JPH0448626B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an inkjet recording method, and more particularly to an inkjet recording method that performs recording by ejecting ink droplets onto a recording medium according to recording information.

[Prior Art] Conventionally, it has been known that the recording quality (print density, dot shape after printing, etc.) of this type of recording apparatus is greatly influenced by the physical properties of the recording medium. Therefore, it is recommended to use paper recommended for inkjet printers, which is a type of special paper, in any recording device, and the current situation is that the desired print quality can be obtained when using this paper. .

The recommended paper is the isotropic diffusion of the droplets printed on it.
Physical properties such as diffusion speed, adsorption speed, and reflection density are determined in detail, and when recording is performed by loading a light-transmitting recording medium such as film for an overhead projector (hereinafter referred to as OHP) into such a printer. Due to differences in the physical properties of the recording medium, the quality of the print may deteriorate significantly, or in severe cases, the print may not be fixed.
Therefore, attempts have been made to improve the fixing properties by surface-treating the OHP film and forming a thin film of gelatin or PVA on the surface layer.

However, improvements in fixation affect all OHPs.
The characteristics of the printing film have not been improved, and the printing density is low due to the fundamental difference in physical properties from plain paper, which will be described below.

That is, unlike paper, OHP film has low diffusivity (that is, the spread of dots is small), and improved fixing performance also means a decrease in the diffusivity of OHP film. Therefore, when such an OHP film is loaded into a conventional inkjet printer and recorded, the dot of each pixel becomes small, thereby reducing the printing density and resulting in a pale colored and blurred recording. That is, the second
As shown in the figure, in the case of OHP film, 1
The dot diameter 3 ejected onto the pixel area 1 is smaller than the dot diameter 2 in the case of plain paper illustrated in FIG.

Furthermore, OHP films transmit light, while conventional recording paper uses the reflected light to express images, so even ink with relatively low ink density can be colored throughout (the dots are diffused). Even if the reflection density and ink density are not so low, when viewing an object with wide dot spacing and small dot diameter using transmitted light, the reflection density may seem higher.

There is a method of increasing the dye concentration in order to increase the printing density, but increasing the dye causes problems such as clogging if left for a long time and dye precipitation, so increasing the dye beyond a certain concentration causes problems such as clogging and dye precipitation. The problem is that I can't.

A method has also been proposed in which multiple ink droplets are continuously ejected to form one pixel to improve the recording density. In such cases, there were problems such as a decrease in resolution, ink leakage, etc., and deterioration of image quality.

The present invention has been made in view of the above points, and its purpose is to provide an inkjet recording method capable of recording high-quality images at appropriate density even on optically transparent recording media. There is a particular thing.

That is, the present invention provides an inkjet recording method in which an image is recorded on a recording medium by moving a recording means that discharges ink droplets according to recording information relative to the recording medium in the main scanning direction and the sub-scanning direction. When the recording medium is a light-transmitting recording medium, the recording means performs multiple main scans on the same pixel of the recording medium, and in the multiple main scans, a plurality of ink droplets are displaced by a predetermined amount from each other and are overlaid. An object of the present invention is to provide an inkjet recording method characterized by recording one pixel.

[Example] Hereinafter, the present invention will be described in detail according to an example shown in the drawings.

Normally, printers use four colors: Y (yellow), M (magenta), C (cyan), and Black.
Equipped with color ink ejection nozzles, Y,
When representing the monochromatic areas of M, C, and Black, one dot of ink of the required color is placed in area 1 of one pixel to create the color, and also for R (red), G (green), and B (blue). When color is developed by the subtractive color mixing method, dots of the required color are placed one by one to develop the color.

In the present invention, special attention is paid to the fact that when the recording medium is optically transparent, such as an OHP film, the dot diameter is small and the recording density is reduced as shown in FIG.
Ink droplets are ejected multiple times to area 1 of a normal pixel, and the ejection method uses a configuration in which the positions of multiple ink droplets are shifted by a predetermined amount from each other and overlapping is performed to improve the recording density. ing.

That is, in the example shown in FIG. 3, ink droplets are ejected three times in the left-right direction with a predetermined amount shifted in the area 1 of one pixel, thereby forming one pixel with three dots of diameter 3.

