Method for manufacturing a microstructure, method for manufacturing a liquid ejection head, microstructure and liquid ejection head

Abstract

To provide a method for manufacturing a fine structure which suppresses an interaction of an initiator in the vicinity of each layer in a laminate structure, and enables formation of a desired shape.SOLUTION: A method for manufacturing a fine structure containing a cured product of a photosensitive resin composition includes the steps of: forming at least two layers of a photosensitive resin composition containing a photopolymerization initiator; pattern exposing each of the at least two formed layers of the photosensitive resin composition; and collectively developing the at least two exposed layers of the photosensitive resin composition to obtain a fine structure, wherein in the at least two layers of the photosensitive resin composition, 90 mass% or more of the photopolymerization initiator contained in at least one of the two adjacent layers of the photosensitive resin composition is a non-ionic photopolymerization initiator.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a microstructure using a photosensitive resin composition, a method for manufacturing a liquid ejection head, a microstructure, and a liquid ejection head. [Background technology]

[0002] In the field of cutting-edge devices such as semiconductor elements and display panels, there is a method of processing photosensitive material films into microstructures using photolithography technology. Depending on the application of the microstructure, as typified by microdevices, high precision is required down to the fine three-dimensional shape.

[0003] Patent Document 1 discloses a method for manufacturing a package consisting of a laminate of two types of negative photosensitive resin layers, characterized in that the method forms an integrated laminate having a width of about 10 μm and an aspect ratio of greater than 1:1. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2007 / 109090 Summary of the Invention [Problem to be solved by the invention]

[0005] Photosensitive materials used in forming microstructures by photolithography include photoradical, cationic, and anionic polymerizable resin materials. Among them, cationic and anionic polymerizable resin materials are used in adhesives and semiconductor applications because they have fewer restrictions on the exposure environment and have high adhesion to substrates. However, in a laminate structure such as that described in Patent Document 1, initiators with different acidic or basic strengths are used in each layer (taking into account patterning properties). In this case, it has been found that interactions between initiators (salt exchange) tend to occur near the layer interface. As a result, the initiator's inherent function cannot be expressed, and the desired pattern shape may not be obtained. Therefore, the present disclosure provides a method for manufacturing a microstructure, a method for manufacturing a liquid ejection head, a microstructure, and a liquid ejection head that can suppress interactions between initiators near the interlayer spaces in a laminate structure and form a desired shape. [Means for solving the problem]

[0006] The present disclosure provides a method for producing a microstructure containing a cured product of a photosensitive resin composition, comprising: forming at least two layers of a photosensitive resin composition, each layer containing a photopolymerization initiator; a step of patterning each of the at least two layers of the photosensitive resin composition formed by the method; a step of simultaneously developing at least two exposed layers of the photosensitive resin composition to obtain a microstructure, The present invention relates to a method for producing a microstructure, wherein, in at least two layers of the photosensitive resin composition, 90% by mass or more of the photopolymerization initiator contained in at least one of two adjacent layers of the photosensitive resin composition is a nonionic photopolymerization initiator.

[0007] Another aspect of the present disclosure is a method for manufacturing a liquid ejection head, including the method for manufacturing a microstructure, comprising: The liquid ejection head includes a substrate, a flow path forming member provided on the substrate and forming a flow path for the liquid, and an ejection port forming member provided on the flow path forming member and having an ejection port for ejecting the liquid, the step of forming at least two photosensitive resin composition layers is a step of forming two layers, a first photosensitive resin composition layer and a second photosensitive resin composition layer, in this order, on a substrate; The flow path forming member is a cured product of the first photosensitive resin composition, and the discharge port forming member is a cured product of the second photosensitive resin composition. The present invention relates to a method for manufacturing a liquid ejection head. Another aspect of the present disclosure is a microstructure containing at least two layers of a cured product of a photosensitive resin composition, the photosensitive resin composition contains a photopolymerization initiator, The present invention relates to a microstructure in which, in at least two layers of the photosensitive resin composition, 90% by mass or more of the photopolymerization initiator contained in at least one of the two adjacent layers of the photosensitive resin composition is a nonionic photopolymerization initiator. Another aspect of the present disclosure is a liquid ejection head including: a substrate; a flow path forming member provided on the substrate and forming a flow path for liquid; and an ejection port forming member provided on the flow path forming member and having an ejection port for ejecting liquid, the flow path-forming member is a cured product of a first photosensitive resin composition containing a photopolymerization initiator, the discharge port-forming member is a cured product of a second photosensitive resin composition containing a photopolymerization initiator, The liquid ejection head is characterized in that 90% by mass or more of the photopolymerization initiator contained in at least one of the first photosensitive resin composition and the second photosensitive resin composition is a nonionic photopolymerization initiator. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a method for manufacturing a microstructure and a method for manufacturing a liquid ejection head that can suppress interactions between initiators near the interlayer spaces in a laminate structure and form a desired shape. [Brief explanation of the drawings]

[0009] [Figure 1] Schematic diagram of an inkjet recording head [Figure 2] A perspective view of an example of a microstructure. [Figure 3] Cross-sectional views showing a method for forming a microstructure [Figure 4] FIG. 1 is a diagram illustrating the angle θ formed between patterns of a microstructure. [Figure 5] Example of a method for forming an inkjet recording head DETAILED DESCRIPTION OF THE INVENTION

[0010] In the present disclosure, unless otherwise specified, the expressions "XX or more and YY or less" or "XX to YY" representing a numerical range mean a numerical range including the lower and upper limits, which are the endpoints. When a numerical range is described in stages, the upper and lower limits of each numerical range can be combined in any way.

