WO2014121914A2

WO2014121914A2 - Method for the free-form production of a shaped glass article with a predetermined geometry, use of a glass article produced according to the method and shaped glass article

Info

Publication number: WO2014121914A2
Application number: PCT/EP2014/000272
Authority: WO
Inventors: Andreas Langsdorf; Frank BÜLLESFELD
Original assignee: Schott Ag
Priority date: 2013-02-05
Filing date: 2014-02-03
Publication date: 2014-08-14
Also published as: TW201437158A; DE102014200921A1; WO2014121914A3

Abstract

Method for the free-form production of a shaped glass article with a predetermined geometry, the method comprising at least the following steps: - providing a starting glass, - holding the starting glass, - heating a partial region of the starting glass in such a way that a viscosity of the starting glass of 10⁹ to 10⁴ dPas, in particular from 10⁸ to 10⁴ dPas, is obtained in this partial region and in such a way that a viscosity of the starting glass does not go below 10¹³ dPas at the points at which the starting glass is held, wherein the heating is performed by means of at least one laser beam along a continuous line, and - deforming the heated starting glass by an externally applied force until the predetermined geometry of the glass article is achieved. A shaped glass article obtained from a starting glass and having at least one depression T for which T > (AdpBg) / (γ I), where A = the surface area of the starting glass to be depressed; p = the density of the glass; g = the acceleration due to gravity; γ = the surface tension of the heated starting glass; d = the thickness of the starting glass; B = the width of the heating zone heated on the starting glass, I = the length of the line heated on the starting glass, and wherein the surface of the shaped glass article after the deforming does not have any defects of greater than 1 µm, in particular of greater than 0.1 µm.

Description

A method of molding a molded glass article having a predetermined geometry, using a method according to the method

manufactured glass article and molded glass article

description

The invention relates to a method for the production of a molded glass article with a predetermined geometry, the use of a

according to the method produced glass article and a molded glass article.

The prior art is used for the formation of glass articles

Flat glass used methods that use forms - that is not free of form - to which the glass article has contact at the end of the molding.

The document US 2010/0000259 A1 essentially describes the bending of glasses with the preferential use of medium-wave IR radiation, which is preferably absorbed in the glass.

The document DE 10 2010 020 439 A1 describes several methods for

Deformation of individual glass articles u.a. using a mold and by choosing different temperatures at different locations of the

Glass molding.

The document US 2012/0114901 A1 describes a method for the production of cover glasses by bending individual disks by the suitable choice of the temperature distribution and suitable choice of the radii of the mold.

CONFIRMATION COPY The molding process is terminated as soon as the product has mold contact over the entire surface.

WO 2011/000012 A1 describes a laser-heated bending press of materials.

All of these methods require either forms with very good surface quality, the production of which is very complicated and expensive, or finishing by grinding and polishing. This leads to high costs and costs.

DE 10 2011 050628 A1 describes a molding-free bending process, but here the radiation sources are designed as radiation burners and these must be mechanically repositioned depending on the bending geometry to be achieved,

DE 10 2007 012146 B4 describes a laser beam and a scanner mirror in order to locally raise the glass pane to be deformed

Bring temperatures and deform by the action of gravity. In this case, a temperature measurement is essential, since the deformation is controlled by the viscosity, with the temperature in a direct

Context stands.

If one follows the specifications of DE 10 2007012146 B4 for thin flat glasses and small surfaces to be deformed, it is found that gravity alone is no longer sufficient for deformation, since the surface tension keeps the glass in shape.

For glass thicknesses for which the relationship Adpg <γ I holds, the pure leads

Weight to an insufficient lowering T, where

A = area to be lowered in m ² ;

p = glass density in kg / m ³ ;

g = 9.81 m / s ² γ = surface tension in N / m;

d = thickness of the glass in m;

B = width of the heating zone in m,

I = length of the heated line in m.

The reduction T in m is no longer for such geometries by the

Viscosity time course determined, but purely by the external forces F (in N) determines:

T = (Adp B + F) / (y I).

This eliminates the need for accurate temperature monitoring. The

Viscosity determines the rate of deformation and need only be sufficiently low to ensure deformation in finite time.

The document WO 2005/042420 A1 discloses a method for producing a glass molded part with polygonal plate-shaped and optionally at least partially bulged base surface and at least one limb bent along an edge of the base surface with the following steps:

Providing a polygonal planar, optionally at least partially bulged, glass pane,

Heating the edge on at least one side of the glass sheet with a line burner up to the softening point of the glass,

- bending over the low-viscous edge protruding

Glass edge along the bending edge as a leg of the glass molded part up to a predetermined angle,

- Cooling of the glass molding.

