JP4639067B2 - Manufacturing method of ceramic substrate - Google Patents

Description

The present invention relates to a ceramic substrate mainly composed of forsterite. More specifically, the present invention relates to a ceramic substrate useful for an inorganic EL substrate.

The forsterite substrate is a ceramic substrate whose main crystal is forsterite (2MgO · SiO2), and ceramics mainly composed of forsterite have a low dielectric loss against microwaves and a high volume resistivity. It is used for high-frequency circuit components and resistance core materials. In addition, since it can be fired at a considerably lower temperature than other ceramic materials such as an alumina substrate, it is an advantageous ceramic material in terms of production efficiency.

  When used in the above various applications, it is necessary to polish the forsterite substrate obtained by baking to smooth the surface of the forsterite substrate by sanding. Appear. When a circuit pattern is printed on this surface using a conductive paste, there is a problem that an accurate print pattern cannot be obtained because the paste flows into the void.

  In addition, when used for a flat display substrate such as an inorganic EL (electroluminescence) substrate having a large area and a small thickness, for example, it has an area of about A4 size or more, and the thickness is about 3 mm. Bending strength is required.

Even if the surface is polished to obtain a smooth surface, the present invention has few voids appearing on the surface, has high strength, can be fired at a relatively low temperature, has low dielectric loss with respect to microwaves, and is inherent in volume. It is to provide a ceramic substrate having a characteristic of high resistance.

As a result of investigations to achieve the above object, it has been found useful to obtain a ceramic substrate by firing a molded body having a specific composition, and the present invention having the following constitution has been completed.
1. A method for producing a ceramic substrate comprising firing a molded body comprising at least 80-99.8% by weight of forsterite and 0.2-5% by weight of yttria, wherein the particle size represented by a median diameter D50 of yttria is 4 μm or less. 2. A method for producing a ceramic substrate as described in 1 above.
2 . 2. The method for producing a ceramic substrate according to 1 above, wherein the ceramic substrate is a substrate for a flat panel.
3 . 3. The method for producing a ceramic substrate according to 1 or 2 above, wherein the flat panel is an inorganic EL panel.
4 . A flat panel comprising a ceramic substrate obtained by firing a compact comprising at least 80-99.8% by weight of forsterite and 0.2-5% by weight of yttria as a substrate ,
4. The flat panel as described in 3 above, wherein the flat panel is an EL flat panel.

The present invention has been made to solve the above problems, and even if the surface is polished to obtain a smooth surface, there are few voids appearing on the surface, the strength is high, and firing is possible at a relatively low temperature. And having an effect of providing a ceramic substrate having characteristics of low dielectric loss to microwaves and high volume resistivity.

The ceramic substrate of the present invention is a ceramic substrate characterized by firing a molded body made of a specific amount of forsterite and yttria.
Forsterite is 80-99.8% by weight in the whole molded body,
It is preferable that yttria is contained in an amount of 0.2 to 5% by weight,
95-99.5% by weight of forsterite in the whole molded body
More preferably, 0.5 to 2% by weight of yttria is contained.

If the forsterite composition is less than the above lower limit value, the forsterite substrate can be fired at a relatively low temperature, and the characteristic value of low dielectric loss against microwaves and high volume resistivity decreases. When the composition value exceeds the above upper limit, the amount of yttria is relatively reduced, so that the number of voids increases.
If the composition of yttria is the above lower limit, the effect of yttria addition is reduced and the number of voids increases, and if the upper limit is exceeded, yttria is expensive and the number of voids only increases the cost of the substrate. This is not preferable because it does not decrease any further.

Particle size expressed by the median diameter D50 of the yttria is preferably less than 4 [mu] m, and even more preferably less 2.mu. m.
If the value of D50 is 4 μm or more, the effect of adding yttria is reduced and the number of voids is increased.

The ceramic substrate of the present invention may contain compounds other than forsterite and yttria, and minerals in amounts that do not impair the values of the specific content of forsterite and yttria.

The ceramic substrate of the present invention is a slurry sheet formed by extrusion molding, injection molding, calender roll, coating, etc., using a ceramic slurry containing a predetermined proportion of various molded body materials, and the slurry sheet is dried to obtain a green sheet. Thereafter, it is obtained by firing.
From the viewpoint of obtaining a flat sheet, the slurry sheet is preferably produced by coating a ceramic slurry.

