Printing And Copying Employing Materials With Surface Variations

Abstract

A printing plate is coated with an amorphous semiconductor material capable of being switched between a generally amorphous or disordered state and a crystalline or more ordered state in response to light. In the crystalline or more ordered state the surface of the material is rough or grainy, while in the generally amorphous or disordered state the surface of the material is smoother. Solutions adhere to the rough surface of the material and do not adhere to the smooth surface. Ink may be fixed directly to the material or transferred to a document or offset roller. The material may be cleaned and reset into one of its states in preparation for recording another image.

Description

This invention relates to copying and printing and may be used to prepare many copies from an original, or print out data stored in a data processing system. Photo-offset lithography has been found to be a suitable technique for making duplicate copies of an original image. The process employs a sensitized plate which is exposed to a strong light through a transparent film. The image is transferred to the plate by photochemical action. The end result is a plate that is receptive to greasy ink wherever it is supposed to print, and receptive only to water where it is not supposed to print. This process requires the use of chemicals and is not reversible. Accordingly the plate cannot be used again and does not lend itself to completely automated operation. Also, it is not a process that is adaptable for on-line use with data processing systems as output printers. Additionally, corrections cannot be made to the plate once the plate has been exposed.

One of the principal objects of the present invention is to provide new and improved techniques for forming an image on a surface. The surface has a variable sensitivity to liquid which adheres to some portions of the surface, but not others. The solution may contain ink which may be viewed directly on the surface, or the ink may be transferred to a document by direct printing or offset printing techniques.

One example of a group of materials which exhibit variations in structure have been called amorphous semiconductor materials, and are described and illustrated in U.S. Pat. No. 3,271,591 by Stanford R. Ovshinsky issued Sept. 6, 1966. These materials have been employed to form printing plates in U.S. application Ser. No. 3454 entitled PRINTING EMPLOYING MATERIALS WITH VARIABLE VOLUME by Stanford R. Ovshinsky, and have also been employed in information storage systems as described in U.S. application Ser. No. 791,441 entitled METHOD AND APPARATUS FOR PRODUCING, STORING AND RETRIEVING INFORMATION by Stanford R. Ovshinsky now U.S. Pat. No. 3,530,441. Amorphous semiconductor materials can be switched between two stable states in response to the application of electromagnetic energy such as a light beam, electron beam, or electrical current, and may also be switched in response to energy such as heat. As described in more detail in the aforementioned patent and patent applications amorphous semiconductor materials are preferably polymeric in structure and undergo structural changes involving configurational and conformational changes in atomic structure. In one state the material is substantially disordered and generally amorphous having only a certain degree of local order and/or localized bonding between atoms. In the other state the atomic structure of the material is changed to a different local order and/or localized bonding such as, for example toward a more ordered crystalline-like condition, wherein a number of atoms are linked together in longer chains. This material may be anisotropic, appearing to be in one state when measuring its properties along a given axis, and in the other state when measuring its properties along a different axis. For the purposes of the present invention one of the states will be called hereinafter the generally amorphous or disordered state, and the other state will be called hereinafter the crystalline or more ordered state. The present invention utilizes the difference in the structure of materials, such as amorphous semiconductor materials, to provide new and improved copying and printing techniques which do not require photochemicals, and which are reversible, correctable and reusable.

In one mode of operation of the present invention a laser beam is used to write on the surface of an amorphous semiconductor material which is initially in the crystalline or more ordered state. The laser beam produces a generally amorphous or disordered state wherever the beam strikes the material. A wetting solution is applied to the entire surface and adheres only to the crystalline or more ordered regions. Ink which is repelled by the wetting solution is next applied to the entire surface, but can only adhere to the exposed generally amorphous or disordered regions. An offset roller transfers the ink onto a document. Since the material can be reset into the initial crystalline or more ordered state, the printing plate can be used over and over again. Further, the writing speeds are compatible with the print-out speeds from data processing systems, and accordingly the present invention may be employed in such applications.

Still another advantage of the present invention is the ability to copy or print varying shades of gray. This may be accomplished for example by varying the energy content in the laser or other electromagnetic beam to vary the density of the rough or granular surface structure of the material.

Other objects, advantages and features of this invention will become apparent to those skilled in the art upon reference to the accompanying specification, claims and drawings in which:

FIG. 1 is a diagram illustrating a copier forming an image on a printing plate using light passing through a transparent film;

FIG. 2 is an enlarged partial view of the printing plate in FIG. 1;

FIG. 3 is a diagram illustrating an output printer forming a printing plate by controlling the movement of a laser beam;

FIG. 4 is an enlarged partial view of the printing plate in FIG. 3;

FIG. 5 is a diagram of a printing plate wherein images are formed by electrical currents; and

FIG. 6 is a wave form diagram illustrating the current pulses utilized in the printing plate of FIG. 5.

