JP3299509B2 - Optical writing type printer head and optical writing type printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer capable of selecting a printing color by an optical writing wavelength and controlling a color density by an optical writing power, for example, a printer using printing paper coated with photosensitive microcapsules. The present invention relates to a suitable optical writing type printer head and an optical writing type printer equipped with the printer head.

[0002]

2. Description of the Related Art A printer using printing paper coated with photosensitive microcapsules scans the printing paper with a printer head having three types of light emitting elements of red, green and blue to form a latent image. The printing paper on which the latent image is formed is developed by applying mechanical pressure by a print roller. The printing paper is obtained by uniformly coating a photosensitive microcapsule having a diameter of about 4 microns on a base paper, coating an image receiving layer containing a color developing agent thereon, and further laminating a polyester film thereon.
The microcapsules themselves are merely transparent gelatin microvessels that are light-transmissive and strong enough to be broken by the mechanical pressure of the print roller.

When one type of light among R, G, and B, that is, monochromatic light is selected and irradiated on a full-color printing paper coated with three types of photosensitive microcapsules, M, Y, C
Of the three types of photosensitive microcapsules, only the photosensitive microcapsules enclosing a photocurable substance having a complementary color relationship with the selected monochromatic light are cured in response to light, and the other two types are not cured. That is, when the light of R is irradiated, the photosensitive microcapsule of C hardens in response to the red light of the photocurable substance, and the other two types, that is, the photosensitive microcapsules of M and Y do not harden. When the pressure of the print roller is applied to the print paper in this state, the photosensitive microcapsules of M and Y are completely destroyed, but the photosensitive microcapsules of C are not destroyed or are incomplete depending on the degree of curing. Destroyed. For this reason, the M and Y coloring substances come into contact with the image receiving layer of the printing paper, and the area develops red mixed with M and Y. The color of the red color obtained by mixing M and Y changes depending on the degree of curing of the photosensitive microcapsule C. This is because, although incomplete, the photosensitive microcapsules of C are destroyed, and the color-forming substance for C comes into contact with the image receiving layer. Similarly, when the light of G is irradiated, a green color is obtained by mixing Y and C, and when the light of B is further irradiated, M and C are emitted.
And blue.

[0004] In short, when three types of light having different wavelengths, that is, one type of light of R, G, and B are selected and irradiated on a full-color printing paper coated with three types of photosensitive microcapsules, The region irradiated with the selected light emits a color of M and Y, Y and C, or a mixture of C and M. In addition, R, G, B
When two types of light are selected and irradiated, the region irradiated with the selected two types of light emits a color corresponding to one of M, Y, or C. The region not irradiated with any type of light exhibits black color because colors corresponding to all of M, Y, and C are performed. The color tone, saturation, and brightness of the print are adjusted by adjusting the intensity of irradiation light and the irradiation time.

A printer that prints on a full-color print sheet coated with photosensitive microcapsules in accordance with the above-described process has a light emitting element as shown in FIG. 6 , for example, and selectively irradiates light to the print sheet to form a latent image. The printer includes a printer head 1 to be formed, a print roller 2 for applying pressure to the print paper on which a latent image is formed and developing the paper, a carriage 3, a paper feed mechanism 4 for moving the print paper in one direction at a predetermined speed, and a solid-state display element. Display device 5, a driving unit 6, and a control unit 7. The drive unit 6 is a PW which controls the selective light emission and irradiation amount of the light emitting element of the printer head 1
An M-type photosensitive control circuit, a carriage driving unit that reciprocates the carriage 3 at right angles to the moving direction of the printing paper,
It includes a roller drive unit for driving the print roller 2, a paper feed drive unit for driving the paper feed mechanism 4, and a display device drive unit. The printer further includes an input unit 8 for inputting image data of an imaging device such as a digital camera provided by a flash memory card or a transmission signal to the control unit 7, a control unit 7.
A setting unit 9 for setting various parameters of the printer, editing images, and the like.

