JP4842388B2 - Magenta toner for developing electrostatic image, developer, image forming method, and image forming apparatus - Google Patents

Description

  The present invention relates to an electrostatic image developing magenta toner used for electrophotographic image formation, and a developer, an image forming method, and an image forming apparatus using the same.

  Conventionally, a toner for developing an electrostatic charge image (hereinafter, also simply referred to as “toner”) that visualizes a latent image has been used in various image forming processes. For example, an electrophotographic image forming process is used. It is known to be used.

  In an image forming apparatus using an electrophotographic system, a charging process, an exposure process, a development process, a transfer process, a cleaning process, and a fixing process are generally performed as an image forming process. In the charging step, the photosensitive layer on the surface of the photoreceptor, which is a latent image carrier, is uniformly charged. In the exposure process, the signal light of the original image is projected onto the charged photoreceptor surface to form an electrostatic latent image (electrostatic charge image). In the development step, a toner image (visible image) is formed by supplying electrophotographic toner (hereinafter, simply referred to as “toner” unless otherwise specified) to the electrostatic latent image on the surface of the photoreceptor. In the transfer process, the toner image on the surface of the photoreceptor is transferred to a recording medium such as paper or an OHP sheet. In the fixing step, the toner image is heated and pressed by a fixing roller or the like to be fixed on the recording medium. In the cleaning process, the toner remaining on the surface of the photoconductor after the toner image is transferred is removed by a cleaning blade and cleaned.

  An image forming apparatus using an electrophotographic system forms a desired image on a recording medium through the above steps. The full-color image forming apparatus performs the steps from the charging step to the cleaning step three times according to the three colors of yellow, magenta, and cyan, or four times with black added thereto. In the developing process, toner of three colors of yellow, magenta, and cyan, or four colors obtained by adding black to this is used.

  By the way, as the toner used for such full-color image formation, a toner excellent in color reproducibility is required so that an image faithful to the original can be obtained. As a magenta colorant constituting such a magenta toner for color printing having excellent color reproducibility, for example, Patent Documents 1 to 4 describe the use of rhodamine compounds. As a red toner for electrophotography that reproduces a red image recorded by an office stationery or the like with high saturation, for example, Patent Document 5 describes the use of Pigment Red 48-1 as a colorant.

JP 2008-287239 A JP 2009-047814 A JP 2009-058745 A JP 2009-169407 A JP-A-63-173066 JP 2006-330320 A

  Today, with the widespread use of full-color image forming apparatuses, the use of image forming apparatuses to copy stamped documents and to form images according to image data including stamped images has increased. There is an increasing demand for repeatability. That is, the color of the seal is a vermilion color for a seal, and is a bright vermilion color having high brightness. Vermilion is usually made by mixing yellow toner with magenta toner. The ratio of yellow toner to be mixed with magenta toner is determined by image processing technology.

  However, it was found that the vermilion color made by mixing yellow toner with conventional magenta toner has low brightness because the color is clouded by the mixed color, and the vermilion color cannot be reproduced sufficiently. In the conventional magenta toner, as the magenta colorant, C.I. I. Pigment red 269, C.I. I. Pigment red 57-1, C.I. I. Pigment Red 122 and the like are exclusively used.

  It was also confirmed that even the red toner using Pigment Red 48-1 as the colorant described in Patent Document 5 cannot sufficiently reproduce the color of vermilion. In countries with cultures that use seals, excellent color reproducibility is required for the bright vermilion color.

  On the other hand, it was confirmed that the magenta toner using the rhodamine compound as the colorant described in Patent Documents 1 to 4 can sufficiently reproduce the color of vermilion. This is because the rhodamine compound is a fluorescent pigment. Rhodamine compounds are known to absorb light in the vicinity of 520 nm and emit fluorescence having a fluorescence peak wavelength in a wavelength range of 560 to 600 nm. By including a fluorescent pigment in the colorant, it is possible to easily increase the brightness and saturation, and to produce a bright vermilion with high brightness.

  However, fluorescent pigments can easily increase brightness and saturation, but have poor light resistance. For this reason, there arises a problem that a stamped image included in a copy or an image formed product fades in a relatively fast time, and a device for improving light resistance is required separately.

  The present invention has been made in view of the above problems, and its object is to provide a magenta toner capable of sufficiently reproducing the vermilion color, which is bright and bright vermilion, without using a fluorescent pigment having poor light resistance. There is to do.

  As described above, the vermilion color can be easily realized by including a fluorescent pigment in the magenta toner, but there is a problem of fading by including the fluorescent pigment. In order to solve this problem, a person skilled in the art would normally take measures such as adding a substance for increasing light resistance to the toner or developing a fluorescent pigment having high light resistance.

  On the other hand, the applicant of the present application uses a fluorescent pigment having a problem in light resistance, not a common sense approach such as adding a substance for increasing light resistance to the toner or increasing the light resistance of the fluorescent pigment. An attempt was made to verify whether or not sufficient reproduction of vermilion color using various magenta colorants was impossible. This is because there is a concern about the appearance of a new problem in color developability and the like due to the inclusion of a substance for increasing light resistance in the toner, and the development of fluorescent pigments with high light resistance is costly. It is.

  The applicant of the present invention uses a number of magenta colorants, uses them alone, shakes the addition amount, uses them in combination, shakes the mixing ratio, and changes the type of yellow toner to be mixed. As a result of repeating the experiment to measure whether or not the color of vermilion is included in the result of intensive studies, finally, as a magenta colorant, a mixture of existing specific magenta pigments at a specific ratio was used. In addition, it has been confirmed that the vermilion color, which is bright and bright vermilion, can be sufficiently reproduced without including fluorescent pigments.

  That is, the magenta toner for developing an electrostatic charge image of the present invention has C.I. I. Pigment red 48-3 and C.I. I. Pigment Red 48-1 is contained at a ratio of 8: 2 to 5: 5.

  According to this, it is possible to sufficiently reproduce the vermilion color, which is a bright vermilion with high brightness, without including the fluorescent pigment in the magenta toner.

  The electrostatic charge image developing magenta toner of the present invention preferably further has a light transmittance of a wavelength of 440 nm of 30% to 45%.

  As a result of intensive studies, if the transmittance of light with a wavelength of 440 nm in the magenta toner is higher than 45%, no matter how much the mixing ratio of the yellow toner is devised in the image processing, a sufficiently bright vermilion color is sufficient. Confirmed that reproduction is difficult.

  As in the above configuration, C.I. I. Pigment red 48-3 and C.I. I. Pigment Red 48-1 is contained at a ratio of 8: 2 to 5: 5, whereby the transmittance of light having a wavelength of 440 nm can be reduced to 45% or less, and the fluorescent pigment is not included in the magenta toner. The color of vermilion, which is bright vermilion with high brightness, can be reproduced more fully.

  Further, the present invention provides a one-component developer using the above-described magenta toner for developing an electrostatic image of the present invention as it is, and a two-component mixture obtained by mixing the above-described magenta toner for developing an electrostatic image of the present invention and a carrier. Developers are also within the scope of the invention.

  The present invention also includes an image forming method and an image forming apparatus for forming an image by developing an electrostatic image using a developer containing the above-described magenta toner for developing an electrostatic image of the present invention. Yes.

  The image forming method of the present invention is an image forming method for forming an image by exposing a charged photoreceptor surface to form an electrostatic image and developing the electrostatic image using a developer. The electrostatic charge image is developed using a developer containing the magenta toner for developing an electrostatic charge image of the present invention to form an image on a recording paper.

  The image forming apparatus of the present invention includes a photosensitive member, a charging unit that charges the photosensitive member, an exposure unit that exposes the charged photosensitive member to form an electrostatic charge image on the photosensitive member, and the electrostatic charge image. In the electrophotographic image forming apparatus, comprising: a developing unit that supplies a developer to the formed photoreceptor to develop the electrostatic image; and a transfer unit that transfers the developed image to a recording material. Includes the above-described magenta toner for developing an electrostatic image according to the present invention.

In the image forming method and the image forming apparatus of the present invention, a recording material having a whiteness of 60 or more and a density of 0.70 (g / cm ³ ) or more is used as the recording material. preferable.

By defining the characteristics of the recording material to be used as whiteness of 60 or more and density of 0.70 (g / cm ³ ) or more, the color (base color) of the recording material and the surface roughness (unevenness) are affected. In this way, the color of vermilion can be reproduced more satisfactorily, and a good high-quality image can be obtained without image roughness (graininess).

  The magenta toner for developing an electrostatic image of the present invention contains C.I. I. Pigment red 48-3 and C.I. I. CI Pigment Red 48-1 is contained in a ratio of 8: 2 to 5: 5, and this makes it possible to obtain a bright vermilion color that is bright and bright without including a fluorescent pigment in the magenta toner. It can be reproduced.

