JP2007017956A - Liquid developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wet developer having high storage stability and good positive charging property. <P>SOLUTION: The liquid developer uses vegetable oil as a carrier liquid, wherein a colorant has positive charging property and comprises a benzimidazole pigment represented by formula 1 and a charge control agent of straight polarity, wherein R1 is OCH<SB>3</SB>, COOCH<SB>3</SB>or COOC<SB>4</SB>H<SB>9</SB>(n); R2 is NO<SB>2</SB>, H, CONHC<SB>6</SB>H<SB>5</SB>or SO<SB>2</SB>NHCH<SB>3</SB>; and R is H or CH<SB>3</SB>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid developer used in an electrophotographic image forming apparatus used for a copying machine, a printer, or the like.

An image forming apparatus using a liquid developer has a feature that even when fine toner particles are used, a problem due to scattering outside the apparatus does not occur and a high-definition image can be formed. . In an electrophotographic image forming apparatus using a liquid developer, a developer in which a toner mainly composed of a resin and a colorant is dispersed in a carrier liquid is used, and an image is formed on a photoreceptor by exposure. The electrostatic latent image formed is developed into a liquid developer.
After the development, an image is formed by transferring the obtained toner image onto a recording medium such as paper and thermally fixing it.

Petroleum-based volatile hydrocarbon solvents have been used in wet developers, but volatile hydrocarbon-based solvents are stable substances with low electrical conductivity, but have been transferred or recorded on recording media. When fixing the toner, it is necessary to volatilize or evaporate the volatile hydrocarbon organic solvent in the carrier liquid. When the volatile hydrocarbon organic solvent used as the carrier liquid is discharged, there is a possibility of causing environmental pollution.
Therefore, in order to consider the usage environment, it is necessary to provide a means for collecting the evaporated or volatilized carrier liquid in the vicinity of the fixing device. However, the size of the image forming apparatus is increased by the means for collecting the carrier liquid. In other words, it was disadvantageous for miniaturization.

It has also been proposed to prevent evaporation or volatilization of the carrier liquid by using non-volatile silicone oil or liquid paraffin as the carrier liquid. However, since the carrier liquid is stable, the recording medium can be used even after fixing. Will continue to exist. As a result, there have been problems such as a decrease in print quality and the presence of a carrier liquid on the paper surface, resulting in a decrease in sealability and a decrease in writing characteristics of a writing instrument using water-based ink.
Also, when manufacturing a conventional liquid developer, each component is dispersed in a non-aqueous non-polar solvent, which is a carrier liquid, and the properties of the non-polar solvent increase the size of the apparatus and the quality of recorded matter. As a result, problems such as deterioration in storage and storage stability of the liquid developer remain.

  On the other hand, many proposals have been made to use vegetable oil as a carrier liquid instead of a volatile hydrocarbon-based organic solvent (for example, Patent Document 1). By using vegetable oil as a carrier liquid for a liquid developer, the particle size is reduced. It is said that it is small and odorless and can improve image density, resolution and fixability.

In a liquid developer using vegetable oil as a carrier liquid, a magenta pigment is dispersed in a carrier liquid to prepare a positively charged liquid developer, and its polarity is examined by electrophoresis. Due to the polarity, a magenta colored image having a sufficient image density could not be formed. Therefore, it has been considered that the use of a large amount of a positively chargeable charge control agent (CCA) is indispensable for positively charging a magenta pigment. Further, when the amount of the charge control agent is increased, the storage stability of the dispersion becomes unstable. In particular, when a liquid metal soap is used, the viscosity increases due to the polymerization of vegetable oil in the carrier liquid during long-term storage, and liquid development. There was a problem that it was difficult to perform the function of the agent.
JP 2000-19787 A

  In the liquid developer for positive charging using vegetable oil as a carrier liquid, the present invention makes positive chargeability and storage stability even if the amount of the charge control agent that adjusts the chargeability to positive polarity is very small. An object of the present invention is to provide an excellent liquid developer. In addition, the dispersed primary particle size of the colored pigment fine particles is small, and in a vegetable oil, it can be controlled positively by adding a slight positive charge control agent, and the amount of fog toner on the photoreceptor can be reduced. It is an object of the present invention to provide a liquid developer that can be cleaned simultaneously with development.

