TW202120445A - Round bar molding glass and method for manufacturing the same capable of reducing the cost for manufacturing glass, suppressing the amount of glass waste (sludge) discharged along with cut glass, and being advantageous to the environment - Google Patents

Abstract

The present invention provides a round bar molding glass used as a material for a glass molded product and a method for manufacturing the same. A round bar molding glass which has a cross-sectional diameter of 3.5 mm or less, a side surface roughness Ra of 1.5 or less, and an aspect ratio (major axis/cross-sectional radius) of 35 or more. The method for manufacturing a round bar glass includes a step of forming a round bar glass having a cross-sectional diameter of 3.5 mm or less by using a plurality of rollers having irregularities on the surface to perform hot drawing on a square glass or a round bar glass.

Description

Round rod shaped glass and its manufacturing method

The present invention relates to round rod shaped glass having a very small diameter and a method of manufacturing the same.

Optical glass is usually obtained as a strip-shaped material or an elongated plate-shaped material called E-bar, which is formed into a glass product having a prescribed shape. Specifically, first, a small glass piece with a relatively simple shape is produced with the same glass volume as the target, and then the small glass piece is precisely molded. From the viewpoint of industrial convenience, optical glass is expected to be able to mass-produce products of the same shape. Therefore, in the production of the glass pieces, it is also desired to be able to mass-produce products of the same shape.

As an example of the method of manufacturing the glass pieces, the following method can be cited: prepare a slender cuboid glass with one side sufficiently longer than the other sides, shape the cuboid glass into a cylindrical round rod shaped glass, and then align the glass with the height of the cylinder. Cut in the vertical direction, thereby obtaining a sheet-shaped (here, disk-shaped or cylindrical-shaped) glass piece. The sheet-shaped glass pieces are preferably used as the material of the optical lens due to the similarity of shapes.

As a method of manufacturing the above-mentioned sheet-shaped glass piece, the method of patent document 1 is mentioned, for example. Patent Document 1 discloses "a method of manufacturing a lens, which is characterized by inserting a glass block heated to a softening temperature or higher and lower than the flow temperature between three or more rollers that are parallel to each other and rotating in the same direction. The interval between the rotating rollers is reduced to form a round glass rod with a predetermined diameter, and then the round glass rod is cut, shaped, and ground to form a lens with a predetermined radius of curvature".

In addition, Patent Document 2 discloses "a method of manufacturing a round glass rod, which is ^{introduced by moving a glass blank heated to at least its surface to have a viscosity of 10 10} poise or less on a guide slope (chute). The guide slopes are provided on a plurality of rollers that are arranged parallel to each other and rotate in the same direction, and are arranged parallel to the rotation axis of the rollers, by making the glass blank face the opposite direction of the rotation of the rollers Direction rotation to form the glass blank into a round rod shape with a circular cross-section. The method for manufacturing the glass round rod is characterized in that the movement of the glass blank on the guide slope (chute) is performed by The glass blank rolls down on the guide slope (chute)."

Patent Document 3 discloses "a method for manufacturing small divided glass blanks for lenses, which is characterized in that when a plurality of small divided glass blanks for lenses are manufactured from glass round rods, the glass circles are inserted between two rollers rotating in the same direction. The rod narrows the gap between the two rollers, and presses the glass round rod heated to above the softening temperature from both sides. At least one of the two rollers is provided with a plurality of flange-like blades at equal intervals in the axial direction. After forming a plurality of grooves in the circumferential direction on the glass round rod at the same time, each groove part of the glass round rod is cut to form small divided glass blanks of equal weight suitable for the lens." [Existing technical literature] [Patent Literature]

[Patent Document 1]: (Japan) Unexamined Publication No. 54-117514 [Patent Document 2]: (Japan) Unexamined Publication No. 2000-16822 [Patent Document 3]: (Japan) Unexamined Patent Publication No. 2002-114532

[Problems to be solved by the invention]

As can be seen from Patent Documents 1 to 3, the development of a method for manufacturing round rod glass (hereinafter also referred to as round rod shaped glass) as a material of the sheet glass small pieces is being widely advanced. On the other hand, as glass products, there is a high demand for miniaturized glass products, and in the field of optical lenses, there is also a demand for smaller diameter lenses. If the diameter of the cross-section of the round rod shaped glass as the material of the optical lens can be made close to the diameter of the optical lens as the final product, the time and amount of cutting of the glass on the side of the round rod shaped glass can be reduced. The glass manufacturing cost can be suppressed, and the amount of glass chips (sludge) discharged with the cutting of glass can be suppressed, which is also advantageous in terms of the environment.

