JPH04332691A - Powder ink - Google Patents

Abstract

PURPOSE:To drastically extend the use number of times of an ink sheet and to always provide a stable image by eliminating possibility such that powder ink is also bonded to the bonding part of an ink layer or possibility such that image deterioration such as optical density irregularity or the reproducibility inferiority of a fine line is generated in a formed image even when the regeneration/image formation of the ink sheet is repeated many times using powder ink. CONSTITUTION:Powder ink 11 is formed by externally adding carbon black to the periphery of a matrix particle 21 and the amount of carbon black to be externally added is 5-10 pts.wt. per 100 pts.wt. of the matrix particle.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder ink used in an image forming method and apparatus having a step of forming an image by a thermal transfer method and a step of recycling an ink sheet. More specifically, the present invention relates to a powder ink that is a further development of the powder ink disclosed in Japanese Patent Application No. 1-89009 and Japanese Patent Application No. 1-89010.

0002

[Prior Art] As a conventional powder ink, the present inventor has
Japanese Patent Application No. 1-89009 discloses a powder ink in which carbon black is externally added to the surface of the base particles at a coverage rate of 50% or more, and 1/3 or less of the particle size of the carbon black is fixed in the base particles. proposed an embedded powder ink.

As described in Japanese Patent Application No. 1-89010, a powder ink was proposed in which powder ink matrix particles are not exposed on the surface of the powder ink.

In the case of these powder inks, the amount of powder ink adhering to the ink layer adhesion area is approximately 1% or less of the amount of powder ink adhering to the ink layer transfer area, and this adhesion results in a Even when image formation and reproduction were repeated more than once, the formed image did not suffer from image deterioration such as uneven optical density or poor reproducibility of thin lines.

[0005]

[Problems to be Solved by the Invention] When recycling and image formation on an ink sheet using powder ink are repeated many times, the ink layer formed by the powder ink is repeatedly melted and cooled by the heat of the fixing means, and the ink layer Due to the melting of
Migration of externally added solids may occur. In particular, when externally added carbon black moves and aggregates due to heating, the resistance value of the ink layer increases locally. This may cause the powder ink to adhere to the adhesion areas of the ink layer, resulting in optical density unevenness and unevenness in the formed image.
Image deterioration such as poor reproducibility of thin lines may occur.

[0006] Therefore, the present invention is disclosed in Japanese Patent Application No. 1-89009.
This is a further development of the powder ink disclosed in Japanese Patent Application No. 1-89010, and its purpose is to
An object of the present invention is to provide a powder ink that can be used in an image forming method and apparatus having a step of forming an image by a thermal transfer method and a step of recycling an ink sheet. Another object of the present invention is to provide a powder ink in which the physical properties of the ink layer are not easily changed by heat even if the ink sheet is recycled and images are formed many times. Another object is to provide a powder ink that does not cause deterioration in image quality even if the ink sheet is recycled and image formed many times.

[0007]

[Means for Solving the Problems] The powder ink of the present invention is
In powder ink in which carbon black is externally added to the surface, which is 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, the weight of the powder ink base particles When is set as 100,
It is characterized in that the weight of externally added carbon black is 5 to 10.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to the drawings.

FIG. 1 shows a cross-sectional view of a powder ink according to the present invention.

The powder ink 11 is made up of base particles 21 and carbon black 31 externally added thereto. The amount of carbon black added externally is 5 to 10, when the weight of the base particles is 100.

[0011] Here, carbon black 31 is as follows:
Carbon blacks such as furnace black, channel black, thermal black, lamp black, and acetylene black can be used. The amount of carbon black added externally is 5 to 10, when the weight of the base particles is 100. Further, the externally added carbon black may be two or more types of carbon black.

The constituent material of the base particles 21 is selected from the group of substances listed below. 1) Acrylic resins such as polyacrylate and polymethacrylate, styrene resins such as polystyrene and poly-1-methylstyrene, butyral resins, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, polyester resins, polycarbonate resins, Simple substances, copolymers, and mixtures of resins selected from thermoplastic resins such as cellulose resins, polyarylate resins, and polyethylene resins.

2) Polyvinyl alcohol, polyallyl alcohol, polyvinylpyrrolidone, polyvinylamine,
Polyallylamine, polyvinyl acrylic acid, polyvinyl methacrylic acid, polyvinyl sulfate, polylactic acid, casein,
A simple substance, copolymer, or mixture of resins selected from water-soluble resins such as hydroxypropyl cellulose, starch, gum arabic, polyglutamic acid, polyaspartic acid, and nylon resin.

3) A resin selected from thermosetting resins such as epoxy resins, silicone resins, urethane resins, melamine resins, and alkyd resins.

