DE1089631B - Non-flammable liquid developer for electrostatic images - Google Patents

Description

GERMAN

It is already known to subject electrostatic images to liquid development in a carrier, whose electrical resistance is large enough to prevent the electrostatic image from decaying during the To prevent development.

Liquids with the required properties are generally flammable. To the related Eliminating dangers, the invention is intended to improve this type of developer, it is thus guaranteed that the risk of fire is completely eliminated or at least largely reduced will.

Since such liquid developers are generally handled in various ways by workers it is also desirable to select them from a group that is non-toxic. Therefore, the invention seeks to provide a liquid developer for electrostatic images, which is both non-flammable and non-toxic in normal use.

Such a developer can be formed according to the invention in that as a liquid carrier with sufficiently high electrical resistance substances from the group of chlorofluoromethanes or chlorofluoroethanes be used.

The substances that have been shown to be particularly suitable here include those that are also chlorinated and fluorinated hydrocarbon solvents or coolants or propellants.

It is known that these substances are non-flammable, non-explosive and relatively non-toxic sufficiently stable in use provided the correct composition is chosen are contributing to their commercial use as suspending agents for dyes or developers to enable electrostatic image development.

As already said, the chlorinated and at the same time fluorinated derivatives of methanes or ethanes are suitable Fabrics.

The substances should have a dielectric constant of less than 3, preferably less than 2.5 and sufficiently stable under certain temperature conditions and other ^ working conditions available at the place of their use.

One of the advantages of using both chlorinated and fluorinated hydrocarbon solvents is that a high degree of volatility can be achieved. So that can develop be accelerated, whereby a very quick removal from the carrier liquid is possible and consequently, rapid fixing and drying of the developed image is brought about.

Two substances have proven to be particularly beneficial, namely trichloromanofluoromethane (CCl ₃ F), non-flammable liquid developer
for electrostatic images

Applicant:

The Commonwealth of Australia,

represented by

The Secretary of the Department of Supply, Melbourne (Australia)

Representative: Dipl.-Ing. E. Rathmann, patent attorney,
Frankfurt / M., Neue Mainzer Str. 40-42

Claimed priority:
Australia October 1, 1957

Kenneth Archibald Metcalfe, Graymore,

and Robert John Wright, Hectorville (Australia),

have been named as inventors

such as is commercially available under the trademark "Freon MF", and trichlorotrifluoroethane (C Cl ₂ F · C Cl F ₂ ), as it is traded under the trademark "Freon TF".

These substances are good carriers for pigments and have the necessary dissolving effect for dissolving of resins or other substances used with the liquid developer to make Control or fixative to act.

The invention is explained in more detail below with the aid of a few examples.

example 1

150 g of phthalocyanine blue, which forms the pigment substance, are chlorinated in 3 l of one and at the same time fluorinated hydrocarbon, such as "Freon MF" or "Freon TF", dispersed and the resulting Mixture used as a developer. The electrical resistance of the carrier liquid is high enough to cause migration of the carrier particles under the action of their own surface charge (which they under such a high level of insulation) and under the influence of the selective electrostatic field to enable a charged image-modified photoconductor surface. The pigment particles are unfixed and thus in a state in which they can be transferred to another surface, or they are by applying a spray fixative or the like. Fixed.

0D9 608/296

Example 2

About 25 g of an oil, for example a boiled linseed oil, are added to the above mixture. At the When the development is carried out, the oil with the pigment to which it is attached remains on the image. When drying, the oil forms the fixative for the pigment.

Example 3

15 g of a phenol-modified pentaerythritol ester of a resin, e.g. B. the fabric under the designation "Pentarol 20" commercially located (acid value of 7 to 15, specific gravity 1.09 at 20 ° C, melting range 110 to 120 ⁰ C) are mixed with 25 g of xylene, and after the complete dissolution 15 g of linseed oil-modified Alcyd resin with a medium oil content (about 52 ^fl / o, acid number 6 to 10, specific weight at 20 ° C. 0.955 to 0.965), such as the substance known under the trade name "Rhodene L6 / 100", was added.

Then 150 g of phthaloxyanine blue are added and the above mixture in a ball mill or a Three-roll mill grind until mixing is complete and the size of the pigment particles is up is reduced to the required fineness (for example 0.5 μ on average). Usually an eight hour session is enough Grind in a ball mill, after which the pigment particles with a thin continuous or discontinuous film of the coating mix are coated. One component is proportional insoluble in the vehicle so that it acts as a controlling agent, and the other is sufficient soluble to act as a fixative when the carrier liquid is evaporated.

