JP2000037888A - Ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an image efficiently by providing a plurality of heads where the volume of an ink drop being ejected from one nozzle is different and forming an image at a part of low resolution using a head having high volume of ink drop depending on the resolution of a first image. SOLUTION: Line heads 21, 22, 23 for solid part of background and a head for forming a high resolution image are arranged such that a recording sheet P is carried while being clamped by a pair of carrying rollers 31, 32 of a carrying mechanism 3 to face the face PS between the rollers 31, 32. A piezoelectric element 122 is mounted on a base substrate 124 while being connected with FPCs 41-44 through a circuit lead wire 123 and a nozzle 121 is coupled through a thin tube with the piezoelectric element 122. Volume of an ink drop being ejected from the nozzle 121 of a line head 21-23 is set higher than that of an ink drop being ejected from the nozzle 121 of the head 24 and an image is formed on the recording sheet P by ejecting ink drops simultaneously line by line from the nozzles 121 of the line heads 21-24 according to an image signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer which forms an image on a recording medium by discharging ink from a nozzle of a head onto the recording medium.

[0002]

2. Description of the Related Art In order to form a color image, there is an ink jet printer having a head for discharging ink of each color of Y (yellow), M (magenta), C (cyan), and K (black).

The image formed by the ink jet printer includes a portion where the resolution may be low such as a solid portion, a hatched portion and a pattern portion of the background, and a portion where a high resolution such as a character is required.

[0004] Conventionally, a head is usually provided according to the highest resolution. In order to form a low-resolution image, the same data is supplied to a plurality of nozzles, and the same data is repeatedly ejected from different nozzles.

Further, such an ink jet printer has a frame memory (page memory) in order to transfer data to a head at a high speed. In the case of a color printer, a frame memory is provided for each color head. are doing.

[0006]

However, in the ink jet printer described in the background art, a frame memory is used, so that a high-resolution image or a low-resolution image is formed. , The same amount of data needs to be expanded in the frame memory.

Therefore, when a low-resolution image is formed, the low-resolution image data must be converted to a high-resolution image data amount on the printer side or the side supplying the image data to the printer.

For this reason, there is a problem that even a low-resolution image which originally has a small amount of data is not efficiently processed, and the efficiency of the printer is reduced. Further, even when a coating is applied to a recording medium using a head in order to protect the formed image or to improve the image forming surface of the recording medium, the head is the same as the head that performs image recording. , Which is costly.

Further, when an image is formed with a head corresponding to the highest resolution, there is a problem in that white streaks appear in a formed image due to landing accuracy of ink droplets and a feeding error of a recording medium or a head.

For example, as shown in FIG. 8, in the case of an ink jet printer having a resolution of 360 dpi for Y, M, C, and K and having dark and light color heads, as shown in FIG. Even when designing and manufacturing to perform image formation,
White streaks WL appear in the formed image as shown in FIG. 8C due to the landing accuracy of the ink droplets and the feeding error of the recording medium and the head.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an ink jet printer capable of efficiently forming an image in accordance with the resolution of a first image.

A second object is to provide an ink jet printer that can reduce costs. A third object is to provide an ink jet printer that can prevent white streaks from occurring.

[0013]

According to a first aspect of the present invention, there is provided an ink-jet printer comprising a plurality of heads each having a different amount of one droplet of ink ejected from one nozzle. It is a printer.

Where high resolution is required, the
An image is formed by a head having a small amount of ejected droplets, and an image is formed at a low resolution portion by a head having a large amount of one droplet of ink.

By forming an image of a portion where the resolution may be low with a head having a large amount of liquid droplets, the amount of image data to be processed is reduced, and efficient image formation becomes possible.
Further, by using a head having a large amount of one droplet of ink, when the head is a line head, the number of nozzles can be reduced and the cost is reduced.

In the present invention, the image formation using a head having a small amount of one droplet of ink is performed from the viewpoint of preventing a mask by the image formation using a head having a large amount of one droplet of ink. It is desirable to carry out.

