GB2226647A - Colour image recording apparatus - Google Patents

Abstract

The present invention provides colour image recording apparatus in which a latent image is formed on a recording medium (20) for reproduction. The apparatus comprises an intermediate image receiving medium (10, 11, 12), and means (30) for recording on the intermediate image receiving medium an intermediate image and a positioning mark (49) (see Figure 1, not shown). The apparatus further comprises means (32) for transferring the intermediate image from the intermediate image receiving medium to the recording medium, a detection device (54) for detecting the positioning mark, and means (9, 13, 29) for positioning the intermediate image receiving medium relative to the transfer means in accordance with an output from the detection device. <IMAGE>

Description

COLOUR IMAGE RECORDING APPARATUS The present invention relates to colour image recording apparatus.

Conventional colour image recording apparatus reproduces a colour manuscript on regular paper as follows.

The conventional apparatus irradiates the colour manuscript with visible light, and directs the light reflected by the colour manuscript to a photo-sensitive drum through a visible light dissolution filter device, including a red-filter, a green-filter and a bluefilter, for forming an electro-static latent image on a surface on the photo-sensitive drum. The electro-static latent image is developed using a cyan toner, a yellow toner and a magenta toner, and is then transferred to the regular paper.

Although the present invention is primarily directed to any novel integer or step, or combination of integers or steps, herein disclosed and/or as shown in the accompanying drawings, nevertheless, according to one particular aspect of the present invention to which, however, the invention is in no way restricted, there is provided colour image recording apparatus in which a latent image is formed on a recording medium for reproduction, the apparatus comprising an intermediate image receiving medium, means for recording on the intermediate image receiving medium an intermediate image and a positioning mark, means for transferring the intermediate image from the intermediate image receiving medium to the recording medium, a detection device for detecting the positioning mark, and means for positioning the intermediate image receiving medium relative to the transfer means during image transfer in accordance with an output from the detection device.

In its preferred form as described below, the colour image recording apparatus of the present invention has plural intermediate image medium locations, a detection unit, a photo-sensitive film, a projection/exposure system for projecting an image on each intermediate image medium location onto the photosensitive film for exposing the same, and a receiver sheet for receiving the image from the photo-sensitive film.

In use, each intermediate image medium location has written into a write area thereof a colour image representing one of the yellow, magenta and cyan image components and has written in a pre-determined position outside the write area a respective positioning mark.

The positioning marks are always written at the same time as writing the colour image and are always at the same position with respect to the write area. Each of the colour images written into its intermediate image medium location is formed successively on the photosensitive film by the projection/exposure system, so that the colour images representing the yellow, magenta and cyan image components overlap in the latent image formed on the photo-sensitive film. It is possible to position each of the intermediate image medium locations accurately in a pre-determined position relative to the projection/exposure system by detecting the positioning mark using the detection unit, because the position of the positioning mark relative to the write area is the same in each of the intermediate image medium locations.

The latent image is subsequently transferred to the receiver sheet and a colour image is reproduced on the receiver sheet.

The reproduction image in this preferred form of the invention has excellent image quality with less colour deviation than in the case of the prior art.

One application of the present invention is in a digital printer.

The present invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic view of a portion of an image write unit of colour image recording apparatus according to the present invention; Figure 2 is a schematic view of a portion of an intermediate image medium conveyor unit of the colour image recording apparatus according to the present invention; Figure 3 is a schematic view of the overall colour image recording apparatus according to the present invention; Figure 4 is a sectional view through a liquid crystal panel of the colour image recording apparatus according to the present invention; and Figure 5 is a flow chart representing the operation of the colour image recording apparatus according to the present invention.

Figure 1 is a schematic illustration for assistance in explaining a position mark writing operation in a colour image recording apparatus in accordance with the present invention. As shown in Figure 1, the colour image recording apparatus includes a laser scanner as follows.

The laser scanner shown in Figure 1 has as a laser source a semi-conductor laser 45, whose laser emission is turned ON and OFF by laser modulation signals input in accordance with image signals. Besides this semi- conductor laser 45, the laser scanner has a collimator lens 44 for collimating the light emitted from the semiconductor laser 45 into substantially parallel beams, a polygonal mirror 5 arranged to rotate at a predetermined number of revolutions in a given time so as to direct the beams issuing from the collimator lens 44 in the main scanning direction, and an fO lens 42, disposed between the polygonal mirror 5 and a liquid crystal panel 47, for converging the beams reflected by the polygonal mirror 5 onto the liquid crystal panel 47.

