JP2000330272A - Photosensitive resin composition for photosensitive film and photosensitive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photosensitive resin composition and a photosensitive film having superior resolution and adhesiveness to a substrate and capable of stably forming a resist pattern in a line width of <=20 μm after development. SOLUTION: This photosensitive resin composition for photosensitive films contains an acrylic resin having a high acid value, wherein the acrylic resin is a copolymer comprising (meth)acrylic acid and 2-50 wt.% benzyl(meth)acrylate or 12-18C-alkyl(meth)acrylate as constituent monomers and having a weight average molecular weight of 8,000-200,000 and a molecular weight distribution (Mw/Mn) of <=2.5. The photosensitive film has a photosensitive layer composed of this 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 for a photosensitive film used for manufacturing a printed wiring board and the like, and a photosensitive film using the same.

[0002]

2. Description of the Related Art As a resist material used for manufacturing a printed wiring board, a photosensitive resin composition and a photosensitive film using the same are widely known. This photosensitive resin composition usually comprises a binder resin such as a high acid value resin, a crosslinking agent such as a polyfunctional (meth) acrylate, a photopolymerization initiator, and a dye, and an additive such as a heat stabilizer. is there. This photosensitive resin composition is coated on a polyester film or the like and dried to produce a photosensitive film having a photosensitive layer composed of the photosensitive resin composition.

The manufacture of a printed wiring board using this photosensitive film is usually performed as follows. A photosensitive film is laminated on a polished or chemical-treated copper-clad substrate with the photosensitive layer facing the substrate, and a negative mask is overlaid thereon to expose and cure the photosensitive film. After exposure, development is carried out using an aqueous solution of an alkali such as a 0.5 to 3% by weight aqueous sodium carbonate solution to form a resist pattern on the substrate.

As a method of forming a wiring pattern on a substrate, there are a tenting method and a plating method. Tenting method is a method in which through holes for chip mounting are protected with a resist at the same time as the formation of a resist pattern, etching is performed to form a wiring pattern, and the resist is peeled off using an aqueous sodium hydroxide solution or the like. is there. On the other hand, in the plating method, copper is deposited on a substrate on which no through-hole or resist pattern is formed by electroplating, the copper is protected by solder plating, the resist pattern is peeled off, and solder is applied using aqueous ammonia or the like. In this method, a portion other than the plating is etched to form a wiring pattern.

[0005]

The wiring pattern thus formed is perpendicular to the substrate and the line width is reduced, so that the density of the wiring pattern is increased and the printed wiring board is formed. The size can be reduced. However, since the resolution of the photosensitive film using the conventional photosensitive resin composition was not less than 20 μm, the resist pattern after development and the wiring pattern after etching were reduced to 20 μm.
It has been difficult to form a line with a line width of μm or less stably.

[0006] The resist pattern and the wiring pattern
In order to stably mold with a line width of 0 μm or less, a method using a liquid resist agent as a resist material has been adopted. However, the liquid resist agent is disadvantageous as compared with the photosensitive film in terms of controlling the thickness of the film formed on the substrate after coating, and exposing the circuit (etch cut) and the stability of fog (bleeding).

Therefore, in order to increase the resolution of the photosensitive film, the solubility of the binder resin is increased by increasing the acid value of the binder resin used in the photosensitive resin composition or decreasing the molecular weight thereof, thereby improving the developing property. The idea of improving is made. However, when the acid value of the binder resin is increased or the molecular weight is decreased, there is a problem that the adhesiveness of the resist pattern to the copper foil on the substrate is deteriorated. In particular, the line width of the resist pattern is 30 μm.
Below m, the erosion of the aqueous alkali solution tends to cause peeling of the bonded portion between the resist pattern and the substrate and dents in a convex pattern (hereinafter referred to as relief),
There is a problem that a resist pattern perpendicular to the substrate cannot be formed stably. On the other hand, if the molecular weight of the binder resin is increased in order to improve the adhesiveness of the resist pattern to the substrate and the stability of the vertical development of the relief in an alkaline aqueous solution, the solubility of the uncured portion in the alkaline aqueous solution decreases during resist development. However, there is a problem that developability is deteriorated.

