Method for forming printed material and system for forming printed material

1. A method for forming a printed material, the method comprising:

forming an image on a recording medium;

applying particles to a surface of the recording medium, the surface having the image formed thereon;

heating the particles applied to the recording medium; and

pressurizing, in a thickness direction, a multilayer body obtained by folding the recording medium so that the heated particles are sandwiched between flaps of the recording medium or a multilayer body obtained by placing another recording medium on top of the recording medium with the heated particles therebetween,

wherein the particles contain a styrene resin and a (meth)acrylic acid ester resin,

the (meth)acrylic acid ester resin contains two (meth)acrylic acid ester monomer units, and a mass ratio of the (meth)acrylic acid ester monomer units relative to a total of polymerization components is 90 mass % or more,

the particles have two glass transition temperatures, and a difference between the lowest glass transition temperature and the highest glass transition temperature is 30° C. or more, and

the particles have a sea phase containing the styrene resin and island phases containing the (meth)acrylic acid ester resin and being dispersed in the sea phases.

2. The method for forming a printed material according to claim 1 , wherein the heating involves heating the particles by causing a member to contact the particles, the member having a surface having a set temperature in a range of 130° C. to 200° C.

3. The method for forming a printed material according to claim 1 , wherein the heating further involves pressurizing the particles.

4. The method for forming a printed material according to claim 1 , wherein the pressurizing involves pressurizing the multilayer body in the thickness direction by causing the multilayer body to pass between a pair of rolls separated from each other by an interval C, and the interval C is in a range of 0.01 mm to 0.40 mm.

5. The method for forming a printed material according to claim 1 , wherein, in the pressurizing, a pressure applied in the thickness direction of the multilayer body is in a range of 48 MPa to 120 MPa as measured by using a pressure measuring film.

6. The method for forming a printed material according to claim 1 , wherein a ratio of styrene monomer unit to a total of polymerization components of the styrene resin in the particles is in a range of 60 mass % to 95 mass %.

7. The method for forming a printed material according to claim 1 , wherein a mass ratio between the two (meth)acrylic acid ester monomer units contained as polymerization components in the (meth)acrylic acid ester resin in the particles is in a range of 80:20 to 20:80.

8. The method for forming a printed material according to claim 1 , wherein the (meth)acrylic acid ester resin in the particles contains two (meth)acrylic acid alkyl ester monomer units, and a difference in the number of carbon atoms in an alkyl group between the two (meth)acrylic acid alkyl ester monomer units is in a range of 1 to 4.

9. The method for forming a printed material according to claim 1 , wherein the styrene resin in the particles further contains a (meth)acrylic acid ester monomer unit.

10. The method for forming a printed material according to claim 1 , wherein the (meth)acrylic acid ester monomer unit contained as a polymerization component in the styrene resin is selected from n-butyl acrylate and 2-ethylhexyl acrylate.

11. The method for forming a printed material according to claim 1 , wherein the styrene resin and the (meth)acrylic acid ester resin in the particles contain the same (meth)acrylic acid ester monomer unit.

12. The method for forming a printed material according to claim 1 , wherein the (meth)acrylic acid ester resin contains 2-ethylhexyl acrylate monomer unit and n-butyl acrylate monomer unit.

13. The method for forming a printed material according to claim 1 , wherein the island phases have an average size in a range of 200 nm to 500 nm.

14. The method for forming a printed material according to claim 1 , wherein a temperature at which the particles exhibit a viscosity of 10000 Pa·s at a pressure of 4 MPa is 90° C. or less.

15. A system for forming a printed material, the system comprising:

an image forming unit that forms an image on a recording medium;

a particle applying unit that applies particles to the recording medium having the image formed thereon;

a particle heating unit that heats the particles applied to the recording medium; and

a multilayer body pressurizing unit that pressurizes, in a thickness direction, a multilayer body obtained by folding the recording medium so that the heated particles are sandwiched between flaps of the recording medium or a multilayer body obtained by placing another recording medium on top of the recording medium with the heated particles therebetween,

wherein the particles contain a styrene resin and a (meth)acrylic acid ester resin,

the (meth)acrylic acid ester resin contains two (meth)acrylic acid ester monomer units, and a mass ratio of the (meth)acrylic acid ester monomer units relative to a total of polymerization components is 90 mass % or more,

the particles have two glass transition temperatures, and a difference between the lowest glass transition temperature and the highest glass transition temperature is 30° C. or more, and

the particles have a sea phase containing the styrene resin and island phases containing the (meth)acrylic acid ester resin and being dispersed in the sea phases.

16. The system for forming a printed material according to claim 15 , wherein the island phases have an average size in a range of 200 nm to 500 nm.

17. The system for forming a printed material according to claim 15 , wherein the (meth)acrylic acid ester resin in the particles contains two (meth)acrylic acid alkyl ester monomer units, and a difference in the number of carbon atoms in an alkyl group between the two (meth)acrylic acid alkyl ester monomer units is in a range of 1 to 4.