Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G9/00—Developers
  • G03G9/08—Developers with toner particles
  • G03G9/12—Developers with toner particles in liquid developer mixtures
  • G03G9/13—Developers with toner particles in liquid developer mixtures characterised by polymer components
  • G03G9/131—Developers with toner particles in liquid developer mixtures characterised by polymer components obtained by reactions only involving carbon-to-carbon unsaturated bonds

Definitions

• the invention relates to an electrophotographic liquid developer for the reverse development of negatively charged charge images consisting of an insulating carrier liquid of high electrical resistance and low dielectric constant, in which pigment, resinous binder, charge control agent from a copolymer of N-vinyl-2-pyrrolidone and methacrylic acid ester and conventional additives are dispersed or are solved, as well as a process for its preparation.
• a negative working electrostatic toner composition for producing positive images and reversed images is also known (US Pat. No. 3,542,681), which in one electrically insulating carrier liquid contains pigment and an alkylated polymer of heterocyclic N-vinyl monomer, such as N-vinyl-2-pyrrolidone.
• liquid developers of this type especially in reverse development, do not provide sufficient image quality. Accordingly, from the document D E-OS 1 930 -783 based on this citation, a liquid developer with control means emerges, which is only shown for a positive development process. Comparative experiments show that the liquid developer is not suitable for the reverse development of negatively charged charge images with the production of copies of satisfactory quality.
• a liquid developer for the reverse development of negatively charged charge images is also known (DE-AS 2 125 668), consisting of a mixture of pigment, polycyclopentadiene resin and a phospholipid as a control agent, dispersed in an aliphatic carrier liquid. Control with lecithin, for example, does not always prove to be reproducible.
• an electrophotographic liquid developer of the type mentioned at the outset which is characterized in that it additionally contains a poly-N-vinyl-2-pyrrolidone alkylated with an a-olefin.
• the liquid developer preferably contains 0.005 to 1.0 percent by weight of alkylated poly-N-vinyl-2-pyrrolidone. It is hereby achieved that a liquid developer for reverse development can be made available which is built on the basis of a liquid developer for the development of positive charge images and which is dissolved by diluting the toner concentrate with an alkylated poly-N-vinyl-2-pyrrolidone containing carrier liquid can be used for use as a reverse developer.
• the poly-N-vinyl-2-pyrrolidone alkylated with an a-olefin is known per se (US Pat. No. 3,417,054). It is produced by reaction at elevated temperature of the poly-N-vinyl-2-pyrrolidone with the corresponding ⁇ -olefins in the presence of organic peroxide catalysts.
• Those poly-N-vinyl-2-pyrrolidones which are substituted with ⁇ -olefins and have 12 to 20 carbon atoms have proven particularly suitable according to the invention. These include e.g. B.
• a mixture of the different olefins can also be present.
• Such alkylated poly-N-vinyl-2-pyrrolidones, which contain about 20 percent by weight of vinyl-2-pyrrolidone, can be advantageous according to the invention because the high degree of alkylation gives particularly good solubility properties.
• alkylated poly-N-vinyl-2-pyrrolidone used according to the invention is limited, on the one hand, by the fading of images produced if too much of the additive should be present, and, on the other hand, by a decrease in the effectiveness of the liquid developer.
• Suitable insulating carrier liquids are, for example, petroleum-like aliphatic hydrocarbons such as n-hexane, ligroin, n-heptane, n-pentane, isododecane and Isooctane as well as their halogen derivatives such as perchlorethylene, all of which have a high insulating capacity (the specific resistance is greater than 10 9 ⁇ ⁇ cm) and a low dielectric constant (less than 3).
• the commercially available aliphatic hydrocarbons such as "Isopar ( R ) E, G, L, H or K" from Esso-Chemie, Hamburg, are particularly suitable. These can be used alone or in combination.
• Carbon blacks such as gas black, furnace black or flame black (CI no. Of all types of carbon black 77 266) are generally used to produce black developers.
• Organic pigments such as phthalocyanine blue (CI No. 74 160), phthalocyanine green (CI No. 74 260 or 42 040), sky blue (CI No. 42 780), rhodamine (CI No. 45 170), malachite Green (CI No. 42 000), methyl violet (CI No. 42 535), peacock blue (CI No. 42 090), naphthol green B (CI No.
• a pigment or pigment mixture is preferably used in the preparation of the toner.
• Pigments are generally superior to dyes in terms of bleaching ability.
• it can usually be used to produce high-contrast image copies compared to toners containing dye.
• the resinous binders that can be used are known per se and are selected from the group of natural or synthetic resins. They serve to fix the pigment particles on the charge image or, after transfer, to fix them on the appropriate medium, such as paper, plastic or metal foil.
• Suitable resins are, for example, resins which are practically insoluble in the aliphatic hydrocarbons used as carrier liquid, for example maleic acid resins modified with natural resins, Dammar, Kopal, shellac, rosin, hardened rosin, ester gum, glycerol ester-modified maleic resins, styrene / butadiene mixed polymers, vinyl toluene / butadiene Copolymers and the like.
