JPH03271752A - Electrophotographic liquid developer - Google Patents

Abstract

PURPOSE:To improve fixing property and a coating film forming property by incorporating 1-20 wt.% aliphatic polyester oligomer with the amount of thermoplastic resin. CONSTITUTION:The aliphatic polyester oligomer is mixed into a toner particulate forming resin at a ratio of 1-20 wt.% of the thermoplastic resin. Preferable aliphatic polyester oligomers are the polymers with the molecular weight of 1,000-10,000 and the saturated aliphatic polyester oligomers consisting of saturated aliphatic diols and saturated aliphatic dicarboxylic acids and preferably without incorporating a crosslinking group in the structure. Thus the self-fixing property and film forming property are simultaneously improved.

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, etc.

[Prior art]

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 overlaid on a conductive support is developed and visualized using a developer. The developed image may be fixed directly onto the photoconductor or transferred and fixed onto a carrier such as paper.

Methods for developing electrostatic latent images include dry developing methods such as the cascade method and magnetic brush method, and liquid developers in which toner particles are dispersed in a non-aqueous solvent with high electrical insulation and low dielectric constant. A liquid development method using . In particular, the liquid development method can make toner particles very small, so it can be said to be the most suitable method for faithfully reproducing fine images.

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

Various rubbers such as styrene-butadiene rubber, cyclized rubber, and natural rubber, and styrene resins such as polystyrene.

Synthetic resins such as vinyltoluene resin, acrylic resin, methacrylic resin, polyvinyl acetate, ethylene copolymer, polyester resin, polycarbonate, rosin resin, alkyd including modified alkyd such as linseed oil modified alkyd resin Examples include natural resins such as resins and polyterpenes. Other phenolic resins including modified phenolic resins.

Natural resin modified maleic acid resin, phthalate pentaerythride resin, chroman-indene resin, ester gum resin,
Vegetable polyamides are known.

Among them, resins classified as thermoplastic resins, which have the property of plasticizing when heated and solidifying when cooled, are widely used because they are easy to obtain strong and glossy coatings by heating and fixing, and are used in various forms. Disclosed.

For example, JP 61-180248, JP 62-135
No. 842 discloses a liquid developer using an ethylene copolymer, JP-A-60-10263 discloses a liquid developer using a styrene-methacrylic acid ester resin, and JP-A No. 51-8942 discloses a liquid developer using a styrene-methacrylic acid ester resin.
No. 8 discloses a thermoplastic polyester resin.

In addition to the above-mentioned image strength and gloss, electrophotographic developers are required to have properties such as chargeability, storage stability, stability, and transferability. Among these, transferability is a particularly important practical performance in applications where it is required to transfer the toner image formed on the photoconductor to another desired image carrier, such as paper, plastic film, metal plate, etc. be. An example of such an application is the well-known flat paper electrostatic printing of office documents and the like. Various methods are known as means for improving the transferability of this toner image.

For example, the above-mentioned Japanese Patent Application Publication Nos. 61-180248 and 62-1
No. 3582 discloses that transferring and fixing properties can be improved by changing the shape of toner particles into an amorphous shape having 7 eyelets. To improve fixing properties, JP-A-58-50
No. 0541 discloses an example in which an aliphatic polyester oligomer is used as a polyester plasticizer for the purpose of improving self-fixing properties and film properties.

However, when aliphatic polyester is used in the amount shown in JP-A-58-500541, the toner image formed by development has strong adhesion to the photoconductor, making it difficult to transfer it onto the desired transfer carrier. However, there was a drawback that a good transferred image could not be obtained.

[Purpose of the invention]

An object of the present invention is to provide a liquid developer for electrophotography which has good dispersion stability of toner particles, good charging properties, fixing properties and film forming properties, and particularly excellent transfer properties.

[Structure of the invention]

An object of the present invention is to include an electrically insulating non-aqueous carrier liquid,
An electrophotographic liquid developer comprising toner particles containing at least one type of thermoplastic resin and an aliphatic polyester oligomer suspended and dispersed, wherein the amount of the aliphatic polyester oligomer is 1 to 10% of the amount of the thermoplastic resin. This is achieved with a liquid developer that is 2Qvt%.

In addition, in the embodiment of the present invention, it is preferable that the aliphatic polyester oligomer and the thermoplastic resin are homogeneously dissolved in each other. Furthermore, it is preferable that the aliphatic polyester oligomer does not contain a crosslinkable group.

