JP2005324987A - Ito molded product, ito sputtering target using the same and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a molded product from cracking at depressurization when manufacturing the molded product through cold isostatic press for obtaining an ITO sputtering target, and to prevent the molded product from cracking on processing. <P>SOLUTION: In a manufacturing method, an indium oxide powder, a tin oxide powder, water and an organic binder are mixed, ground, sprayed and dried to yield a granulated powder which is subsequently uniformly mixed and press-molded to yield the molded product which is subsequently baked to yield a sintered compact. Here, polyvinyl alcohol having a saponification number of 85-94 mol% and a polymerization degree of 200-700 is used as the organic binder and is added in an amount of 1.0-3.0 mass% against the total mass of the indium oxide powder and the tin oxide powder. Preferably, the molded product has a three-point bending strength of ≥6.7 MPa. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ITO molded body for obtaining an ITO (indium tin oxide) transparent conductive film widely used as a transparent conductive film, an ITO sputtering target produced from the molded body, and a method for producing the target.

  Examples of a method for producing a ceramic functional film such as an ITO transparent conductive film include a sputtering method, a vacuum deposition method, a CVD method, and a spray pyrolysis method. In particular, the sputtering method is widely used industrially because it can easily increase the area and obtain a high-performance film. In the sputtering method, an ITO sputtering target is used as a raw material.

  However, when an ITO transparent conductive film is produced by the sputtering method, if a low-density ITO sputtering target is used for sputtering, abnormal discharge occurs due to variation in resistance value, and film formation stability is impaired. Further, when the particles adhere and deposit on the ITO sputtering target, black deposits called nodules are generated, which similarly causes abnormal discharge. Furthermore, due to the generation of nodules, the film formation rate decreases, and further, an arc is generated and particles are deposited on the film. For this reason, the ITO sputtering target is required to have a high density.

  A high-density ITO sputtering target is produced using a molded body produced by a method such as a dry pressure molding method or a casting molding method. Among these, in the dry pressure molding method, an organic binder and a plasticizer are mixed with raw material powder having an average particle size of about 0.5 μm to 2.0 μm, and granules (granulated powder) of several tens μm to several hundred μm are mixed. The granulated powder is filled into a mold, rubber, or the like, and is usually pressed at a pressure of 100 MPa to 200 MPa using a uniaxial press or a cold isostatic press (CIP) and molded into a predetermined shape. Thus, a high-density molded body is obtained. As described above, by forming the granulated powder by pressurization, the density of the sputtering target obtained from the molded body is increased.

  In many cases, the granulated powder is prepared by mixing water with raw material powder, organic binder, dispersant and plasticizer, adjusting the slurry, and spraying and drying the resulting slurry with a spray dryer. The As the organic binder to be added, polyvinyl alcohol (PVA) is the most common, and usually 1 to 10 parts by mass is added to 100 parts by mass of the raw material powder. Polyvinyl alcohol having a saponification degree of 85 mol% to 99 mol% and a polymerization degree of 200 to 700 is generally used.

  The obtained molded body is subjected to end face processing if necessary, and then becomes a sintered body by degreasing and firing, and further processed into a predetermined shape to become a sputtering target.

  By the way, in recent years, displays and the like have become larger, and accordingly, it is desired to increase the size of the ITO sputtering target. In order to produce a large ITO sputtering target, it is necessary to first mold the raw material powder to obtain a large molded body. However, when a large molded body is molded by cold isostatic pressing, cracks are generated in the molded body at the time of depressurization, and the yield tends to decrease. Moreover, when processing a molded object as needed, a crack is easy to generate | occur | produce during the process, and such a crack is easy to become a starting point of a crack at the time of baking for sintering a molded object.

  In order to solve these problems, it is necessary to further improve the strength of the molded body. In order to increase the strength of the molded body, it is effective to increase the amount of the organic binder added. However, if the amount of the organic binder added is too large, as described in JP-A-8-277168, the degreasing time becomes longer, the density after sintering becomes lower, or the molded body by firing is reduced. Since the shrinkage increases, it becomes difficult to control the dimensions. Moreover, since the granulated powder becomes too hard and the granulated powder is difficult to be deformed at the time of pressure molding, the density of the molded body is lowered, and the strength may be reduced.

