JPH0542377B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a glass molding method.

BACKGROUND ART In recent years, with the development of electronics, the demand for glass parts has increased. Many types of glasses are being developed, not only in terms of their composition and properties, but also in their shapes. Typical shapes of glass include plates, powders, tubes, capillaries, rods, disks, fibers, etc., and the present invention relates to a method for forming glass rods.

Below, as an example to explain the prior art, a sealing glass for a magnetic headgap will be taken up and explained. Figure 2 shows a typical manufacturing process for magnetic heads used in VTRs.

Material is extracted from a ferrite ingot (a), and the material is shaped into a rod of an appropriate size by external grinding (b). Next, grooves for the reinforced glass are made using track processing (c), and the glass is molded into these grooves.
(d) to do. Next, the excess glass is ground, and the gap surface is polished (e) after winding. Next, after sputtering gap glass, adhesion and gap formation (f) are performed. Next, chip it (g) and polish the sides.
(h) to an appropriate size. Next, glue the chip to the base (i), polish the tape running surface (j), and wind the wire (k).
to complete the head.

In step (d) above, the molded glass generally has a rod shape, and recently, rectangular cross sections have been used rather than circular ones.
The reason for this is that in the case of a circular rod, as shown in Fig. 3, a back groove 9 is provided on the opposite side of the track groove of the ferrite rod 8 to prevent the rod 7 from rolling.
Although the tilting jig 10 must be used, in the case of a rectangular shape, as shown in FIG. 4, the above two points do not need to be considered. Although FIG. 4 shows a rectangular rod as an example, a triangular rod may also be used.

There are typically two methods for forming polygonal rods, such as triangles or squares, which are conventionally used for such purposes. One method is to cut a glass block (Fig. 5a) to the desired thickness using a diamond cutter or the like (Fig. 5b, c). However, since this method first uses water for cutting, there is a problem in that the glass near the cut surface is likely to change in quality. Second, cut marks remain on the cut surface and the glass surface becomes rough and opaque. For these two reasons, molding with such rods leaves air bubbles in the glass. This caused demagnetization of the recording signal, scratches on the tape, and the tendency for the chip to break in the completed head.

Another method is to use the glass block diagram (6th
In this method, the material shown in Figure a) is cut into pieces approximately 10 times thicker than the desired thickness (Figure 6B), and then heated and stretched (Figure 6C). However, even with this method, deterioration of the quality of the glass near the cut surface cannot be avoided, and therefore, when glass molding is performed using the rod after stretching, the same problem occurs.

Taking the above conventional examples into consideration, it is necessary to use no water at all when molding square rods, and it is necessary that the surfaces of the obtained rods be transparent and smooth.

Problems to be Solved by the Invention In the conventional method of forming glass rods, scratches are formed on the cut surface and bubbles remain during molding, resulting in deterioration of transparency. Also, the glass block is mechanically fragile.

In order to solve the above-mentioned problems, the present invention provides a molding method for obtaining transparent and smooth polygonal glass rods without using water during molding.

Means for Solving the Problems The present invention involves pouring molten glass into a polygonal slit provided on the dividing surface of a mold that can be divided into two parts.
forming a seed rod with a polygonal cross section that is 5 to 20 times thicker than the final desired thickness; heating the seed rod to a temperature 100 to 150 degrees Celsius higher than the softening temperature of the glass;
It is characterized by a step of stretching and shaping.

Effects According to the method of the present invention, it is possible to easily obtain a glass rod that is transparent, smooth, and has a polygonal cross section without deterioration of the glass surface.

EXAMPLE The glass forming method of the present invention will be explained with reference to FIG. In the figure, glass 1 is melted in a crucible 2, and the crucible 2 is heated from the outside using an electric furnace or the like. The molten glass 1 is poured into a polygonal slit 4 provided on the dividing surface of the mold 3 and left to cool to obtain a seed rod. Although a rectangular slit is illustrated here, a triangular seed rod can be obtained by using one side of the mold without V-grooving.
The mold is divided, the seed rod 5 is removed, and it is heated and expanded to obtain a polygonal rod 6 of the desired thickness.