4) Candelilla wax, carnauba wax, rice wax, beeswax, lanolin, montan wax, ozokerite, paraffin wax, microcrystalline wax, perotoratum, polyethylene wax, Fischer-Tropsch wax, montan wax derivative, paraffin wax derivative, hardening Castor oil, waxes such as synthetic wax, stearic acid,
Higher fatty acids such as palmitic acid, polyolefins such as low molecular weight polyethylene, polyethylene oxide, and polypropylene, olefin copolymers such as ethylene/acrylic acid copolymer, ethylene/acrylic acid ester copolymer, ethylene/vinyl acetate copolymer, etc. A single object selected from a union class,
Or a compound.

5) Fe3O4, Fe2O3, F
Magnetic powder such as e, Cr, Ni, etc.

6) Surfactants or dispersants such as metal soaps and polyethylene glycols.

7) Charge control agents such as electron-accepting organic complexes, chlorinated polyesters, nitrofnic acids, quaternary ammonium salts, and pyridinium salts.

8) Fillers such as talc.

9) Fluidity improvers such as SiO2 and TiO2.

10) Colorants such as black pigments (dyes and pigments) such as furnace black, channel black, thermal black, lamp black, acetylene black, and nigrosine.

11) Carbon black such as furnace black, channel black, thermal black, lamp black, and acetylene black, metal powder such as Al powder and Cu powder, metal oxidation powder such as ITO powder and SnO2 powder, quaternary ammonium salt, etc. Conductive materials such as organic conductive materials.

[0023] The base particle 21 may have an inner core and an outer shell, even if the constituent substances are present uniformly in the particle (even if they are present non-uniformly), and each may have a different structure, or It may have some different constituent substances.

[0024] Considering the fluidity, blocking property, moisture resistance, long-term storage stability, etc. of the powder ink, the base particles 21 are of substance group 2 whose softening point or glass transition point is 50°C or higher. ) and 4) It is preferable that an outer shell is formed that contains a material selected from among the above as a constituent material.

[0025] The method for producing the powder ink of the present invention is as follows:
A method known as a normal toner manufacturing method can be applied. Note that methods for externally adding carbon black include, for example, a method using a mixer such as a ball mill, a method using a mechanochemical reaction, and a spray drying method, which are known as ordinary dry/wet external addition methods.

FIG. 2 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 the ink sheet.

The ink sheet 1 having the ink layer 3 on the insulating support 2 moves in the direction of arrow 4, and the ink is transferred by the thermal head 5 to the recording medium 7 moving in the direction of arrow 6. An image is formed on 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.

An electrode 10 is arranged so as to be in contact with the insulating support 2 of the ink sheet 1, and a conductive electrode is provided to sequentially supply powder ink 11 onto the ink sheet 1 on the opposite side of the electrode 10 with the ink sheet 1 in between. A roller 12 is placed. Power supply 1
3, 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. 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. , and adheres to the insulating support 2 by electrostatic force. However, the attachment portion 9 of the ink layer of the ink sheet 1 and
The powder ink 11 that has come into contact with the powder ink adhered to the insulating support 2 merely serves as a path for electric charges and does not have any adhesive force because the ink layer and the powder ink are conductive. Furthermore, since the powder ink is made by externally adding carbon black around the base particles, it is possible to reduce the interaction between the powder ink and the ink layer of the ink sheet. It is possible to almost eliminate the ink layer from adhering to the adhering portion. In this way, powder ink can be replenished only to the peeled portion of the ink layer of the ink sheet. Ink sheet 1 filled with powder ink
is fixed onto the ink sheet by the powder ink fixing means 14. Through the above steps, the ink sheet is recycled.

Here, when the fixing means 14 uses heat,
When the ink sheet is recycled and image formed many times, the ink layer formed by the powder ink will melt and melt due to heat.
As cooling is repeated and the ink layer melts, there is a risk that solid content added internally and externally may move. In particular, when externally added carbon black moves and aggregates due to heating, the resistance value of the ink layer increases locally. As a result, there is a possibility that the powder ink may also adhere to the attachment portion of the ink layer, and image deterioration such as optical density unevenness and poor reproducibility of thin lines may occur in the formed image.

However, when the amount of externally added carbon black is increased and the weight of the base particles is 100, and the weight of the externally added carbon black is 5 to 10, even if the ink sheet is recycled and image formed many times, , No image deterioration occurred in the formed image. Here, as the insulating support of the ink sheet, a polymer film such as polyethylene terephthalate, polyphenylene sulfide, polyimide, polyamide, polyaramid, etc. can be used, and as the thermal head 5, in addition to the head used in the melt thermal transfer method, etc. A stylus head used in an electric thermal transfer method can also be used, and in the case of an electric thermal transfer method, the structure of the ink sheet is such that a 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, a magnetic brush development method known in the electrophotographic method,
Methods such as a contact development method, a heat roll fixing method, a flash fixing method, a pressure fixing method, etc. can be applied.

The present invention will be explained in more detail below.

(Example 1) Base particles 2 of powder ink 11
As 1, styrene acrylic copolymer 10wt%
paraffin wax 20
wt% carnauba wax
20wt%Fe3O4
50 wt% were mixed, kneaded, crushed, and classified to produce base particles with a particle size of 11 μm. This base particle is referred to as base particle A.