The copying system of FIG. 1 employs a printing plate 10 in the form of a rotating drum. The image to be copied appears on a transparent film 12 which is moved through the focal line of a cylindrical lens 14. Lens 14 focuses light 16 from a source 18. The light 16 passing through film 12 is collected by a spherical lens 20 and re-imaged on the surface of the plate 10. The image formed on plate 10 is inked by a roller 22 and the inked image is transferred to a rubber-covered cylinder 24 which is also rotated in synchronism with plate 10. The ink is then transferred from cylinder 24 to a document 26 which is pressed against the cylinder 24 by an impression roller 28. pg,5

The plate 10 is composed of an amorphous semiconductor layer 30 applied to a structural support cylinder 32. The plate 10 is shown in a partial expanded view in more detail in FIG. 2 where the same numbers are applied to the same elements in FIG. 1. The amorphous semiconductor material 30 may be composed of Se.sub.95 Te.sub.4.9 Pt.sub. .1, Se.sub.95 Te.sub.4.0 Ga.sub.1.0 ; or other materials, such as those described in U.S. Pat. No. 3,271,591 and U.S. Pat. application Ser. No. 791,441, which can be switched from a generally amorphous or disordered state to a crystalline or more ordered state in response to energy from light source 18. For amorphous semiconductor materials, light source 18 may be a laser or other strong light source. The material 30 may be initially in the generally amorphous or disordered state and selectively switched into the crystalline or more ordered state to produce an image, such as the letters ECD illustrated in FIG. 2. The image results from heating the surface of material 30 to the transition temperature of the amorphous semiconductor. The crystalline regions of material 30 represented by ECD exhibit a rough or grainy surface while the remainder of the surface 30 is relatively smooth. Accordingly the ink on roller 22 does not wet the smooth areas of the surface of material 30, but adheres to the rough or grainy areas represented by the letters ECD.

Additional copies may be made by rotating plate 10 a number of times, re-inking the rough areas of material 30 with inking roller 22. When it is desired to print a new image roller 22 is retrieved by an actuator 34 and the surface of material 30 is rotated past a cleaning station 36 which may include a shower of appropriate cleaning fluid and blast of dry air. The material 30 is then rotated past a focused line of high intensity electromagnetic energy which may be produced by increasing the intensity of light source 18. This causes the temperature at the surface of material 30 to rise past its melting point. As the plate 10 rotates the surface of material 30 is quickly passed under a quenching roller 38 which is placed into contact with material 30 by an actuator 40. The sudden drop in temperature of the surface of material 30 returns the crystalline or more ordered regions to the generally amorphous or disordered state. A new transparent film 12 may be passed through the focal line of lens 14 and imaged on the surface of material 30 forming a new image which may be inked by roller 22 after actuator 34 places roller 22 in contact with material 30.

FIG. 3 illustrates another application of the present invention for performing the function of a non-impact printer or photo-composer. Like numbers are used to designate similar elements in FIGS. 1-3. The image is formed on plate 10 by a laser beam 42 generated by a source 44. The beam 42 is modulated in intensity by a modulator 46. After passing through modulator 46 beam 42 is deflected by a scanner 48 which directs beam 42 onto a particular location on plate 10. A data processing system 50 controls the operation of source 44, modulator 46 and scanner 48 through a group of lines 52 - 54, respectively. The image can be formed on plate 10 by a series of laser pulses scanning across the width of the plate 10 similar to the raster scan of a television receiver. Beam 42 may also be deflected to form a continuous curved trace. Alternatively, alpha-numeric characters can be formed by placing a mask in deflector 48 and shaping laser beam 42 into a desired character prior to directing beam 42 onto plate 10.

FIG. 4 illustrates a typical image comprising the letters ECD recorded on plate 10 by the system of FIG. 3. Like numbers are applied to the same elements in FIGS. 3 and 4. In this system the amorphous semiconductor material 30 is initially in the crystalline or more ordered state, and beam 42 switches the surface of material 30 into the generally amorphous or disordered state represented by the regions of letters ECD. The material 30 is heated past its melting point by beam 42 and is quenched by the rapid dissipation of heat into the surrounding material. In operation the system of FIG. 3 rotates the image formed by beam 42 under a roller 56 which applies a solution to the surface of material 30. This solution may be composed of a mixture of water and alcohol at a ratio of about 60 per cent alcohol and 40 per cent distilled water. Such a solution wets the regions of material 30 in the crystalline or more ordered state, but does not adhere to the letters ECD which are in the generally amorphous or disordered state. After being wet by roller 56, the image is rotated under inking roller 22 where ink is repelled by the regions of surface 30 which have been wet by the solution on roller 56. Ink from roller 22 adheres to the letters ECD which are not wet from the solution on roller 56. The inked image is then transferred to cylinder 24 and subsequently to document 26.

