JP2009162956A - Toner set, two-component developer set, developing device, image forming apparatus, and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner set exhibiting excellent fixability even in an image forming apparatus whose process speed of forming a monochromatic image is accelerated in the consideration of the preservation of global environment. <P>SOLUTION: The toner set is used in an image forming apparatus having a process speed for forming a monochromatic image higher than a process speed for forming a color image, wherein the toner set contains a black toner and color toners including at least a binder resin and a colorant, the binder resin includes a polylactic resin which is a copolymer of L-form and D-form, and the black toner includes a larger content of the D-form in the polylactic resin than the color toners. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a toner set, a two-component developer set, a developing device, an image forming apparatus, and an image forming method.

  In recent years, various efforts have been made in the field of electrophotography from the viewpoints of safety, waste disposal and environmental protection.

  Many conventional toners use a styrene-acrylic acid ester resin or a polyester resin as a binder resin, and volatile gas such as styrene is generated, which may affect the human body during heat fixing. There's a problem. In particular, when a color image forming apparatus or an image forming apparatus corresponding to high speed is used, the amount of toner consumption increases, and as a binder resin for toner, there is no odor caused by volatile gas, which is more safe. There is a need to use expensive ones. Further, the conventional toner has a problem that it is difficult to dispose of waste because it does not have biodegradability.

  At present, the raw materials of many products such as toner are manufactured from fossil resources such as petroleum, and efforts to reduce the use of fossil resources are extremely important in terms of preventing the depletion of fossil resources. It is.

  In order to solve the above-described problems, a technique has been proposed in which a polylactic acid resin, which is a biodegradable material, is used as a toner binder resin.

  For example, Patent Document 1 discloses a toner for developing an electrostatic image using a urethanized polyester resin obtained by crosslinking polylactic acid with a trifunctional or higher polyvalent isocyanate as a binder resin (binder resin). Yes.

  Patent Document 2 discloses an electrophotographic toner that uses a resin obtained by blending a polylactic acid-based biodegradable resin and a terpene phenol copolymer as a binder resin.

  Further, in recent color image forming apparatuses, in order to improve the printing efficiency when forming a monochrome image (hereinafter referred to as “monochrome image”) using black toner that is frequently used, There has been proposed a technique for making the process speed faster than the process speed at the time of color image formation, and a toner that can be used for such an image forming apparatus is required.

JP-A-9-281746 JP 2001-166537 A

  The toners of Patent Document 1 and Patent Document 2 are not configured to be sufficiently compatible with an image forming apparatus in which a process speed at the time of forming a black and white image is increased, and there is a possibility that fixing failure may occur at the time of forming a black and white image.

  Further, the toners of Patent Document 1 and Patent Document 2 have a problem of poor long-term storage stability because they have good biodegradability. That is, if left in a high temperature and high humidity environment for a long time, the toner may be hydrolyzed and cannot be used. Furthermore, when the printed materials are left in a stacked state under the above-described conditions, the printed materials may stick to each other due to the softened toner.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide good fixability even in an image forming apparatus in which the process speed at the time of monochrome image formation is increased in consideration of global environmental conservation. The present invention provides a toner set, a two-component developer set, a developing device, an image forming apparatus, and an image forming method.
Another object of the present invention is to provide a toner having excellent long-term storage stability.

The present invention is a toner set for use in an image forming apparatus having a process speed when forming an image using black toner faster than a process speed when forming an image using color toner,
Including black toner and color toner comprising at least a binder resin and a colorant,
The binder resin includes a polylactic acid resin that is a copolymer of L-form and D-form,
The black toner is a toner set characterized in that the content of the D form in the polylactic acid resin is larger than that of the color toner.

  In the toner set of the present invention, the black toner has a D-form content in the polylactic acid resin of 3 mol% or more higher than that of the color toner.

  The toner set of the present invention is characterized in that the content of D-form in the polylactic acid resin is 8 mol% or less.

  In the toner set of the present invention, the black toner and the color toner are characterized in that the external additive is added so that the coverage is 50% or more and less than 120%.

  In the toner set of the present invention, the external additive has a hydrophobicity of 40 or more.

  The present invention is the two-component developer set, wherein the black toner and the color toner in the toner set each include a carrier to form a two-component developer.

  In addition, the present invention is a developing device including a developing unit that stores black toner in the toner set, and a developing unit that stores color toner in the toner set.

The present invention also provides an image carrier on which an electrostatic latent image is formed by being exposed to light according to image information, and the developing device for developing the electrostatic latent image by supplying toner to the image carrier. A transfer device that transfers a toner image formed by development onto a recording medium, and a fixing device that heats and fixes the toner image on the recording medium,
An image forming apparatus characterized in that a process speed when forming an image using black toner is higher than a process speed when forming an image using color toner.

  The image forming apparatus of the present invention is characterized in that the separation distance between the developing unit that stores black toner and the fixing device is longer than the separation distance between the developing unit that stores color toner and the fixing device.

Further, the present invention is an image forming method for forming an image using the toner set,
An image forming method characterized in that a process speed when forming an image using black toner is higher than a process speed when forming an image using color toner.

  According to the present invention, when an image is formed using black toner (hereinafter, sometimes referred to as “monochrome image formation”), the process speed is the same as when forming an image using color toner (hereinafter referred to as “color image formation”). In a toner set used in an image forming apparatus that is faster than a process speed (which may be referred to as “time”), the toner set includes black toner and color toner including at least a binder resin and a colorant, The binder resin includes a polylactic acid resin that is a copolymer of L-form and D-form.

  As described above, when the binder resin includes the polylactic acid resin, a highly safe toner set including the black toner and the color toner can be obtained. In addition, since the polylactic acid resin is biodegradable, it is easy to dispose of the toner. Furthermore, since polylactic acid resin is a material derived from non-fossil resources, the use of fossil resources can be reduced and the environmental load can be reduced.

  Further, the black toner has a higher D content in the polylactic acid resin than the color toner. Thus, since the softening point of the black toner becomes lower than the softening point of the color toner by making the content of D-form in the polylactic acid resin in the black toner larger than the content in the color toner, the black toner Becomes easier to fix at lower temperatures. Therefore, by increasing the process speed, it is possible to obtain a good fixing property even when forming a black and white image in which the passage time of the recording medium in the fixing nip portion is shortened, and to improve the printing efficiency when forming a black and white image. Can do.

  Therefore, the toner set of the present invention is able to exhibit good fixability even in an image forming apparatus in which the process speed at the time of monochrome image formation is increased in consideration for the global environment conservation.

  According to the invention, it is preferable that the black toner has a D-form content in the polylactic acid resin of 3 mol% or more than the color toner.

  As a result, the softening point of the black toner can be lowered by 15 ° C. or more than the softening point of the color toner, and the black toner can be easily fixed at a lower temperature. Therefore, it is possible to obtain a good fixing property even when forming a black and white image in which the passage time of the recording medium at the fixing nip portion is greatly shortened by greatly increasing the process speed, and the printing efficiency when forming a black and white image. Can be further improved.

  Further, when forming the black and white image, good fixability can be obtained without setting the fixing temperature to be significantly high. Accordingly, it is possible to reduce the difference between the fixing temperature setting values when forming a black and white image and when forming a color image, and even when a color image is formed after forming a black and white image, a high temperature offset occurs in the color toner. Can be prevented.

  Moreover, according to this invention, it is preferable that content of the D body in polylactic acid resin is 8 mol% or less. Thereby, the storage stability of the black toner and the color toner in a high temperature and high humidity environment can be kept better.

  According to the invention, it is preferable that the black toner and the color toner are added so that the external additive has a coverage of 50% or more and less than 120%. Thereby, it is possible to prevent the black toner and the color toner in the toner set of the present invention using the polylactic acid resin having a relatively large D-form content from being deteriorated by hydrolysis.

  According to the invention, the external additive preferably has a hydrophobicity of 40 or more. Thereby, it is possible to more reliably prevent the black toner and the color toner in the toner set of the present invention using the polylactic acid resin having a relatively large D-form content from being deteriorated by hydrolysis.

  According to the invention, in the two-component developer set of the invention, the black toner and the color toner in the toner set each include a carrier to constitute a two-component developer. Accordingly, it is possible to obtain a two-component developer set capable of exhibiting good fixability even in an image forming apparatus that takes into consideration the global environment conservation and has increased the process speed during monochrome image formation.

  According to the invention, the developing device of the invention includes a developing unit that stores the black toner in the toner set and a developing unit that stores the color toner in the toner set.

  As described above, by performing development using the toner set of the present invention, the printing efficiency at the time of black and white image formation is improved in the image forming apparatus in which the process speed at the time of black and white image formation is increased with consideration for global environment conservation. And a developing device capable of forming a better image can be obtained.

  According to the present invention, the image forming apparatus of the present invention includes an image carrier on which an electrostatic latent image is formed by exposure with light according to image information, and supplies toner to the image carrier to The image forming apparatus includes the developing device that develops the electrostatic latent image, a transfer device that transfers a toner image formed by development onto a recording medium, and a fixing device that heats and fixes the toner image on the recording medium. The process speed when forming an image using black toner is configured to be higher than the process speed when forming an image using color toner.

  As described above, by providing the developing device of the present invention, it is possible to further increase the safety. Therefore, it is possible to obtain an image forming apparatus that can be installed at a position close to the user in the office. In addition, since the difference in the set value of the fixing temperature during monochrome image formation and color image formation can be reduced, the start-up time during monochrome image formation can be shortened and high when monochrome image formation is performed. A good image can be formed with printing efficiency.

  Further, according to the present invention, it is preferable that the separation distance between the developing unit containing black toner and the fixing device is longer than the separation distance between the developing unit containing color toner and the fixing device.

  As described above, the developing unit that stores the black toner having a low softening point is installed at a position away from the fixing device having the heating unit, thereby maintaining the storage stability of the black toner in a good state for a long period of time. be able to.

  Further, according to the present invention, the image forming method of the present invention is an image forming method for forming an image using the toner set, and the process speed when forming an image using the black toner is determined using a color toner. To make it faster than the process speed for image formation. As a result, the process speed is increased, so that it is possible to obtain a good fixing property even when forming a black and white image in which the passage time of the recording medium in the fixing nip portion is shortened, and to improve the printing efficiency when forming a black and white image. be able to.

  INDUSTRIAL APPLICABILITY The present invention is used for an image forming apparatus in which an image forming process using black toner (during monochrome image formation) is faster than a process speed forming an image using color toner (during color image formation). A toner set, wherein the toner set includes at least a black toner and a color toner including a binder resin and a colorant, and the binder resin is a copolymer of an L body and a D body. Containing lactic acid resin.

  As described above, when the binder resin includes the polylactic acid resin, a highly safe toner set including the black toner and the color toner can be obtained. In addition, since the polylactic acid resin is biodegradable, it is easy to dispose of the toner. Furthermore, since polylactic acid resin is a material derived from non-fossil resources, the use of fossil resources can be reduced and the environmental load can be reduced.

  Further, the black toner has a higher D content in the polylactic acid resin than the color toner. Thus, since the softening point of the black toner becomes lower than the softening point of the color toner by making the content of D-form in the polylactic acid resin in the black toner larger than the content in the color toner, the black toner Becomes easier to fix at lower temperatures. Therefore, by increasing the process speed, it is possible to obtain a good fixing property even when forming a black and white image in which the passage time of the recording medium in the fixing nip portion is shortened, and to improve the printing efficiency when forming a black and white image. Can do.

  Therefore, the toner set of the present invention is able to exhibit good fixability even in an image forming apparatus in which the process speed at the time of monochrome image formation is increased in consideration for the global environment conservation.

  In this specification, black toner refers to toner that includes a colorant for black toner described later, and color toner refers to toner that includes a colorant for color toner described later. In this embodiment, a colorant for magenta toner, a colorant for cyan toner, and a colorant for yellow toner are used as the colorant for color toner.

