JP2000297137A - Photosensitive resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photosensitive resin composition having high heat resistance, excellent developing property and high sensitivity by compounding a reaction product of an epoxy acrylate and a polybasic acid anhydride of a specific base number, an epoxy resin and a photopolymerization initiator. SOLUTION: An epoxy acrylate comprising a reaction product of a two functional epoxy resin and an acrylic acid, and a polybasic acid anhydride of base number: 4 are used. As the epoxy acrylate, among them, a bisphenol A epoxy acrylate is suitable. Usually, per 1 mole of the epoxy acrylate, 0.1-0.9 mole of the polybasic acid anhydride is used. An acid value of the reaction product is preferably about 50-100 mg KOH/g. As the epoxy resin in the case of use for a resist ink, triglycidyl isocyanurate is preferable. The epoxy resin and a photopolymerization initiator are usually used not more than 50 wt.% and 0.1-20 wt.%, respectively, on the basis of a resin component in the composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive resin composition used as a material for a printed wiring board, and more particularly to a photosensitive resin composition having high photosensitivity, good resolution, and high heat resistance. The present invention relates to a photosensitive resin composition used as a material for a printed wiring board.

[0002]

2. Description of the Related Art In recent years, in response to the demand for smaller and higher-density electronic devices, it has become important to reduce the size and weight of printed wiring boards and to make them lighter and thinner. Until now, the solder resist material applied on the substrate has been generally used, which has been cured by ultraviolet rays, can be developed with dilute alkali, and has excellent plating resistance and solvent resistance. For example, pop-up phenomena occur at the solder resist / encapsulation resin interface in a built-up substrate or the like, and there have been problems with the heat resistance of the solder resist.

Further, when the light sensitivity of the solder resist is low, a large amount of exposure is required, and the exposure time becomes long. Although it is advantageous to shorten the exposure time economically, the current resist has a high minimum exposure amount and it is impossible to shorten the exposure time. There is a strong demand for high sensitivity solder resists with low minimum exposure. JP-A-61-243869 discloses that a novolak type epoxy compound is reacted with an unsaturated carboxylic acid to impart photosensitivity, and then a saturated or unsaturated polybasic anhydride is reacted to impart alkali developability. An example using the photosensitive resin described above is disclosed (hereinafter, this resin is referred to as a novolak type photosensitive resin). It is said that a novolak type photosensitive resin has a high crosslink density of a cured product and as a result exhibits high heat resistance. However, in practical use, they are used in combination with various additives from the viewpoints of sensitivity and resolution, and therefore have insufficient heat resistance.

[0004]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a photosensitive resin composition having high heat resistance, excellent developability, and high sensitivity.

[0005]

Means for Solving the Problems The present inventors have made intensive studies in view of the above problems, and as a result, completed the present invention. That is, the present invention provides a reaction product (I) of an epoxy acrylate (a) comprising a reaction product of a bifunctional epoxy resin and acrylic acid and a polybasic acid anhydride (b) having 4 bases, an epoxy resin (c) and It is a photosensitive resin composition containing a photopolymerization initiator (d).

Epoxy acrylate is obtained by reacting an epoxy resin with acrylic acid, and is known, for example, by Kiyomi Kato and Shoji Nakahara, “Introduction to UV Curing Technology”, Polymer Publishing Association (1984). . The epoxy acrylate (a) of the present invention uses a bifunctional epoxy resin. Epoxy acrylate (a) has unsaturated bonds at both ends of the molecule, and the distance between unsaturated bonds in the molecule is longer than that of the novolak type. This is presumed that the reaction of unsaturated bonds between molecules of the bifunctional epoxy proceeds, and it is expected that long-chain molecules will be formed with a small amount of light.

Specifically, bisphenol A type epoxy acrylate, bisphenol Z type epoxy acrylate, xylene novolak epoxy acrylate, and a composition or a reaction product obtained by mixing these alone or two or more of them as appropriate. . Among them, bisphenol A type epoxy acrylate which is easily available is suitable.

