JP2002011864A - Inkjet printer - Google Patents

Abstract

(57) [Summary] [Object] To provide an ink jet printing apparatus for printing a proper image on both sides at high speed. A line type printer (30) includes a pair of transport rollers (31a, 31b) for transporting a sheet (26) and a sheet (26).
And an upper head 32 and a lower head 33 provided to face each other. The upper head 32 and the lower head 33 include a print head having a print element corresponding to substantially the entire width of the paper 26 in the main scanning direction, and an ink supply device for supplying ink to the print head. The ejection nozzles 34 of the same nozzle number of the upper head 32 and the lower head 33 are arranged at positions corresponding to each other via the paper 26 so as to face each other. Lands at the same position on both sides. After printing on one side, the printing timing on the front and back sides may be made different so that the other side is printed before waving of the paper surface occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printing apparatus for printing an image on both sides appropriately and at high speed.

[0002]

2. Description of the Related Art In recent years, ink jet printers have been widely used. Printers using the inkjet system include a piezo system in which ink droplets are ejected by deformation of a piezoresistive element (piezoelectric element) and a thermal jet system in which ink droplets are ejected by the force of generating film bubbles. Furthermore, the thermal jet method has two types of configurations depending on the direction of ink droplet ejection, and one is called a side shooter type in which ink droplets are ejected in a direction parallel to the heating surface of the heating element. The other is called a roof shooter type or a top shooter type in which ink droplets are ejected in a direction perpendicular to the heat generating surface of the heat generating element. It is known that a printer equipped with a roof shooter type print head requires extremely low power consumption and is economical.

[0003] As a small printer used personally at home, a relatively simple carriage-moving printer is mainly used and widely used. A carriage-moving printer is a printer in which a small print head and an ink cartridge are integrally mounted on a carriage, and the carriage reciprocates in the width direction of the paper while printing characters and images on the surface of the paper conveyed vertically. Print (print).

FIG. 5A is a perspective view schematically showing the structure of such a carriage moving type printer.
(b) is an enlarged view from the paper side when the print head shown in FIG. (a) is for monochrome printing (enlarged view from arrow A in FIG. (a)), and FIG. FIG. 3 is an enlarged view as viewed from an arrow A when the print head shown in FIG.

As shown in FIG. 1A, a printer 1 is provided with a print head 3 for performing printing on a carriage 2 and an ink cartridge 4 containing ink. The carriage 2 is slidably supported on one side by a guide rail 5 and is fixed to a toothed drive belt 6 on the other hand.

As a result, the print head 3 and the ink tank 4 are reciprocated in the width direction of the apparatus main body (printer 1) indicated by a double-headed arrow B in the drawing, ie, in the main scanning direction of printing. A flexible communication cable 7 is connected between the print head 3 and a control device (not shown) of the apparatus main body, and print data and a control signal are sent from the control device to the print head 3 via the flexible communication cable 7.

A platen 9 is disposed at the lower end of the frame 8 of the apparatus main body so as to face the print head 3 and extend in the reciprocating direction of the print head 3 indicated by a double-headed arrow B in the drawing. . The sheet 11 comes into contact with the platen 9 so that the paper feed roller pair 12 (the lower roller is shaded by the paper 11 and cannot be seen in the drawing) and the paper discharge roller pair 13 (the lower roller is similarly shaded. ), The sheet is intermittently conveyed in the printing sub-scanning direction indicated by arrow C in FIG.

During the intermittent conveyance stoppage of the sheet 11,
The print head 3 is driven by the motor 14 by the toothed drive belt 6.
While being driven via the carriage 2, the ink is ejected in proximity to the paper 11 and printed on the paper surface. This paper 1
Printing can be performed on the entire surface of the paper 11 by repeating the intermittent conveyance 1 and the printing during the reciprocating movement by the print head 3.

