JPH03274066A - Electrophtographic liquid developer - Google Patents

Abstract

PURPOSE:To provide the liquid developer good in dispersibility and dispersion stability, freed of fluctuation of characteristics due to replenishment, good in electric charging efficiency and image transferability by using as a resin for forming a toner and a chain polyester having repeating units derived from a dicarboxylic acid and >=2 kinds of specified diols. CONSTITUTION:The chain polyester to be used for forming the toner has the repeating units derived from the dicarboxylic acid, such as succinic acid, sebacic acid, 2-methyladipic acid, diglycolic acid, or thioglycolic acid, and the >=2 kinds of diols, one of them has a polar group, and at least one of them has a group affinitive to the carrier solvent of the liquid developer. As the useful diols, bisphenols, alkylene glycols, and monocylic and polycyclic diols are enumerated, and the typical usable bisphenol has a structure represented by formula I.

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.

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 particularly fine images because it is possible to make toner particles minute.

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, chromanindene 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.

(Groove Bottom of the Invention) The object of the present invention is to provide an electrophotographic liquid developer in which toner particles are suspended and dispersed in an electrically insulating non-aqueous carrier liquid, in which at least one type of resin forms the toner particles. A chain containing a dicarbon rIIFR component of It is distantly related to liquid developers that are polyesters.

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 10 carbon atoms is included, and the solvent affinity group containing the alkyl group R is -CH□OR, -0H20COR, -CIl□C00
Preferably, it is a group selected from R, -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.

Dicarboxylic acids useful in the synthesis of the polyesters of the present invention include:
Any one selected from various 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 from which such acids are derived.

Other useful difunctional precursors corresponding to the free acid form of dicarboxylic acids are lower-hydric alcohol esters or phenyl esters of dicarboxylic acids and dicarboxylic acid halides (eg chloride or bromide).

Examples of typical dicarboxylic acids used in the present invention include succinic acid, sebacic acid, 2-methyladipic acid, diglycolic acid, thiodiglycolic acid, fumaric acid, cyclohexane-1,2-; carboxylic acid, cyclohexane-1,
3-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid, cyclohebutane-1,3-dicarboxylic a, 2.5
-Norbornanedicarboxylic acid (the above-mentioned acids are effective in either cis or trans form), 7-thalic acid, isophthalic acid, terephthalic acid, t-butyl isophthalic acid, phenylene diacetic acid, phenylene dipropionic acid, 2.6 -naphthalene dicarboxylic acid, l, 4-su7tale dicarboxylic acid, 1,5-su 7 tale dicarboxylic acid, ■, 7-naphthalene dicarboxylic acid, 4,4'-diphenic acid, 4,4'-
Sulfonyl dibenzoic acid, 4,4'-oxydibenzoic acid,
Examples include binaphthyldicarboxylic acid, 4,4'-stilbenedicarboxylic acid and 9,10-tributycenedicarboxylic acid.

These dicarboxylic acids mentioned above may contain a nor\rogen atom, a nitro group, an ano group or an alkoxy group having 1 to 5 carbon atoms; an alkyl group having 1 to 5 carbon atoms (provided that substituted alkyl groups, e.g. fluoromethyl,
Difluoromethyl, trifluoromethyl, dichlorofluoromethyl, 2-(2゜3.4.5-tetrahydro-
2,2-dimethyl-4-oxofuran-3-yl]ethyl, etc.), cycloalkyl groups having 4 to 6 carbon atoms (e.g. cyclohexyl), aromatic groups having 6 to 20 carbon atoms ( example lf, phenyl, 3
．． 4-dichlorophenyl, 2,4-dichlorophenyl)
It may be substituted with a group having no affinity for the carrier liquid, such as.

Particularly effective dicarboxylic acids for the polyester of the present invention include at least one 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 hisphenols 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),
an alkyl group having 1 to 5 carbon atoms,
It is selected from groups consisting of alkoxy groups having 1 carbon atoms. However, R2 and R3 may be the same or different. R' and R6 represent an aliphatic, monocyclic or bicyclic group,
and an alkyl group each having a hydrogen atom, 1 to 5 carbon atoms (with the exception of substituted alkyl groups such as fluoromethyl, difluoromethyl, trifluoromethyl,
cycloalkyl having 4 to 6 carbon atoms; Groups (eg cyclohexyl): optionally substituted with aromatic groups having 6 to 20 carbon atoms (eg phenyl, 3,4-dichlorophenyl, 2,4-dichlorophenyl). R4 and R6 can be taken together to form a monocyclic, bicyclic, or heterocyclic group containing 4 to 7 atoms.

