JP2004302436A - Liquid developer and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make colored particles such as toner particles less liable to agglomerate mutually in a nonpolar insulating liquid used as a nonaqueous solvent, and to achieve high-speed electrophoresis of the colored particles by an electric field. <P>SOLUTION: A silicone group and a basic group of a one-end methacryloxy-modified silicone are present on surfaces of toner particles dispersed in a carrier liquid comprising dimethylsilicone. By the silicone group, mutual agglomeration of the toner particles is suppressed. The silicone group functions as an affinity group and imparts affinity for the carrier liquid to the toner particles. Thus, the toner particles can be uniformly dispersed in the carrier liquid. By the basic group present on the surfaces of the toner particles, a charge amount of the toner particles can be ensured. Colored particles such as the toner particles are made less liable to agglomerate mutually in a nonpolar insulating liquid used as a nonaqueous solvent, and high-speed electrophoresis of the colored particles by an electric field can be achieved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid developer that contains colored particles such as toner in a liquid and develops the latent image by attaching the colored particles to a latent image formed by an electrophotographic process or the like. The present invention also relates to an image forming apparatus such as a copying machine, a facsimile, and a printer that forms an image using the liquid developer.

  Conventionally, as this type of liquid developer, a liquid developer in which a toner is dispersed in an organic solvent containing an isoparaffinic hydrocarbon as a main component is known (for example, Patent Document 1). Examples of such an organic solvent include Isopar (trade name) manufactured by Exxon Corporation, Shellsol (trade name) manufactured by Shell Chemical Co., Ltd., and Soltol (trade name) manufactured by Philippe Oil Company. I have.

  On the other hand, various liquid developers in which colored particles are dispersed in a non-volatile liquid are also known. As a non-volatile liquid, a liquid using silicone oil is typical (for example, Patent Document 2).

  Further, as a liquid image forming apparatus that forms an image using a liquid developer, for example, one described in Patent Document 3 is known.

JP-A-5-045937 JP-A-12-206738 JP-A-2001-305887

  As in the case of the liquid developer described in Patent Literature 1, the conventional liquid using a highly volatile organic solvent containing a highly volatile isoparaffinic hydrocarbon as a main component has the following problems. That is, isoparaffinic hydrocarbons have high volatility and are very troublesome to handle.

  On the other hand, a liquid developer using a non-volatile liquid like the liquid developer described in Patent Document 2 does not generate a harmful volatile gas, so that the above-described problem can be solved. However, in this type of liquid developer, in a series of image forming processes including a developing process, a transfer process, and a fixing process, if the ratio between the colored particles and the liquid is not properly controlled for each process, image quality is likely to deteriorate. . For example, in the development step, colored particles are electrophoresed from a developer carrier carrying a liquid developer toward a latent image carrier carrying a latent image. If the amount is too small, the colored particles cannot be favorably electrophoresed. Similarly, the transfer step requires a liquid amount sufficient to cause the colored particles constituting the visible image to be sufficiently electrophoresed from the latent image carrier to a recording medium such as transfer paper. Nevertheless, while the colored particles electrophoresed in the previous development step adhere to the latent image, most of the liquid remains on the developer carrier and is separated from the visible image after development. In the transfer step, electrophoresis of the colored particles becomes more difficult. As described above, from the development step to the transfer step, it is necessary to control so as not to remove an excessive amount of liquid from the visible image. However, when heating and fixing a visible image transferred to a recording medium such as transfer paper, if an excessive amount of liquid is sucked into the recording medium, fixing of the visible image to the recording medium will be hindered. Will worsen the nature. Since a non-volatile liquid is used as the liquid, if the liquid is absorbed by the recording medium along with the transfer of the visible image, the deterioration of the fixing property cannot be avoided. In the transfer step, it is necessary to secure a sufficient amount of liquid to cause electrophoresis of a visible image and to suppress the amount of liquid so as not to hinder the subsequent fixing process.

  In view of the above, the applicant of the present invention disclosed in Patent Document 3 described above, prior to transferring a visible image obtained by development to a recording medium, a liquid image forming method for removing excess liquid from the visible image. The device was proposed. According to this liquid image forming apparatus, by removing excess liquid exceeding the amount required for transfer from a visible image containing a large amount of liquid enough to hinder the fixing process, good transferability can be obtained. , And the subsequent defective fixing can be suppressed.

  However, the inventors of the present invention have conducted intensive research and have found that even with this liquid image forming apparatus, fixation of a visible image may be hindered. Specifically, if there is unevenness in the dispersibility of the colored particles in the liquid developer, uneven development density is inevitably caused. This is because a portion where the toner density is high and a portion where the toner concentration is low occur in the liquid developer. Therefore, a liquid developer in which a toner as colored particles and a dispersant for accelerating dispersion of the toner were dispersed in silicone oil as a non-volatile liquid was experimentally manufactured. The dispersant adsorbs on the surface of the toner particles and suppresses the contact between the toner particles by its three-dimensional structure, so that each toner particle can be dispersed well in the liquid. The prototype liquid developer was set in the above-described liquid image forming apparatus, and an image was actually output. Then, while the development density unevenness could be effectively suppressed by good dispersion of the toner particles, the fixability was deteriorated. This is for the following reason. That is, when an excessive liquid component is removed from the visible image before the transfer, the dispersant is inevitably left in the visible image. Then, the fixing property was deteriorated by the dispersant itself and the liquid component absorbed therein.

  The present invention has been made in view of the above background, and an object of the present invention is to provide the following liquid developer. That is, a liquid developer capable of suppressing development density unevenness due to uneven dispersion of colored particles, transfer failure due to insufficient liquid amount, and fixing failure due to excessive liquid amount without deteriorating handling properties due to generation of volatile gas. It is.

  The present inventors have completed the present invention based on intensive studies as described below. That is, the present inventors at one time trial-produced a liquid developer using a dispersant having a charge of a polarity opposite to that of the toner. Then, when an image was actually output by this, surprisingly, excellent fixability was obtained despite the mixing of the dispersant. Instead, white spots were generated due to poor transfer. Part of the toner image was left on the intermediate transfer member of the transfer source during the transfer. This is because the amount of liquid was insufficient at the time of transfer and the toner could not be electrophoresed satisfactorily from the intermediate transfer member to the recording member (transfer paper). Almost no dispersant was present on the recording material or intermediate transfer material after the transfer step. Not only the liquid but also the dispersant was scarcely present during the transfer process. This is because during the developing process, the toner in the liquid developer is electrophoresed from the developer carrier (developing roller) side to the latent image carrier (photoconductor) side, while the dispersant having the opposite polarity to the toner is removed. This is because the particles were electrophoresed in the opposite direction and collected on the developer carrier.

  Next, the present inventors conducted a similar experiment by increasing the ratio of the dispersant in the liquid developer. As a result, it was possible to form a high-quality image in which neither fixing failure nor transfer failure occurred. Almost no liquid or dispersant was found on the recording medium after the transfer step. On the other hand, on the intermediate transfer member, a dispersant could be confirmed together with an appropriate amount of liquid. From this, it is possible to favorably electrophores the toner in the visible image by holding an appropriate amount of liquid in the gap formed between the dispersant and the toner particles remaining until the transfer step. It is considered possible. In addition, because the dispersant remaining until the transfer step attracted the surrounding liquid and electrophoresed in the opposite direction to the toner toward the intermediate transfer body, it was possible to suppress excessive liquid absorption to the recording body. Conceivable.

  As described above, it was found that the amount of the liquid in each step can be controlled well by using a dispersant having a charge opposite in polarity to the toner and appropriately adjusting the concentration in the liquid. As a result of further intensive studies, the present inventors have found that a good image can be formed by mixing a dispersant in a range of 0.05 to 20 parts by weight with respect to 1 part by weight of toner. If the mixing ratio of the dispersant is less than 0.05 parts by weight, the toner cannot be favorably electrophoresed during the transfer step, and white spots occur. On the other hand, when the amount exceeds 20 parts by weight, a large amount of dispersant or liquid is absorbed into the recording medium, thereby causing poor fixing.

In order to achieve the above object, the invention of claim 1 includes at least colored particles composed of a resin and a colored substance, and a liquid serving as a dispersion medium for the particles, and the latent image on the latent image carrier is In a liquid developer for attaching the colored particles to develop the latent image, as a dispersion accelerating substance for accelerating the dispersion of the colored particles in the liquid, one having a charge of a polarity opposite to that of the colored particles is added by 1 weight. Of the colored particles in the liquid in an amount of 0.05 to 20 parts by weight.
According to a second aspect of the present invention, in the liquid developer of the first aspect, a substance having a polar group having a polarity opposite to that of the colored particles on the surface is used as the dispersion promoting substance. .
The invention according to claim 3 is the liquid developer according to claim 2, wherein the dispersion promoting substance has at least one of a carboxyl group and a hydroxyl group as the polar group.
A fourth aspect of the present invention is the liquid developer according to the first, second or third aspect, wherein the dispersion-promoting substance having an average molecular weight of 1,000 or more is used.
According to a fifth aspect of the present invention, in the liquid developer according to the first, second, third, or fourth aspect, methyl methacrylate (acryl) or a compound containing the same as a main component is used as the dispersion promoting substance. It is assumed that.
According to a sixth aspect of the present invention, in the liquid developer of the fifth aspect, a graft copolymer is used as the compound.
According to a seventh aspect of the present invention, in the liquid developer according to the sixth aspect, a silicone oil is used as the liquid, and the graft copolymer contains silicone in a graft portion thereof. Things.
The invention of claim 8 is the liquid developer of claim 6 or 7, wherein the graft copolymer has an average molecular weight of 500 to 10,000.
According to a ninth aspect of the present invention, in the liquid developer according to the first, second, third, fourth, fifth, sixth, seventh, or eighth aspect, an aprotic liquid is used as the liquid. It is.
According to a tenth aspect, in the liquid developer according to the ninth aspect, the liquid has a viscosity of 10 to 1000 [mPa · s], an electric resistance of 1 × 10 ¹² [Ω · cm] or more, and a surface tension of the liquid. It is characterized by using a material having a boiling point of not more than 30 [dyne / cm] and not less than 100 [° C].
According to an eleventh aspect of the present invention, in the liquid developer according to the tenth aspect, a silicone-based liquid containing at least one of phenylmethylsiloxane, dimethylpolysiloxane, and polydimethylcyclosiloxane is used as the liquid. It is characterized by the following.
A twelfth aspect of the present invention is the liquid developer according to any of the first to eleventh aspects, wherein a granular material is used as the dispersion promoting substance.
A thirteenth aspect of the present invention is the liquid developer according to the twelfth aspect, wherein the dispersion promoting substance having an average particle diameter of 0.001 to 1 [μm] is used.
According to a fourteenth aspect of the present invention, in the liquid developer according to any one of the first to thirteenth aspects, the colored particles have a volume average particle diameter of 0.1 to 6.0 [μm]. The particle concentration is 5 to 40% by weight.
The invention according to claim 15 is the liquid developer according to claim 1, wherein the colored particles are provided on the surface with the dispersion promoting substance, a basic group, and an affinity group that imparts affinity to the liquid. It is characterized by using a thing.
According to a sixteenth aspect of the present invention, in the liquid developer according to the first aspect, the color particles include, on the surface thereof, the dispersion promoting substance, an acidic group, and an affinity group that imparts affinity to the liquid. Is used.
The invention according to claim 17 is the liquid developer according to claim 15 or 16, wherein a charge controlling agent having compatibility with the liquid and having an acidic group is contained in the liquid together with the colored particles. It is characterized by containing.
The invention according to claim 18 is the liquid developer according to claim 15 or 16, wherein the charge control agent having compatibility with the liquid and having a basic group is combined with the colored particles in the liquid developer. It is characterized by containing.
According to a nineteenth aspect of the present invention, in the liquid developer according to the fifteenth or sixteenth aspect, a charge control agent having a compatibility with the liquid and having a metal is contained in the liquid together with the colored particles. It is characterized by having done.
According to a twentieth aspect of the present invention, there is provided a developing device for developing a latent image by contacting a latent image carrier with a liquid developer on the surface of the latent image carrier and attaching colored particles to the latent image on the surface. An image forming apparatus for forming an image by finally transferring a toner image obtained by attaching the colored particles to a latent image on the surface of the latent image carrier by the developing unit onto a recording material, A liquid developer according to any one of claims 1 to 19 is used as the liquid developer.

In these inventions, by using a non-volatile liquid as the liquid, it is possible to eliminate a situation in which handling properties are deteriorated due to generation of volatile gas.
Further, by making the dispersibility of the colored particles in the liquid uniform by the dispersion promoting substance, it is possible to suppress unevenness in development density due to the non-uniform dispersion of the colored particles.
Further, by mixing 0.05 to 20 parts by weight of a dispersion promoting substance having a charge of a polarity opposite to that of the colored particles with respect to 1 part by weight of the colored particles, an appropriate amount of liquid can be added to the visible image in the transfer step. It is possible to perform appropriate liquid amount control such that an excessive amount of liquid is not left in a visible image in a fixing process while leaving. As a result, it is possible to suppress both a transfer failure due to an insufficient liquid amount and a fixing failure due to an excessive liquid amount. Therefore, without deteriorating handling properties due to generation of volatile gas, it is possible to suppress development density unevenness due to uneven dispersion of colored particles, transfer failure due to insufficient liquid amount, and fixing failure due to excessive liquid amount. effective.

