KR101158598B1 - Method of manufacturing glass parts having a structured surface - Google Patents

Abstract

A mold 10 is provided having a surface 20 from which one or more recesses 16 extend, a glass substrate is disposed on the surface of the mold 10, and the glass substrate 12 has a glass transition temperature ( Tg) or more, and the glass substrate 12 is pressed against the mold 10 surface 20 so that the ridges 18 do not come into contact with the bottom of the recess 16. Disclosed is a method of making a glass part having a structured surface, which is formed in.

Description

METHOD OF MANUFACTURING GLASS PARTS HAVING A STRUCTURED SURFACE}

1 shows a simplified view of a cross section of a mold according to the invention in contact with a glass substrate pressed onto a mold using a pressure stamp.

FIG. 2 is an enlarged cross-sectional view through the mold according to FIG. 1, showing the inside of the recess region; FIG.

3 shows a cross section of a recess modified for the configuration according to FIG. 2;

4 a plan view of a reduced scale of the mold according to FIG. 1;

5 is a partial plan view of a mold in a modified configuration.

Fig. 6 shows the dependence of the radius of curvature of the ridge on the pressing force.

7 is an enlarged view of a photograph of a sample press body.

<Explanation of symbols for the main parts of the drawings>

10: Mold

12: glass substrate

16: recess

18: ridge

24: first region

26: second area

The present invention relates to a method of making a glass part having a structured surface, in particular a surface that takes the shape of a microlens.

In modern optical systems, various glass parts are used in which microlenses or lens arrays are formed on a surface. The manufacture of such parts using typical methods such as grinding and polishing or bright pressing is very time consuming and laborious. Since such parts require a very large number, known manufacturing methods are not suitable for manufacturing such parts.

The manufacture of such parts using lithographic methods is also not suitable for mass production.

For production by bright pressing, very precise press molds will be needed. This leads to high production costs. In addition, contamination occurs due to the mold being particularly in contact with the lens area to be produced, which leads to poor quality.

According to a method for producing a glass piece having a structured surface known from DE 199 56 654, first a first substrate is provided with a recess formed on the surface. The glass substrate is placed onto the surface of the first substrate and the glass substrate is bonded to the surface of the first substrate using a suitable method, preferably anodic bonding at reduced pressure. Thereafter, the glass substrate is annealed together with the first substrate so that a ridge is formed on the surface of the glass substrate so that a glass material flow into the recess of the first substrate is formed. Thereafter, preferably, the first substrate is removed from the structured glass body by etching. Preferably, the first substrate is formed of a silicon wafer.

Such a manufacturing method is relatively complicated and expensive due to the complicated bonding procedure and the etching step for removing the subsequent first substrate, thereby destroying the first substrate. In addition, the bonding technique relies on movable cations in glass (eg, boron or sulfur) and therefore cannot be used for any type of glass. More serious constraints are imposed by the fact that the glass that is bonded to the silicon wafer must have its thermal expansion behavior adjusted for silicon with a coefficient of thermal expansion of about 3-10 ⁻⁶ K ⁻¹ .

Accordingly, it is an object of the present invention to disclose a method for producing a glass part having a structured surface, which is cost effective and easy to manufacture and suitable for mass production.

This purpose is

Providing a mold having a surface on which one or more recesses extend;

Placing a glass substrate on the surface of the mold,

Heating the mold and the substrate to a temperature higher than the glass transition temperature (Tg), and

Pressing the glass substrate against the surface of the mold to form a ridge without contacting the bottom of the recess in each recess in the mold

It is achieved by a method of manufacturing a glass part having a structured surface comprising a.

By this, the object of the present invention is completely achieved.

