Apparatus and method for colour inket printing

Claim 1

An apparatus in which a print head (15K,15CMY) thereof executes a horizontal scanning and a vertical scanning on a surface of a print medium (1) for printing the surface of the print medium, the apparatus comprising: a dot formation element array (17K,17C,17M,17Y) having N dot formation elements (19 1 ,19 2 ,19 3 ,19 4 ) for forming dots of a single colour, said dot formation elements being arranged on a surface of the print head and facing the print medium at constant pitches (k) in the vertical scanning direction; horizontal scanning drive means (3) for executing the horizontal scanning of the print head; head drive means for driving said dot formation element array during the horizontal scanning; and vertical scanning drive means (9, 11) for executing the vertical scanning of the print head by a predetermined distance each time the horizontal scanning terminates; characterised in that the following conditions are satisfied; s is an integer between more than one and less than N, k is an integer between more than one and less than N, where k is not a factor of N/s and vice versa, and L = N/(s · D · k) ; wherein L is a vertical scanning pitch which is the distance of one vertical scanning, s is the number of scan repetitions which is the number of horizontal scanning repetitions required for printing a line continuous in a horizontal scanning direction, k is an element pitch which is a value representing a distance between centre points of the dot formation elements as a multiple of a dot pitch of a print image, and D is an element density which is the number of the dot formation elements existing per unit distance in said dot formation element array.

Claim 8

A method of printing on a surface of a print medium (1) with a print head (15K, 15CMY) having a dot formation element array (17K, 17C, 17M, 17Y) including N dot formation elements (19 1 , 19 2 , 19 3 , 19 4 ) for forming dots of a single colour arranged at constant pitches (k) in a vertical scanning direction, the method comprising the steps of: executing horizontal scanning of the print head; driving said dot formation element array during the horizontal scanning; executing vertical scanning of the print head by a predetermined distance each time the horizontal scanning terminates and characterised by further comprising the steps of: selecting s which is an integer between more than one and less than N; selecting k which is an integer between more than one and less than N such that k is not a factor of N/s and vice versa; and selecting L which satisfies the following equation, L = N/(s·D·k); wherein L is a vertical scanning pitch which is the distance of one vertical scanning, s is the number of scan repetitions which is the number of horizontal scanning repetitions required for printing a line continuous in a horizontal scanning direction, k is an element pitch which is a value representing a distance between centre points of the dot formation elements as a multiple of a dot pitch of a print image, and D is an element density which is the number of the dot formation elements existing per unit distance in said dot formation element array.

Claim 11

The method as claimed in any one of claims 8 to 10, wherein said step of driving said dot formation element array includes a step of driving said dot formation element array at intermittent timing corresponding to dots at intervals of (s-1) dots during the horizontal scanning.

Claim 13

The method as claimed in any one of claims 8 to 12, wherein said step of driving said dot formation element array includes a step of driving a plurality of dot formation element arrays for forming dots of different colours at different timings so that dots of different colours are formed at different dot positions.

Claim 14

The method as claimed in any one of claims 8 to 13, wherein said step of driving said dot formation element array includes a step of driving said dot formation element array for both go way and return way of the horizontal scanning, said step of executing the vertical scanning includes performing the vertical scanning by a given distance each time each of the go way and the return way terminates, wherein said step of selecting the number of scan repetitions s includes a step of setting a first even number as the number of scan repetitions s and said step of selecting the element pitch k includes a step of setting a second even number as the element pitch k.