Hereinafter, an embodiment of a liquid developer to which the present invention is applied will be described.
The liquid developer is obtained by dispersing, in a non-volatile liquid, toner particles, which are colored particles composed of at least a resin and a colored substance, and a dispersion accelerating substance for accelerating the dispersion in the liquid. The dispersion ratio between the toner and the dispersion promoting substance is set to 0.05 to 10 parts by weight of the dispersion promoting substance per 1 part by weight of the toner.

The present inventors prototyped seven types of liquid developers in which silicone oil was used as the non-volatile liquid and the mixing ratio between the toner and the dispersion promoting substance was adjusted as follows.
(1) Developer A: dispersion medium 9, toner solid content 1, dispersion promoting substance 0
(2) Developer B: dispersion medium 9, toner solid content 1, dispersion promoting substance 0.05
(3) Developer C: dispersion medium 9, toner solid content 1, dispersion promoting substance 0.1
(4) Developer D: dispersion medium 9, toner solid content 1, dispersion promoting substance 0.3
(5) Developer E: dispersion medium 9, toner solid content 1, dispersion promoting substance 1
(6) Developer F: dispersion medium 9, toner solid content 1, dispersion promoting substance 10
(7) Developer G: dispersion medium 9, toner solid content 1, dispersion promoting substance 20

  Then, an image was actually output using these liquid developers. The printer shown in FIG. 1 was used for image output. In FIG. 1, a printer as a liquid type image forming apparatus includes a charging device 2, a developing device 10, an intermediate transfer drum 3, a static eliminator 4, a photoconductor cleaning device around a drum-shaped photoconductor 1 serving as a latent image carrier. 5 and the like. Further, a transfer roller 6 that rotates while abutting on the intermediate transfer drum 3 and an exposure device disposed in a region (not shown) are also provided.

  The photoreceptor 1 has a surface formed of amorphous silicon (a-Si), and is driven to rotate clockwise in the figure at a constant speed by a driving unit (not shown) during printing. Then, it is uniformly charged to, for example, 600 [V] in the dark by corona discharge from the charger 2. The exposure apparatus includes a scanning optical system, and performs a scanning process using LED light or laser light based on image information to expose the uniformly charged surface of the photoreceptor 1. The exposed portion of the photoreceptor 1 has an attenuated potential and becomes an electrostatic latent image of, for example, 50 [V] or less. This electrostatic latent image is developed into a toner image as a visible image by a developing device 10 using a liquid developer. Note that an organic photoconductor (OPC) may be used as the photoconductor 1. In addition, as the charger 2, a device that applies a predetermined charging bias to a charging member such as a charging roller brought into contact with the photoreceptor 1, in addition to a device that realizes charging by corona discharge as illustrated, may be used. it can. Instead of forming an electrostatic latent image by exposure, a latent image may be formed by a dielectric serving as a latent image carrier and an ion flow device serving as a latent image forming unit.

  The intermediate transfer drum 3 is rotated counterclockwise in the drawing so that the surface thereof is moved in the forward direction with the photoconductor by the nip while forming a primary transfer nip by contacting the photoconductor. In the primary transfer nip, a primary transfer electric field is formed by a potential difference between the electrostatic latent image on the photoconductor 1 and the intermediate transfer drum 3. The toner image that has entered the primary intermediate transfer nip with the rotation of the photoconductor 1 is electrostatically primary-transferred onto the intermediate transfer drum 3 under the action of the primary transfer electric field and the nip pressure. Note that, instead of the intermediate transfer drum 3 shown in the figure, an intermediate transfer belt that moves endlessly while being stretched by a plurality of rollers may be used as the intermediate transfer body.

  The transfer roller 6 is rotated clockwise in the drawing so that the surface of the transfer roller 6 is moved in the forward direction with the intermediate transfer drum 3 by the nip while forming a secondary transfer nip by contacting the intermediate transfer drum 3. A secondary transfer bias is applied by a power supply (not shown). By this application, a secondary transfer electric field is formed in the secondary transfer nip. On the other hand, a feeding unit (not shown) feeds the transfer paper P, which is a recording medium, toward the secondary transfer nip at a timing that can be synchronized with the toner image on the intermediate transfer drum 3. The toner image on the intermediate transfer drum 3 brought into close contact with the transfer paper P at the secondary transfer nip is secondarily transferred onto the transfer paper P under the influence of the secondary transfer electric field and the nip pressure. Then, the sheet P is transported together with the transfer sheet P to a fixing unit (not shown), where it is heated and fixed on the transfer sheet P.

  After the residual charge is removed from the surface of the photoconductor 1 that has passed through the primary transfer nip by the static eliminator 4, the transfer residual liquid developer adhering to the surface is cleaned by the photoconductor cleaning device 5. By this cleaning, the surface of the photoconductor 1 is initialized, and is prepared for the next image formation.

  The developing device 10 includes a developing unit 11 and a collecting unit 20. The developing unit 11 stores a liquid developer in a tank 12. The liquid developer is not a low-viscosity, low-concentration liquid developer that has been widely used, but a high-viscosity, high-concentration liquid developer. Here, the low-viscosity, low-concentration liquid developer contains, for example, a toner at a concentration of about 1 [wt%] in an insulating liquid carrier called Isopar (registered trademark) widely available on the market. It has a viscosity of about 1 [cSt]. On the other hand, a high-viscosity, high-concentration liquid developer contains a high concentration of toner in a non-volatile liquid carrier such as silicone oil, normal paraffin, vegetable oil, or mineral oil. Specifically, the toner contains about 5 to 40 wt% and has a viscosity of about 10 to 5000 mPa · s.

  In the tank 12, the two stirring screws 13 and 14 are arranged in parallel with each other so as to be immersed in the liquid developer, and are rotated in opposite directions by driving means (not shown) as shown by arrows in the drawing. I'm sullen. When the developing device 10 enters the developing operation, the two stirring screws 13 and 14 rotate in the opposite directions as described above, and the liquid developer in the tank 12 is stirred. Due to this stirring, the liquid surface of the liquid developer rises between the two stirring screws 13 and 14 and adheres to the anilox roller 15 disposed above the screw.

  The anilox roller 15 of the developing unit 11 draws up the liquid developer in the tank 12 while being rotationally driven by a driving unit (not shown). A spiral groove line pattern (not shown) is engraved on the peripheral surface of the anilox roller 15 with a fineness of, for example, 100 to 200 [lpi]. In this groove line pattern, a plurality of minute concave portions are formed so as to be arranged in a line direction. Part of the liquid developer pumped up by the anilox roller 15 is accommodated in these minute concave portions.

  A doctor blade 16 made of a metal material such as stainless steel is in contact with the surface of the anilox roller 15, and regulates the amount of the liquid developer pumped up by the anilox roller 15. Due to this regulation, the amount of the liquid developer carried on the anilox roller 15 is accurately measured to a value corresponding to the capacity of the minute concave portion.

  In the developing device 10, a developing roller 17 as a developer carrier is disposed above the anilox roller 15 in the drawing so as to rotate while contacting the anilox roller 15. At the contact portion, the liquid developer on the surface of the anilox roller 15 is applied with a uniform thickness. The developing roller 17 is provided with a conductive elastic layer made of conductive urethane rubber or the like on the peripheral surface thereof. The developing roller 17 rotates at a constant speed and contacts the photosensitive member 1 to form a developing nip. Further, a developing bias is applied from a developing bias power supply circuit (not shown). The developing bias is set to a value (for example, 500 V) having the same positive polarity as the charging polarity of the toner and smaller than the uniform charging potential of the photoconductor 1. At the developing nip, the developing roller 17, the background portion (non-exposed portion) of the photoreceptor 1, and the electrostatic latent image have the same potential as the toner. In addition, the value decreases in the order of the background portion, the developing roller 17, and the electrostatic latent image (600V, 500V, 50V). For this reason, a non-development potential acts such that the toner is electrostatically moved toward the development roller 17 having a smaller potential (600 V → 500 V) between the background portion and the development roller 17. Further, between the developing roller 17 and the electrostatic latent image, a developing potential acts to move the toner toward the electrostatic latent image having a lower potential (50V ← 500V). Therefore, in the developing nip, the toner in the thin developer layer electrophoreses and aggregates between the developing roller 17 and the background portion toward the surface of the developing roller 17. On the other hand, between the developing roller 17 and the electrostatic latent image, the toner is electrophoretically attached to the electrostatic latent image. Then, the adhesion causes the electrostatic latent image to be developed into a toner image.

  The liquid developer adhering to the developing roller 17 after passing through the developing nip is collected by the collecting roller 18 rotating while being in contact with the developing roller, and then sent to the collecting unit 20 by the transport screw 19.

  The collection unit 20 includes a collection tank 21, a stirring propeller 22, a return pump 23, and the like. Further, it also has a density adjusting means (not shown). The recovered developer sent from the transport screw 19 is stored in a recovery tank 21. The liquid developer cleaned from the photoconductor 1 by the photoconductor cleaning device 5 is also stored in the recovery tank 21. While being agitated by the agitation propeller 22, these developers are subjected to toner replenishment and liquid replenishment by the density adjusting means, and the toner density is returned to the initial value. Then, the developer is returned to the tank 12 of the developing unit 11 by the return pump 23 and is reused for development.

Images were output to the printer having the above configuration while individually setting the above seven types of liquid developers. This output was performed under the following conditions.
-Toner concentration in liquid developer: 20 [%]
・ Average charge amount of toner in liquid developer: 100 [μC / g]
A process linear velocity, which is the peripheral velocity of the photosensitive member 1 and the like: 300 [mm / sec]
・ Length of the developing nip in the circumferential direction of the roller: 3 [mm]
・ Developing time: 10 [msec]
・ Thickness of developer thin layer in development nip: 10 [μm]
-Length of the primary transfer nip in the circumferential direction of the drum: 9 [mm]
・ Intensity of primary transfer electric field (between latent image and intermediate transfer drum): -300 [V]
・ Primary transfer time: 30 [msec]
-Length of the secondary transfer nip in the circumferential direction of the drum: 6 [mm]
・ Secondary transfer time: 20 [msec]
・ Heating temperature by fixing means: 120 [° C]

  FIG. 2 is a graph showing “the ratio of the dispersion promoting substance to the toner” created based on the result of this experiment and the transferability of the toner image. The transferability was evaluated as follows. That is, the primary transfer rate is calculated using the image density on the intermediate transfer body after the primary transfer as a denominator and the difference between the image density before the primary transfer and the image density after the primary transfer as a numerator. The secondary transfer rate can be determined in the same manner. When the intermediate transfer member is not used, the difference between the image density before and after the transfer can be determined using the image density on the photosensitive member as the denominator. In the figure, when the toner concentration is 30% or less, the developer A exhibits a transfer rate of about 90% (to transfer paper) and forms a good image with few image defects. Then, as the toner density increases, the transfer rate decreases. In the drawing, if the transfer rate is 50% or more, it is within the allowable range. When the toner concentration reaches 70%, the transfer rate falls below an allowable range, and secondary transfer failure occurs. At this time, the transfer rate of the developer D was good. From this, it can be seen that the transferability can be secured even when the toner concentration is high by physically setting the dispersion distance of the toner fine particles by the dispersant. It is believed that the ratio of dispersion promoting substance to 1 part by weight should be at least 0.05 parts by weight or more. Therefore, in the liquid developer according to the present embodiment, 0.05 to 20 parts by weight of the dispersion promoting substance is mixed with 1 part by weight of the toner.

  FIGS. 3A and 3B are schematic diagrams illustrating a dispersion state of toner particles and a dispersion accelerating substance in the liquid developer according to the present embodiment. As shown in FIG. 3A, in the liquid developer before the development process and the transfer process, that is, in the liquid developer in which the electric field for development and transfer is not acting, the charge is positively charged. A plurality of negatively charged dispersion promoting substances D are adsorbed on the surface of the toner particles T. The dispersion promoting substance D that could not be adsorbed is uniformly dispersed in the insulating silicone oil. Between the toner particles, the dispersion-promoting substance D adsorbed on each particle and the dispersion-promoting substance D dispersed in the silicone oil are sterically interposed. It is evenly dispersed. On the other hand, in the liquid developer placed in the electric field in the developing step or the transferring step, the toner particles T are electrophoresed (downward in the illustrated example) toward the electrostatic latent image or the transfer destination, while the toner particles T are dispersed. The accelerating substance D electrophoreses toward the developing roller and the transfer source. Accordingly, the distribution of the toner particles T is biased toward the latent image side and the transfer destination side, and the distribution of the dispersion promoting substance is biased toward the developing roller side and the transfer source side. However, not all the toner particles T and the dispersion promoting substance D electrophores in each direction. This is because, due to collisions between the electrophoreses in the opposite directions, the ones that cannot be completely electrophoresed appear. Therefore, in the electrostatic latent image or the liquid at the transfer destination, a small amount of the dispersion promoting substance D remains in the large amount of toner particles T. When the dispersion-promoting substance D is left in this way, a gap that can hold the silicone oil between the toner particles is secured, and in the subsequent transfer step, the toner particles T are dispersed in the silicone oil held in the gap. Good electrophoresis.

