JP4939090B2 - Protective agent for image carrier, protective layer forming apparatus, image forming method, image forming apparatus, and process cartridge - Google Patents

Description

  The present invention protects the surface of an image carrier and protects the image carrier for use in electrophotographic image formation, and a protective layer forming apparatus for forming a protective layer comprising the protective agent on the surface of the image carrier, The present invention also relates to an image forming method, an image forming apparatus, and a process cartridge using the same.

  Conventionally, in electrophotographic image formation, an electrostatic latent image is formed by an electrostatic charge on an image carrier having a photosensitive layer containing a photoconductive substance, and a charged toner is attached to the electrostatic latent image. To form a visible image. This visible image is transferred to a recording medium such as paper and then fixed on the recording medium by heat, pressure, solvent gas, etc., and an output image is obtained.

  In such image formation, a two-component development method using frictional charging by stirring and mixing the toner and the carrier and a method of charging the toner without using a carrier by a method of charging the toner for visualization. It is roughly divided into a one-component development system. This one-component development method is further classified into a magnetic one-component development method and a non-magnetic one-component development method depending on whether or not a magnetic force is used to hold toner on the developing roller.

Conventionally, in a copying machine that requires high speed and image reproducibility, or a multi-function machine based on a copying machine, the requirements for charging stability of the toner, start-up property, long-term stability of image quality, etc. Many component development methods are employed. On the other hand, one-component development systems are often used in small printers, facsimiles, and the like, which have great demands for space saving and cost reduction.
In recent years, in any of the development methods, the colorization of output images has progressed, and the demand for higher image quality and stabilization of image quality has become stronger than ever. In order to achieve such high image quality, the average particle size of the toner is reduced, the particle shape has no angular portion, and the toner has a more round shape.

  In addition, an electrophotographic image forming apparatus generally charges a drum-shaped or belt-shaped image carrier uniformly while rotating the image carrier, regardless of the development method, and the image carrier by laser light or the like. A latent image pattern is formed thereon, the latent image pattern is visualized with toner (toner image), and transferred onto a recording medium. Then, the toner component that has not been transferred remains on the image carrier after the toner image is transferred to the recording medium. When these residuals are conveyed to the charging process as they are, the charging of the image carrier is prevented from being uniformly charged. Usually, after the transfer process, the toner remaining on the image carrier is removed by a cleaning blade or the like. Is removed by the cleaning means, and the surface of the image carrier is sufficiently cleaned, and then charging is performed.

  As described above, the surface of the image carrier is subjected to various physical stresses and electrical stresses in each process such as charging, development, transfer, and cleaning, and the surface state changes as the usage time elapses. Of these stresses, stress due to friction in the cleaning process wears the image carrier and causes scratches. In order to solve this problem, in order to reduce the frictional force between the image carrier and the cleaning blade, many proposals have been made on various lubricants, supply of lubricating components, and a method of forming a lubricating film. ing.

For example, Patent Document 1 proposes that a lubricant film is formed by supplying a solid lubricant mainly composed of zinc stearate to the surface of the photoreceptor in order to extend the life of the photoreceptor and the cleaning blade.
Further, in Patent Document 2, by using a lubricant supply device that supplies a lubricant containing a higher alcohol having 20 to 70 carbon atoms, the higher alcohol stays as irregular particles at the tip of the blade nip portion. It describes that the lubrication performance is maintained because it has wettability to the surface of the image bearing member.
Further, in Patent Document 3, since a powder of a specific alkylenebisalkylamide compound is used as a lubricating component, the powder is present at the interface where the cleaning blade contacts the surface of the image carrier. Is described as being able to hold for a long period of time.

However, as described above, the stress on the image carrier is not only received from the cleaning process, but the electrical stress particularly in the charging process greatly changes the state of the surface of the image carrier. Such an electrical stress is conspicuous in the contact charging method and the proximity charging method accompanied by a discharge phenomenon near the surface of the image carrier. In these charging methods, many active species and reaction products are generated on the surface of the image carrier, and many active species and reactive organisms generated in the atmosphere in the discharge region are adsorbed on the surface of the image carrier. .
For this reason, a lubricant using zinc stearate as described in Patent Document 1 covers the surface of the image carrier relatively evenly and gives good lubricity. However, when this lubricating layer repeatedly passes through the charging step, The acid decomposes and may eventually remain on the surface of the image carrier or the charging member as zinc oxide. Residual zinc oxide has hygroscopicity, and the resistance decreases due to moisture adsorption in the atmosphere, so in a high humidity environment, the electrostatic charge on the image carrier cannot be retained, and the electrostatic latent image is obscured, A so-called blurred image, in which an image defect occurs, may occur.

  Further, the higher alcohol lubricant of Patent Document 2 is easily wetted on the surface of the image carrier and can be expected to be effective as a lubricant. However, the higher alcohol molecules adsorbed on the image carrier, the adsorption occupation area occupied per molecule, Since the density of molecules adsorbed per unit area of the image carrier (adsorbed molecular weight per unit area) is small, the above-mentioned electrical stress easily penetrates the protective layer, and the image carrier It is difficult to obtain an effect that sufficiently protects the body.

  In addition, the lubricant having a nitrogen atom in the molecule as in Patent Document 3 is similar to a nitrogen oxide or an ammonium-containing compound as a decomposition product when the lubricant itself is subjected to the electrical stress described above. An ion dissociable compound is generated and taken into the lubricating layer, and the lubricating layer may have a low resistance under high humidity, causing image blurring.

Further, extending the life of the image forming apparatus and the members used in the image forming apparatus is highly interested in the market from the viewpoint of reducing the running cost and protecting the global environment by reducing waste. For example, in order to extend the life of the image carrier, an attempt has been made to improve the mechanical durability by providing a specific surface layer having a crosslinked structure on the surface of the image carrier (see Patent Document 4).
However, as described above, when a low-resistance substance is taken into the lubricating layer of the image carrier, in order to remove the low-resistance substance, it is necessary to scrape the entire lubricating layer by a cleaning mechanism, for example. For ease of removal, not only a large force is required for the removal, but also a large mechanical stress is applied to the image carrier during the removal. Even if a specific surface layer is provided on the surface of the image carrier, the life of the image carrier cannot be extended more than ever.

  Recently, in order to improve image quality and reduce manufacturing energy, a polymerization method toner manufactured by a polymerization method has been put on the market. Such a polymerized toner has excellent characteristics that it has fewer angular portions and a smaller average particle diameter than a pulverized toner manufactured by a pulverization method. However, in the system in which the edge of a cleaning member such as a rubber cleaning blade is pressed against the surface of the image carrier to clean the surface of the image carrier, the toner is edged due to the shape and particle size of the polymerization toner. There is a problem that it is difficult to dam at the portion, and cleaning of the remaining toner component is liable to occur.

As a cleaning device that can improve such toner cleaning failure, for example, Patent Document 5 discloses an image forming method that uses a volume average particle diameter D and an average circularity S of a toner to set a pressure contact force that satisfies a predetermined condition. A device has been proposed. According to this proposal, if the pressure contact force f is increased with a counter type cleaning blade, problems such as squealing and creaking of the cleaning blade occur, so it is necessary to set an upper limit as an empirical value. Are listed.
Further, Patent Document 6 discloses that the friction coefficient between the toner and the image carrier, the friction coefficient between the toner and the blade, and the friction coefficient between the toner and the image carrier in order to clean the toner having a smaller toner average particle size and a more spherical shape. There has been proposed a cleaning apparatus that defines the relationship between the adhesion force, the force that the toner receives from the blade, and the angle formed between the blade and the image carrier (cleaning angle).
In the above-mentioned patent documents 5 and 6, proposals have been made for improving toner cleaning properties while reducing stress on the image carrier in the cleaning mechanism in the cleaning of spherical toner typified by polymerized toner. However, there has been no disclosure or suggestion about extending the life in consideration of electrical stress on the image carrier, and no improvement has been achieved.

  Therefore, protecting the surface of the image carrier from electrical stress in the charging process is an extremely important issue for extending the life of the image carrier and the charging member and stabilizing the image quality. Until now, it has not been fully examined, and it remains as an unsolved issue.

Japanese Patent Publication No.51-22380 JP 2005-274737 A JP 2002-97483 A JP 2004-302451 A JP 2000-330441 A JP 2005-99125 A

  An object of the present invention is to solve various problems in the prior art and achieve the following objects. That is, the present invention relates to a protective agent for an image carrier that protects the image carrier from electrical stress due to charging and the like, and the protective agent deteriorated by the electrical stress hardly affects the image quality and peripheral members. It is an object of the present invention to provide a protective layer forming apparatus using an agent, and an image forming method, an image forming apparatus, and a process cartridge capable of stably forming good image quality using these.

Means for solving the above problems are as follows. That is,
<1> It is characterized by being at least one selected from alkyl carboxylic acid sugar alcohol ester which is an esterified product of an alkyl carboxylic acid having 15 to 35 carbon atoms in the alkyl group and a sugar alcohol, and a substitution product thereof. It is a protective agent for an image carrier.
<2> The protective agent for an image carrier according to <1>, wherein the alkylcarboxylic acid sugar alcohol ester is obtained by esterifying an alkylcarboxylic acid represented by the following structural formula (1) and a sugar alcohol. .
C _n H _2n + 1 COOH ··· structural formula (1)
However, in said structural formula (1), n shows the integer of 15-35.
<3> The protective agent for an image carrier according to any one of <1> to <2>, wherein the number average carbon number per molecule of sugar alcohol is 4 to 8.
<4> The protective agent for an image carrier according to any one of <1> to <3>, wherein the total number of carbon atoms of the alkyl group moiety in the alkylcarboxylic acid sugar alcohol ester and the substitution product thereof is 15 to 125.
<5> The image carrier protecting agent according to any one of <1> to <4>, wherein the alkylcarboxylic acid is a linear alkylcarboxylic acid.
<6> The protective agent for an image carrier according to any one of <1> to <5>, wherein the alkylcarboxylic acid sugar alcohol ester has an HLB value of 1.0 to 6.5.
<7> An image carrier and means for forming a protective layer by applying the image carrier protective agent according to any one of <1> to <6> to the surface of the image carrier. This is a protective layer forming apparatus.
<8> a pressing force applying member that presses the image carrier protective agent to contact the protective agent supply member; a protective agent supply member that supplies the image carrier protective agent to the surface of the image carrier; The protective layer forming apparatus according to <7>, further comprising a protective layer forming member that forms a protective layer by thinning a protective agent for an image carrier.
<9> An electrostatic latent image forming step of forming an electrostatic latent image on an image carrier, a developing step of developing the electrostatic latent image with toner to form a visible image, and the visible image And a protective layer for forming a protective layer by applying the image carrier protective agent according to any one of <1> to <6> to the surface of the image carrier after the transfer An image forming method comprising at least a forming step and a fixing step of fixing a transfer image transferred to the recording medium.
<10> An image carrier, an electrostatic latent image forming unit that forms an electrostatic latent image on the image carrier, and a developing unit that develops the electrostatic latent image with toner to form a visible image Transfer means for transferring the visible image to a recording medium, protective layer forming means according to any one of <7> to <8>, and fixing means for fixing the transferred image transferred to the recording medium And an image forming apparatus characterized by comprising:
<11> The image forming apparatus according to <10>, further including a cleaning unit that removes toner remaining on the surface of the image carrier on the downstream side of the transfer unit and the upstream side of the protective layer forming unit.
<12> The image forming apparatus according to any one of <10> to <11>, wherein the outermost surface layer contains at least a thermosetting resin.
<13> The image forming apparatus according to any one of <10> to <12>, wherein the image carrier is any one of a photosensitive member and an intermediate transfer member.
<14> The image forming apparatus according to any one of <10> to <13>, wherein the electrostatic latent image forming unit includes a charger disposed in contact with or close to the surface of the image carrier.
<15> The image forming apparatus according to <14>, wherein the charger includes a voltage applying unit that applies a voltage having an AC component.
<16> The image formation according to any one of <10> to <15>, wherein an average circularity that is an average value of the circularity SR represented by the following mathematical formula 1 of the toner is 0.93 to 1.00. Device.
<Formula 1>
Circularity SR = (perimeter of circle having the same area as the projected area of toner particles) / (perimeter of projected image of toner particles)
<17> Any one of <10> to <16>, wherein a ratio (D4 / D1) of the mass average particle diameter (D4) to the number average particle diameter (D1) of the toner is 1.00 to 1.40. The image forming apparatus described.
<18> A process cartridge comprising an image carrier and at least the protective layer forming means according to any one of <7> to <8>, wherein the process cartridge is detachable from the main body of the image forming apparatus. It is.
<19> The process cartridge according to <18>, further including a cleaning unit that removes toner remaining on the surface of the image carrier on the upstream side of the protective layer forming unit.
<20> The process cartridge according to any one of <18> to <19>, wherein the outermost surface layer contains at least a thermosetting resin.
<21> The process cartridge according to any one of <18> to <20>, further including a charger disposed in contact with or close to the surface of the image carrier.
<22> The process cartridge according to any one of <18> to <21>, wherein an average circularity that is an average value of the circularity SR expressed by the following mathematical formula 1 of the toner is 0.93 to 1.00: It is.
<Formula 1>
Circularity SR = (perimeter of circle having the same area as the projected area of toner particles) / (perimeter of projected image of toner particles)
<23> Any one of <18> to <22>, wherein the ratio (D4 / D1) of the mass average particle diameter (D4) to the number average particle diameter (D1) of the toner is 1.00 to 1.40. It is a process cartridge of description.

  The protective agent for an image carrier of the present invention is at least selected from alkyl carboxylic acid sugar alcohol ester, which is an esterified product of alkyl carboxylic acid having 15 to 35 carbon atoms in the alkyl group and sugar alcohol, and a substitution product thereof. One type. In the protective agent for an image carrier of the present invention, the use of a specific alkylcarboxylic acid sugar alcohol ester increases the hydrophilicity due to electrical stress at the hydrophilic part derived from the sugar alcohol. In order to form a protective layer while adsorbing densely to the surface and hydrophobizing the part with an alkylcarboxylic acid-derived portion after adsorption, the protective layer decomposes even when repeatedly subjected to electrical stress, The deterioration of the image carrier can be prevented from being promoted, and the image carrier can be used for an extremely long period of time.

  The protective layer forming apparatus of the present invention has an image carrier and means for forming a protective layer by applying the protective agent for an image carrier of the present invention to the surface of the image carrier. Many of the protective agents for image carriers of the present invention are relatively soft and easily plastically deformed. Therefore, when an attempt is made to form a protective layer by directly pressing the protective agent for the image carrier onto the surface of the image carrier, the supply becomes excessive and the protective layer formation efficiency is not good, and the protective layer becomes multi-layered. Since it may become a factor that impedes light transmission in an exposure process such as when forming an electrostatic latent image, the types of protective agents for the image carrier that can be used are limited. On the other hand, when the protective layer forming apparatus is configured as described above and the supply member is interposed between the image carrier protective agent and the image carrier, a soft image carrier protective agent is used. Even in such a case, the protective agent for the image carrier can be supplied evenly to the surface of the image carrier.

Since the image forming apparatus of the present invention has the protective layer forming means of the present invention having the above-mentioned protective agent for the image carrier, it can continue to be used without exchanging the image carrier for a very long time. In particular, when the image carrier includes a thermosetting resin in the outermost surface layer, an image containing the thermosetting resin is prevented by preventing the image carrier from being deteriorated by an electrical stress with a protective agent for the image carrier. The durability of the carrier against mechanical stress can be continuously expressed over a long period of time. As a result, the durability of the image carrier can be increased to a level where it can be used substantially without replacement.
Further, in the charging device arranged in contact with or close to the surface of the image carrier, the electrical stress tends to be large because the discharge region exists in the very vicinity of the image carrier. If the image forming apparatus of the present invention in which is formed, the image carrier can be used without being exposed to electrical stress.
Further, since the image carrier protecting component of the present invention does not substantially contain a metal component, the charging device disposed in contact or close to the image bearing member is not contaminated with a metal oxide or the like. Can also be improved.
In addition, since the surface state of the image carrier can be made extremely small due to the effect of the protective layer formed, the average quality is such that the quality of the cleaning changes sensitively to the state change of the image carrier. Even a toner having a large degree of circularity or a toner having a small average particle diameter can be stably cleaned over a long period of time.

