JP7167612B2 - Electrophotographic imaging method - Google Patents

Description

The present invention relates to an electrophotographic image forming method, and more particularly, in the case of forming a visible image by superimposing a white toner image layer and a chromatic or black image layer, the white toner image layer and the chromatic or black image are formed. The present invention relates to an electrophotographic image forming method capable of suppressing color mixture of layers and obtaining a visible image having high chroma or contrast.

2. Description of the Related Art In recent years, in the field of electrostatic charge image developing toner (hereinafter also simply referred to as "toner") used in electrophotographic image formation, development has been made in response to various demands from the market. In particular, since the types of recording media on which images are formed are increasing, there is an extremely high demand from the market for compatibility with these various recording media.

For example, when forming an image on color paper (color paper other than white and non-white recording media such as transparent films), full-color toners, specifically, chromatic toners such as yellow toner, magenta toner, and cyan toner, Sufficient color development cannot be obtained with only four color toners of black toner and black toner. Therefore, it has been proposed to use a white toner as a fifth color toner to form a base layer that serves as a background (see, for example, Japanese Unexamined Patent Application Publication No. 2002-100003).

Since the base layer formed of white toner is white, ideally, it is necessary to scatter all the light incident on the base layer from the viewpoint of concealability. Therefore, studies have been made to improve the hiding property of the white toner that forms the base layer (see, for example, Patent Document 2).

On the other hand, in order to achieve the target density on the image, the optical density of the toner amount on the intermediate transfer belt is measured by an IDC (Image Density Control) sensor, the voltage bias during the primary transfer is controlled, and the single layer is formed. Density is feedback-controlled to determine the density (saturation, brightness) on the image.

According to studies by the present inventors, when the particle size of the white toner and the particle size of the chromatic or black toner are about the same (for example, both are about 7 μm), the image layer of the white toner and the chromatic or black toner are mixed. When the image layers are overlaid and printed, even if the target density (especially the saturation) is achieved in the measurement of the IDC sensor, the chromatic or black image layer becomes cloudy (mixed color) visually, and the color becomes unsatisfactory. It has been found that a problem arises where the power or contrast does not reach the target.

However, since the optical measurement by the IDC sensor is performed only for a single layer, it is difficult to predict and solve the problem at the time of layering, and it is impossible in principle to correct it by image processing.

Further, the invention described in Patent Document 2 has a problem of "high hiding rate, good chargeability and fixability", and does not pay attention to white turbidity (color mixture) of chromatic or black toner and white toner. It is not possible to improve the white turbidity of the chromatic color or black.

This phenomenon has become a problem due to the strict quality requirements in the current printing industry. A solution is needed.

JP 2006-220694 A JP 2018-49160 A

The present invention has been made in view of the above problems and circumstances, and the problem to be solved is to form a visible image by superimposing a white toner image layer and a chromatic or black image layer. An object of the present invention is to provide an electrophotographic image forming method capable of suppressing color mixture between a layer and a chromatic or black image layer and obtaining a visible image having high chroma or contrast.

In order to solve the above problems, the inventors of the present invention, in the process of studying the causes of the above problems, have found an electrophotographic image forming method using a white toner and a chromatic or black toner, wherein the white toner and the chromatic or black toner are By setting the average particle diameter of the toner particles constituting the black toner and the particle diameter difference thereof within specific ranges, color mixing between the white toner image layer and the chromatic or black image layer is suppressed, and high chroma or It has now been found that an electrophotographic imaging process is provided which is capable of producing visible images having contrast.

That is, the above problems related to the present invention are solved by the following means.

1. An electrophotographic imaging method using a white toner and a chromatic or black toner, comprising:
The average particle diameter dw of the toner particles constituting the white toner is 12.5 . within the range of 0 to 18.0 μm,
The average particle diameter dc of the toner particles constituting the chromatic or black toner is in the range of 4.0 to 8.0 μm, and
The difference (dw-dc) between the average particle diameter dw and the average particle diameter dc is 5.9-8 . within 0 μm , and
An electrophotographic image forming method , wherein the toner particles constituting the white toner are polymerized toner particles .

2. The image layer of the white toner and the image layer of the chromatic or black toner as a laminate are simultaneously primarily transferred onto an intermediate belt, then secondarily transferred onto a recording medium, and then fixed. 2. The electrophotographic image forming method according to claim 1.

3. 3. The method of forming an electrophotographic image according to claim 2, wherein the white toner image layer is positioned at either the bottom layer or the top layer in the stack of image layers fixed on the recording medium.

4. 4. The electrophotographic image forming method of any one of items 1 to 3, wherein the toner particles constituting the white toner contain rutile-type titanium oxide.

5. 5. The electrophotographic image forming method according to any one of items 1 to 4, wherein the coefficient of variation of toner particles constituting the white toner is in the range of 21 to 29% .

6. 6. The electrophotography according to any one of items 1 to 5 , wherein the average particle size dw of the toner particles constituting the white toner is in the range of 14.0 to 18.0 μm. Imaging method.

When a visible image is formed by superimposing a white toner image layer and a chromatic or black image layer by the means of the present invention, color mixing between the white toner image layer and the chromatic or black image layer is suppressed, It is possible to provide an electrophotographic imaging method capable of obtaining visible images having high chroma or contrast.

Although the expression mechanism or action mechanism of the effects of the present invention has not been clarified, it is speculated as follows.

As a result of investigations by the present inventors, the cause of white turbidity (color mixture) when a white toner image layer and a chromatic or black image layer are superimposed is that the white toner image layer in the primary transfer image on the intermediate transfer belt and the chromatic or black image layer is unclear. This phenomenon occurs when the white toner image layer is above the chromatic or black image layer on the intermediate transfer belt. In the lower layer of the image layer), toner particles constituting chromatic or black toner (hereinafter referred to as chromatic or black toner particles) and toner particles constituting white toner (hereinafter referred to as white toner particles). is small (e.g. less than 2.0 μm), the white toner particles enter between the chromatic or black toner particles. and white toner particles are mixed with each other, and the interface between the image layers becomes unclear as a primary transfer image. It is speculated that a decrease in contrast occurs.

FIG. 1 is a schematic diagram for explaining the generation of white turbidity (mixed colors) when a white toner image layer and a chromatic or black image layer are overlaid.

FIG. 1(a) is a schematic side view showing a case where the difference in particle size between chromatic or black toner particles (2) and white toner particles (3) is small. and a chromatic or black image layer, mixing of toner particles occurs at the interface. FIG. 1(b) shows a schematic view of the secondary transfer onto the recording medium (4) as seen from the normal direction of the recording medium, in which a chromatic or black image layer is mixed with a white toner image layer. occurs and the saturation or contrast is reduced.

FIG. 1(c) shows a schematic side view of the case where the particle size of white toner particles (3) is larger than that of chromatic or black toner particles (2). Furthermore, when a white toner image layer and a chromatic or black image layer are superimposed, mixing of toner particles does not occur at the interface. FIG. 1(d) shows a schematic diagram of the secondary transfer onto the recording medium (4) as seen from the normal direction of the recording medium, in which a chromatic or black image layer is mixed with a white toner image layer. It does not occur, and a decrease in saturation or contrast is suppressed.

Therefore, it is presumed that the white toner particles and the chromatic or black toner particles must have the particle size difference specified in the present invention in order to suppress the generation of white turbidity in the chromatic or black image layer. .

Schematic diagram for explaining occurrence of white turbidity (color mixture) between a white toner image layer and a chromatic or black image layer.

The electrophotographic image forming method of the present invention is an electrophotographic image forming method using a white toner and a chromatic or black toner, wherein the average particle diameter dw of toner particles constituting the white toner is 12.5 . 0 to 18.0 μm, the average particle diameter dc of the toner particles constituting the chromatic or black toner is in the range of 4.0 to 8.0 μm, and the average particle diameter dw and the The difference (dw-dc) from the average particle diameter dc is 5.9-8 . It is characterized in that the toner particles that are within the range of 0 μm and that constitute the white toner are polymerized toner particles . This feature is a technical feature common to or corresponding to the following embodiments.

As an embodiment of the present invention, from the viewpoint of exhibiting the effects of the present invention, the image layer of the white toner and the image layer of the chromatic or black toner are simultaneously primarily transferred onto an intermediate belt as a laminate, and then onto a recording medium. It is preferable to have a step of fixing after secondary transfer to the image. This is preferable from the viewpoint of achieving high-speed image formation and high-quality visible images that are required in the production market.

In the stack of image layers fixed on the recording medium, the presence of the white toner image layer as either the bottom layer or the top layer reduces the saturation or contrast of the chromatic or black image layers. The white toner image layer can serve as the base layer for the image without the need for toner, which is preferred.

Further, it is preferable that the white toner particles contain rutile-type titanium oxide in terms of hiding power, and the average particle size dw of the white toner particles is in the range of 12.0 to 18.0 μm. , from the viewpoint of suppressing white turbidity (mixed colors) in a chromatic or black image layer, and enhancing the hiding power of a base layer with a white toner. Furthermore, it is more preferable that the average particle size dw of the white toner particles is in the range of 14.0 to 18.0 μm from the viewpoint of further suppressing the occurrence of white turbidity (mixed colors).

Further, the white toner particles are preferably polymerized toner particles or pulverized toner particles, both of which can exhibit the effects of the present invention. Among them, a polymerized toner is preferable because it becomes particles (monodisperse particles) having a small coefficient of variation (also referred to as a CV value) of the particle size distribution, so that the effects of the present invention can be exhibited more effectively.

DETAILED DESCRIPTION OF THE INVENTION The present invention, its constituent elements, and embodiments and modes for carrying out the present invention will be described in detail below. In the present application, "-" is used to mean that the numerical values before and after it are included as the lower limit and the upper limit.

<<Overview of Electrophotographic Image Forming Method of the Present Invention>>
The electrophotographic image forming method of the present invention is an electrophotographic image forming method using a white toner and a chromatic or black toner, wherein the average particle diameter dw of toner particles constituting the white toner is 12.5 . 0 to 18.0 μm, the average particle diameter dc of the toner particles constituting the chromatic or black toner is in the range of 4.0 to 8.0 μm, and the average particle diameter dw and the The difference (dw-dc) from the average particle diameter dc is 5.9-8 . It is characterized in that the toner particles that are within the range of 0 μm and that constitute the white toner are polymerized toner particles .