According to a second aspect of the present invention, there is provided an ink jet printer according to the first aspect, wherein the nozzles of the head have different diameters. Large diameter nozzles eject ink with a large amount of droplets, and small diameter nozzles eject ink with a small amount of droplets.

According to a third aspect of the present invention, there is provided an ink jet printer according to the first aspect of the invention, wherein voltages applied to the nozzles of the head are different. In the case of heads having the same configuration, increasing the voltage increases the droplet volume.

In the case of a head having a different configuration, a head having large droplets may have a low discharge speed, so that the voltage is low and a head having small droplets is required to increase the discharge speed. It is necessary to increase the voltage.

According to a fourth aspect of the present invention, in the first aspect of the present invention, a control unit for determining the resolution of an image and driving a nozzle having a droplet amount according to the determination result is provided. An ink jet printer characterized in that:

By determining the resolution of an image and driving a nozzle having a droplet amount according to the result of the determination, the amount of image data to be processed is reduced, and efficient image formation becomes possible.
According to a fifth aspect of the present invention, in the first aspect of the present invention, a control unit is provided for determining a resolution of each part in the image and driving a nozzle having a droplet amount according to the determination result. The inkjet printer according to any one of claims 1 to 3, wherein:

By determining the resolution of each part in the image and driving a nozzle having a droplet amount according to the determination result, the amount of image data to be processed is reduced, and efficient image formation is possible.

According to a sixth aspect of the present invention, in the first aspect of the present invention, a head for discharging ink droplets and a head for discharging coating liquid droplets are provided, and The head for ejecting droplets of high-resolution ejects small droplets of ink, and the head for ejecting droplets of the coating liquid ejects large-resolution coating liquid at low resolution. Is an inkjet printer.

The coating used to protect the formed image or to improve the image forming surface of the recording medium may be applied uniformly. Since the head that discharges the droplets of the coating liquid has a low resolution and discharges the coating liquid of the large droplets, the cost is lower than when a head that discharges the small liquid droplets is used.

According to a seventh aspect of the present invention, in the first aspect of the present invention, a head for discharging a droplet of a dark color ink, a liquid of a light color ink of the same color as the dark color is provided. A head for discharging droplets of the dark color ink is provided at a high resolution; a head for discharging small droplets of ink at high resolution; An ink jet printer which discharges large droplets of ink at a resolution.

A head that discharges light-color ink droplets having little effect on resolution can prevent generation of white streaks by discharging large-droplet ink at low resolution.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to the drawings. (1) First Embodiment First, an overall mechanical configuration of an ink jet printer according to a first embodiment of the present invention will be described with reference to FIG.

In the ink jet printer 1, a recording paper P as a recording medium is transported by a transport roller pair 3 of a transport mechanism 3.
1 and 32, and further transported in the Y direction (sub-scanning direction) in the figure by a transport roller pair 31 that is rotated and driven by a transport motor 33.

Four line heads are arranged between the pair of transport rollers 31 and 32 so as to face the surface PS of the recording paper P.
That is, the first line head 21 for Y (yellow), the second line head 22 for M (magenta), and C for mainly forming an image of a background solid portion, a hatched portion, a pattern portion, and the like.
A third line head 23 for (cyan) and a fourth line head 24 for K (black) for forming an image of a place where a high resolution such as a character is required are provided.

The first to fourth line heads 21 and 2
2,23,24 are flexible cables (FPC)
It is connected to a control board on which a control unit is provided via 41, 42, 43, 44.

Next, the first line head 21 will be described with reference to FIG. In addition, the second to fourth line heads 22,
The structures of 23 and 24 are also the same as those of the first line head 21, and redundant description will be omitted.

As shown in the figure, the first line head 21
Can be divided into a base substrate 124 and a lid substrate 125. The piezoelectric elements 122 are arranged in a row on the base substrate 124.
3 to the FPC 41.

On the lid substrate 125, nozzles 121 forming pairs with the respective piezoelectric elements 122 are formed in a line at the same pitch, and each nozzle 121 is connected to a thin tube provided with a place for receiving the ink discharge pressure by the piezoelectric element 122. The thin tube is connected to an ink tank provided on the lid substrate 125.