Example 1 SiO ₂ = 4%, B ₂ O ₃ = 13%, PbO = 80 in weight%
%, ZnO = 1%, Al ₂ O ₃ = 2% glass (softening temperature 400℃) was placed in a crucible, and after heating to 900℃, one side
The mixture was poured into a stainless steel mold with a rectangular slit of 10 mm and 100 mm in length, and allowed to cool. The formed seed rod was removed from the mold, heated to 500-520°C and stretched to obtain a 1 mm square rod. The surface of the obtained rod was smooth and transparent.

The process (Fig. 3d) was carried out using this rod. The conditions were a temperature of 480°C and a time of 30 minutes. No bubbles were observed in the glass after completion of the process. As a result, the yield in the chip cutting process (Fig. 3g) was over 85%. It was also possible to mold the rod even if the thickness of the seed rod was 5 mm square or 20 mm square.

If you pour molten glass into a mold that is not a two-part mold, but simply has a rectangular hole, you will not be able to pull out the glass from the hole, and you will not be able to obtain a seed rod. Ta.

Also, if the seed rod is thinner than 5 mm, it may be difficult to pour the molten glass into the slit, or even if it is poured successfully, it may solidify in the middle of the slit.
There were cases where the seed rods could not be obtained because they broke when removed from the mold. Also, if it is thicker than 20mm, the inside of the seed rod will be heated during heating and stretching.
The temperature had to be raised to over 520°C, which softened the glass so much that it became a rod with a circular cross section.

Furthermore, if the heating temperature of the seed rod is lower than 500℃,
It was difficult to draw the rod because the glass was not sufficiently softened. When the temperature was higher than 520°C, the cross section became a circular rod as mentioned above.

Comparative Example 1 Using the glass of Example 1, a square rod was obtained by the conventional method shown in FIG. First, glass is melted in a crucible at 900℃, then poured into a stainless steel mold.
A block diagram (Figure 5a) of 20 x 20 x 25 mm was made. After gluing and fixing this on an alumina plate, it was cut into 1 x 20 x 25 mm plates (Fig. 5b) using an internal diamond cutting machine, and the plate was glued and fixed on another alumina plate, and further cut into 1 mm Corner, length 25mm rod (5th
Figure c) was obtained. The feeding speed of the diamond saw was 15 mm/min; water was used for cooling.

In order to investigate the deterioration of the glass on the rod surface, the surfaces of the rod according to this example and the rod according to Example 1 were examined.
When the Pb/Si ratio was examined by ESCA analysis and the intensity of the 4f7/2 peak of Pb and the 2p peak of Si, the rod ratio in this example was 2, and the rod ratio in Example 1 was 10. Ta. From the above results, it is clear that on the surface of the rod of this example using water during cutting, the Pb in the glass
was eluted, and it was found that the amount was 1/5 compared to Example 1.

Further, the process using the rod of this example (Fig. 3 d)
When this was done, many bubbles were created in the glass. As a result, in the chip cutting process (Fig. 3g), approximately 7
It was split.

Comparative Example 2 Using the glass of Example 1, a square rod was obtained by the conventional method shown in FIG. Block (Figure 6a)
used Comparative Example 1, and cut it into a 10 x 10 x 100 mm block (No. 6) using an internal diamond cutting machine.
Figure b). The cutting conditions were the same as in Comparative Example 1, and water was used for cooling. Block b was heated to about 500°C in an electric furnace and stretched to obtain a 1 mm square rod (Fig. 6c).

When the surface of the glass rod was analyzed by ESCA in the same manner as in Comparative Example 1, the Pb/Si ratio was 2, and the alteration of the surface was obvious. In addition, many air bubbles were observed in the glass after the completion of the step (FIG. 3d). As a result, approximately 70% of the chips were broken during the chip cutting process (Fig. 3g).

Example 2 SiO ₂ = 35.4%, PbO = 50.7%, ZnO =
4.8%, Na ₂ O = 4.8%, K ₂ O = 3.8%, As ₂ O ₃ = 0.5
% glass (softening temperature 570℃), the heating temperature of the crucible was 1400℃, and the heating temperature of the seed rod was 700-720℃.
It was molded in the same manner as in Example 1 except that.

The process (Fig. 3d) was carried out using this rod. The conditions were a temperature of 750°C and a time of 30 minutes. No bubbles were observed in the glass after completion of the process. As a result, the yield in the chip cutting process (Fig. 3g) was over 90%.