The polybasic anhydride (b) having 4 bases according to the present invention includes, for example, pyromellitic anhydride, naphthalene-1,
4,5,8-tetracarboxylic dianhydride, benzophenone tetracarboxylic anhydride, ethylene glycol bis (anhydrotrimellitate), glycerin bis (anhydrotrimethate), 3,3 ', 4,4'- Examples thereof include diphenylsulfonetetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride, and other compounds having an acid anhydride in the molecule, and a composition containing these alone or in combination of two or more.

A reaction product (I) of an epoxy acrylate (a) comprising a reaction product of the above-mentioned bifunctional epoxy resin and acrylic acid and a polybasic anhydride (b) having 4 bases is produced.
As the amount of (b) used increases relative to (a), the molecule of the reactant (I) obtained usually becomes larger, and the acid value of the resin also becomes larger. In the present invention, (b)
It is used in the range of 0.1 to 0.9 mol, preferably 0.4 to 0.7 mol. The reaction is carried out at a temperature of 60 to 100 ° C under conditions selected from the range of 1 to 100 hours.

The reaction between (a) and (b) is mainly such that the hydroxyl group of epoxy acrylate (a) reacts with the acid anhydride group of (b) to form an ester bond and a carboxyl group. The end point of the reaction is when substantially all of the acid anhydride groups in (b) have reacted. Specifically, the end point of the reaction is FT
The reaction is carried out while monitoring with -IR, etc., and the end point is preferably when the acid anhydride peak (around 1850 cm ^-1 ) disappears.

The resin acid value obtained above is 40 to 400 mgKOH /
g. However, the developability is such that the acid value is 50-100.
Good degree. Therefore, it is preferable to select the amount of the polybasic acid anhydride (b) to be used in accordance with the kind of the polybasic acid anhydride (b) so that the acid value falls within this range. When the acid value is out of the preferable range, the acid value may be appropriately reduced by adding an epoxy compound or the like and reacting, or the acid value may be increased by additionally adding a polybasic acid anhydride (b). I can, and
A polybasic acid anhydride having 3 or less bases may be added. Examples of the polybasic acid anhydride having 3 or less bases include tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and trimellitic anhydride.

Further, a solvent can be used for adjusting the viscosity during the reaction and the like, and those having a boiling point in a range that allows most of the photosensitive resin composition to evaporate when the coating film is dried are preferable. For example, ketones such as acetone and methyl ethyl ketone, esters such as dipropylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether, diethyl ether monomethyl ether acetate and diethyl ether monomethyl ether, and aromatics such as solvent naphtha, toluene, xylene, and ethylbenzene Hydrocarbons or the like are used alone or in combination of two or more.

The reaction product (I) produced above is mixed with an epoxy resin (c) and a photopolymerization initiator (d) to be used for various applications as a photosensitive resin composition. Here, as the epoxy resin (c), bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin, methylated biphenyl type epoxy resin, novolak type epoxy resin, triglycidyl isocyanurate, alicyclic epoxy resin And the like, and used singly or as a mixture of two or more. Among them, when a resist ink is used, triglycidyl isocyanurate, which progresses slowly in the dark reaction upon drying, is preferable. The amount of the epoxy resin (d) must be at least the equivalent of the carboxylic acid contained in the photosensitive resin, and is usually 50 parts by weight or less, preferably 3 to 45 parts by weight of the resin component in the composition.

The photopolymerization initiator (d) is a known one, for example, α-diketones such as benzyl and diacetyl, acyloin ethers such as benzoylethyl ether and benzoin isopropyl ether, thioxanthone and 2,4-diethylthioxanthone. Thioxanthones, benzophenone, benzophenones such as 4,4′-bis (dimethylamino) benzophenone, acetophenone, acetophenones such as 2,2′-dimethoxy-2-phenylacetophenone, β-methoxyacetophenone, anthraquinone,
Quinones such as 4-naphthoquinone and peroxides such as di-t-butyl peroxide are used alone or in combination of two or more. The amount used is the amount of the resin component in the composition
It is 0.1 to 20% by weight, preferably 0.2 to 10% by weight.

