DK145067B - TONS FOR ELECTROPOTOGRAPHIC DEVELOPER - Google Patents

Description

in 145067

The invention relates to a toner of the kind specified in the preamble of claim 1.

From the disclosure of U.S. Patent No. 2,297,691, a method of electrophotographic copying is known by which an electrostatic charge image similar to the original can be produced, which is then produced by deposition of finely divided powdered developer or toner on the charge image, which in turn may be transmitted on an image-receiving material such as paper. Subsequently, the transmitted image 10 can be permanently fixed to the image-receiving material, e.g. by heating. Alternatively, the toner image may be fixed to the photoconductive layer if the step of transferring the powder image is to lapse.

15 Such toner includes the two initially listed. Since the developer does not contain any carrier particles, the quality of the developed image is very stable for a long time, which means that the photocopier corresponding to the developer can be simplified.

In a conventional method of producing such toner, e.g. is known from DE-AS 1 936 651 or DE-OS 2 431 200 as follows: First, the plastic binder and magnetic particles are mixed at a temperature at which the plastic binder melts and the resulting mixture after the cooling is pulverized and the resulting particles dispersed in a hot air stream (from, for example, 505-537 ° C or 480-595 DC) and thereby made spherical; the spherical particles are then mixed with electrically conductive particles, whereupon the resulting mixture is again dispersed in a hot air stream (from, for example, 383 ° C or 370-430 ° C), so that the electrically conductive particles are enclosed in the surface layer of the spherical liner toner particles; the particles are finally classified or screened for a suitable particle size.

In this context, it has been known in detail as a plastic binder to use a mixture of a waxy compound and a thermoplastic synthetic resin (see, for example, DE-OS 2 431 200), wherein the waxy compound is polyethylene, a aliphatic wax or hydroxylated fatty acid, while thermoplastic synthetic resin 10 is a cellulose ester, vinyl polymer, vinyl copolymer, polyamide or polystyrene, for the magnetic particles, magnetite, barium ferite, nickel zinc ferite, chromium oxide and OS 2,431,200) and for the electrically conductive particles, very good conductive carbon such as carbon black is used (see DE-OS 2,431,200); Finally, as epoxy resin binder, solid epoxide resin (epi-chlorohydrin / bisphenol-A, m.p. 95 - 105 ° C, epoxide equivalent 875 -1025 MW 1400) is used (see DE-AS 1 937 651).

The toner particles may have a diameter of e.g. 5-25 20 µm at a (specific) electrical resistance of the toner from 1QJ - 107> s'cm in an electric DC field of 100 V / cm and from 10 ^ - 10 ^ £? * Cm in an electric DC field of 10,000 V / cm (see DE-OS 2 431 200); preferably, the toner particles have a diameter of 2 - 15 µm (see DE-AS 25 1 937 651).

In another conventional process for producing powdered developer, the plastic binder and magnetic particles are mixed at a temperature at which the plastic binder melts, the mixture is pulverized upon cooling and the resulting particles classified or screened to a suitable particle size; the particles are then dispersed in a hot liquid which does not dissolve the particles into which the electrically conductive particles are dispersed; the resulting particles are dried after rinsing; then the particles are made spherical and the electrically conductive particles are also enclosed in the surface of the toner particles 5.

The toner particles produced by this conventional process have an insulating core and an electrically conductive outer layer. In addition, such particles have low electrical resistance at high electric field strength and high electrical resistance at low field strength.

As a result, the toner particles have good electrical adhesive properties for electric charges after removal of the toner from the strong electric field. Thus, it is believed that the adhesive properties of electrical wires are of particular importance when the toner image pattern is to be transferred from the photoconductive surface to an image-receiving material without particle loss.

Admittedly, the toner particles produced by this conventional process contain no electrically conductive particles in the interior, so that the particles have a high tendency to clump.

Similarly, in the prior methods of making developer powder, it is extremely difficult to disperse the powdered particles uniformly 25 in a hot air stream, thereby increasing the average particle size. In addition, difficulties in applying electrically conductive particles uniformly to the resulting spherical particles in the mixture; therefore, the developing powder 30 thus produced has no uniform electrically conductive outer layer.

