JP2002249382A - Method for manufacturing ito molded form - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an ITO molded form by slip casting capable of maintaining or improving productivity, improving molded form strength to prevent crack initiation and realizing stable production. SOLUTION: The method for manufacturing an ITO molded form by slip casting of ITO slurry containing a mixture of indium oxide powder and tin oxide powder, water, a dispersing agent and a binder comprises adding a dispersing agent having a carboxylic group and controlling slurry viscosity prior to ITO slurry casting at 1.0-50 dPa.s at 25 deg.C. The dispersing agent having a carboxylic group preferably has a weight average molecular weight of 10,000-50,000 and a pH of 7-11 and consists of a carboxylic acid polymer or copolymer neutralized by a basic solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an indium tin oxide (ITO) molded article, and more particularly to a method for producing an ITO molded article for producing an ITO sintered body used as a sputtering target for forming a transparent conductive film. is there.

[0002]

_2. Description of the Related Art ITO (indium tin oxide) composed of indium oxide (In ₂ O ₃ ) and tin oxide (SnO ₂ ) is
It is widely used as a material for transparent electrodes of liquid crystal displays, as well as transparent conductive films for solar cells and image pickup tubes.

In order to form an ITO film as a transparent conductive film, DC sputtering using an ITO sintered body as a target is generally used. In addition, ITO sintered body
It has been manufactured by mixing a binder or the like with indium oxide powder and tin oxide powder, molding and sintering the obtained molded body.

Recently, as the size of an ITO sintered body, which is a sputtering target, increases with the increase in size of a liquid crystal display or the like, a casting method is mainly used as a manufacturing method thereof. That is, this is a method in which water, a dispersant, a binder, an antifoaming agent, a lubricant, and the like are kneaded with a mixed powder of indium oxide and tin oxide, and the obtained ITO slurry is cast into a predetermined mold.

[0005]

The ITO molded body obtained by the above-mentioned casting method is then sintered to obtain an
It becomes an O sintered body and becomes a sputtering target.
However, the molded body is dried before sintering to remove the contained water. However, cracks are apt to occur in the initial stage of the drying, and the ITO molded body cannot be manufactured stably.

[0006] In order to solve this problem, it has been studied to prevent cracks from occurring by controlling the drying conditions of the cast molded body by devising various drying conditions, for example, reducing the drying speed. However, such a method has a disadvantage that productivity is extremely deteriorated.

The present invention has been made in view of such a conventional situation,
An object of the present invention is to provide a method for producing an ITO molded body capable of performing stable production by improving the strength of the molded body while preventing or generating cracks, while maintaining or improving the productivity in the casting method of the ITO slurry. And

[0008]

In order to achieve the above object, the present invention provides a method for producing an ITO molded article, which comprises preparing an ITO slurry containing a mixed powder of indium oxide and tin oxide, water, a dispersant, and a binder. In the method for producing an ITO molded body to be cast, a dispersant having a carboxyl group is added to adjust the viscosity of the ITO slurry before casting at 25 ° C. to 1.0 to 50 dPa · s, preferably 5 to 20 d.
It is characterized by adjusting to Pa · s.

In the method for producing an ITO molded article of the present invention, the dispersant having a carboxyl group has a weight average molecular weight in the range of 10,000 to 50,000 and a pH of 7 to 11. . The dispersant having a carboxyl group is a carboxylic acid polymer or copolymer neutralized with a basic solvent.

In the above method for producing an ITO molded article of the present invention, the dispersant having a carboxyl group is
It is characterized in that 0.1 to 3% by weight is added to the total weight of the indium oxide powder and the tin oxide powder. Furthermore,
Using a resin mold, 5 kg / cm ² or more and 10 kg / cm
It is characterized by being cast-molded at a molding pressure of less than ^2, and the molded body after demolding is aged, and the drying speed is 3.0 g.
/ Hr, followed by complete drying after initial drying.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventor has conducted intensive studies on the causes of cracks generated during initial drying of a molded article obtained by a casting method. 1) Moisture from the surface of the molded article to the inside immediately after demolding Distribution is non-uniform, 2) residual strain due to pressure during casting is released during drying,
Were found to be the main causes. That is, it was found that the molded body immediately after demolding had insufficient strength, and thus could not withstand the difference in shrinkage between the surface and the interior due to uneven moisture or residual strain, and cracks occurred.