The above-mentioned components are kneaded with a three-roll mill, a homogenizer or the like to obtain a photosensitive resin composition of the present invention. At the time of mixing, known additives such as a filler, a curing accelerator, a defoaming agent, a surface treatment agent, a flame retardant, a pigment, and a dye can be added according to the use. Examples of fillers include silicas such as natural silica, fused silica and amorphous silica, white carbon, titanium white, aerosil, alumina, talc, natural mica, synthetic mica, kaolin, clay, aluminum hydroxide, barium sulfate, and E-glass. ,
A-glass, C-glass, L-glass, D-glass, S
-Glass, M-glass, G20-glass, etc., as curing accelerators, 2-methylimidazole, 2-ethyl-4
-Methylimidazole, 2-undecylimidazole,
Examples thereof include imidazoles such as 2-heptadecylimidazole, 2-phenylimidazole and 1-benzyl-2-methylimidazole, tertiary amines such as benzyldimethylamine, and phosphine and phosphonium-based phosphorus compounds.

Here, when used as a resist ink, the content of the resin component in the photosensitive resin composition is less than the total amount.
It is preferable to prepare so as to be 30 to 90% by weight. If the amount of the resin is less than 30% by weight, it is difficult to secure a uniform film thickness of the resin, and the quality becomes unstable, so that the resin cannot be used as a printed wiring board. When the amount of resin component exceeds 90%,
It may cause peeling on the applied printed wiring board or cause variations in electrical characteristics.

The photosensitive resin composition (A) of the present invention is useful as a resist ink for a permanent resist such as an etching resist, a solder resist, and an insulating resist for a built-up wiring board, and a paint, a coating agent, and an adhesive. It can be used as an agent and the like. The photosensitive resin composition of the present invention is cured, for example, as follows to obtain a cured product. That is, the photosensitive resin composition of the present invention is applied to a printed wiring board in a film thickness of 10 to 160 μm by a method such as a screen printing method, a spray method, a roll coating method, an electrostatic coating method, and a curtain coating method, After drying the coating at 60-110 ° C,
After irradiating ultraviolet rays through a negative film and developing the unexposed portions with a dilute alkaline aqueous solution, the composition is sufficiently cured by irradiating with ultraviolet rays or heating to further improve physical properties to obtain a cured film.

The light source for irradiating active energy rays for curing the photosensitive resin composition (A) of the present invention includes a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a xenon lamp and a metal hydride lamp. is there. The exposure amount is 100 to 2000 mJ / cm ² , preferably,
00 mJ / cm ² . If the amount of exposure is small, the irradiated portion does not cure and dissolves during development. The reason why the resin of the present invention has higher sensitivity than the novolak type photosensitive resin is not clearly understood, but since the acrylic group is not adjacent in the molecule, a cross-linking reaction proceeds between other molecules and light is effectively used. It is thought that it was done.

The photosensitive resin composition of the present invention (A) may be developed by irradiation with a known method such as a spray developing method of spraying with a spray or a dip developing method of dipping a printed wiring board in a developing solution and vibrating. Can be used. Developer temperature is 5-50
° C, preferably 25 ° C to 40 ° C. If the temperature is low, problems such as a long development time and poor developability occur. If the temperature is high, the cured part irradiated with light will dissolve. As the developing solution, a known dilute alkali aqueous solution such as an aqueous solution of sodium carbonate, sodium hydroxide or ammonium hydroxide can be used. The amount of the alkaline agent in the aqueous solution is preferably from 0.1 to 5.0% by weight.

The resin of the present invention can form a finer pattern than a novolak type photosensitive resin. That is, a phenomenon was observed in which solubility in an alkali developing solution was good and developability was good. The photosensitive resin derived from the bifunctional epoxy of the present invention is a molecule that is enlarged by a photocrosslinking reaction, and the higher the molecular weight, the higher the acid value. That is, it is considered that high molecular weight molecules, which are originally difficult to dissolve, are easily dissolved in the developer. On the other hand, in the novolak type photosensitive resin,
Not all high molecular weight ones have high acid numbers. For these reasons, it is thought that the photosensitive resin derived from the bifunctional epoxy of the present invention has good resolution, but the details are not known.

When the photosensitive resin composition (A) of the present invention is heated and cured after development, the curing temperature is 100 to 250 ° C., preferably 120 to 200 ° C. If the temperature is low, it takes a long time to cure, and if the temperature is high, problems such as discoloration and partial swelling occur.

