JP6743879B2 - Photosensitive resin composition, pattern forming method and circuit forming substrate using the same - Google Patents

Description

The present invention relates to a photosensitive resin composition, a pattern forming method using the same, and a circuit forming substrate.

BACKGROUND ART Conventionally, a polyimide resin having excellent heat resistance, electrical characteristics, mechanical characteristics, and the like has been used for a surface protective film and an interlayer insulating film of a semiconductor element. However, in recent years, as semiconductor elements have become highly integrated and large, thinning and miniaturization of encapsulating resin packages are required, and LOC (lead-on-chip) and surface mounting methods such as solder reflow are adopted. There has been a growing demand for polyimide resins having excellent mechanical properties and heat resistance.

On the other hand, a photosensitive polyimide in which a photosensitive property is imparted to a polyimide resin itself has been used. However, the use of this has a feature that a pattern forming process can be simplified and a complicated manufacturing process can be shortened.

In recent years, attention has been paid to applying such a photosensitive polyimide to a circuit forming substrate on a suspension for mounting a magnetic head of a hard disk drive described below.

From the viewpoint of increasing the storage capacity and speed of a hard disk drive, a magnetoresistive MR (Magnet Resistive) element and a thin film are used in place of a conventional MIG (metal in gap) or magnetic induction type thin film as a magnetic head. A so-called MR-thin film composite type head in which the above are integrated has attracted attention.

Whereas the conventional head uses one head for both reading and writing magnetic signals, the MR head has twice the number of terminals (adding a ground terminal if necessary) to divide the reading and writing within one head. Therefore, it is necessary to make the wire connecting the head and disk body thinner.
However, if the wire is thinned, the wire tends to corrode. Further, there arises a problem that impedance matching becomes difficult and a head mounting becomes difficult. As a method for solving such a new problem, a method of directly forming a circuit on a suspension for mounting a head has been proposed (see Patent Documents 1 and 2).

JP, 2010-266843, A U.S. Patent Application Publication No. 2013-143011

JOURNAL OF MICROELECTROME CHANICAL SYSTEMS, 1483-1488, VOL. 20, NO. 6, DECEMBER 2011

A polyimide resin layer having excellent heat resistance, electrical characteristics, mechanical characteristics, and the like is used as an interlayer insulating film or a protective layer of a circuit in the circuit forming substrate as described above. As described in Patent Document 1, when forming a stepped circuit, a first layer of polyimide resin is applied, exposed, developed, and cured, and then a second layer is applied, exposed, developed, and cured. However, it is necessary to form a stepped circuit, which requires a long process and high cost.

By the way, in recent years, in forming a complicated structure such as a microlens, application of a gray scale mask in which light transmittance is controlled by applying light and shade to the mask has been studied (Non-Patent Document 1). It has been found that this method can significantly shorten the process and can form a complicated structure having a step.

Therefore, for the purpose of manufacturing a suspension for a hard disk drive, we attempted batch manufacturing of step shapes by patterning using a gray scale mask, but a photosensitive polyimide resin that has both low thermal expansion and low hygroscopic expansion that have been used conventionally. Since the gamma value is high, there is no difference between the residual film rate at low exposure amount and the high exposure amount, and the residual film rate is large due to slight blurring of the exposure amount in the gray scale area. It was found that there is a problem that it is difficult to form a stepped shape because of the change, and the process margin is low. Further, it has been newly found that there is a problem that the resin is exuded after development due to insufficient crosslinking because the exposure amount becomes low in the gray scale portion.

An object of the present invention is to provide a photosensitive resin composition having a process margin such that a pattern having a step can be sufficiently formed when exposed by using a gray scale mask, a pattern forming method and a circuit using the same. It is to provide a forming substrate.

（式（Ａ）中、Ｒ^１は３価又は４価の有機基、Ｒ^２は２価の有機基、Ｒは、炭素炭素不飽和二重結合を有する一価の有機基又はＯ⁻Ｍ^＋で表される基であり、Ｍ^＋は、水素イオン又は炭素炭素不飽和二重結合を有する化合物のイオンであり、Ｒの少なくとも１つは、炭素炭素不飽和二重結合を有する一価の有機基か、Ｏ⁻Ｍ^＋で表される基であってかつＭ^＋が炭素炭素不飽和二重結合を有する化合物のイオンであり、ｎは１又は２である。）

（式（Ｂ）中、Ｒ^１１及びＲ^１２は、それぞれ独立に、炭素数１〜２０のアルキル基、フェニル基、カルバゾール基又はフルオレニル基である。前記アルキル基、フェニル基、カルバゾール基及びフルオレニル基は置換基を有してもよい。前記カルバゾール基が複数の置換基を有する場合、隣り合う置換基同士は結合して環を形成してもよい。）

（式（ＢＢ）中、Ｒ^５０は、炭素数１〜２０のアルキル基、１以上のエーテル結合を含む炭素数２〜２０のアルキル基、炭素数１〜１２のアルコキシ基、炭素数１〜４のアルキル基又は１以上のエーテル結合を含む炭素数２〜２０のアルキル基で置換されたフェニル基、フェニル基、ハロゲン原子、炭素数１〜１２のアルケニル基、又はビフェニリル基であり、Ｒ^５１は、式（１１）で表される基、又は上記Ｒ^５０と同じの基であり、Ｒ^５２〜Ｒ^５４は、各々独立に、炭素数１〜１２のアルキル基、炭素数１〜１２のアルコキシ基又はハロゲン原子である。）

（式（１１）中、Ｒ^５５〜Ｒ^５７は、各々独立に、炭素数１〜１２のアルキル基、炭素数１〜１２のアルコキシ基又はハロゲン原子である。）
２．前記（ａ）成分が、下記式（１）で表わされる構造単位を有するポリマーである１に記載の感光性樹脂組成物。

（式（１）中、Ｒ^１、Ｒ^２、Ｍ^＋及びｎは、それぞれ、前記式（Ａ）のＲ^１、Ｒ^２、Ｍ^＋及びｎと同じである。）
３．Ｒ^２が、下記式（２）又は（３）で表わされる構造である１又は２に記載の感光性樹脂組成物。

（式（２），（３）中、複数あるＲ^４は、各々独立に、フッ素原子、又は酸素原子、硫黄原子若しくはハロゲン原子を有していてもよい炭素数１〜１０の１価の有機基を表す。ｓ、ｔ及びuは各々独立に０〜４の整数を表す。）
４．Ｒ^２が、下記式（４）で表わされる構造である１又は２に記載の感光性樹脂組成物。

（式（４）中、Ｒ^５は各々独立にフッ素原子又はトリフルオロメチル基である。）
５．前記式（Ｂ）で表される化合物が、下記式（６）又は（７）で表される化合物である１〜４のいずれかに記載の感光性樹脂組成物。

（式（６）及び（７）中、Ｒ^１１は前記式（Ｂ）のＲ^１１と同じである。Ｒ^１４〜Ｒ^２０はそれぞれ独立して水素原子、−ＮＯ_２基又は下記式（８）で表される基である。ＸはＣ（Ｒ^３）_２又はＮＲ^３である。Ｒ^３は、それぞれ独立に、水素原子又は炭素数１〜２０のアルキル基である。）

（Ｒ^２１は、それぞれ独立に、１価の有機基である。ｐは０〜５の整数である）
６．前記式（Ｂ）で表される化合物が、下記式（Ｂ−３）〜（Ｂ−７）で表される化合物のいずれかである１〜４のいずれかに記載の感光性樹脂組成物。