Document DE 38 37 552 A1 describes a process for the preparation of a

Glass product with a smooth surface, wherein a glass plate is placed on a molding die with the inner dimensions of the glass product corresponding dimensions so that the mold die touches the inner peripheral edge region of the glass plate. The outer to be deformed

Peripheral area of the glass plate is heated to a temperature that larger than that of the central portion of the glass plate, so that the latter is deformed on the Formpatrize by its own weight. The thus deformed glass plate is pressed by a molding die whose dimensions correspond to the outer dimensions of the glass product.

The document WO 20/055587 A1 likewise discloses a method for deforming a flat glass.

The object of the invention is to find a method for the shape-free production of a molded glass article with a predetermined geometry, which overcomes the disadvantages of the prior art described. Furthermore, it is an object of the invention to produce molded glass articles with high surface quality inexpensive and easy and in particular to avoid post-processing steps.

The object is achieved according to claim 1 by a method for the shape-free production of a molded glass article having a predetermined geometry, wherein the method has at least the following steps:

Providing a starting glass,

Holding the starting glass,

- Heating a portion of the starting glass so that in this

Partial region, a viscosity of the starting glass from 0 ⁹ to 0 ⁴ dPas, in particular from 10 ⁸ to 0 ⁴ dPas, is obtained, and such that a viscosity of the starting glass at the points where the

Starting glass is maintained, is not exceeded by 10 ¹³ dPas, wherein the heating by means of at least one laser beam along a closed line, and

- Deformation of the heated starting glass by external force until the predetermined geometry of the glass article is reached. The object is achieved according to claim 19 by a molded glass article obtained from a starting glass, which has at least one reduction T for which applies

T> (AdpBg) / (y I), where

A = surface of the starting glass to be lowered in m;

p = glass density in kg / m

g = 9.81 m / s ² ;

γ = surface tension of the heated starting glass N / m;

d = thickness of the starting glass in m;

B = width of the heating zone heated in starting glass in m,

I = length of the line heated in the starting glass in m and,

wherein the surface of the molded glass article after deformation has no impurities of greater than 1 pm, in particular greater than 0.1 pm.

A, d, p, B, γ and I can be measured on the shaped glass article (see also Figure 6).

By impurities are meant essentially surface defects that may be caused by mold contact.

The term form-free according to the invention means in particular that the heated part does not come into contact with a mold.

Advantageous embodiments of the invention are described in the dependent claims.

Preferably, the starting glass used is a flat glass which is shaped by means of the method according to the invention to obtain a shaped glass article. A soda-lime glass, a borosilicate glass or an aluminosilicate glass is preferably used as the starting glass.

According to a further embodiment of the method, the starting glass is preheated. The preheating is preferably carried out in a separate oven.

Preferably, heating parameters, in particular the viscosity to be maintained of the starting glass in the partial region, and deformation parameters, in particular the deformation time and deformation force, are selected such that the deformation comes to a standstill when the starting glass has reached the predetermined geometry.

According to a further embodiment of the method, the heating of the subarea is effected by means of at least one burner or by means of IR radiation.

The heating of the subregion can also be effected by means of at least one

Laser beam done, the sub-area is particularly preferably scanned with a frequency of the laser beam of at least 2 Hz.

The entire subarea can be heated simultaneously or in a chronological order.

Preferably, the heating is along a closed line.

The heating can be carried out in such a way that a predetermined thermal gradient is set between the partial region and the remaining regions of the starting glass.

The heat card is preferably used by means of suitable measuring methods,

in particular by means of a thermal image sensor, measured and / or is the Deformation by means of suitable measuring methods, in particular by means of optical sensors and / or acoustic sensors, measured.

The additional force can act in particular on the heated starting glass by applying overpressure and / or underpressure.

The further force can be exerted by a pressure gradient over the starting glass.

The further force can also be transmitted via a mechanical punch, which preferably acts on locations of the glass plate which are at high viscosity.

Advantageous are forces that do not attack in areas of the glass with viscosities <10 ¹³ dPas.

The resulting glass article preferably has no impurities (pits) with a dimension of greater than 1 μm, in particular greater than 0.1 μm.

In particular, the glass article obtained has a half-shell-shaped

Geometry on.

By reversing the force effect when a new one is concerned

TemperaturA / iskositätsverlaufes can also represent other geometries. In particular, those which have sections already lowered over the plane of the original glass pane.

According to the invention, the glass article produced by the method according to the invention can be used for electronic devices, in particular as part of a housing or a screen. EXAMPLES

FIG. 1 shows a flowchart with preferred method steps.

Figure 2. shows the production of a recess in a flat glass, which is kept outside during the deformation and a novel invention

Glassware. Above in plan view and below along the section line A-A.

FIG. 3 shows the lowering of an area in a flat glass, which is kept outside during the deformation, as well as a section according to the invention

Glassware. Above in plan view and below along the section line A-A.