In the latter process, the toner particles have equal (no uniform electrically conductive outer layer) and the productivity of this process is obviously not so good.

Furthermore, when in this known method, as electrically conductive particles, e.g. For example, when carbon black is used, the electrical resistance changes significantly by just slight oscillations of the amount of carbon black in the range of 10 - 10> <1 cm in an electric DC field of 100 µl / cm. Therefore, in order to obtain good image copies, especially according to the so-called PPC-10 (Plain Paper Copier) method - copies on plain or plain paper - the (specific) electrical resistance must be precisely controlled.

Accordingly, it is an object of the invention to provide a toner for electrophotographic developer of the type indicated initially, whose electrical properties are relatively insensitive to oscillations of the content of electrical particles and which can also be produced without difficulty.

This object is achieved according to the invention in that the toner initially indicated is characterized by the characteristic part of claim 1.

For the toner of the invention, the following advantages can be stated: (1) its electrical resistance is highly reproducible, especially in the range of 10 ^ - 10 ^ CVcm at an electric DC field of 100 V / cm, which is especially too copious when copied on plain paper ( so-called PPC method); (2) the fixed image density of the copy is very high; (3) it is significantly simpler to manufacture and thus productivity is higher than before; (4) the characteristics of the toner image, e.g. image resolution, background, and adhesive properties are comparable to those of the usual images; and (5) using carbon black as electrically conductive particles, black images can be produced, although non-black magnetic particles, e.g.

metal powder, Mn-Zn ferrite or Ni-Zn ferrite.

Advantageous further developments of the toner are given in claims 2 - 11.

In details: The content of plastic binder ranges from 30-60% by weight, preferably at 40- 53% by weight. When the amount is less than 30% by weight, the toner particles can only be made spherical with difficulty. The flowability of the toner is similarly not so good that the developed image shows irregularities. Furthermore, in this case, the adhesive between the toner and the image-receiving material is no longer sufficient for fixation. On the other hand, when more than 60% by weight of plastic binder is used, the content of magnetic particles is no longer sufficient for "magnetic brush" development so that the background density grows and the image resolution becomes poorer.

The usual resin can be used as a plastic binder for heat fixation as well as for pressure fixation.

25 The heat-fixed resins used include e.g. rubber, natural resin such as rosin, styrene, butadiene-styrene copolymer, acrylic resin, polyvinyl chloride, polyvinyl acetate, silicone resin, terpene resin, vinyl chloride-vinyl acetate copolymer, epoxy resin, polyester resin copolymer, styrene-acrylic resin aerosol, phenol, ketone, or male.

145067 6

As molding agents for pressure fixation, e.g. plastics are disclosed which are described in JP-OS 5 011 276 and 5 011 277. wax, polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic resin copolymer, isomer or polyoxyethylene. The melting point of the plastic binder is about 60 to 170 ° C, preferably about 75 to 130 ° C.

The content of magnetic particles ranges from 35-65% by weight, preferably at 40-60% by weight. If the amount is less than 35% by weight, the magnetic force of the toner is not sufficient to elicit an electrostatic latent image with a magnetic brush process. In this case, the toner is easily dispersed by the magnetic roller, thereby reducing the background density as well as the image resolution.

When the amount is above 65%, the plastic binder content will be less than 33%. Fixing the copied image as well as the density in the solid state will thereby deteriorate accordingly.

The magnetic particles are selected from metals such as Fe, Ni and Co, magnetic alloys of Fe, Ni, Co,

Al, Cu, Pb, Mg, Sn, Zn, Au, Ag, Sb, Be, Cd, Ca, Mn, Se,

Ti, W, V or Zr, oxides such as iron oxide, alumina, nickel oxide, zinc oxide, zirconia, titanium oxide and magnesium oxide, nitrides such as vanadium nitride and chromium nitride, carbides such as u / olfram carbide and cilicium carbide, and ferrites such as Mn-Z , Ni-Zn ferrite, Sr ferrite and Ba ferrite.