That is, due to the pressing of the glass substrate against the surface of the mold such that the raised portion does not contact the bottom of the recess, according to the present invention, unlike conventional bright pressing, non-contact raised molding is performed in the recess of the mold. . Thus, although there is no direct contact with the mold surface, the dimension of the ridge is only determined by the cross section of the recess in the mold. Thus, the mold should only provide a perimeter to each recessed area, and the maximum dimensions of each ridge to the surface of the glass substrate may vary with other parameters such as pressurization pressure, pressurization temperature and pressurization time. Determined by Thus, the manufacture of the mold is considerably simpler than bright pressing. In addition, very high quality surfaces can be formed in the ridges, since the ridges are molded without any contact and thus are free of contamination. In addition, the surface has a very low surface roughness (Rms <1 nm), such as a fire polished surface. With regard to sagging without pressure as known in the prior art, the significantly increased precision of the pressurized body is achieved without the necessary vacuum hermetic contact between the glass substrate surface and the mold, which is essential in the prior art, and by means of an etching process. It is achieved without any removal of the substrate.

Alternatively, the mold surface according to the invention is configured such that the pressurized body is simply released from the mold after the pressing step. Moreover, the mold can be used more than 10,000 times.

In contrast to methods known from DE 199 56 654, where the predetermined pressure is from 0 MPa to 0.1 MPa (atmospheric pressure), according to the present invention the predetermined pressure is from 0.1 MPa to 100 MPa (pressing force of 10 kN on the surface of 1 cm 2). Set high, this pressure can be higher and can change over time. Thereby, a significantly increased parameter space is available, allowing the manufacture and precise adjustment of a wide variety of shapes.

One or more ridges may preferably be configured as a lens.

Accordingly, the glass parts to be manufactured can have various microlens shapes on the glass substrate surface. The ridge to form may have any type of perimeter. For example, a mold surface with a recess having a circular cross section, an elliptical cross section, a square cross section or a rectangular cross section can be used. Thus, a lens with unique characteristics can be formed. In addition, the mold may have a flat surface as well as a mold using a curved surface may be used. Thus, for this purpose, properly stamped pressure stamps are commonly used to press the glass substrate against the mold.

In this way, it is also possible to produce a glass part having a curved surface on which a plurality of ridges formed as microlenses extend.

According to another aspect of the present invention, a mold having one or more recesses having walls parallel to each other and extending vertically from the mold surface is used.

According to another aspect of the invention, a mold is used that includes one or more recesses with walls inclined with respect to each other.

According to another configuration of the invention, a mold having a recess is used, wherein the mold extends from the mold surface and the second region comprises a first region, the cross section of the second region being smaller than the cross section of the first region.

Here, the first region may be composed of, for example, an inclined edge.

By these methods, it is possible to achieve specific configurations of ridges and microlenses to be formed on the surface of the glass substrate. In particular by the shape of the recess in the transition region between the surface of the mold and the beginning of each of the recesses, the flow properties of the glass can be influenced in particular during the pressing step. In addition to the inclined edges, the curved shape of the first region can also be considered.

Accordingly, the appearance of the lens or ridge to be formed may be influenced in a specific manner, respectively.

According to a preferred embodiment of the present invention, the viscosity of the glass substrate during the pressing step is set to 0.5-10 ⁸ dPas to 2-10 ⁹ dPas, preferably 10 ⁸ dPas to 10 ⁹ dPas.

When using the viscosity of such a glass substrate, a sufficiently short press time can be achieved on the one hand during the pressing step, and a good molding treatment on the other hand can be achieved. Also, because the glass substrate is not very fluid, the recess is almost completely filled. Alternatively, in this viscous range, the pressing step can be controlled to form a ridge with a certain radius of curvature.

For this purpose, by using a specific mold and a specific glass and controlling the viscosity, pressurization pressure and pressurization time, it is possible to obtain a specifically predetermined radius of curvature in each recess.

Here, the pressing step may end when a preset time or a preset radius of curvature is reached.

According to another aspect of the invention, cooling is initiated after a predetermined elapsed time or upon reaching a predetermined radius of curvature of the ridge.

In this way, the molding process can be stopped as soon as the desired shape of the ridge is reached, and the configuration thus obtained can be determined as the final vitreous body.

Preferably, the pressurization pressure is set to 0.5 to 10 MPa, more preferably 1 to 8 MPa, particularly preferably 1 to 6 MPa.

In particular within such viscosity ranges such pressurization pressures can be used to meet the demanding requirements for the height and radius of curvature of the ridges to be formed.