７．前記式（ＢＢ）で表される化合物が、下記式（ＢＢ−１）又は（ＢＢ−２）で表される化合物である１〜６のいずれかに記載の感光性樹脂組成物。

８．前記（ｂ）成分の含有量が、前記（ａ）成分１００質量部に対して、０．１〜２０質量部である１〜７のいずれかに記載の感光性樹脂組成物。
９．ハードディスクドライブサスペンション用である１〜８のいずれかに記載の感光性樹脂組成物。
１０．グレイスケールマスク露光用である１〜９のいずれかに記載の感光性樹脂組成物。
１１．１〜１０のいずれかに記載の感光性樹脂組成物を、基板上に塗布、乾燥して感光性樹脂膜を形成する工程と、
前記感光性樹脂膜を露光する工程と、
露光後の樹脂膜を現像する工程と、
現像後の樹脂膜を加熱処理する工程と
を含むパターン形成方法。
１２．１〜１０のいずれかに記載の感光性樹脂組成物の硬化物。
１３．１２に記載の硬化物を、層間絶縁膜又は保護膜として有する回路形成基板。
１４．支持基板と、層間絶縁膜と、導電層と、保護膜をこの順に含み、
前記層間絶縁膜と保護膜の少なくとも１つが１２に記載の硬化物である回路形成基板。
１５．１３又は１４に記載の回路形成基板を含むハードディスクドライブ用サスペンション。According to the present invention, the following photosensitive resin composition, a pattern forming method using the same, and a circuit forming substrate are provided.
1. (A) a polymer having a structural unit represented by the following formula (A), and (b) a compound which generates a radical upon irradiation with actinic rays, represented by the following formula (B) and the following formula (BB) A photosensitive resin composition containing the compound described above.

(In the formula (A), R ¹ is a trivalent or tetravalent organic group, R ² is a divalent organic group, R is a monovalent organic group having a carbon-carbon unsaturated double bond, or O ^- M ^+. And M ⁺ is a hydrogen ion or an ion of a compound having a carbon-carbon unsaturated double bond, and at least one of R is a monovalent organic group having a carbon-carbon unsaturated double bond. Group or a group represented by O ⁻ M ⁺ , and M ⁺ is an ion of a compound having a carbon-carbon unsaturated double bond, and n is 1 or 2.)

(In the formula (B), R ¹¹ and R ¹² are each independently an alkyl group having 1 to 20 carbon atoms, a phenyl group, a carbazole group, or a fluorenyl group. The alkyl group, the phenyl group, the carbazole group, and the fluorenyl group. May have a substituent. When the carbazole group has a plurality of substituents, adjacent substituents may be bonded to each other to form a ring.)

(In the formula (BB), R ⁵⁰ represents an alkyl group having 1 to 20 carbon atoms, an alkyl group having 2 to 20 carbon atoms containing one or more ether bonds, an alkoxy group having 1 to 12 carbon atoms, and 1 to 4 carbon atoms. Is a phenyl group substituted with an alkyl group having 2 to 20 carbon atoms containing one or more ether bonds, a phenyl group, a halogen atom, an alkenyl group having 1 to 12 carbon atoms, or a biphenylyl group, and R ⁵¹ is , A group represented by formula (11), or the same group as R ⁵⁰ , wherein R ^{52 to} R ⁵⁴ are each independently an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms. Or a halogen atom.)

(In the formula (11), R ^{55 to} R ⁵⁷ are each independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or a halogen atom.)
2. 2. The photosensitive resin composition according to 1, wherein the component (a) is a polymer having a structural unit represented by the following formula (1).

(In the formula (1), R ¹ , R ² , M ⁺ and n are respectively the same as R ¹ , R ² , M ⁺ and n in the formula (A).)
3. 3. The photosensitive resin composition according to 1 or 2, wherein R ² has a structure represented by the following formula (2) or (3).

(In formulas (2) and (3), a plurality of R ^4's each independently represent a monovalent organic group having 1 to 10 carbon atoms, which may have a fluorine atom, or an oxygen atom, a sulfur atom or a halogen atom. Represents a group, and s, t, and u each independently represent an integer of 0 to 4.)
4. ^3. The photosensitive resin composition according to 1 or 2, wherein R ² has a structure represented by the following formula (4).

(In the formula (4), each R ⁵ is independently a fluorine atom or a trifluoromethyl group.)
5. The photosensitive resin composition according to any one of 1 to 4, wherein the compound represented by the formula (B) is a compound represented by the following formula (6) or (7).

(In the formulas (6) and (7), R ¹¹ is the same as R ^{11 in the} formula (B). R ^{14 to} R ²⁰ are each independently a hydrogen atom, a —NO ₂ group or the following formula (8). X is C(R ³ ) ₂ or NR ^3. R ³ is each independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

(R ²¹ is each independently a monovalent organic group. p is an integer of 0 to 5)
6. The photosensitive resin composition according to any one of 1 to 4, wherein the compound represented by the formula (B) is any of compounds represented by the following formulas (B-3) to (B-7).

7. 7. The photosensitive resin composition according to any one of 1 to 6, wherein the compound represented by the formula (BB) is a compound represented by the following formula (BB-1) or (BB-2).

8. Content of the said (b) component is a photosensitive resin composition in any one of 1-7 which is 0.1-20 mass parts with respect to 100 mass parts of the said (a) component.
9. 9. The photosensitive resin composition according to any one of 1 to 8 for a hard disk drive suspension.
10. 10. The photosensitive resin composition according to any one of 1 to 9, which is for gray scale mask exposure.
11. A step of applying the photosensitive resin composition according to any one of 11.1 to 10 on a substrate and drying to form a photosensitive resin film,
Exposing the photosensitive resin film,
A step of developing the resin film after exposure,
And a step of heat-treating the resin film after development.
A cured product of the photosensitive resin composition according to any one of 12.1 to 10.
A circuit-forming substrate having the cured product according to 13.12 as an interlayer insulating film or a protective film.
14. A support substrate, an interlayer insulating film, a conductive layer, and a protective film are included in this order,
13. A circuit forming substrate, wherein at least one of the interlayer insulating film and the protective film is the cured product according to 12.
15. A suspension for a hard disk drive, which includes the circuit-formed board according to 13.13 or 14.

According to the present invention, a photosensitive resin composition having a process margin such that a pattern having a step can be sufficiently formed when exposed using a gray scale mask, a pattern forming method and a circuit using the same A formed substrate can be provided.

It is a schematic sectional drawing explaining the process of forming a pattern using the photosensitive resin composition concerning one Embodiment of this invention. It is a schematic sectional drawing explaining the process of forming a pattern using the photosensitive resin composition concerning one Embodiment of this invention. It is a schematic sectional drawing explaining the process of forming a pattern using the photosensitive resin composition concerning one Embodiment of this invention. It is a schematic sectional drawing explaining the process of forming a pattern using the photosensitive resin composition concerning one Embodiment of this invention. It is a schematic sectional drawing explaining the process of forming a pattern using the photosensitive resin composition concerning one Embodiment of this invention. It is a schematic sectional drawing explaining the process of forming a pattern using the photosensitive resin composition concerning one Embodiment of this invention. It is a schematic sectional drawing explaining the process of forming a pattern using the photosensitive resin composition concerning one Embodiment of this invention. It is a schematic sectional drawing explaining the process of forming a pattern using the photosensitive resin composition concerning one Embodiment of this invention. It is a schematic sectional drawing explaining the process of forming a pattern using the photosensitive resin composition concerning one Embodiment of this invention. 1 is a schematic plan view showing a suspension for a hard disk drive manufactured by using a photosensitive resin composition according to an embodiment of the present invention. FIG. 6 is a schematic cross-sectional view illustrating a step of forming a pattern having a step shape by providing two polyimide resin layers, which is a conventional method. FIG. 6 is a schematic cross-sectional view illustrating a step of forming a pattern having a step shape by providing two polyimide resin layers, which is a conventional method. FIG. 6 is a schematic cross-sectional view illustrating a step of forming a pattern having a step shape by providing two polyimide resin layers, which is a conventional method. FIG. 6 is a schematic cross-sectional view illustrating a step of forming a pattern having a step shape by providing two polyimide resin layers, which is a conventional method. FIG. 6 is a schematic cross-sectional view illustrating a step of forming a pattern having a step shape by providing two polyimide resin layers, which is a conventional method. FIG. 6 is a schematic cross-sectional view illustrating a step of forming a pattern having a step shape by providing two polyimide resin layers, which is a conventional method. FIG. 6 is a schematic cross-sectional view illustrating a step of forming a pattern having a step shape by providing two polyimide resin layers, which is a conventional method. FIG. 6 is a schematic cross-sectional view illustrating a step of forming a pattern having a step shape by providing two polyimide resin layers, which is a conventional method. FIG. 6 is a schematic cross-sectional view illustrating a step of forming a pattern having a step shape by providing two polyimide resin layers, which is a conventional method. FIG. 6 is a schematic cross-sectional view illustrating a step of forming a pattern having a step shape by providing two polyimide resin layers, which is a conventional method.