  In the liquid developer according to the embodiment, it is desirable to use, as the dispersion accelerating substance, a substance having a polarity opposite to that of the toner due to a polar group. This is because the charge of the polar group is retained on the surface of the dispersion accelerating substance, and the electric charge allows the dispersion accelerating substance to be satisfactorily adsorbed on the surface of the toner particles, so that the toner particles can be more reliably dispersed. Examples of the polar group include an acidic group, a basic group, and a hydroxyl group, and an acidic group or a hydroxyl group capable of finely dispersing the toner or accelerating a crosslinking reaction is preferable. As in the present embodiment, when a positively charged toner is used, a material having an acidic group such as a carboxyl group, a sulfonic acid group, and a phosphonic acid group having a negative charge is used as the dispersion promoting substance. Good. Further, considering that the toner particles are hardly aggregated and the reaction speed of the crosslinking reaction, it is preferable to use a carboxyl group having a weak acid strength. The basic group is not particularly limited, and examples thereof include primary to quaternary amino groups. In addition, you may use the thing of amphoteric which has both an acidic group and a basic group.

Further, in the liquid developer to which the present invention is applied, the liquid in which the toner particles are dispersed has a high flash point thermally and has electrical insulation. In the insulating liquid, toner particles containing a pigment component are dispersed. Further, the resin as the dispersion promoting substance, the insulating liquid, the toner particles, and the charge control agent may be uniformly dispersed by dispersing an appropriate amount thereof. Here, in the case of toner particles using a conductive substance having a low electric resistance value such as carbon black as a pigment component, the conductive particles exist on the outer periphery. For this reason, when the toner particles aggregate, a current flows between the toner particles, and it becomes difficult to control the behavior by the electric field. The difficulty in controlling the behavior due to the aggregation increases as the toner concentration increases. If a volatile liquid is used as the insulating liquid, the carrier liquid evaporates during the process, so that the toner concentration is high in the developing region and the transfer region where the behavior of the toner particles is controlled by an electric field. Become. Therefore, in this case, it becomes more difficult to control the behavior of the toner particles by the developing electric field and the transfer electric field. Further, even when a non-volatile insulating liquid is used, the behavior of the toner particles is difficult to control because the toner concentration at the destination after the toner particles are moved by the electric field becomes high. In addition, in order to meet the demand for higher image forming speeds, it is necessary to minimize the amount of the carrier liquid, so that even if the carrier liquid is non-volatile, the toner concentration will increase as a result. However, it is difficult to control the behavior of the toner particles.
In addition, when the toner concentration is increased, the ratio of the carrier liquid to the toner particles decreases, so that the insulating liquid that has served as an insulating film on the outer periphery of the toner particles cannot be sufficiently interposed between the toner particles. As a result, the insulating properties of the toner particles cannot be maintained, and when a reverse bias is applied during the primary transfer or the secondary transfer, charges of the opposite polarity are injected into the toner particles, and the polarity of the toner particles is inverted. Would. Such a polarity reversal of the toner particles is also one of the causes that the behavior of the toner particles cannot be controlled by the transfer electric field.
As described above, the liquid developer increases the toner concentration during the image forming process and makes it difficult to secure the insulating properties of the toner particles. It is important that the insulating liquid can be interposed.

  It is desirable to use a substance having an acid value of 5 to 200 [KOH mg / g] as a dispersion accelerating substance that is capable of self-dispersion (it disperses itself in a liquid depending on its chemical properties). When the acid value is less than 5 [KOH mg / g], it is difficult to make the toner adsorb well and the electrophoresis cannot be performed well due to the small charge. . If the acid value exceeds 20 [KOHmg / g], self-dispersion becomes difficult due to the strength of the acid.

  It is desirable to use a substance having an average molecular weight of 1,000 or more as the dispersion promoting substance. This is because the toner can be finely dispersed.

  The material of the dispersion accelerating substance to be self-dispersed is not particularly limited, and examples thereof include acrylic, polyester, polyurethane, epoxy, and amino polymer compounds. One of these may be used alone, or two or more of them may be used in combination. Above all, it is desirable to use methyl methacrylate (acryl) or an acrylic polymer compound containing this as a main component. This is because even if the acrylic monomer / polymer is polymerized, it does not form a lump but can be dispersed in a fine state, and the introduction of a polar group (carboxyl group or hydroxyl group) is relatively easy. Further, it is desirable to use a graft copolymer as the acrylic polymer compound. The part that adsorbs to the toner and the part that is compatible with non-volatile liquid such as silicone oil have a structure that is chemically branched. This is because they exhibit reliable dispersion performance. The graft portion of the graft polymer preferably has a molecular weight of 500 to 10,000. This is because good affinity with the non-volatile liquid can be exhibited, and good dispersion performance can be exhibited. Examples of the type of the graft portion include polyether, polyester, styryl, (meth) acrylate, and silicone. Among them, silicone is preferred. This is because when silicone oil is used as the non-volatile liquid, the silicone in the graft portion and the silicone oil can be made to have a good affinity and the dispersion performance thereof can be brought out well.

  The method for producing the acrylic polymer compound is not particularly limited.For example, a monomer having a polar group and another monomer that can be polymerized therewith are reacted in a non-reactive solvent in the presence or absence of a catalyst. And the method of obtaining it. Among them, a method in which a monomer having a polar group and a silicone-based macromonomer are polymerized as essential components is preferable. Alternatively, a method in which an acrylic polymer having a reactive group is synthesized and then reacted with a reactive silicone to perform grafting may be used.

  Among the polar group-containing acrylic monomers, examples of the monomer having an acidic group as a polar group include a monomer having a carboxyl group. Acrylic acid, methacrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, fumaric acid, acroyloxyethyl phthalate, acroyloxysuccinate and the like. Further, for example, a monomer having a phosphonic acid group may also be used. Monomers having a sulfonic acid group, such as ethyl acrylate 2-ethyl sulfonic acid, ethyl methacrylate 2-ethyl sulfonic acid, butyl acrylamide sulfonic acid, etc., ethyl methacrylate 2-ethyl phosphonate, and ethyl acrylate 2-ethyl phosphonate. Further, for example, a monomer having a hydroxyl group may also be used. 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate and the like. Among them, monomers having a carboxyl group or a hydroxyl group are preferred.

  On the other hand, examples of the acrylic monomer having a basic group include a monomer having a primary amino group. Acrylamide, aminoethyl acrylate, aminopropyl acrylate, methacrylamide, aminoethyl methacrylate, aminopropyl methacrylate and the like. Further, for example, a monomer having a secondary amino group may also be used. Methylaminoethyl acrylate, methylaminopropyl acrylate, ethylaminoethyl acrylate, ethylaminopropyl acrylate, methylaminoethyl methacrylate, methylaminopropyl methacrylate, ethylaminoethyl methacrylate, ethylaminopropyl methacrylate, etc. . Further, for example, a monomer having a tertiary amino group may also be used. Examples thereof include dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminopropyl acrylate, diethylaminopropyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminopropyl methacrylate, and diethylaminopropyl methacrylate. Further, for example, a monomer having a quaternary amino group may also be used. Dimethylaminoethyl methyl acrylate acrylate, dimethylaminoethyl methyl methacrylate, dimethylaminoethyl benzyl acrylate, dimethylaminoethyl benzyl methacrylate, and the like.

  Examples of the macromonomer for introducing the graft portion include a polyether-based macromonomer in which an alkylene oxide is added to hydroxyalkylene monomethacrylate by using a cationic catalyst. Further, for example, an ester macromer obtained by polyesterifying a polybasic acid and a polyhydric alcohol and then esterifying with glycidyl methacrylate may be used. Further, for example, a styryl-based macromonomer obtained by anionic polymerization of styrene and treating the living terminal thereof with an appropriate terminator may be used. Further, for example, a silicone-based macromonomer obtained by introducing methacrylate at the terminal after methoxylation using water glass as a starting material may be used. Further, a macromonomer obtained by another method may be used.

  Among the monomers listed so far, silicone-based macromonomers are most preferred from the viewpoint of affinity for nonpolar liquids. Examples of the macromonomer include a macromer in which dimethylsiloxane is bonded to a known general methacryl group directly or via an alkyl group. Examples include FM0721 manufactured by Chisso Corporation and AK-5, AK-30, AK-32 manufactured by Toagosei Co., Ltd.

  Other monomers that can be polymerized to the monomers listed so far include, for example, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-propyl acrylate, n-butyl acrylate, t-butyl acrylate, Benzyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, tridecyl methacrylate, benzyl methacrylate, acrylic 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, octyl acrylate, octyl methacrylate, lauryl acrylate, lauryl methacrylate, cetyl acrylate, cetyl methacrylate, stearyl acrylate, stearyl methacrylate (Meth) acrylates such as behenyl acrylate and behenyl methacrylate; styrene monomers such as styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene and p-tert-butylstyrene No. Also, for example, itaconic acid esters such as benzyl itaconate may be used. Further, for example, a maleic ester such as dimethyl maleate may be used. Further, for example, fumarate esters such as dimethyl fumarate may be used. Further, for example, acrylonitrile, methacrylonitrile, vinyl acetate and the like may be used. Further, for example, hydroxyl group-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate may be used. In addition, for example, amino group-containing monomers such as ethylethyl acrylate, aminopropyl acrylate, methacrylamide, aminoethyl methacrylate, aminopropyl methacrylate, dimethylaminoethyl acrylate, and dimethylaminoethyl methacrylate may be used. Further, for example, an α-olefin such as ethylene may be used.

  Examples of the catalyst used in the production process include a polymerization initiator. For example, peroxides such as t-butylperoxybenzoate, di-t-butyl peroxide, cumene peroxide, acetyl peroxide, benzoyl peroxide, lauroyl peroxide and the like. Further, for example, azo compounds such as azobisisobutylnitrile, azobis-2,4-dimethylvaleronitrile, and azobiscyclohexanecarbonitrile may be used.

  Examples of the non-reactive solvent include aliphatic hydrocarbon solvents such as hexane and mineral spirits. Further, for example, aromatic hydrocarbon solvents such as benzene, toluene and xylene may be used. Further, for example, an ester solvent such as butyl acetate may be used. Further, for example, alcohol solvents such as methanol and butanol may be used. Further, for example, a ketone solvent such as methyl ethyl ketone and isobutyl methyl ketone may be used. Further, for example, aprotic polar solvents such as dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone and pyridine may be used. The agents listed above may be mixed and used.

  Examples of the reaction method include known reactions such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, and redox polymerization. Among them, simple solution polymerization of the reaction system is preferable. The reaction conditions for solution polymerization vary depending on the type of polymerization initiator and solvent, but the reaction temperature is preferably 180 ° C. or lower (more preferably 30 to 150 ° C.). The reaction time is preferably 30 minutes to 40 hours (more preferably 2 hours to 30 hours).

  The method of crosslinking is not particularly limited, and examples thereof include an ester bond, an amino bond, a urethane bond, an ether bond, and a C-C bond by a radical reaction. Among them, an ester bond or an amino bond is particularly preferable from the viewpoint of the reaction rate, the reaction time, and the stability during dispersion of the toner.

  Examples of a method of crosslinking a self-dispersing dispersion promoting substance include a method using a crosslinking agent and a method of introducing a crosslinking functional group into the dispersion promoting substance. Since the acrylic polymer has only one functional group, a crosslinking agent may be required. Any crosslinking agent may be used as long as it reacts with a polar group in the polymer compound. For example, amino resins such as melamine resin, benzoguanamine resin, urea resin and the like can be exemplified. Further, for example, isocyanate resins such as tolylene diisocyanate prepolymer, polyfunctional aromatic polyisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate prepolymer, xylene diisocyanate prepolymer and lysine isocyanate prepolymer. Good. Also, for example, an epoxy resin such as bisphenol A or an acrylic resin having a glycidyl group may be used. Further, for example, a chelate compound such as Ti, Al, and Zr may be used. From the viewpoint of the reaction rate and the reaction temperature, among these, amino resins and epoxy resins are particularly preferable.

  Examples of the functional group for crosslinking to be introduced into the dispersion promoting substance include an amino group, a hydroxyl group, a methoxy group, a glycidyl group and the like. From the viewpoint of reaction rate and reaction temperature, a hydroxyl group and a glycidyl group are particularly preferable. A known method can be used as a method for introducing a functional group for crosslinking. For example, a method of polymerizing or condensing a polymer compound having a functional group for crosslinking, polyhydric alcohol, hydroxyamine, polyamine, or the like at the time of synthesizing a polymer compound having an acidic group. Further, for example, a method of synthesizing a prepolymer of a polymer compound having an acidic group and then introducing a crosslinking functional group by polymerization, condensation or addition reaction may be used. It goes without saying that the dispersion accelerating substance into which the functional group for crosslinking is introduced is self-dispersed.

  Examples of the monomer having a cross-linking functional group used for synthesizing a self-dispersible dispersion accelerating substance include a hydroxyl group-containing monomer. 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, glycerol monomethacrylate, polyethylene glycol monomethacrylate, propylene glycol monomethacrylate, polyethylene glycol monoacrylate, propylene glycol monoacrylate, etc. is there. Further, for example, glycidyl group-containing monomers such as glycidyl acrylate and glycidyl methacrylate; and methoxy group-containing monomers such as methoxy polyethylene glycol acrylate and methoxy polyethylene glycol methacrylate may be used. Also, for example, amino group-containing monomers such as acrylamide and methacrylamide may be used. Among them, a glycidyl group-containing monomer is preferable because a hydroxyl group is generated after the reaction to improve the charge.

