JPH03274065A - Liquid developer for electrophotography - Google Patents

Abstract

PURPOSE:To provide the liquid developer which has good dispersibility and dispersion stability, is free from the fluctuation in characteristics by replenishing and has good electrification efficiency and image transferability by using chain polyester contg. a dicarboxylic acid component having a polar group and a diol component having a solvent affinity group to a carrier liquid as a polymn. unit as a resin for forming toner particles. CONSTITUTION:The copolymer polyester contg. the polyester block of the dicarboxylic acid component having the polar group and the diol component having no solvent affinity group and the polyester block of the dicarboxylic acid component having no polar group and the diol component having the solvent affinity group is useful as the chain polyester to be used as the resin for forming the toner particles suspension dispersed into a nonaq. carrier liquid having an electrical insulating characteristic. The examples of the dicarboxylic acid include succinic acid, sabaccinic acid, 2-methyladipic acid, diglycolic acid, thioglycolic acid, etc. Bisphenol, alkylene glycol and mono cyclic and polycyclic diols are included in the useful diol. The representative bisphenol which can be used has the following structure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid developer used in electrophotography, electrostatic recording, electrostatic printing, and the like.

[Conventional technology]

Image forming methods and developing methods using electrophotography are widely known from various documents and patents.

Generally, in these methods, an electrostatic latent image formed on a photoconductive insulating layer coated on a conductive support is developed and visualized using a developer.

The developed image is fixed directly onto the photoconductor, or
Alternatively, it is transferred and fixed onto a medium such as paper.

Cascade is a method for developing electrostatic latent images.

Typical methods are known as dry development methods, such as the magnetic brush method, and liquid development methods, which use a liquid developer in which toner particles are suspended and dispersed in a non-aqueous solvent with high insulation and low dielectric constant. It is being Among these, the liquid development method can be said to be the most suitable method for faithfully reproducing detailed images, since it is possible to make toner particles very small.

Butadiene rubber is a resin used to form toner particles used in liquid developers.

Rubbers such as styrene-butadiene rubber, cyclized rubber, natural rubber, styrene resins, vinyltoluene resins, acrylic resins, methacrylic resins, polyvinyl acetates, ethylene copolymers, polyester resins, polycarbonates, etc. Examples include synthetic resins, rosin resins, alkyd resins containing modified alkyds such as linseed oil modified alkyds, and natural resins such as polyterpenes. Other known resins include phenolic resins containing modified phenols, natural resin-modified maleic acid resins, pentaerythritol phthalate, chroman-indene resins, ester gum resins, and vegetable oil polyamides.

Among them, JP-A-51-89428 and JP-A-59-50164.
The polyester resin shown in No. 3 has a sharp melting point range and is very advantageous in terms of heat fixability.

However, JP-A-51-89428, JP-A-59-5
The polyester resin disclosed in No. 01643 has an insufficient affinity for the carrier liquid, so it settles soon after being dispersed, and has the disadvantage that it must be redispersed whenever it is used.

(Objective of the Invention) The object of the present invention is to provide a liquid developer that has good dispersibility and dispersion stability, and therefore does not change in characteristics due to replenishment (high replenishment constancy), has good charging efficiency, and has good image transfer properties. It is in.

(Structure of the Invention) The object of the present invention is to provide a liquid developer for electrophotography in which toner particles are suspended and dispersed in an electrically insulating non-aqueous carrier liquid, wherein the resin forming the toner particles is at least one of:
a dicarboxylic acid component having a polar group, and at least one type of dicarboxylic acid component having a polar group;
This is achieved by using a liquid developer which is a chain polyester containing as a polymerized unit a diol component having a solvent affinity group for the carrier liquid.

Further, in an aspect of the present invention, the solvent affinity group has 6
It is preferable that the alkyl group R having at least 5 carbon atoms is included, and the solvent affinity group containing the alkyl group R is
-CH, O1i! , ~CH20COR, -CH,C0O
R.