The print head 3 may be a piezo type print head using the above-described piezo element or a thermal type print head utilizing the growth force of film bubbles. When the print head is for monochrome printing, a single nozzle row 15 for performing printing by discharging ink is formed on the ink discharge surface, as in a print head 3 'shown in FIG. Have been.

In one nozzle row 15, depending on design reasons, about 64, 128 or 256 discharge nozzles 16 are arranged vertically in one row at a density of, for example, 300 per 25.4 mm. They are arranged side by side. Ink is supplied from the ink tank 4 to these ejection nozzles 16.

When the print head is for full-color printing, the printing is normally performed by discharging ink on the ink discharge surface, as in a print head 3 ″ shown in FIG.
Nozzle row 17 (17y, 17m, 17c, 17b)
k) is formed. These four nozzle rows 17
The yellow (y), magenta (m), cyan (c) and black (bk) inks are respectively discharged. Also in this case, 64, 128 or 256 ejection nozzles 18 are arranged in one nozzle row 15.

FIGS. 6 (a) and 6 (b) are plan views showing the appearance of a print head for a line type printer having a printing element corresponding to almost the entire width of the paper in the main scanning direction. FIG. 1B shows a print head, and FIG. 2B shows a full-color print head. In the monochrome print head 20 shown in FIG. 5A, element chips 21 having substantially the same configuration as the print head 3 'shown in FIG. 5B are alternately arranged in a staggered manner in the longitudinal direction of the parent substrate 22. It is configured. Such a long monochrome print head 20 is fixed to the printer main body, and the paper is transported in the sub-scanning direction indicated by arrow D in the drawing.

A full-color print head 23 shown in FIG. 5B includes an element chip 24 having substantially the same configuration as that of the print head 3 ″ shown in FIG. And are arranged alternately in a staggered pattern.
The full-color print head 23 is also fixed to the printer main body, and the paper is transported in the sub-scanning direction indicated by the arrow E in the drawing.

As described above, the long monochrome print head 20 (or the full-color print head 23) is not formed as one chip but is formed by using a plurality of element chips. This is because there is a limit to the size of the print head chip to be produced. Even if a large single-crystal silicon wafer is obtained, the number of long print heads that can be formed along the diameter of the silicon wafer is limited because the silicon wafer is round, and the yield is extremely poor. Impractical from.

Recently, however, a technique for forming a print head on a glass substrate instead of a silicon wafer has been developed. In this case, the print head 3 'shown in FIG.
Alternatively, it is also possible to realize an inexpensive long print head having a simple structure in which the shape of the print head 3 ″ shown in FIG.

In general, when printing on paper, it is more convenient to print on only one side, so single-sided printing has been the mainstream for a long time. However, printing on only one side of the paper in such a way is uneconomical on the white background, and the consumption of wood, which is the raw material of the paper, is doubled compared to printing on both sides. Double-sided printing is often performed for the purpose.

In order to perform such double-sided printing with a printer or a copying machine (hereafter, only the printer will be described), printing is performed on the front side (one side) of the sheet, and the sheet waits until the surface is fixed (dried). Using an automatic reversing mechanism (in the case of a large machine), or ejecting paper once and then manually (in the case of a small machine), reversing the paper, printing on the back side (other side) of the paper Double-sided printing is performed by a work process. That is, the print head is located on only one side of the paper,
The paper is turned over and printing is performed on both sides.

If the above-mentioned steps are omitted, there is a problem that one of the printing surfaces, for which printing has just been completed, is stained with incompletely fixed ink, so that the steps cannot be omitted.

[0019]

By the way, in an electrophotographic printer or a thermal transfer printer, a printed image is fixed on paper at the same time as printing is completed. Therefore, even when performing double-sided printing, printing on one side is completed. It is possible to immediately shift to printing on the other side, and the time required for the above process is almost zero, and there is no particular problem.

However, in the ink jet type printer, it takes a relatively long time from when printing is completed to when the printed image is fixed on the paper (the printing ink is completely dried). Since a relatively long time is required, there is a problem that double-sided printing is not practical.