[0022]

EXAMPLES Hereinafter, the present invention will be specifically described based on examples and comparative examples, but the present invention is not particularly limited by the following examples. Synthesis Example 1 100 parts of bisphenol A type epoxy acrylate (SP1509 manufactured by Showa Polymer) and 17.8 parts of pyromellitic anhydride (equivalent to 40% of the mole number of epoxy acrylate) and dipropylene glycol monomethyl ether acetate / solvent naphtha (solvent) as a solvent (50/50) 117.8 parts were added, and the mixture was stirred at a reaction temperature of 70 ° C., and the peak of carboxylic anhydride (1850 cm ⁻¹ ) was traced by an infrared absorption spectrum, and disappeared after 6 hours. The carboxylic acid value of this resin was 75 mgKOH / g (hereinafter referred to as “resin (a)”).

SYNTHETIC EXAMPLE 2 The procedure of Example 1 was repeated except that 21.8 parts of pyromellitic anhydride (corresponding to 50% of the moles of epoxy acrylate) were added. The carboxylic acid value of this resin was 95 mgKOH / g (hereinafter referred to as “resin (b)”).

Synthesis Example 3 The same procedure as in Synthesis Example 1 was carried out except that 27 parts of pyromellitic anhydride (corresponding to 60% of the number of moles of epoxy acrylate) were added. The carboxylic acid value of this resin was 100 mgKOH / g (hereinafter referred to as “resin (c)”).

Synthesis Example 4 The same procedure as in Synthesis Example 1 was carried out except that 31.5 parts (corresponding to 70% of the mole number of epoxy acrylate) of pyromellitic anhydride were added. The carboxylic acid value of this resin was 130 mgKOH / g (hereinafter referred to as “resin (d)”).

Comparative Synthesis Example 1 100 parts of novolak type epoxy acrylate (epoxy equivalent before acryl modification: 270 g / eq), 33.8 parts of tetrahydrophthalic anhydride (corresponding to 60% of the mole number of epoxy acrylate hydroxyl group), and propylene as a solvent 66.9 parts of glycol monomethyl ether acetate and solvent naphtha
136.9 parts of 66.9 parts were added to adjust the solid content to 50%. Mechanical stirring was carried out under heating at 70 ° C., and the peak of carboxylic anhydride (1850 cm ⁻¹ ) was traced by infrared absorption spectrum, and disappeared after 8 hours. The carboxylic acid value of this resin was 93 mgKOH / g (hereinafter referred to as “resin (d)”).

Example 1 A three-roll mill (manufactured by IMEX Co., Ltd.) was mixed using the resin (c) prepared as described above with the composition shown in Table 1.
And kneaded with a screen printer (LS15GX, manufactured by Neurong Seimitsu Kogyo Co., Ltd.) so as to coat the copper-clad laminate having a surface mechanically polished to a film thickness of 40 μm. The coated substrate was placed in a dryer at 70 ° C. for 30 minutes, and after confirming that tackiness had disappeared, an exposure pattern film was mounted on the substrate using a parallel light exposure machine and exposed to light of 250 mJ / cm ² . After exposure, development was performed with a 1% aqueous solution of sodium carbonate for 60 seconds at a spray pressure of 1.5 kg / cm ² . After washing with water, it was placed in a hot air drier at 160 ° C. for 1 hour to perform heat curing. The test piece having the obtained cured film was measured for glass transition temperature (Tg), photosensitivity, developability, and resolution. The results are shown in Table 2.

The test method and the evaluation method are as follows. (Measurement of glass transition temperature (Tg))
The substrate was peeled off from the twice-coated substrate and measured by a TMA tensile test according to the test method of JIS C 6481. (Evaluation of photosensitivity) A light intensity of 500 mJ / cm ² was applied to the resist film after coating and drying through a 25-step step density tablet (Riston Density 0.5 to 1.7 ΔD = 0.05 manufactured by DuPont) at 30 ° C., 1% sodium carbonate. After the development with the aqueous solution, the number of the remaining column was read. A larger number indicates that the exposure was performed with a smaller amount of light, indicating a higher sensitivity.