Preferably, it is a group selected from -CH and CONHR.

Furthermore, it is preferable that the polar group is a group selected from carboxylic acid, sulfonic acid, phosphonic acid, phosphinic acid and salts thereof, and residues of sulfonamide, sulfonimide, and disulfonimide.

Furthermore, the chain polyester comprises a polyester block of a dicarboxylic acid component having the polar group and a diol component having no solvent affinity group, and a diol having the dicarboxylic acid component having no polar group and the solvent affinity group. Copolymer polyesters containing components and polyester blocks are useful.

The dicarboxylic acids useful in the polyesters of this invention are selected from any of a variety of aliphatic, cycloaliphatic, and aromatic dicarboxylic acids. Useful dicarboxylic acids as defined herein include the free acid forms of such materials, as well as the bifunctional precursors to which such acids are derived. Other useful difunctional precursors corresponding to the free acid forms of dicarboxylic acids are lower-hydric alcohol esters or phenyl esters of dicarboxylic acids and dicarboxylic acid halides (eg chloride, bromide).

Examples of typical dicarboxylic acids that can be used in the present invention include succinic acid, sebacic acid, 2-methyladipic acid, diglycolic acid, thiodiglycolic acid, fumaric acid, cyclohexane-1,2-dicarboxylic acid, and cyclohexane. -1,
3-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid, cycloheptane-1,3-dicarboxylic acid, 2.5
- norbornanedicarboxylic acid (the acids mentioned above are effective in either the cis or trans form), phthalic acid, isophthalic acid, terephthalic acid, t-butyl isophthalic acid, phenylene diacetic acid, phenylene dipropionic acid, 2.6- Naphthalene dicarboxylic acid, l,4-naphthalene dicarboxylic acid, l,5-7thalene dicarboxylic acid, 1,7-naphthalene dicarboxylic acid, 4.4'-diphenic acid, 4.4'-
Sulfonyl dibenzoic acid, 4,47-oxydibenzoic acid,
Examples include binaphthyldicarboxylic acid, 4,4'-stilbenedicarboxylic acid, and 9°IO-tributycenedicarboxylic acid.

These dicarboxylic acids mentioned above include a halogen atom, a nitro group, a cyano group, an alkoxy group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms (however, substituted alkyl groups such as fluoromethyl, Difluoromethyl, trifluoromethyl, dichlorofluoromethyl, 2-(2゜3.4.5-tetrahuman r:1-
2.2-dimethyl-4-oxo7ran-3-yl]ethyl, etc.), cycloalkyl groups having 4 to 6 carbon atoms (e.g. cyclohexyl), aromatic groups having 6 to 20 carbon atoms Group groups (e.g., tlf, phenyl,
The carrier liquid may be substituted with a group having no affinity for the carrier liquid, such as 3,4-dichlorophenyl or 2,4-dichlorophenyl. At least one of the dicarboxylic acids particularly effective for the polyester of the present invention is an aromatic dicarboxylic acid (substituted or unsubstituted), more preferably selected from terephthalic acid, isophthalic acid, and derivatives thereof.

The diol according to the present invention can be selected from various known diols.

Useful diols include bisphenols, alkylene glycols, and monocyclic and polycyclic diols. Typical bisphenols that can be used have the following structure: where R2 and R3 are each a hydrogen atom, an aryl group (e.g. phenyl, including substituted phenyl), 1 to 5
An alkyl group having 1 to 5 carbon atoms, an alkoxy group having from 1 to 5 carbon atoms, and the like.