Therefore, in order to solve the strength shortage of the molded body, the inventors conducted repeated investigations focusing on the relationship between the slurry viscosity of the ITO slurry and the molded body density. As a result, by using a dispersant having a carboxyl group, a small amount was obtained. Even with the addition of a dispersant, the slurry viscosity can be significantly reduced,
In addition, the inventors have found that the density of a molded article is improved without impairing the sedimentation stability, and the present invention has been accomplished.

That is, by adding a small amount of a dispersant having a carboxyl group, the slurry viscosity at 25 ° C. can be adjusted to 1.0 to 50.
dPa · s, preferably 5 ~ 20 dPa · s can be easily adjusted, thereby dramatically improving the fluidity and dispersibility of the slurry, the filling of the molded body is enhanced,
As a result of uniform casting, the density of the molded body is increased and the strength can be improved. As a result, even if there is a difference in shrinkage or residual distortion between the surface and the interior due to uneven moisture in the molded product, the molded product can have sufficient strength to withstand the difference and prevent cracking during drying.

As a means for improving the strength of the molded article, it is conceivable to increase the amount of the binder to be added. However, when the added amount of the binder is increased to 5% by weight or more, the deposition rate decreases during casting, and consequently, the density of the compact decreases, and the strength further decreases.

The dispersant having a carboxyl group in the present invention may be a commercially available one, and comprises a polymer having a carboxyl group as a functional group, for example, a polymer of a carboxylic acid such as maleic acid, acrylic acid or methacrylic acid. Alternatively, the copolymer is preferably neutralized with a basic solvent such as ammonia.

The dispersant having a carboxyl group preferably has a weight average molecular weight (Mw) in the range of 10,000 to 50,000 and a pH in the range of 7 to 11. When the amount average molecular weight (Mw) of the dispersant is out of the range of 10,000 to 50,000,
Since the adhesiveness and elasticity of the binder are lost, the molded article may be weakened. Further, the pH of the dispersant is 7 to 11
Outside the range, the slurry viscosity is 1.0 to 50 dPa · s.
Is not preferable because it is easy to deviate from the range and it becomes difficult to perform stable casting.

Next, the method for producing an ITO molded article according to the present invention will be specifically described. For example, first add water and the dispersant to a mixed powder of indium oxide and tin oxide, mix
Pulverize to a slurry, then add a desired amount of a binder, defoamer, lubricant, etc., knead the mixture,
Obtain an O slurry. At this time, in order to adjust the viscosity of the ITO slurry to the above-mentioned 1.0 to 50 dPa · s, 0.1 to 3% by weight of a carboxyl group based on the total amount of the raw material powders of indium oxide powder and tin oxide powder is required. May be added. Thereafter, the ITO slurry is cast into a predetermined mold to form an ITO molded body.

In the present invention, the viscosity of the slurry is measured by stabilizing the viscosity by leaving the ITO slurry before casting in a room maintained at 25 ° C. for 3 hours, and then extracting 100 cc into a beaker at random. JIS in a room kept at ℃
The measurement was performed using a single cylindrical rotational viscometer according to -K7117. The viscometer used was a Bistometron viscometer (SB type) manufactured by Shibaura System Co., Ltd., and the rotation speed was 60 rpm and the measurement time was 1 minute.

As the indium oxide powder and tin oxide powder as raw material powders, those having a specific surface area of 4 to 15 m ² / g, a maximum particle diameter of 4 μm or less, and a primary particle diameter of 0.2 μm or less are preferably used. If the ratio is out of this range, cracks are likely to occur during drying of the compact, and it is difficult to achieve high density during sintering.

