JPS5826602B2 - Ink for shielding film during pattern formation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shielding ink that is suitable for use when forming a transparent conductive film, also called a Nesa film, and is particularly capable of clearly forming a finely shaped pattern.

Generally, in a display device using, for example, a liquid crystal, a transparent electrode of a predetermined shape is formed on a glass substrate, and desired numbers, characters, etc. are displayed by applying a voltage to the transparent electrode.

As a method for forming this transparent electrode, a process as shown in FIG. 1 is adopted, for example.

First, as shown in FIG. 1A, a glass substrate 1 is prepared, and on this glass substrate 1, as shown in FIG. 1B, a shielding film 3 that can withstand high temperatures is coated on the glass substrate 1 except for the portion 2 where the transparent electrode is to be formed. Then, as shown in FIG.
A NESA film such as No. 2 is deposited and then the shielding film 3 is peeled off and removed by washing with water to form a transparent electrode 4 made of the NESA film having a desired pattern on the glass substrate 1 as shown in Figure 1.
I try to form it on top.

Conventionally, the shielding film 3 is made of BaSO4tTi02 as the main material.
A shielding film ink prepared by mixing a mixture of metal oxides such as tCaSO3tFe203 with a cellulose binder and a solvent such as terpineol or ethylene glycol is applied to the glass substrate 1 by screen printing, for example. .

As described above, since the film is mainly composed of metal oxides, it has stable characteristics within the spraying temperature range of Nesa film (maximum 650°C), so it has been widely used in the past.

However, in this shielding film ink, the main ingredient particles are at most 1
The first problem is that it is not suitable for forming fine patterns because it can only be formed up to a size of about 50 to 250 mμ.
As shown in FIG. B, when a predetermined pattern is printed on the glass substrate 1, solvent, binder, etc. seep into the blank area 2 and contaminate the blank area 2 where the transparent electrode is to be formed.

For this reason, the NESA film is coated on top of the oozing binder, solvent, etc., so when the shielding film 3 is removed, the oozing binder, solvent, etc. is firmly suppressed by the NESA film. This portion remains, and a so-called residue is likely to occur.

As a result, there is a drawback that the outline of the transparent electrode 4 formed on the glass substrate 1 is not clear as shown in FIG.

That is, FIG. 2 shows a microscopic photograph of a transparent electrode formed using a conventional shielding ink, in which the white part is the transparent electrode 4 and the halftone part is the surface of the glass substrate 1.

As is clear from this photograph, it can be seen that some residue is left on the edge of the transparent electrode 4 due to seepage from the shielding ink.

In addition, in the conventional method, the edges of the transparent electrodes 4 are left behind and the outline is not clear, so when the transparent electrodes 4 are formed close to each other, there is a limit to how close they can get, and if they are made too close together, the leftovers will come into contact with each other. Therefore, the maximum approach width must be made relatively large.

For this reason, it has the disadvantage that it is difficult to make a display for small characters, such as when making a digital display for a wristwatch.

Furthermore, when removing the shielding film 3 by washing with water or the like, since the shielding film 3 contains heavy metals such as Ba and Ti as main ingredients, if the washing water is directly discharged, it may cause pollution, so the washing water must be disposed of. There are also drawbacks that must be addressed.

It is an object of the present invention to eliminate such drawbacks and to provide an ink for a shielding film that can clearly form fine patterns and that does not cause pollution with the washing water used when removing the shielding film.

In the present invention, the ink for the shielding film is composed of carbon and graphite, which are easily obtained as fine powder and have high heat resistance, as main ingredients.

Therefore, according to the present invention, by using carbon and graphite as main ingredients, the particles of the main ingredient can be made fine, so that the ink itself can be deposited in a fine pattern.

However, by selecting materials that are easily absorbed by carbon as the binder and solvent, it is possible to prevent the binder, solvent, etc. from seeping into the blank area 2, and to obtain an ink that is unlikely to leave residue.

Example 1 Main agent: Carbon black 1000,! li', graphite 500g, white carbon (S102 type particles) 1
00. ! 9 Bainter: Ethyl cellulose 300.9. Homogenol 100g Solvent Nibutyl carpitol acetate 1, 270
09 First, these materials are mixed with carbon black, graphite, and ethyl cellulose, and then butylcarpitol acetate is added to mix the particles uniformly.
Mix while heating to 50°C.

The mixing order does not have to follow this example, but you can mix all the ingredients at the same time. Also, mix carbon, graphite, and white carbon, stir well, then mix ethyl cellulose.
A solvent may be added at the end.

The mixture is turned into a paste by passing it between rolls several times, then passing it through a Raikai machine for about 2 hours, and then stirring it to finish it.

In this way, by using carbon, graphite and white carbon as the main ingredients, ethyl cellulose and homogenol as binders, and butyl carpitol acetate as a solvent, these binders and solvents have the property of being easily absorbed by carbon black. 1
When printing on the blank area 2, it is possible to prevent the binder and solvent from seeping into the blank area 2.

