Toner set for developing electrostatic images, image forming system, and image forming method

Abstract

To provide a toner set for electrostatic charge image development which is used for multicolor printing using toner having different pigment contents, and has good color development property, heat-resistant storage property and fixability, and an image formation system and an image formation method using the same.SOLUTION: In a toner set for electrostatic charge image development, both first toner base particles contained in first toner and second toner base particles contained in second toner contain at least pigments and crystalline resins, and the first toner and the second toner satisfy the following expressions (1A) and (2A). Expression (1A): 10≤WP1-WP2, and Expression (2A): ΔHC1 / ΔHC2≤0.15. WP1: a pigment content [mass%] of the first toner base particles, WP2: a pigment content [mass%] of the second toner base particles, ΔHC1: a peak endothermic quantity [kJ / g] derived from crystalline resin of the first toner base particles, and ΔHC2: a peak endothermic quantity [kJ / g] derived from crystalline resin of the second toner base particles.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a toner set for developing electrostatic images, an image forming system, and an image forming method. More specifically, the present invention relates to a toner set for developing electrostatic images, which is used for multicolor printing using toners with different pigment contents and has good color development, heat-resistant storage stability, and fixability. [Background technology]

[0002] Each toner in the toner set for developing electrostatic images (hereinafter simply referred to as the "toner set") contains a different type of pigment. The pigment content of each toner can be adjusted depending on the type of pigment, taking into account color development properties, etc.

[0003] For example, Patent Document 1 describes an example of image formation using colored toners and white toners, in which the carbon black content in the colored toner is 6% by mass, while the titanium oxide content in the white toner is adjusted to a relatively high level of 18 to 52% by mass in order to improve whiteness and glossiness.

[0004] On the other hand, when the pigment content is different, the degree of deterioration in the thermal melting properties due to the filler effect is different, resulting in differences in the thermal melting properties of each toner. Specifically, a toner with a high pigment content tends to have good heat-resistant storage stability but poor fixability. Conversely, a toner with a low pigment content tends to have good fixability but poor heat-resistant storage stability.

[0005] Such differences in the thermal melting properties of the toners are disadvantageous in terms of toner set management and image formation, and therefore there is a demand for toner sets that have good heat-resistant storage stability and fixability even when the pigment content differs due to color development. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-177763 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above problems and circumstances, and the problem to be solved is to provide a toner set for developing electrostatic images, which is for multi-color printing using toners with different pigment contents and has good color development, heat-resistant storage properties, and fixing properties, as well as an image forming system and image forming method using the same. [Means for solving the problem]

[0008] In order to solve the above problems, the present inventors have investigated the causes of the above problems and have found that both the first toner and the second toner contain a crystalline resin in the toner base particles, and further, the peak endothermic amount ΔH C [J / g], the inventors have found that the color development, heat-resistant storage stability, and fixability can be improved, and have arrived at the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0009] 1. A toner set for developing electrostatic images, comprising a first toner and a second toner, the toner base particles of which contain different types of pigments, the first toner base particles contained in the first toner and the second toner base particles contained in the second toner each contain at least the pigment and a crystalline resin; The first toner and the second toner satisfy the following formulas (1A) and (2A): death, The peak endothermic heat ΔH derived from the crystalline resin of the second toner base particles C2 is in the range of 8 to 15 J / g, The pigment content W of the first toner base particles P1 is 30 mass% or more and 60 mass% or less A toner set for developing electrostatic images, comprising: Formula (1A) 10≦W P1 -W P2 Formula (2A) ΔH C1 / ΔH C2 ≦0.15 W P1 : Pigment content of first toner base particles [mass %] W P2 : Pigment content of second toner base particles [mass %] ΔH C1 : Peak endothermic heat amount derived from the crystalline resin of the first toner base particles [J / g] ΔH C2 : Peak endothermic heat amount derived from the crystalline resin of the second toner base particles [J / g]

[0010] 2. The first toner and the second toner satisfy the following formula (2B): 2. The toner set for developing electrostatic images according to claim 1, Formula (2B) ΔH C1 / ΔH C2 ≦0.08 ΔH C1 : Peak endothermic heat amount derived from the crystalline resin of the first toner base particles [J / g] ΔH C2 : Peak endothermic heat amount derived from the crystalline resin of the second toner base particles [J / g]

[0013] 3 The crystalline resin content W of the second toner base particles C2 is in the range of 5 to 10 mass% 2. The toner set for developing electrostatic images according to claim 1,

[0014] 4 The pigment content W of the second toner base particles P2 is in the range of 2 to 10 mass% 2. The toner set for developing electrostatic images according to claim 1,

[0015] 5 The pigment contained in the second toner base particles is an organic pigment. 2. The toner set for developing electrostatic images according to claim 1,

[0016] 6 The pigment contained in the first toner base particles is an inorganic pigment. 2. The toner set for developing electrostatic images according to claim 1,

[0017] 7 An image forming system using a toner set for developing electrostatic images, The toner set for developing electrostatic images comprises: 6 The toner set for developing electrostatic images according to any one of claims 1 to 5. An image forming system comprising:

[0018] 8 An image forming method using a toner set for developing electrostatic images, The toner set for developing electrostatic images comprises: 6 The toner set for developing electrostatic images according to any one of claims 1 to 5. An image forming method comprising: [Effects of the Invention]

[0019] The above-mentioned means of the present invention can provide a toner set for developing electrostatic images, which is for multicolor printing using toners with different pigment contents and has good color development, heat-resistant storage properties, and fixability, as well as an image forming system and an image forming method using the same. In the following description, where the unit of the peak endothermic heat quantity derived from the crystalline resin is [kJ / g], it will be read as [J / g].

[0020] The mechanism by which the effects of the present invention are manifested or the mechanism by which it acts has not been clarified, but is speculated as follows.

[0021] As mentioned above, toner with a high pigment content tends to melt less easily and have poor fixability due to the large filler effect. C By relatively lowering [kJ / g], the amount of heat required for melting can be reduced, so that it can be controlled to melt more easily, and fixability can be improved.

[0022] On the other hand, toner with a low pigment content tends to melt easily due to its small filler effect, and has poor heat-resistant storage properties. C By relatively increasing [kJ / g], the amount of heat required for melting can be increased, so that melting can be controlled to be more difficult, and heat-resistant storage stability can be improved.

[0023] Furthermore, in the present invention, it is important not only to achieve a good balance between the heat-resistant storage stability and fixability of each toner, but also to eliminate differences in heat-resistant storage stability and fixability between toners with different pigment contents that constitute a toner set.

[0024] In the invention described in Patent Document 1, the ratio (Q1 / Q2) of the heat absorption amount Q1 derived from the crystalline resin of the white toner to the heat absorption amount Q2 derived from the crystalline resin of the color toner is controlled to 0.2 or more and 0.8 or less. However, this control is intended to reduce the difference in gloss between the white image area and the color image area, and does not eliminate the difference in heat resistance storage property or fixability between toners.

[0025] In contrast to this, the present invention is to adjust the peak endothermic heat ΔH derived from the crystalline resin of the first toner base particles so as to satisfy the formula (2A). C1 and the peak endothermic heat ΔH derived from the crystalline resin of the second toner base particles C2 Ratio of peak endothermic heat derived from crystalline resin (ΔH C1 / ΔH C2 ) to 0.15 or less, it is possible to eliminate differences in heat-resistant storage stability and fixability even when the pigment content differs by 10% by mass or more so as to satisfy formula (1A).

[0026] By the above means, it is possible to achieve a good balance between the heat-resistant storage stability and fixability of each toner, and to eliminate the differences in heat-resistant storage stability and fixability between toners with different pigment contents. It is believed that this mechanism is what allows the toner set of the present invention to have good color development, heat-resistant storage stability, and fixability. [Brief explanation of the drawings]

[0027] [Figure 1] A cross-sectional schematic diagram showing an example of an image forming system DETAILED DESCRIPTION OF THE INVENTION

[0028] The toner set for developing electrostatic images of the present invention is a toner set for developing electrostatic images, comprising a first toner and a second toner, the toner base particles of which contain different types of pigments, characterized in that the first toner base particles contained in the first toner and the second toner base particles contained in the second toner both contain at least the pigment and a crystalline resin, and the first toner and the second toner satisfy the above formulas (1A) and (2A). This feature is a technical feature common to or corresponding to the following embodiments.

[0029] As an embodiment of the toner set for developing electrostatic images of the present invention, it is preferable that the first toner and the second toner satisfy the above formula (2B) from the viewpoint of heat-resistant storage stability and fixability.

[0030] In an embodiment of the toner set for developing electrostatic images of the present invention, the peak endothermic heat ΔH C2 is preferably in the range of 8 to 15 kJ / g from the viewpoint of heat-resistant storage stability and fixability.

[0031] In an embodiment of the toner set for developing electrostatic images of the present invention, the pigment content W of the first toner base particles is P1 However, it is preferable that the content of the inorganic filler is 30% by mass or more in order to obtain the effects of the present invention remarkably.

[0032] In an embodiment of the toner set for developing electrostatic images of the present invention, the crystalline resin content W of the second toner base particles is C2 In view of heat-resistant storage stability and fixability, it is preferable that the content of the toner is within the range of 5 to 10% by mass.

[0033] In an embodiment of the toner set for developing electrostatic images of the present invention, the pigment content W of the second toner base particles is P2 It is preferable that the content of the inorganic filler is in the range of 2 to 10 mass % from the viewpoint of obtaining the effects of the present invention remarkably.

[0034] In an embodiment of the toner set for developing electrostatic images of the present invention, it is preferable that the pigment contained in the second toner base particles is an organic pigment, and the pigment contained in the first toner base particles is an inorganic pigment, from the viewpoint of significantly achieving the effects of the present invention.

[0035] The image forming system of the present invention is an image forming system that uses a toner set for developing electrostatic images, and is characterized in that the toner set for developing electrostatic images is the toner set for developing electrostatic images of the present invention.

[0036] The image forming method of the present invention is an image forming method using a toner set for developing electrostatic images, characterized in that the toner set for developing electrostatic images is the toner set for developing electrostatic images of the present invention.

[0037] The present invention, its components, and embodiments for carrying out the present invention will be described in detail below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as lower and upper limits.

[0038] <1 Overview of the toner set for developing electrostatic images> The toner set of the present invention is a toner set for developing electrostatic images, comprising a first toner and a second toner, the toner base particles of which contain different types of pigments, characterized in that the first toner base particles contained in the first toner and the second toner base particles contained in the second toner both contain at least a pigment and a crystalline resin, and the first toner and the second toner satisfy the following formulas (1A) and (2A):

[0039] Formula (1A) 10≦W P1 -W P2 Formula (2A) ΔH C1 / ΔHC2 ≦0.15

[0040] W P1 : Pigment content of first toner base particles [mass %] W P2 : Pigment content of second toner base particles [mass %] ΔH C1 : Peak endothermic heat amount [kJ / g] derived from the crystalline resin of the first toner base particles ΔH C2 : Peak endothermic heat amount [kJ / g] derived from the crystalline resin of the second toner base particles

[0041] The toner set of the present invention includes at least a first toner and a second toner whose toner base particles contain different types of pigments, but may further include other toners.

[0042] In the present invention, "toner" refers to an aggregate of toner particles. Furthermore, "toner particles" refers to toner base particles to which external additives have been added. In the present invention, when there is no need to distinguish between toner base particles and toner particles, they may be simply referred to as toner particles.

[0043] <1.1 Pigment content in toner base particles> The toner set of the present invention has a pigment content W of the first toner base particles. P1 and the pigment content W of the second toner base particles P2 is characterized in that the following formula (1A) is satisfied.

[0044] Formula (1A) 10≦W P1 -W P2

[0045] Formula (1A) indicates that in the present invention, the toner base particles having a higher pigment content are designated as the first toner, and the toner base particles having a lower pigment content are designated as the second toner, and that the respective pigment contents differ by 10% by mass or more. The pigment contents of the respective toners are adjusted for color development, and the toner set of the present invention aims to further improve heat-resistant storage stability and fixability in a toner set including toners having different pigment contents for color development.

[0046] In the present invention, the "pigment content of the toner base particles" refers to the content of the pigment when the total amount of each component of the toner base particles is taken as 100% by mass.

[0047] Generally, the greater the difference in pigment content, the greater the difference in heat-resistant storage stability and fixability, making it more difficult to improve the heat-resistant storage stability and fixability of the toner set. In contrast, the toner set of the present invention is characterized by being able to eliminate the difference in heat-resistant storage stability and fixability even when the difference in pigment content is large, and is therefore particularly effective the greater the difference in pigment content. Therefore, from this perspective, the pigment content W of the first toner base particles is P1 and the pigment content W of the second toner base particles P2 It is preferable that the following formula (1B) is satisfied.

[0048] Formula (1B) 20≦W P1 -W P2

[0049] In addition, when paying attention to the pigment content of each toner, the pigment content W of the first toner base particles is P1 The pigment content W of the second toner base particles is preferably 30% by mass or more and 60% by mass or less. P2 is preferably in the range of 2 to 10 mass %.

