GB2223604A

GB2223604A - Colour printer

Info

Publication number: GB2223604A
Application number: GB8919781A
Authority: GB
Inventors: Takafumi Nishioka; Shigeo Tsuda
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1988-09-06
Filing date: 1989-09-01
Publication date: 1990-04-11
Anticipated expiration: 2009-09-01
Also published as: DE3929639A1; IT1231403B; GB8919781D0; GB2223604B; IT8921597A0

Description

MD6670 1 The present invention relates to a printer such as color and

monochromatic printer or the like and method for printing therewith, using toner for producing an image on a paper sheet, and especially relates to a printer and the method not using any photoconductor.

""-), 6 t"".4.' A- 23 Printer Conventional printer forming an electro-static latent image on a photoconductor and developing the latent image by toner, is known by disclosure of, for example, Japanese Unexamined Patent Publication Sho 62- 6278 as a monochromatic one and or Japanese Unexamined Patent Publication Sho 62-982 as a colored printing one.

Transcription of an image in the conventional printer is described in the following by giving an example of a document copier.

At first, when a copy starting signal is issued, a photoconductive drum starts to rotate and exposure is executed by scanning on a document. An image of the document is formed on the photoconductive drum, and thereby, an electro-static latent image of the document is formed on a surface photoconductor layer of the photoconductive drum. According to the rotation of the 1 A drum, the latent image is developed by adhesion of toner in the developer on the drum. The developed toner image is transcribed on a paper sheet. And the toner image is fixed on a paper sheet by heating and/or pressing the toner.

In case of a color copier, the above-mentioned processes of exposure, development and transcription are repeated three times for respective toners of magenta, yellow and cyan colors. Next, toners corresponding to the magenta, yellow and cyan colors are fused and mixed by heating on the paper sheet, whereon a color image of three kind of toners is transcribed. By fixing the melted toner image on the paper sheet, a desired color image is produced.

As the conventional printer uses the photoconductive drum, there is a problem that the photoconductor layer laminated on the surface of the photoconductive drum fatigues as time of service passes. Thereby, the conventional printer has the disadvantage that the life of the photoconductive drum is short. Furthermore, in the case of color printer, it is necessary to repeat the processes of the exposure, development and transcription for three times or four times. Thereby, discrepancy of the positions of respective images of magenta, yellow and cyan is liable to at superposing of occur these images on the paper sheet.

2 Object of the present invention is to provide an improved printer of toner development without using any photoconductor, which is especially suitable to be used as a color printer.

A printer in accordance with the present invention comprises:

a drum, surface thereof being to be charged with electric charge; a charging means for charging the surface of the drum uniformly; toner consisting of at least one kind of microcapsule containing a kind of photo-curing agent which is cured by irradiation of light of a specific wavelength and a kind of coloring agent; an applicator for spreading the toner on the surface of the drum evenly; exposing means for exposing light having the specific wavelength on the toner on the drum for selectively curing the curing agent of the toner; and transcription means for closely winding a paper sheet on the drum and pressing or/and heating the paper for breaking the micro-capsules which are not cured, thereby coloring agent being transcribed on the paper.

The invention will now be described further by way of examole with reference to the accompanying drawings in which:- FIG.1 is a cross-sectional view showing a 3 construction of first preferred embodiment of a printer in accordance with the present invention.

FIG.2 is a cross-sectional view showing a construction of second preferred embodiment of a printer in accordance with the present invention.

FIG.3 is a cross-sectional view showing a construction of third preferred embodiment of a printer in accordance with the present invention.

FIG.4 is a cross-sectional view showing detail of exposing apparatus in FIG.3.

A first preferred embodiment of a printer in accordance with the present invention is described referring to FIG.1. FIG.1 is a crosssectional view showing the construction of main elements of the printer. In FIG.1, a drum 1 is rotatably born and to be rotated, for example, in clockwise direction. Surface of the drum 1 is made of a chargeable material. A charger 2 for charging the surface la of the drum 1, an applicator 5 for spreading toners 50 evenly on the surface la of the drum 1 and a cleaner 6 for removing the remainder of toner on the drum 1 are provided around the drum 1. A paper cassette 7 for supplying a paper sheet 7a whereon an image is to be transcribed is provided below the drum 1. A transcription roller 12 naturally contacting the drum 1 and pressing the paper sheet 7a during the image transcription processes is 4 also provided below the drum 1. On the side of the transcription roller 12, a paper carrier 9 for peeling off the paper sheet 7a from the drum 1 and carrying out it from the printer is provided.