One example of a conventional printer head 1 used for printing on a full-color print sheet has nine LEDs arranged in three columns and three rows on a head substrate 10 as shown in FIG. . The first row is a group of red LEDs, consisting of 11R1, 11R2 and 11R3.
The columns are green LED groups, 11G1, 11G2 and 11G3.
And the third column is a group of blue LEDs, 11B
1, 11B2 and 11B3. Aperture plate 1
Reference numeral 3 has nine beam apertures formed in three columns and three rows. The first row is a group of red LED beam apertures.
12R1, 12R2, and 12R3, the second row is a group of beam apertures for green LEDs, 12G1, 12G2, and 12G3, and the third row is a group of beam apertures for blue LEDs, 12B1, 12B2, and 12B3. Consists of Each of these beam apertures has a corresponding L
The ED is provided so as to face the ED with its center line aligned.

As described above, the printer head 1 is provided with three LEDs, not one, for each of red, green, and blue as light emitting elements. This is because in order to form a latent image with a resolution that can be expressed by a printer on print paper coated with photosensitive microcapsules, it is necessary to narrow the light beam of the LED to a color development diameter of about the resolution. This is because light energy is not enough. Here, the color diameter of the light beam refers to the trajectory circle where the light beam of the LED, which is the light emitting element, irradiates the printing paper coated with the photosensitive microcapsules, that is, the diameter of the exposure dot, which is the beam aperture of the aperture plate. About the same as the hole diameter.

If four or more light emitting elements are used instead of three, sufficient light energy can be obtained. However, cost reduction, downsizing of the apparatus, and energy saving are required for a small printer. It is not realistic because it would conflict with the conditions. Although it is conceivable to increase the sensitivity of the print paper coated with the photosensitive microcapsules, the current situation is that the sensitivity cannot be increased so much in terms of handling. Therefore, a printer head having two or three red, green and blue LEDs instead of one light emitting element has been put to practical use. In order to obtain sufficient light energy required for printing under the limited number of light emitting elements, the diameter of the beam aperture of the aperture plate 13 cannot be set to the resolution, and is about 1.5 times as large as that of the aperture. (See the circle in FIG. 4). For this reason, there is a problem that the pixels adjacent to the print pixels are also irradiated, the resolution of the print pixels is reduced, and the image is blurred. Also,
Since light energy is used to cause image blur, there is a problem of wasting energy.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical writing type which can form a clear latent image on a photosensitive printing paper such as a printing paper coated with photosensitive microcapsules. An object of the present invention is to provide a printer head and an optical writing type printer including the printer head. Another problem to be solved is a light-emitting module having a plurality of N (N is an integer of 1 or more) light-emitting sources, each having a different wavelength, mounted on a substrate.
A beam aperture formed at a position corresponding to the light emitting source, and an aperture plate disposed at a predetermined distance from the light emitting module, wherein the energy irradiated by the light emitting source is used for optical writing. It is to use it efficiently.

[0010]

In order to solve the above-mentioned problems, an optical writing type printer head is provided with N types having different wavelengths.
Having a light emitting source for printing and a light emitting source for pre-exposure, respectively.
Multiple emission sources for printing and one emission source for pre-exposure for each wavelength
A light-emitting module having a light source disposed on a substrate; and
A beam aperture is formed at a position corresponding to the light source and
The aperture located at a predetermined distance from the light emitting module
And the light emitting source is a PWM type photosensitive system.
The selective light emission and irradiation amount are controlled by the control circuit.
It was configured as follows. And the light emission for printing on the aperture plate.
Adjust the diameter of the beam aperture corresponding to the source to the resolution of the printer.
And a beam stop corresponding to the pre-exposure light source.
The diameter of the hole was made larger.

The pre-exposure light emitting source includes a white LED.
A white light source was used. The N kinds of printing light sources having different wavelengths include a red LED, a green LED, and a blue LED.
Those composed of discharge luminous lamps,
Alternatively, a lamp composed of a filament lamp using a wavelength filter and an optical shutter was used.

In order to solve the above-mentioned problems, a printing paper coated with photosensitive microcapsules is scanned by an optical writing type print head to form a latent image, and printing is performed on the printing paper on which the latent image is formed. In an optical writing type printer which develops by applying mechanical pressure by a roller, the optical writing type print head is provided with a plurality of red LEDs for printing and one red LED for pre-exposure , and a plurality of green LEDs for printing and one green LED. A light-emitting module comprising a pre-exposure green LED, a plurality of printing blue LEDs, and one pre-exposure blue LED disposed on a substrate;
A beam aperture formed at a position corresponding to D has a beam aperture of about the resolution of the printer, and a beam aperture formed at a location corresponding to the pre-exposure LED has a beam aperture larger than the resolution of the printer. And an aperture plate arranged at a predetermined distance from the light emitting module, and the LED is configured such that its selective light emission and irradiation amount are controlled by a PWM type photosensitive control circuit. Then, the other optical writing type printer is set to the pre-exposure red LED, the pre-exposure green LED, and the pre-exposure blue LED L.
The ED was replaced with a white LED.

