Photosensitive element, method for forming resist pattern, and method for producing printed circuit board

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/mm 2 ; 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.

2. 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.

3. 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.

4. 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.

5. 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.

6. 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), R 5 and R 6 each independently represent hydrogen or a methyl group, Y represents a C2-6 alkylene group, n 1 and n 2 each independently represent a positive integer, n 1 +n 2 is 2-40, and when n 1 +n 2 is 2 or greater the multiple Y groups may be the same or different.

7. 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), R 7 , R 8 and R 10 each independently represent hydrogen or a methyl group, R 9 represents a C1-4 alkyl group, a C1-3 alkoxy group, a hydroxyl group or a halogen atom, R 11 represents a C1-6 alkyl group, p represents an integer of 0-5, and when p is 2 or greater the multiple R 9 groups may be the same or different.

8. 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), R 12 represents hydrogen or a methyl group, R 13 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 R 13 groups may be the same or different.