The ceramic slurry can be obtained by mixing a molded body raw material, a solvent, and, if necessary, a known dispersant, binder resin, plasticizer, lubricant and the like.

When a ceramic slurry is dried to produce a green sheet, most of the solvent is volatilized and disappears. However, a uniform drying is possible to make the ceramic slurry have an appropriate viscosity or when the ceramic slurry is dried. Therefore, it is important to select the type and amount. In particular, in the drying process, if a low-boiling solvent is used, the drying proceeds rapidly, the film cracks, and conversely, if a high-boiling solvent is used, the drying becomes slow. Is preferred.

The solvent is not particularly limited, and examples thereof include benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha. Aromatic hydrocarbons; for example, aliphatic or alicyclic hydrocarbons such as n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, turpentine oil, etc. Esters such as ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, methyl benzoate; for example, acetone, methyl ethyl ketone, methyl- ketones such as i-butyl ketone, isophorone, cyclohexanone, methylcyclohexanone; for example, ethylene glycol monomer Glycol ethers such as ether ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether; for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n -Alcohols such as butyl alcohol, i-butyl alcohol, s-butyl alcohol, t-butyl alcohol; water and the like.

The binder resin is not particularly limited, and examples thereof include ethylene vinyl acetate resin, polystyrene, APP, methacrylic resin, polyacetal, cellulose, ethylene vinyl acetate, polyvinyl butyral, and polyvinyl acetate.

The raw materials can be mixed by a known mixing device such as a ball mill, a vibration mill, a homomixer, or a roll mill to obtain a ceramic slurry.

  The viscosity of the ceramic slurry is preferably 5000 to 40000 mPa · s (millipascal second), more preferably 10000 to 30000 mPa · s. The viscosity can be adjusted by adjusting the amount of solvent added. When it is low, the inorganic powder tends to settle, and when the viscosity is high, the coating property is lowered.

  The proportion of components other than the solvent in the ceramic slurry is preferably 50 to 90%, more preferably 65 to 80%.

When obtaining a slurry sheet by applying ceramic slurry, apply it on the base film using a coating machine such as a comma coater, die coater, curtain coater, fountain coater, etc. Layers can be manufactured.

As the base film for applying the ceramic slurry, a known synthetic resin sheet, paper, cloth, non-woven fabric or the like can be used, but from the viewpoint of surface accuracy, a synthetic resin sheet such as a polyester resin can be used. Those obtained by subjecting the surface to mold release treatment are preferred.

Although coating thickness will vary depending on the application, if the ceramic substrate of the present invention is used for the circuit board dry thickness is preferably 200 [mu] m to 2 mm, dry thickness when used for the inorganic EL substrate preferably Adjust the coating thickness to be 1mm to 5mm.

The slurry sheet coated on the substrate film can be dried with a hot air dryer, hot air dryer, far-infrared dryer or the like to obtain a green sheet. If the solvent remains in the sheet after the drying operation, there is a possibility that the film may crack. Therefore, it is preferable that the slurry surface is not dried before the solvent in the slurry is completely removed. The drying temperature is preferably 20 to 150 ° C, more preferably 40 to 120 ° C, the drying time is preferably 5 to 60 minutes, more preferably 10 to 40 minutes, and the temperature is raised stepwise or continuously from low to high temperatures. And drying.

Prior to firing the green sheet, the obtained green sheet is cut according to the purpose of use, and a plurality of sheets are laminated as necessary.

When firing the green sheet from which the base film has been peeled off, the binder resin must be decomposed before the molded body such as forsterite in the green sheet starts sintering, and then the molded body needs to be fired. is there.
For this reason, for example, after the binder resin is sufficiently decomposed by heating at 200 to 500 ° C. for about 1 to 10 hours, it is heated at 1000 to 1500 ° C. for several hours to take a firing step of sintering the molded body. it can.

The ceramic substrate obtained as described above can be used by polishing the surface or the like by a known method according to the purpose of use.

EXAMPLES Examples will be given below to specifically describe the effects of the present invention, but the present invention is not limited to these examples. The test methods and evaluation methods used in the examples are as follows.

