Photosensitive element, method for forming resist pattern, and method for manufacturing printed wiring board

Abstract

A photosensitive element comprising a support film, an optical adjustment layer, and a photosensitive layer in this order, wherein the optical adjustment layer has an absorbance of 0.060 or less with respect to light having a wavelength of 365 nm, and the optical adjustment layer has a refractive index of 1.800 or less with respect to light having a wavelength of 365 nm.

Description

Photosensitive element, method for forming resist pattern, and method for manufacturing printed wiring board

[0001] The present disclosure relates to a photosensitive element, a method for forming a resist pattern, and a method for producing a printed wiring board.

[0002] Conventionally, in the field of manufacturing printed wiring boards, photosensitive resin compositions and photosensitive elements comprising a layer formed on a support film using the photosensitive resin composition (hereinafter also referred to as a "photosensitive layer") have been widely used as resist materials used in etching processes, plating processes, and the like (see, for example, Patent Document 1 listed below).

[0003] A printed wiring board is manufactured using the photosensitive element, for example, by the following procedure. That is, first, the photosensitive layer of the photosensitive element is laminated onto a circuit-forming substrate such as a copper-clad laminate. At this time, the surface of the photosensitive layer opposite to the surface in contact with the support film is laminated so as to be in close contact with the surface of the circuit-forming substrate on which the circuit is to be formed. Lamination is performed, for example, by heat-pressure bonding the photosensitive layer onto the circuit-forming substrate (atmospheric pressure lamination method).

[0004] Next, a desired region of the photosensitive layer is exposed to light through a support film using a mask film or the like, thereby generating radicals. The generated radicals pass through several reaction pathways and contribute to a crosslinking reaction (photocuring reaction) of the photopolymerizable compound. Next, after peeling off the support film, the uncured portion of the photosensitive layer is dissolved or dispersed and removed in a developer to form a resist pattern. Next, using the resist pattern as a resist, an etching process or a plating process is performed to form a conductor pattern, and finally, the photocured portion of the photosensitive layer (resist pattern) is peeled off (removed).

[0005] JP 2013-195712 A

[0006] With the recent trend toward higher density printed wiring boards, there is a demand for forming finer resist patterns on package substrates with a line width / space width ratio of 2 / 2 (unit: μm) or less. Conventional photosensitive resin compositions and photosensitive elements have room for further improvement in resolution. Furthermore, in the process of forming a resist pattern, the photosensitive layer may be exposed to light and then developed after a certain period of time has elapsed. This is also known as post-exposure storage. However, post-exposure storage can result in degradation of resolution.

[0007] The present disclosure has been made in consideration of the problems associated with the above-described conventional techniques, and aims to provide a photosensitive element, a method for forming a resist pattern, and a method for manufacturing a printed wiring board that can improve resolution and suppress degradation of resolution due to post-exposure delay.

[0008] The present disclosure provides the following photosensitive element, method for forming a resist pattern, and method for manufacturing a printed wiring board. [1] A photosensitive element comprising, in this order, a support film, an optical adjustment layer, and a photosensitive layer, wherein the optical adjustment layer has an absorbance of 0.060 or less for light with a wavelength of 365 nm and a refractive index of 1.800 or less for light with a wavelength of 365 nm. [2] The photosensitive element according to [1] above, wherein the optical adjustment layer contains a water-soluble resin. [3] The photosensitive element according to [1] or [2] above, wherein the optical adjustment layer has a thickness of 1 to 15 μm. [4] The photosensitive element according to any one of [1] to [3] above, wherein the photosensitive layer has a thickness of 1 to 14 μm. [5] A method for forming a resist pattern, comprising the steps of: using the photosensitive element according to any one of [1] to [4] above to arrange a photosensitive layer, an optical adjustment layer, and a support film on a substrate in this order from the substrate side; removing the support film and exposing the photosensitive layer to actinic light through the optical adjustment layer; and removing the uncured portion of the photosensitive layer and the optical adjustment layer from the substrate. [6] The method for forming a resist pattern according to [5] above, wherein exposure is performed using an exposure machine having a lens with a numerical aperture of 0.16 or more. [7] A method for producing a printed wiring board, comprising the step of etching or plating a substrate on which a resist pattern has been formed by the method for forming a resist pattern according to [5] or [6] above to form a conductor pattern.

[0009] According to the present disclosure, it is possible to provide a photosensitive element, a method for forming a resist pattern, and a method for manufacturing a printed wiring board, which can improve resolution and suppress deterioration of resolution due to post-exposure delay.

[0010] 1 is a schematic cross-sectional view showing one embodiment of a photosensitive element according to the present disclosure. 2 is a diagram showing an example of a process for producing a printed wiring board by a semi-additive method.

[0011] Preferred embodiments of the present disclosure will be described in detail below, with reference to the drawings as necessary. It goes without saying that, in the following embodiments, the components (including element steps, etc.) are not necessarily essential unless otherwise specified or considered to be clearly essential in principle. The same applies to numerical values ​​and ranges, and they should not be construed as unduly limiting the present disclosure.

[0012] In this specification, (meth)acrylic acid means at least one of acrylic acid and its corresponding methacrylic acid. The same applies to other similar expressions such as (meth)acrylate.

[0013] As used herein, the term "process" refers not only to an independent process, but also to processes that cannot be clearly distinguished from other processes, as long as the process achieves its intended function. As used herein, the term "layer" encompasses not only a structure that is formed over the entire surface when observed in a plan view, but also a structure that is formed only partially. As used herein, "solid content" refers to the non-volatile content of the resin composition, excluding volatile substances such as water and organic solvents. In other words, it refers to components other than water, organic solvents, and other solvents that remain unvolatilized during the drying process, and includes liquid, starch syrup, and wax-like substances at room temperature (25°C, hereinafter the same).

[0014] In this specification, numerical ranges indicated using "to" indicate ranges that include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit of a numerical range in one stage may be replaced with the upper or lower limit of a numerical range in another stage. In numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in the examples.

[0015] Unless otherwise specified, the materials exemplified below may be used alone or in combination of two or more. When a plurality of substances corresponding to each component are present in the composition, the content of each component in the composition means the total amount of the plurality of substances present in the composition unless otherwise specified.

[0016] [Photosensitive Element] As shown in Fig. 1 , the photosensitive element 1 according to this embodiment includes a support film 2, an optical adjustment layer 3, and a photosensitive layer 4 in this order, and may further include other layers such as a protective layer 5. Hereinafter, each layer in the photosensitive element according to this embodiment will be described in detail.

[0017] <Support Film> The support film can be any film without particular limitations. Examples include polyester films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene-2,6-naphthalate (PEN), as well as polyolefin films such as polypropylene and polyethylene. Among these, polyester films may be used. Using a polyester film as the support film tends to improve the mechanical strength and heat resistance of the support film. Furthermore, using a polyester film tends to suppress defects such as wrinkles in the optical adjustment layer that occur when forming the optical adjustment layer on the support film, thereby improving workability. From the viewpoint of suppressing the occurrence of minute voids in the resist pattern, polyester films containing particles (lubricants, etc.) may be used. When using a polyester film containing particles (lubricants, etc.), an optical adjustment layer may be formed on the surface having the particles (lubricants, etc.). Examples of such polyester films include polyester films into which particles (lubricants, etc.) are kneaded, polyester films having layers containing particles (lubricants, etc.) formed on both sides, and polyester films having a layer containing particles (lubricants, etc.) formed on one side. The support film may be a single layer or a multilayer.

[0018] Methods for adding particles such as a lubricant to a support film include, for example, a method of kneading particles (lubricant, etc.) into a support film, and a method of forming a layer containing particles (lubricant, etc.) on a support film using a known method such as roll coating, flow coating, spray coating, curtain flow coating, dip coating, or slit die coating.

[0019] The haze of the support film may be 0.01 to 5.0%, 0.01 to 1.5%, 0.01 to 1.0%, or 0.01 to 0.5%. A haze of 0.01% or more tends to facilitate the production of the support film itself, while a haze of 5.0% or less tends to facilitate the detection of foreign matter in the photosensitive layer when forming the photosensitive layer of the photosensitive element. Here, "haze" refers to cloudiness. The haze in the present disclosure refers to a value measured using a commercially available haze meter (turbidity meter) in accordance with the method specified in JIS K 7105. Haze can be measured, for example, using a commercially available turbidity meter such as NDH-5000 (product name, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0020] The support film may be obtained from commercially available general industrial films that can be used as a support film for a photosensitive element and processed appropriately. Specific examples include PET films such as "FB-40" (product name, manufactured by Toray Industries, Inc.), "A4100" and "A1517" (product names, manufactured by Toyobo Co., Ltd.), and "G2H" (product name, manufactured by Teijin DuPont Films Japan Co., Ltd.).