Typical useful bisphenols include the following: That is, bisstopphenol A1
2.2-bis(4-hydroxyphenyl)furopane [bisphenol A], l-phenyl-1,1-bis(4-
hydroxyphenyl)ethane: l-phenyl-1,1-
Bis(4-hydroxyphenyl)ethane, 2,2-bis(4hydroquinphenyl)-4-(2,3,4,5-tetrahydro-2,2-diethyl-5-oxo7lane-3
-yl)]butane, bis(4-hydroxyphenyl)methane, phenylbis(4-hydroxyphenyl)methane, 1. l-bis(4-hydroxyphenyl)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-naphthalenediol, bis(4-hydroxy-2-methyl-3propylphenyl)methane, 1.1-bis(2-ethyl-4hydroxy-5-s-butylphenyl) ) ethane, 2.2-bis(4-hydroquinphenyl)propane, 2.2-bis(4-hydroquine-2-methyl-5-ynoctylphenyl)isobutane, bis-(2-ethyl-4-hydroxyphenyl) )-4,4-di-111-tolylmethane, etc.

Additional useful bisphenols include those disclosed in US Pat. 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 5 to 5 carbon atoms, resorcinol, resorcinol substituted with a lower alkyl group, an alkoxy group, etc., 1,4-cyclohexanediol, 1,4-cyclohexanediol methanol,
4-cyclohexanejetanol, 1,4-bis(2-
hydroxyethoxy)cyclohexane, 1,4-benzenedimetatool, 1°4-benzenedethanol, etc.

Examples of polycyclic diols include norpornylene glycol, decahydro-2,6-naphthalene dimetatool, and the compounds listed under the heading ``Bisphenol J'' in Table 1 of U.S. Pat. No. 3,317.466. etc.

Typical alkylene glycols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-furopanediol, 1,3-propanediol, 1,4-butanediol, 2,3-butanediol, l,5- Bentanediol, 1.6-hexanediol, 7-hebutanediol, 1.8-octanediol, 1.9-nonanediol, 1.10-decanediol, 1.12-dodecanediol, neopentyl glycol, 2,2.4-) riftyl-1,6-hexanediol and 4-oxa-2,6-heptanediol.

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.

These diols mentioned above include alkoxy groups having 1 to 5 carbon atoms, alkyl groups having 1 to 5 carbon atoms (with the proviso that substituted alkyl groups such as fluoromethyl, difluoromethyl, trifluoromethyl, dichloro cycloalkyl groups having 4 to 6 carbon atoms (e.g. cyclohexyl), aromatic groups having 6 to 20 carbon atoms (e.g. phenyl, 3,4-dichlorophenyl, 21-dichlorophenyl) and the like.

In the present invention, the diol having the polar group (carboxylic acid, sulfonic acid, phosphonic acid, phosphinic acid, sulfonic acid, phosphonic acid, phosphinic acid and salts thereof, sulfonamide, sulfonimide, etc. in the other side chain or main chain), It is a diol having a group selected from disulfonimide residues.

That is, it may be one in which a group containing the above groups is introduced as a substituent into the various diols described above.

Examples of diols containing phosphinic acid, sulfonimide, and disulfonimide include those represented by the following general formula.

1-IQ -R-So2NMSO□-R' -0H)1
0-R-5o2NIJ-R' -OH In the above formula, R and R' represent an alkylene, cycloalkylene, or arylene group, and R and R' may be the same or 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 preferred are saturated alkylene diols.

The carrier liquid affinity group is preferably a group having an alkyl group R having 6 or more carbon atoms. More preferably, CH2OR, -C)1.0cOR, -C112COOR
,-CI(,C0NHR.

The diol component having a polar group accounts for 2 to 20% of the total diol components.
It is preferably 20 mol%, more preferably 5 to 20% by mole.
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 copolycondensed polyester used in the present invention is produced by (1) mixing and polycondensing multiple types of low molecular weight polyesters that have been pre-synthesized; (2) mixing and polycondensing one type of low-molecular weight polyester that has been pre-synthesized; Synthetic leather can be made by either of the following methods: (3) mixing all the components and polycondensing them; or (3) mixing all the components and polycondensing them. The polyester of the present invention is useful even if it is made into synthetic leather by any method, but (
Methods 1) and (2) yield copolycondensed 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 heat-fixed.

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 according to the present invention has a relatively sharp rg range, it is particularly advantageous for non-contact heat fixing, and the resulting image has good gloss. Polyesters that are particularly advantageous for non-contact heat fixing have a Tgl of 30 to 100°C, more preferably 50
It has a Tg of ~80°C.

The carrier liquid useful in the liquid developer of the present invention has an electrical resistance of 1
It is a volatile organic solvent with a dielectric constant of 0'Ω·C- 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), Shellzol 70, Shellzol 71 (Shellzol: Shell Oil Co., Ltd.) (trade name), Amsco OMS, Amsco 460 solvent (Amsco: trade name of Spirinz), 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.

One method of coloring is to physically disperse pigments or dyes into the resin. A large number of pigments or dyes for use are known. Examples include magnetic iron oxide powder, powdered iodide powder, carbon black, nigrosine, alkali blue, fast yellow disazo yellow, quinacridone magenta, na7tol carmine, permanent red, brilliant carmino 6B10-damine lake, and phthalocyanine blue.

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, as described in No. 8 and others. Or, as another method,
There is a method of chemically bonding a resin and a dye, as disclosed in JP-A-53-54029, or as described in JP-B No. 44-22955, etc.
When producing by a polymerization granulation method, there is a method of making a dye-containing copolymer using a monomer containing a dye in advance.