[0011] When the embodiments for carrying out the present disclosure are specifically illustrated with reference to the drawings, the dimensions, materials, shapes, and relative positions of the components described in the embodiments should be appropriately changed depending on the configuration of the members to which the disclosure is applied and various conditions. In other words, it is not intended to limit the scope of the disclosure to the following embodiments.

[0012] The method for producing a microstructure containing a cured product of a photosensitive resin composition includes a step of forming a laminate of at least two layers of the photosensitive resin composition. Each of the at least two layers of the photosensitive resin composition contains a photopolymerization initiator. The method for producing a microstructure further includes a step of patterning each of the at least two layers of the photosensitive resin composition formed by exposing the layers to light, and The method includes a step of simultaneously developing at least two irradiated photosensitive resin composition layers to obtain a microstructure. The method is characterized in that, in the at least two photosensitive resin composition layers, 90% by mass or more of the photopolymerization initiator contained in at least one of the two adjacent photosensitive resin composition layers is a nonionic photopolymerization initiator. This makes it possible to suppress interactions between initiators near the layer interface. Because nonionic photopolymerization initiators do not have a salt structure, reactions between nonionic initiators or between nonionic initiators and ionic initiators do not occur, thereby suppressing interactions such as salt exchange caused by ion exchange within each initiator.

[0013] The microstructure is a microstructure containing a cured product of at least two layers of a photosensitive resin composition, and the photosensitive resin composition contains a photopolymerization initiator. The microstructure is characterized in that, in the at least two layers of the photosensitive resin composition, 90% by mass or more of the photopolymerization initiator contained in at least one of the two adjacent layers of the photosensitive resin composition is a nonionic photopolymerization initiator.

[0014] In at least two photosensitive resin composition layers, 90% by mass or more of the photopolymerization initiator contained in both of the two adjacent photosensitive resin composition layers may be a nonionic photopolymerization initiator. Preferably, in at least two photosensitive resin composition layers, 90% by mass or more of the photopolymerization initiator contained in one of the two adjacent photosensitive resin composition layers is a nonionic photopolymerization initiator. Preferably, the photopolymerization initiator contained in the other of the two adjacent photosensitive resin composition layers is an ionic photopolymerization initiator.

[0015] The content of the nonionic photopolymerization initiator among the photopolymerization initiators is preferably 90% by mass to 100% by mass, more preferably 95% by mass to 100% by mass, even more preferably 98% by mass to 100% by mass, and particularly preferably 100% by mass.

[0016] The components constituting at least two layers of photosensitive resin composition will be described below using two layers of photosensitive resin composition as an example. First, the photosensitive resin composition forming the first photosensitive resin composition layer will be described. The first photosensitive resin composition is an example of a resin composition containing a nonionic photopolymerization initiator in an amount of 90% by mass or more of the photopolymerization initiator. The first photosensitive resin composition is a negative photosensitive resin composition consisting of a photosensitive resin, a nonionic photopolymerization initiator, and, if necessary, a solvent. Each of the components will be described below.

[0017] A first photosensitive resin composition that forms a layer of the first photosensitive resin composition <Photosensitive resin> As the photosensitive resin, an epoxy resin is preferably used because of the high resolution of the pattern that is formed. The epoxy resin is not particularly limited, but can be appropriately selected from alicyclic epoxy resins, cresol novolac epoxy resins, bisphenol A epoxy resins, bisphenol F epoxy resins, dicyclopentadiene epoxy resins, etc., in terms of reactivity and adhesion. The epoxy resin is preferably an epoxy resin having two or more epoxy groups in one molecule.

[0018] When a photobase generator is used as a nonionic polymerization initiator, the base generated is often weakly basic, which may result in low reactivity. Therefore, resins with a low steric hindrance structure that are highly reactive to epoxy resins or strongly polarized epoxy resins are preferably used. Specifically, the epoxy resin is preferably at least one selected from the group consisting of alicyclic epoxy resins, novolac epoxy resins (e.g., cresol novolac epoxy resins, phenol novolac epoxy resins, etc.), 1,6-dihydroxynaphthalene epoxy resins, and bisphenol S, A, and F epoxy resins. At least one selected from the group consisting of epoxy resins and bisphenol S type epoxy resins is more preferred.

[0019] Commercially available epoxy resins include "jER157S70" (trade name) manufactured by Mitsubishi Chemical, "Epiclon HP-4032" (trade name) manufactured by Dainippon Ink and Chemicals, Inc., and "Denacol EX-251" (trade name) manufactured by Nagase ChemteX.

[0020] The epoxy equivalent of the epoxy resin is preferably 2000 or less, more preferably 1000 or less, and even more preferably 500 or less. There is no particular lower limit, but it is preferably 50 or more, and more preferably 100 or more. When the epoxy equivalent is 2000 or less, the crosslink density does not decrease during the curing reaction, and it is possible to prevent a decrease in the glass transition temperature and adhesion of the cured product. The epoxy equivalent is a value measured in accordance with JIS K-7236.