  A compound having a cross-linking functional group for introducing by polymerization, condensation or addition reaction by a method of introducing a cross-linking functional group by polymerization, condensation or addition reaction after synthesizing a prepolymer of a self-dispersible dispersion promoting substance. Has only to have two or more reactive groups. For example, polyhydric alcohol, polyamine, hydroxyamine, bisphenol A, polyisocyanate and the like can be mentioned.

  An example of a method for synthesizing a basic group-containing charge control agent is, for example, as follows. That is, 180 parts by weight of dimethyl silicone, 1 part by weight of dimethylaminomethyl methacrylate, 19 parts by weight of methacryloxy-modified silicone at one end, and 1 part by weight of azobisisobutyronitrile were placed in a reaction vessel equipped with a thermometer and a nitrogen inlet tube. The mixture is stirred and mixed under a nitrogen stream, and further reacted at 85 [° C.] for 3 hours while stirring at 90 [° C.] for 2 hours to obtain a basic group charge controlling agent.

  An example of a method for synthesizing an acidic group-containing charge control agent is, for example, as follows. That is, 180 parts by weight of dimethyl silicone, 1 part by weight of methacrylic acid, 19 parts by weight of methacryloxy-modified silicone at one end, and 1 part by weight of azobisisobutyronitrile were placed in a reaction vessel equipped with a thermometer and a nitrogen inlet tube. In addition, the mixture is stirred and mixed, and further reacted at 85 ° C. for 3 hours while stirring under a nitrogen stream, and subsequently reacted at 90 ° C. for 2 hours to obtain an acidic group charge control agent. Other charge controlling agents include, for example, metal salts of dialkyl sulfosuccinates such as cobalt dialkyl sulfosuccinate, manganese dialkyl sulfosuccinate, zirconium dialkyl sulfosuccinate, yttrium dialkyl sulfosuccinate, nickel dialkyl sulfosuccinate; manganese naphthenate, calcium naphthenate , Zirconium naphthenate, cobalt naphthenate, iron naphthenate, lead naphthenate, nickel naphthenate, chromium naphthenate, zinc naphthenate, magnesium naphthenate, manganese octylate, calcium octylate, zirconium octylate, iron octylate, octylate Lead acid, cobalt octylate, chromium octylate, zinc octylate, magnesium octylate, manganese dodecylate, calcium dodecylate, dodecylate Metal soaps such as ruconium, iron dodecylate, lead dodecylate, cobalt dodecylate, chromium dodecylate, zinc dodecylate and magnesium dodecylate; alkylbenzenes such as calcium dodecylbenzenesulfonate, sodium dodecylbenzenesulfonate and barium dodecylbenzenesulfonate Metal salts of sulfonic acid; phospholipids such as lecithin and seharin; and organic amines such as n-decylamine can be used. The charge control agent may be added in the minimum amount that exhibits the charge control effect. Usually, the charge control agent is added to the liquid developer at a ratio of 0.01 to 50% by weight. The charge control agent exhibits a charge control effect when added at any stage after the formulation process described below or after the solvent is removed. However, granulation is preferably performed in the presence of the charge control agent. For example, in the prescription process described below, a pre-formulation process is performed by adding it to another substance, a solvent or an intermediate product at a stage prior to the prescription process, and a resin solution or varnish and an electrically insulating dispersion medium are mixed with the colored particles and the charge control. Mix in the presence of the agent.

  In the present embodiment, the charge control agent may be used to control the charge amount and / or the charge polarity of the toner particles. As described above, in a non-equilibrium state of the insulating liquid (carrier liquid), a polarity bias occurs and the charge amount of the toner particles increases, so that the toner charge amount in the carrier liquid is assisted. To do this, a charge control agent is added.

  When a liquid developer is prepared, toner particles composed of the above-described components may be mixed and dispersed in a nonpolar nonaqueous solvent. In this case, a ball mill, a sand mill, an attritor, or the like may be used as the dispersing means. The mixing order is not particularly limited. Further, the control of the charge by the charge control agent can appropriately control the amount of addition even in response to environmental fluctuations, and the stability is improved.

  Examples of the colored substance to be contained in the toner include an inorganic pigment, an organic pigment, a dye, a filler, a medicine, a polymerization initiator, a catalyst, and an ultraviolet absorber.

  Examples of the inorganic pigment include carbon black, titanium oxide, zinc oxide, zinc oxide, tripon, iron oxide, aluminum oxide, silicon dioxide, kaolinite, montmorillonite, talc, barium sulfate, calcium carbonate, and the like. Further, for example, silica, alumina, cadmium red, red iron oxide, molybdenum red, chromium vermillion, molybdate orange, graphite, chrome yellow, cadmium yellow, yellow iron oxide, titanium yellow, chromium oxide and the like may be used. Further, for example, pyridian, cobalt green, titanium cobalt green, cobalt chrome green, ultramarine blue, ultramarine blue, navy blue, cobalt blue, cerulean blue, manganese violet, cobalt violet, mica and the like may be used.

  Examples of organic pigments include, for example, azo, azomethine, polyazo, phthalocyanine, quinacridone, anthraquinone, indigo, thioindigo, quinophthalone, benzimidazolone, isoindoline, and isoindolinone pigments. Is mentioned. These pigments can be used alone or in combination of two or more as necessary. The content of the pigment in the toner particles of the exemplary embodiment is preferably 2 to 20 parts by weight, more preferably 3 to 15 parts by weight, based on 100 parts by weight of the resin component (polymer). The pigment may be surface modified. Conventionally known pigment surface modifiers can be used. For example, a silane coupling agent, a titanium coupling agent, an aluminum coupling agent, or the like can be used. Examples of the silane coupling agent include alkoxysilanes such as methyltrimethoxysilane, finyltrimethoxysilane, methylfinyldimethoxysilane, and diphanyldimethoxysilane, siloxanes such as hexamethyldisiloxane, γ-chloropropyltrimethoxysilane, and vinyltrimethoxysilane. Chlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-ureido Propyltriethoxysilane and the like. The addition amount of these surface modifiers is preferably from 0.01 to 20% by weight, more preferably from 0.1 to 5% by weight, based on the pigment. Examples of the method for modifying the surface of the pigment fine particles include a method in which a surface modifier is added to a dispersion of the pigment fine particles, and the dispersion is heated and reacted. The surface-modified pigment fine particles are collected by filtration, and are subjected to drying treatment after repeated washing and filtration with the same solvent. Even when a substance that can be chemically bonded by grafting or the like, such as carbon black or a metal oxide, is used, it can be synthesized in the same manner as described above.

  Examples of the dye include azo, anthraquinone, indigo, phthalocyanine, carbonyl, quinone imine, methine, quinoline, and nitro dyes. Among them, disperse dyes are particularly preferred.

It is desirable to use an aprotic liquid as the non-volatile liquid. An aprotic substance is an inert liquid that does not show acidity or basicity, and although it conducts electricity by dispersion of a conductive substance, it itself becomes an ionic substance when dispersed in a solvent. Reduces electrical resistance. Therefore, it is possible to maintain an electric resistance that does not hinder the electrophoresis of the toner under an electric field. Furthermore, the aprotic liquid has a viscosity of 10 to 1000 [mPa · s], an electric resistance of 1 × 10 ¹² [Ω · cm] or more, a surface tension of 30 [dyne / cm] or less, and a boiling point of It is desirable to use a material having a temperature of 100 ° C. or more. According to the experiments of the present inventors, if a material having a viscosity of 1000 [mPa · s] or less is used, it is absorbed into the paper fiber of the recording medium, and dust or the like adheres to the liquid on the surface of the paper fiber. This is because there is no occurrence of stain on the recording medium after fixing. However, if the viscosity is less than 10 [mPa · s], the toner will flow due to a decrease in viscosity, causing image flow. If the boiling point is less than 100 ° C., the recording medium may burst due to rapid evaporation of water. On the other hand, when the electric resistance is lower than 1 × 10 ¹² [Ωcm], a current leaks between the toner particles due to poor insulation, and it becomes extremely difficult to develop the electrophoresis and hence the electrostatic latent image. On the other hand, if the surface tension exceeds 30 [dyne / cm], the wettability of the toner rapidly deteriorates, causing the toner mass to adhere to a latent image carrier such as a photoconductor, thereby causing image quality deterioration such as background contamination. . Note that, in a system in which 15 to 30% of toner is dispersed in a dispersion medium of dimethyl silicone (1 × 10 ¹⁴ [Ωcm]), the specific resistance of the dispersion medium by an impedance method is of the order of 10 ⁶ [Ωcm].

  Further, as the aprotic liquid, it is desirable to use a silicone oil containing at least one of phenylmethylsiloxane, dimethylpolysiloxane, and polydimethylcyclosiloxane. This is because silicone oil is extremely poor in wettability, so that adhesion to a movable member such as a stirring member that applies a stress load to the liquid developer can be suppressed, and the frequency of maintenance can be reduced.

In consideration of charge generation and non-volatility, the liquid having a concentration of 1 × 10 ¹² [Ω · cm] or more may be, for example, mineral spirits, aliphatic hydrocarbons such as Isopar series manufactured by Exxon Chemical Company, or dialkyl polyalkylene. Aprotic organic solvents such as series corn oil such as siloxane and cyclic polydialkylsiloxane, olive oil, safflower oil, sunflower oil, vegetable oil such as soybean oil and linseed oil, and the electric resistivity is 1 × 10 ¹² [Ω] Cm] or more is more preferable. These solvents can be used alone or in combination of two or more.

  The amount of the dispersion promoting substance adsorbed on the toner can be measured, for example, as follows. That is, for example, after adjusting the concentration in the non-volatile liquid to about several [%], the liquid developer is centrifuged until the supernatant becomes transparent, and the concentration of the dispersion promoting substance in the supernatant is reduced. You measure.

  Further, it is desirable to use a granular substance as the dispersion promoting substance. This is because electrophoresis can be favorably performed without applying resistance even in a liquid having a high viscosity. Furthermore, it is desirable to use those having an average particle diameter of 0.001 to 1 [μm]. If the thickness is smaller than 0.001 [μm], the toner cannot be covered. On the other hand, if it is larger than 1 [μm], it becomes difficult to maintain the dispersion stability of the toner particles. The average particle size can be measured with a general known particle size distribution measuring device, for example, a laser type particle size distribution meter, a centrifugal sedimentation type particle size distribution meter, or the like. The average particle size can be adjusted, for example, by a method in which a precursor of the dispersion promoting substance is put into a ball mill or the like together with a grinding medium such as a ball and dry-milled. Further, for example, a method in which the precursor of the dispersion promoting substance is wet-pulverized together with a pulverizing medium such as a ball in a solvent may be used. Further, for example, a method of dissolving the precursor of the dispersion accelerating substance in a specific solvent and then precipitating (for example, a method of dissolving in sulfuric acid and adding water or adding to water to precipitate).

  Further, as a group of toner particles dispersed in a non-volatile liquid, those having a volume average particle diameter of 0.1 to 6.0 [μm] are used, and the concentration is adjusted to 5 to 40 [% by weight]. It is desirable to do. This is because the resolution of an image can be improved substantially in inverse proportion to the particle size of the toner. Generally, toner particles are present as an aggregate of about 5 to 10 particles on a printed-out recording medium, and the gap between the developing roller and the photoreceptor is as small as about 10 μm. This is because the size of this range will be considered if it is possible. On the other hand, when the average particle diameter of the toner is 0.1 μm or less, the physical adhesion between the transfer source and the toner in the transfer process is excessively increased, and the toner image cannot be transferred to the transfer destination. This is because This is for the following reason. That is, as the toner becomes smaller, the migration speed becomes slower due to the viscous resistance of the dispersion medium. On the other hand, if it is smaller than this, the influence of the unevenness of the medium increases, and the image density and the uniformity of the image cannot be maintained. The reason for setting the concentration to 5 to 40% by weight is as follows. That is, considering the dispersion, the specific gravity of the dispersion medium and the specific gravity of the colored particles are considered to be substantially equal. Therefore, the weight ratio and the volume ratio are almost the same. If the density exceeds 50%, it means contact development, and there is toner that cannot move in both the image area and the non-image area. In particular, the toner that cannot move sufficiently in the non-image portion remains on the photoconductor, so that non-image stains or the addition of a cleaning device increase. When the weight ratio is used, the specific gravity of the toner slightly increases with respect to the dispersion medium. Therefore, the upper limit of the weight ratio is appropriately set at 40% by weight.

  The liquid developer contains, in addition to colored particles such as toner and a dispersion accelerating substance, a surfactant, an antiseptic, a deodorant, an anti-peeling agent, a fragrance, a pigment dispersant, and a pigment derivative as required. May be.

  A liquid developer can be manufactured by mixing at least a toner and a dispersion promoting substance in a non-volatile liquid, and then depositing the dispersion promoting substance and adsorbing the dispersion promoting substance on the toner. Specifically, for example, first, a mixing step of mixing the toner and the dispersion promoting substance in a solvent in which the dispersion promoting substance is soluble and the toner is not dissolved is performed. Next, a precipitation step of injecting a liquid in which the dispersion promoting substance is not dissolved into the obtained mixed liquid to precipitate the dispersion promoting substance and adsorb it on the surface of the toner particles is performed. Further, a cross-linking step of cross-linking and fixing the dispersion accelerating substance or a concentration step of distilling a liquid component and concentrating a solid content may be performed as necessary.

