TWI786235B - Glass mold - Google Patents

Abstract

The present invention relates to a glass forming model. In order to obtain a glass forming model with excellent formability, the solution is to form a glass forming model for pressing and forming glass to be formed from glass satisfying the following conditions: (1) Young's modulus (Young's Modulus) above 85GPa, (2) glass transition temperature above 650°C, (3) average thermal expansion coefficient from 100°C to 300°C is 30×10 ^-7 /°C to 80×10 ^-7 /°C.

Description

glass molded model

The invention relates to a molding model for pressing glass to be shaped.

In the manufacture of optical elements such as lenses, a method in which glass as a material is formed into a rough shape and then ground or polished is used to complete the process. In recent years, a method of manufacturing optical elements without grinding or polishing by press-forming glass in a softened state through a molding mold (hereinafter referred to as molding mold) has been put into practical use. By performing molding using such a molding die, not only spherical lenses but also complex-shaped aspheric lenses, etc. can be produced in large quantities at low cost.

In press forming, since the surface shape (forming surface) of the forming model is transferred to the object to be formed, it is necessary to have a very high accuracy of the forming model. For example, forming molds are required to have high rigidity and heat resistance so as not to deform due to load or heat applied during pressing. In addition, in order to prevent the to-be-formed object from sticking to the forming mold or the to-be-formed object from breaking, the forming mold must have an appropriate thermal expansion coefficient with respect to the to-be-formed object.

As a material that satisfies the above conditions, molding dies made of metal and ceramics are widely used. However, it is costly and time-consuming to separately manufacture such a shaped pattern while avoiding differences in accuracy when cutting or the like. In particular, when mass-producing glass lenses for optical instruments When , many forming models are required. As a countermeasure, a technique using a forming mold made of glass has been proposed (for example, Patent Documents 1 to 12).

Specifically, a master mold (master mold) having a reference molding surface is prepared, and a molding model softened by heating is press-molded with a glass material with the master mold, so that a glass-made molding model (replica mold) that transfers the molding surface of the master mold can be obtained. ). The molding model made of glass has advantages in that once a high-precision master mold is produced, mass production is easy and the degree of freedom in shape setting is high.

[Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent Application Laid-Open No. 62-226825

[Patent Document 2] Japanese Patent Application Laid-Open No. 1-239030

[Patent Document 3] Japanese Patent No. 2616964

[Patent Document 4] Japanese Patent No. 2723497

[Patent Document 5] Japanese Patent No. 4832939

[Patent Document 6] Japanese Patent Laid-Open No. 2007-284300

[Patent Document 7] Japanese Unexamined Patent Publication No. 2006-206394

[Patent Document 8] Japanese Patent Laid-Open No. 2005-97009

[Patent Document 9] Japanese Patent Laid-Open No. 2004-210550

[Patent Document 10] Japanese Patent Laid-Open No. 2008-56540

[Patent Document 11] Japanese Patent Laid-Open No. 2007-254234

[Patent Document 12] Japanese Unexamined Patent Publication No. 2005-15266

Even in a molding mold made of glass, the above-mentioned conditions of rigidity, heat resistance, and thermal expansion coefficient are required, but it is difficult to satisfy all these conditions at a high level and put it into practical use. In particular, there is a demand for a high-performance forming mold for glass, which has excellent formability for the glass to be formed and which is also easy to produce. Accordingly, it is an object of the present invention to provide a glass forming mold excellent in formability.

The present applicant devised the present invention based on the idea that by satisfying certain conditions, a glass-made molding model of a practical use level that can be reasonably manufactured and has excellent molding performance can be obtained. That is, the present invention relates to a glass forming mold for press-forming glass to be formed, which is characterized in that it is formed from glass that satisfies the following conditions: (1) Young's Modulus (Young's Modulus) is 85 GPa or more, (2) vitrified The transition temperature is above 650°C, and (3) the average coefficient of thermal expansion from 100°C to 300°C is 30×10 ^-7 /°C to 80×10 ^-7 /°C.