Here, the toner particles in the present invention refer to toner particles for electrostatic charge image development in electrophotography. Further, the toner particles refer to toner base particles to which an external additive is added. In the present invention, when there is no need to distinguish between the toner base particles and the toner particles, they may simply be referred to as toner particles.

Further, the "toner particles" according to the present invention contain at least a crystalline resin and a release agent in addition to the colorant. Further, the toner particles preferably contain internal additives such as a release agent, a charge control agent, and a surfactant in the binder resin, for example. Further, it is preferable that toner particles to which an external additive is added are usually used as toner particles, but the external additive may not be added.

In the electrophotographic image forming method of the present invention, an image layer containing white toner particles of white toner and an image layer containing chromatic or black toner particles of chromatic or black toner are superimposed on a recording medium. The toner image layer and the chromatic or black toner image layer (hereinafter also referred to as a toner image) undergo a process of fixing. Specifically, for example, the following steps (1) to (5) are included.
(1) a charging step of charging the surface of the image carrier; (2) an exposure step of forming an electrostatic latent image on the image carrier by exposure; (3) an electrostatic latent image formed on the image carrier; (4) A transfer step of transferring the toner image formed on the image carrier onto a recording medium (5) The toner transferred onto the recording medium. Fixing step for thermally fixing the image In the transfer step (4), a toner image laminate in which a white toner image layer and a chromatic or black toner image layer are superimposed is formed on a recording medium. . The toner image stack is preferably formed simultaneously in a so-called one-pass. That is, it is preferable that the white toner image layer and the chromatic or black toner image layer are simultaneously primarily transferred onto the intermediate belt as a laminate.

In the fixing step (5), the white toner image layer and the chromatic or black image layer forming the toner image laminate formed on the recording medium are simultaneously fixed.

In the toner image laminate fixed on the recording medium, it is preferable that the image layer of the white toner is located at either the bottom layer or the top layer. More preferably, the white toner image layer is arranged as the lowermost layer to form the base image.

Here, the term “white toner” refers to CIEL ^* a ^* b ^* measured with a spectrophotometer in accordance with JIS Z 8781-4:2013 on the surface of a transfer material when only the white toner is transferred. A toner having a color (white) in which the lightness L ^* in the color system is 80 or more, and a ^* and b ^* satisfy the conditions of −10≦a ^* ≦10 and −10≦b ^* ≦10, respectively. .

A "chromatic toner" basically means a toner having three attributes of hue, lightness, and saturation, such as yellow toner, magenta toner, and cyan toner.

"Black toner" basically refers to toner that has only lightness without hue and saturation.

In this specification, the chromatic toner and the black toner are also referred to as "color toner". That is, most commonly, since a recording medium (for example, recording paper) is usually white, white is used as a reference color, and chromatic toners and toners that are recognized as being different from the white color are used. For convenience, black toner will be referred to as "colored toner".

Here, the chromatic or black image layer formed by chromatic or black toner particles may be one formed by one type of chromatic or black toner particles, or a secondary chromatic or black image. A layer or a tertiary chromatic or black image layer may be formed of two or more kinds of colored toners.

The average particle diameter dw of the white toner particles and the average particle diameter dc of the chromatic or black toner particles used in the present invention each refer to a volume-based median diameter (d ₅₀ ).

The volume-based median diameter (d ₅₀ ) of white toner particles and chromatic or black toner particles was measured using a computer equipped with data processing software "Software V3.51" in "Multisizer 3" (manufactured by Beckman Coulter, Inc.). It is measured and calculated using a measuring device connected to the system.

Specifically, 0.02 g of toner particles is added to 20 mL of a surfactant solution (for example, a surfactant solution obtained by diluting a neutral detergent containing a surfactant component with pure water 10 times for the purpose of dispersing the toner particles). After the addition and familiarization, ultrasonic dispersion is performed for 1 minute to prepare a toner particle dispersion, and this toner particle dispersion is placed in a beaker containing "ISOTON II" (manufactured by Beckman Coulter, Inc.) in a sample stand. , pipet until the indicated concentration on the measuring device is 8%. Here, by using this concentration range, it is possible to obtain reproducible measured values. Then, in the measuring device, the frequency value is calculated with the measured particle count number of 25,000 and the aperture diameter of 100 μm, and the particle diameter of 50% from the largest volume integrated fraction is taken as the volume-based median diameter.

The average particle diameter dw of the white toner particles according to the present invention is 12 .mu.m. It is characterized by being within the range of 0 to 18.0 μm. The average grain size dw is 12 . If it is less than 0 μm, the difference in particle size from the chromatic or black toner particles becomes small, and the occurrence of white turbidity (mixed colors) cannot be suppressed. If the average particle size dw exceeds 18.0 μm, the transfer efficiency will be low and the hiding rate will also be low . It is preferably within the range of 14.0 to 16.0 μm.

The average particle diameter dc of the chromatic or black toner particles is in the range of 4.0 to 8.0 μm. If the average particle size dc is less than 4.0 μm, the transfer efficiency and the image forming efficiency are low. If the average particle diameter dc exceeds 8.0 μm, the image quality of halftones deteriorates, and the image quality of fine lines and dots deteriorates. It is preferably within the range of 6.0 to 8.0 μm.

The difference (dw-dc) between the average particle diameter dw and the average particle diameter dc is 5.9-8 . It is characterized by being within the range of 0 μm. If the thickness is less than 5.9 μm, when an image layer of a chromatic or black toner and an image layer of a white toner are overlaid, the white toner particles and the chromatic or black toner particles tend to mix on the intermediate transfer belt, resulting in color mixture. occurs and the saturation or contrast is reduced .

The coefficient of variation (CV value) in the particle size distribution of the white toner particles and the chromatic or black toner particles is preferably within the range of 20 to 30%, from the viewpoint of further suppressing mixing between the toner particles. preferable. The coefficient of variation in the volume-based particle size distribution of toner particles is calculated from the following equation.

Coefficient of variation (CV value) (%) = (S2/Dn) x 100
(In the formula, S2 indicates the standard deviation in the volume-based particle size distribution, and Dn indicates the average particle size on the volume-based basis.)
The average particle size of the toner particles is controlled by the concentration of the coagulant used, the amount of the organic solvent added, the fusion time, the composition of the binder resin, etc. can do. When the volume-based median diameter is within the above range, the transfer efficiency is increased, the image quality of halftones is improved, and the image quality of fine lines and dots is improved.

Each component of the present invention will be described below.

[1] White toner and chromatic or black toner The white toner used in the electrophotographic image forming method of the present invention contains at least a binder resin and a white colorant (hereinafter also referred to as a "white colorant"). It is configured. Furthermore, if necessary, other additives such as release agents and external additives may be included. On the other hand, the chromatic or black toner contains a binder resin and a colored coloring agent other than white (hereinafter also referred to as "colored coloring agent"). Furthermore, if necessary, other additives such as release agents and external additives may be included. Note that the chromatic color means a color other than white (for example, yellow, magenta, cyan, etc.).

[1.1] Colorant The white toner according to the present invention is characterized by being a white toner containing at least a binder resin and a white colorant.

Colorants for white toners include inorganic pigments (for example, titanium white, zinc white, titanium strontium white, heavy calcium carbonate, light calcium carbonate, titanium dioxide, aluminum hydroxide, satin white, talc, calcium sulfate, barium sulfate, , zinc oxide, magnesium oxide, magnesium carbonate, amorphous silica, colloidal silica, white carbon, kaolin, calcined kaolin, delaminated kaolin, aluminosilicate, sericite, bentonite, smexite, etc.), or organic pigments (e.g., polystyrene resin particles, urea formalin resin particles, etc.).

Among these, in the present invention, rutile-type crystal titanium oxide and anatase-type crystal titanium oxide are particularly preferred because of their high whiteness. The use of titanium oxide having a particle size in the range of 10 to 1000 nm is preferable because a white toner with high pigment dispersibility can be obtained. Among them, it is preferable to use rutile-type crystal titanium oxide from the viewpoint of concealability.

In order to stabilize the electrostatic properties of the toner, the electrical resistivity of the pigment used as the colorant is preferably in the range of 1×10 ⁸ to 1×10 ¹² Ω·cm.

By treating the surface of the pigment with, for example, a silane coupling agent, silicone oil, a fatty acid such as stearic acid, an alcohol, or an amine such as trimethanolamine, both extremely high pigment dispersibility and toner charging stability can be achieved. Easy to implement.

The content of the colorant is preferably in the range of 20 to 170 parts by mass, more preferably 40 to 80 parts by mass, and even more preferably 50 to 70 parts by mass with respect to 100 parts by mass of the binder resin in the toner particles. part range.

The chromatic or black toner according to the present invention is also characterized by being a toner containing at least a binder resin and a colored colorant.

As a yellow colorant for a yellow toner, C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, etc., and C.I. I. Pigment Yellow 14, Pigment Yellow 17, Pigment Yellow 74, Pigment Yellow 93, Pigment Yellow 94, Pigment Yellow 138, Pigment Yellow 155, Pigment Yellow 180, Pigment Yellow 185, etc., and mixtures thereof.

As a magenta colorant for a magenta toner, C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, etc., and C.I. I. Pigment Red 5, Pigment Red 48:1, Pigment Red 53:1, Pigment Red 57:1, Pigment Red 122, Pigment Red 139, Pigment Red 144, Pigment Red 149, Pigment Red 166, Pigment Red 177, Pigment Red 178, Pigment Red 222, etc. Mixtures can also be used.

As a cyan colorant for a cyan toner, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95, etc., C.I. I. Pigment Blue 1, Pigment Blue 7, Pigment Blue 15:3, Pigment Blue 18:3, Pigment Blue 60, Pigment Blue 62, Pigment Blue 66, Pigment Blue 76, etc. can be used.

Orange colorants for orange toners include C.I. I. Solvent Orange 63, 68, 71, 72, 78, etc., and C.I. I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, 71, etc. can be used.

As a green colorant for green, C.I. I. Solvent Green 3, 5, 28, etc., and C.I. I. Pigment Green 7 or the like can be used.

As a colorant for black toner, carbon black, magnetic material, iron-titanium composite oxide black, etc. can be used, and as carbon black, channel black, furnace black, acetylene black, thermal black, lamp black, etc. can be used. Available. Ferrite, magnetite, etc. can be used as the magnetic material.

[1.2] Binder Resin The binder resin used in the toner particles according to the present invention preferably contains an amorphous resin and a crystalline polyester resin.

<Crystalline polyester resin>
The crystalline polyester resin is a known polyester resin obtained by a polycondensation reaction of a dihydric or higher carboxylic acid (polyhydric carboxylic acid component) and/or hydroxycarboxylic acid and a dihydric or higher alcohol (polyhydric alcohol component). Among them, in differential scanning calorimetry (DSC), it refers to a resin that has a clear melting peak instead of a stepwise endothermic change. A clear melting peak is, specifically, a DSC curve obtained by differential scanning calorimetry of the above-mentioned crystalline polyester resin alone, in which the half width of the melting peak in the second heating process is within 15 ° C. means peak.

The melting point of the crystalline polyester resin is preferably in the range of 65-85°C, more preferably in the range of 75-85°C. When the melting point of the crystalline polyester resin is within the above range, sufficient low-temperature fixability and excellent image storability can be obtained. The melting point of the crystalline polyester resin can be controlled by the resin composition. Here, the melting point of the crystalline polyester resin is the peak top temperature of the melting peak in the second heating process in the DSC curve obtained by differential scanning calorimetry of the crystalline polyester resin alone. When a plurality of melting peaks exist in the DSC curve, the peak top temperature of the melting peak with the largest endothermic amount is taken as the melting point.

The melting point (Tm) of the crystalline polyester resin is the peak top temperature of the endothermic peak, and can be measured by DSC using Diamond DSC (manufactured by PerkinElmer). Specifically, the sample was placed in an aluminum pan KITNo. B0143013, set in a sample holder of a thermal analysis apparatus Diamond DSC (manufactured by PerkinElmer), and change the temperature in the order of heating, cooling, and heating. The temperature was raised from room temperature (25 ° C.) during the first heating, from 0 ° C. during the second heating, to 150 ° C. at a rate of 10 ° C./min, and maintained at 150 ° C. for 5 minutes. The temperature is lowered from 150° C. to 0° C. at a temperature lowering rate of° C./min, and the temperature of 0° C. is maintained for 5 minutes. The peak top temperature of the endothermic peak in the endothermic curve obtained during the second heating is measured as the melting point.

A polyvalent carboxylic acid component for forming a crystalline polyester resin is a compound containing two or more carboxy groups in one molecule. Specifically, for example, saturated aliphatic dicarboxylic acids such as succinic acid, sebacic acid and dodecanedioic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid; Trivalent or higher polyvalent carboxylic acids such as trimellitic acid and pyromellitic acid; and anhydrides of these carboxylic acid compounds or alkyl esters having 1 to 3 carbon atoms. A saturated aliphatic dicarboxylic acid is preferably used as the polyvalent carboxylic acid component for forming the crystalline polyester resin. These may be used individually by 1 type, and may be used in combination of 2 or more type.

A polyhydric alcohol component for forming a crystalline polyester resin is a compound containing two or more hydroxy groups in one molecule. Specifically, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7- Aliphatic diols such as heptanediol, 1,8-octanediol, neopentyl glycol, and 1,4-butenediol; trihydric or higher polyhydric alcohols such as glycerin, pentaerythritol, trimethylolpropane, and sorbitol; . As the polyhydric alcohol component for forming the crystalline polyester resin, it is preferable to use an aliphatic diol. These may be used individually by 1 type, and may be used in combination of 2 or more type.

The method for producing the crystalline polyester resin is not particularly limited, and it can be produced using a general polyester polymerization method in which the above-described polycarboxylic acid and polyhydric alcohol are reacted in the presence of a catalyst. It is preferable to use the polycondensation method or the transesterification method properly depending on the type of the monomer.

Linear aliphatic hydroxycarboxylic acids can also be used in combination with the polyhydric carboxylic acids and/or polyhydric alcohols. Linear aliphatic hydroxycarboxylic acids for forming crystalline polyester resins include 5-hydroxypentanoic acid, 6-hydroxyhexanoic acid, 7-hydroxypentanoic acid, 8-hydroxyoctanoic acid, 9-hydroxynonanoic acid, 10 -Hydroxydecanoic acid, 12-hydroxydodecanoic acid, 14-hydroxytetradecanoic acid, 16-hydroxyhexadecanoic acid, 18-hydroxyoctadecanoic acid: and lactone compounds obtained by cyclization of these hydroxycarboxylic acids, or alcohols having 1 to 3 carbon atoms and alkyl esters with. These may be used individually by 1 type, and may be used in combination of 2 or more type.

Moreover, when forming a crystalline polyester resin, it is preferable to use a polyhydric carboxylic acid and a polyhydric alcohol component because the reaction can be easily controlled and a resin having a desired molecular weight can be obtained.

Catalysts that can be used for the production of crystalline polyester resins include, for example, titanium catalysts such as titanium tetraethoxide, titanium tetrapropoxide, titanium tetraisopropoxide and titanium tetrabutoxide, dibutyltin dichloride, dibutyltin oxide and diphenyltin oxide. and tin catalysts such as

The use ratio of the polyhydric carboxylic acid component and the polyhydric alcohol component is the equivalent ratio between the hydroxy group [-(OH)] of the polyhydric alcohol component and the carboxy group [-(COOH)] of the polyhydric carboxylic acid component. [-(OH)]/[-(COOH)] is preferably in the range of 1.5/1 to 1/1.5, more preferably 1.2/1 to 1/1.2.

The crystalline polyester resin preferably has an acid value in the range of 5 to 30 mgKOH/g, more preferably 10 to 25 mgKOH/g, still more preferably 15 to 25 mgKOH/g. The acid number is the mass in mg of potassium hydroxide (KOH) required to neutralize the acid contained in 1 g of sample. The acid value of the resin is measured by the following procedure according to JIS K 0070-1992.

<Method for measuring acid value of resin>
(Reagent preparation)
A phenolphthalein solution is prepared by dissolving 1.0 g of phenolphthalein in 90 mL of ethyl alcohol (95% by volume) and adding ion-exchanged water to bring the total volume to 100 mL. 7 g of JIS special grade potassium hydroxide is dissolved in 5 mL of deionized water, and ethyl alcohol (95% by volume) is added to make 1 liter. The mixture is placed in an alkali-resistant container so as not to come in contact with carbon dioxide gas, and left for 3 days, then filtered to prepare a potassium hydroxide solution. Orientation follows the description of JIS K 0070-1992.

(Main test)
2.0 g of the pulverized sample is accurately weighed in a 200 mL Erlenmeyer flask, 100 mL of a mixed solution of toluene/ethanol (toluene:ethanol is 2:1 in volume ratio) is added, and dissolved over 5 hours. Next, a few drops of the prepared phenolphthalein solution are added as an indicator, and titration is performed using the prepared potassium hydroxide solution. The end point of the titration is when the light red color of the indicator continues for about 30 seconds.

(blank test)
The same operation as in the main test is performed except that no sample is used (that is, only a mixed solution of toluene/ethanol (toluene:ethanol is 2:1 in volume ratio) is used).

The acid value is calculated by substituting the titration results of the main test and the blank test into the following formula (1).

Formula (1) A = [(CB) x f x 5.6]/S
A: Acid value (mgKOH/g)
B: Amount of potassium hydroxide solution added during blank test (mL)
C: Amount (mL) of potassium hydroxide solution added during this test
f: factor of 0.1 mol/liter potassium hydroxide ethanol solution S: mass of sample (g)
The molecular weight of the crystalline polyester resin has a weight average molecular weight (Mw) calculated from the molecular weight distribution measured by gel permeation chromatography (GPC) in the range of 5000 to 50000, and a number average molecular weight (Mn) in the range of 1500 to 25000. is preferably within the range of

<Method for measuring molecular weight of resin>
Molecular weight measurement by GPC is performed as follows.

That is, using an apparatus "HLC-8320" (manufactured by Tosoh Corporation) and columns "TSKgel guardcolumn SuperHZ-L" and "TSKgel SuperHZM-M" (manufactured by Tosoh Corporation), while maintaining the column temperature at 40 ° C., as a carrier solvent Tetrahydrofuran (THF) is flowed at a flow rate of 0.2 mL/min. A measurement sample (crystalline polyester resin) is dissolved in tetrahydrofuran to a concentration of 1 mg/mL under the dissolution conditions of treating with an ultrasonic disperser for 5 minutes at room temperature, and then a membrane filter with a pore size of 0.2 μm. to obtain a sample solution. 10 μL of this sample solution is injected into the device together with the above carrier solvent, detected using a refractive index detector (RI detector), and the molecular weight distribution of the measurement sample is measured using monodisperse polystyrene standard particles. Calculate using a line.

As standard polystyrene samples for calibration curve measurement, Pressure Chemical's molecular weights of 6×10 ² , 2.1×10 ³ , 4×10 ³ , 1.75×10 ⁴ , 5.1×10 ⁴ , 1 Using 1×10 ⁵ , 3.9×10 ⁵ , 8.6×10 ⁵ , 2×10 ⁶ , and 4.48×10 ⁶ , standard polystyrene samples of at least 10 points are measured, and a calibration curve is obtained. to create

The content of the crystalline polyester resin in the binder resin is preferably in the range of 5 to 20% by mass, more preferably in the range of 5 to 10% by mass. When the content of the crystalline polyester resin in the binder resin is 5% by mass or more, sufficient low-temperature fixability can be reliably obtained. Further, since the content of the crystalline polyester resin in the binder resin is 20% by mass or less, the crystalline polyester resin can be reliably introduced into the toner during the production of the toner.

As the crystalline polyester resin, a styrene/acrylic modified crystalline polyester resin in which a styrene/acrylic polymerized segment and a crystalline polyester polymerized segment are bonded may be used.

Here, "styrene-acrylic modified crystalline polyester resin" means chemically bonding a styrene-acrylic copolymer molecular chain (styrene-acrylic polymerized segment) to a crystalline polyester molecular chain (crystalline polyester polymerized segment). Also, it is a resin composed of polyester molecules with a block copolymer structure.

A method for forming the crystalline polyester polymer segment is not particularly limited. The specific types of the polyhydric carboxylic acid and polyhydric alcohol used for forming the polymerized segment and the polycondensation conditions for these monomers are the same as described above, so the description is omitted here.

On the other hand, the styrene/acrylic polymerized segment constituting the styrene/acrylic modified crystalline polyester resin is formed by addition polymerization of at least a styrene monomer and a (meth)acrylate monomer. The styrene monomer and (meth)acrylic acid ester monomer used are not particularly limited, but one or more selected from the following may be used, for example.

(1) Styrene monomer styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert- butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene and derivatives thereof;
(2) (meth)acrylate monomers methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate (n-butyl (meth)acrylate), isopropyl (meth)acrylate , isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-stearyl (meth)acrylate, dodecyl (meth)acrylate , phenyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate and derivatives thereof;
In this specification, "(meth)acrylic acid" includes both acrylic acid and methacrylic acid.

The styrene/acrylic polymerized segment may be formed by further using the following monomers in addition to the above monomers.

(3) vinyl esters vinyl propionate, vinyl acetate, vinyl benzoate, etc.;
(4) vinyl ethers vinyl methyl ether, vinyl ethyl ether and the like;
(5) vinyl ketones vinyl methyl ketone, vinyl ethyl ketone, vinyl hexyl ketone, etc.;
(6) N-vinyl compounds N-vinylcarbazole, N-vinylindole, N-vinylpyrrolidone and the like;
(7) Other monomers Vinyl compounds such as vinylnaphthalene and vinylpyridine, acrylic acid and methacrylic acid derivatives such as acrylonitrile, methacrylonitrile and acrylamide.

The method for forming the styrene/acrylic polymerized segment is not particularly limited. A method of polymerizing by a known polymerization method such as polymerization, solution polymerization, emulsion polymerization, mini-emulsion method, dispersion polymerization method, and the like can be mentioned.

The content of the crystalline polyester polymerized segment in the styrene/acrylic-modified crystalline polyester resin is not particularly limited, but is preferably in the range of 60 to 99% by mass with respect to 100% by mass of the styrene/acrylic-modified polyester resin. , more preferably in the range of 70 to 98% by mass.

The content ratio of the styrene-acrylic polymerized segment in the styrene-acrylic modified crystalline polyester resin (hereinafter also referred to as "styrene-acrylic modified amount") is not particularly limited, but the styrene-acrylic modified crystalline polyester resin is 100% by mass. On the other hand, it is preferably in the range of 1 to 40% by mass, more preferably in the range of 2 to 30% by mass.

Specifically, the amount of styrene/acrylic modification is the total mass of the resin material used to synthesize the styrene/acrylic modified crystalline polyester resin, that is, the unmodified crystalline polyester resin that becomes the crystalline polyester polymerized segment. For the total mass of the total mass of the monomers for synthesis, the styrene monomers and (meth)acrylic acid ester monomers that form the styrene/acrylic polymerization segment, and the two reactive monomers that bind them together , the ratio of the total mass of styrene monomers and (meth)acrylic acid ester monomers.

Here, the "dually reactive monomer" is a monomer that bonds the styrene/acrylic polymerized segment and the crystalline polyester polymerized segment, and the hydroxy group, carboxyl group, and epoxy group that form the crystalline polyester polymerized segment. , a group selected from a primary amino group and a secondary amino group, and an ethylenically unsaturated group forming a styrene-acrylic polymer segment in the molecule.

Specific examples of the bi-reactive monomer include acrylic acid, methacrylic acid, fumaric acid, maleic acid, etc., and esters of these hydroxyalkyl (having 1 to 3 carbon atoms) may also be used. However, from the viewpoint of reactivity, acrylic acid, methacrylic acid or fumaric acid is preferable. The styrene/acrylic polymerized segment and the crystalline polyester polymerized segment are linked via this bi-reactive monomer.

From the viewpoint of improving low-temperature fixability, the amount of both reactive monomers to be used is preferably in the range of 1 to 20% by mass based on 100% by mass of the total amount of monomers constituting the styrene/acrylic polymerized segment.

The method for producing the styrene/acrylic modified crystalline polyester resin is particularly limited as long as it is a method capable of forming a polymer having a structure in which the crystalline polyester polymerized segment and the styrene/acrylic polymerized segment are chemically bonded. not a thing Specific methods for producing the styrene/acrylic-modified crystalline polyester resin include, for example, the following methods.

(A) A crystalline polyester polymerized segment is polymerized in advance, a bi-reactive monomer is reacted with the crystalline polyester polymerized segment, and a styrene monomer for forming a styrene-acrylic polymerized segment and ( A method of forming a styrene-acrylic polymerized segment by reacting a meth)acrylate monomer;
(B) A styrene/acrylic polymerized segment is polymerized in advance, a bi-reactive monomer is reacted with the styrene/acrylic polymerized segment, and a polyvalent carboxylic acid and a polyvalent carboxylic acid for forming a crystalline polyester polymerized segment are added. A method of forming a crystalline polyester polymerized segment by reacting a hydric alcohol;
(C) A method in which a crystalline polyester polymerized segment and a styrene/acrylic polymerized segment are polymerized in advance and then reacted with a bi-reactive monomer to bond the two.

Among the forming methods (A) to (C) above, the method (A) is preferable from the viewpoint of simplifying the production process.

<Amorphous resin>
In the present invention, amorphous polyester resins and amorphous vinyl resins can be used as the amorphous resin.

An amorphous resin means a resin in which no clear endothermic peak is observed in differential scanning calorimetry (DSC). In other words, it usually does not have a melting point (clear endothermic peak in a DSC curve measured using a differential scanning calorimeter (DSC) measuring apparatus) and has a relatively high glass transition point (Tg). More specifically, the Tg of the amorphous resin measured by a differential scanning calorimeter is preferably in the range of 35 to 70°C, more preferably in the range of 50 to 65°C. When the Tg of the amorphous resin is 35° C. or higher, the toner can be given sufficient thermal strength and sufficient heat-resistant storage stability can be obtained. Further, when the Tg of the amorphous resin is 70° C. or less, sufficient low-temperature fixability can be reliably obtained.

The Tg of the amorphous resin is measured by the method (DSC method) specified in ASTM (American Society for Testing and Materials Standard) D3418-82. That is, 4.5 mg of a measurement sample (amorphous resin) is accurately weighed to two decimal places, sealed in an aluminum pan, and set in a sample holder of a differential scanning calorimeter "DSC8500" (manufactured by PerkinElmer). . As a reference, an empty aluminum pan was used, and the temperature was controlled from -10 to 120°C, with a temperature increase rate of 10°C/min and a temperature decrease rate of 10°C/min. Analysis is performed based on the data in the second heating. The glass transition point is defined as the intersection point between the extended line of the baseline before the rise of the first endothermic peak and the tangent line indicating the maximum slope from the rise of the first endothermic peak to the apex of the peak.

The molecular weight of the amorphous resin measured by gel permeation chromatography (GPC) is preferably in the range of 1,500 to 25,000 in number average molecular weight (Mn) and 10,000 to 80,000 in weight average molecular weight (Mw). When the molecular weight of the amorphous resin is within the above range, both sufficient low-temperature fixability and excellent heat-resistant storage stability can be reliably obtained. The molecular weight measurement of the amorphous resin by GPC is carried out in the same manner as described above, except that the amorphous resin is used as the measurement sample.

(amorphous polyester resin)
Amorphous polyester resins are polyester resins other than crystalline polyester resins.

The acid value of the amorphous polyester resin is preferably in the range of 5-45 mgKOH/g, more preferably in the range of 5-30 mgKOH/g. An acid value of 45 mgKOH/g or less is preferable in that the hygroscopicity does not increase and the chargeability can be prevented from decreasing even under high humidity. Further, when the concentration is 5 mgKOH/g or more, the dispersion stability of the resin particles can be maintained, and the toner can be easily produced, which is preferable. The acid value can be obtained in the same manner as described in the description of the crystalline polyester resin.

The amorphous polyester resin may be one type of amorphous polyester resin, or may be a mixture of two or more types of amorphous polyester resins.

Known polyester resins can be used as the amorphous polyester resin. An amorphous polyester resin is synthesized from a polyhydric carboxylic acid component and a polyhydric alcohol component. As the amorphous polyester resin, a commercially available product or a synthesized product may be used.

Examples of polyhydric alcohol components include ethylene glycol, propylene glycol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, neo Pentyl glycol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, bisphenol A, hydrogenated bisphenol A, BPA-PO (propylene oxide n-mol adduct of bisphenol A), BPA-EO (bisphenol A diols such as ethylene oxide (n moles adduct of ) can be used. Further, for example, trihydric or higher alcohols such as glycerin, sorbitol, 1,4-sorbitan and trimethylolpropane can be used. Among these, bisphenol A, hydrogenated bisphenol A, BPA-PO or BPA-EO are preferable, BPA-PO or BPA-EO are more preferable, 2 mol propylene oxide adduct of bisphenol A or bisphenol More preferably, it is an ethylene oxide 2-mol adduct of A. These may be used individually by 1 type, and may be used in combination of 2 or more type.

Examples of polyvalent carboxylic acid components include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid and naphthalene dicarboxylic acid; aliphatic saturated dicarboxylic acids such as 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, and 1,18-octadecanedicarboxylic acid; maleic acid, Aliphatic unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, itaconic anhydride, citraconic acid, citraconic acid and mesaconic acid; alicyclic polyvalent carboxylic acids such as cyclohexanedicarboxylic acid; salts and lower alkyl esters thereof and acid anhydrides. Among these, aromatic dicarboxylic acids, salts thereof, lower alkyl esters or acid anhydrides are preferable, and terephthalic acid, phthalic acid, salts thereof, lower alkyl esters or acid anhydrides are more preferable. One of these polyvalent carboxylic acid components may be used alone, or two or more thereof may be used in combination.

By containing a carboxylic acid having a valence of 3 or more as a polyvalent carboxylic acid component, the polymer chain can take a crosslinked structure, and by taking the crosslinked structure, crystals once compatible with the amorphous polyester resin are formed. It is possible to further obtain the effect of fixing the flexible polyester resin and making it difficult to separate.