  In the mixing step, after mixing the toner and the dispersion accelerating substance in the solvent, a dispersion medium such as glass beads, steel beads, zirconia beads, or the like is added to the mixture as needed. Then, the mixed liquid is subjected to a dispersing machine such as a bead mill such as a Dyno mill or a DSP-mill, a roll mill, a sand mill, an attritor, a kneader, or a high-pressure jet mill such as a Nanomizer to uniformly disperse the toner in the mixed liquid. If necessary, various additives such as a surfactant, a pigment dispersant, a pigment derivative, and a charge generating agent may be added. The dispersion condition of the toner depends on the material of the toner and the type of dispersion means, but from the viewpoint of economy, it is desirable to complete the dispersion in a temperature range of 0 to 150 ° C. in as short a time as possible. . As the dispersion time, 0.1 to 10 [hour / kg] is appropriate. The crosslinking agent for crosslinking the dispersion accelerating substance may be mixed before dispersing the toner particles, or may be mixed after dispersing. However, since there is a possibility that an effect such as a reaction may occur at the time of dispersion, it is preferable to mix after dispersion if possible. The addition ratio of the crosslinking agent may be any value as long as the dispersion promoting substance can be crosslinked and adsorbed to the toner.

  In the precipitation step, a liquid in which the dispersion promoting substance is not dissolved is slowly injected into the liquid mixture obtained in the mixing step and mixed. The former liquid may be injected into the mixture. During or after the injection, the liquid is uniformly mixed with a stirrer such as a three-one motor, a magnetic stirrer, a disper, and a homogenizer. The former liquid and the mixed liquid may be mixed at once using a mixer such as a line mixer. After the injection, a dispersing machine such as a bead mill or a high-pressure jet mill may be used for the purpose of making the deposited dispersion promoting substance finer. The liquid in which the dispersion promoting substance is not dissolved is not particularly limited as long as the polymer compound is not dissolved, but an organic solvent having a solubility parameter of 7.8 or less is particularly preferred. Examples of the organic solvent having a solubility parameter of 7.8 or less include aliphatic hydrocarbons such as hexane, mineral spirit, and Isopar series manufactured by Exxon Chemical Co., and silicone oils such as dialkylpolysiloxane and cyclic polydialkylsiloxane. And vegetable oils such as olive oil, safflower oil, sunflower oil, soybean oil and linseed oil, and diethyl ether. The proportion of the organic solvent used here is preferably in the range of 0 to 10000 parts by weight with respect to 100 parts by weight of the polymer compound in order to increase the concentration of particulate matter in the liquid developer to be produced.

  There is no particular limitation on the crosslinking method in the crosslinking step. For example, a crosslinking method using heating, ultraviolet irradiation, electron beam, or the like can be used. From the viewpoint of reactivity and simplicity, a method by heating is preferable. The temperature of the crosslinking by heating is not particularly limited as long as the temperature does not destroy the dispersed state of the toner, but is preferably 200 ° C. or less, more preferably 180 ° C. or less.

  The concentration step is appropriately performed depending on the use of the toner. Moreover, you may implement before a crosslinking process. Examples of the concentration method include a general normal pressure or reduced pressure distillation method. For example, when a silicone-based liquid is used as a dispersion, a solvent having a lower boiling point than the silicone-based liquid is used as a solvent in which the dispersion promoting substance can be dissolved, and the solvent is concentrated by distillation under normal pressure or reduced pressure. Conversely, when a liquid developer is used as an organic solvent in which a polymer compound is dissolved, a silicone-based solvent having a boiling point lower than that of the organic solvent in which the polymer compound is dissolved is used, and concentrated by distillation under normal pressure or reduced pressure. Further, if necessary, it can be used for powder coatings, toners, plastics, etc. by distilling it or replacing it with water and drying it. In the field of liquid toner, there is no need to use a special charge generating agent, and the charge is stably fixed to the surface of the particulate material, so that the long-term use stability is excellent. In order to use the liquid developer for these applications, a binder, an organic solvent, and various additives are added depending on the application to adjust the concentration of the particulate material or the binder to a predetermined concentration. Examples of the binder include natural proteins, celluloses, polyvinyl alcohol, polyacrylamide, aromatic amide, polyacrylic acid, polyvinyl ether, polyvinylpyrrolidone, acrylic, polyester, alkyd, urethane, amide resin, melamine resin, ether resin, and fluorine. Resin, synthetic polymers such as styrene-acrylic resin and styrene-maleic acid resin, photosensitive resins, thermosetting resins, ultraviolet-curing resins, electron beam-curing resins, and the like, include, but are not limited to, known general ones. Not done. As the various additives, known general substances such as anionic, cationic and nonionic surfactants, anti-peeling agents, leveling agents, charge control agents such as metal soaps and lecithin, wetting agents and the like can be used. However, the present invention is not particularly limited to these. In order to adjust the final liquid toner by adding the binder, organic solvent and various additives to the liquid developer, a simple stirrer such as a disper may be used, and a conventional disperser or the like is required. Energy saving and low-cost production. Furthermore, by modifying the non-volatile liquid to contain the polar group of the dispersion as described above, it is also possible to change the two components of the non-volatile liquid and the dispersion into one component.

  In a dispersion in which particles of a resin, a pigment, a magnetic material, and the like are dispersed in an appropriate solvent, the stability of the dispersed particles is an important issue whether it is a non-aqueous solvent or an aqueous solvent. It is generally known that the stability of such dispersed particles can be obtained by an electrostatic effect or a three-dimensional effect (also referred to as an adsorption layer effect) due to electrostatic repulsion. Regarding the electrostatic effect, the DLVO theory has been established, in which the spread of the electric double layer and the interface potential (so-called ζ potential) are important factors. Therefore, the dispersed particles require the presence of ions forming them, and some studies have been made on aqueous solvent systems in which the presence of ions is clear. On the other hand, a steric effect equivalent to the DLVO theory has not yet been established, but a non-aqueous solvent system (mainly a petroleum solvent) is described in, for example, "FAWaite, J. Oil Col. Chem. Assoc., 54, 342 (1971) "(hereinafter referred to as Document A). This work relates to a basic method for producing a stable solvent, apolar dispersion. This production method is to produce a block or graft copolymer containing a component compatible with dispersed particles (insoluble in a solvent) dispersed in the solvent and a component soluble in the solvent. It is.

  Japanese Patent Publication No. 40-7047 (hereinafter referred to as Document B) discloses a method for obtaining a non-aqueous solvent-based dispersion using this production method. According to this method, methyl methacrylate (MMA) is subjected to radical polymerization in a hydrocarbon solvent in the presence of a degraded rubber to obtain a stable polymethyl methacrylate (PMMA) dispersion. In this method, it is not considered that the degraded rubber is adsorbed on the PMMA particles, and it is considered that MMA is graft-polymerized on the degraded rubber based on the fact that the PMMA particles are dispersed and stabilized. It is considered that the graft polymer has an insoluble portion on the surface of the dispersed particles and the dissolved portion has a steric effect, so that the dispersion stability of the dispersed particles is maintained.

Further, Japanese Patent Publication No. Hei 8-23005 (hereinafter referred to as Document C) discloses that solid particles are clearly charged with ions in a solvent such as a non-polar aprotic solvent to be used in a non-aqueous solvent. A method is described in which an electrostatic effect is additionally exerted in addition to the steric effect to obtain a nonpolar solvent-based dispersion having long-term stability.
JP-A-2002-212423, JP-A-2002-241624, and JP-A-2002-256133 describe the following. That is, regarding a hydrocarbon or silicone oil dispersion, a dispersion having excellent dispersion stability due to a steric effect, or a non-aqueous solvent dispersion capable of improving dispersibility by electrostatic repulsion and enabling electrophoresis of dispersed particles. Has been described.

  However, the present inventors consider the matters described in these documents as follows. That is, when the above-described dispersion liquid that is a non-aqueous solvent is applied to a liquid developer, the dispersion particles dispersed in the dispersion liquid correspond to toner particles (colored particles) dispersed in a carrier liquid of the liquid developer. . Generally, toner particles have a relatively large volume average particle size of 0.1 [μm] or more. Therefore, it is difficult to improve the dispersibility of the toner particles in the carrier liquid, which is a non-aqueous solvent, due to the electrostatic effect and the three-dimensional effect due to the electrostatic repulsion, and the toner particles are likely to be close to each other and aggregate. If the toner particles tend to aggregate with each other, it is difficult to control the behavior of the toner particles by an electric field. For example, when the toner particles aggregate with each other in the developing region, a current flows between the toner particles due to the conductive material contained in the toner particles, and even if a developing electric field is formed in the developing region, the toner particles are electrostatically latent. It is difficult to move toward the image.

  In addition, the toner particles, which are dispersed particles, have a relatively large volume average particle diameter of 0.1 [μm] or more as described above, and thus have a relatively low charge amount. Therefore, it is difficult to perform high-speed electrophoresis in a non-aqueous solvent by an electric field such as a developing electric field. As a result, it is difficult to increase an image forming speed.

  Therefore, it is desirable to use a toner having on its surface a dispersion promoting substance, a basic group or an acidic group, and an affinity group for imparting affinity to an insulating liquid such as silicone oil. In a liquid developer using such a toner, a dispersion promoting substance, a basic group or an acidic group, and an affinity group are formed on the surface of colored particles dispersed in a non-polar insulating liquid serving as a non-aqueous solvent. Equipped. This dispersion accelerating substance is a substance which suppresses aggregation of toner particles with each other, and is, for example, a material which causes a silicone group to appear on the surface of toner particles. In this case, the toner particles cannot be aggregated with each other due to the silicone group on the surface, and are in a state of being dispersed at a certain interval. Therefore, the insulating liquid is interposed between the toner particles, and the toner particles are in an insulated state. Therefore, it becomes difficult for a current to flow between the toner particles even in an electric field, and the behavior of the toner particles can be controlled by the electric field. In addition, if the insulating liquid is a silicone-based solvent, the silicone group functions as an affinity group, giving the toner particles an affinity for the insulating liquid. As a result, the toner particles hardly precipitate in the insulating liquid, and the toner particles can be uniformly dispersed in the insulating liquid. In addition, since a basic group or an acidic group is present on the surface of the toner particles, the charge amount of the colored particles can be secured by the basic group or the acidic group. If an image is formed using such a liquid developer, the toner particles can be appropriately and rapidly controlled by an electric field.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the following description, “parts” and “%” mean “parts by weight” and “% by weight” unless otherwise specified. In addition, reagents without precautions were all reagent grade 1 manufactured by Tokyo Chemical Industry Co., Ltd.

The toner particles used in the exemplary embodiment can be manufactured by the following method.
100 parts by weight of a monomer, methyl methacrylate (MMA), and 300 parts by weight of water were charged into a 1-liter four-necked flask equipped with a thermometer and a nitrogen inlet tube, followed by stirring and mixing. The temperature was increased to 80 ° C. while stirring under a nitrogen stream. Next, 0.5 parts by weight of potassium persulfate is added to the mixture, and the mixture is reacted for 6 hours while maintaining the temperature at 80 ° C. to obtain a dispersion (a) of polymer particles. Observation of the polymer particles in the dispersion (a) by an electron micrograph revealed that the polymer particles were true spheres having a substantially constant particle diameter, and the average particle diameter was 0.41 [μm]. there were.
Next, 91.7 parts by weight of MMA and 1.0 part by weight of benzoyl peroxide were charged into a four-necked flask having a capacity of 1 liter equipped with a thermometer and a nitrogen introducing tube, and dissolved therein. To this solution, 200 parts by weight of water, 3.3 parts by weight of Newcol 707SN (manufactured by Nippon Emulsifier Co., Ltd.) and 0.1 part by weight of sodium nitrite were added, and mixed for 10 minutes with vigorous stirring and stirring. Further, 35 parts by weight of the polymer particles in the dispersion liquid (a) obtained in the first-stage polymerization were added to this mixture, and the mixture was gently stirred at 50 ° C. for 30 minutes, and then at 75 ° C. The reaction is performed for 2 hours to obtain a dispersion liquid (b) of the polymer particles. Observation of the polymer particles in the dispersion (b) by an electron micrograph revealed that the polymer particles were true spherical monodisperse particles having an average particle size of 0.93 [μm].
Next, using the same apparatus, 95.0 parts by weight of MMA and 1.0 part by weight of benzoyl peroxide were mixed and dissolved, and further, 200 parts by weight of water and Newcol 707SN ( 3.3 parts by weight of Nippon Emulsifier Co., Ltd.) and 0.1 part by weight of sodium nitrite were added, and mixed for 10 minutes under strong stirring. Next, 15.6 parts by weight of the polymer particles in the dispersion liquid (b) were added to this mixture, and the mixture was gently stirred at 50 ° C. for 30 minutes, and then reacted at 75 ° C. for 2 hours. A dispersion (c) of polymer particles was obtained. Observation of the polymer particles in the dispersion (b) by an electron micrograph showed that the seed particles, which were polymer particles, were true spherical monodisperse particles having an average particle size of 2.12 μm.