  Hereinafter, a method for producing a black toner and a color toner (hereinafter, simply referred to as “toner”) constituting the toner set of the present invention will be described. The toner manufacturing method constituting the toner set of the present invention is, for example, the toner manufacturing method shown in the flowchart of FIG. FIG. 1 is a flowchart showing an example of a procedure in a method for producing black toner and color toner constituting the toner set of the present invention.

  As shown in FIG. 1, the method for producing the toner constituting the toner set of the present invention comprises a pre-mixing step (step S1) in which at least a binder resin and a colorant are mixed to produce a mixture, and the mixture is melt-kneaded. A melt-kneading step for preparing a melt-kneaded product (step S2), a pulverizing step for pulverizing the melt-kneaded product to prepare a pulverized product (step S3), and a classification step for removing excessively pulverized product and coarse powder from the pulverized product. (Step S4).

  Below, each manufacturing process of step S1-step S4 is demonstrated in detail. By shifting from step S0 to step S1, manufacture of the toner constituting the toner set of the present invention is started.

[Pre-mixing process]
In the pre-mixing step of step S1, at least the binder resin and the colorant are dry-mixed by a mixer to prepare a mixture. The mixture may contain other toner additive components in addition to the binder resin and the colorant. Examples of other toner additive components include a release agent and a charge control agent.

  A known mixer can be used for dry mixing. For example, a Henschel mixer (trade name: FM mixer, manufactured by Mitsui Mining Co., Ltd.), a super mixer (trade name, manufactured by Kawata Co., Ltd.), a mechano mill (product) Name, Okada Seiko Co., Ltd. and other Henschel type mixing devices, Ongmill (trade name, manufactured by Hosokawa Micron Co., Ltd.), hybridization system (trade name, manufactured by Nara Machinery Co., Ltd.), Cosmo System (trade name, Kawasaki Heavy Industries, Ltd.) Etc.).

Below, each toner raw material contained in a mixture is demonstrated.
(A) Binder Resin The binder resin includes a polylactic acid resin that is a copolymer of an L body and a D body. Here, the L-form and the D-form represent optical isomers having different steric configurations, each represented by DL notation based on the IUPAC nomenclature. The DL notation is a nomenclature in which a compound that can be obtained without destroying the configuration of the d-glyceraldehyde is referred to as a D-form and its enantiomer is represented as an L-form.

  As described above, when the binder resin includes the polylactic acid resin, a toner set including a highly safe toner can be obtained. In addition, since the polylactic acid resin is biodegradable, it is easy to dispose of the toner. Furthermore, since polylactic acid resin is a material derived from non-fossil resources, the use of fossil resources can be reduced and the environmental load can be reduced.

  The polylactic acid resin constituting the binder resin is a lactic acid-based polymer mainly containing a lactic acid component, and specifically includes a polylactic acid homopolymer or a copolymer of lactic acid and other hydroxycarboxylic acid. Examples of other hydroxycarboxylic acids used as comonomers include glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid, hydroxycaproic acid, hydroxyheptanoic acid and the like.

  When the polylactic acid resin is a copolymer of lactic acid and another hydroxycarboxylic acid, the content of the lactic acid component in the polylactic acid resin is preferably 80 mol% or more based on the total amount of the polylactic acid resin.

  The polylactic acid resin is particularly preferably a polylactic acid homopolymer among the lactic acid polymers described above. As described above, since the binder resin is configured to include the polylactic acid homopolymer, further consideration is given to the conservation of the global environment, and even better in an image forming apparatus in which the process speed at the time of monochrome image formation is increased. A toner capable of exhibiting excellent fixability can be obtained.

  These polylactic acid resins are selected from L-lactic acid (L-form), D-lactic acid (D-form), and the D-form and L-form of other hydroxycarboxylic acids as raw materials. It can be obtained by dehydration condensation polymerization. In particular, it is preferably obtained by ring-opening polymerization by selecting a desired structure from lactide, which is a cyclic dimer of lactic acid, glycolide, which is a cyclic dimer of glycolic acid, and caprolactone.

  Lactide, which is a raw material for polylactic acid resin, includes L-lactide, which is a cyclic dimer of L-lactic acid, D-lactide, which is a cyclic dimer of D-lactic acid, and D-lactic acid and L-lactic acid. There are quantified meso-lactide and DL-lactide, which is a racemic mixture of D-lactide and L-lactide. Any lactide can be used in the present invention.

  It does not specifically limit as a manufacturing method of polylactic acid resin, A conventionally well-known method can be used. For example, as a method for producing a polylactic acid homopolymer, lactide, which is a cyclic dimer of lactic acid, is heated and melted and uniformly mixed, and then heated by ring-opening polymerization using a known polymerization catalyst, or heating and For example, a method in which dehydration polycondensation is performed directly from a lactic acid monomer under reduced pressure.

  The polymerization catalyst used in the above-described polymerization reaction is not particularly limited, but a known lactic acid polymerization catalyst can be used. For example, tin compounds such as tin octylate, tin lactate, tin tartrate, tin dicaprylate, tin dilaurate, tin dipalmitate, tin distearate, tin dioleate, α-naphthoate, β-naphthoate; Powdered tin, tin oxide; zinc dust, zinc halide, zinc oxide, organic zinc compounds; titanium compounds such as tetrapropyl titanate; zirconium compounds such as zirconium isopropoxide; antimony compounds such as antimony trioxide; oxidation Examples thereof include bismuth compounds such as bismuth (III); aluminum compounds such as aluminum oxide and aluminum isopropoxide. The amount of these polymerization catalysts used is, for example, about 0.001 to 5% by weight based on lactide when ring-opening polymerization is performed. The polymerization reaction varies depending on the catalyst type in the presence of the above-described polymerization catalyst, but can be usually performed at a temperature of 100 ° C to 220 ° C.

  As a copolymerization molar ratio of the L-form and D-form in a polylactic acid resin, it is preferable that it is L-form / D-form = 98/2-92/8. When the copolymer molar ratio is within the above range, better storage stability can be obtained.

  The copolymerization molar ratio between the L-form and the D-form can be controlled, for example, by adjusting the charge amounts (feed ratio) of the L-form and D-form that are raw materials at the start of polymerization.

  In the binder resin, the black toner is configured so that the content of the D-form in the polylactic acid resin is larger than that of the color toner, and is particularly preferably 3 mol% or more.

  Among the polylactic acid resins, the polylactic acid resin in which the L-form content occupies nearly 100 mol% exhibits crystallinity. When the content of D-form is increased with respect to such a crystalline polylactic acid resin, the polylactic acid resin tends to be amorphous, and in particular when the content exceeds 12 mol%, it is amorphous. Of polylactic acid resin. Amorphous polylactic acid resin has no melting point and has a low glass transition point of about 50 ° C. Thus, the softening point and glass transition point of the polylactic acid resin can be adjusted to desired temperatures by adjusting the degree of amorphization by changing the content of D-form.

  As described above, the black toner has a softening point lower than that of the color toner by increasing the content of D-form in the polylactic acid resin in the black toner more than the content in the color toner. The toner becomes easier to fix at a lower temperature. Therefore, by increasing the process speed, it is possible to obtain a good fixing property even when forming a black and white image in which the passage time of the recording medium in the fixing nip portion is shortened, and to improve the printing efficiency when forming a black and white image. Can do.

  Further, by increasing the content of D-form in the polylactic acid resin in the black toner by 3 mol% or more than the content in the color toner, the softening point of the black toner is lower by 15 ° C. or more than the softening point of the color toner. This makes it easier to fix the black toner at a lower temperature. Therefore, it is possible to obtain a good fixing property even when forming a black and white image in which the passage time of the recording medium at the fixing nip portion is greatly shortened by greatly increasing the process speed, and the printing efficiency when forming a black and white image. Can be further improved.

  Further, when the black and white image is formed, good fixability can be obtained without setting the fixing temperature significantly high. Accordingly, it is possible to reduce the difference between the fixing temperature setting values when forming a black and white image and when forming a color image, and even when a color image is formed after forming a black and white image, a high temperature offset occurs in the color toner. Can be prevented.

  On the other hand, if the amount is less than 3 mol%, the difference in softening point between the color toner and the black toner is small, so that the process speed when forming a black-and-white image may not be able to be significantly increased compared to when forming a color image. There is. Therefore, there is a possibility that the printing efficiency when forming a frequently used black and white image cannot be improved. Further, in this case, it is possible to increase the process speed by increasing the setting value of the fixing temperature at the time of monochrome image formation, but in that case, the temperature inside the apparatus around the fixing device becomes high, There is a possibility that a serious problem such as toner fusing in the adjacent toner cartridge may occur.

  Moreover, it is preferable that content of D body in the polylactic acid resin in a binder resin is 8 mol% or less. Thereby, the storage stability of the toner in a high temperature and high humidity environment can be kept better. If the content of D-former exceeds 8 mol%, the effect of hydrolysis of the polylactic acid resin will be prominent, so the storage stability in a high-temperature and high-humidity environment will deteriorate rapidly.

  In addition to the polylactic acid resin, one or more known binder resins for toner may be used in combination as the binder resin. Known binder resins include, for example, polyester resins, styrene resins such as polystyrene and styrene-acrylic acid ester copolymer resins, acrylic resins such as polymethyl methacrylate, polyolefin resins such as polyethylene, polyurethane, and epoxy resins. In addition, a resin obtained by mixing a raw material monomer mixture with a release agent and performing a polymerization reaction may be used.

  When the binder resin contains a polylactic acid resin and the above-described known binder resin, the above-mentioned known binder resin is contained in an amount of 1% by weight to 50% by weight with respect to the binder resin. Is preferred.

  In this embodiment, magenta toner, cyan toner, and yellow toner are used as color toners. As described above, when there are a plurality of color toners, the D-body content relationship between the color toners is not particularly limited, but the D-body content in all the color toners is configured to be equal. It is preferred that

(B) Colorant Examples of the colorant include colorant for color toner such as colorant for magenta toner, colorant for cyan toner and colorant for yellow toner, and colorant for black toner. Hereinafter, the color index is abbreviated as “CI”.

  Examples of the colorant for magenta toner include C.I. I. Pigment red 49, C.I. I. Pigment red 57, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 81, C.I. I. Pigment red 122, C.I. I. Solvent Red 19, C.I. I. Solvent Red 49, C.I. I. Solvent Red 52, C.I. I. Basic Red 10 and C.I. I. Disperse Red 15 etc. are mentioned.

  Examples of the colorant for cyan toner include C.I. I. Pigment blue 15, C.I. I. Pigment blue 16, C.I. I. Solvent Blue 55, C.I. I. Solvent Blue 70, C.I. I. Direct Blue 25, and C.I. I. Direct Blue 86 and the like can be mentioned.

  Examples of the colorant for yellow toner include C.I. I. Pigment yellow 1, C.I. I. Pigment yellow 5, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 15 and C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 180, C.I. I. Organic pigments such as CI Pigment Yellow 185, inorganic pigments such as yellow iron oxide and ocher, C.I. I. Nitro dyes such as Acid Yellow 1, C.I. I. Solvent Yellow 2, C.I. I. Solvent Yellow 6, C.I. I. Solvent Yellow 14, C.I. I. Solvent Yellow 15, C.I. I. Solvent Yellow 19, and C.I. I. Examples thereof include oil-soluble dyes such as Solvent Yellow 21.

  Examples of the colorant for black toner include carbon black such as channel black, roller black, disk black, gas furnace black, oil furnace black, thermal black, and acetylene black. From these various types of carbon black, an appropriate carbon black may be appropriately selected according to the design characteristics of the toner to be obtained.

  In addition to these pigments, red pigments and green pigments can be used. A coloring agent can be used individually by 1 type, or can use 2 or more types together. Two or more of the same color can be used, and one or more of the different colors can also be used.

  The colorant is preferably used as a masterbatch. A master batch of a colorant can be produced, for example, by kneading a synthetic resin melt and a colorant. As the synthetic resin, the same kind of resin as the toner binder resin or a resin having good compatibility with the toner binder resin is used. The use ratio of the synthetic resin and the colorant is not particularly limited, but is preferably 30 parts by weight or more and 100 parts by weight or less with respect to 100 parts by weight of the synthetic resin. That is, it is preferable that the colorant is contained in an amount of 23% by weight to 50% by weight with respect to the master batch. The master batch is used after being granulated to a particle size of about 2 mm to 3 mm, for example.