By satisfying the condition (1), it is possible to ensure rigidity against a load when press-forming the glass to be formed. By satisfying the condition (2), the glass transition temperature is higher than that of the glass to be formed as a material for optical elements and the like, deformation of the glass forming mold at the forming temperature (temperature heated until the glass to be formed is softened) can be prevented. By satisfying the condition (3), the effects of preventing the glass to be formed from sticking to the glass forming mold, preventing the glass to be formed from breaking, preventing the glass material for forming the mold from sticking to the mother mold, and preventing the glass material for forming the mold from breaking can be obtained . Therefore, excellent forming results can be obtained by preventing sticking, cracking of the glass to be formed without causing deflection of the glass forming mold.

When the glass transition temperature of the glass (glass material for the forming model) constituting the glass forming mold is set as Tg (A), and the glass transition temperature of the glass to be formed is Tg (B), preferably Tg (A)-Tg ( B) 30°C or higher.

When the average thermal expansion coefficient of the glass (glass material for the forming model) constituting the glass forming model is set to α(A) at 100°C~300°C, the average thermal expansion coefficient of the glass to be formed at 100°C~300°C is α(B) When α(A)-α(B) is preferably +20×10 ^-7 /°C to -120×10 ^-7 /°C.

The present invention is suitable for forming a glass forming model for forming an optical element by pressing the glass to be formed.

As described above, according to the present invention, it is possible to obtain a glass forming mold having excellent formability.

10: Glass forming device

11: Upper mold (model made of glass)

12: Lower mold (formed model made of glass)

13: Guidance mode

14: Forming surface

15: Forming surface

16: Coating layer

17: Coating layer

20: lens

21: Glass block (glass to be formed)

Fig. 1 is a cross-sectional view of a glass forming apparatus having a glass forming mold.

FIG. 1 shows an example of a glass forming apparatus equipped with a glass forming mold of the present invention. The glass forming apparatus 10 of FIG. 1 is manufactured by press-forming a lens 20 as an optical element from a glass block 21 of glass to be formed, and includes an upper mold 11 and a lower mold 12 which are glass forming molds. The upper mold 11 and the lower mold 12 are relatively movably supported in the guide mold 13, and the interval from each other can be changed. Both the upper die 11 and the lower die 12 can be movable movable dies, or one of them is a movable die and the other is a non-movable fixed die.

The upper mold 11 and the lower mold 12 have a molding surface 14 and a molding surface 15 on sides opposite to each other. The lens 20 is a biconvex lens with aspheric surfaces on both sides, and the molding surface 14 and the molding surface 15 are concave surfaces (aspherical surfaces) corresponding to the shapes of the respective convex surfaces (aspherical surfaces) of the lens 20 . and also That is, the shapes of the molding surface 14 and the molding surface 15 are transferred by molding and form the convex surface of the lens 20 . In addition, the glass molding mold of the present invention can also be applied to molding objects other than lenticular lenses, and the shape of the molding surface of the glass molding mold is appropriately set according to the shape of the object to be molded. For example, as an optical element, it can also be used suitably for manufacturing the lens and prism etc. which have a concave surface.

Coating layers 16 , 17 are formed on the molding surfaces 14 , 15 . The coating layers 16, 17 are made of a carbon film or the like, and have an effect of suppressing fusion (fusing) of the glass to be formed. In addition, although the coating layers 16, 17 shown in FIG. 1 are of a single-layer structure, coating layers of a multi-layer structure formed of different compositions may be provided. Alternatively, a structure in which the molding surfaces 14 and 15 are exposed without providing the coating layers 16 and 17 may also be selected.

A heater (not shown) is provided outside the guide die 13 . When forming, it is heated by a heater to the forming temperature at which the glass to be formed (glass block 21) softens.

