Display panel, method for producing the same and composition of ink used by the method for producing the same

1. A display panel comprising:

a resin substrate; and

a printed layer formed on at least a part of the resin substrate by inkjet printing, wherein

the printed layer comprises cured products of UV-curable inks containing UV-curable monomers which are polymerized and cured by UV irradiation and the UV-curable ink contains a monofunctional monomer and a polyfunctional monomer as the UV-curable monomers, and

the printed layer has at least the two cured products having different pencil hardness values which are formed by a low concentration polyfunctional monomer ink containing the polyfunctional monomer having an amount of 5 parts by weight or less relative to 100 parts by weight of the UV-curable monomers,

a high concentration polyfunctional monomer ink containing the polyfunctional monomer in an amount of 10 parts by weight or more in 100 parts by weight of the UV-curable monomers,

the display panel has a pressed part where at least a part of the display panel is pressed by another member and the display panel is used in an automotive instrument panel,

the printed layer has the cured product formed from the high concentration polyfunctional monomer ink, at least at the pressed part,

the surface of the display panel has a graphical design part formed to comprise scales and characters and formed on the surface of the display panel, the graphical design part being composed of the printed layer,

the display panel is held inside the casing and has a pressed part being pressed by the casing when the display panel is held inside the casing, the pressed part being at least part of the display panel, and

the printed layer comprising the cured products has a pencil hardness value, and

the pencil hardness value at the pressed part being set to be relatively higher than the pencil hardness value at a part of the display panel, the part of the display panel being except for the pressed part.

2. The display panel according to claim 1 , wherein the printed layer has one cured product at the pressed part and another cured product at a part except for the pressed part, and the one cured product and the other cured product having same color.

3. The display panel according to claim 1 , wherein the UV-curable ink contains at least phenoxyethyl acrylate as the monofunctional monomer, and has the phenoxyethyl acrylate as a main component.

4. The display panel according to claim 1 , wherein the at least two cured products having different pencil hardness values are formed in a laminated state or in parallel on approximately the same plane, on the resin substrate.

5. A method for producing a display panel according to claim 1 , the method comprising:

jetting, by means of inkjet printing, at least two such UV-curable inks which obtain different pencil hardness values after curing, on at least a part of the resin substrate, and irradiating the UV-curable inks with UV to cure the UV-curable inks, and to thereby form the cured products.

6. The method for producing a display panel according to claim 5 , wherein inks of the same color are used for the inkjet printing, as the at least two such UV-curable inks which obtain different pencil hardness values after curing.

7. The method for producing a display panel according to claim 5 , wherein the UV-curable ink contain a monofunctional monomer and a polyfunctional monomer as the UV-curable monomers, and as the at least two such UV-curable inks which obtain different pencil hardness values after curing, at least two inks are having different contents of the polyfunctional monomer.

8. The method for producing a display panel according to claim 7 , wherein as the at least two such UV-curable inks which obtain different pencil hardness values after curing, a low concentration polyfunctional monomer ink containing the polyfunctional monomer in an amount of 5 parts by weight or less in 100 parts by weight of the UV-curable monomers, and a high concentration polyfunctional monomer ink containing the polyfunctional monomer in an amount of 10 parts by weight or more in 100 parts by weight of the UV-curable monomers.

9. The method for producing a display panel according to claim 8 , wherein the display panel has a pressed part at which at least a part of the display panel is pressed by another member, and in the inkjet printing process, the cured product formed from the high concentration polyfunctional monomer ink is formed at least at the pressed part on the resin substrate.

10. The method for producing a display panel according to claim 8 , wherein the display panel has a molded part and/or a processed part at which at least a part of the display panel is subjected to molding and/or processing, and in the inkjet printing process, the cured product formed from the lower concentration polyfunctional monomer ink is formed at least at the molded part and/or the processed part on the resin substrate.

11. The method for producing a display panel according to claim 7 , wherein the UV-curable ink contains at least phenoxyethyl acrylate as the monofunctional monomer, and has the phenoxyethyl acrylate as a main component.

12. The method for producing a display panel according to claim 5 , wherein in the inkjet printing process, the at least two such cured products having different pencil hardness values are formed in a laminated state or in parallel on approximately the same plane, on the resin substrate.

13. The method for producing a display panel according to claim 5 , wherein the inkjet printing is performed using an inkjet printing apparatus equipped with at least two ink tanks respectively containing at least two UV-curable inks which obtain different pencil hardness values after curing.

14. The method for producing a display panel according to claim 5 , wherein the display panel is used as an automotive instrument panel.

15. A method for producing a display panel according to claim 1 , the method comprising:

jetting, by means of inkjet printing, a UV-curable ink containing UV-curable monomers which are polymerized and cured by UV irradiation, on at least a part of the resin substrate; and irradiating the UV-curable ink with UV to cure the UV-curable ink, and to thereby form a printed layer;

wherein the UV-curable ink contains monofunctional monomers and a polyfunctional monomer as the UV-curable monomers, and

the UV-curable ink contains at least vinylcaprolactam and N-acryloyloxyethyl hexahydrophthalimide as the monofunctional monomers.