This coating mixture thus becomes the surface charge of the coated particles affect and form the binder after the pigment in a liquid development process has been used. The paste produced in this way is then used as a basis for a dispersion in the at the same time chlorinated and fluorinated hydrocarbon solvents for forming the development carrier liquid used. About 0.5 g of the developer paste is dispersed in 100 ml of the liquid.

To develop the electrostatic image, the liquid developer thus formed is simply mixed with the Image brought into contact, and the coated pigment particles that move freely in the liquid can, are reflected on those surface particles of the image on which a sufficient Potential is present until the charge of the image is saturated by the deposited particles. the Particles are held in place by the electrical force until the carrier liquid evaporates is whereupon the pigment particles are held by direct adherence to the surface of the particles will.

During development, the presence of the resin affects the particle charge, and it has has shown that rapid precipitation of the particles is possible if they are so coated.

As stated, the coating mixture according to the above example is only partially in the carrier liquid soluble and consequently acts as a surface charge modifier to control the migration of the Particles in an electric field during development because the partially dissolved surface of the Coating is in a state in which it is an effective binder after evaporation of the Solvent forms. When using trichlorotrifluoroethane, it is desirable to use the paste in the To grind carrier liquid, otherwise the solubility of the paste in the liquid is too low and Difficulty in achieving effective adhesion of the coated pigment particles after evaporation of the liquid carrier can occur.

The developer paste described is more soluble in trichloromonofluoromethane, and easy to mix without grinding has been found to be sufficient.

ίο If desired, a mixture made from two of the mentioned carriers can be used, for example from 60% "Freon MF" and 40% "Freon TF". "Freon MF" or "Freon TF" can be combined with a carrier of lower volatility or a combustible carrier, provided the combined carrier has a volume resistivity of more than ΙΟ ¹⁰ ohm / cm and a dielectric constant of no more than 3. A suitable mixture consists of 80 parts of "Freon MF" and 20 parts of xylene.

The resulting mixture is not yet combustible or flammable.

The proportions can of course vary according to the other working conditions will.

Example 4

The developer according to Example 3 can be modified by replacing the "Rhodene L 6/100" with the the same proportion of "Pentarol 20" is replaced, with the result that the developer has good fixing properties has, but is not able to modify the surface charge of the pigment particles to the same extent is because "Pentarol 20" is relatively soluble in both chlorinated and fluorinated hydrocarbons and is a sticky substance so that it tends to leave the pigment particles when in the developer and precipitation is present as a fixing substance.

When there is so much developer on the pigment particles that it will be there during development remains, the developer can act as both a charge modifier and a fixative Matter to be addressed.

. _g Example 5

In the developer according to Example 3, the “Pentarol 20” is made up of an equal amount of “Rhodene L 6/100 «, ie due to a less soluble in both chlorinated and fluorinated hydrocarbons Substance replaced. The developer then has a largely controlling effect on the surface charge of the pigment particles due to the coating substance that is on the pigment particles with possibly so little Solubility remains on the surface so that there is no noticeable binding of the pigment particles after evaporation the carrier liquid takes place.

Claims (10)

Patent claims: 1. Non-flammable liquid developer for electrostatic images, characterized in that it consists of a carrier liquid consists of chlorinated and at the same time fluorinated hydrocarbon, in the pigment particles acting selectively on the image charge are dispersed. 2. Developer according to claim 1, characterized in that the dielectric constant of the Carrier liquid is less than 2.5. 3. Developer according to claim 2, characterized in that the carrier liquid consists of trichloromonofluoromethane consists. 4. Developer according to claim 2, characterized in that the carrier liquid consists of trichlorotrifluoroethane consists. 5. Developer according to claims 1 to 4, characterized in that a smaller proportion of a non-polar liquid is added to the carrier liquid, the volume resistivity of which is not less than 10 ¹⁰ ohms / cm and whose dielectric constant is less than 3. 6. Developer according to claims 1 to 5, characterized in that the pigment particles with are coated with a control substance whose insolubility in the carrier liquid is sufficient to To ensure that the control substance remains on the particles during the development process. 7. Developer according to claims 1 to 6, characterized by a fixative for the particles on the image area which is at least partially soluble in the carrier liquid. 8. Developer according to claims 1 to 7, characterized by the addition of one at the same time as Control and fixing agent acting substance that is only partially soluble in the carrier liquid. 9. Developer according to claims 6 to 8, characterized in that the controlling and / or fixing substance is an alkyd resin, which coats the pigment particles and at least somewhat in the carrier liquid is soluble. 10. Developer according to claim 8, characterized in that that the pigment particles are previously coated with resins which come from two groups, one of which is in the carrier liquid relatively soluble and the other relatively insoluble, with the less the soluble one acts as the controlling substance and the more soluble one acts as the fixing substance. Considered publications:
German publication No. 1 047 616. © 009 608/296 9.60