[0013]

FIG. 1 is a perspective view of a printer head 1 according to an embodiment of the present invention, which is used for printing on a full-color print sheet. In FIG. 1, the printer head 1 has a light emitting module including nine LEDs mounted on a head substrate 10 in three rows and three rows.
The first row is a group of red LEDs, 11R1, 11R2 and 11R.
R3, the second column is a group of green LEDs, 11G1,
11G2 and 11G3, and the third row is a group of blue LEDs, 11B1, 11B2 and 11B3.

Of the nine LEDs constituting the light-emitting module, the pre-exposure light-emitting sources mounted on the substrate are the red LED 11R1 and the green LED 11 arranged in the first row.
G1 and blue LED 11B1.

Here, pre-exposure means printing on a medium that cannot be printed by an optical writing type printer head unless a certain amount of light energy is applied, for example, printing paper coated with photosensitive microcapsules. Immediately before performing, it means preliminary light irradiation that gives light energy to the medium that is of a size that does not allow printing and that is large enough to allow efficient printing operation immediately after. FIG. 2 is a diagram showing the printing characteristics of the printing paper coated with the photosensitive microcapsules. The horizontal axis represents the light energy given to the printing paper from the optical writing type printer head, and the vertical axis represents the printing density of the printing paper. . In the case of the print paper coated with the photosensitive microcapsules having the characteristics shown in FIG. 2, the threshold level (characteristic) at which the light energy used for the pre-exposure shifts from a state that hardly changes with an increase in the light energy to a state that greatly changes. (Point P on the curve).

Of the nine LEDs constituting the light emitting module, N kinds of printing light sources having different wavelengths mounted on the substrate are arranged in three kinds of light emitting elements having different wavelengths, that is, arranged in the second row. Red LED11R2, Green LED11
G2 and blue LED 11B2, and red LED 11R3, green LED 11G3 and blue LED arranged in the third row
11B3.

The aperture plate 13 has nine beam apertures formed in three columns and three rows. The first row is a group of beam apertures for red LED, 12R1, 12R2 and 1R.
2R3, the second row is a group of beam apertures for green LEDs, 12G1, 12G2 and 12G3, and the third row is a group of beam apertures for blue LEDs, 12B.
1, 12B2 and 12B3. These beam apertures are provided so as to face the corresponding LEDs with their center lines aligned.

Further, among the nine beam apertures, the red LED 11R of the first row arranged on the head substrate 10 is provided.
1, the red LED beam apertures 12R in the first row corresponding to the green LED 11G1 and the blue LED 11B1, respectively.
1. Beam stop hole 12G1 for green LED and blue LED
The pore size of use beam throttle hole 12B1, these beamstop
And as coloring diameter of the light beam irradiated it is larger than the resolution of about printer by holes. This is considerably larger than the diameter of the beam aperture provided in the aperture plate 13 of the conventional printer head 1 shown in FIG.

Of the nine beam apertures, the first row of red LED beam apertures 12R2 corresponding to the second row of red LEDs 11R2, green LEDs 11G2, and blue LEDs 11B2 arranged on the head substrate 10; The LED beam aperture 12G2 and the blue LED beam aperture 12B2, and the second row of red LEDs corresponding to the third row of red LEDs 11R3, green LEDs 11G3 and blue LEDs 11B3 arranged on the head substrate 10, respectively.
The diameters of the D beam aperture 12R3, the green LED beam aperture 12G3, and the blue LED beam aperture 12B3 are determined by the diameter of the light beam irradiated by these beam apertures.
The color diameter is set to be about the resolution of the printer.

The side plate 14 fixes the aperture plate 13 to the head substrate 10 at a predetermined interval, and functions as a cover. A separator plate provided between the LEDs so that the light of the LEDs does not leak in the lateral direction is also provided in the printer head according to the present invention, but in order to clearly show the positional relationship between the LEDs and the beam apertures, FIG. 1 is omitted.