Since the process cartridge of the present invention has the protective layer forming means of the present invention having the protective agent for the image carrier, the replacement interval of the process cartridge can be set to be extremely long. And the amount of waste can be greatly reduced. In particular, when the image carrier includes a thermosetting resin in the outermost surface layer, an image containing the thermosetting resin is prevented by preventing the image carrier from being deteriorated by an electrical stress with a protective agent for the image carrier. The durability of the carrier against mechanical stress can be sustained over a long period of time.
In addition, since the protective agent for an image carrier of the present invention does not substantially contain a metal component, the charging member disposed in contact with or in the vicinity thereof is not contaminated with a metal oxide or the like. Change can be reduced. For this reason, it becomes easy to reuse process cartridge components such as an image carrier and a charging member, and the amount of waste can be further reduced.

  According to the present invention, the conventional problems can be solved, the image carrier is protected from electrical stress due to charging or the like, and the protective agent deteriorated by the electrical stress hardly affects the image quality and peripheral members. PROBLEM TO BE SOLVED: To provide a protective agent for a carrier, a protective layer forming apparatus using the protective agent, and an image forming method, an image forming apparatus, and a process cartridge capable of stably obtaining good image quality using the protective agent. Can do.

(Protective agent for image carrier)
The protective agent for an image carrier of the present invention is at least selected from alkyl carboxylic acid sugar alcohol ester, which is an esterified product of alkyl carboxylic acid having 15 to 35 carbon atoms in the alkyl group and sugar alcohol, and a substitution product thereof. It contains 1 type and further contains other components as required. In addition, when using 2 or more types of alkyl carboxylic acids, the carbon number of an alkyl group part shall take the number average of the carbon number of the alkyl group which each alkyl carboxylic acid has.

  Carbon number of the alkyl group part of the said alkylcarboxylic acid is 15-35, and 16-25 are preferable. When the number of carbon atoms is less than 15, sufficient hydrophobicity is not expressed, and in particular, the image may be blurred or disturbed due to leakage of latent image charges in a high-temperature and high-humidity environment. The crystallinity of the material tends to be high, and when the protective agent for the image carrier is molded, crystallization may partially progress, density uniformity is impaired, uniform coating becomes difficult, and uneven coating occurs. However, image unevenness may occur.

The alkylcarboxylic acid sugar alcohol ester is obtained by esterifying an alkylcarboxylic acid represented by the following structural formula (1) and a sugar alcohol.
C _n H _2n + 1 COOH ··· structural formula (1)
However, in said structural formula (1), n shows the integer of 15-35, and 16-25 are preferable.

  Examples of the alkylcarboxylic acid represented by the structural formula (1) include normal palmitic acid (n = 15), normal margaric acid (n = 16), normal stearic acid (n = 17), and normal arachidic acid (n = 19), normal behenic acid (n = 21), normal lignoceric acid (n = 23), normal serotic acid (n = 25), normal montanic acid (n = 27), normal melicic acid (n = 29) ), Isostearic acid (n = 17), or substitutes thereof. These may be used individually by 1 type and may use 2 or more types together.

The alkylcarboxylic acid represented by the structural formula (1) is preferably a linear alkylcarboxylic acid because the adsorption density of the protective agent molecule for the image carrier is particularly high.
Further, when the protective agent for the image carrier existing on the surface of the image carrier is subjected to electrical stress, the low molecular weight component at the end is vaporized and conveyed outside the image forming system by an air flow. On the other hand, a degraded component having a relatively large molecular weight, although the alkyl group is cleaved, has its own hydrophilicity, but is surrounded by surrounding alkylcarboxylic acid sugar alcohol esters and takes a form similar to micelles. The liquid is present in a state that is not easily affected by humidity, and is discharged out of the image forming system by a cleaning mechanism or the like.

  The sugar alcohol means a polyhydric alcohol obtained by reducing a carbonyl group of a monosaccharide or a homologue thereof. In a broad sense, it includes a cyclic one, and includes inositol which is a hexahydric alcohol having a cyclohexane ring, quercitol which is a pentavalent alcohol, and the like. In any case, the alkylcarboxylic acid sugar alcohol ester can have a plurality of alkyl groups because it can perform ester bonding at a plurality of positions in one molecule. For this reason, the alkylcarboxylic acid sugar alcohol ester is sufficiently adsorbed on the surface of the image carrier having deteriorated and high hydrophilicity at the hydrophilic part derived from the sugar alcohol, covering the deteriorated part, The surface derived from the alkyl carboxylic acid can make the surface highly hydrophobic. As a result, the image carrier is highly protected from electrical stress, and can be used without replacement over a long period of time.

  The number average carbon number per molecule of the sugar alcohol is preferably 4-8. When the number of carbon atoms is less than 4, the hydrophilic portion tends to be relatively small, and the alkylcarboxylic acid that can be selected may be limited in order to maintain sufficient adsorption performance. On the other hand, when the number of carbon atoms exceeds 8, the hydrophilic portion tends to be relatively large, and the molecular weight of the alkyl carboxylic acid necessary for hydrophobizing the surface of the image carrier must be increased. However, in this case, the alkylcarboxylic acid sugar alcohol molecule also becomes large, and the protective agent becomes hard, has a high viscosity, and may become brittle.

  Examples of the sugar alcohol include 1,2,3,4-butanetetraol, 1,2,3,4,5-pentanepentaol (pentitol), 1,2,3,4,5,6-hexane. Carbonyl groups of monosaccharides such as hexaol (hexitol), 1,2,3,4,5,6,7-heptaneheptaol, 1,2,3,4,5,6,7,8-octaneoctaol And polyhydric alcohols obtained by reducing the above or homologues thereof; inositol, quercitol having a cyclohexane ring, or a substitution thereof. These may be used individually by 1 type and may use 2 or more types together.

Examples of such alkylcarboxylic acid sugar alcohol esters include hexitol monostearate, hexitol distearate, hexitol tristearate, inositol tristearate, monostearic acid 1,2,3. , 4-butanetetraol ester, monostearic acid pentitol ester, tristearic acid pentitol ester, monobehenic acid 1,2,3,4-butanetetraol ester, monopalmitic acid hexitol ester, or a substitute thereof Is mentioned. These may be used individually by 1 type and may use 2 or more types together.
Examples of the substituent include all or part of hydrogen atoms bonded to carbon atoms, halogen atoms such as fluorine, chlorine and bromine, and functional groups such as phenyl, cyclohexyl, cyclopentyl and alkylsilsesquioxyl groups. And those substituted with.

In addition to the above, the alkyl carboxylic acid sugar alcohol ester includes those using unsaturated aliphatic carboxylic acid. However, these unsaturated carboxylic acid parts naturally oxidize in the atmosphere, resulting in alteration or heat generation. This is not preferable.
In the case of an alkylcarboxylic acid having a branched structure in the middle, when the protective agent is adsorbed on the surface of the image carrier, the adsorption density may not be sufficiently high due to the steric barrier of the alkyl chain. Therefore, the alkyl carboxylic acid is preferably a linear alkyl carboxylic acid.

  15-125 are preferable, as for the total carbon number of the alkyl group part in the said alkylcarboxylic acid sugar alcohol ester and its substitution, 15-105 are more preferable, and 16-75 are still more preferable. When the total number of carbon atoms is less than 15, sufficient hydrophobicity is not exhibited, and in particular, there may be image blurring and disturbance due to leakage of latent image charges in a high-temperature and high-humidity environment. , The crystallinity of the material tends to be high, and when the protective agent is molded, crystallization may partially progress, density uniformity is impaired, uniform application becomes difficult, application unevenness occurs, image May be uneven. In addition, when using 2 or more types of alkyl carboxylic acid sugar alcohol esters, the total carbon number of an alkyl group part shall take the number average of the total carbon number of the alkyl group which each alkyl carboxylic acid sugar alcohol ester has.

According to the present invention, the image carrier is protected from electrical stress by deteriorating the adsorbed image carrier protective agent instead of being subjected to electrical stress and consuming the deteriorated components as needed to renew the protective layer. Therefore, it is preferable that the deteriorated protective agent component is quickly removed. Therefore, it is preferable that the hydrophobicity parameter (HLB value) of alkylcarboxylic acid sugar alcohol ester is 1.0-6.5.
Here, the HLB value is a value representing the degree of affinity of the surfactant to water and oil (an organic compound insoluble in water), and the larger the value, the higher the affinity to water. The HLB value can be calculated by the following Kawakami equation.
HLB = 7 + 11.7 × log (Mw / Mo)
However, Mw represents the molecular weight of a hydrophilic part. Mo represents the molecular weight of the lipophilic group. log represents the common logarithm.

The HLB value (hydrophobic parameter) of the alkyl carboxylic acid sugar alcohol ester is preferably 1.0 to 6.5. Among the alkyl carboxylic acid sugar alcohol esters, for example, monostearic acid 1, 2, 3, 4 -Butanetetraol ester (HLB value = 4.6), monostearic acid pentitol ester (HLB value = 5.5), tristearic acid pentitol ester (HLB value = 1.3), monobehenic acid 1,2, 3,4-butanetetraol ester (HLB value = 3.5), monostearic acid hexitol ester (HLB value = 6.3), and the like.
Further, the melting point of the alkylcarboxylic acid sugar alcohol ester is preferably 40 to 100 ° C. If the melting point is too low, it is difficult to melt in the apparatus depending on the use environment and to exhibit the desired function. Conversely, if it is too large, the protective agent component is stably applied to the surface of the image carrier. It may be difficult to supply.

The number of alkyl carboxylic acid sites in one molecule of the alkyl carboxylic acid sugar alcohol ester indicates hydrophobicity, and the larger number prevents the dissociable substance generated by air discharge from being adsorbed on the surface of the image carrier, In addition, it is effective to reduce the electrical stress on the surface of the image carrier in the charged region. However, if the proportion of the alkyl carboxylic acid moiety is too large, the sugar alcohol portion exhibiting hydrophilicity is obscured, and sufficient adsorption performance may not be exhibited depending on the surface state of the image carrier.
Therefore, the average number of ester bonds per molecule of the alkylcarboxylic acid polyhydric alcohol ester is preferably 75% or less of the alcoholic OH group of the sugar alcohol. The average number of ester bonds per molecule of these alkylcarboxylic acid sugar alcohol esters may be adjusted by selecting one or more alkylcarboxylic acid sugar alcohol esters having different numbers of ester bonds and mixing them. .

  As the method for molding the protective agent for an image carrier of the present invention into a fixed shape, for example, a prismatic shape or a cylindrical shape, a known method can be used as a method for molding a solid substance, for example, a melt molding method. , Powder molding method, hot press molding method, cold isostatic pressing method (CIP), hot isostatic pressing method (HIP) and the like.

Specifically, as the melt molding method, a predetermined amount of the heated and melted alkylcarboxylic acid sugar alcohol ester is poured into a mold having a predetermined shape, which is heated in advance to the melting temperature of the protective agent for the image carrier. If necessary, after maintaining for a certain period of time at a temperature equal to or higher than the melting point, the molded body can be obtained by cooling by standing or cooling. In addition, in order to remove internal distortion of the molded product, after cooling proceeds to a temperature below the phase transition temperature of the alkylcarboxylic acid sugar alcohol ester during cooling, it is gradually reheated to a temperature above the phase transition temperature again. May be.
Next, after cooling to a temperature in the vicinity of room temperature, the molded body is removed from the mold to obtain a molded body of the protective agent for the image carrier. Thereafter, the shape of the protective agent for the image carrier may be adjusted by cutting or the like.

  The mold is preferably a metal mold such as steel, stainless steel or aluminum because of its good thermal conductivity and good dimensional accuracy. The inner wall surface of the mold is preferably coated with a release agent such as a fluororesin or a silicone resin in order to improve the releasability.

(Protective layer forming device)
The protective layer forming apparatus of the present invention comprises at least a means for forming an image carrier and a protective layer by applying the protective agent for the image carrier of the present invention to the surface of the image carrier. Other means are available accordingly.

The protective layer forming means includes a pressing force applying member that presses the image carrier protective agent to contact the protective agent supply member, and a protective agent supply member that supplies the image carrier protective agent to the surface of the image carrier. And a protective layer forming member for forming a protective layer by thinning the supplied image carrier protective agent, and further having other configurations as necessary.
In addition, when the protective layer forming apparatus includes the protective layer forming member, the protective layer forming member may also serve as a cleaning member. It is preferable to remove the residue mainly composed of toner on the carrier so that the residue does not enter the protective layer.

Here, FIG. 1 is a schematic view showing an example of the protective layer forming apparatus of the present invention.
The protective layer forming apparatus 2 disposed opposite to the photosensitive drum 1 serving as an image carrier includes an image carrier protective agent 21, a protective agent supply member 22, a pressing force applying member 23, and a protective layer formation according to the present invention. It is mainly composed of the member 24 and the like.

The protective agent 21 for an image carrier of the present invention is in contact with, for example, a brush-like protective agent supply member 22 by a pressing force from a pressing force applying member 23. The protective agent supply member 22 rotates and rubs with the image carrier 1 with a linear velocity difference. At this time, the protective agent for the image carrier held on the surface of the protective agent supply member is supplied to the surface of the image carrier.
The protective agent for the image carrier supplied to the surface of the image carrier may not be a sufficient protective layer at the time of supply depending on the selection of the substance type. Therefore, in order to form a more uniform protective layer, for example, The protective layer forming member having the member is thinned to form a protective layer.

The image bearing member on which the protective layer is formed is, for example, in a minute gap by bringing the charging roller 3 to which a DC voltage or a voltage obtained by superimposing an AC voltage is applied with a high voltage power source (not shown) into contact or in proximity. The image carrier is charged by discharging. At this time, a part of the protective layer is decomposed or oxidized due to electrical stress, and air discharge products adhere to the surface of the protective layer.
Such decomposition products, oxides, or air discharge products are generally hydrophilic or contain hydrophilic groups. The protective agent for an image carrier comprising the alkylcarboxylic acid sugar alcohol ester of the present invention belongs to a nonionic surfactant in terms of molecular structure, and has a hydrophilic part and a hydrophobic part in one molecule. Has a part. Further, when the alkyl group portion of the alkylcarboxylic acid has a carbon number in the range of 15 to 35, it is possible to achieve both the protective effect of the image carrier by the protective layer and the removability of the deteriorated protective agent for the image carrier. It becomes.

  The deteriorated protective agent for the image carrier is removed by the cleaning mechanism together with components such as toner remaining on the image carrier by a normal cleaning mechanism. Such a cleaning mechanism may be used also as the above-described protective layer forming member. However, the function of removing the residue on the surface of the image carrier and the function of forming the protective layer are based on an appropriate member rubbing state. Therefore, it is preferable to provide a cleaning mechanism 4 including a cleaning member 41, a cleaning pressing mechanism 42, and the like on the upstream side of the image carrier protective agent supply unit as shown in FIG.

  The material of the blade used for the protective layer forming member is not particularly limited and can be appropriately selected from known materials for cleaning blades according to the purpose. For example, urethane rubber, hydrin rubber, silicone rubber, fluorine For example, rubber. These may be used individually by 1 type and may use 2 or more types together. In these blades, the contact portion with the image carrier may be coated or impregnated with a low coefficient of friction material. Moreover, in order to adjust the hardness of an elastic body, you may disperse fillers, such as an organic filler and an inorganic filler.

