阅读说明：本技术 非等温玻璃模压方法 (Non-isothermal glass molding method ) 是由 李莉华 杨任明 何佳益 宋博洋 张爱琴 夏菲 于 2021-09-14 设计创作，主要内容包括：本发明涉及非等温玻璃模压过程中为了提高模具使用寿命而提供的模压成型方法。所述方法为在下模具(102)上放置待压玻璃制品(103),电机驱动下模具(102)以一定速度上升,利用电压给下模具(102)加热,以此传热给所述玻璃制品(103),使所述玻璃制品(103)的温度上升到玻璃的转化温度(Tg)及以上；电机继续驱动下模具(102)继续上升,同时携带所述玻璃制品(103)位移,使玻璃制品(103)接触上模具(101),完成压制过程；所述上模具(101)和下模具(102)由单晶硅材料制成。采用本发明的模压成型方法,能够在镜头的模压成型的过程中只对玻璃材料产生模压形变,保持硅模具的形状和形态不变,从而延长硅模具的使用寿命,整体上降低生产成本。(The invention relates to a compression molding method for prolonging the service life of a mold in a non-isothermal glass compression molding process. The method comprises the steps that a glass product (103) to be pressed is placed on a lower die (102), the lower die (102) is driven by a motor to rise at a certain speed, the lower die (102) is heated by voltage, heat is transferred to the glass product (103) through the heating, and the temperature of the glass product (103) rises to be equal to or higher than the glass transition temperature (Tg); the motor continuously drives the lower die (102) to continuously rise, and simultaneously carries the glass product (103) to move, so that the glass product (103) is contacted with the upper die (101), and the pressing process is finished; the upper die (101) and the lower die (102) are made of a single crystal silicon material. By adopting the compression molding method, only the glass material can be subjected to compression molding deformation in the compression molding process of the lens, and the shape and the form of the silicon mold are kept unchanged, so that the service life of the silicon mold is prolonged, and the production cost is integrally reduced.)

1. A non-isothermal glass press molding method comprising:

a heating step: placing a glass product (103) to be pressed on a lower die (102), driving the lower die (102) to rise at a certain speed by a motor, heating the lower die (102) by using voltage, thereby transferring heat to the glass product (103), and raising the temperature of the glass product (103) to the glass transition temperature (T)_g) And the above;

the viscosity η of the glass article (103) is defined by the following equation:

wherein f represents friction, S represents contact area, V represents velocity, velocity gradientThe lower die (102) in the vertical direction drives the motor to rise at the speed whenAt this time, the unit is Pa, which represents the pressure intensity;

a pressing step: the motor continuously drives the lower die (102) to continuously rise, and simultaneously carries the glass product (103) to move, so that the glass product (103) is contacted with the upper die (101), and the pressing process is finished; the upper die (101) and the lower die (102) are made of a monocrystalline silicon material;

and (3) annealing: slow annealing the glass article (103) to form a molded lens, and releasing internal stress of the molded lens in an upper mold (101) and a lower mold (102);

cooling and mold taking: cooling the annealed molded lens to room temperature; the cooled mold-formed lens is released from the upper mold (101) and the lower mold (102).

2. A molding press molding method according to claim 1, wherein: the glass product is a glass ball and is prepared from borosilicate glass, silicate glass, phosphoric acid glass and lanthanide glass.

3. A molding press molding method according to claim 1, wherein: the Debye temperature of the monocrystalline silicon is 650K, the hardness is not obviously reduced in the range from room temperature to 350 ℃ (623K), and the hardness gradually changes obviously after the temperature exceeds 350 ℃ (623K); wherein the activation energy is defined by the following equation (1):

wherein H is the hardness of silicon, T is the temperature above the transition point, k is the Boltzmann constant, (sinh is a hyperbolic sine function), the activation energy U and the fitting parameters A and beta are changed, the temperature dependence curve above the transition point is accurately fitted, and the hardness-temperature curve of silicon is fitted according to the equation (1).