Although illustration is omitted, the upper mold 11 and the lower mold 12 are produced by press molding using a mother mold (master mold). Mother molds for manufacturing the upper mold 11 and the lower mold 12 are prepared respectively. These mother dies are formed of metal or the like, and have a reference molding surface as a base for molding surface 14 and molding surface 15 . By pressing a heated and softened glass material for a molding model (glass that satisfies the various conditions described later, which is different from the glass to be molded for the lens 20) on the reference molding surface of each master mold, the reference molding surface is formed as the molding surface 14 and the molding surface 14. The upper mold 11 and the lower mold 12 that are transferred to the surface 15.

In addition, the glass forming mold in the present invention refers to a part having a surface for shape transfer corresponding to the forming surfaces 14 and 15 . For example, the upper mold 11 and the lower mold 12 other than the coating layers 16, 17 may be entirely made of glass. Or, also can be, the part that only comprises forming surface 14 and forming surface 15 of upper mold 11 and lower mold 12 is made into forming model as glass, and in this glass The molding mold made of glass is joined to other base parts (not shown) made of metal to form an upper mold 11 and a lower mold 12 .

As a result of studies and experiments, the present applicants have found that glass satisfying the following conditions (1), (2) and (3) is suitable as a glass material constituting glass forming molds such as upper mold 11 and lower mold 12 .

(1) Young's Modulus (Young's Modulus) is above 85GPa.

(2) The glass transition temperature (Tg) is above 650°C.

(3) The average coefficient of thermal expansion (α100-300) from 100°C to 300°C is 30×10 ^-7 /°C to 80×10 ^-7 /°C.

The condition (1) concerns the rigidity of the glass forming model. During press forming, if the glass forming mold is deflected, the shape of the forming surface cannot be maintained, and the forming accuracy of the glass to be formed is affected. When the Young's modulus is above 85GPa, even if a predetermined pressure is applied when the glass to be formed is formed, the deflection of the glass forming model due to the load can be prevented, and the forming can be performed without compromising the accuracy of the forming surface .

The condition (2) relates to the influence of the heating at the time of forming on the forming model of the glass. By using glass having a higher glass transition point than the glass to be formed as the glass material for forming molds, and setting a temperature lower than the glass transition point of the glass material for forming molds as the forming temperature, it is possible to soften only the glass to be formed without Accompanied by the softening of the glass material used for forming the model.

30℃。進一步地，優選Tg(A)-Tg(B)

50℃，更優選Tg(A)-Tg(B)

100℃。 More specifically, when the glass transition temperature of the glass material for forming the mold is set as Tg(A), and the glass transition temperature of the glass to be formed is Tg(B), it is preferable that Tg(A)-Tg(B)

30°C. Further, preferably Tg(A)-Tg(B)

50°C, more preferably Tg(A)-Tg(B)

100°C.

For example, in the glass material for glass molded lenses produced by the present applicant, the glass transition point is the highest at 612° C. (glass material name M-TAFD305). Therefore, by satisfying the condition (2), it is possible to set a molding temperature effective for various glasses for optical elements while preventing thermal deformation of the glass molding mold.

Condition (3) is a condition for properly controlling the difference between the thermal expansion coefficients of the glass forming mold and the glass to be formed to prevent adhesion and cracking of the object to be formed and to perform good forming. If the coefficient of thermal expansion of the glass-making forming mold is relatively too large for the glass to be formed, cracking of the glass to be formed tends to occur during forming. In addition, if the difference in thermal expansion coefficient between the glass-making forming mold and the glass to be formed is too small, sticking of the glass to be formed to the glass-making forming mold is likely to occur.

More specifically, when the average thermal expansion coefficient (100°C~300°C) of the glass material used for the forming model is set to be α(A), and the average thermal expansion coefficient (100°C~300°C) of the glass to be formed is set to be α(B), α (A)-α(B) is +20×10 ^-7 /°C to -120×10 ^-7 /°C. Further, preferably α(A)-α(B) is +10×10 ^-7 /°C~-120×10 ^-7 /°C, more preferably α(A)-α(B) is 0×10 ^-7 /°C °C~-100×10 ^-7 /°C. The α(B) of the glass material of the lens for glass molding is mostly about 70×10 ^-7 /°C to 90×10 ^-7 /°C, and by satisfying the condition (3), it is possible to obtain the prevention of breakage and adhesion of the glass to be formed. to the effect on the glass-made model.

