GB2311257A - Multi-colour ink ribbon in a thermal transfer colour printer - Google Patents

Description

THERMAL TRANSFER PRINTER 2311257 The present invention relates to a

thermal transfer printer for printing a colour image on a recording medium.

Conventionally, a thermal transfer printer for printing an image on a cut sheet having a predetermined size (page length) has been known. Such a thermal transfer printer includes a paper feed mechanism, a thermal printing head, an ink sheet, and an ink sheet feed mechanism. If a colour image is to be printed on the recording sheet, the ink sheet is provided with a plurality of pages of different colours of ink which are sequentially arranged along the length (i.e., the feeding direction) of the ink sheet. Each page of the ink sheet is coated with, for example, one of yellow, magenta or cyan thermal transfer ink. The length of each segment of the ink sheet is equivalent to the page length of the recording sheet that is advanced through the thermal transfer printer by the paper feed mechanism.

In a printing process, first, for example, the paper feed mechanism and ink sheet feed mechanism advance both the recording sheet and a yellow page of the ink sheet which is overlapped on the recording sheet, by one page length to pass through the thermal printing head so that a yellow component of a desired image is transferred onto the recording sheet, and then the recording sheet is ejected. Next, the recording sheet is re-inserted in the printer, and the recording sheet is advanced again together with the ink sheet. This time, for example, a magenta page of the ink sheet is overlapped on the recording sheet and passes through the thermal printing head. Thus, a magenta component is transferred onto the same recording sheet. The recording sheet is ejected again, and then re-inserted in the printer again so that a cyan component of the image is transferred on the same recording sheet. Thus, a complete colour image can be formed on the recording sheet.

In this process described above for forming a colour image on one page of the recording sheet, the recording sheet is advanced past through the thermal printing head three times, and the ink sheet is fed by the amount corresponding to three pages, which is equal to the amount corresponding to three pages of the recording sheet. According to the above-described method, if the image to be formed on the recording sheet occupies only a part of a page of the recording sheet, although most part of each page is - 3 not used for forming the image, the Ink sheet will be advanced by three pages, which is a waste of the portions of the ink sheet. and the ink sheet is consumed quite quickly.

It is therefore an object of the present invention to provide an improved thermal transfer printer in which the consumption of the Ink sheet is varied in accordance with the image to be formed on a recording paper.

According to an aspect of the invention, there is provided a thermal transfer printer for forming a colour image on an effective page of a recording sheet, comprising:

an ink sheet, the ink sheet having a plurality of colour sets, each of the colour sets having a predetermined number of colour ink segments arranged in a predetermined order, a length of each of the colour ink segments being less than a length of the effective page; and an image forming system which forms the colour image on the effective page with use of one set of the plurality of colour sets of the ink sheet, wherein the colour sets are consumed only for areas on which the colour image is formed.

Optionally, a length of the colour segment may be 1IN of a length of the effective page of the recording sheet, where N is an integer greater than 1. Specifically, N may be equal to five.

Further optionally, the image forming system may comprise: a first feeding system which advances the recording sheet by an amount corresponding to a length of one of the plurality of areas; a second feeding system which only advances ink sheet by the amount corresponding to the length of one of the plurality of areas; a third feeding system which only reverses the recording sheet by the amount, wherein when the colour image is formed on one of the plurality of areas, the first and second feeding systems are actuated, and wherein when the colour image has been formed on one of the plurality of areas, the third feeding system is actuated.

Further, the plurality of colour segments may include yellow ink, magenta ink and cyan ink segments.

According to another aspect of the invention, there is provided a thermal transfer system, comprising: a recording sheet having an effective page on which a colour image is printed; and an ink sheet having a plurality of colour sets each having a plurality of colour ink segments arranged in a predetermined order along the lengthwise direction of the ink sheet, a length of each of the plurality of colour ink segments being shorter than a length of the effective page.

According to a turther aspect of the invention, there is provided an ink sheet for a thermal colour printer which forms a colour image on an effective page of a recording sheet, the ink sheet has a plurality of colour sets each having a plurality of different colour ink segments, a length of the colour ink segments in a direction where the recording sheet is fed being smaller than a length of the effective page.