[0021] The thickness of the support film may be 1 to 200 μm, 1 to 100 μm, 1 to 60 μm, 5 to 60 μm, 10 to 60 μm, 10 to 50 μm, 10 to 40 μm, 10 to 30 μm, or 10 to 25 μm. When the thickness of the support film is 1 μm or more, tearing of the support film when peeling the support film tends to be suppressed. Furthermore, when the thickness of the support film is 200 μm or less, economic benefits tend to be easily obtained.

[0022] <Optical Adjustment Layer> The photosensitive element according to this embodiment includes an optical adjustment layer between the support film and the photosensitive layer. The optical adjustment layer has an absorbance of 0.060 or less for light with a wavelength of 365 nm and a refractive index of 1.800 or less for light with a wavelength of 365 nm.

[0023] The photosensitive element of this embodiment is provided with an optical adjustment layer having a specific absorbance and a specific refractive index as described above, so that when the support film is peeled off and the photosensitive layer is exposed through the optical adjustment layer, scattering of light reaching the photosensitive layer can be suppressed, improving resolution, and the contrast between the exposed and unexposed areas can be improved, suppressing the progress of polymerization in the unexposed areas, thereby suppressing deterioration in resolution due to storage after exposure.

[0024] From the viewpoint of further improving the resolution and further suppressing the deterioration of the resolution due to the post-exposure delay, the absorbance of the optical adjustment layer with respect to light having a wavelength of 365 nm may be 0.050 or less, 0.040 or less, 0.030 or less, 0.025 or less, or 0.020 or less. The lower limit of the absorbance of the optical adjustment layer with respect to light having a wavelength of 365 nm is not particularly limited, but may be 0.001 or more. The absorbance of the optical adjustment layer can be adjusted by a conventionally known method (for example, increasing or decreasing the film thickness). The absorbance can be measured by the method described in the examples.

[0025] From the viewpoint of further improving the resolution and further suppressing the deterioration of the resolution due to the post-exposure delay, the refractive index of the optical adjustment layer with respect to light having a wavelength of 365 nm may be 1.750 or less, 1.700 or less, 1.650 or less, 1.600 or less, or 1.550 or less. The lower limit of the refractive index of the optical adjustment layer with respect to light having a wavelength of 365 nm is not particularly limited, but may be 1.300 or more. The refractive index of the optical adjustment layer can be adjusted by a conventionally known method (for example, changing the component ratio of the resin composition for forming the optical adjustment layer). The refractive index can be measured by the method described in the examples.

[0026] The optical adjustment layer may be a layer formed using a resin composition for forming an optical adjustment layer. The resin composition for forming an optical adjustment layer may contain a water-soluble resin. The optical adjustment layer may be water-soluble or soluble in a developer. From the viewpoint of being able to suppress unintended peeling of the optical adjustment layer and the photosensitive layer when peeling the support film from the photosensitive element, the adhesive strength between the support film and the optical adjustment layer may be smaller than the adhesive strength between the optical adjustment layer and the photosensitive layer.

[0027] (Water-soluble resin) The optical adjustment layer may contain a water-soluble resin. Here, the "water-soluble resin" is a resin having a solubility of 5 g / 100 mL-C in 100 mL of hexane at 25°C. ６ H １４ This refers to a resin whose solubility is less than or equal to 100 mL. This solubility can be calculated by mixing hexane at 25°C with the dried water-soluble resin and examining whether or not it becomes cloudy. Specifically, Sample 1 is prepared by placing a mixture of the dried water-soluble resin A (g) and 100 mL of hexane in a colorless, transparent glass container with a ground glass stopper, and Sample 2 is prepared by placing 100 mL of hexane alone in the container. Next, the sample in the glass container is thoroughly shaken and mixed, and it is confirmed that the bubbles have disappeared. Immediately after this confirmation, the two containers are placed side by side under diffuse daylight or light equivalent thereto, and the liquid state of Sample 1 is compared with the liquid state of Sample 2. Sample 1 and Sample 2 are compared, and the amount A (g) added when Sample 1 begins to become more cloudy or when floating solids begin to be observed is taken as the solubility of the water-soluble resin in 100 mL of hexane at 25°C.

[0028] Examples of water-soluble resins include polyvinyl alcohol, polyvinylpyrrolidone, and water-soluble polyimides. Polyvinyl alcohol can be obtained, for example, by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate. The saponification degree of the polyvinyl alcohol used in this embodiment may be 50 mol% or more, 70 mol% or more, or 80 mol% or more. The upper limit of the saponification degree is 100 mol%. In this specification, the "saponification degree" refers to a value measured in accordance with JIS K 6726 (1994) (Testing method for polyvinyl alcohol) specified by the Japanese Industrial Standards.

[0029] Two or more types of polyvinyl alcohols may be used in combination, each having a different degree of saponification, viscosity, degree of polymerization, modified species, etc. The average degree of polymerization of the polyvinyl alcohol may be 300 to 5000, 300 to 3500, or 300 to 2000.

[0030] The water-soluble resin may be used alone or in combination of two or more. The water-soluble resin may contain, for example, polyvinyl alcohol and polyvinylpyrrolidone. In this case, the mass ratio of polyvinyl alcohol to polyvinylpyrrolidone (PVA:PVP) may be 40:60 to 90:10, 50:50 to 90:10, or 60:40 to 90:10.

[0031] The content of the water-soluble resin in the resin composition for forming an optical adjustment layer may be 50 to 700 parts by mass, 60 to 650 parts by mass, or 70 to 600 parts by mass relative to 500 parts by mass of water.

[0032] The content of the water-soluble resin in the optical adjustment layer may be 99.0 to 99.95 mass %, 99.3 to 99.9 mass %, or 99.5 to 99.8 mass %, based on the total solid content of the optical adjustment layer.

[0033] (Leveling Agent) The resin composition for forming an optical adjustment layer may contain a leveling agent. The leveling agent is oriented on the coating film surface and equalizes the tension on the coating film surface. Examples of types of leveling agents include acrylic polymers, vinyl-based, silicone-based, and fluorine-based.

[0034] From the viewpoint of solubility in the developer, the leveling agent may contain an acrylic polymer. From the viewpoint of suppressing unintended peeling between the layers while keeping the adhesion between the optical adjustment layer and the support film within an appropriate range and making the adhesive strength between the support film and the optical adjustment layer smaller than the adhesive strength between the optical adjustment layer and the photosensitive layer, and from the viewpoint of easily suppressing defects on the surface of the optical adjustment layer when forming the optical adjustment layer on the support film (repelling is less likely to occur), the acrylic polymer preferably contains a copolymer having a structural unit derived from at least one selected from the group consisting of butyl (meth) acrylate, isobutyl (meth) acrylate, and terminal methoxy group EO-modified (meth) acrylate, more preferably contains a copolymer having a structural unit derived from butyl (meth) acrylate and isobutyl (meth) acrylate, and even more preferably contains a copolymer having a structural unit derived from butyl (meth) acrylate, isobutyl (meth) acrylate, and terminal methoxy group EO-modified (meth) acrylate.

[0035] The content of each structural unit constituting the acrylic polymer may be, for example, in the following ranges, based on the total amount of structural units. The content of the structural unit derived from butyl (meth)acrylate may be 2 to 20% by mass, 5 to 15% by mass, or 5 to 10% by mass, from the viewpoint of further reducing the number of defects on the surface of the optical adjustment layer and further suppressing damage to the optical adjustment layer when the support film is peeled off. The content of the structural unit derived from isobutyl (meth)acrylate may be 40 to 80% by mass, 50 to 70% by mass, or 55 to 65% by mass, from the viewpoint of further reducing the number of defects on the surface of the optical adjustment layer and further suppressing damage to the optical adjustment layer when the support film is peeled off. The content of the structural unit derived from the terminal methoxy group EO-modified (meth)acrylate may be 15 to 45% by mass, 20 to 40% by mass, or 25 to 35% by mass, from the viewpoint of further reducing the number of defects on the surface of the optical adjustment layer and further suppressing damage to the optical adjustment layer when the support film is peeled off. The weight average molecular weight of the acrylic polymer may be 10,000 to 40,000, or 10,000 to 20,000, from the viewpoint of further reducing the number of defects on the surface of the optical adjustment layer and further suppressing damage to the optical adjustment layer when the support film is peeled off.

[0036] The content of the leveling agent in the optical adjustment layer may be 0.01 to 1.0 mass%, 0.05 to 0.7 mass%, or 0.10 to 0.5 mass%, based on the total solid content of the optical adjustment layer, from the viewpoint of further reducing the number of defects on the surface of the optical adjustment layer and further suppressing damage to the optical adjustment layer when the support film is peeled off.

[0037] (Other Components) The resin composition for forming an optical adjustment layer may contain an alcohol having 3 or more carbon atoms. The alcohol having 3 or more carbon atoms may be a monohydric alcohol or a polyhydric alcohol. The alcohol having 3 or more carbon atoms may contain at least one selected from the group consisting of compounds represented by the following formulas (1) to (4). By containing these alcohols having 3 or more carbon atoms, the peelability between the optical adjustment layer and the support film tends to be improved. Therefore, when peeling the support film from the photosensitive element, unintended peeling between the optical adjustment layer and the photosensitive layer can be suppressed, and a decrease in resolution due to such unintended peeling tends to be suppressed.