  An object of the present invention is a liquid developer using vegetable oil as a carrier liquid, wherein the carrier liquid colorant contains a benzimidazole pigment represented by Chemical Formula 1 and a positive charge control agent and is positively charged. It is.

ここに、Ｒ１：ＯＣＨ₃ 、ＣＯＯＣＨ₃、ＣＯＯＣ₄Ｈ₉（ｎ）であり、Ｒ２：ＮＯ₂、Ｈ、ＣＯＮＨＣ₆Ｈ₅、ＳＯ₂ＮＨＣＨ₃ であり、Ｒ：Ｈ、ＣＨ₃である。

Here, R1: OCH ₃ , COOCH ₃ , COOC ₄ H ₉ (n), R2: NO ₂ , H, CONHC ₆ H ₅ , SO ₂ NHCH ₃ , and R: H, CH ₃ .

The coloring agent is at least one of pigment red 171 represented by the following chemical formula 2, pigment red 175 represented by the chemical formula 3, pigment red 176 represented by the chemical formula 4, and pigment red 208 represented by the chemical formula 5. The benzimidazole pigment is a liquid developer containing a colorant.

In the liquid developer, the vegetable oil is at least one selected from safflower oil, sunflower oil, soybean oil, corn oil, cottonseed oil, rapeseed oil, and sesame oil.
The vegetable oil is the above-mentioned liquid developer containing 60% by mass or more of the oleic acid composition in the fatty acid constituting the triglyceride.
The vegetable oil is the above liquid developer containing 50% by mass or more of the linoleic acid composition in the fatty acid constituting the triglyceride.
The vegetable oil is the above liquid developer containing 50% by mass or more of the linolenic acid composition in the fatty acid constituting the triglyceride.
The liquid developer containing an organic titanate compound which is a positive charge control agent.
Further, in the method for producing a liquid developer using vegetable oil as a carrier liquid, the magenta pigment represented by the chemical formulas 1 to 5 is mixed with a positive charge control agent and vegetable oil, and mixed with a ball mill, a bead mill, a sand mill, an atomizer. This is a method for producing a liquid developer dispersed by at least one dispersion mixing means selected from lighters.

In the positively chargeable liquid developer using vegetable oil as a carrier liquid, the present invention employs a specific benzimidazolone pigment as a pigment, thereby adding a slight amount of a positively chargeable charge control agent, It is possible to provide a positively chargeable liquid developer that is free from problems such as polymerization caused by the addition of a large amount of a charge control agent, and has excellent storage stability.
In addition, when vegetable oil with a high content of linoleic acid composition or linolenic acid composition of triglyceride is used, the toner image formed by the developer and the carrier liquid itself oxidatively polymerize to fix the toner image. In addition, it is possible to simplify the fixing unit or to provide an image forming apparatus that does not include the fixing unit.

Even when acidic paper is used as the recording medium, the pigment used is basic, so that it acts in the direction of neutralizing the pH of the paper, and the storage stability after recording increases. This acid also acts as a catalyst for the oxidative polymerization of the attached vegetable oil.
In addition, since the dispersed primary particle diameter of the colored pigment fine particles is 1 μm or less, in the vegetable oil, the pigment is easily positively charged, and it can be more positively controlled by adding a positive charge control agent, Simultaneous development cleaning is realized because the amount of fog toner on the photoreceptor is reduced.