[0050] <1.2 Peak endothermic heat amount derived from crystalline resin in toner base particles> The toner set of the present invention has a peak endothermic heat ΔH C1and the peak endothermic heat ΔH derived from the crystalline resin of the second toner base particles C2 is characterized in that the following formula (2A) is satisfied.

[0051] Formula (2A) ΔH C1 / ΔH C2 ≦0.15

[0052] Formula (2A) is the ratio of the peak endothermic heat amount derived from the crystalline resin of the toner base particle (ΔH C1 / ΔH C2 ) is 0.15 or less. This means that the toner set of the present invention has small differences in heat-resistant storage stability and fixability, and the toner set has good heat-resistant storage stability and fixability.

[0053] In addition, from the viewpoint of improving heat-resistant storage stability and fixability, the peak endothermic amount ΔH C1 and the peak endothermic heat ΔH derived from the crystalline resin of the second toner base particles C2 It is preferable that the following formula (2B) is satisfied.

[0054] Formula (2B) ΔH C1 / ΔH C2 ≦0.08

[0055] In addition, when focusing on the respective peak endothermic amounts, the peak endothermic amount ΔH C1 is preferably in the range of 0.64 to 1.2 kJ / g, and the peak endothermic heat ΔH C2 is preferably in the range of 8 to 15 kJ / g.

[0056] Peak endothermic heat ΔH derived from crystalline resin C can be measured by the following method in accordance with ASTM D3418-8, with reference to Patent Document 1 (JP 2012-177763 A).

[0057] 1) 10 mg of sample (toner) is placed in an aluminum cell and the lid is closed (this is called the sample cell). For comparison, 10 mg of alumina is placed in an aluminum cell of the same type and the lid is closed (this is called the comparison cell). 2) Place the sample cell and the control cell in the measuring device, and heat them from 30°C to 200°C at a rate of 10°C / min in a nitrogen atmosphere, then leave them at 200°C for 10 minutes. Obtain the endothermic and exothermic curves. 3) After leaving it, use liquid nitrogen to lower the temperature to -30°C at a rate of -10°C / min, and leave it at -30°C for 10 minutes. 4) After leaving it, increase the temperature from -30°C to 200°C at a rate of 20°C / min. At this time, obtain the endothermic and exothermic curves again.

[0058] The endothermic and exothermic curves obtained during the procedures 2) and 4) are compared, and endothermic peaks within a range of ±5°C are judged to be endothermic peaks derived from the same material.

[0059] In accordance with Section 9 of JIS-K7122, the endothermic heat per mass of the sample calculated from the peak area enclosed by the baseline and the endothermic peak is taken as the peak endothermic heat calculated from the endothermic peak.

[0060] Among endothermic peaks derived from the same material, endothermic peaks for which the ratio (B / A) of the peak endothermic amount A obtained from the endothermic peak obtained in operation 2) to the peak endothermic amount B obtained from the endothermic peak obtained in operation 4) is 0.8 or less are determined to be endothermic peaks derived from a crystalline resin.

[0061] In the endothermic-exothermic curve obtained during the operation of 2), the peak endothermic amount determined from the endothermic peak derived from the crystalline resin is called the peak endothermic amount ΔH C Adopted as.

[0062] As a measuring device, a differential scanning calorimeter DSC-7 manufactured by PerkinElmer can be used.

[0063] <2 Toner composition> The first toner and the second toner according to the present invention contain toner base particles as a constituent component, and may also contain an external additive as a constituent component.

[0064] 2.1 Toner base particles In the present invention, the toner base particles contained in the first toner are referred to as "first toner base particles," and the toner base particles contained in the second toner are referred to as "second toner base particles." Both the first toner base particles and the second toner base particles are characterized by containing at least a pigment and a crystalline resin, and may further contain an amorphous resin, wax, etc.

[0065] 2.1.1 Pigments The type of pigment that can be used in the present invention is not particularly limited, and for example, the following pigments can be used.

[0066] Examples of organic yellow or orange pigments include CI Pigment Orange 31, CI Pigment Orange 43, CI Pigment Yellow 12, CI Pigment Yellow 13, CI Pigment Yellow 14, CI Pigment Yellow 15, CI Pigment Yellow 17, CI Pigment Yellow 74, CI Pigment Yellow 93, CI Pigment Yellow 94, CI Pigment Yellow 138, CI Pigment Yellow 155, CI Pigment Yellow 180, and CI Pigment Yellow 185.

[0067] Examples of organic magenta or red pigments include CI Pigment Red 2, CI Pigment Red 3, CI Pigment Red 5, CI Pigment Red 6, CI Pigment Red 7, CI Pigment Red 15, CI Pigment Red 16, CI Pigment Red 48;1, CI Pigment Red 53;1, CI Pigment Red 57;1, CI Pigment Red 122, CI Pigment Red 123, CI Pigment Red 139, CI Pigment Red 144, CI Pigment Red 149, CI Pigment Red 150, CI Pigment Red 166, CI Pigment Red 177, CI Pigment Red 178, Pigment Red 184, CI Pigment Red 222, and CI Pigment Red 238.

[0068] Examples of organic cyan or blue pigments include CI Pigment Blue 15, CI Pigment Blue 15;2, CI Pigment Blue 15;3, CI Pigment Blue 15;4, CI Pigment Blue 16, CI Pigment Blue 60, CI Pigment Blue 62, CI Pigment Blue 66, and CI Pigment Green 7.

[0069] Examples of organic black pigments include carbon black, such as channel black, furnace black, acetylene black, thermal black, and lamp black.

[0070] Examples of inorganic black pigments include magnetic materials, titanium black, etc. Examples of magnetic materials include ferromagnetic metals such as iron, nickel, and cobalt, alloys containing these ferromagnetic metals, ferromagnetic metal compounds such as ferrite and magnetite, and alloys that do not contain ferromagnetic metals but exhibit ferromagnetism upon heat treatment. Examples of alloys that exhibit ferromagnetism upon heat treatment include Heusler alloys such as manganese-copper-aluminum and manganese-copper-tin, and chromium dioxide.

[0071] Examples of organic white pigments include polystyrene resin particles, urea formalin resin particles, hollow resin particles, and the like.

[0072] Examples of inorganic white pigments include heavy calcium carbonate, light calcium carbonate, titanium oxide (titanium dioxide), aluminum hydroxide, titanium 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, and hollow silica.

[0073] Examples of inorganic luster pigments include metal powders such as aluminum, brass, bronze, nickel, stainless steel, zinc, copper, silver, gold, and platinum; mica coated with titanium oxide or yellow iron oxide; coated flaky inorganic crystalline substrates such as barium sulfate, layered silicates, and layered aluminum silicates; single-crystal plate-like titanium oxide; basic carbonates; bismuth acid oxychloride; natural guanine; flaky glass powder; metal-deposited flaky glass powder; and pearl pigments.

[0074] Examples of organic fluorescent pigments include polyphenyls, stilbenes, oxazoles, oxadiazoles, coumarins, xanthenes, oxazines, thiazines, and polymethines.

[0075] Inorganic fluorescent pigments include those that use metal oxides such as Y2O3 and Zn2SiO4, phosphates such as Sr5(PO4)3Cl, and sulfides such as ZnS, SrS, and CaS as crystal nuclei, and combine these crystal nuclei with rare earth metal ions such as Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb, or metal ions such as Ag, Al, Mn, and Sb as an activator or co-activator. Preferred examples of the crystal nuclei include YO3, Y2O3, Y2O2S, Y2SiO3, YAlO3, and Y3Al5O 12 , (Y,Gd)3Al5O 12 , SnO2, Zn2SiO4, Sr4Al14 O 25 , CeMgAl 11 O 19 , BaAl 12 O 19 , BaAl2Si2O8, BaMgAl 10 O 17 , BaMgAl 14 O 23 , Ba2Mg2Al 12 O 22 , Ba2Mg4Al8O 18 , Ba3Mg5Al 18 O 35 , (Ba,Sr,Mg)O·aAl2O3, (Ba,Sr)(Mg,Mn)Al 10 O 17 , (Ba,Sr,Ca)(Mg,Zn,Mn)Al 10 O 17 , (Y,Gd)BO3, GdMgBO 10 , Sr2P2O7, (La,Ce)PO4, Ca5(PO4)3Cl, Ca 10 (PO4)6(F,Cl)2, (Sr,Ca,Ba,Mg) 10 (PO4)6C l2 , ZnS, (Zn,Cd)S, CaS, SrS, SrGa2S4, etc. The above crystal mother nuclei and activators or co-activators are not particularly limited in elemental composition, and may be partially substituted with elements of the same group. These inorganic fluorescent pigments are preferably those that absorb ultraviolet light and emit visible light.

[0076] The average particle size of the pigments other than the luster pigment is preferably within a range of 10 to 1,000 nm, more preferably within a range of 50 to 500 nm.The average particle size of the luster pigment is preferably within a range of 10 to 10,000 nm.

[0077] The shape of the bright pigment may be, for example, flat (scale-like).

[0078] The average length of the bright pigment in the major axis direction is preferably within a range of 1 to 30 μm, more preferably within a range of 3 to 20 μm, and even more preferably within a range of 5 to 15 μm.

[0079] The aspect ratio of the bright pigment (the ratio of the average length in the major axis direction to the average length in the thickness direction, which is 1) is preferably within the range of 5 to 200, more preferably within the range of 10 to 100, and even more preferably within the range of 30 to 70.

[0080] The average length in the major axis direction and the average length in the thickness direction of the bright pigment can be measured by calculating the number average value for 1,000 bright pigment particles using SEM images taken at a measurable magnification (300 to 100,000 times). The scanning electron microscope used to take the SEM images may be, for example, an S-4800 manufactured by Hitachi High-Technologies Corporation.

[0081] From the viewpoint of color development, it is preferable that the pigment content of inorganic pigments is relatively high. Therefore, in the toner set of the present invention, it is preferable that the pigment contained in the first toner base particles having a high pigment content is an inorganic pigment, and the pigment contained in the second toner base particles having a low pigment content is an organic pigment.

[0082] <2.1.2 Binder resin> The first toner base particles and the second toner base particles according to the present invention contain a crystalline resin as a binder resin. This allows the peak endothermic heat ΔH C The ratio [kJ / g] is controlled. Furthermore, an amorphous resin may be further contained as the binder resin.

[0083] "Crystalline resin" refers to a resin that has a melting point, i.e., a clear endothermic peak when heated, in an endothermic curve obtained by differential scanning calorimetry (DSC). A clear endothermic peak refers to a peak with a half-width of 15°C or less in an endothermic curve when heated at a rate of 10°C / min.

[0084] On the other hand, the term "amorphous resin" refers to a resin in which, in an endothermic curve obtained by performing differential scanning calorimetry similar to that described above, a baseline curve indicating the occurrence of glass transition is observed, but no clear endothermic peak as described above is observed.

[0085] (crystalline resin) The content of the crystalline resin in the toner base particles is not particularly limited, and the peak endothermic heat ΔH C However, taking into consideration the pigment content and filler effect of each of the second toner base particles and the first toner base particles, the crystalline resin content W of the second toner base particles is adjusted appropriately from the viewpoint of heat-resistant storage stability and fixability. C2 is preferably in the range of 5 to 10% by mass, and the crystalline resin content W of the first toner base particles is C1 is preferably in the range of 0.1 to 20% by mass.

[0086] From the viewpoint of achieving both fixability and heat-resistant storage stability, the melting point of the crystalline resin is preferably within a range of 55 to 80° C., and more preferably within a range of 70 to 80° C. The melting point of the crystalline resin can be measured by differential scanning calorimetry (DSC).

[0087] The molecular weight of the crystalline resin is preferably in the range of 8,500 to 12,500 in terms of number average molecular weight, and more preferably in the range of 9,000 to 11,000.

[0088] The type of crystalline resin is not particularly limited, but examples thereof include polyolefin resins, polydiene resins, and crystalline polyester resins. Among these, crystalline polyester resins are preferred in terms of improving fixability and ease of use. Hybrid crystalline polyester resins are also acceptable.

[0089] The crystalline polyester resin can be obtained by a polycondensation reaction between a divalent or higher alcohol (a polyhydric alcohol component) and a divalent or higher carboxylic acid (a polycarboxylic acid component).

[0090] Examples of polyhydric alcohol components include dihydric alcohols such as ethylene glycol, propylene glycol, butanediol, diethylene glycol, hexanediol, cyclohexanediol, octanediol, decanediol, dodecanediol, an ethylene oxide adduct of bisphenol A, and a propylene oxide adduct of bisphenol A; trihydric or higher polyols such as glycerin, pentaerythritol, hexamethylolmelamine, hexaethylolmelamine, tetramethylolbenzoguanamine, and tetraethylolbenzoguanamine; and ester compounds and hydroxycarboxylic acid derivatives thereof.