FIG. 5 is a sectional view of a main part of an embodiment of the carriage 3 on which the printer head 1 and the print roller 2 are mounted. The carriage 3 is generally composed of a substantially box-shaped carriage member 18 running on a guide rail 21, a printer head support member 19 and a print roller support member 20 fixed to the lower portion of the carriage member 18, respectively. To reciprocate at right angles to the paper feed direction. The drive mechanism 22 that drives the carriage member 18 forms a part of a carriage drive unit that includes a drive motor and a force transmission mechanism (not shown). The separator plate 15 omitted in FIG.
Between the first row of red LEDs and the second row of green LEDs,
And between the green LED group in the second row and the blue LED group in the third row.

In one embodiment of the optical writing type printer according to the present invention, a printing paper coated with photosensitive microcapsules is scanned by an optical writing type printer head to form a latent image, and the latent image is formed. In an optical writing type printer for applying a mechanical pressure to a printing paper by a print roller for development, the optical writing type printer head is configured as shown in FIG.

That is, as shown in FIG. 1, the optical writing type printer head used in the optical writing type printer according to the present invention includes red printing LEDs 11R2 and 11R3 mounted on a head substrate 10, and green printing LEDs 11R.
G2 and 11G3 and blue LEDs 11B2 and 11B3 for printing, a red LED 11R1 for pre-exposure and a green L for pre-exposure provided for each of red, green and blue
The light emitting module including the ED 11G1 and the blue LED 11B1 for pre-exposure, and the hole diameter formed at the position corresponding to each of the LED for printing are irradiated by the hole.
As the coloring diameter of the light beam becomes the resolution about the printer that
The beams throttle hole 12R2 and 12R3,12G2
And the 12G3 and 12B2 and 12B3, the pore size formed at a position corresponding to the pre-exposure LED, this
Beam throttle bore 12 color diameter of the light beam irradiated by the hole has a size Kunar so than the resolution about the printer
R1, 12G1, and 12B1, and an aperture plate 13 disposed at a predetermined distance from the light emitting module.

As shown in FIG. 6, for example, a printer for printing on a full-color print sheet coated with photosensitive microcapsules according to the present invention includes a printer head 1, a print roller 2, a carriage 3, a paper feed mechanism 4, a solid-state display. It includes a display device 5 having elements, a drive unit 6, a control unit 7, an input unit 8, and a setting unit 9. The control unit 7 includes a CP
U, ROM, RAM, input / output interface I / O,
And a bus connecting them. The drive unit 6 includes a PWM type photosensitive control circuit for controlling the selective light emission and irradiation amount of the light emitting element of the printer head 1, a carriage drive unit, a roller drive unit, a paper feed drive unit, and a display device drive unit.

The optical writing type printer head 1 shown in FIG. 1 provided with a light emitting module comprising a light emitting source for printing and a light emitting source for pre-exposure is used to apply a photosensitive microcapsule having the printing characteristics shown in FIG. When printing, the printer head 1 performs exposure when moving in the direction of the arrow in FIG. That is, first, the pre-exposure light emitting sources arranged in the first row, that is, the red LED 11R1 and the green LED
11G1 and blue LED 11B1 perform pre-exposure by irradiating the print paper with light through corresponding beam apertures 12R1, 12G1 and 12B1.

Immediately after the pre-exposure, the light emitting sources for printing arranged in the second row, that is, the red LED 11R2 and the green LED 11
The G2 and the blue LED 11B2 irradiate the print paper with light through the corresponding beam apertures 12R2, 12G2 and 12B2 to perform first-stage printing. Immediately after the printing in the first row, the light emitting sources for printing arranged in the third row, that is, the red LED 11R3, the green LED 11G3, and the blue LED
11B3 is the corresponding beam aperture 12R3, 12G3
The second printing is performed by irradiating the print paper with light through the second and third prints 12B3, thereby completing the printing for a specific pixel.

FIG. 4 in which 18 circles of the same diameter are regularly arranged is shown by a red line L as shown in FIG. 3, that is, a width corresponding to the resolution of the printer and a length four times as long. When printing the red line on a full-color print paper coated with photosensitive microcapsules,
The trajectories of the light beams emitted from the LEDs of the printer head 1 through the respective beam apertures are indicated by circles. In FIG. 3, 14 cells W around the red line L represent white data.