The particle size of the magnetic particles is preferably at 0.1-1.0 µm. For the production of black car conductor, magnetite is preferably used.

U5067 7

According to the invention, the content of electrically conductive particles uniformly distributed in the toner is in the range of 2 to 30% by weight, preferably at 4 to 20% by weight Si. The electrically conductive particles of the invention useful include carbon black, metal such as Cu, Al, Ag, Ni or Co as well as alloys, oxides and mixtures of these substances. In addition, surface activators, e.g. metal soaps of organic acids such as naphthenic acid, octenoic acid and stearic acid are used with metals such as Na, K, Ca, Ba, Mn, Co, Ni, Cu, 10 Zn, Pb, Zr as well as transition metals, in addition organic phosphides such as triphenylphosphide and trioctadesylphosphide, organic tin compounds such as butyltin maleate and dibutyltin oxide, organic esters of polyhydric alcohols, phenol derivatives of aliphatic compounds, polyoxyethylene, alkylamine such as alkylpyridinium salt, alkylbetaine and tetraalkylammonium sulfate or alkylsulfonic acid salt.

When the amount of electrically conductive particles is less than 2% by weight, the electrical resistance of the toner is over 10 µm at an electric DC field of 100 V / cm, whereby the properties of the copies such as e.g. density, resolution, background, and nuances of the image are getting worse. On the other hand, when the amount is above 30% by weight, the content of plastic binders and magnetic particles is less than 70% by weight. Therefore, the fixation of the image, the tightness and 1 in 25 - 25 become worse. In order to obtain a black image, it is preferred to use carbon black having a particle size in the range 10 - 40 µm.

The electrical resistance of toner produced by conventional methods is critically altered by just a few electrically conductive particles in the range of 10µ-10c-cid in an electric DC field of 100 l / cm. Therefore, it is very difficult to obtain toner with electrically specific resistance in the same area. In order to obtain good copies, especially by the PPC method, it is necessary to precisely control the electrically specific resistance in the range 10 - 10 J <* cm in an electric DC field of 100 V / cm.

The electrical resistance of the toner according to the invention is very stable in the range of 10z - 101 / cm • at an electric DC voltage field of 100 V / cm. Therefore, the toner of the invention can be used in the PPC method which requires electrically specific resistance in the range of 10 ^ - 10 ^ A * cm in an electric DC field 100 V / cm.

10 Electrical resistance measurements are made on the toner of the present invention in a 1 cm * 1 cm sample between mercury electrodes.

By using light colored and transparent magnetic particles such as metal, alloys, oxides and other transparent magnetic materials, light colored or transparent electrically conductive materials such as metals and alloys, plastic binders and color materials, corresponding colored tones can be obtained. The colorants include chromophore containing polymer and colorants such as lithol maroon toner, alizarin lacquer B, bonred toner 5B, caulitol toner, ba lithol toner, pigment scar, bonred toner-Y, lithol ruby, brilliant red lacquer R, lacquer red C, benzidine-orange, hansa-yellow, benzidine-yellow, rhodamine 6G lacquer, rhodamine toner-B, para-red-toner-light, PTA violet toner, 25 peacock tones, permanent peacock-blue , victoria blue tones, Cu phthalocyanin, alkali blue tones, malachite green tones, phthalocyanin green and the like.

The toner of the invention may additionally contain dry lubricating material which enhances the flowability of the toner in the magnetic developer apparatus. However, the electrically specific resistance and triboelectric properties of the toner are greatly influenced by dry lubricating materials. If the amount of dry lubricating materials is too large, the properties of the copied image, such as image resolution, background and image shades, will be poorer.

Suitable dry lubricating materials contain stearate masses, silicic anhydride, alumina, titanium oxide and the like having a particle size in the range of 3 - 40 µm. The amount of dry lubricating material in the toner of the invention is preferably up to 1.0% by weight.

The particle size of the toner according to the invention is about 1 to 100 µ. Preferably, it is about 5 - 40 µm to obtain a good image such as background, resolution and halftone.

