Data processing method of printing apparatus and the printing apparatus

1. A data processing method of a printing apparatus for printing a multi-color image on a printing medium by a first printing head and a second printing head while transporting the printing medium relative to the first printing head and the second printing head in a printing medium-feed direction, the first printing head being disposed upstream of the printing medium-feed direction and the second printing head being spaced away from the first printing head and being disposed downstream of the paper-feed direction, the method comprising:

a skew detecting step of detecting a degree of skew of the printing medium;

a correction printing-data generating step of shifting print data for performing multi-color image printing for every printing color in a locatable area in a direction orthogonal with respect to the medium-feed direction in accordance with the degree of skew to generate correction printing-data, the locatable area being set for locating the print data for the every printing color; and

a printing step of performing printing on the printing medium with the first printing head and the second printing head in accordance with the correction printing-data,

wherein in the correction printing-data generating step, the locatable area being set wider than a locatable area with no skew, and a shift amount of the first printing head being larger than a shift amount of the second printing head in the printing medium-feed direction and the direction orthogonal with respect to the printing medium-feed direction.

2. The data processing method of the printing apparatus according to claim 1 , wherein

in the correction printing-data generating step, the correction printing data printed by the second printing head is shifted more largely than the correction printing data printed by the first printing head in a skewed direction of the printing medium in accordance with the degree of skew of the printing medium.

3. The data processing method of the printing apparatus according to claim 2 , wherein

in the correction printing-data generating step, the correction printing data printed by the second printing head is shifted more largely than the correction printing data printed by the first printing head in the medium-feed direction in accordance with the degree of skew of the printing medium.

4. The data processing method of the printing apparatus according to claim 3 , wherein

in the correction printing-data generating step, the correction printing data printed by the second printing head is shifted more largely than the correction printing data printed by the first printing head in the medium-feed direction and the direction orthogonal with respect to the medium-feed direction by a distance in accordance with the degree of skew.

5. The data processing method of the printing apparatus according to claim 4 , wherein

the skew detecting step is performed by a first sensor and a second sensor sandwiching the first print head and the second print head for detecting positions of side ends of the printing medium.

6. The data processing method of the printing apparatus according to claim 1 , wherein in the correction printing-data generating step, when the degree of skew is high, the locatable area corresponding to the correction printing data printed by the second printing head is shifted more largely than the locatable area corresponding to the correction printing data printed by the first printing head in the medium-feed direction and the direction orthogonal with respect to the medium-feed direction in consideration of the degree of skew.

7. The data processing method of the printing apparatus according to claim 1 , wherein the printing medium includes a long printing medium.

8. A printing apparatus for printing a multi-color image on a printing medium, the apparatus comprising:

a printing unit having a first printing head disposed at an upstream end in a medium-feed direction and a second printing head spaced away from the first printing head in a downstream end in the medium-feed direction, the printing unit enabling at least two-color printing;

a transport section for transporting the printing medium relative to the printing heads in the medium-feed direction;

a skew detecting section for detecting a degree of skew of the printing medium in the transport section; and

a correction printing-data generating section for shifting print data from the printing unit for performing multi-color image printing for every printing color in a locatable area in the direction orthogonal with respect to the medium-feed direction in accordance with the degree of skew to generate correction printing-data and output the correction printing-data into the printing unit, the locatable area being set for locating the print data for the every printing color, the locatable area being set wider than a locatable area with no skew, and a shift amount of the first printing head being larger than a shift amount of the second printing head in the printing medium-feed direction and the direction orthogonal with respect to the printing medium-feed direction.

9. The printing apparatus according to claim 8 , wherein

the correction print data generating section shifts the correction printing data printed by the second printing head more largely than the correction printing data printed by the first printing head in a skewed direction of the printing medium in accordance with the degree of skew of the printing medium.

10. The printing apparatus according to claim 9 , wherein

The correction printing-data generating section shifts the correction printing data printed by the second printing head more largely than the correction printing data printed by the first printing head in the medium-feed direction in accordance with the degree of skew of the printing medium.

11. The printing apparatus according to claim 10 , wherein

The correction printing-data generating section shifts the correction printing data printed by the second printing head more largely than the correction printing data printed by the first printing head in the medium-feed direction and the direction orthogonal with respect to the medium-feed direction by a distance in accordance with the degree of skew.

12. The printing apparatus according to claim 11 , wherein the skew detecting section includes a first sensor and a second sensor sandwiching the first print head and the second print head for detecting positions of side ends of the printing medium.

13. The printing apparatus according to claim 8 , wherein when the degree of skew is high, a correction printing-data generating section shifts the locatable area corresponding to the correction printing data printed by the second printing head more largely than the locatable area corresponding to the correction printing data printed by the first printing head in the medium-feed direction and the direction orthogonal with respect to the medium-feed direction in consideration of the degree of skew.

14. The printing apparatus according to claim 8 , wherein the printing medium includes a long printing medium.