The binder is preferably an aqueous acrylic emulsion, and the amount of the binder is preferably 0.5 to 5% by weight based on the total weight of the raw material powder in the slurry. still,
The above-mentioned aqueous acrylic emulsion, in an aqueous solution containing a surfactant, acrylonitrile, methacrylic acid ester, acrylic acid ester, methyl methacrylate, resin particles mainly containing a polymer such as methyl acrylate or a copolymer. What is dispersed. When the resin particle diameter of the binder exceeds 0.1 μm, the adhesion of the raw material powder to the particle surface becomes incomplete and flows out at the time of casting to cause segregation of the binder, so that the range of 0.05 to 0.1 μm is obtained. Is preferred.

The viscosity of the binder is preferably in the range of 1 to 50 dPa · s. If the viscosity is outside this range, the adhesive strength to the raw material powder particles decreases, and the viscosity of the slurry increases, so that a normal molded product cannot be obtained. The viscosity of the binder can be controlled by, for example, adding an acrylic acid resin added to the acrylic emulsion, and the amount of the binder resin is usually adjusted to 5 to 40% by weight of the whole resin. still,
As acrylic resin, higher acrylic acid ester,
Ethyl acrylate, butyl acrylate and the like are generally used.

The glass transition point of the binder is 27 ° C.
By doing so, the resin particles become soft and easily deformed, and the adhesive force of the raw material powder to the particle surface is improved. However, if the glass transition point is too low, the strength of the binder itself decreases, so that the temperature is preferably 15 ° C. or higher. Control of the glass transition point is performed by copolymerization of a hard component resin and a soft component resin. Examples of the hard component resin include methacrylate and acrylonitrile, and examples of the soft component resin include vinyl acetate, higher acrylate, higher acrylate, and ethylene. The glass transition point of the binder can also be controlled by adding a small amount of a plasticizer such as ethylene glycol, carbitol, xylene or the like, if necessary.

Furthermore, when methanol or ethanol is added to the binder, for example, 5 to 20% by weight based on the weight of the aqueous acrylic emulsion, the surface of the acrylic resin can be easily modified to be tacky, and the adsorption on the particle surface of the raw material powder can be easily achieved. By substituting water, the adhesive force to the powder particles can be improved. However, when the added amount of methanol or ethanol exceeds 20% by weight, solidification gradually starts, and 50% by weight.
Above this, it becomes difficult to adjust the slurry. As a method for adding the binder, it is desirable to add an appropriate amount of alcohol to the acrylic emulsion binder, stir and mix, and then add the resultant to the dispersant. In addition, in the case of stirring and mixing, controlling the stirring temperature to 25 to 40 ° C. has a great effect.

As an antifoaming agent, ether type, mineral oil type and the like are used. The addition amount is preferably 0.05% by weight or less based on the total weight of the raw material powder in the slurry. In the case where the defoaming agent is not added, if bubbles appear after the preparation of the slurry, it can be avoided by vacuum degassing while stirring the slurry. A small amount of lubricant is added to the slurry for the purpose of improving the filling property. As the type of the lubricant, stearic acid is preferable. The addition amount is preferably 0.05% by weight or less based on the total weight of the raw material powder in the slurry.

For mixing and pulverizing the raw material powder in the method of the present invention, a wet ball mill or a vibrating mill can be used. However, in order to obtain uniformly fine crystal grains and pores, the agglomeration efficiency of the aggregate is high. It is most preferable to use a high-speed medium stirring mill in which the dispersion state of the additive is good. As a ball used for pulverization, a ZrO ₂ ball having a diameter of 0.3 mm is used, and the peripheral speed is preferably about 10 m / s. Further, the filling rate of the powder is preferably about 80%. This mixture
During grinding, the dispersant is diluted with water and added to the slurry.

The stirring for forming the slurry is carried out for 5 hours or more using a stirring blade or the like, but preferably for 12 hours or more, the generation of cracks can be further suppressed. This is because by sufficient stirring, it is possible to improve the adhesion of the binder to the raw material powder particles, remove fine bubbles, and the like. When the slurry foams due to stirring, it is desirable to perform vacuum defoaming as necessary. The degree of vacuum at the time of defoaming is 76 cmHg or less, and the evacuation time must not exceed 1 hour. Evacuation at a high degree of vacuum or for a long time is not preferable because the properties and composition of the dispersion medium are impaired.