In addition, the specific weight of the toner according to the invention is preferably in the range of 1.4 to 2.3. If it is less than 15 1.4, the total amount of magnetic particles and electrically conductive particles is insufficient to obtain good copies. If it is more than 2.3, the amount of plastic binder is not sufficient to achieve good retention.

If the electrically conductive particles are combined with a colorant, it is not necessary to apply a color to those agents and the colorant is uniformly dispersed in the toner of the invention, which is why it is able to obtain a well-copied image such as contrast, solid density and the like with the pressure fixing method.

23 With the toner of the invention, an electrostatic latent image is excellently elicited by the magnetic brushing process. In particular, the toner of the invention has a stable electrically specific resistance in the range of 10 ~ 10 ~ 10 cm in an electric DC field of 100 volts per meter. cm, where -30 is particularly suitable for PPC (plain paper copier) methods. Furthermore, the tones of the invention are very easy to manufacture or fabricate.

145067 10

The invention is further illustrated by the following examples.

All parts and percentages are percentages by weight unless otherwise stated.

EXAMPLE 1

There were produced plastic binder by mixing 7 parts by weight of a microcrystalline wax polymerized with ethylene and having a molecular weight of 560, a density of 0.94 g / cm 2 and a softening point of 160 ° C, 2 parts of 10 an ethylene-vinyl acetate copolymer with a vinyl acetate content of -19 wt% and a density of 0.94 g / cm 2 and 1 part of f-methyl-styrene-vinyltoluol copolymer with a density of 1.04 g / cm in a conventional mixer at a temperature between 130 and 150 ° C. The seven species of blends for the toner listed in Table I were obtained by adding various amounts of carbon black as a colorant and electrically conductive particles to the plastic binder and by homogenization in a rubber roller mill at a temperature between 130 and 150 °. C, while magnetite (Fe 2 O 2) was still being added and each of the mixtures 20 was mixed with the same rubber rolling mill.

The sample # 1 in Table I is given as a comparative example.

TABLE I

Composition Sample no.

1 2 3 4 5 6 7 Carbon black (weight? O) 1 2 3 5 7 9 10

Plastic Binder (weight 35) 49 48 47 45 43 41 40

Magnetite (wt%) 50 50 50 50 50 50 50

Each of the blends was ground in a conventional particle size pulse of usually 1 mm in diameter, and then in a conventional fine powder ball mill in which carbon black particles were homogeneously mixed.

Then, each powder was classified by a conventional grading apparatus. The particle size distribution of the classified particles was as follows: diameter 100 - 200 µm: 6 - 9 wt% diameter 50 - 100 µm: 17 - 25 wt% diameter <50 µm: 65 - 75 wt%.

The resistance of the individual toner (particle size <50 µm) was determined by the method already mentioned. The resistance of Sample # 1 was at least 10 10 cm at an electric DC field of 100 V / cm. The electrical resistance decreased with increasing carbon black content. The resistance of Sample No. 7 was 3-10 µm or 1'10 µm at an electric DC field of 100 V / cm or 1000 V / cm.

In addition, the specific weight was determined for each sample.

The density was almost linearly dependent on the carbon black amount.

The specific weight of Sample Nos. 1 and 7 was respectively 1.65 and 1.79 g / ml.

Since the aforementioned toners contained certain amounts of electrically conductive particles, electrostatically latent images could be elicited with each of these toners according to the CPP and PPC method by conventional electrophotographic processes for visible images. The fixing properties of the hard copy were excellent for each of the toner mentioned.

Toner # 1 copies admittedly had the following drawbacks: the amount of toner applied was poor, the image density and resolution were insufficient, and too much toner was applied at the edge of the latent image.

On the other hand, with tones # 2 to # 7, copies produced were very clear and precisely delimited. It was clear that the image density, contrast ratio, and gloss of the duplicated image increased as the amount of sex-smoke in the toner increased.

The flowability of a toner according to the invention can be further improved by depositing well-known dry lubricating materials or by spheroidizing the particles in the toner. Eg. for example, any magnetic toner as stated above may have a small amount of finely powdered silicic anhydride (particle size 3 - 10m 2) on the surfaces of the particles, and the particles may then be spheroidized in hot aerosol at a temperature between 400 and 450 ° C and, if necessary. , finely powdered silicic anhydride can be re-applied to the surfaces of the particles. In this way, toner particles with excellent flowability and almost spherical spherical shape were obtained.