In addition, the condition (3) is also related to the moldability when the glass material for a model is molded by master mold press molding. As an example, when silicon carbide (SiC) is used as the main material to form the master mold, since the average thermal expansion coefficient (100°C to 300°C) of silicon carbide is about 40×10 ^-7 /°C, the condition (3) can be obtained A molding model made of glass that is made of a glass material for a molding model. In particular, by satisfying the lower limit value of the condition (3), the coefficient of thermal expansion of the master mold is not relatively too large, and cracking of the glass forming mold can be made difficult to occur.

For example, glass materials for forming models satisfying the conditions (1), (2) and (3) can be obtained according to the following raw material compositions.

The glass is expressed in mol% and contains: 50~75% of SiO ₂ , 0~5% of Al ₂ O ₃ , 0~5% of ZnO, 3~15% of Na ₂ O and K ₂ O in total, total 14~35% of MgO, CaO, SrO and BaO, total of 2~9% of ZrO ₂ , TiO ₂ , La ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , Ta ₂ O ₅ , Nb ₂ O ₅ and HfO ₂ , wherein the molar ratio {(MgO+CaO)/(MgO+CaO+SrO+BaO)} is in the range of 0.85~1, and the molar ratio {Al ₂ O ₃ /(MgO+CaO)} In the range of 0~0.30.

<Example>

In the glass forming device 10, the glass block 21 as the glass to be formed is disposed between the forming surfaces 14, 15 of the upper mold 11 and the lower mold 12 as a glass forming model, and is heated to the forming temperature by a heater, Table 1 - Table 3 shows examples and comparative examples of glass forming molds suitable for the present invention. Tables 1 to 3 show an embodiment in which the upper mold 11 and the lower mold 12 are moved close together to press 21 with a predetermined pressure to shape the lens 20 . Examples 1 and 2 show the results of forming the two kinds of glasses to be formed by glass forming models made of the three glass materials of GA, GB and GC to which the present invention is applied.

●Glass material GA for molding models (sample name)

Young's modulus (GPa): 85

Glass transition temperature (Tg): 682°C

Average coefficient of thermal expansion (α100-300) from 100°C to 300°C: 77×10 ^-7 /°C

Specific gravity: 2.96g/ ^cm3

●Glass material GB for molding models (sample name)

Young's modulus (GPa): 95

Glass transition temperature (Tg): 691°C

Average coefficient of thermal expansion (α100-300) from 100°C to 300°C: 51×10 ^-7 /°C

Specific gravity: 2.59g/ ^cm3

●Glass material GC for molding models (sample name)

Young's modulus (GPa): 87

Glass transition temperature (Tg): 720°C

Average coefficient of thermal expansion (α100-300) from 100°C to 300°C: 32×10 ^-7 /°C

Specific gravity: 2.60g/ ^cm3

─由於模型變形而不能夠成形─由於模型變形而不能夠成形

─Unable to form due to deformation of the model ─Unable to form due to deformation of the model

<Example 1>

●M-NBFD130 glass to be formed (manufactured by HOYA Co., Ltd.)

Glass transition temperature (Tg): 567°C

Average coefficient of thermal expansion (α100-300) from 100°C to 300°C: 74×10 ^-7 /°C

<Example 2>

●M-BACD5N glass to be formed (manufactured by HOYA Co., Ltd.)

Glass transition temperature (Tg): 521°C

Average coefficient of thermal expansion (α100-300) from 100°C to 300°C: 88×10 ^-7 /°C

[molding result]

As shown in Tables 1 to 3, in each of Examples 1 and 2, in each of the glass molding models made of glass materials GA, GB, and GC for molding models, there was no Detrimental deformation occurs, the surface shape of the surface to be formed in the glass to be formed is proper, breakage of the glass to be formed does not occur, and good forming results are obtained.