Examples of trivalent or higher carboxylic acids include trimellitic acids such as 1,2,4-benzenetricarboxylic acid and 1,2,5-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, hemimellitic acid, trimesic acid, merophanic acid, prenitic acid, pyromellitic acid, mellitic acid, 1,2,3,4-butanetetracarboxylic acid, salts thereof, lower alkyl esters and acid anhydrides, trimellitic acid, Salts, lower alkyl esters or anhydrides thereof are particularly preferred.

When a dicarboxylic acid and a tricarboxylic or higher carboxylic acid are contained as the polycarboxylic acid component, the amount of the tricarboxylic or higher carboxylic acid added is 1 to 30 mol with respect to the total number of moles of the polycarboxylic acid component. %, more preferably 5 to 20 mol %, and preferably 10 to 15 mol %.

In addition to the compounds described above, the polyvalent carboxylic acid component may also contain a dicarboxylic acid component having a sulfonic acid group.

The production of the amorphous polyester resin is not particularly limited, but the polymerization temperature is set to 180 to 260 ° C., the polycondensation reaction of the polyhydric carboxylic acid component and the polyhydric alcohol component is performed, and if necessary, the pressure in the reaction system is reduced. It is preferable to carry out the reaction while removing water and alcohol generated during the condensation. The polymerization time is not particularly limited, but preferably 1 to 10 hours, more preferably 2 to 6 hours.

If the polymerizable monomers (polycarboxylic acid component, polyhydric alcohol component) are not soluble or compatible at the reaction temperature, a solvent with a high boiling point may be added as a solubilizing agent to dissolve them. The polycondensation reaction is carried out while distilling off the solubilizing agent. If a polymerizable monomer with poor compatibility is present in the copolymerization reaction, the polymerizable monomer with poor compatibility, the polymerizable monomer, and the acid or alcohol to be polycondensed are condensed in advance. polycondensation together with the main component.

Examples of catalysts that can be used in the production of amorphous polyester resins include alkali metal compounds containing sodium, lithium, etc.; group 2 metal compounds containing magnesium, calcium, etc.; zinc, manganese, antimony, titanium, tin. , zirconium, germanium and the like; phosphorous compounds; phosphoric acid compounds; and amine compounds. These may be used individually by 1 type, and may be used in combination of 2 or more type. Among these, metal compounds containing zinc, manganese, antimony, titanium, tin, zirconium, germanium, etc. are preferable from the viewpoint of making Mw/Mn smaller, and metal compounds of tin (tin-based catalysts). is more preferable. Examples of tin-based catalysts include, but are not limited to, dibutyltin oxide.

The amount of the catalyst to be added is not particularly limited, but it is preferably in the range of 0.00001 to 10% by mass with respect to the total amount of the polycarboxylic acid. When the amount of catalyst added increases, the reaction can proceed more reliably, and when the amount of catalyst added decreases, it is more economical.

The content of the amorphous polyester resin is preferably 5 to 30% by mass, more preferably 5 to 20% by mass, based on the total binder resin. Within this range, the resulting toner has excellent anti-blocking properties and low-temperature fixability.

(amorphous vinyl resin)
The amorphous vinyl resin is not particularly limited as long as it is obtained by polymerizing a vinyl compound, and examples thereof include acrylic acid ester resins, styrene-(meth)acrylic acid ester resins, and ethylene/vinyl acetate resins. These may be used individually by 1 type, and may be used in combination of 2 or more type.

Among the above amorphous vinyl resins, styrene/(meth)acrylic acid ester resins (hereinafter also referred to as “styrene/acrylic resins”) are preferred in consideration of plasticity during heat fixing. Therefore, the styrene-acrylic resin as the amorphous vinyl resin will be described below.

A styrene-acrylic resin is formed by addition polymerization of at least a styrene monomer and a (meth)acrylate monomer. The styrene monomer referred to herein includes, in addition to styrene represented by the structural formula of CH ₂ ═CH—C ₆ H ₅ , those having a structure having known side chains and functional groups in the styrene structure. Further, the (meth)acrylic acid ester monomers referred to herein include, in addition to acrylic acid esters and methacrylic acid esters represented by CH ₂ =CHCOOR (R is an alkyl group), acrylic acid ester derivatives and methacrylic acid ester derivatives. It contains an ester having a known side chain or functional group in the structure such as.

Specific examples of styrene monomers and (meth)acrylic acid ester monomers capable of forming styrene-acrylic resins are shown below, but the monomers used in the present invention are limited to the following: is not.

Specific examples of styrene monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene and 2,4-dimethylstyrene. , p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene and the like. These styrene monomers can be used alone or in combination of two or more.

Further, specific examples of (meth)acrylic ester monomers include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-butyl acrylate, isobutyl acrylate, n-octyl acrylate, and 2-ethylhexyl acrylate. , acrylic acid ester monomers such as stearyl acrylate, lauryl acrylate, phenyl acrylate; Examples include methacrylic acid ester monomers such as stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, and the like. These acrylic acid ester monomers or methacrylic acid ester monomers can be used alone or in combination of two or more. That is, forming a copolymer using a styrene monomer and two or more acrylic acid ester monomers, or copolymerizing a styrene monomer and two or more methacrylic acid ester monomers. It is possible either to form a coalescence or to form a copolymer using a combination of styrene monomers and acrylate and methacrylate monomers.

The content of structural units derived from styrene monomers in the styrene-acrylic resin is preferably in the range of 60 to 85% by mass based on the total amount of the styrene-acrylic resin. Further, the content of structural units derived from (meth)acrylic acid ester monomers in the styrene-acrylic resin is preferably in the range of 15 to 40% by mass relative to the total amount of the styrene-acrylic resin.

Furthermore, styrene-acrylic resins include, in addition to the above styrene monomers and (meth)acrylic acid ester monomers, acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid, Compounds having a carboxy group such as alkyl esters and itaconic acid monoalkyl esters; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) A compound having a hydroxy group such as acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, etc. may be addition polymerized.

The content of structural units derived from the above compounds in the styrene-acrylic resin is preferably in the range of 0.1 to 15% by mass relative to the total amount of the styrene-acrylic resin.

The content of the amorphous vinyl resin is preferably in the range of 40 to 95% by mass, more preferably in the range of 60 to 90% by mass, based on the total binder resin. Within this range, the resulting toner has a high degree of freedom in resin design, and charging control is easy.

[1.3] Other constituents <Releasing agent>
The toner according to the present invention may contain a releasing agent. Various known waxes can be used as the release agent.

Specifically, polyolefin waxes such as polyethylene wax and polypropylene wax; branched hydrocarbon waxes such as microcrystalline wax; long-chain hydrocarbon waxes such as paraffin wax and sazol wax; dialkyl such as distearyl ketone; Ketone waxes; carnauba wax, montan wax, behenyl behenate, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerol tribehenate, 1,18-octadecanediol diol ester waxes such as stearate, tristearyl trimellitate and distearyl maleate; and amide waxes such as ethylenediamine behenylamide and tristearylamide trimellitate.

As the release agent, it is preferable to use a release agent that does not have an interaction such as compatibility with the resin constituting the binder resin.

Among these, those having a low melting point, specifically those having a melting point in the range of 60 to 100° C., are preferably used from the viewpoint of releasability during low-temperature fixing. Further, it is preferable to use a release agent having a melting point of about (Mp1-10) to (Mp1+20)° C. relative to the melting point Mp1 of the crystalline polyester resin constituting the binder resin.

The content of the release agent is preferably in the range of 1 to 20 mass %, more preferably in the range of 5 to 20 mass % in the toner. When the content of the releasing agent in the toner is within the above range, both separability and fixability can be reliably achieved.

As a method for introducing the release agent into the toner, particles composed only of the release agent are mixed with amorphous resin particles, crystalline polyester resin particles, etc. in an aqueous medium in the aggregation and fusion steps of the toner production method described later. A method of aggregating and fusing with is mentioned. The release agent particles can be obtained as a dispersion liquid in which the release agent is dispersed in an aqueous medium. A dispersion of release agent particles is prepared by heating an aqueous medium containing a surfactant to a temperature higher than the melting point of the release agent, adding the molten release agent solution, and applying mechanical energy such as mechanical stirring or ultrasonic wave. It can be prepared by applying energy or the like to finely disperse and then cooling.

Further, when the amorphous resin is, for example, a styrene/acrylic resin, the amorphous resin particles (styrene/acrylic resin particles) to be subjected to the aggregating and fusing steps should be mixed in advance with a release agent. The release agent can also be introduced into the toner by

Specifically, a release agent is dissolved in a solution of polymerizable monomers for forming a styrene-acrylic resin. This solution is added to an aqueous medium containing a surfactant, and finely dispersed by applying mechanical energy such as mechanical stirring or ultrasonic energy in the same manner as described above. A dispersion of amorphous resin particles containing a release agent can be prepared by a so-called mini-emulsion polymerization method in which polymerization is carried out at a polymerization temperature of .

<Charge control agent>
Various known compounds can be used as the charge control agent.

The content of the charge control agent is preferably in the range of 0.1 to 10 mass %, more preferably in the range of 1 to 5 mass % in the toner.

<Average Circularity of Toner>
In the toner according to the present invention, the average circularity of individual toner particles constituting the toner should be in the range of 0.930 to 1.000 from the viewpoint of stability of charging characteristics and low-temperature fixability. It is preferably within the range of 0.950 to 0.995. When the average circularity is within the above range, the individual toner particles are less likely to be crushed, contamination of the triboelectrifying member is suppressed, the chargeability of the toner is stabilized, and the image quality of the formed image is high. become a thing.

In the present invention, the average circularity of toner is measured using "FPIA-3000" (manufactured by Sysmex).

Specifically, the sample (toner) was soaked in an aqueous solution containing a surfactant and dispersed by performing an ultrasonic dispersion treatment for 1 minute. In the high-magnification imaging mode, photographing is performed at an appropriate density of 3000 to 10000 HPF detection numbers, the circularity of each toner particle is calculated according to the following formula (T), the circularity of each toner particle is added, It is calculated by dividing by the total number of toner particles.

