JPH082661B2 - Gradation recording method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gradation recording method used in a printer or the like for recording image information and the like.

2. Description of the Related Art A conventional gradation recording method will be described below with reference to the drawings. Conventionally, an area gradation method and a density gradation method have been widely used as gradation recording methods. Among them, the area gradation method is a method used in a heat-sensitive transfer recording method using a heat-meltable ink, etc., in which the area and density of each unit pixel printed by a printing element are made constant and the area gradation method is composed of a plurality of unit pixels. This is a method of expressing gradation by changing a certain number of pixels to be printed in this unit division area with a certain division as a unit division area. For example, in the form shown in FIGS. 7 (a) to 7 (e). The gradation is expressed. Pixel 1 indicated by diagonal lines in the figure represents a pixel to be printed. In the case of FIG. 7, a matrix composed of 16 pixels of 4 × 4 is set as a unit division area, and gradation is expressed by the number of pixels to be printed in this unit division area. e) and the number of pixels in the unit divided area increases, the density in the unit divided area increases. On the other hand, the density gradation method is a method used in thermosensitive color recording or the like, which changes the energy input to the print element in each pixel to change the density of the pixel printed in each print element. The density of each pixel is changed by changing the applied energy to each pixel in the form shown by the curve 2 in FIG. (For example, "Nikkei Electronics"
May 1984, May 21, p159. ) Problems to be Solved by the Invention However, the gradation recording methods as described above each have drawbacks. That is, in the area gradation method, the number of gradations that can be represented by the number of pixels in a unit area having a certain area is small, and if the number of gradations is increased, the number of pixels in the unit area for expressing gradation must be large. However, as a result, the resolution of printing is lowered. For example, in the case of FIG. 7, only a density of 17 gradations can be expressed by a 4 × 4 matrix, and if a density of 37 gradations is expressed, it will be 6 × 6.
Matrix is required, and the image resolution decreases. On the other hand, in the density gradation method, it is necessary to change the energy applied to the printing element for each pixel, which complicates the control. Further, in the density gradation method, the gradient of the rising edge of the density curve with respect to the applied energy is generally large, and it is difficult to stably print a predetermined density. For this reason, the print density may be different from the desired density due to the influence of fluctuations in the ambient temperature and applied voltage. Further, in the thermal recording method or the like, heat may be accumulated in the recording head due to the past printing operation to change the temperature of the recording head, and the printed pixel may be affected by the accumulated heat to change the density. Therefore, it is necessary to lengthen the cooling time in order to remove the influence of heat accumulated in the recording head, so that the printing speed cannot be increased.

The present invention solves the above problems and makes it possible to increase the number of gradations that can be expressed by pixels in a unit area having a certain area and to stably print a predetermined density by a simple method. A key recording method is provided.

Means for Solving the Problems In order to solve the above problems, the gradation recording method of the present invention uses two or more types of printing elements for printing pixels, and the same type of printing element has the same pixel. The number of pixels to be printed in a unit division area composed of pixels to be printed by at least two or more types of printing elements so that different types of printing elements are printed on different types of printing elements. The print density in the unit area is changed by changing the combination of types.

The present invention uses the method as described above to print only elements having a single area and a single density that are preset for each printing element, and print elements of different types have different pixels in area or density. Is printed, and the print density in the unit division area is changed by the combination of the number and type of these pixels. Since it is sufficient that the same pixel is always printed for each pixel, input is made for each pixel unit. Since it is not necessary to change energy, control can be facilitated and stable printing can be performed. Further, gradations can be expressed by changing the number and combination of kinds of pixels in a unit divided area composed of plural kinds of pixels, and a large number of gradations can be expressed with a small number of pixels by a simple method. be able to.

Embodiment A gradation recording method according to an embodiment of the present invention will be described below with reference to the drawings.