Additional copies can be made by rotating the image on the surface of material 30 under rollers 56 and 22. After a desired number of copies have been produced, roller 56 is disengaged by an actuator 58 and roller 22 is disengaged by actuator 34. Cleaning station 36 operates to remove the ink and wetting solution deposited by rollers 22 and 56. The material 30 is then reset into the crystalline or more ordered state by sweeping the entire surface, or portions thereof with laser beam 42. Beam 42 is adjusted by modulator 46 under control of data processing system 50 so that the temperature on the surface of material 30 is raised to the transition point causing the generally amorphous or disordered portion of the material to be transformed into the crystalline or more ordered state. The transition temperature in amorphous semiconductors is usually found to be lower than the melting temperature. After the surface of material 30 is returned to the crystalline or more ordered state, another image may be formed by applying laser beam 42.

FIG. 5 illustrates another technique for forming an image on a printing plate 60. The image is formed in this case by the application of heat generated by electromagnetic energy in the form of electrical current. The printing plate 60 is composed of a glass, or other non-conducting supporting structure 62 having seven resistor segments 64- 70 deposited thereon. Conductors 74-81 are connected to a group of electrodes 84-95 electrically contacting the ends of segments 64-70. Amorphous semiconductor material 30 is deposited over the top of the segments 64-70 and conductors 74-81.

A character generator 98 supplies current on lines 74-81 which are connected to printing plate through a group of connector pins 100 allowing the plate to be disconnected from character generator 98. Current is selectively coupled to the segments 64-70 to cause one or more of the segments to radiate heat. For example current from character generator 98 on line 78 passes through electrode 85, resistor segment 65, electrode 84 and returns to ground via line 74. The current passing through resistor segment 65 causes this segment to radiate heat. The heat radiated from segment 65 is transferred into the portion of amorphous semiconductor material 30 coating segment 65. Referring to the wave form diagram shown in FIG. 6 wherein current is plotted along the ordinate and time is plotted along the abscissa, a set pulse 102 is shown having a duration of about ten milliseconds and a reset pulse 104 is shown having a higher intensity, but shorter period of approximately ten microseconds. Set pulse 102 causes the material 30 coating the selected segments 64-70 to switch into the crystalline or more ordered state, while reset pulse 104 switches material 30 into the generally amorphous or disordered state following the rapid decline of the reset pulse 104.

In operation, the printing plate 60 of FIG. 5 can be made to form all the numbers from zero to nine, and a few letters by selectively applying current to segments 64-70. After the amorphous semiconductor material 64-70 is switched into the appropriate pattern, printing can be accomplished by any one of the techniques described in connection with the systems of FIG. 1 and FIG. 3. The segments 64-70 can be deposited in any shape, including a matrix of points which may be selected by orthogonal conductors in accordance with the usual matrix selection techniques. In some applications it may be preferable to pass current directly through the amorphous material to cause heating, instead of through an underlying resistor such as segments 64-70.

Gray scale printing and copying can also be achieved in the systems of FIGS. 1, 3 and 5. For example in the system of FIG. 1, the intensity of beam 16 after passing through transparent film 12 can produce a highly rough or grainy surface where a dark image is to be printed, and a slightly rough or grainy surface where a light gray image is desired. Ink from roller 22 will adhere in an amount depending upon the condition of surface 30. In a similar manner the system of FIG. 3 can be made to produce gray scale by varying the intensity of laser beam 42 which can be made to switch material 30 from the initially crystalline or more ordered state into a generally amorphous or disordered state in varying amounts. Some residual crystalline or more ordered structure may remain in the surface of material 30 causing some slight wetting by the solution on roller 56. Accordingly, ink from roller 22 will not adhere to such an area to the same degree that it adheres to an area that has been completely switched to the generally amorphous or disordered state. In this manner the shade of gray can be varied to produce different contrasts in the image ultimately printed on document 26.