Furthermore, by using a recording paper having a whiteness of 60 or more and a density of 0.70 (g / cm ³ ) or more, it is affected by the color (background color) of the recording material and the roughness (unevenness) on the surface. Therefore, the color of vermilion can be reproduced more satisfactorily, and a good high-quality image can be obtained with very little image roughness (graininess).

2 is a graph two-dimensionally showing a color gamut obtained by multiplying each magenta toner and yellow toner in Examples and Comparative Examples, with the horizontal axis representing chroma C ^* and the vertical axis L ^* . 2 is a graph two-dimensionally showing a color gamut obtained by multiplying each magenta toner and yellow toner in a comparative example, with the horizontal axis representing chroma C ^* and the vertical axis L ^* . 2 is a graph two-dimensionally showing a color gamut obtained by multiplying each magenta toner and yellow toner in a comparative example, with the horizontal axis representing chroma C ^* and the vertical axis L ^* . 2 is a graph two-dimensionally showing a color gamut obtained by multiplying each magenta toner and yellow toner in a comparative example, with the horizontal axis representing chroma C ^* and the vertical axis L ^* . It is a graph which shows the result of the light resistance test of each magenta toner of an Example, a reference example, and a comparative example. A graph showing the color gamut obtained by multiplying the magenta toner of the comparative example using the fluorescent pigment rhodamine and the yellow toner in a two-dimensional manner, with the horizontal axis representing the chroma C ^* and the vertical axis L ^*. It is. It is a graph which shows the result of having investigated the light transmittance in a visible light range about each magenta toner of an Example and a comparative example. FIG. 8A is a diagram illustrating an image sample without image roughness, and FIG. 8B is a diagram illustrating an image sample with image roughness. FIG. 9A is an electron micrograph of an image without image roughness, and FIG. 9B is an electron micrograph of an image with image roughness. 1 is a diagram illustrating an overall configuration of an electrophotographic image forming apparatus in which a magenta toner of the present invention is used.

  The invention will be specifically described below.

  The electrostatic image developing magenta toner of the present invention (hereinafter also simply referred to as “magenta toner”) is an electrostatic image comprising magenta toner particles containing at least a binder resin, a colorant, and a release agent (wax). A developing magenta toner in which magenta toner particles contain at least a specific two kinds of magenta pigments as a colorant at a specific ratio.

  The magenta toner particles constituting the magenta toner of the present invention are prepared by a pulverization method, a suspension polymerization method, an emulsion polymerization method, a dissolution suspension method, an ester extension polymerization method, or the like. Further, it may be of a core-shell structure comprising core particles containing a binder resin and a magenta colorant and a shell layer that substantially covers no magenta colorant and covers the outer peripheral surface thereof.

The magenta toner of the present invention has a vermilion visible image formed on plain paper by mixing the magenta toner with yellow toner, the lightness is L ^* , the hue in the red-green direction is a ^* , and the hue in the yellow-blue direction. B ^* is the vermilion color gamut (L ^* , a ^* , b ^* ) = (55, 62, 33) when expressed in the L ^* a ^* b ^* system color system (Munsell color system) In the color gamut. Alternatively, the color gamut (L ^* , C ^* ) = (55, 70), which is the color gamut of vermilion, is expressed by a color system (Munsell color system) with lightness L ^* and saturation C ^*. Is included.

The L ^* a ^* b ^* system color system is a means that is useful for representing a color numerically. L ^{* in the} z-axis direction represents lightness, and a ^* and b ^{* on the} x-axis and y-axis ^. Both represent hue and saturation. “Lightness” refers to the relative brightness of a color, “hue” refers to a hue such as red, yellow, green, blue, and purple, and “saturation” refers to the degree of vividness of the color.

  Since yellow toner has high brightness regardless of the yellow colorant used, the color gamut of the vermilion visible image is determined by the characteristics of the magenta toner.

<Magenta colorant>
The magenta toner particles constituting the magenta toner of the present invention contain two specific types of magenta pigments at a specific ratio.

  The two specific types of magenta pigments are C.I. I. Pigment red 48-3, C.I. I. Pigment Red 48-1. These two types of magenta pigments are C.I. I. Pigment Red 48-3, C.I. I. Pigment Red 48-1 is mixed as a side.

  C. I. Pigment Red 48-3 has characteristics such as a strong reddish transmission characteristic and high purple transmittance. On the other hand, C.I. I. Pigment Red 48-1 has a characteristic that the transmittance of purple is low and the coloring power is weak.

The specific ratio (mixing ratio) is C.I. when the total weight of the magenta pigment is 10. I. Pigment red 48-3: C.I. I. Pigment Red 48-1 is in the range of 8: 2 to 5: 5. C. I. C.I. for Pigment Red 48-3 I. As the ratio of Pigment Red 48-1 increases, the lightness L ^{* of the} visible image formed on the plain paper increases. However, C.I. I. When the ratio of Pigment Red 48-1 is less than 20%, C.I. I. Since the characteristics of Pigment Red 48-3 are strong, the lightness L ^* of the vermilion color does not appear, and the color of the vermilion cannot be reproduced. Conversely, C.I. I. When the ratio of Pigment Red 48-1 exceeds 50%, C.I. I. Due to the characteristics of CI Pigment Red 48-1, the ratio of the pigment to the binder resin is high, and the chroma C ^* of the vermilion color does not appear and the color cannot be reproduced in vermilion.

C. I. Pigment red 48-3 and C.I. I. By setting the mixing ratio of Pigment Red 48-1 to 8: 2 to 5: 5, the color gamut of the vermilion visible image formed on plain paper is the color gamut of vermilion (L ^* , a ^* , b ^* ) = (55, 62, 33) or (L ^* , C ^* ) = (55, 70).

  The magenta colorant comprising these two types of magenta pigments is preferably used as a master batch. The master batch of pigment 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 pigment 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. The master batch is used after being granulated to a particle size of, for example, about 2 to 3 mm.

  The content of the magenta colorant comprising these two types of magenta pigments in the magenta toner particles is not particularly limited, but is preferably 4 parts by weight or more and 15 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 magenta colorant in the toner of the present invention falls within the above range. By setting the content of the magenta colorant in the above range, it is possible to form a good image having a sufficient image density, high color developability and excellent image quality.

<Binder resin>
The binder resin used for the magenta toner particles constituting the magenta toner of the present invention is not particularly limited, and a binder resin for color toner is used. Examples thereof include 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.

  Alternatively, as the binder resin, a resin obtained by mixing a release agent with a raw material monomer mixture and performing a polymerization reaction may be used. In this case, it is preferable to include a polyester resin. By including a polyester resin in the binder resin, the dispersion state controllability of the release agent is improved, and a toner having further excellent fixing properties can be obtained. Furthermore, the toner can be provided with excellent durability and transparency. Binder resin can be used individually by 1 type, or can also use 2 or more types together.

  The polyester resin is not particularly limited and a known one is used. For example, a polycondensation product of polybasic acids and polyhydric alcohols can be mentioned. Polybasic acids are polybasic acids and derivatives of polybasic acids such as acid anhydrides or esterified products of polybasic acids. Polyhydric alcohols are compounds containing two or more hydroxyl groups, and include both alcohols and phenols.

  As polybasic acids, those commonly used as monomers for polyester resins can be used. Examples include aromatic carboxylic acids such as terephthalic acid, isophthalic acid, phthalic anhydride, trimellitic anhydride, pyromellitic acid and naphthalenedicarboxylic acid, and aliphatic carboxylic acids such as maleic anhydride, fumaric acid, succinic acid and adipic acid. used. Polybasic acids may be used alone or in combination of two or more.

  As polyhydric alcohols, those commonly used as monomers of polyester resins are used. For example, aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol and glycerin, alicyclic polyhydric alcohols such as cyclohexanediol, cyclohexanedimethanol and hydrogenated bisphenol A, bisphenol Aromatic diols such as an ethylene oxide adduct of A and a propylene oxide adduct of bisphenol A are exemplified.

  “Bisphenol A” is 2,2-bis (p-hydroxyphenyl) propane. Examples of the ethylene oxide adduct of bisphenol A include polyoxyethylene-2,2-bis (4-hydroxyphenyl) propane. Examples of the propylene oxide adduct of bisphenol A include polyoxypropylene-2,2-bis (4-hydroxyphenyl) propane. Polyhydric alcohols may be used alone or in combination of two or more.

  The polyester resin can be synthesized by a condensation polymerization reaction. For example, it can be synthesized by polycondensation reaction, specifically dehydration condensation reaction of polybasic acids and polyhydric alcohols in the presence of a catalyst in an organic solvent or without solvent. At this time, a demethanol polycondensation reaction may be carried out using a methyl esterified product of a polybasic acid as part of the polybasic acid. The polycondensation reaction between polybasic acids and polyhydric alcohols may be terminated when the acid value and softening point of the produced polyester resin reach the values in the polyester resin to be synthesized.