The ITO slurry which has been sufficiently degassed by vacuum is cast and molded using a mold such as gypsum or resin as usual. The viscosity of the slurry at the time of molding was 1.0 to 1.0 due to the addition of the dispersant having a carboxyl group as described above.
Within the range of 50 dPa · s, preferably 5 to 20 dPa · s
Adjust within the range of s. The mold used is preferably made of a resin having excellent strength and desorption properties, for example, a phenol resin. The molding pressure is 5 kg / cm ² or more. However, in the present invention, since the fluidity and dispersibility of the slurry are enhanced, even if the mold is made of resin, good filling properties can be obtained with a pressure of less than 10 kg / cm ² . Is obtained.

After casting, the mold is removed and dried.
When the aging treatment is performed for the purpose of removing the unevenness of the water distribution and the residual strain generated in the molded body immediately after the mold is released, the crack is more effectively prevented. That is, the molded body before drying obtained by casting is completely covered with a sheet having low moisture permeability made of polyvinyl chloride or the like, and the temperature is 20 to 40.
The aging treatment is performed by keeping the film in an oven in a dehumidifying atmosphere controlled at a temperature of 5 ° C. for 5 hours or more, or in a constant temperature and humidity chamber controlled at a temperature of 20 to 40 ° C. and a humidity of 85 to 98% or less.

In the process of drying the molded product, the initial drying conditions vary depending on the density of the molded product and the amount of the binder added, but it is necessary to select conditions such that the drying rate does not become 3.0 g / hr or more. The drying speed during the initial drying is 3.0 g /
If it exceeds hr, it may cause cracks,
Drying of only the surface proceeds, and internal drying is delayed, and the final drying time becomes longer. Preferably, the temperature is 30 to 40 ° C,
The initial drying can be completed in 3 to 10 days under the condition of a humidity of 75 to 85%.

When the initial drying is completed, no crack occurs even if the subsequent drying speed is high. This is because when the initial drying is completed, the strength of the molded body is remarkably improved together with the decrease in the water content. Therefore, the subsequent complete drying is 3
It can be performed in a dehumidifying and drying atmosphere at 0 to 150 ° C,
For example, at a temperature of about 100 ° C., water can be completely removed in one to two days.

The ITO of the present invention obtained as described above
The molded article has excellent molded article strength and does not crack even when dried. In addition, ITO in the present invention
The measurement of the strength of the molded body was performed by measuring the molded body sample at 30 × 10 × 10
The resultant was cut into a strip having a width of 25 mm, and subjected to a three-point bending test 10 times in a room kept at 25 ° C. to determine the anti-deposition strength. The bending tester is Autograph AG-5000 manufactured by Shimadzu Corporation.
Was used.

The ITO molded body of the present invention is sintered in an oxygen atmosphere to obtain a sintered body in order to finally obtain a sputtering target. When sintering is performed by introducing oxygen during the temperature rise process during sintering, a sintered body having a high density of 98% or more can be obtained. The oxygen flow rate when introducing oxygen is 2
If it is less than 1 liter / min, the effect of introducing oxygen is weakened, and if it exceeds 20 liter / min, it is cooled by the oxygen flow and the soaking in the sintering furnace is reduced.
The range of min is preferable.

The rate of temperature rise during sintering is 800 to 1
It is necessary to increase the heating rate between 500 ° C., especially between 1000 and 1300 ° C., to 1 to 10 ° C./min. That is,
The temperature range of 1000 to 1300 ° C is the temperature range in which the sintering of the raw material powder is most active, and the rate of temperature rise in this temperature range is 1
When the temperature is lower than ℃ / min, the crystal grain size growth becomes remarkable. On the other hand, if the heating rate is higher than 10 ° C./min, the soaking in the sintering furnace will be reduced, and the shrinkage during sintering will be distributed, causing cracks in the sintered body.

The sintering temperature is generally in the range of 1000 to 1500 ° C., 1400 to 1500 ° C. for obtaining a high density sintered body, and the sintering time is 15 hours or less. Sintering temperature is 100
If the sintering temperature exceeds 1500 ° C. or the sintering time exceeds 15 hours, the density of the sintered body is decreased or the crystal growth is remarkable due to the activation of evaporation.
It is not preferable because the crystal grain size and the pores become coarse.