  The content of the colorant in the toner of the present invention is not particularly limited, but is preferably 4 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the binder resin. When using a masterbatch, it is preferable to adjust the usage amount of the masterbatch so that the content of the colorant in the toner of the present invention falls within the above range. By using the colorant content within the above range, it is possible to form a good image having a sufficient image density, high color developability and excellent image quality. When the content of the colorant exceeds 20 parts by weight, the elasticity of the toner may increase due to the filler effect of the colorant, and the fixability of the toner may decrease.

(C) Release agent The release agent is added to impart releasability to the toner when the toner is fixed on the recording medium. Therefore, compared with the case where a mold release agent is not used, the high temperature offset start temperature can be increased and the high temperature offset resistance can be improved. Further, the low temperature fixability can be improved by melting the release agent by heating at the time of fixing the toner to lower the fixing start temperature.

  The release agent is not particularly limited and known ones can be used. For example, paraffin wax and its derivatives, and petroleum wax such as microcrystalline wax and its derivatives, Fischer-Tropsch wax and its Derivatives, polyolefin waxes and derivatives thereof, low molecular weight polypropylene waxes and derivatives thereof, and hydrocarbon synthetic waxes such as polyolefin polymer waxes and derivatives thereof, carnauba wax and derivatives thereof, ester waxes, and the like.

  The content of the release agent is not particularly limited and can be appropriately selected from a wide range, but is preferably 0.2 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the binder resin. When the content of the release agent exceeds 20 parts by weight, a phenomenon called filming in which the toner is fused in the form of a film (film) on the surface of an image carrier such as a photoconductor or a spent on the carrier is likely to occur. There is a risk. If the content of the release agent is less than 0.2 parts by weight, functions of the release agent such as an effect of improving low-temperature fixability and hot offset resistance may not be sufficiently exhibited.

The melting point (Tm) of the release agent is preferably 50 ° C. or higher and 150 ° C. or lower, and more preferably 80 ° C. or lower. If the melting point is less than 50 ° C., the release agent may melt in the developing device and the toner particles may be aggregated or may cause defects such as filming on the surface of the photoreceptor. When the melting point exceeds 150 ° C., the release agent cannot be sufficiently eluted when the toner is fixed on the recording medium, and the effect of improving the hot offset resistance may not be sufficiently exhibited. In this specification, the melting point (Tm) is the differential scanning calorimetry (
It is the temperature of the endothermic peak corresponding to melting of the DSC curve obtained by Differential Scanning Calorimetry (abbreviation DSC).

(D) Charge control agent By containing the charge control agent, it is possible to impart preferable chargeability to the toner. As the charge control agent, a charge control agent for positive charge control or negative charge control can be used. For example, positive dyes such as nigrosine dyes, basic dyes, quaternary ammonium salts, quaternary phosphonium salts, aminopyrines, pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, nigrosine dyes and derivatives thereof, triphenylmethane derivatives, guanidine salts, and amidine salts. Charge control agents for charge control and, for example, oil-soluble dyes such as oil black and spiron black, metal-containing azo compounds, azo complex dyes, metal salts of naphthenic acid, metal complexes and metal salts of salicylic acid and its derivatives (metal is Chromium, zinc, zirconium, etc.), boron compounds, fatty acid soaps, long-chain alkyl carboxylates, and charge control agents for controlling negative charges such as resin acid soaps.

  One charge control agent can be used alone, or two or more charge control agents can be used in combination. The amount of the charge control agent used is preferably 0.5 parts by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the binder resin, and more preferably 0.5 parts by weight or more with respect to 100 parts by weight of the binder resin. 3 parts by weight or less. If the charge control agent is contained in an amount of more than 5 parts by weight, the carrier may be contaminated and toner scattering may occur. If it is less than 0.5 parts by weight, there is a possibility that sufficient charging characteristics cannot be imparted to the toner.

  In the color toner, it is desirable to use a colorless charge control agent. For example, it is desirable to use a metal complex and a metal salt of salicylic acid and its derivatives.

[Melting and kneading process]
In the melt-kneading process of step S2, the mixture prepared in the pre-mixing process is melt-kneaded to prepare a melt-kneaded product. Melt kneading of the mixture is performed by heating to a temperature not lower than the softening point of the binder resin and lower than the thermal decomposition temperature. The binder resin is melted or softened so that each toner raw material other than the binder resin is contained in the binder resin. Disperse.

  As a kneader used for melt kneading, a known kneader can be used. For example, a general kneader such as a kneader, a twin-screw extruder, a two-roll mill, a three-roll mill, or a lab blast mill can be used. Specific examples of such a kneader include, for example, TEM-100B (trade name, manufactured by Toshiba Machine Co., Ltd.), PCM-65, PCM-65 / 87, and PCM-30 (all of which are trade names, Ikegai Corporation). And an open roll type kneader such as Nidex (trade name, manufactured by Mitsui Mining Co., Ltd.). The mixture of toner raw materials may be melt-kneaded using a plurality of kneaders.

  Among the above kneaders, it is particularly preferable to use an open roll type continuous kneader. An open roll type continuous kneader includes a heating roll and a cooling roll having spiral grooves on the surface and rotating inward from each other.

  According to the open roll type continuous kneader, the toner raw material mixture obtained in the pre-mixing step is fed from a heating roll on one side end of the open roll by a raw material conveying and feeding device composed of a screw feeder, a vibration feeder, and the like. Supplied. The supplied mixture stays at one end supply side between both open rolls and is melted. Then, a bank is formed by the molten binder resin and the like, and convection is formed by the rotation of the open roll, and the mixture supplied into the bank is swallowed. Note that the bank is not in a completely melted state, but in a state in which a lump of a mixture that has not melted exists in a state in which several bumps are formed.

  Next, in the bank, the mixture swallowed by the convection is melted by heating and rotation of the open roll, and the binder resin becomes a viscous fluid. The molten mixture is wound around the surface of the open roll of the heating roller, and the mixture is kneaded while being transferred to the other end side (the end side opposite to the supply side) by rotation of the open roll to produce a melt-kneaded product. Is done.

  In open roll type continuous kneaders, the mixture is usually melted and kneaded at a low temperature, so the binder resin does not progress and the high viscosity fluid binder resin is kneaded to generate a large compressive force and shear force. To do. The pigment and additive are refined by the compressive force and shear force, and the mixture is melt-kneaded while being uniformly dispersed in the binder resin. And the produced melt-kneaded material is discharged | emitted from the other end discharge side of an open roll, and is cooled and solidified.

  Thus, by melt kneading the mixture using an open roll type continuous kneader, the dispersibility of the toner raw material is further improved as compared with the case of using another conventional kneader. Therefore, it is possible to obtain a toner that can stably exhibit a certain performance.

[Crushing process]
In the pulverization step of step S3, the melt-kneaded product obtained in the melt-kneading step is cooled and solidified, and then pulverized to produce a pulverized product. That is, the cooled and solidified melt-kneaded product is first roughly pulverized into a coarsely pulverized product having a volume average particle size of about 100 μm to 5 mm, for example, by a hammer mill or a cutting mill. Thereafter, the obtained coarsely pulverized product is further finely pulverized to, for example, a pulverized product having a volume average particle diameter of 15 μm or less. For finely pulverizing coarsely pulverized products, for example, a jet type pulverizer that uses a supersonic jet stream, or a space formed between a rotor (rotor) and a stator (liner) that rotate at high speed. An impact pulverizer that introduces and pulverizes coarsely pulverized material can be used.

  The cooled and solidified melt-kneaded product may be directly pulverized by a jet pulverizer or an impact pulverizer without being coarsely pulverized by a hammer mill or a cutting mill.

[Classification process]
In the classification step of step S4, by using a classifier from the pulverized product produced in the pulverization step, excessively pulverized toner particles (hereinafter sometimes referred to as “over-pulverized product”) and coarse toner particles (hereinafter referred to as “over-pulverized product”). (Sometimes referred to as “coarse”). The excessively pulverized product or coarse powder can be recovered and used for reuse in the production of other toners.

  For classification, it is possible to use a known classifier that can remove excessively pulverized materials and coarse powders by centrifugal force classification or wind classification, for example, using a swirling wind classifier (rotary wind classifier) can do.

  The classification is preferably carried out by appropriately adjusting the classification conditions so that the toner particles obtained after classification have a volume average particle diameter of 3 μm or more and 15 μm or less. In particular, in order to obtain a high-quality image, it is preferable that the volume average particle diameter of the toner particles is 3 μm or more and 9 μm or less, and in order to further improve the image quality, the volume average particle diameter of the toner particles is 5 μm or more and 8 μm or less. It is preferable that

  If the volume average particle size of the toner particles is less than 3 μm, the particle size of the toner becomes too small, and there is a possibility that high charge and low fluidity may occur. When this high charging and low fluidity occur, it becomes impossible to stably supply the toner to the photoreceptor as the image carrier, and there is a possibility that background fogging and a decrease in image density may occur. When the volume average particle size of the toner particles exceeds 15 μm, the toner particle size is large, so that a high-definition image cannot be obtained. Further, as the toner particle size increases, the specific surface area decreases and the charge amount of the toner decreases. When the charge amount of the toner is small, the toner is not stably supplied to the photoconductor, and there is a possibility that in-machine contamination due to toner scattering occurs. The classification condition to be adjusted is, for example, the rotational speed of the classification rotor in a swirl type wind classifier (rotary type wind classifier).

  The toner particles produced as described above have functions such as powder flowability improvement, triboelectric chargeability improvement, heat resistance improvement, long-term storage stability improvement, cleaning property improvement and photoreceptor surface wear property control. A responsible external additive may be added.

The external additive is preferably added so that the coverage is 50% or more and less than 120%. Here, the coverage is a value X obtained by the following formula (1)).
X = (3 ^1/2 / 2π) × (dt / da) × (ρt / ρa) × Ca × 100 (1)
X: Coverage rate da: Average particle diameter of external additive dt: Number average particle diameter of toner ρt: True specific gravity of toner ρa: True specific gravity of external additive Ca: Weight of external additive / (weight of external additive + toner weight )

  In general, the polylactic acid resin used in the toner constituting the toner set of the present invention is easily hydrolyzed. In particular, as the D-form content increases, the hydrolysis proceeds more easily. Therefore, the toner which is a fine powder having a large surface area is easily affected by the hydrolysis described above. For example, when a toner using a polylactic acid resin having a high D-form content in a high temperature and high humidity environment is left for a long time, hydrolysis occurs and the molecular weight of the toner decreases, resulting in deterioration of the toner. There is a possibility that the melting temperature of the toner is lowered and fixing failure occurs.

  The above problem can be solved by coating the surface of the toner particles with an external additive to prevent the toner particles from being directly exposed to a high temperature and high humidity environment.

  When the coverage of the external additive is 50% or more and less than 120%, the toner in the toner set of the present invention using the polylactic acid resin having a relatively large D-form content is prevented from being deteriorated by hydrolysis. be able to. If the coverage is less than 50%, the effect of coating with an external additive cannot be obtained, and hydrolysis of the polylactic acid resin may not be prevented in a high temperature and high humidity environment. On the other hand, if it is 120% or more, the external additive released from the toner increases, causing carrier contamination and reducing the charge amount of the toner, which may cause a reduction in image quality such as fogging.

  As the external additive, those commonly used in this field can be used, and examples thereof include silica fine particles, silica oxide fine particles, titanium oxide fine particles, and alumina fine particles.

  These inorganic fine powders are used for the purpose of hydrophobizing, charging control, etc. Silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane coupling agents, silane coupling agents having functional groups, and other organic It is preferably treated with a treating agent such as a silicon compound. The above-mentioned external additives can be used alone or in combination of two or more.

  The degree of hydrophobicity of the external additive treated as described above is preferably 40 or more. When the degree of hydrophobicity of the external additive is 40 or more, the toner in the toner set of the present invention using the polylactic acid resin having a relatively large D-form content is more reliably prevented from being degraded by hydrolysis. be able to. If the degree of hydrophobicity is less than 40, hydrolysis of the polylactic acid resin may not be prevented in a high temperature and high humidity environment.

  Here, the degree of hydrophobicity refers to adding 50 mL of pure water to a 200 mL beaker and adding methanol from a burette whose tip is immersed in water while adding 0.2 g of external additive and gently stirring. This is a value specified by the amount of methanol (mL) required until the floating external additive starts to sink.

  The addition amount of the external additive is 5 with respect to 100 parts by weight of the toner particles in consideration of the charge amount necessary for the toner, the influence on the abrasion of the photoreceptor due to the addition of the external additive, the environmental characteristics of the toner, and the like. Part by weight or less is preferred.

  The external additive preferably has a number average particle diameter of primary particles of 7 nm to 20 nm. By using an external additive having such a particle size, the toner can be effectively coated, and the effect of suppressing the hydrolysis of the polylactic acid resin is more easily exhibited.

  As described above, the black toner and the color toner, in which the external additive is externally added to the toner particles as necessary, are produced, and the combination thereof is used as the toner set of the present invention.

  The black toner and the color toner constituting the toner set of the present invention can be used as they are as a one-component developer, or can be mixed with a carrier and used as a two-component developer.

  In the two-component developer set of the present invention, the black toner and the color toner in the toner set of the present invention each include a carrier to constitute a two-component developer. For example, when the color toner is composed of magenta toner, cyan toner, and yellow toner, the two-component developer set of the present invention includes four types of two-component developers composed of yellow, magenta, cyan, and black. Consists of.

  As the carrier, magnetic particles can be used. Specific examples of the particles having magnetism include metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum or lead. Among these, ferrite is preferable.

  Alternatively, a resin-coated carrier in which magnetic particles are coated with a resin, or a resin-dispersed carrier in which magnetic particles are dispersed in a resin may be used as the carrier. Although there is no restriction | limiting in particular as resin which coat | covers the particle | grains which have magnetism, For example, an olefin resin, a styrene resin, a styrene acrylic resin, a silicone resin, ester resin, a fluorine-containing polymer system resin, etc. are mentioned. Further, the resin used for the resin-dispersed carrier is not particularly limited, and examples thereof include styrene acrylic resin, polyester resin, fluorine resin, and phenol resin.

  The shape of the carrier is preferably a spherical shape or a flat shape. Further, the volume average particle diameter of the carrier is not particularly limited, but is preferably 10 μm to 100 μm, more preferably 50 μm or less in consideration of high image quality.

  As described above, by setting the volume average particle diameter of the carrier to 50 μm or less, the contact opportunity between the toner and the carrier is increased, and charging of each toner particle can be appropriately controlled, so that non-image area fog does not occur. In addition, a high-quality image can be achieved.

Furthermore, the resistivity of the carrier is preferably 10 ⁸ Ω · cm or more, more preferably 10 ¹² Ω · cm or more. The carrier resistivity is determined by placing the carrier in a container having a cross-sectional area of 0.50 cm ² and tapping it, then applying a load of 1 kg / cm ² to the particles packed in the container and placing the load between the load and the bottom electrode. This is a value obtained by reading a current value when a voltage generating an electric field of 1000 V / cm is applied. When the resistivity is low, when a bias voltage is applied to the developing sleeve, charges are injected into the carrier, and carrier particles easily adhere to the photoreceptor. In addition, breakdown of the bias voltage is likely to occur.

  The magnetization strength (maximum magnetization) of the carrier is preferably 10 emu / g to 60 emu / g, more preferably 15 emu / g to 40 emu / g. The magnetization strength depends on the magnetic flux density of the developing roller, but under the general magnetic flux density conditions of the developing roller, if it is less than 10 emu / g, the magnetic binding force does not work and causes carrier scattering. There is a fear. On the other hand, if the magnetization strength exceeds 60 emu / g, it is difficult to maintain a non-contact state with the image carrier in the non-contact development in which the carrier spikes are too high. Further, in the contact development, there is a risk that a sweep is likely to appear in the toner image.

The ratio of the toner and the carrier used in the two-component developer is not particularly limited and can be appropriately selected according to the type of the toner and the carrier, but an example is a resin-coated carrier (density 5 g / cm ^{2 to} 8 g / cm ² ). For example, the toner may be used so that the toner is contained in 2% to 30% by weight, preferably 2% to 20% by weight of the total amount of the developer. In the two-component developer, the carrier coverage with the toner is preferably 40% to 80%.

  As described above, in the two-component developer set of the present invention, the black toner and the color toner in the toner set of the present invention each include a carrier to constitute the two-component developer. Accordingly, it is possible to obtain a two-component developer set capable of exhibiting good fixability even in an image forming apparatus that takes into consideration the global environment conservation and has increased the process speed during monochrome image formation.

[Image forming apparatus]
FIG. 2 is a cross-sectional view schematically showing the configuration of the image forming apparatus 1 of the present invention. The image forming apparatus 1 is a multifunction machine having both a copying function, a printer function, and a facsimile function, and forms a full-color or monochrome image on a recording medium in accordance with transmitted image information. That is, the image forming apparatus 1 has three types of printing modes, ie, a copier mode (copy mode), a printer mode, and a FAX mode, and an operation input from an operation unit (not shown), a personal computer, a portable terminal device, information A print mode is selected by a control unit (not shown) in response to reception of a print job from an external device using a recording storage medium, a memory device, or the like.

Further, the image forming apparatus 1 has a process speed set so that the process speed at the time of monochrome image formation is faster than the process speed at the time of color image formation. The process speed here is a fixing speed. When the fixing speed at the time of monochrome image formation is Vk (mm / s) and the fixing speed at the time of color image formation is Vc (mm / s), Vk. And Vc preferably satisfy the following formula (2).
((Vk−Vc) / Vc) × 100 ≧ 3 (2)

The reason why the formula (2) is derived will be described below. The toner used in the present invention changes the melting temperature of the color toner and the black toner by changing the softening point by changing the contents of the D-form and L-form in the polylactic acid resin. The melting temperature of a toner using a polylactic acid resin having an L-form content of 100 mol% is 175 ° C. On the other hand, when the D-form content is increased, the melting temperature is suitable as a fixing temperature. A toner having a temperature of 170 ° C. or lower can be obtained. Since the specific heat of the toner hardly changes even when the melting temperature changes, for example, from the following formula (3), the heat capacity of the toner having a melting temperature of 170 ° C. is about 3% of the heat capacity of the toner having a melting temperature of 175 ° C. It turns out that it becomes small. Therefore, when a toner having a melting temperature of 170 ° C. is used, the fixing strength similar to that of the toner having a melting temperature of 175 ° C. can be maintained even if the fixing nip passage time, that is, the fixing speed is shortened by 3%.
((175-170) / 175) × 100≈3% (3)

  From the above, it can be said that when a toner having a melting temperature of 170 ° C. or lower is used, Vk and Vc satisfy the following formula (2).

  The image forming apparatus 1 includes a toner image forming unit 2, a transfer device 3, a fixing device 4, a recording medium supply unit 5, and a discharge unit 6. Each member constituting the toner image forming unit 2 and some members included in the transfer device 3 are cyan (c), magenta (m), yellow (y), and black (b) colors included in the color image information. In order to correspond to the image information, four each are provided. Here, each member provided by four according to each color is distinguished by attaching an alphabet representing each color to the end of the reference symbol, and when referring collectively, only the reference symbol is used.

  The toner image forming unit 2 includes a photosensitive drum 11, a charging unit 12, an exposure unit 13, a developing device 14, and a cleaning unit 15. The charging unit 12, the developing device 14, and the cleaning unit 15 are arranged around the photosensitive drum 11 in this order. The charging unit 12 is disposed below the developing device 14 and the cleaning unit 15 in the vertical direction.

  The photosensitive drum 11 is an image carrier, and is supported by a driving unit (not shown) so as to be rotatable around an axis, and includes a conductive substrate (not shown) and a photosensitive layer formed on the surface of the conductive substrate. The conductive substrate can take various shapes, and examples thereof include a cylindrical shape, a columnar shape, and a thin film sheet shape. Among these, a cylindrical shape is preferable. The conductive substrate is formed of a conductive material. As the conductive material, those commonly used in this field can be used. For example, metals such as aluminum, copper, brass, zinc, nickel, stainless steel, chromium, molybdenum, vanadium, indium, titanium, gold, platinum, etc. A conductive layer made of one or more of aluminum, aluminum alloy, tin oxide, gold, indium oxide, etc. is formed on a film-like substrate such as two or more alloys, synthetic resin film, metal film, paper, etc. And a resin composition containing at least conductive particles or a conductive polymer. In addition, as a film-form base | substrate used for an electroconductive film, a synthetic resin film is preferable and a polyester film is especially preferable. Moreover, as a formation method of the electroconductive layer in an electroconductive film, vapor deposition, application | coating, etc. are preferable.

  The photosensitive layer is formed, for example, by laminating a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material. In that case, it is preferable to provide an undercoat layer between the conductive substrate and the charge generation layer or the charge transport layer. By providing an undercoat layer, the scratches and irregularities present on the surface of the conductive substrate are coated to smooth the surface of the photosensitive layer, preventing deterioration of the chargeability of the photosensitive layer during repeated use, at least at a low temperature or The advantage of improving the charging characteristics of the photosensitive layer in a low humidity environment can be obtained. Further, a laminated photoreceptor having a three-layer structure having a high durability and having a photoreceptor surface protective layer as the uppermost layer may be used.

  The charge generation layer is mainly composed of a charge generation material that generates a charge when irradiated with light, and contains a known binder resin, plasticizer, sensitizer and the like as necessary. As the charge generation material, those commonly used in this field can be used. Phthalocyanine pigments such as metal-free phthalocyanine, squalium dye, azulenium dye, thiapyrylium dye, carbazole skeleton, styryl stilbene skeleton, triphenylamine skeleton, dibenzothiophene skeleton, oxadiazole skeleton, fluorenone skeleton, bis stilbene skeleton, distyryl oxa And azo pigments having a diazole skeleton or a distyrylcarbazole skeleton. Among these, metal-free phthalocyanine pigments, oxotitanyl phthalocyanine pigments, bisazo pigments containing at least a fluorene ring or a fluorenone ring, bisazo pigments composed of aromatic amines, trisazo pigments, etc. have high charge generating ability and are highly sensitive. Suitable for obtaining layers. One type of charge generating material can be used alone, or two or more types can be used in combination. The content of the charge generation material is not particularly limited, but is preferably 5 parts by weight to 500 parts by weight, more preferably 10 parts by weight to 200 parts by weight with respect to 100 parts by weight of the binder resin in the charge generation layer. As the binder resin for the charge generation layer, those commonly used in this field can be used. For example, melamine resin, epoxy resin, silicone resin, polyurethane, acrylic resin, vinyl chloride-vinyl acetate copolymer resin, polycarbonate, phenoxy resin , Polyvinyl butyral, polyarylate, polyamide, polyester and the like. The binder resin for the charge generation layer can be used alone or in combination of two or more as required.

  The charge generation layer generates charge by dissolving or dispersing appropriate amounts of charge generation materials, binder resins and, if necessary, plasticizers and sensitizers in an appropriate organic solvent capable of dissolving or dispersing these components. It can be formed by preparing a layer coating solution, applying this charge generation layer coating solution to the surface of the conductive substrate and drying. The film thickness of the charge generation layer thus obtained is not particularly limited, but is preferably 0.05 μm to 5 μm, more preferably 0.1 μm to 2.5 μm.