  In this polycondensation reaction, by appropriately changing the reaction conditions such as the blending ratio of polybasic acids and polyhydric alcohols and the reaction rate, for example, the content of carboxyl groups bonded to the terminal of the resulting polyester resin, and thus The acid value, softening point, and other physical properties of the resulting polyester resin can also be adjusted.

  The acid value of the binder resin is preferably 5 mgKOH / g or more and 30 mgKOH / g or less. When the acid value of the binder resin is less than 5 mgKOH / g, the affinity between the binder resin and the release agent is greater than when the acid value of the binder resin is 5 mgKOH / g or more. During fixing, the release agent is less likely to elute on the toner surface, and high temperature offset is likely to occur as a fixing failure. When the acid value of the binder resin exceeds 30 mgKOH / g, the functional value remaining on the toner surface increases and the moisture is easily absorbed, compared to the case where the acid value of the binder resin is less than 30 mgKOH / g. Under such conditions, the charge amount of the toner may be reduced, and charging stability may be impaired.

  Furthermore, since the dispersibility of the release agent in the binder resin tends to be lowered, if the kneading is insufficient during the production of the toner, the dispersion diameter of the release agent on the toner surface may increase. There is. When the acid value of the binder resin is 5 mg KOH / g or more and 30 mg KOH / g or less, the dispersibility of the release agent in the toner particles is set to a desired range. Specifically, the release agent on the toner surface The dispersion diameter can be stabilized to less than 300 nm, the decrease in toner charge amount under high-humidity conditions can be suppressed, and the affinity between the binder resin and the release agent is controlled so that the fixability is good. can do.

  Therefore, the charging stability can be further improved and the fixing property can be improved, so that a high-definition and high-resolution high-quality image can be formed more stably over a long period of time. it can. The acid value of the binder resin is determined by the reaction conditions such as the blending ratio and reaction rate of polybasic acids and polyhydric alcohols in the case of a binder resin raw material monomer mixture, for example, a polyester resin. By appropriately changing the content, the content of the carboxyl group bonded to the terminal of the obtained binder resin, and thus the acid value of the obtained binder resin can be adjusted.

<Release agent>
The release agent used for the magenta toner particles constituting the magenta toner of the present invention is not particularly limited, and known ones can be used. For example, paraffin waxes and derivatives thereof, and petroleum waxes such as microcrystalline wax and derivatives thereof, Fischer-Tropsch wax and derivatives thereof, polyolefin waxes and derivatives thereof, low molecular weight polypropylene waxes and derivatives thereof, and polyolefin polymer waxes and derivatives thereof Examples thereof include hydrocarbon synthetic waxes such as derivatives, carnauba wax and derivatives thereof, and ester waxes.

  The content of the release agent in the magenta toner particles is preferably 1.5% by weight or more and 5% by weight or less with respect to the total weight of the magenta toner particles. If it is less than 1.5% by weight, the releasability of the toner with respect to the intermediate transfer belt is lowered and fixing offset occurs. On the other hand, if it exceeds 5% by weight, the fixing property is good, but the toner aggregates due to the heat of stirring in the developing device, and a good image cannot be obtained.

  The acid value of the release agent is less than 4 mgKOH / g. When the acid value of the release agent is 4 mgKOH / g or more, the affinity between the release agent and the binder resin is higher than when the acid value of the release agent is less than 4 mgKOH / g. During fixing, the release agent is less likely to elute from the toner, and high temperature offset is likely to occur.

<Charge control agent>
The magenta toner particles constituting the magenta toner of the present invention preferably contain a toner additive component such as a charge control agent in addition to the binder resin, the magenta colorant, and the release agent. By containing a 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 is used.

  Examples of the charge control agent include 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 charge control agents for positive charge control such as amidine salts and oil-soluble dyes such as oil black and spiron black, metal-containing azo compounds, azo complex dyes, metal salts of naphthenic acid, salicylic acid and derivatives thereof And metal salt (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 in the magenta toner particles 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 is 0.1 parts by weight with respect to 100 parts by weight of the binder resin. 5 parts by weight or more and 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. When the content of the charge control agent is less than 0.5 parts by weight, sufficient charging characteristics cannot be imparted to the toner.

<Magenta toner particle size>
In the magenta toner particles constituting the magenta toner of the present invention, the content of toner particles having a volume average particle diameter of 5.0 μm or more and 7.0 μm or less and a number average particle diameter of 5.0 μm or less is the total content of toner particles. It is preferably less than 40% by number of toner particles. When the toner particle size distribution and number distribution satisfy this range, toner scattering is suppressed, and a high-definition and high-resolution high-quality image is formed. When the volume average particle diameter is less than 5.0 μm, toner scattering occurs due to a decrease in fluidity, and when the volume average particle diameter exceeds 7.0 μm, a sufficiently high-definition and high-resolution image is not formed. When the content of the toner particles having a number average particle diameter of 5.0 μm or less is 40% by number or more of all the toner particles, the toner scatters due to a decrease in fluidity and the fogging due to the deterioration of transfer efficiency occurs.

The toner particles having a volume average particle diameter (D _50V ) and a content ratio (volume%, number%) of toner particles having a number average particle diameter of 5.0 μm or less are determined by a particle size distribution measuring apparatus “Multisizer 3” manufactured by Beckman Coulter, Inc. Is measured. The measurement conditions are shown below.

Aperture diameter: 100 μm
Number of particles: 50,000 counts Analysis software: Coulter Multisizer AccuComp version 1.19 (Beckman Coulter, Inc.)
Electrolyte: ISOTON-II (Beckman Coulter, Inc.)
Dispersant: Sodium alkyl ether sulfate ester The measurement procedure is as follows: 50 ml of electrolyte, 20 mg of sample toner and 1 ml of dispersant are added to a beaker. The particle size is measured with the apparatus “Multisizer 3”. From the obtained measurement results, the volume particle size distribution and the number particle size distribution of the sample particles are obtained, and the volume average particle diameter (D _50V ) of the toner is obtained from the volume particle size distribution. Further, the content (number%) of toner particles having a number average particle diameter of 5.0 μm or less is determined from the number particle size distribution.

<External additive>
The magenta toner particles constituting the magenta toner of the present invention have functions such as powder flowability improvement, triboelectric chargeability improvement, heat resistance, long-term storage stability improvement, cleaning property improvement and photoreceptor surface wear property control, for example. An external additive may be mixed. Examples of the external additive include silica fine powder, titanium oxide fine powder, and alumina fine powder. One type of external additive can be used alone, or two or more types can be used in combination.

  The addition amount of the external additive in the magenta toner of the present invention is the toner particle 100 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. 0.1 parts by weight or more and 10 parts by weight or less is preferable with respect to parts by weight, and 2.0 parts by weight or more and less than 4.0 parts by weight is more preferable. By containing 2.0 parts by weight or more and less than 4.0 parts by weight of the external additive, the fluidity is further improved and the charging of individual toner particles can be controlled appropriately, so that the fixing property is not impaired and the fogging is not impaired. It is possible to form a high-quality image that does not occur.

If the content of the external additive is less than 2.0 parts by weight, sufficient fluidity cannot be imparted to the toner (particularly small-diameter toner), so that the individual toner particles are not sufficiently charged and are not imaged. It becomes easy for fogging to occur at the part. When the content of the external additive is 4.0 parts by weight or more, the external additive particles tend to aggregate with each other, so that the toner surface cannot be efficiently covered and the fluidity cannot be increased. The toner particles are not sufficiently charged, and fog is likely to occur in the non-image area.
<Recording paper>
The recording paper (recording material) used in the image forming method and the image forming apparatus of the present invention desirably has a whiteness of 60 or more and a density of 0.70 (g / cm ³ ) or more.

  The whiteness is an index indicating the degree of whiteness of the surface color of paper or the like. For recording paper having a whiteness of less than 60, no matter how the magenta toner of the present invention having excellent reproducibility of vermilion color is used, the paper color (background color) of the recording paper influences and the color of vermilion There is a risk that the reproducibility cannot be ensured. If the recording paper has a whiteness of 60 or more, the above problem due to the influence of the paper color of the recording paper can be avoided. Here, only the lower limit of whiteness is defined, but the closer to white, that is, the whiteness approaches 100, the better the reproducibility of the vermilion color. Therefore, the upper limit of whiteness is 100.