[0035]

【Example】Example 1  Specific surface area 6m²/ G, 0.1 μm primary particle diameter
40.00 kg of indium powder and a specific surface area of 8 m²/ G, one
To 4.44 kg of tin oxide powder having a primary particle size of 0.1 μm or less
Acrylic and methacrylic acid with ammonium at 10.58 kg
Dispersant (solid content 40% by weight,
(Mw: 17000, pH 7.5)
5mm ZrO₂24 hours in a ball mill using balls
The mixture was ground and mixed to obtain a slurry having a concentration of 75% by weight.

10 kg of this slurry was taken out, and an acrylic emulsion binder (solid content: 40% by weight, viscosity: 46 dPa · s, resin particle size: 0.06 μm, Tg: 27 ° C.,
pH 9) 600 g and a stearic acid emulsion lubricant (solid content 30% by weight, LU-641 manufactured by San Nopco)
8) 2.7 g of an ether-based antifoaming agent (solid content: 100% by weight, 387 manufactured by San Nopco) were further added and kneaded to obtain an ITO slurry. The viscosity of this ITO slurry was 7.1 dPa · s.

Next, the ITO slurry was degassed in vacuum for 40 minutes, and further stirred for 5 hours.
It was cast into a phenolic ceraplast (Nikko) mold of × 750 × 10 mm at a pressure of 5 kg / cm ² for 45 minutes. After drying the demolded compact in a dehumidified atmosphere at 100 ° C., the compact density obtained from its dimensions is 3.58.
g / cc. Further, 3.0 g /
40 ° C. × for initial drying at a drying speed of hr or less.
It was dried in a thermo-hygrostat maintained at 80% RH for 80 hours.

When the ITO molded body obtained after the initial drying was taken out of a thermo-hygrostat to examine the occurrence of cracks, no cracks were found, and no cracks were found in the subsequent complete drying and sintering. The same slurry after the defoaming and stirring was cast into a phenolic ceraplast mold having a size of 70 × 70 × 10 mm at a pressure of 5 kg / cm ² for 30 minutes. 10m
m, and the three-point bending test was performed to measure the anti-deposition strength of the molded body immediately after demolding. The result was 0.53 kgf / m
It was m ^2.

[0039]Example 2  Specific surface area 6m²/ G, 0.1 μm primary particle diameter
40.00 kg of indium powder and a specific surface area of 8 m²/ G, one
To 4.44 kg of tin oxide powder having a primary particle size of 0.1 μm or less
Reaction of acrylic acid with ammonia in 10.58 kg of water
Dispersant (solid content 40% by weight, Mw: 300)
888 g of Zr having a diameter of 5 mm.
O₂Using a ball mill with a ball mill for 24 hours,
A slurry having a concentration of 75% by weight was obtained.

An acrylic emulsion binder (solid content: 40% by weight, viscosity: 46 dPa · s, resin particle diameter: 0.06 μm, Tg: 27 ° C.,
pH 9) 600 g and a stearic acid emulsion lubricant (solid content 30% by weight, LU-641 manufactured by San Nopco)
8) 2.7 g of an ether-based antifoaming agent (solid content: 100% by weight, 387 manufactured by San Nopco) were further added and kneaded to obtain an ITO slurry. The viscosity of this ITO slurry was 9.6 dPa · s.

Next, this ITO slurry was degassed in vacuum for 40 minutes, and further stirred for 5 hours.
A phenolic ceraplast mold of × 750 × 10 mm was cast at a pressure of 5 kg / cm ² for 45 minutes. After drying the demolded compact in a dehumidified atmosphere at 100 ° C., the compact density obtained from the dimensions was 3.52 g / cc. Further, in order to initially dry the demolded molded body at a drying speed of 3.0 g / hr or less, the molded body was dried for 80 hours in a thermo-hygrostat maintained at 40 ° C. × 80% RH.

When the occurrence of cracks was examined for the obtained ITO molded article, no crack was generated, and no crack was generated even in the subsequent complete drying and sintering.
The same slurry after the defoaming and stirring was used for molding and demolding in the same manner as described above, and the depositing strength of the compact immediately after demolding was measured by a three-point bending test.
It was mm ^2.