Hereinafter, modes for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the present specification, “A or B” may include either A or B, or may include both. Further, in the present specification, the term “process” is used not only as an independent process but also in the case where the intended action of the process is achieved even when it cannot be clearly distinguished from other processes. included.
The numerical range indicated by "-" indicates the range including the numerical values before and after "-" as the minimum value and the maximum value, respectively. In addition, in the present specification, the content of each component in the composition is the sum of the plurality of substances present in the composition unless there is a plurality of substances corresponding to each component in the composition, unless otherwise specified. Means quantity. Furthermore, unless otherwise specified, the exemplified materials may be used alone or in combination of two or more kinds.

In addition, in this specification, "(meth)acrylate" means "acrylate" and its corresponding "methacrylate."

The photosensitive resin composition of the present invention comprises (a) a polymer having a structural unit represented by the following formula (A) (hereinafter sometimes referred to as “component (a)”), and (b) radicals upon irradiation with actinic rays. Examples of the compound that generates a compound include a compound represented by the following formula (B) and a compound represented by the following formula (BB) (hereinafter sometimes referred to as component (b)).

式（Ａ）中、Ｒ^１は３価又は４価の有機基、Ｒ^２は２価の有機基、Ｒは、炭素炭素不飽和二重結合を有する一価の有機基又はＯ⁻Ｍ^＋で表される基であり、Ｍ^＋は、水素イオン又は炭素炭素不飽和二重結合を有する化合物のイオンであり、Ｒの少なくとも１つは、炭素炭素不飽和二重結合を有する一価の有機基か、Ｏ⁻Ｍ^＋で表される基であってかつＭ^＋が炭素炭素不飽和二重結合を有する化合物のイオンであり、ｎは１又は２である。

In formula (A), R ¹ is a trivalent or tetravalent organic group, R ² is a divalent organic group, R is a monovalent organic group having a carbon-carbon unsaturated double bond or O ^- M ⁺ . Is a group represented, M ⁺ is a hydrogen ion or an ion of a compound having a carbon-carbon unsaturated double bond, and at least one of R is a monovalent organic group having a carbon-carbon unsaturated double bond. Or a group represented by O ⁻ M ⁺ , and M ⁺ is an ion of a compound having a carbon-carbon unsaturated double bond, and n is 1 or 2.

式（Ｂ）中、Ｒ^１１及びＲ^１２は、それぞれ独立に、炭素数１〜２０のアルキル基、フェニル基、カルバゾール基又はフルオレニル基である。前記アルキル基、フェニル基、カルバゾール基及びフルオレニル基は置換基を有してもよい。前記カルバゾール基が複数の置換基を有する場合、隣り合う置換基同士は結合して環を形成してもよい。

In formula (B), R ¹¹ and R ¹² are each independently an alkyl group having 1 to 20 carbon atoms, a phenyl group, a carbazole group, or a fluorenyl group. The alkyl group, phenyl group, carbazole group and fluorenyl group may have a substituent. When the carbazole group has a plurality of substituents, adjacent substituents may be bonded to each other to form a ring.

式（ＢＢ）中、Ｒ^５０は、炭素数１〜２０のアルキル基、１以上のエーテル結合を含む炭素数２〜２０のアルキル基、炭素数１〜１２のアルコキシ基、炭素数１〜４のアルキル基又は１以上のエーテル結合を含む炭素数２〜２０のアルキル基で置換されたフェニル基、フェニル基、ハロゲン原子、炭素数１〜１２のアルケニル基、又はビフェニリル基であり、Ｒ^５１は、式（１１）で表される基、又は上記Ｒ^５０と同じの基であり、Ｒ^５２〜Ｒ^５４は、各々独立に、炭素数１〜１２のアルキル基、炭素数１〜１２のアルコキシ基又はハロゲン原子である。

In formula (BB), R ⁵⁰ is an alkyl group having 1 to 20 carbon atoms, an alkyl group having 2 to 20 carbon atoms containing one or more ether bonds, an alkoxy group having 1 to 12 carbon atoms, and an alkyl group having 1 to 4 carbon atoms. A phenyl group substituted with an alkyl group or an alkyl group having 2 to 20 carbon atoms containing one or more ether bonds, a phenyl group, a halogen atom, an alkenyl group having 1 to 12 carbon atoms, or a biphenylyl group, and R ⁵¹ is A group represented by formula (11) or the same group as R ⁵⁰ , wherein R ^{52 to} R ⁵⁴ are each independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or It is a halogen atom.

式（１１）中、Ｒ^５５〜Ｒ^５７は、各々独立に、炭素数１〜１２のアルキル基、炭素数１〜１２のアルコキシ基又はハロゲン原子である。

In formula (11), R ^{55 to} R ⁵⁷ are each independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or a halogen atom.

The photosensitive resin composition of the present invention can be suitably used for gray scale mask exposure.
Further, the photosensitive resin composition of the present invention can be used for an interlayer insulating film or a protective film of a circuit forming substrate described later.

Component (a) (polymer)
In the polymer having the structural unit represented by the formula (A), R ¹ in the formula (A) is a trivalent or tetravalent organic group. This group is generally a residue of tetracarboxylic acid (dianhydride) or tricarboxylic acid (anhydride) used as a raw material other than a carboxy group and an acid anhydride group, and is a group having an aromatic ring such as a benzene ring. Preferably. Specific examples include a residue of tetracarboxylic dianhydride described below.

Further, R ² in the formula (A) is a divalent organic group. This group is generally a residue of a diamine compound used as a raw material, and specific examples thereof include a residue of a diamine compound described below.

In formula (A), n is 1 or 2. When n is 2, a plurality of R may be the same or different.

R in the formula (A) is a monovalent organic group having a carbon-carbon unsaturated double bond or a group represented by O ⁻ M ⁺ . O ^- M ⁺ is a group in which a hydrogen atom or a compound having a carbon-carbon unsaturated double bond (a monovalent organic group) is ionically bonded to an oxygen atom. At least one R is a monovalent organic group having a carbon-carbon unsaturated double bond, or an ion of a compound represented by O ⁻ M ⁺ , wherein M ⁺ has a carbon-carbon unsaturated double bond. Is.

Examples of the monovalent organic group or compound having a carbon-carbon unsaturated double bond here include monovalent organic groups or compounds containing an acryloyl group, a methacryloyl group, an allyl group, and the like. Then, a monovalent organic group or compound containing an acryloyl group or a methacryloyl group is preferable.

Specific examples of R include acryloxyalkyl group _{(CH 2 = CH-COO-} R'-O-), methacryloxy alkyl group _{(CH 2 = C (CH 3} ) -COO-R'-O-) , acryloxyalkyl amino group _{(CH 2 = CH-COO-} R'-NH-), methacryloxy alkyl amino group _{(CH 2 = C (CH 3} ) -COO-R'-NH-) monovalent such as an organic Groups. Examples of R'include an alkylene group (for example, having 1 to 10 carbon atoms, preferably 1 to 4 carbon atoms).