Formula (T): Circularity = (perimeter of a circle having the same projected area as the particle image)/(perimeter of the projected particle image)
[1.4] Method for producing toner The method for producing the toner (toner particles) according to the present invention is not particularly limited, and known methods such as pulverization, suspension polymerization, emulsion polymerization aggregation, and dispersion polymerization are known. polymerization method.

Among them, the white toner according to the present invention can be either polymerized toner particles or pulverized toner particles. Among them, in order to adjust the coefficient of variation of the particle size distribution to the range of 20 to 30%, it is preferable to adopt the polymerization method, and it is particularly preferable to adopt the emulsion polymerization aggregation method. The emulsion polymerization aggregation method will be described later.

The pulverization method includes, for example, mixing and pulverizing all toner components in predetermined amounts to thoroughly mix all the components, and then pulverize the resulting mixture. Another known method of forming toner powders is by ball milling colorants, resins and solvents and spray drying the toner formulation mixture.

Further, the toner according to the present invention may have a core-shell structure in which the surfaces of core particles made of a core resin are coated with a shell layer made of a shell resin, or may have a single-layer structure. There may be. In the case of a core-shell structure, the shell resin is preferably amorphous polyester resin or amorphous vinyl resin.

The shell is not limited to covering the core particle completely, and the core particle surface may be partly exposed. Since the toner has a core-shell structure, charging stability and heat-resistant storage stability can be obtained.

The core-shell structure can be confirmed by observing the cross-sectional structure of the toner using a known means such as a transmission electron microscope (TEM) or a scanning probe microscope (SPM).

The obtained dried toner particles may be used as the toner as it is, or the toner used in the present invention may be obtained by adding a known external additive by a dry method in which an external additive is added and mixed. .

As a mixing device for the external additive, various known mixing devices such as a Turbular mixer, a Henschel mixer, a Nauta mixer, and a V-type mixer can be used.

Specific examples of the method for producing the toner according to the present invention and the method for producing the yellow toner will be described in detail below. In addition, in the method of manufacturing toner other than yellow toner, such as magenta toner, cyan toner, black toner, and white toner, the method of manufacturing yellow toner can be suitably adopted by changing the coloring agent to be used.

Note that the method for producing the toner according to the present invention is not limited to the following.

<Preparation of aqueous dispersion of colorant particles>
Sodium dodecyl sulfate is stirred and dissolved in ion-exchanged water, a yellow colorant is added, and a dispersion treatment is performed to prepare an aqueous dispersion of colorant particles in which yellow colorant particles are dispersed.

<Preparation of Aqueous Dispersion of Release Agent-Containing Amorphous Vinyl Polymer>
(First polymerization)
Sodium dodecylsulfate and ion-exchanged water are charged into a reaction vessel equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introduction device, and the temperature is raised while stirring under a nitrogen stream to dissolve potassium persulfate in the ion-exchanged water. For example, styrene (St) as a styrene monomer, n-butyl acrylate (BA) as a (meth)acrylic acid ester monomer, a carboxy group [-COOH] or a hydroxy group [-OH ] as a compound containing methacrylic acid (MAA) or the like is added dropwise, and then polymerized by heating and stirring to prepare a dispersion liquid (1) of resin particles.

(Second polymerization)
A reaction vessel equipped with a stirring device, a temperature sensor, a cooling pipe, and a nitrogen introduction device is charged with a solution of polyoxyethylene (2) sodium dodecyl ether sulfate dissolved in ion-exchanged water, and after heating, the resin particles are dispersed. Liquid (1), for example, styrene (St) as a styrene-based monomer, n-butyl acrylate as a (meth)acrylic acid ester monomer, a compound having a carboxy group [-COOH] or a hydroxy group [-OH] As a solution, a solution containing monomers such as methacrylic acid (MAA), n-octyl-3-mercaptopropionate, and a release agent (behenylbehenate (melting point 73°C)) and a release agent is added. are mixed and dispersed to prepare a dispersion containing emulsified particles (oil droplets).

Next, an initiator solution prepared by dissolving potassium persulfate in ion-exchanged water is added to this dispersion, and the system is heated and stirred to carry out polymerization to prepare a dispersion (2) of resin particles.

(Third polymerization)
After ion-exchanged water is added to the resin particle dispersion (2) and mixed well, a solution obtained by dissolving potassium persulfate in ion-exchanged water is added. n-butyl acrylate (BA) as a meth)acrylic ester monomer, methacrylic acid (MAA) as a compound having a carboxy group [-COOH] or a hydroxy group [-OH], n-octyl-3-mercaptopropionate A monomer mixed liquid consisting of, etc. is added dropwise.

After completion of dropping, polymerization is carried out by heating and stirring, followed by cooling to prepare an aqueous dispersion of a releasing agent-containing amorphous vinyl polymer.

<Preparation of aqueous dispersion of crystalline polyester resin>
(Synthesis of crystalline polyester resin)
Raw material monomers and radical polymerization initiators for the addition polymerization resin segment (here, referred to as the styrene/acrylic resin segment) include, for example, styrene, n-butyl acrylate, acrylic acid, polymerization initiators (di-t-butyl per oxide) into the dropping funnel.

In addition, as raw material monomers for the polycondensation resin segment (here, referred to as a crystalline polyester resin segment), for example, sebacic acid, which is an aliphatic dicarboxylic acid, and 1,12-dodecanediol, which is an aliphatic diol, are introduced into nitrogen. Place in a 4-necked flask equipped with a tube, dehydration tube, stirrer and thermocouple and heat to dissolve.

Next, while stirring, the raw material monomers for the addition polymerizable resin segment and the radical polymerization initiator in the dropping funnel are added dropwise, and after aging, unreacted addition polymerizable monomers are removed under reduced pressure.

After that, an esterification catalyst is added, the temperature is raised, the reaction is carried out under normal pressure, and the reaction is further carried out under reduced pressure.

Next, after cooling, the mixture is reacted under reduced pressure to obtain a crystalline polyester resin, which is a hybrid resin.

(Preparation of aqueous dispersion of crystalline polyester resin)
The crystalline polyester resin obtained in the above synthesis example is dissolved in a solvent (eg, methyl ethyl ketone) with stirring. Next, an aqueous sodium hydroxide solution is added to this solution. An emulsified liquid is prepared by adding water dropwise while stirring the solution.

Then, by removing the solvent from this emulsion by distillation, an aqueous dispersion in which the crystalline polyester resin is dispersed can be prepared.

<Preparation of Aqueous Dispersion of Amorphous Polyester Resin>
(Synthesis of amorphous polyester resin)
A reaction vessel equipped with a nitrogen inlet tube, a dehydration tube, a stirrer and a thermocouple is charged with, for example, bisphenol A propylene oxide 2 mol adduct, terephthalic acid, fumaric acid, and an esterification catalyst (e.g., tin octylate), After condensation polymerization reaction, further reaction under reduced pressure, and cooling, for example, acrylic acid as a compound having a carboxy group [-COOH] or a hydroxy group [-OH], styrene as a styrene monomer, (meth) acrylic A mixture of butyl acrylate as an acid ester monomer and a polymerization initiator (eg, di-t-butyl peroxide) is added dropwise. By removing a compound having a carboxy group [-COOH] or a hydroxy group [-OH], a styrene monomer, and a (meth)acrylic acid ester monomer, the vinyl resin segment and the crystalline polyester resin segment are bonded. Synthesize an amorphous polyester resin.

(Preparation of aqueous dispersion of amorphous polyester resin)
The amorphous polyester resin obtained in the above synthesis example is dissolved in a solvent (eg, methyl ethyl ketone) with stirring. Next, an aqueous sodium hydroxide solution is added to this solution. An emulsified liquid is prepared by adding water dropwise while stirring the solution.

Then, by removing the solvent from this emulsion by distillation, an aqueous dispersion in which the amorphous polyester resin is dispersed can be prepared.

<Production of yellow toner>
An aqueous dispersion of a release agent-containing amorphous vinyl polymer and ion-exchanged water are charged into a reaction vessel equipped with a stirring device, a temperature sensor, and a cooling pipe, and then an aqueous sodium hydroxide solution is added to adjust the pH. .

After that, an aqueous dispersion of colorant particles is added, and then an aqueous solution of magnesium chloride is added to prepare a mixed solution. The temperature of this mixed solution is raised, and an aqueous dispersion of a crystalline polyester resin is added to promote aggregation. When the desired particle size is obtained, an aqueous dispersion of the amorphous polyester resin is added, an aqueous solution of sodium chloride dissolved in ion-exchanged water is added to stop particle growth, and then heated and stirred. , to promote coalescence of the particles. Then cool.

Next, solid-liquid separation, washing, and drying are performed to obtain yellow toner particles.

A yellow toner can be produced by adding an external additive to the obtained toner particles.

(Manufacturing method of yellow developer)
A yellow developer can be produced by adding and mixing the following external additives to the yellow toner.

<External Additives>
An external additive is attached to the surface of the toner base particles for the purpose of controlling fluidity and chargeability.

As the external additive, conventionally known metal oxide particles can be used, such as silica particles, titanium oxide particles, alumina particles, zirconia particles, zinc oxide particles, chromium oxide particles, cerium oxide particles, and antimony oxide particles. , tungsten oxide particles, tin oxide particles, tellurium oxide particles, manganese oxide particles, and boron oxide particles. These may be used alone or in combination of two or more.

Regarding silica particles, silica particles produced by a sol-gel method can be used. Silica particles produced by the sol-gel method are characterized by a narrow particle size distribution, and are therefore preferable in terms of suppressing variations in adhesion strength.

The number average primary particle size of the silica particles formed by the sol-gel method is preferably in the range of 70 to 150 nm. Silica particles having a number-average primary particle size within this range have a larger particle size than other external additives, so they play a role as a spacer. Stirring and mixing in the machine has the effect of preventing embedding in the toner base particles, and also has the effect of preventing the toner base particles from being fused together.

Further, organic particles such as homopolymers such as styrene and methyl methacrylate, and copolymers thereof may be used as an external additive.

The metal oxide particles used as the external additive are preferably those whose surfaces have been subjected to hydrophobizing treatment with a known surface treatment agent such as a coupling agent. As the surface treating agent, dimethyldimethoxysilane, hexamethyldisilazane (HMDS), methyltrimethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane and the like are preferable.