There is no description in Patent Document 1 about the diameter of the round rod shaped glass after the round rod molding. In addition, in Patent Document 2, paragraph [0061] discloses round rod shaped glass with a diameter of 6 mm, but does not disclose round rod shaped glass with a smaller diameter. Furthermore, in Patent Document 3, paragraph [0029] discloses round rod shaped glass with a diameter of 7 mm, but does not disclose round rod shaped glass with a smaller diameter. [Proposal to solve the problem]

The present inventors focused on the above-mentioned problems and developed a method for obtaining round rod glass with a diameter of 3.5 mm or less from a round rod forming apparatus without grinding or polishing the side surface by adopting a characteristic manufacturing method. That is, the present invention includes the following contents. [1] "A round rod shaped glass having a cross-sectional diameter of 3.5 mm or less, a side surface roughness Ra of 1.5 or less, and an aspect ratio (major axis/cross-sectional radius) of 35 or more. [2] "The round rod shaped glass according to [1], wherein at least one end has a radius of curvature R of 1500 μm or less. [3] "The round rod shaped glass as described in [1] or [2], which has not been subjected to grinding treatment. [4] "The round rod shaped glass according to any one of [1] to [3], which contains a component derived from a mold release agent. [5] "The round rod shaped glass according to any one of [1] to [3], wherein the content of the release agent on at least one end surface of the round rod shaped glass is relative to that of the round rod shaped glass The ratio of the content of the release agent in the center part (inside the glass) in the cross section perpendicular to the longitudinal direction of the product is 0.5 or less. [6] "The round rod shaped glass according to [4] or [5], wherein the release agent is boron nitride. [7] "An optical glass material obtained by cutting and grinding the round rod shaped glass described in [1] to [6]. [8] "A method of manufacturing round rod shaped glass, which includes a step of thermally elongating prismatic glass or round rod glass by a plurality of rollers having uneven surfaces on the surface to form round rod shaped glass with a cross-sectional diameter of 3.5 mm or less. [9] "The manufacturing method according to [8], wherein the diameter of the roller is 20 mm or less. [10] "The manufacturing method according to [8] or [9], wherein the difference between the maximum height and the minimum height of the unevenness is 0.1 mm or more and 1.0 mm or less. [Invention Effect]

Since the round rod shaped glass of the present invention has a small diameter of 3.5 mm or less in cross section, if it is used as a material, the amount of cutting glass can be suppressed when small glass products (especially optical glass lenses) are manufactured. The glass manufacturing cost can be suppressed, and the amount of glass waste can be reduced.

In this manual, unless otherwise specified, the "%" used when expressing the glass composition means "mass%". In addition, in this specification, the upper limit and the lower limit of "~" used when determining the numerical range are included in the range. For example, when the content of the glass constituent is expressed as "10 to 20%", it means 10% by mass or more and 20% by mass or less. In addition, the content (content rate) of the glass constituents can be quantified by known methods such as inductively coupled plasma emission spectrometry (ICP-AES), inductively coupled plasma mass analysis (ICP-MS), etc. In the present invention, the content of the glass constituent component being 0% means that the constituent component is not substantially contained, and it is allowed to contain the component at an unavoidable impurity level.

[Method for manufacturing round rod shaped glass] (Round rod forming device) The method for manufacturing round rod shaped glass of the present invention includes a step of thermally elongating prismatic glass or round rod glass by a plurality of rollers having irregularities on the surface to form round rod shaped glass with a cross-sectional diameter of 3.5 mm or less. Hereinafter, a detailed description will be given with reference to FIG. 1.