[0091] Examples of polycarboxylic acid components include oxalic acid, succinic acid, maleic acid, mesaconic acid, adipic acid, β-methyladipic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, fumaric acid, citraconic acid, diglycolic acid, cyclohexane-3,5-diene-1,2-dicarboxylic acid, malic acid, citric acid, hexahydroterephthalic acid, malonic acid, pimelic acid, tartaric acid, mucic acid, phthalic acid, isophthalic acid, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-carboxyphenylacetic acid, and p-phenylenediacetic acid. Examples of suitable carboxylic acids include dicarboxylic acids such as m-phenylenediglycolic acid, p-phenylenediglycolic acid, o-phenylenediglycolic acid, diphenylacetic acid, diphenyl-p,p'-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracenedicarboxylic acid, and dodecenylsuccinic acid; tricarboxylic or higher carboxylic acids such as trimellitic acid, pyromellitic acid, naphthalenetricarboxylic acid, naphthalenetetracarboxylic acid, pyrenetricarboxylic acid, and pyrenetetracarboxylic acid; and alkyl esters, acid anhydrides, and acid chlorides thereof.

[0092] The monomers (polyhydric alcohol component and polycarboxylic acid component) constituting the crystalline polyester resin preferably contain 50% by mass or more, more preferably 80% by mass or more, of linear aliphatic monomers. When aromatic monomers are used, the melting point of the crystalline polyester often becomes high, and when branched aliphatic monomers are used, the crystallinity often becomes low. Therefore, linear aliphatic monomers are preferably used. Furthermore, by making the linear aliphatic monomer 50% by mass or more, crystallinity can be maintained in the toner. By making it 80% by mass or more, sufficient crystallinity can be maintained.

[0093] The ratio of the polyhydric alcohol component to the polycarboxylic acid component is preferably set within a range of 1.5 / 1 to 1 / 1.5, more preferably 1.2 / 1 to 1 / 1.2, in terms of the equivalent ratio of the hydroxyl groups of the polyhydric alcohol component to the carboxyl groups of the polycarboxylic acid component.

[0094] It is also preferable that the number of carbon atoms in the polyhydric alcohol component (C(alcohol)) and the number of carbon atoms in the polycarboxylic acid component (C(acid)) satisfy the relationships of the following formulas (A) to (C).

[0095] C(acid)-C(alcohol)≧4 Formula (A) C(acid)≧10 Formula (B) C(alcohol)≦6 Formula (C)

[0096] A crystalline polyester resin with a specified carbon number of raw materials is formed using a polyhydric alcohol component and a polycarboxylic acid with different main chain lengths, resulting in branched chains with short carbon numbers and branched chains with long carbon numbers alternately bonded to the polyester chain. Therefore, it is believed that there will be areas of low regularity during crystallization. Therefore, by using a crystalline polyester resin with a specified carbon number of raw materials as the crystalline polyester resin constituting the binder resin, when thermal energy is applied at a temperature higher than the melting point of the crystalline polyester resin during thermal fixation, the crystals will melt sequentially starting from the areas with low regularity, resulting in good fixability.

[0097] The relationship between the above C(acid) and the above C(alcohol) preferably satisfies C(acid)-C(alcohol)≧4 as shown in the above formula (A), and more preferably satisfies C(acid)-C(alcohol)≧6.

[0098] When two or more polycarboxylic acid components are contained, the above C(acid) is the number of carbon atoms of the polycarboxylic acid component with the largest content (in moles).When the amounts are equal, the number of carbon atoms of the polycarboxylic acid component with the largest carbon number is taken as C(acid).

[0099] Similarly, when two or more polyhydric alcohol components are contained, the above C(alcohol) is the number of carbon atoms of the polyhydric alcohol component with the largest content (in moles).When the amounts are equal, the number of carbon atoms of the polycarboxylic acid component with the largest carbon number is taken as C(alcohol).

[0100] The method for producing the crystalline polyester resin is not particularly limited, and the resin can be produced by polycondensing (esterifying) the polyhydric alcohol component and the polycarboxylic acid component using a known esterification catalyst.

[0101] Examples of esterification catalysts include alkali metal compounds such as sodium and lithium, alkaline earth metal compounds such as magnesium and calcium, metal compounds such as aluminum, zinc, manganese, antimony, titanium, tin, zirconium, and germanium, phosphorous compounds, phosphate compounds, and amine compounds. Examples of tin compounds include dibutyltin oxide, tin octoate, tin dioctoate, and salts thereof. Examples of titanium compounds include titanium alkoxides such as tetra-n-butyl titanate, tetraisopropyl titanate, tetramethyl titanate, and tetrastearyl titanate, titanium acylates such as polyhydroxytitanium stearate, and titanium chelates such as titanium tetraacetylacetonate, titanium lactate, and titanium triethanolamine. Examples of germanium compounds include germanium dioxide, and examples of aluminum compounds include oxides such as polyaluminum hydroxide, aluminum alkoxides, and tributylaluminate. These compounds may be used alone or in combination of two or more.

[0102] The polycondensation temperature and the polymerization / polycondensation time are not particularly limited, and the pressure in the reaction system may be reduced during the polycondensation, if necessary.

[0103] The crystalline polyester resin may also be a hybrid crystalline polyester resin in which a crystalline polyester polymer segment synthesized by a polycondensation reaction between a polyhydric alcohol component and a polycarboxylic acid component is copolymerized with an amorphous polymer segment other than the polyester resin.

[0104] The crystalline polyester polymer segment refers to a portion derived from a crystalline polyester resin, and the amorphous polymer segment other than polyester resin refers to a portion derived from an amorphous resin other than polyester resin.

[0105] Examples of amorphous resins other than polyester resins include vinyl resins, urethane resins, and urea resins. Among these, vinyl resins are preferred, and styrene-acrylic resins are more preferred. The amorphous polymer segments other than polyester resins may be used alone or in combination of two or more.

[0106] The hybrid crystalline polyester resin may be in the form of a block copolymer, a graft copolymer, or the like, as long as it contains a crystalline polyester polymer segment and an amorphous polymer segment other than the polyester resin. However, a graft copolymer is preferred. By using a graft copolymer, it becomes easier to control the orientation of the crystalline polyester polymer segment, and sufficient crystallinity can be imparted to the hybrid crystalline polyester resin.

[0107] The crystalline polyester polymerized segment is preferably grafted onto an amorphous polymerized segment other than the polyester resin as the main chain. That is, the hybrid crystalline polyester resin is preferably a graft copolymer having an amorphous polymerized segment other than the polyester resin as the main chain and a crystalline polyester polymerized segment as a side chain. This structure can further enhance the orientation of the crystalline polyester polymerized segment, thereby improving the crystallinity of the hybrid crystalline polyester resin.

[0108] The hybrid crystalline polyester resin may further contain a substituent such as a sulfonic acid group, a carboxy group, or a urethane group, which may be introduced into the crystalline polyester polymer segment or into an amorphous polymer segment other than the polyester resin.

[0109] When the crystalline polyester resin is a hybrid crystalline polyester resin, the content of the crystalline polyester polymer segment is preferably 50% by mass or more and less than 98% by mass based on the total amount of the hybrid crystalline polyester resin. By setting the content within this range, sufficient crystallinity can be imparted to the hybrid crystalline polyester resin. The constituent components and content of each polymer segment in the hybrid crystalline polyester resin can be determined, for example, by NMR measurement or methylation reaction P-GC / MS measurement.

[0110] The method for producing the hybrid crystalline polyester resin is not particularly limited as long as it is a method capable of copolymerizing a crystalline polyester polymer segment with an amorphous polymer segment other than a polyester resin. Specific examples of the method for producing the hybrid crystalline polyester resin include the following methods.

[0111] (A) A method in which a crystalline polyester polymer segment is polymerized in advance, a bireactive monomer is reacted with the crystalline polyester polymer segment, and a monomer for forming an amorphous polymer segment other than a polyester resin is further reacted to form the amorphous polymer segment other than a polyester resin. (B) A method of forming a crystalline polyester polymer segment by polymerizing an amorphous polymer segment other than a polyester resin in advance, reacting the amorphous polymer segment with a bireactive monomer, and further reacting a polycarboxylic acid component and a polyhydric alcohol component for forming a crystalline polyester polymer segment. (C) A method in which a crystalline polyester polymer segment and an amorphous polymer segment other than the polyester resin are polymerized in advance, and then the two are bonded together by reacting them with a bireactive monomer.

[0112] Here, the "ambireactive monomer" is a monomer that bonds a crystalline polyester polymerized segment with an amorphous polymerized segment other than polyester resin, and has, in its molecule, both a group selected from a hydroxy group, a carboxy group, an epoxy group, a primary amino group, and a secondary amino group that forms a crystalline polyester polymerized segment, and an ethylenically unsaturated group that forms a styrene-acrylic polymerized segment.

[0113] Specific examples of the bireactive monomer include acrylic acid, methacrylic acid, fumaric acid, maleic acid, etc., and may also be esters of these hydroxyalkyls (having 1 to 3 carbon atoms), but from the viewpoint of reactivity, acrylic acid, methacrylic acid, or fumaric acid is preferred. The crystalline polyester polymerized segment and the amorphous polymerized segment other than the polyester resin are bonded via this bireactive monomer.

[0114] From the viewpoint of improving fixability, the amount of the bireactive monomer used is preferably 1 to 20% by mass, and more preferably 5 to 15% by mass, based on the total amount of monomers constituting the amorphous polymer segment other than the polyester resin.

[0115] The monomer constituting the amorphous polymer segment other than the polyester resin is not particularly limited, and for example, the vinyl monomers described in the section on amorphous vinyl resins below can be used.

[0116] The amorphous polymerized segment other than the polyester resin is preferably a styrene-acrylic polymerized segment derived from a styrene-acrylic resin. In this case, the amorphous polymerized segment other than the polyester resin is formed by addition polymerization of at least a styrene monomer and a (meth)acrylic acid ester monomer. The styrene monomer is preferably styrene, and the (meth)acrylic acid ester monomer is preferably n-butyl acrylate.

[0117] (amorphous resin) The amorphous resin is not particularly limited, and examples thereof include amorphous vinyl resins and amorphous polyester resins.

[0118] The glass transition temperature Tg of the amorphous resin is preferably in the range of 35 to 80°C, more preferably in the range of 45 to 65°C, from the viewpoint of maintaining a better balance between low-temperature fixability and fixation separability.

[0119] The glass transition temperature Tg can be measured by the DSC method described above using a differential scanning calorimeter such as "Diamond DSC" (manufactured by PerkinElmer), a DSC-7 differential scanning calorimeter (manufactured by PerkinElmer), or a TAC7 / DX thermal analyzer controller (manufactured by PerkinElmer).

[0120] From the viewpoint of easy control of the plasticity of the amorphous resin, the weight average molecular weight Mw of the amorphous resin is preferably in the range of 20,000 to 150,000, and more preferably in the range of 25,000 to 130,000. Moreover, from the viewpoint of easy control of the plasticity of the amorphous resin, the number average molecular weight Mn of the amorphous resin is preferably in the range of 5,000 to 150,000, and more preferably in the range of 8,000 to 70,000.

[0121] The weight-average molecular weight Mw of the amorphous resin can be determined from the molecular weight distribution measured by gel permeation chromatography (GPC). Specifically, a sample to be measured is first added to tetrahydrofuran to a concentration of 1 mg / mL, dispersed for 5 minutes using an ultrasonic disperser at room temperature, and then filtered through a membrane filter with a pore size of 0.2 μm to prepare a sample solution. For example, a GPC system HLC-8120GPC (manufactured by Tosoh Corporation) and columns ("TSKgel guard column SuperHZ-L" and "TSKgel SuperHZM-M", manufactured by Tosoh Corporation) are used. The column temperature is maintained at 40°C, and tetrahydrofuran is used as a carrier solvent at a flow rate of 0.2 mL / min. 10 μL of the prepared sample solution is injected into the GPC system together with the carrier solvent. The sample is detected using a refractive index detector (RI detector). The molecular weight distribution of the sample is calculated using a calibration curve measured using monodisperse polystyrene standard particles. The calibration curve is based on a molecular weight of 6 × 10 2 , 2.1×10 3 , 4×10 3 , 1.75×10 4 , 5.1×10 4 , 1.1×10 5 , 3.9 × 10 5 , 8.6×10 5 , 2 × 10 6 , 4.48×10 6 It is prepared by measuring 10 polystyrene standard particles (manufactured by Pressure Chemical Co.) of the following values.

[0122] Amorphous vinyl resins are formed using a monomer having a vinyl group (hereinafter referred to as "vinyl monomer"). Examples of amorphous vinyl resins include styrene-acrylic resins, styrene resins, and acrylic resins, with styrene-acrylic resins being preferred.

[0123] Examples of the vinyl monomer include styrene-based monomers, (meth)acrylic acid ester-based monomers, vinyl ester-based monomers, vinyl ether-based monomers, vinyl ketone-based monomers, and N-vinyl compound-based monomers.

[0124] Examples of styrene-based monomers include 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.

[0125] Examples of the (meth)acrylic acid ester monomer include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, phenyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and derivatives thereof.

[0126] Examples of vinyl ester monomers include vinyl propionate, vinyl acetate, and vinyl benzoate.