As a result of research in line with the above-mentioned objective, the present inventors have found that when an aliphatic polyester oligomer is mixed with the toner particle forming resin at a ratio of 1 to 2 Qwt% of the thermoplastic resin, transferability is significantly improved. discovered. Further, the aliphatic polyester oligomer used in the present invention is disclosed in JP-A-58
As introduced in No. 500541, self-fixing properties and film properties can be improved at the same time.

The aliphatic polyester oligomer used in the present invention is
It is a polymer with a molecular weight of about 1000 to 1000, and its amount is 1 to 2 Qv of the thermoplastic resin forming the toner particles.
It is used in the range of t%. More preferably 5-15vt
Used in the range of %.

A preferred aliphatic polyester oligomer is a saturated aliphatic polyester oligomer composed of a saturated aliphatic diol and a saturated aliphatic dicarboxylic acid, and more preferably does not have a crosslinkable group in its structure. There are no particular problems with the types of substituents that are not crosslinkable, and in particular, alkyl groups, alkoxy groups, alkyl ester groups, etc. do not impede the purpose of the present invention. Furthermore, a polyester oligomer having an ether bond in the structure can also be used. Examples include polyesters of glycols such as 2-hydroxyethyl ether-1,2-bis(1-hydroxyethoxy)ethane and polymethylenecarboxylic acid.

The glass transition point (Tg) and melting point (T-th) of the aliphatic polyester oligomer preferred for the present invention do not need to be particularly defined.

Thermoplastic resins for forming the toner particles of the present invention include polyethylene, ethylene vinyl acetate resin, polyacrylic acid, polymethacrylic acid, polymethyl acrylate,
Polyacrylic esters such as polyethyl acrylate, polymethicrylic esters, ethylene/acrylic acid copolymers, ethylene/methacrylic acid copolymers, polystyrene,
Known thermoplastic resins such as styrene/acrylic acid copolymer, styrene/methacrylic acid copolymer, polyvinyl chloride, and thermoplastic polyester can be used.

The thermoplastic resin and the aliphatic polyester oligomer can be used simply by kneading them, or more preferably, they are used by making them compatible.

One particularly preferred thermoplastic resin is thermoplastic polyester. Thermoplastic polyester is a non-crosslinked polyester composed of repeating diol units and repeating dicarboxylic acid units, and is a polyester that does not contain crosslinkable groups in its structure.

Another particularly preferred thermoplastic resin is an acrylic acid or methacrylic acid resin. These include copolymers with respective esters and vinyl monomers such as ethylene and styrene. i.e. polyacrylic acid polymethacrylic acid, polyacrylic acid ester, polymethacrylic acid ester, ethylene/acrylic acid or methacrylic acid copolymer, ethylene/acrylic acid or methacrylic acid ester or copolymer of methacrylic acid ester styrene/acrylic acid or methacrylic acid copolymers, styrene/acrylic acid or methacrylic acid/acrylic esters or methacrylic ester copolymers.

It was also shown in the above-mentioned JP-A-60-10263 that the affinity for carrier liquids is improved by using esters with aliphatic alcohols having 6 or more carbon atoms as acrylic esters and methacrylic esters. There is. Such ester monomers can be used in amounts up to 80 w[%]. Also acrylic acid.

The methacrylic acid resin can be R-substituted with various substituents like the above-mentioned polyester resin. Polar substituents are known to improve the charging of toner particles, and monomers having polar substituents can be used in amounts up to 201% of the total.

The preferred polyester according to the invention is #I
The constituting diol can be selected from various known diols. Examples include bisphenols, alkylene glycols, monocyclic and polycyclic diols.

Typical sphenols have the following structure.

In the formula, R1 and R8 are each selected from the group consisting of a hydrogen atom, an aryl group (eg, an evaphenyl group, a substituted phenyl group), a halogen atom, a nitro group, a cyano group, an alkoxy group, and the like. However, R1 and R3 may be the same or different. The substituent on the substituted phenyl group is a halogen atom or a nitro group.

It can be a cyano group or an alkoxy group.

R3 and R4 represent an aliphatic, monocyclic or polycyclic group, each of which is a hydrogen atom and an alkyl group having 1 to 6 carbon atoms (
However, fluoromethyl, difluoromethyl, trifluoromethyl, dichlorofluoromethyl, 2- (2,3
, 4,5-tetrahydro-2,2-dimethyl-4-oxofuryl-3-yl] (including substituted alkyl groups such as ethyl), cycloalkyl groups having 4 to 6 carbon atoms, cycloalkyl groups having 6 to 20 carbon atoms aromatic groups (e.g. phenyl, 31-
dichlorophenyl, 2,4-dichlorophenyl).