For example, the time from when printing is performed to the time when the ink is fixed immediately after printing when using general OA paper in an ink jet printer is several times after the printing ink lands on the paper surface when the slow penetrating ink is used. It takes about 10 seconds to start permeating the paper in milliseconds and complete fixation. Further, even when the super-penetrating ink is used, it takes 100 to 200 μsec after the printing ink lands on the paper surface to start penetrating into the paper, and it takes several tens of meters to complete the permeation.
Seconds, and several hundred milliseconds until it is completely fixed. Therefore, as an office printer used in a busy office, time efficiency is poor and cannot be used for duplex printing.

However, when used personally at home, the length of waiting time in the process is not unbearable. However, when actually performing double-sided printing, another problem occurred. Originally, recent inkjet printers form extremely high-definition images that far surpass silver halide photographs, and the high-definition images are also a distinctive advantage of inkjet printers. Such high-definition images cannot be printed on the back side of duplex printing. That is, it was found that a high-definition image was printed on the first side (front side), but a defective image was printed on the other side (back side) for some reason. In pursuit of this cause, a cause of occurrence of a defective image peculiar to an ink jet printer was found.

FIGS. 7A to 7D are diagrams schematically showing basic microscopic operations from landing of ink droplets discharged from a discharge nozzle on a paper sheet to fixing in an ink jet printer. . FIGS. 8A to 8D are diagrams for explaining a problem that adversely affects double-sided printing that occurs on a printing surface in an ink jet printer.

First, in FIGS. 7 (a) to 7 (d), FIG.
As shown in FIG. 1, the print head (the print head 3 'in FIG.
The print head 3 ″ shown in FIG. 2C, the monochrome print head 20 shown in FIG. 2A or the full-color print head 2 shown in FIG.
The ink droplets 27 ejected toward the sheet 26 from (3, the same applies hereinafter) land on the sheet 26 as shown in FIG. 7B.

The ink droplets 27 landed on the paper 26
Is caused by the capillary phenomenon as shown in FIG.
Start infiltration into. In the same figure (c), the unpenetrated part 27-1
Are shown in white, and the permeated portion 27-2 is shown in satin. All the landing ink droplets 27 eventually penetrate into the paper 26 and are fixed, as shown in FIG.

When the state of the sheet from the time when the ink droplet lands on the sheet to the time when it is fixed is macroscopically observed by setting a rather wide printing range in FIGS. 8 (a) to 8 (d), first, FIG.
As shown in (a), a printing surface having a length W of one side on the paper 26 is assumed. W = 25.4 mm, that is, the printing surface to be observed is 25.4 mm × 25.4 mm, and the printing resolution is 2
If printing is performed at a printing rate of 100% with 600 dots per 5.4 mm, the above-mentioned 25.4 mm × 25.4 m
On the printing surface of m, ink droplets of 600 × 600 = 360,000 are ejected.

FIG. 2B shows a state immediately after 360,000 ink droplets have landed on the paper 26. 2 above
360,000 on a 5.4 mm x 25.4 mm printing surface
A group of printing inks 28 formed by landing ink droplets is formed. After a predetermined period of time has elapsed after the ink droplets land, the group of printing inks 28, as shown in FIG.
Infiltration into the inside starts (see the non-penetrated portion 28-1 and the penetrated portion 28-2), and then the sheet 26 as shown in FIG.
The ink completely penetrates into the ink and is fixed as the fully penetrated ink 28-3. Then, as shown in FIG. 6D, a undulation occurs on the printing surface of the sheet 26. This waving is not eliminated even after the printing ink is completely dried.

When printing on the other side in double-sided printing, the paper 2 having a sharply undulating surface, which is wavy as described above, is used.
6, the printing device that forms a high-definition image with high accuracy, such as an ink jet printer, cannot correctly reproduce the image on such a wavy paper surface. . This is the reason why a defective image having uneven printing is printed on the other surface during double-sided printing in an ink jet printer.