4. A molding press molding method according to claim 1, wherein:

conversion in glass (T)_g) Temperature started until viscosity of glass became 10^4.6And d Pa s, gradually converting the viscous body into the elastic body through the viscoplastomer and the viscoelastomer, wherein the temperature interval is the processing interval of the glass product.

5. A molding press molding method according to claim 1, wherein:

the contact surfaces of the glass product (103) and the upper die (101) and the lower die (102) are changed along with the difference of the contact degree, and the contact surfaces are the same relative to the upper die (101) and the lower die (102) which are siliceous and the glass product (103); the pressure relationship between the siliceous upper mold (101) and lower mold (102) and the glass product (103) is compared to determine a range of pressure values and velocity values such that the siliceous upper mold (101) and lower mold (102) press the glass product (103) without deforming the siliceous upper mold (101) and/or lower mold (102).

6. A molding forming method according to claim 5,

the glass product is K9 glass and exceeds T_gThe glass softening speed of K9 at the temperature is high, so the pressing step can not damage the siliceous upper die (101) and lower die (102) and can not reach T_gBefore the temperature, the pressure in the state of the glass body is higher than that of silicon, and the pressing step can cause damage to the silicon.

Technical Field

The invention belongs to the field of ultra-precision machining and non-isothermal glass forming, and particularly relates to a compression molding method for prolonging the service life of a mold in a non-isothermal glass molding process of a high-efficiency ultra-precision glass lens.

Background

The glass lens has good optical performance and imaging quality, increases light transmittance, reduces the volume and weight of an optical system, and is widely applied to optical, photoelectric and opto-mechanical systems. In recent years, ultra-precision manufacturing techniques for glass lenses have been sought, and the press molding method is the most efficient and simple method for mass production of aspherical lenses. In this method, the softened glass semi-finished product is compressed at a high temperature by a specific mold to produce a lens. In the conventional process, the die is generally formed by ultra-fine grinding of tungsten carbide (WC), silicon carbide (SiC), or Yttrium Aluminum Silicate (YAS), and then finely dressed by a diamond cutter, and finally precisely polished.

CN104176911A discloses a high-efficiency ultra-precision glass lens non-isothermal compression molding device and a molding method, wherein the characteristics of heating, molding, annealing and cooling in the non-isothermal compression molding process are utilized to be parallel, and a method for separating the temperature control of a glass preform from a molding die in the non-isothermal compression molding (NGMP) process is provided. Firstly, heating a workpiece to be above a forming temperature (namely a softening point temperature) in a preheating device; secondly, pressing the high-temperature preheated workpiece into a lens by a forming die with a slightly lower temperature; thirdly, the molded lens is annealed in a molding die for releasing internal stress; finally, the annealed molded lens is removed from the molding die, placed on a cooling tray and cooled individually to room temperature. The temperature of the die is only dozens of degrees centigrade, which is much smaller than that of an isothermal glass compression molding (IGMP) method, and the cold and hot fatigue of the die is effectively reduced, so that the service life of the die is obviously prolonged (at least improved by more than 2-3 times), the utilization rate is obviously improved, and the service life of the die is effectively prolonged.

However, as a material that can be preferably used for the mold of the related art, for example, various heat-resistant alloys (stainless steel and the like) exemplified by CN102557393A, a superhard material containing tungsten carbide as a main component, various ceramics (silicon carbide, silicon nitride and the like), a carbon-containing composite material, and the like are exemplified. Or a metal mold according to CN 105814005A.

Lens molding techniques have become a popular solution for current lens manufacturing, and because of the deficiencies of conventional processes, non-isothermal glass molding processes using silicon as a mold are being developed. However, since silicon is less expensive than tungsten carbide and has advantages that are not comparable to other compounds as a semiconductor having excellent properties.

When the technical process is complete, it is found that silicon in a silicon mold is deformed in the molding process, which results in the produced lens not being regulated on one hand and the mold loss on the other hand, and a new mold needs to be replaced for experiments, thereby increasing the time cost and the material cost.

