JPH09278458A - Molding die for glass and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a molding die having excellent mechanical strength and release property at high temp. which hardly produces defects on the surface of a formed glass by using a stainless alloy as the base body and forming a specified coating film on the outermost surface of the molding face. SOLUTION: This molding die consists of a stainless alloy as the base body and has a specified coating film on the outermost surface of the molding face. The coating film consists of an alloy of one or more iron group elements in the periodical table and one or more group VI elements (except for Cr) or Re (e.g. Ni-W alloy) as a matrix and contains carbon black having preferably 0.001 to 0.5μm average particle size dispersed in the matrix preferably by 0.1 to 15wt.% density. The coating film is preferably formed to 1 to 500μm thickness. More preferably, a thin film essentially comprising one or more elements selected from VIII to XI groups in the periodical table (e.g. Ni) is formed to 0.1 to 50μm thickness between the stainless base body and the outermost surface coating film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for molding glass, and more particularly to a mold for molding glass for television cathode ray tubes and a method for producing the same.

[0002]

2. Description of the Related Art A television cathode ray tube is manufactured by separately forming a front panel and a funnel-shaped funnel and a neck, applying phosphor on the inner surface of the panel, attaching electrodes, and then connecting them. Therefore, extremely strict quality control is required for the properties of the inner surface of the panel. Molding of the panel is performed by loading molten glass at a high temperature of about 1000 ° C. into a mold and pressing a metal mold (plunger) against the glass. The mold is required to have properties such as mechanical strength, heat resistance, chemical stability against high temperature glass, and generation of defects such as microcracks on the surface of the molded glass.

As a molding die suitable for such a purpose,
Conventionally, chromium alloy or nickel-tungsten alloy plating is applied on a stainless steel alloy, or for bottle making, graphite particles having lubricity are dispersed from its own layered crystal structure in a nickel-based matrix coating. What has been done (for example, Japanese Patent Publication No. 7-35259) has been used. Since the plating film deteriorates with use, the mold substrate is recycled by peeling off the film and newly plating.

However, the chromium plating suitable for the mold includes a Sargent bath, a mixed catalyst bath, a high efficiency bath, etc.
There are drawbacks in that the glass surface is likely to be scratched during molding, a release agent must be frequently applied, corrosion is easily caused by halogen, and highly toxic hexavalent chromium is contained.

On the other hand, when the nickel-tungsten plating film developed in recent years is used as a surface film of a panel molding die, the release agent is applied less frequently than chromium, but the tungsten contained in the film is not required. Since it is easily oxidized and its mechanical strength at high temperature is not always sufficient, it has the drawback that it tends to cause non-uniformity of the panel surface.

Further, in the nickel-tungsten plating film using graphite as dispersed particles, graphite itself is easily broken into layers due to its crystal structure, and flat particles having a large aspect ratio with a long side of several to several tens of μm are preferred. It is difficult to obtain isotropically small particles, and when a film is formed by the dispersion plating method using these particles, the flat surface properties of the die surface required for the inner surface of the panel are obtained. There is a drawback that it is difficult to obtain.

[0007]

With respect to the application of the release agent, this work requires a high degree of skill, and if the release agent is peeled from the mold, it may cause a defect on the panel surface. Therefore, there is a demand for the development of a mold that does not require the release agent coating.

[0008]

Means for Solving the Problems The inventors of the present invention have made earnest studies on a mold for glass molding in which a release agent is used less frequently and scratches on the glass surface are less likely to occur. An alloy composed of one or more iron group elements and one or more group 6 elements (excluding chromium) or rhenium was used as a matrix on the outermost surface of the molding surface portion, and carbon black was contained in the matrix as dispersed particles. A glass molding die with a coating is less likely to be scratched on the glass surface during molding than conventional chromium coatings, nickel tungsten coatings, and nickel coatings containing dispersed graphite particles, and the surface roughness of the molding surface can be controlled well. It has been found that the mechanical strength at high temperature and the mold releasability are excellent and the mold life is longer than that of the chromium plating film, and the present invention is provided.

Further, the present invention provides a method for manufacturing a glass molding die in which the above coating film is formed on the outermost surface of the molding surface portion of the die by a dispersion plating method.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below along with embodiments. In the present invention, an electroplating method or a chemical plating method can be applied to the method for forming the outermost surface coating on the mold. Above all, the electroplating method is preferable because it has a relatively low cost.

