JPH02302474A - Powder ink - Google Patents

Abstract

PURPOSE:To provide a powder ink containing magnetic powder composed of electrically conductive powder having a thermoplastic resin coating layer on the surface, capable of forming an image by thermal-transfer process and suitable for forming an image to regenerate an ink sheet. CONSTITUTION:The objective powder ink contains magnetic powder composed of electrically conductive powder having a thermoplastic resin coating layer on the surface. The loss modulus of the powder ink is preferably <=4X10<3> dyne/cm<2> measured at 180 deg.C under small shear strain of 3Hz. The ink forms an image by thermal transfer process and is used in an image-forming process to regenerate an ink sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a powder ink used in an image forming method that includes a step of forming an image by a thermal transfer method and a step of recycling an ink sheet.

[Prior Art] Conventionally, powder ink has generally been made using fine powder, which is a mixture of thermoplastic resin and coloring agent called "toner."The purpose of this toner is to fix it on paper. Depending on the method used, there are different types of toners, such as insulating and conductive, as well as magnetic and non-magnetic. Because they are fundamentally different,
It is not possible to form an ink sheet for thermal transfer using conventional toner as it is, so the inventors proposed a process for forming an image using a thermal transfer method and a method for recycling the ink sheet in Japanese Patent Application No. 63-214441. As a powder ink used in an image forming method having a step of I suggested ink. It is proposed that the powder ink has a volume resistivity of 10 8 Ω or less, and that the volume resistivity of the ink layer of an ink sheet recycled with the powder ink is 10 7 Ω or less.

[Problems to be Solved by the Invention] However, the process of forming an image using the conventional thermal transfer method,
In a powder ink used in an image forming method including a step of recycling an ink sheet, the volume resistivity of an ink layer of an ink sheet recycled with the powder ink is 10'Ωc.
m or less, a large amount of conductive fine particles must be added, which increases the viscosity of the powder ink, making the formation of an ink layer on the sheet by heat fixation uneven.

For this reason, when an image is formed using a thermal transfer method, there is a problem in that the optical temperature (hereinafter referred to as oD value) varies. Furthermore, if the viscosity of the powder ink is high, uneven transfer of the ink onto the recording medium occurs, resulting in a decrease in image quality. Also,
Since a large amount of thermal energy is required, there are problems in that the durability of the device decreases and running costs increase.

Therefore, an object of the present invention is to solve the above problems, and to provide a powder ink with low viscosity while maintaining the conductivity of the ink layer, to produce an ink sheet with low energy and no surface irregularities, and to be recyclable. Further, it is an object of the present invention to provide a powder ink that can form a clear image without uneven transfer on a recording medium.

[Means for Solving the Problems] The powder ink of the present invention is a component of the powder ink used in an image forming method that includes a step of forming an image by a thermal transfer method and a step of recycling an ink sheet. A magnetic powder having conductive fine particles fixed to its surface is characterized by using conductive fine powder whose surface is coated with a thermoplastic resin.

Furthermore, the loss elastic modulus of the powder ink when a slight strain of 3 Hz is applied at 180°C is 4×10” dyn e /
cm2 or less.

[Operation] It is generally known that as solid content is mixed into a matrix, the viscosity of the mixture increases. Therefore, it is considered that by fixing the resin-coated conductive fine powder around the magnetic powder, which is a feature of the present invention, the apparent solid content can be reduced and the increase in viscosity can be suppressed. Furthermore, when adhering conductive fine powder to magnetic powder, since they are both inorganic substances, the adhesion force will be weakened due to repulsive force if left untreated. For this reason, it is thought that the resin coated on the surface of the conductive fine particles acts as a binder between the magnetic powder and the conductive fine particles to firmly bond them together. Furthermore, since the distances between the magnetic powders in the powder ink are close to each other, it is thought that stractures are likely to be formed by the conductive magnetic powders, thereby ensuring conductivity in the mixed system. Therefore, by applying pressure under heat, the powder ink can be spread and fixed on the ink sheet without surface irregularities.

〔Example〕

The present invention will be specifically explained by the following examples.

The powder ink of the present invention can be produced by a general kneading and pulverization method, a spray drying method, or a polymerization method. Further, a conductive layer is externally added to impart conductivity to the powder ink.