The first to third (Y, M, C) of this embodiment
The line heads 21, 22, and 23 have a resolution (dot pitch) of 90 dpi (dots / inch), the fourth (K) line head 24 has a resolution of 720 dpi, and the first to third line heads 2
1, 2, and 23 of the ink ejected from the nozzles 121
The amount of the ejected droplet is determined by the nozzle 121 of the fourth line head 24.
It was set to be larger than the amount of one droplet of ink ejected from. Adjustment of the droplet amount can be performed by changing the diameter of the nozzle 121 or changing the voltage applied to the piezoelectric element 122.

Next, the operation of the ink jet printer having the above configuration will be described. When the transport motor 33 is driven to rotate, the recording paper P is transported by the transport roller pairs 31 and 32 in FIG.
At a constant speed in the Y direction.

On the other hand, the control unit drives the piezoelectric elements 122 of the respective line heads 21 to 24 in accordance with the image signals,
Nozzles 12 of fourth line heads 21, 22, 23, 24
Ink droplets of ink are simultaneously discharged from one line to one line,
An image is formed on the recording paper P.

In the ink jet printer having the above configuration,
First to third line heads 21, 22, and 23 having a large amount of droplets
Thus, by forming an image of a portion where the resolution may be low, the amount of image data to be processed is reduced, and efficient image formation can be performed.

Further, the first to the first inks in which the amount of one droplet of ink is large
The number of nozzles 121 of the third line heads 21, 22, and 23 can be reduced, resulting in low cost. Further, the image formation by the fourth line head 24 having a small amount of one droplet of ink is performed by the first to third line heads 21, 22, and 23 having a large amount of one droplet of ink. The first to third line heads 2
1, 22, 23 can be prevented from being masked. (2) Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS.

The mechanical configuration of the ink jet printer of this embodiment is the same as that of the first embodiment shown in FIGS. 1 and 2, and a description thereof will be omitted. However, in the first embodiment, the first to third (Y, M, C) line heads 21,
22 and 23 have a resolution (dot pitch) of 90 dpi (dot / inch), the fourth (K) line head 24 has a resolution of 720 dpi, and the nozzles 121 of the first to third line heads 21, 22, and 23 have The amount of one droplet of the ink ejected is set to be larger than the amount of one droplet of the ink ejected from the nozzle 121 of the fourth line head 24. 1st to 4th line heads 21, 22, 23,
The reference numerals 24 each have a resolution of 720 dpi, change the voltage applied to the piezoelectric element 122 of each nozzle, and reduce the number of nozzles 121 to be driven, thereby enabling image formation from a resolution of 90 dpi to 720 dpi.

Next, the electrical configuration of the ink jet printer having the above configuration will be described with reference to FIG. In the figure,
Reference numeral 50 denotes an image processing unit for decomposing input image data into four image data of Y, M, C, and K; 51, a first frame memory in which Y image data decomposed by the image processing unit 50 is expanded; 52 is a second frame memory in which the M image data decomposed by the image processing unit 50 is expanded, 53 is an image processing unit 50
A third frame memory 54 in which the C image data decomposed in the step S is expanded is a fourth frame memory in which the K image data decomposed by the image processing unit 50 is expanded.

Reference numeral 61 denotes a first driver for taking in the Y image data developed in the first frame memory 51 and driving the first line head 21, and 62 denotes M image data developed in the second frame memory 52. And a second driver 63 for driving the second line head 22 takes in the C image data developed in the third frame memory 53,
A third driver for driving the third line head 23, 6
Reference numeral 4 denotes a third driver which takes in the K image data developed in the fourth frame memory 54 and drives the third line head 23.

Reference numeral 70 denotes the first to fourth frame memories 51,
The resolution of each part of the image data expanded to 52, 53, and 54 is determined, and the droplet amount of the nozzle 121 is determined according to the determination result.
(Voltage applied to the piezoelectric element 122 of the nozzle 121) and the nozzle 121 to be driven are determined, and the drivers 61, 62, 63,
64 is a control unit that controls

Next, the operation of the ink jet printer having the above configuration will be described. When the transport motor 33 is driven to rotate, the recording paper P is transported by the transport roller pairs 31 and 32 in FIG.
At a constant speed in the Y direction.