The matrix in the coating film is an alloy composed of at least one iron group element consisting of iron, cobalt and nickel and at least one group 6 element (except chromium) or at least two elements of rhenium. To use. In particular, it is preferable to use nickel as a main component from the viewpoint of cost and environmental protection, and if one or more elements of tungsten, molybdenum, or rhenium of Group 6 elements other than chromium are added to these,
It is more preferable in terms of oxidation resistance. In addition to these matrix active ingredients, the inclusion of impurities such as phosphorus and boron is acceptable as long as they are in a very small amount that does not substantially affect the coating.

If the thickness of the coating is less than 1 μm, it is susceptible to oxidation and mechanical deformation due to high temperature, and the thickness is 500 μm.
If the thickness is thicker, it takes time to form a coating, which exceeds the technically and cost-effective range.

The presence of carbon black in the coating as dispersed particles has the effect of increasing the mechanical strength of the coating at high temperatures and imparting lubricity. In order to obtain these effects sufficiently, carbon is required. The black concentration is preferably 0.1 to 15% by weight. Further, the average particle size of the dispersed particles is preferably 0.001 to 0.5 μm in order to form a plated film for obtaining a smooth molding surface.
Further, 0.003 to 0.3 μm is more preferable in order to form a flat molding surface with high precision suitable for a cathode ray tube panel or the like.

Since carbon black itself is more easily pulverized than graphite, which is known to have excellent releasability due to its layered crystal structure, it can be made finer and more uniform in the matrix by the plating method. Since it can be dispersed, it is particularly suitable for a glass molding die that has strict quality control standards for surface properties, from the viewpoint of enabling precise roughness control of the surface of the molding die.

Carbon black is a particulate carbon material obtained by incomplete combustion or thermal decomposition of hydrocarbons such as natural gas and petroleum in the gas phase. Depending on the production method, channel black, furnace black, thermal black, lamp black, Rollers and disc blacks are roughly classified, and those using acetylene as a raw material are called acetylene blacks, and any carbon black can be used in the present invention.

Between the die substrate and the outermost alloy coating, 8
By forming a thin film containing at least one metal selected from Group 10, Groups 9, 10 and 11 these bonds can be strengthened and the outermost surface alloy coating can be easily produced. Examples of one or more metal elements selected from Groups 8 to 11 include iron, ruthenium, cobalt, rhodium,
Nickel, palladium, platinum, copper, silver, gold and the like are preferable.

For example, nickel, cobalt, iron, chromium, palladium, or the like is formed by a thin film forming method such as plating, CVD, PVD, or thermal spraying. In particular, the plating method is suitable in terms of film forming rate, smoothness, cost and the like. Further, it is preferable that the content of these elements as the main component is 40 to 100% in order to utilize the characteristics of these elements. If the thickness of the thin film is less than 0.1 μm, it is difficult to effectively cover the entire surface, and if it is more than 50 μm, the residual strain increases and the meaning of the intermediate layer is lost.
Is preferred.

As the base material of the mold, martensitic stainless steel is preferable from the viewpoints of mechanical strength, corrosion resistance, thermal conductivity, thermal expansion characteristics and the like.

[0019]

The function of the dispersion-plated coating of the present invention is remarkably reduced when used at high temperature. The reason for this is not necessarily clear, but by the dispersed particles are dispersed and fixed in the metal, at least a part of the contact with the molten glass will be carried out through the carbon black of the dispersed particles, high temperature, The surface energy is greatly different from that of a matrix metal or alloy whose surface is oxidized by use in the atmosphere. It is difficult to wet, and it is brittle compared to the matrix. By supplying a part of it,
This is probably because it acts as a lubricant.

Further, the dispersion plating film of the present invention has higher mechanical strength at high temperature than the chromium film and the nickel tungsten film. Although the reason is not always clear, by fixing the dispersed particles dispersed in the metal, the deformation of the matrix at high temperatures is suppressed,
And because the fine irregularities due to the dispersed particles and the low thermal conductivity compared to the matrix of the dispersed particles, the thermal contact with the molten glass and the thermal conduction are reduced, and the temperature rise of the mold is substantially suppressed. Conceivable.

[0021]

EXAMPLES Examples of the present invention (Examples 1 and 2) and comparative examples (Examples 3, 4, and 5) will be shown below, but the present invention is not necessarily limited thereto. High dimensional accuracy like a CRT panel,
It can be applied to various glass molding dies as well as molding dies that require high quality.

(Example 1) SUS420J2 (JISG43
03) Using a nickel chloride bath on the mold surface of the substrate, 2μ
a nickel layer of m thickness is deposited, then nickel sulfate,
Carbon black-dispersed nickel-tungsten alloy (70% by weight: 30% by weight) in which 5% by weight of carbon black having an average size of 0.05 μm is dispersed using a plating bath containing sodium tungstate and citric acid as its main components. And an outermost coating having a film thickness of 11 μm was formed. A hardness test and a Taber abrasion test were performed on this coating, and a CRT panel was molded using a mold provided with this coating. The results are shown in Table 1.

