WO2001095032A1

WO2001095032A1 - Photosensitive resin composition and photosensitive material using the same

Info

Publication number: WO2001095032A1
Application number: PCT/JP2001/004570
Authority: WO
Inventors: Tetsuzo Miki; Katsumasa Kikkawa; Shihoko Komatsu; Naohiro Tarumoto
Original assignee: Hodogaya Chemical Co., Ltd.
Priority date: 2000-06-02
Filing date: 2001-05-30
Publication date: 2001-12-13
Also published as: AU6066401A; JP2006171015A

Abstract

A photosensitive resin composition comprising: (A) a carboxyl group-containing polymer; (B) a photopolymerizable compound having an ethylenic unsaturated group, and (C) 2-(2-trifluoromethylphenyl)-4,5-bis(4-methoxyphenyl)imidazole dimer shown as Compound (1) below, as a photoinitiator compound.

Description

DESCRIPTION PHOTOSENSITIVE RESIN COMPOSITION AND PHOTOSENSITIVE MATERIAL USING THE SAME TECHNICAL FIELD The present invention relates to a highly sensitive photosensitive material used for preparing print circuit boards and a photosensitive resin composition used therein. BACKGROUND ART In manufacturing print circuit boards or the like, photosensitive materials such as a dry film resist or the like are generally used. As the electric and electronic technologies continuously call for increasingly higher density of the print circuits, the photosensitive materials are required to become proportionately photosensitive, so as to provide a higher resolution. It has been reported (U.S. Patent No. 3,479,185) that a photosensitive composition containing a photoinitiator , 2- (2-chlorophenyl) -4, 5-diphenylimidazole dimer (hereinafter referred to as "B-CIM"), as expressed as Compound (2), provides the highest level of resolution.

Compound (2 [

Another photoinitiator, hexaarylbisimidazole (hereinafter referred to as "HABI"), which is of the same type of compound with B-CIM, is also commercially used in manufacturing the dry film resists. However, recently, highly sensitive -aminoketone type photoinitiator compounds such as 2-benzyl-2- dimethylamino-1- (4-morpholinophenyl) -butanone 1 (BDMB) have been developed and are increasing the acceptance. As compared with this type of compounds, the HABI type photoinitiator compounds, including B-CIM, give a higher resolution but a lower sensitivity.

Also, B-CIM is rather low in its solubility in a solvent, and it is necessary to use this compound by fully stirring for several tens of minutes for completely dissolving. Thus, working efficiency is poor.

DISCLOSURE OF THE INVENTION The objective of the present invention is to provide a compound of the HABI type with an excellent resolution, having a remarkably higher sensitivity, and, at the same time, a much higher solubility in a solvent, as compared with the conventional B-CIM.

The present inventors have synthesized a plurality of compounds belonging to the HABI type group in search for an initiator having a high sensitivity, and have selected compounds excellent in solvent-solubility. As a result of evaluation tests carried out by preparing photosensitive resin compositions and photosensitive materials, and by comparing the relative sensitivity, the present inventors have discovered that the following Compound (1) has a solvent-solubility and sensitivity remarkably higher than those of the compounds having similar structures, and the present invention has been accomplished on the basis of this discovery.

Compound (1)

Thus, the present invention provides a photosensitive resin composition comprising (A) a binder polymer having a carboxyl group, (B) a photopolymerizable compound having an ethylenic unsaturated group, and (C) a photoinitiator compound identified as Compound (1) as a photoinitiator, and also provides a photosensitive material characterized by the use of such a photosensitive resin composition.

BRIEF DESCRIPTION OF THE DRAWING Fig. 1 illustrates a UV ray-absorption spectrum of the compound prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION The photoinitiator compound of the present invention has a substantially superior sensitivity to that of the conventional B-CIMs.

In the present invention, examples of (A) a polymer having carboxyl groups include copolymers of methacrylic acid with styrene, alkyl or substituted alkyl acrylate, methacrylate or the like. The average molecular weight of the copolymers is preferably 10,000 to 100,000.

In the present invention, examples of (B) a compound having a polymerizable ethylenic unsaturated group include vinyl monomers or the like. Examples of a monofunctional vinyl monomer include monoacrylate or monomethacrylate , and examples of a difunctional vinyl monomer include diacrylate or dimethacrylate, and examples of a polyfunctional vinyl monomer include compounds obtained by reacting an , j8 -unsaturated carboxylic acid with a polyhydric alcohol or a glycidyl group-containing compound.

In the present invention, a blending amount of the Component (A) is preferably 0.6 to 4 times the amount of the Component (B) by weight.

In the present invention, a blending amount of the photoinitiator compound (C) is preferably 0.005 to 0.15 time the combined amount, by weight, of the Component (A) and the Component (B) .

The photosensitive resin composition of the present invention may further contain an N,N' -tetraalkyl-4, 4 ' - diaminobenzophenone, an N-aryl- a -a ino acid such as N- phenylglycine, or the like as an additive, and may further contain a heat polymerization inhibitor, an adhesiveness-imparting agent, a colorant or the like, if necessary.

The photosensitive material of the present invention is prepared by coating a solution of the photosensitive resin composition of the present invention as a liquid resist on the surface of a metal as a substrate, and by drying the coated layer to form a photosensitive layer. A print circuit board can be produced by printing a device pattern on the photosensitive material by means of lithography technique and, then, processing by etching, plating or the like. Also, the photosensitive material of the present invention may be produced by coating the solution of the photosensitive resin composition of the present invention on a polymeric film such as polyethylene terephthalate by a well known method, drying to form a dry film, and then, laminating the dry film on the surface of a metal as a substrate to form a photosensitive layer.