It is possible to adjust the radius of curvature of the ridges to be formed without changing the pressure and changing any other remaining parameters. Higher pressurization pressures can be used to form smaller radii of curvature.

According to another aspect of the invention, the distance between the bottom of each of the recesses and the mold surface is at least two times, or preferably three or four times, the height of the ridges to form with respect to the surface of the glass substrate.

In this way, contact between the ridge formed and the recess bottom can be safely avoided. At the same time, it is possible to avoid a significant increase in pressure in the recess due to gas trapping while the glass flows into the recess.

According to another aspect of the present invention, a mold made of metal, ceramic, glass ceramic or glass is used that is sufficiently stable within the required temperature range and allows easy removal of the pressurized glass body from the mold.

The mold may for example consist of steel, tungsten carbide, silicon carbide, silicon nitride or silicon.

The choice of mold material is influenced by the temperature range in which the pressing step is carried out. Basically this depends on the type of glass used.

It is also possible to use a mold comprising a coating which allows for a particularly easy removal of the pressed glass body from the mold.

The recess itself may be formed in the mold by any suitable method such as drilling, milling, etching, lapping, lithographic methods, and the like. Using laser light to form the recess is advantageous in producing very precise structures.

 It is to be understood that the foregoing features, which will be described below, are not applicable only to a given specific combination, but may be applicable to other combinations or independently without departing from the scope of the present invention.

Other features and advantages of the invention will be apparent from the following description of the preferred embodiments of the drawings.

First, the basic principle of the method according to the invention will be explained with reference to FIG.

Using the glass substrate 12 and the mold 10 provided with the plurality of recesses 16, the ridges 18 on the glass substrate 12 in the regions of the recesses 16 in the mold 10, respectively. A glass part having a structured surface is prepared by a pressing step to form a).

The treatment is carried out under a predetermined pressure at a temperature higher than the glass transition temperature Tg of the glass. During the molding process, the glass substrate 12 is pressed onto the mold 10 by the pressure stamp 14. Here, the parameter is selected so that the glass flows only partially into the recess 16 of the mold 10, unlike the prior art bright pressing, thereby forming a ridge 18 shaped as a microlens. As will be described below, the shape and radius of curvature of the ridges 18 depends not only on the shape and size of the recess 16, but also on the glass type used, ie the glass transition temperature Tg of the glass used, It is also dependent on the pressurization pressure and other parameters.

Since the glass transition temperature Tg can basically vary significantly depending on the glass component, the overall temperature during the pressing step represents only a limited part of the process. In contrast, by specifying the viscosity of the glass substrate, a favorable range of characteristics in which viscous flow occurs during the pressing process is formed. The viscosity of the glass substrate 12 during the pressing step is preferably selected from 0.5-10 ⁸ dPas to 2-10 ⁹ dPas, in particular 10 ⁸ dPas to 10 ⁹ dPas.

This viscosity range is clearly different from the simple flow or sagging treatment according to DE 199 56 654 A1, since they are carried out at significantly lower viscosity, at least one order lower than the viscosity in the above-mentioned range. Flow treatment of glass of the prior art is carried out at viscosities ranging from 4-10 ⁷ dPas to 1-10 ⁴ dPas.

However, according to the invention such low viscosity ranges are avoided. In contrast, the present invention operates at higher viscosity and higher pressure.

Since the parameter is selected such that the ridges 18 formed during the pressing step do not contact the recesses 16 bottom 30, the ridges 18 have a smooth surface and thus have a high surface quality.

The recess 16 has a depth d, i.e. the distance from the mold 10 surface 20 to the bottom 30 of the recess 16, which depth is the height h of the ridges 18 formed. Is at least twice, but preferably the ratio is significantly larger and at least four times. In this way, the gas remaining in the recess during the pressurization step is avoided to form a significantly increased gas pressure which may be detrimental to the shaping of the ridges 18 during the pressurization step.

The method according to the invention is used in particular for the manufacture of glass parts comprising microlenses or microlens arrays, as required for various applications.

A possible configuration of the pressing tool 10 is shown by way of example in FIG. 4.