Further, for coloring, 80.0 parts by weight of methyl methacrylate (MMA) as an acrylic monomer and C.I. I. 2.0 parts by weight of Solvent Blue 35 (solubility in MMA: 4.2 parts by weight), V-601 which is an azo polymerization initiator (manufactured by Wako Pure Chemical Industries, Ltd., dimethyl-2,2'-azobis) (2-methylpropionate)) was added and dissolved in 1.0 part by weight. Further, 200 parts by weight of water, 10.0 parts by weight of Newcol 707SN (manufactured by Nippon Emulsifier Co., Ltd.) as an emulsifier, Further, 0.05 parts by weight of sodium nitrite as a polymerization inhibitor was added, and mixed for 10 minutes under strong stirring. Next, 62.3 parts by weight of the seed particles in the dispersion liquid (c) was added to the mixture, and the mixture was gently stirred at 50 ° C. for 30 minutes, and then reacted at 80 ° C. for 2 hours. The mixture was reacted at 90 ° C. for 2 hours to obtain a dispersion of colored particles. When the colored particles in the obtained dispersion were observed by an electron microscope photograph, the colored polymer particles were true spherical monodispersed particles having an average particle size of 3.98 [μm].
As the dye, an oil-soluble dye exhibiting solubility in methyl methacrylate is desirable, and is usually 1.0 part by weight or more, preferably 2.0 parts by weight or more, more preferably 4 parts by weight, based on 100 parts by weight of MMA at 25 ° C. An oil-soluble dye that dissolves at least 0.0 parts by weight is used.
Examples of the oil-soluble dye preferably used in the present embodiment include, for example, oil-soluble dyes having a color index number (CI) of Solvent Blue 35, Solvent Red 132, Solvent Black 27, Solvent Yellow 16 and Solvent Blue 70. , OIL GREEN 502 (manufactured by Orient Chemical Industry Co., Ltd.), OIL GREEN BG (manufactured by Orient Chemical Industry Co., Ltd.), and VALIFAST RED 3306 (manufactured by Orient Chemical Industry Co., Ltd.). Those having a solubility of 4.0 parts by weight or more are particularly preferred. When an oil-soluble dye having a high solubility in MMA is used, a sufficient amount of the dye can be used, and the colored polymer particles having a uniform color tone can be obtained without fading of the dye in a process of producing the colored polymer particles such as during polymerization. It is preferable in that it can be obtained. Such oil-soluble dyes may be used alone or in combination. In this embodiment, the oil-soluble dye is used in an amount of usually 1.0 to 20 parts, preferably 2.0 to 10 parts, based on 100 parts by weight of the acrylic monomer, depending on a desired color tone and the like. Can be used.

[Synthesis Example 1 (Preparation of polymer compound)]
In a reaction vessel, 180 parts of Isopar L (manufactured by Exxon) are stirred, and 14 parts of methmethyl methacrylate, 2 parts of methacrylic acid, 4 parts of lauryl methacrylate, and 1 part of azobisisobutyronitrile (manufactured by Wako Pure Chemical Industries) are added dropwise. The reaction was carried out at 85 ° C. for 5 hours while refluxing argon gas.
The monomer in the solution after the reaction was treated with ethyl alcohol, and when a DC voltage was applied to this polymer dispersion, all the dispersed particles were electrodeposited on the anode.

[Synthesis Example 2 (Preparation of polymer compound)]
In a reaction vessel, 180 parts of Isopar L (manufactured by Exxon) are stirred, and 14 parts of methmethyl methacrylate, 2 parts of dimethylaminomethyl methacrylic acid, 4 parts of lauryl methacrylate, 1 part of azobisisobutyronitrile (manufactured by Wako Pure Chemical) , And reacted at 85 ° C. for 5 hours while refluxing argon gas.
The monomer in the solution after the reaction was treated with ethyl alcohol, and when a DC voltage was applied to the polymer dispersion, all the dispersed particles were electrodeposited on the cathode.

[Synthesis Example 3 (Preparation of polymer compound)]
In a reaction vessel, 180 parts of dimethyl silicone KF-96-1.0 (manufactured by Shin-Etsu Chemical Co., Ltd.) are stirred, and 14 parts of methmethyl methacrylate, 2 parts of methacrylic acid, 4 parts of methacryloxy-modified silicone FM0711 (manufactured by Chisso) 4 parts, and azo One part of bisisobutyronitrile (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise and reacted at 85 ° C. for 5 hours while refluxing argon gas.
The monomer in the solution after the reaction was treated with ethyl alcohol, and when a DC voltage was applied to this polymer dispersion, all the dispersed particles were electrodeposited on the anode.

[Synthesis Example 4 (Preparation of polymer compound)]
In a reaction vessel, 180 parts of dimethyl silicone KF-96-1.0 (manufactured by Shin-Etsu Chemical Co., Ltd.) are stirred, and 14 parts of methmethyl methacrylate, 2 parts of dimethylaminomethyl methacrylic acid, one end methacryloxy-modified silicone FM0711 (manufactured by Chisso) 4 And 1 part of azobisisobutyronitrile (manufactured by Wako Pure Chemical Industries, Ltd.) were dropped, and the mixture was reacted at 85 ° C. for 5 hours while refluxing argon gas.
The monomer in the solution after the reaction was treated with ethyl alcohol, and when a DC voltage was applied to the polymer dispersion, all the dispersed particles were electrodeposited on the cathode.

[Synthesis Example 5 (Preparation of non-self-dispersing polymer compound)]
In a reaction vessel, 180 parts of dimethyl silicone KF-96-1.0 (manufactured by Shin-Etsu Chemical Co., Ltd.) is stirred, and 14 parts of methmethyl methacrylate, 2 parts of dimethylaminomethyl methacrylic acid, 4 parts of n-butyl methacrylate, azobisisobutyro One part of nitrile (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise and reacted at 85 ° C. for 5 hours while refluxing argon gas.
The monomer in the solution after the reaction was treated with ethyl alcohol, and when a DC voltage was applied to the polymer dispersion, all the dispersed particles were electrodeposited on the cathode.

[Synthesis Example 6 (Preparation of non-self-dispersing polymer compound)]
In a reaction vessel, 180 parts of dimethyl silicone KF-96-1.0 (manufactured by Shin-Etsu Chemical Co., Ltd.) are stirred, and 14 parts of methmethyl methacrylate, 2 parts of dimethylaminomethyl methacrylic acid, one-terminal methacryloxy-modified silicone TM0701 (manufactured by Chisso) 4 And 1 part of azobisisobutyronitrile (manufactured by Wako Pure Chemical Industries, Ltd.) were dropped, and the mixture was reacted at 85 ° C. for 5 hours while refluxing argon gas.
The monomer in the solution after the reaction was treated with ethyl alcohol, and when a DC voltage was applied to the polymer dispersion, all the dispersed particles were electrodeposited on the cathode.

[Example 1]
As a toner particle substance, an acrylic resin mainly composed of methmethyl methacrylate containing dimethylaminomethyl methacrylic acid was subjected to seed polymerization to obtain positively charged monodisperse particles having a particle diameter of 4 μm. Further, 2-ethylhexyl methacrylate was graft-polymerized on the surface of the particles. 20.0 parts by weight of the toner resin particles and 30.0 parts by weight of the polymer compound of Synthesis Example 1 were weighed out and dispersed for 2 hours with a paint shaker (manufactured by Aishin), and thereafter, Isopar H (manufactured by Exxon) 50.0 parts by weight were added and mixed to obtain a dispersion slurry. The evaluation device shown in FIG. 4 was used for the measurement of the moving current measurement cell. The obtained liquid developer showed good dispersibility. When a DC voltage was applied to this dispersion, all the toner particles were electrodeposited on the cathode and the liquid became transparent. When the electrodeposited toner resin was fixed by a heat roller, the resins exhibited good coating properties.

[Example 2]
As a toner particle material, an acrylic resin containing methacrylic acid-containing methmethyl methacrylate as a main component was subjected to seed polymerization to obtain negatively charged monodisperse particles having a particle size of 4 μm. Further, 2-ethylhexyl methacrylate was graft-polymerized on the surface of the particles. 20.0 parts by weight of the toner resin particles and 30.0 parts by weight of the polymer compound of Synthesis Example 2 were weighed and dispersed with a paint shaker (manufactured by Aishin) for 2 hours, and then Isopar H (manufactured by Exxon) 50.0 parts by weight were added and mixed to obtain a dispersion slurry. The obtained liquid developer showed good dispersibility. When a DC voltage was applied to this dispersion, all the toner particles were electrodeposited on the anode and the liquid became transparent. When the electrodeposited toner resin was fixed by a heat roller, the resins exhibited good coating properties.

[Comparative Example 1]
As a toner particle material, an acrylic resin containing methacrylic acid-containing methmethyl methacrylate as a main component was subjected to seed polymerization to obtain negatively charged monodisperse particles having a particle size of 4 μm. Further, 2-ethylhexyl methacrylate was graft-polymerized on the surface of the particles. 20.0 parts by weight of the toner resin particles and 30.0 parts by weight of the polymer compound of Synthesis Example 6 were weighed and dispersed for 2 hours with a paint shaker (manufactured by Aishin), and then Isopar H (manufactured by Exxon) 50.0 parts by weight were added and mixed to obtain a dispersion slurry. The obtained liquid developer was a poorly dispersible liquid which settled out immediately. In addition, when a pigment or dye is contained in the toner resin, the dispersibility is poor, so current leakage is caused. When a DC voltage is applied to the dispersion, movement of the toner particles due to an electric field is hindered, and the toner particles are charged to the anode. It was worn but the liquor remained cloudy.

[Example 3]
As a toner particle substance, an acrylic resin mainly composed of methmethyl methacrylate containing dimethylaminomethyl methacrylic acid was subjected to seed polymerization to obtain positively charged monodisperse particles having a particle diameter of 4 μm. Further, methacryloxy-modified silicone FM0711 (manufactured by Chisso Corporation) was graft-polymerized on the surface of the particles. 20.0 parts by weight of the toner resin particles and 30.0 parts by weight of the polymer compound of Synthesis Example 3 were weighed and dispersed for 2 hours with a paint shaker (manufactured by Aisin Co.), and then 50.0 parts by weight of KF96-50 Additional portions were mixed to obtain a dispersion slurry. The obtained liquid developer showed good dispersibility. When a DC voltage was applied to this dispersion, all the toner particles were electrodeposited on the cathode and the liquid became transparent. When the electrodeposited toner resin was fixed by a heat roller, the resins exhibited good coating properties. Further, when an electric field is applied by applying heat to the dispersion at 80 ° C., the toner particles are all electrodeposited on the cathode, and the electrodeposited toner resin has a cohesive property between the resins more than when no heat is applied. it was high. When the electrodeposited toner resin was fixed with a heat roller, even better coating properties were exhibited.

[Example 4]
As a toner particle material, an acrylic resin containing methacrylic acid-containing methmethyl methacrylate as a main component was subjected to seed polymerization to obtain negatively charged monodisperse particles having a particle size of 4 μm. Further, methacryloxy-modified silicone FM0711 (manufactured by Chisso Corporation) was graft-polymerized on the surface of the particles. 20.0 parts by weight of the toner resin particles and 30.0 parts by weight of the polymer compound of Synthesis Example 4 were weighed and dispersed for 2 hours using a paint shaker (manufactured by Aisin Co.), and then 50.0 parts by weight of KF96-50 Additional portions were mixed to obtain a dispersion slurry. The obtained liquid developer showed good dispersibility. When a DC voltage was applied to this dispersion, all the toner particles were electrodeposited on the anode and the liquid became transparent. When the electrodeposited toner resin was fixed by a heat roller, the resins exhibited good coating properties. When the electrodeposited toner resin was fixed by a heat roller, the resins exhibited good coating properties. Further, when heat is applied to the dispersion and an electric field is applied at 80 ° C., the toner particles are all electrodeposited on the anode, and the electrodeposited toner resin has a cohesive property between the resins more than when no heat is applied. it was high. When the electrodeposited toner resin was fixed with a heat roller, even better coating properties were exhibited.

[Comparative Example 2]
As a toner particle material, an acrylic resin containing methacrylic acid-containing methmethyl methacrylate as a main component was subjected to seed polymerization to obtain negatively charged monodisperse particles having a particle size of 4 μm. Further, methacryloxy-modified silicone FM0711 (manufactured by Chisso Corporation) was graft-polymerized on the surface of the particles. 20.0 parts by weight of the toner resin particles and 30.0 parts by weight of the polymer compound of Synthesis Example 5 were weighed and dispersed for 2 hours with a paint shaker (manufactured by Aisin Co.), and then 50.0 parts by weight of KF96-50 Additional portions were mixed to obtain a dispersion slurry. The obtained liquid developer was a poorly dispersible liquid which settled out immediately. In addition, when a pigment or dye is contained in the toner resin, the dispersibility is poor, so current leakage is caused. When a DC voltage is applied to the dispersion, movement of the toner particles due to an electric field is hindered, and the toner particles are charged to the anode. It was worn but the liquor remained cloudy.

In Examples 3 and 4, the mobility of the toner due to the electrodeposition current and the fixability of the moved toner were observed at the composition ratios shown in Table 1 below.

[Example 5]
In a reaction vessel equipped with a thermometer and a nitrogen inlet tube, 180 parts by weight of dimethyl silicone, 16 parts by weight of colored particles, 1 part by weight of dimethylaminomethyl methacrylate, 2 parts by weight of methacryloxy-modified silicone at one end, and azobisvalero One part by weight of nitrile was added and mixed by stirring, and further reacted at 50 [° C.] for 10 hours while stirring under a nitrogen stream. Then, 30 parts by weight of the obtained toner particles were added to 70 parts by weight of dimethyl silicone (100 [cSt]) as an insulating liquid, and the mixture was ultrasonically dispersed to obtain a liquid developer.
It has been found that these toner particles have an excellent property that they hardly aggregate with each other. In this regard, the present inventors have confirmed that since the silicone groups of the methacryloxy-modified silicone at one end as a dispersion accelerating substance are present on the surface of the toner particles, the toner particles hardly aggregate with each other. It is considered that it has become.
Further, when a DC voltage was applied to the liquid developer, all of the particles (toner particles) in the liquid developer were electrophoresed promptly and electrodeposited on the cathode, and the liquid became transparent. In this regard, the present inventors have confirmed that the amount of positive polarity charge increased due to the basic group of dimethylaminomethyl methacrylate on the surface of the toner particles, and that high-speed electrophoresis was enabled. Conceivable.