In FIG. 4, one LED for each of red, green, and blue and a corresponding beam stop hole having the same diameter are provided for each LED.
When using a printer head having pieces, one color LED of
Consider irradiating all the circles a, b, c, and d. what if
When printing white data in this area , the three-color LED illuminates all of the circles a, b, c, and d, so that the area A receives 12 irradiations. However, the putter shown in FIG.
When printing an image, only one irradiation is for printing red data, so that the area A is 10 times and the area B is 5 times.
Times, the region C is 4 times, the region D is irradiated twice. 3 each
In the case of using the conventional printer head of FIG. 7 having one beam stop hole of the same diameter corresponding to each LED, the number of irradiations of each of these becomes three times. As is clear from FIGS. 3 and 4, in the conventional printer head, in the printing range of the red line surrounded by white data, the number of irradiations by the LED is not uniform, the central area is small, the peripheral area is large,
Up to 5 times different. Therefore, a clear red line as shown in FIG. 3 could not be printed.

On the other hand, the optical writing type printer head according to the present invention, which performs pre-exposure and irradiation for printing,
Pre exposure greater than the light beam color diameter of printer resolution, specifically greater illumination than the irradiation locus ¥ 4
Irradiation is performed by the pre-exposure LED through the beam stop hole with a hole diameter that forms a locus circle, but the printing LED emits a light beam.
Irradiation is performed through a beam aperture having a diameter such that the color diameter is substantially equal to the resolution of the printer. In the present invention, although the irradiation trajectory circles of the pre-exposure still overlap,
The irradiation energy of the pre-exposure LED does not reach the threshold value but is close to the threshold value, so that printing is not performed on print paper coated with the photosensitive microcapsules.

Immediately after such pre-exposure preparation, irradiation by the printing LED is performed. Therefore, the increase in the light energy given by the irradiation of the print is shown in FIG.
, The print density immediately starts to change and decreases substantially linearly along the characteristic curve shown in FIG. Moreover, since the printing LED emits light through a beam aperture having a diameter such that the color diameter of the light beam is substantially the same as the resolution of the printer, the irradiation trajectory circles of adjacent printing may overlap. Since there is no printing, the printing is very clear.

The above-mentioned red, green and blue LEDs each having three LEDs
Are arranged in three columns and three rows in the embodiment of the optical writing type printer head, the pre-exposure LED is only the first column, but the second column is added thereto, and the printing LED is only the third column. It may be. In this case, the pore size of the second row of beam aperture holes of the aperture plate 13 corresponding to the second column pre exposure LED of, like the hole diameter of the first row of beam throttle hole, these bi
Preferably as coloring diameter of over beam aperture hole by the light beam is greater than the printer resolution.

It should be noted that the optical writing type printer head according to the present invention uses a light emitting source for pre-exposure other than the one shown in FIG. A device using a white light source such as an LED can also be realized.

Similarly, the optical writing type printer head according to the present invention comprises a red LED, a green LED and a blue LED as N types of printing light sources having different wavelengths as shown in FIG.
In addition to the ED, a discharge lamp or a filament lamp using a wavelength filter and an optical shutter can be used.

[0034]

According to the present invention, there is provided an optical writing printer comprising: a light emitting module including a pre-exposure light emitting source and a printing light emitting source;
An optical plate having a beam aperture formed at a position corresponding to the light source and an aperture plate arranged at a predetermined distance from the light emitting module, wherein the light emitting source for printing on the aperture plate is provided. The beam diameter of the beam aperture corresponding to
The excellent feature that extremely clear printing is possible because the color diameter of the system is about the resolution of the printer and the diameter of the beam aperture corresponding to the light source for pre-exposure is larger than that. Having.

In addition, in the conventional optical writing type printer head, not only the printing is not sharp, but also the light energy is wasted for performing the unsharp printing. Thus, light energy was efficiently used, and various effects such as energy saving, power saving, and reduction in heat generation were brought about. For this reason, not only the optical writing type printer head itself according to the present invention, but also a printer having this characteristic printer head,
This has the effect of reducing the size and cost of the device.