1 to 5 show an embodiment in which the gradation recording method of the present invention is applied to a recording apparatus of an electric recording method.
In FIG. 2, reference numeral 3 is a recording head, and the recording head 3 is composed of a recording electrode 4 serving as a printing element and a support 5 for supporting the recording electrode 4. 4 recording electrodes
It is composed of wires of two types of cross-sectional areas, a and 4b.
Are alternately arranged in a line. Also, the recording electrodes 4a and 4b
Is set to have a cross-sectional area ratio of 3: 4. Third
In the figure, reference numeral 6 denotes an electrically conductive recording sheet. The electrically conductive recording sheet 6 comprises an electrically conductive layer 7 made of a resistor, a conductive layer 8 composed of a vapor deposition film of alumina, and a heat-meltable ink layer 9 which are laminated in this order. It is configured. The recording layer 4 of the recording head 3 is brought into contact with the conducting layer 7 of the electrically conductive recording sheet 6, and the return electrode 10 is brought into contact with the recording electrode 4 at a position separated from the recording head 3 by a predetermined distance. Voltage is selectively applied. Thereby, the recording current is applied to the recording electrode 4
To the conductive layer 7, the conductive layer 8 and the recording electrode 10 directly below the recording electrode 4.
The current flows to the return electrode 10 via the current-carrying layer 7 immediately below. At this time, since the resistance value of the conductive layer 8 is sufficiently smaller than the resistance value of the conductive layer 7, the voltage drop in the conductive layer 8 is small and almost no heat is generated in this portion. Further, since the contact area of the return electrode 10 with respect to the conducting layer 7 is sufficiently larger than the contact area of the recording electrode 4 with respect to the conducting layer 7, as a result, the current density in the conducting layer 7 directly below the recording electrode 4 becomes large and in this portion. It mainly produces heat. The heat generated in the current-carrying layer 7 is transferred to the ink layer 9 by heat conduction, the ink in the ink layer 9 is melted by this heat, and the ink is transferred to a recording paper (not shown). At this time, in the electrically conductive recording sheet 6, since the resistance of the electrically conductive layer 8 is sufficiently lower than that of the electrically conductive layer 7, the current flowing from the recording electrode 4 through the electrically conductive layer 7 causes the contact area of the recording electrode 4 to the electrically conductive layer 7. On the other hand, the current does not spread so much and flows into the conductive layer 8 directly below the recording electrode 4. Therefore, the pixel applied by the recording electrode 4 has an area that is considerably faithful to the contact area of the recording electrode 4 with the conductive layer 7. At this time, if printing is performed at a saturation level such that the size of the pixel to be printed hardly changes with respect to the energy applied to the recording electrode 4, even if the energy applied to the recording electrode 4 changes, printing is performed. Pixels hardly change and stable printing can be performed. Also,
Since the recording electrodes 4 have two types of cross-sectional areas 4a and 4b, even if the recording electrodes 4a and 4b are energized with the same voltage and the same pulse width, printing is performed by the recording electrodes 4a and 4b. The pixels to be formed have different areas as shown by 11a and 11b in FIG. 1, and the areas are approximately 3: 4.

FIG. 4 is a diagram showing a drive circuit for driving the recording head 3. A switching transistor 12 is connected in series to each recording electrode 4, and these transistors 12 are connected to a drive control circuit 13. The drive control circuit 13 is connected and the voltage is switched by a signal from the drive control circuit 13. For the drive control circuit 13, for example, a microcomputer is used. Further, 14 is a gradation signal indicating the print density to be printed on each unit division area, and 15 is a memory in which a print pattern in the unit division area corresponding to the gradation signal 14 is stored in advance. . When the gradation signal 14 is input, the drive control circuit 13 is configured to sequentially read the print pattern corresponding to the gradation signal 14 from the memory 15 and sequentially drive the transistors 12 according to the print pattern read from the memory 15. ing.

In the above configuration, when the transistor 12 is turned on, a voltage is applied between the recording electrode 4 and the return electrode 10 to print pixels. At this time, the recording electrodes 4 have 4a and 4b.
There are two types with different cross-sectional areas, and each electrode prints pixels with different areas. That is, as described above, even if printing is performed with the same voltage and the same pulse width, it is possible to print pixels having different areas due to the different cross-sectional areas of the recording electrodes 4. At this time, since each recording electrode 4 prints only one kind of pixel, it is possible to use an area where changes in pixel density and pixel size with respect to applied energy are saturated, and stable printing is possible. Is. In addition, there is no change in density due to subtle changes in input energy or changes in surrounding environmental conditions such as density gradation recording, and temperature changes caused by temperature changes in the print head due to heat accumulation in the print head are less likely to occur. Therefore,
Stable printing is possible and high-speed printing is possible.

