Image-forming method and device utilizing a shim member arrangement

Abstract

An image forming method and device utilizes an imaging member to expose a photosensitive media to form a latent image on the media. The photosensitive media is of the type that comprises a plurality of microcapsules that encapsulate imaging material. The device and method of the present invention is adapted to utilize the application of pressure to create a compressive force on the media that is sufficient to rupture selected microcapsules in developing an image. In the arrangement of the present invention, a shim member arrangement is adapted to locate a thin member such as a plastic or film member over an imaging side of the media so as to protect the imaging side of the media during the application of pressure on the medium.

Description

FIELD OF THE INVENTION

The present invention relates to an image forming method and device adapted to develop images on photosensitive media that includes microcapsules that encapsulate material such as coloring material. The device and method of the present invention includes the use of a thin shim member during a pressure develop of the media to minimize artifacts on the media.

BACKGROUND OF THE INVENTION

Image forming devices are known in which media having a layer of microcapsules containing a chromogenic material and a photohardenable composition, and a developer, which may be in the same or a separate layer from the microcapsules, is image-wise exposed. In these devices, the microcapsules are ruptured, and an image is produced by the differential reaction of the chromogenic material and the developer. More specifically, in these image-forming devices, after exposure and rupture of the microcapsules, the ruptured microcapsules release a color-forming agent, whereupon the developer material reacts with the color-forming agent to form an image. The image formed can be viewed through a transparent support or a protective overcoat against a reflective white support as is taught in, for example, U.S. Pat. No. 5,783,353 and U.S. Publication No. 2002/0045121 A1. Typically, the microcapsules will include three sets of microcapsules sensitive respectively to red, green and blue light and containing cyan, magenta and yellow color formers, respectively, as taught in U.S. Pat. No. 4,772,541. Preferably a direct digital transmission imaging technique is employed using a modulated LED print head to expose the microcapsules.

Conventional arrangements for developing the image formed by exposure in these image-forming devices include using spring-loaded balls, micro wheels, micro rollers or rolling pins, and heat from a heat source is applied after this development step to accelerate development.

The photohardenable composition in at least one and possibly all three sets of microcapsules can be sensitized by a photoinitiator such as a cationic dye-borate complex as described in, for example, U.S. Pat. Nos. 4,772,541; 4,772,530; 4,800,149; 4,842,980; 4,865,942; 5,057,393; 5,100,755 and 5,783,353.

The above-described imaging technology utilizes light sensitive microcapsules incorporated into a photographic coating, and produces a continuous tone digital imaging member. With regard to the media used in this technology, a substrate is coated with millions of light sensitive microcapsules, which contain either cyan, magenta or yellow image forming dyes (in leuco form). The microcapsule comprises a monomer and the appropriate cyan, magenta or yellow photoinitiator that absorb red, green or blue light respectively. Exposure to light, after the induction period is reached, induces polymerization.

When exposure is made, the photoinitiator absorbs light and initiates a polymerization reaction, converting the internal fluid (monomer) into polymer, which binds or traps leucodye from escaping when pressure is applied.

With no exposure, microcapsules remain soft and are easily broken, permitting all of the contained dye to be expelled into a developer containing binder and developed which produces the maximum color available. With increasing exposure, an analog or continuous tone response occurs until the microcapsules are completely hardened, to thereby prevent any dye from escaping when pressure is applied.

Conventionally, as describe above, in order to develop the image, pressure is uniformly applied across the image. As a final fixing step, heat is applied to accelerate color development and to react all un-reacted liquid from the microcapsules. This heating step also serves to assist in the development of available leucodye for improved image stability. Generally, pressure ruptured capsules (unhardened) expel luecodye into the developer matrix.

Approximately 100 mega Pascal or 14,500 psi normal pressure was required for capsule crushing as documented in prior art. This application of pressure (high compressive forces) on a small surface area of the media by way of, for example, a stylus or rollers tended to create artifacts such as scratches or surface deformations on the media. As an example, the rollers for conventional pressure development apparatuses utilized hard metallic rollers or balls as the processing rollers (balls) on the media to deliver high stress to the microcapsules. Since the required stress to rupture the microcapsules are rather high, significant stress or deformation are also observed in the media support. As a result of such high stress or deformation, defects in the media support can be seen on the image side of the media as random patterns that compromise the quality of the image. More specifically, the compression forces required for processing may make an “image” of the fiber pattern in the print, thus making the print corrupt.

It would be advantageous to provide a means or method of processing that utilized pressure application members such as rollers or styluses but minimized or eliminated the creation of artifacts on the media from the compressive forces.

