GB2159972A

GB2159972A - Toners for the development of latent electrostatic images

Info

Publication number: GB2159972A
Application number: GB08514401A
Authority: GB
Inventors: Satoru Inoue; Yasuo Asahina; Hidemi Ochiai
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 1984-06-07
Filing date: 1985-07-07
Publication date: 1985-12-11
Also published as: GB8514401D0; FR2565706A1; GB2159972B; FR2565706B1; DE3520290C2; DE3520290A1

Abstract

A toner for developing latent electrostatic images comprises a binder resin together with a compound classified as C.I. Solvent Blue 70 in an amount of 0.1 wt.% to 20 wt.% based on the weight of the binder resin.

Description

SPECIFICATION Toners for the development of latent electrostatic images The present invention relates to toners for the development of latent electrostatic images.

Conventionally, toners for developing latent electrostatic images comprise finely-divided particles with a particle size ranging from about 1 Fm to about 30 wm, the particles comprising a binder agent such as polystyrene and a colourant (e.g. a pigment or dye, such as carbon black). Such toners are usually employed in combination with a carrier material such as glass beads, iron powder or a fur or brush.

However, some conventional toners have the following shortcomings.

(1) The toners are not charged to the desired polarity when they are mixed with carriers.

(2) Even if the toners are charged to the desired polarity with the desired quantity of electric charge, the triboelectric characteristics thereof are susceptible to changes in ambient humidity.

(3) During the course of continuous and repeated use, the carriers are caused to deteriorate. As a result, the toners are charged to a polarity opposite to the desired polarity.

It is an object of the present invention to provide an improved toner for developing latent electrostatic images.

According to the invention there is provided a toner for developing latent electrostatic images which comprises a binder together with a compound classified as C.l. Solvent Blue 70, which compound serves as a charge control agent as well as a colourant. In order to prepare particularly coloured toners, compounds classified as C.l. Pigment Blue 15 can also be added to the toner.

Specific examples of compounds classified as C.l. Solvent Blue 70 (hereinafter simply referred to as C.l.

Solvent Blue 70) suitable for use in the present invention are Oil Blue No. 615 and Valifast Blue No. 2606 (commercially available from Oriental Chemical Industrial Ltd.).

C.l.Solvent Blue 70 serves as a charge control agent by means of which the toner of the present invention is uniformly charged to a negative polarity. This negative polarity is very stable to the changes in the ambient temperature. Further, C.l. Solvent Blue 70 serves as a colourant for the toner.

It is preferable that the C.l. Solvent Blue 70 be present in the toner in an amount of from 0.1 wt. % to 20 wt. %, more preferably from 0.5 wt % to 10 wt. %, based on the weight of the binder resin in the toner.

As binder resins for use in the present invention, there may be used, for example, the following conventional binder resins: styrene resins (i.e. homopolymers and copolymers or styrene and substituted styrenes) such as polystyrene, polychlorostyrene, poly-a-methylstyrene, styrene/chlorostyrene copolyers, styrene/propylene copolymers, styrene/butadiene copolymers, styrene/vinyl chloride copolymers, styrene/ vinyl acetate copolymers, styrenelmaleic acid copolymers, styrene/acrylic ester copolymers (e.g. styrene methyl acrylate copolymers, styrene/ethyl acrylate copolymers, styrene/butyl acrylate copolymers, styrene/octyl acrylate copolymers and styrene/phenyl acrylate copolymers), styrene/methacrylate ester copolymers (e.g. styrene/methyl methacrylate copolymers, styrene/ethyl methacrylate copolymers, styrene/ butyl methacrylate copolyers, and styrene/phenyl methacrylate copolymers), styrene/methyl-a-chloroacry- late copolymers and styrene/acrylonitrile/acrylic acid ester copolymers; vinyl chloride resins; styrene/vinyl- acetate copolymers; rosin modified maleic acid resins; phenolic resins; epoxy resins; polyester resins; low-molecular-weight polyethylene; low-molecular-weight polypropylene; ionomer resins; polyurethane resins; silicone resins; ketone resins; ethylene/ethylacrylate copolymers; xylene resins; and polyvinylbutyral.

These binder resins can be used alone or in combination.

Of the above binder resins, styrene resins, polyester resins, silicone resins and epoxy resins are preferred for use in the invention.

Of the polyester resins, polyester resins having softening points of from 50"C to 1500C and derived from bisphenol type diols and polycarboxylic acids (having two or more carboxylic groups) are suitable for use in combination with C.l. Solvent Blue 70, since the stability of the charging polarity of the polyester resins is significantly improved by the use of C.l. Solvent Blue 70.