It is to be understood that this configuration is merely exemplary and that any other type and type of recess or ridge is possible respectively.

FIG. 5 shows a mold 10b, also just an example, for producing a longitudinal microlens comprising a rectangular recess 16b.

The mold itself may be formed of any suitable material that has sufficient temperature resistance and allows easy removal of the pressurized body from the mold after the pressing step is completed. The mold may be formed of, for example, tungsten carbide, silicon carbide, steel, silicon, glass, silicon nitride as well as other ferrous materials, nonferrous alloys or other ceramics. Depending on the glass, material and temperature range, a coating may also be applied to the mold to prevent sticking of any glass.

To prepare the recess, any suitable method may be used, including drilling, milling, etching, lapping, lithographic methods, laser methods, and the like.

The length and dimensions of the recess 16 are determined by the method of making the recess. Very fine and fine recesses are prepared by laser drilling. The particular method is determined by the specific geometry of the optical component to be manufactured from the mold.

If the shape of the recess 16 deviates from the circular or cylindrical shape, different focal points can be obtained depending on the direction. This may be desirable for example for longitudinal lenses. Along the longer side, get a larger focus, and a shorter side get a smaller focus. In this way the two functions can be combined in one lens.

The shape of the ridges 18 or lenses formed is also influenced by the configuration of the transition region between the mold surface and the recess, respectively. This is mainly shown in FIG. 3. In this figure, the mold 10a includes a recess 16a having a first region 24 extending from the surface 20 and continuing to the second region 26. While the second region 26 has a cylindrical shape, the first region 24 according to the configuration according to FIG. 3 is formed by an inclined edge, so that the second region 26 and the mold are formed through the first region 24. (10a) An inclined transition is caused between the surfaces 20.

Basically, it is to be understood that this angle of inclination can vary, in particular other forms with curved surfaces can also be considered.

In the arrangement according to FIGS. 1 to 5, the recesses 16, 16a or 16b each have a wall 22 which is usually parallel to each other and extends inwardly vertically starting from the mold surface 20. Configurations with 22 are also possible.

The shape of the ridges 18 or lenses to be formed is influenced by various parameters, respectively. These parameters include the type and composition of the glass, the viscosity during the pressing step, the pressing pressure, the pressing time, the dimensions and shape of the recesses, the overall temperature, the individual temperatures of the mold 10 and the pressing stamp 14 A pressure profile over time (e.g., depressurization prior to starting the cooling process). Other parameters are, for example, the surface tension of the glass and the thickness of the glass substrate 12 that affect the flow characteristics.

7 shows a photograph of a pressurized body 30 mm in diameter prepared according to the present invention. The individual lens has a diameter of 2.5 mm. Individual lenses are prepared by using glass P-LaSF 47 (short glass catalog, Tg = 530 ° C.) and applying a pressing force of 2256 N (230 kp) over 200 seconds using a steel stamp of 10 ⁸ dPsa. In the left part of FIG. 7, the pressurized body is seen, and in the right part of FIG. 7, a light and silhouette photograph focused on the focus of the individual lens can be seen.

6 shows how the radius of curvature of each of the ridges or microlenses can be affected by pressure during the pressing process. Here, the pressurized body made of P-LaSF 47 is pressed for a pressing time of 200 seconds with a viscosity of 10 ⁸ dPas. The diameter of the mold 10 recess 16 was 0.7 mm.

It can be seen from FIG. 6 that the radius of curvature r of the formed microlens can be influenced by changing the pressing force while keeping other parameters constant during the pressing step. Thus, at a pressing force of about 850 N (85 kp), for example, a radius of curvature of about 5.25 mm is reached. However, at a pressing force of about 3100 N (320 kp), a radius of curvature of about 1.8 mm is reached.

It will be appreciated that other recesses may also be provided in one mold to form a lens having different optical properties at different locations.

The method according to the invention also offers the possibility of structuring the glass substrate surface on the opposite side of the ridge by, for example, a diffractive structure, thereby increasing or optimizing the optical function of the individual optical component, respectively.