[0127] Examples of the vinyl ether monomer include vinyl methyl ether and vinyl ethyl ether.

[0128] Examples of vinyl ketone monomers include vinyl methyl ketone, vinyl ethyl ketone, and vinyl hexyl ketone.

[0129] Examples of N-vinyl compound monomers include N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone.

[0130] Examples of other vinyl monomers include vinyl compounds such as vinylnaphthalene and vinylpyridine, and (meth)acrylic acid derivatives such as acrylonitrile, methacrylonitrile and acrylamide.

[0131] The above vinyl monomers can be used alone or in combination of two or more.

[0132] As the vinyl monomer, it is preferable to use a monomer having an ionically dissociable group such as a carboxy group, a sulfonic acid group, a phosphate group, etc. Specific examples include the following:

[0133] Examples of the monomer having a carboxy group include acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl ester, and itaconic acid monoalkyl ester.

[0134] Examples of the monomer having a sulfonic acid group include styrene sulfonic acid, allyl sulfosuccinic acid, and 2-acrylamido-2-methylpropane sulfonic acid.

[0135] Examples of the monomer having a phosphate group include acidophosphooxyethyl methacrylate.

[0136] Furthermore, polyfunctional vinyls may be used as the vinyl monomer to give a vinyl polymer having a crosslinked structure.

[0137] Examples of polyfunctional vinyls include divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, and neopentyl glycol diacrylate.

[0138] The content of the amorphous vinyl resin in the toner base particles is not particularly limited, and the peak endothermic heat ΔH C The ratio [kJ / g] can be adjusted appropriately to control the ratio.

[0139] Next, we will explain amorphous polyester resins. Among known polyester resins obtained by polycondensation reaction of a divalent or higher carboxylic acid component (polycarboxylic acid component) and a divalent or higher alcohol component (polyhydric alcohol component), amorphous polyester resins are resins that do not have a clear melting point and have a relatively high glass transition temperature Tg. This can be confirmed by performing differential scanning calorimetry (DSC) on the amorphous polyester resin. Furthermore, since the monomers constituting crystalline polyester resins are different, they can also be distinguished from crystalline polyester resins by analysis such as NMR.

[0140] There are no particular limitations on the amorphous polyester resin, and any amorphous polyester resin known in the art can be used.

[0141] As the polycarboxylic acid component constituting the amorphous polyester resin, it is preferable to use unsaturated aliphatic polycarboxylic acids, aromatic polycarboxylic acids, and derivatives thereof. In addition, it is more preferable to include unsaturated aliphatic polycarboxylic acids from the viewpoint of further promoting compatibility with the crystalline polyester resin and improving low-temperature fixability. As long as an amorphous resin can be formed, saturated aliphatic polycarboxylic acids may be used in combination. The polycarboxylic acid component is not limited to one type, and two or more types may be mixed and used.

[0142] Examples of unsaturated aliphatic polycarboxylic acids include unsaturated aliphatic dicarboxylic acids, unsaturated aliphatic tricarboxylic acids, and unsaturated aliphatic tetracarboxylic acids. Lower alkyl esters and acid anhydrides of these can also be used. Examples of unsaturated aliphatic dicarboxylic acids include methylenesuccinic acid, fumaric acid, maleic acid, 3-hexenedioic acid, 3-octenedioic acid, and succinic acid substituted with an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms. Examples of unsaturated aliphatic tricarboxylic acids include 3-butene-1,2,3-tricarboxylic acid, 4-pentene-1,2,4-tricarboxylic acid, and aconitic acid. Examples of unsaturated aliphatic tetracarboxylic acids include 4-pentene-1,2,3,4-tetracarboxylic acid.

[0143] Specific examples of succinic acid substituted with an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms include dodecylsuccinic acid, dodecenylsuccinic acid, octenylsuccinic acid, decenylsuccinic acid, etc. Lower alkyl esters or acid anhydrides of these may also be used.

[0144] Examples of aromatic polycarboxylic acids include aromatic dicarboxylic acids, aromatic tricarboxylic acids, aromatic tetracarboxylic acids, and aromatic hexacarboxylic acids. Lower alkyl esters and acid anhydrides of these compounds can also be used. Examples of aromatic dicarboxylic acids include phthalic acid, terephthalic acid, isophthalic acid, t-butylisophthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-phenylenediacetic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and anthracenedicarboxylic acid. Examples of aromatic tricarboxylic acids include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid (trimesic acid), 1,2,4-naphthalenetricarboxylic acid, and hemimellitic acid. Examples of aromatic tetracarboxylic acids include pyromellitic acid and 1,2,3,4-butanetetracarboxylic acid. Examples of aromatic hexacarboxylic acids include mellitic acid.

[0145] Examples of saturated aliphatic polycarboxylic acids include saturated aliphatic dicarboxylic acids (for example, dodecanedioic acid) among the polycarboxylic acid components listed in the section on the crystalline polyester resin.

[0146] The number of carbon atoms of the dicarboxylic acid is not particularly limited, but is preferably in the range of 1 to 20, more preferably in the range of 2 to 15, and particularly preferably in the range of 3 to 12, since this makes it easier to optimize thermal properties.

[0147] The number of carbon atoms in the trivalent or higher polycarboxylic acid component is not particularly limited, but is preferably in the range of 3 to 20, more preferably in the range of 5 to 15, and particularly preferably in the range of 6 to 12, since this makes it easier to optimize the thermal properties.

[0148] As the polyhydric alcohol component constituting the amorphous polyester resin, from the viewpoint of chargeability and toner strength, it is preferable to use unsaturated aliphatic polyhydric alcohols, aromatic polyhydric alcohols, and derivatives thereof. As long as an amorphous polyester resin can be formed, saturated aliphatic polyhydric alcohols may be used in combination. The polyhydric alcohol component is not limited to one type, and two or more types may be mixed and used.

[0149] Examples of unsaturated aliphatic polyhydric alcohols include unsaturated aliphatic diols such as 2-butene-1,4-diol, 3-butene-1,4-diol, 2-butyne-1,4-diol, 3-butyne-1,4-diol, and 9-octadecene-7,12-diol. Derivatives of these may also be used.

[0150] Examples of aromatic polyhydric alcohols include bisphenols, alkylene oxide (ethylene oxide, propylene oxide, etc.) adducts of bisphenols, 1,3,5-benzenetriol, 1,2,4-benzenetriol, and 1,3,5-trihydroxymethylbenzene. Derivatives of these alcohols can also be used. Examples of bisphenols include bisphenol A and bisphenol F. Among these, it is preferable to use an alkylene oxide adduct of bisphenol A, particularly from the viewpoint of improving the charging uniformity of the toner and easily optimizing the thermal properties.

[0151] Examples of saturated aliphatic polyhydric alcohols include glycerin, trimethylolpropane, pentaerythritol, sorbitol, etc. Derivatives of these alcohols may also be used.

[0152] The number of carbon atoms in the polyhydric alcohol component is not particularly limited, but is preferably within the range of 3 to 30, as this makes it easier to optimize the thermal properties.

[0153] The weight average molecular weight Mw of the amorphous polyester resin is not particularly limited, but is preferably in the range of 5,000 to 100,000, and more preferably in the range of 5,000 to 50,000. If the weight average molecular weight Mw is 5,000 or more, the heat-resistant storage stability of the toner can be improved, and if it is 100,000 or less, the fixability can be further improved.

[0154] The content of the amorphous polyester resin in the toner base particles is not particularly limited, and the peak endothermic heat ΔH C The ratio [kJ / g] can be adjusted appropriately to control the ratio.

[0155] The method for producing the amorphous polyester resin is not particularly limited, and the resin can be produced by polycondensing (esterifying) the polycarboxylic acid component and the polyhydric alcohol component using a known esterification catalyst.

[0156] Examples of esterification catalysts include alkali metal compounds such as sodium and lithium, alkaline earth metal compounds such as magnesium and calcium, metal compounds such as aluminum, zinc, manganese, antimony, titanium, tin, zirconium, and germanium, phosphorous compounds, phosphate compounds, and amine compounds. Examples of tin compounds include dibutyltin oxide, tin octoate, tin dioctoate, and salts thereof. Examples of titanium compounds include titanium alkoxides such as tetra-n-butyl titanate, tetraisopropyl titanate, tetramethyl titanate, and tetrastearyl titanate, titanium acylates such as polyhydroxytitanium stearate, and titanium chelates such as titanium tetraacetylacetonate, titanium lactate, and titanium triethanolamine. Examples of germanium compounds include germanium dioxide, and examples of aluminum compounds include oxides such as polyaluminum hydroxide, aluminum alkoxides, and tributylaluminate. These compounds may be used alone or in combination of two or more.

[0157] The polycondensation temperature is not particularly limited, but is preferably within the range of 150 to 250° C. The polycondensation time is not particularly limited, but is preferably within the range of 0.5 to 15 hours. During polycondensation, the reaction system may be reduced in pressure as necessary.

[0158] The amorphous polyester resin may also be a hybrid amorphous polyester resin in which an amorphous polyester polymer segment synthesized by a polycondensation reaction between a polyhydric alcohol component and a polycarboxylic acid component is copolymerized with an amorphous polymer segment other than a polyester resin.

[0159] The amorphous polyester polymer segment refers to a portion derived from an amorphous polyester resin, and the amorphous polymer segment other than polyester resin refers to a portion derived from an amorphous resin other than polyester resin.

[0160] Examples of amorphous resins other than polyester resins include vinyl resins, urethane resins, and urea resins. Among these, vinyl resins are preferred, and styrene-acrylic resins are more preferred. The amorphous polymer segments other than polyester resins may be used alone or in combination of two or more.

[0161] The hybrid amorphous polyester resin may be in any form, such as a block copolymer or a graft copolymer, as long as it contains an amorphous polyester polymer segment and an amorphous polymer segment other than the polyester resin.

[0162] The hybrid amorphous polyester resin may further contain a substituent such as a sulfonic acid group, a carboxy group, or a urethane group, which may be introduced into the amorphous polyester polymerized segment or into an amorphous polymerized segment other than the polyester resin.

[0163] The method for producing the hybrid amorphous polyester resin is not particularly limited as long as it is a method that can copolymerize an amorphous polyester polymer segment with an amorphous polymer segment other than a polyester resin. Specific examples of the method for producing the hybrid amorphous polyester resin include the following methods.

[0164] (A) A method of forming an amorphous polymerized segment other than a polyester resin by polymerizing an amorphous polyester polymerized segment in advance, reacting the amorphous polyester polymerized segment with a bireactive monomer, and further reacting the bireactive monomer with a monomer for forming an amorphous polymerized segment other than a polyester resin. (B) A method of forming an amorphous polyester polymer segment by polymerizing an amorphous polymer segment other than a polyester resin in advance, reacting the amorphous polymer segment with a bireactive monomer, and further reacting the amorphous polymer segment with a polycarboxylic acid component and a polyhydric alcohol component for forming the amorphous polyester polymer segment. (C) A method in which an amorphous polyester polymerized segment and an amorphous polymerized segment other than the polyester resin are polymerized in advance, and then the two are bonded together by reacting them with a bireactive monomer.

[0165] The bireactive monomer and the monomer constituting the amorphous polymer segment other than the polyester resin are the same as those described in the section on the method for producing the hybrid crystalline polyester resin.

[0166] The method for forming the amorphous polymerized segment other than the polyester resin is not particularly limited, and examples thereof include a method in which polymerization is carried out by a known polymerization method such as bulk polymerization, solution polymerization, emulsion polymerization (emulsion association method), miniemulsion method, or dispersion polymerization method using any polymerization initiator typically used in the polymerization of the above-mentioned monomers, such as peroxides, persulfides, persulfates, or azo compounds.

[0167] The content of the amorphous polyester polymer segment in the hybrid amorphous polyester resin is not particularly limited, but is preferably in the range of 60 to 95% by mass, more preferably in the range of 70 to 85% by mass.

[0168] The content of amorphous polymerized segments other than polyester resins in the hybrid amorphous polyester resin (hereinafter also referred to as "modification amount") is preferably within a range of 5 to 40 mass %, more preferably within a range of 10 to 30 mass %.

[0169] Specifically, the modification amount refers to the ratio of the total mass of monomers constituting the amorphous polymerized segment other than the polyester resin to the total mass of the resin raw materials used to synthesize the hybrid amorphous polyester resin.

[0170] <2.1.3 Wax> The first toner base particles and the second toner base particles according to the present invention may contain wax as a release agent, and various known waxes may be used as the wax.

[0171] Examples of waxes include hydrocarbon waxes such as polypropylene wax, polyethylene wax, polypropylene-polyethylene copolymer wax, microcrystalline wax, paraffin wax, Fischer-Tropsch wax, and Sasol wax, and oxides thereof; ester waxes such as carnauba wax, montan wax, and deacidified waxes thereof, and fatty acid ester wax; fatty acid amides, fatty acids, higher alcohols, and fatty acid metal salts, which may be used alone or in combination. Among these, carnauba wax is preferred from the viewpoint of durability.