[Brief description of the drawings]

FIG. 1 is a perspective view of an embodiment of an optical writing type printer head according to the present invention.

FIG. 2 is a diagram showing printing characteristics of print paper coated with photosensitive microcapsules, that is, a relationship between irradiation energy and color density.

FIG. 3 is a diagram showing a red line on the print paper coated with the photosensitive microcapsules, which is approximately the same as the resolution of the printer.

FIG. 4 is a view for explaining the size and number of irradiation trajectory circles and the number of irradiations when a print sheet coated with photosensitive microcapsules is irradiated when the red line in FIG. 3 is printed.

FIG. 5 is a cross-sectional view of an embodiment of a carriage provided with a printer head of a printer using print paper coated with photosensitive microcapsules.

FIG. 6 is a block diagram showing a configuration of a printer using print paper coated with photosensitive microcapsules.

FIG. 7 is a perspective view of a conventional optical writing printer head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Printer head 2 Print roller 3 Carriage 4 Paper feed mechanism 5 Display device 6 Drive part 7 Control part 8 Input means 9 Setting means 10 Head substrate 11R1, 11R2, 11R3 Red LED 11G1, 11G2, 11G3 Green LED 11B1, 11B2, 11B3 Blue LED 12R1, 12R2, 12R3 Beam stop hole for red LED 12G1, 12G2, 12G3 Beam stop hole for green LED 12B1, 12B2, 12B3 Beam stop hole for blue LED 13 Aperture plate 14 Side plate 15 Separator plate 18 Carriage member 19 Head support member 20 Roller support member 21 Guide member 22 Carriage drive part a, b, c, d LED irradiation trajectory circles A, B, C, D Areas with different number of irradiations L Red line P Point corresponding to threshold of printing characteristic curve W Data

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Claims (8)

(57) [Claims] An N-type printing light source and a pre-exposure light source having different wavelengths, and a plurality of printing light sources and one pre-exposure light source for each wavelength are provided on a substrate. A light emitting module disposed thereon, and an aperture plate having a beam aperture formed at a position corresponding to the light emitting source and arranged at a predetermined distance from the light emitting module, and wherein the light emitting source is provided. An optical writing type printer head configured to control its selective light emission and irradiation amount by a PWM type photosensitive control circuit, wherein a diameter of a beam stop hole corresponding to a light emitting source for printing on the aperture plate is adjusted by a printer. An optical writing type printer head, wherein the resolution is about the same and the diameter of the beam aperture corresponding to the light source for pre-exposure is made larger than that. 2. The optical writing type printer head according to claim 1, wherein said light source for pre-exposure is a white light source. 3. The optical writing type printer head according to claim 1 , wherein the light source for pre-exposure is a white LED. 4. The optical writing type printer head according to claim 1, wherein the N kinds of printing light sources having different wavelengths are constituted by a red LED, a green LED and a blue LED. 5. An optical writing type printer head according to claim 1, wherein said N kinds of printing light sources having different wavelengths are constituted by discharge light emitting lamps. 6. The optical writing type printer head according to claim 1, wherein said N kinds of printing light sources having different wavelengths are constituted by a filament lamp using a wavelength filter and an optical shutter. 7. A printing paper coated with the photosensitive microcapsules is scanned by an optical writing type print head to form a latent image, and a mechanical pressure is applied to the printing paper on which the latent image is formed by a print roller. in the optical writing type printer for developing, the light writing type printheads
The head is composed of multiple red LEDs for printing and one red LED for pre-exposure.
Color LED , multiple green LEDs for printing and one pre-exposure
Green LED and multiple blue LEDs for printing and one pre-dew
A light emitting module in which a blue LED for light is disposed on a substrate, a beam aperture formed at a position corresponding to the LED for printing, and a beam aperture hole whose size is about the resolution of a printer, and correspond to the LED for pre-exposure. A beam aperture having a diameter larger than the resolution of the printer, and an aperture plate disposed at a predetermined distance from the light emitting module, and wherein the LED is a PWM type photosensitive control circuit. An optical writing type printer characterized in that the selective light emission and the irradiation amount are controlled by the printer. 8. The optical writing type printer according to claim 7 , wherein said pre-exposure red LED, pre-exposure green LED and pre-exposure blue LED are replaced by white LEDs.