US 7,119,821 B2 · Color thermal printer and color thermal printing method

Abstract

In a color thermal printer, printing units for each color image are disposed along transporting path of recording sheet. In each printing unit, a thermal head and a platen roller are provided. Recording sheet is pressed on the thermal head by the platen roller and thermal head executes heat recording on recording sheet. The platen roller is provided with a pulse encoder for detecting transporting speed fluctuation amount thereof. Sheet transporting correction quantity is determined from a relation with the transporting speed fluctuation amount. The sheet transporting correction quantity is serially accumulated for the length of the recoding area, to correct recording start position of the color image to print next. Therefore, occurrence of registration deviation caused from heat deformation of the platen roller is suppressed, thereby to obtain high quality printing.

Claims23

Dependent claims

A color thermal printer for recording full color image by recording one color image at each of printing units during transportation of a long recording sheet by a couple of transporting rollers, a plurality of said printing units being disposed along the transporting path, each of said printing units including a platen roller for supporting said long recording sheet, and a thermal head for executing thermal recording of each color image by pressing said recording sheet which is supported by said platen roller, said color thermal printer comprising:

a rotating speed detector disposed on at least one said platen roller for detecting rotating speed of the at least one said platen roller;
and
a controller for recording image by driving said thermal head of each printing unit when transporting quantity of said recording sheet transported by said transporting roller couple reaches target value corresponding to the recording start position, the controller calculating the transporting correction quantity of said recording sheet from the rotating speed fluctuation amount of the at least one said platen roller, to correct said target value so as to correspond to the recording start position of a directly downstream printing unit.

A color thermal printing method of recording full color image by recording one color image at each of printing units during transportation of a long recording sheet by a couple of transporting rollers, a plurality of said printing units being disposed along the transporting path, each of said printing units including a platen roller for supporting said long recording sheet, and a thermal head for executing thermal recording of each color image by pressing said recording sheet which is supported by said platen roller, said color thermal printing method comprising the steps of:

determining whether transporting quantity of said recording sheet by said transporting roller couple reaches target value corresponding to the recording start position;
when said transporting quantity reaches said target value, recording image by driving said thermal head of each printing unit;
detecting rotating speed of at least one said platen roller;
calculating the transporting correction quantity of the said recording sheet from rotating speed fluctuation amount of said platen roller;
and
correcting said target value so as to correspond to a recording start position of a directly downstream printing unit.

3 more elements

Dependencies are inferred from the claim text.

Color thermal printer and color thermal printing method

Life of this patent

Color thermal printer and color thermal printing method

Life of this patent

Abstract

Claims23