DD287392A7 - ELECTROPHOTOGRAPHIC DEVELOPER - Google Patents

Abstract

The invention relates to an improved electrophotographic developer consisting of a carrier material and a toner. Addition of α-alumina to the toner as the abrasive and spacer results in the developer having a higher yield with the highest quality of copies.

Description

Field of application of the invention

The invention relates to an electrophotographic developer which consists of a toner material and a carrier component and can be used as a dry developer in electrophotographic processes.

Characteristic of the known technical solutions In the known electrophotographic process, the template as a latent electrostatic charge pattern on a Photoconductor (US 2618551, US 2618552, US 2803542, US 2970906, US 3121006, US 3121007, US 3151092). This

The latent image is then developed by using a developer. The developed image is then on the

Image carrier (paper) transferred or fixed in the case of identity of photoconductor and image carrier. Depending on the functional principle

different developer compositions (J. WEIGL, Angew. Chem. 89 [1977] 386).

In the case of cascade development (US 2618552, US 3301126, US 3166432), the developer substance actually consists of

coloring toner and the carrier material. The latter uses macroparticles of different materials,

Glass beads, salt grains, plastic coated glass or steel balls. In the development, the opinion about the latent image

cascaded, wherein in particular by the carrier material exerted tribochemical forces charge formation on the

Toner particles and ultimately cause their electrostatic adhesion in the form of Tonbildbildos. Another method for the development of latent electrostatic images is the Mngnetbürsten method (US Pat. No. 2,874,063, US Pat. US 3003462). In this method, the developing agent acts by raising the effective dielectric constant as its

own development electrode. Realized by a permanent magnet, which is a mixture of fine

Toner particles with coarse magnetic carrier particles, eg. As iron, in the form of a soft brush-like structure carries

(Two-component magnetic brush development). Contact with the iron and the toner causes the iron to be positively charged and the toner negatively charged. In addition, the toner is given the desired frictional charge because the

Carrier beads are generally coated with a thin polymer layer. With proper choice of triboelectric Characteristics and sufficient movement of the mixture is a magnetic brush capable of, by gently brushing over the

latent image of Phctoleiters there to create a powder image.

The currently most commonly used methods of electrophotographic imaging and image development are Cascade and the two-component magnetic brush method (R.M. SCHAFFERT, Electrophotography, Focal Press, London

1975). In both cases, when copying only the toner is consumed while the respective carrier component remains in the device and must be renewed only after a long time. The economy of the electrophotographic process is therefore determined essentially by the price of the toner and its consumption per copying step (yield).

Of the various methods of image fixation, thermofixing is the most commonly used. Basic constituents of each toner are known in the art, a low-melting thermoplastic (US 2401766, US 2434461, US Pat. US 2618552, US 2638416, US 265S670, US 2788288, US 2917460, DE 1772669, DE 2401766) and a pigment. Old. Thermoplastics are preferably polystyrene, acrylic resins, polyethylenes, polyvinyl chlorides, polymethacrylic acid derivatives, Epoxy resins, polyamides, Polyethylenthermoplaste and copolymers of those mentioned used. Come as a pigment Dyes and carbon black used (US 3577345). For an optimum electrophotographic process, additives have to be added to these basic ingredients. It is

when using very hard thermoplastics to lubricants that degrade excessive mechanical stress on the friction of the toner, in particular with the photoconductor (DE 2450922, DE 2 249 385).

The second type of additives are silicon compounds, which have a much higher hardness than the toner (US. "986521, DE 1089265, DE 1522708, GB 1172839). These additives cause as abrasive the continuous self-cleaning of Photoconductor. This prevents that after the copying step still existing on dom photoconductor toner residues

next copy step

- cause ghosting,

- cause a background haze,

- disturb the charging process,

- hinder the photoinduced discharge process.

The third addition relates to spacers (DE 2 249 385), the function of which is to strengthen one during heat-setting To prevent contact between the toner image and the fixing roller, and thus to prevent the formation of undesirable glossy images

avoid.