  Moreover, when the addition amount of an organic binder is increased too much, the collapsibility of granulated powder will worsen. As a result, the strength of the molded body decreases and the density of the sintered body decreases.

  In this way, the strength of the molded body is increased, and the molded body is made into a sintered body by firing, and the density of the sputtering target obtained by processing the sintered body is simultaneously achieved at a high level. It was difficult.

JP-A-8-277168

  An object of the present invention is to prevent cracks during decompression from occurring in a molded body and to process the molded body when producing a molded body by cold isostatic pressing to obtain an ITO sputtering target. At this time, an object is to prevent the occurrence of cracks.

  The manufacturing method of the ITO sputtering target of the present invention is a mixture of indium oxide powder, tin oxide powder, water, and an organic binder to form a slurry, and the slurry is sprayed and dried to obtain granulated powder, After the granulated powder is pressure-molded to obtain a molded body, the molded body is sintered and processed into a predetermined shape to produce an ITO sputtering target. Polyvinyl alcohol having a degree of 85 to 92 mol% and a degree of polymerization of 200 to 700 is used, and the polyvinyl alcohol is added in an amount of 1.0 to 3.0 mass% with respect to the total mass of indium oxide powder and tin oxide powder. It is characterized by doing.

The obtained molded body preferably has a three-point bending strength of 6.7 MPa or more, and the sintered body density obtained by sintering the molded body is 7.10 g / cm ^3. The above is desirable.

  The ITO molded body of the present invention was obtained by mixing indium oxide powder, tin oxide powder, water, and polyvinyl alcohol to form a slurry, and spraying and drying the slurry to obtain granulated powder. It is obtained by pressure-molding the granulated powder, and the three-point bending strength of the molded body is 6.7 MPa or more.

  According to the present invention, since a high-strength molded body is obtained, it is possible to prevent cracking during molding, cracking during processing of the molded body, and cracking of the molded body during firing due to the crack. Thereby, the yield can be improved.

  Further, by improving the collapsibility of the granulated powder, the conflicting purposes of improving the strength of the molded body and increasing the density of the target can be achieved simultaneously at a high level.

  In the present invention, the relationship between the chemical structure of polyvinyl alcohol, the strength of the molded body, and the density after sintering is studied, and when polyvinyl alcohol having a specific chemical structure is used as an organic binder, a favorable result is obtained. As a result, the present invention has been completed.

  In the method for producing an ITO sputtering target of the present invention, it is desirable that the three-point bending strength of the molded body is 6.7 MPa or more. If it is less than 6.7 MPa, cracking occurs during firing. The molded body strength test was measured using an autograph AG-5000 manufactured by Shimadzu Corporation.

  As the organic binder, polyvinyl alcohol having a saponification degree of 85 mol% to 92 mol% and a polymerization degree of 200 to 700 is added in an amount of 1.0 mass% to 3.0 mass% with respect to the total mass of indium oxide powder and tin oxide powder. In use. Thereby, the density of the large ITO sputtering target obtained by baking this molded object improves, while the obtained molded object has sufficient intensity | strength.

  When polyvinyl alcohol having a saponification degree of over 92 mol% or a polymerization degree of over 700 is used as an organic binder, the crushed property of the granulated powder at the time of molding is deteriorated, and voids in the molded body increase. The strength of the molded body is reduced, and the density of the large ITO sputtering target after firing is not improved. Here, the collapsibility of the granulated powder is evaluated by SEM observation.

  Further, when polyvinyl alcohol having a saponification degree of less than 85 mol% or a polymerization degree of less than 200 is used, the strength of the polyvinyl alcohol itself is lowered, and thus cracking occurs during molding.