On the other hand, the image data inputted to the image processing section 50 is decomposed into four image data of Y, M, C, K, and each image data is divided into first to fourth frame memories 51, 52,. 5
Expanded to 3,54.

The control unit 70 determines the resolution of each part of the image data developed in the first to fourth frame memories 51, 52, 53, and 54. The voltage applied to the element 122) and the nozzle to be driven are determined.

That is, a portion where the resolution may be low, such as a solid portion of the background, a shaded portion, a pattern portion, etc.
The number of ink droplets ejected from 1 is increased, and the number of nozzles 121 to be driven is reduced.

On the other hand, in places where high resolution is required, such as characters, the amount of ink droplets ejected from one nozzle 121 is reduced, and the number of nozzles 121 to be driven is increased. In accordance with the result of the determination, the control unit 70 sets the drivers 61, 62,
63, 64, the first to fourth line heads 21, 2
2, 23, 24, and the first to fourth line heads 2
Ink droplets of ink are simultaneously discharged from the nozzles 121 of 1, 22, 23, and 24 one line at a time to form an image on the recording paper P.

In the ink jet printer having the above configuration,
The image formation at the place where the resolution may be low is performed by one nozzle 1
By increasing the amount of ink droplets ejected from the nozzle 21 and reducing the number of nozzles 121 to be driven, the amount of image data to be processed is reduced, the image output time is shortened, and high-speed image output can be performed. Efficient image formation becomes possible.

The present invention is not limited to the above embodiment. In the above embodiment, the control unit 70
In the above, the resolution of each part in the image is determined, but the resolution of the entire image may be determined. (3) Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS.

The difference between the present embodiment and the first and second embodiments is the line head portion, and the other portions are the same. As shown in FIG. 4, in the present embodiment, Y, M, C,
K line heads 301, 303, 305, and 307 and a line head 309 for coating application for preventing water wetting of a color image formed with a resolution of 180 dpi.

In the ink jet printer having such a configuration, first, the line heads 301, 303, 305, 30
7, a color image having a resolution of 360 dpi is formed as shown in FIG. 5A, and then a color image having a resolution of 180 dpi is formed on the color image formed by the line head 309 as shown in FIG. Application is made.

According to the above configuration, since the coating is transparent, it may be applied uniformly. Accordingly, as in the present embodiment, the line head 309 for applying the coating is used.
Even if the resolution is low, the resolution of the image formed by the other formed head does not decrease.

The line head 309 for discharging the coating liquid droplets is configured to discharge the large liquid droplets with low resolution, thereby discharging the coating liquid as described in the conventional example. The cost of the line head can be reduced as compared with the case where the resolution is increased even for the line head.

Further, for the 180 dpi line head 309 for performing coating, an inexpensive frequency dividing circuit may be provided for the ejection trigger signal in the conventional ink jet printer, so that the cost can be reduced.

In the above-described embodiment, the coating is applied after forming an image because the coating is for preventing water wetting. However, the coating is applied to improve the image forming surface of the recording medium. In this case, the order of the heads is changed, and an image is formed after coating. (4) Fourth Embodiment Next, a fourth embodiment of the present invention will be described with reference to FIGS.

The difference between this embodiment and the first and second embodiments is the line head portion, and the other portions are the same. As shown in FIG. 6, in the present embodiment, the resolution is 360 dpi and the color is dark.
Y, M, C, K line heads 401, 403, 405, 407
And a light-colored Y, M, C, K line head 4 with a resolution of 180 dpi
11, 413, 415, and 417 are used.

According to the above configuration, the design, the manufacturing,
Even if an image is formed as in (a), even if white streaks occur in a conventional inkjet printer due to the landing accuracy of ink droplets and recording paper and head feed errors, As shown in FIG. 7B, line heads 411, 413, and 41 for ejecting light color ink droplets
By using 5,417, an image is formed up to the portion where white streaks occur, and the occurrence of white streaks can be prevented.