In addition to the colorant, various charge control agents can be added to the developer of the present invention, if desired.

For example, Yuji Harasaki "Electronic Photography" Volume 16, No. 2, 44~
Those specifically described on page 51 are used.

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

metal soaps such as zirconium octoate and copper oleate are known. Suitable negative charge control agents include lecithin, barium petronate, calcium petronate (WiLco Che+*1calCor
p., New York, NY), alkyl succinimide (Cbeveron Chemical Com
pany of California), 0LOA
California Chemical Company (Califor)
Compositions sold by the Oronite division of Nia Cheo+1cal Coa+pany are known.

Also, U.S. Patent No. 3,788. issued on January 29, 1974.
Various polymeric charge control agents can also be used, such as terpolymers such as those 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 metal ion-accepting substance to ensure the dissociation of metal ions. Examples include various chelating agents that form coordination compounds with metal ions, polyethylene glycol, crown ether, 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 resin and colorant as main components are preferably 0.5 parts by weight to 50 parts by weight based on 1000 parts by weight of the solvent liquid. If it is less than 0.5 parts by weight, the image density will be insufficient, and if it exceeds 50 parts by weight, 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.

In addition, the charge control agent as described above has a zero charge against the carrier liquid.
．． 01=10.0wt% is preferable. 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, if the electrical resistance of the liquid developer with toner particles removed is lower than 10'Ωcm, it will be difficult to obtain a high-quality continuous tone image, so the amount of each additive added should be within this limit. It is necessary to control it. 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.

(I') Method for producing polyester The structural formulas of each component of the polyester used in Example I below and their mixing ratios are shown in Table 1.

Weighed the raw materials shown in Table 1 into a polyester 1° flask so that the molar ratios shown in Table 1 were obtained (dicarboxylic acid was dimethyl ester), and added 2 drops of tetraisobutyl orthotitanate under a nitrogen stream. The reaction was carried out at 230°C as a catalyst. After methanol generation has finished, continue stirring for 0.5 s.
The reaction was continued by reducing the pressure to +mHg to obtain the desired polyester.

Polyester 2 A low molecular weight polyester block A was obtained from dimethyl terephthalate and potassium glyceric acid by a transesterification method (molecular weight: 2000).

An equimolar mixture of dimethyl terephthalate/dimethyl isophthalate and σ-heptadecyl glycerin ether were
A transesterification reaction was carried out under an iF4 catalyst to obtain a low molecular weight co-condensed polyester block B (molecular weight: 2500).

Weigh A and B so that the diol components have the molar ratio shown in Table 1, and heat them at 200° under a nitrogen stream using manganese acetate as a catalyst.
Polyester 2 was obtained by reaction with C.

Polyesters 3 and 5 The raw materials shown in Table 1 were mixed at desired molar ratios, and desired polyesters were obtained by direct polymerization.

Polyester 4 Low molecular weight polyester C (molecular weight: 2000) was obtained from dimethyl terephthalate and dihydroquine ethyl [bis(imino)disulfone] under a nitrogen stream using tetraisopropyl orthotitanite as a catalyst.

Low molecular weight polyester D (molecular weight 30
00) was obtained. C and D have a molar ratio of diol components of 10
+90 and reacted in the same manner as Polyester 2 to obtain Polyester 4.

(II) Preparation of liquid developer Examples 1 to 6 The above mixture was placed in a Super Mill (manufactured by Bengami Seisaku Shin), heated to 60°C, mixed for 3 hours, cooled to room temperature, and added with additional Isopar L to reduce the solid content. The liquid developers 1 to 5 of Examples were prepared by diluting the developer to 2%.

Comparative Example (1) A liquid developer was obtained in the same manner using Polymer I (composition shown in Table 2) described in JP-A-59-501643.

The characteristics of the samples obtained as described above were evaluated using the following evaluation method and are shown in Table 2.

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

A case where no precipitation was observed even after 4 months was indicated, and a case where precipitation occurred in less than 14 months were 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 (
B [ILK, LIQ, respectively]. The difference between the two,
The value of BULK-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 layer (positively chargeable) was coated on a polyethylene terephthalate film (thickness 100 μm) on which transferable palladium was vapor-deposited to create a photoconductive member.

The surface of this film was charged to +400 V 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.

The transfer efficiency wL/(vt+wp) is calculated from the weight wt of the transferred toner and the weight wp of the toner remaining on the photoconductor.

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

To provide a liquid developer which can be stored for a long period of time without deteriorating its performance and has good transfer efficiency to paper.

The polyester resin of the present invention also allows for the formation of finer particles than conventional ones.

Claims (4)

[Claims] (1) An electrophotographic liquid developer in which at least toner particles are suspended and dispersed in an electrically insulating non-aqueous carrier liquid, wherein the resin forming the toner particles contains at least one dicarboxylic acid component and two types of dicarboxylic acid components. contains the above diol components as polymerized units, and at least one of the diol components
A liquid developer characterized in that one species has a polar group and at least one other species is a chain polyester having a carrier liquid solvent affinity group. (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.