[0008] Therefore, the object of the present invention is to provide a resolution,
Provided is a photosensitive resin composition for a photosensitive film, which has excellent adhesion to a substrate and can stably form a resist pattern formed after development with a line width of 20 μm or less, and a photosensitive film using the same. It is in.

[0009]

The present inventors have made intensive studies on the molecular weight distribution of the binder resin and the balance between the hydrophilic group component and the lipophilic group component in the binder resin, and as a result, have narrowed the molecular weight distribution of the binder resin. By doing so, the solubility of the binder resin in an aqueous alkali solution is improved, and benzyl (meth) acrylate or an alkyl (meth) acrylate having an alkyl group having 12 to 18 carbon atoms is used as a constituent monomer having a lipophilic group. Introduces a good balance between the hydrophilic group component and the lipophilic group component in the binder resin, that is, the balance between the solubility of the uncured portion in an alkaline aqueous solution and the stability of the cured portion in an alkaline aqueous solution (erosion resistance). Found that a resist pattern can be formed stably with a line width of 20 μm or less. It has completed the present invention.

That is, the photosensitive resin composition for a photosensitive film of the present invention is a photosensitive resin composition for a photosensitive film containing an acrylic high acid value resin, wherein the acrylic high acid value resin is: (Meth) acrylic acid and 2 to 50% by weight of benzyl (meth) acrylate or alkyl (meth) acrylate having an alkyl group having 12 to 18 carbon atoms
And an acrylic high acid value resin having a weight average molecular weight of 8,000 to 20.
Wherein the molecular weight distribution (Mw / Mn) of the acrylic high acid value resin is 2.5 or less. Further, the photosensitive film of the present invention has a photosensitive layer comprising the photosensitive resin composition for a photosensitive film.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The acrylic high acid value resin in the present invention refers to an acrylic resin having an acid value enough to dissolve in an aqueous alkaline solution used for developing a resist pattern. The acid value of the acrylic high acid value resin is not particularly limited as long as it is an acid value enough to dissolve in an alkaline aqueous solution, and is, for example, 80 mgKOH / g or more, and preferably 120 mgKOH / g or more. Acid value is 80m
If it is less than gKOH / g, the solubility in an aqueous alkali solution may be insufficient.

The weight average molecular weight of the acrylic high acid value resin in the present invention is in the range of 8,000 to 200,000, preferably in the range of 20,000 to 90,000. If the weight average molecular weight is less than 8,000, the solubility in an alkaline aqueous solution becomes too high, and peeling of a resist pattern or the like occurs. If it exceeds 200,000, the solubility in an alkaline aqueous solution is reduced, and the developability is deteriorated. .

The molecular weight distribution (Mw / Mn) of the acrylic high acid value resin in the present invention is 2.5 or less, preferably 1.5 to 2.0. Molecular weight distribution (Mw / Mn)
If it exceeds 2.5, the high molecular weight component in the acrylic high acid value resin increases, so that the solubility in an aqueous alkali solution decreases, and at the same time, the low molecular weight component in the acrylic high acid value resin also increases. As a result, the stability of the vertical development of the relief of the resist pattern with respect to the aqueous alkali solution decreases, and it becomes impossible to form a resist pattern perpendicular to the substrate.
Here, Mw is a weight average molecular weight, and Mn is a number average molecular weight.

The acrylic high acid value resin in the present invention comprises:
It is a copolymer containing (meth) acrylic acid and benzyl (meth) acrylate or an alkyl (meth) acrylate having an alkyl group having 12 to 18 carbon atoms as constituent monomers. Here, (meth) acrylic acid refers to acrylic acid and / or methacrylic acid, and benzyl (meth) acrylate refers to benzyl acrylate and / or
Or benzyl methacrylate, and alkyl (meth) acrylate is an alkyl acrylate and / or
Or refers to alkyl methacrylate.