[0038] In formula (4), R １１ represents an alkyl group, and R １２ represents an alkylene group. １１ and R １２ The sum of the carbon numbers of the groups R １１ and R １２ From the viewpoint of affinity with water, the sum of the carbon atoms of the R １１ The alkyl group represented by R may be an alkyl group having 1 to 4 carbon atoms, １２ The alkylene group represented by formula (4) may be an alkylene group having 1 to 3 carbon atoms. The alcohol having 3 or more carbon atoms represented by formula (4) may be 2-butoxyethanol or 1-methoxy-2-propanol.

[0039] The alcohols having 3 or more carbon atoms may be used alone or in combination of two or more. The solubility of the alcohols having 3 or more carbon atoms in water at 20° C. is 300 mL / 100 mL-H from the viewpoint of suppressing layer separation of the optical adjustment layer. ２ O or more, 500mL / 100mL-H ２ O or more, or 1000mL / 100mL-H ２ It may be O or more.

[0040] As used herein, the "solubility of alcohols having 3 or more carbon atoms in water at 20°C" can be calculated by mixing the alcohol with water at 20°C and examining whether or not the mixture becomes cloudy. Specifically, a colorless, transparent glass container with a ground glass stopper is filled with a mixture of A mL of the alcohol and 100 mL of water to prepare sample 3, and 100 mL of water alone to prepare sample 4. Samples 3 and 4 are then thoroughly shaken and mixed in the glass containers, and the disappearance of bubbles is confirmed. Immediately after confirmation, the two containers are placed side by side under diffuse daylight or a light equivalent thereto, and the state of the liquid in sample 3 is compared with the state of the liquid in sample 4. Samples 3 and 4 are compared, and the amount A mL of the alcohol added when sample 3 is observed to be more cloudy is defined as the solubility of the alcohol in water at 20°C.

[0041] The content of the alcohol having 3 or more carbon atoms in the resin composition for forming an optical adjustment layer may be 100 to 2000 parts by mass, or 125 to 1600 parts by mass, relative to 500 parts by mass of water. If this content is 100 parts by mass or more, the peelability between the optical adjustment layer formed and the support film tends to be improved, and if it is 2000 parts by mass or less, the solubility of the water-soluble resin tends to be improved, making it easier to form the optical adjustment layer.

[0042] The content of the alcohol having 3 or more carbon atoms in the optical adjustment layer may be more than 0 mass% and 2.0 mass% or less, 0.001 to 2.0 mass%, or 0.005 to 1.0 mass%, based on the total amount of the optical adjustment layer (the total solid content of the resin composition for forming the optical adjustment layer that forms the optical adjustment layer). A content of 2.0 mass% or less tends to suppress diffusion of the alcohol in subsequent steps, and a content of 0.001 mass% or more tends to improve the peelability between the optical adjustment layer and the support film.

[0043] The resin composition for forming an optical adjustment layer may contain an alcohol having less than 3 carbon atoms. When an alcohol having less than 3 carbon atoms is contained, the content thereof may be 50 to 375 parts by mass or 60 to 325 parts by mass relative to 500 parts by mass of water. When this content is 50 parts by mass or more, the solubility of the water-soluble resin tends to be improved, and the optical adjustment layer tends to be easier to form, while when the content is 375 parts by mass or less, the peelability between the formed optical adjustment layer and the support film tends to be improved. From the viewpoint of improving the peelability between the optical adjustment layer and the support film, the content of the alcohol having less than 3 carbon atoms in the optical adjustment layer may be 0.1 to 10 mass% (i.e., the amount of the alcohol having less than 3 carbon atoms is 0.1 to 10 parts by mass relative to 100 parts by mass of the total amount of alcohols having 3 or more carbon atoms) based on the total amount of alcohols having 3 or more carbon atoms in the optical adjustment layer.

[0044] The resin composition for forming an optical adjustment layer and the optical adjustment layer may contain known additives such as plasticizers, surfactants, and release promoters, as long as the effects of the present disclosure are not impaired.

[0045] The optical adjustment layer can be formed, for example, by applying the resin composition for forming an optical adjustment layer onto a support film and drying it.

[0046] The thickness of the optical adjustment layer is not particularly limited. From the viewpoint of ease of removal of the optical adjustment layer, the thickness of the optical adjustment layer may be 15 μm or less, 12 μm or less, 10 μm or less, 8 μm or less, 7 μm or less, or 6 μm or less. From the viewpoint of ease of formation of the optical adjustment layer and resolution, the thickness of the optical adjustment layer may be 1 μm or more, 2 μm or more, 3 μm or more, or 4 μm or more.

[0047] <Photosensitive Layer> The photosensitive layer of this embodiment is a layer formed using a photosensitive resin composition described below. The photosensitive resin composition can be used for a desired purpose as long as its properties change upon exposure to light (for example, it is photocured), and it may be either negative or positive. The photosensitive resin composition may contain (A) a binder polymer, (B) a photopolymerizable compound, and (C) a photopolymerization initiator. Furthermore, it may contain (D) a photosensitizer, (E) a polymerization inhibitor, (F) an ultraviolet absorber, or other components, as necessary. Each component used in the photosensitive resin composition of this embodiment will be described in more detail below.

[0048] ((A) Binder Polymer) The (A) binder polymer (hereinafter also referred to as "component (A)") can be produced, for example, by radical polymerization of a polymerizable monomer. Examples of the polymerizable monomer include polymerizable styrene derivatives substituted at the α-position or at the aromatic ring, such as styrene, vinyltoluene, and α-methylstyrene; acrylamides such as diacetone acrylamide; acrylonitrile; ethers of vinyl alcohol such as vinyl-n-butyl ether; (meth)acrylic acid alkyl esters; (meth)acrylic acid benzyl esters such as benzyl methacrylate; (meth)acrylic acid tetrahydrofurfuryl esters; (meth)acrylic acid dimethylaminoethyl esters; and (meth)acrylic acid diethylaminoethyl esters. Examples of suitable acrylic acid include esters, (meth)acrylic acid glycidyl esters, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate, (meth)acrylic acid, α-bromoacrylic acid, α-chloroacrylic acid, β-furyl (meth)acrylic acid, β-styryl (meth)acrylic acid, maleic acid, maleic anhydride, maleic acid monoesters such as monomethyl maleate, monoethyl maleate, and monoisopropyl maleate, fumaric acid, cinnamic acid, α-cyanocinnamic acid, itaconic acid, crotonic acid, and propiolic acid. These may be used alone or in combination of two or more.

[0049] Among these, from the viewpoint of improving plasticity, the polymerizable monomer may contain a (meth)acrylic acid alkyl ester. Examples of the (meth)acrylic acid alkyl ester include compounds represented by the following formula (I) and compounds in which the alkyl group of these compounds is substituted with a hydroxyl group, an epoxy group, a halogen group, or the like. ２ C=C(R ６ )-COOR ７ (I)

[0050] In formula (I), R ６ represents a hydrogen atom or a methyl group, and R ７ represents an alkyl group having 1 to 12 carbon atoms. ７ The alkyl group represented by R may be linear, branched, or cyclic. ７ Examples of the alkyl group represented by the formula (I) include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, and structural isomers of these groups.

[0051] Examples of (meth)acrylic acid alkyl esters represented by formula (I) include (meth)acrylic acid methyl ester, (meth)acrylic acid ethyl ester, (meth)acrylic acid propyl ester, (meth)acrylic acid butyl ester, (meth)acrylic acid pentyl ester, (meth)acrylic acid hexyl ester, (meth)acrylic acid heptyl ester, (meth)acrylic acid octyl ester, (meth)acrylic acid 2-ethylhexyl ester, (meth)acrylic acid nonyl ester, (meth)acrylic acid decyl ester, (meth)acrylic acid undecyl ester, (meth)acrylic acid dodecyl ester, and (meth)acrylate compounds having an alicyclic structure. Examples of (meth)acrylate compounds having an alicyclic structure include cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, cyclopentanyl (meth)acrylate, and dicyclopentanyl (meth)acrylate. These compounds can be used alone or in combination of two or more.

[0052] From the viewpoint of further improving the resolution and further suppressing the deterioration of the resolution due to the delay after exposure, the component (A) may have a structural unit derived from a (meth)acrylate compound having an alicyclic structure. The content of the structural unit derived from a (meth)acrylate compound having an alicyclic structure may be 1.0 mass% or more, 2.0 mass% or more, 4.0 mass% or more, or 5.0 mass% or more, and may be 15.0 mass% or less, 10.0 mass% or less, 8.0 mass% or less, or 7.0 mass% or less, based on the total mass of the structural units derived from the polymerizable monomers constituting the binder interpolymer.