(1) Polishing A test side was prepared by cutting a 1.7 mm thick ceramic substrate obtained in each example into a square with a side of 5 cm. This test piece was pressed on the polishing surface of a polishing machine (manufactured by Marumoto Streas Co., Ltd .: Marumoto Sample Preparation Polishing Machine Model 6525 / B), 1 minute with C80 abrasive, 5 minutes with C400 abrasive, Polishing with a C1500 abrasive for 10 minutes gave a smooth new surface with a thickness of 1.5 mm.

(2) a polishing surface voids measuring the polishing test piece was observed with 50x optical microscope to measure the number of 5 [mu] m or more voids per piece polishing sample.

(3) Strength
A sample obtained by firing was cut into a length of 50 mm and a width of 12 mm to prepare a measurement sample, and the strength was measured according to JIS C-2141.

Example 1
(1) Preparation of ceramic slurry 99 parts by weight of forsterite (manufactured by Kyoritsu Material Co., Ltd .: synthetic forsterite FF-200), yttria (manufactured by Japan Yttrium Co., Ltd .: fine powder 99.9% yttrium oxide, median diameter D50 = 1.38) 1 weight Parts, methanol 23 parts by weight, toluene 27 parts by weight, polyvinyl butyral (Sekisui Chemical Co., Ltd .: ESREC BM-S) 10 parts by weight, dibutyl phthalate 8 parts by weight are added to a ball mill, mixed for 30 hours, viscosity 15,000 A ceramic slurry of centipoise (BM type viscometer 10 rpm) was obtained.

(2) Preparation of green sheet Apply the above ceramic slurry onto a PET release sheet to a length of 20cm, a width of 20cm, and a dry thickness of 2mm, and dry at 80 ° C for 60 minutes in a hot air dryer to obtain a green sheet. Obtained.

(3) Preparation of ceramic substrate The above green sheet was cut into 15 cm length and 15 cm width, heated in a firing furnace at 400 ° C for 8 hours, and further heated at 1350 ° C for 4 hours to obtain a 1.7 mm thick ceramic substrate. .
Table 1 shows the results of physical properties tests performed on the obtained ceramic substrate original plate under the above conditions.
There was no void and a good surface was obtained.

Example 2
A ceramic substrate was obtained in the same manner as in Example 1 except that the amount of forsterite was 99.4 parts by weight and the amount of fine powder yttria was 0.6 parts by weight.

Example 3
A ceramic substrate was obtained in the same manner as in Example 1 except that 93 parts by weight of forsterite, 1 part by weight of fine powder yttria, and 6 parts by weight of calcium carbonate were used as the compact.

Example 4
A ceramic substrate was obtained in the same manner as in Example 1, except that 99.2 parts by weight of forsterite and 0.8 parts by weight of yttria (manufactured by Japan Yttrium Co., Ltd .: 99.9% yttrium oxide, median diameter D50 = 3.8) were used.

Reference example 1
A ceramic substrate was obtained in the same manner as in Example 1 except that only 100 parts by weight of forsterite was used as a molded body. The substrate had a large number of voids.

Reference example 2
A ceramic substrate was obtained in the same manner as in Example 1 except that 99 parts by weight of alumina 96% ceramic powder made of alumina, calcia, magnesia, silica, etc. and 1 part by weight of fine powder yttria were used as the molded body. Under low-temperature firing conditions for firing forsterite, the strength of the substrate obtained due to insufficient firing was not measurable.

The ceramic substrate of the present invention can be used for various circuit boards and display substrates. Since it has the above-mentioned characteristics, it is useful for a large area flat display panel, particularly an inorganic EL substrate.

Claims (5)

A method for producing a ceramic substrate, comprising firing a molded body comprising at least 80-99.8% by weight of forsterite and 0.2-5% by weight of yttria ,
A method for producing a ceramic substrate, wherein the particle size expressed by the yttria median diameter D50 is less than 4 μm. The method for manufacturing a ceramic substrate according to claim 1, wherein the ceramic substrate is a substrate for a flat panel. The method for producing a ceramic substrate according to claim 1 or 2 before Symbol flat panel is an inorganic EL panel. A flat panel comprising a ceramic substrate obtained by firing a compact comprising at least 80-99.8% by weight of forsterite and 0.2-5% by weight of yttria as a substrate , wherein the yttria median A flat panel having a particle size represented by a diameter D50 of less than 4 μm . The flat panel according to claim 4 , wherein the flat panel is an inorganic EL flat panel.