• Common additives are understood to mean those which influence the most diverse toner properties and which may be present in some cases. They influence the charge level, the sedimentation behavior, the service life, the redispersibility of agglomerates, the transferability and the smudge resistance of the Liquid developer or the toner particles on the K opieologi.
• Possible additives are conventional substances such as waxes, especially polyethylene, paraffin and chloroparaffin waxes. According to the invention, such a wax or polyethylene with a softening point in the range from 60 to 130 ° C. can be used.
• the waxes or polyethylenes mentioned have properties which - in terms of specific weight - resemble those of the carrier liquid used.
• Polymers which are soluble in aliphatics such as polyvinyl alkyl ethers, polyisobutylene, polyvinyl stearate and polyacrylates or polymethacrylates with a higher alcohol radical, or plasticizers such as, for example, dialkyl phthalates, are also suitable.
• the invention also relates to a method for producing the electrophotographic liquid developer for the reverse development of negatively charged charge images, in which a mixture of electrically insulating carrier liquid of high electrical resistance and low dielectric constant, pigment, resinous binder, charge control agent from a copolymer of N-vinyl-2-pyrrolidone and methacrylic acid esters and conventional additives to a homogeneous paste, diluted with carrier liquid, which may contain charge control substance, to a toner concentrate and mixed with further carrier liquid to form the finished liquid developer, which is characterized in that the toner concentrate is mixed with a carrier liquid in which a-olefin alkylated poly-N-vinyl-2-pyrrolidone dissolved is.
• a liquid developer is preferably prepared which contains 0.005 to 1.0 percent by weight of alkylated poly-N-vinyl-2-pyrrolidone. This ensures that a liquid developer suitable for reverse development is produced in a simple manner from a finished toner concentrate which can be used for normal development, with not even a new dispersing step or additional operation being necessary because the toner concentrate must be diluted anyway.
• the homogenization to a paste can be carried out with a three-roll mill, a ball or colloid mill or an agitator ball mill, which is generally preferred, at temperatures in the range from room temperature to about the boiling range of the carrier liquid. The duration of exposure depends on the grinding result.
• the finished particles have sizes in the range between about 0.05 and 10 pm.
• the toner concentrates are adjusted to a solids content of about 5 to 10 percent by weight by diluting the paste with high-speed stirrers.
• the further mixing with carrier liquid to the finished, usable liquid developer can take place, for example, before the liquid developer is used in the developing device.
• mixing is done at concentrations ranging between 0.05 and about 5 percent by weight.
• the invention is illustrated by the following comparative examples and examples.
• the finished liquid developer was prepared by mixing 7 ml of the toner concentrate with 1 1 of said aliphatic hydrocarbon. With this liquid developer, reverse development was carried out using a microfilm enlarger on ZnO paper. The pictures were very solid and unsuitable for practical use.
• 60 g of carbon black, described as in Comparative Example 1 were made up with 600 g of an aliphatic hydrocarbon (boiling range 160-180 ° C.) and 160 g of one 20% by weight solution of a grafted terpolymer made of 76% dodecyl methacrylate, 20% methyl methacrylate and 4% N-vinyl-2-pyrrolidone in the hydrocarbon (boiling range 160 - 180 ° C), 30 g of a polyethylene wax (dropping point 103 - 107 ° C) and 16 g of a chlorinated paraffin wax (softening point 105 ° C.) mixed and ground in a stirred ball mill under the same conditions as in Comparative Example 1.
• the dispersion was diluted with 900 g of the aliphatic hydrocarbon.
• the toner concentrate thus obtained was diluted 1:10 with the aliphatic hydrocarbon.
• this liquid developer was used for reverse development on Zno paper, very basic copies were obtained that were unusable for practical use. Even with a 1:20 dilution, no better result was achieved.
• a toner concentrate prepared according to Comparative Example 2 was treated with a solution containing 0.075% by weight alkylated poly-N-vinyl-2-pyrrolidone (Antaron V 220) with an average chain length of 20 carbon atoms and 20% by weight vinyl-2-pyrrolidone in an aliphatic hydrocarbon (boiling range 160 - 180 ° C) diluted 1:20.
• An aliphatic hydrocarbon oiling range 160 - 180 ° C
• the liquid developer proved to be well storable for several weeks.
• a liquid developer produced according to Example 1 gave images of good quality on reverse development using a commercially available microfilm re-enlarger on a polyvinyl carbazole photoconductor.
• a toner concentrate prepared according to Comparative Example 2 was diluted with a 0.3% by weight alkylated poly-N-vinyl-2-pyrrolidone solution (average alkyl chain length 16 carbon atoms) in an aliphatic hydrocarbon (boiling range 175-190 ° C.) in a ratio of 1:30.
• the liquid developer produced gave good quality copies when reversed on ZnO paper.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Liquid Developers In Electrophotography (AREA)

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• 1982
  • 1982-08-25 DE DE19823231505 patent/DE3231505A1/de not_active Withdrawn
• 1983
  • 1983-08-04 JP JP58142004A patent/JPS5949553A/ja active Pending
  • 1983-08-19 US US06/524,590 patent/US4497886A/en not_active Expired - Fee Related
  • 1983-08-19 DE DE8383108200T patent/DE3363403D1/de not_active Expired
  • 1983-08-19 EP EP83108200A patent/EP0102039B1/fr not_active Expired
  • 1983-08-19 AT AT83108200T patent/ATE19698T1/de active

Patent Citations (4)

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