The cleaning blade is fixed to the blade support by any method such as adhesion or fusion so that the tip can be pressed against the surface of the image carrier. The thickness of the blade is not uniquely defined in consideration of the force applied by pressing, but is preferably 0.5 to 5 mm, and more preferably 1 to 3 mm.
Also, the length of the cleaning blade that protrudes from the support and can bend, that is, the so-called free length, is not unambiguously defined by the balance with the force applied by pressing, but preferably 1 to 15 mm. 2-10 mm is more preferable.

  As another configuration of the protective layer forming blade member, the surface of the elastic metal blade such as a spring plate is coated with a coating layer of resin, rubber, elastomer or the like via a coupling agent or a primer component as necessary. It may be formed by a method such as dipping, heat-cured or the like if necessary, and further subjected to surface polishing if necessary.

The coating layer contains at least a binder resin and a filler, and further contains other components as necessary.
The binder resin is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include fluorine resins such as PFA, PTFE, FEP, and PVdF; silicone elastomers such as fluorine rubber and methylphenyl silicone elastomer; Is mentioned.

  The thickness of the elastic metal blade is preferably 0.05 to 3 mm, more preferably 0.1 to 1 mm. In the elastic metal blade, in order to suppress twisting of the blade, a process such as bending may be performed in a direction substantially parallel to the support shaft after the attachment.

  The force that presses the image carrier with the protective layer forming member is sufficient to spread the protective agent for the image carrier to form a protective layer, and the linear pressure is preferably 5 to 80 gf / cm, preferably 10 to 60 gf. / Cm is more preferable.

A brush-like member is preferably used as the protective agent supply member. In this case, in order to suppress mechanical stress on the surface of the image carrier, it is preferable that the brush fiber has flexibility. The material for the flexible brush fiber is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include polyolefin resins (for example, polyethylene and polypropylene); polyvinyl resins and polyvinylidene resins (for example Polystyrene, acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, polyvinyl ketone); vinyl chloride-vinyl acetate copolymer; styrene-acrylic acid copolymer; styrene- Butadiene resin; fluororesin (eg, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene); polyester; nylon; acrylic; rayon; ; Polycarbonate; phenolic resins; amino resins (e.g. urea - formaldehyde resins, melamine resins, benzoguanamine resins, urea resins, polyamide resins).
In order to adjust the degree of bending, for example, diene rubber, styrene-butadiene rubber (SBR), ethylene propylene rubber, isoprene rubber, nitrile rubber, urethane rubber, silicone rubber, hydrin rubber, norbornene rubber, etc. may be combined. .

As the support for the protective agent supply member, there are a fixed mold and a rotatable roll. Examples of the roll-shaped supply member include a roll brush obtained by winding a tape having brush fibers piled around a metal core bar in a spiral shape. The brush fiber has a fiber diameter of about 10 to 500 μm, the length of the brush fiber is 1 to 15 mm, and the brush density is 10,000 to 300,000 per square inch (1.5 × 10 ^{7 to} 4.5 per square meter). × 10 ⁸ ) is preferable.

  As the protective agent supply member, it is preferable to use a high brush density in terms of supply uniformity and supply stability, and one fiber is produced from several to hundreds of fine fibers. It is preferable. For example, bundling 50 fine fibers of 6.7 decitex (6 denier), such as 333 decitex = 6.7 decitex × 50 filament (300 denier = 6 denier × 50 filament), and implanting as one fiber Is preferred.

  Moreover, you may provide a coating layer in the brush surface for the purpose of stabilizing the surface shape, environmental stability, etc. of a brush as needed. As a component constituting the coating layer, it is preferable to use a coating layer component that can be deformed according to the bending of the brush fiber. The coating layer component is not particularly limited as long as it is a material that can maintain flexibility, and can be appropriately selected according to the purpose. For example, polyethylene, polypropylene, chlorinated polyethylene, chlorosulfonated polyethylene, etc. Polyolefin resin: Polystyrene such as polystyrene, acrylic (for example, polymethyl methacrylate), polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, polybiliketone, or polyvinylidene resin such as polyvinyl chloride-acetic acid Vinyl copolymer; silicone resin composed of organosiloxane bonds or modified products thereof (modified products such as alkyd resin, polyester resin, epoxy resin, polyurethane resin, etc.); Fluororesins such as oloalkyl ether, polyfluorovinyl, polyfluorovinylidene, polychlorotrifluoroethylene; polyamides; polyesters; polyurethanes; polycarbonates; amino resins such as urea-formaldehyde resins; epoxy resins or composite resins thereof It is done.

(Image forming method and image forming apparatus)
The image forming method of the present invention includes at least an electrostatic latent image forming step, a developing step, a transfer step, a protective layer forming step, and a fixing step, preferably including a cleaning step, and further appropriately as necessary. It includes other selected processes such as a static elimination process, a recycling process, and a control process.
The image forming apparatus of the present invention comprises at least an image bearing member, an electrostatic latent image forming unit, a developing unit, a transfer unit, a protective layer forming unit, and a fixing unit, and preferably includes a cleaning unit. And other means appropriately selected as necessary, for example, static elimination means, recycling means, control means, and the like.

  The image forming method of the present invention can be preferably carried out by the image forming apparatus of the present invention, the electrostatic latent image forming step can be performed by the electrostatic latent image forming means, and the developing step is the developing The transfer step can be performed by the transfer unit, the protective layer forming step can be performed by the protective layer forming unit, and the fixing step can be performed by the fixing unit, The other steps can be performed by the other means.

<Electrostatic latent image forming step and electrostatic latent image forming means>
The electrostatic latent image forming step is a step of forming an electrostatic latent image on the image carrier.
-Image carrier-
The image carrier (sometimes referred to as “electrostatic latent image carrier” or “photoreceptor”) is not particularly limited in terms of material, shape, structure, size, etc., and is appropriately selected from known ones. The shape is preferably a drum shape, and examples of the material include inorganic photoconductors such as amorphous silicon and selenium, and organic photoconductors such as polysilane and phthalopolymethine.

  The image carrier (photoreceptor) used in the image forming apparatus of the present invention has a conductive support and at least a photosensitive layer on the conductive support, and further has other layers as necessary. It becomes.

  As the photosensitive layer, a single layer type in which a charge generation material and a charge transport material are mixed, a forward layer type in which a charge transport layer is provided on the charge generation layer, or a charge generation layer is provided on the charge transport layer. There is a reverse layer type. In order to improve the mechanical strength, abrasion resistance, gas resistance, cleaning property, etc. of the photoreceptor, an outermost surface layer can be provided on the photosensitive layer. An undercoat layer may be provided between the photosensitive layer and the conductive support. Moreover, an appropriate amount of a plasticizer, an antioxidant, a leveling agent or the like can be added to each layer as necessary.

The conductive support is not particularly limited as long as it has a volume resistance of 1.0 × 10 ¹⁰ Ω · cm or less, and can be appropriately selected according to the purpose. For example, aluminum, Metals such as nickel, chromium, nichrome, copper, gold, silver and platinum, metal oxides such as tin oxide and indium oxide, film or cylindrical plastic, paper coated or aluminum by vapor deposition or sputtering A plate made of aluminum alloy, nickel, stainless steel or the like, and a tube processed into a drum shape by a method such as extrusion or drawing, and then subjected to surface treatment such as cutting, superfinishing, or polishing can be used.
The drum-shaped support preferably has a diameter of 20 to 150 mm, more preferably 24 to 100 mm, and still more preferably 28 to 70 mm. When the diameter of the drum-shaped support is less than 20 mm, it may be physically difficult to arrange each step of charging, exposure, development, transfer, and cleaning around the drum. When the diameter exceeds 150 mm, The image forming apparatus may become large. In particular, when the image forming apparatus is a tandem type, since it is necessary to mount a plurality of photoconductors, the diameter is preferably 70 mm or less, and more preferably 60 mm or less. Further, an endless nickel belt or an endless stainless steel belt as disclosed in JP-A-52-36016 can also be used as the conductive support.

The undercoat layer of the photoconductor may be composed of a single layer or a plurality of layers. For example, (1) the resin is the main component, and (2) the white pigment and the resin are the main components. And (3) a metal oxide film obtained by chemically or electrochemically oxidizing the surface of a conductive substrate. Among these, those containing a white pigment and a resin as main components are preferable.
Examples of the white pigment include metal oxides such as titanium oxide, aluminum oxide, zirconium oxide, and zinc oxide. Among these, titanium oxide is particularly preferable because it is excellent in preventing injection of charges from the conductive support.
Examples of the resin include thermoplastic resins such as polyamide, polyvinyl alcohol, casein, and methyl cellulose; thermosetting resins such as acrylic, phenol, melamine, alkyd, unsaturated polyester, and epoxy. These may be used individually by 1 type and may use 2 or more types together.
There is no restriction | limiting in particular in the thickness of the said undercoat layer, According to the objective, it can select suitably, 0.1-10 micrometers is preferable and 1-5 micrometers is more preferable.

  Examples of the charge generation material in the photosensitive layer include monoazo pigments, bisazo pigments, trisazo pigments, tetrakisazo pigments and other azo pigments, triarylmethane dyes, thiazine dyes, oxazine dyes, xanthene dyes, Cyanine dyes, styryl dyes, pyrylium dyes, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, bisbenzimidazole pigments, indanthrone pigments, squarylium pigments, phthalocyanine pigments, etc. Organic pigments or dyes; selenium, selenium-arsenic, selenium-tellurium, cadmium sulfide, zinc oxide, titanium oxide, amorphous silicon, and other inorganic materials. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the charge transport material in the photosensitive layer include anthracene derivatives, pyrene derivatives, carbazole derivatives, tetrazole derivatives, metallocene derivatives, phenothiazine derivatives, pyrazoline compounds, hydrazone compounds, styryl compounds, styryl hydrazone compounds, enamine compounds, butadiene compounds, distyryl. Examples thereof include compounds, oxazole compounds, oxadiazole compounds, thiazole compounds, imidazole compounds, triphenylamine derivatives, phenylenediamine derivatives, aminostilbene derivatives, and triphenylmethane derivatives. These may be used individually by 1 type and may use 2 or more types together.

  As the binder resin used to form the photosensitive layer, it is electrically insulating and may be a known thermoplastic resin, thermosetting resin, photocurable resin, photoconductive resin, or the like. it can. Examples of the binder resin include polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, ethylene-vinyl acetate copolymer, polyvinyl butyral, Polyvinyl acetal, polyester, phenoxy resin, (meth) acrylic resin, polystyrene, polycarbonate, polyarylate, polysulfone, polyethersulfone, ABS resin and other thermoplastic resins, phenol resin, epoxy resin, urethane resin, melamine resin, isocyanate Examples thereof include thermosetting resins such as resins, alkyd resins, silicone resins, thermosetting acrylic resins, polyvinyl carbazole, polyvinyl anthracene, and polyvinyl pyrene. These may be used individually by 1 type and may use 2 or more types together.

Examples of the antioxidant include phenolic compounds, paraphenylenediamines, organic sulfur compounds, and organic phosphorus compounds.
Examples of the phenol compound include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearyl-β- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate, 2,2'-methylene-bis- (4-methyl-6-t-butylphenol), 2,2'-methylene-bis- (4-ethyl- 6-t-butylphenol), 4,4′-thiobis- (3-methyl-6-tert-butylphenol), 4,4′-butylidenebis- (3-methyl-6-tert-butylphenol), 1,1,3 -Tris- (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxy Ben ) Benzene, tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane, bis [3,3′-bis (4′-hydroxy-3 ′) -T-butylphenyl) butyric acid] cricol ester, tocopherols and the like.
Examples of the paraphenylenediamines include N-phenyl-N′-isopropyl-p-phenylenediamine, N, N′-di-sec-butyl-p-phenylenediamine, N-phenyl-N-sec-butyl- Examples include p-phenylenediamine, N, N′-di-isopropyl-p-phenylenediamine, N, N′-dimethyl-N, N′-di-t-butyl-p-phenylenediamine, and the like.
Examples of the hydroquinones include 2,5-di-t-octyl hydroquinone, 2,6-didodecyl hydroquinone, 2-dodecyl hydroquinone, 2-dodecyl-5-chlorohydroquinone, 2-t-octyl-5-methyl. Examples include hydroquinone and 2- (2-octadecenyl) -5-methylhydroquinone.
Examples of the organic sulfur compounds include dilauryl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, ditetradecyl-3,3′-thiodipropionate, and the like. .
Examples of the organic phosphorus compounds include triphenylphosphine, tri (nonylphenyl) phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, tri (2,4-dibutylphenoxy) phosphine, and the like.
These compounds are known as antioxidants such as rubbers, plastics and fats and oils, and commercially available products can be easily obtained.
The addition amount of the antioxidant is preferably 0.01 to 10% by mass with respect to the total mass of the layer to be added.

As the plasticizer, those used as plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the amount used is about 0 to 30 parts by mass with respect to 100 parts by mass of the binder resin. Is appropriate.
Further, a leveling agent may be added to the photosensitive layer. Examples of the leveling agent include silicone oils such as dimethyl silicone oil and methylphenyl silicone oil; polymers having a perfluoroalkyl group in the chain or oligomers. As for the usage-amount of the said leveling agent, 0-1 mass part is preferable with respect to 100 mass parts of said binder resins.

  The outermost surface layer of the photoreceptor is provided to improve the mechanical strength, abrasion resistance, gas resistance, cleaning properties, and the like of the photoreceptor. As the outermost surface layer, a polymer having a mechanical strength higher than that of the photosensitive layer and a material in which an inorganic filler is dispersed in the polymer are suitable. The resin used for the outermost surface layer may be either a thermoplastic resin or a thermosetting resin, but the thermosetting resin has high mechanical strength and suppresses abrasion due to friction with the cleaning blade. This is particularly preferable because of its extremely high capacity. If the surface layer is thin, there is no problem even if it does not have the charge transport capability, but if the surface layer without the charge transport capability is formed thick, the sensitivity of the photoreceptor decreases, the potential increases after exposure, and the residual layer Since the potential rise is likely to occur, it is preferable to include the above-described charge transport material in the surface layer or to use a polymer having charge transport ability as the polymer used in the surface layer.

  Since the mechanical strength of the photosensitive layer and the outermost surface layer is generally greatly different, the outermost surface layer is worn away due to friction with the cleaning blade. It is important that the outermost surface layer has a sufficient thickness, preferably 0.1 to 12 μm, more preferably 1 to 10 μm, and still more preferably 2 to 8 μm. When the thickness is less than 0.1 μm, it is too thin and easily disappears due to friction with the cleaning blade, and wear of the photosensitive layer may proceed from the disappeared portion. In the case of using a polymer having a charge transport ability, the cost of the polymer having a charge transport ability may be increased.

  The resin used for the outermost surface layer is preferably one that is transparent to writing light at the time of image formation and excellent in insulation, mechanical strength, and adhesion. For example, ABS resin, ACS resin, olefin-vinyl monomer Copolymer, chlorinated polyether, allyl resin, phenol resin, polyacetal, polyamide, polyamideimide, polyacrylate, polyallylsulfone, polybutylene, polybutylene terephthalate, polycarbonate, polyethersulfone, polyethylene, polyethylene terephthalate, polyimide, acrylic resin , Polymethyl bentene, polypropylene, polyphenylene oxide, polysulfone, polystyrene, AS resin, butadiene-styrene copolymer, polyurethane, polyvinyl chloride, polyvinylidene chloride, epoxy resin, etc. And the like. These polymers may be thermoplastic resins, but in order to increase the mechanical strength of the polymers, they are crosslinked with a crosslinking agent having a polyfunctional acryloyl group, carboxyl group, hydroxyl group, amino group, etc. By using a functional resin, the mechanical strength of the outermost surface layer is increased, and wear due to friction with the cleaning blade can be greatly reduced.