Also, R3 and R6 together form 4 to 7 in the ring.
Monocyclic, bicyclic or arsenic ring groups can be created having .

Typical and useful sphenomes include the following. Bisphenol A, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)furopane [tetrachlorbisphenol A), l-phenyl-1,1-bis(4-hydroxyphenyl)ethane, 1
- ((3,4-dichlorophenonyl-1,1-bis(
4-hydroxyphenyl)-4-(2,3,4,5-tetrahydro-2,2-diethyl-5-oxo7lyru3
-yl)] butane, bis(4-hydroxyphenyl)methane, 2,4-dichlorophenylbis(4-hydroxyphenyl)methane, 1.1-bis(4-hydroxyphenyl)cyclohexane, 1,1.1. 3.3.3-hexafluoro-2,2-bis(4-hydroxyphenyl)
Propane, diphenylbis(4-hydroxyphenyl)
Methane,
propylphenyl)methane, 1.1-bis(2-ethyl-4-hydroxy-5-2-butylphenyl)ethane, 2.2-bis(4-hydroxyphenyl)propane,
2.2-bis(4-t: )'roxy2-methyl-5
-inoctylphenyl)isobutane, bis-(2-ethyl-4-hydroxyphenyl)=4,4-di-valatrylmethane, and the like.

Representative monocyclic diols include the following. Hydroquinone, hydroquinone substituted with an alkyl group having 1 to 15 carbon atoms or a halogen atom, resorcinol, resorcinol substituted with a lower alkyl group or a halogen atom, etc. 1.
4-cyclohexanediol, 1.4-cyclohexane dimetatool, 1.4-cyclohexanejetanol,
1.4-bis(2-hydroxyethoxy)cyclohexane, 1.4-benzenedimetatool, 1.4-benzenedetanol, 1-methyl-4゜5-bishydroxy-
Examples include 1-cyclohexane.

Examples of polycyclic diols include norpolnylene glycol;
Examples include decahydro-2,6-su7talediol.

Typical alkylene glycols include ethylene glycol, diethylene glycol, triethylene glycol, 1.2-furopanediol, 1.3propanediol, 1.4-butanediol, 2.3-butanediol, and 1.5-bentane. Diol, l, 6-hexanediol, l, 7-hebutanediol, 1,8-octanediol, ■, 9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, neopentyl glycol, 2 ,2. -4-trimethyl-1,6-hexanediol, 4-oxa-2,6-hebutanediol and the like can be mentioned.

Various other diols can also be used.

The dicarboxylic acids constituting the preferred polyesters are selected from any of aliphatic, cycloaliphatic and aromatic dicarboxylic acids. The dicarboxylic acids include, of course, difunctional precursors such as these, as well as difunctional precursors corresponding to the free acid form of such substances, such as dicarboxylic acids with low a-functionality. alcohol or phenyl esters and dicarboxylic acid halides (eg chloride, bromide).

Examples of typical dicarboxylic acids 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. acid, cyclohexanoic acid-1,4-dicarboxylic acid, toclohebutane-1,3-dicarboxylic acid, 2.5-1 nalepornanedicarboxylic acid (both cis and trans forms of the improved acid are effective), 7-tal Acid, isophthalic acid, terephthalic acid, t-butylin heptathalic acid, phenylene diacetic acid, phenylene dipropion ml, 2,6-naphthalenedicarbone f
i, 1,4-7taledicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,7-7taledicarboxylic acid,
4.4'-dicitric acid, 4.4'-sulfonyl dibenzoic acid, 4.4'-oxydibenzoic acid, binaphthyldicarboxylic acid, 4.4'-stilbenzinecarboxylic acid and 9.1
Examples include 0-tributycenedicarboxylic acid.

Various other dicarboxylic acids can also be used.

The diol and dicarboxylic acid mentioned above may be substituted with a substituent. For example, alkyl groups, substituted alkyl groups, cycloalkyl groups, alkoxy groups, acyl groups, alkoxy groups, alkoxycarbonyl groups, halogen atoms, nitro groups,
Cyano group, amino group, alkylamino group, amide group, alkylamido group, pyridyl group, imino group, sulfonic acid group, sulfinic acid group, sulfonamide group, sulfonimide group, disulfonimide group, mercapto group, alkylmercapto group, Examples include substituents such as a phosphonic acid group, a phosphinic acid group, a carboxylic acid group, a phosphonium group, and a sulfonium group.

