Image recording apparatus

An image recording apparatus comprises a heat-developing section for heat-developing a latent image formed on a photo/heat-sensitive material sheet in which antistatic agent is added, and conveying rollers made of resin for conveying the photo/heat-sensitive material sheet along a sheet feeding path including at least the heat-developing section.

BACKGROUND OF THE INVENTION
 The present invention relates to a heat-development recording apparatus and
 heat sensitization which is performed in a film conveying apparatus for
 conveying a film, such as a heat-development photosensitive material, and
 more particularly to an antistatic technique for use when a film, such as
 a heat-development photosensitive material, is conveyed.
 As an image recording apparatus for recording a medical image for use in a
 digital radiography system, a CT, an MR or the like, a wet system has been
 known which obtains a reproduced image by performing a wet process after a
 process for photographing or recording an image on a silver-salt
 photosensitive material has been performed.
 In recent years, a recording apparatus has attracted attention which
 employs a dry system in which the wet process is not performed and which
 uses a heat-development photosensitive material.
 FIG. 3 is a block diagram showing a related heat-development recording
 apparatus.
 The foregoing apparatus is an apparatus for performing all of recording of
 a latent image on a recording material, development of the latent image
 and transference of the image in a dry state. Referring to FIG. 3, a
 heat-development photosensitive material which is a recording material is,
 in an exposure section 4, irradiated (scanned) with a laser beam modulated
 by a laser modulation section 3 in accordance with image data 1 so that a
 latent image is formed. Then, the exposed heat-development photosensitive
 material is, in a heat-development section 5, brought into contact with a
 heating means so that heat-development is performed. As a result, an image
 is obtained.
 When the above-mentioned sequential heat-development process is performed,
 the photosensitive material is, while being nipped by conveying rollers,
 conveyed from a magazine loaded into the heat-development recording
 apparatus to the exposure section 4 after which the photosensitive
 material is conveyed from the exposure section 4 to the heat-development
 section 5. During the conveyance, an emulsion binder of a conventional
 wet-type silver-salt film containing water in a large quantity has
 inhibited easy electrification.
 On the other hand, a dry silver material for use in a method in which all
 of the processes for obtaining an image are performed in a dry state must
 maintain the hardness of the surface of the dry silver material.
 Therefore, an emulsion binding having a low water content must be
 employed, causing undesirable electrification to sometimes occur during
 conveyance or in a manufacturing process.
 If the electrification of the photosensitive material occurs, adhesion of
 dust or the like easily takes place. It leads to a fact that an irregular
 image occurs. What is worse, a plurality of the photosensitive materials
 sometimes adsorb one another. In the foregoing case, introduction of the
 sheet material encounters a problem, causing a malfunction to occur.
 SUMMARY OF THE INVENTION
 It is therefore an object of the present invention is to provide an image
 recording apparatus which is capable of preventing electrification of a
 film, which is a heat-development photosensitive material or the like,
 preventing a malfunction or the like during the heat-development process
 and improving conveyance easiness of the sheet and which can be
 manufactured at a low cost.
 In order to achieve the foregoing object, according to the present
 invention, there is provided an image recording apparatus comprising: a
 heat-developing section for heat-developing a latent image formed on a
 photo/heat-sensitive material sheet in which an antistatic agent is added;
 and conveying rollers made of resin for conveying the photo/heat-sensitive
 material sheet along a sheet feeding path including at least the
 heat-developing section.
 The foregoing structure is arranged such that the antistatic agent is added
 to the film, such as the heat-development photosensitive material.
 Therefore, electrification during the manufacturing process and the
 conveying process can be prevented. Thus, any antistatic brushes and
 adhesive rollers are not required. Moreover, use of the resin roller for
 conveying the heat-development photosensitive material sheet enables the
 manufacturing cost to be reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Referring to the drawings, an embodiment of the present invention will now
 be described. FIG. 1 is a schematic section view showing a
 heat-development recording apparatus according to one embodiment of the
 present invention. FIG. 2 is a section view showing a heat-development
 photosensitive material.
