate shown in FIG. This panel includes a liquid crystal cell 51, a plasma cell 52, and a common intermediate plate 53 interposed therebetween.
And has a laminated structure. The liquid crystal cell 51 is formed by using an upper glass substrate 54, and a stripe-shaped signal electrode 55 made of a transparent conductive film is formed on the inner main surface thereof. The glass substrate 54 is adhered to the intermediate plate 53 via a spacer 56 with a predetermined gap. A liquid crystal layer 57 is filled in the gap.

On the other hand, the plasma cell 52 is formed by using the lower glass substrate 58. On the inner main surface of the glass substrate 58, stripe-shaped discharge electrodes 59 orthogonal to the signal electrodes 55 are formed. The discharge electrode 59 is formed by the screen printing pattern forming method according to the present invention, and can be miniaturized and has a sharp edge. The discharge electrode 59 alternately functions as the anode A and the cathode K. The ridges 60 are formed in stripes along the discharge electrodes 59. This ridge 60
Is also produced by the screen printing pattern forming method according to the present invention, and the line width can be made finer with high accuracy. The top of the ridge 60 is in contact with the intermediate plate 53 and functions as a spacer. Lower glass substrate 58
Is joined to the intermediate plate 53 using a frit seal 61. A hermetically sealed discharge channel 62 is formed between the two. The discharge channel 62 is divided or divided by the above-described ridge 60 and serves as a scanning unit individually. An ionizable gas is enclosed in the airtight discharge channel 62. The gas species is, for example, helium,
It can be selected from neon, argon or a mixed gas of these.

In such a plasma addressed liquid crystal display panel, since the discharge channels 62 for scanning in the row direction are formed, the ridges 60 are formed for each channel to prevent the plasma gas from leaking between the channels and to generate the plasma discharge. Has the role of securing the necessary space. The production of convex stripes by the screen printing method involves repeating the printing several times to several tens of times on the same screen and gradually stacking them in the height direction. However, when the conventional screen printing method is adopted, if the viscosity of the paste is low, the printed ink spreads and spreads beyond the originally required width, and the number of printings is increased in order to stack the ridges to the target height. Will increase. Also, since the ridges are stacked on the discharge electrode, if the width of the ridges becomes larger than the specified value,
Covers the underlying discharge electrode, causing plasma discharge failure. On the contrary, when the viscosity of the paste is high, the printing ink does not spread on the screen, resulting in the failure to transfer to the glass substrate well. If the top of the ridge is damaged due to insufficient transfer, charged particles will leak between the adjacent discharge channels in the vicinity of it, so when the panel is assembled and an image is displayed, the written data will be stored in the adjacent channel. It is canceled at the time of discharge. This is because when displaying black on the entire panel, it is displayed white only in the vicinity of the defect,
This means that normal image display cannot be performed. On the other hand, when the screen printing pattern forming method according to the present invention is adopted, the width of the ridge can be made narrower than that of the conventional structure because the printed paste does not laterally drip. In addition, since the direction in which the paste drips coincides with the height direction of the ridge, the printing height per printing can be increased and the number of printings can be reduced. Furthermore, the probability that a defect will occur at the top of the ridge is reduced.

[0014]

As described above, according to the present invention, the screen printing apparatus has an inverted structure, and the printing ink such as paste is transferred to the substrate such as glass. As a result, not only can stripe patterns and the like be formed with higher accuracy than in the past, but also miniaturization is possible. Further, the viscosity condition of the paste is relaxed and the production yield is improved. Further, in the case of repeatedly performing repeated printing, it is possible to reduce the number of times of printing as compared with the conventional method.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing a screen printing pattern forming method according to the present invention.

FIG. 2 is an explanatory diagram showing an improved example of the screen printing pattern forming method shown in FIG.

FIG. 3 is a block diagram showing an example of a printing apparatus used for carrying out the screen printing pattern forming method according to the present invention.

FIG. 4 is a block diagram for explaining the operation of the printing apparatus shown in FIG.

FIG. 5 is a perspective view showing an example of a screen printing pattern formed according to the present invention.

FIG. 6 is a schematic cross-sectional view showing a plasma addressed liquid crystal display panel assembled using a substrate manufactured according to the present invention.

FIG. 7 is an explanatory diagram showing a conventional screen printing pattern forming method.

[Explanation of symbols]

 1 substrate 2 screen 3 ink 4 squeegee 5 transfer pattern

Claims (3)

[Claims] 1. A first step of arranging a surface of a substrate to be printed facing downward, and a second step of arranging a printing screen having a predetermined pattern so as to face the surface of the substrate from the lower side. A third step of transferring a pattern of printing ink to the surface of the printing screen by bringing a squeegee into contact with the lower surface of the printing screen and bringing the upper surface of the printing screen into contact with the surface of the substrate; and printing performed by heating the substrate. A method for forming a screen printing pattern, which comprises performing a fourth step of firing an ink pattern. 2. The method for forming a screen printing pattern according to claim 1, wherein in the third step, the printing ink is supplied to the lower surface of the printing screen through a tube provided on the squeegee. 3. The second step comprises arranging a printing screen having a striped pattern facing the surface of the substrate, and the third step is repeatedly stacking striped patterns of printing ink made of an insulating material. 2. The method for forming a screen printing pattern according to claim 1, wherein the striped pattern of the printing ink is transferred, and the convex pattern is formed in the fourth step by baking.