  The outermost surface layer preferably has a charge transporting capability. In order to provide the outermost surface layer with a charge transporting capability, the polymer used for the outermost surface layer and the above-described charge transporting material are mixed and used. A method using a polymer having a charge transporting capability for the outermost surface layer is conceivable, and the latter method is preferable because a high-sensitivity photoconductor and a small increase in residual potential can be obtained.

Preferred examples of the polymer having the charge transport layer ability include those having a group represented by the following structural formula (i) as a group having a charge transport ability in the polymer.
However, in the structural formula (i), Ar ¹ represents an arylene group which may have a substituent. Ar ² and Ar ³ may be the same as or different from each other, and each represents an aryl group that may have a substituent.

Such a group having a charge transporting ability is preferably added to a side chain of a polymer having high mechanical strength such as a polycarbonate resin and an acrylic resin, and the monomer can be easily produced, and the coating property and curability are also improved. It is particularly preferable to use an excellent acrylic resin.
The acrylic resin having such a charge transporting capability is a surface layer having high mechanical strength, excellent transparency, and high charge transporting capability by polymerizing the unsaturated carboxylic acid having the group of the structural formula (i). Can be formed. Further, the acrylic resin has a crosslinked structure by mixing a polyfunctional unsaturated carboxylic acid, preferably a tri- or higher functional unsaturated carboxylic acid, with the monofunctional unsaturated carboxylic acid having the group of the structural formula (i). When formed, it becomes a thermosetting polymer, and the mechanical strength of the surface layer becomes extremely high. The polyfunctional unsaturated carboxylic acid may be added with the group of the structural formula (i). However, since the production cost of the monomer is increased, the polyfunctional unsaturated carboxylic acid has the above structure. It is preferable to use a photocurable polyfunctional monomer without adding the group of the formula (i).

Examples of the monofunctional unsaturated carboxylic acid having the group of the structural formula (i) include the following structural formula (ii) or structural formula (iii).

In the structural formulas (ii) and (iii), R ₁ represents a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, or a substituent. An aryl group which may have a cyano group, a nitro group, an alkoxy group which may have a substituent, -COOR ₇ (wherein R ₇ is a hydrogen atom, an alkyl which may have a substituent) Group, an aralkyl group which may have a substituent, or an aryl group which may have a substituent, a carbonyl halide group, CONR ₈ R ₉ (where R ₈ and R ₉ are It may be the same or different, and has a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, or a substituent. The aryl group which may be ).
In Structural Formula (ii) and Structural Formula (iii), Ar ₁ and Ar ₂ may be the same as or different from each other, and represent an arylene group that may have a substituent.
In Structural Formula (ii) and Structural Formula (iii), Ar ₃ and Ar ₄ may be the same as or different from each other, and each represents an aryl group that may have a substituent.
In the structural formulas (ii) and (iii), X has a single bond, an alkylene group which may have a substituent, a cycloalkylene group which may have a substituent, or a substituent. Represents an alkylene ether group, an oxygen atom, a sulfur atom or a vinylene group which may be substituted.
In the structural formula (ii) and the structural formula (iii), Z has an alkylene group which may have a substituent, an alkylene ether divalent group which may have a substituent, or a substituent. Represents an optionally substituted alkyleneoxycarbonyl divalent group.
m and n each represent an integer of 0 to 3.
In the structural formulas (ii) and (iii), examples of the alkyl group in the substituent of R ₁ include a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the aryl group include a phenyl group and a naphthyl group. Examples of the aralkyl group include a benzyl group, a phenethyl group, and a naphthylmethyl group. Examples of the alkoxy group include a methoxy group, an ethoxy group, and a propoxy group. These include halogen atoms, nitro groups, cyano groups; alkyl groups such as methyl groups and ethyl groups; alkoxy groups such as methoxy groups and ethoxy groups; aryloxy groups such as phenoxy groups; aryl groups such as phenyl groups and naphthyl groups; It may be substituted with an aralkyl group such as a benzyl group or a phenethyl group. Of these R ₁ substituents, a hydrogen atom or a methyl group is particularly preferred.

Examples of the aryl group of Ar ₃ and Ar ₄ include a condensed polycyclic hydrocarbon group, a non-condensed cyclic hydrocarbon group, and a heterocyclic group.
As the condensed polycyclic hydrocarbon group, those having 18 or less carbon atoms forming a ring are preferable. For example, a pentanyl group, an indenyl group, a naphthyl group, an azulenyl group, a heptaenyl group, a biphenylenyl group, an as-indacenyl group, s-indacenyl group, fluorenyl group, acenaphthylenyl group, preadenyl group, acenaphthenyl group, phenalenyl group, phenanthryl group, anthryl group, fluoranthenyl group, acephenanthrenyl group, aceanthrylenyl group, triphenylyl group, pyrenyl group, Examples include a chrycenyl group and a naphthacenyl group.
Examples of the non-condensed cyclic hydrocarbon group include monovalent groups of monocyclic hydrocarbon compounds such as benzene, diphenyl ether, polyethylene diphenyl ether, diphenyl thioether, diphenyl sulfone; biphenyl, polyphenyl, diphenylalkane, diphenylalkene, diphenylalkyne , Monovalent groups of non-condensed polycyclic hydrocarbon compounds such as triphenylmethane, distyrylbenzene, 1,1-diphenylcycloalkane, polyphenylalkane, and polyphenylalkene; ring assembly carbonization such as 9,9-diphenylfluorene And monovalent groups of hydrogen compounds.
Examples of the heterocyclic group include monovalent groups such as carbazole, dibenzofuran, dibenzothiophene, oxadiazole, and thiadiazole.

The content of the polyfunctional unsaturated carboxylic acid is preferably 5 to 75% by mass, more preferably 10 to 70% by mass, and still more preferably 20 to 60% by mass with respect to the entire outermost surface layer. When the content is less than 5% by mass, the mechanical strength of the outermost surface layer is insufficient, and when it exceeds 75% by mass, cracks are likely to occur when a strong force is applied to the outermost surface layer. Degradation may also occur easily.
When an acrylic resin is used for the outermost surface layer, after applying the unsaturated carboxylic acid to the photoreceptor, electron beam irradiation or actinic rays such as ultraviolet rays are irradiated to cause radical polymerization to form a surface layer. can do. When performing radical polymerization with actinic rays, a solution obtained by dissolving a photopolymerization initiator in an unsaturated carboxylic acid is used. As the photopolymerization initiator, materials used for photocurable paints can be used.

  The outermost surface layer preferably contains metal fine particles, metal oxide fine particles, and other fine particles in order to increase the mechanical strength of the outermost surface layer. Examples of the metal oxide include titanium oxide, tin oxide, potassium titanate, TiO, TiN, zinc oxide, indium oxide, and antimony oxide. Examples of the other fine particles include fluorine resins such as polytetrafluoroethylene, silicone resins, or those obtained by dispersing inorganic materials in these resins for the purpose of improving wear resistance.

  Next, the formation of the electrostatic latent image can be performed, for example, by uniformly charging the surface of the image carrier and then performing imagewise exposure, and by the electrostatic latent image forming unit. Can do. The electrostatic latent image forming unit includes, for example, at least a charger that uniformly charges the surface of the image carrier and an exposure unit that exposes the surface of the image carrier imagewise.

The charging can be performed, for example, by applying a voltage to the surface of the image carrier using the charger.
The charger is not particularly limited and may be appropriately selected depending on the purpose. And non-contact chargers utilizing corona discharge such as corotrons and corotrons.
The charger preferably has voltage applying means for applying a voltage having an AC component.

The exposure can be performed, for example, by exposing the surface of the image carrier imagewise using the exposure device.
The exposure device is not particularly limited as long as it can perform image-like exposure on the surface of the image carrier charged by the charger, and can be appropriately selected according to the purpose. Examples include various exposure devices such as a copying optical system, a rod lens array system, a laser optical system, and a liquid crystal shutter optical system.
In the present invention, an optical back side system in which imagewise exposure is performed from the back side of the image carrier may be adopted.

<Development process and development means>
The developing step is a step of developing the electrostatic latent image using a toner or a developer to form a visible image.
The visible image can be formed, for example, by developing the electrostatic latent image using the toner or the developer, and can be performed by the developing unit.
The developing unit is not particularly limited as long as it can be developed using, for example, the toner or the developer, and can be appropriately selected from known ones. For example, the toner or developer is accommodated. Preferred examples include those having at least a developing unit capable of bringing the toner or developer into contact or non-contact with the electrostatic latent image.

-Toner-
The toner preferably has an average circularity of 0.93 to 1.00, which is an average value of the circularity SR represented by the following formula 1, and more preferably 0.95 to 0.99. This average circularity is an index of the degree of unevenness of the toner particles, and indicates 1.00 when the toner is a perfect sphere, and the average circularity becomes smaller as the surface shape becomes more complicated.
<Formula 1>
Circularity SR = (perimeter of circle having the same area as the projected area of toner particles) / (perimeter of projected image of toner particles)

  When the average circularity is in the range of 0.93 to 1.00, the surface of the toner particles is smooth, and the toner particles and the contact area between the toner particles and the photosensitive member are small, so that the transferability is excellent. Further, since the toner particles have no corners, the developer agitation torque in the developing device is small, and the agitation drive is stabilized, so that no abnormal image is generated. In addition, since there are no angular toner particles in the toner that forms the dots, the pressure is uniformly applied to the entire toner that forms the dots when pressed against the recording medium during transfer, and the transfer is not easily lost. Further, since the toner particles are not angular, the abrasive power of the toner particles themselves is small, and the surface of the image carrier is not damaged or worn.

The circularity SR can be measured using, for example, a flow particle image analyzer (manufactured by Toa Medical Electronics Co., Ltd., FPIA-1000).
First, 0.1 to 0.5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of water from which impure solids have been removed in advance. Add ~ 0.5g. The suspension in which the sample is dispersed is subjected to dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the shape and particle size of the toner are measured by the above apparatus with the dispersion concentration being 3000 to 10000 / μl.

The toner has a mass average particle diameter (D4) of preferably 3 to 10 μm, and more preferably 4 to 8 μm. In this range, since the toner particles have a sufficiently small particle size with respect to the minute latent image dots, the dot reproducibility is excellent. When the mass average particle diameter (D4) is less than 3 μm, phenomena such as a decrease in transfer efficiency and a decrease in blade cleaning properties may occur. is there.
The toner has a mass average particle diameter (D4) to number average particle diameter (D1) ratio (D4 / D1) of preferably 1.00 to 1.40, and more preferably 1.00 to 1.30. This means that the closer the ratio (D4 / D1) is to 1, the sharper the particle size distribution of the toner. Since image quality does not occur, the image quality is stable. In addition, since the toner particle size distribution is sharp, the triboelectric charge amount distribution is also sharp and the occurrence of fog is suppressed. Further, when the toner particle diameter is uniform, the latent image dots are developed so as to be arranged densely and orderly, so that the dot reproducibility is excellent.

Here, the mass average particle diameter (D4) and the particle size distribution of the toner are measured by, for example, a Coulter counter method. Examples of the measuring device for the particle size distribution of toner particles by the Coulter counter method include Coulter Counter TA-II and Coulter Multisizer II (both manufactured by Coulter).
First, 0.1 to 5 ml of a surfactant (preferably alkyl benzene sulfonate) is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution. Here, the electrolytic solution is a solution prepared by preparing a 1% NaCl aqueous solution using primary sodium chloride. For example, ISOTON-II (manufactured by Coulter) can be used. Here, 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the measurement device is used to measure the volume and number of toner particles or toner using a 100 μm aperture as the aperture. Volume distribution and number distribution are calculated. From the obtained distribution, the mass average particle diameter (D4) and the number average particle diameter (D1) of the toner can be obtained.
As channels, 2.00 to less than 2.52 μm; 2.52 to less than 3.17 μm; 3.17 to less than 4.00 μm; 4.00 to less than 5.04 μm; 5.04 to less than 6.35 μm; 6 Less than 35 to 8.00 μm; less than 8.00 to less than 10.08 μm; less than 10.08 to less than 12.70 μm; less than 12.70 to less than 16.00 μm; less than 16.00 to less than 20.20 μm; Uses 13 channels of less than 40 μm; 25.40 to less than 32.00 μm; 32.00 to less than 40.30 μm, and targets particles having a particle size of 2.00 μm to less than 40.30 μm.

  As the toner having such a substantially spherical shape, a toner composition containing a polyester prepolymer having a functional group containing a nitrogen atom, a polyester, a colorant, and a release agent is crosslinked in the presence of resin fine particles in an aqueous medium. It can be prepared by an extension reaction. The toner produced by this reaction can reduce the hot offset by curing the toner surface, and can prevent the fixing device from becoming dirty and appearing on the image.

Examples of the prepolymer made of the modified polyester resin include a polyester prepolymer (A) having an isocyanate group, and examples of the compound that extends or crosslinks with the prepolymer include amines (B).
Examples of the polyester prepolymer (A) having an isocyanate group include a polycondensate of a polyol (1) and a polycarboxylic acid (2) and a polyester having an active hydrogen group, which is further reacted with a polyisocyanate (3). Is mentioned. Examples of active hydrogen groups possessed by the polyester include hydroxyl groups (alcoholic hydroxyl groups and phenolic hydroxyl groups), amino groups, carboxyl groups, mercapto groups, and the like. Among these, alcoholic hydroxyl groups are particularly preferable.

Examples of the polyol (1) include diol (1-1), trivalent or higher polyol (1-2), (1-1) alone or (1-1) and a small amount of (1-2). Mixtures are preferred.
Examples of the diol (1-1) include alkylene glycol (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, etc.); alkylene ether glycol (Diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, etc.); Alicyclic diols (1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.); Bisphenols (bisphenol A) Bisphenol F, bisphenol S, etc.); alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) adduct of the above alicyclic diol Alkylene oxide of the bisphenols (ethylene oxide, propylene oxide, butylene oxide, etc.), etc. adducts. Among these, alkylene glycols having 2 to 12 carbon atoms and alkylene oxide adducts of bisphenols are preferable, and combined use of alkylene oxide adducts of bisphenols and alkylene glycols having 2 to 12 carbon atoms is particularly preferable.

  Examples of the trivalent or higher polyol (1-2) include 3 to 8 or higher polyhydric aliphatic alcohols (glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitol, etc.); (Trisphenol PA, phenol novolak, cresol novolak, etc.); alkylene oxide adducts of the above trivalent or higher polyphenols.

Examples of the polycarboxylic acid (2) include dicarboxylic acid (2-1) and trivalent or higher polycarboxylic acid (2-2). Among these, (2-1) alone and (2-1) ) And a small amount of (2-2).
Examples of the dicarboxylic acid (2-1) include alkylene dicarboxylic acids (succinic acid, adipic acid, sebacic acid, etc.); alkenylene dicarboxylic acids (maleic acid, fumaric acid, etc.); aromatic dicarboxylic acids (phthalic acid, isophthalic acid, Terephthalic acid, naphthalenedicarboxylic acid, etc.). Among these, alkenylene dicarboxylic acid having 4 to 20 carbon atoms and aromatic dicarboxylic acid having 8 to 20 carbon atoms are particularly preferable.
Examples of the trivalent or higher polycarboxylic acid (2-2) include aromatic polycarboxylic acids having 9 to 20 carbon atoms (such as trimellitic acid and pyromellitic acid). In addition, as polycarboxylic acid (2), you may make it react with polyol (1) using the acid anhydride or lower alkyl ester (methyl ester, ethyl ester, isopropyl ester, etc.) of the above-mentioned thing.