[0172] The melting point of the wax is preferably 60°C or higher, more preferably 70°C or higher, from the viewpoint of toner transferability, and is preferably 160°C or lower, more preferably 140°C or lower, even more preferably 130°C or lower, and even more preferably 120°C or lower, from the viewpoint of fixability.

[0173] The melting point of the wax can be measured, for example, using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan) by the following method.

[0174] First, weigh 0.01 to 0.02 g of sample into an aluminum pan, heat it to 200°C at a rate of 10°C / min, and then cool it to -10°C at a rate of 5°C / min. Next, heat the sample to 180°C at a rate of 10°C / min and measure. The highest endothermic peak temperature observed in the resulting melting endothermic curve is taken as the melting point of the wax.

[0175] From the viewpoints of the fixability and offset resistance of the toner and the dispersibility in the binder resin, the amount of wax used is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 1.5 parts by mass or more, relative to 100 parts by mass of the binder resin, and is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 7 parts by mass or less.

[0176] <2.1.4 Other additives> The first toner base particles and the second toner base particles according to the present invention may contain other additives as needed, such as a charge control agent, a magnetic powder, a flowability improver, a conductivity adjuster, a reinforcing filler such as a fibrous substance, an antioxidant, and a cleaning property improver.

[0177] The charge control agent is not particularly limited as long as it is a substance that can impart a positive or negative charge through frictional charging and is colorless, and various known positively charged charge control agents and negatively charged charge control agents can be used.

[0178] The content of the charge control agent in the toner base particles is preferably in the range of 0.01 to 30% by mass, and more preferably in the range of 0.1 to 10% by mass.

[0179] <2.2 External additives> In order to improve the fluidity, chargeability, cleaning properties, etc. of the toner, it is preferable to attach an external additive to the surface of the toner base particles.

[0180] The external additive may be inorganic or organic fine particles. Examples of inorganic fine particles include silica, alumina, titania, zirconia, tin oxide, zinc oxide, stearic acid compounds such as aluminum stearate and zinc stearate, and titanic acid compounds such as strontium titanate and zinc titanate. Examples of organic fine particles include resin fine particles such as melamine resin and polytetrafluoroethylene resin, and fine particles made of homopolymers such as styrene and methyl methacrylate, or copolymers thereof. These may be used alone or in combination of two or more.

[0181] Among these, silica is preferred, and from the viewpoint of toner transferability, hydrophobic silica that has been subjected to a hydrophobic treatment is more preferred.

[0182] Examples of hydrophobic treatment agents for hydrophobizing the surfaces of silica particles include hexamethyldisilazane (HMDS), dimethyldichlorosilane (DMDS), silicone oil, octyltriethoxysilane (OTES), and methyltriethoxysilane.

[0183] From the viewpoint of the chargeability, fluidity and transferability of the toner, the average particle size of the external additive is preferably within a range of 10 to 250 nm, more preferably within a range of 15 to 200 nm, and even more preferably within a range of 15 to 90 nm.

[0184] The average particle size is a number average particle size, which is determined by measuring the particle sizes (average values ​​of major and minor axes) of 500 particles in a scanning electron microscope (SEM) photograph and calculating the number average value thereof.

[0185] From the viewpoint of the chargeability, fluidity, and transferability of the toner, the content of the external additive in the toner particles is preferably in the range of 0.05 to 5 mass %, more preferably in the range of 0.1 to 3 mass %, and even more preferably in the range of 0.3 to 3 mass %, relative to the total mass of the toner before treatment with the external additive.

[0186] From the viewpoint of toner fluidity and durability, the coverage of the toner base particles with the external additive is preferably 50% or more, more preferably 80% or more, even more preferably 90% or more, and particularly preferably 95% or more. From the viewpoint of preventing the external additive from migrating to the photoreceptor, the coverage is preferably 200% or less, more preferably 170% or less, and even more preferably 150% or less.

[0187] The coverage of the toner base particles with the external additive can be calculated by the following formula: When two or more types of external additives are used in combination, the total coverage with the external additives is the sum of the coverages calculated for each external additive.

[0188] Coverage rate (%)=(√3 / 2π)×{(D·ρt) / (d·ρs)}×C×100

[0189] In the formula, D is the volume-based median diameter D50 [μm] of the toner base particles, d is the number-average particle size [μm] of the external additive, ρt is the specific gravity of the toner base particles, ρs is the specific gravity of the external additive, and C is the mass ratio of the external additive to the toner base particles (external additive / toner base particles).

[0190] <3. Particle size of toner base particles> The particle sizes of the first toner base particles and the second toner base particles are not particularly limited and can be adjusted, but the volume-based median diameter D50 is preferably in the range of 4 to 10 μm, and more preferably in the range of 4 to 7 μm. When the volume-based median diameter D50 is in the above range, transfer efficiency is increased and image quality of fine lines, dots, etc. is improved.

[0191] The volume-based median diameter D50 of toner particles is measured and calculated using a measuring device consisting of a "Coulter Counter 3" (manufactured by Beckman Coulter, Inc.) connected to a computer system (manufactured by Beckman Coulter, Inc.) equipped with data processing software "Software V3.51."

[0192] Specifically, 0.02 g of the measurement sample (toner) is added to 20 mL of surfactant solution (for example, a surfactant solution prepared by diluting a neutral detergent containing surfactant components 10 times with pure water in order to disperse the toner particles), and after mixing, ultrasonic dispersion is performed for 1 minute to prepare a toner particle dispersion. This toner particle dispersion is then pipetted into a beaker containing an ISOTON II (manufactured by Beckman Coulter, Inc.) in the sample stand until the concentration indicated on the measuring device reaches 8%.

[0193] By setting the concentration range to this, reproducible measurement values ​​can be obtained. Then, in the measurement device, the particle count is set to 25,000 and the aperture diameter is set to 50 μm, and the measurement range from 1 μm to 30 μm is divided into 256 parts to calculate the frequency value. The particle size with the largest volume cumulative fraction (50%) is taken as the volume-based median diameter D50.

[0194] <4 Toner manufacturing method> The method for producing each toner contained in the toner set of the present invention is not particularly limited, and any known method can be used, but the emulsion polymerization aggregation method and emulsion aggregation method can be particularly preferably used.

[0195] The emulsion aggregation method is a method for producing toner particles by adding a poor solvent dropwise to a binder resin solution dissolved in a solvent to carry out phase inversion emulsification, followed by removing the solvent, to obtain a resin particle dispersion, mixing this resin particle dispersion with a pigment dispersion or the like, aggregating the particles to a desired toner particle size, and further controlling the shape by fusing the binder resin particles together.

[0196] An example of each step constituting the method for producing toner base particles by emulsion aggregation will be described below. (1) A step of preparing a pigment dispersion in which pigment particles are dispersed in an aqueous medium. (2) A step of preparing a resin particle dispersion in which binder resin particles containing internal additives as needed are dispersed in an aqueous medium. (3) A step of mixing a pigment dispersion and a resin particle dispersion to aggregate, associate, and fuse the pigment particles and binder resin particles to form toner base particles. (4) A process of filtering the toner base particles from the dispersion system (aqueous medium) and removing surfactants, etc. (5) Drying the toner base particles (6) A process of adding external additives to the toner base particles

[0197] In the above step (3), it is preferable to perform annealing treatment. By the annealing treatment, the peak endothermic heat ΔH derived from the crystalline resin of the toner base particles is reduced. C can be controlled, and in turn, the peak endothermic heat ΔH C1 and the peak endothermic heat ΔH derived from the crystalline resin of the second toner base particles C2 Ratio of (ΔH C1 / ΔH C2 ) can be controlled.

[0198] In the above step (3), it is preferable to add a flocculant to aggregate the binder resin particles and the like. The flocculant is not particularly limited, but a flocculant selected from metal salts is preferably used. Examples include monovalent metal salts such as salts of alkali metals such as sodium, potassium, and lithium; divalent metal salts such as calcium, magnesium, manganese, and copper; and trivalent metal salts such as iron and aluminum. Specific salts include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, copper sulfate, magnesium sulfate, and manganese sulfate. Among these, divalent metal salts are particularly preferred. The use of divalent metal salts allows for aggregation to proceed with a smaller amount. These salts may be used alone or in combination of two or more.

[0199] An example of the above step (3) will be specifically described below.

[0200] A dispersion of binder resin particles, such as crystalline polyester resin, amorphous polyester resin, or amorphous vinyl resin, and a pigment dispersion are placed in a reaction vessel equipped with a stirrer, temperature sensor, and cooling tube. A solution of a flocculant (e.g., magnesium chloride) is added under stirring to aggregate, associate, and fuse the binder resin particles and colorant particles, resulting in particle growth. An aqueous solution of sodium chloride is added at the desired timing to stop particle size growth. The mixture is then heated and stirred to promote particle fusion until the average circularity of the toner particles reaches the desired value, after which it is cooled to lower the liquid temperature.

[0201] Thereafter, as an annealing treatment, the mixture is heated to 60°C over about 30 minutes while stirring, and maintained at that temperature for about 3 hours. The mixture is then cooled to a temperature of 30°C or less. Thereafter, steps (4) to (6) are carried out to produce the toner for electrostatic charge development of the present invention.

[0202] Furthermore, the toner base particles preferably have a core-shell structure, and the above-mentioned emulsion aggregation method for producing toner base particles is suitable for producing such core-shell structured toner base particles. Specifically, core particles are first prepared by aggregating, associating, and fusing binder resin particles for the core particles with colorant particles. Next, binder resin particles for the shell layer are added to the dispersion of the core particles, and the binder resin particles for the shell layer are aggregated and fused to the surface of the core particles to form a shell layer that covers the surface of the core particles. This process yields toner base particles with a core-shell structure.

[0203] A mechanical mixer can be used for the external addition and mixing process of the external additives to the toner base particles in the above step (6). Examples of mechanical mixers that can be used include a Henschel mixer, a Nauta mixer, and a Turbula mixer. Among these, it is preferable to use a mixer that can impart shear force to the particles being treated, such as a Henschel mixer, and to perform the mixing process by lengthening the mixing time or increasing the rotational peripheral speed of the stirring blades. Furthermore, when multiple types of external additives are used, all of the external additives may be mixed with the toner base particles at once, or they may be mixed in multiple batches depending on the external additive.

[0204] Furthermore, the steps other than the step (3), i.e., the steps (1), (2), and (4) to (6) above, are not particularly limited, and known methods can be suitably adopted. Furthermore, known steps other than the steps (1) to (6) above can be adopted as long as they do not impede the manifestation of the effects of the present invention.

[0205] <5 Two-component developer> Each toner contained in the toner set of the present invention can be used as a two-component developer containing, for example, a toner and carrier particles. The two-component developer is obtained by mixing the toner and carrier particles.

[0206] The mixing device used for mixing is not particularly limited, but examples thereof include a Nauta mixer, a W-cone mixer, a V-type mixer, etc. The toner content (toner concentration) in the two-component developer is not particularly limited, but is preferably in the range of 4.0 to 12.0 mass %.

[0207] The carrier particles are composed of at least a magnetic material, and known carrier particles can be used, such as coated carrier particles in which the surface of core particles made of at least a magnetic material is coated with a resin, and dispersed carrier particles in which magnetic material fine powder is dispersed in a resin.

[0208] The average particle size of the carrier particles is preferably in the range of 10 to 500 μm, more preferably 30 to 100 μm, in terms of volume-based median diameter D50 measured in the same manner as for the toner base particles.

[0209] The carrier particles are preferably coated carrier particles from the viewpoint of suppressing adhesion of the carrier particles to the photoreceptor. Hereinafter, coated carrier particles will be described.

[0210] The core particles in the coated carrier particles are composed of at least a magnetic material, for example, a material that is strongly magnetized in a direction by a magnetic field. Examples of magnetic materials include ferromagnetic metals such as iron, nickel, and cobalt, alloys or compounds containing these metals, and alloys that become ferromagnetic when heat-treated. These magnetic materials may be used alone or in combination of two or more.

[0211] Examples of ferromagnetic metals and alloys or compounds containing these metals include iron, ferrite represented by the following formula (a), and magnetite represented by the following formula (b). M in formulas (a) and (b) represents a monovalent or divalent metal, and specific examples include Mn, Fe, Ni, Co, Cu, Mg, Sr, Zn, Cd, and Li. These metals may be used alone or in combination of two or more. Formula (a): MO·Fe2O3 Formula (b): MFe2O4

[0212] Examples of alloys that become ferromagnetic upon heat treatment include Heusler alloys such as manganese-copper-aluminum and manganese-copper-tin, and chromium dioxide.

[0213] The magnetization of the core particles that make up the carrier particles is 30 to 75 A·m 2 / kg, and residual magnetization is 5.0 A m 2 By using core particles having such magnetic properties, partial aggregation of the carrier particles is prevented and the two-component developer is uniformly dispersed on the surface of the developer transport member, so that a uniform, high-resolution toner image can be formed without uneven density.

