JPH0459384A - Image forming method and image forming device - Google Patents

Abstract

PURPOSE:To form a high-quality image having a low roughness and sufficient hiding properties by a method wherein ink is passed through a hole part of a stencil, and the ink passed through the hole part is transferred to a transfer member and further transferred to an ink receiving body. CONSTITUTION:Ink 2 changing its properties from adherent to non-adherent by the application of a voltage is charged in a stencil roll 1. In this construction, the ink is extruded patternwise from a hole part of a stencil by the application of pressure. The stencil roll 1 is in contact with a blanket cylinder 3 as a transfer member. The ink extruded with the rotation of the stencil roll l in an arrow direction A adheres on the surface of the blanket cylinder 3 to form an ink image 5 thereon. The blanket cylinder 3 is made of a metal, such as stainless, aluminum, and copper, or a conductive body obtained by dispersing conductive powder, such as carbon, in a silicon rubber. With the rotation of the blanket cylinder 3 in an arrow direction B, the ink image 5 formed on the blanket cylinder 3 is transferred under pressure onto an image receiving body 6 clamped between an impression cylinder 4 and the blanket cylinder 3, thereafter being fed in an arrow direction E to form an ink image 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming method and apparatus for forming an ink image using a region through which ink passes and a region through which ink does not pass through the holes of a stencil. The image forming method and apparatus of the present invention are very useful in the field of recording peripheral devices for printers such as computers.

[Conventional technology]

Hitherto, printing techniques such as lithographic printing, letterpress printing, and gravure printing have been used, but they require dampening water for ink patterning and are extremely troublesome to handle. Furthermore, the adhesion of ink is easily affected by temperature and humidity, and it lacks environmental stability. Furthermore, these prints require a large number of rollers. For this reason, there are many difficulties in applying conventional printing techniques to recording peripheral devices such as computers.

On the other hand, the stencil printing method is superior in handling and environmental stability compared to these methods, does not require dampening water, and requires fewer rollers, and is therefore relatively suitable for use in recording peripheral equipment. It's a method. However, in the conventional stencil printing method,
In the image area formed by the ink transferred to the image-receiving paper, voids corresponding to the mesh of the screen are created, resulting in a lack of hiding ability and a low-quality image with noticeable roughness.

(31 Problems to be Solved by the Invention) The present invention has been made to solve the problems as described above. In other words, an object of the present invention is to provide a method and apparatus that sufficiently provide the above-mentioned performance such as ease of handling required when used in recording peripheral equipment, etc., and that can produce high-quality images with little roughness and sufficient concealment. The object of the present invention is to provide a method and apparatus capable of forming the present invention.

(Means for Solving the 31 Problems) The image forming method of the present invention includes a step of allowing ink to pass through a hole in a stencil, a step of transferring the ink that has passed through the hole to a transfer member, and a step of transferring the ink that has passed through the hole to a transfer member. This method includes the step of transferring the image to an image receptor.

Further, the image forming apparatus of the present invention is an apparatus including a stencil, a transfer member to which ink is transferred from the stencil, and an image receptor to which ink is transferred from the transfer member.

Furthermore, in a preferred embodiment of the present invention, in the method and apparatus described above, the transfer member is a conductive member, the ink is an ink whose adhesion decreases in response to voltage application, and the ink transferred to the transfer member is This method includes the step of removing by applying a voltage, and the apparatus used for the removal.

(Function) In the method of the present invention, the ink that has passed through the hole is once transferred to the transfer member. The ink image formed on the transfer member in this step tends to have a lot of roughness and poor hiding properties, similar to the conventional stencil printing method described above. However, in the present invention, since the ink image on the transfer member is transferred again to the image receptor, the pressure naturally applied during this retransfer crushes the ink layer and fills the gaps, resulting in a high-quality ink image. can be obtained on the image receptor.

Then, if this ink image is transferred to a desired recording paper or the like, a good image can be obtained.

Furthermore, as the ink used in the present invention, an ink having a property that adhesiveness decreases depending on voltage application is used,
If a conductive member is used as the transfer member, residual ink on the transfer member can be removed very easily by applying a voltage.
It can be removed without staining the hands of the worker. In other words, the so-called handleability is further improved since residual ink can be easily cleaned. Furthermore, a conductive material such as metal or carbon paper is used as the image receptor,
If a voltage is applied between the image receptor and the transfer member to reduce the adhesion of the ink to the transfer member and then transfer the ink onto the image receptor, a sufficient amount of ink will be transferred and the image density will be reduced. It is advantageous for improvement.

〔Example〕

Hereinafter, the present invention will be explained in more detail by way of examples with reference to the drawings.

FIG. 1 is a schematic cross-sectional view illustrating main parts of an image forming apparatus of the present invention.