Figure 4. shows the lowering of the edge region of a flat glass, which is held inside during the deformation and a novel invention

Glassware. Top in top view and bottom along a cut line.

FIG. 5 shows the shaping of a flat dome in a flat glass and a glass article according to the invention. Top in top view and bottom along the

Section line A-A.

FIG. 1 shows an exemplary flowchart with preferred

Process steps for the shape-free production of a molded glass article with a predetermined geometry. Thus, first of all, the geometry of the glass article to be formed was predetermined (specified). Then a suitable temperature (viscosity) time-force curve was calculated. That It was determined which part of the starting glass has to be heated for how long, to soft temperature at which force, until the desired deformation occurs. The heating should be done by means of a laser beam. That a suitable laser scanner has been programmed so that the desired

Temperature (viscosity) - time-course can be achieved. The force is adjusted via the size of the pressure gradient across the glass. The starting glass (flat glass) was provided, held in the appropriate places and the temperature (viscosity) time-force program under

Deformation of the starting glass to the molded glass article predetermined Geometry gone. In a final step, the molded glass article was removed.

FIG. 2 shows the production of a depression in an aluminosilicate flat glass (deformed flat glass 1), which was kept outside during the deformation. The heating of a starting glass (flat glass) was carried out in the partial area 2 to a temperature such that a viscosity of 10 ⁷ to 10 ¹³ dPas was obtained in this partial area, and in the partial area 3 to a temperature such that a viscosity of 10 ⁴ in this partial area until 10 ⁸ dPas was obtained. The heating was carried out in such a way that a viscosity of the starting glass was not fallen below 10 ¹³ dPas at the points at which the starting glass was held. The thus heated starting glass was through

Force by a pressure difference across the glass plate deformed until the predetermined geometry of the glass article was reached.

FIG. 3 shows the production of an asymmetrical recess in a flat glass (deformed flat glass 1), which was kept outside during the deformation. The heating of a starting glass (flat glass) took place in the subregions 2, 3, 4, 5 and 6 to different temperatures, so that different viscosities were obtained in these subregions. The

Heating was carried out in such a way that a viscosity of the starting glass was not fallen below 10 ¹³ dPas at the points at which the starting glass was held. The thus heated starting glass was through

Force force deformed until the predetermined geometry of the glass article was reached.

FIG. 4 shows the deformation of the edge region of a flat glass which was held inside during the deformation. According to the invention, the deformation was controlled purely by the time-viscosity-force exposure, that is, there was no two-dimensional form contact, so that no expensive forms accrue.

According to the invention, a flat glass (starting glass) was at least partially brought to a temperature which corresponded to a viscosity of 10 ¹³ dPas. The flat glass was held in an area that should not be deformed. In this area, the glass remained at a viscosity> 10 ¹³ dPas, so that no damage to the glass surface could result from the support. In some areas, the viscosity has now been lowered so much that "sagging" or subsidence of partial areas of the flat glass has occurred, the minimum viscosity values being in the range of 10 ⁸ dPas or even 10 ⁵ dPas, depending on the thickness of the glass and desired

Degree of deformation and the weight acting on the site to be deformed. The time-viscosity-force curve was chosen so that the deformation came to a standstill at a time when the desired shape or a desired intermediate shape was achieved.

Depending on the predetermined geometry of the glass article to be produced very high viscosity and thus temperature gradients are necessary. These were preferably achieved by heating by means of laser radiation (laser scanner). With the choice of suitable laser sources different wavelengths can be used, due to the different absorption in the

Starting glass penetrate different depths and thus act in different depths of the starting glass. However, other sources of heat were also used, especially when a small amount of deformation was desired that required a low viscosity gradient.

To monitor the temperature distribution, preferably a planar thermal image sensor was used. To control the deformation, sensors can also be used which detect the position of the deformed glass. In one embodiment, these sensors were used to determine the final geometry. In another embodiment, these sensors were used to control the process. In particular, ultrasonic sensors and / or optical

Sensors used.

The flat glass to be formed was taken up by a frame, so that portions could deform inside the flat glass. The flat glass can also be supported centrally, so that the edges can be deformed. In any case, the bearing surface was so

dimensioned that the flat glass was not deformed in the immediate vicinity of the support surface.

Depending on the shape to be achieved, it may be advantageous to heat certain points on the flat glass in a timed sequence to use the high viscosity glass as a holder for the glass to be formed. The corresponding bending point can then, depending on the lever length, be adjusted to an average viscosity, eg in the range 0 ⁹ dPas to 10 ⁸ dPas.

In the transition region between flexures and lowered areas, e.g. between points B and C in Figure 3, the viscosity must change steadily.

With the described method, it is possible to generate any geometries that can be produced by sinks. Figure 5 shows, for example, the production of a flat dome in a flat glass 1, e.g. the guidance of the finger can serve for a touch-sensitive screen (touch screen). The heating took place here in subarea 3.

