DE1934613A1 - Reversible developer for electrostatic latent images - Google Patents

Description

Kabushiki Kaisha-Ricoh Jjyy

Tokyo ,, Japan

Reversible developer for electrostatic latent images

The invention relates to an electrostatic developer Latent images * in which the positive or negative The polarity of the developer particles dispersed in it are reversible is. .

A liquid developer for electrostatic latent images usually contains pigment particles in the form of organic pigments of various kinds or carbon black ₃ dispersed in a so-called carrier liquid of high electrical resistance and low dielectric constant. With only a few exceptions, almost all of these pigment particles, when independently dispersed in the carrier liquid, usually have a positive electrical charge. “Generally speaking, however, the amount of electricity absorbed is not always sufficient, and on the other hand, in some cases the dispersed particles must have a negative electrical charge. λ sen. It has therefore proven more practical to regulate the polarity of dispersed particles by allowing a suitable synthetic resin, the so-called polarity regulator, to adhere to them "

The invention now represents a successful further development of a liquid developer for electrostatic latent images, through which the technique of adjusting the polarity of dispersed Particles improved by means of synthetic resins and a polarity reversal by simply changing the development temperature can be reached.

009824/1727

The principle of the invention is that you get a special Copolymer of the type defined below can adhere to the pigment particles and the particles treated in this way in one Carrier liquid with a relative resistance greater than ICr Ohm. cm and a dielectric constant below 3. This particular copolymer has the property that it In addition to its ability to regulate the polarity of the pigment particles, it also has the ability to adhere to them is variable as a function of the carrier liquid temperature in such a way that it decreases with increasing temperature and ^ that temperatures between 20 ° and 40 ° C above room temperature the amount of the adhered copolymer becomes so small that its polarity regulating ability is impaired. However, the copolymer detached from the pigment particles under these circumstances can be made to adhere again by that the carrier liquid is allowed to return to room temperature, which also increases the ability to regulate polarity of the copolymer is restored. As already said, it is possible to use the liquid developer according to the invention change the polarity of the developer parts by simply changing the Reverse the carrier fluid temperature.

The copolymers which can be used according to the invention can be divided into two groups I and II according to the monomers forming them which each consist of two monomers and which are occupied by them Pigment particles at room temperature in the case of group I have a positive polarity and in the case of group II a negative polarity To give.

The two types of copolymers are made up of the following monomers :

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Group I off

_tt 193A6T3

Group II off

OH ₂ -O

-f

COOR

(a)

OH ₂ = OX

(b)

CH ₂ = c

f ¹ + CH ₂ = C

σο OR

(a)

(c)

exists and there

β -CH, or -H

= - ^G n ^H 2n ₊ l

CH

OH

, -CN, -COOH,

-CH ₂ OH, - <( ^ - COOCH ₂ CH CH ₂ or -COOR ₃

with

R_ = - (CH _Om ), C ₉ H.OH or -CH ₉ CH CH ₉ 3 m 2m ⁷ 2 2 4 ^ ₀ /

and

or -CON (C _m H _{2m + 1} ) ₂

-CONH ₂ , -COOR ₄

with

^R 4 - -

mean.

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So you can a developer according to the invention, the Is able to reversibly change the polarity of its pigment particles simply by heating or cooling the carrier liquid, manufacture by either participating in pigment that alone in a carrier liquid of the type described dispersed in a negative electrical charge, a group I copolymer or pigment particles that stand alone dispersed positive charge, a Group II copolymer can adhere. In addition, by first having pigment particles, one can obtain one, i.e. Group I or Group II, copolymer and then the other, i.e. Group II or Group I polymer can adsorb, get a reversible developer that is not influenced by the intrinsic polarity of its pigment particles will.

This group I or Il copolymers may be prepared from their monomers by conventional polymerization, namely, by 5 to 15 hours heating at 60 ° to 110 ⁰ C in the presence of a polymerization initiator such as azobisisobutylonitrile, benzoyl peroxide or the like as well as a liquid such as toluene, are obtained and contain Acrylic acid ester or ester methacrylate as components. The molar ratio of the monomers is chosen in the case of group I copolymers so that b) to a) is equal to 0.2 to 0.6, and in the case of group II copolymers such that c) to a) is equal to 0.01 to 0.3 is. The ratio of acrylic acid ester or ester methacrylate to the copolymer and the length of the residual alkyl chain contained therein both have a comparatively large influence on the adhesive strength of the two types of copolymers, as the temperature resistance of their adhesion decreases on the one hand with increasing ester content compared to the a) monomer and on the other hand with increasing alkyl residual chain length “So if you want to allow the copolymers to adhere in multiple layers, taking into account the above-mentioned copolymer properties, the copolymer that is most adhesive depending on the temperature change is allowed to be attached to the pigment particles first.

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1334613

From the foregoing it can be seen that the inventive, temperature reversible developers serve a dual purpose, namely both positive-to-positive can also serve the negative-to-positive development.

Suitable pigment particles for the developers according to the invention In addition to soot, there are various organic pigments and dyes, including real yellow G, benzidine yellow TR, gyanine blue BM, real red 2B, pigment scarlet TR, brilliant carmine PB, and 6b as commercial products of Sanyo Color Works Ltd., Aizen, Spilon Yellow, Aizen Spilon Red, Aizen Spilon Blue and Aizen Spilon Victoria Blue as commercial products of Hodogaya Chemical " Co., Ltd, as well as Spritschwarz AB, SB, SSB and SA, VaIi real yellow, VaIi real red, VaIi real brown, VaIi real blue, VaIi real black, Oil blue BO, oil green BG and oil black BS, BW and BY as commercial products by Orient Chemical Industries Ltd, These substances have already been used in the manufacture of the usual liquid developers used for electrostatic latent images.