[Example 6]
In a reaction vessel equipped with a thermometer and a nitrogen inlet tube, 180 parts by weight of dimethyl silicone, 17 parts by weight of colored particles, 1 part by weight of methacrylic acid, 2 parts by weight of methacryloxy-modified silicone at one end, and azobisvaleronitrile were added. One part by weight was added, mixed with stirring, and further reacted at 50 [° C.] for 10 hours while stirring under a nitrogen stream. Then, 30 parts by weight of the obtained toner particles were added to 70 parts by weight of dimethyl silicone (100 [cSt]) as an insulating liquid, and the mixture was ultrasonically dispersed to obtain a liquid developer.
It has been found that these toner particles have an excellent property that they hardly aggregate with each other. The reason is the same as in the fifth embodiment.
Further, when a DC voltage was applied to the liquid developer, all of the particles (toner particles) in the liquid developer were electrophoresed promptly and electrodeposited on the anode, and the liquid became transparent. When the present inventors confirmed this point, it is considered that high-speed electrophoresis was enabled because the amount of negative polarity charge increased due to the acidic group of methacrylic acid on the surface of the toner particles.

[Comparative Example 3]
Next, Comparative Example 3, which is a comparative experiment between the liquid developer of Example 5 and the liquid developer described below, will be described.
180 parts by weight of dimethyl silicone, 17 parts by weight of colored particles, 1 part by weight of dimethylaminomethyl methacrylate, and 1 part by weight of azobisvaleronitrile are added to a reaction vessel equipped with a thermometer and a nitrogen inlet tube, and stirred and mixed. The reaction was further performed at 50 ° C. for 10 hours while stirring under a nitrogen stream. Then, 30 parts by weight of the obtained toner particles were added to 70 parts by weight of dimethyl silicone (100 [cSt]) as an insulating liquid, and the mixture was ultrasonically dispersed to obtain a liquid developer.
When a DC voltage was applied to the liquid developer, all of the particles (toner particles) in the liquid developer were electrophoresed promptly and electrodeposited on the cathode, as in Example 5, and the liquid was It became transparent.
If there is no affinity group (silicone group) for the insulating liquid (dimethyl silicone) on the surface of the toner particles, the toner particles immediately precipitate in the insulating liquid, making it difficult to form an appropriate image. It is important that the molecular weight of the one-terminal methacryloxy-modified silicone having this affinity group be adjusted to the molecular weight of the insulating liquid. The molecular weight of dimethyl silicone (100 [cSt]) used in Example 1 is an average molecular weight of several thousand. On the other hand, the one-terminal methacryloxy-modified silicone used in Example 5 can maintain dispersibility by using a material having a molecular weight of 1,000, 5,000, or 10,000. Dispersibility is extremely poor. When the molecular weight is 1000, it depends on the grafting time, but is better than the case where the molecular weight is 400, but slightly poor in dispersibility, and sedimentation occurs in the order of several months. As a result, the molecular weight of the one-terminal methacryloxy-modified silicone is desirably at least as high as the average molecular weight of the insulating liquid.

FIGS. 5A and 5B are graphs showing the results obtained by observing the response characteristics of the toner particles when the liquid developers of Example 5 and Comparative Example 3 were respectively placed in an AC electric field. is there.
FIG. 5A shows the observation result of the liquid developer of the fifth embodiment, and FIG. 5B shows the observation result of the liquid developer of the third comparative example. In each graph, the upper part shows the waveform of the AC electric field, and the lower part shows the observation result of the pressure waveform of the toner particles moving in response to the AC electric field. In the case of toner particles having no affinity group as in Comparative Example 3, the electric field response is poor as shown in FIG. 5B, but in the case of toner particles having an affinity group as in Example 5, As shown in FIG. 5A, it was confirmed that the electric field response was good.

  Also, 180 parts by weight of dimethyl silicone, 17 parts by weight of colored particles, 1 part by weight of methacrylic acid, and 1 part by weight of azobisvaleronitrile were added to a reaction vessel equipped with a thermometer and a nitrogen inlet tube, and stirred and mixed. The reaction was further performed at 50 ° C. for 10 hours while stirring under a nitrogen stream. Then, 30 parts by weight of the obtained toner particles were added to 70 parts by weight of dimethyl silicone (100 [cSt]) as an insulating liquid, and the mixture was ultrasonically dispersed to obtain a liquid developer. This liquid developer is different from Example 6 in that it does not have an affinity group. In a comparative experiment with the liquid developer of Example 6, the same observation result as described above was obtained. .

[Comparative Example 4]
In a reaction vessel equipped with a thermometer and a nitrogen inlet tube, 180 parts by weight of dimethyl silicone, 17 parts by weight of colored particles having a small particle diameter of 0.09 [μm], and 1 part of dimethylaminomethyl methacrylate were added. 2 parts by weight of methacryloxy-modified silicone at one end and 1 part by weight of azobisvaleronitrile were added and mixed by stirring, and further reacted at 50 ° C. for 10 hours while stirring under a nitrogen stream. Then, 30 parts by weight of the obtained toner particles were added to 70 parts by weight of dimethyl silicone (100 [cSt]) as an insulating liquid, and the mixture was ultrasonically dispersed to obtain a liquid developer. When a DC voltage was applied to the liquid developer, all of the particles (toner particles) in the liquid developer were electrophoresed promptly and electrodeposited on the cathode, as in Example 5, and the liquid was It became transparent. However, since the liquid developer has a small particle diameter of the toner particles, the liquid developer has a large viscous resistance to the amount of charge per particle, and it is difficult to move through the insulating liquid at high speed even when subjected to an electric field.
In a reaction vessel equipped with a thermometer and a nitrogen inlet tube, 180 parts by weight of dimethyl silicone, 17 parts by weight of colored particles having a large particle diameter of 10 [μm] and 1 part of dimethylaminomethyl methacrylate were added. 2 parts by weight of methacryloxy-modified silicone at one end and 1 part by weight of azobisvaleronitrile were added and mixed by stirring, and further reacted at 50 ° C. for 10 hours while stirring under a nitrogen stream. Then, 30 parts by weight of the obtained toner particles were added to 70 parts by weight of dimethyl silicone (100 [cSt]) as an insulating liquid, and the mixture was ultrasonically dispersed to obtain a liquid developer. When a DC voltage was applied to the liquid developer, all of the particles (toner particles) in the liquid developer were electrophoresed promptly and electrodeposited on the cathode, as in Example 5, and the liquid was It became transparent. However, the increase in the toner particle diameter makes it difficult to form a high-resolution image.
In Examples 1 to 6 described above and Examples 7 to 13 described below, the colored particles having a volume average particle diameter of 0.1 μm or more and 6.0 μm or less are used. The toner particles can move at a high speed in the insulating liquid, and a high-resolution image can be sufficiently formed.

[Example 7]
In a reaction vessel equipped with a thermometer and a nitrogen inlet tube, 180 parts by weight of dimethyl silicone, 17 parts by weight of colored particles, 1 part by weight of dimethylaminomethyl methacrylate, 2 parts by weight of methacryloxy-modified silicone at one end, and azobisvalero One part by weight of nitrile was added and mixed under stirring, and further reacted at 50 [° C.] for 10 hours while stirring under a nitrogen stream. Then, 30 parts by weight of the toner particles thus obtained is added to 68 parts by weight of dimethyl silicone (100 [cSt]) as an insulating liquid, and 2 parts by weight of an acidic group-containing charge control agent is added, and ultrasonic dispersion is performed. Thus, a liquid developer was obtained.
As in the case of the fifth embodiment, the toner particles have an excellent property that they hardly aggregate with each other. Further, when a DC voltage was applied to the liquid developer, all of the particles (toner particles) in the liquid developer were electrophoresed promptly and electrodeposited on the cathode, and the liquid became transparent. At this time, it was confirmed that the liquid developer of Example 7 had a higher moving speed than the liquid developer of Example 5 containing no charge control agent having an acidic group. This is considered to be due to the fact that an acidic group-containing charge control agent having a polarity opposite to the charge polarity of the toner particles was dispersed in the insulating liquid.

FIG. 6 is a graph showing the relationship between the amount of the acidic group-containing charge control agent added and the mobility of the toner particles.
As shown, as the amount of the acidic group-containing charge control agent increases, the mobility of the toner particles also tends to increase. However, when the amount of the acidic group-containing charge control agent added to the surface area of the toner is larger than 5 × 10 ¹⁶ [unit / m ² ], some of the toner particles whose polarity is reversed begin to be present. Thus, an optimal amount exists and needs to be adjusted. Conversely, by including a large amount of the acidic group-containing charge controlling agent, even toner particles having a basic group on the surface can be used as a negative polarity toner.

FIG. 7 is a graph showing the relationship between the bias value applied to the developing roller (17) and the mobility of the toner particles. In addition, the addition amount of the acidic group-containing charge control agent (CCA) is 1/10 of the legend.
Ideally, the voltage value indicates 0 [V] when a positive bias is applied to the developing roller (17) and 9 [V] when a negative bias is applied. Compared to the liquid developer of Example 5, the more the amount of the acidic group-containing charge control agent added, the closer to the ideal result.

FIG. 8 is a graph showing a relationship between a bias value applied to the developing roller (17) and a current value flowing between the photoconductor (1) and the developing roller (17). In addition, the addition amount of the acidic group-containing charge control agent (CCA) is 1/10 of the legend.
When an acid group-containing charge control agent having a polarity opposite to that of the toner particles having a basic group on the surface is added, the value of the current flowing between the photoreceptor (1) and the developing roller (17) decreases, and excess ions are suppressed. Was observed. As a result, the potential difference between the photoconductor (1) and the developing roller (17) does not become narrow, so that the toner particles can be appropriately moved by the developing electric field.

Example 8
In a reaction vessel equipped with a thermometer and a nitrogen inlet tube, 180 parts by weight of dimethyl silicone, 17 parts by weight of colored particles, 1 part by weight of dimethylaminomethyl methacrylate, 2 parts by weight of methacryloxy-modified silicone at one end, and azobisvalero One part by weight of nitrile was added and mixed under stirring, and further reacted at 50 [° C.] for 10 hours while stirring under a nitrogen stream. Then, 30 parts by weight of the toner particles thus obtained is added to 40 parts by weight of dimethyl silicone (100 [cSt]) as an insulating liquid, and 30 parts by weight of a basic group-containing charge control agent is added, and ultrasonic waves are added. It was dispersed to obtain a liquid developer. Note that the toner particles have the excellent property that they hardly aggregate with each other, as in the case of the fifth embodiment.

FIG. 9 is a graph showing the relationship between the amount of the basic group-containing charge control agent added and the mobility of the toner particles.
When a DC voltage was applied to the liquid developer, all of the particles (toner particles) in the liquid developer were quickly electrophoresed and electrodeposited on the anode, and the liquid became transparent. This is because the polarity of the toner particles was reversed to a minus polarity by dispersing the basic group-containing charge control agent having the same polarity as the charge polarity of the toner particles in the insulating liquid. Further, as shown in the figure, as the amount of the basic group-containing charge control agent increases, the mobility of the toner particles also tends to increase. Therefore, it was confirmed that the liquid developer of Example 8 had a higher moving speed than the liquid developer of Example 5 not including the basic group-containing charge control agent.

[Example 9]
In a reaction vessel equipped with a thermometer and a nitrogen inlet tube, 180 parts by weight of dimethyl silicone, 17 parts by weight of colored particles, 1 part by weight of dimethylaminomethyl methacrylate, 2 parts by weight of methacryloxy-modified silicone at one end, and azobisvalero One part by weight of nitrile was added and mixed under stirring, and further reacted at 50 [° C.] for 10 hours while stirring under a nitrogen stream. Then, 30 parts by weight of the toner particles thus obtained is added to 68 parts by weight of dimethyl silicone (100 [cSt]) as an insulating liquid, and 2 parts by weight of zirconium octylate as a metal is added and ultrasonically dispersed. Thus, a liquid developer was obtained. Note that the toner particles have the excellent property that they hardly aggregate with each other, as in the case of the fifth embodiment.

FIG. 10 is a graph showing the relationship between the amount of zirconium octylate added and the mobility of toner particles.
When a DC voltage was applied to the liquid developer, all of the particles (toner particles) in the liquid developer were quickly electrophoresed and electrodeposited on the cathode, and the liquid became transparent. As shown in the figure, as the amount of zirconium octylate increases, the mobility of the toner particles also tends to increase. Therefore, it was confirmed that the liquid developer of Example 9 had a higher moving speed than the liquid developer of Example 5 containing no zirconium octylate.