An optical exposing system 20 is provided above the drum 1. The optical exposing system 20 comprises a lamp 21 (for example a fluorescent lamp), a reflector 23, a slit 24 and mirrors M,, M2, M39 M4 and M5. A unit of the lamp 21, reflector 23, the slit 24 and the mirror M, moves along a document 22 for scanning the surface thereof. The light reflected by the document 22 is guided to an exposing part 4 by the mirrors M2, M3, M4 and M5.

Toner 50 used in the printer consists of micro- capsules containing photo-curing agent and a coloring agent. The photo- curing agent is a mixture of photopolymerization material and photo- sensitizer. The photocuring agent is cured or hardened when a light having a specific wavelength is exposed and a coloring agent. The toner 50 is contained in the applicator 5. The lamp 21 as a light source radiates the light having the specific wavelength which cures the photo- curing agent.

Operation of the above-mentioned embodiment is described. First, the drum 1 is driven to rotate by printing signal, and the toner 50 is evenly and thinly spread on the surface la of the drum 1 by the applicator 5. Next, the optical exposing system 20 starts scanning of the document 22 by moving the lamp 21 and the slit 24 when head of an area where the toner is spread on reaches to the exposing part 4. The light reflected by the document 22 passes the slit 24 and led to the exposing part 4 by reflections of the mirrors M1 to M5 to expose the image of the document 22-on the surface of the drum 1. Hereupon, the scanning speed of the optical exposing system 20 and the peripheral speed of the drum 1 are kept to be equal.

Bright and dark patterns on the document 22 is scanned by the lamp 21 and the slit 24 and the reflected light exposes the toner 50 on the drum 1 with reversal bright and dark patterns, intensity whereof are in revers proportion to that of the pattern on the document 22. Namely, intensity of the light reflected from a bright portion of the document (a portion wherein any information such as letters is not written) is strong and the intensity of the light reflected from the other portion wherein some information is written is weak because the irradiated light from the lamp 21 is absorbed by pigment of the information such as ink on the document. Toner particles which have been strongly exposed by the reflected light is hardened by curing of the photo-curing agent in the micro-capsules, and toner particles which have been weakly exposed remains without being hardened.

The toner 50 on the drum 1 which is exposed at 6 the exposing part 4 is then transferred to the part of the transcription part, where the toner 50 is pressed and heated on the paper sheet 7a by the transcription roller 12, which is heated and pressed toward the drum 1. The transcription roller 12 is disposed at a position suitably distant from the exposing part 4, therefore the exposed toner 50 on the drum 1 has been sufficiently hardened during the transferring from the exposing part 4 to the transcription roller 12. Hereupon, when the curing agent is sufficiently cured, the micro-capsules in the toner are not broken, or when they are half cured and the microcapsules are broken, the coloring agent little adhere on the paper sheet 7a. Only the micro-capsule which is not exposed hence not cured is broken, to color the paper sheet 7a. Thereby, an image corresponding to the document 22 is formed on the paper sheet 7a. The remainder of the toner on the drum 1 is swept out by the cleaner 6 for preparation for the next image forming.

FIG.2 shows a second preferred embodiment of the printer in accordance with the present invention. In this embodiment, the printer produces an image based on image signals. In FIG.2, elements designated by numerals 1, 2, 4 to 7, 9 and 12 and the toner 50 are respectively the same in the first embodiment shown in FIG.l. An exposing apparatus 13 is an array of light emitting diodes (hereinafter abbrevialed as LED array). The LED array has 7 the width and pixels necessary for printing the image. Furthermore, these LEDs emit the light having a wavelength capable for curing the photo- curing agent in the toner.