However, R2 and R3 may be the same or different. R
' and Rs represent an aliphatic, monocyclic or bicyclic group, each of which is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms (however, substituted alkyl groups such as fluoromethyl, difluoromethyl, trifluoromethyl Methyl, dichlorofluoromethyl, 2-(2,3,4,5-tetrahydro-2゜2-dimethyl-4-oxofuran-3-yl]ethyl, etc.), having 4 to 6 carbon atoms cycloalkyl group (e.g. cyclohexyl), 6 to 20
Aromatic groups having 3 carbon atoms (e.g. phenyl, 3
．． 4-dichlorophenyl, 2,4-dichlorophenyl)
may be replaced with . R4 and R6 can be taken together to form a monocyclic, bicyclic, or heterocyclic group containing 4 to 7 atoms.

Typical useful suphenols include the following: Bisphenol A: 2
, 2-his(4-hydroxyphenyl)propane [bisphenol A), l-phenyl-1,1-bis(4-hydroxyphenyl)ethane, 1-phenyl-1,1-his(4-hydroxyphenyl)ethane, 2.2-bis(
4-hydroxyphenyl)-4-(2,3,4,5-tetrahydro-2,2-diethyl-5-oxofuran-3-
yl)] butane, bis(4-hydroxyphenyl)methane, phenylbis(4-hydroxyphenyl)methane,
l,■-bis(4hydroxyphenyl)cyclohexane, 1,1.1,3,3゜3-hexafluoro-2,2-
Bis(4-hydroxyphenyl)propane, diphenyl-bis(4-hydroxyphenyl)methane, etc.

Other useful bisphenols include: 1,4-naphthalenediol, 2,5-su7thalenediol, bis(4-hydroxy-2-methyl-3-propylphenyl)methane, 111-bis(2-ethyl-4
-hydroxy-5-5-butylphenyl)ethane, 2.
2-bis(4-hydroxyphenyl)propane, 2.2
-bis(4-hydroxy-2-methyl-5-ynoctylphenyl)isobutane, bis-(2-ethyl-4-hydroxyphenyl)-4,4-di-p-tolylmethane.

Additional useful bisphenols include those disclosed in US Patent No. 3,030.335 and Canadian Patent No. 576.491.

Representative monocyclic diols include the following. Hydroquinone, hydroquinone substituted with an alkyl group or alkoxy group having 1 to 5 carbon atoms, resorcinol, resorcinol substituted with a lower alkyl group, an alkoxy group, etc., 4-cyclohexanediol, 1,4-cyclohexanediol Metatool, 1.
4-cyclohexanejetanol, l,4-bis(2-
hydroxyethoxy)cyclohexane, 1,4-benzenedimetatool, 1°4-benzenedethanol, etc.

Examples of polycyclic diols include norpolnylene glycol, decahydro-2,6-naphthalene dimetatool, and the compounds listed under the heading "Bisphenols" in Table 1 of U.S. Pat. No. 3,317.466. etc.

Typical alkylene glycols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, ■,4-butanediol, 2,3-butanediol, l,5-bentane. Diol, 1.6-hexanediol, 1.7-hebutanediol, ■, 8-octanediol, 1.9-nonanediol, 1.10-decanediol, 1.12-dodecanediol, neopentyl glycol, 2 .2.4-Trimethyl-1,6-hexanediol and 4-oxa-2,6-heptanediol can be mentioned.

Of course, various diols, such as cycloaliphatic diols such as other cycloalkylene diols, can also be used in the preparation of the polyester materials used in the present invention.

The above-mentioned diols include an alkoxy group having 5 to 5 carbon atoms, an alkyl group having 5 to 5 carbon atoms (however, substituted alkyl groups such as fluoromethyl, difluoromethyl, trifluoromethyl, dichloro Fluoromethyl, 2-(2,3,4.5-tetrahydro-2.2-dimethyl-4-oxofuran-3-yl)
cycloalkyl groups having 4 to 6 carbon atoms (e.g. cyclohexyl), aromatic groups having 6 to 20 carbon atoms (e.g. phenyl, 31-dichlorophenyl, 2,4-dichloro) may be substituted with a substituent such as phenyl).