  The charge transport layer laminated on the charge generation layer has a charge transport material having the ability to accept and transport the charge generated from the charge generation material and a binder resin for the charge transport layer as essential components. Contains known antioxidants, plasticizers, sensitizers, lubricants and the like. As the charge transport material, those commonly used in this field can be used, for example, poly-N-vinylcarbazole and derivatives thereof, poly-γ-carbazolylethyl glutamate and derivatives thereof, pyrene-formaldehyde condensation product and derivatives thereof, Polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, 9- (p-diethylaminostyryl) anthracene, 1,1-bis (4-dibenzylaminophenyl) propane, styrylanthracene, styrylpyrazoline, pyrazoline Derivatives, phenylhydrazones, hydrazone derivatives, triphenylamine compounds, tetraphenyldiamine compounds, triphenylmethane compounds, stilbene compounds, 3-methyl-2-benzothiazoline -Donating substances such as azine compounds, fluorenone derivatives, dibenzothiophene derivatives, indenothiophene derivatives, phenanthrenequinone derivatives, indenopyridine derivatives, thioxanthone derivatives, benzo [c] cinnoline derivatives, phenazine oxide derivatives, tetracyano Examples include electron-accepting substances such as ethylene, tetracyanoquinodimethane, promanyl, chloranil, and benzoquinone. The charge transport materials can be used alone or in combination of two or more. The content of the charge transport material is not particularly limited, but is preferably 10 parts by weight to 300 parts by weight, more preferably 30 parts by weight to 150 parts by weight with respect to 100 parts by weight of the binder resin in the charge transport material. As the binder resin for the charge transport layer, those commonly used in this field and capable of uniformly dispersing the charge transport material can be used. For example, polycarbonate, polyarylate, polyvinyl butyral, polyamide, polyester, polyketone, epoxy resin, polyurethane , Polyvinyl ketone, polystyrene, polyacrylamide, phenol resin, phenoxy resin, polysulfone resin, and copolymer resins thereof. Among these, in consideration of film formability, wear resistance of the resulting charge transport layer, electrical characteristics, etc., polycarbonate containing bisphenol Z as a monomer component (hereinafter referred to as “bisphenol Z type polycarbonate”), bisphenol Z type polycarbonate And a mixture of polycarbonate with other polycarbonates are preferred. The binder resin for the charge transport layer can be used alone or in combination of two or more.

  The charge transport layer preferably contains an antioxidant together with the charge transport material and the binder resin for the charge transport layer. As the antioxidant, those commonly used in this field can be used, and examples thereof include vitamin E, hydroquinone, hindered amine, hindered phenol, paraphenylenediamine, arylalkane and derivatives thereof, organic sulfur compounds, and organic phosphorus compounds. It is done. One antioxidant can be used alone, or two or more antioxidants can be used in combination. The content of the antioxidant is not particularly limited, but is 0.01% to 10% by weight, preferably 0.05% to 5% by weight, based on the total amount of components constituting the charge transport layer. The charge transport layer is dissolved or dispersed in a suitable organic solvent that can dissolve or disperse these components in an appropriate amount such as a charge transport material and a binder resin, and if necessary, an antioxidant, a plasticizer, and a sensitizer. The charge transport layer coating liquid is prepared, and the charge transport layer coating liquid is applied to the surface of the charge generation layer and dried. The thickness of the charge generation layer thus obtained is not particularly limited, but is preferably 10 μm to 50 μm, more preferably 15 μm to 40 μm. Note that a photosensitive layer in which a charge generation material and a charge transport material are present can be formed in one layer. In that case, the type, content, binder resin, and other additives of the charge generation material and the charge transport material may be the same as in the case of separately forming the charge generation layer and the charge transport layer.

  In this embodiment, the photosensitive drum formed by forming the organic photosensitive layer using the charge generation material and the charge transport material as described above is used. Instead, an inorganic photosensitive layer using silicon or the like is formed. Can be used.

  The charging unit 12 faces the photosensitive drum 11 and is arranged so as to be separated from the surface of the photosensitive drum 11 along the longitudinal direction of the photosensitive drum 11 with a gap, and the surface of the photosensitive drum 11 has a predetermined polarity and Charge to potential. As the charging unit 12, a charging brush type charger, a charger type charger, a sawtooth type charger, an ion generator, or the like can be used. In the present embodiment, the charging unit 12 is provided so as to be separated from the surface of the photosensitive drum 11, but is not limited thereto. For example, a charging roller may be used as the charging unit 12 and the charging roller may be disposed so that the charging roller and the photosensitive drum are in pressure contact with each other, or a contact charging type charger such as a charging brush or a magnetic brush may be used. .

  The exposure unit 13 causes the light of each color information emitted from the exposure unit 13 to pass through between the charging unit 12 and the developing units 14c, 14m, 14y, and 14b and irradiate the surface of the photosensitive drum 11. Be placed. The exposure unit 13 branches the image information into light of each color information of c, m, y, b in the unit, and the surface of the photosensitive drum 11 charged to a uniform potential by the charging unit 12 is light of each color information. To form an electrostatic latent image on the surface. As the exposure unit 13, for example, a laser scanning unit including a laser irradiation unit and a plurality of reflecting mirrors can be used. In addition, a unit in which an LED array, a liquid crystal shutter, and a light source are appropriately combined may be used.

  FIG. 3 is a cross-sectional view schematically showing an example of the configuration of the developing means 14c constituting the developing device 14 of the present invention. The developing device 14 of the present invention contains a two-component developer containing black toner or color toner in the toner set of the present invention, and a plurality of developing means 14c, 14m, 14y, which perform development according to the color of the toner contained therein. 14b. The developing means 14c contains a two-component developer containing cyan toner, the developing means 14m contains a two-component developer containing magenta toner, and the developing means 14y contains a two-component developer containing yellow toner. 14b accommodates a two-component developer containing black toner.

  Since the developing units 14c, 14m, 14y, and 14b have the same configuration, the configuration of the developing unit 14c will be described below as a representative of the developing units 14c, 14m, 14y, and 14b.

  The developing means 14c includes a developing tank 20c and a toner hopper 21c. The developing tank 20c is disposed so as to face the surface of the photosensitive drum 11c, and is a container that supplies toner to the electrostatic latent image formed on the surface of the photosensitive drum 11c and develops it to form a visible toner image. It is a shaped member. The developing tank 20c contains toner in its internal space, and contains a roller member such as the developing roller 201, the supply roller 202, and the stirring roller 203 or a screw member, and rotatably supports the developing tank 20c. An opening is formed in the side surface of the developing tank 20c facing the photosensitive drum 11c, and the developing roller 201 is rotatably provided at a position facing the photosensitive drum 11c through the opening. The developing roller 201 is a roller-like member that supplies toner to the electrostatic latent image on the surface of the photoconductor 11c at the pressure contact portion or the closest portion to the photoconductor drum 11c. When supplying the toner, a potential having a polarity opposite to the charging potential of the toner is applied to the surface of the developing roller 201 as a developing bias voltage (hereinafter simply referred to as “developing bias”). As a result, the toner on the surface of the developing roller 201 is smoothly supplied to the electrostatic latent image. Further, by changing the developing bias value, the amount of toner (toner adhesion amount) supplied to the electrostatic latent image can be controlled. The supply roller 202 is a roller-like member that faces the developing roller 201 and can be driven to rotate, and supplies toner around the developing roller 201. The agitation roller 203 is a roller-like member provided so as to be able to be driven to rotate while facing the supply roller 202, and feeds toner newly supplied from the toner hopper 21c into the developing tank 20c to the periphery of the supply roller 202. The toner hopper 21c is provided such that a toner replenishing port (not shown) provided at the lower part in the vertical direction communicates with a toner receiving port (not shown) provided at the upper part in the vertical direction of the developing tank 20c. The toner is replenished according to the toner consumption status of 20c. Further, the toner hopper 21c may not be used, and the toner may be directly supplied from each color toner cartridge.

  In the image forming apparatus 1, the developing units 14c, 14m, 14y, and 14b are arranged in this order from the fixing device 4 side toward a transfer belt cleaning unit 29 described later.

  As described above, the separation distance between the developing unit 14b containing black toner and the fixing device 4 is configured to be longer than the separation distance between the developing units 14c, 14m, and 14y containing color toner and the fixing device 4. It is preferred that

  In this way, by installing the developing means 14b containing black toner having a low softening point at a position away from the fixing device 4 having the heating means, the storage stability of the black toner can be maintained in a good state for a long time. Can be maintained.

  As described above, the developing device 14 according to the present invention is developed with the toner set according to the present invention, so that consideration is given to environmental protection, and the image forming apparatus 1 has a faster process speed when forming a monochrome image. Therefore, it is possible to improve the printing efficiency when forming a black and white image and to obtain a developing device capable of forming a better image.

  The cleaning unit 15 removes the toner remaining on the surface of the photosensitive drum 11 after transferring the toner image to the recording medium, and cleans the surface of the photosensitive drum 11. For the cleaning unit 15, for example, a plate-like member such as a cleaning blade is used. In the image forming apparatus 1 of the present invention, an organic photosensitive drum is mainly used as the photosensitive drum 11, and the surface of the organic photosensitive drum is mainly composed of a resin component. Surface degradation is likely to proceed due to the chemical action of ozone generated by the discharge. However, the deteriorated surface portion is worn by receiving a rubbing action by the cleaning unit 15 and is gradually but surely removed. Therefore, the problem of surface deterioration due to ozone or the like is practically solved, and the charging potential by the charging operation can be stably maintained over a long period of time. Although the cleaning unit 15 is provided in this embodiment, the present invention is not limited to this, and the cleaning unit 15 may not be provided.

  According to the toner image forming unit 2, the surface of the photosensitive drum 11 that is uniformly charged by the charging unit 12 is exposed by irradiating the exposure unit 13 with signal light corresponding to the image information, thereby exposing the electrostatic latent image. A toner image is formed by supplying toner from the developing device 14 and developing the toner image. After the toner image is transferred to the intermediate transfer belt 25, the toner remaining on the surface of the photosensitive drum 11 is removed from the cleaning unit. Remove at 15. This series of toner image forming operations is repeatedly executed.

  The transfer device 3 is disposed above the photosensitive drum 11, and includes an intermediate transfer belt 25, a driving roller 26, a driven roller 27, an intermediate transfer roller 28 (c, m, y, b), and a transfer belt cleaning unit. 29 and the transfer roller 30. The intermediate transfer belt 25 is an endless belt-like member that is stretched by a driving roller 26 and a driven roller 27 to form a loop-shaped movement path. It is rotationally driven so as to move in the direction from the body drum 11b to 11c.

  When the intermediate transfer belt 25 passes through the photosensitive drum 11 while being in contact with the photosensitive drum 11, an intermediate transfer roller 28 disposed on the surface of the photosensitive drum 11 is opposed to the photosensitive drum 11 via the intermediate transfer belt 25. A transfer bias having a polarity opposite to the charging polarity of the toner is applied, and the toner image formed on the surface of the photosensitive drum 11 is transferred onto the intermediate transfer belt 25. In the case of a full-color image, each color toner image formed on each photoconductor drum 11 is sequentially transferred onto the intermediate transfer belt 25 to form a full-color toner image. The driving roller 26 is provided so as to be rotatable around its axis by driving means (not shown), and the intermediate transfer belt 25 is driven to rotate in the direction of arrow B by the rotational driving. The driven roller 27 is provided so as to be able to be driven and rotated by the rotational drive of the driving roller 26, and applies a certain tension to the intermediate transfer belt 25 so that the intermediate transfer belt 25 does not loosen. The intermediate transfer roller 28 is provided in pressure contact with the photosensitive drum 11 via the intermediate transfer belt 25 and capable of being driven to rotate about its axis by a driving unit (not shown). The intermediate transfer roller 28 is connected to a power source (not shown) for applying a transfer bias as described above, and has a function of transferring the toner image on the surface of the photosensitive drum 11 to the intermediate transfer belt 25. The transfer belt cleaning unit 29 is provided so as to face the driven roller 27 through the intermediate transfer belt 25 and to contact the outer peripheral surface of the intermediate transfer belt 25. Since the toner adhering to the intermediate transfer belt 25 due to contact with the photosensitive drum 11 causes the back surface of the recording medium to be contaminated, the transfer belt cleaning unit 29 removes and collects the toner on the surface of the intermediate transfer belt 25. The transfer roller 30 is provided in pressure contact with the drive roller 26 via the intermediate transfer belt 25, and can be driven to rotate about an axis by a drive unit (not shown). At the pressure contact portion (transfer nip portion) between the transfer roller 30 and the drive roller 26, the toner image carried and conveyed by the intermediate transfer belt 25 is transferred to the recording medium fed from the recording medium supply means 5 described later. Is done. The recording medium carrying the toner image is fed to the fixing device 4. According to the transfer device 3, the toner image transferred from the photosensitive drum 11 to the intermediate transfer belt 25 at the pressure contact portion between the photosensitive drum 11 and the intermediate transfer roller 28 rotates the intermediate transfer belt 25 in the arrow B direction. It is conveyed to a transfer nip portion by driving, and transferred to a recording medium there.