  As for the ratio of the polyol (1) and the polycarboxylic acid (2), the equivalent ratio [OH] / [COOH] of the hydroxyl group [OH] and the carboxyl group [COOH] is preferably 2/1 to 1/1. 5/1 to 1/1 is more preferable, and 1.3 / 1 to 1.02 / 1 is still more preferable.

  Examples of the polyisocyanate (3) include aliphatic polyisocyanates (tetramethylene diisocyanate, hexamethylene diisocyanate, 2,6-diisocyanatomethylcaproate, etc.); alicyclic polyisocyanates (isophorone diisocyanate, cyclohexylmethane diisocyanate, etc.) Aromatic diisocyanates (tolylene diisocyanate, diphenylmethane diisocyanate, etc.); araliphatic diisocyanates (α, α, α ′, α′-tetramethylxylylene diisocyanate, etc.); isocyanurates; phenols, oximes, polyisocyanates; Those blocked with caprolactam, etc. These may be used individually by 1 type and may use 2 or more types together.

  As for the ratio of the polyisocyanate (3), the equivalent ratio [NCO] / [OH] of the isocyanate group [NCO] and the hydroxyl group [OH] of the polyester having a hydroxyl group is preferably 5/1 to 1/1. 1 to 1.2 / 1 is more preferable, and 2.5 / 1 to 1.5 / 1 is still more preferable. If the [NCO] / [OH] exceeds 5, the low-temperature fixability may be deteriorated. If the molar ratio of [NCO] is less than 1, the urea content in the modified polyester becomes low, and hot offset resistance Sex worsens.

  The content of the polyisocyanate (3) component in the prepolymer (A) having an isocyanate group at the terminal is preferably 0.5 to 40% by mass, more preferably 1 to 30% by mass, and 2 to 20% by mass. Is more preferable. When the content is less than 0.5% by mass, the hot offset resistance deteriorates, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability. When the content exceeds 40% by mass, low-temperature fixability is obtained. May get worse.

  The average number of isocyanate groups contained per molecule in the prepolymer (A) having the isocyanate group is preferably 1 or more, more preferably 1.5 to 3 on average, and 1.8 to 2.5 on average. Further preferred. When the number is less than 1 per molecule, the molecular weight of the urea-modified polyester is lowered, and the hot offset resistance may be deteriorated.

  As the amines (B), the diamine (B1), trivalent or higher polyamine (B2), amino alcohol (B3), amino mercaptan (B4), amino acid (B5), and amino groups of B1 to B5 were blocked. (B6) etc. are mentioned. Examples of the diamine (B1) include aromatic diamines (phenylenediamine, diethyltoluenediamine, 4,4′diaminodiphenylmethane, etc.); alicyclic diamines (4,4′-diamino-3,3′dimethyldicyclohexylmethane, diaminecyclohexane, Isophorone diamine etc.); and aliphatic diamines (ethylene diamine, tetramethylene diamine, hexamethylene diamine etc.) and the like. Examples of the trivalent or higher polyamine (B2) include diethylenetriamine and triethylenetetramine. Examples of amino alcohol (B3) include ethanolamine and hydroxyethylaniline. Examples of amino mercaptan (B4) include aminoethyl mercaptan and aminopropyl mercaptan. Examples of the amino acid (B5) include aminopropionic acid and aminocaproic acid. Examples of the B1-B5 amino group blocked (B6) include ketimine compounds and oxazoline compounds obtained from the B1-B5 amines and ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.). Among these amines (B), preferred are B1 and a mixture of B1 and a small amount of B2.

  Furthermore, if necessary, the molecular weight of the urea-modified polyester can be adjusted using an elongation terminator. Examples of the elongation terminator include monoamines (diethylamine, dibutylamine, butylamine, laurylamine, etc.), or those obtained by blocking them (ketimine compounds).

The ratio of the amines (B) is the equivalent ratio [NCO] / [NHx] of the isocyanate group [NCO] in the prepolymer (A) having an isocyanate group and the amino group [NHx] in the amine (B). Is preferably 1/2 to 2/1, more preferably 1.5 / 1 to 1 / 1.5, and still more preferably 1.2 / 1 to 1 / 1.2. When the [NCO] / [NHx] exceeds 2 or less than 1/2, the molecular weight of the urea-modified polyester (i) becomes low, and the hot offset resistance deteriorates.
In the present invention, the polyester (i) modified with a urea bond may contain a urethane bond together with a urea bond. The molar ratio between the urea bond content and the urethane bond content is preferably 100/0 to 10/90, more preferably 80/20 to 20/80, and still more preferably 60/40 to 30/70. When the molar ratio of the urea bond is less than 10%, the hot offset resistance may be deteriorated.

By these reactions, the modified polyester used in the toner, especially the urea-modified polyester (i) can be produced. These urea-modified polyesters (i) are produced by a one-shot method or a prepolymer method. The mass average molecular weight of the urea-modified polyester (i) is preferably 10,000 or more, more preferably 20,000 to 10,000,000, and still more preferably 30,000 to 1,000,000. When the mass average molecular weight is less than 10,000, the hot offset resistance may be deteriorated.
The number average molecular weight of the urea-modified polyester is not particularly limited when the unmodified polyester (ii) described later is used, and may be a number average molecular weight that can be easily obtained to obtain the mass average molecular weight. (I) When used alone, the number average molecular weight is preferably 20,000 or less, more preferably 1,000 to 10,000, and still more preferably 2,000 to 8,000. When the number average molecular weight exceeds 20,000, low temperature fixability and glossiness when used in a full color image forming apparatus may be deteriorated.

In the present invention, not only the polyester (i) modified with a urea bond but also the polyester (ii) not modified can be included as a binder resin component together with the (i). By using (ii) in combination, the low-temperature fixability and the gloss when used in a full-color apparatus are improved, so that it is preferable to use alone. Examples of (ii) include the same polycondensates of polyol (1) and polycarboxylic acid (2) as in the polyester component (i), and preferred ones are also the same as (i). Further, (ii) is not limited to unmodified polyester, but may be modified with a chemical bond other than a urea bond, for example, may be modified with a urethane bond. It is preferable that (i) and (ii) are at least partially compatible with each other in terms of low-temperature fixability and hot offset resistance.
Therefore, the polyester component (i) and (ii) preferably have similar compositions. When (ii) is contained, the mass ratio of (i) and (ii) is preferably 5/95 to 80/20, more preferably 5/95 to 30/70, and further preferably 5/95 to 25/75. 7/93 to 20/80 is particularly preferable. When the mass ratio of (i) is less than 5% by mass, the hot offset resistance may be deteriorated, and it may be disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability.

  The peak molecular weight of (ii) is preferably 1,000 to 30,000, more preferably 1,500 to 10,000, and still more preferably 2,000 to 8,000. When the peak molecular weight of (ii) is less than 1,000, the heat-resistant storage stability may be deteriorated, and when it exceeds 10,000, the low-temperature fixability may be deteriorated. The hydroxyl value of (ii) is preferably 5 or more, more preferably 10 to 120, and still more preferably 20 to 80. If the hydroxyl value is less than 5, it may be disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability. 1-30 are preferable and, as for the acid value of said (ii), 5-20 are more preferable. By having an acid value, it tends to be negatively charged.

The glass transition temperature (Tg) of the binder resin is preferably 50 to 70 ° C, and more preferably 55 to 65 ° C. When the glass transition temperature is less than 50 ° C., blocking of the toner during high temperature storage may be deteriorated, and when it exceeds 70 ° C., the low temperature fixability becomes insufficient. Due to the coexistence of the urea-modified polyester resin, the toner used in the present invention tends to have good heat storage stability even when the glass transition point is low, as compared with known polyester-based toners.
As the storage elastic modulus of the binder resin, the temperature (TG ′) at which the measurement frequency is 20 Hz is 10,000 dyne / cm ² is preferably 100 ° C. or more, and more preferably 110 to 200 ° C. When the temperature (TG ′) is less than 100 ° C., the hot offset resistance may be deteriorated.
As the viscosity of the binder resin, the temperature (Tη) at 1000 poise at a measurement frequency of 20 Hz is preferably 180 ° C. or less, and more preferably 90 to 160 ° C. When the temperature (Tη) exceeds 180 ° C., the low-temperature fixability deteriorates. That is, TG ′ is preferably higher than Tη from the viewpoint of achieving both low temperature fixability and hot offset resistance. In other words, the difference between TG ′ and Tη (TG′−Tη) is preferably 0 ° C. or higher, more preferably 10 ° C. or higher, and still more preferably 20 ° C. or higher. The upper limit of the difference is not particularly limited. Further, from the viewpoint of achieving both heat-resistant storage stability and low-temperature fixability, the difference between Tη and Tg is preferably 0 to 100 ° C, more preferably 10 to 90 ° C, and still more preferably 20 to 80 ° C.

The binder resin can be produced by the following method.
First, the polyol (1) and the polycarboxylic acid (2) are produced at 150 to 280 ° C. in the presence of a known esterification catalyst such as tetrabutoxytitanate or dibutyltin oxide, and reduced pressure as necessary. Water is distilled off to obtain a polyester having a hydroxyl group. Subsequently, this is made to react with polyisocyanate (3) at 40-140 degreeC, and the prepolymer (A) which has an isocyanate group is obtained. Further, (A) is reacted with amines (B) at 0 to 140 ° C. to obtain a polyester modified with a urea bond. When reacting (3) and reacting (A) and (B), a solvent may be used as necessary.
Usable solvents include, for example, aromatic solvents (toluene, xylene, etc.); ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.); esters (ethyl acetate, etc.); amides (dimethylformamide, dimethylacetamide, etc.), Inactive to isocyanate (3) such as ethers (tetrahydrofuran, etc.).
When using polyester (ii) not modified with urea bond, (ii) is produced in the same manner as polyester having a hydroxyl group, and this is dissolved in the solution after completion of the reaction of (i). , Mix.

Further, the toner used in the present invention can be produced by the following method, but is not limited thereto.
The toner may be formed by reacting a dispersion made of a prepolymer (A) having an isocyanate group in an aqueous medium with (B), or using a urea-modified polyester (i) produced in advance. Good. As a method for stably forming a dispersion comprising urea-modified polyester (i) or prepolymer (A) in an aqueous medium, a toner raw material comprising urea-modified polyester (i) or prepolymer (A) in an aqueous medium is used. And a method of dispersing by shearing force.
The prepolymer (A) and other toner compositions (hereinafter sometimes referred to as toner raw materials), colorants, colorant master batches, release agents, charge control agents, unmodified polyester resins, Mixing may be performed when the dispersion is formed in the medium, but it is more preferable to mix the toner raw materials in advance and then add and disperse the mixture in the aqueous medium. In the present invention, other toner raw materials such as a colorant, a release agent, and a charge control agent do not necessarily have to be mixed when forming particles in an aqueous medium. It may be added later. For example, after forming particles not containing a colorant, the colorant can be added by a known dyeing method.
As the aqueous medium, water alone may be used, but a solvent miscible with water may be used in combination. Examples of miscible solvents include alcohol (methanol, isopropanol, ethylene glycol, etc.), dimethylformamide, tetrahydrofuran, cellosolves (methyl cellosolve, etc.), lower ketones (acetone, methyl ethyl ketone, etc.) and the like.

  The amount of the aqueous medium used relative to 100 parts by mass of the toner composition containing the urea-modified polyester (i) and the prepolymer (A) is preferably 50 to 2000 parts by mass, and more preferably 100 to 1000 parts by mass. When the amount used is less than 50 parts by mass, the toner composition is not well dispersed, and toner particles having a predetermined particle size may not be obtained. When the amount used exceeds 2000 parts by mass, it is not economical.

Moreover, a dispersing agent can also be used as needed. It is preferable to use a dispersant because the particle size distribution becomes sharp and the dispersion is stable.
The dispersion method is not particularly limited and may be appropriately selected depending on the intended purpose. For example, known equipment such as a low-speed shear method, a high-speed shear method, a friction method, a high-pressure jet method, and an ultrasonic wave can be applied. . In order to make the particle diameter of the dispersion 2 to 20 μm, a high-speed shearing method is preferable. When a high-speed shearing disperser is used, the number of rotations is not particularly limited, but is preferably 1000 to 30000 rpm, more preferably 5000 to 20000 rpm. The dispersion time is not particularly limited, but in the case of a batch method, it is usually 0.1 to 5 minutes. As temperature at the time of dispersion | distribution, 0-150 degreeC is preferable normally and 40-98 degreeC is more preferable. Higher temperatures are preferred in that the dispersion made of urea-modified polyester (i) or prepolymer (A) has a low viscosity and is easy to disperse.

  In the step of synthesizing the urea-modified polyester (i) from the prepolymer (A), the amine (B) may be added and reacted before the toner composition is dispersed in the aqueous medium, or may be dispersed in the aqueous medium. An amine (B) may be added later to cause a reaction from the particle interface. In this case, urea-modified polyester is preferentially produced on the surface of the manufactured toner, and a concentration gradient can be provided inside the particles.

In the reaction, it is preferable to use a dispersant as necessary.
There is no restriction | limiting in particular as said dispersing agent, According to the objective, it can select suitably, For example, surfactant, a slightly water-soluble inorganic compound dispersing agent, a polymeric protective colloid, etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together. Among these, surfactants are preferable.

Examples of the surfactant include an anionic surfactant, a cationic surfactant, a nonionic surfactant, and an amphoteric surfactant.
Examples of the anionic surfactant include alkylbenzene sulfonates, α-olefin sulfonates, phosphate esters, and the like. Among these, those having a fluoroalkyl group are preferable. Examples of the anionic surfactant having a fluoroalkyl group include a fluoroalkylcarboxylic acid having 2 to 10 carbon atoms or a metal salt thereof, disodium perfluorooctanesulfonylglutamate, 3- [omega-fluoroalkyl (6 carbon atoms). -11) Oxy] -1-alkyl (carbon number 3-4) sodium sulfonate, 3- [omega-fluoroalkanoyl (carbon number 6-8) -N-ethylamino] -1-propanesulfonic acid sodium, fluoroalkyl (Carbon number 11-20) carboxylic acid or its metal salt, perfluoroalkyl carboxylic acid (carbon number 7-13) or its metal salt, perfluoroalkyl (carbon number 4-12) sulfonic acid or its metal salt, perfluoro Octanesulfonic acid diethanolamide, N-propyl-N- (2-hydroxy Ethyl) perfluorooctanesulfonamide, perfluoroalkyl (carbon number 6-10) sulfonamidopropyltrimethylammonium salt, perfluoroalkyl (carbon number 6-10) -N-ethylsulfonylglycine salt, monoperfluoroalkyl (carbon number) 6-16) Ethyl phosphate and the like. Examples of commercially available surfactants having a fluoroalkyl group include Surflon S-111, S-112, S-113 (Asahi Glass Co., Ltd.); Fluorard FC-93, FC-95, FC-98, FC- 129 (manufactured by Sumitomo 3M); Unidyne DS-101, DS-102 (manufactured by Daikin Industries); Megafac F-110, F-120, F-113, F-191, F-812, F-833 (large) Nippon Ink Chemical Co., Ltd.); Xtop EF-102, 103, 104, 105, 112, 123A, 123B, 306A, 501, 201, 204 (manufactured by Tochem Products); Neos) and the like.