As shown in FIG. 1, the manufacturing method of round rod shaped glass is performed by the round rod shaping|molding apparatus provided with a plurality of rollers, preferably three. The details are explained using the case of using three rollers as an example. First, by rolling on the supply member 3, the softened prismatic glass 11 is supplied to the two rollers 21 and 22 which are in contact with or close to each other (FIG. 1 (a) and (b)). Next, the movable roller 23 is arranged to be in contact with the prismatic glass 11, and the three rollers are rotated in the same direction (FIG. 1( c )). When the rollers 21, 22, and 23 are rotated, the prismatic glass 11 also rotates, and the prismatic glass 11 is gradually deformed from a prism to a cylindrical shape while being elongated in the longitudinal direction (long axis direction). The rotation of the rollers 21, 22, and 23 is continued to extend to a desired diameter (3.5 mm or less) (FIG. 1(d)), and then removed from the rollers 21, 22, and 23 to obtain a round rod shaped glass 12.

The plural rollers used in the round rod forming glass may be in contact with each other or may be separated. The upper limit of the gap between the rollers is preferably 1.5 mm or less, more preferably 1.0 mm or less, still more preferably 0.8 mm or less, and still more preferably 0.5 mm or less. When manufacturing round rod shaped glass with a small cross-sectional diameter, the gap is preferably small. The parallelism between the rollers is preferably less than 0.1, more preferably 0.05 or less.

The roller 2 is composed of a roller shaft 201 and a glass contact portion 202 arranged on the outside of the roller shaft. The side surface of the prismatic glass 11 or the round rod shaped glass 12 is in contact with the glass contact portion 202. As a specific example of the roller 2, FIG.2(a), (b), (c) can be mentioned. The surface of the glass contact portion 202 can be processed (for example, knurling processing) capable of forming irregularities. FIG. 2(a) is knurling embossing processing, and FIG. 2(b) is knurling twill processing. In addition, the glass contact portion 202 may be coated without knurling. For example, the roller shown in FIG. 2(c) is a roller in which a coating having unevenness (for example, constructed by Gripping Venus Japan Coating Center Co., Ltd.) is applied to the glass contact portion 202. In addition, even with a roller coated with Gripping Venus, the effect of suppressing slippage can be seen, but it may be inferior in repeatability compared to a roller with a processed roller shape.

When the cross-sectional diameter of the round rod shaped glass is 3.5 mm or less, the glass is further softened compared with the case of manufacturing a large diameter round rod shaped glass, so the temperature of the roller is set higher. Therefore, the glass slips easily with respect to the roller. However, since the glass contact portion 202 has irregularities on the surface, it is possible to improve the grip force on the glass and suppress the slip phenomenon. In addition, by knurling or coating, the roller surface has unevenness of 1 μm or more and 1.0 mm or less, which is expected to improve grip. However, when the roller is used repeatedly, it is preferable to have the unevenness by knurling from the viewpoint of maintaining the shape of the unevenness. The difference (maximum height-minimum height) of the unevenness formed by the knurling process is preferably 0.1 mm or more and 1.0 mm or less. The lower limit of the difference in unevenness is preferably 0.3 mm, more preferably 0.5 mm, and still more preferably 0.6 mm. The upper limit of the difference in unevenness is preferably 0.9 mm, more preferably 0.8 mm, and still more preferably 0.7 mm.

In order to obtain round rod shaped glass with a small diameter, it is necessary to reduce the cross-sectional diameter of the roller (the glass contact portion of the roller). The cross-sectional diameter of the roller is preferably 20.0 mm or less, more preferably 18.0 mm or less, and still more preferably 16.0 mm or less. In order to reduce the cross-sectional diameter of the round rod shaped glass, it is necessary to reduce the cross-sectional diameter of the roller. However, if the cross-sectional diameter is too small, sufficient rigidity to withstand glass deformation cannot be obtained. Therefore, the cross-sectional diameter of the roller is preferably 5.0 mm or more, more preferably 7.0 mm or more, and still more preferably 9.0 mm or more.