[0053] From the viewpoint of alkaline developability, the component (A) may contain a carboxy group. The component (A) containing a carboxy group can be produced, for example, by radical polymerization of a polymerizable monomer having a carboxy group with another polymerizable monomer. The polymerizable monomer having a carboxy group may be (meth)acrylic acid or methacrylic acid. The acid value of the component (A) containing a carboxy group may be 50 to 250 mgKOH / g, 50 to 200 mgKOH / g, or 100 to 200 mgKOH / g.

[0054] From the viewpoint of improving the alkali developability and alkali resistance in a well-balanced manner, the carboxy group content of the component (A) (the incorporation ratio of polymerizable monomers having a carboxy group relative to the total amount of polymerizable monomers used in the binder polymer) may be 12 to 50 mass%, 12 to 40 mass%, 15 to 35 mass%, 15 to 30 mass%, 20 to 30 mass%, or 25 to 30 mass%. When this carboxy group content is 12 mass% or more, alkali developability tends to be improved, and when it is 50 mass% or less, alkali resistance tends to be excellent.

[0055] The content of the structural unit derived from the polymerizable monomer having a carboxy group in the component (A) correlates with the blending ratio of the polymerizable monomer having a carboxy group, and may be 12 to 50 mass%, 12 to 40 mass%, 15 to 35 mass%, 15 to 30 mass%, 20 to 30 mass%, or 25 to 30 mass%.

[0056] From the viewpoint of adhesion and chemical resistance, component (A) may use styrene or a styrene derivative as the polymerizable monomer. When styrene or a styrene derivative is used as the polymerizable monomer, its content (the blending ratio of styrene or a styrene derivative to the total amount of polymerizable monomers used in component (A)) may be 10% by mass or more, 30% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, or 65% by mass or more from the viewpoint of further improving resolution and further suppressing deterioration of resolution due to post-exposure delay, and may be 80% by mass or less or 70% by mass or less from the viewpoint of shortening the peeling time.

[0057] The content of structural units derived from styrene or a styrene derivative in component (A) correlates with the blending ratio of the styrene or styrene derivative, and may be 10% by mass or more, 30% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, or 65% by mass or more, or may be 80% by mass or less, or 70% by mass or less.

[0058] From the viewpoints of resolution and aspect ratio, component (A) may use a (meth)acrylic acid benzyl ester as a polymerizable monomer. From the viewpoints of resolution and aspect ratio, the content of structural units derived from a (meth)acrylic acid benzyl ester in component (A) may be 15 to 50 mass%, 15 to 45 mass%, 15 to 40 mass%, 15 to 35 mass%, 20 to 30 mass%, or 20 to 25 mass%.

[0059] The component (A) can be used alone or in combination of two or more. When two or more types are used in combination, examples of the component (A) include two or more binder polymers made of different polymerizable monomers, two or more binder polymers having different weight average molecular weights, and two or more binder polymers having different dispersities.

[0060] Component (A) can be produced by a conventional method, for example, by radical polymerization of an alkyl (meth)acrylate, (meth)acrylic acid, and styrene or the like.

[0061] From the viewpoint of improving mechanical strength and alkaline developability in a well-balanced manner, the weight average molecular weight (Mw) of component (A) may be 8,000 or more, 9,000 or more, 9,500 or more, or 10,000 or more, and may be 150,000, 100,000, 50,000 or less, or 40,000 or less. When component (A) has an Mw of 8,000 or more, developer resistance tends to be excellent, while when it is 150,000 or less, prolonged development time tends to be suppressed. Mw is a value measured by gel permeation chromatography (GPC) and converted using a calibration curve prepared using standard polystyrene.

[0062] The content of component (A) may be 30 to 80 parts by mass, 40 to 75 parts by mass, 50 to 70 parts by mass, or 50 to 60 parts by mass, relative to 100 parts by mass of the total solid content of component (A) and component (B), which will be described later. When the content of component (A) is within this range, the film-forming properties of the photosensitive resin composition and the strength of the photocured part are improved.

[0063] ((B) Photopolymerizable Compound) The (B) photopolymerizable compound (hereinafter also referred to as "component (B)") can be any photopolymerizable or photocrosslinkable compound without any particular limitation. For example, a compound having at least one ethylenically unsaturated bond in the molecule can be used.

[0064] The component (B) may contain a bisphenol-type (meth)acrylate compound. Examples of the bisphenol-type (meth)acrylate compound include 2,2-bis(4-((meth)acryloxypolyethoxy)phenyl)propane, 2,2-bis(4-((meth)acryloxypolypropoxy)phenyl)propane, and 2,2-bis(4-((meth)acryloxypolyethoxypolypropoxy)phenyl)propane. These may be used alone or in combination of two or more. Examples of the bisphenol-type (meth)acrylate compound include 2,2-bis(4-(methacryloxypentaethoxy)phenyl)propane and 2,2-bis(4-(methacryloxydiethoxy)phenyl)propane.

[0065] Commercially available bisphenol (meth)acrylate compounds include, for example, 2,2-bis(4-(methacryloxydiethoxy)phenyl)propane ("BPE-200" manufactured by Shin-Nakamura Chemical Co., Ltd.), 2,2-bis(4-(methacryloxypentaethoxy)phenyl)propane ("BPE-500" manufactured by Shin-Nakamura Chemical Co., Ltd. or "FA-321M" manufactured by Resonac Corporation), 2,2-bis(4-(methacryloxypentadecaethoxy)phenyl)propane ("BPE-1300" manufactured by Shin-Nakamura Chemical Co., Ltd.), and 2,2-bis(4-(methacryloxypolyethoxy)phenyl)propane ("BP-2EM" manufactured by Kyoeisha Chemical Co., Ltd. (EO group: 2.6 (average value)).

[0066] From the viewpoint of chemical resistance, the content of the bisphenol type (meth)acrylate compound may be 1 to 50 mass%, 3 to 45 mass%, 10 to 45 mass%, 20 to 45 mass%, or 30 to 45 mass%, relative to the total amount of solids of the (A) component and the (B) component.

[0067] From the viewpoint of chemical resistance, the content of the bisphenol type (meth)acrylate compound may be 30 to 99 mass%, 50 to 97 mass%, 60 to 95 mass%, 70 to 95 mass%, or 80 to 95 mass%, relative to the total solid content of the component (B).

[0068] The content of component (B) may be 20 to 70 parts by mass, 25 to 60 parts by mass, or 30 to 50 parts by mass, relative to 100 parts by mass of the total solid content of components (A) and (B). When the content of component (B) is within this range, the photosensitive resin composition tends to have better resolution, adhesion, and suppression of resist tail formation, as well as better photosensitivity and film-forming properties.

[0069] (Photopolymerization initiator (C)) The photopolymerization initiator (C) (hereinafter also referred to as "component (C)") is not particularly limited as long as it can polymerize component (B), and can be appropriately selected from commonly used photopolymerization initiators.

[0070] Examples of component (C) include aromatic ketones such as 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propanone-1, quinones such as alkylanthraquinones, benzoin ether compounds such as benzoin alkyl ethers, benzoin compounds such as benzoin and alkylbenzoins, benzyl derivatives such as benzyl dimethyl ketal, 2,4,5-triarylimidazole dimers such as 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer and 2-(o-fluorophenyl)-4,5-diphenylimidazole dimer, and acridine derivatives such as 9-phenylacridine and 1,7-(9,9'-acridinyl)heptane. These can be used alone or in combination of two or more.

[0071] Among these, from the viewpoint of improving resolution, 2,4,5-triarylimidazole dimer may be contained. Examples of 2,4,5-triarylimidazole dimers include 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, 2-(o-chlorophenyl)-4,5-bis-(m-methoxyphenyl)imidazole dimer, and 2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer. Among these, from the viewpoint of photosensitivity stability, 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer may be contained.

[0072] An example of a commercially available 2,4,5-triarylimidazole dimer is B-CIM (product name, manufactured by Hodogaya Chemical Co., Ltd.).

[0073] The amount of component (C) may be 0.01 to 30 parts by mass, 0.1 to 10 parts by mass, 1 to 7 parts by mass, 1 to 6 parts by mass, or 2 to 6 parts by mass, relative to 100 parts by mass of the total solids of components (A) and (B). When the amount of component (C) is 0.01 part by mass or more, photosensitivity, resolution, and adhesion tend to be improved, while when it is 30 parts by mass or less, the resist pattern shape tends to be excellent.

[0074] (Photosensitizer (D)) The photosensitive resin composition according to this embodiment may contain a photosensitizer (D) (hereinafter also referred to as "component (D)"). By containing the component (D), it tends to be possible to effectively utilize the absorption wavelength of actinic rays used for exposure.