[0214] The magnetic material used for the core particles is preferably ferrite, from the viewpoint of obtaining favorable magnetic properties. Furthermore, the ferrite is preferably a porous particle having pores, and the pores are preferably filled with a resin. By adopting such a configuration, the specific gravity can be made relatively small, which can prevent the carrier particles from cracking or chipping due to the impact force of stirring in a developing machine, thereby obtaining carrier particles with excellent durability.

[0215] As the coating resin constituting the coated carrier particles, known resins used for coating core particles of carrier particles can be used. From the viewpoint of reducing the moisture adsorption of the carrier particles and increasing the adhesion of the coating layer to the core particles, the coating resin is preferably a resin having a cycloalkyl group.

[0216] Examples of the cycloalkyl group include a cyclohexyl group, a cyclopentyl group, a cyclopropyl group, a cyclobutyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, and a cyclodecyl group. Among these, a cyclohexyl group or a cyclopentyl group is preferred, and a cyclohexyl group is more preferred from the viewpoint of adhesion between the coating resin layer and the core particles (e.g., ferrite particles).

[0217] The coating resin can be obtained, for example, by polymerizing a polymerizable compound containing a monomer having a cycloalkyl group. As the monomer having a cycloalkyl group, a cycloalkyl ester of methacrylic acid is preferably used. The coating resin may also be a copolymer of the monomer and a monomer not having a cycloalkyl group, for example, an alkyl ester of methacrylic acid (but not having a cyclic structure).

[0218] The weight average molecular weight Mw of the coating resin can be measured by GPC (gel permeation chromatography) and is preferably within a range of, for example, 10,000 to 800,000, and more preferably within a range of 100,000 to 750,000, based on polystyrene.

[0219] The cycloalkyl group content in the coating resin is preferably within the range of 10 to 90% by mass. The cycloalkyl group content in the coating resin can be determined, for example, by pyrolysis-gas chromatography / mass spectrometry (P-GC / MS) or 1H-NMR.

[0220] From the viewpoint of achieving both durability and low electrical resistance of the carrier particles, the thickness of the coating resin layer on the carrier particles is preferably within a range of 0.05 to 4.0 μm, and more preferably within a range of 0.2 to 3.0 μm. By keeping the thickness within the above range, it is possible to set the chargeability and durability within preferred ranges.

[0221] <6 Image formation> An image forming system and an image forming method using the toner set of the present invention will now be described.

[0222] Fig. 1 is a schematic cross-sectional view showing an example of an image forming system. Fig. 1 shows an example in which four types of toners, yellow Y, magenta M, cyan C, and black K, are used as color toners, and white W is used as a special color toner. Two of these five types of toners are the first toner and the second toner contained in the toner set of the present invention.

[0223] First, an outline of a color electrophotographic image forming system equipped with a detection sensor and a secondary transfer device will be described.

[0224] The image forming system GS is a so-called tandem color image forming system, in which image forming units that form yellow, magenta, cyan, and black color toner images and a white toner image, which is a type of special color toner, are arranged along the movement direction of the intermediate transfer body 36, and the color toner images and white toner images formed on the image carriers of each image forming unit are multiple-transferred and superimposed onto the intermediate transfer body, and then transferred all at once onto a recording medium.

[0225] In FIG. 1, an original image placed on an image reading device SC disposed at a position above the image forming system GS is scanned and exposed by an optical system and read into a line image sensor CCD. The analog signal photoelectrically converted by the line image sensor CCD undergoes analog processing, A / D conversion, shading correction, image compression processing, etc. in an image processing unit, and then sends an image data signal to an exposure optical system 33 as an image writing means.

[0226] The intermediate transfer body 36 may be a drum type or an endless belt type, both of which have similar functions, but in the following description, the intermediate transfer body refers to the endless belt type intermediate transfer body 36.

[0227] 1, five process units 100 are provided around the periphery of intermediate transfer body 36 for forming images of each color: yellow (Y), magenta (M), cyan (C), black (K), and white (W). The process units 100, as means for forming color toner images and white toner images, are arranged in a vertical column along intermediate transfer body 36, with respect to the rotation direction of intermediate transfer body 36, which is the vertical direction indicated by the arrow in the figure, in the order of Y, M, C, K, and W.

[0228] All five process units 100 have a common structure, and each comprises a photosensitive drum 31, a charger 32 as a charging means, an exposure optical system 33 as an image writing means, a developing device (developing machine) 34, and a photosensitive cleaning device 190 as an image carrier cleaning means.

[0229] Photosensitive drum 31 is, for example, a cylindrical substrate made of a metal member such as aluminum and having an outer diameter of about 40 to 100 mm, on the outer periphery of which a photosensitive layer having a thickness of about 20 to 40 μm is formed. Photosensitive drum 31 is rotated by power from a drive source (not shown) in the direction of the arrow with the substrate grounded, at a linear velocity of, for example, about 80 to 280 mm / s, preferably 220 mm / s.

[0230] An image forming unit consisting of a charger 32 as a charging means, an exposure optical system 33 as an image writing means, and a developing device (developing machine) 34 is arranged around the photosensitive drum 31 in the direction of rotation of the photosensitive drum 31 as indicated by the arrow in the figure.

[0231] The charger 32 serving as charging means is attached in close proximity to and facing the photosensitive drum 31 in a direction parallel to the rotation axis of the photosensitive drum 31. The charger 32 has a discharge wire as a corona discharge electrode that applies a predetermined potential to the photosensitive layer of the photosensitive drum 31, and performs charging (negative charging in this embodiment) by corona discharge of the same polarity as the toner, thereby applying a uniform potential to the photosensitive drum 31.

[0232] The exposure optical system 33, which is an image writing means, rotates and scans laser light emitted from a semiconductor laser (LD) light source (not shown) in the main scanning direction using a rotating polygonal mirror (no symbol), and exposes (writes an image) the photosensitive drum 31 using an electrical signal corresponding to the image signal via an fθ lens (no symbol), a reflecting mirror (no symbol), etc., thereby forming an electrostatic latent image corresponding to the original image on the photosensitive layer of the photosensitive drum 31.

[0233] Developing device 34, which serves as a developing means, contains two-component developers of the colors yellow (Y), magenta (M), cyan (C), black (K), and white (W), each charged to the same polarity as that of photosensitive drum 31, and is equipped with developing roller 34a, a cylindrical developer carrier made of non-magnetic stainless steel or aluminum, for example, 0.5 to 1 mm thick and 15 to 25 mm in outer diameter. Developing roller 34a is kept out of contact with photosensitive drum 31 by abutting rollers (not shown), leaving a predetermined gap, for example, 100 to 1000 μm, between developing roller 34a and photosensitive drum 31, and rotates in the same direction as photosensitive drum 31. During development, a DC voltage of the same polarity as the toner (negative polarity in this embodiment) or a developing bias voltage consisting of a DC voltage superimposed on an AC voltage is applied to developing roller 34a, thereby performing reverse development on the exposed portion of photosensitive drum 31.

[0234] The intermediate transfer member 36 has a volume resistivity of 1.0×10 7 ~1.0×10 9 Ω·cm, with a surface resistivity of 1.0×10 10 ~1.0×10 12A semiconductive, endless (seamless) resin belt with a resistance of approximately Ω / □ is used. The resin belt may be a semiconductive resin film with a thickness of 0.05 to 0.5 mm, which is made of an engineering plastic such as modified polyimide, thermosetting polyimide, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, or nylon alloy, with a conductive material dispersed therein. Alternatively, the intermediate transfer member 36 may be a semiconductive rubber belt with a thickness of 0.5 to 2.0 mm, which is made of silicone rubber, urethane rubber, or the like, with a conductive material dispersed therein. The intermediate transfer member 36 is wound around multiple roller members, including a tension roller 36a and a backup roller 36B facing the secondary transfer member, and is supported so as to be rotatable in the vertical direction.

[0235] The primary transfer roller 37, which serves as the first transfer means for each color, is made of a roller-shaped conductive member made of foamed rubber such as silicone or urethane, and is disposed opposite the photosensitive drum 31 for each color, sandwiching the intermediate transfer body 36 therebetween, and presses against the back surface of the intermediate transfer body 36 to form a transfer area between the roller and the photosensitive drum 31. A constant DC current of the opposite polarity to that of the toner (positive polarity in this embodiment) is applied to the primary transfer roller 37 by constant current control, and the toner image on the photosensitive drum 31 is transferred onto the intermediate transfer body 36 by a transfer electric field formed in the transfer area.

[0236] The toner image transferred onto the intermediate transfer body 36 is then transferred onto a recording medium P. A detection sensor 38 is provided on the periphery of the intermediate transfer body 36 to measure the density of the patch image toner.

[0237] Fixing device 47, which fixes the transferred recording medium P, is provided with heating roller 47a and pressure belt 47b, which form a nip portion. Therefore, in FIG. 1, the fixing member that comes into contact with the upper layer (toner layer) of the multiple toner layers transferred onto recording medium P is heating roller 47a.

[0238] Note that a conventionally known fixing device (not shown) that uses a fixing belt for fixing may also be used to accommodate high-speed printing. In a fixing method using such a fixing belt, the recording medium P bearing an unfixed toner image is fed to the fixing device and guided by a guide plate to the nip portion. The fixing belt then comes into close contact with the recording medium P, quickly fixing the unfixed toner image to the recording medium P. The recording medium P also receives an airflow from an airflow separating device at the downstream end of the fixing nip portion. This promotes separation of the recording medium P from the fixing belt. Once separated from the fixing belt, the recording medium P is guided by a guide roller toward the outside of the image forming system.

[0239] On the downstream side of the fixing device 47, there are provided a paper discharge roller 54 for clamping and discharging the fixed recording medium P, and a paper discharge tray 55 for placing the recording medium P discharged outside the machine.

[0240] On the other hand, in order to clean the residual toner on the intermediate transfer body 36, a cleaning device 190A is provided.

[0241] Furthermore, a secondary transfer device 70 is provided to clean the patch image toner on the secondary transfer member 37A.

[0242] Next, the image forming method will be described.

[0243] When image recording starts, a photoconductor drive motor (not shown) starts, causing the yellow (Y) photoconductor drum 31 to rotate in the direction indicated by the arrow in the figure, and a potential is applied to the Y photoconductor drum 31 by a Y charger 32. After the Y photoconductor drum 31 is applied with a potential, a Y exposure optical system 33 exposes (writes an image) the Y photoconductor drum 31 using an electrical signal corresponding to a first color signal, i.e., Y image data, and an electrostatic latent image corresponding to the yellow (Y) image is formed on the Y photoconductor drum 31. This latent image is reverse-developed by a Y developing device 34, and a toner image made of yellow (Y) toner is formed on the Y photoconductor drum 31. The Y toner image formed on the Y photoconductor drum 31 is transferred onto an intermediate transfer member 36 by a primary transfer roller 7 serving as primary transfer means.

[0244] Next, a potential is applied to the M photoconductor drum 31 by the magenta (M) charger 32. After the M photoconductor drum 31 has been applied with a potential, it is exposed (image written) by the M exposure optical system 33 using an electrical signal corresponding to the first color signal, i.e., M image data, and an electrostatic latent image corresponding to the magenta (M) image is formed on the M photoconductor drum 31. This latent image is reverse developed by the M developing device 34, and a toner image made of magenta (M) toner is formed on the M photoconductor drum 31. The M toner image formed on the M photoconductor drum 31 is transferred onto the intermediate transfer body 36 by the primary transfer roller 37, which serves as primary transfer means, in a state superimposed on the Y toner image.

[0245] By a similar process, a toner image made of cyan (C) toner formed on the cyan (C) photosensitive drum 31 and a toner image made of black (K) toner formed on the black (K) photosensitive drum 31 are sequentially superimposed on the intermediate transfer body 36, and a superimposed color toner image made of Y, M, C, and K toners is formed on the peripheral surface of the intermediate transfer body 36.

[0246] Next, the white (W) photoconductor drum 31 rotates in the direction indicated by the arrow in the figure, and a potential is applied to the W photoconductor drum 31 by the W charger 32. After the W photoconductor drum 31 is applied with a potential, the W exposure optical system 33 exposes (writes an image) the W photoconductor drum 31 with an electrical signal corresponding to the first color signal, i.e., W image data, and an electrostatic latent image corresponding to the white (W) image is formed on the W photoconductor drum 31. This latent image is reverse-developed by the W developing device 34, and a toner image made of white (W) toner is formed on the W photoconductor drum 31. The W toner image formed on the W photoconductor drum 31 is transferred onto the intermediate transfer body 36 by the primary transfer roller 7 as primary transfer means. As a result, a superimposed color toner image made of Y, M, C, and K toners is formed on the circumferential surface of the intermediate transfer body 36, and a white toner image made of W toner is formed on the color toner image.

[0247] After transfer, the toner remaining on the circumferential surface of each photosensitive drum 31 is cleaned by a photosensitive drum cleaning device 190 .