In the method of manufacturing round rod shaped glass, first, glass of a material of a predetermined shape is put into a softening furnace to soften the glass. In addition, as a standard for the temperature of the softening furnace, the actual temperature of the furnace environment of the softening furnace (in this specification, sometimes simply referred to as "the furnace temperature of the softening furnace") is preferably set as the softening point (T ₁₀ ^7.65 ) above and below the flow temperature. This is because if the temperature in the softening furnace is lower than the softening point of the glass, the deformation of the glass will be insufficient. On the other hand, if the temperature in the softening furnace is higher than the flow temperature, the glass will be welded to the roll surface. The reason is not good. By adjusting the furnace temperature of the glass softening furnace to the above range, in the subsequent steps, the glass can be fully elongated, and round rod shaped glass of 3.5 mm or less can be obtained. The furnace temperature of the softening furnace is preferably the softening point +50°C or higher, more preferably softening point +80°C or higher, still more preferably softening point +90°C or higher. On the other hand, the upper limit of the furnace temperature in the softening furnace for softening glass is preferably the softening point + 250°C or less, more preferably the softening point + 200°C or less, and still more preferably the softening point + 180°C or less. In addition, in the actual softening step, it is important to soften the glass within a certain period of time. At this time, the heat generated by the product of the furnace temperature Tf, the temperature Ts of the glass placed in the furnace, and the holding time t is Q= (Tf-Ts)×t is set to a certain size so that the temperature Ts of the glass reaches the softening point in a limited time. Based on such an idea, the furnace internal temperature Tf or the holding time t is determined. Therefore, in the present invention, the furnace internal temperature Tf or the holding time t is not limited to the specific temperature or time of the embodiment.

Next, the glass softened in the softening furnace is moved to the round bar forming machine, and the roller is rotated, thereby performing round bar forming. The roll temperature for round bar molding is not particularly limited. However, if the roll temperature is too high, it becomes difficult to control the adhesion of the glass due to thermal deterioration of the roll. Therefore, the roll temperature is preferably 800° C. or less. The upper limit of the softening point of glass is preferably 750°C or lower, more preferably 700°C or lower, still more preferably 650°C or lower, still more preferably 600°C or lower, and particularly preferably 550°C or lower. The preferable lower limit of the softening point is not particularly limited, and the softening point may be 400°C or higher as a standard.

(Release agent) Before molding the prismatic glass (sometimes round-bar glass) of the material with the round rod forming device, a mold release agent may be applied to the surface of the prismatic glass. By applying the mold release agent, the round rod forming glass 12 can be easily removed from the round rod forming apparatus. In addition, the release agent can be coated not only on the prismatic glass (or round bar glass), but also on the roll.

The mold release agent adheres to the surface of the glass and is used to easily remove the round rod shaped glass from a roll, etc. Therefore, the mold release agent tends to spread thinly toward the both ends of the round rod shaped glass by elongation. . Therefore, regarding the content of the mold release agent contained in the round rod shaped glass of the present invention, when the mold release agent content in the center part (inside the glass) in the cross section perpendicular to the longitudinal direction is set to 1 The ratio of the content of the release agent at at least one end may be 0.5 or less. Sometimes it is 0.4 or less and 0.2 or less.

Since the round rod shaped glass 12 is formed by the above-mentioned method, the component derived from a mold release agent may be contained in the vicinity of the surface of the round rod shaped glass 12 obtained. In addition, as the mold release agent, a mold release agent containing boron nitride (BN) is preferably used. Molybdenum disulfide can also be used, but since it has lower heat resistance than boron nitride, boron nitride is preferred.

[Round rod shaped glass] The cross-sectional diameter of the round rod shaped glass of the present invention is 3.5 mm or less, the surface roughness Ra of the side surface is 1.5 or less, and the aspect ratio (major axis/cross-sectional radius) is 35 or more. Hereinafter, a specific description will be given.

(shape) The round rod shaped glass of the present invention is an elongated round rod having a cylindrical shape. Since the round rod shaped glass is formed by thermal elongation as described above, the end becomes a curved surface protruding in the longitudinal direction.

The cross-sectional diameter of the round rod shaped glass is 3.5 mm or less. If it is 3.5 mm or less, the amount of glass waste can be reduced when forming into a final product, and the glass manufacturing cost can be reduced. The cross-sectional diameter is preferably 3.0 mm or less, more preferably 2.8 mm or less.