As the magnetic powder used in the powder ink of the present invention, Fe5
O4, Fears, Fe, Cr, Ni, etc. are used. In addition, examples of conductive fine particles include furnace black, channel black, thermal black, lamp black,
Carbon black such as acetylene black, A1 powder, C
Metal powder such as u powder, organic conductive material such as engineered TO powder, SnO2 powder, etc. can be used.Next, the method of coating the conductive fine particles with a thermoplastic resin includes a polymerization method,
Process by spray drying method etc. The thickness of the resin layer is preferably 0.05 μm or less. In addition, waxy substances used as the main component of the powder ink of the present invention include plant-based natural waxes such as candelilla wax, carnauba wax, and rice wax, animal-based natural waxes such as beeswax and lanolin, montan wax, and osikelite. Mineral natural waxes, paraffin waxes, microcrystalline waxes, natural petroleum waxes such as petrolatum, polyethylene waxes, synthetic hydrocarbon waxes such as Fischer-Tropsch waxes, modified waxes such as montan wax derivatives, paraffin wax derivatives, etc.
Hydrogenated waxes such as hydrogenated castor oil and hydrogenated castor oil derivatives, waxes such as synthetic waxes, higher fatty acids such as stearic acid and valmitic acid, polyolefins such as low molecular weight polyethylene, polyethylene oxide, and polypropylene, ethylene/acrylic acid copolymers, One or more of olefin copolymers such as ethyl ester/acrylic acid ester copolymer and ethylene/vinyl acetate copolymer are used. Furthermore, the following resins can be mixed as main components other than wax.

Polystyrene and copolymers, such as hydrogenated styrene resins, styrene-isobutylene copolymers, ABS resins,
ASA resin, As resin, AASAs resin CS
tree ffa, ABS resin, styrene/P-chlorostyrene copolymer, styrene/propylene copolymer, styrene/
Butadiene crosslinked polymer, styrene.

Butadiene/chlorinated paraffin copolymer, styrene/allyl/alcohol copolymer, styrene/butadiene rubber emulsion, styrene/maleic acid ester copolymer, styrene/isobutylene copolymer, styrene/maleic anhydride copolymer, Acrylate resin or methacrylate resin and its copolymer, styrene-acrylic resin and its copolymer, such as styrene-acrylic copolymer, styrene-diethylamino-ethyl methacrylate copolymer, styrene-butadiene-acrylic Acid ester copolymer, styrene/methyl methacrylate copolymer, styrene/n-butyl methacrylate copolymer, styrene/diethylamino/ethyl methacrylate copolymer, styrene/methyl methacrylate/
n-butyl acrylate copolymer, styrene/methyl methacrylate/butyl arylate/N-(ethoxymethyl) acrylamide copolymer, styrene/glycidyl methacrylate copolymer, styrene/butadiene/dimethyl/aminoethyl methacrylate copolymer , styrene/acrylic ester/maleic ester copolymer, styrene/methyl methacrylate/acrylic acid 2-
Ethylhexyl copolymer, styrene/n-butyl arylate/ethyl glycol methacrylate copolymerization styrene/n-butyl methacrylate/acrylic acid copolymer, styrene/n-butyl methacrylate/maleic anhydride Copolymer, styrene/butyl acrylate/
Isobutyl maleate hafester/divinylbenzene copolymer, polyester and its copolymer, polyethylene and its copolymer, epoxy resin, silicone resin, polypropylene and its copolymer, fluorine resin, polyamide resin, polyvinyl alcohol resin, polyurethane One type of resin, polyvinyl butyral resin, etc., or a blend of two or more types can be used.

As the coloring agent, black dyes and pigments such as carbon black, spirit black, and nigrosine are used. For coloring, dyes such as phthalocyanine, rhodamine B lake, solar pure yellow 8 G, quinacridone, polytungstophosphoric acid, inxrene blue, and sulfonamide derivatives can be used. Furthermore, metal soap, polyethylene glycol, etc. can be added as a dispersant.

FIG. 1 schematically shows an image forming method comprising a step of forming an image by a thermal transfer method using the powder ink of the present invention and a step of recycling an ink sheet.

Ink sheet 1 having an ink layer 3 on an insulating support 2
moves in the direction of the arrow 4, and by the thermal head 5,
The ink is transferred to the recording medium 7 moving in the direction of arrow 6,
An image is formed on the recording medium 7 (step of forming an image using a thermal transfer method).

By forming the image, a peeling part 8 of the ink layer and an adhesion part 9 of the ink layer are formed on the ink sheet 1.

The electrode 1 is placed in contact with the insulating support 2 of the ink sheet 1.
A conductive roller 12 that sequentially supplies powder ink 11 onto the ink sheet 1 is placed on the opposite side of the electrode 10 with the ink sheet 1 in between. The powder ink 11 is supplied onto the ink sheet 1 while a bias voltage (hereinafter referred to as Vb) is applied between the electrode 10 and the conductive roller 12 by a power source 13. The powder ink 11 that has come into contact with the peeled part 8 of the ink layer of the ink sheet is charged with an amount proportional to the product of the capacitance of the insulating support 2 and vb because the peeled part 8 of the ink layer exhibits insulation. The injected material adheres to the insulating support 2 by electrostatic force. However, the ink layer adhering portion 9 of the ink sheet 1 and the insulating support 2
Since the ink layer and the powder ink are conductive, the powder ink 11 that has come into contact with the powder ink that has adhered to the surface of the powder ink merely acts as a path for the charge and does not acquire any adhesion force. Powder ink can be replenished only to the peeled portion of the ink layer of the ink sheet. The ink sheet 1 replenished with powder ink is fixed onto the ink sheet by the powder ink fixing means 14, and the ink sheet is regenerated through zero or more steps.

Here, a polymer film such as polyethylene terephthalate, polyphenylene sulfide, polyimide, polyamide, etc. can be used as the insulating support of the ink sheet, and as the thermal head 5, in addition to the head used in the fusion heat transfer method, electric heat transfer A stylus head used in this method can also be used, and in the case of an electrically conductive thermal transfer method, the structure of the ink sheet is such that an electrically conductive layer or the like is formed on the opposite side of the ink layer across the ink sheet. As the recording medium 7, rough paper, plain paper, OHP sheet, etc. are used. Further, as the conductive roller 12 for conveying the powder ink and the powder ink fixing means 14, methods such as a magnetic brush development method and a contact development method, which are known in electrophotography, can be applied, and methods such as a heat roll fixing method, Methods such as a flash fixing method and a pressure fixing method can be applied.

The present invention will be explained in more detail below.

[Example 1] (Formation of resin layer on conductive fine particles) Carbon black was used as the conductive fine particles and polybutyl methacrylate (PBMA) was used as the resin, and these were dissolved and dispersed in acetone and spray-dried using a spray drying method. Then, a resin layer was formed around the carbon black. The composition is shown below.

Acetone 200 parts by weight PBMA
10fi parts carbon black
8 parts by weight Carbon black was dispersed into the above solution using an ultrasonic homogenizer, and a two-fluid nozzle was used for spraying. Spraying conditions are pressure 5kg/cm2,
The drying temperature was 30 degrees. When the obtained powder was observed with an electron microscope, the particle size was 0.05 μm and the coating resin film thickness was 0.
．． It was a fine powder with a diameter of 0.01 μm.

(Preparation of Magnetic Powder) Next, the magnetic powder and the resin-coated conductive fine particles were mixed and fixed to the surface of the magnetic powder using a mechanochemical system. The manufacturing method is shown below.

4100 parts by weight of FeaO 40 parts by weight of resin-coated carbon black Further, the mechanochemical reaction treatment temperature was 55°C.

(Preparation of powder ink) As a powder ink, 30 parts by weight of ethylene/vinyl acetate copolymer, 25 parts by weight of paraffin wax, 30 parts by weight of resin covering power - Bomb black treatment, 30 g of Fe, 45 parts by weight, using the raw materials having the above composition, were kneaded in a screw extruder. death,
After cooling and coarsely pulverizing, the mixture was finely pulverized using a jet pulverizer and classified to produce a powder ink having a size of 5 to 20 μm (average particle size 10 μm). Further, 3 parts by weight of carbon black was externally added to 1 part by weight of the powder ink to prepare a powder ink.

The powder ink produced in this way is applied to an ink sheet on which an ink layer is not formed (in other words, all the parts are the peeled parts of the ink layer) by the step of recycling the ink sheet of the image forming method shown in Figure 1. When the powder ink was applied and fixed, and then an image was formed on recording paper, there was no transfer unevenness.
A clear image with a D value of 1.5 or more could be formed.

Furthermore, even after 1000 playbacks, the image quality remained as clear as the initial one.