In the liquid developer for positive charging using vegetable oil as a carrier liquid, the present invention pays attention to the charging characteristics of the pigment when a charge control agent is added. It has been found that it is possible to improve the problem of deterioration in storage stability of the obtained liquid developer.
That is, when investigating the charging characteristics of the pigment used in the positively charged liquid developer using vegetable oil as the carrier liquid, it is charged in both positive and negative polarities, and a large amount of charge control agent is used to make it positively chargeable. However, the present inventors have found that certain positive pigments can be obtained with good positive charge characteristics and can have good storage stability by adding a small amount of charge control agent.

FIG. 1 is a diagram illustrating a measurement cell for charging characteristics of a pigment dispersed in a vegetable oil according to the present invention, FIG. 1 (A) is a perspective view showing the measurement cell, and FIG. 1 (B) is an electrode. It is a perspective view explaining a part.
In the measurement cell 1, an anode side electrode part 3 and a cathode side electrode part 4 are installed in a container 2 made of an electrically insulating member such as glass or synthetic resin.
The anode terminal 5 provided on the anode side electrode unit 3 is connected to a power supply anode side lead wire 6 coupled to a current supply device (not shown), and is provided on the cathode side electrode unit 4. A cathode-side lead wire 8 coupled to a current supply device (not shown) is connected to the cathode terminal 7.
The anode-side electrode portion 3 and the cathode-side electrode portion 4 are provided with a holding member mounting groove 9 for holding both electrode portions at a predetermined interval on the upper portion thereof. Is held at a predetermined interval.
A flow groove 10 is provided below the anode electrode portion 3 and the cathode electrode portion 4 so that the pigment dispersion can be smoothly supplied.

FIG. 1B illustrates the anode electrode portion, and the cathode electrode portion is also formed of the same structure and members.
As the anode electrode portion 3, a molded body in which a projection 11 for anode engagement is provided on a resin having high oil resistance and solvent resistance such as polyacetal resin (POM) is used.
An anode 12 is attached to the anode engaging projection 11 together with a spacer 13 made of an insulating member that maintains a constant distance from the counter electrode.
The anode 12 is preferably formed on a transparent glass plate by forming a transparent conductive film 14 such as ITO that does not elute due to the applied current when a current is applied. By using a transparent conductive film formed on a transparent glass plate, it is easy to optically observe and measure the pigment deposited on the anode removed from the anode electrode part after electrophoresis for a predetermined time. Can be performed.

Alternatively, the pigment concentration may be measured with a reflection densitometer or the like after the anode removed from the anode electrode portion is pressed against a transfer material such as paper or a synthetic resin film to transfer the pigment.
For each of the anode and the cathode, it is possible to determine whether it has a positive or negative charge characteristic by comparing the deposited pigment or its transferred image.

By the above method, the magenta pigment is dispersed in the vegetable oil as the carrier liquid together with the charge control agent, and the polarity is measured by electrophoresis. Depending on the type of the magenta pigment, the charge control agent acts greatly in the vegetable oil. It has been found that there is a positive chargeability.
Specifically, the magenta pigment represented by the following chemical formula 1 has good positive chargeability when a charge control agent is added.

ここに、Ｒ１：ＯＣＨ₃ 、ＣＯＯＣＨ₃、ＣＯＯＣ₄Ｈ₉（ｎ）であり、Ｒ２：ＮＯ₂、Ｈ、ＣＯＮＨＣ₆Ｈ₅、ＳＯ₂ＮＨＣＨ₃ であり、Ｒ：Ｈ、ＣＨ₃である。

Here, R1: OCH ₃ , COOCH ₃ , COOC ₄ H ₉ (n), R2: NO ₂ , H, CONHC ₆ H ₅ , SO ₂ NHCH ₃ , and R: H, CH ₃ .

  Further preferably, any one of the benzimidazoles of Pigment Red 171 represented by Chemical Formula 2, Pigment Red 175 represented by Chemical Formula 3, Pigment Red 176 represented by Chemical Formula 4, and Pigment Red 208 represented by Chemical Formula 5 Mention may be made of pigments.