The length of the long axis of the round rod shaped glass depends on the shape of the glass used in the material, and is not particularly limited, and may be 30 mm or more, for example.

(Surface roughness of the side surface Ra, Rz) The surface of the side surface of the round rod shaped glass of the present invention other than the end is formed by the method of elongation by the roller 2. Therefore, the values of Ra and Rz are small compared with the cut side surface, which is less likely to occur during transportation or Advantages such as cracks or notches in the process of impact. The Ra of the side surface of the round rod shaped glass is preferably 1.5 μm or less, more preferably 1.4 μm or less, and still more preferably 1.3 μm or less. In addition, the Rz of the side surface of the round rod shaped glass is preferably 10.0 μm or less, more preferably 9.0 μm or less, and still more preferably 8.0 μm or less. In addition, Ra and Rz described in this manual are values obtained using a surface roughness and profile measuring machine (model: SURFC•M 2900SD3 (manufactured by Tokyo Seiki Co., Ltd.)).

(aspect ratio) The round rod shaped glass of the present invention is further elongated than before, and the diameter of the cross section is 3.5 mm or less. Therefore, when materials of the same shape are used, it is possible to obtain round rod shaped glass with a large aspect ratio compared to the conventional method. The aspect ratio (length of the major axis/radius of section) of the round rod shaped glass of the present invention is preferably 35 or more, more preferably 38 or more, and still more preferably 40 or more.

(The radius of curvature of the end R) The round rod shaped glass of the present invention is stretched from a prismatic glass of a size that is easy to handle (round rod glass in some cases) to obtain round rod shaped glass with a cross-sectional diameter of 3.5 mm or less. Therefore, the radius of curvature R at the end is higher than that of the cold-worked product. (Grinding, grinding, etc. on the side surface) is smaller, and has the advantage that it is less likely to generate cracks or notches due to impact on the end during transportation or processing. The radius of curvature R of at least one end of the round rod shaped glass is preferably 1500 μm or less, more preferably 1300 μm or less, still more preferably 1200 μm or less, still more preferably 1100 μm or less, and still more preferably 1000 μm or less. The radius of curvature R described in this manual is a value obtained using a surface roughness and profile measuring machine (model: SURFC‧M 2900SD3 (manufactured by Tokyo Seiki Co., Ltd.)).

(Face angle α) At least one end of the round rod shaped glass of the present invention has a face angle α smaller than when the side surface is ground, polished, or the like. Here, the surface angle α refers to the angle formed by the side surface portion of the cylinder at the end of the round bar and the tangent line (contact surface). In the case of grinding the side surface, if the outer circumference of the cylindrical shaped glass is ground, the upper side of the circular end is left and the side surface is ground. Therefore, the tangent (contact surface) between the side surface of the cylinder and the end of the round bar ) Becomes larger. The curvature radius R is shown in FIG. 3 together with the surface angle α. Fig. 3 (a) is an enlarged view of the end of the round rod shaped glass of the present invention, and Fig. 3 (b) is an enlarged view of the end of the round rod glass when the side surface is ground and polished. It can also be understood from Figure 3 (a) and (b) that the side angle of the round bar glass that is ground and polished is relatively large, and the round bar glass is difficult to produce with other parts or round bars during transportation or processing. Advantages of cracks or gaps when the glasses are in contact with each other. The face angle α of at least one end of the round rod shaped glass of the present invention is preferably 27∘ or less, more preferably 25∘ or less, still more preferably 23∘ or less, and still more preferably 21∘ or less. The surface angle α described in this manual is a value obtained using a surface roughness and profile measuring machine (model: SURFC‧M 2900SD3 (manufactured by Tokyo Seiki Co., Ltd.)).

(Material of round rod shaped glass (prismatic glass, round rod glass)) As the material of the round rod shaped glass, rectangular prism glass and cylindrical round rod glass are used. By arranging these glasses in a round rod forming device, and extending the glass, round rod shaped glass can be obtained. The shape of the prismatic glass or the round rod glass that is the material of the round rod forming glass is not particularly limited as long as it can be arranged in a round rod forming device and can be formed. In the case of prismatic glass, in order to prevent the cross section of the obtained round rod shaped glass from becoming an ellipse, the cross section is preferably a square. Prismatic glass can be directly cut out after solidifying the flowing glass from a glass melting furnace into a plate shape, so it is easy to obtain.