In the present invention, the dicarboxylic acid having a polar group includes carboxylic acid, sulfonic acid, phosphonic acid, phosphinic acid, sulfonic acid, phosphonic acid, phosphinic acid and salts thereof, sulfonamide, sulfonimide, It is a dicarboxylic acid having a group selected from disulfonimide residues.

That is, the various dicarboxylic acids mentioned above may have a group containing the above-mentioned groups introduced therein as a substituent.

The dicarboxylic acid having phosphinic acid, sulfonimide, and disulfonimide has the following general formula % formula % In the above formula, R and R' are either alkylene, cycloalkylene, or arylene group, and R and R' are the same. But it can be different. M is a hydrogen atom or an alkali metal atom.

The basic structure of the diol having an affinity group for the carrier liquid can be selected from the various diols described above. Among these, it is preferable to select from cycloalkylene diols and alkylene diols that do not contain aromatics. Particularly preferably, the dicarboxylic acid component having a saturated alkylene diol polar group is 2 of the total dicarboxylic acids.
It is preferably 20 mol%, more preferably 5 to 20 mol%.
It is 15 mol%.

The diol component having a carrier liquid affinity group preferably accounts for at least 40 mol% of the total diol component, and more preferably 60 to 95 mol%.

The polyester of the present invention can be obtained by copolycondensing the above dicarboxylic acid or its precursor with a diol or its precursor by a known method. The copolycondensation polyester used in the present invention is produced by (1) mixing and polycondensing multiple types of pre-synthesized low-molecular-weight polyesters; (2) adding the remaining components to one type of pre-synthesized low-molecular-weight polyester; Mix and polycondensate. and (3) mixing all the components and polycondensing them. The polyester of the present invention synthesized by any method is useful, but (
Methods 1) and (2) yield copolymer polyesters with high blocking properties and are particularly useful.

The molecular weight of the chain polyester material used in the present invention is
It can be varied within a fairly wide range depending on the glass transition temperature (Tg) to be set. For example, when a developed toner image is self-fixed on a smooth photoconductor at ambient temperature,
Tg below ambient temperature as found in No. 501643
It can be a polyester having When a developed toner image is transferred from the surface of the photoconductor to another carrier such as paper to obtain an image, the toner image is preferably fixed by heat.

Known methods of heat fixing include a heat roller fixing method using a heating roll, an oven fixing method using an electric heater, an infrared lamp method, a xenon flash method, and a high frequency fixing method.

Since the polyester of the present invention has a relatively sharp 7 g range, it is particularly advantageous for non-contact heat fixing, and the resulting image has good gloss. A polyester particularly advantageous for non-contact heat fixing has a Tg of 30 to 100°C, more preferably 50 to 8
It has a Tg of 0°C.

The carrier liquid useful in the liquid developer of the present invention has an electrical resistance of 1
A volatile organic solvent with a dielectric constant of 0"Ω・C111 or more and a dielectric constant of 3.5 or less. Preferably, linear or branched aliphatic hydrocarbons and halogen-substituted products thereof can be used. For example, octane, isooctane , Decane, Isodecane, Decalin, Nonane, Dodecane, Indodecane, Isopar E1 Isopar G1 Isopar H1 Isopar L (
Isopar: Exxon product name), Shersol 70
, Shellsol 71 (Shellsol: Shell Oil Co. product f = ), Amsco OMS, Amsco 460 solvent (
Amsco (trade name of Spirits Co.) etc. can be used alone or in combination.

If necessary, a coloring agent may be used in the liquid developer of the present invention.

The coloring agent does not need to be specified in particular, and various conventionally known pigments or dyes can be used.

When coloring the resin itself, for example, one method of coloring is to physically disperse a pigment or dye in the resin, and there are a large number of known pigments or dyes. Examples include magnetic iron oxide powder, powdered lead iodide, carbon blank, Nigrone, Alkali Blue 7 Asto Yellow, Quinacridone Magenta, Naphthol Carmine, Permanent Red, Brilliant Carmine 6B, Rhodamine Lake, Phthalo/Anine Blue, and the like.