Examples of vegetable oils that can be used in the liquid developer of the present invention include safflower oil, sunflower oil, soybean oil, corn oil, cottonseed oil, rapeseed oil, and linseed oil.
It is also known that fats and oils are esters of 1 molecule of glycerin and 3 molecules of fatty acid, that is, triglyceride, and by reacting this with alcohol or fatty acid, a transesterified oil in which the properties of the raw oil and fat are changed can be obtained. However, the vegetable oil of the present invention includes transesterified oil produced by transesterification using vegetable oil as a raw material. The vegetable oil may be one type or a mixture of plural types, or may be a mixture of esters obtained by decomposition of the vegetable oil.
In particular, triglycerides having a fatty acid composition with a high proportion of unsaturated bonds such as oleic acid, linoleic acid, and linolenic acid cause oxidative polymerization, so that fixing means can be eliminated or simplified.
An example of the composition of triglyceride in the vegetable oil used in the liquid developer of the present invention is as shown in Table 1 below when the percentages of oleic acid, linoleic acid and linolenic acid in the fatty acids constituting each are expressed in mass%. . In the table, it is represented by a non-fatty acid name.

Therefore, it is preferable that the vegetable oil of a carrier liquid contains the rapeseed oil which contains 60 mass% or more of oleic acid compositions in the fatty acid which comprises triglyceride.
The vegetable oil of the carrier liquid contains at least one of safflower oil, sunflower oil, soybean oil, corn oil and cottonseed oil containing 50% by mass or more of the linoleic acid composition in the fatty acid constituting the triglyceride. Is preferred.
Moreover, it is preferable that the vegetable oil of a carrier liquid contains a linseed oil which contains 50 mass% or more of linolenic acid composition in the fatty acid which comprises triglyceride.

  The liquid developer of the present invention can contain a charge control agent, a resin, an antioxidant and the like together with the pigment. Specifically, as the charge control agent, for example, tetraethyl titanate, tetraisopropyl titanate, tetra-n-propyl titanate, tetra-n-butyl titanate, tetra-tert-butyl titanate, tetra-2-ethylhexyl titanate, tetraoctyl Examples include titanate, tetramethoxytitanium and the like, titanium chelates such as titanyl acetyl acetate, and other examples include titanate coupling agents such as isopropyl triisostearoyl titanate, isopropyl tridecylbenzenesulfonyl titanate, isopropyl tris. (Dioctyl pyrophosphate) titanate, tetraisopropyl bis (dioctyl phosphite) titanate, tetraoctyl bis (ditridecyl phosphite) Titanate, tetra (2,2-diallyloxydylmethyl-1-butyl) bis (di-tridecyl), bis (dioctylpyrophosphate) ethylene titanate, isopropyltrioctanoyl titanate, isopropyldimethacrylisostearoyl titanate, isopropylisostearoyl Examples include diacryl titanate, isopropyl tri (dioctyl phosphate) titanate, isopropyl tricumyl phenyl titanate, and isopropyl tri (N-aminoethyl-aminoethyl) titanate.

  Resins include ethylene / vinyl acetate copolymer, polyester resin, styrene / acrylic resin, rosin-modified resin, polyethylene, ethylene / acrylic acid copolymer, ethylene / maleic anhydride copolymer, polyvinylpyridine, polyvinylpyrrolidone. One or two or more resins selected from ethylene / methacrylic acid copolymers or ethylene / acrylic acid ester copolymers can be used.

  Examples of the antioxidant include dibutylhydroxyanisole, dibutylhydroxytoluene, tocophenol, L-ascorbic acid, erythorbic acid, catechin and the like.

  The liquid developer of the present invention is blended with vegetable oil, pigment, etc., and dispersed by an attritor, sand mill, ball mill, vibration mill, or the like, so that the primary particle diameter of the colored fine particles is a number average particle diameter of 1 μm or less. It is preferable.