[0075] Examples of component (D) include pyrazolines, dialkylaminobenzophenones, anthracenes, coumarins, acridines, xanthones, oxazoles, benzoxazoles, thiazoles, benzothiazoles, triazoles, stilbenes, triazines, thiophenes, naphthalimides, and triarylamines. These can be used alone or in combination of two or more. From the viewpoint of more effectively utilizing the absorption wavelength of the actinic radiation used for exposure, component (D) may include pyrazolines, anthracenes, coumarins, acridines, or dialkylaminobenzophenones, and particularly may include coumarins, acridines, or dialkylaminobenzophenones, or may include dialkylaminobenzophenones. Commercially available dialkylaminobenzophenones include, for example, "EAB" manufactured by Hodogaya Chemical Co., Ltd.

[0076] When the (D) component is contained, its content may be 1.0 part by mass or less, 0.5 part by mass or less, 0.15 part by mass or less, 0.12 part by mass or less, or 0.10 part by mass or less, relative to 100 parts by mass of the total solid content of the (A) component and the (B) component. When the (D) component content is 1.0 part by mass or less, relative to 100 parts by mass of the total solid content of the (A) component and the (B) component, deterioration of the resist pattern shape and the occurrence of resist tailing can be suppressed, and resolution tends to be improved. From the viewpoint of easily obtaining high photosensitivity and good resolution, the (D) component content may be 0.01 part by mass or more, relative to 100 parts by mass of the total solid content of the (A) component and the (B) component.

[0077] ((E) Polymerization Inhibitor) The photosensitive resin composition according to this embodiment may contain (E) a polymerization inhibitor (hereinafter also referred to as "component (E)"). Examples of component (E) include alkyl catechols such as catechol, resorcinol (resorcin), 1,4-hydroquinone, 2-methylcatechol, 3-methylcatechol, 4-methylcatechol, 2-ethylcatechol, 3-ethylcatechol, 4-ethylcatechol, 2-propylcatechol, 3-propylcatechol, 4-propylcatechol, 2-n-butylcatechol, 3-n-butylcatechol, 4-n-butylcatechol, 2-tert-butylcatechol, 3-tert-butylcatechol, 4-tert-butylcatechol, and 3,5-di-tert-butylcatechol; Examples of the resorcinol include alkyl resorcinols such as orcinol, 4-methylresorcinol, 5-methylresorcinol (orcinol), 2-ethylresorcinol, 4-ethylresorcinol, 2-propylresorcinol, 4-propylresorcinol, 2-n-butylresorcinol, 4-n-butylresorcinol, 2-tert-butylresorcinol, and 4-tert-butylresorcinol, alkylhydroquinones such as methylhydroquinone, ethylhydroquinone, propylhydroquinone, tert-butylhydroquinone, and 2,5-di-tert-butylhydroquinone, pyrogallol, and phloroglucinol. These may be used alone or in combination of two or more.

[0078] (Ultraviolet Absorber (F)) The photosensitive resin composition according to this embodiment may contain an ultraviolet absorber (F) (hereinafter also referred to as "component (F)"). By including the component (F), the photosensitive resin composition according to this embodiment tends to be able to form a fine resist pattern with excellent resolution.

[0079] Component (F) may be a compound that absorbs light in the range of 340 to 430 nm, or may be a compound that efficiently absorbs light with a wavelength of 365 nm. The molar absorption coefficient of component (F) for light with a wavelength of 365 nm is in the range of 500 to 50,000 L / (mol cm). The molar absorption coefficient is an index of the ease of light absorption.

[0080] When the photosensitive layer is exposed to actinic rays of 340 to 430 nm, component (F) may contain at least one compound selected from the group consisting of benzophenone compounds, benzotriazole compounds, and triazine compounds, since it effectively absorbs light of the exposure wavelength. The benzophenone compound may be a benzophenone compound in which some of the hydrogen atoms are substituted with groups having oxygen atoms, or a benzophenone compound having a hydroxy group.

[0081] Examples of benzophenone compounds include 4,4'-dimethoxybenzophenone, 4,4'-bis(trimethylacetoxy)benzophenone, 2,4,4'-trihydroxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2,3,4,4'-tetrahydroxybenzophenone, 2,2',3,4,4'-pentahydroxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-(octyloxy)benzophenone, and 2-hydroxy-4-methoxy-benzophenone-5-sulfonic acid. Examples of benzotriazole compounds include 2,2-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol], 2-(2'-hydroxy-5'-methacryloxyethylphenyl)-2H-benzotriazole, 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol, and 2-(5-chloro-2H-benzotriazol-2-yl)-6-tert-butyl-4-methylphenol. Examples of triazine compounds include 2-[4,6-di(2,4-xylyl)-1,3,5-triazin-2-yl]-5-octyloxyphenol, and 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine.

[0082] The content of the component (F) may be 0.05 to 5.0 parts by mass, 0.1 to 4.0 parts by mass, or 0.2 to 2.0 parts by mass, per 100 parts by mass of the total amount of the components (A) and (B).

[0083] (Other Components) The photosensitive resin composition according to this embodiment may contain, as needed, 0.01 to 20 parts by mass of each of the following additives, relative to 100 parts by mass of the total solids content of component (A) and component (B): dyes such as malachite green, Victoria Pure Blue, brilliant green, and methyl violet; photocoloring agents such as tribromophenyl sulfone, leuco crystal violet, diphenylamine, benzylamine, triphenylamine, diethylaniline, and o-chloroaniline; thermal color-forming inhibitors; plasticizers such as p-toluenesulfonamide; pigments; fillers; defoamers; flame retardants; adhesion promoters; leveling agents; release promoters; antioxidants; fragrances; imaging agents; and thermal crosslinking agents. These additives may be used alone or in combination of two or more.

[0084] The photosensitive resin composition according to this embodiment may contain at least one organic solvent as needed to improve the handleability of the photosensitive composition or to adjust the viscosity and storage stability. As the organic solvent, any commonly used organic solvent can be used without particular limitation. Specific examples include organic solvents such as methanol, ethanol, acetone, methyl ethyl ketone, methyl cellosolve, ethyl cellosolve, toluene, N,N-dimethylformamide, and propylene glycol monomethyl ether, as well as mixed solvents thereof. These may be used alone or in combination of two or more.

[0085] <Protective Layer> In the photosensitive element of this embodiment, a protective layer may be laminated on the surface of the photosensitive layer opposite to the surface in contact with the optical adjustment layer. As the protective layer, for example, a polymer film such as polyethylene or polypropylene may be used. The protective layer may be the same polymer film as the support film, or a different polymer film.

[0086] A method for producing a photosensitive element in which a support film, an optical adjustment layer, a photosensitive layer, and a protective layer are laminated in this order will be described below.

[0087] <Method for producing photosensitive element> First, for example, a resin composition for forming an optical adjustment layer is applied to a support film and dried to form an optical adjustment layer. The resin composition for forming an optical adjustment layer can be applied to the support film by a known method such as roll coating, comma coating, gravure coating, air knife coating, die coating, bar coating, or spray coating.

[0088] The drying of the applied resin composition for forming an optical adjustment layer is not particularly limited as long as it can remove at least a portion of the solvent such as water, but it may be dried for 5 to 30 minutes at 70 to 150° C. After drying, the amount of solvent remaining in the optical adjustment layer may be 2% by mass or less, from the viewpoint of preventing diffusion of the solvent in subsequent steps.

[0089] Next, a photosensitive resin composition may be applied to the optical adjustment layer of the support film on which the optical adjustment layer is formed, in the same manner as the application of the resin composition for forming the optical adjustment layer, and dried to form a photosensitive layer on the optical adjustment layer.

[0090] Next, a protective layer is laminated onto the photosensitive layer thus formed, thereby producing a photosensitive element having a support film, an optical adjustment layer, a photosensitive layer, and a protective layer in this order. Alternatively, a photosensitive element having a support film, an optical adjustment layer, a photosensitive layer, and a protective layer in this order may be obtained by laminating a support film having an optical adjustment layer formed thereon and a protective layer having a photosensitive layer formed thereon.

[0091] The melt viscosity of the photosensitive layer in the photosensitive element at 110°C can be appropriately selected depending on the type of substrate (undercoat) that comes into contact with the photosensitive layer, but may be 50 to 10,000 Pa s, 100 to 5,000 Pa s, or 200 to 1,000 Pa s at 110°C after drying. When the melt viscosity at 110°C is 50 Pa s or more, wrinkles and voids do not occur during the lamination step, and productivity tends to improve. When the melt viscosity at 110°C is 10,000 Pa s or less, adhesion to the undercoat improves during the lamination step, and adhesion defects tend to be reduced.

[0092] The thickness of the photosensitive layer in the photosensitive element can be appropriately selected depending on the application, and may be 1 μm or more, 2 μm or more, 3 μm or more, or 4 μm or more after drying, or 14 μm or less, 12 μm or less, 10 μm or less, 9 μm or less, 8 μm or less, or 7 μm or less. When the thickness of the photosensitive layer is 1 μm or more, industrial coating becomes easy and productivity tends to improve. When the thickness of the photosensitive layer is 14 μm or less, photosensitivity is high and photocuring properties at the bottom of the resist are excellent, so that a resist pattern with excellent resolution and aspect ratio tends to be formed.