 Referring to FIG. 1, the structure of the heat-development recording
 apparatus will now be described. An image forming apparatus 10 is an
 apparatus arranged to use a heat-development photosensitive material
 (hereinafter called a "recording material sheet A") which does not require
 the wet development process. Moreover, scanning exposure using laser beam
 L is performed to expose the recording material sheet A to correspond to a
 required image so that a latent image is formed. Then, heat-development is
 performed so that a visible image is obtained.
 The image forming apparatus 10 comprises a recording-material supply
 section 12, a width aligning section 14, an image exposure section 16 and
 a heat-development section 18 disposed in this order in a direction in
 which the recording material sheet A is conveyed. Thus, conveying rollers
 indicated with circles in the drawing convey the recording material sheet
 A. Therefore, the passage formed by the conveying rollers can be
 considered as a film conveying apparatus according to the present
 invention.
 The recording-material supply section 12 has two sections having inside
 portions 22 and 24 to permit selective use of the recording material
 sheets A (for example, B4-size sheets or half-cut sheets) set in the
 foregoing sections through a magazine 100. The recording material sheet A
 is a recording material on which an image is recorded (exposed) by the
 laser beam L and which is developed with heat to develop color. In
 accordance with a print command, an uppermost recording material sheet A
 in the magazine 100 selected by suction cups 26 and 28 structured for each
 sheet is taken out in a state in which the cover of the magazine is opened
 Then, the recording material sheet A is guided by paired supply rollers 30
 and 32, paired conveying rollers 34 and 36 and conveying guides 38, 40 and
 42 disposed downstream in the conveying direction so as to be conveyed to
 the width aligning section 14.
 The width aligning section 14 aligns the position of the recording material
 sheet A with a direction (hereinafter called a "widthwise direction")
 perpendicular to the conveying direction. In the downstream image exposure
 section 16, the width aligning section 14 performs alignment of the
 recording material sheet A in the main scanning direction, that is,
 so-called side regist. Then, a conveying roller pair 44 conveys the
 recording material sheet A to the downstream image exposure section 16.
 The downstream image exposure section 16 uses a light beam to expose the
 recording material sheet A to correspond to the image, the image exposure
 section 16 incorporating an exposing unit 46 and a sub-scan conveying
 means 48.
 Then, the recording material sheet A caused to have the latent image formed
 by the image exposure section 16 is conveyed to the heat-development
 section 18 by conveying roller pairs 64, 66 and 132. The heat-development
 section 18 is a section for heating the recording material sheet A to
 perform the heat-development to convert the latent image into a visible
 image. A plate heater 320 accommodated in the heat-development section 18
 includes a heating member which is a plate-like heating member including a
 heating member, such as a nichrome wire, which is laid flatly. Thus, the
 development temperature for the recording material sheet A is maintained.
 As shown in the drawing, the plate heater 320 projects upwards. Moreover,
 there are provided a supply roller 326 serving as a conveying means for
 relatively moving the recording material sheet A with respect to the plate
 heater 320 while making contact the recording material sheet A with the
 surface of the plate heater 320; and a pressing roller 322 which transmits
 heat from the plate heater 320 to the recording material sheet A and
 disposed adjacent to the lower surface of the plate heater 320.
 Moreover, a heat insulating cover 325 for maintaining the temperature is
 disposed opposite to the plate heater 320 of the pressing roller 322.
 As a result of the foregoing structure, the recording material sheet A
 passes through a space between the pressing roller 322 and the plate
 heater 320 by dint of the conveying rotations of the paired roller 326.
 Then, the heat treatment is performed so that the recording material sheet
 A is developed with heat. Then, the exposure process is performed so that
 the latent image recorded by the exposure is converted into a visible
 image. Since the conveyance is performed such that the leading end of the
 recording material sheet A is pressed against the plate heater 320,
 buckling of the recording material sheet A can be prevented.