[Example 10]
In a reaction vessel equipped with a thermometer and a nitrogen inlet tube, 180 parts by weight of dimethyl silicone, 17 parts by weight of colored particles, 1 part by weight of methacrylic acid, 2 parts by weight of methacryloxy-modified silicone at one end, and azobisvaleronitrile were added. One part by weight was added, mixed with stirring, and further reacted at 50 [° C.] for 10 hours while stirring under a nitrogen stream. Then, 30 parts by weight of the toner particles thus obtained are added to 68 parts by weight of dimethyl silicone (100 [cSt]) as an insulating liquid, and 2 parts by weight of a basic group-containing charge control agent are added, and ultrasonic waves are added. It was dispersed to obtain a liquid developer.
The toner particles have the excellent property that they hardly aggregate with each other, as in the case of the sixth embodiment. Further, when a DC voltage was applied to the liquid developer, all of the particles (toner particles) in the liquid developer were electrophoresed promptly and electrodeposited on the anode, and the liquid became transparent. At this time, it was confirmed that the liquid developer of Example 10 had a higher moving speed than the liquid developer of Example 6 not containing the basic group-containing charge control agent. The reason is the same as the reason described in the seventh embodiment.

[Example 11]
In a reaction vessel equipped with a thermometer and a nitrogen inlet tube, 180 parts by weight of dimethyl silicone, 17 parts by weight of colored particles, 1 part by weight of methacrylic acid, 2 parts by weight of methacryloxy-modified silicone at one end, and azobisvaleronitrile were added. One part by weight was added, mixed with stirring, and further reacted at 50 [° C.] for 10 hours while stirring under a nitrogen stream. Then, 30 parts by weight of the toner particles thus obtained is added to 40 parts by weight of dimethyl silicone (100 [cSt]) as an insulating liquid, and 30 parts by weight of an acidic group-containing charge control agent is added, and ultrasonic dispersion is performed. Thus, a liquid developer was obtained.
The toner particles have the excellent property that they hardly aggregate with each other, as in the case of the sixth embodiment. Further, when a DC voltage was applied to the liquid developer, all of the particles (toner particles) in the liquid developer were electrophoresed promptly and electrodeposited on the cathode, and the liquid became transparent. This is because the polarity of the toner particles was inverted to a positive polarity by dispersing the acidic group-containing charge control agent having the same polarity as the charging polarity of the toner particles in the insulating liquid. Further, when the added amount of the acidic group-containing charge control agent is increased, the charge amount of the toner particles is also increased. Therefore, in the liquid developer of Example 11, the liquid developer of Example 11 containing no basic group-containing charge control agent is used. It was confirmed that the moving speed was higher than that of the liquid developer.

[Example 12]
In a reaction vessel equipped with a thermometer and a nitrogen inlet tube, 180 parts by weight of dimethyl silicone, 17 parts by weight of colored particles, 1 part by weight of methacrylic acid, 2 parts by weight of methacryloxy-modified silicone at one end, and azobisvaleronitrile were added. One part by weight was added, mixed with stirring, and further reacted at 50 [° C.] for 10 hours while stirring under a nitrogen stream. Then, 30 parts by weight of the toner particles thus obtained is added to 68 parts by weight of dimethyl silicone (100 [cSt]) as an insulating liquid, and 2 parts by weight of zirconium octylate as a metal is added and ultrasonically dispersed. Thus, a liquid developer was obtained.
The toner particles have the excellent property that they hardly aggregate with each other, as in the case of the sixth embodiment. Further, when a DC voltage was applied to the liquid developer, all of the particles (toner particles) in the liquid developer were electrophoresed promptly and electrodeposited on the anode, and the liquid became transparent. At this time, it was confirmed that the liquid developer of Example 12 had a higher moving speed than the liquid developer of Example 6 containing no zirconium octylate.

[Example 13]
When the insulating liquid of Example 5 was changed from dimethyl silicone to Isopar G and a DC voltage was applied to the liquid developer, all of the particles (toner particles) in the liquid developer were quickly electrophoresed. Then, the electrode was electrodeposited, and the liquid became transparent.

As described above, in the liquid developer according to the embodiment, if the liquid developer has a polarity opposite to that of the toner due to the polar group, the toner particles can be more reliably dispersed.
In addition, if a dispersion promoting substance having a carboxyl group or a hydroxyl group is used as a polar group having a polarity opposite to that of the toner, the toner can be finely dispersed, a crosslinking reaction can be promoted, toner particles can be hardly aggregated, and The reaction speed of the reaction can be increased.
Further, if methyl methacrylate or an acrylic polymer compound containing the same as a main component is used as the dispersion accelerating substance, it is possible to avoid agglomeration when polymerized and to self-disperse in a fine state, Further, a polar group can be easily introduced.
Further, when a graft copolymer is used as the acrylic polymer compound, it can be adsorbed on the toner satisfactorily while floating well in the liquid, and more reliable dispersion performance can be obtained.
In addition, when silicone oil is used as the non-volatile liquid and a graft copolymer containing silicone is used as the above-mentioned graft copolymer, the dispersion performance of the toner can be more favorably obtained.
When the graft copolymer having an average molecular weight of 500 to 10000 is used, the affinity with the non-volatile liquid can be favorably exhibited, and the excellent dispersion performance can be exhibited.
If an aprotic liquid is used as the non-volatile liquid, an electric resistance that does not hinder the electrophoresis of the toner under an electric field can be maintained, so that good developing performance and transfer performance can be obtained.
Further, if a liquid having an electric resistance of 1 × 10 ¹² [Ω · cm] or more is used, it is possible to suppress development failure due to current leakage between toner particles.
In addition, if a liquid having a surface tension of 30 [dyne / cm] or less is used, it is possible to suppress image quality deterioration such as background contamination caused by attaching a toner mass to a latent image carrier such as a photoconductor.
Further, when a silicone-based liquid containing at least one of phenylmethylsiloxane, dimethylpolysiloxane, and polydimethylcyclosiloxane is used as the liquid, the frequency of maintenance of the apparatus can be reduced.
If a dispersion-promoting substance is used, it can be favorably electrophoresed in a high-viscosity liquid without applying resistance.

  Further, the liquid developer used in the embodiment includes at least toner particles that are colored particles composed of a resin and a colored substance, and an insulating liquid that is a non-polar insulating liquid that is a non-aqueous solvent for the toner particles. The latent image is developed by attaching toner particles to the latent image on the photoreceptor 1 as a carrier. This liquid developer, as described above, as a toner particle, a methacryloxy-modified silicone at one end that is a dispersion promoting substance that suppresses aggregation of the toner particles, a basic group, and an insulating liquid composed of dimethyl silicone. A silicone group, which is an affinity group for imparting affinity, is provided on the surface. Therefore, as described in the fifth embodiment, the toner particles hardly aggregate with each other in the insulating liquid, and the toner particles can be electrophoresed at high speed by the electric field.

  Further, the liquid developer used in the present embodiment may use an acidic group instead of the basic group as described in the sixth embodiment. In this case, the same effect as in the case of the basic group can be obtained except that the charging polarity is different.

  Further, in the present embodiment, a charge controlling agent having compatibility with the insulating liquid and having an acidic group is contained in the insulating liquid together with the toner particles. As a result, as long as the toner particles have a basic group on the surface, the speed at which the toner particles electrophoreses in the insulating liquid can be increased as described in the seventh embodiment. On the other hand, if the toner particles have an acidic group on the surface, as described in Example 11, the toner particles can be used in a state where the polarity of the toner particles is inverted, and the toner particles are electrophoresed in the insulating liquid. It is also possible to increase the speed of doing.

  Further, in the present embodiment, the charge controlling agent having compatibility with the insulating liquid and having a basic group is contained in the insulating liquid together with the toner particles. As a result, as long as the toner particles have a basic group on the surface, the toner particles can be used in a state in which the polarity of the toner particles is inverted as described in the above-mentioned Example 8, and the insulating liquid can be used in the insulating liquid. It is also possible to increase the speed of electrophoresis. On the other hand, if the toner particles have an acidic group on the surface, the speed at which the toner particles electrophores in the insulating liquid can be increased as described in the tenth embodiment.

  In the present embodiment, a charge control agent having a compatibility with the insulating liquid and having a metal is contained in the insulating liquid together with the toner particles. This makes it possible to increase the speed at which the toner particles electrophoreses in the insulating liquid, as described in Examples 9 and 12, regardless of whether the groups on the surface of the toner particles are basic groups or acidic groups. Can be.

FIG. 1 is a configuration diagram illustrating a main configuration of a liquid image forming apparatus. 4 is a graph showing a ratio of a dispersion promoting substance to a toner and transferability of a toner image. FIGS. 3A and 3B are schematic diagrams illustrating a dispersion state of toner particles and a dispersion accelerating substance in a liquid developer. Evaluation device used for measuring the moving current measurement cell. (A) is a graph showing the results obtained by observing the response characteristics of toner particles when the liquid developer of Example 5 was placed in an AC electric field. (B) is a graph showing the results obtained by observing the response characteristics of toner particles when the liquid developer of Comparative Example 3 was placed in an AC electric field. 9 is a graph showing the relationship between the amount of an acidic group-containing charge control agent added and the mobility of toner particles in Example 7. 14 is a graph illustrating a relationship between a bias value applied to a developing roller and mobility of toner particles in Embodiment 7. 14 is a graph showing a relationship between a bias value applied to a developing roller and a current value flowing between a photoconductor and a developing roller in Example 7. 14 is a graph showing the relationship between the amount of a basic group-containing charge control agent added and the mobility of toner particles in Example 8. 19 is a graph showing the relationship between the amount of zirconium octylate added and the mobility of toner particles in Example 9.

Explanation of reference numerals

1 Photoconductor (latent image carrier)
17 Developing roller (developer carrier)
T Toner particles (colored particles)
D Dispersion promoting substance

Claims (20)

In a liquid developer having at least a resin and colored particles composed of a colored substance, and a liquid serving as a dispersion medium thereof, a liquid developer for developing the latent image by attaching the colored particles to a latent image on a latent image carrier,
As a dispersion accelerating substance for accelerating the dispersion of the colored particles in the liquid, one having a charge having a polarity opposite to that of the colored particles may be used in an amount of 0.05 to 20 parts by weight per 1 part by weight of the colored particles. A liquid developer, characterized in that the liquid developer is contained in the liquid. The liquid developer according to claim 1,
A liquid developer, wherein a substance having a polar group having a polarity opposite to that of the colored particles on the surface is used as the dispersion promoting substance. The liquid developer according to claim 2, wherein
A liquid developer, wherein the dispersion promoting substance has at least one of a carboxyl group and a hydroxyl group as the polar group. The liquid developer according to claim 1, 2 or 3,
A liquid developer characterized by using an average molecular weight of 1,000 or more as the dispersion promoting substance. The liquid developer according to claim 1, 2, 3, or 4,
A liquid developer characterized by using methyl methacrylate (acryl) or a compound containing the same as a main component as the dispersion promoting substance. The liquid developer according to claim 5,
A liquid developer, wherein a graft copolymer is used as the compound. The liquid developer according to claim 6,
A liquid developer, wherein a silicone oil is used as the liquid and a graft copolymer containing silicone is used as the graft copolymer. The liquid developer according to claim 6, wherein
A liquid developer, wherein the graft copolymer has an average molecular weight of 500 to 10,000. The liquid developer according to claim 1, 2, 3, 4, 5, 6, 7, or 8,
A liquid developer, wherein an aprotic liquid is used as the liquid. The liquid developer according to claim 9,
The above liquid has a viscosity of 10 to 1000 [mPa · s], an electric resistance of 1 × 10 ¹² [Ω · cm] or more, a surface tension of 30 [dyne / cm] or less, and a boiling point of 100 [° C.] or more. A liquid developer, comprising: The liquid developer according to claim 10,
A liquid developer, wherein a silicone-based liquid containing at least one of phenylmethylsiloxane, dimethylpolysiloxane, and polydimethylcyclosiloxane is used as the liquid. The liquid developer according to any one of claims 1 to 11,
A liquid developer, wherein a granular material is used as the dispersion promoting substance. The liquid developer according to claim 12,
A liquid developer, wherein the dispersion accelerating substance has an average particle diameter of 0.001 to 1 [μm]. The liquid developer according to any one of claims 1 to 13,
A liquid developer, wherein the colored particles have a volume average particle diameter of 0.1 to 6.0 [μm], and the concentration of the colored particles is 5 to 40 [% by weight]. The liquid developer according to claim 1,
A liquid developer comprising, as the colored particles, particles having on the surface thereof the dispersion accelerating substance, a basic group, and an affinity group for imparting affinity to the liquid. The liquid developer according to claim 1,
A liquid developer comprising, as the colored particles, particles having on the surface thereof the dispersion promoting substance, an acidic group, and an affinity group for imparting affinity to the liquid. The liquid developer according to claim 15, wherein
A liquid developer comprising a charge control agent having compatibility with the liquid and having an acidic group in the liquid together with the colored particles. The liquid developer according to claim 15, wherein
A liquid developer comprising a charge controlling agent having compatibility with the liquid and having a basic group in the liquid together with the colored particles. The liquid developer according to claim 15, wherein
A liquid developer comprising a charge control agent having compatibility with the liquid and having a metal, together with the colored particles, in the liquid. A latent image carrier,
Developing means for bringing a liquid developer into contact with the surface of the latent image carrier and developing the latent image by attaching colored particles to the latent image on the surface,
An image forming apparatus for forming an image by finally transferring a toner image obtained by attaching the colored particles to a latent image on the surface of the latent image carrier by the developing means on a recording material,
20. An image forming apparatus, wherein the liquid developer according to claim 1 is used as the liquid developer.

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