According to further aspect of the invention, there is provided a method of printing a colour image on an effective page of a recording sheet with use of a thermal transfer printer having a thermal line head, comprising: feeding the recording sheet and a colour ink sheet by a predetermined length with actuating the thermal line head, the predetermined length being less than a length of the effective page of the recording sheet, the ink sheet having a plurality of colour sets each including a plurality of different colour ink segments, each of the colour ink segments having a length equal to the predetermined length; determining if the image has been formed on an area with use of one of the colour sets; reversely feeding only the recording sheet by the predetermined length if the image has not been formed on the area with use of all segments of one of the colour sets; further feeding only the recording sheet by the predetermined length; judging whether image is to be formed on at least one of subsequent areas of the recording sheet; repeating the feeding, determining, reversely feeding and further feeding steps if image is to be formed on at least one of the subsequent areas of the recording sheet; and ejecting the effective page of the recording sheet on which the colour image has been formed.

According to still further aspect of the invention, there is provided a thermal transfer printer for forming a colour image on a page of a recording sheet with use of an ink sheet, the page including a plurality of areas, the printer comprising: a first feeder for feeding the recording sheet; a second feeder for feeding the ink sheet; a printing system, the printing system driving the first and second feeder and executing a printing operation for each of the plurality of areas; determining system, which determines whether an image is to be formed on each of the plurality of areas; and a controlling system for controlling the printing system to execute the printing operation on an area when the determining system determines that the image is to be printed on the area, and for controlling the first feeder to feed the recording sheet by an amount corresponding to an area if the determining system determines that the image is not to be printed on the area.

According to a further aspect of the invention, there is provided a thermal transfer printer for forming a colour image on a page of a recording sheet with use of an ink sheet, the page including a plurality of areas, the printer comprising: a first feeder for feeding the recording sheet; a second feeder for feeding the ink sheet; a printing system, which drives the first and second feeder and executing a printing operation for each of the plurality of areas; a determining system, which determines whether an image is to be formed on remaining ones of the plurality of areas; and a controlling system for controlling the printing system to execute the printing operation if the determining system determines that the image is to be formed on the remaining ones of the plurality of areas of the page, and for controlling the first system to feed the recording sheet to eject the page from the printer if the determining system determines that the image is not to be formed on any one of remaining ones of the plurality of area of the page.

is Examples of the present invention will now be described with reference to the accompanying drawings, in which:- Fig.1 is a schematic view of a general arrangement of a thermal transfer printer of an embodiment of the invention; Fig.2 shows an arrangement of colour segments on an ink sheet; Fig.3 shows an area distribution on a page of recording sheet; Fig.4 is a flow chart of a control program for printing a colour image on recording sheet; and Fig. 5 is a flow chart illustrating a second embodiment.

Fig.1 is a schematic side view of a general arrangement of a thermal transfer printer 100 of an embodiment of the invention.

The thermal transfer printer 100 includes a sheet sensor 24, a platen roller 21, a thermal line head 22, an ink sheet take-up roller 15, and a controller 50. A recording sheet PP is loaded in the thermal transfer printer 100 from an inlet 101, and ejected from an outlet 102, a sheet feed path being defined between the inlet 101 and the outlet 102. An ink sheet IS is accommodated in a cartridge 20, and the cartridge 20 is detachably attached in the printer 100 as shown in Fig. 1.

The consumable ink sheet IS is fed from an ink sheet roller 23 to the take-up roller 15 such that the ink sheet IS passes over the thermal line head 22 in the area between the platen roller 21 and the thermal line head 22. It should be noted that the take-up roller 15 is connected to a one-way clutch mechanism (not shown), so that the take-up roller 15 cannot rotate in the direction opposite to a direction Indicted by an arrow in the drawing. Accordingly, a portion of the ink.sheet IS passed over the thermal line head 22 cannot move in the opposite direction. F%u-ther, the Ink sheet roller 23 is slightly biased such that the ink sheet does not loosen between the rollers 23 and 15. In other words, a certain tension is applied to the ink sheet IS between the rollers 15 and 23.

The sheet sensor 24, for example an optical sensor or the like, is provided for detecting whether the recording sheet PP has been loaded into the printer 100. If the sheet sensor 24 detects an absence of the recording sheet PP, printing operation will not be carried out.

The thermal line head 22 is positioned below the plate roller 21.

