JPS6023066A - Apparatus for printing and copy - Google Patents

Abstract

PURPOSE:To obtain the full color picture of not less than 2 times higher quality than those of traditional ones by using traditional line heads, by printing the printig position of each coloring material shifting it within a range of not more than picture element pitch. CONSTITUTION:Each coloring material is printed shifting it within a range of not more than picture element pitch and coloring materials are let not to concentrate at one position. Thereby, the dynamic range of the change of lightness when microscopically observed is narrowed and the granular feeling is softened. For the measures for shifting the position of printing and copy of each material, there are the method shifting the line head and the method shifting the transfer mechanism represented by the roller wound round with recording paper as to the direction (lateral direction) perpendicular to the transfer direction (vertical direction) of recording paper. For the measures for shifting the position of printing and copy in the vertical direction, there are said methods and otherwise the method how the change of the timing for start of the printing and copy is carried out with a driving circuit, too.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a printing device, and more particularly to a full-color printing device that obtains prints by melting heat-melting ink by heat generated by electricity and transferring it onto recording paper.

In recent years, there has been an increasing need for full-color printing devices for use in hard copies of color televisions, computer output, electronic still cameras, color copying machines, and the like. In response to such demands, thermal transfer methods are being developed as an effective method, and many of them have line heads to increase speed.

By the way, in order to obtain a beautiful full-color image as a collection of color material dots, when observing at a distance of clear vision,
At least 5 or more pixels are required per gram, and if possible, printing with 10 or more pixels per parrot is desired. However, manufacturing and driving the line head at such a high density results in high costs in terms of production and the size of the drive circuit.

The present invention eliminates the above-mentioned problems and provides a printing method that uses a conventional line head and can obtain a full-color image with more than twice the fineness of the conventional method, and will be described in detail below.

FIG. 1 is an enlarged schematic diagram of printing in an example of a conventional printing method using a line head, and shows Y, M.

Each color material of C is printed at the same location. When printing with a coverage rate of 25% using the conventional method using a line head in which circular heating parts are arranged in a row at a pitch of 0.2 M, each coloring material is placed in the same position in a circle with a diameter of about 0.11 M. It will be printed. In this case, the distance between the color materials is approximately 0.09 WIL, and if the distance of clear vision is 50 cm, the visual angle is approximately 1
It's a minute. The resolution of the eyes of people with visual acuity of 1 or higher is about 1 minute, so if a person with visual acuity of 1 or higher uses the conventional method,
Full-color images using a line head with pixels,
When observed from a distance of 39 cm, the image will have a grainy feel from the middle density area to the highlight area. The situation is shown in Figure 2.

FIG. 3 is an enlarged schematic diagram of printing in an example of the printing method of the present invention. In printing according to the present invention, each color material is printed with a shift within a range equal to or less than the pixel pitch.

By the way, in a high frequency range near the resolution of the human eye, color vision is low and only the brightness component is sensed, and the graininess in an image is also mainly caused by the brightness of each coloring material. Therefore, according to the printing method of the present invention, since the coloring material is not concentrated in one place, when viewed microscopically, the range of brightness changes on the recording paper is narrow, and there is an effect of softening the graininess.

The situation is shown in Figure 4.

As mentioned above, as a means of shifting the printing position for each color material,
Regarding the direction (seedling direction) perpendicular to the conveyance direction (M direction) of the recording paper, there are two methods: a method of shifting the line head, and a method of shifting the conveyance mechanism, typified by a roller around which the recording paper is wound. FIG. 5 shows an example of a method for shifting the line head. Only when printing magenta, the line head is shifted by half the pixel pitch in the horizontal direction by the cam 86. Methods for shifting the printing position in the vertical direction include a method of shifting the line head, a method of shifting the conveyance mechanism, and a method of changing the timing of starting printing using a drive circuit. FIG. 6 shows an example of a timing chart when the timing of printing start is shifted. When the pulse ps indicating the page start becomes Hl, the pulse L indicating the line start is immediately applied when printing yellow and magenta.
S is set and data DA is transferred line by line.