As described above, the waving phenomenon of the printed paper is a characteristic peculiar to the ink jet printer due to the penetration of the ink droplets into the paper. Was thought to be impossible to avoid. SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet printing apparatus that prints an image on both sides appropriately and at high speed in view of the above-mentioned conventional circumstances.

[0030]

The construction of the ink jet printing apparatus according to the present invention will be described below. The inkjet printing apparatus of the present invention includes a conveying unit that conveys a sheet, a first printing unit provided to face the surface of the sheet conveyed by the conveying unit, and the sheet conveyed by the conveying unit. A second printing unit provided to face the rear surface of the first printing unit, and control means for controlling the first printing unit and the second printing unit, wherein the control means is provided by the second printing unit. The first printing unit and the second printing unit so that a printing position on the back surface of the paper is coincident with a printing position on the front surface of the paper by the first printing unit through the paper. It is configured to control the unit.

After the control means prints on the paper by means of the first printing unit, the second printing unit determines the printing time of the first printing unit. The print control is performed so that the time for delaying the printing timing by the first printing unit falls within the time shorter than the time until the waving occurs at the printing position of the paper due to the influence of the printing ink by the first printing unit. .

The first printing unit and the second printing unit each include a printing element corresponding to substantially the entire width of the paper in the main scanning direction. In this case, for example, the sheets may be arranged at a predetermined distance in the sub-scanning direction of the sheet.

The first printing unit and the second printing unit are carriage moving type printing units in which the printing unit moves in the main scanning direction of the paper, respectively. Is done. Also,
For example, as set forth in claim 6, a transporting means for transporting the paper, and a carriage moving type provided so as to face the surface of the paper transported by the transporting means and a printing unit moves in a main scanning direction of the paper. A first printing unit, and a sheet provided in the sub-scanning direction facing the back surface of the sheet conveyed by the conveying unit with respect to the first printing unit, and a position in the sub-scanning direction relative to the first printing unit. And a second printing unit of a carriage moving type in which a printing unit moves in the main scanning direction of the paper, and is printed on the paper by the first printing unit. Thereafter, the time for delaying the printing timing of the second printing unit from the printing timing of the first printing unit is set to be longer than the above-mentioned time due to the influence of the printing ink by the first printing unit. And control means for performing printing control so as to fall within a time shorter than the time until the waving occurs at the printing position of the first printing unit, and the first printing unit and the second printing unit are, for example, As described in claim 7, the positions in the sub-scanning direction may be arranged to be separated from each other by a predetermined distance.

[0034]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view schematically showing a configuration of a main part of the line type printer according to the first embodiment, and FIG. 2 is a sectional view taken along the line FF 'in FIG.

As shown in FIGS. 1 and 2, the line type printer 30 includes a pair of transport rollers 31 (31a, 31b) as transport means for transporting the sheet 26, and a sheet 26 transported by the pair of transport rollers 31. And a lower head 33 as a second printing unit also provided opposite the back surface of the paper 26.

The above upper head 32 and lower head 33
Includes a print head similar to that shown in FIG. 6 (a) (of course, it may be a long integrated print head formed on a glass substrate) on a surface facing the paper 26. And an ink supply device for supplying ink to the printer. Further, the above-mentioned print head has 2,000 ejection nozzles 34 (see FIG. 2) as printing elements, respectively.
Are provided corresponding to substantially the entire width in the main scanning direction.

The upper and lower heads 32 and 33 have the same nozzle numbers (P1, P2,..., P2000) for the discharge nozzles 34 (the simplified sectional view in FIG. (Only the position is shown), a control pulse is supplied from a control device (not shown) so that the ink 35 is ejected at the same timing.