The thermal transfer printer 100 further includes a first drive motor NI for rotating the platen roller 21, a second drive motor M2 for rotating the take-up roller 15. The motors M1 and M2 are controlled to rotate by the controller 50. The first motor M1 is controlled to rotate the platen roller 21 in either direction indicated by an arrow A or B in Fig. 1, and the second motor M2 is rotated only in one direction to rotate the takeup roller in the direction indicated.by an arrow C.

When printing is executed, the platen roller 21 is - 10 rotated in a direction indicated by the arrow W, so that the recording sheet PP is advanced in a direction from an inlet 101 to an outlet 102. At the same time, the take-up roller 15 is rotated such that the ink sheet IS and the recording sheet PP proceed at the same speed in the same direction. While the recording sheet PP and the ink sheet IS proceed at an image forming position between the platen roller 21 and the thermal line head 22, the controller 50 drives the thermal line head 22 to transfer ink from the ink sheet IS to the recording sheet PP.

In this embodiment, the platen roller 21 can be rotated in the direction B so that the recording sheet PP is reversely fed. When the recording sheet PP is reversely fed, due to the one-way clutch mechanism, the take- up roller 15 does not rotate and therefore the ink sheet IS does not move. The reverse rotation of the platen roller 21, and reverse movement of the recording sheet PP will be described in detail later.

Fig. 2 shows the arrangement of colour segments on the ink sheet IS. The ink sheet IS includes, in this embodiment, a plurality of colour sets each having three colour segments, which are arranged in a predetermined order; e.g., yellow (Y), magenta (M), and cyan (C). The colour sets including the three colour segments are repeatedly provided along the lengthwise direction (the feeding direction) of the ink - 11 sheet IS such that the colours appear in the predetermined order as the ink sheet is fed from the ink sheet roller 23 to the take-up roller 15. The colour segments are rectangular having a longer dimension in the width direction of the ink 5 sheet IS and a length IL In the length (feeding) direction. Alternatively, colours other than those used in this example or additional colours,. for example, a black colour segment, may be additionally provided on the ink sheet IS depending on the desired type of printing.

Fig. 3 shows a page of the recording sheet PP. The recording sheet PP is a cut sheet, which is fed from the inlet 101 (see Fig. 1). An image is formed on a predetermined effective page on the recording sheet. The predetermined effective page of the recording sheet PP has an effective page length X which is a length of the effective page. For the purposes of control, each effective page of the recording sheet PP includes first to fifth areas which are arranged in the feeding direction (i.e., the lengthwise direction) of the recording sheet PP, and extend along the width direction of the recording sheet PP. Thus, each effective page of the recording sheet PP is divided equally by splitting lines D as shown in Fig. 3. Note that the splitting lines shown in Fig. 3 are not actually indicated lines on the recording sheet PP, but are merely imaginary. The length of each area along the feeding direction of the - 12 recording sheet PP is PL. The number of image pixels included in one image line is for example, 2400 dots, and number of the image lines in one effective page is, for example, 3000. That is, in this case, the number of image 5 lines for each of the first through fifth areas is 600.

The length of each area PL is identical to the length IL of each of the colour segments of the ink sheet IS in the longitudinal direction (i.e., feeding direction). In other words, the length of each colour segment where a single colour ink is provided is shorter than the effective page length of the recording sheet PP. In this embodiment, the length of each colour segment is one-fifth of the length of the effective page length. However, the length of the colour segments may be altered to another value. In such a case, the length of the each segment is preferably 1IN (where N is an integer) of the effective page length X of the recording sheet PP.