With the toner, which was spheredized by the above method, electrostatically latent images according to the CPC and PPC method were generated for a conventional electrophotographic process and then fixed by pressure. As the flowability of the spheroidized particles was improved, the nuances of the duplicated images improved remarkably. Duplicated images obtained with notes 2-7 were excellent.

EXAMPLE 2 A plastic binder of a homogenous blend of 75 parts by weight of microcrystalline wax having a molecular weight of 580 - 850, a density of 0.846g / cm 2 and a melting point of 220 ° C and 25 parts of an ethylene-vinyl acetate-co. polymer having a vinyl acetate content of 25% by weight and a density of 0.95 g / cm 2 in a conventional mixer at a temperature between 120 and 140 ° C. Then three different mixtures of magnetic toner as given in Table II were obtained by adding different amounts of carbon black to the plastic binder, and each was homogeneously mixed in a rubber rolling mill between 140 and 170 ° C, then finally added. magnetite (Fe ^ O ^) and mixed homogeneously in the same rubber roller mill.

TABLE 2

Composition Sample no.

8__9_10 Carbon black (weight -, “O 10 13 15

Plastic Binder (% by weight) 50 47 45

Magnetite (weight-S) 40 40 40

Each of the blends was ground first in a conventional particle size powder of mostly 1 mm in diameter and then in a conventional ball mill for a fine powder in which the carbon black particles were homogeneously mixed. Then each powder was classified into a conventional grading apparatus. The classified powder was spheroidized and the specific resistance of the spheroidized powder was measured by the same method as in Example 1.

The specific resistance of Sample # 8 was 3 * 10 ^ A'cm in an electric DC field of 100 V / cm and 1.3 A * cm in an electric DC field of 1000 V / cm, and the specific resistance of Sample No. 10 was 2'10 ° A'cm in an electric 2 dc field of 100 V / cm and 9-10z A * cm in an electric dc field of 1000 V / cm. The density of the spheroidized powders measured by the same method as in Example 1 was 1.50 (No. 8), 1.53 (No. 9) and 1.57 (No. 10).

To the magnetic toners (spheroidized powders) about 0.1 to 1.0% by weight of finely powdered silicic anhydride was added to improve the flow performance. With the tones, electrostatically latent images were elicited and fixed in accordance with conventional electrophotographic processes. The duplicate images with each of the tones were good, especially in terms of image density and the smoothness of the images.

EXAMPLE 3

A plastic binder was obtained by a homogeneous mixture of 10 5 parts by weight of a polyethylene having a density of 0.92, 3 parts of β-pinene resin (terpentermoplastic resin of β-pinene) having a density of 0.97 and 2 parts of epoxy resin having a molecular weight of 900 and an epoxy equivalent of 430 - 500 in a conventional mixer at a temperature between 130 and 150 ° C. On it, 5 different mixtures of toner are listed in Table 3 prepared by adding different amounts of carbon black as color material and electrically conductive particles as plastic binder and finally homogeneous mixture in a rubber rolling mill at a temperature between 140 and 170 ° C, 20 magnetite (Fe 2 O 2) was still added, which was homogeneously mixed in the same rubber rolling mill at a temperature between 140 and 190 ° C.

In the table below, sample # 15 is listed as a comparative example.

TABLE III

Composition Sample no.

11 12 13 14 15 Carbon black (wt%) 15 20 25 30 35

Plastic Binder (% by weight) 55 50 45 40 35

Magnetite (wt%) 30 30 30 30 30 145067 15

With each mixture, the toner was obtained without grinding, grading and spheroidizing in the same manner as in Example 2.