(Meth) in acrylic high acid value resin
The ratio of the acrylic acid component is not particularly limited as long as the acid value of the acrylic high acid value resin is dissolved in the aqueous alkali solution, and is not particularly limited, but is, for example, 12 to 28% by weight, and preferably 18 to 25% by weight. %. If the proportion of the (meth) acrylic acid component is less than 12% by weight, the solubility in the aqueous alkali solution may decrease. If the proportion of the (meth) acrylic acid component exceeds 28% by weight, the solubility in the aqueous alkaline solution may be reduced. It may be too high, and the resist pattern may be peeled off.

The proportion of the benzyl (meth) acrylate component or the alkyl (meth) acrylate component having an alkyl group having 12 to 18 carbon atoms in the acrylic high acid value resin is 2 to 50% by weight. If the proportion of these components is less than 2% by weight, the adhesion of the resist pattern to the substrate and the stability of the vertical development of the relief in an alkaline aqueous solution are reduced, and a resist pattern perpendicular to the substrate cannot be formed. On the other hand, when the proportion of these components exceeds 50% by weight, the solubility in an aqueous alkali solution decreases,
Developability deteriorates. The benzyl (meth) acrylate component is preferably 15 to 35% by weight, and has 12 to
The content of the alkyl (meth) acrylate component having 18 alkyl groups is preferably 30 to 50% by weight.

The acrylic high acid value resin of the present invention may contain another vinyl monomer as a constituent monomer. Examples of the other vinyl monomers include alkyl having a C1 to C11 alkyl group such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. (Meth) acrylate; hydroxyalkyl (meth) acrylate such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate; ethylene glycol (meth) acrylate, butylene glycol (meth) acrylate, vinyl acetate, ) Acrylonitrile, styrene and the like. The ratio of the other vinyl monomer component in the acrylic high acid value resin is in the range of 0 to 70% by weight.

In the present invention, the acrylic high acid value resin is
It is manufactured by a known polymerization method such as a suspension polymerization method, an emulsion polymerization method, and a solution polymerization method. Among them, the molecular weight distribution (Mw / M
Polymer having n) of 2.5 or less (polymer having a narrow molecular weight distribution)
The suspension polymerization method is suitably used because it is easy to obtain.

The photosensitive resin composition for a photosensitive film of the present invention contains the above-mentioned acrylic high acid value resin. If necessary, a photopolymerizable crosslinking agent, a photopolymerization initiator,
Additives and the like are blended.

The crosslinking agent may be any one usually used in a photosensitive resin composition, such as trimethylolpropane triacrylate, tetraethylene glycol diacrylate, dipentaerythritol hexaacrylate, 1,6- Acrylic esters of polyhydric alcohols such as hexanediol diacrylate and diethylene glycol diacrylate; epoxy acrylates such as trimethylolpropane triglycidyl ether triacrylate and cardepoxy diacrylate; urethane acrylate, bisphenol A polyoxyethylene dimethacrylate, and polyethylene glycol diacrylate Acrylate and the like.

The photopolymerization initiator may be any one usually used in a photosensitive resin composition, and examples thereof include derivatives such as benzophenone, anthraquinone, thioxanthone and acetophenone. Examples of the additive include a dye, a pigment, a thermal polymerization inhibitor, a copper chelating agent, and, if necessary, a filler and an antifoaming agent.

The amount of the acrylic high acid value resin is not particularly limited, but is, for example, 40 to 80 parts by weight based on 100 parts by weight of the photosensitive resin composition for a photosensitive film.
Preferably it is 50 to 70 parts by weight. If the blending amount of the acrylic high acid value resin is less than 40 parts by weight, the solubility in an aqueous alkali solution may decrease, and if it exceeds 80 parts by weight, mechanical properties after curing may be insufficient. .