[0021] <Nonionic photopolymerization initiator> There are two types of nonionic photopolymerization initiators: photoacid generators and photobase generators, and either can be used. The nonionic photoacid generators and photobase generators are not particularly limited, and known ones can be used. The nonionic photopolymerization initiator is preferably a photobase generator.

[0022] Specific examples of nonionic photoacid generators include benzoin esters of toluenesulfonic acid, o- or p-nitrobenzyl esters of toluenesulfonic acid, 2,6-dinitrobenzyl esters of toluenesulfonic acid; N-hydroxyamides and N-hydroxysulfonates described in U.S. Patent No. 4,371,605; and arylnaphthoquinone diazide-4-sulfonates. Commercially available nonionic photoacid generators include, for example, "NAI-105," "SI-100," "NDI-105," and "PI-105" (trade names) manufactured by Midori Chemical Industry Co., Ltd.

[0023] Specific examples of nonionic photobase generators include at least one selected from the group consisting of imidazole-based photobase generators and amine-based photobase generators, which have a catalytic effect on the curing of epoxy resins. At least one selected from the group consisting of amine-based photobase generators is more preferred. For example, 9-anthrylmethyl N,N-diethylcarbamate, (2-nitrophenyl)methyl 4-(methacryloyloxy)piperidine-1-carboxylate, and (E)-1-piperidino-3-(2-hydroxyphenyl)-2-propen-1-one can be used. Commercially available nonionic photobase generators include, for example, "WPBG-018," "WPBG-027," "WPBG-140," and "WPBG-165" (trade names) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. In particular, when exposing to i-line, a base generator can be preferably used because there are almost no photoacid generators that have an absorption wavelength of i-line.

[0024] The content (addition amount) of the nonionic photopolymerization initiator in the photosensitive resin composition is not particularly limited as long as it is a concentration that can cure the epoxy resin. Specifically, the content is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, per 100 parts by mass of the epoxy resin.

[0025] As described above, in the case of nonionic photobase generators, the base generated is weakly basic, and therefore it is preferable to use a sensitizer or a base amplifier in combination to enhance the reactivity of the resin. That is, a photosensitive resin composition containing a photobase generator as a nonionic photopolymerization initiator preferably contains a sensitizer. There are no restrictions on the sensitizer, as long as it is a substance that efficiently generates a base through photosensitization. Specific examples of the sensitizer that can be used include 1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanidium=n-butyltriphenylborate and (Z)-{[bis(dimethylamino)methylidene]amino}-N-cyclohexyl(cyclohexylamino)methaniminium.

[0026] Furthermore, a photosensitive resin composition containing a photobase generator as a nonionic photopolymerization initiator preferably contains a base amplifier. The base amplifier is a substance that decomposes under the action of a base to generate a basic substance, and any such substance can be used without particular limitation. Specific examples include compounds described in JP-A-2000-330270 and JP-A-2002-128750. For example, a urethane-based compound having a structure represented by the following formula (1) can be mentioned. [ka]

[0027] In formula (1), R 1 and R 2 R each independently represents a hydrogen atom, a substituent, or an electron-withdrawing group, and at least one of them represents an electron-withdrawing group. 3 , R 4 each independently represents a hydrogen atom or a substituent, and A represents an amino group. The electron-withdrawing group includes electron-withdrawing groups commonly used in organic electronics, such as a fluorenyl group, organic sulfoxide group, cyano group, nitro group, ester group, carbonyl group, amide group, pyridyl group, etc. The fluorenyl group is preferred.

[0028] The substituent includes an alkyl group having 1 to 12 carbon atoms (preferably 1 to 6), a cycloalkyl group having 5 to 10 carbon atoms (preferably 6 to 8), an aryl group having 6 to 14 carbon atoms (preferably 6 to 10), an arylalkyl group having 7 to 15 carbon atoms (preferably 7 to 11), etc. Specific examples thereof include methyl, ethyl, propyl, butyl, cyclohexyl, phenyl, tolyl, naphthyl, benzyl, phenethyl, naphthylmethyl, etc.

[0029] The amino group includes unsubstituted and substituted amino groups. The substituted amino group includes mono-substituted and di-substituted amino groups. The amino group is represented by -NR 5 R 6 It can be expressed as R 5 and R 6 represents hydrogen or an organic group. The number of carbon atoms in the organic group is 1 to 18, preferably 6 to 12. The organic group includes an alkyl group, a cycloalkyl group, an aryl group, and an arylalkyl group.

[0030] The urethane compound used as the base amplifier may contain two or more urethane bonds. Examples of such urethane compounds include those represented by the following formula (2): [ka]

[0031] In equation (8), R 1 and R 2 are each independently a hydrogen atom, a substituent, or an electron-withdrawing R is an electron-withdrawing group, at least one of which is an electron-withdrawing group. 3 and R 4 are each independently a hydrogen atom or a substituent. 1’ and R 2’ R are each independently a hydrogen atom, a substituent, or an electron-withdrawing group, at least one of which is an electron-withdrawing group. 3’ and R 4’ are each independently a hydrogen atom or a substituent. Y is an alkylene group having 1 to 8 carbon atoms (preferably 2 to 6). n and m are integers of 1 to 6 (preferably 2 to 4). n+m is 4 to 12 (preferably 4 to 8). p and q are integers of 1 to 6 (preferably 2 to 4). p+q is 4 to 12 (preferably 4 to 8). Examples of the electron-withdrawing group and the substituent include those similar to those in formula (1). The base multiplier is particularly preferably 4,4'-[bis[[(9-fluorenylmethyl)oxy]carbonyl]trimethylene]dipiperidine.