Subsequently, a comparative example is shown in which the same glass to be formed as in Examples 1 and 2 is formed using a glass forming mold made of a glass material different from that in Examples.

<Comparative example 1>

●ZnSF8 glass material for molding models (manufactured by Sumita Optical Glass Co., Ltd.)

Young's modulus (GPa): 87

Glass transition temperature (Tg): 518°C

Average coefficient of thermal expansion (α100-300) from 100°C to 300°C: 60×10 ^-7 /°C

Specific gravity: 3.72g/ ^cm3

Japanese Patent Application Laid-Open No. 2004-210550 describes a glass molding model obtained by using ZnSF8 as a material.

[molding result]

The glass transition temperature of ZnSF8 is lower than the condition (2) of the present invention. In addition, the glass transition temperature of ZnSF8 is lower than that of M-NBFD130 and M-BACD5N, which are glasses to be formed. And, even when molding any one of M-NBFD130 and M-BACD5N to-be-molded glass, the deformation of the glass forming mold exceeded the allowable range, resulting in poor molding.

<Comparative example 2>

製) ●Glass material for forming models S-BSL7 (Co., Ltd.

system)

Young's modulus (GPa): 80

Glass transition temperature (Tg): 576°C

Average coefficient of thermal expansion (α100-300) from 100°C to 300°C: 86×10 ^-7 /°C

Specific gravity: 2.52g/ ^cm3

Japanese Patent Application Laid-Open No. 2008-56540 describes a glass molding model obtained by using S-BSL7 as a material.

[molding result]

The Young's modulus of S-BSL7 is lower than the condition (1) of the present invention, the glass transition temperature is lower than the condition (2) of the present invention, and the coefficient of thermal expansion exceeds the upper limit of the condition (3) of the present invention value. And, even when molding any one of M-NBFD130 and M-BACD5N to-be-molded glass, the deformation of the glass forming mold exceeded the allowable range, resulting in poor molding.

<Comparative example 3>

製) ●Glass material for forming models S-BSM14 (Co., Ltd.

system)

Young's modulus (GPa): 84.9

Glass transition temperature (Tg): 663°C

Average coefficient of thermal expansion (α100-300) from 100°C to 300°C: 73×10 ^-7 /°C

Specific gravity: 3.43g/ ^cm3

Japanese Patent Application Laid-Open No. 2007-254234 describes a glass molding model obtained by using S-BSL14 as a material.

[molding result]

The Young's modulus of S-BSL14 was lower than the condition (1) of this invention. Furthermore, even when either of M-NBFD130 and M-BACD5N glass to be formed was formed, the surface shape accuracy of the surface to be formed could not reach the standard.

<Comparative example 4>

株式會社製) ●Glass material for molding models NA32SG (

Co., Ltd.)

Young's modulus (GPa): 74

Glass transition temperature (Tg): 705°C

Average coefficient of thermal expansion (α100-300) from 100°C to 300°C: 34×10 ^-7 /°C

Specific gravity: 2.41g/ ^cm3

[molding result]

The Young's modulus of NA32SG is lower than the condition (1) of the present invention. Furthermore, even when any one of M-NBFD130 and M-BACD5N was molded, the surface shape accuracy of the surface to be molded could not reach the standard.

<Comparative example 5>

●Glass material GD for molding models (sample name)

Young's modulus (GPa): 69

Glass transition temperature (Tg): 670°C

Average coefficient of thermal expansion (α100-300) from 100°C to 300°C: 46×10 ^-7 /°C

[molding result]

The Young's modulus of GD (sample name) was lower than the condition (1) of this invention. Furthermore, even when any one of M-NBFD130 and M-BACD5N was molded, the surface shape accuracy of the surface to be molded could not reach the standard.

