# US 9,439,291 B2 · Photosensitive element, method for forming resist pattern, and method for producing printed circuit board

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- Number: US 9,439,291 B2
- Document ID: US9439291B2
- Status: Granted
- Kind: B2
- Application number: 13/994,971
- Filed: 2011-12-15
- Published: 2013-10-10
- Granted: 2016-09-06
- Earliest claimed: 2010-12-16
- Assignees: Hitachi Chemical Company, Ltd.
- Applicants: Masao Kubota
- Inventors: Masao Kubota
- Web page: https://patentgrep.com/patent/US9439291B2

## CPC

- H05K 3/064: {Photoresists}
- G03F 7/031: Organic compounds not covered by group G03F7/029
- G03F 7/033: the binders being polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds, e.g. vinyl polymers
- G03F 7/085: Photosensitive compositions characterised by adhesion-promoting non-macromolecular additives (G03F7/075 takes precedence)
- G03F 7/09: characterised by structural details, e.g. supports, auxiliary layers (supports for printing plates in general B41N)
- G03F 7/20: Exposure; Apparatus therefor (photographic printing apparatus for making copies G03B27/00)
- G03F 7/40: Treatment after imagewise removal, e.g. baking
- H05K 3/0076: {characterised by the composition of the mask}
- H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- 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)

## Abstract

The invention relates to a photosensitive element comprising a support film and a photosensitive layer derived from a photosensitive resin composition formed on the support film, wherein the support film haze is 0.01-1.5%, the total number of particles with diameters of 5 μm and larger and aggregates with diameters of 5 μm or larger in the support film is no greater than 5/mm2, the photosensitive layer contains a binder polymer, a photopolymerizable compound with an ethylenically unsaturated bond and a photopolymerization initiator, and the thickness T of the photosensitive layer and the absorbance A of the photosensitive layer at 365 nm satisfies the relationship represented by inequality (I): 0.001≦A/T≦0.020 (I).

## Claims

### Claim 1

A method for forming a resist pattern, the method comprising the steps of:
(a) providing a combination of a photosensitive element and a circuit-forming board, the combination comprising
a circuit-forming board with a surface roughness (Ra) of less than 300 nm;
a support film, wherein a support film haze is 0.01-1.5% and a total number of particles with diameters of 5 μm and larger and aggregates with diameters of 5 μm or larger in the support film is no greater than 5/mm2; and
a photosensitive layer derived from a photosensitive resin composition formed on the support film that comprises,
a binder polymer,
a photopolymerizable compound with an ethylenically unsaturated bond, and
a photopolymerization initiator that contains
a 2,4,5-triarylimidazole dimer, and
a pyrazoline compound represented by the following general formulas (XI) or (XII),
wherein, in the formulas (XI) or (XII), R each independently represents a C1-12 straight-chain or branched alkyl group, a C1-10 straight-chain or branched alkoxy group or a halogen atom, a, b and c each independently represent an integer of 0 to 5, the total of a, b and c being between 1 and 6, and when the total of a, b and c is 2 or greater the multiple R groups may be the same or different,
wherein the pyrazoline compound is 0.5 to 5.0 wt % based on a total amount of the 2,4,5-triarylimidazole dimer and the pyrazoline compound,
and wherein the thickness T of the photosensitive layer and the absorbance A of the photosensitive layer at 365 nm satisfies the relationship represented by the following inequality (I):
0.001≦A/T≦0.020 (I)
(b) laminating the photosensitive element on the circuit-forming board in the order of (1) the photosensitive layer, and then (2) the support film,
wherein a surface of the circuit-forming board that is in contact with the photosensitive element has the surface roughness (Ra) of less than 300 nm;
(c) exposing prescribed sections of the photosensitive layer to irradiation with active light rays through the support film and thereby photocuring the prescribed sections on the photosensitive layer; and
(d) removing by developing the non-photocured sections of the photosensitive layer.

### Claim 2 (depends on 1)

A method for producing a printed wiring board, wherein the method comprises the steps of:
(a) providing a circuit-forming board having a resist pattern formed by the method for forming a resist pattern according to claim 1; and
(b) etching or plating the circuit-forming board.

### Claim 3 (depends on 1)

The method for forming a resist pattern according to claim 1, wherein the pyrazoline compound of the photosenstive element is 0.5 to 4.0 wt % based on the total amount of the 2,4,5-triarylimidazole dimer and the pyrazoline compound.

### Claim 4 (depends on 1)

The method for forming a resist pattern according to claim 1, wherein at least one of the R groups of the photosensitive element is an isopropyl group.

### Claim 5 (depends on 1)

The method for forming a resist pattern according to claim 1, wherein at least one of the R groups of the photosensitive element is a methoxy or ethoxy group.

### Claim 6 (depends on 1)

The method for forming a resist pattern according to claim 1, wherein the photopolymerizable compound of the photosensitive element contains a compound represented by the following general formula (II),
wherein, in the formula (II), R5 and R6 each independently represent hydrogen or a methyl group, Y represents a C2-6 alkylene group, n1 and n2 each independently represent a positive integer, n1+n2 is 2-40, and when n1+n2 is 2 or greater the multiple Y groups may be the same or different.

### Claim 7 (depends on 1)

The method for forming a resist pattern according to claim 1, wherein the binder polymer of the photosensitive element has a divalent group represented by the following general formulas (III), (IV) and (V),
wherein, in the formulas (III), (IV) and (V), R7, R8 and R10 each independently represent hydrogen or a methyl group, R9 represents a C1-4 alkyl group, a C1-3 alkoxy group, a hydroxyl group or a halogen atom, R11 represents a C1-6 alkyl group, p represents an integer of 0-5, and when p is 2 or greater the multiple R9 groups may be the same or different.

### Claim 8 (depends on 7)

The method for forming a resist pattern according to claim 7, wherein the binder polymer also has a divalent group represented by the following formula (VI),
wherein, in the formula (VI), R12 represents hydrogen or a methyl group, R13 represents a C1-4 alkyl group, a C1-3 alkoxy group, a hydroxyl group or a halogen atom, q represents an integer of 0-5, and when q is 2 or greater, the multiple R13 groups may be the same or different.