A control circuit 14 comprises: an image signal reading circuit 16 for reading the Image signal from an input terminal 15 and converting it to image data; an image data memory 17 for storing the image data as data of a matrix of pixels; and an exposure control circuit 18 for reading out the data from the image data memory 17 and outputting bright and dark signals to the diodes on the positions corresponding to the respective pixels.

Generally, the image data stored in the image data memory 17 are signals corresponding to bright part and dark part of pattern of the meshed pixels of the original document. The exposure control circuit 18 issues an output in proportion to the intensity of bright signal in the image data to the LED which corresponds to the position in the LED array.

Operation of the above-mentioned second embodiment is described. The drum 1 is driven to rotate by printing signal and the toner 50 is evenly and thinly spread on the surface of the drum 1 by the applicator 5. When the head or start edge of an area where the toner is spread reaches to the exposing part 4, the control circuit 14 outputs such portion of the image data stored in the image data memory 17 that which is corresponding to a line 8 of the pixels to the LED array 13 via the exposure control circuit 18. At this time, time period of scanning by an LED around the drum 1 and the exposing time period of the LED array 13 corresponding to one line of the image data stored in the image data memory 17 are synchronized each other. Accordingly, the toner on the drum 1 is exposed by LED array corresponding to the bright and dark pattern of the image data. Other operations are the same as those of the first embodiment.

FIG.3 shows a third preferred embodiment of the printer in accordance with the present invention. FIG.4 shows the detail of the exposing apparatus of the third embodiment.

In the figures, elements designated by numerals 1, 2, 4, 5, 6, 7 and 9 designate substantially the same parts and components as those of the above-mentioned embodiments. An exposing apparatus 33 comprises three LED arrays 331, 332 and 333 as shown in FIG.4. The LED arrays 331, 332 and 333 output light beams having specific wavelengths corresponding to yellow, magenta and cyan, respectively, and these three arrays are disposed parallel to the axis of the drum 1 for irradiating the same line on the drum 1.

A control circuit 40 is for controlling the exposing apparatus 33 and comprises an image signal reading circuit 41, an image data memory 42 and a color 9 inversing circuit 43. The image signal reading circuit 41 reads the image signals from an input terminal 34 via an interface (not shown in the figure) and separates the image signals which are issued from respective pixels into three data groups corresponding to the primaries. The Image data memory 42 stores the color separation data of yellow, magenta and cyan separated by the image signal reading circuit 41. The color inversing circuit 43 inverses the bright-and-dark pattern of the color separation data. Namely, it issues an output of an address in the image data memory 42 where the color separation data is stored as low level and another output of another address where the color separation data is not stored as high level.

The toner 51, which is to be spread on the surface la of the drum I by the applicator 5, consists of three kinds of micro-capsules. A first kind of the microcapsule contains a first kind of photo-curing agent to be cured by light from the LED array 331 corresponding to yellow color and a coloring agent of yellow. A second kind of the micro-capsule contains a second kind of photocuring agent to be cured by light from the LED array 332 corresponding to magenta color and a coloring agent of magenta. The rest of the micro-capsule contains a third kind of photo-curing agent to be cured by light from the LED array 333 corresponding to cyan color and a coloring agent of cyan.

Operation of the above mentioned third embodiment is described. First, the surface la of the drum 1 is evenly charged by the charger 2 and the toner 51 is also evenly spread by the applicator S. The toner 51 adheres on the surface la of the drum 1 by electrostatic force. The toner particles 51 are exposed by light beams emitted from the LED array 331, 332 and 333. Output data from the image data memory 42 corresponding to color separation of respective pixels are inverted by the color inverting circuit 43. For example, when yellow component is contained in data of a pixel, an LED in the LED array 331 corresponding to the pixel dose not emit the light. Accordingly, the photo-curing agent in the micro-capsules including the coloring agent of yellow on the position corresponding to the pixel remains as it is without being cured. On the contrary, when the yellow component is not contained in data of a pixel, the LED array 331 emits a light, and the photo-curing agent Jn the micro-capsules on a position corresponding to the pixel is cured with coloring agent of yellow. As a result, after exposure by the exposing apparatus 33, a negative latent image corresponding to the image data stored in the image data memory 42 by cured toner particles are formed on the drum 1.