[0093] The form of the photosensitive element is not particularly limited. For example, it may be in the form of a sheet, or may be in the form of a roll wound around a core. When wound into a roll, it may be wound so that the support film is on the outside. Examples of materials for the core include plastics such as polyethylene resin, polypropylene resin, polystyrene resin, polyvinyl chloride resin, and ABS resin (acrylonitrile-butadiene-styrene copolymer).

[0094] The end faces of the photosensitive element roll thus obtained may be provided with end separators from the viewpoint of end face protection, or moisture-proof end face separators from the viewpoint of edge fusion resistance. The photosensitive element roll may be packaged in a black sheet with low moisture permeability.

[0095] The photosensitive element according to this embodiment can be suitably used, for example, in the method for forming a resist pattern and the method for producing a printed wiring board, which will be described later.

[0096] [Method for forming a resist pattern] The method for forming a resist pattern according to this embodiment includes: (i) a step of using the photosensitive element to arrange a photosensitive layer, an optical adjustment layer, and a support film on a substrate in this order from the substrate side (hereinafter also referred to as "(i) photosensitive layer and optical adjustment layer forming step"); (ii) a step of removing the support film and exposing the photosensitive layer to active light through the optical adjustment layer (hereinafter also referred to as "(ii) exposure step"); and (iii) a step of removing the uncured portion of the photosensitive layer and the optical adjustment layer from the substrate (hereinafter also referred to as "(iii) development step"); and may include other steps as necessary. The resist pattern can also be referred to as a photocured product pattern of a photosensitive resin composition or a relief pattern. Depending on the purpose, the resist pattern according to this embodiment may be used as a resist or for other purposes such as a protective film.

[0097] (i) Photosensitive Layer and Optical Adjustment Layer Forming Step) In the photosensitive layer and optical adjustment layer forming step, the photosensitive layer and the optical adjustment layer are formed on a substrate using the above-mentioned photosensitive element.

[0098] The substrate is not particularly limited, but typically includes a circuit-forming substrate having an insulating layer and a conductor layer formed on the insulating layer, or a die pad (substrate for lead frame) such as an alloy substrate. The surface roughness (Ra) of the substrate may be 10 to 200 nm, 30 to 100 nm, or 40 to 100 nm from the viewpoint of resolution.

[0099] As a method for forming the photosensitive layer and the optical adjustment layer on the substrate, for example, when a photosensitive element having a protective layer is used, the protective layer is removed, and then the photosensitive layer of the photosensitive element is pressed onto the substrate while being heated, thereby forming the photosensitive layer and the optical adjustment layer on the substrate, thereby obtaining a laminate having the substrate, the photosensitive layer, the optical adjustment layer, and the support film in this order.

[0100] When the photosensitive layer and optical adjustment layer forming step is carried out using a photosensitive element, the step may be carried out under reduced pressure from the viewpoint of adhesion and followability. Heating during pressure bonding may be carried out at a temperature of 70 to 130°C, and pressure bonding may be carried out at 0.1 to 1.0 MPa (1 to 10 kgf / cm２ These conditions can be appropriately selected as needed. Note that if the photosensitive layer of the photosensitive element is heated to 70 to 130°C, it is not necessary to preheat the substrate, but the substrate can be preheated in order to further improve the adhesion and followability.

[0101] (ii) Exposure Step) In the exposure step, the support film is removed, and the photosensitive layer is exposed to actinic rays through the optical adjustment layer. As a result, the exposed portion irradiated with the actinic rays may be photocured to form a photocured portion (latent image).

[0102] As the exposure method, known exposure methods can be applied, such as a method of irradiating an actinic ray imagewise through a negative or positive mask pattern called artwork (mask exposure method), an LDI (laser direct imaging) exposure method, or a method of irradiating an actinic ray imagewise through a lens using a projected image of a photomask (projection exposure method). From the viewpoint of resolution, exposure may be performed using an exposure machine having a lens numerical aperture (NA) of 0.16 or more. The NA may be 0.17 or more, 0.20 or more, or 0.22 or more.

[0103] The light source for actinic rays is not particularly limited as long as it is a commonly used, well-known light source. For example, those that effectively emit ultraviolet light, such as carbon arc lamps, mercury vapor arc lamps, ultra-high pressure mercury lamps, high-pressure mercury lamps, xenon lamps, gas lasers such as argon lasers, solid-state lasers such as YAG lasers, and semiconductor lasers such as gallium nitride blue-violet lasers, can be used. Also, those that effectively emit visible light, such as photographic flood lamps and sun lamps, can be used. Among these, from the viewpoint of improving resolution and alignment in a well-balanced manner, light sources capable of emitting monochromatic i-line light with an exposure wavelength of 365 nm, light sources capable of emitting monochromatic h-line light with an exposure wavelength of 405 nm, or light sources capable of emitting actinic rays with exposure wavelengths that are crossed by i, h, and g may be used. In particular, light sources capable of emitting monochromatic i-line light with an exposure wavelength of 365 nm may be used. Examples of light sources capable of emitting monochromatic i-line light with an exposure wavelength of 365 nm include ultra-high pressure mercury lamps.

[0104] (iii) Development Step) In the development step, the uncured portions of the photosensitive layer and the optical adjustment layer are removed from the substrate. The development step forms a resist pattern on the substrate consisting of photocured portions of the photosensitive layer. If the optical adjustment layer is water-soluble, the optical adjustment layer may be removed by washing with water, and then the uncured portions other than the photocured portions may be removed with a developer; if the optical adjustment layer is soluble in a developer, the optical adjustment layer may be removed with a developer together with the uncured portions other than the photocured portions. Development methods include wet development.

[0105] In the case of wet development, development can be carried out by a known wet development method using a developer suitable for the photosensitive resin composition. Examples of wet development methods include dipping, puddling, high-pressure spraying, brushing, slapping, scrubbing, and swinging immersion, and from the viewpoint of improving resolution, the high-pressure spraying method is most suitable. These wet development methods may be used alone or in combination of two or more methods.

[0106] The developer is appropriately selected depending on the composition of the photosensitive resin composition, and examples thereof include alkaline aqueous solutions and organic solvent developers.

[0107] From the viewpoints of safety, stability, and ease of use, an alkaline aqueous solution may be used as the developer. Examples of the base for the alkaline aqueous solution include alkali hydroxides such as lithium, sodium, or potassium hydroxide, alkali carbonates such as carbonates or bicarbonates of lithium, sodium, potassium, or ammonium, alkali metal phosphates such as potassium phosphate and sodium phosphate, alkali metal pyrophosphates such as sodium pyrophosphate and potassium pyrophosphate, sodium borate, sodium metasilicate, tetramethylammonium hydroxide, ethanolamine, ethylenediamine, diethylenetriamine, 2-amino-2-hydroxymethyl-1,3-propanediol, 1,3-diamino-2-propanol, and morpholine.

[0108] Examples of alkaline aqueous solutions used for development include a dilute solution of 0.1 to 5% by weight sodium carbonate, a dilute solution of 0.1 to 5% by weight potassium carbonate, a dilute solution of 0.1 to 5% by weight sodium hydroxide, and a dilute solution of 0.1 to 5% by weight sodium tetraborate. The pH of the alkaline aqueous solution used for development may be in the range of 9 to 11, and the temperature of the alkaline aqueous solution can be adjusted according to the developability of the photosensitive layer. The alkaline aqueous solution may contain, for example, a surfactant, an antifoaming agent, or a small amount of an organic solvent to promote development. Examples of organic solvents used in alkaline aqueous solutions include 3-acetone alcohol, acetone, ethyl acetate, alkoxyethanols having an alkoxy group having 1 to 4 carbon atoms, ethyl alcohol, isopropyl alcohol, butyl alcohol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether.

[0109] Examples of organic solvents used in the organic solvent developer include 1,1,1-trichloroethane, N-methylpyrrolidone, N,N-dimethylformamide, cyclohexanone, methyl isobutyl ketone, and γ-butyrolactone. From the viewpoint of preventing ignition, these organic solvents may be used as the organic solvent developer by adding water in a range of 1 to 20% by mass.

[0110] (Other Steps) In the method for forming a resist pattern according to this embodiment, after removing the uncured portion in the development step, heating at 60 to 250° C. or irradiating with 0.2 to 10 J / cm 2 is performed as necessary. ２ The method may further include a step of hardening the resist pattern by exposing the resist pattern to light at an exposure dose of 1000 ppm or more.

