JPH0532334B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of manufacturing glass products by pressing using glass plates, and particularly to a method of forming glass products with large curvature such as funnels of cathode ray tubes (CRTs).

Conventional technology To form glass products such as funnels for cathode ray tubes from glass plates, heated glass plates are heated using a mold made of a material that does not have an affinity for glass, such as carbon, in an inert gas atmosphere such as nitrogen gas. The other method is to apply a mold release agent such as boron nitride (hereinafter referred to as BN) to a glass plate by spraying, heat the glass plate, and then press-form it using a metal mold. There is.

Problems to be Solved by the Invention In the method of forming a glass plate using a mold made of a material that has no affinity with glass, such as carbon, it is necessary to control the atmosphere with an inert gas.
This has resulted in disadvantages such as high equipment operating costs and difficulty in increasing productivity through continuous production.

On the other hand, the method of spraying a mold release agent such as BN onto a glass plate and then molding the glass plate using a metal mold is simple and easy to increase productivity, but the rate of adhesion of the mold release agent to the glass plate is low. is as low as approximately 50%, and in order to apply a mold release agent thick enough to prevent hot adhesion between the mold and the glass plate, expensive BN is wasted, which increases costs. In addition, if measures are required to prevent air pollution caused by BN scattering in the atmosphere, or if a flat surface is to be formed on a part of the glass product, the glass can be removed by applying a mold release agent. Another drawback was that the air between the plate surface and the mold surface was insufficiently removed, causing the glass molding surface to deform due to the trapped air.

Means for Solving the Problems In order to solve the above-mentioned drawbacks, the present invention provides a method of heating a glass plate above its softening point and press-molding it with a mold to form a glass molded part. , BN fine powder made into a paste with a dispersion medium is applied to at least the main part of the pressing surface of the glass plate, and the thickness of the fine powder when dried is 15 μm to 50 μm, and fine lattice-like recesses caused by the screen mesh are formed. It is applied by screen printing method to form glass products.

In the present invention, an aqueous solution of polyvinyl alcohol (hereinafter referred to as PVA), which is a water-soluble adhesive resin, is used as a dispersion medium, and BN fine powder with an average particle size of 5 μm is dispersed. It is preferable to make the paste into a viscous paste and apply it onto a glass plate by screen printing. The thickness of the coating film after drying is 15 μm to 50 μm.

At this time, if the viscosity is less than 5,000 CPS, a uniform printed surface cannot be obtained, whereas if the viscosity is more than 30,000 CPS, paste breakage etc. occur and a good printed surface cannot be formed.

In addition, in the present invention, increasing the viscosity of the BN fine powder paste to 25,000 to 30,000 is achieved by screen printing, which leaves screen mesh marks on the printed surface, and the coating film of the boron nitride fine powder paste. This is preferable for forming lattice-like recesses.

Note that it is also effective to add a small amount of polyethylene glycol or glycerin to adjust the fluidity of the BN paste and the vaporization speed of volatile components.

Function The present invention is a method for molding glass products by applying BN fine powder made into a paste with a dispersion medium to at least the main part of the press surface of the glass plate by screen printing method before heating the glass plate. There is no wasted use of the molding agent, it can be recovered, and there is no air pollution. By adding grid-like recesses to the coating film of the BN fine powder paste, air can be easily removed between the glass plate to be molded and the surface of the mold.

Example Examples of the present invention will be described below.

1 and 2 relate to one embodiment of the present invention.

BN fine powder with an average particle size of approximately 5 μm (trade name “Denka Boron GP” manufactured by Denki Kagaku Co., Ltd.) is mixed with a viscosity of approximately
Aqueous solution in weight ratio to 850CPS PVA aqueous solution
Added at a ratio of 27 parts of BN fine powder to 100 parts,
Mixed until homogeneous in an alumina mortar. This mixture is in the form of a paste with a viscosity of approximately 10,000 CPS, and is made into 200 meshes with an aperture ratio of 0.4 and an emulsion layer.
Using a 50 μm Tetron screen, the size is 150
Screen printing was performed on a glass plate measuring mm x 180 mm and having a thickness of 3 mm. After drying, the film thickness was measured and was approximately 30 μm. This is placed on a mold 1 heated to about 650°C as shown in Figure 1,
Glass plate G was heated to about 830°C using heater 2. At this time, the temperature of the mold was approximately 760°C. In this state, as shown in Figure 2, press the glass plate into the press mold 3.
was used to press and at the same time, the pressure was reduced through the vacuum exhaust hole 4 to form a glass product. After demolding and slow cooling, the glass product was immersed in water and subjected to ultrasonic cleaning to recover the BN fine powder adhering to the molded product.

3 to 5 relate to other embodiments of the present invention. 3 is a plan view of a glass product molded by the method according to the present invention, and FIG. 4 is a sectional view showing the glass product of FIG. 3 molded with the mold 1.

In this example, the above-mentioned PVA aqueous solution and
BN fine powder was mixed uniformly at a weight ratio of 100:34 to obtain a paste with a viscosity of about 30,000 CPS. This was placed on a 4 mm thick glass plate using a Tetron screen with a 120 mesh aperture ratio of 0.4 and an emulsion layer of approximately 50 μm.
Printed at a thickness of 30 μm. At this time, traces 6 of the screen mesh were left in the form of a grid on the BN fine powder paste layer 5, as shown in FIG. A glass plate was placed on the mold with this lattice-shaped surface facing the mold, and the glass plate was heated to about 830°C. In this state, press the glass plate with a pressure of 40Kgf/ ^cm2 ,
A glass product having a cross-sectional shape as shown in FIG. 4 was molded. At this time, the thickness of part A of the glass product is approximately
It was 1.4 mm, and part B was about 3 mm.

Effects of the Invention As explained above, according to the present invention, when applying BN fine powder paste to a glass plate, BN
The amount of BN fine powder used was reduced to about 1/3 by relying on the conventional spray method, as it is possible to prevent the fine powder from scattering or dissipating, and a portion of the fine BN powder can be recovered after molding. . Additionally, air pollution prevention equipment such as exhaust hoods is no longer required.

Furthermore, when pressing a glass plate at high temperatures to form a flat, thin surface, by adjusting the viscosity of the paste and the screen, and by creating depressions in the BN fine powder paste layer with the screen mesh, it is possible to , deformation of the thin plane (plane A) after pressing due to residual air between the glass and the mold no longer occurs.

[Brief explanation of the drawing]

The drawings show examples of the present invention, in which Fig. 1 is a cross-sectional view showing a state in which a glass plate placed on a mold is being heated, and Fig. 2 is a cross-sectional view showing a state in which a glass plate is press-molded. 3 is a plan view of the glass product molded according to the present invention; FIG. 4 is a vertical sectional view showing the glass product of FIG. 3 molded with mold 1; and FIG. The figure is a longitudinal cross-sectional view showing a layer of BN fine powder paste coated on the surface of a glass plate. G: glass plate, 1: mold, 2: heater,
3: Press mold, 4: Exhaust hole, 5: BN fine powder paste layer.

Claims (1)

[Claims] 1 In a method of heating a glass plate above its softening point and press-forming it with a mold to form a glass molded product, prior to heating the glass plate, at least a major part of the pressed surface of the glass plate is coated with a dispersion medium in the form of a paste. The fine boron nitride powder prepared in the above process was applied by screen printing so that the dry thickness of the fine powder was 15 μm to 50 μm, and fine lattice-like recesses due to the screen mesh were formed. A method for forming glass products, which is characterized by the following steps: