JPH04250090A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent unevenness of an image resulting from a contact pressure reduction between an electrode and a plate through ink caused by the electrical fusion of the electrode corresponding to the plate in an image forming device in which the ink is supplied between the electrode pair, one of which is the plate, the ink is turned from adhesive to non-adhesive to at least one of the electrodes by a voltage application, and a voltage is applied between the electrodes to transfer the ink applied on the plate to a recording medium. CONSTITUTION:The diameter of a roller 4 is gradually reduced by an anode fusion by an electric conduction at the time of image forming. The reduction of the diameter is detected by a sensor 10. With the decrease of the diameter of the roller 4, a contact pressure of the roller 4 with a plate 9 is gradually decreased. Therefore, the roller 4 is pressurized toward the plate 9 by an actuator 11 by the amount of a reduced pressure depending on a displacement amount detected by the sensor 10, thereby being recovered to a required contact pressure.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a pair of electrodes, one of which is a plate, an ink supply means for supplying between the pair of electrodes an ink that changes from adhesive to non-adhesive when voltage is applied, and The present invention relates to an image forming apparatus having a voltage applying means for applying a voltage between electrodes and a transfer means for transferring ink deposited on the plate onto a recording medium.

0002

2. Description of the Related Art Conventional printing methods using ink include lithographic printing, letterpress printing, and gravure printing.

[0003] These methods require dampening water for patterning the ink in the image and non-image areas on the plate, and also require complicated operations to control the ink adhesion of the resin on the plate surface. There were points that needed improvement, such as:

[0004] Therefore, the present applicant has previously proposed an image forming apparatus that performs printing using ink whose adhesion changes depending on voltage application (Japanese Patent Application No. 12617/1983, etc.). These image forming devices can control the amount of ink transferred by the amount of electrical charge, so there is no need to adjust the amount of ink with multiple rollers like in conventional printing machines, and the printing process is relatively simple. Therefore, the device configuration is relatively simple.

[0005]

[Problems to be Solved by the Invention] In the image forming apparatus described above, one of the pair of electrodes is used as a plate, ink is sandwiched between the pair of electrodes, and the amount of ink transferred is controlled by applying electricity between the electrodes. , the electrode facing the plate gradually dissolves due to energization, and the contact pressure between this electrode and the plate through the ink weakens, resulting in a change in the amount of electrical charge and a decrease in the amount of ink that adheres to the plate. This has the disadvantage that the resulting image may be uneven.

An object of the present invention is to provide an image forming apparatus that can always maintain constant contact pressure between a plate and an electrode facing the plate.

[0007]

SUMMARY OF THE INVENTION The image forming apparatus of the present invention includes pressure setting means for setting the contact pressure between a pair of electrodes to a desired pressure.

[0008]

[Operation] According to the present invention, the contact pressure between the plate and the electrode facing the plate can always be maintained at a constant value, so the amount of electric charge applied can be reliably controlled, and the amount of ink deposited on the plate can be maintained at a constant value. Since the value is always constant, an image of good quality can be obtained.

In order to always keep the contact pressure between the plate and the electrode facing the plate at a constant value, first detect the contact pressure between the plate and the electrode facing the plate, and if the desired pressure is not reached, The contact pressure may be increased by bringing the electrodes closer together, or the desired contact pressure may be applied at all times. As means for detecting the contact pressure between the plate and the electrode facing the plate, there are known sensors such as optical sensors, metal sensors, and pressure sensors. The pressure may be determined by measuring a small amount. Furthermore, if the measured contact pressure does not reach the desired pressure, the contact pressure between the plate and the electrode facing the plate can be maintained at a constant value by an actuator attached to the plate and/or the electrode facing the plate. can.

The contact pressure between the plate and the electrode facing the plate is:
It varies depending on the type of ink used, viscosity, etc., but 1kg/
It is preferable to keep it constant between cm2 and 10 kg/cm2 in order to obtain good images.

[0011]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a perspective view of a plate 9 in FIG.

The rollers 1 to 4 are means for supplying the ink 8, and the roller 4 is configured to form a pair of electrodes with the conductive base material 9a of the plate 9 mounted on the plate cylinder 5.

The material of the surfaces of the rollers 1 to 3 is not particularly limited, and for example, metal materials such as stainless steel, rubber materials such as silicone rubber, plastic materials, etc. are used. The surface material of the roller 4, which also serves as one of the electrodes, is not particularly limited as long as it has conductivity; for example, conductors such as aluminum, stainless steel, copper, and platinum, carbon, Ni, etc. A material made by dispersing powder to provide electrical conductivity is used, and platinum is particularly preferred because it is durable and dissolves little when energized.

As shown in FIG. 2, the plate 9 is constructed by forming an insulating pattern 9b on a conductive base material 9a whose surface is made of, for example, aluminum or copper. The form can be, for example, a plate-like one using only a conductor (metal, etc.), or a support made of PET, polyimide, etc.
It is possible to use a material coated with a foil of copper or the like, or a resin coated with a powder of carbon, Ni, etc. dispersed therein. The thickness of the conductive base material 9a is arbitrarily determined depending on the quality of the conductive material. The insulating pattern 9b formed on the conductive base material 9a is made of, for example, an insulating ink containing a polymer, wax, etc. used in a conventional thermal transfer method;
It can be formed using toner or the like used in electrophotography. Further, a polymerizable polymer precursor layer is formed on the conductive base material 9a, and a pattern image consisting of a polymerized part and an unpolymerized part is formed on the precursor layer by applying light and/or heat to this precursor layer. However, it is also possible to remove the unpolymerized portions by etching or peel-apart method to form an insulating pattern consisting of the polymerized portions. In addition, any other material that can be coated with an electrically insulating material may be used, such as a material using an electrically insulating material such as crayon, marker, or paint.

As described above, the plate 9 is mounted on the plate cylinder 5, and has an insulating pattern 9b formed on a conductive base material 9a.

The ink 8 used for printing using the apparatus of this embodiment is an ink whose adhesion changes depending on the polarity of the applied voltage. For example, it is sticky when no voltage is applied, and when the voltage is An example of this is ink whose tackiness disappears when it is applied. When this ink is energized by voltage application, the ink electrolyzes and generates gas, changing its adhesion from adhesive to non-adhesive.

[0018] 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 is dissolved. The lower the electrical resistance of the ink, the better, with a volume resistivity of 10
It is preferable to set it to 5Ω·cm or less. Volume resistance is 1
If it exceeds 0.05 Ω·cm, the amount of current flowing decreases or a high voltage is required to prevent the amount of current flowing, which is not preferable.

[0019] This ink has a weak cohesive force when used with liquids such as water or alcohol, and suitable adhesion cannot be obtained. In addition, for example, when ink is applied to a platinum-plated stainless steel plate held vertically to a thickness of 2 mm,
It is preferable that the ink be 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, the ink did not appear on either plate. It is preferable that the two adhere to the same extent.

[0020] This ink basically consists of a liquid dispersion medium and inorganic or organic fine particles. The fine particles in the ink make it easier to cut the ink and improve the resolution of the image. The ink controlled by the present invention is a colloidal sol, an amorphous solid, and non-Newtonian in fluidity.

[0021] The liquid dispersion medium used in this ink is as follows:
Ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (weight average molecular weight, about 100 to 1000), ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, methyl carbitol, ethyl Carbitol, butyl carbitol, ethyl carbitol acetate, diethyl carbitol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, glycerin, triethanolamine, formamide, dimethyl formamide,
Dimethyl sulfoxide, N-methyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, N-methylacetamide, ethylene carbonate, acetamide, succinonitrile, dimethyl sulfoxide, sulfolane, furfuryl alcohol, N,N-dimethylformamide , 2-ethoxyethanol, hexamethylphosphoric triamide (hexamethylphosphoric triamide), 2-nitropropane, nitroethane, γ-butyrolactone, propylene carbonate, 1,2,6-hexanetriol, dipropylene glycol, hexylene glycol It is possible to use a single medium or a mixture of two or more of the following. The liquid dispersion medium is preferably contained in an amount of 40 to 95 parts by weight, more preferably 60 to 85 parts by weight, per 100 parts by weight of the ink.

More preferred liquid dispersion media include water, alcohols such as methanol and ethanol, solvents with hydroxyl groups such as glycerin, ethylene glycol and propylene glycol, and solvents in which electrolytes such as sodium chloride and potassium chloride are dissolved. used. In particular, it is preferable to use water or something containing water as the liquid dispersion medium because hydrogen gas is easily 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 a preferred embodiment, in order to control the viscosity of the ink, the above-described polymer soluble in the liquid dispersion medium is added to the ink material in an amount of 1 to 90 parts by weight per 100 parts by weight of the ink material.
Parts by weight, even 1 to 50 parts by weight, especially 1 to 20 parts by weight
It can be contained in a proportion of parts by weight. Such polymers include guar gum, locust bean gum,
Plant-based polymers such as gum arabic, taragant, carrageenan, vectin, mannan, and starch; Microbial-based polymers such as xanthan gum, dextrin, succinoglucan, and curdlan; Animal-based polymers such as gelatin, casein, albumin, and collagen; Methyl cellulose, ethyl cellulose , cellulose polymers such as hydroxyethyl cellulose, starch polymers such as soluble starch, carboxymethyl starch, and methyl starch, alginic acid polymers such as propylene glycol alginate and alginates, and semi-synthetic polymers such as other polysaccharide derivatives; polyvinyl Alcohol, polyvinylpyrrolidone, polyvinyl methyl ether, carboxyvinyl polymer, vinyl polymers such as sodium polyacrylate; other polyethylene glycol, ethylene oxide, propylene oxide block copolymer, alkyd resin, phenol resin, epoxy resin, amino alkyd resin, Synthetic polymers such as polyester resin, polyurethane resin, acrylic resin, polyamide resin, polyamideimide resin, polyesterimide resin, and silicone resin can be used alone or in combination of two or more. It is also possible to use greases such as silicone grease and liquid polymers such as polybdenum.

The fine particles contained in the ink include metal (Au, Ag, Cu, etc.) particles, sulfide (zinc sulfide, ZnS, etc.)
, antimony sulfide Sb2 S3 , potassium sulfide K2
S, calcium sulfide CaS, germanium sulfide GeS,
Cobalt sulfide CoS, tin sulfide SnS, iron sulfide FeS,
Copper sulfide Cu2S, manganese sulfide MnS, molybdenum sulfide Mo2S3, etc.) particles, silicic acid (orthosilicic acid H4)
SiO4 , metasilicic acid H2 SiO3 , mesodisilicate H2 Si2 O5 , mesotrisilicate H4 SiO
3, mesotetrasilicate H6 Si4 O11 etc.) particles, polyamide resin particles, polyamideimide resin particles, iron hydroxide particles, aluminum hydroxide particles, fluorinated mica particles, polyethylene particles, montmorillonite particles, fluororesin, silica, fluoride Carbon, titanium oxide, carbon black, carbon fluoride, and various polymer particles used as electrophotographic toners can also be used.

The above-mentioned fine particles have an average particle diameter of 10
0 μm or less, preferably 0.1 μm to 20 μm,
Among them, those with a diameter of 10 μm or less can be used, and
Such fine particles can be contained in the ink in an amount of 1 part by weight or more, preferably 3 parts to 90 parts by weight, more preferably 5 parts to 60 parts by weight, per 100 parts by weight of the ink.

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 the fine particles in the ink. Such swellable fine 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-teniolite, synthetic mica, and silica.