SUMMARY OF THE INVENTION

An object of the present invention is to eliminate or reduce unwanted random patterns from an image caused by compressive forces of a pressure development member by reducing the stress on the media support while maintaining the required high stress on the microcapsule. The present invention provides for an image-forming device having a pressure application member that utilizes a shim member between the media and the pressure application member. The arrangement of the present invention enables the application of pressure to develop a latent image on microencapsulated media in a manner in which the stress on the media support is reduced while the pressure on the imaging side of the media is sufficient to enable the development of the latent image.

The present invention therefore relates to an image forming method that comprises exposing a photosensitive medium comprising a plurality of microcapsules which encapsulate imaging material to form a latent image; placing a thin member over an imaging surface of the photosensitive medium; and applying a pressure to the medium by pressing on the thin member, with the pressure being sufficient to cause a compressive force to be applied to the imaging side of the photosensitive medium to rupture selected microcapsules, and cause a release of imaging material from the microcapsules to develop the latent image on said photosensitive medium. The thin member is adapted to protect the imaging surface of the photosensitive medium during the applying step to minimize artifacts on the photosensitive medium from the compressive force.

The present invention further relates to an image forming device that comprises an imaging member adapted to expose a photosensitive medium to form a latent image on the photosensitive medium, with the photosensitive medium comprising a plurality of microcapsules which encapsulate imaging material; a shim member arrangement configured to locate a thin member over the imaging side of the photosensitive medium; and a processing member adapted to develop the latent image, with the processing member comprising a pressure application member adapted to contact the thin member and apply a compressive force to the imaging side of said photosensitive medium that is sufficient to rupture selected microcapsules and cause a development of the latent image on the photosensitive medium, and the thin member being adapted to protect the imaging side of said photosensitive medium to minimize artifacts on said photosensitive medium from the compressive force.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A schematically shows an image-forming device;

FIG. 1B schematically shows an example of a pressure applying system that can be used in the image-forming device of FIG. 1;

FIG. 2 is a schematic illustration of an image-forming device in accordance with the present invention;

FIG. 3 is a side view of the image-forming device of FIG. 2;

FIG. 4 is a schematic view of an image-forming device in accordance with a second embodiment; and

FIG. 5 is a side view of the device of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, wherein like reference numerals represent identical or corresponding parts throughout the several views, FIG. 1A is a schematic view of an image-forming device 15 pertinent to the present invention. Image forming device 15 could be, for example, a printer that includes an opening 17 that is adapted to receive a cartridge containing photosensitive media. As described in U.S. Pat. No. 5,884,114, the cartridge could be a light tight cartridge in which photosensitive sheets are piled one on top of each other. When inserted into image forming device 15, a feed mechanism that includes, for example, a feed roller 21a in image forming device 15, working in combination with a mechanism in the cartridge, cooperate with each other to pull one sheet at a time from the cartridge into image forming device 15 in a known manner. Although a cartridge type arrangement is shown, the present invention is not limited thereto. It is recognized that other methods of introducing media into to the image-forming device such as, for example, individual media feed or roll feed are applicable to the present invention.

Once inside image forming device 15, photosensitive media travels along media path 19, and is transported by, for example, drive rollers 21 connected to, for example, a driving mechanism such as a motor. The photosensitive media will pass by an imaging member 25 in the form of an imaging head that could include a plurality of light emitting elements (LEDs) that are effective to expose a latent image on the photosensitive media based on image information. After the latent image is formed, the photosensitive media is conveyed past a processing assembly or a development member 27. Processing assembly 27 could be a pressure applicator or pressure assembly, wherein an image such as a color image is formed based on the image information by applying pressure to microcapsules having imaging material encapsulated therein to crush the microcapsules. The pressure could be applied by way of spring-loaded balls, micro wheels, micro rollers, rolling pins, etc.

FIG. 1B schematically illustrates an example of a pressure applicator 270 for processing assembly 27 which can be used in the image-forming device of FIG. 1A. In the example of FIG. 1B, pressure applicator 270 is a crushing roller arrangement that provides a point contact on photosensitive medium 102. More specifically, pressure applicator 270 includes a support 45 that extends along a width-wise direction of photosensitive medium 102. Moveably mounted on support 45 is a crushing roller arrangement 49 that is adapted to move along the length of support 45, i.e., across the width of photosensitive medium 102. Crushing roller arrangement 49 is adapted to contact one side of photosensitive medium 102. A beam or roller type member 51 is positioned on an opposite side of photosensitive medium 102 and can be provided on a support or spring member 57. Beam or roller type member 51 is positioned so as to contact the opposite side of photosensitive medium 102 and is located opposite crushing roller arrangement 49. Beam or roller type member 51 and crushing roller arrangement 49 when in contact with photosensitive medium 102 on opposite sides provide a point contact on photosensitive medium 102. Crushing roller arrangement 49 is adapted to move along a width-wise direction of photosensitive material 102 so as to crush microcapsules and release coloring material. Further examples of pressure applicators or crushing members that can be used in the image-forming device of FIG. 1A are described in U.S. Pat. Nos. 6,483,575 and 6,229,558.