In particular, an alkyl group or alkoxy group having 6 or more carbon atoms,
Containing a diol or dicarboxylic acid substituted with a substituent having an acyl group having 7 or more carbon atoms or an alkyl chain of long steel such as an alkoxycarbonyl group has the effect of improving the dispersion stability of toner particles. . Diols or dicarboxylic acids substituted with substituents having such long alkyl chains each account for 40% of the total dicarboxylic acids.
It is more effective to contain it in a proportion of ~100 mol%.

Furthermore, it is widely known that polar substituents such as halogen atoms and nitro groups have the effect of improving the chargeability of toner particles. The preferred polyester used in the present invention preferably contains diols or dicarboxylic acids having these polar substituents in an amount of 5 to 20 mol % of the total diols or total diols or total dicarboxylic acids, respectively.

The preferred polyester used in the present invention can be obtained by polycondensing the above-mentioned dicarboxylic acid or its precursor with a diol or its precursor by a known method. The dicarboxylic acids and diols are not limited to one type each, and several types of dicarboxylic acids and diols can be used in combination depending on the purpose. Such a co-condensed polyester having 3 IR components or more can be obtained by a known method.

That is, (1) mixing and polycondensing multiple types of low molecular weight polyesters that have been synthesized in advance, (2) mixing the remaining components with one type of low molecular weight polyester that has been synthesized in advance, and (3) polycondensing the mixture. Synthetic leather can be made by mixing all the ingredients and polycondensing them. Those obtained by method (1) or (2) are particularly useful because they yield cocondensates with rich blocking properties.

The molecular weight of the thermoplastic resin used in the present invention can be varied within a fairly wide range depending on the target Tg and the aliphatic polyester oligomer used in combination and its amount. When a toner image formed on a photoconductor is transferred to a carrier such as paper to obtain an image, and then the image is heat-fixed, the required Tg range differs depending on the heat-fixing method. For example, in a heat roller fixing method that uses a heat roller, the temperature is 60 to 150℃.
It is said that a range of 40 to 100[deg.] C. is preferable, and a range of 40 to 100[deg.] C. is preferable for oven fixing using an electric heater, infrared lamp, xenon flash warm air fixing, high frequency fixing, and the like.

That is, in the present invention, it is preferable that the thermoplastic resin and the aliphatic polyester oligomer are blended in a desired ratio, and that the Tg of the blend at t2 is within the above range.

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 Impar L (Isopar: Exxon product name), Shellzol 70, Shellzol 71 (Shellzol: Shell Oil Co., Ltd.) (trade name), Amsco OMS, Amsco 460 solvent (Amsco: brand name of Spirits Inc.), 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 way to color the resin itself is to
There are methods of physically dispersing pigments or dyes in resins, and a wide variety of pigments or dyes are known. For example, magnetic powder, powder iodide, carbon black, nigrosine, alkali blue, 77st yellow, disazo yellow, quinacridone magenta, na7tolkamine,
Examples include Peranent Red, Brilliant Carmino 6B, Rhodamine Lake, and 7 Talocyanine Plue.

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. 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 Equity VII 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.

The amount of colorant varies widely depending on the type of colorant used, but in general, toner particle type 1 contains a resin (inventor, thermoplastic resin and aliphatic polyester oligomer). It is about 0.1 to 200vt% with respect to the sum of the amounts.

In addition to the colorant, the developer of the present invention can also contain various charge control agents, if necessary.

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

Suitable positive charge control agents include dioctyl sodium sulfosuccinate (American Cyanimid
Co.

), zirconium octoate and copper oleate A
Which metal soap etc. are there? Suitable negative charge control agents include lecithin, barium betronate, calcium betronate (Witco Chemical Corp.).

NawYork, NY), alkyl succinimide (C
heveron Chemical Company o
f California), California Chemical Co. (California Ch.
Oronite (Oro) from chemical Company
Compositions sold by Ni te) division are known.

Also, US Patent No. 3.7889 issued on January 29, 1974.
Various polymeric charge control agents can also be used, such as terpolymers (eg, 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.

These charge control agents may be added to the liquid developer in any form, either before or after dispersing the toner particles, or in a mixed form with the polyester resin forming 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 density of both images will be insufficient. When the amount exceeds 50 parts by weight, fogging tends to occur in non-image areas.

The above-mentioned charge control agent is preferably used in an amount of 0.001-1:0 parts by weight per 1000 parts by weight of the solvent liquid, and 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. In other words, if the electrical resistance of the liquid developer with toner particles removed is lower than 10' Ω CI, good continuous gradation will be obtained, so the amount of each additive added must be within this limit. It is necessary to control it.