The compound having a carbon-carbon unsaturated double bond preferably forms an ester bond with adjacent CO by a covalent bond. In order for a compound having a carbon-carbon unsaturated double bond to form an ester bond with an adjacent carbonyl group, for example, an alcohol having a carbon-carbon unsaturated double bond and a tetracarboxylic acid dicarboxylic acid constituting the acid part of the polymer are used. React with anhydride.
Also, O compound having a carbon-carbon unsaturated double bond is ionically bound ^- as M ⁺ of the group represented by M ^+, dialkylaminoalkyl acrylates ions or dialkylaminoalkyl methacrylate ion _{(CH 2 = CH-COO-} R _{^{'-N + H (C n H}} 2n + 1) 2, CH 2 = C (CH 3) -COO-R'-n + H (C n H 2n + 1) 2, n are each independently a positive integer (e.g. 1 to 10, preferably 1 to 6) and R′ is an alkylene group (for example, 1 to 10 carbon atoms, preferably 1 to 4)) and the like.

Examples of monovalent organic groups having a carbon-carbon unsaturated double bond or ions of compounds include, for example, N,N-diethylaminopropyl methacrylate, N,N-dimethylaminopropyl methacrylate, N,N-diethylaminopropyl acrylate, N , N-diethylaminoethylmethacrylate and other N,N-dialkylaminoalkyl(meth)acrylate monovalent organic groups or ions, but are not limited thereto.

In the component (a), the total amount of the monovalent organic group having a carbon-carbon unsaturated double bond and the ion of the compound is 20 to 200 mol% with respect to 100 mol% of the carboxy group of the polyamic acid. It is preferable.

Among these, at least one of R's is preferably a group represented by O ^- M ⁺ to which a compound having a carbon-carbon unsaturated double bond is ionically bonded, is preferable from the viewpoint of reactivity and the like. A polymer having a structural unit represented by the formula (1) is preferable.

式（１）中、Ｒ^１、Ｒ^２、Ｍ^＋及びｎは、それぞれ、式（Ａ）のＲ^１、Ｒ^２、Ｍ^＋及びｎと同じである。

Wherein ^{(1), R 1, R} 2, M + and n are respectively the same as ^{R 1, R 2, M +} and n of formula (A).

The polymer having the structural unit represented by the above formula (A) or (1) is, for example, acryloyl in order to impart photosensitivity to a polyamic acid obtained by addition-polymerizing a tetracarboxylic dianhydride and a diamine compound. By adding and stirring an amine compound having a group or a methacryloyl group, the amine compound can be ionically bonded to the polyamic acid to obtain the polyamic acid. The polymer thus obtained has a structural unit represented by formula (A) or (1), and has an ion of a compound having an acryloyl group or a methacryloyl group in the polymer.

In the above formula (A) or ^{(1), [CO-R} 1 -CONH-R 2 -NH] ( for ^{R 1} is the side groups omitted.) The number of structural units represented by the When m number thereof Is not particularly limited, but is preferably m=30 to 150. Further, the polymer may have a structural unit other than the structural unit represented by the formula (A) or (1), but is usually represented by the formula (A) or (1). It is preferably composed of a structural unit and has terminal groups such as hydrogen atom and OH group at both ends thereof. As a structural unit other than the structural unit of formula (A) or (1), a structural unit having no side chain of COR or —COO ⁻ M ⁺ in formula (A) or (1), or COR or —COO ⁻ M. Structural units in which all ⁺ are -COOH (carboxy groups) and the like are included. When the number of structural units other than the structural unit of the formula (A) or (1) is t, the content thereof is preferably equal to or less than the above-mentioned m, and t is 0 with respect to the sum of m+t. It is preferably less than or equal to 0.3.

The weight average molecular weight (Mw) of the component (a) is preferably about 10,000 to 200,000. When the component (a) contains O ⁻ M ⁺ , the weight average molecular weight (Mw) in a state before the compound having a carbon-carbon unsaturated double bond is bonded by an ionic bond, that is, in the state of polyamic acid is 10, It is preferably 000 to 90,000, and more preferably 20,000 to 60,000. The Mw can be calculated by gel permeation chromatography and converted into standard polystyrene.

Examples of the tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride, 3,3′,4,4′-biphenyltetracarboxylic acid. Acid dianhydride, 4,4′-oxydiphthalic acid dianhydride, 1,2,5,6-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 4, Examples thereof include, but are not limited to, 4'-sulfonyldiphthalic acid dianhydride and 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride.

Examples of the diamine compound include p-phenylenediamine, m-phenylenediamine, 2,2′-dimethyl-4,4′-diaminobiphenyl, p-xylylenediamine, m-xylylenediamine, and 1,5-diamino. Naphthalene, benzidine, 3,3'-dimethoxybenzidine, 4,4'-(or 3,4'-, 3,3'-, 2,4'-)diaminodiphenylmethane, 4,4'-(or 3,4 '-, 3,3'-, 2,4'-) diaminodiphenyl ether, 4,4'- (or 3,4'-, 3,3'-, 2,4'-) diaminodiphenylsulfone, 4,4 '- (or 3,4'-, 3,3'-, 2,4'-) diaminodiphenyl sulfide, 4,4'-benzophenone diamine, 3,3'-benzophenone diamine, 4,4'-di(4 -Aminophenoxy)phenyl sulfone, 4,4'-bis(4-aminophenoxy)biphenyl, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,1 ,1,3,3,3-hexafluoro-2,2-bis(4-aminophenyl)propane, 2,2′-bis(trifluoromethyl)benzidine, 2,2-bis[4-(4-amino) Phenoxy)phenyl]propane, 3,3-dimethyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane, 4,4'-di(3- Aminophenoxy)phenyl sulfone, 3,3'-diaminodiphenyl sulfone, 2,2'-bis(4-aminophenyl)propane, 5,5'-methylene-bis-(anthranilic acid), 3,5-diaminobenzoic acid , 3,3'-dihydroxy-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3' -Aromatic diamines such as dimethyl-4,4'-diaminobiphenyl-6,6'-disulfonic acid, 2,6-diaminopyridine, 2,4-diaminopyridine, 2,4-diamino-s-triazine, 2, Heterocycles such as 7-diaminobenzofuran, 2,7-diaminocarbazole, 3,7-diaminophenothiazine, 2,5-diamino-1,3,4-thiadiazole, 2,4-diamino-6-phenyl-s-triazine Formula diamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, 2,2-dimethylpropene Examples thereof include, but are not limited to, aliphatic diamines such as diamine and diaminopolysiloxanes represented by the following formula (5).

式（５）中、Ｒ^６は、各々独立に炭素数１〜６のアルキル基を示し、ｏは、各々独立に１〜１０の整数である。

Wherein (5), ^{R 6} represents each independently an alkyl group having 1 to 6 carbon atoms, o is, independently at each occurrence 1 to 10 integer.

The above tetracarboxylic dianhydride and the like and the diamine compound are used alone or in combination of two or more kinds.

In the above formula (A) or (1), when R ² has a structure represented by the following formula (2) or (3), it provides transparency suitable as a photosensitive resin, and also an interlayer insulating film of a suspension or It is preferable because it provides low thermal expansion and low hygroscopic expansion suitable for use as a protective film.

式（２），（３）中、複数あるＲ^４は、各々独立に、フッ素原子、又は酸素原子、硫黄原子若しくはハロゲン原子を有していてもよい炭素数１〜１０の１価の有機基を表す。ｓ、ｔ及びuは各々独立に０〜４の整数（好ましくは０〜１）を表す。

In formulas (2) and (3), a plurality of R ^4's each independently represent a fluorine atom, or a monovalent organic group having 1 to 10 carbon atoms which may have an oxygen atom, a sulfur atom or a halogen atom. Represents. s, t and u each independently represent an integer of 0 to 4 (preferably 0 to 1).