[0248] Meanwhile, recording medium P as recording paper stored in paper feed cassettes 50A, 50B, and 50C is fed by a feed roller 51 and a paper feed roller 52A provided in each of paper feed cassettes 50A, 50B, and 50C, transported on transport path 52 by transport rollers 52B, 52C, and 52D, and transported via registration roller 53 to secondary transfer member 37A as secondary transfer means to which a voltage of the opposite polarity to that of the toner (positive polarity in this embodiment) is applied, and in the transfer region of secondary transfer member 37A, the superimposed color toner image formed on intermediate transfer body 36 and the white toner image on the color toner image are transferred together onto recording medium P. As a result, an image is formed on recording medium P with a white toner image as the lower layer and a color toner image as the upper layer.

[0249] In the example of Figure 1, the white toner image is formed below the color toner image. By forming color toner images on the white toner image, the visibility of the color toners is improved, and the added value of the image can be increased. However, a toner image made of a special color toner such as white (W) toner may also be formed below the color toner image depending on the intended use.

[0250] The recording medium P onto which the white toner image and the color toner image have been transferred is heated and pressurized in the nip formed by the heating roller 47a and pressure belt 47b of the fixing device 47, where the images are fixed, and is then sandwiched between the paper discharge rollers 54 and placed on the paper discharge tray 55 outside the machine.

[0251] After the white toner image and the color toner image are transferred onto the recording medium P by the secondary transfer member 37A as a secondary transfer means, the residual toner on the intermediate transfer body 36 from which the recording medium P has been separated by curvature is removed by the intermediate transfer body cleaning device 190A.

[0252] Furthermore, the patch image toner on the secondary transfer member 37A is cleaned by a cleaning blade 71 of the secondary transfer device .

[0253] The recording medium (also referred to as media, image support, recording material, recording paper, or recording sheet) used in the image forming method of this embodiment may be any commonly used medium and is not particularly limited. Usable recording media include, for example, plain paper ranging from thin to thick paper, coated printing paper such as fine paper, art paper, and coated paper, commercially available Japanese paper and postcards, plastic film for overhead projectors, cloth, soft transparent film, and synthetic paper such as Yupo paper. The image forming method using the toner set of the present invention, particularly when outputting onto special recording media such as colored paper, black paper, aluminum-deposited paper, and transparent film, provides excellent low-temperature fixability and fixation separation even when a special color toner layer is formed on the upper or lower layer of a full-color image in high-value-added printing, resulting in a high adhesion amount. Furthermore, it prevents the upper layer image from bleeding into adjacent layers, thereby preventing a decrease in image density of the upper layer image. This improves the visibility of color toners, provides good color reproducibility for color images, and enables the formation of high-quality images with no color bleeding or image peeling, thereby enhancing the added value of the image. [Example]

[0254] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, operations were carried out at room temperature (25°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass," respectively.

[0255] [1. Preparation of Cyan Toner 1] (1.1) Preparation of amorphous vinyl resin particle dispersion X1 -First stage polymerization- A 5 L reaction vessel equipped with a stirrer, temperature sensor, cooling tube, and nitrogen introducing device was charged with 8 parts by mass of sodium dodecyl sulfate and 3,000 parts by mass of ion-exchanged water, and the internal temperature of the reaction vessel was raised to 80°C while stirring at a stirring speed of 230 rpm under a nitrogen stream. After the temperature was raised, an aqueous solution prepared by dissolving 10 parts by mass of potassium persulfate in 200 parts by mass of ion-exchanged water was added to the resulting mixture, and the temperature of the resulting mixture was again raised to 80°C. A monomer mixture 1 having the following composition was added dropwise to the mixture over 1 hour, and the mixture was then heated and stirred at 80°C for 2 hours to polymerize, thereby preparing a dispersion a1 of resin microparticles.

[0256] (Monomer mixture 1) Styrene 480 parts by mass n-Butyl acrylate 250 parts by mass Methacrylic acid 68 parts by mass

[0257] -Second-stage polymerization- A 5L reaction vessel equipped with a stirrer, temperature sensor, condenser, and nitrogen supply was charged with a solution of 7 parts by weight of sodium polyoxyethylene (2) dodecyl ether sulfate dissolved in 3,000 parts by weight of ion-exchanged water. The solution was heated to 80°C, and then 80 parts by weight (solids equivalent) of resin microparticle dispersion a1 and monomer mixture 2, prepared by dissolving the monomer and release agent with the composition shown below at 90°C, were added. The mixture was mixed and dispersed for 1 hour using a mechanical disperser equipped with a circulation system, "CLEARMIX" (manufactured by M-Technique Co., Ltd.; "CLEARMIX" is a registered trademark of the company), to prepare a dispersion containing emulsified particles (oil droplets). Hydrocarbon wax 1, shown below, is a release agent and has a melting point of 80°C.

[0258] (Monomer mixture 2) Styrene 285 parts by mass n-Butyl acrylate 95 parts by mass Methacrylic acid 20 parts by mass n-Octyl-3-mercaptopropionate 8 parts by mass Hydrocarbon wax 1 (C80, manufactured by Sasol) 190 parts by mass

[0259] Next, an initiator solution prepared by dissolving 6 parts by mass of potassium persulfate in 200 parts by mass of ion-exchanged water was added to the dispersion, and the resulting dispersion was polymerized by heating and stirring at 84°C for 1 hour to prepare dispersion a2 of resin microparticles.

[0260] -Third-stage polymerization- Further, 400 parts by mass of ion-exchanged water was added to dispersion a2 of resin fine particles and mixed thoroughly, and then a solution of 11 parts by mass of potassium persulfate dissolved in 400 parts by mass of ion-exchanged water was added to the resulting dispersion, and monomer mixture 3 having the following composition was added dropwise over 1 hour at a temperature of 82° C. After completion of the dropwise addition, the dispersion was heated and stirred for 2 hours to carry out polymerization.

[0261] (Monomer mixture 3) Styrene 307 parts by mass n-Butyl acrylate 147 parts by mass Methacrylic acid 52 parts by mass n-Octyl-3-mercaptopropionate 8 parts by mass

[0262] Thereafter, the mixture was cooled to 28°C to prepare amorphous vinyl resin particle dispersion X1 made of vinyl resin (styrene-acrylic resin).

[0263] The physical properties of the obtained amorphous vinyl resin particle dispersion X1 were measured, and the volume-based median diameter D50 of the amorphous vinyl resin particles was 220 nm, the glass transition temperature Tg was 46°C, and the weight average molecular weight Mw was 32,000.

[0264] (1.2) Preparation of Crystalline Polyester Resin Particle Dispersion Y1 281 parts by mass of sebacic acid and 283 parts by mass of 1,10-decanediol were placed in a reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube. After purging the reaction vessel with dry nitrogen gas, 0.1 parts by mass of Ti(OBu)4 was added, and the resulting mixture was stirred at approximately 180°C for 8 hours under a nitrogen gas flow to carry out a reaction. Further, 0.2 parts by mass of Ti(OBu)4 was added to the mixture, and the temperature of the mixture was raised to approximately 220°C. The mixture was stirred and reacted for 6 hours. The pressure inside the reaction vessel was then reduced to 1333.2 Pa, and the reaction was carried out under reduced pressure to obtain crystalline polyester resin P1.

[0265] The crystalline polyester resin P1 had a number average molecular weight Mn of 5,500, a weight average molecular weight Mw of 18,000, and a melting point Tm of 70°C.

[0266] 30 parts by mass of crystalline polyester resin P1 was melted and transferred to an emulsifying / dispersing machine "Cavitron CD1010" (manufactured by Eurotech) at a transfer rate of 100 parts by mass per minute. Simultaneously, diluted ammonia water with a concentration of 0.37% by mass was heated to 100°C using a heat exchanger and transferred to the emulsifying / dispersing machine at a transfer rate of 0.1 L per minute. The diluted ammonia water was prepared by diluting 70 parts by mass of reagent ammonia water with ion-exchanged water in an aqueous solvent tank. The emulsifying / dispersing machine was then operated at a rotor rotation speed of 60 Hz and a pressure of 5 kg / cm. 2 (490 kPa) to prepare a crystalline polyester resin particle dispersion Y1 having a solid content of 30 parts by mass.

[0267] The physical properties of the obtained crystalline polyester resin particle dispersion Y1 were measured, and it was found that the volume-based median diameter D50 of the crystalline polyester resin particles was 200 nm.

[0268] (1.3) Preparation of Hybrid Amorphous Polyester Resin Microparticle Dispersion S1 Monomer mixture 4 having the following composition containing a bireactive monomer (acrylic acid) was placed in the dropping funnel. Note that di-t-butyl peroxide is a polymerization initiator.

[0269] (Monomer mixture 4) Styrene 80 parts by mass n-Butyl acrylate 20 parts by mass Acrylic acid 10 parts by mass Di-t-butyl peroxide 16 parts by mass

[0270] The raw material monomers for the amorphous polyester polymer segment described below were placed in a four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer and a thermocouple, and heated to 170° C. to dissolve them.

[0271] (raw material monomer for amorphous polyester polymerization segment) Bisphenol A propylene oxide 2 mole adduct 285.7 parts by mass Terephthalic acid 66.9 parts by mass Fumaric acid 47.4 parts by mass

[0272] Next, to the resulting solution, the monomer mixture 6 was added dropwise over 90 minutes while stirring, and after aging for 60 minutes, unreacted monomers from the monomer mixture 4 were removed from the four-neck flask under reduced pressure (8 kPa).

[0273] Then, 0.4 parts by mass of Ti(OBu)4 was added to the four-neck flask as an esterification catalyst, and the mixture in the four-neck flask was heated to 235°C. The reaction was carried out under normal pressure (101.3 kPa) for 5 hours and then under reduced pressure (8 kPa) for 1 hour to obtain hybrid amorphous polyester resin s1. The hybrid amorphous polyester resin s1 had a number-average molecular weight Mn of 10,500 and a weight-average molecular weight Mw of 29,500.

[0274] 100 parts by mass of hybrid amorphous polyester resin s1 was dissolved in 400 parts by mass of ethyl acetate (Kanto Chemical Co., Ltd.), and mixed with 638 parts by mass of a 0.26% by mass sodium lauryl sulfate solution prepared in advance.

[0275] The resulting mixture was ultrasonically dispersed with stirring for 30 minutes using an ultrasonic homogenizer "US-150T" (manufactured by Nippon Seiki Seisakusho) at a V-LEVEL of 300 μA.

[0276] The mixture was then heated to 40°C and stirred under reduced pressure for 3 hours using a diaphragm vacuum pump "V-700" (manufactured by BUCHI) to completely remove the ethyl acetate, thereby preparing a hybrid amorphous polyester resin particle dispersion (shell dispersion) S1 with a solid content of 13.5% by mass.

[0277] The physical properties of the obtained hybrid amorphous polyester resin microparticle dispersion S1 were measured, and the volume-based median diameter D50 of the hybrid amorphous polyester resin microparticles was found to be 160 nm.

[0278] (1.4) Preparation of cyan pigment dispersion C1 90 parts by weight of sodium dodecyl sulfate was dissolved in 1,600 parts by weight of ion-exchanged water with stirring, and 420 parts by weight of CI Pigment Blue 18:3 was gradually added while stirring this solution. The resulting dispersion was then dispersed using a stirring device "Clearmix" (manufactured by M Technique Co., Ltd.) to prepare cyan pigment dispersion C1.

[0279] The volume-based median diameter D50 of the pigment in the cyan pigment dispersion C1 was measured using a Microtrac particle size distribution measuring device "UPA-150" (manufactured by Nikkiso Co., Ltd.) and was found to be 150 nm.

[0280] (1.5) Production of toner base particles 288 parts by mass (solid content equivalent) of amorphous vinyl resin microparticle dispersion X1 and 2000 parts by mass of ion-exchanged water were added to a reaction vessel equipped with a stirrer, a temperature sensor, and a cooling tube, and then a 5 mol / L aqueous sodium hydroxide solution was further added to adjust the pH of the dispersion in the reaction vessel to 10 (measurement temperature 25°C).

[0281] To the dispersion, 30 parts by mass (solids content equivalent) of cyan pigment dispersion C1 was added. Next, an aqueous solution prepared by dissolving 30 parts by mass of magnesium chloride as a flocculant in 60 parts by mass of ion-exchanged water was added to the dispersion over 10 minutes at 30°C while stirring. The resulting mixture was heated to 80°C, and 40 parts by mass (solids content equivalent) of crystalline polyester resin microparticle dispersion Y1 was added to the mixture over 10 minutes to promote aggregation.

[0282] The particle size of the particles associated in the mixture was measured using a Coulter Multisizer 3 (manufactured by Beckman Coulter, Inc.), and when the volume-based median particle size D50 of the particles reached 6.0 μm, 37 parts by mass (solid content equivalent) of hybrid amorphous polyester resin microparticle dispersion (shell dispersion) S1 was added to the mixture over 30 minutes.When the supernatant of the resulting reaction solution became transparent, an aqueous solution of 190 parts by mass of sodium chloride dissolved in 760 parts by mass of ion-exchanged water was added to the reaction solution to stop particle growth.