Within the context of the present invention, the imaging material comprises a coloring material (which is used to form images) or material for black and white media. After the formation of the image, the photosensitive media is conveyed past heater 29 (FIG. 1A) for fixing the image on the media. In a through-feed unit, the photosensitive media could thereafter be withdrawn through an exit 32. As a further option, image-forming device 15 can be a return unit in which the photosensitive media is conveyed or returned back to opening 17.

An image-forming device 150 in accordance with one embodiment of the present invention is illustrated in FIG. 2. More specifically, as shown in FIG. 2, image-forming device 150 includes a processing assembly or development member 270 that is in the form of a pressure applicator or a pressure assembly. Processing assembly 270 includes a pressure application member or pressure roller arrangement that comprises a first rotatably mounted pressure roller 270a and an opposing backing member that can be a rotatably mounted pressure roller 270b. Pressure roller 270a is rotatably mounted via a shaft 272 on a frame or mount 276, while roller 270b is rotatably mounted via a shaft 274 on frame 276. Each of the rollers 270a and 270b are mounted so as to define a nip portion 270′ there-between for the passage of media 152 and to provide a pressure or a compressive force to media 152 that is conveyed through the nip portion 270′. Pressure rollers 270a, 270b can be mounted in a manner where a predetermined pressure is applied at the nip portion based on the mounting of the rollers on the frame 276, or a well known adjustment member can be provided to control the pressure applied by the pressure rollers 270a, 270b by varying the position of at least one of the rollers 270a, 270b relative to the other.

In a feature of the present invention, a shim member arrangement 154 is located at the processing assembly and comprises a shim in the form of a thin piece of plastic or film 154a that is wrapped around first and second support shafts or rollers 280 and 282, as well as pressure roller 270b. Therefore, as shown, the portion of the plastic or film 154a that is wrapped around the pressure roller 270b passes through the nip portion 270′ between the rollers 270a, 270b, so that in essence, the nip portion 270′ is formed between roller 270a and the portion of plastic or film 154a that faces roller 270a. With the arrangement of the present invention, the plastic or film 154a is provided so as to completely cover the imaging side of media 152 as the media passes through the nip portion 270′.

As illustrated in the schematic view of FIG. 2 and the side view of FIG. 3, in order to develop an image on microencapsulated media 152, the media 152 is conveyed in direction 400 past an exposing device 250 where a latent image on the media is exposed. The media 152 is then conveyed to nip portion 270′ where pressure through pressure rollers 270a, 270b provides a compressive force on at least the imaging side of the media 152. This compressive force is sufficient to apply pressure to the microcapsules on the imaging side of the media having imaging material encapsulated therein to crush the microcapsules and develop the image.

Since plastic or film member 154 is wrapped around pressure roller 270b, the pressure or compressive force is applied to the imaging side via the portion of the plastic or film member that faces the imaging side of the media 152. Accordingly, the imaging side of the media 152 is protected by the plastic or film member 154 during the pressure application step.

With the arrangement of the present invention, the pressure applied by pressure rollers 270a, 270b should be of a sufficient force to quickly and rapidly crush selected microcapsules of the media 152 and develop the image. At the same time, shim member arrangement 154 having plastic or film 154a is sufficient to protect the media 152 and specifically, the imaging side of the media, so that any stress and deformation applied by the pressure roller 270a will not effect the resulting image and, more specifically, will not cause any defect, image patterns or other artifacts on the media from the compressive forces.

Additionally, the arrangement as shown in FIGS. 2 and 3 is compact since the plastic or film member 154a of the shim member arrangement 154 is wrapped around pressure roller 270b and therefore provides for a reduced footprint. Also, since plastic or film member 154a is wrapped around rollers 280 and 282, as well as pressure roller 270b, the film or plastic member 154a can be rotated about the rollers 280, 282, 270b in either direction 402a, 402b as the plastic or film member is degraded or worn over time in order to present a new portion of the plastic or film member 154a at the nip portion 270′.

Further, plastic or film member 154a, along with rollers 270a, 270 generally have a width the matches a width of the media 152, so as to enable the processing along the full width of the media, while at the same time, as noted above, the shim member arrangement 154 protects the imaging side of the media by providing a cushioning effect to prevent any unwanted artifacts on the media and reduce the stress in the media support or base layer of the media.