The above-mentioned fluorinated mica can be represented by the following general formula (1). General formula (1) W1 ~1/3 (X, Y)2.5 ~3(Z4 O1
0)F2 In the above formula, W is Na or Li, X and Y
are Mg2+, Fe2+, Ni2+, Mn2+, Fe3+
, Li+ and other six-coordinate ions, Z is Al3+, Si4
represents an ion with a coordination number of 4, such as +, Ge4+, Fe3+, B3+, or a combination thereof (Al3+/Si4+).

[0028] The average particle diameter of the swellable fine particles is 100 μm.
The thickness is preferably 1 to 20 μm, preferably 10 μm or less.

[0029] If necessary, the ink can contain colorants such as carbon black and other dyes and pigments that are generally used in the fields of printing and recording. When the ink contains a colorant, the content of the colorant is 0.1 to 40 parts by weight, more preferably 1 to 20 parts by weight, based on 100 parts by weight of the ink.
Parts by weight are preferred. Furthermore, instead of or together with the colorant, a color-forming compound that develops color upon application of voltage may be contained.

[0030] In addition, the ink may contain electrolytes, thickeners, thinners, surfactants, etc. that impart conductivity. Further, it is also possible to cause the above-mentioned fine particles themselves to also function as a coloring material.

The ink 8 having the above-described structure is applied to the rollers 1 and 2.
Ink 8 is supplied onto plate 9 by rollers 1 to 4, as shown in FIG. At the same time, a voltage is applied between the plate 9 with the ink 8 interposed therebetween and the roller 4 from a power source 12 serving as a voltage applying means. Then, the adhesion of the ink 8 that comes into contact with the conductive base material 9a of the plate 9 changes to non-adhesion, so that an ink image is formed only on the insulating pattern 9b of the plate 9. Practically speaking, the applied voltage at this time is preferably a DC voltage of 3 to 100 V, more preferably a DC voltage of 5 to 80 V, and an AC bias voltage may be supplementarily applied.

Note that in FIG. 1, the plate 9 side is the cathode, and the roller 4 side is the cathode.
Although the side is the anode, this may be reversed depending on the properties of the ink used.

Next, a recording medium 7 (paper, cloth, metal sheet, etc.) passes between the impression cylinder 6, which is a transfer means, and rotates in the direction of arrow F while pressing the ink image on the plate 9 against the plate 9. ) to form the ink image on the recording medium 7. In some cases, the ink image on the plate 9 may be transferred once to an intermediate transfer body such as a blank cylinder and then transferred again to the recording medium 7.

[0034] Here, the diameter of the roller 4 gradually decreases due to anode dissolution due to energization during image formation. A sensor 10 is provided close to the roller 4 to detect this decrease in diameter. Furthermore, as the diameter of the roller 4 decreases, the contact pressure between the roller 4 and the plate 9 gradually weakens. Therefore, an actuator 11 is provided that presses the roller 4 toward the plate 9 by the amount of pressure reduction caused by the amount of displacement detected by the sensor 10 to restore the desired contact pressure. The sensor 10 and the actuator 11 constitute pressure setting means. Specific Example 1 An apparatus having the following configuration based on FIG. 1 was prepared. Rollers 1 to 4: 34mmφ, width 80mm, stainless steel plate cylinder 5: 80mmφ, width 80mm,
Silicone rubber pasted on a stainless steel shaft, rubber hardness 75 degree version 9: Conductive base material 9
a: Copper plate, thickness 0.1 mm Insulating pattern 9b: Formed with photoresist Gap between rollers 1 and 2: 0.
5 mm Between rollers 2 and 3: 0.1
mm Roller 4 contacts roller 3 Initial contact pressure between roller 4 and roller 5 is 4 kg/cm
2 Rollers 1 to 5 are driven by a motor. The ink 8 is 200 g of glycerin, lithium teniolite (average particle size 2.5 μm, LiMg2Li (Si
4O10)F2), and 140 g of cyan pigment (Supranol Cyanin manufactured by Bayer AG) as a coloring agent.
e 78F) 10g in a homogenizer at 100 revolutions
After kneading at 00 rpm for 30 minutes, 200 g of water was added and mixed on a roll mill to prepare a gray amorphous solid sol ink.