Typically, 1 to 2001 grams of charge control agent per gram of toner solids is required.

〔Example〕

Next, the present invention will be specifically explained with reference to Examples.

The thermoplastic resins used in the examples of the present invention are as follows.

1. Ethylene/acrylic acid (89/11) copolymer 2
, ethylene/methacrylic acid/butyl methacrylate (8
0/10/10) copolymer 3, styrene/stearyl methacrylate (22/78) copolymer 4, polyester 1 5, polyester 2 6, polyester 3 7, polyester 4 8, polyester 5 9. Polyester 6 The diol components of the polyesters 1 to 6, and the aliphatic polyester oligomers used in the examples are as follows.

7g A, polyethylene sebacate -30B, polyethylene adipate -500, polydiethylene malonate -8D, polydiethylene ethyl malonate -29E, polytetramethylene sebacate -57CI) thermoplastic polyester resin (polyester 1 to 6) Polyester l Dimethyl terephthalate and ethylene glycol are heated in a nitrogen stream and in the presence of magnesium acetate to 230°C).
After the generation of methanol was completed, the pressure was reduced to obtain 250-b ethylene terephthalate.

Polyester 2 Dimethyl terephthalate and dimethyl iso-7-thalate were mixed in equimolar amounts and condensed with ethylene glycol in the same manner as in Polyester 1 to obtain co-condensed polyester 2.

Polyester 3 Polyester 3 was obtained from dimethyl terephthalate and 1-hydroxy-1-hydroxymethylundecane in the same manner as Polyester 1.

Polyester 4 0.005 mol of sodium glycerosulfate was added to 0.1 mol of dimethyl terephthalate and heated to 230°C under a nitrogen stream in the presence of titanium fluoride, and when methanol generation was completed, 1,3-dihydropentatecane was added. Total 0.09
5 mol was added, and when the generation of methanol was completed, the pressure was reduced and the reaction was carried out at 250 DEG C. H2-Hg for 2 hours to obtain Polyester 4.

Polyester 5 A low molecular weight polyester block (
I) was obtained.

A low molecular weight polyester block (1) was obtained from dimethyl nitrate and 1,2-dihydrotetradecane.

(I) and (If) were mixed so that the dicarboxylic acid molar ratio was 15:85, and heated under a nitrogen stream to obtain polyester 5.

Polyester 6 Dimethyl ester of each dicarboxylic acid and neopentyl glycol were mixed at the molar ratio shown in Table 1, and under a nitrogen stream,
220 using tetraisopropylorthotitanate as a catalyst
The reaction was carried out at 240°C for 2 hours, and then the temperature was raised to 240°C, the pressure was reduced, and the reaction was carried out at 240°C/1 mmHg for 2 hours to obtain polyester 6.

(I [) Preparation of liquid developer 20 g of thermoplastic resin and aliphatic polyester oligomer were mixed at 100°C, 100 g of carbon black Log and Isopar L were added, cooled to room temperature, and heated in Super Mill (manufactured by Bengami Seisakusho Co., Ltd.). Dispersion was continued for 5 hours. Further, Ainpart 1 was added to dilute the solid content to 2 wt%.

As a charge control agent, a 3% lecithin Isopar H solution was added after cooling to room temperature.

(I[[] Evaluation of transferability) An electrostatic latent image is formed on a photoconductive film made by depositing palladium on polyethylene terephthalate and then provided with a photoconductive layer, and this is developed with each liquid developer. After squeezing the carrier liquid, high-quality paper was layered and pressure transfer was performed using a roller.

Measure the amount of toner transferred x (g) and the amount of toner remaining on the photoconductor y (g), x / (x + y) x 1
00 (%) was taken as the transfer rate. The results are shown in Table 2.

Table 2-(1) *The numbers in parentheses are wt% relative to the thermoplastic resin.As is clear from the table, the samples of the present invention exhibit a good transfer rate.

Claims (3)

[Claims] (1) An electrophotographic liquid developer comprising at least toner particles containing at least one thermoplastic resin and an aliphatic polyester oligomer suspended and dispersed in an electrically insulating non-aqueous carrier liquid, the developer comprising: A liquid developer characterized in that the amount of group polyester oligomer is 1 to 20 wt% of the amount of the thermoplastic resin. (2) The liquid developer according to claim 1, wherein the aliphatic polyester oligomer and the thermoplastic resin are homogeneously compatible with each other. (3) The liquid developer according to claim 1 or 2, wherein the aliphatic polyester oligomer is a saturated aliphatic polyester oligomer containing no crosslinkable group.