  Examples of the cationic surfactant include amine salt type surfactants and quaternary ammonium salt type cationic surfactants. Examples of the amine salt type surfactant include alkylamine salts, aminoalcohol fatty acid derivatives, polyamine fatty acid derivatives, imidazolines, and the like. Examples of the quaternary ammonium salt type cationic surfactant include alkyltrimethylammonium salt, dialkyldimethylammonium salt, alkyldimethylbenzylammonium salt, pyridinium salt, alkylisoquinolinium salt, benzethonium chloride and the like. . Among the cationic surfactants, aliphatic quaternary ammonium such as aliphatic primary, secondary or tertiary amine acids having a fluoroalkyl group, perfluoroalkyl (6 to 10 carbon atoms) sulfonamidopropyltrimethylammonium salt, etc. Salts, benzalkonium salts, benzethonium chloride, pyridinium salts, imidazolinium salts, and the like. Commercially available products of the cationic surfactant include, for example, Surflon S-121 (manufactured by Asahi Glass Co., Ltd.); Florard FC-135 (manufactured by Sumitomo 3M Co.); Unidyne DS-202 (manufactured by Daikin Industries Ltd.), MegaFuck F-150 F-824 (manufactured by Dainippon Ink & Chemicals, Inc.); Xtop EF-132 (manufactured by Tochem Products);

Examples of the nonionic surfactant include fatty acid amide derivatives and polyhydric alcohol derivatives.
Examples of the amphoteric surfactant include alanine, dodecyldi (aminoethyl) glycine, di (octylaminoethyl) glycine, N-alkyl-N, N-dimethylammonium betaine and the like.

Examples of the poorly water-soluble inorganic compound dispersant include tricalcium phosphate, calcium carbonate, titanium oxide, colloidal silica, and hydroxyapatite.
Examples of the polymeric protective colloid include acids, (meth) acrylic monomers containing a hydroxyl group, vinyl alcohol or ethers of vinyl alcohol, esters of vinyl alcohol and a compound containing a carboxyl group, amides Examples thereof include homopolymers or copolymers such as compounds or their methylol compounds, chlorides, those having a nitrogen atom or a heterocyclic ring thereof, polyoxyethylenes, and celluloses.
Examples of the acids include acrylic acid, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid, maleic anhydride, and the like. Examples of the (meth) acrylic monomer containing a hydroxyl group include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, and γ-acrylate. -Hydroxypropyl, γ-hydroxypropyl methacrylate, 3-chloro-2-hydroxypropyl acrylate, 3-chloro-2-hydroxypropyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, glycerol monoacrylate Glycerin monomethacrylate, N-methylol acrylamide, N-methylol methacrylamide and the like. Examples of the vinyl alcohol or ethers with vinyl alcohol include vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, and the like. Examples of the esters of vinyl alcohol and a compound containing a carboxyl group include vinyl acetate, vinyl propionate, and vinyl butyrate. Examples of the amide compound or these methylol compounds include acrylamide, methacrylamide, diacetone acrylamide acid, or these methylol compounds. Examples of the chlorides include acrylic acid chloride and methacrylic acid chloride. Examples of the homopolymer or copolymer such as those having a nitrogen atom or a heterocyclic ring thereof include vinyl pyridine, vinyl pyrrolidone, vinyl imidazole, and ethylene imine. Examples of the polyoxyethylene are polyoxyethylene, polyoxypropylene, polyoxyethylene alkylamine, polyoxypropylene alkylamine, polyoxyethylene alkylamide, polyoxypropylene alkylamide, polyoxyethylene nonylphenyl ether, polyoxyethylene Examples thereof include oxyethylene lauryl phenyl ether, polyoxyethylene stearyl phenyl ester, and polyoxyethylene nonyl phenyl ester. Examples of the celluloses include methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose.

In the preparation of the dispersion, a dispersion stabilizer can be used as necessary. Examples of the dispersion stabilizer include acids that are soluble in acids and alkalis such as calcium phosphate salts.
When the dispersion stabilizer is used, the calcium phosphate salt can be removed from the fine particles by a method of dissolving the calcium phosphate salt with an acid such as hydrochloric acid and then washing with water or a method of decomposing with an enzyme.

  In the preparation of the dispersion, a catalyst for the extension reaction or the crosslinking reaction can be used. Examples of the catalyst include dibutyltin laurate and dioctyltin laurate.

Furthermore, in order to lower the viscosity of the toner composition, a solvent in which the urea-modified polyester (i) or the prepolymer (A) is soluble can be used. The use of a solvent is preferable in that the particle size distribution becomes sharp. The solvent is preferably volatile from the viewpoint of easy removal.
Examples of the solvent include toluene, xylene, benzene, carbon tetrachloride, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, chloroform, monochlorobenzene, dichloroethylidene, methyl acetate, ethyl acetate, Examples thereof include methyl ethyl ketone and methyl isobutyl ketone. These may be used individually by 1 type and may use 2 or more types together. Among these, aromatic solvents such as toluene and xylene; halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, chloroform and carbon tetrachloride are preferable, and aromatic solvents such as toluene and xylene are more preferable.
0-300 mass parts is preferable, as for the usage-amount of the solvent with respect to 100 mass parts of said prepolymers (A), 0-100 mass parts is more preferable, and 25-70 mass parts is still more preferable. When a solvent is used, it is removed by heating under normal pressure or reduced pressure after the elongation and / or crosslinking reaction.

  The elongation and / or crosslinking reaction time is selected depending on the reactivity of the isocyanate group structure of the prepolymer (A) and the amines (B), but is usually preferably 10 minutes to 40 hours, and preferably 2 to 24 hours. More preferred. The reaction temperature is preferably 0 to 150 ° C, more preferably 40 to 98 ° C. Furthermore, a known catalyst can be used as necessary. Specific examples include dibutyltin laurate and dioctyltin laurate.

  In order to remove the organic solvent from the obtained emulsified dispersion, a method in which the temperature of the entire system is gradually raised to completely evaporate and remove the organic solvent in the droplets can be employed. It is also possible to spray the emulsified dispersion in a dry atmosphere to completely remove the water-insoluble organic solvent in the droplets to form toner fine particles, and also remove the aqueous dispersant by evaporating it. is there. As a dry atmosphere in which the emulsified dispersion is sprayed, a gas obtained by heating air, nitrogen, carbon dioxide gas, combustion gas, or the like, in particular, various air currents heated to a temperature equal to or higher than the boiling point of the highest boiling solvent used is generally used. Sufficient quality can be obtained with a short treatment such as spray dryer, belt dryer or rotary kiln.

When the particle size distribution at the time of emulsification dispersion is wide and washing and drying processes are performed while maintaining the particle size distribution, the particle size distribution can be adjusted by classifying into a desired particle size distribution.
In the classification operation, the fine particle portion can be removed in the liquid by a cyclone, a decanter, centrifugation, or the like. Although classification operation may be performed after obtaining as powder after drying, it is preferable in terms of efficiency to be performed in a liquid. The unnecessary fine particles or coarse particles obtained can be returned to the kneading step and used for the formation of particles. At that time, unnecessary fine particles or coarse particles may be wet.
The dispersant used is preferably removed from the obtained dispersion as much as possible, but it is preferable to carry out it simultaneously with the classification operation described above.

  By mixing the resulting dried toner powder with dissimilar particles such as release agent fine particles, charge control fine particles, fluidizing agent fine particles, and colorant fine particles, or by giving mechanical impact force to the mixed powder By immobilizing and fusing on the surface, it is possible to prevent detachment of the foreign particles from the surface of the resulting composite particle.

  As specific means, (1) a method of applying an impact force to the mixture by blades rotating at high speed, (2) the mixture is injected into a high-speed air stream, accelerated, and particles or composite particles are mixed with an appropriate collision plate. There is a method of making it collide. As equipment, Ong mill (manufactured by Hosokawa Micron Corporation), I-type mill (manufactured by Nippon Pneumatic Co., Ltd.), with reduced pulverization air pressure, hybridization system (manufactured by Nara Machinery Co., Ltd.), kryptron system ( Kawasaki Heavy Industries, Ltd.) and automatic mortar.

  As the colorant used in the toner, pigments and dyes conventionally used as toner colorants can be used. Specifically, carbon black, lamp black, iron black, ultramarine, nigrosine dye, Aniline blue, phthalocyanine blue, phthalocyanine green, Hansa yellow G, rhodamine 6C lake, calco oil blue, chrome yellow, quinacridone red, benzidine yellow, rose bengal and the like can be used alone or in combination.

  Further, if necessary, in order to give the toner particles magnetic properties, for example, iron oxides such as ferrite, magnetite and maghemite; metals such as iron, cobalt and nickel, or alloys of these with other metals, etc. The magnetic component may be contained alone or in combination in the toner particles. These components can also be used as a colorant component.

  Further, the number average particle diameter of the colorant in the toner used in the present invention is preferably 0.5 μm or less, more preferably 0.4 μm or less, and further preferably 0.3 μm or less. When the number average particle diameter exceeds 0.5 μm, the dispersibility of the pigment does not reach a sufficient level, and preferable transparency may not be obtained. On the other hand, the colorant having a fine particle diameter of less than 0.1 μm is sufficiently smaller than a half wavelength of visible light, and thus is considered not to adversely affect the light reflection and absorption characteristics. Therefore, the colorant particles having a number average particle size of less than 0.1 μm contribute to good color reproducibility and transparency of the OHP sheet having a fixed image. On the other hand, when there are many colorants having a particle size larger than 0.5 μm, the transmission of incident light is hindered or scattered, and the brightness of the projected image of the OHP sheet is reduced. There is a tendency to decrease the color. Further, when a large amount of colorant having a particle size larger than 0.5 μm is present, the colorant is detached from the surface of the toner particles, which may cause various problems such as fogging, drum contamination, and poor cleaning. The colorant having a particle size larger than 0.7 μm is preferably 10% by number or less, more preferably 5% by number or less of the total colorant.

  Further, by mixing the colorant together with part or all of the binder resin in advance after adding a wetting liquid, the binder resin and the colorant are initially sufficiently attached, In the subsequent toner production process, the colorant is dispersed more effectively in the toner particles, the dispersed particle diameter of the colorant is reduced, and better transparency can be obtained.

  As the binder resin used for kneading in advance, the resins exemplified as the binder resin for toner can be used as they are, but are not limited thereto.

  As a specific method for kneading the mixture of the binder resin and the colorant with the wetting liquid in advance, for example, the binder resin, the colorant and the wetting liquid are obtained after mixing with a blender such as a Henschel mixer. The obtained mixture is kneaded at a temperature lower than the melting temperature of the binder resin by a kneader such as a two-roll or three-roll to obtain a sample.

In addition, as the wetting liquid, a general one can be used in consideration of the solubility of the binder resin and the paintability with the colorant. It is preferable from the viewpoint of dispersibility. Among these, the use of water is particularly preferable from the viewpoint of environmental considerations and maintaining the dispersion stability of the colorant in the subsequent toner production process.
According to this manufacturing method, not only the particle diameter of the colorant particles contained in the obtained toner is reduced, but also the uniformity of the dispersion state of the particles is increased, so that the color reproducibility of the projected image by OHP is further improved. Get better.

The toner preferably contains a release agent together with the binder resin and the colorant.
The release agent is not particularly limited and may be appropriately selected from known ones according to the purpose. For example, polyolefin wax (polyethylene wax, polypropylene wax, etc.); long chain hydrocarbon (paraffin wax) And waxes containing carbonyl groups. Among these, a carbonyl group-containing wax is particularly preferable.
Examples of the carbonyl group-containing wax include polyalkanoic acid esters (carnauba wax, montan wax, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1 , 18-octadecanediol distearate, etc.); polyalkanol esters (tristearyl trimellitic acid, distearyl maleate, etc.); polyalkanoic acid amides (ethylenediamine dibehenyl amide, etc.); polyalkylamides (trimellitic acid tristearyl amide) Etc.); dialkyl ketones (distearyl ketone, etc.) and the like. Among these, polyalkanoic acid esters are particularly preferable.

40-160 degreeC is preferable, as for melting | fusing point of the said mold release agent, 50-120 degreeC is more preferable, and 60-90 degreeC is still more preferable. If the melting point is less than 40 ° C., the heat resistant storage stability may be adversely affected, and if it exceeds 160 ° C., cold offset may easily occur during fixing at a low temperature.
The melt viscosity of the release agent is preferably 5 to 1000 cps, more preferably 10 to 100 cps at a temperature 20 ° C. higher than the melting point. When the melt viscosity exceeds 1000 cps, the effect of improving hot offset resistance and low-temperature fixability may be poor.
The content of the release agent in the toner is preferably 0 to 40% by mass, and more preferably 3 to 30% by mass.

Further, in order to accelerate the toner charge amount and its rise, a charge control agent may be contained in the toner as necessary. Since a color change occurs when a colored material is used as the charge control agent, a colorless or nearly white material is preferable.
The charge control agent is not particularly limited and may be appropriately selected from known ones according to the purpose. For example, triphenylmethane dyes, molybdate chelate pigments, rhodamine dyes, alkoxy amines, Examples include quaternary ammonium salts (including fluorine-modified quaternary ammonium salts), alkylamides, phosphorus simple substances or compounds, tungsten simple substances or compounds, fluorine-based activators, salicylic acid metal salts, and metal salts of salicylic acid derivatives.
As the charge control agent, a commercially available product can be used. Examples of the commercially available product include quaternary ammonium salt Bontron P-51, oxynaphthoic acid metal complex E-82, and salicylic acid metal complex. E-84, E-89 of a phenol-based condensate (both manufactured by Orient Chemical Industries); TP-302, TP-415 of a quaternary ammonium salt molybdenum complex (both manufactured by Hodogaya Chemical Co., Ltd.); Quaternary ammonium salt copy charge PSY VP2038, triphenylmethane derivative copy blue PR, quaternary ammonium salt copy charge NEG VP2036, copy charge NX VP434 (both manufactured by Hoechst); LRA-901, boron complex LR-147 (all manufactured by Nippon Carlit Co., Ltd.), quinacridone, azo face , Sulfonate group, carboxyl group, and polymer compounds having a functional group such as a quaternary ammonium salt.

  The amount of the charge control agent added varies depending on the type of the binder resin, the presence or absence of the additive, the toner production method including the dispersion method, and the like, and cannot be uniquely defined. 0.1-10 mass parts is preferable and 0.2-5 mass parts is more preferable. When the addition amount exceeds 10 parts by mass, the chargeability of the toner is too high, the effect of the charge control agent is reduced, the electrostatic attraction force with the developing roller is increased, the flowability of the developer is reduced, and the image The concentration may decrease. These charge control agents can be melted and kneaded together with a masterbatch and resin and then dissolved and dispersed, or they can be added directly when dissolved and dispersed in an organic solvent, or fixed after the toner particles are prepared on the toner surface. You may let them.

  Further, when the toner composition is dispersed in the aqueous medium during the toner production process, resin fine particles mainly for stabilizing the dispersion may be added.

The resin fine particles may be any resin as long as it can form an aqueous dispersion, and may be a thermoplastic resin or a thermosetting resin. For example, vinyl resins, polyurethane resins, epoxy resins, polyester resins , Polyamide resin, polyimide resin, silicon resin, phenol resin, melamine resin, urea resin, aniline resin, ionomer resin, polycarbonate resin and the like. These may be used individually by 1 type and may use 2 or more types together. Among these, a vinyl resin, a polyurethane resin, an epoxy resin, a polyester resin, or a combination thereof is preferable because an aqueous dispersion of fine spherical resin particles can be easily obtained.
As the vinyl resin, a polymer obtained by homopolymerization or copolymerization of a vinyl monomer is used. For example, a styrene- (meth) acrylic acid ester resin, a styrene-butadiene copolymer, a (meth) acrylic acid-acrylic acid ester. Examples thereof include a polymer, a styrene-acrylonitrile copolymer, a styrene-maleic anhydride copolymer, and a styrene- (meth) acrylic acid copolymer.

As an external additive for assisting the fluidity, developability and chargeability of the toner particles, inorganic fine particles are suitable.
Examples of the inorganic fine particles include silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, silica sand, clay, mica, wollastonite, and diatomaceous earth. , Chromium oxide, cerium oxide, pengala, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, silicon nitride and the like.
The primary particle diameter of the inorganic fine particles is preferably 5 nm to 2 μm, and more preferably 5 nm to 500 nm. The specific surface area of the inorganic fine particles by BET method is preferably 20 to 500 m ² / g. The addition amount of the inorganic fine particles in the toner is preferably 0.01 to 5% by mass, and more preferably 0.01 to 2.0% by mass.