[Example 2] Powder ink was prepared in the same manner as in Example 1 except that the resin IL (coating thickness) coated on the carbon black of Example 1 was changed. Regarding these powder inks, 3
The loss modulus when a minute shear strain of Hz is applied at 180°C and the volume resistivity are determined by heating the prepared powder ink and using a wire bar to form a film with a thickness of 3 to 4 μm. It was measured using The results are shown in Table 1.

Table 1 As is clear from Table 1, the film thickness of the resin coating is 0°00
If it is smaller than 1 μm, the loss modulus is small, but the volume resistivity becomes 10′Ωcm or more, making it impossible to perform selective attachment, which is not preferable.

Furthermore, when the film thickness of the resin coating exceeds 0.05, the volume resistivity and loss modulus increase, causing unevenness on the ink sheet.
This is not preferable because it reduces image quality.

Therefore, it is appropriate that the film thickness of the resin coating is in the range of 0.001 to 0.05, and in this example, 0.005
A resin-coated carbon black-treated magnetic powder having a film thickness in the range of 0.02 to 0.02 was produced in the same manner as in Example 1, and a powder ink was produced in the same manner as in Example 1. When an image was formed, the same results as in Example 1 were obtained.

[Example 3] Example 1 (formation of a resin layer on conductive fine particles) was carried out by a seed polymerization method. The manufacturing method and composition are shown below.

Carbon black 20 parts by weight Styrene resin 25 parts by weight Potassium persulfate (polymerization initiator) 0.4 parts by weight Pure water 2
50 parts by weight Using these raw materials, carbon black was first dispersed in pure water using an ultrasonic homogenizer and a mechanical stirrer, and then potassium persulfate as a polymerization initiator was added and dispersed in the same manner as above. let

Thereafter, half the amount of styrene resin (20 parts by weight) is added, the temperature of the dispersion liquid is set at 45° C., and polymerization is carried out for 2 hours. Further, the remaining styrene resin was added, the temperature was raised to 75°C, and polymerization was carried out for 4 hours. Once the polymerization is complete, the solution is centrifuged, solids are separated, filtered, and washed with acetone.
Thereafter, vacuum drying was performed to create resin-coated carbon black. When the obtained powder was observed with an electronic mirror, the particle size was 0.05 μm, and the thickness of the resin layer was 0.01 μm.
Met. The following (preparation of magnetic powder) and (preparation of powder ink) were performed in the same manner as in Example 1. However, in (preparation of magnetic powder), the mechanochemical treatment temperature was 50°C. Example 1 in the powder ink prepared in this way
An image was formed using the same image forming method as in Example 1, and the image was evaluated in the same manner as in Example 1. As a result, the same results as in Example 1 were obtained.

[Effects of the Invention] As described above, according to the present invention, components of powder ink used in an image forming method including a step of forming an image by a thermal transfer method and a step of recycling an ink sheet. In magnetic powder with certain conductive fine particles fixed to the surface,
By using conductive fine powder whose surface is coated with thermoplastic resin, the loss modulus of the powder ink is 4xlO3dyne/c when a minute shear strain of 3Hz is applied at 180°C.
m2 or less, and by fixing the resin-coated conductive fine particles to the surface of the magnetic powder through a mechanochemical reaction, it is possible to suppress the thickening effect of the powder ink and to produce and recycle ink sheets without unevenness. As a result, it is possible to obtain clear images without transfer defects or decreases in image density.Furthermore, since images can be formed with low energy, it has the great effect of significantly reducing running costs. .

Further, the powder ink of the present invention can be used in devices such as printers, copiers, facsimile machines, etc. that use an image forming method that includes a step of forming an image by a thermal transfer method and a step of recycling an ink sheet. It can also be applied.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an image forming method using the powder ink of the present invention, which includes a step of forming an image by a thermal transfer method and a step of recycling and using an ink sheet.

Claims (2)

[Claims] (1) Magnetic powder with conductive fine particles fixed to the surface, which is a component of powder ink used in an image forming method that includes a step of forming an image by a thermal transfer method and a step of recycling an ink sheet, A powder ink characterized by using conductive fine powder whose surface is coated with a thermoplastic resin. (2) The loss modulus of the powder ink when a 3Hz minute shear strain is applied at 180°C is 4 x 10^3 dyne/cm
The powder ink according to claim 1, wherein the powder ink is ^2 or less.