When gradation recording is performed, four continuous recording electrodes 4 a and 4 b are operated as a set of four recording electrodes 4 and a 4 × 4 4 × 4 structure is formed by scanning these recording electrodes 4 in four columns. It is possible to print by changing the print density in the unit divided area by changing the combination of the number and the type of pixels to be printed in the unit divided area with the pixels of the matrix as the unit divided area. That is, the pixels printed on the same row by the same recording electrode 4 have the same size, but by changing the type of pixels to be printed in the unit partition area formed by the pixel matrix, the pixels to be printed on the unit partition area can be changed. The total area can be changed to change the concentration in the unit division area. For example, FIGS. 5 (a) to 5 (c) show the case where two pixels are printed in a unit divided area composed of 4 × 4 matrix pixels. The print density in the unit division area can be changed by (a)
It can be changed in three ways (1) to (c). here,
The direction of the arrow in the figure is the scanning direction of the recording head 3. Fifth
FIG. 5A shows two pixels 11a printed by the recording electrode 4a, and FIG. 5B shows one pixel 11a, 11b printed by the recording electrodes 4a and 4b. , FIG. 5 (c) shows two pixels 11b printed by the recording electrode 4b, and the ratio of the total area of the printed pixels in the unit division area by these printings should be 6: 7: 8. You can On the other hand, according to the conventional area gradation method, when two pixels are printed, no matter which two pixels in the unit divided area are selected, the sum of the print areas of the pixels in the unit divided area does not change. There is no such thing. In addition, hatched lines in FIGS. 1A to 1J indicate pixels on which printing is performed, but the number and type of pixels are different in a unit divided area formed by pixels of a 4 × 4 matrix. By changing the combination, it is possible to gradually change the density in the unit divided area. As described above, according to the present invention, it is possible to change not only the number of pixels in the unit divided area but also the print density in the unit divided area by changing the combination of pixel types.

In the above structure, when the gradation signal 14 indicating the density to be printed in each unit divided area is input to the drive control circuit 13, the drive control circuit 13 outputs the gradation signal 14 from the memory 15. The print pattern of the unit division area corresponding to is called, and the transistor 12 is first switched by the recording signal corresponding to the pixel pattern to be printed in the first row. A voltage is applied to the desired recording electrode 4 by the switching of the transistor 12, and recording for one pixel is performed. Next, the recording head 3 is moved relative to the energized recording sheet 6 by one row, and thereafter recording is performed by a recording signal corresponding to the pixel pattern to be printed in the second row. Further, in the same manner, the third row and the fourth row are recorded, and the unit divisional area composed of pixels in a 4 × 4 matrix is recorded.
At this time, as described above, by changing the combination of the number and type of pixels in the unit divided area as shown in FIG. It can be changed gradually.
As described above, using a pixel of two types with a ratio of 3: 4,
When a × 4 matrix is formed, the total area of the printed pixels in the unit divided area formed by the pixels of the 4 × 4 matrix can be changed in 51 ways. That is, when the case where no printing is performed is included, printing with a density of 52 gradations can be performed. In addition, in this embodiment,
In the recording electrode 4, the area ratio of the two kinds of 4a and 4b is 3: 4, and the ratio of the wire diameters of the recording electrode 4 is 1: 4.
It is 1.15, and there is not much difference between the two diameters. For this reason, when printing character information and the like, printing can be performed without changing the line thickness or the like even when recording is performed in pixel units, and printing with high resolution and less discomfort can be performed. Also, when printing character information
One pixel may be printed by the pair of recording electrodes 4a and 4b. At this time, the area of each pixel is the same.