16. The method for producing a display panel according to claim 15 , wherein the UV-curable ink contains the vinylcaprolactam and the N-acryloyloxyethyl hexahydrophthalimide at a weight ratio of vinylcaprolactam: N-acryloyloxyethyl hexahydrophthalimide=1:0.2 to 2.

17. The method for producing a display panel according to claim 15 , wherein the UV-curable ink contains phenoxyethyl acrylate as the monofunctional monomer.

18. The method for producing a display panel according to claim 15 , wherein the UV-curable ink contains 55 to 93% by weight of phenoxyethyl acrylate, 5 to 30% by weight of vinylcaprolactam, and 2 to 15% by weight of N-acryloyloxyethyl hexahydrophthalimide.

19. The method for producing a display panel according to claim 15 , wherein the UV-curable ink contains oligo(2-hydroxy-2-methyl-1-(4-(methylvinyl)phenyl)propanone as a photopolymerization initiator.

20. A display panel produced according to the method according to claim 15 .

21. A display panel comprising:

a resin substrate; and

a printed layer formed on at least a part of the resin substrate by inkjet printing; wherein

the printed layer comprises cured products of UV-curable inks containing UV-curable monomers which are polymerized and cured by UV irradiation and the UV-curable ink contains a monofunctional monomer and a polyfunctional monomer as the UV-curable monomers; and

the printed layer has at least the two cured products having different pencil hardness values which are formed by a low concentration polyfunctional monomer ink containing the polyfunctional monomer in an amount of 5 parts by weight or less in 100 parts by weight of the UV-curable monomers, a high concentration polyfunctional monomer ink containing the polyfunctional monomer having an amount of 10 parts by weight or more relative to 100 parts by weight of the UV-curable monomers; wherein

the display panel has a processed part at which at least a part of the display panel is subjected to processing, the display panel is used in an automotive instrument panel;

the printed layer has the cured product formed from the low concentration polyfunctional monomer ink at least at the processed part;

the surface of the display panel has a graphical design part formed to comprise scales and characters and formed on the surface of the display panel, the graphical design part being composed of the printed layer;

the display panel comprises a pointer arranged on the graphical design part, the pointer having a support part disposed in a though-hole formed through the display panel;

the printed layer comprising the cured products has a pencil hardness value; and

the pencil hardness value at a processed part in which the through-hole is formed being set to be relatively lower than the pencil hardness value at a part of the display panel, the part of the display panel being except for the processed part.

22. The display panel according to claim 21 , wherein the UV-curable ink contains at least phenoxyethyl acrylate as the monofunctional monomer, and has the phenoxyethyl acrylate as a main component.

23. The display panel according to claim 21 , wherein the at least two cured products having different pencil hardness values are formed in a laminated state or in parallel on approximately the same plane, on the resin substrate.

24. A display panel comprising:

a resin substrate and

a printed layer formed on at least a part of the resin substrate by inkjet printing, wherein

the printed layer comprises cured products of UV-curable inks containing UV-curable monomers which are polymerized and cured by UV irradiation and the UV-curable ink contains a monofunctional monomer and a polyfunctional monomer as the UV-curable monomers,

the printed layer has at least the two cured products having different pencil hardness values which are formed by a low concentration polyfunctional monomer ink containing the polyfunctional monomer in an amount of 5 parts by weight or less in 100 parts by weight of the UV-curable monomers, a high concentration polyfunctional monomer ink containing the polyfunctional monomer in an amount of 10 parts by weight or more in 100 parts by weight of the UV-curable monomers,

the display panel has a molded part at which at least a part of the display panel is subjected to molding, the display panel is used in an automotive instrument panel, and the printed layer has the cured product formed at least at the molded part and formed from the low concentration polyfunctional monomer ink,

the surface of the display panel has a graphical design part formed to comprise scales and characters and formed on the surface of the display panel, the graphical design part being composed of the printed layer,

the printed layer comprising the cured products has a pencil hardness value, and

the pencil hardness value at a molded part in which the graphical design part is partially three-dimensionally molded being set to be relatively lower than the pencil hardness value at a part of the display panel, the part of the display panel being except for the molded part.

25. The display panel according to claim 24 , wherein the UV-curable ink contains at least phenoxyethyl acrylate as the monofunctional monomer, and has the phenoxyethyl acrylate as a main component.

26. The display panel according to claim 24 , wherein the at least two cured products having different pencil hardness values are formed in a laminated state or in parallel on approximately the same plane, on the resin substrate.

27. A display panel comprising:

a resin substrate and

a printed layer formed on at least a part of the resin substrate by inkjet printing, wherein

the printed layer comprises cured products of UV-curable inks containing UV-curable monomers which are polymerized and cured by UV irradiation,

the UV-curable ink contains at least phenoxyethyl acrylate as the monofunctional monomer, and has the phenoxyethyl acrylate as a main component, and

the printed layer has at least the two cured products having different pencil hardness values.