[0032] The contents (addition amounts) of the sensitizer and base amplifier in the photosensitive resin composition are not particularly limited as long as they are concentrations that can cure the epoxy resin. Specifically, the contents are preferably 0.1 to 20 parts by mass, and more preferably 0.5 to 10 parts by mass, respectively, per 100 parts by mass of the epoxy resin.

[0033] Furthermore, additives can be added to the photosensitive resin composition as needed. For example, a silane coupling agent can be added to improve adhesion. A preferred example is a silane coupling agent having an epoxy group or a glycidyl group. An example of a commercially available silane coupling agent is "SILQUEST A-187" (trade name) manufactured by Momentive Performance Materials. The content of the silane coupling agent is not particularly limited, but is preferably 1 to 30 parts by mass, more preferably 2 to 15 parts by mass, per 100 parts by mass of the solid content of the epoxy resin.

[0034] <Solvent> The photosensitive resin composition may contain a solvent. The solvent is not particularly limited as long as it allows the photosensitive resin and the nonionic photopolymerization initiator to be uniformly dispersed. For example, from the viewpoints of resin solubility and coatability, xylene and propylene glycol monomethyl ether acetate (PGMEA) can be used.

[0035] From the viewpoint of coatability, the content of the solvent in the photosensitive resin composition (total amount if two or more types are used) is preferably 60 to 200 parts by mass, and more preferably 70 to 150 parts by mass, per 100 parts by mass (solid content) of the photosensitive resin.

[0036] Next, the second photosensitive resin composition that forms the second photosensitive resin composition layer will be described. The second photosensitive resin composition is an example of a photosensitive resin composition used in the other photosensitive resin composition layer of the two adjacent photosensitive resin composition layers described above. The photosensitive resin composition that forms the second photosensitive resin composition layer is a negative photosensitive resin composition consisting of a photosensitive resin, a photopolymerization initiator, and, if necessary, a solvent. Each of the components will be described below.

[0037] A second photosensitive resin composition that forms a layer of the second photosensitive resin composition <Photosensitive resin> The photosensitive resin can be selected from the same viewpoint as the first photosensitive resin. In particular, by using the same photosensitive resin as the first photosensitive resin, the linear expansion coefficient and other properties can be made close to each other, thereby ensuring high adhesion.

[0038] <Photopolymerization initiator> As the photopolymerization initiator, ionic or nonionic, or both, can be used. As the nonionic photopolymerization initiator, the same ones as those listed in the first photosensitive resin composition can be used. As the ionic photopolymerization initiator, those capable of curing the photosensitive resin can be used. In at least two photosensitive resin composition layers, the photopolymerization initiator contained in the other of the two adjacent photosensitive resin composition layers is preferably an ionic photoacid generator.

[0039] Specific examples of photoacid generators include sulfonate esters, carboxylic acid esters, and onium salts. Commercially available photoacid generators include CPI-410S (trade name) manufactured by San-Apro, and ADEKA Arcles SP-150, SP-151, SP-170, SP-171, and SP-172 (trade names) (all manufactured by ADEKA).

[0040] Specific examples of the photobase generator include carbamate derivatives and oxime ester derivatives. Commercially available photobase generators include CGI-325, Irgacure OXE01, and Irgacure OXE02 (trade names) (all manufactured by BASF Japan), N-1919, and NCI-831 (trade names) (all manufactured by ADEKA).

[0041] The content (addition amount) of the photopolymerization initiator in the second photosensitive resin composition is not particularly limited as long as it is a concentration that can cure the photosensitive resin. Specifically, the content is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, per 100 parts by mass of the photosensitive resin. The second photosensitive resin composition may contain, as in the first photosensitive resin composition, a sensitizer, a base multiplier, a solvent, and additives such as a silane coupling agent, if necessary.

[0042] Next, the manufacturing method will be described. <Method of manufacturing a microstructure> The method for manufacturing the microstructure is as follows. The method for manufacturing a microstructure includes: The method includes the steps of forming at least two layers of a photosensitive resin composition containing a photopolymerization initiator, exposing each of the formed photosensitive resin composition layers to patterning, and developing the at least two exposed photosensitive resin composition layers together (removing unexposed areas) to obtain a microstructure. In the at least two photosensitive resin composition layers, 90% by mass or more of the photopolymerization initiator contained in at least one of the two adjacent photosensitive resin composition layers is a nonionic photopolymerization initiator.

[0043] At least two layers of the photosensitive resin composition are preferably formed on a substrate, which is not particularly limited, but may be, for example, a silicon substrate. The at least two layers of the photosensitive resin composition are preferably two to four layers of the photosensitive resin composition, more preferably two or three layers of the photosensitive resin composition, and even more preferably two layers of the photosensitive resin composition. For example, in the case of a three-layer photosensitive resin composition, the central layer may contain 90% by mass or more of the nonionic photopolymerization initiator, or the first and third layers may contain 90% by mass or more of the nonionic photopolymerization initiator.