  If the addition amount of the organic binder is less than 1.0 mass% with respect to the total mass of the indium oxide powder and the tin oxide powder, the strength of the molded body is lowered, and cracking occurs in the molding process. On the other hand, when it exceeds 3.0 mass%, the void | hole by polyvinyl alcohol will become large and the sintered compact density of the large sized ITO sputtering target obtained by sintering will fall. Therefore, shrinkage at the time of firing increases and cracks occur.

  When the polymerization degree of the added polyvinyl alcohol exceeds 700, cracks occur in the ITO sputtering target. This is probably because the degree of saponification of the added polyvinyl alcohol is too high, the crushed property of the granulated powder is deteriorated, and the adhesion area between the granulated powders is reduced.

(Example 1)
To 100 parts by mass of the raw material powder of indium oxide and tin oxide having an average particle size of about 0.5 μm, 1.25 parts by mass of polyvinyl alcohol having a saponification degree of 92.7 mol% and a polymerization degree of 500 is added, and the dispersant is 0.6 parts by mass. Part was added and water was added to prepare a slurry having a powder concentration of 60%.

  Using a spray dryer, granulation was performed from the obtained slurry to obtain a granulated powder having a particle size of about 60 μm. The obtained granulated powder was filled in a predetermined rubber mold and molded by a cold isostatic press at about 255 MPa. The obtained molded body was fired under the condition of 1550 ° C. to produce an ITO sputtering target.

  For the molded body, a 10 × 10 × 80 mm sample is used, a three-point bending test is performed under the conditions of a distance between fulcrums of 50 mm and a head speed of 0.5 mm / min, and the sintered body density of the sputtering target is measured after firing and processing. Went.

(Examples 2 to 4)
A large ITO sputtering target was prepared and measured in the same manner as in Example 1 except that the saponification degree of the added polyvinyl alcohol was changed to the value shown in Table 1. The measurement results are shown in Table 1.

(Examples 5-7)
A large ITO sputtering target was prepared and measured in the same manner as in Example 2 except that the amount of polyvinyl alcohol added was changed to the value shown in Table 1. The measurement results are shown in Table 1.

(Comparative Example 1)
A large ITO sputtering target was prepared and measured in the same manner as in Example 1 except that the saponification degree of the added polyvinyl alcohol was changed to the value shown in Table 1. The measurement results are shown in Table 1.

  The large ITO sputtering targets of Examples 1 to 7 had sufficiently high bending strength, and the target density was sufficiently high.

  The large ITO sputtering target of Comparative Example 1 had cracks and was not strong enough. This is considered to be because the degree of saponification of the added polyvinyl alcohol is too high, the crushability of the granulated powder is deteriorated, and the adhesion area between the granulated powders is reduced.

Claims (5)

  Indium oxide powder, tin oxide powder, water, and an organic binder are mixed to form a slurry. The slurry is sprayed and dried to obtain granulated powder, and the granulated powder is pressure-molded and molded. After obtaining the body, the molded body is sintered and processed into a predetermined shape, thereby producing an ITO sputtering target. As the organic binder, the saponification degree is 85 to 92 mol%, and the polymerization degree is 200 to 200. A method for producing an ITO sputtering target, comprising using 700 polyvinyl alcohol and adding 1.0 to 3.0% by mass of the polyvinyl alcohol to the total mass of indium oxide powder and tin oxide powder.   The method for producing an ITO sputtering target according to claim 1, wherein the three-point bending strength of the molded body is 6.7 MPa or more. ^{3. The} method for producing an ITO sputtering target according to claim 1, wherein a density of the sintered body of the ITO sputtering target is 7.10 g / cm ³ or more.   By mixing indium oxide powder, tin oxide powder, water, and polyvinyl alcohol into a slurry, spraying and drying the slurry to obtain granulated powder, and press molding the granulated powder An ITO molded body obtained, wherein the molded body has a three-point bending strength of 6.7 MPa or more. An ITO sputtering target obtained by the production method according to claim 1, wherein a density of the sintered body of the sputtering target is 7.10 g / cm ³ or more.