Among these, R ⁴ is preferably a fluorine atom, an alkyl group having 1 to 6 carbon atoms, or a fluorinated alkyl group having 1 to 6 carbon atoms, and a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a fluorine atom, A group or atom selected from the group consisting of trifluoromethyl groups is more preferable from the viewpoint of low hygroscopic expansion. Particularly preferably, R ⁴ is a fluorine atom or a trifluoromethyl group.

Further, in the formula (2), it is preferable that the two R ^{4 s} are positioned at the ortho position with respect to the bond connecting both benzene rings, from the viewpoint of providing low thermal expansion and low hygroscopic expansion. Among such structures, preferred is a structure in which R ² is represented by the following formula (4).

式（４）中、Ｒ^５は各々独立にフッ素原子又はトリフルオロメチル基である。

In formula (4), R ^5's each independently represent a fluorine atom or a trifluoromethyl group.

Component (b) The component (b) is a compound that generates a radical upon irradiation with actinic rays. The photosensitive resin composition of the present invention contains, as the component (b), the compound represented by the formula (B) and the compound represented by the formula (BB).

R ¹¹ and R ^{12 in} the formula (B) are each independently an alkyl group having 1 to 20 carbon atoms (preferably 1 to 10, more preferably 1 to 8), a phenyl group, a carbazole group or a fluorenyl group, A methyl group, a phenyl group and a carbazole group are preferable.
Examples of the substituent that the alkyl group having 1 to 20 carbon atoms of R ¹¹ and R ¹² may have, a phenyl group, a carbazole group or a fluorenyl group (hereinafter, also referred to as an arbitrary substituent) include a nitro group and a halogenated ( Alkoxy group having 1 to 20 (preferably 1 to 10, more preferably 1 to 8) carbon atoms which may be fluorinated, and 1 to 20 carbon atoms which may be halogenated (preferably fluorinated) The alkyl group of 1-10, more preferably 1-8, and the group represented by formula (8) are preferable.

式（８）中、Ｒ^２１は、それぞれ独立に、１価の有機基である。ｐは０〜５（１〜３が好ましい）の整数である。
Ｒ^２１の一価の有機基としては、炭素数１〜２０（好ましくは１〜１０、より好ましくは１〜８）のアルキル基又は炭素数１〜２０（好ましくは１〜１０、より好ましくは１〜８）のアルコキシ基、（２，２−ジメチル−１，３−ジオキソラン−４−イル）メトキシ基等が挙げられる。

In formula (8), R ^21's are each independently a monovalent organic group. p is an integer of 0 to 5 (preferably 1 to 3).
The monovalent organic group for R ²¹ is an alkyl group having 1 to 20 carbon atoms (preferably 1 to 10, more preferably 1 to 8) or 1 to 20 carbon atoms (preferably 1 to 10, more preferably 1). ~8) alkoxy group, (2,2-dimethyl-1,3-dioxolan-4-yl)methoxy group and the like.

In addition, as a substituent that the alkyl group having 1 to 20 carbon atoms, a phenyl group, a carbazole group, or a fluorenyl group of R ¹¹ and R ¹² may have, CH ₃ C(═O)—ON═C(R ¹¹ )- may be used. R ¹¹ is the same as R ^{11 in the} formula (B).

Examples of R ¹¹ , R ¹² , R ²¹ and the alkyl group having 1 to 20 carbon atoms as the optional substituent include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an n-hexyl group, and 2 -Methyl-1-hexyl group, n-heptyl group, n-decyl group, n-dodecyl group and the like.
Examples of R ¹¹ , R ¹² , R ²¹ and the alkoxy group having 1 to 20 carbon atoms as an arbitrary substituent include a group in which an oxygen atom is bonded to the alkyl group having 1 to 20 carbon atoms.

When the carbazole group has a plurality of substituents, the ring formed by bonding adjacent substituents is preferably a benzene ring.

The compound represented by the formula (B) is preferably a compound represented by the following formula (6) or (7) from the viewpoint of satisfying both the gamma value and the sensitivity for producing a step shape. The gamma value represents the high contrast, and the higher the gamma value, the higher the contrast. Also, the smaller the gamma value, the larger the process margin. Therefore, in the photosensitive resin composition of the present invention, it is preferable to set the gamma value within an appropriate range.

In formulas (6) and (7), R ¹¹ is the same as R ^{11 in} formula (B).
R ^{14 to} R ²⁰ are each independently a hydrogen atom, a —NO ₂ group, or a group represented by the above formula (8). X is C(R ³ ) ₂ or NR ³ .
R< ³ > is a hydrogen atom or a C1-C20 alkyl group each independently. Examples of the alkyl group having 1 to 20 carbon atoms for R ³ include those similar to the alkyl groups having 1 to 20 carbon atoms for R ¹¹ and R ¹² , such as ethyl group, n-propyl group and 2-methyl-1-hexyl group. Groups are preferred.

Since the photosensitive resin composition of the present invention contains the compound represented by the formula (B) as the component (b), it has excellent sensitivity and R ² has a structure represented by the formula (2) or (3). In the case of the component (a) which is, especially the component (a) in which R ² has a structure represented by the formula (4), a significantly good pattern can be given.
In particular, in the case of the component (a) in which R ² is the structure represented by the formula (4), good photosensitivity is often not obtained, and it may not be possible to deal with gray scale mask exposure. Even if it is, by including the compound represented by the formula (B), good sensitivity and a residual film ratio can be obtained, and a step shape can be formed. Among them, particularly preferred compounds represented by the formula (B) are compounds represented by the following formulas (B-3) to (B-7).

The photosensitive resin composition of the present invention is particularly suitable for use as a protective film of a suspension for a hard disk drive, but it is extremely preferable that the photosensitive resin composition has a function of not increasing the hygroscopic expansion coefficient and sometimes further lowering it. -3) is a compound represented.

R ⁵⁰ of the formula (BB) is an alkyl group having 1 to 20 carbon atoms, an alkyl group having 2 to 20 carbon atoms (preferably 2 to 10 and more preferably 2 to 8) containing one or more ether bonds, and a carbon number. An alkoxy group having 1 to 12 (preferably 1 to 8), an alkyl group having 1 to 4 carbon atoms, or 2 to 20 carbon atoms (preferably 2 to 10, more preferably 2 to 8) having an ether bond of 1 or more. It is a phenyl group substituted with an alkyl group, a phenyl group, a halogen atom, an alkenyl group having 1 to 12 (preferably 1 to 8) carbon atoms, or a biphenylyl group. A phenyl group and a phenyl group substituted with an alkyl group having 1 to 4 carbon atoms or an alkyl group having 2 to 20 carbon atoms (preferably 2 to 10, more preferably 2 to 8) containing one or more ether bonds, It is preferable from the viewpoint of photosensitivity.
Examples of the alkyl group having 1 to 20 carbon atoms of R ^{50 in} the formula (BB) are the same as the alkyl groups having 1 to 20 carbon atoms such as R ¹¹ , R ¹² and R ²¹ described above, a cyclopentyl group, a cyclohexyl group and the like. Is mentioned.
The alkyl group having 2 to 20 carbon atoms and containing at least one ether bond represented by R ^{50 in} formula (BB) is preferably an alkoxyalkyloxy group having 2 to 20 carbon atoms, and examples thereof include a methoxymethyloxy group.
A methoxy group, an ethoxy group, a propoxy group etc. are mentioned as a C1-C12 alkoxy group of R< ⁵⁰ > of a formula (BB).
Examples of the phenyl group substituted by an alkyl group having 1 to 4 carbon atoms of R ⁵⁰ of formula (BB) or an alkyl group having 2 to 20 carbon atoms containing one or more ether bonds include a tolyl group and a methoxymethyloxyphenyl group. Is mentioned.
Examples of the halogen atom represented by R ^{50 in} formula (BB) include a fluorine atom.
The alkenyl group having 1 to 12 carbon atoms ^{R 50} of formula (BB), a vinyl group.