Example 1
(Preparation of liquid developer 1)
In a stainless steel container with a capacity of 500 ml, put 320 g of zirconia balls having a diameter of 5 mm, 100 g of soybean oil, 0.11 g of a dispersant (Ajinomoto Finetechno Azisper PA111), and 15 g of benzimidazolone pigment: Pigment Red 171 represented by Chemical Formula 2. The mixture was dispersed and mixed for 14 hours at a rotation speed of 504 ppm using a stirrer (Torunedo SM type propeller stirring blade manufactured by Chuo Rika Seisakusho). After the dispersion was completed, 5 g of a dispersion sample was collected, added to 30 g of sunflower oil, and mixed well.

(Evaluation of charging characteristics by electrophoresis)
The charging behavior of the pigment dispersion was examined using the charging characteristic measuring cell shown in FIG. In the measurement cell for charging characteristics, a 300 V DC voltage was applied for 10 seconds at a distance of 2 mm between the electrodes, and colored fine particles were adhered to the ITO transparent electrode by electrophoresis. Remove the ITO transparent electrode from the measurement cell, press the colored fine particles adhering to the anode and cathode onto the transfer paper (Fuji Xerox Office Supply PPC fine paper J paper), and attach the color to the electrodes. Fine particles could be obtained as a colored solid image on the transfer paper.

The density of the obtained colored solid image was measured as the reflection density using a reflection densitometer (model 520 type spectral densitometer manufactured by X-Rite) after being left for 1 day. The amount attached to the electrode is such that the reflection density value on the cathode side is larger than the reflection density value on the transfer paper, the pigment-dispersed fine particles are positively charged, and the reflection density on the anode side is higher than that on the cathode side. It can be evaluated that the pigment-dispersed fine particles are negatively charged, and those having the same reflection density on the anode side and the cathode side can be evaluated as neutrally charged.
In Table 2, these results are represented by + when the charging characteristics are positive,-when the charging characteristics are negative, and-when positive and negative are similar.

Further, 0.21 g of titanium tetra-n-butoxide monomer was added as a positive charge control agent (CCA) to the liquid developer prepared in the same manner, and the mixture was sufficiently stirred to contain the charge control agent. Table 2 shows the measurement results of the electrode-attached solid reflection density on the negative electrode side and the positive electrode side when the chargeability of the dispersed fine particles was examined in the same manner using a charging characteristic measurement cell.
For comparison, a similar experiment was performed using a compound represented by the following chemical formula 6 known as naphthol red PR 112, and the results are shown in Table 2.

  According to the results in Table 2, the benzimidazolone organic pigment of the present invention is positively charged by adding a positive charge control agent. However, halogen is used as a substituent, and chlorine is used in this comparative example. Even when a positive charge control agent was added, the charge polarity was almost neutral, and the amount of colored dispersed fine particles adhering to the negative electrode side and the positive electrode side was almost the same.

Example 2-9, Comparative Example 1
Table 3 shows the unsaturated fatty acid composition in the fatty acids constituting the main triglycerides of typical vegetable oils, with the names of each fatty acid expressed in mass%.

Moreover, the positive charge control agent and vegetable oil used in combination with each colorant are shown in Table 4 together with the electrophoresis results. Table 4 also shows a comparative example using an aluminum coupling agent (alkyl acetoacetate aluminum diisopropylate). The amount of each charge control agent added was 0.21 g, the same amount as in Example 1.
The preparation of each color dispersant was carried out in the same manner as in Example 1 except that 0.2 g of Ajimoto Fine Techno Ajisper PN411 was used as the dispersant, and the aggregated particle diameter of the colorant after 14 hours of dispersion treatment was determined. When measured using a laser microscope (manufactured by Keyence Corporation, VH-7000), it was 1 μm or less in any case.
The electrophoresis evaluation test was performed in the same manner as in Example 1. The results are shown in Table 4.