 Although the plate heater has been described, the present invention is not
 limited thereto. A method which is other than heat-development method, for
 example, a combination of a heat drum and a belt member may, of course, be
 employed.
 The recording material sheet A discharged from the heat-development section
 18 is, by a conveying roller pair 140, guided to a guide plate 142. Then,
 the recording material sheets A are accumulated in a tray 146 through
 paired discharge rollers 144.
 In the image recording apparatus 10 shown in FIG. 1, any antistatic brushes
 and adhesive rollers are not employed in the passage for the recording
 material sheet A. All of the conveying rollers are resin rollers. That is,
 the low-cost resin rollers and rubber rollers are employed so that a
 significant sheet conveyance characteristic is realized and the
 manufacturing cost can be reduced.
 The resin rollers may be made of rubber or the like including phenol resin,
 polyacetal (POM), thermoplastic elastomer, ABS and polyurethane.
 The reason why the low-cost resin rollers or the rubber rollers can be
 employed lies in that electrification does not easily occur because an
 antistatic agent (an AS agent) is added to the recording material sheet A.
 The antistatic agent and the recording material sheet A will now be
 described.
 (1) Antistatic Agent Using Surface Active Agent:
 Any one of a nonion type agent, an anion type agent, a cation type agent
 and a fluorine type agent may be employed. Specifically, the following
 materials are exemplified: fluorine-type polymer surface active agents
 disclosed in Japanese Patent Publication No. 62-170950A and U.S. Pat. No.
 5,380,644; fluorine-type surface active agent disclosed in Japanese Patent
 Publication Nos. 60-244945A and 63-188135A; and surface active agents,
 such as polyalkyleneoxide and anion type surface active agent disclosed in
 Japanese Patent Publication No. 6-301140A.
 (2) Antistatic Agent having an antistatic agent effect or an effect of
 conductivity:
 For example, any one of the following materials may be employed: soluble
 salt (for example, chlorides or nitrates); an evaporated metal layer; and
 ionic polymers disclosed in U.S. Pat. No. 2,861,056 and U.S. Pat. No.
 3,206,312.
 Moreover, a layer containing insoluble inorganic salt disclosed in U.S.
 Pat. No. 3,428,451 and Japanese Patent Publication No. 61-20033A may be
 provided.
 The antistatic agent is added to a PC layer (a surface protective layer) of
 the recording material sheet A which will now be described.
 The layer structure of the heat-development photosensitive material which
 is the recording material sheet A for use in the embodiment of the present
 invention will now be described.
 FIG. 2 is a cross sectional view showing the heat-development
 photosensitive material. Referring to FIG. 2, the material incorporates,
 when viewed from the surface on which the laser beam is made incident
 (from the upper portion of the drawing), a PC layer which is a surface
 protective layer for protecting an image forming layer and preventing
 adhesion; an Em (emulsion) layer for forming an image; a PET layer which
 is a support layer and which is usually made of PET; and a back coating
 (BC) layer (and an AH (antihalation) layer in some cases).
 The Em layer is an image forming layer formed on the surface of the support
 layer on which the laser beam L is made incident and containing a binder
 composed of latex at a ratio of 50% or higher and a reducing agent which
 is organic silver salt. When the image forming layer is exposed to
 incident laser beam L, a photocatalyst, such as photosensitive silver
 halide, forms a core for a latent image. When the core of the latent image
 is heated, the action of the reducing agent moves silver of the ionized
 organic silver salt so as to be bonded with the photosensitive silver
 halide and formed into crystal silver with which an image is formed. As
 the organic silver salt, silver salt of an organic acid, preferably silver
 salt of long-chain fatty carboxylic acid having 10 to 30 carbon atoms and
 organic or inorganic silver salt, the ligant of which has a stability
 factor coefficient of complex of 4.0 to 10.0 are exemplified.