Specific examples of bisphenol type diols for use in the preparation of such polyester resins are polyoxypropylene (2,2)-2,2-bis(4-hydroxyphenyl)propane, polyoxyethylene(2)-2,2-bis(4-hydroxyphenyl)propane, polyoxystyrene(6)-2,2-bis(4-hydroxyphenyl)propane, polyhydroxybutylene(2)-2,2-bis(4hydroxyphenyl)propane, polyoxypropylene(3)-bis(4-hydroxyphenyl)thioesther, polyoxypropylene(2)-2,2bis(4-cyclohexanol)propane, polyoxyethylene(2)-2,6-dichloro-4-hydroxyphenyl, polyoxyethylene(2,5)-p,pbisphenol, polyoxybutylene(4)-bis(4-hydroxyphenyl)ketone, oxylene-2,2-bis(4-hydroxyphenyl)propane and oxypropylene-2,2-bis(4-hydroxyphenyl)propane.

Specific examples of suitable polycarboxlic acids (or anhydrides thereof) for preparing the polyester resins are maleic acid, fumaric acid, glutaric acid, phthalic acid, maleic anhydride, fumaric anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, trimellitic acid, and 1,2,4-benzenetricarboxylic acid.

Specific examples of the polyester resins are as follows.

Polyester Resin No. 1 A polyester having a softening point of 100"C prepared from polyoxypropylene(2,2)-2,2-bis(4-hydroxy- phenyl)propane and fumaric acid.

Polyester Resin No. 2 A polyester having a softening point of 100"C prepared from polyoxyethylene(2)-2,2-bis(4-hydroxyphenyl)propane and terephthalic acid.

Polyester Resin No 3 A polyester having a softening point of 100"C prepared from polyoxypropylene(3)-bis(4-hydroxyphenyl)thioether and isophthalic acid.

Polyester Resin No. 4 A polyester having a softening point of 100"C prepared from polyoxypropylene(2,2)-2,2-bis(4-hydroxyphenyl(propane, fumaric acid and trimellitic acid.

Polyester Resin No. 5 A polyester having a softening point of 100 C prepared from oxyethylene-2,2-bis(4-hydroxyphenyl)propane and fumaric acid.

When the above polyester resins are employed, it is preferred that such polyester resins form 70% or more, more preferably 80% or more, of the total binder resins contained in the toner. As sub-component resins, the following resins (which can be mixed with the polyester resins) can be employed: polystyrene resins, polyacrylic ester resins, styrene/acrylic ester copolymers, polyvinyl chloride resins, polyvinylacetate resins, epoxy resins and phenolic resins.

As colourants which may be used in combination with C.l. Solvent Blue 70 in the present invention, the following can, for example, be employed, compounds classified as C.l. Pigment Blue 15, carbon black, copper phthalocyanine pigments, Phthalocyanine Green, Marachite Green, Rhodamine, Oil Black, Benzidine Yellow, quinacridone pigments, ultramarine, prussian blue, chrome yellow and Carmine 6B.

Specific examples of compounds classified as C.l. Pigment Blue 15 are Dainichi Cyanine Blue B (made by Dainichi Seika Co. Ltd.), Phthalocyanine Blue (Nippon Pigment Co. Ltd), Sumitomo Cyanine Blue HB (made by Sumitomo Chemical Co. Ltd), Monastrai Fast Blue BC (made by E.l. Du Pont de Nemours & BR< Co.) and Phthalocyanine Blue BC (made by Tokyo Ink Co. Ltd). It is preferred that a compound classified as C.l. Pigment Blue 15 is used in an amount of from 0.1 wt.% to 20 wt.%, more preferably from 0.5 wt.% to 10 wt.%.

Of course, C.l. Solvent Blue 70 can be used alone.

In order that the invention may be well understood the following Examples are given by way of illustration only. In the examples all parts are by weight unless otherwise stated.

Example 1 A mixture of the following components was kneaded under application of heat in a roll mill: Parts Styreneln-butyl methacrylate copolymer (polymerization ratio 8:2, M.W. 80,000) 100 Valifast Blue 2606 2 Carbon Black 10 After the above kneaded mixture was cooled, it was ground to give finely-divided particles and the particles were then classified, so that particles with a particle size ranging from 5 Fm to 20 Fm were obtained, whereby a toner according to the present invention was prepared.

5 Parts of the toner and 95 parts of iron powder serving as carrier particles (commercially available from Nippon Teppun Co. Ltd. under the trade EFV 200/300) were mixed to prepare a developer.

The quantity of the electric charge of the toner per unit weight thereof, CIM (C/g), contained in the developer was measured by the conventional blow- off method to give Q/M = -15 ,eLC/g.

By use of this developer in a commercially available electrophotographic plain paper copying machine ("Ricopy FT 4060" made by Ricoh Company Ltd), 20,000 copies were continuously made. The copies were clear and free from fogging and the image quality was not degraded throughout the copy making test.