[0044] The method for producing a microstructure preferably includes the steps of forming a layer of a first photosensitive resin composition, forming a layer of a second photosensitive resin composition, patterning the layer of the first photosensitive resin composition by exposure, patterning the layer of the second photosensitive resin composition by exposure, and collectively developing the exposed first and second photosensitive resin layers to produce the microstructure.

[0045] Here, when a layer of a second photosensitive resin composition is provided on a layer of a first photosensitive resin composition, each layer is subjected to patterning exposure when patterning. Therefore, it is preferable to use a nonionic initiator with lower sensitivity for the lower layer so that the lower layer is not exposed to light when the upper layer is exposed. That is, In the step of photoexposing, it is preferable that the layer containing 90% by mass or more of a nonionic photopolymerization initiator of the photopolymerization initiator among the at least two layers of the photosensitive resin composition is located on the opposite side of the light source in the direction of exposure irradiation. Furthermore, when a plurality of layers of photosensitive resin compositions are provided, it is also preferable to vary the exposure sensitivity of the polymerization initiator in the plurality of layers.

[0046] <Method of manufacturing liquid ejection head> An example of a microstructure is a liquid ejection head. That is, a method for manufacturing a liquid ejection head includes the method for manufacturing a microstructure described above, and the photosensitive resin composition can be applied to the liquid ejection head. The step of forming at least two layers of a photosensitive resin composition is a step of forming two layers, a layer of a first photosensitive resin composition and a layer of a second photosensitive resin composition, in this order, on a substrate. The liquid ejection head includes, for example, a substrate, a flow path forming member provided on the substrate to form a liquid flow path, and a discharge port forming member provided on the flow path forming member and having a discharge port for discharging the liquid. The flow path forming member is a cured product of the first photosensitive resin composition, and the discharge port forming member is a cured product of the second photosensitive resin composition.

[0047] As an example, a method for manufacturing an inkjet recording head, which is one form of liquid ejection head, is described below. This method for manufacturing a liquid ejection head includes at least a substrate, a flow path-forming member disposed on the substrate to form a liquid flow path, and a discharge port-forming member disposed on the flow path-forming member and having discharge ports for ejecting liquid. The manufacturing method includes at least the steps of laminating two layers, a first layer of photosensitive resin composition and a second layer of photosensitive resin composition, each containing a photopolymerization initiator, on the substrate, exposing each of the two photosensitive resin composition layers to patterning, and developing the exposed at least two photosensitive resin composition layers together (removing the unexposed portions) to form a flow path-forming member and a discharge port-forming member on the substrate. Furthermore, 90% by mass or more of the photopolymerization initiator contained in at least one of the two photosensitive resin composition layers is a nonionic photopolymerization initiator.

[0048] In the step of forming the first photosensitive resin composition layer and the step of forming the second photosensitive resin composition layer, for example, the photosensitive resin composition may be applied to form a coating film. The application method is not particularly limited as long as it is a method that can form a uniform film.

[0049] For example, spin coating or slit coating can be used. Furthermore, when applying a second photosensitive resin composition onto a layer of a first photosensitive resin composition, there is a concern that the two resin layers may become miscible with each other. Therefore, a method of laminating a dry film of the second photosensitive resin composition or both the first and second photosensitive resin compositions can be suitably used. This method can prevent miscibility between the layers of the first and second photosensitive resin compositions, thereby preventing the patterning properties of each layer from being impaired. Next, the layer of the first photosensitive resin composition, which is the lower layer, is exposed to light, and then the layer of the second photosensitive resin composition, which is the upper layer, is exposed to light.

[0050] When using a negative photosensitive resin composition as described above, it is preferable to perform a heating step after exposure at a wavelength at which the photocuring reaction of the resin composition proceeds. In this case, since the catalyst may diffuse to the unexposed area due to retention after exposure, it is preferable to perform a heat treatment immediately after exposure in terms of patterning accuracy. Therefore, it is preferable to perform a heat treatment on the first photosensitive resin composition layer and the second photosensitive resin composition layer immediately after exposure.

[0051] Furthermore, when a plurality of layers, such as a layer of a first photosensitive resin composition and a layer of a second photosensitive resin composition, are patterned and exposed with light of the same wavelength, it is preferable to adjust the exposure amount in each exposure so that the other layers are not exposed to light. Specifically, when the layer of the second photosensitive resin composition is patterned and exposed, the first photosensitive resin layer, which is the underlying layer, is not exposed to light. It is preferable that the exposure dose for the first photosensitive resin composition layer and the exposure dose for the second photosensitive resin composition layer are different by about 5 times. For example, in the layer of the second photosensitive resin composition, the radiation intensity is preferably 500 to 4000 J / m 2 and more preferably 800 to 3000 J / m 2 In the layer of the first photosensitive resin composition, the irradiance is 5000 to 30000 J / m 2 It is preferable that the energy density is 8000 to 22000 J / m or more. 2 Such a difference in the amount of exposure can be achieved by selecting the photopolymerization initiator and adjusting the amount added.