The density of the recording paper is a value obtained by dividing the basis weight of the paper by the paper thickness. If the density of the recording material is less than 0.70 (g / cm ³ ), no matter how much the magenta toner of the present invention having excellent reproducibility of vermilion color is used, the toner having image roughness (graininess) There is a risk that the image becomes inferior in concealment. This is because, in the case of recording paper having a density of less than 0.70 (g / cm ³ ), the gap between inorganic fibers such as pulp fibers and added Ca, Ti, Al, etc. on the surface of the recording paper is widened, and the toner is uniform. This is thought to be due to the occurrence of image roughness as a result of the loss of concealment. The pulp fibers constituting the recording paper and the added inorganic substances such as Ca, Ti, and Al greatly affect the surface properties of the recording paper. If the recording paper has a density of 0.70 (g / cm ³ ) or more, the toner concealment property is improved, and a good image can be reproduced without image blur.

<Toner production method>
As described above, the magenta toner particles constituting the magenta toner of the present invention are toners prepared by a pulverization method, a suspension polymerization method, an emulsion polymerization method, a dissolution suspension method, an ester extension polymerization method, or the like. Further, it may be of a core-shell structure comprising core particles containing a binder resin and a magenta colorant and a shell layer that substantially covers no magenta colorant and covers the outer peripheral surface thereof.

  Hereinafter, an example of a toner manufacturing method in which toner particles are manufactured by a pulverization method will be described.

  A resin composition containing at least a binder resin, a colorant (magenta colorant) and a release agent is dry-mixed (premixed), melt-kneaded, and pulverized and classified to prepare toner particles (matrix, core). Next, the toner particles and the external additive are dry mixed to obtain a desired toner. 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.) and 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.), and Cosmo System (trade name, Kawasaki) Heavy Industries, Ltd.).

  In the toner particles, the addition amount of the release agent in the above-mentioned premixing is 2.5 parts by weight or more and 6.0 parts by weight or less with respect to 100 parts by weight of the binder resin. As the kneading machine, a known kneading machine is used. For example, a general kneading machine such as a twin-screw extruder, a three-roll mill and a lab blast mill is used. For example, uniaxial or biaxial extruders such as TEM-100B (trade name, manufactured by Toshiba Machine Co., Ltd.), PCM-65 / 87, and PCM-30 (all of which are trade names, manufactured by Ikegai Co., Ltd.), Needex ( Open roll type kneaders such as trade name, manufactured by Mitsui Mining Co., Ltd.). Among these, an open roll type kneader is preferable. The toner raw material mixture may be melt-kneaded using a plurality of kneaders.

  The toner particles are pulverized by, for example, a jet type pulverizer that pulverizes using a supersonic jet stream or a space formed between a rotor that is a rotor that rotates at high speed and a liner that is a stator. An impact pulverizer that introduces and pulverizes the pulverized material is used.

  For classification, a known classifier capable of removing excessively pulverized toner particles and coarse toner particles by classification by centrifugal force or classification by wind force is used. For example, a swirl type wind classifier (rotary type wind classifier) or the like is used. The toner particles may be spheroidized. As the impact spheroidizing device used for the spheroidizing treatment by mechanical impact force, a commercially available device can be used, for example, Faculty (trade name, manufactured by Hosokawa Micron Corporation) or the like is used. A commercially available device can be used as the hot air spheronizing device used for the spheroidizing treatment with hot air. For example, a surface reformer meteoreinbo (trade name, manufactured by Nippon Pneumatic Kogyo Co., Ltd.) is used.

  The spheroidizing treatment is preferably performed so that the circularity of the toner is in the above-described preferable range of circularity of the toner, specifically, 0.950 or more and 0.960 or less.

<Developer>
The magenta toner of the present invention produced as described above can be used as it is as a one-component developer, or can be mixed with a carrier and used as a two-component developer. By including the magenta toner of the present invention, it is possible to reproduce a vermilion color, which is a bright vermilion with high brightness, and to obtain a magenta developer excellent in light resistance.

  Further, the magenta toner of the present invention has good fixability and good charge stability, and can be a developer having stable characteristics over a long period of use, so that good developability can be maintained. A developer that can be obtained is obtained.

  The developer is preferably a two-component developer comprising the toner of the present invention and a carrier. Since the toner of the present invention is excellent in storage stability, it is possible to obtain a two-component developer having excellent charge stability and developability by suppressing a decrease in developer fluidity. By using such a two-component developer, high-definition and high-resolution high-quality images can be stably formed over a long period of time without toner scattering.

  As the carrier constituting the two-component developer, magnetic particles are 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.

  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 used for a resin-coated carrier, For example, an olefin resin, a styrene resin, a styrene / acrylic resin, a silicon resin, an ester resin, a fluorine-containing polymer resin, etc. are mentioned. Moreover, although it does not restrict | limit especially as resin used for a resin dispersion type carrier, For example, a styrene acrylic resin, a polyester resin, a fluorine resin, a phenol resin, etc. are mentioned.

  The shape of the carrier is preferably a spherical shape or a flat shape. Although the volume average particle diameter of the carrier is not particularly limited, it is preferably 10 μm or more and 100 μm or less, more preferably 30 μm or more and 50 μm or less in view of high image quality. When the volume average particle diameter of the carrier is less than 10 μm, the magnetic force between the carrier and the developing roller is weaker than when the volume average particle diameter of the carrier is 10 μm or more. The carrier is easily developed together with the toner.

  When the volume average particle diameter of the carrier exceeds 100 μm, there is a possibility that the individual toner particles cannot be sufficiently charged. Since the volume average particle diameter of the carrier is 10 μm or more and 100 μm or less, the chance of contact between the toner and the carrier can be increased as compared with the case where the volume average particle diameter of the carrier exceeds 100 μm. Can be controlled to provide sufficient toner chargeability. Therefore, a two-component developer having good toner developability can be obtained. When the volume average particle diameter of the carrier is 30 μm or more and 50 μm or less, the above effect can be more stably exhibited.

In the present embodiment, the volume average particle diameter of the carrier is measured using a laser diffraction, scattering type particle size distribution measuring device Microtrac (trade name: Microtrac MT3000, manufactured by Nikkiso Co., Ltd.).
<Example of image forming apparatus>
The overall configuration of the electrophotographic image forming apparatus 100 using the magenta toner of the present invention manufactured as described above will be described with reference to FIG.

  In the figure, reference numeral 100 denotes an image forming apparatus. The image forming apparatus 100 is an apparatus that forms a multi-color or single-color image on a recording sheet as a recording medium based on image data transmitted from the outside or image data obtained by reading a document. 110 and an automatic document processing device 120.

  The apparatus main body 110 includes an exposure unit 1, four image forming units P, an intermediate transfer unit (transfer unit) 6 including an intermediate transfer belt 61, a fixing unit 7, an internal paper feed unit 81, and a manual paper feed unit. 82 and a paper discharge unit 91. A document placing table 92 made of transparent glass on which a document is placed is provided on the upper portion of the apparatus main body 110, and an automatic document processing device 120 is attached to the upper side of the document placing table 92. The automatic document processor 120 automatically conveys the document onto the document table 92. The automatic document processing device 120 is configured to be rotatable in the direction of arrow M, and the document can be manually placed by opening the document table 92.

  The image forming apparatus 100 supports black (K) and four hues of cyan (C), magenta (M), and yellow (Y) which are three subtractive primary colors obtained by color separation of a color image. The image forming unit P forms an image using the image data that has been processed. The four image forming portions P are arranged in a line in the moving direction (rotating direction) of the intermediate transfer belt 61.

  Each of the four image forming portions P has the same configuration, and includes a charging device (charging portion) 5, a photoreceptor 3, a cleaner unit 4, and a developing device (developing portion) 2. The photosensitive member 3 is an image carrier, and a developing device 2, a cleaner unit 4, and a charging device 5 are disposed around the photosensitive member 3. Further, each developing device 2 of the four image forming units P accommodates toners (developers) of yellow (Y), magenta (M), cyan (C), and black (K). In this embodiment, a two-component development method using a two-component developer composed of a toner and a carrier is exemplified, but a one-component development method may be used.

  The photosensitive member 3 has a cylindrical drum shape, and is driven to rotate around an axis by driving means (not shown). The photoreceptor 3 has a cylindrical conductive substrate and a photosensitive layer provided on the surface of the conductive substrate.

  The charging device 5 includes, for example, a scorotron type discharger, and the discharger is disposed close to the photoconductor 3 along the axial direction of the photoconductor 3. Then, the surface of the photoreceptor 3 is uniformly charged to a predetermined potential by a discharger. In FIG. 10, the non-contact type charging device 5 is illustrated, but a contact type charging device including a charging roller may be used.

