JPS60253549A - Recording method - Google Patents

Abstract

PURPOSE:To obtain recording image density sufficiently high and well balanced to a monochromic recording part and a compound color recording part, by performing recording by adhering almost the same amount of recording liquid droplets to all of picture elements to be recorded. CONSTITUTION:In a recording method for recording a color image on a material to be recorded by using two or more of different color recording liquids and adhering liquid droplets of said recording liquids onto the material to be recorded, almost the same amount of recording liquid droplets are adhered to all of picture elements to be recorded to perform recording. By this method, the picture element density of each picture element is made sufficient and becomes almost same and a condition for obtain well-balanced image density as mentioned above can be satisfied.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a method of recording a color image on a recording material by using a plurality of colored recording liquids and combining these primary colors, and particularly relates to a method of recording a color image on a recording material with sufficient image density. The present invention also relates to a recording method using an inkjet system that produces clear, high-quality images.

[Prior art]

The ic jet recording method includes an electrostatic suction method using high voltage application, a method that applies mechanical vibration or displacement to the colored recording liquid (ink) using a piezoelectric element, and a method that uses the pressure of heating the ink to foam it and use the resulting pressure. Using various ink ejection methods, small droplets of ink are generated, which fly and adhere to recording materials such as paper, forming ink cartridges to perform recording, which generates less noise. This is a recording method that allows for high-speed printing and multicolor printing.

Prints recorded using this inkjet recording method can be used, for example, for surface image observation using paper or so-called inkjet recording paper as the recording material, or by using a transparent recording material as the recording material. equipment used to project and observe recorded images onto screens using optical devices such as slides and OHPs (overhead projectors), color separation plates used to create positive plates for color printing, and color displays such as liquid crystals. It is applied to various uses such as being used as a CMF (color mosaic filter) used in

On the other hand, color m
In the case of forming an image, a typical method is a recording method using a subtractive color mixing method.

When a color image is formed by subtractive color mixing, the three primary colors cyan (C), magenta (M) and yellow (Y) are generally used. Basically, colors that can be expressed by mixing two or more predetermined colors out of these three primary colors in the same pixel, that is, by recording ink droplets of different colors and depositing them on the same pixel, are basically The following four colors are available.

1) C+M-B (Blue) 2) C+Y-G (Green) 3) M+Y+R (Red) 4) C+M+Y-BK (Black) In this way, C
, M, and Y are basically seven colors: C, M, Y, R, G, B, and BK.
A color-fast image composed of colors is called a false color image.

Therefore, when recording by such a recording method, it is basically sufficient to prepare three inks for the three primary colors of C, M, and Y.

However, when recording is generally performed, BK is often used for recording, and when BK is represented by the three primary color inks of C1M and Y, ink droplets of the three primary colors of C, M, and Y are overlapped. BK is printed, and since the same volume of ink droplets are used for each color,
Three ink droplets overlap and adhere to the recording material, and the dots formed are enlarged more than necessary compared to the area recorded in colors other than BK, resulting in thick lines and an unnatural appearance. Generally, in addition to the three primary color inks of C, M, and Y, BK ink is used. added and used.

However, even when recording is performed using the three primary color inks of C, M, and Y and the four color inks of BK ink, as mentioned above, in the printing portions of B, G, and R, C, M, Y, B are recorded with one color ink (monochrome recording) while ink droplets of different colors are overlaid (mixed color recording).
Only 1 droplets of ink will adhere to the K print area. Therefore, in the B, G, and R printed areas, the image density increases and the lines become thicker due to the enlargement of the dots, and as a result, when the image is visually observed, the image of the C, M, Y, and BK printed areas is The density gives the impression that the density is lower than that of the B, G, and H printed areas, and when lines such as letters and symbols are recorded by monochromatic recording as described above, they are observed as thin lines.

This caused the recorded images to become unclear and unnatural. This is especially true for prints using translucent recording materials that utilize the transmitted light of recorded images.

Since it is very important to obtain well-balanced image density, there has been a demand for solving the above problems.

One method for increasing the image density in a monochrome recording section is to increase the density of recorded ink dots by using ink with a high recording agent concentration.

However, inks with high recording agent concentrations have problems such as poor storage stability, and the ink must be specially adjusted to obtain good recording liquid characteristics. Moreover, simply increasing the recording agent concentration of the ink does not correspond to, for example, increasing the size of the dots and giving the lines sufficient thickness when recording lines.

As a result of intensive studies in view of the above-mentioned problems, the inventors of the present invention have determined that two
By using ink of a different color or more and recording so that the amount of ink droplets attached to all pixels where recording is done is almost the same, a sufficiently high and well-balanced image density is given to the recorded image, Furthermore, the inventors have discovered that even in the case of an image having line portions, lines of sufficient thickness can be recorded, and the present invention has been achieved.