 Specifically, the following materials are exemplified: silver salt of
 behenic acid, silver salt of arachidic acid, silver stearate, silver
 olerate, silver laurate, silver caproate, silver myristate, silver
 palmitate, silver maleate, silver fumarate, silver tartrate, silver
 linoleate, silver butyrate and silver camphorate. The image forming layer
 of the recording material contains a material, for example, photosensitive
 silver halide (hereinafter called "silver halide") which is converted into
 a photocatalyst after it has been exposed to light.
 The image forming layer of the recording material or another layer on the
 same surface of the image forming layer may contain an additive which is
 known as a tone adjuster in a preferred quantity of 0.1 to 50 mol % with
 respect to one mol of silver to raise the optical density. Note that the
 tone adjuster may be a precursor induced to have an effective function
 only when the development process is performed. The tone adjuster may be
 any one of a variety of known tone adjusters for use in the recording
 material. Specifically, the following materials are exemplified: a
 phthalimide compound, such as phthalimide or N-hydroyphthalimide; cyclic
 imide, such as succinimide, pyrazoline-5-on; naphthalic imide, such as
 N-hydroxy-1, 8-naphthalic imide; cobalt complex, such as cobalt hexamine
 trifluoroacetate; mercaptan, such as 3-mercapto-1, 2, 4-triazole or 2,
 4-dimercaptopyrimidine; phthalazinone derivative, such as 4-(1-naphtyl)
 phthalazinone; and its metal salt. The foregoing tone adjuster is added to
 the solution, which must be applied, as solution, powder or dispersed
 solid particles.
 The sensitizing coloring matter must be capable of spectrosensitizing
 silver halide in a required wavelength region when the sensitizing
 coloring matter has been adsorbed to silver halide particles. To add the
 sensitizing color matter to the silver halide emulsion, it may directly be
 dispersed in the emulsion or it may be dissolved in single or a mixed
 solution of water, methanol, ethanol, N, N-dimethylformamide or the like,
 followed by adding the solution to the emulsion.
 The surface protective PC layer is formed by an adhesion preventive
 material exemplified by wax, silica particles, elastomer-type block
 copolymer containing styrene (styrene-butadiene-styrene or the like),
 cellulose acetate, cellulose acetate butylate and cellulose propionate.
 When the halation preventive dye is employed, any compound capable of
 satisfying the following requirement may be employed: the dye must be
 cable of performing required absorption in the wavelength and; the
 absorption must sufficiently be restrained in the visible region after the
 process has been completed; and a preferred absorbance spectrum shape of
 the antihaltion layer AH can be obtained. Although the following materials
 are exemplified, the material is not limited to the following materials.
 As single dye, compounds disclosed in Japanese Patent Publication Nos.
 7-11432A and 7-13295A are exemplified. As dye which performs decoloration
 by carrying out processes, compounds disclosed in Japanese Patent
 Publication Nos. 52-139136A and 7-199409A are exemplified. It is
 preferable that the foregoing recording material has the image forming
 layer on either surface of the support member and a back layer on another
 surface.
 To improve conveyance easiness, a matting agent may be added to the back BC
 layer. In general, the matting agent is in the form of particles of
 organic or inorganic compound which is dissoluble in water. The preferred
 organic compound is exemplified by water dissoluble vinyl polymer, such as
 polymethylacrylate, methyl cellulose, carboxy starch and carboxy
 nitrophenyl starch. The preferred inorganic compound is exemplified by
 silicon dioxide, titanium dioxide, magnesium dioxide, aluminum oxide and
 barium sulfate.
 The binder for forming the back layer may be any one of a variety of
 colorless, transparent or semitransparent resins. The resin is exemplified
 by gelatin, arabic rubber, polovinyl alcohol, hydroxyethyl cellulose,
 cellulose acetate, cellulose acetate butylate, casein, starch, poly
 (metha) acrylate, polymethylmethacrylate and polyvinyl chloride.
 It is preferable that the back layer is a layer, the maximum absorption is
 0.3 to 2 in a required wavelength range. If necessary, the halation
 preventive dye for use in the foregoing antihalation layer may be added to
 the back layer.