The stencil roll 1 is a member having a cylindrical shape and rotating in six directions indicated by arrows. The plate for this roll 1 is made by pasting silk, nylon, or fine-mesh W4 (screen mesh cloth, etc.) on a strong metal frame, coating it with photosensitive resin, drying it, and attaching a net positive to it. This is exposed to light in a desired pattern, and then the unexposed areas are removed to obtain a screen plate or a heat-melted material such as wax is applied to the silk, nylon, or metal mesh described above, and heated and melted in a pattern. Various types of plates can be used, such as plates obtained by removing them.

The inside of the stencil roll 1 is filled with ink 2, which changes from adhesive to non-adhesive by applying a voltage, and is extruded in a pattern from the holes in the plate by applying pressure. There is. The stencil roll 1 is in contact with a plan copper 3 as a transfer member, and as it rotates in the direction of arrow A, the extruded ink 2 adheres to the surface of the plan copper 3, forming an ink image 5. The plan copper 3 is made of a conductor made of a metal such as stainless steel, aluminum, copper, or silicone rubber in which conductive powder such as carbon is dispersed.

The ink image 5 formed on the plan copper 3 rotates in the direction of arrow B, is transferred under pressure onto the image receptor 6 held between the press copper 4 and the plan copper 3, and then moves in the direction of arrow E. The ink image 7 is formed by being transported. It is sufficient to apply pressure between the plan copper 3 and the pressed copper 4 to the extent that the ink image 5 is crushed in the thickness direction and the roughness caused by the mesh of the plate is eliminated.

After the ink image is transferred to the image receptor 6, the ink remaining on the plan copper 3 is transferred onto the cleaning roll 8 by applying a voltage between the plan copper 3 and the cleaning roll 8 in contact with the plan copper 3 by a DC power source 9. Plan copper 3 can be cleaned. Follower, cleaning roll 8
It is also made of a conductor similar to plan copper.

Conventionally, in offset printing using plan copper, cleaning the plan copper stains hands and makes maintenance complicated. If the method of cleaning plan copper by applying voltage of the present invention is used, this problem will not occur and ink on plan steel can be easily removed by pressing a button. In FIG. 1, the plan copper 3 is the cathode and the cleaning roll 7 is the anode, but the reverse may be used depending on the ink. Practically speaking, the voltage of the power source 9 is preferably 3 to 100 volts, more preferably a direct current voltage of 5 to 8 ov.

From this point of view, the ink used in the method of the present invention is of a type that has adhesive properties when no voltage is applied, but loses its adhesive properties when a voltage is applied.

Ink whose adhesion properties change will be explained below.

A possible mechanism by which the ink changes from adhesive to non-adhesive due to voltage application is that the ink is electrolyzed by energization due to voltage application and gas is generated, causing the adhesive to change.

In this case, the ink is adjusted so that it inherently has adhesive properties, and when a voltage is applied, the ink generates gas near one of the electrodes, and this gas prevents the ink from adhering to the electrode. In order for the ink to electrolyze and generate gas, the ink contains a solvent such as water, alcohol, or glycol, or a solvent in which an electrolyte such as sodium chloride or potassium chloride is dissolved. The lower the electrical resistance of the ink, the better, and the volume resistivity is preferably 10 5 Ω·cm or less. When the volume resistance exceeds 10 5 Ω·Cm, the amount of current flowing decreases, or a high voltage is required to prevent the amount of current flowing from decreasing.

Further, regarding the transfer of ink to the plate, almost the entire thickness direction of the portion of the ink layer to which the voltage is applied is transferred (hereinafter referred to as bulk transfer).

If the ink is a liquid such as water or alcohol, its cohesive force is weak and suitable adhesiveness cannot be obtained. This ink can be applied, for example, to a platinum-plated stainless steel plate placed vertically.
It is preferable that the ink be such that when the ink is deposited to a thickness of fi, the ink is substantially retained on the platinum-plated stainless steel plate.

In addition, ink was sandwiched between two platinum-plated stainless steel plates to make the ink thickness 2 mm, and when the two platinum-plated stainless steel plates were separated from each other with no voltage applied, ink did not appear on either plate. It is preferable that they adhere to the same degree.

The viscosity of the ink is a shear rate of 10 rad/s and a temperature of 2.
At 5°C, 101~IO'. Poise, even 10'
~108 poise is preferred.

Ink that uses the above-mentioned mechanism is basically composed of inorganic or organic fine particles and a liquid dispersion medium. The fine particles in the ink make it easier to cut the ink and improve the resolution of the image. Ink is an amorphous solid of a colloidal sol and is a non-Newtonian fluid in terms of fluidity.

