JP2006339037A - Manufacturing method of glass spacer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method whereby a glass spacer having high dimensional accuracy can be obtained at a low cost. <P>SOLUTION: Glass, the arithmetic mean surface roughness Ra of which is within a range from 0.05μm to 1.2μm, is used as a glass base material, and after extending the glass while heating it, it is cut to a desired length to manufacture this glass spacer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a glass spacer, and more particularly to a method for manufacturing a glass spacer for flat display applications and the like that require high dimensional accuracy at a low cost.

  An alternative to a large and heavy cathode ray tube is a thin and light self-luminous flat electron beam excitation display. This flat electron beam excitation display includes a front plate made of a glass substrate having an image forming member formed on the inner surface, and a back plate made of a glass substrate on which an electron-emitting device group is mounted. The image forming member includes a phosphor that emits light when irradiated with an electron beam from an electron-emitting device. The front plate and the back plate are hermetically bonded to each other via a support frame to form a vacuum vessel that forms an airtight and atmospheric pressure resistant structure together with the support frame.

In such a flat electron beam excitation display, an electron beam source, a phosphor, and other components are formed in order to form an image by irradiating the phosphor with an electron beam to generate fluorescence. The inside of the vacuum vessel is maintained in a vacuum atmosphere of about 1.33 × 10 ⁻³ Pa (about 10 ⁻⁵ torr) or less. For this reason, as the display image on the display becomes larger, the front plate and the rear plate may be deformed or brought into contact with each other due to a pressure difference between the inside and outside of the vacuum vessel. In order to prevent this deformation or contact and to keep the distance between the front plate and the back plate constant, a plurality of glass spacers are inserted as an atmospheric pressure support member between the front plate and the back plate.

  This glass spacer is manufactured by stretching the base glass while heating, and then cutting the stretched glass to a desired length with a cutter or the like.

  Specifically, using a manufacturing apparatus in which two pairs of heaters that are independently controlled by a control device are provided inside a heating furnace having a substantially rectangular cross section, and a pair of stretching rolls is installed immediately below the heating furnace, A method has been proposed in which the base glass erected in the manufacturing apparatus is sequentially fed from the lower end to the heating furnace while controlling the supply speed by motor drive, and is stretched at a predetermined stretching speed while sandwiching the spacer glass drawn from the heating furnace. (See Patent Document 1).

As another manufacturing method, a material bar (base material) having a polygonal cross section whose side has been polished in advance is fixed to a mechanical system that can be lowered vertically, and inserted and melted sequentially from the lower end into a ring-shaped heating device. A method of stretching by a pair of drive belts installed below the heating device has been proposed (see Patent Document 2).
JP 2004-14199 A JP-A-7-144939

  In recent years, with the development for the practical application of flat display, the demand for higher accuracy is increasing for spacers compared to the conventional ones. In some cases, a deviation of less than 10 μm is allowed. Therefore, in order to ensure this accuracy with a good yield in the longitudinal direction, the surface condition of the base material is an important factor as well as the high accuracy of the drawing apparatus.

  When the surface of the base material is polished to a mirror surface or a state close to the mirror surface, it is considered that if the apparatus is operating stably, drawing can be performed with a variation of the outer diameter dimension of less than 0.20% of the target dimension. It is done. As conditions for stable operation, the apparatus must ensure that the gas flow in the furnace is stabilized, the speed of the take-up roll or belt, the linearity of the glass pass line, etc. is there. On the other hand, when the surface of the base material is rough, the deformation of the glass is not always stable during melting and stretching in the drawing furnace, and the target dimension is not exceeded despite the fact that the device is operating stably. A periodic outer diameter of about 0.5 to 1.0% is generated.

  Here, in Patent Document 1, there is no detailed description regarding the roughness of the surface of the base material and the width accuracy of the spacer after drawing, and the surface of the base material glass is almost fire-formed when heated and stretched. The processing accuracy does not matter so much, that is, the fired surface is microscopically flat because the minute unevenness of the base glass mold is not transferred. However, even if the microscopic flatness of the spacer surface after drawing is not a problem, the surface processing accuracy of the glass, that is, the surface roughness is a big problem from the viewpoint of dimensional stability in the longitudinal direction.

  A base material having a true circular cross-sectional shape can be mirror-finished relatively easily by mounting it on a glass lathe and heating and polishing the surface with heat such as flame while rotating. However, in a case other than a true circle, the glass is softened by surface processing by heat and surface tension is generated. In particular, the corner portion is deformed into a rounded shape. It is not easy to mirror finish the side of the polygonal base material.

  Therefore, in order to finish the side surface of the base material having a polygonal cross section to a mirror surface or a state close to the mirror surface, mechanical polishing is often applied. However, in order to finish the glass base material surface to a mirror surface by mechanical polishing, a lot of work time is required compared with thermal polishing, and the processing cost becomes high.

  As described above, the conventional method does not quantify the polishing finish level of the base material surface, that is, the optimum value of the surface roughness, and does not rely on costly mirror surface processing of the base material surface. The drawing technique has not been established yet. That is, the cost reduction of the surface finish of the base material and the drawing of the high-precision spacer are not always compatible.