  The fixing device 4 is provided downstream of the transfer device 3 in the conveyance direction of the recording medium, and includes a fixing roller 31 and a pressure roller 32. The fixing roller 31 is rotatably provided by a driving unit (not shown), and heats and melts the toner constituting the unfixed toner image carried on the recording medium to fix it on the recording medium. A heating unit (not shown) is provided inside the fixing roller 31. The heating unit heats the fixing roller 31 so that the surface of the fixing roller 31 reaches a predetermined temperature (heating temperature). For example, a heater or a halogen lamp can be used as the heating means. The heating means is controlled by fixing condition control means described later. A temperature detection sensor is provided near the surface of the fixing roller 31 to detect the surface temperature of the fixing roller 31. The detection result by the temperature detection sensor is written in the storage unit of the control means described later. The pressure roller 32 is provided so as to be in pressure contact with the fixing roller 31 and is supported so as to be driven to rotate by the rotation drive of the pressure roller 32. The pressure roller 32 assists fixing of the toner image on the recording medium by pressing the toner and the recording medium when the toner is melted and fixed on the recording medium by the fixing roller 31. A pressure contact portion between the fixing roller 31 and the pressure roller 32 is a fixing nip portion. According to the fixing device 4, the recording medium onto which the toner image is transferred in the transfer device 3 is sandwiched between the fixing roller 31 and the pressure roller 32, and the toner image is recorded under heating when passing through the fixing nip portion. By being pressed against the medium, the toner image is fixed on the recording medium and an image is formed.

  The recording medium supply unit 5 includes an automatic paper feed tray 35, a pickup roller 36, a transport roller 37, a registration roller 38, and a manual paper feed tray 39. The automatic paper feed tray 35 is a container-like member that is provided in the lower part of the image forming apparatus 1 in the vertical direction and stores a recording medium. Recording media include plain paper, color copy paper, overhead projector sheets, postcards, and the like. The pick-up roller 36 takes out the recording medium stored in the automatic paper feed tray 35 one by one and feeds it to the paper transport path S1. The conveyance rollers 37 are a pair of roller members provided so as to be in pressure contact with each other, and convey the recording medium toward the registration rollers 38. The registration rollers 38 are a pair of roller members provided so as to be in pressure contact with each other, and the recording medium fed from the conveyance roller 37 is used to convey the toner image carried on the intermediate transfer belt 25 to the transfer nip portion. Synchronously, it is fed to the transfer nip. The manual paper feed tray 39 is a device for taking a recording medium into the image forming apparatus 1 by manual operation, and the recording medium taken from the manual paper feed tray 39 passes through the paper conveyance path S2 by the conveyance roller 37. Then, it is fed to the registration roller 38. According to the recording medium supply means 5, the toner image carried on the intermediate transfer belt 25 is conveyed to the transfer nip portion of the recording medium supplied one by one from the automatic paper feed tray 35 or the manual paper feed tray 39. In synchronism with this, the sheet is fed to the transfer nip portion.

  The discharge unit 6 includes a conveyance roller 37, a discharge roller 40, and a discharge tray 41. The conveyance roller 37 is provided downstream of the fixing nip portion in the sheet conveyance direction, and conveys the recording medium on which the image is fixed by the fixing device 4 toward the discharge roller 40. The discharge roller 40 discharges the recording medium on which the image is fixed to a discharge tray 41 provided on the upper surface in the vertical direction of the image forming apparatus 1. The discharge tray 41 stores a recording medium on which an image is fixed.

The image forming apparatus 1 includes a control unit (not shown). The control means is provided, for example, in the upper part of the internal space of the image forming apparatus 1 and includes a storage unit, a calculation unit, and a control unit. The storage unit of the control unit includes various setting values via an operation panel (not shown) arranged on the upper surface of the image forming apparatus 1, detection results from sensors (not shown) arranged at various locations inside the image forming apparatus 1, external devices, and the like. The image information from is input. In addition, programs for executing various means are written. Examples of the various means include a recording medium determination unit, an adhesion amount control unit, and a fixing condition control unit. As the storage unit, those commonly used in this field can be used, and examples thereof include a read only memory (ROM), a random access memory (RAM), and a hard disk drive (HDD). As the external device, an electric / electronic device that can form or acquire image information and can be electrically connected to the image forming apparatus 1 can be used. For example, a computer, a digital camera, a television receiver, a video recorder , DVD (Digital
Examples include a Versatile Disc (Recorder), HDDVD (High-Definition Digital Versatile Disc), Blu-ray Disc recorder, facsimile machine, and portable terminal device. The arithmetic unit takes out various data (image formation command, detection result, image information, etc.) written in the storage unit and programs of various means, and performs various determinations. The control unit sends a control signal to the corresponding device according to the determination result of the calculation unit, and performs operation control. The control unit and the calculation unit include a processing circuit realized by a microcomputer, a microprocessor, or the like provided with a central processing unit (CPU). The control means includes a main power supply together with the processing circuit described above, and the power supply supplies power not only to the control means but also to each device in the image forming apparatus 1.

  As described above, the image forming apparatus 1 according to the present invention supplies a photosensitive drum 11 on which an electrostatic latent image is formed by exposure with light according to image information, and supplies toner to the photosensitive drum 11 to statically. A developing device 14 of the present invention that develops an electrostatic latent image, a transfer device 3 that transfers a toner image formed by development onto a recording medium, and a fixing device 4 that heats and fixes the toner image on the recording medium. Prepare. The process speed when forming an image using black toner is configured to be higher than the process speed when forming an image using color toner.

  As a result, the safety can be further increased, so that the image forming apparatus 1 that can be installed at a position close to the user in the office can be obtained. In addition, since the difference in the set value of the fixing temperature during monochrome image formation and color image formation can be reduced, the start-up time during monochrome image formation can be shortened and high when monochrome image formation is performed. A good image can be formed with printing efficiency.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not particularly limited to these Examples as long as the gist thereof is not exceeded.

[Physical property measurement method]
Each physical property value in Examples and Comparative Examples was measured as shown below.

(Softening point of binder resin (T _1/2 ))
Using a flow characteristic evaluation apparatus (trade name: Flow Tester CFT-500C, manufactured by Shimadzu Corporation), 1 g of a sample is inserted into a cylinder, and a load of 10 kgf / cm ² (0.980665 MPa) is applied so as to be extruded from a die. While heating at a heating rate of 6 ° C./min (6 ° C./min), the temperature at which half of the sample flowed out of the die was determined as the softening point (T _1/2 ). A die having a diameter of 1 mm and a length of 1 mm was used.

(Melting point of release agent (Tm))
Using a differential scanning calorimeter (trade name: DSC220, manufactured by Seiko Denshi Kogyo Co., Ltd.), 0.01 g of the sample was heated from a temperature of 20 ° C. to 200 ° C. at a heating rate of 10 ° C./min (10 ° C./min), Subsequently, the operation of rapidly cooling from 200 ° C. to 20 ° C. was repeated twice to obtain a DSC curve. The temperature at the top of the endothermic peak corresponding to the melting of the DSC curve obtained by the second operation was determined as the melting point (Tm) of the release agent.

(Volume average particle diameter ( _D50v ))
20 mL of a sample and 1 mL of sodium alkyl ether sulfate (dispersant, manufactured by Kishida Chemical Co., Ltd.) are added to 50 mL of an electrolytic solution (trade name: ISOTON-II, manufactured by Beckman Coulter), and an ultrasonic disperser (trade name: UH-50, manufactured by SMT Co., Ltd.) was subjected to ultrasonic dispersion treatment at an ultrasonic frequency of 20 kHz for 3 minutes as a measurement sample. For this measurement sample, a particle size distribution measuring device (trade name: Multisizer 3, manufactured by Beckman Coulter, Inc.) was used to measure the particle diameter of the sample particles under the conditions of an aperture diameter of 100 μm and a measurement particle number of 50000 counts. The volume particle size distribution of the sample particles was determined from the measured results, and the volume average particle size D _{50 V} (μm) was calculated from the determined volume particle size distribution. The volume average particle size D _50V (μm) indicates a particle size at which the cumulative volume from the large particle size side in the cumulative volume distribution becomes 50%.

(External additive coverage)
The coverage X (%) of the external additive was determined by the following formula (1).
X = (3 ^1/2 / 2π) × (dt / da) × (ρt / ρa) × Ca × 100 (1)
X: Coverage rate da: Average particle diameter of external additive dt: Number average particle diameter of toner ρt: True specific gravity of toner ρa: True specific gravity of external additive Ca: Weight of external additive / (weight of external additive + toner weight )

(Average particle size of external additives)
Using a scanning electron microscope (trade name: S-4300SE / N, manufactured by Hitachi High-Technologies Corporation), taking 100 external additive particles at a magnification of 50000 times, changing the field of view, and performing primary analysis by image analysis The particle size of each particle was measured. The average particle size was calculated based on the 100 measured values obtained.

(Number average particle diameter of toner)
20 mL of a sample and 1 mL of sodium alkyl ether sulfate (dispersant, manufactured by Kishida Chemical Co., Ltd.) are added to 50 mL of an electrolytic solution (trade name: ISOTON-II, manufactured by Beckman Coulter, Inc.), and an ultrasonic dispersion device (trade name: UH-50, manufactured by SMT Co., Ltd.) was subjected to ultrasonic dispersion treatment at an ultrasonic frequency of 20 kHz for 3 minutes as a measurement sample. For this measurement sample, a particle size distribution measuring device (Multisizer 3, manufactured by Beckman Coulter, Inc.) was used to measure the particle diameter of the sample particles under the conditions of an aperture diameter of 100 μm and a measurement particle count of 50000 counts. From the obtained particle size distribution, the number average particle size of the toner was calculated.

(Hydrophobicity of external additives)
Add 50 mL of pure water to a 200 mL beaker, add 0.2 g of external additive and gently stir it, add methanol from the burette whose tip is immersed in water, and float the external additive The amount of methanol (mL) required to start sinking was measured. The numerical value (mL) of the obtained measurement result was directly used as the degree of hydrophobicity.

(Test Example 1)
[Production of polylactic acid resin]
(Production of polylactic acid resin A)
9.1 kg of L-lactide and 0.9 kg of D-lactide were charged into the polymerization reaction layer, heated and melted with stirring under a nitrogen atmosphere, and mixed uniformly. Subsequently, 1 g of tin octylate was added, and then heated to 135 ° C. and subjected to ring-opening polymerization by heating for 20 hours to obtain polylactic acid resin A (copolymerization molar ratio: L-form / D-form = 91/9, softening point (T _{1 / 2} ): 125 ° C.).

(Production of polylactic acid resin B)
Polylactic acid resin B (copolymerization molar ratio: L) was prepared in the same manner as polylactic acid resin A, except that 9.2 kg of L-lactide and 0.8 kg of D-lactide were charged and 1 g of tin octylate was added and then heated to 135 ° C. Body / D body = 92/8, softening point (T _1/2 ): 130 ° C.).

(Production of polylactic acid resin C)
Polylactic acid resin C (copolymerization molar ratio: L) was prepared in the same manner as polylactic acid resin A except that 9.4 kg of L-lactide and 0.6 kg of D-lactide were added, and 1 g of tin octylate was added and heated to 140 ° C. Body / D body = 94/6, softening point (T _1/2 ): 145 ° C.).