Furthermore, in the embodiment shown in FIG. 4, the ink droplets are shifted vertically and horizontally by a predetermined amount and are ejected four times in the area 1 of one pixel to record one pixel with four dots having a diameter of 3. In the case of the embodiment shown in , recording is also performed at the center of the area of one pixel, and ink droplets are ejected five times at the four corners of one pixel, and one pixel is formed by five dots of diameter 3. are being recorded.

In the recording method described above, all of the plurality of printings may be shifted in the vertical direction and the horizontal direction, or may be limited to the horizontal direction and may be shifted by a predetermined amount. Further, the plurality of printings may be shifted only in the vertical direction. This can be achieved by making the paper feed pitch finer. Further, the shift in the left-right direction may be performed by shifting the amount of delay in the ejection timing, or by making the ejection pitch finer.

Next, a specific example of a configuration for recording will be described with reference to FIG.

CPU (central control unit) that controls the recording system
30 is connected to an up-down counter 31, which counts up in synchronization with the clock from the CPU 30, and the data address corresponding to the counted value is sent to the address decoder 32.
required via. Connected to external data 34
Recorded data 35 at that address is read out from RAM (random access memory) 33 in synchronization with the clock. In that case, the carriage position detection section 3
Check the discharge position using the signal from driver 3.
7 and inkjet unit (IJU) 3.
8, dot recording is performed according to the data 35 described above.

By the way, the OHP film detection section 39
When an OHP film is detected, the ejection delay is determined via the ejection delay calculating section 40, and dot recording is performed by shifting the ejection timing.
For example, if the number of times of smooth printing is N, the dot pitch is D, the carriage speed is V, and the timing time for printing at the regular printing position of a certain dot is T (initial setting value), then the ejection delay is -D/2V+D[(Na+
1)/2]/V(N+1), the dots are ejected at different times, and the dots are printed at different times.
However, Na indicates the number of printing out of N repetitions, and [(Na+1)/2] indicates a Gaussian function.

As in the example shown in FIG. 3, recording is performed by setting N=3 and reciprocating the carriage three times. In this case, the number of times N
Until this point is reached, the contents of the RAM 33 are held and the paper feed mechanism 41 does not feed the paper. When the number N is reached, the RAM 33 is refreshed and the paper is fed.

On the other hand, when returning, counter 31 is used as a down counter.
It is also possible to perform reciprocating printing by taking out data in synchronization with the clock and printing it in the same way as in the past. It is clear that at this time as well, the ejection delay period described above is controlled to be used for T so that printing is performed as shown in FIG.

The method described above is to shift the dots to the left and right, but shifting dots in the vertical direction is performed by changing the paper feed pitch using the paper feed mechanism 41. On the other hand, when changing in the vertical and horizontal directions, the delay and paper feed pitch are changed by a predetermined amount.

[Effect] As explained above, according to the present invention, when recording an image on a light-transmitting recording medium such as an OHP film, a plurality of ink droplets are overlapped with each other by a predetermined amount in multiple main scans. Since one pixel is recorded by striking, it is possible to prevent ink from flowing out even if a plurality of ink droplets are struck into one pixel, and it is possible to record a high-quality image at an appropriate density.

[Brief explanation of the drawing]

Figures 1 and 2 explain the conventional recording method. Figure 1 is an explanatory diagram for explaining the case of recording on plain paper, and Figure 2 is an explanatory diagram for explaining the case of recording on OHP film. 3 to 5 are explanatory diagrams illustrating different embodiments of the inkjet recording method according to the present invention, and FIG. 6 is a block diagram showing a circuit configuration for shifting dots. 1... Pixel area, 2, 3... Dot diameter, 30...
...CPU, 40...Discharge delay calculation section, 38...
...Inkjet unit.

Claims (1)

[Claims] 1. An inkjet recording method in which an image is recorded on a recording medium by moving a recording means that discharges ink droplets according to recording information relative to the recording medium in the main scanning direction and the sub-scanning direction. In the case where the recording medium is a light-transmitting recording medium, the recording means performs main scans on the same pixel of the recording medium multiple times, and the multiple ink droplets are shifted by a predetermined amount from each other during the multiple main scans. An inkjet recording method characterized by recording one pixel by overprinting.