R ^{51 in the} formula (BB) is a group represented by the formula (11) or the same group as the above R ⁵⁰ . A phenyl group or a group represented by the formula (11) is preferable.

R ^{52 to} R ^{57 in} formula (BB) are each independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or a halogen atom.
Examples of the alkyl group having 1 to 12 carbon atoms represented by R ^{52 to} R ^{57 in} formula (BB) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an n-hexyl group, and a 2-methyl- group. 1-hexyl group, n-heptyl group, n-decyl group, n-dodecyl group and the like can be mentioned.
Examples of the alkoxy group having 1 to 12 carbon atoms of R ^{52 to} R ⁵⁷ of formula (BB) include the same as the alkoxy group having 1 to 12 carbon atoms of R ⁵⁰ of formula (BB).
Examples of the halogen atom represented by R ^{52 to} R ⁵⁷ in formula (BB) include the same halogen atoms represented by R ^{50 in} formula (BB).

The compound represented by the formula (BB) is represented by the following formula (BB-1) or (BB-2) from the viewpoint that the gamma value does not become too large and an appropriate process margin can be given. It is preferably a compound.

The content of the component (b) is preferably 0.1 to 20 parts by mass with respect to 100 parts by mass of the component (a). It is more preferably 1 to 15 parts by mass, and most preferably 2 to 12 parts by mass from the viewpoint of achieving both a gamma value and sensitivity.
Within the above range, it is easy to obtain the step shape forming property derived from the excellent photosensitivity and the excellent mechanical property of the film.

The content of the compound represented by the formula (B) is preferably 0.05 to 5 parts by mass, more preferably 0.07 to 2 parts by mass, and 0 to 100 parts by mass of the component (a). 0.1 to 1 part by mass is more preferable.
The content of the compound represented by the formula (BB) is preferably 0.05 to 15 parts by mass, more preferably 1 to 13 parts by mass, and 2 to 12 with respect to 100 parts by mass of the component (a). Part by mass is more preferred.

Component (c) (solvent)
In the present invention, a solvent is usually used when synthesizing the polyamic acid. The photosensitive resin composition of the present invention may contain the component (c) (solvent).
As the solvent, acetone, methyl ethyl ketone, toluene, chloroform, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, xylene, tetrahydrofuran, Dioxane, N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, γ-butyrolactone, dimethylsulfoxide, ethylene carbonate, propylene carbonate, sulfolane and the like can be mentioned. You may use these organic solvents individually or in combination of 2 or more types.

The content of the component (c) is preferably 100 to 500 parts by mass with respect to 100 parts by mass of the component (a).

The photosensitive resin composition of the present invention is generally provided in the form of a varnish (in the present invention, the varnish means a state in which the component (a) and the component (b) are dissolved or dispersed in the component (c). ). Moreover, you may add a sensitizer, a light-shielding agent, a polymerization inhibitor, a crosslinking agent, a dissolution promoter, a stabilizer, an adhesion aid, etc. to a photosensitive resin composition as needed.

The photosensitive resin composition of the present invention may contain a polymerization inhibitor in order to enhance the resolution and the stability during storage. Examples of the polymerization inhibitor include radical polymerization inhibitors and radical polymerization inhibitors.
Examples of such radical polymerization inhibitors or radical polymerization inhibitors include p-methoxyphenol, diphenyl-p-benzoquinone, benzoquinone, hydroquinone, pyrogallol, phenothiazine, resorcinol, orthodinitrobenzene, paradinitrobenzene, metadinitrobenzene, phenanthate. Examples thereof include laquinone, N-phenyl-1-naphthylamine, N-phenyl-2-naphthylamine, cuperone, phenothiazine, 2,5-toluquinone, tannic acid, parabenzylaminophenol, and nitrosamines. You may use these individually or in combination of 2 or more types.

The content of the polymerization inhibitor is preferably 0.01 to 30 parts by mass, and more preferably 0.05 to 10 parts by mass with respect to 100 parts by mass of the component (a). Within the above range, stability during storage, photosensitivity and mechanical properties can be improved.

As the dissolution accelerator, for example, a sulfonamide derivative is preferable, and as examples, benzenesulfonamide, toluenesulfonamide, methoxybenzenesulfonamide, benzenesulfonylanilide, toluenesulfonylanilide, methoxy-toluenesulfonylanilide, acetyl-toluenesulfonylanilide, Toluenesulfonyl-N-methylamide, toluenesulfonyl-N-ethylamide, toluenesulfonyl-N-propylamide, toluenesulfonyl-N-butylamide, toluenesulfonyl-N-phenylamide, toluenesulfonyl-N-dimethylamide, toluenesulfonyl-N- Examples thereof include diethylamide and toluenesulfonyl-N-diphenylamide. Of these, N-phenylbenzenesulfonamide is particularly preferable because it is highly effective.

The addition amount of the dissolution accelerator is preferably 2 to 30 parts by mass, and more preferably 3 to 15 parts by mass with respect to 100 parts by mass of the component (a).
Within the above range, the photosensitive resin can be well dissolved in the developing solution, and a strong pattern can be easily formed.

Except for the component (c), the photosensitive resin composition of the present invention has, for example, 75% by mass or more, 85% by mass or more, 95% by mass or more, 98% by mass or more, or 100% by mass as the component (a), It may consist of only the compound represented by the formula (B) and the compound represented by the formula (BB). In addition to these components, the photosensitive resin composition of the present invention can contain substances such as the above-mentioned additives that do not substantially impair the novel and basic properties of the present invention.

The cured product of the photosensitive resin composition of the present invention can be used for an interlayer insulating film or a protective film of a circuit forming substrate. The cured product may be a patterned cured product having a pattern formed thereon, or a cured product having no pattern formed thereon.

The pattern forming method of the present invention comprises the steps of applying the above-mentioned photosensitive resin composition onto a substrate and drying it to form a photosensitive resin film, exposing the photosensitive resin film, and exposing the resin. It includes a step of developing the film and a step of heat-treating the resin film after development.

Examples of the coating method include a spray method, a screen printing method, and a spin coating method.
Examples of the substrate include a support substrate for a hard disk drive suspension, such as a suspension forming stainless substrate. The substrate may be before circuit formation or after circuit formation.
Drying is not particularly limited, and can be performed by heating using a known method. By drying, the organic solvent in the photosensitive resin composition can be removed and a photosensitive resin film which is a non-tacky coating film can be obtained.

The exposure is performed by irradiating the photosensitive resin film with an actinic ray in a pattern. For example, a latent image having a pattern of through holes is formed. The actinic rays to be irradiated include ultraviolet rays, far ultraviolet rays, visible rays, electron beams, X-rays and the like.
After irradiation with the actinic ray, the desired relief pattern can be obtained by removing the unirradiated portion with an appropriate developing solution.

The developer is not particularly limited, but a flame-retardant solvent such as 1,1,1-trichloroethane, an aqueous solution of sodium carbonate, an aqueous alkali solution such as an aqueous solution of tetramethylammonium hydroxide, N,N-dimethylformamide, dimethylsulfoxide, A good solvent such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone or γ-butyrolactone, a mixed solvent of these good solvents and a poor solvent such as lower alcohol, water or aromatic hydrocarbon may be used. After development, you may rinse with a poor solvent etc. as needed.

By heating the relief pattern thus obtained at 80 to 400° C. for 5 to 300 minutes, the ring closure reaction of the polyimide precursor is carried out to obtain a polyimide, and a pattern cured product can be obtained.