Silicone oil can also be used as the surface treatment agent. Specific examples of silicone oils include cyclic compounds such as organosiloxane oligomers, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, tetramethylcyclotetrasiloxane, and tetravinyltetramethylcyclotetrasiloxane; Branched organosiloxanes may be mentioned. In addition, highly reactive silicone oil modified at least at the terminals may be used by introducing modifying groups into the side chain, one end, both ends, one end of the side chain, both ends of the side chain, or the like. Examples of the modified group include alkoxy group, carboxyl group, carbinol group, higher fatty acid modified group, phenol group, epoxy group, methacryl group, amino group and the like, but are not particularly limited. Moreover, for example, it may be a silicone oil having several types of modifying groups such as amino/alkoxy modification.

In addition, dimethyl silicone oil, the above-mentioned modified silicone oil, and other surface treatment agents may be used for mixed treatment or combined treatment. Examples of treatment agents used in combination include silane coupling agents, titanate coupling agents, aluminate coupling agents, various silicone oils, fatty acids, fatty acid metal salts, esters thereof, and rosin acid. .

A lubricant may be used as an external additive to further improve cleaning properties and transfer properties. For example, the following salts of zinc, aluminum, copper, magnesium, calcium, etc. of stearate, salts of zinc, manganese, iron, copper, magnesium, etc. of oleate, salts of zinc, copper, magnesium, calcium, etc. of palmitate, Metal salts of higher fatty acids such as zinc and calcium linoleic acid salts and zinc and calcium ricinoleic acid salts are included.

The total amount of these external additives added is preferably in the range of 0.1 to 10% by mass, more preferably in the range of 1 to 5% by mass, relative to 100 parts by mass of the toner base particles.

[2] Image Forming Apparatus [2.1] Apparatus The white toner and chromatic or black toner according to the present invention can be used in a general electrophotographic image forming method, and such an image forming method is applicable. As an image forming apparatus, for example, a photoreceptor which is an electrostatic image bearing member, a charging means for applying a uniform potential to the surface of the photoreceptor by corona discharge having the same polarity as the toner, and a uniformly charged image forming apparatus. exposing means for forming an electrostatic charge image on the surface of the photoreceptor by performing image exposure based on image data; An apparatus having developing means for forming the toner image, transferring means for transferring the toner image onto a transfer material via an intermediate transfer body as necessary, and fixing means for heat-fixing the toner image on the transfer material can be used.

Further, the toner according to the present invention can be suitably used in a relatively low-temperature image forming apparatus in which the fixing temperature (surface temperature of the fixing member) is 130 to 200.degree.

Further, the toner according to the present invention can be suitably used in an image forming apparatus having a fixing speed (paper feeding speed) of 50 to 700 mm/sec, preferably 300 to 700 mm/sec.

[2.2] Recording Medium In the electrophotographic image forming method of the present invention, the white toner image and the chromatic or black toner image of the present invention are finally transferred and formed on a recording medium.

The recording medium is not particularly limited, and for example, plain paper from thin paper to thick paper, high-quality paper, coated printing paper such as art paper or coated paper, commercially available paper such as Japanese paper and postcard paper; Resin films such as polypropylene (PP) film, polyethylene terephthalate (PET) film, triacetyl cellulose (TAC) film; cloth, etc., but not limited to these. Moreover, the color of the recording medium is not particularly limited, and recording media of various colors can be used.

Although the embodiments of the present invention have been specifically described above, the embodiments of the present invention are not limited to the above examples, and various modifications can be made.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these. In the examples, "parts" or "%" are used, but "mass parts" or "mass%" are indicated unless otherwise specified.

<Preparation of Toner and Developer>
(Preparation of magenta toner)
0.90 kg of sodium n-dodecylsulfate and 10.0 L of pure water were added and dissolved with stirring. C.I. I. After gradually adding 1.20 kg of Pigment Red 122 and stirring well for 1 hour, a sand grinder (medium-type dispersing machine) was used to continuously disperse the mixture for 20 hours. This was designated as "colorant dispersion liquid 1". A solution composed of 0.055 kg of sodium dodecylbenzenesulfonate and 4.0 L of ion-exchanged water was used as "anionic surfactant solution A".
A solution consisting of 0.014 kg of a nonylphenol polyethylene oxide 10 mol adduct and 4.0 L of deionized water was used as "nonionic surfactant solution B". A solution obtained by dissolving 223.8 g of potassium persulfate in 12.0 L of deionized water was used as "initiator solution C".
A WAX emulsion (polypropylene emulsion with a number average molecular weight of 3000: number average primary particle diameter = 120 nm / solid content concentration = 29.9 %) 3.41 kg, the total amount of "anionic surfactant solution A" and the total amount of "nonionic surfactant solution B" were added, and stirring was started. Then, 44.0 L of ion-exchanged water was added.

Next, heating was started, and when the liquid temperature reached 75° C., the entire amount of “initiator solution C” was added dropwise. Thereafter, while controlling the liquid temperature at 75±1° C., a premixed solution of 12.1 kg of styrene, 2.88 kg of n-butyl acrylate, 1.04 kg of methacrylic acid and 548 g of t-dodecylmercaptan was added dropwise. After completion of dropping, the liquid temperature was raised to 80±1° C., and the mixture was heated and stirred for 6 hours to complete polymerization. Then, the liquid temperature was cooled to 40° C. or lower, stirring was stopped, and the liquid was filtered through a Pall filter to obtain "Latex 1-A".

The resin particles in "Latex 1-A" had a glass transition point of 57° C., a softening point of 121° C., a weight average molecular weight of 12,700, and a weight average particle diameter of 120 nm.

A solution obtained by dissolving 0.055 kg of sodium dodecylbenzenesulfonate in 4.0 L of ion-exchanged pure water was used as "anionic surfactant solution D". Also, a solution obtained by dissolving 0.014 kg of a nonylphenol polyethylene oxide 10 mol adduct in 4.0 L of deionized water was used as "nonionic surfactant solution E".

A solution obtained by dissolving 200.7 g of potassium persulfate (manufactured by Kanto Kagaku Co., Ltd.) in 12.0 L of deionized water was used as "initiator solution F".

WAX emulsion (polypropylene emulsion with a number average molecular weight of 3000: number average primary particle diameter = 120 nm, solid content concentration = 29.9% ) 3.41 kg, the total amount of "anionic surfactant solution D" and the total amount of "nonionic surfactant solution E" were added, and stirring was started. Then, 44.0 L of ion-exchanged water was added. Heating was started, and when the liquid temperature reached 70°C, "initiator solution F" was added. A premixed solution of 11.0 kg styrene, 4.00 kg n-butyl acrylate, 1.04 kg methacrylic acid and 9.02 g t-dodecyl mercaptan was then added dropwise. After completion of dropping, the liquid temperature was controlled to 72° C.±2° C. and heated and stirred for 6 hours, then the liquid temperature was raised to 80° C.±2° C. and heated and stirred for 12 hours to complete polymerization. Then, the liquid temperature was cooled to 40° C. or less, stirring was stopped, and the liquid was filtered through a Pall filter to obtain "Latex 1-B".

The resin particles in "Latex 1-B" had a glass transition point of 58° C., a softening point of 132° C., a weight average molecular weight of 245,000, and a weight average particle size of 110 nm.

A solution obtained by dissolving 5.36 kg of sodium chloride as a salting-out agent in 20.0 L of deionized water was used as "sodium chloride solution G".

20.0 kg of "Latex 1-A" prepared above and 5 kg of "Latex 1-B" were placed in a 100 L SUS reactor equipped with a temperature sensor, a cooling pipe, a nitrogen introduction device, and a particle size and shape monitoring device. 2 kg, 0.4 kg of "colorant dispersion liquid 1", and 20.0 kg of deionized water were added and stirred.

After standing for 10 minutes, the temperature is raised, and the liquid temperature is raised to 85 ° C. in 60 minutes, and the particle size is grown while heating and stirring at 85 ± 2 ° C. to cause salting-out/fusion, and the average of the fused particles. When the particle size reached 6 μm, the “sodium chloride solution G” was added to stop particle size growth. This liquid was designated as "fused particle dispersion liquid 1".

Next, 5.0 kg of the above "fusion particle dispersion liquid 1" was placed in a 5 L reaction vessel equipped with a temperature sensor and a cooling pipe, and the shape change of the fusion particles was observed at a liquid temperature of 92±2°C. Meanwhile, the mixture was heated and stirred until the average value of the shape factor reached 0.98 or more, and "Magenta Particle Dispersion Liquid 1" (average particle diameter: 4.1 µm) was obtained. The CV value was around 25%.

Next, the "magenta particle dispersion 1" was washed with ion-exchanged water and filtered three times, and then the wet cake-like "magenta particle dispersion 1" was pre-dried at an intake air temperature of 50°C using a flash jet dryer. , and further dried at a temperature of 55°C using a fluid bed dryer to produce "Magenta Particles 1". The CV value was around 25%.

A predetermined amount of hydrophobic silica fine particles R805 shown in Table 1 was externally added to each of the obtained "magenta particles 1" and mixed by a Henschel mixer to produce "magenta toner (M toner) 1".

Using the same method, magenta toners (M toner) 2 to 4 were prepared with the average particle size adjusted. All CV values were around 25%.

(Preparation of yellow toner)
In the preparation of Magenta Toner 1, the colorant was C.I. I. Pigment Red 122 instead of C.I. I. Pigment Yellow 17 was used in an amount of 1.05 kg. made.

(Preparation of cyan toner)
In the preparation of Magenta Toner 1, the colorant was C.I. I. Pigment Red 122 instead of C.I. I. Cyan toner (C toner) 1 having an average shape factor of 0.98 or more, an average particle size of 6.8 μm, and a CV value of around 25% was used in the same manner except that 0.60 kg of Pigment Blue 15:3 was used. ” was produced.

(Preparation of black toner)
In the preparation of Magenta Toner 1, the colorant was C.I. I. In the same manner, except that 0.60 kg of carbon black (Regal (registered trademark) 330 manufactured by Cabot Corporation) was used instead of Pigment Red 122, the average value of the shape factor was 0.98 or more, the average particle diameter was 6.3 μm, CV A "black toner (B toner) 1" with a value of about 25% was produced.