[0052] The heat treatment temperature after exposure is preferably adjusted to 70°C or higher, more preferably 80°C or higher, in order to promote the reaction so that the exposed pattern is not removed during the development step. There is no particular upper limit, but the temperature is preferably 120°C or lower, more preferably 100°C or lower. Regarding the cured state of the resin composition before development, when an epoxy resin is used as the photosensitive resin of the first or second photosensitive resin composition, it is preferable to carry out heat treatment so that the reaction rate of the epoxy groups of the epoxy resin (epoxy group ring-opening rate) is 50% or more. The epoxy group ring-opening rate is more preferably 80% or more, even more preferably 90% or more, and even more preferably 95% or more. There is no particular upper limit, but it is preferably 100% or less, more preferably 99% or less. Below, we will explain how to determine the epoxy group ring-opening rate. The epoxy group ring-opening rate indicates the proportion of epoxy groups in the epoxy resin composition that have been ring-opened.

[0053] The epoxy group ring-opening rate can be calculated using the peak area derived from the epoxy group based on the absorbance spectrum of the epoxy resin composition obtained by Fourier transform infrared spectroscopy (FT-IR). Here, the "peak area derived from the epoxy group" refers to the peak area at a wave number of 910 cm. -1 This is the integral value of a peak derived from an epoxy group located nearby, when the line connecting the left and right minimum values ​​nearest to this peak is used as the baseline.

[0054] Specifically, the epoxy group ring-opening rate E (%) is calculated using the following formula, where X is the peak area in the absorbance spectrum before exposure and Y is the peak area in the absorbance spectrum after exposure. E(%) = [(XY) / X] x 100

[0055] Next, the exposed first photosensitive resin composition layer and the exposed second photosensitive resin composition layer are developed together to produce a fine pattern. As a developer used for development, a solvent capable of dissolving the uncured epoxy resin is suitable. Specifically, it is preferable to use a ketone-based organic solvent such as propylene glycol monomethyl ether acetate, methyl ethyl ketone, or methyl isobutyl ketone.

[0056] After development, in order to accelerate the curing of the resin composition, it is preferable to carry out a heat treatment (main baking) at a temperature of 140° C. or higher. From the viewpoint of preventing cracks due to an increase in film stress, it is preferable that the film stress of the cured product obtained by the heat treatment (main baking) is 20 MPa or less.

[0057] Here, a method for determining the membrane stress of the cured product will be described. To confirm the stress difference in the cured product itself, a sample is prepared that has been exposed to full surface rather than patterning exposure during the exposure process. Immediately after the sample has cured, a laser reflection warpage measuring device (KLA-Tencor, FLX-2320-S) is used to measure the change in warpage before and after film formation, and the calculated internal stress is taken as the film stress of the cured product.

[0058] The microstructure formed by the method according to the present disclosure has high resolution and mechanical strength. Therefore, it is suitable for processing into fine structures in various cutting-edge device fields, and can be suitably used in forming nozzles of inkjet heads. For example, as shown in Figs. 1(A) and 1(B), a first photosensitive resin is used as an ink flow path forming member 8 that forms an ink flow path 1. A second photosensitive resin composition can be used as the discharge port forming member 4 that forms the composition, discharge port 2 and nozzle 3. [Example]

[0059] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the configurations embodied in these examples. Furthermore, "parts" used in the examples and comparative examples means "parts by mass" unless otherwise specified.

[0060] <Examples 1 to 8, Comparative Example 1> (Sample fabrication of microstructures) The microstructure shown in Figure 2 was fabricated. Figure 3 shows a schematic cross-sectional view taken along the line A-A' in Figure 2. First, as the first and second photosensitive resin compositions, an epoxy resin, a polymerization initiator, other additives, and a solvent were mixed in the compositions (parts by mass) shown in Table 1, and the mixture was stirred at room temperature for 3 days to obtain a homogeneous solution. Each microstructure was fabricated using the first and second photosensitive resin compositions in the combinations of Examples 1 to 8 and Comparative Example 1 in Table 1. Next, as shown in FIG. 3(A), the first photosensitive resin composition was applied to a silicon substrate 5 to a thickness of 25 μm, and heat-treated at 60° C. for 9 minutes to form a layer of the first photosensitive resin composition 11.

[0061] On the other hand, the second photosensitive resin composition 12 was cast onto a PET film FB50 Lumirror (manufactured by Toray Industries, Inc.) as a base film by a solution casting method to a film thickness of 20 μm, and the film was dried by heating at 90° C. for 5 minutes, and then wound up. Then, a PET film Purex A31 (manufactured by Teijin DuPont Films, Ltd.) as a cover film was placed on top, and the film was heat-treated at 50° C. for 1 minute. Next, the cover film was peeled off from the second photosensitive resin layer, and the cover film was placed on top of the second photosensitive resin layer so that the surface of the first photosensitive resin composition 11 and the surface of the second photosensitive resin composition 12 met, and the layers were transferred by lamination at 70°C under pressure to form a layer of the first photosensitive resin composition 12.