For curing the toner, a predetermined reaction time period is necessary after an exposure. The curing 11 reaction of the toner 51 is made during the rotation of drum 1 from the exposing part 4 to the transmitting roller 12.

On a position where the transmitting roller 12 contacts the drum 1, a paper sheet 7a, which is carried in synchronism, with the rotation of the drum 1 corresponding to the head of the paper sheet 7a and the latent image of the toner from the cassette 7, is pressed or/and heated and pressed over the latent image of the toner. And by breaking the non-cured micro-capsules in the toner, the coloring agents contained in the microcapsules are fixed for coloring and imaging on the paper sheet 7a. In each area of pixels on the paper sheet 7a, respective coloring agents flowing out from the micro-capsules are mixed or superposed to represent the original color. Thereby, a desired color image is formed on the paper sheet 7a. The remainder of the toner in non-cured micro-capsules on the drum is swept out by the cleaner 6, and the drum 1 becomes stand by the next printing operation.

A fourth preferred embodiment is described. In the fourth embodiment, a toner which consists of three kinds of micro-capsules containing different photo-curing agents to be cured by lights of different wavelengths and one of leuco dyes which colors yellow, magenta or cyan when oxidized is used for color printing. In case of monochromatic printing, a toner which consists of a kind 12 1 k) of the micro-capsule containing a photo-curing agent and a leuco coloring dye are used, and an oxidant such as acetic acid has been coated or applied on the paper sheet 7a. In this embodiment, other operations for forming the latent image of the toner on the drum 1 by irradiation of the light beams and so on are the same as in the abovementioned embodiments.

When micro-capsules which have been not cured are broken, the leuco dyes issued from the micro-capsules react with the oxidant, and colorings are executed for forming a color image.

In the above-mentioned embodiments, LED arrays are used in the exposing apparatus 33 to ultraviolet lights. However, an arrangement for controlling the exposure of the toner comprising an LCD (Liquid Crystal Display) shutter and color filters for passing the light for curing respective photo-curing agents can be replaced.

Furthermore, another arrangement comprising a laser light source such as semiconductor laser or gas laser which can output plural light beams having different wavelengths and a polygon mirror for scanning the surface of the drum for respective wavelength can be used.

Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been changed in the details of construction and

13 the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

z i 14 A claims 1. A printer comprising: a drum, surface thereof being to be changed with electric charge; a charging means for charging the surface of said drum uniformly; toner consisting of at least one kind of microcapsule containing a kind of photo-curing agent which is cured by irradiation of light of a specific wavelength and a kind of coloring agent; an applicator for spreading the toner on said surface of said drum evenly; exposing means for exposing light having said specific wavelength on said toner on said drum for selectively curing said curing agent of said toner; and transcription means for closely winding a paper sheet on said drum and pressing or/and heating said paper for breaking said micro-capsules which are not cured, thereby coloring agent being transcribed on said paper. 2. A printer in accordance with claim 1, wherein said coloring agent is a kind of leuco dye and said paper sheet has been coated with an oxidant. 3. A printer in accordance with claim 1 or 2, wherein said exposing means comprises at least one LED array for emitting light beams having said specific a wavelength. 4. wherein said exposing means comprises an LCD shutter and at least one color filter for passing through light beams having said specific wavelength. 5. A printer in accordance with claim 1 or 2, wherein said exposing means comprises a laser light source for emitting light beams having said specific wavelength; and a polygon mirror for scanning said light beams on surface of said drum.

A printer in accordance with claim 1 or 2, 5. A printer substantially as herein described with reference to and as illustrated in the accompanying drawings.

16 Published 1990 at The Pat.- 1 en ce. State House, 66-71 Higl7 HoIborn.LondonWClR4TP.Purther copies mkvbeobtaaned from The PatentOffice Sales Branch. St MaZ,- Crky. Orp)ngton. Rent BRS 3RD- Printed by Multiplex techniques ltd, St Mary Crky. Xent. Co.- I V