Electrical connection of the conductive base material 9a of the plate 9 was made via a stainless steel shaft (not shown) of the plate cylinder 5.

After ink 8 is added as shown in FIG. 1, rollers 1 to 6 are moved in the directions of arrows A to F at a circumferential speed of 100 mm/sec.
I rotated it. After visually confirming that the ink 8 is evenly coated on the roller 4, the roller 4 moves onto the plate 9.
I tried to make contact with it. At this time, at the same time, a DC voltage of 30 V was applied, using the conductive base material 9a of the plate 9 as a cathode (earthed) and the roller 4 as an anode. Also, sensor 10
detects the amount of decrease in the diameter of the roller 4, and compensates for the decrease in the contact pressure on the plate 9 due to the decrease in the roller diameter by pressurizing the roller 4 toward the plate 9 side using the actuator 11, and always maintains the initial contact pressure. 4kg/cm set to
It was maintained at 2.

As a result, the ink 8 adhered only to the insulating pattern of the conductive substrate 9a, and a large number of prints with high image quality and no sharp fogging were obtained. This process was repeated several times, and a large number of prints were also obtained. Specific Example 2 As the roller 4, platinum was plated on the surface of a stainless steel roller having a diameter of 34 mm and a width of 80 mm. Printing was carried out in the same manner as in Example 1 except for the above. As in Example 1, a large number of prints with good image quality were obtained. Specific Example 3 As the roller 4, a conductive rubber (manufactured by Meiji Kasei Rubber Co., Ltd.) containing carbon dispersed in silicone rubber and having a diameter of 34 mm and a width of 80 mm was used. Printing was carried out in the same manner as in Example 1 except for the above. As in Example 1, a large number of prints with good image quality were obtained. Comparative example 1 Sensor 10 and actuator 11 in specific example 1
, and set the initial contact pressure between roller 4 and plate 9 to 4 kg/
cm2, and no pressure means were provided on the roller 4 and the plate 9.

[0038] Printing was carried out in the same manner as in Example 1, and many prints with sharp image quality were obtained, but fogging occurred in the images after repeating the printing several times. The cause of this is that the diameter of the roller 4 is reduced due to anode melting, and the contact pressure of the roller 4 with the plate 9 is reduced, resulting in a change in the amount of electrical charge applied to the plate 9.
This seems to be due to a change in the amount of ink that adheres to the surface.

[0039]

As explained above, the present invention has pressure setting means for setting the contact pressure between the plate and the electrode facing the plate to a desired pressure, thereby making it possible to keep the pressure constant at all times. As a result, the amount of electrical charge applied can be reliably controlled, and the amount of ink deposited on the plate can always be kept constant, which has the effect of printing a large number of images with good image quality.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an image forming apparatus according to an embodiment of the present invention.

2 is a perspective view of the middle plate 9 in FIG. 1. FIG.

[Explanation of symbols]

1 Roller 2 Roller 3 Roller 4 Roller (electrode) 5 Plate cylinder 6 Impression cylinder 7 Recorded object 8 Ink 9th edition 9a Conductive base material 9b Insulation pattern 10 Sensor 11 Actuator 12 Power supply

Claims (2)

[Claims] 1. A pair of electrodes, one of which is a plate, an ink supply means for supplying between the pair of electrodes an ink that becomes non-adhesive to at least one of the electrodes by applying a voltage, and the pair of electrodes. A pressure that sets the contact pressure between the pair of electrodes to a desired pressure in an image forming apparatus that has a voltage application means that applies a voltage between them, and a transfer means that transfers the ink adhered on the plate to a recording medium. An image forming apparatus characterized by having a setting means. 2. The desired contact pressure between the electrodes is 1 kg/
The image forming apparatus according to claim 1, wherein the weight is between 10 kg/cm2 and 10 kg/cm2.