Depending on the cross section of the recess, it may be less or more out of the spherical shape of the ridge. For example, a lens having a diameter of 0.7 mm was formed, and according to FIG. 6, the approximate radius of curvature was 1.8 to 5.2 mm. Here, the deviation from the shape exceeding 80% of the diameter is only about ± 1 μm. In some applications, such tolerances are sufficient to provide a cost effective microlens. At least this tolerance is small enough, for example to focus light with a sensor or for illumination optics for an LED. For example, light incident over a wider area can be focused into the sensing range of the sensor. In addition to the desired shape accuracy, the desired radius and the desired shape (spherical or aspherical) also depend on the particular application. The results presented here for a particular application do not show that the shape and / or the variation in shape achieved by the method according to the invention are limited, but merely show some possible examples.

Thus, the method according to the invention can be used in particular to manufacture micro optics for LEDs and to produce sensors.

According to the present invention, there is provided a method for producing a glass part having a structured surface, which is cost effective and easy to manufacture and suitable for mass production.

Claims (18)

Providing a mold (10, 10a, 10b) having a surface (20) from which at least one recess (16, 16a, 16b) extends, Placing the glass substrate 12 on the mold 20, 10a, 10b surface 20, Heating the molds 10, 10a, 10b and the glass substrate 12 to a temperature higher than the glass transition temperature Tg, and In order to form the ridges 18 without contacting the bottom 30 of the recesses 16, 16a, 16b in each of the recesses 16, 16a, 16b of the mold, the molds 10, 10a, 10b are formed. Pressing the glass substrate 12 against the surface Glass part manufacturing method having a structured surface comprising a. The method of claim 1, wherein at least one of the ridges (18) consists of a lens. The method of claim 1 or 2, wherein a mold (10, 10a, 10b) having a flat surface (20) is used. Method according to one of the preceding claims, wherein a mold (10, 10a, 10b) having a curved surface (20) is used. The mold 10, 10a, 10b of claim 1, wherein one or more recesses 16, 16a, 16b are parallel to each other and extend perpendicularly from the molds 10, 10a, 10b. A glass part manufacturing method having a structured surface comprising a wall (22). 3. The structure according to claim 1, wherein the molds 10, 10a, 10b are used and the one or more recesses 16, 16a, 16b comprise walls which are inclined with respect to one another. Method of manufacturing glass parts. The mold 10a is used, wherein the one or more recesses 16a include a first region 24 extending from the mold surface 20 and continuing with a second region 26, the second region. Has a cross section smaller than the cross section of the first region (24). 8. A method as claimed in claim 7, wherein a mold (10a) is used and the first region (24) consists of inclined edges. The method of claim 1 or 2, wherein during the pressing step, the viscosity of the glass substrate (12) is set from 0.5-10 ⁸ dPas to 2-10 ⁹ dPas. A predetermined predetermined radius of curvature is set for each ridge in the predetermined molds (10, 10a, 10b) and the predetermined glass by adjusting viscosity, pressurization pressure and pressurization time. And a glass part having a structured surface. The method of claim 10, wherein the pressing step ends after a predetermined time or after reaching a predetermined radius of curvature. delete The method of claim 10, wherein the pressurization pressure is set to 0.5 to 10 MPa. The structured structure according to claim 1 or 2, wherein the distance d between the bottom of each recess and the mold surface is at least twice the height h of the ridge formed with respect to the surface 28 of the glass substrate. Method for producing a glass part having a surface. The mold according to claim 1 or 2, wherein the mold is formed of a metal, ceramic, glass ceramic, or glass that is sufficiently stable within the temperature range used and facilitates removal of the pressurized glass body from the molds 10, 10a, 10b. 10, 10a, 10b) is used. 16. The method of claim 15 wherein a mold (10, 10a, 10b) formed of steel, tungsten carbide, silicon carbide, silicon nitride or silicon is used. 3. A structured surface according to claim 1 or 2, wherein molds (10, 10a, 10b) coated with a coating to facilitate removal of pressurized vitreous from molds (10, 10a, 10b) are used. Method of manufacturing glass parts. A pressurized body produced according to the method according to claim 1.

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