Printing method and printing apparatus

1. A printing method for printing a printing medium to produce a printed item, the method comprising:

a non-white ink application step of applying an aqueous non-white ink composition containing a non-white coloring material onto the printing medium, the printing medium being not absorbent or poorly absorbent, and the printing medium being translucent or transparent; and

a white ink application step of applying an aqueous white ink composition containing a white coloring material onto the non-white ink composition on the printing medium to form a superimposed region, the superimposed region being formed by applying the non-white ink composition and the white ink composition at a total rate of 30 mg/inch 2 or less,

wherein

the non-white ink composition and the white ink composition each have an organic solvent content limited to 15% or less relative to the total mass of the corresponding ink composition, and

the mass ratio of the white ink composition to the non-white ink composition in the superimposed region is 1.5 or more in a portion to which the non-white ink composition is applied in an amount largest in the superimposed region.

2. The printing method according to claim 1 , wherein

the non-white ink application step and the white ink application step are each performed by ejecting the corresponding ink composition from an ink jet head.

3. The printing method according to claim 1 , wherein

the non-white ink application step and the white ink application step are each performed by ejecting the corresponding ink composition from an ink jet line head having a dimension larger than the width of the printing medium so as to be able to print one entire line of an image by one scanning motion.

4. The printing method according to claim 3 , wherein

the non-white ink application step and the white ink application step may be performed on the printing medium fed at a speed of 15 m/min or more.

5. The printing method according to claim 1 , further comprising a post-application drying step of heating the printing medium with an infrared heater after the white ink application step.

6. The printing method according to claim 1 , wherein

the superimposed region is formed by applying the non-white ink composition and the white ink composition at a total rate of 25 mg/inch 2 or less.

7. The printing method according to claim 1 , wherein

the printing medium that is not absorbent is a plastic film that is not provided with an ink-absorbent layer, and the printing medium that is poorly absorbent is a coated paper.

8. The printing method according to claim 1 , wherein

the white ink composition contains a wax in a proportion of 2% or less relative to the total mass of the white ink composition.

9. The printing method according to claim 1 , wherein

the non-white ink composition contains a urethane resin.

10. The printing method according to claim 1 , further comprising a treatment liquid application step of applying a treatment liquid containing a flocculant onto the printing medium.

11. The printing method according to claim 1 , wherein

the organic solvent content of each of the non-white ink composition and the white ink composition is 1% to 10% relative to the total mass of the corresponding ink composition.

12. The printing method according to claim 1 , wherein

the printed item is laminated over the printed side thereof.

13. The printing method according to claim 1 , wherein

the printing medium has a thickness of 5 μm to 70 μm.

14. The printing method according to claim 1 , wherein

the white coloring material is an inorganic oxide pigment.

15. The printing method according to claim 1 , wherein

the printing method is performed by using a printing apparatus including a control unit operable to control the amounts of the non-white ink composition and the white ink composition to be applied for printing.

16. A printing apparatus operable to print a printing medium, the printing apparatus comprising:

a non-white ink applying section configured to apply an aqueous non-white ink composition containing a non-white coloring material onto the printing medium, the printing medium being not absorbent or poorly absorbent, and the printing medium being translucent or transparent; and

a white ink applying section configured to apply an aqueous white ink composition containing a white coloring material onto the non-white ink composition on the printing medium to form a superimposed region, the superimposed region being formed by applying the non-white ink composition and the white ink composition at a total rate of 30 mg/inch 2 or less,

wherein

the non-white ink composition and the white ink composition each have an organic solvent content limited to 15% or less relative to the total mass of the corresponding ink composition, and

the mass ratio of the white ink composition to the non-white ink composition in the superimposed region is 1.5 or more in a portion to which the non-white ink composition is applied in an amount largest in the superimposed region.

17. The printing method according to claim 1 , wherein the superimposed region is formed by applying the white ink composition at a rate of 25 mg/inch 2 or less.

18. The printing method according to claim 1 , wherein the mass ratio of the white ink composition to the non-white ink composition in the superimposed region is 1.5 to 3 in a portion to which the non-white ink composition is applied in a greatest amount in the superimposed region.

19. The printing method according to claim 1 , further comprising a post-application drying step of heating the printing medium after the white ink application step,

wherein a surface temperature of the printing medium in the post-application drying step is 120 degrees C. or less.