Another coloring method is disclosed in Japanese Patent Application Laid-open No. 57-4873.
There is a method of dyeing the resin with a preferred dye, such as described in No. 8. Alternatively, as another method, there is a method of chemically bonding a resin and a dye, as disclosed in JP-A No. 53-54029, or,
As described in Japanese Patent Publication No. 44-22955, etc., there is a method of producing a copolymer containing a dye using a monomer containing a dye in advance during production by a polymerization granulation method.

In addition to the colorant, the developer of the present invention can also contain various charge control agents, if desired, in order to uniformize the charge polarity of the toner particles dispersed in the developer. For example, Yuji Harasaki "Electronic Photography" Volume 16, No. 2, 4
Those specifically described on pages 4 to 51 are used.

Suitable positive charge control agents include dioctyl sodium sulfosuccinate (A++erican Cyanimid
Co.

), zirconium octoate, and metal soaps such as copper oleate. Suitable negative charge control agents include lentin, barium petrol corp, ne
vYork, NY), alkyl scunnimide (Ch
everonChe+m1cal Company o
f California), California Chemical Company (CaliforniaCh) under the trademark 0LOA.
Oronite (0ro, chemical Company)
nite) compositions sold by Division J2, etc.

Also, U.S. Patent No. 3,788, issued January 29, 1974,
Various polymeric charge control agents can also be used, such as terpolymers (e.g., styrene-lauryl methacrylate-sulfoethyl methacrylate terpolymers) as described in US Pat. Such polymeric charge control agents are substantially soluble in, or at least readily dispersible in, the carrier liquid.

Particularly when a metal salt is used as a polar group, it is effective to add a small amount of a metal ion-receptive substance to ensure the dissociation of metal ions.

For example, various chelating agents that form coordination compounds with metal ions, polyethylene glycol, crown ether,
Examples include cryptate, thioether, and the like.

These charge control agents may be added to the liquid developer in any form. It may be added before or after the toner particles are dispersed, or it may be added in the form of a mixture with the polyester resin that forms the toner particles.

The amounts of each main component of the liquid developer of the present invention are explained below.

The toner particles containing the polyester resin and colorant of the present invention as main components have a ratio of 0.05 to 20% relative to the carrier liquid.
0% is preferred. If it is less than 0.05wt%, the image density will be insufficient, and if it exceeds 2Qvt%, fogging will tend to occur in non-image areas.

The amount of colorant will vary widely depending on the colorant used, but will range from about 0.1 to 200 vt% based on the amount of polyester resin in the shell.

Further, the charge control agent as described above may be used in a range of 0.01 to 10% relative to the carrier liquid. Ovt% is preferred. Furthermore, various additives may be added as necessary, and the total amount of these additives is
The upper limit is regulated by the electrical resistance of the developer. That is, the electrical resistance of the liquid developer with toner particles removed is 1060·c! If it is lower than l, it is a good quality series! Since image adjustment becomes difficult to obtain, it is necessary to control the amount of each additive added within this limit. Usually 1 to 200 mg of charge control agent can be added per gram of toner solids.

〔Example〕

Next, a concrete explanation will be given using examples.

(1) Polyester manufacturing method Table 1 shows the structural formulas and mixing ratios of each component of the polyester used in the following examples.

Polyester 1, 2, 4.5 and 6 Dimethyl ester of dicarboxylic acid and diol having the basic structure as raw materials are mixed in the molar ratio shown in Table 1, and manganese acetate and antimony oxide are used as catalysts under a nitrogen stream. 1
The reaction was carried out at 80 to 200°C until no methanol was generated, and then heated under reduced pressure to 250° (!, lm
The desired polyester was obtained by reacting at mHg.