The development of the prior art has thus created a need for a new lens molding process that utilizes low cost silicon as the mold while providing a longer useful life for the mold, thereby reducing overall production costs.

Disclosure of Invention

The invention aims to provide a compression molding method, in particular to a compression molding method for preparing ultra-precise glass lens non-isothermal glass, which is provided for prolonging the service life of a mold in the compression molding process.

The invention provides a non-isothermal glass compression molding method, which comprises the following steps: a heating step: placing a glass product (103) to be pressed on a lower die (102), driving the lower die (102) to rise at a certain speed by a motor, heating the lower die (102) by using voltage, thereby transferring heat to the glass product (103), and raising the temperature of the glass product (103) to the glass transition temperature (T)_g) And the above; the viscosity η of the glass article (103) is defined by the following equation:

where f represents friction, S represents contact area, and V represents velocity. Velocity gradientThe lower die (102) in the vertical direction drives the motor to rise at the speed whenAt this time, the unit is Pa, which represents the pressure intensity; a pressing step: the motor continuously drives the lower die (102) to continuously rise, and simultaneously carries the glass product (103) to move, so that the glass product (103) is contacted with the upper die (101), and the pressing process is finished; the upper die (101) and the lower die (102) are made of a monocrystalline silicon material; and (3) annealing: to the aboveThe glass product (103) is subjected to slow annealing treatment to form a molded lens, and the molded lens releases internal stress in the upper die (101) and the lower die (102); cooling and mold taking: cooling the annealed molded lens to room temperature; the cooled mold-formed lens is released from the upper mold (101) and the lower mold (102).

In one aspect of the press molding method of the present invention, wherein: the glass product is a glass ball and is prepared from borosilicate glass, silicate glass, phosphoric acid glass and lanthanide glass.

In another aspect of the press molding method of the present invention, wherein: the Debye temperature of the monocrystalline silicon is 650K, the hardness is not obviously reduced in the range from room temperature to 350 ℃ (623K), and the hardness gradually changes obviously after the temperature exceeds 350 ℃ (623K); among them, activation energy is a key factor, and is defined by the following equation (1):

wherein H is the hardness of silicon, T is the temperature above the transition point, k is the Boltzmann constant, sinh is a hyperbolic sine function, the temperature dependence curve above the transition point can be accurately fitted by changing the activation energy U and the fitting parameters A and beta, and the hardness-temperature curve of silicon is fitted according to the equation (1).

In still another aspect of the press molding method of the present invention, wherein: conversion in glass (T)_g) Temperature started until viscosity of glass became 10^4.6And d Pa s, gradually converting the viscous body into the elastic body through the viscoplastomer and the viscoelastomer, wherein the temperature interval is the processing interval of the glass product.

A further aspect of the compression molding method of the present invention, wherein: the contact surfaces of the glass product (103) and the upper die (101) and the lower die (102) are changed along with the difference of the contact degree, and the contact surfaces are the same relative to the upper die (101) and the lower die (102) which are siliceous and the glass product (103); the pressure relationship between the siliceous upper mold (101) and lower mold (102) and the glass product (103) is compared to determine a range of pressure values and velocity values such that the siliceous upper mold (101) and lower mold (102) press the glass product (103) without deforming the siliceous upper mold (101) and/or lower mold (102).

In still another aspect of the press molding method of the present invention, wherein: the glass product is K9 glass and exceeds T_gThe glass softening speed of K9 at the temperature is high, so the pressing step can not damage the siliceous upper die (101) and lower die (102) and can not reach T_gBefore the temperature, the pressure in the state of the glass body is higher than that of silicon, and the pressing step can cause damage to the silicon.

By adopting the compression molding method, only the glass material is subjected to compression molding deformation in the compression molding process of the lens, and the shape and the form of the silicon mold are kept unchanged, so that the service life of the silicon mold is prolonged, and the production cost is integrally reduced.