  The exposure unit (exposure unit) 1 is a laser scanning unit (LSU) including a laser emitting unit and a reflection mirror. The exposure unit 1 emits a laser beam that emits laser light that is modulated according to image data transmitted from the automatic document processing apparatus 120 or from the outside, and deflects the laser beam emitted from the laser emission unit in the main scanning direction. A polygon mirror, a converging lens that converges the laser beam deflected in the main scanning direction by the polygon mirror so as to form an image on the surface of the photosensitive member 3, and a reflecting mirror that reflects the laser beam converged by the converging lens Consists of.

  The laser beam emitted from the laser emitting unit is deflected by the polygon mirror, further converged by the converging lens, reflected by the reflecting mirror, and irradiated on the surface of the photosensitive member 3 charged to a predetermined potential and polarity, and image data An electrostatic latent image corresponding to the above is formed on the photoreceptor 3. In addition to the laser scanning unit (LSU), the exposure unit 1 uses a writing device (for example, a writing head) in which light emitting elements such as EL (Electro Luminescence) and LED (Light Emitting Diode) are arranged in an array. You can also

  The developing device 2 is provided so as to face the photoconductor 3 and a spacer of the developing roller is pressed against the photoconductor 3, and supplies toner as a developer to the electrostatic latent image formed on the surface of the photoconductor 3. Thus, the electrostatic latent image is visualized.

  The cleaner unit 4 removes and collects toner remaining on the surface of the photoreceptor 3 after development and image transfer. The intermediate transfer unit 6 is disposed above the photoreceptor 3 and includes an intermediate transfer belt 61, an intermediate transfer belt driving roller 62, an intermediate transfer belt driven roller 63, a primary transfer roller 64, and an intermediate transfer belt cleaning unit 65. .

  The intermediate transfer belt 61 is an endless belt member that is stretched between an intermediate transfer belt driving roller 62 and an intermediate transfer belt driven roller 63 to form a loop-shaped movement path, and has a thickness of 100 μm to 100 μm. It is about 150 μm. A primary transfer roller 64 is disposed at a position facing the photoreceptor 3 with the intermediate transfer belt 61 interposed therebetween. The position at which the intermediate transfer belt 61 faces the photoreceptor 3 is the primary transfer position.

  In order to transfer the toner image carried on the surface of the photosensitive member 3 onto the intermediate transfer belt 61, a primary transfer bias having a polarity opposite to the charging polarity of the toner is applied to the primary transfer roller 64 by constant voltage control. As a result, the toner images of the respective colors formed on the photoreceptor 3 are sequentially transferred onto the outer peripheral surface of the intermediate transfer belt 61 and a full-color toner image is formed on the outer peripheral surface of the intermediate transfer belt 61. However, when image data of only a part of the hues of yellow, magenta, cyan, and black is input, it corresponds to the hue of the input image data among the respective photoreceptors 3 of the four image forming units P. Only a part of the electrostatic latent image and the toner image are formed.

  For example, when a monochrome image is formed, an electrostatic latent image and a toner image are formed only on the photoreceptor 3 corresponding to the black hue, and only the black toner image is transferred to the outer peripheral surface of the intermediate transfer belt 61. The The primary transfer roller 64 is configured by covering the surface of a shaft made of a metal (for example, stainless steel) having a diameter of 8 to 10 mm with a conductive elastic material (for example, EPDM: ethylene-propylene copolymer rubber, urethane foam, or the like). The high voltage is uniformly applied to the intermediate transfer belt 61 by a conductive elastic material.

  The toner image transferred to the outer peripheral surface of the intermediate transfer belt 61 by the primary transfer roller 64 is conveyed to a secondary transfer position that is a position facing the secondary transfer roller 10 by the rotation of the intermediate transfer belt 61.

  The secondary transfer roller 10 is pressed against the outer peripheral surface of the intermediate transfer belt 61 whose inner peripheral surface is in contact with the peripheral surface of the intermediate transfer belt driving roller 62 at a predetermined nip pressure during image formation. When the recording paper fed from the internal paper feed unit 81 or the manual paper feed unit 82 passes between the secondary transfer roller 10 and the intermediate transfer belt 61, the charging polarity of the toner on the secondary transfer roller 10 is A high voltage of reverse polarity is applied. As a result, the toner image is transferred from the outer peripheral surface of the intermediate transfer belt 61 to the surface of the recording paper.

  Of the toner adhering to the intermediate transfer belt 61 from a part or all of the photosensitive member 3, the toner remaining on the intermediate transfer belt 61 without being transferred onto the recording paper is used in order to prevent color mixing in the next step. It is removed and collected by the transfer belt cleaning unit 65. The intermediate transfer belt cleaning unit 65 includes a cleaning blade that contacts the intermediate transfer belt 61 and removes toner.

  The fixing unit 7 includes a heat roller 71 and a pressure roller 72. The recording sheet on which the toner image is transferred is guided to the fixing unit 7 and is heated and pressed by passing between the heat roller 71 and the pressure roller 72. As a result, the toner image is firmly fixed on the surface of the recording paper. In the fixing unit 7, an external fixing belt 73 that heats the heat roller 71 is provided in contact with the heat roller 71 from the outside, and the heat roller 71 is based on temperature data detected by a temperature detector (not shown). Control is performed so as to achieve a predetermined fixing temperature. The recording paper on which the toner image is fixed is discharged onto the paper discharge unit 91 by the transport roller 12b.

  In the image forming apparatus 100, the recording paper stored in the internal paper feeding unit 81 and the manual paper feeding unit 82 is discharged between the secondary transfer roller 10 and the intermediate transfer belt 61 and via the fixing unit 7. A sheet conveyance path S extending in a substantially vertical direction for feeding to 91 is provided. In the vicinity of the sheet conveyance path S, pickup rollers 11a and 11b, a plurality of conveyance rollers 12a to 12d, and a registration roller 13 are arranged.

  In the image forming apparatus 100, the recording sheet conveyed from the internal sheet feeding unit 81 and the manual sheet feeding unit 82 is conveyed to the registration roller 13 by the conveyance roller 12 a in the sheet conveyance path S, and is transferred by the registration roller 13 at a predetermined timing. When the toner image is conveyed to the secondary transfer roller 10 and passes between the secondary transfer roller 10 and the intermediate transfer belt 61, the toner image is transferred. The recording paper on which the toner image has been transferred passes through the fixing unit 7 and is fused and fixed by heat, and is discharged onto the paper discharge unit 91 via the transport roller 12b.

  Also, in the image forming apparatus 100, in the case of double-sided printing in which an image is formed on both sides of a recording sheet, single-sided printing is finished, and the trailing end of the recording sheet that has passed through the fixing unit 7 is gripped by the transport roller 12b. Sometimes, the recording roller is guided to the conveying rollers 12c and 12d by the reverse rotation of the conveying roller 12b. The recording paper guided to the transport rollers 12 c and 12 d passes through the registration roller 13, the secondary transfer roller 10, and the fixing unit 7, is printed on the back surface, and is discharged to the paper discharge unit 91.

  Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.

The applicant of the present application uses a number of magenta colorants, used alone, shaking the addition amount, using a combination, shaking the mixing ratio, and changing the type of yellow toner to be mixed. As a result of repeating an experiment for measuring whether or not a color is included in the color gamut and conducting intensive studies, finally, as a magenta colorant, C.I. I. Pigment red 48-3 and C.I. I. It has been found that magenta toner prepared using two types of pigment red 48-1 with a ratio of 7: 3 and an addition amount of 6 parts by weight with respect to 100 parts by weight of the binder resin includes the color of vermilion in the color gamut. It was. This is the magenta toner of Example 1 and the two-component developer containing the same.
(Example 1): As a magenta colorant, C.I. I. Pigment red 48-3 and C.I. I. Magenta toner particles were prepared by using Pigment Red 48-1 at a ratio of 7: 3 and adding 6% by weight of magenta colorant (content) to obtain a magenta toner. This is the magenta toner of Example 1, and the two-component developer of Example 1 plus carrier. The recording paper used was MI paper manufactured by Mitsubishi Paper Industries.

  Specifically, it is as follows. First, a polyester resin A as a binder resin was produced as follows. In an autoclave equipped with a thermometer and a stirrer, 113 parts by weight of dimethyl terephthalate, 75 parts by weight of dimethyl isophthalate, 97 parts by weight of ethylene glycol, 50 parts by weight of propylene glycol, and 0.1 part by weight of tetrabutoxy titanate as a catalyst were added. The reaction was allowed to stir for 120 minutes while heating at a temperature of from ℃. Then, it heated up to 250 degreeC, pressure-reduced the pressure of the reaction system to 1 mmHg or more and 10 mmHg or less, and it stirred for about 1 hour, and also it was made to react, and polyester resin A was obtained.

