JPH02286251A - Ink jet printer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet printer that ejects ink droplets from the ejection ports of a recording head and makes them adhere to a recording paper for recording, and in particular, the present invention relates to an inkjet printer that ejects ink droplets from a jetting port of a recording head and makes them adhere to a recording paper for recording. The present invention relates to an inkjet printer configured to perform gradation recording.

[Prior Art] Conventionally, inkjet printers have features such as non-contact recording, direct recording, low noise, and easy color compatibility. A large number of recording (spouting) methods have been proposed, including on-demand types such as the stemme method and the stemme method. Since the density of the ink recording dots deposited by this inkjet recording method is almost constant, conventional inkjet printers use the density pattern method, dither method, etc. to form the recording dots into a matrix in order to obtain full color or gradation recording. A pseudo gradation expression method was used in which the gradations were placed along the lines. In addition, a level 1!1 expression method has been proposed which combines recording dot sizes from 2 to 4 values or different densities from 2 values to 4 values and the above-mentioned pseudo method. Furthermore, a method has been proposed in which the size of the recording dot is controlled to achieve gradation recording using a single dot.

[Problems and Objectives to be Solved by the Invention] However, such conventional inkjet printers have the following problems.

If a pseudo gradation expression method is used for full-color or gradation recording, the pixel density will be significantly lower than the dot density, and not only will a recorded image quality with less information be obtained, but it will also be complicated. This required a lot of calculations.

In addition, with the method of achieving gradation recording with a single dot by changing the size of the recording dot, there are large variations in environmental conditions, recording paper, etc., and only 4 to 8 levels of dots can be reproduced, resulting in good gradation recording. In addition, a complicated drive circuit was required to change the width, height, etc. of the pulse applied to the recording head. Furthermore, in pseudo gradation expression methods, recording methods that change the size of recording dots, and methods that use a combination of the two, there is an extreme density difference between the ink-attached area and the non-ink-attached area within one pixel. However, as mentioned above, there are large variations due to environmental conditions, recording paper, etc., and the area of the ink adhered part within one pixel is not stable, so the uniformity of pixels is significantly impaired, and graininess is particularly noticeable due to visual characteristics. At medium and high densities with a reflection density of around 1, the roughness became noticeable and the recorded image quality deteriorated. Furthermore, when multiple inks with different densities are used, replenishing the ink becomes complicated, especially when inks of yellow cyan and magenta are used.
When performing full-color recording using primary colors, as many as 6 to 12 types of ink are required.

Therefore, the present invention provides a method that does not reduce pixel density, has a sufficient number of recording gradations, can obtain good recorded image quality without a feeling of roughness, has simple calculations and drive circuits, and uses only one ink per primary color.
The purpose of the present invention is to provide an inkjet printer in which ink can be easily replenished with only a small amount of seed.

[Means for Solving the Problems] The present invention solves such conventional problems, and one pixel is formed by a plurality of dots obtained by ejecting ink droplets from the ejection ports of a recording head and depositing them on recording paper. In an inkjet printer that performs gradation recording, the recording head has multiple ejection ports that eject the same ink as ink droplets with different volumes for each ejection port, and the ink droplet with the largest volume among the ink droplets The area of the dot obtained by the adhesion of the ink droplet is approximately equal to the area of one pixel, and the volume ratio of the ink droplet is 1:2:4:8...:2°. .

[Example] An inkjet printer that realizes 16-step gradation recording will be described below as an example of the present invention.

FIG. 1 is a modeled view of the recording process, in which the recording head 1 performs recording while moving in the directions of arrows A and B parallel to the surface of the recording paper 2. The recording head 1 has four ejection ports 1-a, 1-b, and 1-c.

1-d are arranged along the recording direction. The same ink is supplied to the four ejection ports 1-a, 1-b, 1-C, and 1-d from an ink tank (not shown). Ink droplets 3-a and 3-b ejected from each ejection port
, 3-c, and 3-d have different volumes as shown in the figure, and the ratio is approximately 1:2:4:8 in that order. -b, 3-c, 3-d
The dots adhere as inks 4-a, 4-b, 4-c, and 4-d, and each dot has a different area. FIGS. 2, 3, 4, and 5 show the attached ink 4-
This is a diagram showing the area of dots when inks a, 4-b, 4-c, and 4-d adhere to the recording paper 2. In the figure, the wavy line indicates the area assigned to one pixel, and the adhered ink 4-a The dot area is one-eighth of the area of one pixel, and the adhering ink is 4-
The area b is 1/4, the area of the attached ink 4-C is 1/2, and the area of the attached ink 4-d is approximately equal to the area of one pixel.

FIG. 6 is a block diagram of a circuit that operates the recording head 1. The 4-pit bit data indicating 16 gradation levels is input from the lower bits to the input terminals 11-a and 11-b.
, 11-c, 11-d, and is sent to the driver 14 through the delay means 12 and the pulse width defining means 13, and is sent to the ejection ports 1-a, 1-b, 1-c, of each of the recording head 1.
Ejection means 15-a, 15-b, 1 corresponding to 1-d
5-c and 15-d operate. Each bit data corresponds to each jet port 1-a, 1-b, 1-c, and 1-d on a one-to-one basis. The delay means 12 corrects the deviation between each bit data due to the interval between the respective jet ports 1-a,
Ink droplets 3- ejected from 1-b, 1-c, and 1-d
a, 3-b, 3-c, and 3-d are attached near the center of a desired pixel, and two types of delay times are selected depending on the recording direction (direction of movement of the recording head 1).