When printing an image, after a time delay d corresponding to half the pixel pitch in the vertical direction, LS is raised and data is transferred.

Further, as for the printing position of each color material, it is desirable that the color materials with lower brightness are arranged diagonally. This is 4 as a human visual characteristic.
This is because the spatial frequency characteristics in the direction tilted at 5 degrees are low, making it difficult to perceive and perceive the tilted line.

The present invention described above is effective in combination with a normal thermal transfer method that uses a thermal head, as well as a so-called electrically heated transfer method that uses an electrically heated heat-generating sort having an electrically conductive layer and a heat-melting ink layer.

Examples will be described below.

PET film K with a thickness of 6 μm is used as an electric heating sheet.
, using a carbon layer and heat-melting ink coated,
A line head capable of time-division driving having the structure shown in FIG. 7 was used.

101 is a return electrode, and 102 is a recording electrode. J
,,=4.4 parrots, R,2=0.6mb, 9.3=1 parrots,
Pixel pitch P = 0.2 M ◇The current flows from the recording electrode through the carbon layer of the current heating sheet and into the return electrode ◇At this time, the current density near the recording electrode is high, so the temperature becomes high and the PET film is heated. The heat-melting ink is melted and transferred to the recording paper through the recording paper.

FIG. 8 shows the sampling mechanism and drive circuit in this embodiment. The human input signal is converted into 8-bit data 57 by an 8-bit A/D converter 56, and becomes 4-bit data 39 by passing through a ROM table 68 for uneven sampling that stores 16 levels of thresholds. , enters the line buffer 40 - On the other hand, indicates the beginning of a line from the control unit 41 to the line buffer 40 -j
LS signal 51 and request clock 52 (so.

pu+, 1s).

For LS, the control section 41 is used only when printing cyan.
The process starts after a time delay of half a pixel pitch.

The 4-bit pixel data 50 synchronized with the sent request clock 62 is input to the address of the memory table 42 for signal processing such as gamma correction, and the multi-bit signal 51 is used for signal processing according to each color or output content. When the memory table is selected, 8-bit pixel data 52
The data is transferred to the shift register 44 as a result. The shift register 44 has 1 column of 8 bits) and 10 stages, and after the transfer ends with the transfer clock 65, the preset counter 45 has 10 8-bit inputs and counts with the clock 53.
Create a pulse width according to the input data. A flip-flop 46 is struck by the set signal 35 and the galley obtained from the preset count to generate a pulse according to the data. Since pulse width modulation is performed as described above, the gradation can be selected in increments of 256 gradations, although there are only 16 gradations.

The output signal W1''4 pulses are sent to the distribution unit 47 as a signal 3o.
Two combinations of the two 61-way electrodes that protect each other are selected by the driver 48, and the 21 return paths are converted into a driving voltage by the driver 48.
Output to iL pressure.

On the other hand, a selection signal is generated by a clock 58 and a timing signal 59 in a 50-stage shift register 49, and is output from a high voltage driver 6° of an oven drain to a selection signal electrode. A recording paper 8 wound around a roller 80 shown in a conceptual diagram 8 and an energized heat generating sheet 1 supplied from a sheet supply section 82 via a feed roller 85 are overlapped on the roller 8o, and a recording head 81 records. The head is pressed against the roller 8o by the presser spring 8, maintaining appropriate pressing pressure and maintaining uniform contact between the recording head 81, the energized heating sheet 1-1, and the recording paper.

Cam 86 grin to shift the line head laterally,
The line head shifts horizontally by 0.1 m only when printing magenta.