The glasses thus formed were preferably used in mobile or non-mobile electronic devices as cover glasses (cover glasses). The following table shows surface properties of glass articles according to the invention, which were formed from flat glasses with a dimension 1150 × 850 mm by the method according to the invention:

^* Values were determined using a 0.8mm / 8mm notch filter using a Zeiss Surfcom 1400 measuring system; Sample size 280 x 280 mm.

Inventive glass articles or glass articles produced according to the invention preferably have a thickness tolerance <50 μm, a thickness variation <50 μm, a warp <0.05% and a waviness <150 nm (the last two values refer to the undeformed region of the glass article). LIST OF REFERENCE NUMBERS

1: Deformed flat glass (shaped glass article with predetermined geometry)

2: range of medium viscosity (10 ⁷ to 10 ¹³ dPas)

3: low viscosity range (10 ⁴ to 10 ⁸ dPas)

4: range of medium viscosity (10 ⁷ to 10 ¹³ dPas)

5: bending viscosity (10 ⁷ to 10 ¹² dPas)

6: transition from lower to bending viscosity

7: edition (holder)

8: high viscosity range (> 10 ¹² dPas)

A-A: cutting line

B, C: Transition areas between bending points

Claims

Patent claims

1. Process for the shape-free production of a shaped glass article with a predetermined geometry,

wherein the method has at least the following steps:

- Providing an exit glass,

- holding the exit glass,

- Heating a portion of the original glass in such a way that

Partial area a viscosity of the starting glass of 10 ^a to 10 ⁴ dPas, in particular from 10 ⁸ to 10 ⁴ dPes, is obtained and so that a viscosity of the starting glass at the points where the

Starting glass is held, does not fall below 10 ¹³ dPas, the heating taking place by means of at least one laser beam along a closed line, and

- Deforming the heated initial glass by external force until the predetermined geometry of the glass article is achieved.

2. The method according to claim 1, characterized in that as

The starting glass is a flat glass.

3. Method according to one of the preceding claims, characterized

characterized in that the starting glass is a soda-lime glass

Borosilicate glass or an aluminosilicate glass is used,

4. Method according to one of the preceding claims, characterized

marked that the starting glass is preheated.

5. Method according to one of the preceding claims, characterized

characterized in that heating parameters, in particular the viscosity of the starting glass to be obtained in the partial area, and

Deformation parameters, in particular the deformation time, such as this can be chosen so that the deformation comes to a standstill when the initial glass has assumed the predetermined geometry.

6. Method according to one of the preceding claims, characterized

characterized in that the heating takes place by means of at least one burner or by means of IR radiation.

7. Method according to one of the preceding claims, characterized

characterized in that the partial area is scanned with a frequency of the laser beam of at least 2 Hz.

8. Method according to one of the preceding claims, characterized

characterized in that the entire subarea is heated simultaneously or in a time sequence.

9. Method according to one of the preceding claims, characterized

characterized in that the heating takes place in such a way that a predetermined heat gradient is set between the partial area and the remaining areas of the starting glass.

10. The method according to claim 9, characterized in that the

Thermal gradient is measured using suitable measuring methods, in particular using a thermal image sensor.

11. The method according to any one of the preceding claims, characterized

characterized in that the deformation is measured using suitable measuring methods, in particular using optical sensors and/or acoustic sensors.

12. Method according to one of the preceding claims, characterized in that the external force acts on the heated starting glass by means of excess pressure and/or negative pressure.

13. Method according to one of the preceding claims, characterized

characterized in that the external force is exerted by a pressure gradient across the starting glass.

1 . Method according to one of the preceding claims, characterized

characterized in that the external force effect is exerted by a stamp.

15. The method according to claim 14, characterized in that the external force acts through a stamp in partial areas of the glass which have a viscosity of more than 10 ¹ dPas.

16. experienced according to one of the preceding claims, thereby

characterized in that the glass article obtained has no scratches with a dimension of greater than 1 μπι, in particular greater than 0.1 \im.

17. Method according to one of the preceding claims, characterized

characterized in that the glass article obtained has a half-shell-shaped geometry.

18. Use of the one produced according to one of claims 1 to 17

Glass article for electronic devices, especially as part of one

housing or a screen.

19. Shaped glass article obtained from a starting glass

has at least one reduction T for which applies

T > (AdpBg)/(y I), where A - surface of the initial glass to be lowered;

p = glass density;

g = acceleration due to gravity;

γ - surface tension of the heated initial glass;

d = thickness of the starting glass;

B = width of the heating zone heated in the initial glass, I = length of the line heated in the initial glass and,

wherein the surface of the shaped glass article after deformation has no defects larger than 1 μm, in particular larger than 0.1 μm-η.