Each spout 1-a, 1-b, 1-c, 1
Ink droplets 3-a, 3-b, 3 ejected from -d
-c, the volume of 3-d is 1? The method for setting 2: 4: 8 is to set the jet ports 1-a, 1-b, 1-c.
, a method of changing constants related to ejection such as the shape of 1-d, a method of changing the applied pulse width for each ejecting means 15 using the pulse width specifying means 13, a method of changing the applied pulse width for each ejecting means 15 using the driver 14. There are methods of changing the voltage (voltage), and these methods can be used alone or in combination.

Table 1 shows a method of recording 16 levels of gradation from density levels 0 to 15 using this configuration. In Table 1, O
Recorded dots caused by ink droplets ejected from the marked spout are 0.
By repeating the process four times, 16 density levels can be obtained. Figures 7 and 8 show the recording dots in the medium and high density regions recorded in this way, for example, recording dots at density levels 10 and 13, and Figures 9 and 10 show the cross-sectional density distribution within one pixel. Shown below. The density within one pixel is highest near the center of the pixel, and gradually decreases as it approaches the outer periphery. As can be seen from Table 1, at density levels 8 and above, ink 4-d is always adhered by the jet nozzle 1-d, and the adhered ink 1-d has a dot area that is approximately equal to the area of one pixel. , there are almost no non-attached parts within one pixel.

As described above, as one embodiment of the present invention, a recording head having four ejection ports for ejecting ink droplets of different volumes has been used to print 16
Although the method for realizing gradation recording of step density levels has been described, the present invention does not limit the number of ejection ports, and the method of realizing gradation recording of 20 step density levels with n ejection ports is applicable to the present invention. It will be done.

Further, if three types of ink of the three primary colors of yellow, cyan, and magenta are used, and a recording head having four ejection ports for each color is used as in this embodiment, full-color recording of 4096 colors can be realized.

Table 1 [Effects of the Invention] As explained above, the present invention has the following effects.

Ink droplets ejected from n ejection ports with different volumes of ink droplets are deposited from 0 to n times near the center of the same recording pixel.
It is possible to record pixels with a density level of 0, and there is no decrease in pixel density, and a sufficient number of recording gradations can be obtained.

Recording pixels are formed by depositing recording dots with different attachment areas near the center of the recording pixel, so the density distribution within one pixel is highest near the center, gradually decreases as it approaches the outer periphery, and also in the middle and high density regions. In this case, recording dots with a dot area approximately equal to the area of one pixel are always adhered, and there is almost no non-adherent area within one pixel, so that a good recorded image quality with no roughness can be obtained.

Each bit of bit data indicating the concentration level has a 1:1 correspondence with a jetting port, and the jetting means corresponding to each jetting port is always driven under constant conditions, so that the calculation/driving circuit is very simple.

The ink ejected from each ejection port is the same ink, and even when performing full-color recording, only one type of ink is needed for each primary color, and maintenance such as ink replenishment is not complicated.

[Brief explanation of the drawing]

FIG. 1 is a model of the recording state of an embodiment according to the present invention, and FIGS. 2, 3, 4, and 5 show the dot area of each adhered ink according to an embodiment of the present invention. Figure, 6th
The figure is a block diagram of a circuit for operating a recording head according to an embodiment of the present invention, FIGS. 7 and 8 are diagrams showing recording dots of an embodiment according to the present invention, and FIGS. 9 and 10 are diagrams showing an embodiment according to the present invention. FIG. 3 is a diagram showing an example density distribution within one pixel. 4-a, 4-b, 4-c, 4-d-Adhesive ink 11-a, -b, -c, -d-
- one input terminal 12 - - delay means 13 - m - pulse width regulating means 14 - m - drivers 15 - a, -b, -c, -d - one or more ejection means Applicant Seiko Epson Co., Ltd. Agent Attorney Patent attorney Kizobe Suzuki (and 1 other person) 1-m-recording head 1-a% 1-b, 1-c, 1-d ---1 ejection 2---recording paper 3-a, 3-b, 3-c, 3-d---Ink droplets Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 9 Figure 6 Figure 8 Figure 10

Claims (1)

[Claims] In an inkjet printer that performs gradation recording by forming one pixel by a plurality of dots obtained by ejecting ink droplets from the ejection ports of a recording head and depositing them on a recording paper, the recording head ejects the same ink from the ejection ports. The ink droplet has a plurality of ejection ports each ejecting the ink droplet with a different volume, and the area of the dot obtained by the attachment of the ink droplet having the largest volume among the ink droplets is the area of one pixel. The volume ratio of the ink droplets is approximately equal to 1:2:
An inkjet printer characterized by 4:8...:2^n.