  The obtained polyester resin A had a number average molecular weight: 3200, a volume average molecular weight: 6200, a glass transition point: 63 ° C., an acid value: 2.2 mgKOH / g, and a reduced clay: 0.335. The molecular weight is determined by GPC (gel permeation chromatography), the glass transition point is determined by DSC (differential scanning calorimeter), the sodium sulfonate group equivalent is determined by sulfur, the acid value is determined by acid-base titration, 0.01 g of a polyester resin was dissolved in 250 cc of a mixed solvent of phenol / tetrachloroethane (weight ratio 6: 4), and measured at a measurement temperature of 30 ° C. using an Ostwald clay meter.

  Polyester resin A produced as described above: 100 parts by weight, C.I. I. Pigment red 48-3 and C.I. I. Pigment Red 48-1 at a ratio of 7: 3, 6.8 parts by weight, paraffin wax (release agent, trade name: HNP10PD, manufactured by Nippon Seiki Co., Ltd., acid value 0 mgKOH / g, melting point 75 ° C.): 5 weights A mixture was prepared by mixing 1 part by weight of an alkyl salicylic acid metal salt (charge control agent, trade name: BONTRON E-84, manufactured by Orient Chemical Co., Ltd.) for 10 minutes with a Henschel mixer. The prepared mixture was melt-kneaded with an open roll type continuous kneader (trade name: MOS320-1800, manufactured by Mitsui Mining Co., Ltd.) to prepare a melt-kneaded product.

  The melt-kneaded product was coarsely pulverized with a cutting mill (trade name: VM-16, manufactured by Ryo Kogyo Co., Ltd.) to prepare a coarsely pulverized product, and then the coarsely pulverized product was finely pulverized with a counter jet mill. After pulverization, the excessively pulverized toner was classified and removed with a rotary classifier, thereby producing toner particles (matrix, core) having a volume average particle diameter of about 6.7 μm.

  Using an impact spheroidizing device (trade name: Faculty F-600, manufactured by Hosokawa Micron Corporation), a spheroidized product of pulverized product was produced. 100 parts by weight of spherical magenta toner particles, 2.2 parts by weight of hydrophobic silica (trade name: R-974, manufactured by Nippon Aerosil Co., Ltd.) as an external additive, and hydrophobic titanium (trade name: T-805, A total of 3.8 parts by weight of 1.6 parts by weight (produced by Nippon Aerosil Co., Ltd.) was mixed with a Henschel mixer (trade name: FM mixer, manufactured by Mitsui Mining Co., Ltd.) to externally add external additives to the toner. The magenta toner of Example 1 was produced. The content of paraffin wax is 4.8% by weight based on the total weight of the toner.

  1.5 parts by weight of paraffin wax (content with respect to the total weight of the toner is 1.49% by weight), 2 parts by weight (content with respect to the total weight of the toner is 1.98% by weight), 3.5 parts by weight (toner When the content with respect to the total weight is 3.41% by weight), good fixability can be obtained, and no toner aggregation is observed in the developing device, and a good image can be obtained. The wax content is good when it is 1.5 wt% or more and 4.8 wt% or less.

  However, when 1 part by weight of the paraffin wax (the content with respect to the total weight of the toner is 1.0% by weight), a fixing offset occurs. With 5.5 parts by weight of paraffin wax (content is 5.26% by weight based on the total weight of the toner), the fixability is good, but toner agglomeration occurs in the developing device, and the toner agglomerates appear in the image. Is recognized.

  A two-component developer is produced by using a ferrite core carrier having a volume average particle diameter of 45 μm as a carrier and a V-type mixer (trade name: V) so that the coverage of the toner with respect to the carrier is 60%. -5, manufactured by Tokuju Kogyo Co., Ltd.) for 20 minutes to prepare a two-component developer containing the magenta toner of Example 1.

A color gamut obtained by combining the magenta toner and the yellow toner of Example 1 produced in this way was obtained, and it was determined whether or not the color gamut contained vermilion vermilion. Specifically, it is as follows.
[Evaluation of vermilion reproducibility] (L ^* , a ^* , b ^* )
Since vermilion is a color obtained by multiplying yellow and magenta, a color patch of the above two colors is output. For example, a value obtained by changing the image density of magenta in the main scanning direction and yellow in the sub-scanning direction is multiplied. The larger the number of patches in the main scanning direction and the sub-scanning direction, the better. The output print sample is subjected to color measurement (L ^* , a ^* , b ^* ) with a reflection spectral densitometer (X-Rite 939: manufactured by X-Rite Co., Ltd.). Each line of patches, extracts the data by a constant L ^* value because when attention is paid to the change in L ^* for each column is continuous L ^* is changed. If there is no target L ^* value, it is obtained by interpolation with the nearest two data. C ^* and Hab are calculated for each data obtained above. C ^* is the distance from the origin on the a ^* and b ^* planes (substitute as saturation). Hab is a ^*, a on b ^* plane ^*, (substitute as hue) angle theta ° from the axis (+) direction. In this way, a color gamut obtained by mixing the prepared magenta toner and yellow toner is obtained.

Further, L ^* a ^* b ^* of vermilion to be reproduced is measured using a reflection spectrodensitometer (X-Rite 939: manufactured by X-Rite Co., Ltd.), and whether or not this is included in the obtained color gamut, The reproducibility of vermilion was evaluated. Vermilion vermilion L ^* a ^* b ^* is (55, 62, 33), and vermilion vermilion L ^* a ^* b ^* (in the color gamut obtained by combining the magenta toner of Example 1 with yellow toner. 55, 62, 33).

Therefore, as a magenta colorant, C.I. I. Pigment red 48-3 and C.I. I. The magenta toner of Example 2 and a two-component developer containing the same were used, using two types of pigment red 48-1 and the ratio of 7: 3 as in Example 1 and the amount of magenta colorant added was 4% by weight. Produced.
Example 2 Magenta toner particles were produced in the same manner as in Example 1 except that the amount of the magenta colorant was changed to 4.4 parts by weight to obtain a magenta toner. This was used as the magenta toner of Example 2, and a carrier added to this was used as the two-component developer of Example 2.

  For the magenta toner of Example 2 produced in this way, as in Example 1, the color gamut when combined with yellow toner was calculated, and it was determined whether the color gamut contained vermilion vermilion. As a result, it was found to contain. Although not specifically described, as a result of repeating the experiment while further changing the addition amount, it was found that the reproducibility does not depend on the addition amount of the magenta colorant to the binder resin.

  Next, as a magenta colorant, C.I. I. Pigment red 48-3 and C.I. I. Two types of pigment red 48-1 were used, the amount of magenta colorant was fixed at 6% by weight, and the mixing ratio was changed to 8: 2, 5: 5, 9: 1, 4: 6, A magenta toner and a two-component developer containing the magenta toner were prepared. In addition, it was set as the same as Example 1 except the change point described.

  For the four types of magenta toners produced in this way, as in Example 1, the color gamut when combined with yellow toner is measured and determined, and it is determined whether the color gamut includes vermilion vermilion. did. As a result, it was found that magenta toners having a mixing ratio of 8: 2, 5: 5 were included, and magenta toners having a mixing ratio of 9: 1, 4: 6 were not included. Hereinafter, the magenta toner with the mixing ratio of 8: 2, 5: 5 is referred to as the magenta toner of Examples 3 and 4, and the magenta toner with the mixing ratio of 9: 1 and 4: 6 is the magenta of Comparative Examples 1 and 2. This is called toner. These magenta toners added with a carrier are referred to as two-component developers of Examples 3 and 4 and Comparative Examples 1 and 2.

In FIG. 1, the color gamut obtained by multiplying each of the magenta toner and the yellow toner of Examples 1 to 4 and Comparative Examples 1 and 2 is shown with the saturation C ^{* on} the horizontal axis and the vertical axis L ^* . The graph shown two-dimensionally is shown. The vermilion vermilion (L ^* , C ^* ) = (55, 70) is shown as a target ●.
Table 1 shows the evaluation results for the magenta toners of Examples 1 to 4 and Comparative Examples 1 and 2, together with the blending ratio of the colorant.

In addition to the vermilion reproducibility described above, the image density ID was also evaluated. Also. In the evaluation of vermilion reproducibility, “◯” indicates that vermillion vermilion L ^* a ^* b ^* (55, 62, 33) was included in the color gamut, and “×” indicates that it did not include.
[Evaluation of image density ID]
Using a two-component developer containing magenta toner and using MX-3100 (manufactured by Sharp Corporation), the toner adhesion amount on the paper becomes 0.4 ± 0.05 mg / cm ^ 2 and the image The density ID of the created image was measured. The image density ID is an image density measured using a Macbeth densitometer, where the incident light amount to the image is Pi and the reflected light amount from the image is Po.
ID = 10 · log (Pi / Po)
It is represented by

An image density ID of 1.2 or more was obtained as “◯”, and an image density ID that was not obtained as “x”.
[Cost Evaluation]
“X” indicates that the organic synthetic pigment quinacridone pigment, which is a higher pigment, is used, and “◯” indicates that the normal pigment other than the quinacridone pigment is used.