The present invention may also be used to selectively erase only a portion of the image formed on plate 10. In FIG. 1 a transparent film 12 can be produced with transparent openings in those regions where an erasure is to be made. In FIG. 3 laser beam 42 can be directed onto selected regions of the material 30 to erase certain characters or portions thereof. Corrections can be made in this manner without erasing the entire plate and re-imaging the entire pattern.

The present invention may also be utilized to form a permanent image on plate 10 by applying ink with roller 22 and allowing the ink to dry forming a fixed permanent record of the image. In this case it may be preferable to form material 30 so that it is removable from supporting structure 32.

In some applications of the present invention it may be desirable to deposit material 30 on substrates having various forms, such as a disc, flat rectangular plate, or flexible web such as a tape which can be stored on a reel.

While the present invention has been described with reference to a crystalline or more ordered state it may not be necessary to actually form crystals in the surface of the amorphous material. Other changes of atomic structure may be employed, such as, atoms initially linked together in the form of long chains can be rearranged into rings. Also, chains in the form of a helix or other compressed configuration may be stretched or extended into a new shape. Still other changes in local order or changes in phase may result in new bonds between atoms resulting in new structural or chemical configurations which provide different wetting ability. These variations in atomic structure and the mixture of the various phases of the material may produce a change in the surface roughness of the material causing solutions to adhere to a different degree. Alternatively, the roughness of the surface may remain substantially the same in each state of the amorphous material, but the degree of attraction between the surface and solution may be varied depending upon the phase of the material, thereby changing the wetting ability of the solution on the surface.

Numerous other modifications may be made to various forms of the invention described herein without departing from the spirit and scope of the invention.

Claims

What is claimed is:

1. A method of forming an image comprising:

providing a layer of amorphous material capable of having surface portions thereof changed between a first stable atomic structure state exhibiting a relatively high affinity for aqueous solutions and a second stable atomic structure state exhibiting a relatively low affinity for aqueous solutions, said material being switched in response to energy applied thereto;

applying energy to selected areas of said layer for switching said discrete areas of said layer between said first and second atomic structure states; and

applying an aqueous solution to said layer for wetting said layer in those areas of said layer which are in said first atomic structure state and for not substantially wetting those areas of said layer which are in said second atomic structure state to form an image composed of said aqueous solution corresponding to said selected areas of said layer.

2. The method of claim 1 wherein said layer is composed of an amorphous material having an alterable surface structure which is capable of being changed between a generally amorphous stable state having a certain localized bonding between atoms and a different stable state having a different localized bonding between atoms, said change being produced in response to said energy applied thereto.

3. The method of claim 1 wherein said layer is composed of an amorphous material having an alterable surface structure which is capable of being changed between a generally amorphous stable state having a certain localized bonding between atoms and a more ordered stable state having a different localized bonding between atoms, said change being produced in response to said energy applied thereto.

4. The method of claim 3 wherein said solution adheres to those areas of said layer residing in the more ordered state.

5. The method as defined in claim 4 wherein said solution includes ink, and further characterized by the addition of the step of fixing said ink to said material.

6. The method of claim 4 wherein said solution includes ink, and further characterized by the addition of the step of transferring said solution from said selected areas of said layer to a document.

7. The method as defined in claim 4 further characterized by the addition of the step of applying ink to said layer after wetting said layer with said solution so that ink adheres to those areas of the material which reside in the generally amorphous state and said ink does not adhere to those areas of said material in said more ordered state having said solution adhering thereto.

8. The method of claim 7 further characterized by the step of transferring said ink from said areas of said material to which said ink adheres to a document.

9. The system as defined in claim 4 wherein said solution includes ink, and further characterized by the step of transferring said solution from those areas of said material to which said solution adheres to a document.

10. The method of claim 4 wherein said energy is formed by projecting light transmitted through a transparent medium onto said material.

11. The method of claim 4 wherein said energy is a laser beam directed onto selected areas of said material.

12. The method of claim 4 wherein said energy is in the form of heat applied to selected areas of said material.

13. The system as defined in claim 4 wherein said amorphous semiconductor material is capable of being reversibly switched between said states in response to energy applied thereto.

14. The method of claim 13 wherein said amorphous material is initially in the generally amorphous state and said pattern of energy switches said material to the more ordered state, and further characterized by the addition of the step of applying energy to at least a portion of said material residing in said more ordered state to return said portion to the generally amorphous state, whereby said material may be re-used to form another image thereon.

15. The method of claim 13 wherein said amorphous material initially resides in the more ordered state and said pattern of energy changes said material to the generally amorphous state, and further characterized by the addition of the step of applying energy to at least a portion of said material residing in the generally amorphous state to return said portion to the more ordered state, whereby said material may be re-used to form another image thereon.