[0111] [Method for manufacturing a printed wiring board] The method for manufacturing a printed wiring board according to this embodiment includes a step of forming a conductor pattern by etching or plating a substrate on which a resist pattern has been formed by the above-described method for forming a resist pattern, and may also include other steps such as a resist pattern removal step as necessary. The method for manufacturing a printed wiring board according to this embodiment can be suitably used to form a conductor pattern by using the above-described method for forming a resist pattern using a photosensitive element, but is particularly suitable for application to a method for forming a conductor pattern by plating. The conductor pattern can also be considered a circuit.

[0112] In the etching process, a resist pattern formed on a substrate having a conductive layer is used as a mask to etch away the conductive layer of the substrate that is not covered with the resist, thereby forming a conductive pattern.

[0113] The etching method is appropriately selected depending on the conductor layer to be removed. Examples of the etching solution include a cupric chloride solution, a ferric chloride solution, an alkaline etching solution, and a hydrogen peroxide-based etching solution. A ferric chloride solution may also be used because of its good etch factor.

[0114] In the plating process, a resist pattern formed on a substrate having a conductor layer is used as a mask to plate copper, solder, etc. on the conductor layer of the substrate that is not covered with the resist. After the plating process, the resist is removed by removing the resist pattern as described below, and the conductor layer that was covered with the resist is then etched to form the conductor pattern.

[0115] The plating method may be either electrolytic plating or electroless plating, but electroless plating is particularly preferred. Examples of electroless plating include copper plating such as copper sulfate plating and copper pyrophosphate plating, solder plating such as high-throw solder plating, nickel plating such as Watts bath (nickel sulfate-nickel chloride) plating and nickel sulfamate plating, and gold plating such as hard gold plating and soft gold plating.

[0116] After the etching or plating process, the resist pattern on the substrate is removed. The resist pattern can be removed, for example, with an aqueous solution that is more strongly alkaline than the aqueous alkaline solution used in the development step. Examples of such strongly alkaline aqueous solutions include a 1 to 10% by mass aqueous solution of sodium hydroxide and a 1 to 10% by mass aqueous solution of potassium hydroxide. Of these, a 1 to 5% by mass aqueous solution of sodium hydroxide or potassium hydroxide may also be used.

[0117] Methods for removing the resist pattern include, for example, a dipping method and a spray method, which may be used alone or in combination.

[0118] When the resist pattern is removed after plating, the conductor layer covered with the resist is further etched by etching to form a conductor pattern, thereby manufacturing a desired printed wiring board. The etching method used here is appropriately selected depending on the conductor layer to be removed. For example, the above-mentioned etching solution can be used.

[0119] The method for manufacturing a printed wiring board according to this embodiment can be applied to the manufacture of not only single-layer printed wiring boards but also multi-layer printed wiring boards, and can also be applied to the manufacture of printed wiring boards having small-diameter through holes.

[0120] The method for manufacturing a printed wiring board according to this embodiment can be suitably used for manufacturing high-density packaging substrates, particularly for manufacturing wiring boards using a semi-additive process. An example of a manufacturing process for a wiring board using a semi-additive process is shown in FIG.

[0121] In FIG. 2( a), a substrate (circuit-forming substrate) is prepared in which a conductor layer 40 is formed on an insulating layer 50. The conductor layer 40 is, for example, a copper layer. In FIG. 2( b), a photosensitive layer 30 and an optical adjustment layer 20 are formed on the conductor layer 40 of the substrate through the photosensitive layer and optical adjustment layer formation process. In FIG. 2( c), the exposure process involves irradiating the photosensitive layer 30 with active light 80, which projects a photomask image onto the photosensitive layer 30 through the optical adjustment layer 20, to form a photocured portion in the photosensitive layer 30. In FIG. 2( d), the development process involves removing from the substrate the areas (including the optical adjustment layer) other than the photocured portion formed in the exposure process, thereby forming a resist pattern 32, which is a photocured portion, on the substrate. In FIG. 2( e), a plating process is performed using the resist pattern 32, which is a photocured portion, as a mask to form a plating layer 60 on the conductor layer 40 of the substrate that is not covered by resist. 2(f), the photocured resist pattern 32 is peeled off with a strong alkaline aqueous solution, and then the conductor layer 40 masked by the resist pattern 32 is removed by flash etching, forming a post-etching plating layer 62 and a conductor pattern 70 including the post-etching conductor layer 42. The conductor layer 40 and the plating layer 60 may be made of the same material or different materials. When the conductor layer 40 and the plating layer 60 are made of the same material, the conductor layer 40 and the plating layer 60 may be integrated. Note that although the projection exposure method is described in FIG. 2, other exposure methods may also be used to form the resist pattern 32.

[0122] Although the preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments.

[0123] Hereinafter, the present disclosure will be described more specifically based on examples, but the present disclosure is not limited to the following examples. Unless otherwise specified, "parts" and "%" are based on mass.

[0124] (Binder Polymer (A-1)) 27 parts by mass of methacrylic acid, 50 parts by mass of styrene, 3 parts by mass of 2-hydroxyethyl methacrylate, and 20 parts by mass of benzyl methacrylate were mixed with 0.9 parts by mass of azobisisobutyronitrile to prepare a solution (a). 0.5 parts by mass of azobisisobutyronitrile was dissolved in 50 parts by mass of a mixed solution (x) consisting of 30 parts by mass of propylene glycol monomethyl ether and 20 parts by mass of toluene to prepare a solution (b). 500 g of the mixed solution (x) was placed in a flask equipped with a stirrer, reflux condenser, thermometer, dropping funnel, and nitrogen gas inlet tube, and the mixture was stirred while blowing nitrogen gas into the flask and heated to 80°C. The solution (a) was added dropwise to the mixed solution in the flask at a constant dropping rate over 4 hours, and the mixture was then stirred at 80°C for 2 hours. Next, the solution (b) was added dropwise to the solution in the flask at a constant rate over 10 minutes, and the solution in the flask was then stirred at 80°C for 3 hours. The solution in the flask was then heated to 90°C over 30 minutes and maintained at 90°C for 2 hours. After that, stirring was stopped and the solution was cooled to room temperature (25°C), yielding a solution of binder polymer (A-1). The nonvolatile content (solid content) of the binder polymer (A-1) solution was 49.8% by mass. The Mw of the binder polymer (A-1) was 35,000.

[0125] The Mw was measured by gel permeation chromatography (GPC) and calculated by conversion using a standard polystyrene calibration curve. The GPC conditions are as follows. (GPC conditions) Pump: Hitachi L-6000 type (product name, manufactured by Hitachi, Ltd.) Column: a total of three columns: Gelpack GL-R420, Gelpack GL-R430, Gelpack GL-R440 (all manufactured by Resonac Corporation, product names) Eluent: tetrahydrofuran Measurement temperature: 40°C Flow rate: 2.05 mL / min Detector: Hitachi L-3300 type RI (product name, manufactured by Hitachi, Ltd.)

[0126] (Binder Polymer (A-2)) A solution of binder polymer (A-2) was obtained in the same manner as for obtaining the solution of binder polymer (A-1), except that methacrylic acid, styrene, and dicyclopentanyl methacrylate (TCDMA) were used as polymerizable monomers in the mass ratios shown in Table 1. The nonvolatile content (solid content) of the solution of binder polymer (A-2) was 48.0 mass%.

[0127] Table 1 shows the mass ratio (%) of the polymerizable monomer and Mw of the binder polymers (A-1) and (A-2).

[0128]

[0129] <Preparation of Resin Composition for Forming Optical Adjustment Layer> The components shown in Table 2 below were mixed in the amounts (unit: parts by mass) shown in the table to obtain a resin composition for forming an optical adjustment layer. Specifically, the water-soluble resin was slowly added to a solvent at room temperature, and after the entire amount was added, the mixture was stirred for 1 hour. Then, the leveling agent was mixed in and dissolved uniformly to obtain a resin composition for forming an optical adjustment layer. The amount of the water-soluble resin in Table 2 is the amount in solid content.

[0130]

[0131] Details of each component in Table 2 are as follows: *1: HC-100G (polyvinyl alcohol, manufactured by Taisei Kayaku Co., Ltd., product name: Maltite HC-100G, solid content 13.5% by mass) *2: K-30 (polyvinylpyrrolidone, manufactured by Nippon Shokubai Co., Ltd., product name) *3: WS-314 (acrylic polymer, manufactured by Kyoeisha Chemical Co., Ltd., product name, components: 48% by mass of acrylic polymer and 52% by mass of 3-methoxy-3-methyl-1-butanol, composition of acrylic polymer: copolymer of approximately 6.89 mol% of butyl (meth)acrylate, approximately 61.4 mol% of isobutyl (meth)acrylate, and approximately 31.7 mol% of EO-modified (meth)acrylate with terminal methoxy groups)

[0132] <Preparation of Photosensitive Resin Composition> Photosensitive resin compositions were obtained by mixing the components shown in Table 3 below in the amounts (unit: parts by mass) shown in the same table. The amount of binder polymer in Table 3 is the amount in terms of solid content.