The amount of the crosslinking agent is not particularly limited. For example, the photosensitive resin composition 100 for a photosensitive film may be used.
30 to 50 parts by weight with respect to parts by weight, preferably 3 parts by weight.
5 to 45 parts by weight. If the amount of the crosslinking agent is less than 30 parts by weight, the mechanical properties after curing may be insufficient. If the amount exceeds 50 parts by weight, the solubility in an alkaline aqueous solution may decrease, and the resolution may decrease. is there.

The blending amount of the photopolymerization initiator is not particularly limited. For example, the photosensitive resin composition 1 for a photosensitive film may be used.
3 to 8 parts by weight, preferably 5 to 100 parts by weight.
６6 parts by weight. If the amount of the photopolymerization initiator is less than 3 parts by weight, the sensitivity may be insufficient. If the amount exceeds 8 parts by weight, the cured product may have a low molecular weight and become brittle.

The photosensitive film of the present invention is obtained by forming a photosensitive layer comprising the above-mentioned photosensitive resin composition for a photosensitive film on a film of polyester or the like. The photosensitive film of the present invention may be obtained by applying the above-described photosensitive resin composition for a photosensitive film on a film of polyester or the like, drying the film, and, if necessary, protecting the photosensitive layer with a film of polyolefin or the like. Obtained by The photosensitive resin composition for a photosensitive film is methyl ethyl ketone (ME
K), a solution such as acetone, methanol, isopropyl alcohol, methoxypropyl acetate, or the like, may be used as a solution after coating.

The photosensitive layer is laminated on a substrate, is cured by actinic rays such as ultraviolet rays irradiated through a negative mask, and is developed by a developing solution such as an aqueous alkali solution.
This is used as a resist pattern. As a light source, a high-pressure mercury lamp, a xenon lamp, a metal halide lamp, or the like is used.

In such a photosensitive resin composition for a photosensitive film, the molecular weight distribution of the acrylic high acid value resin is narrow, and benzyl (meth) acrylate or a compound having 12 to 12 carbon atoms is contained in the acrylic high acid value resin. Since a high lipophilic group such as an alkyl (meth) acrylate having an alkyl group of 18 is included, the proportion of (meth) acrylic acid constituting the acrylic high acid value resin is increased, and the solubility in an aqueous alkali solution is increased. However, the formed resist pattern is less likely to be eroded by an aqueous alkaline solution. Therefore, even if the resist pattern is formed with a line width of 20 μm or less, peeling of the bonded portion between the resist pattern and the substrate and dent of the relief hardly occur, and a resist pattern perpendicular to the substrate can be formed stably.

[0028]

The present invention will be described below in detail with reference to examples. [Synthesis Example 1] A polymerization apparatus equipped with a stirrer, a thermometer, and a condenser was charged with 250 parts by weight of deionized water, and polyvinyl alcohol (degree of saponification 80%, degree of polymerization 1700) was added under stirring. 6 parts by weight were added. After completely dissolving the polyvinyl alcohol, methacrylic acid (hereinafter abbreviated as MAA): 20 parts by weight, benzyl methacrylate (hereinafter Bz)
MA): 10 parts by weight, butyl acrylate (hereinafter B)
A: 10 parts by weight, methyl methacrylate (hereinafter M
MA) 60 parts by weight, n-dodecyl mercaptan:
0.5 parts by weight and 0.4 parts by weight of azoisobutyronitrile were added, the temperature was raised to 75 ° C., and the reaction temperature was maintained at 75 ° C.
Allowed to react for hours. Thereafter, the temperature was raised to 90 ° C., and this temperature was maintained for 1 hour to terminate the reaction. Thereafter, the mixture was filtered and washed with a filter cloth having an opening of 10 μm, and dried with a circulating hot air dryer at 50 ° C. to obtain a vinyl polymer. The obtained polymer had a weight average molecular weight Mw = 51,040 and a molecular weight distribution Mw / Mn =
It was 1.84, and the acid value was 132 mgKOH / g. Here, the weight average molecular weight Mw and the number average molecular weight Mn were determined in terms of styrene by gel permeation chromatography (GPC) using HLC-8120GPC manufactured by Tosoh Corporation. THF was used as the solvent.