[Purpose of the invention]

An object of the present invention is to obtain a sufficiently high recorded image density with a good balance between monochrome recorded areas and mixed color recorded areas in an inkjet recording method that performs recording using inks of two or more colors. Our goal is to provide the following.

[Structure of the invention]

The above objects can be achieved by the following invention.

That is, the recording method of the present invention is a recording method in which a color image is recorded on the recording material by using recording liquids of at least two colors and depositing droplets of these recording liquids on the recording material. A feature of this method is that approximately the same amount of recording droplets is attached to each pixel to be recorded.

A pixel in the present invention refers to the minimum area shared by one color when an image is recorded, and a recorded image is formed by a collection of pixels.

In general, in images recorded by inkjet recording, the imbalance in image density between the mixed-color recorded areas with different color inks and the monochrome recorded areas with one color ink, which has been observed in the past, is eliminated, and the recorded image is improved. In order to provide a well-balanced image density, it is necessary to obtain the same pixel density between each pixel.

Therefore, in the method of the present invention, when a small droplet of ink is deposited on a recording material by the inkjet recording method, the amount of ink deposited within each pixel defined above where the ink dot is recorded is almost the same. Recording will be performed as follows.

In the method of the present invention, the method of attaching the recording liquid to the recording material is the above-mentioned inkjet recording method, and in detail, an electrostatic suction method by applying a high voltage, and a method of applying mechanical vibration to the ink using a piezoelectric element. Alternatively, various ink ejection methods such as a method that applies displacement or a method that uses the pressure of heating and foaming the ink are used to make the ink fly as small droplets and adhere to a transparent recording material to form ink dots. It is something.

As the ink used in the recording method of the present invention, all inks that can be used for inkjet recording can be used.

Furthermore, various recording materials such as paper that can be used for inkjet recording can be used as the recording material used in the method of the present invention. Among them, 1. For example, if an image is formed by the method of the present invention using a recording material having translucency, such as a recording material made of a translucent plastic film coated with a water-soluble polymer, etc. , clear images with sufficient and well-balanced image density can be obtained.

In the method of the present invention, a method for depositing the same amount of ink within each pixel is, for example, when a mixed color recording area is recorded with two color inks as in the formation of the above-mentioned false color image. While ejecting ink droplets of the same volume from the recording head for each ink, the first ink droplet is first attached to all pixels to be recorded, and then the pixels to which this first ink droplet is attached are A method in which a second ink droplet of the same color or a different color as the $1 ink is deposited on all of the ink, or a method in which two ink droplets of the same color are deposited consecutively for pixels where monochrome recording is performed, or a method in which two ink droplets of the same color are deposited consecutively, or monochrome recording is performed. Examples include a method in which only one ink droplet is deposited on a pixel where color mixing is performed, and the volume of the ink droplet is controlled to be twice as large as the volume of the ink droplet deposited on the pixel where mixed color recording is performed. can.

In addition, when the mixed-color recording section records with ink of three or more colors, if ink droplets of the same volume are to be ejected from the recording head, the ink droplets used for the mixed-color recording section are placed in the pixels where monochrome recording is performed. It is sufficient to deposit the same number of ink droplets of one color as the number of ink colors, and when changing the ink droplet volume, the same number of ink droplets as the number of ink droplets deposited on the pixel where the mixed color recording is performed is applied Ink droplets may be deposited within pixels where monochrome recording is performed.

Recording of dots into pixels is done by recording the image (W) to be recorded.
This is controlled by signals sent according to the image).

In the method of the present invention, when two or more ink droplets adhere to one pixel, two ink droplets (including 11 or more ink dots) with at least one part overlapping
If only one ink droplet is deposited, it is recorded as one ink dot with a large diameter. Note that when a plurality of ink droplets are deposited within the same pixel, it is preferable that one or more ink dots be recorded with at least an overlapping portion.

Further, in order to make the pixel density of each pixel almost the same, it is preferable that the recording agent components of each ink are adjusted to have the same recording density.

The image recorded by the method of the present invention with such ink dots has sufficient pixel density in each pixel and is approximately the same level, meeting the requirements for obtaining a well-balanced image density as described above. It satisfies the following.

In other words, in the monochrome recording section as well as in the mixed color recording section,
The dots are enlarged and there are overlapping areas, and the pixel density in the monochromatic recording area and the mixed color recording area are about the same, and even when recording lines, the line areas are not visible when visually observed. It is possible to obtain a well-balanced recorded image as a whole, such as by being able to obtain a sufficient thickness.

Hereinafter, the recording method of the present invention will be explained in more detail according to Examples.