After the development of the image at image processing assembly 270, the media is transported pass a roller heating arrangement 160 that includes rollers 160a, and 160b rotatably mounted on a frame 162. At least one of the rollers 160a, 160b respectively includes a heating element such as a thermocouple (164a, 164b) therein to heat the rollers 160a, 160b. Roller heating arrangement 160 also acts as a drive roller arrangement for the media. As the media passes between rollers 160a and 160b, the media is heated to fix the image on the media and thereafter driven to an output of the image-forming device.

FIGS. 4 and 5 illustrate a further embodiment of an image-forming device in accordance with the present invention. As in the embodiment of FIGS. 2 and 3, image forming device 150′ of FIGS. 4 and 5 includes and exposing device 250 the exposes a latent image on media 152 that is conveyed in direction 400. After the exposing device 250, the media is driven by way of a drive roller arrangement 800 having drive rollers 800a, 800b to a processing assembly 270′. Each of the rollers 800a, 800b are preferably mounted on a frame 800′ via shafts 802, 804. One or both rollers 800a, 800b can be driven by a known arrangement such as a motor that drives circular gears, a rack gear etc. In the embodiment of FIGS. 4 and 5, drive rollers do not apply a compressive or crushing force to the media but deliver the media to processing assembly 270′ where a compressive or crushing force is applied to the imaging side of the media.

Processing assembly 270′ includes a pressure application member 870 that comprises a plurality of pressure applying members or elements 872 which could be stylus-like members or alternatively can be rollers, balls or other types of configurations that are sufficient to apply a pressure onto media. Pressure application member 870 can be adapted to move in directions 300a, 300b which are directions that are perpendicular to the direction of conveyance or movement 400 of the media, and basically is adapted to be conveyed along the widthwise direction of the media. In a preferred embodiment, this conveyance can be achieved by a motor 900 that is adapted to rotate a gear 902. Gear 902 meshes with a rack gear 904a that includes a platform 904b that is attached or mounted to pressure application member 870. Therefore, actuation of motor 900 causes a linear movement of rack gear 904a that provides for the linear movement of pressure application member along the width-wise direction of the media. This structure is one example of achieving a movement of pressure application member in a linear direction as shown and the present application is not limited thereto. It is recognized that other linear movement devices such as belts, pneumatics, etc. can also be used. Pressure application member 870 is also adapted to move down towards the media as the media passes between the pressure application member 870 and a backing member 860 as will be described. This downward movement again can be achieved by a variety of known mechanism such as gears, motor, belts, solenoids, air pressure, etc. that can be adapted to move the application member 870 and the driving arrangement down towards the media and upwardly away from the media.

Image-forming device 150′ of FIGS. 4 and 5 also comprises a shim member arrangement 154′ which includes a shim in the form of a thin piece of plastic or film 954 that is wrapped or attached to opposing holding rollers 954a, 954b. Rollers 954a, 954b are provided on opposing ends of backing member 860 and plastic or film member 954 extends between the rollers 954a, 954b so as to pass between the pressure application members 872 and the backing member 860.

Therefore, after the latent image is formed, the photosensitive media 152 is driven by drive roller arrangement 800 between pressure applicator 870 and backing member 860, and more specifically, between the film or plastic member 954 and the backing member 860. It is noted that nip portions are defined between each of the individual pressure-applying members 872 which apply pressure to the media via the plastic or film member 954 and the outer surface of the backing member 860. With the arrangement of the present invention, when the media 152 passes between pressure applicator 870 and backing member 860, pressure applicator 870 can be operated to move downward toward the film or plastic member 954. This causes each of the pressure application members 872 to apply a pressure on the plastic or film member 954 that is converted to a compressive force on the media 152. This compressive force is sufficient to apply pressure to the microcapsules having imaging material encapsulated therein to crush the microcapsules and develop the image.

With the arrangement of the present invention, the pressure applied by pressure applicator 870 and specifically the pressure application members 872 should be of a sufficient force to quickly and rapidly crush selected microcapsules of the media 152 and develop the image. At the same time, film or plastic member 954 of shim member arrangement 154′ is sufficient to protect the media 152 and specifically, the imaging side of the media, so that any stress and deformation applied by the pressure applicator members 872 will not effect the resulting image and, more specifically, will not cause any defect, image patterns or other artifacts on the media from the compressive forces.