In the pattern forming method of the present invention, since the photosensitive resin film has an appropriate gamma value while maintaining good sensitivity, it can be applied to gray scale mask exposure and can contribute to process saving, thus reducing manufacturing cost. Can be made.

Next, as an example of the pattern forming method of the present invention, a process of forming a pattern on a suspension of a hard disk drive will be described with reference to the drawings.

11 to 20 are schematic cross-sectional views illustrating a conventional process of forming a pattern having a step shape by providing two polyimide resin layers. In these FIGS. 1 to 10, for example, a stainless foil is prepared as the supporting substrate 1 that constitutes the suspension (FIG. 11), and then a conventional photosensitive resin composition, a spin coater, or the like is placed on the supporting substrate 1. The insulating layer (polyimide resin layer) 2 is formed by applying it, exposing it, developing it, and curing it (FIG. 12).

Next, in the same manner as described above, the conventional photosensitive resin composition is applied onto the insulating layer 2 using a spin coater or the like (FIG. 13), and exposure, development, and curing are performed to perform the insulating layer (polyimide resin). Layer 3 is formed to form a step (FIG. 14).

Next, in order to grow a plating film on the insulating layers 2 and 3 which are insulators, a seed layer 4 is formed as a base metal layer (FIG. 15). As the seed layer 4, two layers of a chromium thin film and a copper thin film can be formed by a high frequency sputtering method or the like. Next, a resist 5 is applied on the seed layer 4, exposed and developed in a predetermined pattern (FIG. 16), and a circuit having a multilayer structure of copper, nickel, gold or the like is sequentially formed in the openings of the resist pattern by electrolytic plating. The conductors are laminated to form the circuit 6 (FIG. 17).

After forming the circuit 6, the resist 5 is peeled off and the seed layer 4 is removed by etching (FIG. 18). Next, in order to protect the circuit 6, the same conventional photosensitive resin composition as described above is applied onto the circuit 6 and exposed and developed to form the protective layer 7 (FIG. 19). After that, a cover 8 covering a predetermined portion of the protective layer 7 and the support substrate 1 is provided to form a gimbal (FIG. 20).

On the other hand, FIG. 1 to FIG. 9 are schematic cross-sectional views illustrating a step of forming a step shape by a gray scale mask using the photosensitive resin composition according to one embodiment of the present invention. For example, a stainless steel foil is prepared as the supporting substrate 1 constituting the suspension (FIG. 1), and the above-mentioned photosensitive resin composition of the present invention is applied onto the supporting substrate 1 by using a spin coater or the like (FIG. 2). After exposure through a gray scale mask, development and curing are performed to form an insulating layer (pattern cured product) 2 having a step shape (FIG. 3). After forming a seed layer on the stepped insulating layer 2 (FIG. 4), a resist layer 5 is applied and exposed and developed in a predetermined pattern (FIG. 5), and then copper or nickel is formed by electrolytic plating or the like. The circuit 6 is formed by laminating circuit conductors having a multi-layered structure of gold (FIG. 6).

After forming the circuit 6, the resist 4 is peeled off (FIG. 7), and the seed layer 4 is removed by etching. Next, in order to protect the circuit 6, the same photosensitive resin composition of the present invention as described above is applied onto the circuit 6 and exposed and developed to form a protective layer 7 (FIG. 8). After that, a cover 8 that covers a predetermined portion of the protective layer 7 and the support substrate 1 is provided to form a gimbal (FIG. 9).

A patterned cured product of the photosensitive resin composition of the present invention can be obtained by the pattern forming method described above.

The film thickness of the interlayer insulating film or the protective film, which is a cured product of the photosensitive resin composition of the present invention, is preferably 5 to 100 μm, more preferably 8 to 50 μm, and further preferably 5 to 30 μm.

The interlayer insulating film is, for example, the insulating layer 2 shown in FIG. 3, and is formed on a supporting substrate (metal substrate) such as a stainless substrate of a suspension for a hard disk drive.
The protective film is, for example, the protective layer 7 shown in FIG. 8, and protects the electrical signal line (circuit 6, conductive layer) formed on, for example, a metal substrate or a resin substrate.

One aspect of the circuit-forming substrate of the present invention has a cured product of the above-mentioned photosensitive resin composition as an interlayer insulating film or a protective film.
Another aspect of the circuit forming substrate of the present invention includes a support substrate, an interlayer insulating film, a conductive layer, and a protective film in this order, and at least one of the interlayer insulating film and the protective film has the above-mentioned photosensitive resin composition. It is a cured product. A copper layer may be formed on the interlayer insulating film via a chromium layer or a titanium layer. Both the interlayer insulating film and the protective film are preferably cured products of the above photosensitive resin composition.
Since the circuit-formed substrate of the present invention has a pattern having a good shape and characteristics as an interlayer insulating layer or a protective layer of a circuit, reliability can be improved.

The circuit-formed substrate of the present invention can be used for a hard disk drive suspension, a flexible wiring board, and the like.

FIG. 10 is a schematic plan view showing an example of a suspension of a hard disk drive in which a pattern is formed using the photosensitive resin composition of the present invention. In FIG. 10, a suspension 10 is a member on which a magnetic head having a function of writing and reading data to and from a magnetic disk is mounted, and which is a member for accurately controlling the gap between the magnetic disk and the magnetic head to several tens nm, such as stainless steel. It is composed of the plate-shaped member 11 manufactured in. A gimbal 13 is integrally formed by a notch 12 at the tip of a plate-shaped member 11 forming the suspension 10, and a slider (not shown) having a magnetic head is fixed on the gimbal 13.

An insulating layer (not shown) made of the photosensitive resin composition of the present invention is formed on the plate member 11, and a predetermined pattern circuit made of the copper conductor layer 14 is mounted thereon. Further, a protective film 15 made of the photosensitive resin composition of the present invention is formed thereon. Since a predetermined pattern circuit is mounted on the plate-shaped member 11, the suspension 10 is so-called “suspension with a circuit”.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Synthesis example 1 (synthesis of polyamic acid)
After adding 5.4 g (50 mmol) of p-phenylenediamine and 16.0 g (50 mmol) of 2,2′-bis(trifluoromethyl)benzidine to 150 ml of N-methyl-2-pyrrolidone and dissolving them, 3,3 29.4 g (100 mmol) of',4,4'-biphenyltetracarboxylic dianhydride was added and polymerized to obtain a polyamic acid solution.
With respect to the polyamic acid of the obtained polyamic acid solution, the weight average molecular weight was determined by gel permeation chromatography (GPC) method by standard polystyrene conversion under the following conditions. The weight average molecular weight of the polyamic acid was 41,400.

It was measured using a solution of 1 ml of a solvent [tetrahydrofuran (THF)/dimethylformamide (DMF)=1/1 (volume ratio)] against 0.5 mg of polyamic acid.
Measuring device: Detector L4000 UV manufactured by Hitachi, Ltd.
Pump: L6000 manufactured by Hitachi, Ltd.
Shimadzu Corporation C-R4A Chromatopac
Measurement conditions: Column Gelpack GL-S300MDT-5×2 main eluent: THF/DMF=1/1 (volume ratio)
LiBr (0.03 mol/l), H ₃ PO ₄ (0.06 mol/l)
Flow rate: 1.0 ml/min, Detector: UV270nm

N,N-dimethylaminopropyl methacrylate was added to the above polyamic acid solution in a molar equivalent to the carboxy group of the amic acid used, and the mixture was stirred for 60 minutes to obtain a polymer I solution.

Examples 1-8 and Comparative Examples 1-8
1. Preparation of Photosensitive Resin Composition A predetermined amount of the photosensitizer shown in Table 1 was added to the solution of polymer I and stirred to obtain a photosensitive resin solution. The values of the photosensitizer in Table 1 are parts by mass of the photosensitizer when the mass of the polymer I is 100. The components used are as follows.