According to the results of the table, each dispersed colored fine particle was positively charged positively by the addition of the charge control agent that is a positive organic titanate compound, but in Comparative Example 1 in which the aluminum coupling agent was added, the negative electrode side The amount adhered and the amount adhered to the positive electrode side almost antagonized, and were evaluated as almost neutral when viewed as a liquid developer.
In the case of specific pigments that are equally charged to both positive and negative polarities when vegetable oil is used as the carrier liquid, it is shown that a positively charged liquid developer can be obtained by adding an organic titanate compound. It was done.

Further, although it is effective to set the aggregated particle diameter of the dispersed colored fine particles to 1 μm or less, it is preferable to make the diameter larger than 100 nm.
That is, when the dispersed colorant of Example 4 was pulverized and dispersed for 24 hours and finely pulverized so that the primary particle diameter was less than 100 nm, the deposits migrated to the positive and negative electrodes side by electrophoresis were pressed and transferred to transfer paper. When the solid image density obtained in the same manner was measured, the solid image densities attached to the negative electrode side and the positive electrode side were 1.09 and 0.31, and if it is too small, the hiding power tends to decrease. .

Example 10
(Image evaluation test)
The produced liquid developer was developed, transferred, cleaned, and fixed using the image forming apparatus of the liquid development type shown in FIG.
In the image forming apparatus 20, a single layer type positively charged organic photoreceptor is used as the photoreceptor 21, and the developing roller 22 is made of an elastic member. First, the surface of the photosensitive member 21 is charged to +650 V with a scorotron 23, and a laser beam 24 controlled by an image signal is irradiated to form a latent image. Next, development is performed by applying a developing bias of +600 V to the developing roller 22. A liquid developer whose layer thickness is regulated by the regulating blade 26 is supplied to the developing roller 22 while the anilox roller 25 rotates in contact with the developing roller 22 in the same direction.

The anilox roller 25 is supplied with a liquid developer from a supply roller 27 which is a sponge-like elastic roller. The transfer bias is −950 V, and the transfer paper 28 is supplied as indicated by the arrow at a speed of 200 mm / sec while synchronizing the image transfer by the pair of supply rollers 29.
The transfer roller 30 is an elastic roller, and a transfer bias is applied through a control system. The image transferred to the transfer paper passes between the heat fixing rollers 31 made of an oil repellent material and is fixed. The fixing temperature is set to 90 ° C., and can be set so that the toner image developed and transferred from the transfer paper is fixed to the extent that the toner image is not transferred to another member when the contact level is reached.

  When the transfer residual toner is generated, the cleaning elastic roller 32 in contact with the photoconductor removes the liquid developer adhering from the photoconductor by the cleaning blade 33 positioned above. The cleaned photoreceptor can form a monochromatic image while repeating the cycle of charging, exposure, development, transfer and cleaning again.

  In the image forming apparatus shown in FIG. 2, 15 g of each pigment dispersion was added to 200 g of each vegetable oil described in Example 2-8 and mixed well to obtain a liquid developer. A 5% original and a solid image were printed out. To evaluate the fixability, a 12 mm wide adhesive tape (Sumitomo 3M's mending tape) is applied to the printed material formed on the transfer paper (Fuji Xerox Office Supply PPC paper J paper), peeled off, and transferred. The density of the printed matter remaining on the paper and the density before peeling were measured using a reflection densitometer (manufactured by X-Rite), and the ratio to the density before peeling was shown as a percentage in Table 5.

According to the results in Table 5, the fixing rate was 80% or more in all cases. Among them, rapeseed oil having a low linoleic acid composition in the fatty acid constituting triglyceride showed the lowest fixing rate, but the highest fixing rate was the liquid developer containing a linolenic acid composition having three unsaturated bonds. It was oil. According to this result, it was shown that the vegetable oil containing a large amount of unsaturated fatty acid has excellent fixability, and the linoleic acid composition in the fatty acid constituting the triglyceride is 50% by mass or more, or the linolenic acid in the fatty acid constituting the triglyceride. It was found that a vegetable oil containing 50% by mass or more of an acid composition is excellent as a carrier liquid for a liquid developer.
In addition, a printing test was conducted again after leaving these liquid developers at 25 ° C. for one month, and the images before and after being left for one month were compared, but no change was observed.