  Accordingly, it is an object of the present invention to provide a manufacturing method capable of eliminating the above-mentioned drawbacks of the prior art and obtaining a glass spacer having high dimensional accuracy at a low cost.

  In order to achieve the above object, the glass spacer manufacturing method of the present invention is the glass spacer manufacturing method in which the glass spacer is manufactured by stretching the glass base material while heating it, and then cutting the glass spacer into a desired length. As a base material, a glass having an arithmetic average surface roughness Ra of 0.05 μm to 1.2 μm is used.

  In the glass spacer manufacturing method of the present invention, a glass spacer that separates both plates of a front plate having an inner surface on which an image forming member is formed and a back plate on which an electron-emitting device group is mounted is heated on the glass base material. In the method of manufacturing a glass spacer, which is manufactured by cutting to a desired length after stretching, the glass base material has a shape corresponding to the cross-sectional shape of the spacer, and its arithmetic average surface roughness Ra is 0.05 μm. A glass having a thickness of 1.2 μm to 1.2 μm is used.

  The glass may be soda lime glass.

  According to the present invention, by performing surface polishing so that the arithmetic average surface roughness Ra of the base material surface is in the range of 0.05 μm to 1.2 μm, a high-precision glass spacer having a width dimension accuracy within 10 μm is obtained. It becomes possible to manufacture at low cost.

In FIG. 1, the schematic of the glass spacer drawing apparatus used by this embodiment is shown.
This glass spacer drawing apparatus 10 includes a base material gripping part 5 for gripping the base material 1, a slide rail 7 for moving the base material gripping part 5 downward in the vertical direction, and a drawing furnace for melting the base material 1. 3, a laser-type outer diameter measuring device 9 for measuring the outer diameter size of the spacer drawn out from the lower opening of the drawing furnace 3, and arranged below the outer diameter measuring device 9, determining the final size and removing the spacer A take-up roll 11 to be taken up and a control system 13 for feeding back a signal from the outer diameter measuring device 9 to the take-up roll 11 are provided.

  The base material gripping part 5 is driven by a servo motor (not shown). The drawing furnace 3 is a muffle furnace made of high-purity carbon and having an inner diameter of 140 mm, and He gas is introduced into the core through a mass flow controller to prevent oxidative degradation. The outer diameter measuring device 9 is installed so that the laser irradiation direction is orthogonal to the spacer plate width surface, and always measures the width of the spacer. Spacer dimension data measured by the outer diameter measuring instrument 9, particularly a deviation signal from a reference value (for example, 3.0 mm in the present embodiment) is fed back to the take-up roll 11 through the control system 13 to make the outer diameter of the spacer constant. Accordingly, the speed of the take-up roll 11 is controlled.

Next, a method for manufacturing a glass spacer using the glass spacer drawing apparatus 10 will be described.
First, a soda-lime glass base material 1 having a substantially rectangular cross section having a width of 120 mm, a thickness of 6.0 mm, and a length of 1200 mm is connected to a base material gripping part 5 capable of precisely descending vertically, and the base material gripping part 5 is driven at a constant speed of 6.5 mm / min by a servo motor, and the base material 1 is fed into the core of the drawing furnace 3. The core of the drawing furnace 3 is heated to 700 ° C. in advance, and the base material 1 is melted in the drawing furnace 3.
Next, the base material 1 melted in the drawing furnace 3 is taken out from the furnace lower opening while maintaining its cross-sectional shape, and is held and taken up at a speed of about 10 m / min by the take-up roll 11 arranged oppositely.

  FIG. 2 shows the spacers when the glass base material whose surface has been previously ground by mechanical grinding until the surface roughness Ra by arithmetic average (hereinafter referred to as “arithmetic average surface roughness”) Ra is 1.0 μm is drawn. The fluctuation of the outer diameter is shown. The fluctuation width of the width dimension of the spacer over about 1.0 m was within ± 5 μm, and a highly accurate spacer could be stably drawn.

The arithmetic average surface roughness Ra on the surface of the glass base material is preferably 0.05 μm or more and 1.2 μm or less.
The reason why the arithmetic average surface roughness Ra of the glass base material surface is set to 1.2 μm or less is that the dimensional accuracy of the spacer after drawing can be kept within a high accuracy of 10 μm or less as in the examples described later.
On the other hand, the reason why the arithmetic average surface roughness Ra of the glass base material surface is set to 0.05 μm or more is because the processing cost by mechanical grinding of the base material surface is taken into consideration.

  In normal mechanical grinding, the grain size of the grindstone used in stages is reduced in steps of rough polishing, medium polishing, and finish polishing. However, as the particle size decreases, the cutting speed also decreases. For this reason, as the surface roughness is reduced, that is, as it approaches the mirror surface, the time required for polishing is accelerated.

Table 1 shows the required processing time per unit area (1 m ² ) for polishing soda-lime glass to each surface roughness by mechanical grinding.