(Preparation of white toners 1 to 9)
In the preparation of Magenta Toner 1, the colorant was C.I. I. Pigment Red 122 was replaced with 1.6 kg of titanium oxide. Toner) 1” was manufactured.

Using a similar method, white toners (W toner) 2 to 9 were prepared with adjusted average particle diameters. All CV values were around 25%.

(Preparation of white toner 10)
(Preparation of binder resin)
A polyester-based resin prepared as follows was used as the binder.

Polyoxypropylene (2.2)-2,2-bis(4-hydroxyphenyl)propane, polyoxyethylene (2.0)-2,2-bis(4-hydroxyphenyl)propane, and terephthalic acid , in a molar ratio of 3:7:9, together with dibutyltin oxide as a polymerization initiator, in a glass fitted with a hygrometer, a stainless steel stirring rod, a flow-down condenser and a nitrogen inlet tube. It was placed in a four-necked flask manufactured by

Next, this four-necked flask is set in a mantle heater, and while introducing nitrogen into this flask from the nitrogen introduction pipe, the reaction is performed by heating and stirring, and the reaction state is measured while measuring the acid value during this reaction. was tracked, and the reaction was terminated when a predetermined acid value was reached, and this was cooled to obtain a polyester resin.

The physical properties of the polyester resin obtained in this way are a number average molecular weight (Mn) of 3300, a weight average molecular weight (Mw)/number average molecular weight (Mn) of 4.2, and a glass transition temperature (Tg) of 68.5. °C, a softening point (Tm) of 110.3°C, an acid value of 3.3 KOH mg/g and a hydroxy value of 28.1 KOH mg/g.

Here, the glass transition temperature (Tg) was measured using a differential scanning calorimeter (manufactured by Seiko Electronics Co., Ltd.: DSC-200), using alumina as a reference, and measuring 10 mg of a sample at a heating rate of 10 ° C./min. It was measured between ~120°C, and the shoulder value of the main endothermic peak was taken as the glass transition point.

Further, the softening point (Tm) was measured using a flow tester (manufactured by Shimadzu Corporation: CFT-500), using a die with a pore diameter of 1 mm and a length of 1 mm, a pressure of 20 kg/cm ² , and a temperature rise. The softening point was defined as the temperature corresponding to 1/2 the height from the outflow start point to the outflow end point when a 1 cm ² sample was melted out at a rate of 6°C/min.

The acid value was also measured by dissolving 10 mg of sample in 50 mL of toluene and using a 0.1% promothymol blue and phenol red mixed indicator to determine the consumption of a pre-rated N/10 potassium hydroxide/alcohol solution. Calculated from quantity. The hydroxy value is expressed in mg of potassium hydroxide required to hydrolyze the acetyl compound obtained by treating a weighed sample with acetic anhydride and neutralize the liberated acetic acid.

(Preparation of toner)
The synthesized polyester resin was coarsely pulverized so that the particle size was 1 mm or less. Next, this polyester resin and titanium dioxide are charged in a pressure kneader so that the mass ratio is 7:3, kneaded at 120 ° C. for 1 hour, cooled, and then coarsely pulverized with a hammer mill. Thus, a pigment masterbatch having a white colorant content of 30% by mass was obtained.

Next, the above polyester resin and the pigment masterbatch are placed in a Henschel mixer so that the ratio of titanium dioxide to 100 parts by weight of the polyester resin is 7 parts by mass. Thoroughly mixed at 40 m/sec for 180 seconds.

Next, this mixture is melt-kneaded by a twin-screw extruder kneader (manufactured by Ikegai Iron Works Co., Ltd.: PCM-30), the kneaded product is rolled to a thickness of 2 mm with a press roller, cooled with a cooling belt, and then subjected to a feather mill. Coarsely pulverized with After that, this was pulverized with a mechanical pulverizer (manufactured by Kawasaki Heavy Industries, Ltd.: KTM), further pulverized with a jet pulverizer (manufactured by Nippon Pneumatic Industry Co., Ltd.: IDS), and then a rotor type classifier (manufactured by Hosokawa Micron Corporation: Teaplex It was classified using a type classifier (100 ATP) to obtain a white toner (W toner) 10 by a pulverization method. The shape factor was around 0.980, the average particle diameter was 14.3 μm, and the CV value was 30%.

The average particle size is obtained by measuring the volume-based median diameter (d ₅₀ ) of the toner particles by using a computer system equipped with "Multisizer 3" (manufactured by Beckman Coulter, Inc.) and data processing software "Software V3.51". It was measured and calculated using a connected measuring device. Specifically, 0.02 g of toner particles is added to 20 mL of a surfactant solution (for example, a surfactant solution obtained by diluting a neutral detergent containing a surfactant component with pure water 10 times for the purpose of dispersing the toner particles). After the addition and familiarization, ultrasonic dispersion is performed for 1 minute to prepare a toner particle dispersion, and this toner particle dispersion is placed in a beaker containing "ISOTON II" (manufactured by Beckman Coulter, Inc.) in a sample stand. , pipet until the indicated concentration on the measuring device is 8%. Then, in the measuring device, the frequency value is calculated with the measured particle count number of 25000 and the aperture diameter of 100 μm, and the particle diameter of 50% from the larger volume integrated fraction is the volume-based median diameter (average particle diameter). and

The shape factor refers to the average circularity of the toner, and the average circularity of the toner was measured using "FPIA-3000" (manufactured by Sysmex). Specifically, the sample (toner) was soaked in an aqueous solution containing a surfactant and dispersed by performing an ultrasonic dispersion treatment for 1 minute. In the high-magnification imaging mode, photographing is performed at an appropriate density of 3000 to 10000 HPF detection numbers, the circularity of each toner particle is calculated according to the following formula (T), the circularity of each toner particle is added, It was calculated by dividing by the total number of toner particles.

Formula (T): Circularity = (perimeter of a circle having the same projected area as the particle image)/(perimeter of the projected particle image)
The CV value is a value obtained by the following formula from the particle size distribution analysis.
Coefficient of variation (CV value) (%) = (S2/Dn) x 100
(In the formula, S2 indicates the standard deviation in the volume-based particle size distribution, and Dn indicates the average particle size on the volume-based basis.)
Table I shows the types and average particle diameters of magenta toner, yellow toner, cyan toner, black toner and white toner that were prepared.

Using the magenta toner, yellow toner, cyan toner, black toner, and white toner prepared above, white turbidity (color mixture) was evaluated in the following manner.

<Evaluation device>
As an image forming apparatus and a fixing apparatus, those shown in FIGS. 1 and 2 of JP-A-2005-43532 were used.

<Evaluation method>
(White turbidity (mixed color))
Glossy paper "POD Gloss Coat 128 (128 g/m ² ) (Oji (manufactured by Paper Manufacturing Co., Ltd.)", an image is formed on the paper so that the amount of white toner adhered is 8 to 9 g/m ² and the amount of chromatic or black toner adhered thereon is 8 to 9 g/m ² , and the nip width is Thermal fixing was performed under the conditions of 11.2 mm, fixing time of 34 msec, fixing pressure of 133 kPa, system speed of 230 mm/sec, and fixing temperature of 150°C. In other words, the chromatic color toner other than the white toner or the black toner and the white toner are thermally fixed at the same time.

The images are formed in the order of paper, white toner image, and chromatic or black toner image (Sample 1 is expressed as (upper layer) magenta/white (lower layer)). Evaluation was requested to the subject who can judge. The results were expressed according to the following criteria. Evaluation results are shown in Table II. An evaluation of 〇◎ is accepted.

⊚: There is no color mixture of the white image in the chromatic or black toner image, and white turbidity does not occur. , No problem level △: Even if not compared with an image without white turbidity, the saturation or contrast of chromatic colors or black appears low, and it can be seen that white turbidity has occurred ×: The saturation of chromatic colors or black or Low contrast is recognized, and white turbidity is clearly generated in chromatic colors or black.

<Experiment 1>
White turbidity (mixed colors) was evaluated as described above for Samples 1 to 20 in which white toners 1 to 10 and magenta toners 1 to 4 were combined as shown in Table II below.

<Experiment 2>
Similar experiments were conducted with yellow toner, cyan toner and black toner other than magenta toner, and the results are shown in Table II.

<Experiment 3>
The results of forming layers in the order of paper, chromatic or black toner image, and white toner image were evaluated for magenta contamination against white, and the results are shown in Table II (Sample 14: (top layer) white/magenta (lower layer).).

From the results shown in Table II, the range of the average particle size dw of the white toner particles, the range of the average particle size dc of the chromatic or black toner particles, and the particle size difference (dw-dc) satisfy the composition range of the present invention. It can be seen that the occurrence of white turbidity (color mixture) is suppressed. In addition , it can be seen that toner particles produced by a polymerization method having a small CV value are more preferable.

1 intermediate transfer belt 2 chromatic or black toner particles 3 white toner particles 4 recording medium

Claims (6)

An electrophotographic imaging method using a white toner and a chromatic or black toner, comprising:
The average particle diameter dw of the toner particles constituting the white toner is 12.5 . within the range of 0 to 18.0 μm,
The average particle diameter dc of the toner particles constituting the chromatic or black toner is in the range of 4.0 to 8.0 μm, and
The difference (dw-dc) between the average particle diameter dw and the average particle diameter dc is 5.9-8 . within 0 μm , and
An electrophotographic image forming method , wherein the toner particles constituting the white toner are polymerized toner particles . The image layer of the white toner and the image layer of the chromatic or black toner as a laminate are simultaneously primarily transferred onto an intermediate belt, then secondarily transferred onto a recording medium, and then fixed. 2. The electrophotographic imaging method of claim 1. 3. The method of forming an electrophotographic image according to claim 2, wherein the white toner image layer is positioned at either the bottom layer or the top layer in a stack of image layers fixed on the recording medium. 4. The electrophotographic image forming method according to claim 1, wherein the toner particles constituting the white toner contain rutile-type titanium oxide. 5. The electrophotographic image forming method according to claim 1, wherein the coefficient of variation of toner particles constituting said white toner is in the range of 21 to 29% . 6. The electrophotography according to any one of claims 1 to 5 , wherein an average particle size dw of toner particles constituting the white toner is in the range of 14.0 to 18.0 µm. Imaging method.

Images