In the arrangement of the discharge nozzles 34,
The ejection nozzles 34 of the same nozzle number of the upper head 32 and the lower head 33 are arranged in the same manner on the paper 26 (a position where they coincide with each other with the paper 26 interposed therebetween). As a result, the ink droplets 35 ejected from the ejection nozzles 34 of the same nozzle number of the upper head 32 and the lower head 33 land at exactly the same position except for the difference between the front and back of the paper 26.

FIG. 3 is a diagram showing a configuration of a drive circuit of the upper head 32. The drive circuit for the lower head 33 has the same configuration. The drive circuit 36 transfers print data by a block transfer method. That is, first, the print data signal D is set in the shift register circuit 37, and the output of the shift register circuit 37 is taken into the latch circuit 38 by the latch signal L synchronized with the print cycle CK.
The output of the latch circuit 38 and the strobe signal Stb (Stb
0, Stb2,..., Stb9);
The heating elements are driven to generate heat for each of the 0 groups.

In this example, the nozzle row composed of 2000 ejection nozzles 34 is divided into groups of 200 nozzles, and the nozzle numbers P1 to P100 are group 39-0, the nozzle numbers P101 to P200 are group 39-1,. .., Nozzle numbers P1901 to P2000 are grouped into groups 39-9 and divided into ten groups.

For each group, one pulse of the above strobe signal Stb (Stb0, Stb0)
2,..., Stb9), and the printing order of the reprint data signal D is determined by the strobe signal Stb. In this example, group 39-0, group 39-
In accordance with the print data signal D set in the shift register circuit 37, the transistor 42 is driven via the AND circuit 41 in the order of 1,..., 39-9, whereby the heating element 43 is driven to generate heat.

Although not particularly shown, the heating element 43 is, for example, a resistor film having a thickness of 5000 mm and an area of 25 × 25 μm. The driving power supply voltage VH is supplied from the common wiring electrode 44 to the heating element 43. Heat is generated according to D. The heating element 43 is always supplied with ink, and the heat generated by the heating element 43 instantaneously generates and grows a film bubble at an interface between the heating element 43 and the ink. Due to the growth pressure of the film bubble, the surrounding ink is pushed out from the discharge nozzle 34 shown in FIG. 2 formed to face the heating element 43 and is discharged as an ink droplet 35 to the outside.

By performing the above control, the paper 26
The ink droplets 35 can be landed on the front and back sides at the same timing and at the same position (a position where they face each other via the paper 26). At the moment when the ink droplet 35 lands on the front and back of the paper 26, the ink (see the printing ink group 28 in FIG. 8B) has not yet penetrated the paper 26.
No waving occurs on the front and back sides of the sheet 26 at the moment when the 5 has landed, and the normal printing surface is maintained. As a result, a high quality printed image can be simultaneously formed on the front and back of the paper 26.

In the first embodiment, a line type printer in which both upper and lower print heads are provided with print elements corresponding to substantially the entire width of the paper in the main scanning direction will be described. However, the printer is not limited to this, and can be similarly applied to a serial type printer including a carriage moving type in which the upper and lower printing units move in the main scanning direction.

Next, as a second embodiment, after printing is performed on the paper 26 by the upper head 32 (or the lower head 33), the lower head 33 is slightly delayed.
A method for performing printing by the upper head 32 (or the upper head 32) will be described below. This is a printing method utilizing the fact that it takes a little time to generate wavy on the opposite surface of the paper 26 after printing on the paper 26 by the upper head 32.

First, the undulation phenomenon occurring on the sheet 26 will be observed in detail, as shown in FIG.
(D) and any time from the start of ink droplet penetration to the completion of penetration during the process from the landing of the ejected ink droplets on the paper to the fixing shown in FIGS. 8 (a) to (d). Rippling begins to occur. It is difficult to accurately measure the timing, but at least between the impact and the start of penetration, no waving occurs on the paper surface, that is, on the opposite surface. That is, the influence of the printing ink by the upper head has not yet been exerted on the paper surface.