In order to make a solution which can be easily coated, the photosensitive resin composition of the present invention may be diluted with a solvent such as acetone, methyl cellosolve, methyl ethyl ketone, toluene, methanol, propylene glycol monoethyl ether, dimethylformamide or the like, or a mixture thereof. The coating can be carried out with a roll coater, an air knife coater, a bar coater, a spin coater or the like. The drying is carried out at a temperature 60 to 130°C. After drying, the photosensitive layer preferably has a thickness of 5 to 100 μm.

Light exposure of the photosensitive layer is carried out by light generated from a light source such as a high pressure mercury lamp. Development of the exposed photosensitive layer is carried out by using an alkaline aqueous solution of sodium carbonate or other water-soluble alkaline materials. Etching and plating can be carried out by the conventional methods. Then, the subsequent step of removing the light-cured part of the photosensitive layer can be carried out by using a strong alkaline aqueous solution.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention is more concretely illustrated with reference to Examples. EXAMPLE 1 2- (2-trifluoromethylphenyl ) -4, 5-bis (4- methoxyphenyl) imidazole dimer as a photoinitiator compound of the present invention was synthesized in accordance with the method disclosed in JP-B-5-60570 , and was obtained as a yellow brown powder having a melting point of 194 to 198°C. An ultraviolet (UV) ray- absorption spectrum of the obtained powder in acetonitrile is illustrated in Fig. 1. The maximum absorption wavelength of the UV ray- absorption spectrum was 234 n . This compound provided a pale greenish radical coloration as irradiated to ultraviolet rays. Methacrylic acid, ethyl methacrylate and styrene were copolymerized to produce a carboxyl group-containing copolymer material having a molecular weight of 60,000. Having 100 g of this copolymer as the Component (A) , the Component (B) and the solvents were blended therewith as shown in the following Table 1, to obtain a solution of a photosensitive resin composition. Table 1

6.4 g of the photoinitiator compound of the present invention and 25 g of acetone were added to the above obtained solution in the dark. The compound added was easily dissolved. COMPARATIVE EXAMPLE 1

In place of the photoinitiator compound of Example 1, 6.4 g of 2- (2, 3-dichlorophenyl) -4, 5-bis (4-methoxyphenyl) - imidazole dimer as a photoinitiator compound having a similar chemical structure and 25 g of acetone were added to the solution prepared in the same manner as mentioned in Example 1, but the photoinitiator compound added was hardly dissolved in the solution even after being stirred for 2 hours, and only a part of the photoinitiator compound was dissolved even after further adding 50 g of acetone . EXAMPLE 2 The solution of the photosensitive resin composition prepared in Example 1 was coated on a glass fiber-epoxy resin board laminated with a copper sheet (manufactured by Sumitomo Bakelite Co., Ltd.) with a bar coater, and was dried in an oven at 100°C for 10 minutes to form a photosensitive layer having a thickness of 20 μm. The coated substrate was heated on a hot plate, and a PET film (manufactured by Toray Industries, Inc.) with a thickness of 25 μm was suction-adhered thereon under vacuum to produce a photosensitive material with a resist layer.

A Stoufer 21 gradation step tablet (manufactured by Electrophotographic Association) was placed as a negative on the above produced photosensitive material, and a quartz glass plate (manufactured by Seiko Tokushu Glass K.K.) of 2.3 mm in thickness was further placed thereon and was further suction-adhered under vacuum to completely adhere the negative and the photosensitive material, which were then exposed to light from a parallel light-exposing apparatus (manufactured by Ushio Inc.) having a high pressure mercury lamp at 600 mj/cm². Then, after removing the PET film, the photosensitive material was dipped in a 1% sodium carbonate aqueous solution and shaken in a room at 20°C for 90 seconds, and consequently the unexposed part could be easily dissolved and removed. The thickness of the light-cured part of the layer formed on the coated substrate was measured with a contact type film thickness measuring apparatus (manufactured by Tokyo Seimitsu Co., Ltd. ) . As a reference example, a photosensitive resin composition containing B-CIM was prepared in the same manner as above, and the photosensitive resin composition was coated on a substrate in the same manner as above to form a light-cured layer which was then subjected to the same measurement as mentioned above. The layer's thickness of each step of the gradation step tablet was measured, and the highest step number of the gradation step tablet retaining at least 50% of the maximum layer thickness was made as an index for a sensitivity, as shown in the following Table 2. Table 2

As the result, it was proved by the difference in the step numbers shown in Table 2 that the photosensitive material of the present invention had a remarkably high sensitivity.

INDUSTRIAL APPLICABILITY The photosensitive resin composition of the present invention can be easily prepared and has a high sensitivity.

By using the photosensitive material of the present invention, resist patterns which are high in quality and resolution can be efficiently formed on a print circuit board or the like.

Claims

CLAIMS : 1. A photosensitive resin composition comprising (A) a carboxyl group-containing polymer, (B) a photopolymerizable compound having an ethylenic unsaturated group, and (C) 2- (2-trifluoromethylphenyl) - 4, 5-bis (4-methoxyphenyl) imidazole dimer shown as Compound (1) below, as a photoinitiator compound:

Compound ( 1 )

2. A photosensitive material prepared by coating and drying the photosensitive resin composition as defined in Claim 1 on a substrate.