(Production of polylactic acid resin D)
Polylactic acid resin D (copolymerization molar ratio: L) was prepared in the same manner as polylactic acid resin A except that 9.5 kg of L-lactide and 0.5 kg of D-lactide were charged and 1 g of tin octylate was added and then heated to 145 ° C. Body / D body = 95/5, softening point (T _1/2 ): 150 ° C.).

(Manufacture of polylactic acid resin E)
Polylactic acid resin E (copolymerization molar ratio: L) in the same manner as polylactic acid resin A, except that 9.6 kg of L-lactide and 0.4 kg of D-lactide were added and 1 g of tin octylate was added and then heated to 140 ° C. Body / D body = 96/4, softening point (T _1/2 ): 155 ° C.).

(Manufacture of polylactic acid resin F)
Polylactic acid resin F (copolymerization molar ratio: L) was prepared in the same manner as polylactic acid resin A, except that 9.7 kg of L-lactide and 0.3 kg of D-lactide were added and 1 g of tin octylate was added and then heated to 140 ° C. Body / D body = 97/3, softening point (T _1/2 ): 160 ° C.).

(Manufacture of polylactic acid resin G)
Polylactic acid resin G (copolymerization molar ratio: L) in the same manner as polylactic acid resin A, except that 9.8 kg of L-lactide and 0.2 kg of D-lactide were charged and 1 g of tin octylate was added and then heated to 150 ° C. Body / D body = 98/2, softening point (T _1/2 ): 165 ° C.).

(Production of polylactic acid resin H)
Polylactic acid resin H (copolymerization molar ratio: L) in the same manner as polylactic acid resin A, except that 9.9 kg of L-lactide and 0.1 kg of D-lactide were added and 1 g of tin octylate was added and then heated to 155 ° C. Body / D body = 99/1, softening point (T _1/2 ): 170 ° C.).

Table 1 shows the copolymerization molar ratio (L-form / D-form), softening point (T _1/2 ), and reaction temperature at the time of production in the polylactic acid resins A to H.

[Manufacture of toner set]
Example 1
[Premixing step and melt-kneading step]
[Manufacture of magenta toner]
Polylactic acid resin G (binder resin) 82.8% by weight (100 parts by weight) and masterbatch (containing 40% by weight of CI Pigment Red 57: 1 (colorant)) 12% by weight (14.5 Parts by weight), paraffin wax (release agent, trade name: HNP-11, manufactured by Nippon Seiwa Co., Ltd., melting point: 68 ° C.) 4.2% by weight (5.1 parts by weight), metal alkylsalicylate ( Charge control agent, trade name: BONTRON E-84, manufactured by Orient Chemical Co., Ltd. 1 wt% (1.2 parts by weight) of the toner raw material in this blending ratio, Henschel mixer (trade name: FM mixer, Mitsui) (Mine Co., Ltd.) for 10 minutes to prepare a mixture. Subsequently, the obtained mixture was melt-kneaded with a twin-screw extrusion kneader (trade name: PCM-65, manufactured by Ikegai Co., Ltd.) to prepare a melt-kneaded product.

[Crushing process]
The melt-kneaded product obtained in the pre-mixing step and the melt-kneading step was cooled to room temperature and solidified, and then coarsely pulverized with a cutting mill (trade name: VM-16, manufactured by Ryoko Sangyo Co., Ltd.). Subsequently, the coarsely pulverized product obtained by coarse pulverization was finely pulverized by a fluidized bed jet pulverizer (trade name: Counterjet Mill, manufactured by Hosokawa Micron Corporation) to prepare a pulverized product.

[Classification process]
The excessively pulverized toner particles were classified and removed from the pulverized product by a rotary classifier (trade name: TSP separator, manufactured by Hosokawa Micron Corporation) to obtain toner particles having a volume average particle diameter of 6.5 μm.

  Next, 0.92 parts by weight of silica oxide fine particles (external additive, trade name: R-972, manufactured by Nippon Aerosil Co., Ltd., hydrophobicity: 40) is added to 100 parts by weight of the obtained toner particles. The magenta toner of Example 1 was manufactured.

[Manufacture of cyan toner]
In the pre-mixing step, C.I. I. A cyan toner of Example 1 was produced in the same manner as the magenta toner except that a master batch containing 40% by weight of Pigment Blue 15 (colorant) was used.

[Manufacture of yellow toner]
In the pre-mixing step, C.I. I. A yellow toner of Example 1 was produced in the same manner as the magenta toner except that a master batch containing 40% by weight of Pigment Yellow 17 (colorant) was used.

[Manufacture of black toner]
In the premixing step, a master batch containing 71.1% by weight (100 parts by weight) of polylactic acid resin E (binder resin) and 30% by weight of carbon black (colorant) (23.7% by weight (33.3)) The black toner of Example 1 was produced in the same manner as the magenta toner except that the toner was used.

The obtained magenta toner, cyan toner and yellow toner (hereinafter simply referred to as “color toner”) have a volume average particle diameter (D _50V ) of 6.7 μm and a softening point (T _1/2 ) of 125. ° C. The obtained black toner had a volume average particle size (D _50V ) of 6.7 μm and a softening point (T _1/2 ) of 115 ° C. The coverage of the external additive was 80% for both the color toner and the black toner.

(Example 2)
In the same manner as in Example 1, the magenta toner, cyan toner, and yellow toner of Example 2 were produced. A black toner of Example 2 was produced in the same manner as the black toner of Example 1 except that polylactic acid resin D (binder resin) was used.

The obtained color toner had a volume average particle diameter (D _50V ) of 6.7 μm and a softening point (T _1/2 ) of 125 ° C. The obtained black toner had a volume average particle diameter (D _50V ) of 6.6 μm and a softening point (T _1/2 ) of 110 ° C. The coverage of the external additive was 80% for both the color toner and the black toner.

(Example 3)
Magenta toner, cyan toner, and yellow toner of Example 3 were produced in the same manner as Example 1 except that polylactic acid resin H (binder resin) was used. A black toner of Example 3 was produced in the same manner as the black toner of Example 1 except that polylactic acid resin D (binder resin) was used.

The obtained color toner had a volume average particle size (D _50V ) of 6.8 μm and a softening point (T _1/2 ) of 130 ° C. The obtained black toner had a volume average particle diameter (D _50V ) of 6.6 μm and a softening point (T _1/2 ) of 110 ° C. The coverage of the external additive was 80% for both the color toner and the black toner.

Example 4
Magenta toner, cyan toner, and yellow toner of Example 4 were produced in the same manner as in Example 1 except that polylactic acid resin H (binder resin) was used. A black toner of Example 4 was produced in the same manner as the black toner of Example 1 except that polylactic acid resin C (binder resin) was used.

The obtained color toner had a volume average particle size (D _50V ) of 6.8 μm and a softening point (T _1/2 ) of 130 ° C. The obtained black toner had a volume average particle diameter (D _50V ) of 6.8 μm and a softening point (T _1/2 ) of 115 ° C. The coverage of the external additive was 80% for both the color toner and the black toner.

(Example 5)
Magenta toner, cyan toner, and yellow toner of Example 5 were produced in the same manner as Example 1 except that polylactic acid resin D (binder resin) was used. A black toner of Example 5 was produced in the same manner as the black toner of Example 1 except that polylactic acid resin B (binder resin) was used.

The obtained color toner had a volume average particle size (D _50V ) of 6.9 μm and a softening point (T _1/2 ) of 110 ° C. The obtained black toner had a volume average particle size (D _50V ) of 6.7 μm and a softening point (T _1/2 ) of 105 ° C. The coverage of the external additive was 80% for both the color toner and the black toner.

(Example 6)
The color of Example 6 was the same as Example 5 except that 0.2 part by weight of silica oxide fine particles (external additive, trade name: PM-30, manufactured by Tokuyama Corporation, hydrophobicity: 62) was added. Toner and black toner were produced.

The obtained color toner had a volume average particle size (D _50V ) of 6.9 μm and a softening point (T _1/2 ) of 110 ° C. The obtained black toner had a volume average particle size (D _50V ) of 6.7 μm and a softening point (T _1/2 ) of 105 ° C. The coverage of the external additive was 30% for both the color toner and the black toner.

(Example 7)
Example 7 was the same as Example 5 except that 0.45 parts by weight of silica oxide fine particles (external additive, trade name: R-974, manufactured by Nippon Aerosil Co., Ltd., degree of hydrophobicity: 40) was added. Color toner and black toner were produced.

The obtained color toner had a volume average particle size (D _50V ) of 6.9 μm and a softening point (T _1/2 ) of 110 ° C. The obtained black toner had a volume average particle diameter (D _50V ) of 6.7 μm and a softening point (T _1/2 ) of 105 ° C. Both the color toner and the black toner were external additives. The coverage was 40%.

(Example 8)
The color toner of Example 8 was the same as Example 5 except that 0.58 parts by weight of silica oxide fine particles (external additive, trade name: RA200H, manufactured by Nippon Aerosil Co., Ltd., degree of hydrophobicity: 35) was added. And black toner was produced.

The obtained color toner had a volume average particle size (D _50V ) of 6.9 μm and a softening point (T _1/2 ) of 110 ° C. The obtained black toner had a volume average particle size (D _50V ) of 6.7 μm and a softening point (T _1/2 ) of 105 ° C. The coverage of the external additive was 50% for both the color toner and the black toner.

Example 9
Example 9 was the same as Example 5 except that 0.58 parts by weight of silica oxide fine particles (external additive, trade name: R-974, manufactured by Nippon Aerosil Co., Ltd., degree of hydrophobicity: 40) was added. Color toner and black toner were produced.

The obtained color toner had a volume average particle size (D _50V ) of 6.9 μm and a softening point (T _1/2 ) of 110 ° C. The obtained black toner had a volume average particle size (D _50V ) of 6.7 μm and a softening point (T _1/2 ) of 105 ° C. The coverage of the external additive was 50% for both the color toner and the black toner.

(Example 10)
Color toner of Example 10 in the same manner as Example 5 except that 1.38 parts by weight of silica oxide fine particles (external additive, trade name: RA200H, manufactured by Nippon Aerosil Co., Ltd., degree of hydrophobicity: 35) were added. And black toner was produced.

The obtained color toner had a volume average particle size (D _50V ) of 6.9 μm and a softening point (T _1/2 ) of 110 ° C. The obtained black toner had a volume average particle size (D _50V ) of 6.7 μm and a softening point (T _1/2 ) of 105 ° C. The coverage of the external additive was 110% for both the color toner and the black toner.

(Example 11)
The color of Example 11 was the same as Example 5 except that 1.27 parts by weight of silica oxide fine particles (external additive, trade name: Dm-20S, manufactured by Tokuyama Corporation, degree of hydrophobicity: 50) was added. Toner and black toner were produced.

The obtained color toner had a volume average particle diameter (D _50V ) of 6.9 μm, a softening point (T _1/2 ) of 110 ° C., and a coverage of the external additive of 110%. The obtained black toner had a volume average particle size (D _50V ) of 6.7 μm, a softening point (T _1/2 ) of 105 ° C., and the coverage of the external additive was 110%.

Example 12
Except that 1.5 parts by weight of silica oxide fine particles (external additive, trade name: R-974, manufactured by Nippon Aerosil Co., Ltd., degree of hydrophobicity: 40) was added to 100 parts by weight of the obtained toner particles. In the same manner as in Example 5, the color toner and black toner of Example 12 were produced.

The obtained color toner had a volume average particle size (D _50V ) of 6.9 μm and a softening point (T _1/2 ) of 110 ° C. The obtained black toner had a volume average particle size (D _50V ) of 6.7 μm and a softening point (T _1/2 ) of 105 ° C. The coverage of the external additive was 130% for both the color toner and the black toner.

(Example 13)
Magenta toner, cyan toner, and yellow toner of Example 13 were produced in the same manner as Example 6 except that polylactic acid resin H (binder resin) was used. A black toner of Example 13 was produced in the same manner as the black toner of Example 6 except that polylactic acid resin A (binder resin) was used.

The obtained color toner had a volume average particle size (D _50V ) of 6.8 μm and a softening point (T _1/2 ) of 130 ° C. The obtained black toner had a volume average particle diameter (D _50V ) of 6.6 μm and a softening point (T _1/2 ) of 110 ° C. The coverage of the external additive was 50% for both the color toner and the black toner.