Pre- and post-stage cylindrical lenses 43, 41 are disposed between the collimator lens 44 and the polygonal mirror 5 and between the fO lens 42 and the liquid crystal panel 47, respectively, for correcting the surface turn down of the polygonal mirror 5. An optical sensor 40 is also provided for detecting the write start position in the main scanning direction of the laser beam issuing from the post-stage cylindrical lens 41.

The laser scanner writes an image onto an image write area 48 of the liquid crystal panel 47 and simultaneously writes a positioning mark 49 outside the image write area 48. The positioning mark 49 is always placed at the same address, and so its position relative to the image to be written is always the same.

Figure 2 is a schematic illustration for assistance in explaining a position mark reading operation in the colour image recording apparatus in accordance with the present invention.

As shown in Figure 2, the colour image recording apparatus further includes a moving table 29 having laser beam write type liquid crystal panels 10, 11 and 12 for holding colour images representing yellow (Y), cyan (C) and magenta (M) image information, respec tively. Two mark read sensors 54 are disposed in the projection plain of the liquid crystal panels 10, 11, 12 in order to read pairs of positioning marks 49## t 49c 49 written onto the liquid crystal panels 10, 11, 12.

M A differential amplification circuit 52 calculates and amplifies the difference between the outputs of these two mark read sensors 54. A motor driving circuit 53 drives a motor for moving the moving table 29 in response to the output of the differential amplification circuit 52 so that the image on each of the liquid crystal panels 10, 11, 12 is projected at the same position.

Figure 3 is a schematic illustration of the colour image recording apparatus in accordance with the present invention.

The colour image recording apparatus has an image write unit 30, an intermediate image medium conveyor unit 31, a projection/exposure unit 32 and an image transfer unit 33.

The image write unit 30 has a main scanner (for scanning in a direction perpendicular to the sheet of the drawing) containing the semi-conductor laser 45 and the polygonal mirror 5 shown in Figure 1, together with a mirror 6. The image write unit 30 further has a moving table 28 for carrying the main scanner, a ball screw 4 for sub-scanning the moving table 28 in a direction substantially perpendicular to the main scanning direction, a pulse motor 1 for rotating the ball screw 4 for sub-scanning, a slit element 3 fitted to the moving table 28 for representing the present position of the moving table 28, and a photo-interrupter 2, which co-operates with the slit element 3 for detecting the mechanical origin of the moving table 28.

The intermediate image medium conveyor unit 31 comprises the three laser beam write type liquid crystal panels 10, 11, 12, which have exactly the same structure and which serve as intermediate image medium locations for converting yellow, cyan and magenta colour component image signals to two dimensional images, respectively. The conveyor unit 31 also has the moving table 29, on which the three liquid crystal panels 10, 11, 12 are disposed, a ball screw 13 for conveying the moving table 29 in a direction substantially parallel to the sub-scanning direction of the moving table 28 described above, a pulse motor 9 for rotating the ball screw 13, a slit element 8 fitted to the moving table 29 for representing the present position of the moving table 29, and a photointerrupter 7, which co-operates with the slit element 8 for detecting the mechanical origin of the moving table 29.Further, the conveyor unit 31 includes the two mark read sensors 54, the differential amplification circuit 52 and the motor driving circuit 53 shown in Figure 2.

The projection/exposure unit 32 has a halogen lamp 17, a reflecting mirror 18 for focussing the light from the lamp 17, a condenser lens 15 for converting the light emitted by the halogen lamp 17 into a generally convergent beam, and a filter 16 for cutting out thermal rays. A half mirror 14 is provided for reflecting the convergent beam from the halogen lamp 17 and directing it to the liquid crystal panels 10, 11, 12 on the moving table 28 and also for passing the beams reflected from the liquid crystal panels 10, 11, 12 to a projection lens 19 for directing the images from the liquid crystal panels 10, 11, 12 onto a capsule sheet 20 for forming the images thereon. The capsule sheet 20 is mounted between a capsule sheet take up roller 22 for taking up the capsule sheet 20 and a back tension roller 21 for exerting a uniform pull on the capsule sheet 20.