Furthermore, the main ingredients, such as carbon black, graphite, and white carbon, can produce finer particles than conventionally used heavy metals such as B a *T, so the ink itself can be printed in fine patterns.

For example, carbon black is a mixture of 65% carbon black I having particles of about 56 to 58 mμ and 35% carbon black II having fine particles of about 8 to 9 mμ.

As a result, the transparent electrode 4 left on the glass substrate is formed.
No residue is left on the periphery of the pattern, and a pattern with a clear outline as shown in FIG. 3 can be formed.

FIG. 3 shows a microscopic photograph of a transparent electrode 4 formed using the shielding ink according to the present invention, and as is clear from this photograph, the outline of the transparent electrode 4 appears clearly and it can be seen that there is no residue left behind. .

Further, the shielding film 3 can be easily removed by rubbing it with a brush or by soaking it in water or performing ultrasonic cleaning, and no residue will remain.

Furthermore, since the main ingredients are carbon black, graphite, and a small amount of white carbon, there is no risk of causing pollution even if the cleaning water is flushed as it is, and it is safe.

Furthermore, since the main ingredients are carbon and graphite, it is resistant to heat and is stable even when spraying Nesa membrane.

In addition, the shielding film printed on the glass substrate is black because the main ingredients are mainly carbon and graphite, and the glass substrate 1 is heated to about 600°C when spraying the Nesa film, but the shielding film 3 is black. Therefore, it absorbs heat well and the temperature of the substrate surface rises faster than conventional ink (conventional ink is white), making it easier to work with.

Further, it is preferable to expose the surface on which the NESA film is formed into plasma in an oxygen atmosphere after removing most of the shielding film by washing with water or the like.

When this is done, the remaining small portions of the shielding film that could not be completely removed by washing with water, etc. combine with oxygen in the atmosphere, and since this is carbon, it becomes CO2 gas and scatters.

Therefore, when exposed to plasma in an oxygen atmosphere, the shielding film can be almost completely removed. For example, when using a transparent electrode made of Nesa film in a discharge display tube, there is no risk of gas generation due to the remaining shielding film, making it stable. You can make discharge display tubes.

Furthermore, when used in a liquid crystal display, there is an advantage that the remaining shielding film does not mix into the liquid crystal, thereby preventing deterioration of the liquid crystal.

Further, according to the present invention, the spreadability of the ink can be changed by changing the content of graphite in the carbon black, and an ink suitable for the shape of the pattern can be obtained.

For example, as in the first embodiment described above, the amount of carbon to graphite is 2.
By setting = 1, the minimum line width (minimum width of transparent electrode)
It is possible to obtain inks suitable for forming regular patterns with a diameter of about 0.15 degrees.

Generally, increasing the amount of graphite relative to carbon improves the spreadability of the ink, and when the area to which the ink is adhered is large, it is desirable to use an ink with an increased mixing ratio of graphite.

In addition, when forming particularly fine patterns, the desired spreadability can be obtained by setting the ratio of carbon black and graphite to about 3=1, and the minimum drawing width can be set to about 0.1 mttt. Suitable for forming fine patterns.

Therefore, in consideration of the usage conditions, it is possible to consider not only the above-mentioned Example 1 but also other materials.

An example is shown below.

2nd example Main agent: carbon black, graphite, white carbon Binder: ethyl cellulose, homogenol solvent diethylene glycol 3rd example main agent: carbon black, graphite Binder: ethyl cellulose, homogenol solvent: terpineol, diethylene glycol 4th example Example: Main agent: carbon black, graphite Binder: ethyl cellulose Solvent: butyl cerbitol acetate The same shielding ink as in the first example can be obtained even with the formulations shown in these second to fourth examples.

As explained above, according to the present invention, it is possible to provide a shielding film ink suitable for forming fine patterns, and it is suitable for use in making displays with small characters, such as digital displays for wristwatches, for example. be.

In the above description, the ink according to the present invention is used for forming transparent electrodes, but the ink according to the present invention is not limited to this, and can also be used as a mask material used in the manufacturing process of integrated circuits, for example. Since it is possible to form fine patterns, the same effects as described above can be expected for integrated circuits.

[Brief explanation of the drawing]

FIG. 1 is a plan view for explaining the manufacturing process of a suitable transparent electrode using the ink for a shielding film for pattern formation of the present invention, and FIG. 2 is a plan view of a NESA film formed using a conventional shielding ink. Photomicrograph, FIG. 3 is a photomicrograph of a Nesa film formed using a shielding ink according to the present invention.

Claims (1)

[Claims] 1 Form a first film on a substrate in a predetermined pattern, form a conductive second film on the entire surface of the substrate including the pattern, and then peel off the first film from the substrate and place it on the substrate. In the pattern forming method of forming a conductive pattern from the second film that is opposite to the pattern of the first film, the first film is a mixture of carbon particles and graphite particles having a particle size of at least 5 to 70 mμ. The mixing ratio of the mixture is selected so that the content of the carbon particles is 10% or more in the total amount, and the mixture is uniformly kneaded with a solvent together with a binder for shielding during pattern formation. ink.