In order to change the adhesion of ink by applying voltage, fine particles are contained in the ink. A fine particle dispersion is formed by kneading in the above-mentioned liquid dispersion medium, for example, in a homogenizer, a colloid mill, or an ultrasonic disperser. Such particles include metals (Au, Ag,
Cu, etc.) particles, sulfides (zinc sulfide ZnS, antimony sulfide 5B2S3, potassium sulfide 2S, calcium sulfide CaS, germanium sulfide GeS, cobalt sulfide CoS, tin sulfide SnS, iron sulfide FeS, copper sulfide Cu2S, manganese sulfide MnS, Molybdenum sulfide M
o2S, etc.) particles, silicic acid (orthosilicic acid H45i0
4. Metasilicic acid H2S1Os, mesotrisilicate H2S12
0B, mesotrisilicate)14Si303, mesotetrasilicic acid H65i4J1, etc.) particles, polyamide resin particles, polyamideimide resin particles, iron hydroxide particles, aluminum hydroxide particles, fluorinated mica particles, polyethylene particles, montmorillonite particles, fluororesin etc. can be used. Further, polymer particles containing various charge control agents used as toners for electrophotography can also be used.

The above-mentioned fine particles have an average particle diameter of 100 μm or less,
Preferably, particles with a diameter of 0.1 μm to 20 μm, especially 10 μm or less, can be used, and such fine particles are contained in the ink in an amount of 1 part by weight or more, preferably 3 parts by weight to 90 parts by weight, and more preferably 3 parts by weight to 90 parts by weight, based on 100 parts by weight of the ink. Preferably, it can be contained in an amount of 5 parts by weight to 60 parts by weight.

In addition, the liquid dispersion medium used in the ink includes ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (weight average molecular weight, about 100
~1000), ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, methyl calpitol, ethyl calpitol, butyl calpitol, ethyl calpitol acetate, diethyl calpitol, triethylene glycol monomethyl ether, Ethylene glycol monoethyl ether, propylene glycol monomethyl ether, glycerin, triethanolamine, formamide, dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, 1,3
-dimethylimidazolidinone, N-methylacetamide, ethylene carbonate, acetamide, succinonitrile, dimethylsulfoxide, sulfolane, furfuryl alcohol, N,N-dimethylformamide, 2-ethoxyethanol, hexamethylphosphoric triamide (hexamethyl A single medium or a mixed medium of two of them can be used, such as phosphoric acid triamide), 2nitropropane, nitroethane, γ-butyrolactone, propylene carbonate, 1,2,6-hexandriol, dipropylene glycol, and hexylene glycol. Liquid dispersion medium is ink
40 to 95 parts by weight, even 60 to 100 parts by weight
It is preferable to contain 85 parts by weight.

In a preferred embodiment, in order to control the viscosity of the ink, the above-mentioned polymer soluble in the liquid dispersion medium is added to the ink material in an amount of 1 to 90 parts by weight, more preferably 1 to 90 parts by weight, based on 100 parts by weight of the ink material.
It can be contained in an amount of 50 parts by weight, particularly 1 to 20 parts by weight. Such polymers include guar gum, locust bean gum, gum arabic, taragant,
Plant-based polymers such as carrageenan, pectin, mannan, and starch; Microbial polymers such as xanthan gum, dextrin, succinoglucan, and curdlan; gelatin,
Animal-based polymers such as casein, albumin, and collagen; cellulose-based polymers such as methylcellulose, ethylcellulose, and hydroxyethylcellulose; starch-based polymers such as soluble starch, carboxymethyl starch, and methyl starch; alginic acid-based polymers such as propylene glycol alginate, and alginates. , other semi-synthetic polymers such as polysaccharide derivatives: vinyl polymers such as polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl methyl ether, carboxyvinyl polymer, sodium polyacrylate; other polyethylene glycol, ethylene oxide, propylene oxide block copolymers , alkyd resin, phenol resin, epoxy resin, aminoalkyd resin, polyester resin, polyurethane resin, acrylic resin, polyamide resin, polyamideimide resin, polyesterimide resin, silicone resin, and other synthetic polymers are used alone or in combination of two or more. be able to. Also, greases such as silicone grease,
It is also possible to use liquid polymers such as bolybdenum.

Since the change in ink adhesion is caused by the generation of gas due to electrolysis, water, methanol,
A solvent such as ethanol, glycerin, ethylene glycol, or propylene glycol, or a solvent in which an electrolyte such as potassium iodide or lithium borofluoride is dissolved is preferably used. The contents of the liquid dispersion medium and fine particles are the same as those described above. In particular, it is preferable to use water or a liquid containing water as the liquid dispersion medium because hydrogen gas is likely to be generated on the negative electrode side. When water and another liquid dispersion medium are mixed, the content of water is preferably 1 part by weight or more, more preferably 5 parts by weight or more, based on 100 parts by weight of the ink.

In the case of ink that generates gas through electrolysis, the fine particles contained in the ink include, in addition to those listed above, silica, fluorocarbon, titanium oxide, carbon black, fluorocarbon, and the like.