An example of a suitable capsule sheet for the sheet 20 is a micro-capsule sheet produced by Mead Co., U.S.A. This micro-capsule sheet is prepared by coating uniformly, on a PET film, three kinds of micro capsules encapsulating colour precursors a , a2, a of 3 cyan, magenta and yellow and sensitive compositions b b , b sensitive to rays of light of wavelengths A 1' X Z A that are different for each of the colour precursors, and passivating them by changing the viscosity, etc. by a thin film C such as gelatin.

The transfer unit 33 has a receiver sheet feed roller 23 for feeding a receiver sheet, on which developers for reacting with the colour precursors a , a , a on the capsule sheet 20 and causing colouration 3 reaction are coated uniformly. A pressure contact roller 24 is provided for pressing the receiver sheet against the capsule sheet 20 with a pre-determined force determined by a compression spring 25. A cutter 26 cuts the receiver sheet into pre-determined lengths to provide an output sheet 27 cut to a pre-determined length after each transfer is complete.

Figure 4 is a sectional view of one of the liquid crystal panels. A pair of rear and front transparent substrates 60a and 60b made of glass or plastics material are connected to each other by means of a spacer 68 to form a light valve cell for accommodating therein a liquid crystal layer 63 composed of ferroelectric liquid crystal molecules. The front substrate 60b is formed on its inner face sequentially with a transparent electrode layer 61b and an alignment layer 62b. The alignment layer 62b is formed by oblique evaporation of silicon monoxide at an angle of 75 to 85 degrees relative to the normal of the substrate 60b.

The rear substrate 60a is also formed on its inner face with another transparent electrode layer 61a and another alignment layer 62a, the latter being formed in a manner similar to the alignment layer 62b. The pair of substrates 60a and 60b are opposed in controlled spaced relation to each other such that the pair of alignment layers 62a and 62b are disposed in contact with the interposed liquid crystal layer 63 at opposite sides thereof.

Further, a photo-conductive layer 64, a light shielding layer 65 and a dielectric mirror layer 66 are sequentially interposed between the transparent electrode layer 61a and the alignment layer 62a as a multi-layer structure on the inner face of the rear substrate 60a. On the other hand, the front substrate 60b is formed on its outer face with a non-reflective coating layer 67.

The operation of the light valve, including the double layer structure of the photo-conductive layer 64 and the ferro-electric liquid crystal layer 63, is as follows: the double layer structure is irradiated with writing light 69 from the outer or rear face of the transparent substrate 60a to effect switching between two optically different bistable ON and OFF states to thereby write an image pattern into the ferro-electric liquid crystal layer 63, and the light valve is irradiated with reading or projecting light 70 from the outer or front face of the transparent substrate 60b to read out or project the image pattern written in the liquid crystal layer 63.

In the production of the light valve of Figure 4, a pair of transparent glass substrates 60a and 60b are provided, and the transparent electrode layers 61a and 61b are deposited over the entire surface of a respective face of each of the substrates 60a and 60b in the form of ITO transparent electro-conductive film.

The rear substrate 60a is placed within a gas atmosphere composed mainly of SiF . By decomposing SiF with an 4 4 electric spark, intrinsic a-Si:H is deposited on the electrode layer 61a at a thickness of 3 micro-metres to constitute the photo-conductive layer 64. The light shielding layer 65 is formed on the photo-conductive layer 64, which functions to block the reading light from passing into the photo-conductive layer 64, and thereafter silicon and silicon dioxide layers are alternately deposited in a superposed structure of fifteen layers to form the dielectric mirror layer 66.

If the dielectric mirror layer 66 has a sufficient reflectivity to incident visible light to prevent the reading light from affecting the photo-conductive layer 64, the light shielding layer 65 may be eliminated.

Silicon monoxide (SiO) is obliquely evaporated onto the dielectric mirror layer 66 from an angular direction of 82 degrees from the normal of the substrate to a thickness of 2000 Angstroms as measured by a film thickness gauge set along the evaporation direction to thereby form the alignment layer 62a. In a similar manner, the front substrate 60b is also subjected to the oblique evaporation of SiO to form the other alignment layer 62b on the transparent electrode 61b.

The pair of substrates 60a and 60b are coupled to each other, with the respective alignment layers 62a and 62b facing each other, by means of the spacer 68, which is composed of adhesive containing chips of glass fibre having a diameter of about 1.5 micro-metres and is effective to control the spacing between the pair of substrates.