So far, it was common to add all additives individually. Also hitherto substances were unknown, which can perform two or more functions of the above additives. Object of the invention

The object of the invention is to provide an improved developer for electrophotographic processes, which is characterized by a higher yield in the copying process and provides copies of the highest quality (not glossy).

Explanation of the essence of the invention The invention has for its object to provide an improved electrophotographic developer, in addition to the

previous properties such as image quality and blackness is characterized by having a higher yield and delivering copies of the highest quality (not glossy).

The object is achieved in that an electrophotographic developer based on a Carrier material and a toner with the ingredients thermoplastic, pigment and a spacer, which at the same time a Abrasive is used as an additive. The toner contains, in addition to the usual constituents, as additive a-alumina,

Preferably, corundum having a particle size between 0.1 μνη to 100pm and is added in parts by weight of 0.05% to 2%.

From abrasion material of grinding balls of Kcrund existing additives, which are preferably in particle sizes, are particularly suitable

from ΙΟμηι to 63pm in proportions by weight of 0.05% to 0.2% are contained in the thermoplastic-pigment mixture.

The thermoplastic used as described previously known. The proportion of thermoplastic in the toner is 70%

to 96%, preferably 85% to 90%. Depending on the type of toner, it is advantageous to use polymers of different hardness. So it is better to use a soft thermoplastic for two-component magnetic brush toner. Particularly suitable

Polymers of styrene and methacrylic acid and their esters, preferably styrene-acrylate and styrene Möthacrylsäureester copolymers with softening points between 45 ° C and 8O ⁰ C. The color pigments used are the previously known ones, preferably carbon black with corresponding electrostatic properties. The pigment content is 4% to 30%, preferably 10% to 15%. When adding the a-alumina additive, it is important that it be an active, non-aged product. This is

guaranteed if the additive is provided by grinding prior to toner production. A further, particularly advantageous variant consists in that balls of α-aluminum oxide, preferably corundum, are used during the grinding of the toner. The resulting abrasion of the ball material results in the necessary addition of a-alumina. On this

Ways is economically in a sufficient amount of active a-alumina as an abrasive and as Spacer generated and automatically attached to the toner. The toner produced from thermoplastic, carbon black and the additive according to the invention have a particle size of 0.1 μπι to The toner is mixed in a known manner with the process-specific, known support materials. The developer according to the invention is characterized by a surprising, unpredictable yield. Compared

to commercial, commercial toners significantly lower consumption is registered (copy number per unit weight

Toner), which allows 68 to make about 30% more copies with the same amount of toner (see table). The addition of α-alumina according to the invention possesses, in addition to the properties of an abrasive (yield)

a distance, in contrast to DE 3444676. In this PS is expressly noted that neither

Alumina, silica and titanium oxide are suitable as spacers. The improved properties of the developer according to the invention are due to the addition of α-alumina to the toner

due. It is of crucial importance that the additive according to the invention is the α-modification of the aluminum oxide. The use of, for example, γ-alumina gives developers which are the advantageous ones

Properties of the developer according to the invention do not have and even favor the formation of haze and shiny Deliver pictures. Accordingly, when using silica, d 5S is known as an abrasive (DE 1089265, DE 1522708),

depending on the toner type 20% to 30% fewer copies received. This shows that the effect of the abrasive is much more intense in the case of α-alumina. In addition, a-alumina acts as a spacer and thus causes a higher

Picture quality. In summary, the following advantageous properties of the additive according to the invention may be mentioned:

significantly higher toner yield,

- receipt of non-glossy copies,

economically advantageous production of the toner material,

- no impairment of image quality parameters such as resolution and blackening.

