Method for manufacturing liquid ejection head
A method for manufacturing a liquid ejection head includes forming a first negative photosensitive resin layer containing a photopolymerizable compound and a photopolymerization initiator over a substrate, exposing the first negative photosensitive resin layer to light to form a latent image of a flow channel member, forming a second negative photosensitive resin layer containing a photopolymerizable compound and a photopolymerization initiator over the first negative photosensitive resin layer having the latent image, and exposing the second negative photosensitive resin layer to light to form a latent image of an ejection opening member. The first negative photosensitive resin layer has a thickness of 10 μm or less and further contains a sensitivity adjusting agent capable of reducing the sensitivity of the first negative photosensitive resin layer. The transmittance A of the first negative photosensitive resin layer is 0.70 or less for the exposure light for the second negative photosensitive resin layer.
1. A method for manufacturing a liquid ejection head including a substrate, a flow channel member overlying the substrate and having a flow channel therein through which a liquid flows, and an ejection opening member overlying the flow channel member and having an ejection opening therein through which the liquid is ejected, the method comprising:
forming a first negative photosensitive resin layer over the substrate, the first negative photosensitive resin layer containing a photopolymerization initiator, a photopolymerizable compound, and a sensitivity adjusting agent capable of reducing the sensitivity of the first negative photosensitive resin layer, the first negative photosensitive resin layer having a thickness of 10 μm or less;
exposing the first negative photosensitive resin layer to light to form a latent image of the flow channel member;
forming a second negative photosensitive resin layer containing a photopolymerization initiator and a photopolymerizable compound over the first negative photosensitive resin layer having the latent image;
exposing the second negative photosensitive resin layer to light to form a latent image of the ejection opening member; and
removing unexposed portions of the first and the second negative photosensitive resin layer to form the flow channel and the ejection opening,
wherein the first negative photosensitive resin layer has a transmittance A of 0.70 or less for the light used to expose the second negative photosensitive resin layer.
2. The method according to claim 1 , wherein the second negative photosensitive resin layer is exposed to light having a wavelength of 365 nm.
3. The method according to claim 1 , wherein the first and the second negative photosensitive resin layer are exposed to light having the same wavelength.
4. The method according to claim 1 , wherein the first negative photosensitive resin layer contains a photo-acid generator as the photopolymerization initiator.
5. The method according to claim 4 , wherein the photo-acid generator is an onium salt including a cationic structure having at least one skeleton selected from the group consisting of a 9,10-dialkoxyanthracene skeleton, an anthraquinone skeleton, and a thioxanthone skeleton.
6. The method according to claim 1 , wherein the first negative photosensitive resin layer contains an epoxy resin as the photopolymerizable compound.
7. The method according to claim 1 , wherein the sensitivity adjusting agent contains one of a basic substance and an acid generator capable of generating an acid having a pKa in the range of −1.5 to 3.0.
8. The method according to claim 1 , wherein the sensitivity adjusting agent contains an acid generator capable of generating toluenesulfonic acid.
9. The method according to claim 1 , wherein the molar absorption coefficient k of the sensitivity adjusting agent for the light used to expose the second negative photosensitive resin layer is 1/10 or less of the molar absorption coefficient k 0 of the photopolymerization initiator in the first negative photosensitive resin layer for the light used to expose the second negative photosensitive resin layer.
10. The method according to claim 1 , wherein the molar absorption coefficient k 0 of the photopolymerization initiator in the first negative photosensitive resin layer is 1,700 L·mol −1 ·cm −1 or more for the light used to expose the second negative photosensitive resin layer.
11. The method according to claim 1 , wherein the transmittance A is 0.30 or more for the light used to expose the second negative photosensitive resin layer.
12. The method according to claim 1 , wherein the second negative photosensitive resin layer has a transmittance B of 0.30 or more for the light used to expose the second negative photosensitive resin layer.
13. The method according to claim 1 , wherein product A×B of the transmittances A and the transmittance B of the second negative photosensitive resin layer for the light used to expose the second negative photosensitive resin layer is 0.70 or less.
14. The method according to claim 1 , wherein the second negative photosensitive resin layer is exposed to light at a dose in the range of 500 J/m 2 to 5,000 J/m 2 .
15. The method according to claim 1 , wherein the content of the photopolymerizable compound in the first negative photosensitive resin layer is 90% by mass or more relative to the solids content in the first negative photosensitive resin layer.