As can be seen from FIG. I. Pigment red 48-3: C.I. I. If the pigment red 48-1 is in the range of 8: 2 to 5: 5, sufficient vermilion reproducibility can be obtained. In contrast, the C.I. I. C.I. for Pigment Red 48-3 I. When the ratio of Pigment Red 48-1 is 10%, sufficient vermilion reproducibility cannot be obtained. In Comparative Example 1, high brightness L ^* could not be obtained. In addition, C.I. I. Even when the ratio of Pigment Red 48-1 exceeds 50%, sufficient vermilion reproducibility cannot be obtained. In Comparative Example 2, the saturation C ^* has decreased below a necessary value. In Comparative Example 2, the image density ID did not reach 1.2. This is because C.I. I. This is probably because the ratio of Pigment Red 48-1 is large.

  Therefore, in order to obtain sufficient reproducibility for vermilion vermilion, C.I. I. C.I. for Pigment Red 48-3 I. It can be said that the ratio of Pigment Red 48-1 needs to be 20% or more and 50% or less.

  Next, as a magenta colorant, C.I. I. Pigment Red 48-1 was used, and the mixing ratio of main and auxiliary was fixed at 7: 3, and the main colorant “A” was changed to C.I. I. Pigment red 269, C.I. I. Pigment Red 57-1 was shaken, and the addition amount of magenta colorant was changed to 6% by weight and 4% by weight to prepare four types of magenta toner and a two-component developer containing the same. In addition, it was set as the same as Example 1 except the change point described.

  For the four types of magenta toners produced in this way, as in Example 1, the color gamut when the yellow toner is multiplied is obtained by the above-described procedure, and whether or not vermilion vermilion is included in the color gamut. As a result, it was found that neither magenta toner was contained. Hereinafter, the main colorant “A” is C.I. I. A magenta toner containing 6% by weight and 4% by weight of Pigment Red 269 is referred to as a magenta toner of Comparative Examples 3 and 4, and the main colorant “A” is C.I. I. The magenta toner having 6% by weight and 4% by weight of Pigment Red 57-1 is referred to as magenta toner of Comparative Examples 5 and 6. Further, those obtained by adding a carrier to these magenta toners are referred to as two-component developers of Comparative Examples 3 to 4.

FIG. 2 is a two-dimensional graph showing the color gamut obtained by multiplying each magenta toner and yellow toner of Comparative Examples 3 to 6 with the saturation C ^{* on} the horizontal axis and the L ^* on the vertical axis. Indicates. The vermilion vermilion (L ^* , C ^* ) = (55, 70) is shown as a target ●. Table 2 shows the evaluation results for the magenta toners of Comparative Examples 3 to 6 together with the blending ratio of the colorant.

  As can be seen from FIG. 2 and Table 2, the secondary colorant “B” was added to C.I. I. Even if the ratio of Pigment Red 48-1 was 30% and the amount of magenta colorant added to the binder resin was the same as in Examples 1 and 2, the main colorant “A” was C.I. I. If it is not Pigment Red 48-3, it will be understood that sufficient vermilion reproduction cannot be obtained. There was no problem with the image density ID and cost.

  Next, as the magenta colorant, C.I. I. Pigment Red 48-3 was used, the mixing ratio of main and secondary was 7: 3, the amount of magenta colorant was fixed at 6% by weight, and the secondary colorant “B” was changed to C.I. I. Pigment red 122, C.I. I. Pigment red PV19, C.I. I. Three types of pigment red 207 were shaken to prepare three types of magenta toner and a two-component developer containing the same. In addition, it was set as the same as Example 1 except the change point described.

  For the three types of magenta toners produced in this way, as in Example 1, the color gamut when the yellow toner is multiplied is obtained by the above procedure, and whether or not vermilion vermilion is included in the color gamut. As a result, it was found that neither magenta toner was contained. Hereinafter, the secondary colorant “B” is C.I. I. The magenta toner of Pigment Red 122 is referred to as the magenta toner of Comparative Example 7, and the secondary colorant “B” is C.I. I. Pigment Red PV19 magenta toner is referred to as magenta toner of Comparative Example 8, and the secondary colorant “B” is C.I. I. The magenta toner of Pigment Red 207 is referred to as the magenta toner of Comparative Example 9. Further, those obtained by adding a carrier to these magenta toners are referred to as two-component developers of Comparative Examples 7 to 9.

FIG. 3 is a two-dimensional graph showing the color gamut obtained by multiplying the magenta toner and the yellow toner of Comparative Examples 7 to 9 with the saturation C ^{* on} the horizontal axis and the L ^* on the vertical axis. Indicates. The vermilion vermilion (L ^* , C ^* ) = (55, 70) is shown as a target ●. Table 3 shows the evaluation results for the magenta toners of Comparative Examples 7 to 9 together with the blending ratio of the colorant.

  As can be seen from FIG. 3 and Table 3, the main coloring agent “A” I. Pigment Red 48-3, the proportion of which is 30%, and the addition amount of the magenta colorant is 6% by weight. I. If it is not Pigment Red 48-1, it will be understood that sufficient vermilion reproduction cannot be obtained. In particular, the magenta pigment used as the secondary colorant “B” in Comparative Examples 7 to 9 is a highly transparent quinacridone pigment, and even when mixed with yellow toner, the color is hardly turbid and high brightness can be obtained. However, sufficient reproducibility could not be obtained. There was no problem with the image density ID, but since both were quinacridone pigments, there was a problem in terms of cost.

  Further, as a magenta colorant, C.I. I. Pigment Red 269 is used as a secondary colorant “B” mixed with C.I. I. Pigment red 122, C.I. I. Pigment red PV19, C.I. I. Three types of pigment red 207 were shaken to prepare three types of magenta toner and a two-component developer containing the same. The mixing ratio of main and sub was 7: 3, and the amount of magenta colorant added was fixed at 6% by weight. In addition, it was set as the same as Example 1 except the change point described.

  For the three types of magenta toners produced in this way, as in Example 1, the color gamut when the yellow toner is multiplied is obtained by the above procedure, and whether or not vermilion vermilion is included in the color gamut. As a result, it was found that neither magenta toner was contained. Hereinafter, the main colorant “A” is C.I. I. Pigment Red 269, and the secondary colorant “B” is C.I. I. The magenta toner of Pigment Red 122 is referred to as the magenta toner of Comparative Example 10, and the secondary colorant “B” is C.I. I. Pigment Red PV19 magenta toner is referred to as Magenta toner of Comparative Example 11, and the secondary colorant “B” is C.I. I. The magenta toner of Pigment Red 207 is referred to as the magenta toner of Comparative Example 12. Further, those obtained by adding a carrier to these magenta toners are referred to as two-component developers of Comparative Examples 10-12.

FIG. 4 is a two-dimensional graph showing the color gamut obtained by multiplying the magenta toner and the yellow toner of Comparative Examples 10 to 12 with the saturation C ^{* on} the horizontal axis and the L ^* on the vertical axis. Indicates. The vermilion vermilion (L ^* , C ^* ) = (55, 70) is shown as a target ●. Table 4 shows the evaluation results for the magenta toners of Comparative Examples 10 to 12 together with the blending ratio of the colorant.

  As can be seen from FIG. 4 and Table 4, the main colorant “A” used in conventional magenta toner is C.I. I. Even when CI Pigment Red 269 was used and combined with three types of highly transparent quinacridone pigments as a secondary colorant “B”, sufficient reproducibility could not be obtained for vermilion vermilion.

  Next, an image formed using the two-component developer of Example 1 and C.I. I. As the two-component developer of Reference Example 13 containing the magenta toner of Reference Example 1 using Pigment Red 269 alone, and C.I. I. A light resistance test conducted using the two-component developer of Comparative Example 13 containing magenta toner of Comparative Example 13 in which Rhodamine compound represented by the following general formula (1) is added to CI Pigment Red 48-3 will be described. .

Reference Example 1: As a magenta colorant, C.I. I. Magenta toner particles were prepared in the same manner as in Example 1 except that CI Pigment Red 269 was used alone and the addition amount of the magenta colorant was changed to 6% by weight to obtain a magenta toner. This was used as the magenta toner of Reference Example 1, and the carrier added to this was used as the two-component developer of Reference Example 2.
(Comparative Example 13): As a magenta colorant, C.I. I. Magenta toner particles were prepared in the same manner as in Example 1 except that Pigment Red 269 and rhodamine 6G Lake of the general formula (1) described above were used at a ratio of 5: 5 and the addition amount of magenta colorant was changed to 6% by weight. As a result, a magenta toner was obtained. This was the magenta toner of Comparative Example 13, and the one obtained by adding a carrier thereto was the two-component developer of Comparative Example 13.