<Comparative example 6>

●Glass material for molding models GE (sample name)

Young's modulus (GPa): 70.2

Glass transition temperature (Tg): 705°C

Average coefficient of thermal expansion (α100-300) from 100°C to 300°C: 37×10 ^-7 /°C

[molding result]

The Young's modulus of GE (sample name) was lower than the condition (1) of this invention. Also, even when any of the glass to be formed of M-NBFD130 and M-BACD5N was formed, the glass to be formed was broken.

In addition, the following patent documents describe techniques for forming molds from glass obtained by using barium borosilicate glass or borosilicate glass as a material.

Barium borosilicate glass (JP-A-2007-284300, JP-A-2006-206394)

Glass transition temperature (Tg): 690°C

Average coefficient of thermal expansion (α100-300) from 100°C to 300°C: 64×10 ^-7 /°C

●Barium borosilicate glass (Japanese Patent Laid-Open No. 2005-97009)

Glass transition temperature (Tg): 679°C

Average coefficient of thermal expansion (α100-300) from 100°C to 300°C: 55.6×10 ^-7 /°C

●Barium borosilicate glass (Japanese Patent Laid-Open No. 2005-97009)

Glass transition temperature (Tg): 679°C

Average coefficient of thermal expansion (α100-300) from 100°C to 300°C: 55.6×10 ^-7 /°C

●Borosilicate glass (Japanese Patent Laid-Open No. 2005-15266)

Glass transition temperature (Tg): 540°C

These patent documents do not describe the Young's modulus of barium borosilicate glass or borosilicate glass which are glass materials for forming molds. That is, it does not have the technical idea of the present invention to set all the conditions of Young's modulus, glass transition temperature, and thermal expansion coefficient for the glass constituting the glass-making mold to prevent deformation or damage of the glass-making mold, and High-precision molding is possible.

As described above, according to the glass forming mold to which the present invention is applied, since the glass forming mold has both high rigidity and heat resistance, when the glass to be formed is press-molded, the glass forming mold can maintain the surface shape of the forming surface without Will not deform. In addition, by appropriately controlling the thermal expansion coefficients of the glass forming mold and the glass to be formed, adhesion of the glass to be formed to the glass forming mold and breakage of the glass to be formed can be prevented. therefore, Compared with the glass materials for forming models proposed in the past, it is possible to obtain forming models made of glass with excellent formability.

10‧‧‧Glass forming device

11‧‧‧upper mold (model made of glass)

12‧‧‧Lower mold (model made of glass)

13‧‧‧Guide model

14‧‧‧Forming surface

15‧‧‧Forming surface

16‧‧‧coating layer

17‧‧‧coating layer

20‧‧‧Lens

21‧‧‧Glass block (to be formed glass)

Claims (5)

A glass-making forming model, which is a glass-making forming model used to press-form glass to be formed, formed from glass that meets the following conditions: (1) Young's Modulus (Young's Modulus) is above 85GPa, (2) glass transition The temperature is above 650°C and below 720°C, and (3) the average coefficient of thermal expansion from 100°C to 300°C is 30×10 ^-7 /°C to 80×10 ^-7 /°C. The glass forming model according to claim 1, wherein when the glass transition temperature of the glass constituting the glass forming model is set as Tg(A), and the glass transition temperature of the glass to be formed is Tg In the case of (B), Tg(A)-Tg(B) is 30°C or higher. The glass forming model according to claim 1 or 2, wherein the average thermal expansion coefficient of the glass constituting the glass forming model at 100°C to 300°C is set to be α(A), and the glass to be formed When the average thermal expansion coefficient is α(B) at 100°C~300°C, α(A)-α(B) is +20×10 ^-7 /°C~-120×10 ^-7 /°C. The glass forming mold according to claim 1 or 2, wherein the glass to be formed is press-formed to form an optical element. The glass forming mold as claimed in claim 3, wherein the glass to be formed is press-formed to form an optical element.

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