In a preferred embodiment of the ink, considering the viscoelastic properties of the ink, it is preferable to use swellable fine particles capable of retaining the above-mentioned liquid dispersion medium as all or part of the fine particles in the ink. Such swellable particles include, for example, N
a-montmorillonite, Ca-montmorillonite, 3-
Octahedral synthetic smectite, Na-hectolite, Li-
Examples include fluorinated micas such as hectorite, Na-teniolite, Na-tetrasilicic mica, and Li-duolite, synthetic mica, and silica. The above fluorinated mica is as follows −
This can be expressed by formula (1).

Formula (1) % formula %) (In the formula, W is Na or Li, X and Y are g2+Fe
”, Ni”, Mn”, AI”, Fe”, Li
6-coordinate ions such as ``2 is AI'', Si'', Ge
"Fe3""33" or a combination thereof (AI"1
5i4+), which has a coordination number of 4.

) The average particle diameter of the swellable fine particles is preferably 75 μm or less in a dry state, more preferably 0.8 to 15 μm, and particularly preferably 8 μm or less.

The ink may contain colorants such as carbon black and other dyes and pigments that are generally used in the fields of printing and recording, if necessary. When the ink contains a colorant, the content of the colorant is 0 per 100 parts by weight of the ink.
．． 1 to 40 parts by weight, more preferably 1 to 20 parts by weight.

Further, instead of or together with the coloring material, a coloring compound that develops color upon application of voltage may be contained. In addition, the ink may contain an electrolyte, thickener, thinner, surfactant, etc. that impart conductivity.

Furthermore, it is also possible for the above-mentioned fine particles themselves to also function as a coloring material.

To obtain such an ink, for example, a liquid dispersion medium and fine particles may be mixed by a conventional method.

[Experiment example]

The following image formation was performed using the apparatus shown in FIG.

As the stencil roll 1, a cylindrical roll having a diameter of 30 m+a and having a screen plate made of nylon gauze wrapped around a stainless steel mesh was used. Further, as Ink 2, a black amorphous solid ink was used, which was prepared by kneading a mixture having the following composition using a roll mill.

(Ink formulation) - Polyether solvent 514 parts by weight, manufactured by Asahi Denka Kogyo ■, trade name: Niadeka Carpol I E-100, water 130 parts by weight - Carphone black 118 parts by weight Polyvinylpyrrolidone 82 parts by weight, manufactured by BASF Corporation , trade name Nylbiscol-30 Lithium borofluoride
75 parts by weight Colloidal silica 59 parts by weight The above ink was put into the stencil roll 1,
was rotated in the direction of the arrow at a circumferential speed of 5 mm/sec, and the plan copper 3 was rotated in the direction of arrow B. Furthermore, when plain paper was passed through the image receptor 6 in the direction of arrow E, printed matter with sharp image quality was obtained.

When the optical density of the solid black part of this image was measured with a Macbeth densitometer, it showed a value of 1.5 to 1.6, indicating that a sufficient image density was obtained.

(Comparative Experimental Example) In the experimental example, the stencil roll was directly transferred onto plain paper as the image receptor 6 without using the Plan Copper 3 to obtain printed matter. When the optical density of the solid black part of this image was measured, it was 0.8
It showed a value of ~0.9, and sufficient image density was not obtained.

〔Effect of the invention〕

The image forming method and apparatus of the present invention described above have sufficient ease of handling and environmental stability, require a small number of rollers, and are useful for use in recording peripheral equipment and the like. Furthermore, it is possible to form a high-quality image with little roughness and sufficient hiding power.

Furthermore, if the present invention uses an ink that has the property of decreasing adhesion in response to voltage application and a transfer member that has conductivity, the so-called handleability will be further improved in that residual ink can be cleaned easily. I will do it.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view illustrating main parts of an image forming apparatus of the present invention. 1... Stencil roll 2... Ink 3... Plan copper (transfer member) 4... Pressure copper 5... Ink image 6... Image receptor 7... Ink image 8... Cleaning Roll 9...DC power supply

Claims (1)

[Scope of Claims] 1. A method comprising the steps of passing ink through holes in a stencil, transferring the ink that has passed through the holes to a transfer member, and transferring the transferred ink to an image receptor. Image forming method. 2. The method according to claim 1, wherein the transfer member is a conductive member, the ink is an ink whose adhesion decreases in response to voltage application, and the method further comprises the step of removing the ink on the transfer member by applying voltage. image forming method. 3. An image forming apparatus having a stencil, a transfer member to which ink is transferred from the stencil, and an image receptor to which ink is transferred from the transfer member. 4. The image forming apparatus according to claim 3, wherein the transfer member is a conductive member and includes a cleaning roll for removing ink on the transfer member by applying voltage.