# US 7,406,841 B2 · Glass-ceramic product with variably adjustable zero crossing of the CTE-T curve

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- Number: US 7,406,841 B2
- Document ID: US7406841B2
- Status: Granted
- Kind: B2
- Application number: 11/168,573
- Filed: 2005-06-29
- Published: 2005-10-27
- Granted: 2008-08-05
- Earliest claimed: 2001-12-21
- Assignees: Schott Glas
- Inventors: Ina Mitra
- Web page: https://patentgrep.com/patent/US7406841B2

## CPC

- G03F 7/70958: {Optical materials or coatings, e.g. with particular transmittance, reflectance or anti-reflection properties}
- C03B 32/02: Thermal crystallisation, e.g. for crystallising glass bodies into glass-ceramic articles {(C03B27/012 takes precedence)}
- C03C 10/0027: {containing SiO2, Al2O3, Li2O as main constituents}
- G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G)
- C03B: MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03C: CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS

## Abstract

The present invention relates to a process for producing a glass-ceramic with a defined zero crossing of the CTE-T curve (CTE: coefficient of thermal expansion), and glass-ceramic products produced using the process according to the invention.

## Claims

### Claim 1

A process for producing a glass-ceramic which has a zero crossing of the CTE-T curve at a selected temperature TA±10° C., comprising providing a glass-ceramic or a green body of a glass-ceramic and ceramicizing in accordance with a ceramicizing program, determination of which comprises determining the CTE-T curve, wherein
a) the determination of the CTE-T curve comprises
providing a green body or a pre-ceramicized glass-ceramic,
determining Δl/l0−T measurement points for the glass-ceramic in a temperature range TA±50° C.,
matching a polynomial to the Δl/l0−T measurement points, and
deriving the polynomial to obtain a CTE-T curve;
or
b) the zero crossing of the CTE-T curve is set at TA±7° C.;
or
c) the zero crossing of the CTE-curve is set at TA±5° C.;
or
d) the glass-ceramic is ceramicized in at least two ceramicizing steps.

### Claim 2 (depends on 1)

The process as claimed in claim 1, in which a Δl/l0−T set of curves is compiled in order to determine the ceramicizing program.

### Claim 3 (depends on 1)

The process as claimed in claim 1, in which the determination of the CTE-T curve comprises the following steps:
providing a green body or a pre-ceramicized glass-ceramic,
determining Δl/l0−T measurement points for the glass-ceramic in a temperature range TA±50° C.
matching a polynomial to the Δl/l0−T measurement points, and
deriving the polynomial to obtain a CTE-T curve.

### Claim 4 (depends on 1)

The process as claimed in claim 1, in which the zero crossing of the CTE-T curve is set at TA±7° C.

### Claim 5 (depends on 1)

The process as claimed claim 1, in which the zero crossing of the CTE-curve is set at TA±5° C.

### Claim 6 (depends on 1)

The process as claimed in claim 1, in which a glass-ceramic belonging to the Li2O—Al2O3—SiO2 system is provided.

### Claim 7 (depends on 1)

The process as claimed in claim 1, in which ceramicizing is carried out at a temperature at which the mean CTE [TA−50;TA+50] substantially does not change.

### Claim 8 (depends on 1)

The process as claimed in claim 1, in which a glass-ceramic with a mean CTE [(TA−50° C.);(TA+50° C.)] of at most 1.0×10−6/K is provided.

### Claim 9 (depends on 1)

The process as claimed in claim 1, in which the glass-ceramic is ceramicized in at least two ceramicizing steps.

### Claim 10 (depends on 1)

The process as claimed in claim 1, in which the glass-ceramic of a, b, or c is ceramicized from the green body in one ceramicizing step.