  Table 5 shows the mixing ratio of the colorants of Reference Example 1 and Comparative Example 13.

  In the light resistance test, an image formed with the two-component developer of Example 1, Reference Example 1, and Comparative Example 13 was continuously irradiated with ultraviolet rays for 100 hours, and the change in image density ID was measured.

  FIG. 5 shows the results of the light resistance test. As shown in FIG. 5, the deterioration of the image formed with the two-component developer is remarkable. Moreover, the deterioration of the image formed with the two-component developer of Comparative Example 13 has a curve that shows the deterioration from a relatively early stage, such as a continuous irradiation time of 20 hours, and the actual image fading. You can see that it started in a short period. On the other hand, the magenta toner of Example 1 according to the present invention shows a curve curve similar to the light resistance of Reference Example 1, which is a generally known ordinary magenta toner having no problem with light resistance. It was confirmed that there is no problem with sex.

For reference, FIG. 6 shows the color gamut obtained by multiplying the magenta toner of Example 13 using the fluorescent pigment rhodamine and the yellow toner, the saturation C ^{* on} the horizontal axis, and the vertical axis L ^* . Thus, a two-dimensional graph is shown. The vermilion vermilion (L ^* , C ^* ) = (55, 70) is shown as a target ●.

  Further, FIG. 7 shows the results of examining the light transmittance in the visible light region of the magenta toners of Example 1 and Comparative Example 1.

  As shown in FIG. 7, it can be seen that the magenta toner of Example 1 according to the present invention has a light transmittance of about 35% at a wavelength of 440 nm. On the other hand, as shown in FIG. 7, the magenta toner of Comparative Example 1 that cannot sufficiently reproduce the color of vermilion had a light transmittance of about 57% at a wavelength of 440 nm. Although not shown, when the light transmittance in the visible light region was examined for other examples and comparative examples, the magenta toner of the example had a light transmittance of 440 nm at a wavelength of 45% or less. It was confirmed that the magenta toner in the example exceeded 45%.

  From this, it is considered that the transmittance of light having a wavelength of 440 nm needs to be suppressed to 45% or less in order to sufficiently reproduce the vermilion color, which is a bright vermilion with high brightness. If the transmittance of light having a wavelength of 440 nm is less than 30%, blue due to color mixture with cyan toner cannot be reproduced. Therefore, the transmittance of light having a wavelength of 440 nm needs to be 30% or more and 45% or less. It is considered that.

  By the way, in order to reproduce the color of vermilion and obtain a high-quality image, it is necessary to consider the influence of the paper type as well as the brightness and saturation of the hue.

  No matter how magenta toner that can reproduce the color of vermilion, if the recording paper (recording material) to which the toner is transferred has a color that affects the color reproduction of the toner, it is stable. The color of vermilion cannot be reproduced. In addition, when the surface of the recording paper is rough, a rough image with a graininess (feeling of roughness) is formed.

  Patent Document 6 describes that oil is applied to the surface of the pressing member of the fixing device so that a stable and highly glossy image can be formed without being affected by the type of paper such as uneven transfer paper. By applying oil to the fixing to improve the gloss, it is possible to improve the appearance of vermilion. However, since a mechanism for applying oil is necessary, there is a problem that the fixing device is enlarged. In addition, it takes time and effort to control the amount of oil transferred to the transfer paper (recording paper) to an appropriate amount.

Accordingly, the applicant of the present application also paid attention to the characteristics of the recording paper, and intensively studied the characteristics of the recording paper that improves the color developability of the magenta toner of the present invention, which has excellent reproducibility of the vermilion color. That is, image evaluation was performed on various recording papers using magenta toner under the above conditions, and the effects of vermilion color development, whiteness and density of the recording papers were examined. As a result, image formation using a recording paper having a whiteness of 60 or more and a density of 0.70 (g / cm ³ ) or more has good vermilion reproducibility, good concealment, and no roughness. Found to form.

  Tables 6 and 7 show the results of image evaluation on various recording papers using the magenta toner of Example 1. For recording paper, Mitsubishi Paper M paper, igepa Continental LX Premium, FXOS JD paper, Riso Kagaku ideal environmental paper 10, Marusumi Paper Yashima R100, Oji Paper San Ace R100 Recycled PPC100 made by Kishu Paper Co., Ltd., clean copy, α eco paper, fine PPC, Recycle Paper Classic made by Steinbeis Temming, a standard type of Japanese postcard, 70gB5 made by Beijing Paper Co., Ltd. was used.

Tables 6 and 7 show the basis weight, paper thickness, density, and whiteness of each recording paper. The density is a value obtained by dividing the basis weight by the paper thickness. The whiteness was measured with a whiteness measuring device “ZE2000” manufactured by Nippon Denshoku Industries Co., Ltd. In addition to the vermilion reproducibility described above, image roughness was also evaluated as an image evaluation.
[Evaluation of image roughness]
Images as described above were prepared and image roughness was visually evaluated. FIG. 8A shows an image sample without image roughness, and FIG. 8B shows an image sample with image roughness.

  An image sample such as the image sample shown in FIG. 8B has “x”, an image sample without “gray” is indicated with “◯”, and a sample with a slight difference in density is indicated with “Δ”.

  FIG. 9 (a) shows an electron micrograph of the surface of an image without image roughness at a magnification of 1000. FIG. 9 (b) shows the surface of an image with image roughness at a magnification of 1000. An electron micrograph taken is shown. As an electron microscope (analyzer), S-4100 type FE-SEM manufactured by Hitachi, Ltd. was used.

  As can be seen from Table 7, when the Recycle Paper Classic made by Steinbeis Temming having a whiteness of less than 60 was used, sufficient vermilion reproducibility could not be obtained. It can be said that color reproduction is difficult without a certain degree of whiteness of the recording paper, and the whiteness is preferably 60 or more.

Further, in the case of using 70 g B5 made by Beijing Paper Industries Co., Ltd. having a density of less than 0.70 (g / cm ³ ), the image roughness was poor. This is presumably because, in the case of recording paper having a low density, the gaps between the pulp fibers on the surface and inorganic substances such as added Ca, Ti, Al and the like are widened, and the uniform hiding property of the toner is impaired. As shown in FIG. 9A, it can be confirmed that the toner is uniformly adhered and fixed on the paper fiber when there is no image roughness. On the other hand, as shown in FIG. 9B, in the case of image roughness, the gap between the paper fibers is large, and the toner is buried between the paper fibers. Therefore, the density of the recording paper is preferably 0.70 (g / cm ³ ) or more.

From the above results, in order to reproduce good image formation and vermilion, reproduction of vermilion color is achieved by using a recording paper having a whiteness of 60 or more and a density of 0.70 (g / cm ³ ) or more. An image with good properties can be obtained.

  Used in image forming apparatuses that perform image formation by electrophotography such as copiers, printers, and multi-function machines, etc., and by using a mixed color of cyan toner for developing electrostatic images and yellow toner for developing electrostatic images, It can be reproduced.

2 Developing Device 3 Photoreceptor 5 Charging Device 100 Image Forming Device P Image Forming Unit

Claims (7)

  As a colorant, C.I. I. Pigment red 48-3 and C.I. I. Pigment Red 48-1 is contained in a ratio of 8: 2 to 5: 5.   2. The magenta toner for developing an electrostatic charge image according to claim 1, wherein the transmittance of light having a wavelength of 440 nm is 30% or more and 45% or less.   A developer comprising the electrostatic image developing magenta toner according to claim 1 or 2 and a carrier.   3. An image forming method according to claim 1, wherein the charged surface of the photosensitive member is exposed to form an electrostatic charge image, and the electrostatic charge image is developed using a developer to form an image on a recording material. An image forming method comprising developing an electrostatic charge image using a developer containing a magenta toner for developing an electrostatic charge image, and forming an image. The image forming method according to claim 4, wherein a recording material having a whiteness of 60 or more and a density of 0.70 (g / cm ³ ) or more is used as the recording material.   A photosensitive member; a charging unit that charges the photosensitive member; an exposure unit that exposes the charged photosensitive member to form an electrostatic charge image on the photosensitive member; and a developer on the photosensitive member on which the electrostatic charge image is formed. In the electrophotographic image forming apparatus, the developing agent includes: a developing unit that develops the electrostatic charge image by supplying a developing unit; and a transfer unit that transfers the developed image to a recording material. An image forming apparatus comprising the electrostatic image developing magenta toner described above. The image forming apparatus according to claim 6, wherein the recording material has a whiteness of 60 or more and a density of 0.70 (g / cm ³ ) or more.

Images