(Rate of Shape Change) As described above, in the manufacturing method of the present invention, since the material is greatly elongated to obtain round rod shaped glass, the rate of shape change is large. _{For example, the rate of change C L} between the long axis of the prismatic glass as a material and the long axis of the round rod shaped glass depends on the shape of the prismatic glass selected as the material, but is preferably 2.7 or more, more preferably 2.9 or more. Further, a round bar shaped glass prism and glass aspect ratio change rate C _A is preferably 4.0 or more, more preferably 5.0 or more, further preferably 5.5 or more. In addition, here, if the cross-sectional radius used in the calculation of the aspect ratio is prismatic glass, half of the length of either side of the cross-section is used as the cross-sectional radius.

The type of glass that can be used is not particularly limited. As described above, the temperature for softening the glass (the temperature in the softening furnace) is determined by the type of glass, so the softening point (T ₁₀ ^7.65 ) of the glass needs to be confirmed in advance.

(Knoop hardness) In addition, in the present invention, since cracks are less likely to occur than a round bar after grinding, the glass used for the material of the shape of the present invention preferably has a Knoop hardness of 600 or less. It is more preferably 550 or less, still more preferably 500 or less, still more preferably 450 or less, still more preferably 400 or less, particularly preferably 350 or less. The preferable lower limit of the Knoop hardness is not specified, but the Knoop hardness of 100 or more may be considered as a standard.

As a glass material with a low Knoop hardness, a glass whose main component of the glass skeleton is not SiO _{2 is} mentioned, that is _{, the cation% ratio of SiO 2} /(B ₂ O ₃ +P ₂ O ₅ ) is 1 or less, preferably 0.5 Below, it is more preferably 0.2 or less, and more preferably 0.1 or less glass. In addition, in particular _{, the cationic% ratio of (SiO 2} +B ₂ O ₃ )/P ₂ O ₅ ) is 1 or less, preferably 0.5 or less, more preferably 0.2 or less, and further preferably 0.1 or less, and F A glass in which the anion% ratio of /O is 0.01 or more, more preferably 0.10 or more, and still more preferably 0.20 or more.

(Abrasion degree) As another point of view, from the viewpoint of reducing production costs such that round bars can be formed without grinding, the lower the degree of abrasion and the longer the grinding time, the greater the advantage of using this method to produce approximate shapes. . Therefore, it is preferable to use glass whose abrasion degree is 125 or less. A more preferable upper limit of the degree of wear is 100 or less, more preferably 90 or less, still more preferably 80 or less, still more preferably 70 or less, particularly preferably 60 or less. The preferable lower limit of the degree of wear is not particularly limited, and the degree of wear may be 10 or more as a standard. As a glass with a high degree of wear, for example, the total content of Re ₂ O ₃ (Re is a rare earth element containing La, Gd, Yb, Lu, and Y) in _{the glass is 30% or more, and Re 2} O ₃ /(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ ) ratio is 20% or more of glass.

As a glass with a low softening point, a glass with a large value of (10×Li+Na+K+Zn+Bi+F-Si/2-(La+Gd+Y+Yb)/4) can be exemplified. Specifically, if the previous value is -10 or less, the thermal degradation of the component becomes significant. On the other hand, if the value in the previous period is 0 or more, the softening point of the glass tends to be 700°C or less, and the obtained glass can also be supplied to precision pressing, so the utility value of the present invention is high. The value is more preferably 10 or more, still more preferably 20 or more, and still more preferably 30 or more. More preferably, it is 40 or more. [Example]

Example Hereinafter, the present invention will be further described with examples. In addition, this invention is not limited to an Example.

[Production of round rod shaped glass] First, the glass raw materials (content ratio is mass%) are prepared, melted at 1300~1450°C according to the glass state, and then cast into a mold, and then annealed at the Tg temperature of each glass plus a temperature of 50°C to 100°C. Thus, a plate-shaped optical glass is obtained. The composition (mass% of elements) of each glass is shown in Table 6, and the physical properties of the glass are shown in Table 7.