[0133]

[0134] The details of each component in Table 3 are as follows: *4: Binder polymer (A-1) synthesized above *5: Binder polymer (A-2) synthesized above *6: FA-321M (product name, manufactured by Resonac Corporation) 2,2-bis(4-(methacryloxypolyethoxy)phenyl)propane (ethylene oxide adduct with an average of 10 mol) *7: FA-024M (product name, manufactured by Resonac Corporation) (PO)(EO)(PO) modified dimethacrylate (ethylene oxide adduct with an average of 6 mol and propylene oxide adduct with an average of 12 mol (total)) *8: BP-2EM (product name, manufactured by Kyoeisha Chemical Co., Ltd.) 2,2-bis(4-(methacryloxypolyethoxy)phenyl)propane (EO groups: 2.6 (total)) *9: B-CIM (product name, manufactured by Hodogaya Chemical Co., Ltd.) 2,2'-Bis(2-chlorophenyl)-4,4',5,5'-tetraphenylbiimidazole *10: PZ-501D (product name, manufactured by Nippon Chemical Industry Co., Ltd.) 1-phenyl-3-(4-methoxystyryl)-5-(4-methoxyphenyl)-pyrazoline *11: Q-TBC-5P (product name, manufactured by DIC Corporation) 4-tert-butylcatechol *12: LA-7RD (product name, manufactured by Adeka Corporation) 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl *13: SEESORB-106 (benzophenone-based ultraviolet absorber, product name, manufactured by Shipro Chemical Co., Ltd.) *14: LCV (leuco crystal violet, Yamada Chemical Co., Ltd., color developer) *15: SF-808H (product name, adhesion promoter, manufactured by Sanwa Chemical Co., Ltd.) A mixture of carboxybenzotriazole, 5-amino-1H-tetrazole, and methoxypropanol *16: MKG (Malachite Green, manufactured by Osaka Organic Chemical Industry Ltd., dye)

[0135] <Preparation of Photosensitive Element> (Preparation of Photosensitive Element of Example) A 16 μm thick polyethylene terephthalate film (manufactured by Toray Industries, Inc., product name "FS-31") was prepared as a support film. A resin composition for forming an optical adjustment layer was applied to the support film so as to have a uniform thickness, and dried for 5 minutes in a hot air convection dryer at 110°C to form an optical adjustment layer having a thickness of 5 μm after drying. Next, a photosensitive resin composition was applied to the optical adjustment layer so as to have a uniform thickness, and dried for 10 minutes in a hot air convection dryer at 100°C to form a photosensitive layer having a thickness of 6 μm after drying. Next, a polyethylene protective film (manufactured by Tamapoly Corporation, product name "NF-15A", protective layer) was bonded to the photosensitive layer, and a photosensitive element was obtained in which the support film, optical adjustment layer, photosensitive layer, and protective layer were laminated in this order.

[0136] (Preparation of Photosensitive Element of Comparative Example) A photosensitive element having a support film, a photosensitive layer, and a protective layer laminated in this order was obtained in the same manner as in the example, except that no optical adjustment layer was provided.

[0137] <Absorbency> (Absorbency of Optical Adjustment Layer) The photosensitive element of Example 1 was laminated on the surface of a glass slide (manufactured by Matsunami Glass Industrial Co., Ltd., white glass slide, cut-off No. 1 S1126). Lamination was performed using a 110°C heat roll at a pressure of 0.4 MPa and a roll speed of 1.0 m / min, with the photosensitive layer of the photosensitive element in contact with the surface of the glass slide while peeling off the protective layer. After the photosensitive layer was laminated on the glass slide, the support film was peeled off to obtain a laminate 1 composed of the glass slide, the photosensitive layer, and the optical adjustment layer. The absorbance of the laminate 1 was measured using a U-3310 spectrophotometer (manufactured by Hitachi High-Tech Science Corporation) under measurement conditions of a wavelength range of 330 to 700 nm, a scan speed of 300 nm / min, and a scan interval of 0.50 nm. From the obtained absorption spectrum, the absorbance at an exposure wavelength of 365 nm was recorded as absorbance A. Thereafter, the optical adjustment layer was peeled off from the laminate 1, and the absorbance was measured again under the same conditions, and recorded as absorbance B. The value obtained by subtracting absorbance B from absorbance A was taken as the absorbance of the optical adjustment layer.

[0138] (Absorbance of Support Film) The same operation as in measuring the absorbance of the optical adjustment layer was performed, except that laminate 2 composed of a slide glass, a photosensitive layer, and a support film obtained using the photosensitive element of Comparative Example 1 without peeling off the support film was used instead of laminate 1. The absorbance measured for laminate 2 was recorded as absorbance C, and the support film was peeled off from laminate 2 and the absorbance measured again under the same conditions was recorded as absorbance D, and the value obtained by subtracting absorbance D from absorbance C was determined to be the absorbance of the support film.

[0139] <Refractive Index> Using a spectroscopic ellipsometer (UVISEL2, manufactured by Horiba, Ltd.), the refractive index of the optical adjustment layer and the support film in the photosensitive element for light with a wavelength of 365 nm was measured under the following measurement conditions: (Refractive Index Measurement Conditions) Incident angle: 60 degrees Measurement wavelength range: 190 nm to 826 nm Spot diameter: 1 mm x 1.5 mm ellipse (sample surface)

[0140] <Resolution> A substrate (Ra: 40 nm) having a copper layer was pickled and washed with water, and then dried in an air stream. The substrate was then heated to 80°C, and a photosensitive element was laminated onto the copper surface of the substrate to obtain a laminate. The lamination was performed using a heat roll at 110°C, with a pressure of 0.4 MPa and a roll speed of 1.0 m / min, with the photosensitive layer of the photosensitive element in contact with the copper surface of the substrate while peeling off the protective layer.

[0141] In the case of a laminate without an optical adjustment layer, a glass chrome-type phototool (resolution negative: having a wiring pattern with a line width / space width of x / x (x: 1 to 10, unit: μm)) was used as a negative for evaluating resolution on a support film, and the photosensitive layer was exposed to a predetermined energy amount using an exposure device FPA-3000iW (NA = 0.24, manufactured by Canon Inc.) (exposure treatment). After exposure, the support was peeled off to expose the photosensitive layer, and a 1% by mass aqueous sodium carbonate solution at 27°C was sprayed for a time three times the shortest development time (the shortest time required to remove the unexposed portion), thereby removing the unexposed portion (development treatment). In the case of a laminate with an optical adjustment layer, the support film was peeled off and the exposure was performed through the optical adjustment layer, and the exposure and development were performed in the same manner as above.

[0142] After development, the space portions (unexposed portions) were completely removed, and the line portions (exposed portions) were formed without residue, distortion, meandering, or chipping. The smallest space width value (unit: μm) of the resist pattern was defined as the resolution. The smaller the resolution value, the better the resolution.

[0143] After exposure, the laminate was stored at 23°C in a light-shielded state for 6 hours, and then development processing was performed. The resolution was obtained in the same manner as above, and the resolution when left for 6 hours after exposure was evaluated. The laminate without the optical adjustment layer was stored with the support film attached after exposure.

[0144] DESCRIPTION OF SYMBOLS 1... photosensitive element, 2... support film, 3, 20... optical adjustment layer, 4, 30... photosensitive layer, 5... protective layer, 32... resist pattern, 40... conductor layer, 42... conductor layer after etching treatment, 50... insulating layer, 60... plating layer, 62... plating layer after etching treatment, 70... conductor pattern, 80... actinic light

Claims

1. A photosensitive element comprising, in this order, a support film, an optical adjustment layer, and a photosensitive layer, wherein the optical adjustment layer has an absorbance of 0.060 or less for light having a wavelength of 365 nm, and a refractive index of the optical adjustment layer for light having a wavelength of 365 nm of 1.800 or less.

2. The photosensitive element of claim 1, wherein the optical adjustment layer comprises a water-soluble resin.

3. The photosensitive element according to claim 1, wherein the optical adjustment layer has a thickness of 1 to 15 μm.

4. The photosensitive element of claim 1, wherein the photosensitive layer has a thickness of from 1 to 14 μm.

5. A method for forming a resist pattern, comprising the steps of: using a photosensitive element according to any one of claims 1 to 4, arranging a photosensitive layer, an optical adjustment layer and a support film on a substrate in this order from the substrate side; removing the support film and exposing the photosensitive layer to active light through the optical adjustment layer; and removing the uncured portion of the photosensitive layer and the optical adjustment layer from the substrate.

6. The method for forming a resist pattern according to claim 5, wherein exposure is carried out using an exposure machine having a lens numerical aperture of 0.16 or more.

7. A method for manufacturing a printed wiring board, comprising the step of etching or plating a substrate on which a resist pattern has been formed by the method for forming a resist pattern according to claim 5 to form a conductor pattern.

8. A method for producing a printed wiring board, comprising the step of etching or plating a substrate on which a resist pattern has been formed by the method for forming a resist pattern according to claim 6 to form a conductor pattern.

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