The toner and the above iron powder were mixed in the same mixing ratio as mentioned above at a temperature of 30 C and a humidity of 90% RH to prepare a test developer. The QIM of the toner contained in this test developer was -14 FC/g. This indicates that the triboelectric characteristics of the toner according to the invention were not susceptible to changes in ambient humidity.

Example 2 A toner, developer and test developer were prepared as described in Example 1 except that the toner had the following formulation: Parts Epoxy resin ("Epicoate 1004" commercially available from Shell Chemical Co.) 100 Valifast Blue 2606 3 Carbon Black The Q/M of the toner in the developer was -13 FC/g.

The developer was tested in a copying machine in the manner described in Example 1 to give the same results.

The Q/M of the toner contained in the test developer was -13 FC/g.

Example 3 A toner, developer and test developer were prepared as described in Example 1 except that the toner had the following formulation: Parts Styrene resin ("D-125" made by Hercules Inc.) 100 Oil Blue 615 5 The Q/M of the tone contained in the developer was -20 pC/g.

The Q/M of the toner contained in the test developer was -18 AC/g.

Example 4 A toner and developer were prepared as described in Example 1 except that the toner had the following formulation Parts Styrene - butylacrylate copolymer polymerization ratio 7:3, M.W. 50,000) 2 Carbon Black 10 The QIM of the toner contained in the developer was -16 wC/g.

Comparative Example 1 A toner and developer were prepared as described in Example 1 except that the toner had the following formulation (which corresponds to the formulation of Example 2 with the omission of Valifast Blue 2606): Parts Styrene n-butylmethacrylate copolymer (polymerization ratio 8:2, M.W. 80,,000) 100 Carbon Black 10 The QIM of the toner contained in the developer was -1.5 aC/g.

The developer was tested in the same copying machine as that employed in Example 1. However, fogging of the images was considerable and no clear images were obtained.

Example 5 A toner, developer and test developer were prepared as described in Example 1 except that the toner had the following formulation: Parts Polyester Resin No. 1 100 Valifast Blue no. 2606 2 Carbon Black 10 The Q/M of the toner, contained in the developer was -15 pwC/g.

The QIM of the toner contained in the test develper was -14 FC/g.

Example 6 A toner, developer and test developer were prepared as described in Example 1 except that the toner had the following formulation: Parts Polyester Resin No. 2 100 Valifast Blue No. 2606 3 Carbon Black 10 The Q/M of the toner contained in the developer was -13 aC/g.

The OIM of the toner contained in the test developer was -13 ,aC/g.

Example 7 A toner, developer and test developer were prepared as described in Example 1 except that the toner had the following formulation: Parts Polyester Resin No. 3 100 Oil Blue No. 615 5 The Q/M of the toner in the developer was -20 C/g.

The OIM of the toner contained in the test developer was -18 pC/g.

Example 8 A toner and developer were prepared as described in Example 1 except that the toner had the following formulation: Parts Polyester Resin No. 4 100 Oil Blue No. 615 2 Carbon Black 10 The QIM of the toner contained in the developer was -16 IlC/g.

Example 9 A toner and developer were prepared as described in Example 1 except that the toner had the following formulation: Part Polyester Resin No. 2 100 Styrene n-butylmethacrylate copolymer 2 Carbon black 10 The QIM of the toner contained in the developer was -14 IlC/g.

Comparative Example 2 A toner, developer and test developer were prepared as described in Example 5 except that the toner had the following formulation (which corresponds to the formulation in Example 5 with the omission of Valifast Blue 2606): Parts Polyester Resin No. 1 100 Carbon Black 10 The Q/M of the toner, contained in the developer was -20 C/g, which was sufficiently high for practical use. However, the Q/M of the test developer was -5 IlC/g. Thus, the humidity resistance of this toner was very poor.

Comparative Example 3 A toner and developer were prepared as described in Example 5 except that the toner had the following formulation (in which the Valifast Blue 2606 employed in Example 5 was replaced by a chrome-containing azo dye of the following formula which is known as a negative polarity control agent).

Parts Polyester Resin No. 1 100 Chrome-containing Azo Dye 2 Carbon Black 10

The Q/M of the toner contained in the developer was -1.5 FC/g, which was obviously insufficient for practical use.

The chrome-containing azo dye was ineffective for use with the polyester resin.

Example 10 A mixture of the following components was kneaded under application of heat in a roll mill: Parts Polyester Resin No. 1 100 Dainichi Cyanine Blue B 2.5 Oil Blue No. 615 2.0 After the above kneaded mixture was cooled, it was ground to give finely-divided particles and the particles were then classified, that particles with a particle size ranging from 5 ,am to 20 lim were obtained. To the particles, silica (commercially available from Nippon Areosil Co. Ltd. under the trade name "R 972") which was ground by a mixer added in an amount of 1 wt.%, based on the entire weight of the toner.