Polyester 3 Meta-2-sodium phospho-dimethyliso7thaleate, dimethyl isophthalate, and ethylene glycol were mixed and reacted in the same manner as Polyester 1 to obtain a low molecular weight polyester block A (average molecular weight 2000).
. Isophthalic acid chloride, glycerin, and stearic acid were mixed and reacted at 200°C to obtain a low molecular weight polyester block B (average molecular weight: 2500).

Polyester 3 was obtained by mixing A and B so that the diol components had a desired molar ratio, adding manganese acetate (catalytic amount), and reacting at 200°C.

Polyester 7 Sodium m-sulfoisophthalate, terephthalic acid, and glycerol-σ-monostearate are mixed in a desired molar ratio, and preparation of a polyester (II) liquid developer by direct polymerization Examples 1 to 7 The above mixture is supermilled. (Newly made by Bengami Seisakusho) and put it at 60℃.
After heating to room temperature and mixing for 3 hours, cool to room temperature, add additional Isopar L to dilute to 2% solids, and add liquid developer 1.
~7 was prepared.

Comparative Example 1 Using the polymer 1 described in JP-A-59-501643 (the composition is shown in Table 2), a liquid developer was similarly evaluated using the following evaluation method. The results are listed in Table 3.

Evaluation method 1. Dispersion stability Each of the prepared liquid developers was placed in a sealing layer and left at room temperature.

A case where no precipitation was observed after 4 months was indicated as ○, and a case where sedimentation occurred in less than 4 months was indicated as × (visual evaluation).

2. The specific conductivity of the entire chargeable liquid developer was obtained by centrifuging the liquid developer. The specific conductivity of the supernatant liquid was measured at 5 V and 5 Hz (
BULK and LIQ, respectively). Difference between the two BUL
The value of K-LIQ can be regarded as the specific conductivity of the toner particles, and it can be said that the larger this value is, the better the charging property is.

3. A photoconductive member was prepared by applying photoconductive Fl (positive chargeability) onto a polyethylene terephthalate film (thickness 100 μm) on which transferable palladium had been vapor-deposited.

The surface of this film was charged to +400V and exposed through a positive pattern original (transmission), and the resulting electrostatic latent image was developed with each developer.

Excess carrier liquid was squeezed out, high-quality paper was layered, and roller transfer was performed.

From the weight of the transferred toner vt and the weight vp of the toner remaining on the photoconductor, the transfer efficiency vt / (vt + vp
).

4. Average particle size Measured using Coulter Particle Analyzer N4 manufactured by Fulter.

The polyester resin of the present invention provides a liquid developer that can be stored for a long period of time without degrading performance such as developability and chargeability, and has good transfer efficiency to paper.

The polyester resin of the present invention also shows results that enable the formation of finer particles compared to conventional ones.

Claims (5)

[Claims] (1) In an electrophotographic liquid developer in which at least toner particles are suspended and dispersed in an electrically insulating non-aqueous carrier liquid, the resin forming the toner particles is a dicarboxylic acid component having at least one polar group. and at least one diol component having at least one type of affinity group for the carrier liquid as polymerized units. (2) The liquid developer according to claim 1, wherein the solvent affinity group contains an alkyl group having 6 or more carbon atoms. (3) The solvent affinity group is -CH_2OR, -CH_
2OCOR, -CH_2COOR, -CH_2CONH
The liquid developer according to claim 1 or 2, characterized in that it is a group selected from R. However, R is an alkyl group having 6 or more carbon atoms. (4) The polar group is a group selected from carboxylic acid, sulfonic acid, phosphonic acid, phosphinic acid and salts thereof, and residues of sulfonamide, sulfonimide, and disulfonimide. 3. The liquid developer according to any one of 3 to 3. (5) The chain polyester comprises a polyester block of the dicarboxylic acid component having the polar group and the diol component having no solvent affinity group, and the dicarboxylic acid component having no polar group and the solvent affinity group. 5. The liquid developer according to claim 1, wherein the liquid developer is a copolymer polyester containing a diol component and a polyester block.