(Comparative Example 1)
A color toner and a black toner of Comparative Example 1 were produced in the same manner as in Example 7 except that polylactic acid resin G (binder resin) was used.

The obtained color toner had a volume average particle size (D _50V ) of 6.6 μm and a softening point (T _1/2 ) of 125 ° C. The obtained black toner had a volume average particle diameter (D _50V ) of 6.7 μm and a softening point (T _1/2 ) of 125 ° C. The coverage of the external additive was 40% for both the color toner and the black toner.

(Comparative Example 2)
A magenta toner, a cyan toner, and a yellow toner of Comparative Example 2 were produced in the same manner as in Example 12 except that the polylactic acid resin F (binder resin) was used. Further, a black toner of Comparative Example 2 was produced in the same manner as the black toner of Example 12 except that polylactic acid resin G (binder resin) was used.

The obtained color toner had a volume average particle diameter (D _50V ) of 6.7 μm and a softening point (T _1/2 ) of 120 ° C. The obtained black toner had a volume average particle diameter (D _50V ) of 6.7 μm and a softening point (T _1/2 ) of 125 ° C. The coverage of the external additive was 130% for both the color toner and the black toner.

Types of polylactic acid resin in the color toner and black toner in the toner sets of Examples 1 to 13 and Comparative Examples 1 and 2 (simply referred to as “type of resin” in Table 2), D-form in polylactic acid resin Black toner and color toner in content (shown in parentheses in Table 2), volume average particle size ( _D50V ), softening point (T1 _{/ 2} ), D-form content and softening point (T1 _{/ 2} ) Table 2 shows the value of the difference between the two (referred to as “(black toner) − (color toner)” in Table 2), and the hydrophobicity and coverage of the external additive in the color toner and black toner.

[Manufacture of two-component developer]
A ferrite core carrier having a volume average particle diameter of 45 μm is used as the carrier, and the coverage of the toners of Examples 1 to 13 and Comparative Examples 1 and 2 (color toner and black toner) to this carrier is 60%. In a V-type mixer (trade name: V-5, manufactured by Tokuju Kogyo Co., Ltd.), a toner and a carrier were mixed for 20 minutes to produce a two-component developer.

[Evaluation]
The toner sets (color toner and black toner) of Examples 1 to 13 and Comparative Examples 1 and 2 were evaluated for fixability, storage stability, molecular weight change, and charging stability as follows.

[Fixability]
Using a modified color multifunction machine (trade name: MX-7000N, manufactured by Sharp Corporation), recording paper (trade name: PPC paper SF-4AM3, manufactured by Sharp Corporation) as a recording medium is 20 mm long, A sample image including a rectangular solid image portion having a width of 50 mm is adjusted so that the amount of toner adhering to the recording paper in the non-fixed state in the solid image portion is 0.5 mg / cm ^2. Created. The fixed non-offset area of the obtained unfixed image was measured using an external fixing device manufactured using a fixing unit of a color multifunction peripheral. The fixing process speed is 173 mm / second for color image formation and 355 mm / second for black-and-white image formation. The temperature of the fixing roller is increased in steps of 130 ° C. to 5 ° C. for both color image formation and monochrome image formation. The temperature range where neither low-temperature offset nor high-temperature offset occurs was defined as the non-fixing region.

  Further, the definition of high temperature and low temperature offset is that the toner does not fix to the recording paper during fixing but adheres to the recording paper after the roller makes a full rotation while adhering to the fixing roller.

  In the color multifunction peripheral used for fixing property evaluation, the developing units 14c, 14m, 14y, and 14b are arranged in this order from the side closer to the fixing device. That is, the separation distance between the developing unit 14b containing black toner and the fixing device is arranged to be longer than the separation distance between the developing units 14c, 14m and 14y containing color toner and the fixing device.

The evaluation criteria for fixability are shown below.
A: The fixing non-offset region is 35 ° C. or higher.
○: The fixing non-offset region is 25 ° C. or higher and lower than 35 ° C.
Δ: The fixing non-offset region is 15 ° C. or higher and lower than 25 ° C.
X: The fixing non-offset region is less than 15 ° C.

[Storage stability]
After putting 10 g of toner into a petri dish having an outer diameter of 90 mm and uniformly leveling the surface, the petri dish was left in a high temperature and high humidity environment (55 ° C., 85% RH) for 144 hours. The above-described fixing property evaluation was performed using the toner before and after being left, and the change (difference) in the center of the non-offset area of the toner before and after being left as ΔT ° C. The evaluation criteria for storage stability are shown below.
A: ΔT is 0 ° C.
○: ΔT is greater than 0 ° C. and less than 5 ° C.
Δ: ΔT is 5 ° C. or higher and lower than 10 ° C.
X: ΔT is 10 ° C. or more.

[Molecular weight change]
Similarly to the storage stability evaluation, the toner was left in a high-temperature and high-humidity environment (50 ° C., 85% RH) for 144 hours. The weight average molecular weight (Mw) of the toner before and after being left was measured using GPC (Gel Permeation chromatography) (trade name: HLC-8220 GPC, manufactured by Tosoh Corporation). The measurement was performed under the following measurement conditions using a commercially available monodisperse standard polystyrene (trade name: Shodex STANDARD S series, manufactured by Showa Denko KK) as a standard.

(Measurement condition)
Detector: SHODEX RI-71S
Solvent: Tetrahydrofuran (THF)
Column: KF-G + KF-807L × 3 + KF800D
Flow rate: 1.0 mL / min Sample: 0.25% THF solution

  Further, the reliability of the measurement is the polystyrene sample (trade name: NBS706, weight average molecular weight (Mw) = 288,000, number average molecular weight (Mn) = 137,000, molecular weight distribution index (Mw / The molecular weight distribution index (Mw / Mn) of Mn) = 2.11) was confirmed to be 2.11 ± 0.10.

The molecular weight change was evaluated based on the molecular weight change rate obtained from the following formula (4) from the weight average molecular weight Mw (0) of the toner before standing and the weight average molecular weight Mw (144) of the toner after standing. Evaluation criteria for molecular weight change are shown below.
Molecular weight change rate = ((Mw (0) −Mw (144)) / Mw (0)) × 100 (%)
(4)
A: Molecular weight change rate is less than 4% B: Molecular weight change rate is 4% or more and less than 7%.
Δ: Molecular weight change rate is 7% or more and less than 10%.
X: Molecular weight change rate is 10% or more.

[Charging stability]
A 100 mL polyethylene container containing 76 g of a carrier (silicon coated ferrite core carrier) and 4 g of toner was stirred at 172 rpm using a ball mill (trade name: Fine Tabletop Ball Mill Mount MF-1, manufactured by Tokyo Glass Instrument Co., Ltd.) for 5 minutes. The charge amount of the developer after and after 120 minutes was measured with a suction-type charge amount measuring device (trade name: 210H-2A Q / M Meter, manufactured by TREK).

  The amount of charge change after 5 minutes was Q (5) (μC / g), the amount of charge after 120 minutes was Q (120) (μC / g), and the rate of change in charge amount was determined based on the following formula (5). .

Charge amount change rate = ((Q (5) −Q (120)) / Q (5)) × 100 (%) (5)
A smaller charge amount change rate indicates better charging stability. The evaluation criteria for charging stability are as follows.
A: Charge amount change rate is less than 5%.
○: The charge amount change rate is 5% or more and less than 10%.
Δ: Charge amount change rate is 10% or more and less than 15%.
X: Charge amount change rate is 15% or more.

〔Comprehensive evaluation〕
The evaluation criteria for comprehensive evaluation are as follows.
A: Very good. All evaluation results do not have x and Δ.
○: Good. All evaluation results do not have x and Δ is 1.
Δ: No problem in actual use. All evaluation results have no x and Δ is 2 or more.
X: Defect. There is a cross in at least one of the evaluation results.

(Test Example 2)
(Example 14)
Using the toner set of Example 4, the fixability, storage stability, molecular weight change, and charging stability were evaluated in the same manner as in Test Example 1.

  In Example 14, in the color multifunction peripheral used for fixing property evaluation, the developing units 14b, 14c, 14m, and 14y are arranged in this order from the side closer to the fixing device. That is, the separation distance between the developing unit 14b containing black toner and the fixing device is arranged to be shorter than the separation distance between the developing units 14c, 14m and 14y containing color toner and the fixing device.

  Table 3 shows the evaluation results of the fixing property, the storage stability, the molecular weight change and the charging stability, and the overall evaluation evaluated as described above.

  From the results shown in Table 3, it is clear that the toner sets of Examples 1 to 14 in the present invention are superior to the toner sets of Comparative Examples 1 and 2 as follows.

  In the toner sets of Examples 1 to 14, since the content of the D-form of the polylactic acid resin in the black toner is larger than the content in the color toner, good results were obtained in the fixing property and the storage stability.

  On the other hand, in the toner set of Comparative Example 1, since the content of the polylactic acid resin D-form in the black toner was the same as in the color toner, the storage stability and the molecular weight change were deteriorated.

  In the toner set of Comparative Example 2, the content of polylactic acid resin D-form in the black toner was less than the content in the color toner, so the fixability and charging stability were deteriorated.

It is a flowchart which shows an example of the procedure in the manufacturing method of the black toner and color toner which comprise the toner set of this invention. 1 is a cross-sectional view schematically showing a configuration of an image forming apparatus of the present invention. It is sectional drawing which shows typically an example of a structure of the image development means which comprises the image development apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Toner image forming means 3 Transfer apparatus 4 Fixing apparatus 5 Recording medium supply means 6 Ejecting means 11 Photosensitive drum 12 Charging means 13 Exposure unit 14 Developing apparatus 15 Cleaning unit 20 Developing tank 21 Toner hopper 25 Intermediate transfer belt 26 Drive Roller 27 Followed roller 28 Intermediate transfer roller 29 Transfer belt cleaning unit 30 Transfer roller 31 Fixing roller 32 Pressure roller 35 Automatic paper feed tray 36 Pickup roller 37 Transport roller 38 Registration roller 39 Manual paper feed tray 40 Discharge roller 41 Discharge tray

Claims (10)

A toner set used in an image forming apparatus having a process speed when forming an image using black toner faster than a process speed when forming an image using color toner,
Including black toner and color toner comprising at least a binder resin and a colorant,
The binder resin includes a polylactic acid resin that is a copolymer of L-form and D-form,
The toner set, wherein the black toner has a higher content of D-form in the polylactic acid resin than the color toner.   The toner set according to claim 1, wherein the black toner has a D-form content in the polylactic acid resin of 3 mol% or more than the color toner.   The toner set according to claim 1 or 2, wherein the content of D-form in the polylactic acid resin is 8 mol% or less.   The toner set according to claim 1, wherein the black toner and the color toner are added so that the external additive has a coverage of 50% or more and less than 120%.   The toner set according to claim 4, wherein the external additive has a hydrophobicity of 40 or more.   The two-component developer set, wherein the black toner and the color toner in the toner set according to any one of claims 1 to 5 each include a carrier to constitute a two-component developer.   The developing unit for storing black toner in the toner set according to any one of claims 1 to 5, and the developing unit for storing color toner in the toner set according to any one of claims 1 to 3. And a developing device. 8. An image carrier on which an electrostatic latent image is formed by being exposed to light according to image information, and a developing device according to claim 7, wherein the electrostatic latent image is developed by supplying toner to the image carrier. A transfer device that transfers a toner image formed by development onto a recording medium, and a fixing device that heats and fixes the toner image on the recording medium,
An image forming apparatus, wherein a process speed when forming an image using black toner is higher than a process speed when forming an image using color toner.   9. The image forming apparatus according to claim 8, wherein a separation distance between the developing unit that stores black toner and the fixing device is longer than a separation distance between the developing unit that stores color toner and the fixing device. An image forming method for forming an image using the toner set according to any one of claims 1 to 5,
An image forming method, wherein a process speed when forming an image using black toner is higher than a process speed when forming an image using color toner.

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