  The present invention relates to a liquid developer using vegetable oil as a carrier liquid, a benzimidazolone pigment having a specific chemical structure and exhibiting positive chargeability and negative chargeability, and an organic titanate charge control agent as a charge control agent. By adding it, a stable positive charging property can be obtained, and a liquid developer having good storage stability can be provided.

FIG. 1 is a diagram illustrating a measurement cell for charging characteristics of a pigment dispersed in a vegetable oil of the present invention. FIG. 2 is a diagram illustrating a liquid developing type image forming apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Measurement cell, 2 ... Container, 3 ... Anode side electrode part, 4 ... Cathode side electrode part, 5 ... Anode terminal, 6 ... Anode side lead wire, 7 ... Cathode terminal, 8 ... Cathode side lead wire, 9 ... Holding Member mounting groove, 10 ... distribution groove, 11 ... projection for anode engagement, 12 ... anode, 13 ... spacer, 14 ... transparent conductive film, 20 ... image forming apparatus, 21 ... photoconductor, 22 ... developing roller, 23 ... scorotron, 24 ... Laser beam, 25 ... Anilox roller, 26 ... Regulator blade, 27 ... Supply roller, 28 ... Transfer paper, 29 ... Supply roller, 30 ... Transfer roller, 31 ... Heat fixing roller, 32 ... Cleaning elastic roller, 33 ... Cleaning blade

Claims (9)

A liquid developer using vegetable oil as a carrier liquid, wherein the colorant contains a benzimidazole pigment represented by Chemical Formula 1 and a positive charge control agent and is positively charged.

Here, R1: OCH ₃ , COOCH ₃ , COOC ₄ H ₉ (n), R2: NO ₂ , H, CONHC ₆ H ₅ , SO ₂ NHCH ₃ , and R: H, CH ₃ . Pigment Red 171 represented by the following Chemical Formula 2, Pigment Red 175 represented by the Chemical Formula 3, Pigment Red 176 represented by the Chemical Formula 4, and Pigment Red 208 represented by the Chemical Formula 5 The liquid developer according to claim 1, comprising an imidazole pigment.

3. The liquid developer according to claim 1, wherein the vegetable oil comprises at least one selected from safflower oil, sunflower oil, soybean oil, corn oil, cottonseed oil, rapeseed oil, and sesame oil. The liquid developer according to any one of claims 1 to 3, wherein the vegetable oil contains 60 mass% or more of an oleic acid composition in the fatty acid constituting the triglyceride. The liquid developer according to any one of claims 1 to 4, wherein the vegetable oil contains 50% by mass or more of the linoleic acid composition in the fatty acid constituting the triglyceride. The liquid developer according to claim 1, wherein the vegetable oil contains 50% by mass or more of a linolenic acid composition in the fatty acid constituting the triglyceride. The liquid developer according to any one of claims 1 to 6, wherein the primary particle size of the colored fine particles dispersed in the vegetable oil is at least 1 µm or less. The liquid developer according to claim 1, comprising an organic titanate compound which is a positive charge control agent. In a method for producing a liquid developer using vegetable oil as a carrier liquid, a magenta pigment represented by Chemical Formulas 1 to 5 is mixed with vegetable oil and a positive charge control agent and selected from a ball mill, a bead mill, a sand mill, and an attritor. A method for producing a liquid developer, wherein the liquid developer is dispersed by at least one dispersion mixing means.

However, in Chemical Formula 1, R1: OCH ₃ , COOCH ₃ , COOC ₄ H ₉ (n), R2: NO ₂ , H, CONHC ₆ H ₅ , SO ₂ NHCH ₃ , R: H, CH ₃ is there.

Images