[0043]Example 3  Specific surface area 6m²/ G, 0.1 μm primary particle diameter
40.00 kg of indium powder and a specific surface area of 8 m²/ G, one
To 4.44 kg of tin oxide powder having a primary particle size of 0.1 μm or less
10.58 kg of water and ammonium styrene
Dispersant (solid content 40% by weight, M
w: 20000, pH 10.1) 888 g was added, and the
5mm ZrO₂24 hours in a ball mill using balls
The mixture was ground and mixed to obtain a slurry having a concentration of 75% by weight.

An acrylic emulsion binder (solid content: 40% by weight, viscosity: 46 dPa · s, resin particle size: 0.06 μm, Tg: 27 ° C.,
pH 9) 600 g and a stearic acid emulsion lubricant (solid content 30% by weight, LU-641 manufactured by San Nopco)
8) 2.7 g of an ether-based antifoaming agent (solid content: 100% by weight, 387 manufactured by San Nopco) were further added and kneaded to obtain an ITO slurry. The viscosity of this ITO slurry was 13.4 dPa · s.

Next, the ITO slurry was vacuum-degassed for 40 minutes, and further stirred for 5 hours.
A phenolic ceraplast mold of × 750 × 10 mm was cast at a pressure of 5 kg / cm ² for 45 minutes. After drying the demolded compact in a dehumidified atmosphere at 100 ° C., the compact density obtained from the dimensions was 3.42 g / cc. Further, in order to initially dry the demolded molded body at a drying speed of 3.0 g / hr or less, the molded body was dried for 80 hours in a thermo-hygrostat maintained at 40 ° C. × 80% RH.

When the occurrence of cracks was examined for the obtained ITO molded article, no cracks were generated, and no cracks were generated even after complete drying and sintering.
The same slurry after the defoaming and stirring was used for molding and demolding in the same manner as above, and the anti-deposition strength of the molded product immediately after the demolding by a three-point bending test was measured. As a result, 0.43 kgf /
It was mm ^2.

[0047]Example 4  Specific surface area 6m²/ G, 0.1 μm primary particle diameter
40.00 kg of indium powder and a specific surface area of 8 m²/ G, one
To 4.44 kg of tin oxide powder having a primary particle size of 0.1 μm or less
Reaction weight of acrylic acid with ammonia in 10.58 kg of water
Of the copolymer added to the acrylate polymer
Powder (solid content 40% by weight, Mw: 50,000, pH 7.
4) Add 888 g and add 5 mm diameter ZrO₂Use the ball
And crushed and mixed in a ball mill for 24 hours, with a concentration of 75% by weight.
Slurry.

An acrylic emulsion binder (solid content: 40% by weight, viscosity: 46 dPa · s, resin particle diameter: 0.06 μm, Tg: 27 ° C.,
pH 9) 600 g and a stearic acid emulsion lubricant (solid content 30% by weight, LU-641 manufactured by San Nopco)
8) 2.7 g of an ether-based antifoaming agent (solid content: 100% by weight, 387 manufactured by San Nopco) were further added and kneaded to obtain an ITO slurry. The viscosity of this ITO slurry was 10.8 dPa · s.

Next, the ITO slurry was vacuum-degassed for 40 minutes, and further stirred for 5 hours.
A phenolic ceraplast mold of × 750 × 10 mm was cast at a pressure of 5 kg / cm ² for 45 minutes. After the demolded compact was dried in a dehumidified environment at 100 ° C., the compact density obtained from the dimensions was 3.49 g / cc. Further, in order to initially dry the demolded molded body at a drying rate of 3.0 g / hr or less, the molded body was dried for 80 hours in a thermo-hygrostat maintained at 40 ° C. × 80% RH.

When the occurrence of cracks was examined for the obtained ITO molded article, no cracks were generated, and no cracks were generated even after complete drying and sintering.
The same slurry after the defoaming and stirring was used for molding and demolding in the same manner as described above, and the depositing strength of the compact immediately after demolding was measured by a three-point bending test.
It was mm ^2.