A ferro-electric liquid crystal composition is introduced into the space to form the ferro-electric liquid crystal layer 63. The ferro-electric liquid crystal composition may be composed of a mixture of ester type SmC liquid crystal materials with an optically active material added. For example, the mixture may comprise 4-((4'-octyl) phenyl) benzoic acid (3"-fluoro, 4"-octyloxy) phenyl ester:

and 4-((4'-octyloxy) phenyl) benzoic acid (3"-fluoro, 4"-octyloxy) phenyl ester:

at a ratio of 1:1. The optically active material may be composed of 5-octyloxynaphthalene carboxylic acid 1'cyanoethyl ester:

which is added to the mixture by weight at 25% to form the ferro-electric liquid crystal composition.

Next, the operation of the described colour image recording apparatus will be explained with reference to the flow chart shown in Figure 5.

During a first initialisation step, the moving table 28 having the laser scanner fitted thereto is moved in the sub-scanning direction a and, when the photo-interrupter 2 and the slit of the slit element 3 coincide with each other, the movement of the moving table 28 in the direction a is stopped. The moving table 28 is moved in the direction b by a distance W and is then stopped (step 101). This point is the start point for the write operation. Next, as a second initialisation step, the moving table 29 having the three liquid crystal panels 10, 11, 12 fitted thereto is moved in the direction d and, when the photointerrupter 7 and the slit of the slit element 8 coincide with each other, the movement of the moving table 29 in the direction d is stopped (step 102).

Next, the image write operation and the projection/exposure processes are started. First of all, the moving table 28 is sub-scanned in the direction b at a constant speed simultaneously with the start of the image write operation in the main scanning direction by the laser scanner (step 103). Then, when the distance of movement of the moving table 28 reaches W + L from the mechanical origin determined by the photo-interrupter 2, sub-scanning of the moving table 28 in the direction b is stopped (step 104) and, immediately thereafter, its return in the direction a by the distance L is effected (step 105).

Next, movement of the moving table 29 having the three liquid crystal panels 10, 11, 12 fitted thereto in the direction c is started. The moving table 28 is stopped after positioning the same so that the outputs become equal to each other when the two mark read sensors 54 read the positioning marks 49 . As a result, y the yellow exposure liquid crystal panel 10, into which the image has already been written, and the cyan exposure liquid crystal panel 11 are conveyed to predetermined positions relative to the projection/ exposure unit 32 and to the image write unit 30, respectively (step 106).

The write operation of the image to the cyan exposure liquid crystal panel 11 is then started in the same way as in the case of the yellow exposure liquid crystal panel 10. Simultaneously with the start of the image write operation to the cyan exposure liquid crystal panel 11, the image formed on the yellow exposure liquid crystal panel 10 is transferred to the capsule sheet 20 by reflection and projection (step 107).

After the write operation of the image to the cyan exposure liquid crystal panel 11 and the reflection/ projection in relation to the yellow exposure liquid crystal panel 10 are complete, the moving table 28 is returned by the distance L in the direction a. The moving table 29 is also moved and positioned so that the outputs become equal to each other when the two mark read sensors 54 read the positioning marks 49 C Movement of the moving table 29 is then terminated (step 108).The processes described above expose the yellow component of the image, that has been formed on the yellow exposure liquid crystal panel 10, on the capsule sheet 20, and convey the cyan exposure liquid crystal panel 11, to which the cyan component of the image has been written, to the pre-determined position in relation to the projection/exposure unit 32, simultaneously conveying the magenta exposure liquid crystal panel 12 to the pre-determined position relative to the image write unit 30.

Subsequently, the projection/exposure of the image formed on the cyan exposure liquid crystal panel 11 onto the capsule sheet 20 and the write operation of the image to the magenta exposure liquid crystal panel 12 are carried out (step 109). After the image write operation to the magenta exposure liquid crystal panel 12 and the transfer of the image on the cyan exposure liquid crystal panel 11 are complete, the moving table 28 is returned by the distance L in the direction a and the moving table 29 is conveyed in the direction c and is stopped at the pre-determined position relative to the projection/exposure unit 32, by use of the positioning marks 49 in the same way as described above, in order to carry out projection/exposure of the image formed on the magenta exposure liquid crystal panel 12 onto the capsule sheet 20 (step 110).