 As for the recording material sheet A, the following methods and recording
 materials for use in the foregoing methods are exemplified in the present
 invention as well as the structure according to the foregoing embodiment.
 (1) A method in which a photosensitive material exposed to correspond to an
 image is laminated with an image receiving material, and then the laminate
 is heated (and applied with pressure, if necessary) so that an image
 corresponding to a latent image formed on the photosensitive material
 owning to the exposure is transferred to an image receiving material (for
 example, methods disclosed in Japanese Patent Publication Nos. 5-113629A,
 8-42803A, 9-61978A, 9-152705A, 9-258404A, 10-71740A, 10-254111A and
 11-84610A).
 (2) A method with which a photosensitive material exposed to correspond to
 an image is laminated with a material, which must be processed, and then
 the laminate is heated so that an image corresponding to a latent image
 formed on the photosensitive material owning to the exposure is formed on
 the photosensitive material (for example, methods disclosed in Japanese
 Patent Publication Nos. 9-274295A and 11-212230A).
 (3) A method with which a photosensitive material having a photosensitive
 layer in which silver halide serving as a photocatalyst, silver salt
 serving as an image forming substance and reducing agent for silver ions
 are dispersed in a binder is exposed to correspond to an image after which
 the photosensitive material is heated to a predetermined temperature so
 that a latent image formed owing to the exposure is formed into a visible
 image (for example, methods disclosed by B. Shely in "Thermally Processed
 Silver Systems" (Imaging Processes and Materials) Neblette, 8th edition,
 Sturge, V. Walworth and A shepp, pp. 2, 1996, Research Disclosure 17029
 (1978), EP803764A1, EP803765A1 and Japanese Patent Publication No.
 8-211521A).
 (4) A method using a photosensitive and thermosensitive recording material
 and arranged such that a photosensitive and thermosensitive recording
 layer incorporates a recording material which has electron releasing
 colorless dye capsulated in a heat response microcapsule, a compound
 having, in the same molecule thereof, an electron receiving portion and a
 polymerizable vinyl monomer portion and a light polymerization initiator
 disposed on the outside of the microcapsule (for example, a method
 disclosed in Japanese Patent Publication No. 4-249251A). As an alternative
 to this, a method in which the photosensitive and thermosensitive
 recording layer incorporates a recording material having electron
 releasing colorless dye capsulated in a heat response microcapsule and an
 electron receiving compound, polymerizable vinyl monomer and a light
 polymerization initiator disposed on the outside of the microcapsule (for
 example, a method disclosed in Japanese Patent Publication No. 4-211252A).
 In this specification, the photosensitive materials and recording materials
 for use in the foregoing dry development method are collectively called
 "heat-development photosensitive materials". Note that water in a small
 quantity may be used in the foregoing dry development methods (1) and (2)
 in order to enhance development and image formation.
 As described above, according to the present invention, the antistatic
 agent is added to the recording material sheet, such as the
 heat-development photosensitive material. Therefore, electrification
 occurring during the manufacturing process and conveyance can be
 prevented. As a result, the heat-development recording apparatus for
 recording an image on a film, such as the heat-development photosensitive
 material, does not require any antistatic brushes and adhesive rollers for
 removing dust.
 As a result, the heat-development recording apparatus is permitted to
 incorporate low-cost resin rollers. Thus, the materials of the rollers may
 be selected from a variety of materials and low-cost materials. Moreover,
 use of the characteristics of the resin enables the conveyance easiness to
 be improved.
 Since fogging of a film, occurrence of noise and adhesion of a plurality of
 sheets caused from adhesion of dust and discharge can be prevented, a
 malfunction can be prevented.
 Although the present invention has been shown and described with reference
 to specific preferred embodiments, various changes and modifications will
 be apparent to those skilled in the art from the teachings herein. Such
 changes and modifications as are obvious are deemed to come within the
 spirit, scope and contemplation of the invention as defined in the
 appended claims.