[0062] Furthermore, as shown in FIG. 3(C), the layer of the first photosensitive resin composition 11 was exposed to 20,000 J / m 2 through a first photomask 13 using an i-line exposure stepper (manufactured by Canon Inc.). 2 The pattern shape for checking the shape of the microstructure was set to a line / space of 20 μm / 20 μm. Thereafter, the substrate was heat-treated at 90° C. for 4 minutes.

[0063] Next, as shown in FIG. 3(D), the layer of the second photosensitive resin composition 12 was exposed to 2000 J / m 2 through a second photomask 14 using an i-line exposure stepper (manufactured by Canon Inc.). 2The pattern shape for checking the shape of the microstructure was set to a line / space of 10 μm / 30 μm. Thereafter, the substrate was heat-treated at 90° C. for 4 minutes. Next, the uncured portions of the first photosensitive resin composition 11 and the second photosensitive resin composition 12 were removed by developing with propylene glycol monomethyl ether acetate (PGMEA) for 10 minutes, and then cured at 200°C to obtain a microstructure (Figure 3(E)). [Table 1]

[0064] (Evaluation results) The results are shown in Table 1. The angle θ formed between the patterns of the layer of the first photosensitive resin composition and the layer of the second photosensitive resin composition as shown in FIG. 4 was measured. Examples 1 to 8 showed perpendicularity close to 90°, and good patterns were obtained. On the other hand, in Comparative Example 1, the perpendicularity was reduced, and the patterning ability was reduced. For this reason, it is believed that no interaction due to the initiator occurred between the layers in Examples 1 to 8. On the other hand, in Comparative Example 1, salt exchange of the initiator between the layers occurred, which is thought to have improved the sensitivity of the second photosensitive resin composition, resulting in a smaller angle θ.

[0065] (epoxy group ring opening rate) The peak area (wave number 9) derived from the epoxy group before and after exposure of the sample was measured using a "VARIAN 600 UMA FT-IR Microscope" (product name, manufactured by VARIAN). 10cm -1 The epoxy group ring-opening rate was calculated by measuring the temperature (near the center of the film). There were no problems with reactivity before development, and no peeling occurred due to development.

[0066] (Fabrication of Ink Jet Recording Head) 5(a) to 5(j) show a method for forming an inkjet recording head. Each inkjet recording head was fabricated using the first and second photosensitive resin compositions in combination with Examples 1 to 8 and Comparative Example 1 in Table 1. First, as shown in FIG. 5(a), a 100 μm-thick PET film 15 was prepared. Next, as shown in FIG. 5(b), a first photosensitive resin composition 11 listed in Table 1 was applied to the PET film 15 by spin coating, and baked at 90°C for 10 minutes to volatilize the PGMEA solvent, forming a 15.0 μm-thick film. Next, as shown in FIG. 5(c), a silicon substrate 5 was prepared having an energy-generating element 6 made of TaSiN on its surface.

[0067] Next, as shown in Fig. 5(d), a 0.3 µm thick SiCN film was formed as an inorganic material layer 16 on the front surface of the silicon substrate 5 by plasma CVD so as to cover the energy generating elements 6. Subsequently, a 0.25 µm thick Ta film was formed as a protective layer 17 by sputtering. Furthermore, the inorganic material layer 16 and the protective layer 17 were patterned by photolithography and reactive ion etching.

[0068] Next, a supply port 7 was formed as shown in FIG. 5(e). The supply port 7 was formed by forming an etching mask with openings using a positive photosensitive resin made of OFPR (manufactured by Tokyo Ohka Kogyo Co., Ltd.) and performing reactive ion etching through the openings in the etching mask. The reactive ion etching was performed using an ICP etching device (manufactured by Alcatel, model number: 8E) using the Bosch process. After the supply port 7 was formed, the etching mask was removed using a stripper.

[0069] Next, as shown in Fig. 5(f), a first photosensitive resin composition (1) 11 was formed. Specifically, a film having the first photosensitive resin composition 11 prepared in Fig. 5(b) was transferred to a silicon substrate 5 on which an energy generating element 6 and a supply port 7 were arranged by a lamination method (applying pressure under heat treatment at 70°C). Thereafter, the PET film 15 was peeled off from the first photosensitive resin composition 11 with a release tape (not shown).

[0070] Next, as shown in FIG. 5(g), a second photosensitive resin composition 12 was formed. First, the second photosensitive resin composition 12 shown in Table 1 was applied to a 100 μm-thick PET film and baked at 90°C for 5 minutes to volatilize the solvent, forming a 5.0 μm-thick film. Next, the second photosensitive resin composition 12 was transferred and laminated onto the first photosensitive resin composition 11 using a lamination method while applying heat at 50°C.

[0071] Next, as shown in FIG. 5(h), the photosensitive resin composition 11 is exposed to 10,000 J / m irradiated light using an i-line exposure stepper (Canon, product name: i5) through a third photomask 18 having a flow path pattern. 2 As a result, a latent image of the flow path forming member 8 was formed.

[0072] Next, as shown in FIG. 5(i), the second photosensitive resin composition 12 is exposed to 1100 J / m irradiated light using an i-line exposure stepper (Canon, product name: i5) through a fourth photomask 19 having a discharge port pattern. 2 The exposed portion was then cured by heat treatment at 90° C. for 5 minutes, thereby forming a discharge port forming member 4. Next, as shown in Figure 5(j), the uncured portions of the first photosensitive resin composition 11 and the second photosensitive resin composition 12 were removed all at once by developing with PGMEA for 1 hour, forming an ink flow path 1, a discharge port 2, and a nozzle 3, and curing the resultant at 200°C to obtain a liquid discharge head.