Drawings

In order to more clearly illustrate the technical solution in the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly described below. It is obvious that the drawings in the following description are only examples of the invention, and that for a person skilled in the art, other drawings can be derived from them without making an inventive step.

FIG. 1 is a schematic view of a pressing step in the press molding method of the present invention.

Fig. 2 is a schematic view showing deformation of a mold in a pressing step in a conventional press molding method.

FIG. 3 is a graph showing the relationship between hardness and temperature of a single crystal silicon mold according to the method of the present invention.

Figure 4 is a hardness-temperature plot of silicon and germanium fitted according to the activation energy equation of the present invention.

FIG. 5 is a table of data for materials used in the glass spheres of the present invention.

FIG. 6 is a graph of viscosity versus temperature for K9 of the present invention.

Fig. 7 is a temperature-pressure relationship of K9 in kelvin temperature according to the present invention.

FIG. 8 is a simulation diagram of temperature conduction of silicon material and glass material according to the present invention.

Fig. 9 is an enlarged view of the contact position of the silicon material and the glass material according to the present invention.

Table 1 shows viscosity-temperature values for H-K9L.

Table 2 shows the pressure comparison of silicon and K9 glass at a specific temperature.

Detailed Description

Specific embodiments of the present invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided only for the purpose of exhaustive and comprehensive description of the invention so that those skilled in the art can fully describe the scope of the invention. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention.

FIG. 1 is a schematic view of a pressing step in the press molding method of the present invention. In the heating step, a glass product to be pressed, for example, a glass ball 103 is placed on the lower mold 102, and the type of glass that can be used is not particularly limited, and known glass can be used as selected according to the application. For example, borosilicate glass, silicate glass, phosphate glass, lanthanide glass, and other optical glasses are mentioned. A motor (not shown) drives the lower mold 102 to rise, and the lower mold 102 is heated by voltage, thereby transferring heat to the glass ball 103, so that the temperature of the glass ball 103 rises to the glass transition temperature (T)_g) And the above; a pressing step, wherein the motor of the lower die 102 continuously drives the lower die 102 to ascend, and simultaneously carries the glass ball 103 to displace, so that the glass ball 103 is contacted with the upper die 101, and the pressing process is completed; annealing and cooling, namely performing slow annealing treatment, and performing primary annealing treatment on the molded lens in a molding die so as to release internal stress; taking the annealed molded lens out of the molding die, placing the lens on a cooling disc, and separately cooling the lens to room temperature; and a mold removing step of removing the cooled molded article from the upper mold 101 and the lower mold 102.

The upper die 101 and the lower die 102 are commercially available single crystal silicon materials, and when the force applied to the outside is larger than the force that the single crystal silicon material can bear at the temperature, namely the yield stress. Yield strength or yield stress is a property of a material, being the stress corresponding to the yield point at which the material begins to plastically deform.

The glass molded product produced by the production method can be used as various optical elements such as an imaging lens of a digital camera or the like, an optical pickup lens of a DVD or the like, and a coupling lens for optical communication. Further, the glass preform can be used as a glass preform used for manufacturing various optical elements by a reheat press method.

Fig. 2 is a schematic view showing deformation of a mold in a pressing step in a conventional press molding method. When the pressure is higher than the yield stress or the yield strength, plastic deformation occurs, thereby causing the upper mold 101 and the lower mold 102 to deform before the glass ball 103 deforms, and deformation occurs, thereby requiring mold replacement, increasing time and cost consumption. The average pressure above the indentation, called hardness, is a measure of its yield or flow stress.