  Other polymer fine particles such as polystyrene, methacrylic acid ester and acrylic acid ester copolymer obtained by soap-free emulsion polymerization, suspension polymerization and dispersion polymerization, polycondensation system such as silicone, benzoguanamine and nylon, thermosetting resin And polymer particles.

  A fluidizing agent can also be added to the toner. The fluidizing agent performs surface treatment to increase hydrophobicity, and can prevent deterioration of flow characteristics and charging characteristics even under high humidity. Examples of the fluidizing agent include a silane coupling agent, a silylating agent, a silane coupling agent having a fluorinated alkyl group, an organic titanate coupling agent, an aluminum coupling agent, silicone oil, and modified silicone oil. Can be mentioned.

  Examples of the cleaning property improver for removing the developer after transfer remaining on the photosensitive member or the intermediate transfer member include fatty acid metal salts such as zinc stearate, calcium stearate and stearic acid; polymethyl methacrylate fine particles, polystyrene Examples thereof include polymer fine particles produced by soap-free emulsion polymerization of fine particles and the like. The polymer fine particles preferably have a relatively narrow particle size distribution and a volume average particle size of 0.01 to 1 μm.

  By using such a toner, as described above, it is possible to form a high-quality toner image having excellent development stability.

  Further, the image forming apparatus of the present invention can be applied not only to the combined use with the above-described polymerization method toner suitable for obtaining a high quality image, but also to an irregular shaped toner by a pulverization method, Even in this case, the life of the apparatus can be greatly extended. As a material constituting such a pulverized toner, those usually used as an electrophotographic toner can be applied without particular limitation.

  As the binder resin used in the pulverized toner, for example, styrene such as polystyrene, poly p-chlorostyrene, polyvinyltoluene, or the like, or a substituted polymer thereof; styrene / p-chlorostyrene copolymer, styrene / propylene Copolymer, styrene / vinyl toluene copolymer, styrene / vinyl naphthalene copolymer, styrene / methyl acrylate copolymer, styrene / ethyl acrylate copolymer, styrene / butyl acrylate copolymer, styrene / acrylic Octyl acid copolymer, styrene / methyl methacrylate copolymer, styrene / ethyl methacrylate copolymer, styrene / butyl methacrylate copolymer, styrene / α-chloromethyl methacrylate copolymer, styrene / acrylonitrile copolymer Styrene / vinyl methyl ketone copolymer, Styrene copolymers such as tylene / butadiene copolymers, styrene / isoprene copolymers, styrene / maleic acid copolymers; polymethyl acrylate, polybutyl acrylate, polymethyl methacrylate, polybutyl methacrylate, etc. Acrylic ester-based homopolymers or copolymers thereof; polyvinyl derivatives such as polyvinyl chloride and polyvinyl acetate; polyester-based polymers, polyurethane-based polymers, polyamide-based polymers, polyimide-based polymers, polyol-based polymers, Examples thereof include epoxy polymers, terpene polymers, aliphatic or alicyclic hydrocarbon resins, and aromatic petroleum resins. These may be used individually by 1 type and may use 2 or more types together. Among these, a styrene-acrylic copolymer resin, a polyester resin, and a polyol resin are preferable from the viewpoint of electrical characteristics, cost, and the like, and further, polyester resins and polyol resins are preferable as those having good fixing characteristics. Particularly preferred.

  In the pulverized toner, together with these resin components, the colorant component, wax component, charge control component and the like as described above are premixed as necessary, and then kneaded at a temperature close to the melting temperature of the resin component, and then cooled. Thereafter, a toner may be prepared through a pulverizing and classifying step, and the external additive component may be appropriately added and mixed as necessary.

  The developing unit may be a dry developing type, a wet developing type, a single color developing unit, or a multi-color developing unit. For example, a toner having a stirrer for charging the toner or the developer by frictional stirring and a rotatable magnet roller is preferable.

In the developing device, for example, the toner and the carrier are mixed and agitated, and the toner is charged by friction at that time, and held on the surface of the rotating magnet roller in a raised state to form a magnetic brush. . Since the magnet roller is disposed in the vicinity of the image carrier (photosensitive member), a part of the toner constituting the magnetic brush formed on the surface of the magnet roller is caused by the electric attractive force. It moves to the surface of the image carrier (photoreceptor). As a result, the electrostatic latent image is developed with the toner, and a visible image is formed with the toner on the surface of the image carrier (photoconductor).
The developer accommodated in the developing device is a developer containing the toner, but the developer may be a one-component developer or a two-component developer.

<Transfer process and transfer means>
The transfer step is a step of transferring the visible image onto a recording medium. After the primary transfer of the visible image onto the intermediate transfer member using an intermediate transfer member, the visible image is transferred onto the recording medium. A primary transfer step of forming a composite transfer image by transferring a visible image onto an intermediate transfer body using two or more colors, preferably full color toner as the toner, and a composite transfer image; A mode including a secondary transfer step of transferring the transfer image onto the recording medium is more preferable.
The transfer can be performed, for example, by charging the image carrier (photosensitive member) with the transfer charger using the visible image, and can be performed by the transfer unit. The transfer means includes a primary transfer means for transferring a visible image onto an intermediate transfer member to form a composite transfer image, and a secondary transfer means for transferring the composite transfer image onto a recording medium. Embodiments are preferred.
The intermediate transfer member is not particularly limited and may be appropriately selected from known transfer members according to the purpose. For example, a transfer belt and the like are preferable.

The image carrier is an intermediate transfer member used for image formation by a so-called intermediate transfer method in which a toner image formed on a photosensitive member is primarily transferred to perform color superposition and then transferred to a recording medium. It may be.
-Intermediate transfer member-
As the intermediate transfer member, a material exhibiting conductivity of a volume resistance of 1.0 × 10 ^{5 to} 1.0 × 10 ¹¹ Ω · cm is preferable. When the volume resistance is less than 1.0 × 10 ⁵ Ω · cm, so-called transfer dust is generated in which the toner image is disturbed due to discharge when the toner image is transferred from the photosensitive member to the intermediate transfer member. If it exceeds 1.0 × 10 ¹¹ Ω · cm, the counter charge of the toner image remains on the intermediate transfer member after the toner image is transferred from the intermediate transfer member to a recording medium such as paper. May appear as an afterimage on other images.

As the intermediate transfer member, for example, a metal oxide such as tin oxide or indium oxide, a conductive particle such as carbon black, or a conductive polymer, alone or in combination, kneaded with a thermoplastic resin, and then an extrusion molded belt A cylindrical or cylindrical plastic can be used. In addition to this, the above-mentioned conductive particles and conductive polymer are added to a resin solution containing a thermally crosslinkable monomer or oligomer, if necessary, and subjected to centrifugal molding while heating to obtain an intermediate transfer member on an endless belt. You can also
When the surface layer is provided on the intermediate transfer member, among the surface layer materials used for the surface layer of the photoreceptor described above, the composition excluding the charge transport material is appropriately adjusted in combination with a conductive substance, Can be used.

The transfer means (the primary transfer means and the secondary transfer means) includes at least a transfer device that peels and charges the visible image formed on the image carrier (photoconductor) to the recording medium side. It is preferable to have. There may be one transfer means or two or more transfer means. Examples of the transfer device include a corona transfer device using corona discharge, a transfer belt, a transfer roller, a pressure transfer roller, and an adhesive transfer device.
The recording medium is not particularly limited and can be appropriately selected from known recording media (recording paper).

<Protective layer forming step and protective layer forming means>
The protective layer forming step is a step of forming the protective layer by applying the protective agent for an image carrier of the present invention to the surface of the image carrier after transfer.
As the protective layer forming means, the protective layer forming apparatus of the present invention described above can be used.

<Fixing process and fixing means>
The fixing step is a step of fixing the visible image transferred to the recording medium using the fixing unit, and may be performed each time the toner of each color is transferred to the recording medium, or may be applied to the toner of each color. On the other hand, it may be carried out simultaneously at the same time in a state of being laminated.
The fixing unit is not particularly limited and may be appropriately selected depending on the intended purpose, but a known heating and pressing unit is preferable. Examples of the heating and pressing means include a combination of a heating roller and a pressing roller, a combination of a heating roller, a pressing roller, and an endless belt.
The heating in the heating and pressing means is usually preferably 80 ° C to 200 ° C.
In the present invention, for example, a known optical fixing device may be used together with or in place of the fixing step and the fixing unit depending on the purpose.

The neutralization step is a step of performing neutralization by applying a neutralization bias to the image carrier, and can be suitably performed by a neutralization unit.
The neutralization means is not particularly limited, and may be appropriately selected from known neutralizers as long as it can apply a neutralization bias to the image carrier. For example, a neutralization lamp or the like is preferable. It is done.

The cleaning step is a step of removing the electrophotographic toner remaining on the image carrier and can be suitably performed by a cleaning unit.
The cleaning unit is preferably provided downstream of the transfer unit and upstream of the protective layer forming unit.
The cleaning means is not particularly limited, and may be selected from known cleaners as long as the electrophotographic toner remaining on the image carrier can be removed. For example, a magnetic brush cleaner, Suitable examples include electrostatic brush cleaners, magnetic roller cleaners, blade cleaners, brush cleaners, web cleaners, and the like.

The recycling step is a step of recycling the toner removed by the cleaning step to the developing unit, and can be suitably performed by the recycling unit.
There is no restriction | limiting in particular as said recycling means, A well-known conveyance means etc. are mentioned.

The control means is a process for controlling the respective steps, and can be suitably performed by the control means.
The control means is not particularly limited as long as the movement of each means can be controlled, and can be appropriately selected according to the purpose. Examples thereof include devices such as sequencers and computers.

Here, FIG. 2 is a cross-sectional view showing an example of the image forming apparatus 100 including the protective layer forming apparatus of the present invention.
Around the drum-shaped image carriers 1Y, 1M, 1C, and 1K, a protective layer forming device 2, a charging device 3, a latent image forming device 8, a developing device 5, a transfer device 6, and a cleaning device 4 are arranged, respectively. Image formation is performed by the following operation.

Next, a series of processes for image formation will be described using a negative-positive process.
An image carrier represented by a photoconductor (OPC) having an organic photoconductive layer is neutralized by a neutralizing lamp (not shown) or the like, and is uniformly negatively charged by a charging device 3 having a charging member.
When the image carrier is charged by the charging device, an appropriate voltage suitable for charging the image carriers 1Y, 1M, 1C, and 1K to a desired potential from a voltage application mechanism (not shown) to the charging member. A large voltage or a charging voltage obtained by superimposing an AC voltage thereon is applied.
The charged image carriers 1Y, 1M, 1C, and 1K form a latent image with a laser beam irradiated by a latent image forming device 8 such as a laser optical system (the absolute value of the exposed portion potential is the absolute value of the non-exposed portion potential). Is lower than the value).
Laser light is emitted from a semiconductor laser, and the surfaces of the image carriers 1Y, 1M, 1C, and 1K are scanned in the direction of the rotation axis of the image carrier by a polygonal polygonal mirror (polygon) that rotates at high speed.
The latent image formed in this manner is developed with a developer composed of toner particles or a mixture of toner particles and carrier particles supplied on a developing sleeve which is a developer carrying member in the developing device 5, and toner can be transferred. A visual image is formed.
At the time of developing the latent image, a voltage of an appropriate magnitude or a voltage between the exposed portion and the non-exposed portion of the image carrier 1Y, 1M, 1C, 1K is applied to the developing sleeve from a voltage application mechanism (not shown). A developing bias superimposed with an AC voltage is applied.

The toner images formed on the image carriers 1Y, 1M, 1C, and 1K corresponding to the respective colors are transferred onto the intermediate transfer body 60 by the transfer device 6 and fed from the paper feed mechanism 200, such as paper. A toner image is transferred onto the recording medium.
At this time, it is preferable that a potential having a polarity opposite to the polarity of toner charging is applied to the transfer device 6 as a transfer bias. Thereafter, the intermediate transfer member 60 is separated from the image carrier to obtain a transfer image.
Further, the toner particles remaining on the image carrier are collected by the cleaning member into the toner collecting chamber in the cleaning device 4.
As the image forming apparatus, an apparatus in which a plurality of the developing devices described above are arranged is used, and a plurality of toner images, which are sequentially produced by the plurality of developing devices, are sequentially transferred onto a transfer material, and then sent to a fixing mechanism to be heated. Even after a plurality of toner images prepared in the same manner are sequentially sequentially transferred onto an intermediate transfer member and then transferred to a recording medium such as paper, Similarly, a fixing device may be used.

The charging device 3 is preferably a charging device arranged in contact with or close to the surface of the image carrier, and a discharge wire is used. This makes it possible to significantly suppress the amount of ozone generated during charging as compared with a corona discharger called a so-called corotron or scorotron.
In a charging device that charges such a charging member in contact with or close to the surface of the image carrier, discharge is performed in the region near the surface of the image carrier as described above, so that an electrical stress is applied to the image carrier. Tends to grow. However, by using the protective layer forming apparatus using the protective agent for an image carrier of the present invention, the image carrier can be maintained for a long time without deterioration. Fluctuations can be greatly suppressed, and stable image quality can be ensured.

  As described above, the image forming apparatus of the present invention has an excellent tolerance for fluctuations in the surface state of the image carrier, particularly the presence of a low resistance portion, and highly suppresses fluctuations in the charging performance of the image carrier. Therefore, when used in combination with the toner having the above structure, an extremely high quality image can be stably formed over a long period of time.

(Process cartridge)
The process cartridge of the present invention comprises at least an image carrier and the protective layer forming means of the present invention, and further, charging means, exposure means, developing means, transfer means, cleaning means, charge eliminating means as necessary. It has other means such as.
The process cartridge of the present invention can be detachably provided in various electrophotographic apparatuses, and is preferably provided detachably in the above-described image forming apparatus of the present invention.

Here, FIG. 3 is a schematic view for explaining an outline of a process cartridge configuration example using the protective layer forming apparatus of the present invention.
The process cartridge includes a protective layer forming device 2 disposed opposite to the photosensitive drum 1 as the image carrier 1, and includes an image carrier protective agent 21, a protective agent supply member 22, a pressing force applying member 23, It is comprised from the protective layer formation member 24 grade | etc.,.
Further, the image carrier 1 has a surface on which the image carrier protective agent or toner component partially deteriorated after the transfer process remains, but the surface residue is cleaned and cleaned by the cleaning member 41. .
In FIG. 3, the cleaning member is abutted at an angle similar to a so-called counter type (leading type).
An image carrier protective agent 21 is supplied from the protective agent supply member 22 to the surface of the image carrier from which the residual toner on the surface and the deteriorated protective agent for the image carrier have been removed by the cleaning mechanism, and the protective layer forming member By 24, a film-like protective layer is formed. At this time, the protective agent for the image carrier used in the present invention has a better adsorptivity to the portion of the surface of the image carrier that is highly hydrophilic due to electrical stress. Even if a large electrical stress is applied and the surface of the image carrier starts to deteriorate partially, the progress of the deterioration of the image carrier itself can be prevented by adsorption of the protective agent.
The image bearing member thus formed with the protective layer is charged, and then an electrostatic ray image is formed by exposure L such as a laser, developed by the developing device 5 to be visualized, and a transfer roller outside the process cartridge. 6 or the like.