Next, cutting of the plate-shaped glass and the like were performed to obtain material glass (prismatic glass or cylindrical glass) having the shape shown in Table 2.

In addition, for Examples 1 to 6, a round rod forming apparatus A equipped with a roller having a diameter of 9 mm was used to produce round rod shaped glass at the roll temperature shown in Table 1 (the characteristics of the obtained round rod shaped glass are shown in Table 2 ). The material glass used was pre-softened in a softening furnace (temperature and residence time shown in Table 1). In Comparative Example 1, a conventional round rod forming apparatus B equipped with a roller having a diameter of 30 mm was used to similarly produce round rod forming glass. The shape change rate, surface roughness, and end shape of the obtained round rod shaped glass are shown in Table 3.

In addition, for Examples 7 to 9, the round rod forming apparatus A was also used to obtain round rod forming glasses shown in Table 4. In addition, for Comparative Examples 2 to 6, the round rod forming apparatus B was used to obtain round rod shaped glasses with a diameter of 7.5 mm shown in Table 4. It should be noted that, in Comparative Examples 3 to 6, the obtained side surfaces with a diameter of 7.5 mm were cut to form a cut round bar shaped glass that was cut to a predetermined cross-sectional diameter. The obtained cut round rod shaped glass does not satisfy the present invention in terms of aspect ratio, surface roughness, and end shape.

[Table 1]

[Table 2]

[table 3]

[Table 4]

[table 5]

[Table 6]

[Table 7]

Through the improved round rod forming device (round rod forming device A), the round rod forming glass having a diameter of 3.5 mm or less according to the present invention is obtained. The surface roughness Ra of the side surface of the round rod shaped glass is 1.5 or less, and the aspect ratio (major axis/cross-sectional radius) is 35 or more. The glass with this characteristic cannot be manufactured in the conventional round rod shaped glass, but it can be manufactured for the first time according to the present invention. [Industrial availability]

The present invention is useful in the technical field of optical glass. In particular, since the round rod shaped glass of the present invention has a cross section with a small diameter, it is possible to reduce the amount of glass debris when the glass lens is shaped.

11: Prismatic glass 12: Round rod shaped glass 2(21,22,23): roll 201: Roller 202: Glass contact part

Figure 1 (a) ~ (d) is a schematic diagram of the forming of round rod forming glass. Fig. 2 is a diagram showing a surface processing state of a roller used in an embodiment. Fig. 3 is a side view of round rod shaped glass (Fig. 3(a)), and a side view of an end portion of the glass (glass with the side cut) on which the side surface has been cold worked (Fig. 3(b)).

3: supply parts

11: Prismatic glass

12: Round rod shaped glass

21, 22, 23: Roll

Claims (10)

A round rod shaped glass having a cross-sectional diameter of 3.5 mm or less, a side surface roughness Ra of 1.5 or less, and an aspect ratio (major axis/cross-sectional radius) of 35 or more. The round rod shaped glass according to claim 1, wherein at least one end has a radius of curvature R of 1500 μm or less. The round rod shaped glass according to claim 1 or 2, which has not been subjected to grinding treatment. The round rod shaped glass according to any one of claims 1 to 3, which contains a component derived from a mold release agent. The round rod shaped glass according to any one of claims 1 to 3, wherein the release agent content of at least one end surface of the round rod shaped glass is perpendicular to the longitudinal direction of the round rod shaped glass The ratio of the content of the release agent in the center part (inside the glass) in the cross section is 0.5 or less. The round rod shaped glass according to claim 4 or 5, wherein the release agent is boron nitride. An optical glass material obtained by cutting and grinding the round rod shaped glass according to claims 1 to 6. A method for manufacturing round rod shaped glass includes a step of thermally elongating prismatic glass or round rod glass with a plurality of rollers having uneven surfaces on the surface to form round rod shaped glass with a cross-sectional diameter of 3.5 mm or less. The manufacturing method according to claim 8, wherein the diameter of the roller is 20 mm or less. The manufacturing method according to claim 8 or 9, wherein the difference between the maximum height and the minimum height of the unevenness is 0.1 mm or more and 1.0 mm or less.

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