Note that when the heating temperature of the seed rod was set outside the above range, molding could not be performed or the rod became circular as in Example 1.

Example 3 Using the glass of Example 2, a rod was obtained by the method of Comparative Example 1. When the process (Fig. 3 d) is carried out using this rod, many bubbles are generated in the glass.
As a result, approximately 30% of the chips were broken during the chip cutting process (Fig. 3g).

In addition, in the above embodiment, an example of obtaining a rod used in the manufacture of a magnetic head was described in detail, but the molding method of the present invention is also applicable to the manufacture of glass rods used for sealing and sealing various electronic parts, and furthermore to the manufacture of optical fibers. Needless to say, it is also applicable to

Furthermore, it is clear that the present invention is not limited to the molding of triangular and square rods; for example, trapezoidal or hexagonal rods can also be formed by simply changing the slits in the mold.

The composition of glasses suitable for the present invention is at least in weight percent: _SiO2 = 2-7%, _B2O3 = _4-13 %, PbO
=70 _~ 85%, ZnO=1~7%, _Al2O3 =0~5
%, CdO=0 to 15% is desirable. More preferably at least in weight percent, _SiO2 = _3.5-5.5 %, _B2O3
=8~9%, PbO=73~75%, ZnO=2~6.5%,
Al ₂ O ₃ = 1 to 2.5%, and CdO = 3 to 9%. Other glass compositions suitable for the present invention include at least % by weight, SiO ₂ =30-36%, B ₂ O ₃ =0-5%, PbO
= 29 to 51%, MO (M is at least one of Zn and Cd) = 4 to 20%, Al ₂ O ₃ = 0 to 5%, RO (R is an alkaline earth metal) = 0 to 5%, Na ₂ O=0~5%,
_K2O =3-16%, _{As2O3 or Sb2O} =0-0.5%
, and more preferably MO has a weight ratio of CdO/
(CdO+ZnO)≧0.5.

Effects of the Invention As described above, according to the molding method of the present invention, a transparent and smooth rod with no deterioration of the glass surface can be obtained, and when applied to a magnetic head etc., no air bubbles are generated in the glass. Manufacturing yield is improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a glass rod molding method according to an embodiment of the present invention, and FIG. 2 is a typical manufacturing process diagram of a magnetic head for a VTR using the rod according to the same method.
3 and 4 are glass mold process diagrams, and FIGS. 5 and 6 are schematic diagrams of a conventional glass rod molding method. 1... Glass, 2... Crucible, 3... Mold, 4
...slit, 5...seed rod, 6...square rod.

Claims (1)

[Scope of Claims] 1. Molten glass is poured into a polygonal slit provided on the decomposition surface of a mold that can be divided into two parts, and the final cross-section is 5 to 20 times the desired thickness. The method consists of the steps of forming a square seed rod, and heating the seed rod having a polygonal cross section to a temperature 100 to 150 degrees Celsius higher than the softening temperature of glass, and stretching and forming the seed rod while maintaining the cross-sectional shape. A method for forming glass rods with a characteristic polygonal cross section. 2 at least % by weight of glass, SiO ₂ =4%,
B ₂ O ₃ = 13%, PbO = 80%, ZnO = 1%, Al ₂ O ₃ =
2%. A method for forming a glass rod having a polygonal cross section according to claim 1. 3 The glass is melted at 900℃, and the seed rod formed by pouring it into the polygonal slit is heated to 500-520℃.
3. A method for forming a glass rod having a polygonal cross section according to claim 2, wherein the glass rod is heated to a temperature of 100.degree. 4 At least % by weight of glass, SiO ₂ =35.4
%, PbO=50.7%, ZnO=4.8%, _Na2O =4.8%,
2. A method for forming a glass rod having a polygonal cross section according to claim 1, characterized in that K ₂ O = 3.8% and As ₂ O ₃ = 0.5%. 5 The glass is melted at 1400°C, and the seed rod formed by pouring it into the polygonal slit is heated to 700-720°C.
5. A method of forming a glass rod having a polygonal cross section according to claim 4, wherein the glass rod is heated to a temperature of 100.degree.