[0073] <Evaluation> The printing characteristics were evaluated using the obtained liquid ejection head. The printing evaluation was based on the following criteria. Specifically, the printer used for the measurement was a Canon PIXUS TS6330. In this measurement, the printer outputted pigment black ink, and the output image was read by a scanner to evaluate the impact accuracy from the amount of deviation from the target position. A: Impact accuracy is 3μm or less B: Impact accuracy is over 3 μm and 5 μm or less C: Impact accuracy is over 5 μm The results are shown in Table 1. Examples 1 to 7 provided good printing performance, with Example 7 having particularly excellent print quality. On the other hand, print quality was reduced in Comparative Example 1. It is believed that Examples 1 to 7 had good impact accuracy because the ink flow paths and nozzles were precisely patterned. [Explanation of symbols]

[0074] 1: ink flow path, 2: ejection port, 3: nozzle, 4: ejection port forming member, 5: silicon substrate, 6: energy generating element, 7: supply port, 8: ink flow path forming member, 11: first photosensitive resin composition, 12: second photosensitive resin composition, 13: first photomask, 14: second photomask, 15: PET film, 16: inorganic material layer, 17: protective layer, 18: third photomask, 19: fourth photomask

Claims

1. A method for producing a microstructure containing a cured product of a photosensitive resin composition, comprising: forming at least two layers of a photosensitive resin composition, each layer containing a photopolymerization initiator; a step of patterning each of the at least two layers of the photosensitive resin composition formed by the method; a step of simultaneously developing at least two exposed layers of the photosensitive resin composition to obtain a microstructure, in the at least two layers of the photosensitive resin composition, 90 mass % or more of the photopolymerization initiator contained in at least one of the two adjacent layers of the photosensitive resin composition is a nonionic photopolymerization initiator; the nonionic photopolymerization initiator is a photobase generator, The method for producing a microstructure is characterized in that the photosensitive resin composition containing the photobase generator further contains a base multiplier.

2. 2. The method for producing a microstructure according to claim 1, wherein the photobase generator is at least one selected from the group consisting of an imidazole-based photobase generator and an amine-based photobase generator.

3. 3. The method for producing a microstructure according to claim 1, wherein the photosensitive resin composition containing the photobase generator further contains a sensitizer.

4. 4. The method for producing a microstructure according to claim 1, wherein the photosensitive resin composition contains an epoxy resin.

5. 5. The method for producing a microstructure according to claim 4, wherein the epoxy resin is at least one selected from the group consisting of alicyclic epoxy resins, novolac epoxy resins, 1,6-dihydroxynaphthalene epoxy resins, and bisphenol S epoxy resins.

6. The method for producing a microstructure according to any one of claims 1 to 5, wherein the at least two layers of the photosensitive resin composition are two layers of the photosensitive resin composition.

7. In the step of patterning exposure, 7. The method for producing a microstructure according to claim 1, wherein the layer containing the nonionic photopolymerization initiator in an amount of 90 mass % or more of the photopolymerization initiator is located on the opposite side of the light source in the exposure irradiation direction.

8. A method for manufacturing a liquid ejection head, comprising the method for manufacturing a microstructure according to any one of claims 1 to 7, The liquid ejection head includes a substrate, a flow path forming member provided on the substrate and forming a flow path for the liquid, and an ejection port forming member provided on the flow path forming member and having an ejection port for ejecting the liquid, the step of forming at least two photosensitive resin composition layers is a step of forming two layers, a first photosensitive resin composition layer and a second photosensitive resin composition layer, in this order on a substrate; The flow path forming member is a cured product of the first photosensitive resin composition, and the discharge port forming member is a cured product of the second photosensitive resin composition. A method for manufacturing a liquid ejection head.

9. A microstructure containing at least two layers of a cured product of a photosensitive resin composition, the photosensitive resin composition contains a photopolymerization initiator, in the at least two layers of the photosensitive resin composition, 90 mass % or more of the photopolymerization initiator contained in at least one of the two adjacent layers of the photosensitive resin composition is a nonionic photopolymerization initiator; the nonionic photopolymerization initiator is a photobase generator, The microstructure is characterized in that the photosensitive resin composition containing the photobase generator further contains a base multiplier.

10. A liquid ejection head comprising: a substrate; a flow path forming member provided on the substrate and forming a flow path for liquid; and an ejection port forming member provided on the flow path forming member and having an ejection port for ejecting liquid, the flow path-forming member is a cured product of a first photosensitive resin composition containing a photopolymerization initiator, the discharge port-forming member is a cured product of a second photosensitive resin composition containing a photopolymerization initiator, 90% by mass or more of the photopolymerization initiator contained in at least one of the first photosensitive resin composition and the second photosensitive resin composition is a nonionic photopolymerization initiator; the nonionic photopolymerization initiator is a photobase generator, The liquid ejection head is characterized in that the photosensitive resin composition containing the photobase generator further contains a base multiplier.

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