Suitable as a carrier liquid for the developers according to the invention For example, organic liquids from the hydrocarbon family, including such as commercial ice products Naphtha No. 6, Solvesso and Isopar H from Esso Standard Oil Co., Ltd. . ^

The invention is explained in more detail below with reference to a few preferred exemplary embodiments, without being restricted to them to be.

example 1

5 g pigment particles with negative intrinsic charge in the form of the commercial product Cyanine blue GM from Sanyo Dye K.K. are together with 5 g of lauryl methacrylate-hydroxyethyl methacrylate copolymer

- β 009824/1727

¹ T 9 3 «13

(Molar ratio 6: 4) and 40 g naphtha No. 6 for 20 hours in processed in a ball mill. 1 part by weight of this mixture is then dispersed in 100 parts by weight of # β naphtha. Of the The resulting liquid developer contains dispersed pigment particles which are positive electrical at normal room temperature are charged, but are recharged to a negative potential if the developer is kept at 55 ° C for 5 hours, and their regain positive charge when the developer is cooled back to room temperature.

Example 2

The concentrated toner in this case consists of a 20 Mixture of 5 g pigment particles ground in a ball mill for hours with a positive intrinsic charge in the form of the commercial product Cyanine Blue SM from Sanyo Dye K.K., 5g styrene-butyl methacrylate polymer (Molar ratio 1: 1) and 50 g of a 1: 1 mixture of Naphtha No. 6 and Solvesso. 1 part by weight of this is in 100 parts by weight of naphtha No. 6 dispersed. The resulting liquid developer contains pigment particles which at room temperature temperature are negatively charged electrically, can be positively recharged by heating the developer to 60 ° C for 2 hours and get their negative töHHg charge back again when the developer is cooled. .

Example 3

A mixture of 5 g of pigment in the form of the commercial grade XC-550 der Asahi Carbon K.K., 5 g styrene-butyl methacrylate copolymer (molar ratio 2: 3) and 40 g of toluene for 15 hours in one Ball mill ground. Then 1 part by weight of this mixture is mixed with 1 part by weight of lauryl methacrylate-dimethylaminoethyl methacrylate (Molar ratio 9: 1) and 50 g of a 1: 1 mixture of naphtha No. 6 and Solvesso mixed and again for 10 hours long triturated in a ball mill. From this total mixture 1 part by weight in a 2: 8 mixture of Isopar H and

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Naphtha No. β dispersed. The resulting liquid developer contains pigment particles that are negatively electrically charged at normal room temperature, but by J hour Warming the developer to 60 ° C can be positively transferred.

The decision regarding the polarity of the developers described in the preceding examples was made on the basis of this location of images taken with the help of the Ricoh Fax M4 photo device from Ricoh K.K. electrostatic on a photosensitive paper door Latent images in the form of the commercial product Ricoh BS-I also the Ricoh K.K. were produced.

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Claims (4)

Claims 1) Reversible liquid developer for electrostatic latent images in the form of a dispersion of pigment particles in a Carrier liquid with a relative resistance greater than 10 ohms. cm and a dielectric constant below 3, characterized in that that the pigment particles with an adherent ^ en Copolymer, which is composed of two monomers, which in the case where those in the carrier liquid dispersed pigment particles are chargeable with negative electricity, to the following group I or in the case where the pigment particles dispersed in the same carrier liquid have positive electricity are chargeable, belong to Group II below, where - 9 -009824/1727 Group I off and Group II off ^H l 'ft I ¹ fx fi CH ₂ ^s O + CH ₂ «O CH ₂ -C + CH _{2 -C} ^C00R 2 x COoR ₂ Ir ^(a ^ (b) (a) (o) exists and there R _n β -CH, or -H JL f J ^R 2 * - ° n ^H 2n ₊ l -CH ₂ OH, - (/ V COOCH ₂ CH -CH ₂ QÄ.er -COOR ₅ H- = - (CH ₅ J ₉ C ₉ H _A OH or -CH ₉ CH CH ₉ with 3 m 2m ⁷ 2 2 4 N _n / and - (/ Λ ² , - ^> ^ ⁵ ^^, -CONH ₂ , -COOR ₄ or- -C0N (C _m H _{2m + 1} ) ₂ 4 * with mean, 009824/172 7 - ίο - 2) Developer according to claim 1, characterized in that the molar ratio of monomer b) to monomer a) im Group I copolymer 0.2 to 0.6 and that of monomer c) too Monomer a) in the group II copolymer is 0.01 to 0.3. 3) Reversible liquid developer for electrostatic latent images in the form of a dispersion of pigment particles in a carrier liquid with a relative resistance above 10 ^ ohms. cm and a dielectric constant below 3 *, characterized in that the pigment particles with two copolymer layers are covered, one of which is made of a copolymer with two monomers belonging to group I and the other consists of a copolymer with two monomers belonging to group II. 4) developer according to claim 3 # characterized in that the molar ratio of monomer b) to monomer a) in group I copolymer 0.2 to 0.6 and that of monomer c) to monomer a) in the group !! - copolymer is 0.01 to 0.3. 009824/1727