Then the specific resistance of the magnetic developer pulsars was measured. The specific resistance of No. 11 uar 2 · 103Λ • cm in an electric voltage field of 100 V / cm and 9 · 10ζ fVcm in an electric field voltage of 1000 V / cm; pulsed from sample No. 14 uar 10'10 ft'cm in an electric ion voltage field of 100 V / cm and 7-10 ^ A * cm in a 10 electric ion voltage field of 1000 V / cm. The density of samples Nos. 11, 12, 13 and 14 is 1.45, 1.52, 1.58 and 1.65 respectively.

With caps toner, small amounts of finely pulsed silicic anhydride were added, electrostatic latent images were obtained and fixed using the same method as in Example 2. The duplicate images with the tones (samples Nos. 11, 12, 13 and 14) were excellent. in image density, contrast ratio, and image evenness. On the other hand, duplicate toner images (sample # 15) were poor with regard to fastening properties.

EXAMPLE 4

A mixture of 38 parts by weight of a polystyrene resin and 7 parts of carbon black was mixed homogeneously in a conventional rubber rolling mill at a temperature between 130 and 150 ° C; The mixture was then fed 55 parts of magnetite (Fe 2 O 2), where

on it once more was homogeneously mixed in the same rubber-rolling mill. From the mixture, a toner was prepared by grinding, grading and spherodizing by the same method as in Example 2. Then the resistance as well as the specific weight of the toner were determined; the resistance was 2'IQ

n * cm ued an electric ion voltage field of 100 V / cm and 2 * 10 ^ P / cm ued an electric ion voltage field of 1000 V / cm; The specific weight was 2.01 g / ml.

The copies obtained by the use of these toners by conventional electrophotographic methods had excellent image density and resolution.

EXAMPLE 5

A mixture of 50 parts by weight of a biphenyl A epoxy resin and 15 parts by weight of carbon black was homogeneously mixed in a conventional rubber rolling mill at a temperature between 140 and 160 ° C; to the mixture was added 35 parts of ΜηΟ-ΖηΟ-Γβ2θ ^-ferrite-10 powder (Mn-Zn-ferrite), which was then homogenized than now once in the same rubber rolling mill.

From this mixture, a toner according to the invention was prepared by grinding, grading and spherodizing according to the same procedure as in Example 2. Then the resistance and the specific weight of the toner were measured; the resistance was 8 * 10 f / * cm at an electric DC field of 100 V / cm and 2 * 10 ^. $ * cm at an electric DC field of 1000 V / cm; the specific weight was 1.76 g / ml.

With this toner, electrostatically latent images emerged -20. called and fixed by a conventional electrophotographic process. The resolution and fixing properties of the copies made were good.

EXAMPLE 6

A mixture of 35 parts by weight of an acrylonitrile-styrene copolymer and 5 parts by weight of finely powdered nickel as electrically conductive particles was homogeneously mixed in a conventional rubber rolling mill at a temperature between 120 and 140 ° C. 60 parts of magnetite was then gradually added to the mixture, which was then again homogeneously mixed in the same rubber roller mill.

Claims (4)

From this mixture, a toner according to the invention was prepared by grinding, grading and spherodizing by the same procedure as in Example 2. The resistance and specific weight were then determined; The resistance was 3'10 ^ / Vcm at an electric DC field of 100 V / cm and 50 Λ · cm at an electric DC field of 1000 V / cm; the density was 2.23 g / ml. With this toner, electrostatically latent images were elicited and fixed by a conventional electrophotographic process. The resolution and fixation properties of the copies made were good and satisfied the requirement for these properties. P_a t_e n t k r a_v i Electrophotographic developer toner, which contains in a binder magnetic and electrically conductive particles, characterized in that it contains 2 to 30 weight S electrically conductive particles, that both the magnetic and the electrically conductive particles are uniformly distributed. in the toner, the particles of which are substantially spherical, and that the electrical resistance of the toner at 2 is an electric DC voltage field of 100 V / cm and 10 10 ** ohms * cm, and an electric DC voltage field of 1000 1 9 V / cm 10 - 10 ohm * cm. Toner according to claim 1, characterized in that it contains 4-20% by weight of electrically conductive particles. Toner according to claim 1, characterized in that the toner portions have a size in the range 1 - 100 µm. Toner according to claim 3, characterized in that the toner portions have a size in the range 5 - 40 µm.