Comparison of toner consumption based on the copies made

a) cascade development

b) Two-component magnetic brush development

c) Xerox Corp.

toner Quantity ing device type support material Numbers of Copts Example 1 6R90001 ^cl 100g 100g RX7000 · ¹ RX7000 · ¹ 5 R 90001 5 R 90 001 1430 1250 Example 2 6 R 90 005 " 50 g 50 g RX 7000 "· RX 7000" 5 R 90 001 5 R 90 001 780 600 Example 3 6R90Q52 ^c) 6 R 90 053 " 100g 100g 100g RX3107 ^b) RX3107 " ¹ RX3107"' 5 R 90 055 5 R 90055 5 R 90 055 2800 2200 2200

Ausführungsbelsplela example 1

4Line Acrylic Dispersion Type X171 {solids content 43% by weight) of VEB Chemische Werke BUNA-Schkopau, 312g carbon black type

Canal black RGA E (VEB Gummiwerke Berlin, Oranienburg) and 50ml wetting agent (Otroc, VEB Fettchemie Karl-Marx-Stadt)

were packed in a lockable milling drum (hard porcelain KER 110 TGL 7838/02, nominal capacity 101, type no. 58.27.10 / 3,

Manufacturer VEB ceramic works Hermsdorf, 6530 Hermsdorf / Thuringia) filled. Subsequently, in the vessel

Ground corundum balls for grinding drums of the VEB porcelain factory Auma, 6572 Auma (Thuringia), given the following size:

22 balls with a diameter of 35mm and a weight of 91.2g per ball and 22 balls with a diameter of 26.5mm and a weight of 37.5g per ball. The vessel is closed, placed on a rotary roller and with a

Speed of 65 revolutions per midute45 hours rotated. The suspension is filled after the kneading process in ceramic dishes, placed in a warming cabinet WS 983 and at about 35 ⁰ C.

drained in 120 hours. The dried raw toner is dry-crushed for an additional 25 hours in the mill already in use.

For the final sieving a vibrating screen type ANDF 4/5 with a laboratory test sieve 40μπι (VEB metal weaving mill 6710 Neustadt / Orla). On the screen surface were 10 balls of corundum with a diameter of 12mm and a Given weight of 2g per ball. After 15 minutes the sieving process is finished. The yield is 95%. For the electrophotographic application, the toner was prepared according to the device specification with the carrier material

mixed and the developer obtained filled in the device. The copies obtained show no gloss, the

Toner yield is shown in the table. Example 2

430 ml of an acrylic suspension type 170 'solids content 40% by weight), 31.2 g of carbon black and 5 ml of wetting agent, in each case the manufacturer mentioned in Example 1, were filled into a 1 l bottle of glass, with 15 spheres of 16 g each and 5 spheres each 8g and rotated on a laboratory grinder 48 hours. The further work-up was carried out according to Example 1. Die

Yield was 90%. For the electrophotographic testing, the toner was commercialized according to the device specification Carrier material mixed and filled the developer into the device. The copies obtained show no gloss

and the toner yield is shown in the table.

Example 3

41 acrylic suspension type X172 (solids content 40 wt .-%), 360g carbon black and 50ml wetting agents were mixed as in Example 1, filled into the mill, mixed with corundum balls, ground, dried, ground again and screened. The used ball material was produced by Schauenburg, Maschinen und Anlagen GmbH, 4330 Mühlheim (Ruhr), Germany. The yield was 90%.

The testing of the toner in the form of the developer was carried out analogously to Examples 1 and 2.

Claims (5)

1. An electrophotographic developer based on a support material and a toner with the components thermoplastic, pigment and a spacer as an additive, characterized in that the toner contains ci-alumina in addition to the usual ingredients as an additive. 2. An electrophotographic developer according to claim 1, characterized in that the toner contains active, not aged a-alumina. 3. An electrophotographic developer according to claims 1 and 2, characterized in that the toner contains an abrasive material of grinding balls made of corundum. 4. An electrophotographic developer according to claims 1 to 3, characterized in that the toner contains 0.05% to 2%, preferably 0.05% to 0.2% by weight of α-alumina. 5. An electrophotographic developer according to claims 1 to 4, characterized in that the toner is prepared by grinding of thermoplastic and pigment in a grinder using grinding balls of corundum without separate addition of a-alumina.