Pressure applicator 870 with pressure application members 872 as noted above, is adapted to crush the microcapsules, and also move in a widthwise direction to ensure that all of the selected microcapsules are crushed. At the same time, as noted above, the plastic or film member 954 of shim member arrangement 154 that protects the imaging side of the media provides a cushioning effect to prevent any unwanted artifacts on the media and reduce the stress in the media support or base layer of the media. Further, the placement of the plastic or film member 954 on opposing rollers as shown in FIGS. 4 and 5 permits the movement of the plastic or film member in a direction transverse to the direction of movement of the media, such that as the plastic or film member becomes worn or time, a new portion of the plastic or film member can be presented by movement of the rollers 954a, 954b.

After the development of the image at image processing assembly 270′, the media is transported pass a roller heating arrangement 160 that includes rollers 160a, and 160b rotatably mounted on frame 162 as described above with reference to FIGS. 2 and 3. Also as described above with reference to FIGS. 2 and 3, at least one of the rollers 160a, 160b respectively includes a heating element such as a thermocouple (164a, 164b) therein to heat the rollers 160a, 160b. Roller heating arrangement 160 also acts as a drive roller arrangement for the media. As the media passes between rollers 160a and 160b, the media is heated to fix the image on the media and thereafter driven to an output of the image-forming device.

Therefore, the present invention provides for an image-forming device having a pressure development member that can be adapted to provide the necessary pressure to crush selected microcapsules on microencapsulated media, so as to release coloring material and develop an image. The arrangement of the present invention provides for a shim member arrangement that includes a thin piece of plastic or film member that can be located over the imaging side of the media The plastic or film member is effective to provide enough of a cushioning effect so as to reduce the stress in the media from the application of pressure and prevent the occurrence of unwanted artifacts or defects.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Claims

1. An image forming method comprising: exposing a photosensitive medium comprising a plurality of microcapsules which encapsulate imaging material to form a latent image; placing a thin member over an imaging side of the photosensitive medium; applying a pressure to said medium by pressing on said thin member, said pressure being sufficient to cause a compressive force to be applied to the imaging side of said photosensitive medium to rupture selected microcapsules, and cause a release of imaging material from said microcapsules to develop the latent image on said photosensitive medium; wherein said thin member is adapted to protect the imaging side of said photosensitive medium during said applying step to minimize artifacts on said photosensitive medium from said compressive force.

2. An image forming method according to claim 1, wherein said pressure applying step comprises: wrapping said thin member around a pressure roller and applying said pressure via said pressure roller, with a portion of said thin member being located between said pressure roller and said medium.

3. An image forming method according to claim 1, wherein said pressure applying step comprises: using a pressure application member having a plurality of pressure applying elements to apply a pressure on said medium, with a portion of said thin member being disposed between the pressure application member and said medium.

4. An image forming method according to claim 1, further comprising: conveying at least the developed photosensitive medium between a pair of post-heat rollers to fix the image on said photosensitive medium.

5. An image forming device comprising: an imaging member adapted to expose a photosensitive medium to form a latent image on the photosensitive medium, the photosensitive medium comprising a plurality of microcapsules which encapsulate imaging material; a shim member arrangement configured to locate a thin member over the imaging side of said photosensitive medium; and a processing member adapted to develop the latent image, said processing member comprising a pressure application member adapted to contact the thin member and apply a compressive force to the imaging side of said photosensitive medium that is sufficient to rupture selected microcapsules and cause a development of the latent image on said photosensitive medium, said thin member being adapted to protect the imaging side of said photosensitive medium to minimize artifacts on said photosensitive medium from said compressive force.

6. An image forming device according to claim 5, further comprising: a pair of drive rollers adapted to convey the photosensitive medium to said processing member.

7. An image forming device according to claim 4, further comprising: a post heat roller arrangement adapted to fix the development image on the photosensitive medium.

8. An image forming device according to claim 5, wherein said pressure application member comprises a pressure roller and an opposing backing member that permit a passage of the medium there-between, said thin member being wrapped around said pressure roller.

9. An image-forming device according to claim 5, wherein said pressure application member comprises a plurality of pressure applying elements.

10. An image forming device according to claim 8, wherein said thin member forms a part of a shim member arrangement, said shim member arrangement comprising a pair of support shafts and said thin member being wrapped around said pressure roller and said pair of support shafts.

11. An image forming device according to claim 9, further comprising a backing member located opposite to the pressure applying members, wherein said pressure application member is adapted to move along a widthwise direction of the medium.

12. An image forming device according to claim 9, wherein said thin member forms part of a shim member arrangement, said shim member arrangement comprising a pair of opposing holding rollers, such that thin member is attached to the opposing holding rollers and extends in a direction transverse to a direction of movement of the medium.