Further, since the line heads 411, 413, 415 and 417 for forming light-colored images have a low resolution, the line heads for discharging light-colored inks have a high resolution as described in the conventional example. The cost of the line head can be reduced as compared with the case in which this is done.

Further, for the line heads 411, 413, 415 and 417 of 180 dpi for forming a light-colored image,
Since an inexpensive frequency dividing circuit may be provided for the ejection trigger signal in the conventional inkjet printer, the cost can be reduced.

The resolution of the line heads 411, 413, 415 and 417 for ejecting light color ink droplets is 180 dpi.
, The resolution is slightly reduced, but the effect is small since the color is light.

[0061]

As described above, according to the first to third aspects of the present invention, one of the inks ejected from one nozzle is used.
By having multiple heads with different droplet volumes,
By forming an image of a portion where the resolution may be low with a head having a large amount of liquid droplets, the amount of image data to be processed is reduced, and efficient image formation becomes possible.

Further, by using a head having a large amount of one droplet of ink, when the head is a line head, the number of nozzles can be reduced and the cost is reduced. In the present invention, image formation using a head having a small amount of one droplet of ink should be performed last from the viewpoint of preventing a mask by image formation using a head having a large amount of one droplet of ink. Is desirable.

According to the fourth aspect of the present invention, by providing a control unit for determining the resolution in an image and driving a nozzle having a droplet amount corresponding to the determination result, the amount of image data to be processed is reduced. Thus, efficient image formation is possible.

According to the fifth aspect of the present invention, the control unit for determining the resolution of each part in the image and driving the nozzle of the droplet amount according to the determination result is provided, so that the amount of image data to be processed is reduced. This makes it possible to form an image efficiently.

According to the sixth aspect of the present invention, the head for ejecting the droplets of the coating liquid has a low resolution and ejects the coating liquid of the large droplets at a low resolution. It is cheaper than using it.

According to the seventh aspect of the present invention, a head for ejecting light color ink droplets having little effect on the resolution can discharge white streaks by ejecting large ink droplets at a low resolution. Can be prevented

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an ink jet printer according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a line head of FIG. 1;

FIG. 3 is a diagram illustrating an electrical configuration of the ink jet printer shown in FIG.

FIG. 4 is a main part configuration diagram of a third embodiment.

FIG. 5 is a diagram illustrating an image formed by the inkjet printer in FIG.

FIG. 6 is a main part configuration diagram of a fifth embodiment.

FIG. 7 is a diagram illustrating an image formed by the inkjet printer shown in FIG.

FIG. 8 is a diagram illustrating a problem.

[Explanation of symbols]

 21 first line head 22 second line head 23 third line head 24 fourth line head

Claims (7)

[Claims] An ink ejected from one nozzle is provided by a first nozzle.
An ink jet printer comprising a plurality of heads that emit different amounts of droplets. 2. An ink jet printer according to claim 1, wherein said nozzles of said head have different diameters. 3. The ink jet printer according to claim 1, wherein a voltage applied to said nozzle of said head is different. 4. The ink jet printer according to claim 1, further comprising a control unit that determines a resolution of the image and drives a nozzle having a droplet amount according to the determination result. 5. The ink jet printer according to claim 1, further comprising a control unit that determines the resolution of each part in the image and drives a nozzle having a droplet amount according to the determination result. Printer. 6. A head that discharges ink droplets and a head that discharges coating liquid droplets, wherein the head that discharges ink droplets discharges small droplets of ink with high resolution. The ink jet printer according to any one of claims 1 to 3, wherein the head that discharges the coating liquid droplet discharges a large droplet of the coating liquid at a low resolution. 7. A head for ejecting dark ink droplets, and a head for ejecting light ink droplets of the same color as the dark color, and ejecting the dark ink droplets. 4. The head according to claim 1, wherein the head ejects small droplet ink at high resolution, and the head ejects the light ink droplet at low resolution, ejects large droplet ink at low resolution. 3. The inkjet printer according to any one of 3.