# US 12,760,158 B2 · Glass cloth, glass cloth production method, prepreg, and printed wiring board

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- Number: US 12,760,158 B2
- Document ID: US12760158B2
- Status: Granted
- Kind: B2
- Application number: 18/712,844
- Filed: 2023-03-02
- Published: 2025-10-23
- Granted: 2026-10-13
- Earliest claimed: 2022-03-02
- Assignees: Asahi Kasei Kabushiki Kaisha
- Applicants: Asahi Kasei Kabushiki Kaisha
- Inventors: Yuka Fukaya
- Web page: https://patentgrep.com/patent/US12760158B2

## CPC

- C08J 5/244: {using glass fibres}
- D03D 15/267: Glass
- D03D 15/33: Ultrafine fibres, e.g. microfibres or nanofibres
- D06M 13/5135: {Unsaturated compounds containing silicon atoms}
- D06M 13/52: combined with mechanical treatment
- H05K 1/0306: {Inorganic insulating substrates, e.g. ceramic, glass}
- H05K 1/0366: {reinforced, e.g. by fibres, fabrics (H05K1/036 takes precedence)}
- C08J 2363/00: Characterised by the use of epoxy resins; Derivatives of epoxy resins
- D06M 2101/00: Chemical constitution of the fibres, threads, yarns, fabrics or fibrous goods made from such materials, to be treated
- D10B 2505/02: Reinforcing materials; Prepregs
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- D03D: WOVEN FABRICS; METHODS OF WEAVING; LOOMS
- D06M: TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
- H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- D10B: INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES

## Abstract

Provided is a glass cloth with which suitable impregnation properties with low dielectric resins can be obtained. A glass cloth includes glass yarns composed of a plurality of glass filaments, woven as warp and weft yarns, and surface-treated with a surface treatment agent, wherein when embedding the glass cloth in an epoxy resin and curing the resin, and thereafter observing a cross section of the glass cloth, a filament adhesion ratio (a number of adhesion points between filaments adhering to each other/total number of filaments) is greater than 0 and 0.80 or less.

## Claims

### Claim 1

A glass cloth embedded in an epoxy resin, the glass cloth comprising glass yarns comprising a plurality of glass filaments, woven as warp and weft yarns, and surface-treated with a surface treatment agent, wherein
when embedding the glass cloth in the epoxy resin and curing the epoxy resin, and thereafter observing a cross section of the glass cloth, a filament adhesion ratio (a number of adhesion points between filaments adhering to each other/total number of filaments) is greater than 0 and 0.70 or less.

### Claim 2 (depends on 1)

The glass cloth according to claim 1, wherein when curing the resin, the obtained cured product is cut to expose the cross section of the glass cloth, and thereafter the cross section of the glass cloth is observed at a magnification of 2000-fold using a scanning electron microscope, the adhesion ratio is 0.70 or less.

### Claim 3 (depends on 1)

The glass cloth according to claim 1, wherein the adhesion ratio is 0.60 or less.

### Claim 4 (depends on 1)

The glass cloth according to claim 1, wherein a thickness of the glass cloth is less than 40 μm.

### Claim 5 (depends on 1)

The glass cloth according to claim 1, wherein a thickness of the glass cloth is less than 35 μm.

### Claim 6 (depends on 1)

The glass cloth according to claim 1, wherein a thickness of the glass cloth is 25 μm or less.

### Claim 7 (depends on 1)

The glass cloth according to claim 1, wherein a thickness of the glass cloth is 20 μm or less.

### Claim 8 (depends on 1)

The glass cloth according to claim 1, wherein a number of fine particles attached to the glass cloth is 100 particles/μm or less.

### Claim 9 (depends on 1)

The glass cloth according to claim 1, having a loss on ignition value of 0.10 to 1.20% by mass.

### Claim 10 (depends on 1)

The glass cloth according to claim 1, wherein a number of fuzz having a length of 1 mm or more observed when a tension of 100 N/1000 mm is applied by roll-to-roll is 10 pieces/m2 or less.

### Claim 11 (depends on 1)

The glass cloth according to claim 1, wherein a weft distortion rate is 4% or less.

### Claim 12 (depends on 1)

A prepreg, comprising the glass cloth according to claim 1 and a matrix resin composition, with which the glass cloth is impregnated.

### Claim 13 (depends on 1)

A printed circuit board, comprising the glass cloth according to claim 1, and a cured product of a matrix resin composition, with which the glass cloth is impregnated.

### Claim 14 (depends on 1)

A glass cloth production method, for the production of the glass cloth according to claim 1, comprising the step of:
fiber-opening of the glass cloth by a dry ice blasting process.