Next, as shown in FIG. 6, the case where the recording electrode 4 is composed of four types of a to d will be described. Recording electrode 4a-
The ratio of the cross-sectional areas of 4d is 4: 5: 6: 7, and 4x4 1
A matrix composed of 6 pixels is used as a unit division area, and when the density in this unit division area is changed by changing the number and type of pixels to be printed in this unit division area, 84 gradation printing is obtained. It will be possible. Further, regarding these gradation numbers, more gradations can be expressed by selecting an appropriate ratio of the sectional areas of the recording electrodes 4.

According to the present invention, even if the voltage applied to each recording electrode, the pulse width, or the like is not changed for each pixel as described above,
Each recording electrode is switched under the same condition, and a large number of gradations can be expressed only by changing the combination of the number and type of pixels in the unit divided area formed by the pixel matrix.

It should be noted that in the above-mentioned embodiment, the unit division area for expressing the gradation is a 4 × 4 square area, but the shape of the unit division area is not limited to a square, and any shape such as a rectangle or a cross shape may be used. Such a shape may be used, and the same effect as that of the above embodiment can be obtained.

Further, in the above-described embodiment, the gradation is expressed by the number and combination of the pixels of plural kinds of areas, but the plural kinds of recording electrodes are made to print the pixels of different densities in the different kinds of recording electrodes. Even in the same manner as in the above embodiment, however, it is possible to change the density in the unit divided area formed by the print matrix by the number and combination of the pixels of plural kinds of density.

Further, in the above embodiment, the case where the gradation recording method of the present invention is applied to the electric recording method has been described, but the present invention can be applied to other recording methods other than the electric recording method. For example, in the electric discharge recording method or the electrostatic recording method, recording is performed by a plurality of kinds of recording electrodes having different cross-sectional areas in the same manner as in the above-described embodiment, and the number of pixels in a unit divided area formed by a pixel matrix is The print density can be changed by changing the type. Further, in the thermal transfer method, the print head is provided with heating elements having a plurality of types of areas, recording is performed by the heating elements, and similarly, the print density is changed by changing the number and types of pixels in the unit division area. Can be made. Also, in an LED printer in which a large number of LEDs are arranged in a row and the light of the LEDs is applied to the light emitter, and an image is recorded according to the pattern of the light given at this time, if plural types of LED areas are used, Similar to the embodiment, the print density can be changed by changing the number and types of pixels in the unit division area.

As described above, according to the present invention, for two or more types of printing elements, the same type of printing elements are printed with the same pixels, and the different types of printing elements are printed with different pixels. In this way, the print density of this unit division area is changed by changing the combination of the number and type of pixels to be printed in the unit division area composed of the pixel matrix. A large number of gradations can be expressed with a small number of pixels, which facilitates control and increases both resolution and the number of gradations. Further, since each printing element always prints only one type of pixel, it is possible to perform stable printing that is not easily affected by the surrounding environment.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of gradation recording by a gradation recording method according to one embodiment of the present invention, FIG. 2 is a partially enlarged plan view of a recording head of a recording apparatus using the same method, and FIG. Principle diagram showing the recording principle of the device, FIG. 4 is a drive circuit diagram of the device, FIG. 5 is an explanatory diagram showing an example of gradation recording by the device, and FIG. 6 is a diagram showing the gradation recording method of the present invention. A partially enlarged plan view of a recording head of a recording apparatus according to another embodiment, FIG. 7 is an explanatory view showing an example of gradation recording by a conventional gradation recording method, and FIG. 8 is another conventional gradation recording. It is a graph which shows the concentration curve by a method. 3 ... Recording head, 4 ... Recording electrode, 6 ... Electric recording sheet, 10 ... Return electrode, 11 ... Pixel.

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Claims (3)

[Claims] 1. Two or more types of print elements for printing pixels are made to correspond to each other so that the print elements of the same type have the same density and area of the pixels to be printed. The printing elements are made to correspond to each other so that at least one of the density or the area of the printed pixels is different, and the printing is performed in the unit divided area composed of plural kinds of pixels printed by at least two kinds of printing elements. A gradation recording method characterized in that the print density in the unit divided area is changed by changing the combination of the number and type of pixels to be made. 2. The gradation recording method according to claim 1, wherein pixels having different areas are printed on different kinds of printing elements. 3. A gradation recording method according to claim 1, wherein pixels having different densities are printed on different kinds of printing elements.