[Synthesis Examples 2 to 5] Polymerization was carried out in the same manner as in Production Example 1 with the vinyl monomer compositions shown in Table 1. Table 2 shows the characteristic values of the obtained vinyl polymer. SMA in Table 1 represents stearyl methacrylate.

[Comparative Synthesis Examples 1 and 2] Polymerization was carried out in the same manner as in Production Example 1 with the vinyl monomer compositions shown in Table 1. Table 2 shows the characteristic values of the obtained vinyl polymer.
It was shown to. BMA in Table 1 is butyl methacrylate, 2
-EHMA represents 2-ethylhexyl methacrylate.

[Comparative Synthesis Example 3] MEK: 185 parts by weight was added to a polymerization apparatus equipped with a stirrer, a thermometer, and a condenser, followed by stirring. MAA: 20 parts by weight, BzMA: 10
Parts by weight, BA: 10 parts by weight, MMA 60 parts by weight, n-dodecyl mercaptan: 0.1 parts by weight, azoisobutyronitrile: 0.5 parts by weight, the temperature was raised to 60 ° C, and the reaction temperature was raised to 60 ° C. The reaction was maintained for 4 hours. Then 65 ° C
, And the temperature was maintained for 1 hour to terminate the reaction. Table 2 shows the characteristic values of the obtained polymer.

[0032]

[Table 1]

[0033]

[Table 2]

Example 1 The polymer sample of Synthesis Example 1 was used as a photosensitive resin composition by the following method to prepare a photosensitive film, and a resist pattern was formed using the photosensitive film. The performance of the photosensitive film was evaluated by the following method. The results are shown in Table 3 and FIG.

[Examples 2 to 5] Performance evaluation was performed in the same manner as in Example 1 using the polymer samples of Synthesis Examples 2 to 5. The results are shown in Table 3 and FIGS.

[Comparative Examples 1 to 3] Performance evaluation was performed in the same manner as in Example 1 using the polymer samples of Comparative Synthesis Examples 1 to 3. The results are shown in Table 3 and FIGS. The adhesion of the resist pattern to the substrate was poor, and a resist pattern perpendicular to the substrate could not be formed.

[Preparation of Photosensitive Resin Composition] The polymer samples obtained in the synthesis examples and comparative synthesis examples were adjusted to a 50% by weight solution with MEK, and 150 g of this polymer solution and 0.5 g of tribromophenylsulfone were prepared. , Leuco Crystal Violet 1
g, malachite green 0.05 g, P, P′-diethylamino-benzophenone 0.1 g as a photoinitiator,
A solution of the photosensitive resin composition was prepared by blending 5.0 g of benzophenone, 10 g of isopropyl alcohol as a solvent, 20 g of trimethylolpropane triacrylate as a crosslinking agent, and 10 g of bisphenol A polyoxyethylene dimethacrylate.

[Preparation of Photosensitive Film] A solution of this photosensitive resin composition was applied on a polyethylene terephthalate film having a thickness of 20 μm and left at room temperature for 2 minutes.
After drying in an oven for 10 minutes, a photosensitive film having a photosensitive layer thickness of 30 μm was prepared.

[Evaluation of Adhesion] A photosensitive film was laminated on a copper-clad substrate heated at 60 ° C. while heating at 120 ° C. under a roll pressure of 3 kg / cm ² . In accordance with the test method of JIS D0202, 100 cross-cuts were formed in a cross-cut pattern on the laminated substrate. Next, a peeling test was performed, and the stripped state of the squares was evaluated according to JIS D0202 by the number of squares that did not peel. ○ ・ ・ ・ ・ 100 non-peeled squares △ ・ ・ ・ ・ 91-99 non-peeled squares × ・ ・ ・ ・ 90 or less non-peeled squares

"Evaluation of resist pattern formation" Then, using a negative film for evaluation (a pattern mask having a line width and a space width of 20 μm), 70 mJ using a 3 kW high-pressure mercury lamp.
After exposure to light / cm ² , the polyethylene terephthalate film was peeled off, and an unexposed portion was removed by spraying a 1% by weight aqueous solution of sodium carbonate at 30 ° C. for 60 seconds. The photocurable resist pattern formed by the photosensitive resin composition on the copper-clad substrate was observed and evaluated by SEM photograph.