In a printing process, the recording sheet PP is fed into the thermal transfer printer 100, passes the paper sensor 24, and then is fed. at the same time as the Y colour segment of the ink sheet IS, to the area between the platen roller 21 and the thermal line head 22. As the recording sheet PP and the ink sheet IS are fed by a length PL (the same as the length IL), the Y component of the image data corresponding to the first area is printed. After the Y component of the Image has been printed, the platen roller 21 is rotated in the direction 'B" with use of the first motor M1 so that the.recording sheet PP Is reversely fed by the length PL. While the recording sheet PP is reversely fed by 5 the platen roller 21, since the one-way clutch mechanism is Implemented as mentioned before. the ink sheet IS is not reversely fed. and stays at the same position. since a slight tension is applied to the ink sheet IS, the ink sheet IS Is not loosened when the recording sheet PP is reversely fed. It should be noted that the ink sheet IS is a thermal transfer ink sheet IS and the ink is transferred onto the recording sheet PP only when heat is applied thereto. Therefore, although the recording sheet PP keeps contacting the ins sheet IS while the recording sheet PP is reversely fed, the ink is not transferred on the portion of the recording sheet PP which passing through the area between the thermal line head 22 and the platen roller 21. After the recording sheet PP has been reversely fed by the length PL, the recording sheet PP and the next segment (M colour segment) of the ink sheet IS are advanced by the length PL, such that the M image component is printed on the first area of the recording sheet PP. Again, only the recording sheet PP is then reversed by a length PL, and then the C image component is printed on the first area on which the Y image component and the M image component have already been formed. Thereafter, as necessary, similar processes are carried out on the second area, third area, fourth area and fifth area. Accordingly, the complete colour image is formed on an area basis (area by area).

Fig.4 is a flow chart illustrating a process executed by the controller 50 for printing colour images on the recording sheet PP. The process is commenced by, for example, pressing an operation button (not shown) after the recording sheet PP has been loaded into the thermal transfer printer 100. The initial position of the recording sheet PP is such that the leading edge of the recording sheet PP is positioned on a downstream side of the thermal line head 22 by a predetermined amount such that the leading edge of the effective page is located at the thermal line head 22. When printing is executed, the platen roller 21 is driven to rotate in the direction of the arrow uAO so that the recording sheet PP is forwardly fed (advanced).

Simultaneously with the forward movement of the recording sheet PP, the ink sheet IS is also advanced by the take-up roller 15.

In step S101, a counter n corresponding to the number of colour segments is cleared. In the embodiment, the counter n takes the values 0, 1 and 2 respectively corresponding to the Y, M and C colour segments. In step S103, the controller 50 25 judges whether image data of one colour component - 15 equivalent to 600 lines (i.e., image data for one printing area) has been stored in a buffer (not shown) provided in the thermal transfer printer 106. If the image data has not been received (NO at step S103), control loops to wait for the receipt of the image data. When the counter n is 00 Y image data is transferred from an image processing device to the thermal transfer printer. Similarly, when the counter n is 1, N image data is transferred, and when the counter n is 2, C image data is transferred. When image data equivalent to 600 lines has been stored in the buffer (YES at step S103), the image data is printed in step S104.

In step 1040 the first and second drive motors M1 and M7 are driven such that both the recording sheet PP and the ir sheet IS are moved forward a length PL (length IL) in the lengthwise direction (i.e., the sheet feed direction) in synchronization with each other. At the same time, the thermal line head 22 is driven to thermally transfer the coloured ink from the ink sheet IS to the current one of the five areas of the recording sheet PP. 20 In step S105, after the recording sheet PP and the ink sheet IS have been moved by the length PL, the first and second drive motor M1 and M2 are stopped such that the recording sheet PP and the ink sheet IS stop moving. In step S108, the first drive motor M1 is driven in the direction B in Fig. 1 to move the recording sheet PP - 16 backward by the length PL. As mentioned before, during the reverse movement of the recording sheet. the ink sheet IS remains in place.

In step 5110, it is judged whether all image data relating to the first through fifth areas of the current effective page X is completed. If the printing has not been completed in at least one of the remaining areas of the first through fifth areas (NO at step S110), the counter n is increased by 1 in step S112. In step S114, the controller 50 judges whether the counter n has reached 3. If the value of the counter n has not reached 3 (NO at step S114), the printing of each colour of ink has not been completed for the current one of the first through fifth areas. Thus, when the counter n is not equal to 3 at S114, control proceeds to step S103 and the above operations are repeated, except that the ink sheet IS is positioned such that the subsequent printing is performed using the next colour segment of the ink sheet IS. The process repeats until the counter n equals 3 at step S114.