The processes described above synthesize in super position the images corresponding to the yellow, cyan and magenta colour components written into the three liquid crystal panels 10, 11 and 12. Moreover, since the yellow, cyan and magenta images formed in the liquid crystal panels and the positioning marks have the same relative positions, the respective projected images for the different colour beams on the capsule sheet 20 will also correspond and colour deviation will be avoided.

The pressure contact roller 24 and the capsule sheet take up roller 22 then start rotating to advance the exposed capsule sheet 20 to the transfer unit 33.

Simultaneously with the rotation of these rollers 22, 24, the receiver sheet feed roller 23 supplies the receiver sheet. The capsule sheet 20 and the receiver sheet are superposed and pressed against one another by the pressure contact roller 24. As a result, the image on the capsule sheet 20 is transferred to the receiver sheet and, after being cut to a necessary length by the cutter 26, a section of the receiver sheet is supplied as the output paper 27. The used capsule sheet 20 is recovered by the capsule sheet take up roller 22.

Incidentally, although the embodiment described above features a laser write type liquid crystal material as the intermediate medium into which the image is written, the present invention is not limited thereto and other media, such as a conventional photosensitive drum or a selenium flat sheet, can of course be used.

Further, although the described embodiment employs a linear feed system as the conveyor method for the liquid crystal panels, the same effect can be obtained by use of other arrangements, such as a rotary arrangement employing a rotatable disc.

The positioning marks need not necessarily be the two lines described above, and various alternatives such as a single line, a criss-cross mark and the like can of course be employed in combination with an appropriate sensor.

The present invention as described provides various advantages: Repetition positioning accuracy for the image write unit 30 can be lowered, and so a relatively simple and economical sub-scanning system can be employed for the image write unit. The liquid crystal panel conveyor system forms a closed loop, and so positioning errors can be monitored and corrected such that colour deviation does not occur. Also, #positioning errors can be corrected easily whereby a reproduction image having excellent image quality with less colour deviation can be obtained repeatedly.

Claims (12)

1. Colour image recording apparatus in which a latent image is formed on a recording medium for reproduction, the apparatus comprising an intermediate image receiving medium, means for recording on the intermediate image receiving medium an intermediate image and a positioning mark, means for transferring the intermediate image from the intermediate image receiving medium to the recording medium, a detection device for detecting the positioning mark, and means for positioning the intermediate image receiving medium relative to the transfer means during image transfer in accordance with an output from the detection device.

2. Apparatus as claimed in claim 1 in which the intermediate image receiving medium has a plurality of intermediate image receiving locations arranged to receive respective components of the intermediate image and respective positioning marks.

3. Apparatus as claimed in claim 2 in which each of the intermediate image receiving locations includes a respective liquid crystal panel.

4. Apparatus as claimed in claim 3 in which each liquid crystal panel includes a layer of a ferroelectric liquid crystal composition.

5. Apparatus as claimed in any of claims 2 to 4 in which the recording means are arranged to record respective colour components of the intermediate image in each of the image receiving locations.

6. Apparatus as claimed in any preceding claim in which the intermediate image receiving medium is mounted on a movable support, and in which the positioning means are arranged to move the movable support in accordance with the output from the detection device.

7. Apparatus as claimed in any preceding claim in which the transfer means comprise means for projecting the intermediate image onto the recording medium.

8. Apparatus as claimed in any preceding claim including the recording medium and in which the recording medium comprises a base film carrying a plurality of micro-capsules, each of which includes one of a plurality of colour precursors and a corresponding one of a plurality of photo-sensitive compositions.

9. Apparatus as claimed in any preceding claim further comprising additional transfer means for transferring the latent image to a receiver sheet.

10. Colour image recording apparatus comprising intermediate image media for memorising image information, image writing means for writing image information and a positioning mark into the intermediate image media, latent image means for memorising a latent image corresponding with the image information memorised in the intermediate image media, latent image forming means for projecting the image information memorised in the intermediate image media onto and for exposing the latent image means, detecting means for detecting the positioning mark, and positioning means for positioning the intermediate image media in accordance with an output of the detecting means.

11. Colour image recording apparatus substantially as herein particularly described with reference to and as illustrated in the accompanying drawings.

12. Any novel integer or step, or combination of integers or steps, hereinbefore described and/or as shown in the accompanying drawings, irrespective of whether the present claim is within the scope of or relates to the same, or a different, invention from that of the preceding claims.