  From the results in Table 1, it can be seen that the required time is abruptly increased particularly when Ra is smaller than 0.05 μm. The processing time is left as it is, which leads to the cost of processing the base material and the cost of the spacer. A mirror surface is most desirable in terms of the finished dimensional accuracy of the spacer, but from the results shown in Table 1, it is considered that Ra = 0.05 μm or more is desirable considering the balance between the target accuracy of the spacer and the processing cost.

  An experiment was conducted to clarify the correlation between the base material surface roughness and the longitudinal dimension variation of the drawing spacer, and to quantify the minimum necessary base material surface roughness that can suppress the outer diameter variation width to less than 10 μm.

  Specifically, a soda-lime glass base material 1 having a substantially rectangular cross section having a width of 120 mm, a thickness of 6.0 mm, and a length of 1200 mm is set in the glass spacer drawing apparatus 10 shown in FIG. The correlation between the surface roughness of the base material 1 when a 0 mm glass spacer was drawn and the longitudinal dimension variation of the spacer was examined. Regarding the surface roughness, three types of base materials having arithmetic average surface roughness Ra of 0.5, 1.2, and 1.5 μm having the above dimensions were prepared. For the measurement of the arithmetic average surface roughness, an ultra-deep shape measuring microscope VK-8550 manufactured by Keyence Corporation was used.

  The core temperature of the drawing furnace 3 was set to 700 ° C., and the above three kinds of base materials 1 were fed into the core at a constant speed at a speed of 6.5 mm / min. The spacer was pulled out at a rate of about 10 m / min by a pair of take-up rolls 11 below the drawing furnace 3, and the dimensional variation of the spacer when a spacer having a width of about 3.0 mm was drawn was comparatively evaluated.

  Here, the spacer width is originally measured by a laser-type outer diameter measuring device 9 directly under the furnace, and a deviation signal from a reference value is input from the control system 13 to the take-up roll 11 to perform feedback control, and a uniform width is obtained. In order to confirm the influence of the base material surface roughness on the outer diameter fluctuation of the spacer in this embodiment, the take-up roll is used at a constant speed of 10 m / min without using feedback control. 11 was driven.

3 to 5 show fluctuations in the outer diameter of the spacer over about 1.0 m after drawing a glass base material having arithmetic average surface roughness Ra of 0.5, 1.2, and 1.5 μm, respectively. Show.
As shown in FIG. 3, in the case of a relatively smooth base material having an arithmetic average surface roughness Ra of 0.5 μm on the surface of the base material, the variation width of the spacer at a length of 1 m was within ± 5 μm. Further, from FIG. 4, the base material with Ra of 1.2 μm showed a fluctuation of a period of several tens of mm, but the fluctuation width was within ± 10 μm.
On the other hand, from FIG. 5, although a short period of fluctuation was not observed in the base material with Ra of 1.5 μm, the fluctuation range greatly exceeded ± 10 μm.

  From the results of this example, it is clear that the arithmetic average surface roughness Ra of the base material surface needs to be 1.2 μm or less in order to keep the outer diameter variation width of the spacer within ± 10 μm. It was.

  In addition, in the said Example, although the example which used soda-lime glass as a base material material was shown, it is not limited to this, For example, silicate type glass, aluminosilicate type glass, aluminoborosilicate type Even when glass or the like is used, the same effect as soda lime glass can be obtained.

It is the schematic of the glass spacer drawing apparatus used in this embodiment. It is a graph which shows the dispersion | variation in the width dimension in the longitudinal position of the glass spacer drawn from the base material whose arithmetic mean surface roughness Ra is 1.0 micrometer. It is a graph which shows the dispersion | variation in the width dimension in the longitudinal position of the glass spacer drawn from the base material whose arithmetic mean surface roughness Ra is 0.5 micrometer. It is a graph which shows the dispersion | variation in the width dimension in the longitudinal position of the glass spacer drawn from the base material whose arithmetic mean surface roughness Ra is 1.2 micrometers. It is a graph which shows the dispersion | variation in the width dimension in the longitudinal position of the glass spacer drawn from the base material whose arithmetic mean surface roughness Ra is 1.5 micrometers.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base material 3 Wire drawing furnace 5 Base material holding part 7 Slide rail 9 Outer diameter measuring device 11 Take-up roll 13 Control system

Claims (3)

  In the glass spacer manufacturing method for manufacturing a glass spacer by stretching the glass base material while heating, and cutting the glass base material to a desired length, the arithmetic average surface roughness Ra is 0.05 μm to 1 as the glass base material. A method for producing a glass spacer, wherein glass having a thickness of 2 μm is used.   By stretching the glass spacer that separates both the front plate with the image forming member formed on the inner surface and the rear plate with the electron-emitting device group mounted thereon, while heating the glass base material, and then cutting it to a desired length In the manufacturing method of a glass spacer to be manufactured, glass having a shape corresponding to a spacer cross-sectional shape and an arithmetic average surface roughness Ra of 0.05 μm to 1.2 μm is used as the glass base material. A manufacturing method of a glass spacer.   The method for producing a glass spacer according to claim 1, wherein the glass is soda lime glass.

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