[0051]Comparative Example 1  Specific surface area 10m²/ G, oxidation with a primary particle diameter of 0.08 μm
40.00 kg of indium powder and a specific surface area of 8 m²/
g, 4.44 kg of tin oxide powder having a primary particle size of 0.1 μm or less
With pure water 12.46 kg and naphthalenesulfonic acid condensation
Dispersant (solids 4
0% by weight, Mw: 1000, pH 7.6) 888 g
In addition, ZrO with a diameter of 5 mm₂Ball mill using balls
And pulverized and mixed for 48 hours to obtain a slurry having a concentration of 71% by weight.
Was.

An acrylic emulsion binder (solid content: 40% by weight, viscosity: 46 dPa · s, resin particle size: 0.06 μm, Tg: 27 ° C.,
pH 9) 600 g and a stearic acid emulsion lubricant (solid content 30% by weight, LU-641 manufactured by San Nopco)
8) 2.7 g of an ether-based antifoaming agent (solid content: 100% by weight, 387 manufactured by San Nopco) were further added and kneaded to obtain an ITO slurry. The viscosity of this ITO slurry was 67 dPa · s.

Next, the ITO slurry was degassed in vacuum for 40 minutes, and further stirred for 5 hours.
A phenolic ceraplast mold of × 750 × 10 mm was cast at a pressure of 5 kg / cm ² for 45 minutes. After drying the demolded compact in a dehumidified atmosphere at 100 ° C., the compact density obtained from the dimensions was 3.13 g / cc.

In order to initially dry the demolded molded body at a drying rate of 3.0 g / hr or less, the molded body was dried for 80 hours in a thermo-hygrostat maintained at 40 ° C. × 80% RH. However, cracks occurred in the ITO molded body 28 hours after the start of drying. The same slurry after the defoaming and stirring was used to mold and demold in the same manner as in the above example, and the depositing strength of the molded article immediately after demolding by a three-point bending test was measured.
It was 3 kgf / mm ² .

[0055]Comparative Example 2  Specific surface area 12m²/ G, oxidation with a primary particle diameter of 0.07 μm
40.00 kg of indium powder and a specific surface area of 8 m²/
g, 4.44 kg of tin oxide powder having a primary particle size of 0.1 μm or less
Then, 12.46 kg of pure water and acrylic acid with ammonia
Neutralized and polymerized dispersant (solid content 40% by weight, Mw:
60000, pH 7.8) 888 g, 5 mm in diameter
ZrO₂Using a ball mill with a ball mill for 48 hours
Thus, a slurry having a concentration of 71% by weight was obtained.

An acrylic emulsion binder (solid content 40% by weight, viscosity 46 dPa · s, resin particle diameter 0.06 μm, Tg 27 ° C.,
pH 9) 600 g and a stearic acid emulsion lubricant (solid content 30% by weight, LU-641 manufactured by San Nopco)
8) 2.7 g of an ether-based antifoaming agent (solid content: 100% by weight, 387 manufactured by San Nopco) were further added and kneaded to obtain an ITO slurry. The viscosity of this ITO slurry was 80 dPa · s.

Next, the ITO slurry was vacuum-degassed for 40 minutes, and further stirred for 5 hours.
A phenolic ceraplast mold of × 750 × 10 mm was cast at a pressure of 5 kg / cm ² for 45 minutes. After drying the demolded molded body in a dehumidified atmosphere at 100 ° C., the molded body density obtained from the dimensions was 3.32 g / cc.

In order to initially dry the demolded article at a drying rate of 3.0 g / hr or less, it was dried for 80 hours in a thermo-hygrostat maintained at 40 ° C. × 80% RH. However, cracks occurred in the ITO molded body 36 hours after the start of drying. The same slurry after the defoaming and stirring was used to mold and demold in the same manner as in the above example, and the depositing strength of the molded article immediately after demolding by a three-point bending test was measured.
It was 7 kgf / mm ² .