As described above, when general OA paper is used, it takes several milliseconds for the gentle penetrating ink and 100 to 2 for the super penetrating ink from the time the ink lands on the paper surface until the ink starts to penetrate.
00 μs. Therefore, within this period, the printing timing for the front and back sides can be made different from each other, and the other side can be printed with a fixed delay time after printing on one side, without printing simultaneously as described above.

Accordingly, the above description is based on the fact that after printing is performed on the paper 26 by the upper head 32, the printing ink is not affected by the printing by the upper head 32 on the paper surface, that is, until the printing position is wavy. Printing control is performed such that printing is delayed by the lower head 33 so that printing is performed within a time shorter than the time.

In this case, there is no problem at all if the above-mentioned delay time is within a period from the above-mentioned landing to the start of penetration in view of safety. That is, if the period from the impact to the start of penetration is Ts and the delay time is Tt, Tt <Ts
Should be fine. In this case, the paper generally has a front side and a back side. In office paper, the surface having high smoothness is the front side, and the surface having low smoothness is the back side. The penetration of ink is slower as the smoothness of the paper is higher, and penetrates faster as the smoothness of the paper is lower. In other words, the lower the smoothness, the shorter the surface of the paper becomes wavy after the ink has landed. Therefore, in the case where the print timing is made different between the front and back sides of the paper with the delay time Tt as described above, it is preferable to print on the front side of the highly smooth paper and then print on the back side.

In this case, the print timing is made different from that of the upper head 32 which performs printing in advance.
That is, the lower head 33 is moved by the paper transport distance for the time Tt.
Are spaced apart in the sub-scanning direction of the paper 26, the time T
There is no need to stop the transport of the paper 26 during the period t, and the paper 26 may be transported as it is without waiting. Even in such a case, the lower head 33 can print on the paper surface on which no waviness has yet occurred. This eliminates waste of the transport time of the paper 26.

If the other side is printed with different printing timings as described above, the line buffer on the control device side can be shared by the upper head 32 and the lower head 33. There are advantages such that the power can be divided without concentrating the power, thereby improving the power efficiency, and the arrangement of the two upper and lower print heads eases design restrictions.

In the second embodiment, as in the first embodiment, both the upper and lower print heads have their print elements corresponding to almost the entire width of the paper in the main scanning direction. Although a line type printer provided is described, the printer is not limited to this, and in this case also, a serial type printer configured with a carriage moving type in which the upper and lower print heads move in the main scanning direction respectively. The same can be applied to the printer of the above.

In this case, the upper head and the lower head are arranged so that the arrangement positions in the sub-scanning direction of the upper head and the lower head are opposed to each other with the paper interposed therebetween. After printing on the paper, the lower head (or upper head) may be used to delay the carriage movement time by a delay time Tt. Are arranged so as to be spaced apart from each other by a predetermined distance in the sub-scanning direction, and printing is performed on a sheet by a print head (either an upper head or a lower head) that is separated upstream in the sheet transport direction. After that, printing may be performed on the intermittently conveyed paper with a print head (either a lower head or an upper head) separated downstream by a delay time Tt.

In the first and second embodiments, for the sake of simplicity, the description will be made by taking an example of a monochrome printer using a print head having only one row of ink discharge nozzles. However, the present invention can be applied to a color printer having four rows (for normal full color) or six rows (for full color using light magenta and light cyan light inks).

FIG. 4 is a diagram showing a configuration of a tandem type color inkjet line printer according to the third embodiment. The color ink jet line printer 45 shown in FIG. 3 includes a transport roller pair 46 (46a, 46b).
And an upper yellow head 47-1 opposed to a position sandwiching the sheet 26 conveyed by the conveying roller pair 46.
And lower yellow head 48-1, upper magenta head 4
7-2 and a lower magenta head 48-2, an upper cyan head 47-3 and a lower cyan head 48-3, an upper black head 47-4, and a lower black head 48-4.