[0041]

[Table 3]

[0042]

As described above, the photosensitive resin composition for a photosensitive film of the present invention is a photosensitive resin composition for a photosensitive film containing an acrylic high acid value resin,
The acrylic high acid value resin, (meth) acrylic acid,
Benzyl (meth) acrylate or C12-18
(Meth) acrylate 2 having an alkyl group
-50% by weight as a constituent monomer, and the weight average molecular weight of the acrylic high acid value resin is:
Since the molecular weight distribution (Mw / Mn) of the acrylic high acid value resin is 2.5 or less, it is excellent in resolution and adhesion to a substrate, and is formed after development. A resist pattern can be formed stably with a line width of 20 μm or less. Further, since the photosensitive film of the present invention has a photosensitive layer composed of the photosensitive resin composition for a photosensitive film, it has excellent resolution and adhesion to a substrate, and has a resist pattern formed after development of 20 μm.
It can be formed stably with the following line width, and the density of the wiring pattern can be increased, and the size of the printed wiring board can be reduced.

[Brief description of the drawings]

FIG. 1 is an SEM photograph showing a photocurable resist pattern formed on a copper-clad substrate using the photosensitive resin composition of Example 1.

FIG. 2 is an SEM photograph showing a photocurable resist pattern formed on a copper-clad substrate using the photosensitive resin composition of Example 2.

FIG. 3 is an SEM photograph showing a photocurable resist pattern formed on a copper-clad substrate using the photosensitive resin composition of Example 3.

FIG. 4 is an SEM photograph showing a photocurable resist pattern formed on a copper-clad substrate using the photosensitive resin composition of Example 4.

FIG. 5 is an SEM photograph showing a photocurable resist pattern formed on a copper-clad substrate using the photosensitive resin composition of Example 5.

FIG. 6 is an SEM photograph showing a photocurable resist pattern formed on a copper-clad substrate using the photosensitive resin composition of Comparative Example 1.

FIG. 7 is an SEM photograph showing a photocurable resist pattern formed on a copper-clad substrate using the photosensitive resin composition of Comparative Example 2.

FIG. 8 is an SEM photograph showing a photocurable resist pattern formed on a copper-clad substrate using the photosensitive resin composition of Comparative Example 3.

 ──────────────────────────────────────────────────続 き Continued on front page F-term (reference) 2H025 AA02 AA03 AA14 AB11 AB15 AC01 AD01 BC43 BC66 BC74 CA01 CB13 CB14 CB43 CB54 CB55 CB56 FA03 FA17 4J100 AB02R AG04R AJ02P AL03R AL04R AL05Q AL08Q AL09R AM04 CA04 DA04 CC01 CC02 CC10 CD01 CE12 CE16 CF16 CF17 DD02

Claims (2)

[Claims] 1. A photosensitive resin composition for a photosensitive film containing an acrylic high acid value resin, wherein the acrylic high acid value resin comprises (meth) acrylic acid,
Benzyl (meth) acrylate or C12-18
(Meth) acrylate 2 having an alkyl group
And a weight average molecular weight of the acrylic high acid value resin of 8.0 to 50% by weight as a constituent monomer.
Molecular weight distribution (Mw / Mn) of the acrylic high acid value resin
Is 2.5 or less, the photosensitive resin composition for photosensitive films. 2. A photosensitive film comprising a photosensitive layer comprising the photosensitive resin composition for a photosensitive film according to claim 1.