Example 1 On-demand inkjet recording head that discharges recording liquid using a piezo vibrator (discharge orifice diameter: 65 mm)
-; Piezo vibrator drive voltage, 75v; Drive frequency, 1.
Using an inkjet recording device with a frequency of 5 kHz), each of the recording liquids having the compositions shown below was filled into the inkjet recording device, and a dry film thickness of 10-100 kHz was applied to a surface-treated polyester film (manufactured by Ondai) with a thickness of 100 mm. A transparent recording material coated with partially saponified polyvinyl alcohol (trade name, KH-17 manufactured by Nippon Gosei Kagaku Kogyo ■) so that
The volume of the ink droplets of each color is the same, and for each pixel to be recorded, two drops of ink of a different color or the same color are deposited inside the pixel, and a test pattern (black, yellow, magenta, cyan each) is printed. are printed solidly in four 2c+m squares arranged horizontally on the recording material in this order) and a pie chart (yellow, magenta, cyan, red,
It is a pie chart divided by color in the order of green, and within each division, the country names of Japan, America, Germany, England, and France are printed in black in order from the yellow division, and further below this pie chart. A pie chart (on which the title ``A'' is printed) was created.

[Ink composition]

Yellow ink c, r, acid yellow 23 2 parts by weight diethylene glycol 20 parts by weight polyethylene glycol 15 parts by weight (#200) Water 65 parts by weight Magenta ink C91, 7 acid yellow 23 parts by weight diethylene glycol 20 parts by weight polyethylene glycol 15 parts by weight (#200) Water 65 Parts by weight Cyan ink C, 1, Guidekto Blue 86 2 Parts by weight Diethylene glycol 20 Parts by weight Polyethylene glycol 15 Parts by weight (#200) Water 65 Parts by weight Black ink C, 1, Direct black 19 2 Parts by weight Diethylene glycol 20 Parts by weight Polyethylene glycol 15 parts by weight (#200) Water 65 parts by weight The recording conditions of the recorded test patterns and pie charts were evaluated for the following items. The results are shown in Table 1.

(1) For each solid printed portion of each color of the image density test pattern, 00 (optical density) in transmitted light of the recorded image was measured using a photographic densitometer (NLM-5TD-Tr, manufactured by Narumi Shokai). .

(2) Panel test The pie chart obtained as above was projected onto a screen using an OHP (overhead flow projector), and 10 panelists evaluated the visibility of the projected image on the following two items. I made a judgment and evaluated it.

a) When the projected image is visually observed, the entire projected image is clear, the chromaticity of each color is good, and Y, M, C, R
017 Å or less if there are 8 Å or more people who judge that the projected image has a good balance of image density, especially in the monochromatic recording area and the mixed color recording area, and has a natural feel over each part recorded in G and G. The case was marked as ×.

b) When the projected image is 0.7 Å or less if there is a person who visually observes the projected image and determines that the characters and lines such as country names and titles displayed in black are clear and easy to read, if there are 8 Å or more was marked as ×.

Example 2 A test pattern and a pie chart were created in the same manner as in Example 1, except that commercially available inkjet recording paper L (manufactured by Mitsubishi Paper Corporation) was used as the recording material.

About the obtained test pattern and pie chart.

Image density measurements and panel tests as in Example 1 were performed. In the measurement of image density, the OD of reflected light was measured, and in the panel test, the recorded image itself was tested. The results obtained are shown in Table 1.

Example 3 In a pixel where monochromatic recording is performed, the drive voltage of the piezo vibrator is set to 8 when ink is ejected from the recording head.
0■, except that recording is performed so that the amount of ink attached to the pixel where mixed color recording is performed and the amount of ink attached to the pixel where monochrome recording is performed is approximately the same.
A test pattern and a pie chart were created in the same manner as in Example 2.

Regarding the obtained test pattern and pie chart, Example 2
Image density measurements and panel tests were conducted in the same manner as above. The results obtained are shown in Table 1.

Comparative Examples 1 and 2 The volumes of ink droplets of each color were made the same, and in pixels where mixed color recording was performed, two droplets of ink of different colors were deposited in each pixel, and in pixels where monochrome recording was performed, , Example 1 (Comparative Example 1) or Example 2 (Comparative Example 2) except that recording was performed by depositing one drop of ink of one color in a pixel.
In the same manner as above, we created a test pattern and a pie chart.

The test pattern and pie chart obtained in Comparative Example 2 were prepared in the same manner as in Example 1, and the test pattern and pie chart obtained in Comparative Example 2 were prepared in the same manner as in Example 2. , carried out image density measurements and panel tests. The results obtained are shown in Table 1.

Table 1

Claims (1)

[Claims] (+) In a recording method in which recording liquids of at least two colors are used and droplets of these recording liquids are deposited on the recording material to record a color image on the recording material, each pixel on which recording is performed A recording method characterized in that recording is performed by depositing approximately the same amount of recording droplets on all surfaces.