When the counter n equals 3 at step S114, the printing of each of the Y, M, and C colour ink for the current one of the first through fifth areas has been completed. At this point (YES at step S114), control moves to step S116, in which only the first drive motor M1 is driven to rotate the platen roller 21 such that the recording sheet PP is moved - 17 forward by the length PL. Note that when only the first drive motor M1 in driven, the ink sheet IS does not move and only the recording sheet PP is fed forward. In order to ensure that the ink sheet 15 is not fed when only the first drive motor M1 is driven, a lock mechanism for locking the movement of the ink sheet roller 23 may be employed.

After step S116. control returns to step S101 in order to perform printing for the next one of the first through fifth areas.

The process repeats until it is determined, at step Silo, that all of the image data for all of the first to fifth areas has been printed, i.e., the image forming on all of the first to fifth areas has been finished, or there is no image data to be printed on any one of remaining areas of the first through fifth areas (YES at step Silo). The controller 50 then proceeds from step Silo to step S118. In step S118, the first drive motor Mi is driven to rotate the platen 21 such that the recording sheet PP is fed forward until the recording sheet PP is completely ejected from the outlet of thermal transfer printer 100. Thereafter, the process for printing control then finishes or alternatively, loops to wait for the next operation of the thermal transfer printer 100.

As described above, with the first embodiment, in a case where an image is to be formed only on a part of one effective page, the ink sheet IS is consumed for only the image part, in contrast with the prior art where a full colour ink sheet would be used in respect of each colour printed. Therefore, it is possible to prevent the ink sheet material from being used meaninglessly. Further, printing operation is not executed for the part which does not include image to be printed, and the recording sheet PP is ejected as soon as the image to be printed is finished.

Although, the embodiment described above deals with printing colour images on a cut sheet type recording sheet PP, the recording sheet PP described may alternatively be some other form of recording sheet such as a continuous form, a transparency for overhead projectors, or the like.

As described above, according to the invention, even in a case where image is to be formed only on a part of one page, the ink sheet can be effectively utilized.

Although the structure and operation of a thermal transfer printer is described herein with respect to the preferred embodiment, many modifications and changes can be made without departing from the scope of the invention.

Fig. 5 shows a second embodiment. In the second embodiment, printing operation of the thermal transfer printer 100 is modified. Since forming of the colour image on each area of the recording sheet PP is performed in the similar manner as is done in the first embodiment, detail - 19 description on the function of the thermal printer 100 is omitted.

When printing starts, the controller 50 determines whether the current area has an image to be printed at S201. If no image is to be formed on the current area (No at step S201), only the recording sheet PP is fed by the length PL at S202, and the ink sheet IS stays in place. If there is image to be printed on the current area of the recording sheet PP (YES at S201), printing of the image on the area is performed at S203.

At S204, the controller 50 determines whether all the image data is printed. If there is no image to be printed on the remaining areas, i.e., all the image data has been printed (YES at S205), the recording sheet PP is discharged (S205). If the image data to be printed remains (NO at S204), control returns to S201 and the above-described process is repeated.

According to the second embodiment, for example, if the image is to be formed on the first and fifth areas. the ink sheet IS is consumed only for the first and fifth areas, and for the second to fourth areas only the recording sheet PP fed, and ink sheet IS is not fed. Since the printing operation for the second through fourth areas are skipped, and for these areas,.only the recording sheet PP is fed with the ink sheet IS remaining in place, the ink sheet IS is not - 20 meaninglessly consumed, and printing operation is finished quickly.

Claims (18)

CLAIMS:-

1. A thermal transfer printer for forming a colour image on an effective page of a recording sheet, comprising.. an ink sheet, said ink sheet having a plurality of colour sets. each of said colour sets having a predetermined number of colour ink segments arranged in a predetermined order. a length of each of said colour ink segments being less than a length of said effective page; and an image forming system for forming said colour image on one or more of a plurality of areas of said effective page, using one set of said plurality of colour sets of said ink sheet for each said area.

2. A thermal transfer printer according to claim 1, wherein a length of said colour segment is 1IN of a length of said effective page of said recording sheet, where N is an integer greater than 1.

3. A thermal transfer printer according to claim 2, wherein N is equal to five.

4. A thermal transfer printer according to any preceding claim, wherein saidImage forming system comprises:

22 a first feeding system for advancing said recording sheet by an amount corresponding to a length of one of said plurality of areas; a second feeding system for advancing only the ink sheet by said amount corresponding to said length of one of said plurality of areas; and a third feeding system for reversing only said recording sheet by said amount, wherein when said colour image is formed on one of said plurality of areas, said first and second feeding systems are actuated, and wherein when said colour image has been formed on one of said plurality of areas, said third feeding system is actuated.