(Example 2) SUS420J2 (JISG43
03) Using a nickel chloride bath on the die surface of the substrate.
A nickel layer having a thickness of 5 μm is deposited, and thereafter, a plating bath containing cobalt sulfate, nickel sulfate, sodium tungstate, sodium molybdate, and citric acid as main components is used to form carbon black having an average size of 0.1 μm. Carbon black dispersed cobalt-nickel-molybdenum-tungsten alloy (25 wt% dispersed)
% By weight: 45% by weight: 10% by weight: 20% by weight) to form an outermost surface coating having a film thickness of 11 μm. A hardness test and a Taber abrasion test were performed on this coating, and a CRT panel was molded using a mold provided with this coating.
The results are shown in Table 1.

(Example 3) SUS420J2 (JISG43
03) On the die surface of the substrate, a plating bath containing chromium sulfate as a main component was used to form an outermost surface coating of chromium having a thickness of 10 μm. A hardness test and a Taber abrasion test were performed on this coating, and a CRT panel was molded using a mold provided with this coating. The results are shown in Table 1.

(Example 4) SUS420J2 (JISG43
03) Using a nickel chloride bath on the mold surface of the substrate, 2μ
a nickel layer of m thickness is deposited, then nickel sulfate,
Graphite-dispersed nickel-tungsten alloy in which 8% by weight of graphite having an average size of the long side of 3 μm is dispersed in an aqueous solution containing sodium tungstate and citric acid as main components and graphite particles are dispersed therein. An outermost surface coating having a film thickness of 16 μm composed of (68% by weight: 32% by weight) was formed. A hardness test and a Taber abrasion test were performed on this coating, and a CRT panel was molded using a mold provided with this coating. The results are shown in Table 1.

(Example 5) SUS420J2 (JISG43
03) Using a nickel chloride bath on the die surface of the substrate.
A nickel layer having a thickness of 5 μm is deposited, and then a plating bath in which graphite particles are added and dispersed in an aqueous solution containing nickel sulfate, sodium tungstate, and citric acid as its main components is used, and the long side has an average size of 5 μm. An outermost surface coating made of a graphite-dispersed nickel-tungsten alloy (72% by weight: 28% by weight) having a film thickness of 17 μm in which 5% by weight of graphite particles were dispersed was formed. A hardness test and a Taber abrasion test were performed on this coating, and a CRT panel was molded using a mold provided with this coating. The results are shown in Table 1.

In Examples 1 to 5, 62.0% by weight of silicon oxide, 7.5% by weight of sodium oxide, 8.1% by weight of potassium oxide, 11.6% by weight of strontium oxide and barium oxide were used as glass for cathode ray tube panels. CRT glass containing 2.2% by weight and 8.6% by weight of zirconium oxide and the like was used.

In Table 1, the Taber index, panel molding characteristics, and coating frequency are shown as relative values when Example 3 is set to 10.

[0029]

[Table 1]

[0030]

As can be seen from the examples, one or more iron group elements and one or more 6 group elements (excluding chromium) are formed on the outermost surface of the molding surface of a die using a stainless alloy as a base. Or, with an alloy made of rhenium as a matrix, by forming a coating film containing carbon black as dispersed particles in the matrix, excellent releasability as compared with a conventional chromium coating film, less likely to scratch the glass surface,
Moreover, the mechanical strength at a high temperature is superior to that of the graphite-dispersed nickel-tungsten coating film, and the smooth surface texture can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiromi Takahashi 1150 Hazawa-machi, Kanagawa-ku, Yokohama, Kanagawa Prefecture Asahi Glass Co., Ltd. Central Research Laboratory

Claims (3)

[Claims] 1. A carbon alloy comprising a stainless steel alloy as a base, and an alloy of one or more iron group elements and one or more 6 group elements (excluding chromium) or rhenium as a matrix on the outermost surface of the molding surface. A glass molding die, comprising a coating film containing black as dispersed particles in the matrix. 2. Between the stainless substrate and the outermost coating, 8
The glass molding die according to claim 1, comprising a thin film containing, as a main component, one or more elements selected from Group 10, Group 9, Group 10 and Group 11. 3. An alloy consisting of one or more iron group elements and one or more group 6 elements (excluding chromium) or rhenium is provided as a matrix on the outermost surface of the molding surface of a die based on a stainless alloy. The method for producing a glass molding die is characterized in that a coating film containing carbon black as dispersed particles in the matrix is formed by a dispersion plating method.