5 Parts of the toner and 95 parts of the same iron powder as that employed in Example 1 were mixed to prepare a developer.

Example ii A toner and developer were prepared as described in Example 10 except that the toner had the foliowing formulation.

Parts Polyester Resin No. 1 100 Dainichi Cyanine Blue B 2.5 Valifast Blue No. 2606 2.0 The developer was tested in a copying machine in the manner described in Example 1 to give the same results.

Example 12 A toner and developer were prepared as described in Example 10 except that the toner had the following formulation: Parts Polyester Resin No. 2 100 Dainichi Cyanine Blue B 2.5 Oil Blue No. 615 2.0 The developer was tested in a copying machine in the manner described in Example 1 to give the same results.

Example 13 A toner and developer were prepared as described in Example 10 except that the toner had the following formulation: Parts Polyester Resin No. 3 100 Dainichi Cyanine Blue B 2.5 Oil Blue No. 615 2.0 The developer was tested in a copying machine in the manner described in Example 1 to give the same results.

Example 14 A toner and developer were prepared as described in Example 10 except that the toner had the following formulation: Parts Polyester Resin No.3 100 Dainichi Cyanine Blue B 3.0 Oil Blue No. 615 2.5 The developer was tested in a copying machine in the manner described in Example 1 to give the same results.

Example 15 A toner and developer were prepared as described in Example 10 except that the toner had the following formulation Parts Polyester Resin No. 4 100 Dainichi Cyanine Blue B 3.0 Valifast Blue No. 2606 2.5 The developer was tested in a copying machine in the manner described in Example 1 to give the same results.

Excellent reproduction of black colour was attained by superimposing a yellow toner and a magenta toner on the toners of Examples 10-15 when making copies.

Comparative Example 4 A toner and a developer were prepared as described in Example 10 except that the toner had the following formulation (which corresponds to the formulation of Example 10 with the omission of Oil Blue 615): Parts Polyester Resin No. 3 100 Dainichi Cyanine Blue B 2.5 The developer was tested in a copying machine in the manner described in Example 1. However, fogging of the images was considerable and no clear images were obtained.

It was observed that a large amount of the toner was charged to a positive polarity in the above developer.

Reproduction of a black colour by superimposing a yellow toner and a magenta toner on the above toner was very poor.

Example 16 A toner and developer were prepared as described in Example 10 except that the toner had the following formulation.

Parts Polyester Resin No. 3 90 Styrene n-butylmethacrylate copolymer 10 Dainichi Cyanine Blue B 2.5 Oil Blue 615 2.0 The developer was tested in a copying machine in the manner described in Example 10 to give the same results.

The triboelectric characteristics of the toners according to the present invention are not susceptible to changes in humidity and the image quality of the images developer by the toners does not deteriorate with time even if the toners are continuously and repeatedly used.

Claims

1. A toner for developing latent electrostatic images comprising a binder resin and a compound classified as C.l. Solvent Blue 70 in an amount of from 0.1 wt.% to 20 wt.% based on the weight of the binder resin.

2. A toner as claimed in claim 1 further comprising a compound classified as Cl. Pigment Blue 15 in an amount of from 0.1 wt.% to 20 wt.% based on the weight of the binder resin.

3. A toner as claimed in claim 1 or claim 2 in which the binder resin has a softening point of from 50"C to 1500C and is derived from a bisphenol type diol and a polycarboxylic acid.

4. A toner as claimed in claim 3 in which the bisphenol type diol is polyoxypropylene (2,2)-2,2-bis(4hydroxyphenyl)propane, polyoxyethylene(2)-2,2-bis(4- hydroxyphenyl)propane, polyoxystyrene(6)-2,2bis(4- hydroxyphenyl)propane, polyhydroxybutylene(2)-2,2- bis(4-hydroxyphenyl)propane, polyoxypropylene(3)-bis(4- hydroxyphenyl)thioether, polyoxypropylene(2)-2,2-bis(4- cyclohexanol)propane, polyoxyethylene(2)-2,6-dichloro- 4-hydroxyphenyl, polyoxyethylene(2,5)-p,p-bisphenol, polyoxybutylene(4)-bis(4hydroxyphenyl)ketone, oxylene- 2,2-bis(4-hydroxyphenyl)propane, or oxypropylene-2,2- bis(4-hydroxyphenyl)propane.

5. A toner as claimed in claim 3 or claim 4 in which the polycarboxylic acid (or anhydride thereof) is maleic acid, fumaric acid, glutaric acid, phthalic acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, trimellitic acid or 1,2,4- benzenetricarboxylic acid.

6. A toner as claimed in claim 1 substantially as hereinbefore described with reference to the Examples.