Liquid discharge system, image forming apparatus, and liquid discharge method

1. A liquid discharge system comprising:

a pretreatment execution device configured to apply one of multiple types of pretreatment agents having different levels of aggregating agent concentration on a medium;

a liquid discharge head configured to discharge liquid onto the medium based on image information on an image to be output; and

circuitry configured to analyze the image information to determine whether an area of printing on the medium includes a photograph printing area or a line printing area, and to determine whether a dot to be applied to a dot location on the medium by the liquid discharge head belongs to the photograph printing area or the line printing area,

the circuitry configured, in response to determining the dot belongs to the photographic printing area, to direct the pretreatment execution device to apply, at the dot location, pretreatment agent having a first aggregating agent concentration that causes a diameter of the dot to increase and a color density of the dot to be thicker toward a center of the dot, and

the circuitry configured, in response to determining the dot belongs to the line printing area, to direct the pretreatment execution device to apply, at the dot location, pretreatment agent having a second aggregating agent concentration that causes a diameter of the dot to decrease and the color density of the dot to be uniform.

2. The liquid discharge system according to claim 1 ,

wherein the circuitry is configured to control a concentration of a reactant in the pretreatment agent applied to the medium.

3. The liquid discharge system according to claim 1 ,

wherein the circuitry is configured to control the pretreatment execution device to increase a speed of spreading of wetting of the liquid applied onto the medium, based on the image information.

4. The liquid discharge system according to claim 1 ,

wherein the circuitry is configured to control the pretreatment execution device to reduce a speed of spreading of wetting of the liquid applied onto the medium, based on the image information.

5. The liquid discharge system according to claim 1 ,

wherein the circuitry is configured to control an ink dot profile, including a size and color density, with a concentration of a reactant in the pretreatment agent.

6. The liquid discharge system according to claim 1 ,

wherein the image information includes image type information indicating an image type of the image to be output, the image type being one of letter, photograph, and table, and

wherein the circuitry is configured to control the manner of the pretreatment based on the image type information.

7. The liquid discharge system according to claim 1 ,

wherein the liquid discharged by the liquid discharge head contains a colorant, and

wherein, as the pretreatment, the pretreatment execution device is configured to perform a process to change a dispersion state of the colorant contained in the liquid applied onto the medium for controlling a behavior of the liquid.

8. The liquid discharge system according to claim 1 , further comprising an image type determiner configured to determine an image type of the image to be output, the image type being one of letter, photograph, and table,

wherein the circuitry is configured to control the manner of the pretreatment in accordance with the image type determined by the image type determiner.

9. The liquid discharge system according to claim 1 ,

wherein the pretreatment agent has a 15 ms dynamic surface tension of from 35 to 65 mN/m.

10. The liquid discharge system according to claim 1 ,

wherein the pretreatment agent has a static surface tension of from 20 to 35 mN/m.

11. The liquid discharge system according to claim 1 ,

wherein the pretreatment agent contains a multivalent metal salt, glycerin, and a betaine compound having a molecular weight of from 100 to 200, and

wherein a mass ratio of a total amount of the glycerin and the betaine compound to an amount of the multivalent metal salt is from 1.05 to 2.50.

12. The liquid discharge system according to claim 11 , wherein the mass ratio is from 1.05 to 1.40.

13. The liquid discharge system according to claim 11 ,

wherein a mass ratio of an amount of the betaine compound to the total amount of the glycerin and the betaine compound is from 0.1 to 0.5.

14. An image forming apparatus comprising:

a pretreatment execution device to apply one of multiple types of pretreatment agents having different levels of aggregating agent concentration on a medium;

a liquid discharge head to discharge liquid onto the medium based on image information on an image to be output; and

circuitry configured to analyze the image information to determine whether an area of printing on the medium includes a photograph printing area or a line printing area, and to determine whether a dot to be applied to a dot location on the medium by the liquid discharge head belongs to the photograph printing area or the line printing area,

the circuitry configured, in response to determining the dot belongs to the photographic printing area, to direct the pretreatment execution device to apply, at the dot location, pretreatment agent having a first aggregating agent concentration that causes a diameter of the dot to increase and a color density of the dot to be thicker toward a center of the dot; and

the circuitry configured, in response to determining the dot belongs to the line printing area, to direct the pretreatment execution device to apply, at the dot location, pretreatment agent having a second aggregating agent concentration that causes a diameter of the dot to decrease and the color density of the dot to be uniform.

15. A liquid discharge method comprising:

applying one of multiple types of pretreatment agents having different levels of aggregating agent concentration on a medium;

discharging liquid onto the medium based on the image information;

analyzing the image information to determine whether an area of printing on the medium includes a photograph printing area or a line printing area;

determining whether a dot to be applied to a dot location on the medium by the liquid discharge head belongs to the photograph printing area or the line printing area;

in response to determining the dot belongs to the photographic printing area, applying at the dot location pretreatment agent having a first aggregating agent concentration that causes a diameter of the dot to increase and a color density of the dot to be thicker toward a center of the dot; and

in response to determining the dot belongs to the line printing area, applying at the dot location pretreatment agent having a second aggregating agent concentration that causes a diameter of the dot to decrease and the color density of the dot to be uniform.