Upper heads 47 (47-1 to 47-4) for each of the above-mentioned yellow, magenta, cyan and black colors
The positional relationship between the lower head 48 and the lower head 48 (48-1 to 48-4) is the same as the positional relationship between the upper head 32 and the lower head 33 shown in FIG. 2 in the first embodiment.

In FIG. 4, the paper 26 is moved from the upper yellow head 47-1 to the upper black head 47-4, that is, to the position of the lower black head 48-4, or from the lower yellow head 48-1 to the lower black head 48-. 4, that is, the transfer time to the position of the upper black head 47-4, T1, and the discharge nozzle 49 (49a or 4a) of the upper yellow head 47-1 or the lower yellow head 48-1.
9b) ink droplet 51a or ink droplet 51 ejected from
If the time from when the ink droplet b lands on the paper 26 to the time when the ink starts to penetrate and the printing surface of the paper 26 starts to undulate is defined as T2, the inequality “Tl <T2” is satisfied. -4 or the lower black head 48-4 ejects ink droplets, since the printing surface of the paper 26 is kept in a normal surface without ripples, also in this case, high quality is simultaneously applied to the front and back of the paper 26. A printed image can be formed.

When ink droplets 51 (51a or 51b) penetrate into the paper 26, if the ink having a high surface tension is used, the paper 26 is hardly wet, that is, hardly penetrates, and the time T2 becomes longer. Also, the time T2 varies greatly depending on the paper 26. Therefore, T1 may be determined according to the ink or paper used. In this case, T
If 1 can be lengthened, the average power consumption of the printer will be reduced, which is economical.

The above example is a tandem type color inkjet line printer in which four print heads each having one nozzle row are arranged in a multistage manner. The present invention is not limited to this, and can be applied to a color ink jet line printer using a single print head having four or six nozzle rows. Further, the present invention is not limited to the line type, and is applicable to a serial type color printer.

[0060]

As described above in detail, according to the present invention, two print heads are arranged so as to face a position sandwiching a sheet, so that the same print timing or the time from the impact of ink to the start of penetration can be achieved. Since the printing is performed on the front and back of the paper at the shifted printing timing, the printing on the front and back can be performed before the wavy on the other side due to the printing on one side can be performed. It is possible to provide an ink jet printing apparatus capable of obtaining a high quality printed image.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically illustrating a configuration of a main part of a line printer according to a first embodiment.

FIG. 2 is a sectional view taken along the line FF ′ of FIG. 1;

FIG. 3 is a diagram illustrating a configuration of a drive circuit of an upper head or a lower head.

FIG. 4 is a diagram illustrating a configuration of a tandem type color inkjet line printer according to a second embodiment.

5A is a perspective view schematically showing a configuration of a carriage moving type printer, FIG. 5B is an enlarged view of an ink ejection surface of a monochrome print head, and FIG. 5C is an ink ejection of a full color print head. It is an enlarged view of a surface.

FIGS. 6A and 6B are external plan views of a print head for a line type printer having print elements corresponding to substantially the entire width of a paper in the main scanning direction, and FIGS.
(b) is a diagram showing a print head for full color.

FIGS. 7A to 7D are diagrams schematically showing basic operations from landing of print dots on paper to fixing in an ink jet printer.