The energizing heat generating sheet 1 is in the form of a roll, and as shown in FIG. 10, a layer of heat-melting ink is applied to each page in the order of yellow 95, magenta 96, and cyan 97. Therefore, writing is performed three times to obtain one full color record. In order to ensure vertical alignment, in the embodiment, the recording paper 8 is wound around the roll 80.
A fixed rotary encoder 91 [therefore provides the absolute position. The position signal from the rotary encoder 91 is sent to the control unit 9o, and is fed back to the low A/80 for constant speed rotation, the sheet feed roller 82 for positioning, the sheet winding roller 86, and the recording head drive circuit 84. A signal is sent to. As described above, the present invention has achieved highly accurate alignment.

With the above-described printing apparatus, a full-color, extremely fine-grained image of 1Qcm x 10cm could be obtained at low cost.

Furthermore, in addition to the three colors O, M, and Y, it is also possible to apply the present invention to the case where opening plates are used to adjust the tone in the high density region. This is an epoch-making method that allows extremely high-quality full-color images to be obtained at low cost by printing at a printing position in a range equal to or less than the pixel pitch.

Its applications are extremely wide, including color video printers and color copies.

[Brief explanation of drawings]

FIG. 1 shows an enlarged schematic diagram of an example of printing by a conventional printing method. FIG. 2 schematically shows an example of the brightness distribution of a print made by a conventional printing method. FIG. 3 shows an enlarged schematic diagram of an example of printing by the printing method of the present invention. FIG. 4 schematically shows an example of the brightness distribution of a print by the printing method of the present invention; FIG. 5 shows an example of a mechanism for laterally shifting the line head. FIG. 6 shows a timing chart when the printing start timing is shifted to change the printing position in the vertical direction. FIG. 7 shows the structure of the line head used in the example. FIG. 8 shows the sampling mechanism and drive circuit used in the example. FIG. 9 shows a conceptual diagram of the printing apparatus in the example. FIG. 10 shows the energized heat-generating transfer sheet used in the example. 86...Cam for lateral positioning 87...Spring 101...Return electrode 102...Recording electrode 1...Electric heating sheet 8...Recording paper 80 Pa-roller 81... Line head 88...Spring 82...Sheet feed roller 83...Sheet winding roller 91...Position detector 90...Positioning controller and above Applicant Suwa Seikosha Co., Ltd. Agent Patent attorney Tsutomu Mogami 350 @・@[phase] 1st 1 F"=i 3rd L"ri

Claims (1)

[Scope of Claims] 1) A printing device that obtains a record by melting ink by generating heat due to electricity and transferring it to recording paper, the printing device comprising:
A print having a line head consisting of a plurality of printing heads, and further comprising a mechanism that allows the position of pixels formed by the line head on a recording paper to be changed within a range of one pixel pitch or less. Photography device. 2) A special feature that prints by shifting the printing position of each color material of cyan (C), magenta (powder), yellow (Y), and black (BK) as necessary within a range equal to or less than the pixel pitch. F. The printing apparatus according to claim 1. 5) The line head is aligned with respect to the recording paper in the recording paper conveyance direction (
The printing device according to claim 1, further comprising a mechanism capable of shifting in a direction (hereinafter referred to as horizontal direction) perpendicular to the vertical direction (hereinafter referred to as vertical direction) within a range equal to or less than the pixel pitch. ◇4) The printing apparatus according to claim 1, further comprising a mechanism capable of shifting the recording paper conveyance mechanism laterally with respect to the line head within a range equal to or less than the pixel pitch. 5) The printing apparatus according to claim 1, further comprising a mechanism capable of shifting the line head in the vertical direction with respect to the recording paper within a range equal to or less than the pixel pitch. 6) The printing apparatus according to claim 1, further comprising a mechanism capable of shifting the recording paper conveyance mechanism in the vertical direction with respect to the line head within a range equal to or less than the pixel pitch. 7) The printing apparatus according to claim 1, further comprising a line head drive circuit capable of shifting the timing of starting printing within a time range corresponding to a pixel pitch. 8) The printing device according to claim 1, characterized in that it has an electrically conductive heat-generating sheet having an electrically conductive layer and a heat-melting ink layer.