The upper mold 101 and the lower mold 102 are made of single crystal silicon, the debye temperature of which is generally 650K, and fig. 3 is a graph showing the relationship between the hardness and the temperature of the single crystal silicon mold according to the method of the present invention. It can be seen from fig. 3 that the silicon has no significant decrease in hardness between room temperature and 350 deg.c (623K), and slowly changes significantly after exceeding 350 deg.c (623K). Activation energy is a key factor, and is determined by the following equation (1):

h is the hardness of silicon, T is the temperature above the transition point, k is the Boltzmann constant, sinh is a hyperbolic sine function, the temperature dependence curve above the transition point can be accurately fitted by changing the activation energy U and the fitting parameters A and beta, and the hardness-temperature curves of silicon and germanium are fitted according to the equation (1). Figure 4 is a hardness-temperature plot of silicon and germanium fitted according to the activation energy equation. Wherein the unit of hardness of FIG. 4 is kg/mm²There is a corresponding conversion relationship with pressure units GPa. Is composed of

1GPa＝100kg/mm² (2)

FIG. 5 is a table of data for materials used in the glass spheres of the present invention. The glass has strong temperature dependence and has different states at different temperatures. The transition from solid to liquid takes place in a temperature range in which the transition from glass to glass (T) takes place_g) Temperature started until viscosity of glass became 10^4.6Up to a temperature corresponding to dPa · s, below which the glass transition temperature range is reached, the system behaves like a solid, called vitreous, above which the viscosity of the glass becomes 10^4.6The temperature range corresponding to dPa.s is a melt; at the glass transition temperature and the viscosity of the glass became 10^4.6In the temperature range corresponding to dPa · s, the glass liquid is gradually converted from a viscous body to an elastic body through a viscoplastic body and a viscoelastic body, and the gradual change property is the basis of good processability of the glass, so that the glass can be processed only in the temperature range. Among the many properties of glass that appear most sensitive to temperature is the viscosity of the glass.

The viscosity η of the glass is

Where f represents friction, S represents contact area, and V represents velocity. Velocity gradientThe lower die 102 in the vertical direction drives the motor to rise at a speed of 0.01mm/s when At this time, the unit is Pa, which represents the pressure, the contact surface varies depending on the degree of contact, but the contact surface is the same with respect to the silicon upper and lower molds 101 and 102 and the glass ball 103 by comparing the silicon upper and lower molds 101 and 102 and the glass ball 103The pressure relationship of the ball 103 is determined to have a pressure value and a speed value within a certain range, so that the silicon upper die 101 and the silicon lower die 102 can press the glass ball 103 without deforming the silicon upper die 101 and/or the silicon lower die 102, and the loss of time and cost is reduced. The K9 glass is taken as an example of the glass ball 103, and the K9 glass is a glass product made of K9 material and is used in the fields of optical coating and the like. The K9 glass belongs to optical glass, and is glittering and translucent, so that a product processed from the K9 glass can also be called a crystal glass product.

The composition of the K9 glass was as follows: SiO 2₂＝69.13％B₂O₃＝10.75％BaO＝3.07％Na₂O＝10.40％K₂O＝6.29％As₂O₃＝0.36％

Its optical constants are: the national standard for optical glass, which is a glass having a refractive index of 1.51630, a dispersion of 0.00806 abbe number of 64.06, is classified by abbe number, a glass having an abbe number of 50 or more is defined as a crown glass and is denoted by "K", and a glass having an abbe number of 50 is defined as a flint glass and is denoted by "F". Light "Q" s are also used under these two broad categories; heavy "Z"; the special 'T' and chemical element symbols are divided into 18 categories, 141 brand numbers. For example: BaK11 (barium crown) K9 (crown) generally, crown belongs to the alkali silicate system and most flint glasses belong to the lead silicate system. The glass ball 103 material used in one embodiment of the invention is H-K9L glass ball with diameter of 6mm, K9 glass to BK7 glass for Schottky marking.

The polymer science equation (Vogel-Tamman-Fulcher, also known as VFT) equation (equation 4) can be used to model the viscosity-temperature curve of the glass, and in addition, the exponential equation developed by Douglas (the two-exponential equation generated by Douglas) can also be used to model the fitting effect. Wherein, the universality of VFT equation is higher, and the solution is convenient:

wherein R is the molar gas constant (Ris the molar gas constant), unknownComprises A_VTF、B_VTF、T_vAnd the relation between the viscosity and the temperature in the temperature interval expressed by the VTF equation can be obtained only by three pairs of known viscosity-temperature quantities.