As carbon black 31, base particles A
For 100 parts by weight, the particle size of the parts by weight shown in Table 1 is 40n.
Furnace black having a DBP oil absorption of 170 cc/100 g was added externally to prepare powder inks A1 to A9. The following evaluations were performed on this powder ink. Table 1 shows the results.
It is also written in .

1) Amount of carbon black externally added to base particles (base particle weight is taken as 100). Note that the amount of external addition is measured by TGA (thermogravimetric analysis). The decomposition of resins and waxes generally ends at 500°C, and carbon black decomposes at temperatures above 500°C. Note that, based on the fact that magnetic powder hardly decomposes up to 800°C in an inert atmosphere, it was heated to 800°C in an inert gas atmosphere at a temperature increase rate of 20°C/min. When the initial weight of the powder ink is x, the weight lost up to 500°C is y, and the weight after measurement is z, the amount of externally added carbon black is calculated using the formula, assuming that the base particle is 100.

[0035]

[Formula 1] It can be expressed as 100×(x/(y+z)-1). In addition, if carbon black is also added to the base particles, the TGA of both the base particles and the powder ink
By performing the measurement, the amount of externally added carbon black can be calculated.

2) Image quality evaluation. Image quality was evaluated when image formation and ink sheet regeneration were repeated many times (100 times and 1000 times) using the image forming method shown in FIG. The results were shown as ○: good (initial image maintained) and ×: poor (uneven optical density and poor reproducibility of fine lines were present) with respect to the initial image. The experiment was conducted using ink sheet 1.
A 6 μm aramid film, Vb
was 240 volts, and a heated roller maintained at 100° C. was used as the fixing means 14.

[0037]

[Table 1]

As shown in Table 1, it can be seen that as the amount of externally added carbon black increases, image quality deterioration due to repetition disappears. In the case of repeating about 1000 times, the amount of external addition needs to be approximately 4.5 or more, but when the number of repetitions is further increased, it is desired to be 5 or more. However, although not mentioned in the table, when the amount of external addition exceeds approximately 10, the image becomes less clear in fine lines and has many gaps compared to the initial image with the amount of external addition of 5 to 10. Ta.

From the above, the amount of externally added carbon black is 5 to 10 when the weight of the base particle is 100.
was found to be necessary.

(Example 2) Base particles 2 of powder ink 11
As 1, microcrystalline wax 40wt% carnauba wax 10w
t%Fe3O4
The mixture was mixed, kneaded, crushed, and classified, and further encapsulated with a styrene-acrylic copolymer to a film thickness of 0.2 μm to produce base particles with a particle size of 12 μm. Acetylene black having a particle diameter of 40 nm and a DBP oil supply amount of 250 cc/100 g was externally added to the base particles so that the weight was 8 per 100 of the base particle weight, to prepare powder ink B.

When image formation and ink sheet regeneration were repeated 1000 times using this powder ink B using the image forming method shown in FIG. 2, it was possible to continue to obtain good images that were unchanged from the initial images. .

In the experiment, a 6 μm aramid film was used as the insulating support 2 of the ink sheet 1, Vb was 240 volts, and a hot roller maintained at 100° C. was used as the fixing means 14.

The present invention is not limited to this example.

[0044]

Effects of the Invention As described above, the powder ink according to the present invention has a carbon-free surface that is 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. In a powder ink to which black is externally added, when the weight of the powder ink base particles is 100, the weight of externally added carbon black is 5 to 10. Even if image formation is repeated many times, it is possible to prevent the externally added carbon black from moving or agglomerating due to heating. It has become possible to eliminate the possibility of image deterioration such as optical density unevenness and poor reproducibility of fine lines occurring in the resulting image. Therefore, it has become possible to dramatically extend the number of times the ink sheet can be used, and it has also become possible to always provide stable images.

From the above, the powder ink of the present invention has the following characteristics:
It is particularly effective when used in image forming devices such as printers, video printers, facsimile machines, copying machines, and word processor output devices.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a powder ink according to the present invention.

FIG. 2 is a diagram schematically showing an image forming method using the powder ink according to the present invention, which includes a step of forming an image by a thermal transfer method and a step of recycling an ink sheet.

[Explanation of symbols]

1. Ink sheet 2. Insulating support 3. Ink layer 4...Arrow 5. Thermal head 6.Arrow 7. Recording medium 8. Peeling part of ink layer 9. Adhering part of ink layer 10・Electrode 11. Powder ink 12. Conductive roller 13.Power supply 14.Fixing means 21・Mother particle 31・Carbon black

Claims (1)

[Claims] Claim 1: A powder ink having carbon black externally added to the surface, which is used in an image forming method comprising a step of forming an image by a thermal transfer method and a step of recycling an ink sheet. The weight of the ink base particles is 1
00, the weight of externally added carbon black is 5
-10.