FIGS. 8A to 8D are diagrams for explaining a problem that adversely affects double-sided printing that occurs on a printing surface in an ink jet printer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Printer 2 Carriage 3, 3 ', 3 "print head 4 Ink cartridge 5 Guide rail 6 Toothed drive belt 7 Flexible communication cable 8 Frame 9 Platen 11 Paper 12 Paper feed roller pair 13 Paper discharge roller pair 14 Motor 15, 17 nozzle Rows 16 and 18 Discharge nozzle 20 Monochrome print head 21 Element chip 22 Parent substrate 23 Full color print head 24 Element chip 25 Parent substrate 26 Paper 27 Ink droplet 27-1 Non-penetrated part 27-2 Penetrated part 28 Print ink group 28 -1 Non-penetrated part 28-2 Penetrated part 28-3 Completely penetrated ink 30 Line printer 31 (31a, 31b) Conveying roller pair 32 Upper head 33 Lower head 34 Discharge nozzle 35 Ink droplet 36 Drive circuit 37 Shift register circuit 38 Latch circuit 39-0, 39-1,..., 39-9 Driving group 41 AND circuit 42 Transistor 43 Heating element 44 Common wiring electrode VH Drive power supply voltage Stb (Stb0, Stb2,..., Stb9) Strobe signal L Latch signal CK Print cycle D Print data signal 45 Color inkjet line printer 46 (46a, 46b) Transport roller pair 47-1 Upper yellow head 47-2 Upper magenta head 47-3 Upper cyan head 47-4 Upper black head 48-1 Lower side Yellow head 48-2 Lower magenta head 48-3 Lower cyan head 48-4 Lower black head 49 (49a, 49b) Discharge nozzle 51 (51a, 51b) Ink droplet

Claims (7)

[Claims] A transport unit configured to transport a sheet, a first printing unit provided to face a surface of the sheet transported by the transport unit, and a back surface of the sheet transported by the transport unit. A second printing unit provided opposite to the first printing unit; and a control unit for controlling the first printing unit and the second printing unit, wherein the control unit is configured to control the paper by the second printing unit. The first printing unit and the second printing unit so that the printing position on the back surface of the first printing unit coincides with the printing position on the front surface of the paper by the first printing unit via the paper. An inkjet printing apparatus characterized by controlling. 2. The ink jet printing apparatus according to claim 1, wherein each of the first printing unit and the second printing unit has a printing element corresponding to substantially the entire width of the paper in the main scanning direction. 3. The printing apparatus according to claim 1, wherein the first printing unit and the second printing unit are carriage moving type printing units in which a printing unit moves in a main scanning direction of the paper. Inkjet printing device. 4. A transport unit for transporting a sheet, a first printing unit provided to face a surface of the sheet transported by the transport unit, and a back surface of the sheet transported by the transport unit. A second printing unit provided opposite to the first printing unit, and control means for controlling the first printing unit and the second printing unit; After printing, the time for delaying the printing timing by the second printing unit from the printing timing of the first printing unit is corrugated to the printing position of the paper due to the influence of the printing ink by the first printing unit. An ink-jet printing apparatus, wherein printing is controlled so as to be within a time shorter than a time until the occurrence of the printing. 5. The printing apparatus according to claim 1, wherein the first printing unit and the second printing unit are printing heads each having a printing element corresponding to substantially the entire width of the paper in the main scanning direction, and are provided in the sub-scanning direction of the paper. The ink-jet printing apparatus according to claim 4, wherein the ink-jet printing apparatus is arranged at a predetermined distance. 6. A transporting means for transporting a sheet, and a carriage-movable first print provided in opposition to a surface of the sheet transported by the transporting means, and a printing unit is moved in a main scanning direction of the sheet. A unit, which is provided so as to face a back surface of the sheet conveyed by the conveying means with respect to the first printing unit, and a position in the sub-scanning direction opposes the first printing unit via the sheet. And a second carriage-movable type in which a printing unit moves in the main scanning direction of the sheet.
And after printing on the paper by the first printing unit, delaying the printing timing of the second printing unit from the printing timing of the first printing unit by the first printing unit. An ink jet printing apparatus comprising: a control unit that controls printing so as to be within a time shorter than a time until a wave occurs at a printing position of the paper due to the influence of printing ink by the printing unit. 7. The ink-jet printing method according to claim 6, wherein the first printing unit and the second printing unit are arranged so that the positions in the sub-scanning direction are separated from each other by a predetermined distance. apparatus.