Obtaining three groups of viscosity-temperature curves, and respectively obtaining A by using the curves as known quantities_VTF、B_VTF、T_vThey are substituted into VTF equation and plotted to obtain the temperature-viscosity curve at high temperature of H-K9L. Table 1 shows viscosity-temperature values for H-K9L:

temperature (. degree.C.)	Viscosity (dPa s)
		511	1014.5
547	1013
		714	107.6

TABLE 1

FIG. 6 is a graph of viscosity versus temperature for K9 of the present invention. The pressure-temperature relationship of the glass can be obtained by multiplying the obtained viscosity of the glass by the velocity gradient of 0.1 mm/s. The temperature is shifted from degrees celsius to kelvin for ease of comparison with silicon.

Fig. 7 is a temperature-pressure relationship of K9 in kelvin temperature according to the present invention.

The conversion relation among the units is as follows:

1GPa＝100kg/mm²＝10¹⁰dPa (5)

as shown in fig. 7, the point on the abscissa 833 of the temperature-pressure relationship curve corresponds to the Tg temperature of K9, and the temperature-pressure relationship is shown in table 2 by taking several representative points according to the temperature dependence of the germanium and silicon hardnesses shown in fig. 5 and the temperature-pressure relationship of K9 shown in kelvin in fig. 7. Table 2 shows the pressure comparison of silicon and K9 glass at a specific temperature:

TABLE 2

It can be seen from the data in the table above that the K9 glass softening speed above the Tg is sufficiently fast that the pressing step does not damage the silicon, whereas the pressure in the bulk state is higher than that before the Tg, and the pressing step does damage the silicon.

Thermal simulation was further performed to simulate the conditions of glass balls in contact with the upper and lower molds 101 and 102 made of silicon at 590 ℃ and the temperature transfer conditions. FIG. 8 is a simulation diagram of temperature conduction of silicon material and glass material according to the present invention. Fig. 9 is an enlarged view of the contact position of the silicon material and the glass material. Wherein, as can be seen from FIGS. 8 and 9, although the temperature of the whole K9 glass is greatly different even after being contacted for a period of time, the difference between the highest temperature and the lowest temperature is nearly 100 ℃, only the bright yellow part 201 which really reaches the Tg temperature is found through thermal simulation, the part which exceeds the Tg is only the region with the depth of 0.14mm upwards from the part which is contacted with the silicon mould, in FIG. 9, the arrow starts at a point close to the Tg value and goes down to a point higher than the Tg value, and the portion larger than 833K is a portion exceeding the Tg value, when the lower die is driven by the motor to enable the glass ball to be pressed to contact with the upper die for a period of time, only a small part of the glass ball meets the softening degree (namely reaches the Tg value), only a small part of the glass which can be pressed needs to be made slower than the heat conduction speed, and the pressing can be continued only when the temperature of the glass contacted with the mold is higher than the Tg value, so that the mold can not be damaged by the pressing in the method.

Reference herein to "one embodiment," "an embodiment," or "one or more embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Moreover, it is noted that instances of the word "in one embodiment" are not necessarily all referring to the same embodiment.

The above description is only for the purpose of illustrating the present invention, and any person skilled in the art can modify and change the above embodiments without departing from the spirit and scope of the present invention. Therefore, the scope of the claims should be accorded the full scope of the claims. The invention has been explained above with reference to examples. However, other embodiments than the above described are equally possible within the scope of this disclosure. The different features and steps of the invention may be combined in other ways than those described. The scope of the invention is limited only by the appended claims. More generally, those of ordinary skill in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are exemplary and that actual parameters, dimensions, materials, and/or configurations will depend upon the particular application or applications for which the teachings of the present invention is/are used.