(Evaluation of Developability) Three types of test pieces having a line width of a cured resist film of 100, 50, and 25 μm were prepared, and cross-sections were observed. Exposure was 250 mJ / cm ² . In the evaluation, the cross section of the cured resist was regarded as a trapezoid, and the difference between the upper bottom (L1: exposed film side) and the lower bottom (L2: copper surface side) was examined. The value obtained by subtracting the upper base from the lower base is shown as a result. The smaller the absolute value of this value, the better the developability. The coating thickness is
It was converted to 40 μm. (Evaluation of resolution) The line width of the resist cured film is 100, 5
Three types of test pieces of 0 and 25 μm were prepared, and cross-sections were observed. Exposure was 200 mJ / cm ² . For evaluation, any 20 locations were selected as test portions, observed with a microscope, and displayed as the number of normal portions relative to the number of tests.

Comparative Example 1 A resist ink was prepared with the composition shown in Table 1 except that (e) was used as the main resin, and the same operation as in Example 1 was carried out. 2 is shown.

Examples 2 to 4 Resins (a) to (d) were mixed as shown in Table 1 to prepare a resist ink, and Tg and average molecular weight were examined. Table 3 shows the results. Table 3 also shows the case of Example 1 and Comparative Example 1. The average molecular weight of the resin was measured by GPC. The number average molecular weight in terms of polystyrene was determined using an RI detector.

[0032]

[Table 1] Actual 1 Actual 2 Actual 3 Actual 4 Ratio 1 Resin Type Hydro Niho Part 50 50 50 50 50 TGIC 15 15 15 Denakal T 15 15 Irgacure 651 5 5 5 5 5 BYK357 1 1 1 1 1 1 BYK0554 1 1 1 1 1 Phthalocyanine green 1 1 1 1 1 BST # 200 20 20 20 20 20 Barium sulfate 10 10 10 10 10 TGIC: Triglycidyl isocyanurate Denacal T: Xylene novolac epoxy resin,
Nagase Kasei Irgacure 651: Photopolymerization initiator, Ciba Geigy BYK357, BYK054: Antifoaming agent, surface smoothing agent, Big Chemie phthalocyanine green: Sanyo dye BST # 200: Surface treated ground silica

[0033]

[Table 2] Tg light sensitivityDevelopability (μm) Resolution ° C stage 100μm 50μm 25μm 100μm 50μm 25μm Example 1 140 22 5 2 1 20/20 20/20 20/20 Comparative Example 1 105 15 12 5 -5 18/20 0/20 0/20

[0034]

Table 3 Example Comparative Example 1 2 3 4 1 Tg (° C) 140 115 125 160 105 Average molecular weight ^* 2400 1900 2200 2600 2500 Acid value (mgKOH / g) 105 75 95 130 93 * Number average molecular weight in terms of polystyrene

[0035]

As described above, the present invention is a resin obtained by reacting an acrylic-modified bifunctional epoxy resin with a polybasic acid anhydride, which has high sensitivity, good developability, and high heat resistance. It has excellent properties.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Jun Yokoyama 6-1-1 Shinjuku, Katsushika-ku, Tokyo Mitsubishi Gas Chemical Co., Ltd. Tokyo Research Laboratory F-term (reference) 2H025 AA01 AA02 AA04 AA10 AB15 AC01 AD01 BC74 BC85 CA01 CA18 CC20 FA03 FA17 FA29 4J036 AD08 AE05 CA19 CA21 CA25 HA02 JA10 5E314 AA27 AA32 AA33 CC02 CC03 CC07 DD06 FF01 GG08

Claims (4)

[Claims] 1. A reaction product (I) of an epoxy acrylate (a) comprising a reaction product of a bifunctional epoxy resin and acrylic acid and a polybasic anhydride (b) having 4 bases, an epoxy resin (c) and A photosensitive resin composition comprising a photopolymerization initiator (d). 2. The photosensitive resin composition according to claim 1, wherein said polybasic anhydride (b) is used in a ratio of 0.4 to 0.7 mol per mol of said epoxy acrylate (a). 3. The photosensitive resin composition according to claim 1, wherein said polybasic acid anhydride (b) is pyromellitic anhydride. 4. The photosensitive resin composition according to claim 1, wherein said epoxy resin (c) is a bisphenol A type epoxy resin.