Image forming apparatus and image forming method

1. An image forming apparatus, comprising:

a first image forming part that forms a first image on a print medium using a photoluminescent developer containing a photoluminescent pigment;

a second image forming part that forms a second image on the print medium using a coloring developer containing a coloring material; and

a lamination part that laminates the first image and the second image on the print medium, wherein

a viscoelastic phase angle (A) of the coloring developer and a viscoelastic phase angle (B) of the photoluminescent developer when measured at 125[° C.] using a viscoelasticity measuring device satisfy follow:

21.1[°]≤( A−B )≤31.6[°].

where

A means a viscoelastic phase angle of the coloring developer,

B means a viscoelastic phase angle of the photoluminescent developer.

2. The image forming apparatus according to claim 1 , wherein

the viscoelastic phase angle (B) of the photoluminescent developer is less than 46.5[°], and

the viscoelastic phase angle (A) of the coloring developer is 61.3[°] or more.

3. The image forming apparatus according to claim 1 , wherein

the viscoelastic phase angle (A) of the coloring developer is 61.3[°] or more and 68.0[°] or less.

4. The image forming apparatus according to claim 1 , wherein

the viscoelastic phase angle (B) of the photoluminescent developer is 36.4[°] or more and less than 46.5[°].

5. The image forming apparatus according to claim 1 , wherein

the viscoelastic phase angle (B) of the photoluminescent developer is 36.4[°] or more and 40.2[°] or less.

6. The image forming apparatus according to claim 1 , wherein

the lamination part places

the second image on the print medium, and

the first image on the second image such that the medium, the second image and the first image are laminated in this order.

7. The image forming apparatus according to claim 1 , wherein

the print medium is composed with at least a base material and an adhesive layer, which is comprised of an adhesive material,

the base material has two surfaces opposing each other, wherein one of the two surfaces is a transfer surface on which the first and second images are laminated, and

the adhesive layer is spread over the transfer surface such that either the first image or the second image is transferred on the adhesive layer.

8. The image forming apparatus according to claim 7 , wherein

the adhesive layer has two surfaces opposing each other, wherein one of the two surfaces is a contact surface that is placed facing the base material and the other is a transfer surface on which the first and second images are transferred,

a surface roughness of the contact surface is greater than a surface roughness of the transfer surface.

9. The image forming apparatus according to claim 7 , wherein

the adhesive layer is formed of a lipophilic material.

10. The image forming apparatus according to claim 7 , wherein

the adhesive layer has a thickness ranged from 20 to 80 [μm].

11. The image forming apparatus according to claim 7 , wherein

the print medium has a thickness ranged from 100 to 160 [μm].

12. The image forming apparatus according to claim 1 , wherein

the lamination part is composed with a transfer belt, which is an endless belt running in a moving direction (E 1 ),

the first image forming part and the second image forming part are arranged along an outer surface of the transfer belt, and

the first image forming part is positioned at an upstream side from the second image forming part with respect to the moving direction.