Polymer Polymer I (component (a)): Polymer I obtained in Synthesis Example 1

Photosensitizer b-1 (component (b)): DAROCUR TPO (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, a compound having a structure of the following formula (b-1)) manufactured by BASF.
b-2 (component (b)): Irgacure 819 (bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, a compound having the structure of the following formula (b-2)) manufactured by BASF.
b-3 (component (b)): compound having a structure of the following formula (b-3) b-4 (component (b)): ADEKA CORPORATION ADEKA OPTOMER N-1919 (the following formula (b-4)) Compound having the structure of
b-5 (component (b)): IRGACURE OXE-02 (ethanone-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(o-, manufactured by BASF. Acetyl oxime), a compound having a structure of the following formula (b-5))
b-6 (component (b)): DFI-020 manufactured by Daito Chemix Co., Ltd. (a compound having a structure of the following formula (b-6))
b-7 (component (b)): Adeka Cruise NCI-831 (compound having a structure of the following formula (b-7)) manufactured by ADEKA Corporation
b-8: IRGACURE OXE-01 (1,2-octanedione, 1-[4-(phenylthio)phenyl]-2-(O-benzoyloxime) manufactured by BASF, having a structure of the following formula (b-8). Compound)

2. Evaluation of residual film ratio and step shape moldability The obtained photosensitive resin composition was spin-coated on a silicon substrate and dried on a hot plate at 90° C. for 3 minutes to obtain a photosensitive resin film having a thickness of 12 μm. It was This photosensitive resin layer through a photomask, was exposed for 500 mJ / cm ² or 100 mJ / cm ² by a high pressure mercury lamp. Immediately after heating at 110° C. for 1 minute on a hot plate, the unexposed portion was immersed in a developing solution containing an organic solvent (dimethyl sulfoxide/γ-butyrolactone/water=41/51/8 (mass ratio)). Dissolved.

After the unexposed portion was completely dissolved, the substrate was taken out from the developing solution, rinsed with isopropyl alcohol, and the film thickness after development was measured.
The residual film rate was calculated by dividing the obtained film thickness after development by the film thickness before exposure (12 μm).

The residual film rate after irradiation with 500 mJ/cm ² was evaluated as follows.
70% or more: A
65% or more and less than 70%: B
60% or more and less than 65%: C
Less than 60%: D

The residual film rate after irradiation with 100 mJ/cm ² was evaluated as follows.
20% or more and less than 50%: A
50% or more and less than 60%: B
60% or more and less than 70%: C
Less than 20% or more than 70%: D
Also, when the pattern peeled off after development, it was evaluated as D.

The step shape forming property was calculated by dividing the residual film rate after irradiation with 500 mJ/cm ² by the residual film rate after irradiation with 100 mJ/cm ² .
The larger the difference between the remaining film rate at the low exposure amount and the high film exposure amount, the higher the step shape forming property. Therefore, the evaluation was performed as follows.
1.6 or more: A
1.3 or more and less than 1.6: B
1.1 or more and less than 1.3: C
Less than 1.1: D

In Examples 1 to 8, the substrate after the residual film rate was measured was heated in an oven at 375° C. for 60 minutes to obtain a patterned cured film. All were good pattern hardened films.

The photosensitive resin composition of the present invention can be used for suspensions for hard disk drives. The hard disk suspension of the present invention can be used for hard disks and the like.

Although some of the embodiments or examples of the present invention have been described in detail above, those skilled in the art may make many modifications to these exemplary embodiments or examples without substantially departing from the novel teachings and effects of the present invention. Easy to make changes. Therefore, many of these modifications are within the scope of the invention.
The entire contents of the documents described in this specification are incorporated herein by reference.

Claims (15)

(A) a polymer having a structural unit represented by the following formula (1) , and (b) a compound which generates a radical upon irradiation with actinic rays, represented by the following formula (B) and the following formula (BB) A photosensitive resin composition containing the compound described above.

(In the formula (1) , R ¹ is a trivalent or tetravalent organic group, R ² is a divalent organic group, and M ⁺ is a hydrogen ion or an ion of a compound having a carbon-carbon unsaturated double bond. And at least one of M ⁺ is an ion of a compound having a carbon- carbon unsaturated double bond, and n is 1 or 2.)

(In the formula (B), R ¹¹ and R ¹² are each independently an alkyl group having 1 to 20 carbon atoms, a phenyl group, a carbazole group or a fluorenyl group. The alkyl group, the phenyl group, the carbazole group and the fluorenyl group. May have a substituent. When the carbazole group has a plurality of substituents, adjacent substituents may be bonded to each other to form a ring.)

(In the formula (BB), R ⁵⁰ represents an alkyl group having 1 to 20 carbon atoms, an alkyl group having 2 to 20 carbon atoms containing one or more ether bonds, an alkoxy group having 1 to 12 carbon atoms, and 1 to 4 carbon atoms. Is a phenyl group substituted with an alkyl group having 2 to 20 carbon atoms containing one or more ether bonds, a phenyl group, a halogen atom, an alkenyl group having 1 to 12 carbon atoms, or a biphenylyl group, and R ⁵¹ is , A group represented by formula (11), or the same group as R ⁵⁰ , wherein R ^{52 to} R ⁵⁴ are each independently an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms. Or a halogen atom.)

(In the formula (11), R ^{55 to} R ⁵⁷ are each independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or a halogen atom.) The photosensitive resin composition according to claim 1, wherein M ⁺ is a dialkylaminoalkyl acrylate ion or a dialkylaminoalkyl methacrylate ion . The photosensitive resin composition according to claim 1, wherein R ² has a structure represented by the following formula (2) or (3).

(In formulas (2) and (3), a plurality of R ^4's each independently represent a monovalent organic group having 1 to 10 carbon atoms, which may have a fluorine atom, or an oxygen atom, a sulfur atom or a halogen atom. Represents a group, and s, t, and u each independently represent an integer of 0 to 4.) The photosensitive resin composition according to claim 1, wherein R ² has a structure represented by the following formula (4).

(In the formula (4), each R ⁵ is independently a fluorine atom or a trifluoromethyl group.) The photosensitive resin composition according to claim 1, wherein the compound represented by the formula (B) is a compound represented by the following formula (6) or (7).

(In the formulas (6) and (7), R ¹¹ is the same as R ^{11 in the} formula (B). R ^{14 to} R ²⁰ are each independently a hydrogen atom, a —NO ₂ group, or the following formula (8). X is C(R ³ ) ₂ or NR ^3. R ³ is each independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

(R ²¹ is each independently a monovalent organic group. p is an integer of 0 to 5) The photosensitive resin composition according to claim 1, wherein the compound represented by the formula (B) is any of compounds represented by the following formulas (B-3) to (B-7). Stuff.

The photosensitive resin composition according to claim 1, wherein the compound represented by the formula (BB) is a compound represented by the following formula (BB-1) or (BB-2).

Content of the said (b) component is 0.1-20 mass parts with respect to 100 mass parts of the said (a) component, The photosensitive resin composition in any one of Claims 1-7. The photosensitive resin composition according to claim 1, which is for a hard disk drive suspension. The photosensitive resin composition according to claim 1, which is for gray scale mask exposure. A step of applying the photosensitive resin composition according to any one of claims 1 to 10 onto a substrate and drying the composition to form a photosensitive resin film;
Exposing the photosensitive resin film,
A step of developing the resin film after exposure,
And a step of heat-treating the resin film after development. A cured product of the photosensitive resin composition according to claim 1. A circuit forming substrate having the cured product according to claim 12 as an interlayer insulating film or a protective film. A support substrate, an interlayer insulating film, a conductive layer, and a protective film are included in this order,
A circuit forming substrate, wherein at least one of the interlayer insulating film and the protective film is the cured product according to claim 12. A suspension for a hard disk drive, comprising the circuit-formed board according to claim 13.

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