  As described above, the process cartridge of the present invention has an excellent tolerance for fluctuations in the surface state of the image carrier, particularly the presence of a low-resistance portion, and has a configuration in which fluctuations in charging performance to the image carrier are highly suppressed. Therefore, when used in combination with the toner having the above structure, an extremely high quality image can be stably formed over a long period of time.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
-Production of protective agent 1 for image carrier-
40 g of monostearic acid hexitol ester powder was put in a glass container with a lid and melted with stirring by a stirrer whose temperature was controlled at 80 ° C.
Pour molten hexitol monostearate ester into an aluminum mold with an internal dimension of 12 mm x 8 mm x 310 mm heated to 60 ° C in advance, let cool to 40 ° C in a room temperature atmosphere, and set the temperature. It was reheated to 50 ° C. in the constant temperature bath, kept at that temperature for 15 minutes, and then allowed to cool to room temperature.
After cooling, the solid material of hexitol monostearate was removed from the mold, cut and molded to 7 mm × 8 mm × 310 mm, and affixed to a metal support with double-sided tape to produce image carrier protective agent 1. .

(Examples 2 to 10 and Comparative Examples 1 to 4)
-Production of protective agents 2-14 for image carrier-
In Example 1, the protective agent for the image carrier is the same as Example 1 except that the raw materials, melting temperature, mold preheating temperature, and cooling conditions of the protective agent are as described in Tables 1 and 2. 2-14 were produced.

(Example 11)
A counter-type cleaning blade, brush-like, and the like around the image carrier (photoreceptor) having a surface layer having a thickness of 5 μm containing a thermosetting resin (thermal radical reaction type polyfunctional acrylic resin) on the surface. A protective agent supplying member and a trailing blade type protective layer forming member were provided in this order from the upstream side, and a process cartridge having a protective layer forming apparatus using the protective agent 1 for an image carrier of Example 1 was produced.
The obtained process cartridge is mounted on an image forming apparatus (color MFP image Neo Neo C600, manufactured by Ricoh Co., Ltd.) modified so that the process cartridge can be mounted. The continuous image drawing test was conducted. The presence or absence of image abnormality before and after the test was confirmed in a normal temperature and humidity environment of 20 ° C. and 50% RH, a low temperature and low humidity environment of 10 ° C. and 25% RH, and a high temperature and high humidity environment of 35 ° C. and 80% RH.
At this time, the toner was prepared by a polymerization method having a mass average particle diameter (D4) = 5.2 μm, a number average particle diameter (D1) = 4.5 μm, D4 / D1 = 1.16, and an average circularity = 0.98. The toner used was used.
As image abnormalities, streak-like image defects, halftone image unevenness, background fogging, and image blur related to the quality of cleaning performance were evaluated according to the following criteria.

<Evaluation criteria for streak-like image defects>
◎: Extremely good ○: Practical problem level △: Practically acceptable level ×: Unusable

<Evaluation criteria for halftone image unevenness>
◎: Extremely good ○: Practical problem level △: Practically acceptable level ×: Unusable

<Evaluation criteria for image defects in background fog>
◎: Extremely good ○: Practical problem level △: Practically acceptable level ×: Unusable

<Evaluation criteria for image defects in blurred images>
◎: Extremely good ○: Practical problem level △: Practically acceptable level ×: Unusable

In addition, in order to evaluate the magnitude of the effect of deterioration of the image carrier, the cleaning blade, and the charging member on the image, the state of each member is observed at the initial stage and when 100,000 sheets are output, and the presence or absence of abnormality is observed. Confirmed and evaluated according to the following criteria.
<Evaluation criteria for the state of each member>
○: Level equivalent to the initial level Δ: Slightly changed (Actual usable level)
×: Deteriorated

As a result, no deterioration was observed in each member due to an increase in the number of printed sheets, and good image quality was obtained both after initial output of 100,000 sheets. It was found to be useful on both sides.
The image quality evaluation results are shown in Tables 3 to 8, and the observation results of the member deterioration state are shown in Table 9.
The image forming apparatus of Example 11 was subsequently subjected to a paper passing test for a total of 500,000 sheets. As a result, no effect on the image was observed, and the image carrier, cleaning member, and charging member were not observed. Almost no deterioration was observed.

(Examples 12 to 20)
In Example 11, the evaluation was performed in the same manner as in Example 11 except that the image carrier protecting agent 1 was changed to the image carrier protecting agents 2 to 10.
The image quality evaluation results are shown in Tables 3 to 8, and the observation results of the member deterioration state are shown in Table 9.
The image forming apparatus of Example 12 was subsequently subjected to a paper passing test up to a total of 500,000 sheets. As a result, no effect on the image was observed, and the image carrier, cleaning member, and charging member were not observed. Almost no deterioration was observed.

(Comparative Examples 5 to 8)
In Example 11, evaluation was performed in the same manner as in Example 11 except that the image carrier protecting agents 11 to 14 were used instead of the image carrier protecting agent 1.
The image quality evaluation results are shown in Tables 3 to 8, and the observation results of the member deterioration state are shown in Table 9.

(Example 21)
A brush-type protective agent supply member and a counter-type cleaning blade around the image carrier having a surface layer having a thickness of 5 μm containing a thermosetting resin (thermal radical reaction type polyfunctional acrylic resin) on the surface, following the transfer step The protective layer forming member which is also used as the protective layer forming member was provided in this order from the upstream side, and a process cartridge having a protective layer forming apparatus using the protective agent 1 for the image carrier of Example 1 was produced.
Installed in an image forming apparatus (color MFP image Neo Neo C455, manufactured by Ricoh Co., Ltd.) modified so that the above process cartridge can be mounted, and a continuous image drawing test of an A4 size version, an original with a 6% image area ratio, was performed. The test was performed to check whether there was any abnormality in the image before and after the test.

At this time, the toner was prepared by a polymerization method having a mass average particle diameter (D4) = 5.2 μm, a number average particle diameter (D1) = 4.5 μm, D4 / D1 = 1.16, and an average circularity = 0.98. The toner used was used.
As image abnormalities, streak-like image defects, half-tone image unevenness, background fogging, and image blur were evaluated in the same manner as in Example 11.
Further, in the same manner as in Example 11, in order to evaluate the magnitude of the influence of the deterioration of the image carrier, the cleaning blade, and the charging member on the image, the respective states at the initial stage and at the time of 100,000 sheets were observed. The presence or absence of abnormality was confirmed.
The image quality evaluation results are shown in Tables 3 to 8, and the observation results of the member deterioration state are shown in Table 9.

(Example 22)
In Example 11, the test was performed in the same manner as in Example 11 except that the protective agent supply member was removed and the protective agent was changed to be supplied by pressing directly onto the image carrier.
The image quality evaluation results are shown in Tables 3 to 8, and the observation results of the member deterioration state are shown in Table 9.

(Example 23)
In Example 11, a test was performed in the same manner as in Example 11 except that an image carrier that does not contain a thermosetting resin (thermal radical reaction type polyfunctional acrylic resin) in the surface layer was used as the image carrier. .
The image quality evaluation results are shown in Tables 3 to 8, and the observation results of the member deterioration state are shown in Table 9.

(Example 24)
In Example 11, as a toner, a polymerization method having a mass average particle diameter (D4) = 6.0 μm, a number average particle diameter (D1) = 5.3 μm, D4 / D1 = 1.13, and an average circularity = 0.90. A test was performed in the same manner as in Example 11 except that the toner prepared in the above was used.
The image quality evaluation results are shown in Tables 3 to 8, and the observation results of the member deterioration state are shown in Table 9.

(Example 25)
In Example 11, as a toner, a polymerization method having a mass average particle diameter (D4) = 5.4 μm, a number average particle diameter (D1) = 3.5 μm, D4 / D1 = 1.54, and an average circularity = 0.98. A test was performed in the same manner as in Example 11 except that the toner prepared in the above was used.
The image quality evaluation results are shown in Tables 3 to 8, and the observation results of the member deterioration state are shown in Table 9.

From the results of Tables 1 to 9, Examples 11 to 25 using the image carrier protecting agent of the present invention are images of streaks, image unevenness, background fog, image blur, and the like as compared with Comparative Examples 5 to 8. It can be seen that the quality is good and the image carrier, the cleaning member, and the charging member are hardly deteriorated due to an increase in the number of printed sheets.
Further, in Example 14 using the protective agent 4 having an alkylcarboxylic acid ester having a lipophilic group having a branched structure, the lipophilic group of the alkylcarboxylic acid ester is linear alkyl, and the other configurations are the same. 11 (protective agent 1), the amount of surface layer wear of the image carrier was slightly increased, and it was confirmed that the protective effect of the image carrier was slightly inferior.
Further, as in Examples 12, 15, and 17 (protecting agents 2, 5, and 7), when the carbon number of the sugar alcohol to be used is increased, the protecting agent considered to be accompanied by the brittleness of the protecting agent for the image carrier. It was confirmed that the coating unevenness started to occur.
Further, as in Examples 11, 16, and 18 (protective agents 1, 6, and 8), when the number of carbons of the sugar alcohol used is reduced, it is difficult to exhibit the adsorption performance in a low-temperature and low-humidity environment. It is recognized that the reduction in the effect of protecting the image carrier, which is considered to be accompanied, begins to occur.
Moreover, when the evaluation result of Example 19 (protective agent 9) was compared with Example 11 (protective agent 1), when the carbon number of the alkylcarboxylic acid increased and the alkyl chain lengthened, the productivity decreased, It was confirmed that brittleness began to appear in the protective agent for the image carrier, and slight coating unevenness of the protective agent began to occur.
Moreover, when the evaluation result of Example 20 (protective agent 10) was compared with Example 11 (protective agent 1), the hydrophilicity increased when the carbon number of the alkylcarboxylic acid decreased, and the image was observed in a high-temperature and high-humidity environment. It was confirmed that the tendency of blurring to begin to occur and minute filming of the toner component on the image carrier started to occur.

When the evaluation result of Comparative Example 5 (protective agent 11) was compared with Example 11 (protective agent 1) and Example 19 (protective agent 9), when the number of carbon atoms of the alkylcarboxylic acid was too large, it was apparent that productivity was improved. In addition, a lot of uneven application of the image carrier protective agent was observed, which was not the actual use level.
Moreover, when the evaluation result of the comparative example 6 (protective agent 12) was compared with Example 11 (protective agent 1) and Example 20 (protective agent 10), when carbon number of alkylcarboxylic acid is too few, it is high temperature high. The image was blurred in a wet environment, and at the same time, filming on the surface of the image carrier occurred, and severe image unevenness was observed on the entire surface of the image.
From these, it was confirmed that when the carbon number of the alkyl carboxylic acid is not within the specified range of the present invention, the image is affected.
In Comparative Examples 7 and 8 (protective agents 13 and 14) that do not satisfy the requirements of the protective agent for the image carrier of the present invention, the image carrier is maintained while maintaining the image quality against the electrical stress of the image carrier. The protective effect of was not expressed.

  The protective agent for an image carrier and the protective layer forming apparatus of the present invention protect the image carrier from electrical stress due to charging or the like, and the protective agent deteriorated by electrical stress hardly affects the image quality and peripheral members. Therefore, it is suitably used for an electrophotographic image forming method, an image forming apparatus, a process cartridge, and the like.

FIG. 1 is a schematic view showing an example of a protective layer forming apparatus of the present invention. FIG. 2 is a schematic view showing an example of the image forming apparatus of the present invention. FIG. 3 is a schematic view showing an example of the process cartridge of the present invention.

Explanation of symbols

1 Image carrier (photosensitive drum)
DESCRIPTION OF SYMBOLS 2 Protective layer forming apparatus 3 Charging roller 4 Cleaning mechanism 5 Developing apparatus 6 Transfer roller 8 Latent image forming apparatus 21 Protective agent for image carrier 22 Protective agent supply member 23 Pressing force applying member 24 Protective layer forming member 41 Cleaning member 42 Cleaning pressure 42 Member 60 Intermediate transfer member 100 Image forming apparatus 200 Paper feed mechanism L Exposure

Claims (19)

At least 1 selected from alkyl carboxylic acid sugar alcohol ester which is an esterified product of alkyl carboxylic acid having 15 to 35 carbon atoms in the alkyl group and sugar alcohol (excluding sorbitol anhydride and glycerin) and its substitute A protective agent for an image carrier characterized by being a seed. The protective agent for an image carrier according to claim 1, wherein the alkylcarboxylic acid sugar alcohol ester is obtained by esterifying an alkylcarboxylic acid represented by the following structural formula (1) and a sugar alcohol.
C _n H _2n + 1 COOH ··· structural formula (1)
However, in said structural formula (1), n shows the integer of 15-35.     The protective agent for an image carrier according to any one of claims 1 to 2, wherein the number average carbon number per molecule of sugar alcohol is 4 to 8.   The protective agent for an image carrier according to any one of claims 1 to 3, wherein the total number of carbon atoms in the alkyl group moiety in the alkylcarboxylic acid sugar alcohol ester and the substitution product thereof is 15 to 125.   The protective agent for an image carrier according to any one of claims 1 to 4, wherein the alkyl carboxylic acid is a linear alkyl carboxylic acid.   The protective agent for an image carrier according to any one of claims 1 to 5, wherein the alkylcarboxylic acid sugar alcohol ester has an HLB value of 1.0 to 6.5.   A protective layer forming apparatus comprising: an image carrier; and means for forming a protective layer by applying the protective agent for an image carrier according to any one of claims 1 to 6 to the surface of the image carrier.   A pressing force applying member that presses the protective agent for the image carrier to contact the protective agent supply member, a protective agent supply member that supplies the protective agent for the image carrier to the surface of the image carrier, and the supplied image carrier The protective layer forming apparatus according to claim 7, further comprising a protective layer forming member that forms a protective layer by thinning the protective agent for use.   An electrostatic latent image forming step for forming an electrostatic latent image on an image carrier, a developing step for developing the electrostatic latent image with toner to form a visible image, and the visible image on a recording medium A transfer step for transferring to the surface, a protective layer forming step for forming a protective layer by applying the protective agent for an image carrier according to any one of claims 1 to 6 to the surface of the image carrier after the transfer, and the recording An image forming method comprising at least a fixing step of fixing a transferred image transferred to a medium. An image bearing member; an electrostatic latent image forming unit that forms an electrostatic latent image on the image bearing member; a developing unit that develops the electrostatic latent image with toner to form a visible image; It has at least transfer means for transferring a visible image to a recording medium, protective layer forming means according to any one of claims 7 to 8 , and fixing means for fixing the transferred image transferred to the recording medium. An image forming apparatus.   The image forming apparatus according to claim 10, further comprising a cleaning unit that removes toner remaining on the surface of the image carrier on the downstream side of the transfer unit and the upstream side of the protective layer forming unit.   The image forming apparatus according to claim 10, wherein the outermost surface layer of the image carrier includes at least a thermosetting resin.   The image forming apparatus according to claim 10, wherein the image carrier is any one of a photosensitive member and an intermediate transfer member.   The image forming apparatus according to claim 10, wherein the electrostatic latent image forming unit includes a charger disposed in contact with or close to the surface of the image carrier.   The image forming apparatus according to claim 14, wherein the charger includes a voltage applying unit that applies a voltage having an AC component. The image forming apparatus according to claim 10, wherein an average circularity that is an average value of the circularity SR expressed by the following mathematical formula 1 of the toner is 0.93 to 1.00.
<Formula 1>
Circularity SR = (perimeter of circle having the same area as the projected area of toner particles) / (perimeter of projected image of toner particles)   The image forming apparatus according to any one of claims 10 to 16, wherein a ratio (D4 / D1) of the mass average particle diameter (D4) and the number average particle diameter (D1) of the toner is 1.00 to 1.40.   A process cartridge comprising at least an image carrier and a protective layer forming unit according to any one of claims 7 to 8, and detachable from an image forming apparatus main body.   19. The process cartridge according to claim 18, further comprising a cleaning unit that removes toner remaining on the surface of the image carrier on the upstream side of the protective layer forming unit.