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5. A thermal transfer printer according to any preceding claim, wherein said plurality of colour segments include yellow ink, magenta ink and cyan ink segments.

6. A thermal transfer printer according to any preceding claim wherein said colour sets are consumed only for areas on which said colour image is formed.

7. A thermal transfer system, comprising: 25 a recording sheet having an effective page on which a colour image Is printed; and an ink sheet having a plurality of colour sets each having a plurality of colour ink segments arranged in a predetermined order along the lengthwise direction of said ink sheet, a length of each of said plurality of colour ink segments being shorter than a length of said effective page.

8. An ink sheet for a thermal colour printer which forms a colour image on an effective page of a recording sheet. said ink sheet having a plurality of colour sets each having a plurality of different colour ink segments.

9. A method of printing a colour image on an effective page of a recording sheet using a thermal transfer printer having a thermal line head, comprising: feeding the recording sheet and a colour ink sheet by a predetermined length whilst actuating the thermal line head, the predetermined length being less than a length of the effective page of the recording sheet, the ink sheet having a plurality of colour sets each including a plurality of different colour ink segments, each of the colour ink segments having a length equal to the predetermined length; determining if formation of the image has been completed on an area of the recording sheet using one of the colour sets; reversely feeding only the recording sheet by the predetermined length if formation of the image has not been completed on the area with use of all segments of one of the colour sets; further feeding only the recording sheet by the predetermined length; judging whether the image is to be formed on at least one of subsequent areas of the recording sheet; repeating the feeding, determining, reversely feeding and further feeding steps if the image is to be formed on at least one of the subsequent areas of the recording sheet; and ejecting the effective page of the recording sheet on which the colour image has been formed.

10. A thermal transfer printer for forming a colour image on a page of a recording sheet using an ink sheet, said page including a plurality of areas, said printer comprising: a first feeder for feeding said recording sheet; a second feeder for feeding said ink sheet; 20 a printing system for driving said first and second feeder and executing a printing operation for each of said plurality of areas; a determining system, which determines whether an image is to be formed on each of said plurality of areas; and 25 a controlling system for controlling said printing system to execute said printing operation on an area when said determining system determines that the image is to be printed on the area, and for controlling said first feeder to feed said recording sheet by an amount corresponding to an area if said determining system determines that the image is not to be printed on said area.

11. A thermal transfer printer for forming a colour Image on a page of a recording sheet using an ink sheet, said page including a plurality of areas, said printer comprising:

first feeder for feeding said recording sheet; second feeder for feeding said ink sheet; printing system, for driving said first and second feeder and executing a printing operation for each of said plurality of areas; a determining system, for determining whether an image is to be formed on remaining ones of said plurality of areas; and a controlling system for controlling said printing system to execute said printing operation if said determining system determines that the image is to be formed on said remaining ones of said plurality of areas of said page, and for controlling said first system to feed said recording sheet to eject said page from said printer if said determining system determines that the image is not to be - 26 formed on any one of remaining ones of said plurality of area of said page.

12. A method of printing a colour image on a recording 5 sheet, the method comprising:- (a) repeatedly feeding said recording sheet past a thermal line head; and (b) feeding an ink sheet, formed with a number of colour ink segments along its length, between the thermal line head and the recording sheet; wherein (a) and (b) are coordinated such that the colour ink segment provided at the thermal line head is varied for different passes of the recording sheet.

13. A method according to claim 12, wherein the image is printed in a number of consecutive sections, the repeated feeding of the recording sheet being carried out in respect of one section until printing for that section is complete, the recording sheet then being advanced for printing of a next section.

14. A method according to claim 13, wherein the recording sheet is advanced past any sections which do not require printing, with the i - nk sheet being held stationery.

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15. A cartridge for housing the ink sheet according to claim 8.

16. A thermal transfer printer substantially as hereinbefore 5 described with reference to the accompanying drawings.

17. An ink sheet substantially as hereinbefore described with reference to the accompanying drawings.

18. A method of printing a colour image substantially as hereinbefore described with reference to the accompanying drawings.

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