[0059]Comparative Example 3  Specific surface area 10m²/ G, oxidation with a primary particle diameter of 0.08 μm
40.00 kg of indium powder and a specific surface area of 8 m²/
g, 4.44 kg of tin oxide powder having a primary particle size of 0.1 μm or less
Then, 12.13 kg of pure water and acrylic acid with ammonia
Neutralized and polymerized dispersant (solid content 40% by weight, Mw:
8000, pH 6.8) 888 g and a 5 mm diameter
ZrO₂24 hours grinding and mixing with a ball mill using balls
Thus, a slurry having a concentration of 71% by weight was obtained.

An acrylic emulsion binder (solid content 40% by weight, viscosity 46 dPa · s, resin particle diameter 0.06 μm, Tg 27 ° C.,
pH 9) 600 g and a stearic acid emulsion lubricant (solid content 30% by weight, LU-641 manufactured by San Nopco)
8) 2.7 g of an ether-based antifoaming agent (solid content: 100% by weight, 387 manufactured by San Nopco) were further added and kneaded to obtain an ITO slurry. The viscosity of this ITO slurry was 56 dPa · s.

Next, the ITO slurry was vacuum-degassed for 40 minutes, and further stirred for 5 hours.
A phenolic ceraplast mold of × 750 × 10 mm was cast at a pressure of 5 kg / cm ² for 45 minutes. After the demolded compact was dried in a dehumidified atmosphere at 100 ° C., the compact density obtained from the dimensions was 3.29 g / cc.

In order to initially dry the demolded molded body at a drying rate of 3.0 g / hr or less, the molded body was dried for 80 hours in a thermo-hygrostat maintained at 40 ° C. × 80% RH. However, cracks occurred in the ITO molded body 52 hours after the start of drying. The same slurry after the defoaming and stirring was used for molding and demolding in the same manner as in the above example, and the anti-deposit strength of the compact immediately after demolding was measured by a three-point bending test.
It was 5 kgf / mm ² .

The results obtained in the above Examples 1 to 4 and Comparative Examples 1 to 3, namely, the viscosity of the ITO slurry, the density of the compact, the transverse strength of the compact immediately after demolding, and the initial drying of the compact Table 1 below summarizes the occurrence of cracks in the process.

[0064]

[Table 1]

[0065]

According to the present invention, a dispersant having a carboxyl group, preferably having a Mw of 10,000 to 50,000 and a pH of 7 to
11 by adding a dispersant in the range of 11 to adjust the viscosity of the ITO slurry to 1.0 to 50 dPa · s.
It is possible to improve the density and strength of the molded product obtained by casting the TO slurry, and obtain an ITO molded product free from cracks in the initial drying or sintering after demolding. Therefore, a large-sized ITO molded body can be easily and stably manufactured by the casting method while maintaining or improving the productivity.

Claims (7)

[Claims] 1. An indium oxide powder and a tin oxide powder, water,
In a method for producing an ITO molded body by casting an ITO slurry containing a dispersant and a binder, a dispersant having a carboxyl group is added, and the slurry viscosity before casting of the ITO slurry is adjusted to 1.0 to 50 dPa · s at 25 ° C. A method for producing an ITO molded article, characterized in that the method comprises: 2. The method according to claim 1, wherein the viscosity of the ITO slurry before casting is adjusted to 5 to 20 dPa · s at 25 ° C. 3. The dispersant having a carboxyl group,
The weight average molecular weight is in the range of 10,000 to 50,000 and the pH is 7 to
The method for producing an ITO molded article according to claim 1, wherein the method is 11. 4. The dispersant having a carboxyl group,
The method for producing an ITO molded article according to claim 1, wherein the method is a polymer or copolymer of a carboxylic acid neutralized with a basic solvent. 5. The dispersant having a carboxyl group,
2. The composition according to claim 1, wherein said additive is added in an amount of 0.1 to 3% by weight based on the total weight of the indium oxide powder and the tin oxide powder.
5. The method for producing an ITO molded article according to any one of items 1 to 4. 6. The ITO according to any one of claims 1 to 5, wherein the molding is performed using a resin mold at a molding pressure of 5 kg / cm ² or more and less than 10 kg / cm ^2.
A method for producing a molded article. 7. The method according to claim 1, wherein the molded article after demolding is aged, dried initially at a drying speed of less than 3.0 g / hr, and then completely dried.
A method for producing a TO molded article.