[0283] Furthermore, the reaction solution was heated to 80°C and stirred to promote particle fusion. The particles in the reaction solution were measured (HPF detection count: 4,000 particles) using a measuring device "FPIA-2100" (Sysmex Corporation). When the average circularity of the particles reached 0.945, the reaction solution was cooled to 30°C at a cooling rate of 2.5°C / min.

[0284] Thereafter, the mixture was heated to 60°C over about 30 minutes while stirring, and annealed at 60°C for 3 hours. The mixture was then cooled to 30°C.

[0285] Next, the particles were separated from the cooled reaction liquid and dehydrated, and the resulting cake was washed by repeating re-dispersion in ion-exchanged water and solid-liquid separation three times, and then dried at 40°C for 24 hours to obtain toner base particles B1.

[0286] Using a PerkinElmer DSC-7 differential scanning calorimeter, the peak endothermic heat ΔH derived from the crystalline resin of the toner base particles B1 was measured using the method described above. CThe measured value was 11.5 kJ / g.

[0287] (1.6) Mixing of external additives To 100 parts by mass of toner base particles B1, 0.6 parts by mass of hydrophobic silica (number average primary particle size = 12 nm, hydrophobicity = 68) and 1.0 part by mass of hydrophobic titanium oxide (number average primary particle size = 20 nm, hydrophobicity = 63) were added, and these were mixed in a "Henschel Mixer" (manufactured by Nippon Coke & Engineering Co., Ltd.) at a rotor peripheral speed of 35 mm / sec and 32°C for 20 minutes, after which coarse particles were removed using a sieve with 45 μm openings. After performing this external additive treatment, cyan toner 1 was produced.

[0288] [2. Preparation of Cyan Toners 2 to 4] Cyan toners 2 to 4 were each prepared in the same manner as in the preparation of cyan toner 1, except that the amounts of each dispersion liquid added and the annealing conditions were changed as shown in Table I.

[0289] Peak endothermic heat ΔH derived from the crystalline resin of the toner base particles in cyan toners 2 to 4 C are shown in Table I.

[0290] [3. Preparation of Fluorescent Toner 1] 20 g of a fluorescent pigment having a structure represented by the following formula (K-1) was dissolved in 450 g of ethyl acetate. This solution was added dropwise to 750 g of an aqueous solution containing 8 g of surfactant "Aqualon KH-05" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). After stirring, the solution was emulsified for 15 seconds using "Clearmix W Motion CLM-0.8W" (manufactured by M Technique Co., Ltd.). The ethyl acetate was then removed under reduced pressure to obtain a fluorescent pigment dispersion.

[0291] [ka]

[0292] The volume-based median diameter D50 of the pigment in the fluorescent pigment dispersion was measured using an electrophoretic light scattering photometer "ELS-800" (manufactured by Otsuka Electronics Co., Ltd.) and was found to be 4 μm.

[0293] Fluorescent toner 1 was prepared in the same manner as in the preparation of cyan toner 1, except that the fluorescent pigment dispersion was used instead of cyan pigment dispersion C1, and the amounts of each dispersion added and the annealing conditions were changed as shown in Table I.

[0294] Peak endothermic heat ΔH derived from the crystalline resin of the toner base particles in fluorescent toner 1 C are shown in Table I.

[0295] [4. Preparation of Black Toners 1 to 6] 90 parts by mass of sodium dodecyl sulfate was added to 1600 parts by mass of ion-exchanged water, and while stirring this solution, 420 parts by mass of carbon black (Regal 330R; manufactured by Cabot Corporation) was gradually added as a black pigment. The mixture was then dispersed using a mechanical disperser (Clearmix; manufactured by M Technique Co., Ltd.) to obtain a black pigment dispersion.

[0296] The volume-based median diameter D50 of the pigment in the black pigment dispersion was measured using an electrophoretic light scattering photometer (ELS-800; Otsuka Electronics Co., Ltd.) and found to be 110 nm.

[0297] Black toners 1 to 6 were prepared in the same manner as in the preparation of cyan toner 1, except that the black pigment dispersion was used instead of cyan pigment dispersion C1, and the amounts of each dispersion added and the annealing conditions were changed as shown in Table I.

[0298] Peak endothermic heat ΔH derived from the crystalline resin of the toner base particles for black toners 1 to 6 C are shown in Table I.

[0299] [5. Preparation of Glittering Toner 1] A brilliant pigment dispersion was prepared by adding 210 parts by mass of an aluminum pigment (260EA, manufactured by Showa Aluminum Powder Co., Ltd., with the solvent removed from the paste) to a surfactant aqueous solution prepared by dissolving 1% by mass of sodium alkyldiphenyletherdisulfonate in 480 parts by mass of ion-exchanged water, followed by dispersion using an ultrasonic homogenizer. The solids concentration (content of brilliant pigment) in the brilliant pigment dispersion was adjusted to 30% by mass. The average particle size of the brilliant pigment in the brilliant pigment dispersion was 4 μm.

[0300] In the preparation of the above cyan toner 1, the above glitter pigment dispersion was used instead of the cyan pigment dispersion C1, and the amounts of each dispersion added and the annealing treatment conditions were changed as shown in Table I, and the glitter toner 1 was prepared in the same manner.

[0301] Peak endothermic heat ΔH derived from the crystalline resin of the toner base particles in glitter toner 1 C are shown in Table I.

[0302] [6. Preparation of White Toner 1] (6.1) Preparation of crystalline polyester resin particle dispersion A heated and dried three-necked flask was charged with 266 parts by mass of 1,12-dodecanedicarboxylic acid, 169 parts by mass of 1,10-decanediol, and 0.035 parts by mass of tetrabutoxytitanate as a catalyst. The air inside the vessel was then reduced in pressure by a vacuum operation, and an inert atmosphere was created with nitrogen gas. The mixture was refluxed at 180°C for 6 hours with mechanical stirring.

[0303] The temperature was then gradually raised to 220°C by vacuum distillation and stirred for 2.5 hours. When the resin became viscous, the acid value was measured. When the acid value of the resin reached 15.0 mgKOH / g, the vacuum distillation was stopped and the resin was air-cooled to obtain a crystalline polyester resin.

[0304] The weight average molecular weight Mw of the obtained crystalline polyester resin was measured by the above-mentioned method and was found to be 13000. The melting temperature of the obtained crystalline polyester resin was measured using a differential scanning calorimeter (DSC) and was found to be 73°C.

[0305] Next, 180 parts by weight of the crystalline polyester resin and 585 parts by weight of deionized water were placed in a stainless steel beaker, immersed in a hot bath, and heated to 95°C. Once the crystalline polyester resin was melted, the mixture was stirred at 8000 rpm using a homogenizer (Ultra-Turrax T50, manufactured by IKA Corporation), while simultaneously adding dilute aqueous ammonia to adjust the pH to 7.0. Next, 20 parts by weight of an aqueous solution diluted with 0.8 parts by weight of an anionic surfactant (Neogen R, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was added dropwise to emulsify and disperse the mixture, preparing a crystalline polyester resin microparticle dispersion with a volume average particle size of 0.23 μm (resin microparticle concentration: 40% by weight).

[0306] (6.2) Preparation of amorphous polyester resin particle dispersion A heated and dried two-necked flask was charged with 74 parts by mass of dimethyl adipate, 192 parts by mass of dimethyl terephthalate, 216 parts by mass of bisphenol A ethylene oxide adduct, 38 parts by mass of ethylene glycol, and 0.037 parts by mass of tetrabutoxy titanate as a catalyst. Nitrogen gas was introduced into the vessel to maintain an inert atmosphere, and the mixture was heated with stirring and then subjected to a co-condensation polymerization reaction at 160°C for approximately 7 hours.

[0307] Thereafter, the pressure was gradually reduced to 10 Torr while the temperature was raised to 220°C and maintained at that temperature for 4 hours. The pressure was then returned to normal pressure, 9 parts by mass of trimellitic anhydride was added, and the pressure was again gradually reduced to 10 Torr and maintained at that temperature for 1 hour to obtain an amorphous polyester resin.

[0308] The glass transition point of the obtained amorphous polyester resin was measured using a differential scanning calorimeter (DSC) according to the above-mentioned measurement method, and was found to be 60° C. The molecular weight of the obtained amorphous polyester resin was measured using GPC according to the above-mentioned measurement method, and was found to have a weight average molecular weight Mw of 12,000. The acid value of the obtained amorphous polyester resin was also measured, and was found to be 25.0 mg KOH / g.

[0309] Next, 115 parts by mass of the above amorphous polyester resin, 180 parts by mass of deionized water, and 5 parts by mass of an anionic surfactant (Neogen R, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were mixed and heated to 120°C, and the mixture was thoroughly dispersed using a homogenizer (Ultra-Turrax T50, manufactured by IKA Corporation). After that, a dispersion process was carried out for 1 hour using a pressure-discharge Gaulin homogenizer to prepare an amorphous polyester resin microparticle dispersion (resin microparticle concentration 40% by mass).

[0310] (6.3) Preparation of white pigment dispersion The following components were mixed, dissolved, and dispersed for about 1.5 hours using a high-pressure impact disperser, Ultimizer (manufactured by Sugino Machine Co., Ltd., HJP30006) to prepare white pigment dispersion W1.

[0311] Titanium oxide (Ishihara Sangyo Kaisha A-220, primary particle size 0.16 μm) 100 parts by mass Anionic surfactant (Neogen R, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 15 parts by mass Ion-exchanged water 400 parts by mass

[0312] The volume average particle size of titanium oxide in the resulting white pigment dispersion was measured using a laser diffraction particle size analyzer and found to be 0.285 μm, and the solid content of the white pigment dispersion was 23% by mass.

[0313] (6.4) Preparation of release agent dispersion 90 parts by mass of Fischer-Tropsch wax FNP92 (melting temperature 92°C, manufactured by Nippon Seiro Co., Ltd.), 3.6 parts by mass of an anionic surfactant (Neogen R, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and 369 parts by mass of ion-exchanged water were mixed, heated to 100°C, and thoroughly dispersed using a homogenizer (Ultra-Turrax T50, manufactured by IKA), and then further dispersed using a pressure-discharge Gaulin homogenizer to obtain a release agent dispersion. The volume average particle size of the release agent in the obtained release agent dispersion was measured using a laser diffraction particle size analyzer, and was found to be 0.23 μm. The solids content of the release agent dispersion was 20% by mass.

[0314] (6.5) Production of toner base particles 5.4 parts by mass (solids content equivalent) of the crystalline polyester resin microparticle dispersion, 126.6 parts by mass (solids content equivalent) of the amorphous polyester resin microparticle dispersion, 90.0 parts by mass (solids content equivalent) of the white pigment dispersion, 18.0 parts by mass (solids content equivalent) of the release agent dispersion, and 484 parts by mass of deionized water were placed in a round stainless steel flask, and the mixture was thoroughly mixed and dispersed using an Ultra-Turrax T50.

[0315] Next, 0.37 parts by mass of polyaluminum chloride was added to this, and the dispersion operation was continued using the Ultra-Turrax. The flask was then heated to 52°C with stirring in a heating oil bath. After maintaining the temperature at 52°C for 3 hours, 60 parts by mass (solids equivalent) of the amorphous polyester resin microparticle dispersion was slowly added thereto.

[0316] Thereafter, the pH of the system was adjusted to 8.5 with 0.5N aqueous sodium hydroxide solution, the stainless steel flask was sealed, and the mixture was heated to 90°C with continuous stirring using a magnetic seal, and maintained at this temperature for 3.5 hours.

[0317] After the reaction was complete, the mixture was cooled, filtered, thoroughly washed with ion-exchanged water, and then subjected to solid-liquid separation using Nutsche suction filtration. This was then redispersed in 3 L of ion-exchanged water at 40°C, stirred and washed at 300 rpm for 15 minutes. This process was repeated five more times, and solid-liquid separation was performed using Nutsche suction filtration with No. 5A filter paper. The mixture was then vacuum dried for 12 hours to obtain toner base particles of White Toner 1.

[0318] The volume-based median diameter D50 of the toner base particles of White Toner 1 was 6.5 μm.

[0319] Using a PerkinElmer DSC-7 differential scanning calorimeter, the peak endothermic heat ΔH derived from the crystalline resin of the toner base particles was measured using the method described above. C The measured value was 0.58 kJ / g.

[0320] (6.6) Mixing of external additives To 100 parts by mass of the toner base particles, 1 part by mass of hydrophobic silica particles (manufactured by Nippon Aerosil Co., Ltd., RY-50) was added, and external mixing was carried out using a Henschel mixer, thereby obtaining white toner 1.

[0321] [Table 1]

[0322] [7. Evaluation of heat-resistant storage properties] 0.5 g of each toner prepared above was placed in a 10 mL glass bottle with an inner diameter of 21 mm, the lid was closed, and the bottle was shaken 600 times at room temperature using a Tap Denser KYT-2000 (Seishin Enterprise Co., Ltd.), then the bottle was left with the lid removed in an environment of 55°C and 35% RH for 2 hours. Next, the toner was placed on a 48 mesh (350 μm opening) sieve, being careful not to break up the toner aggregates, and set in a powder tester (Hosokawa Micron Corporation), fixed with a pressure bar and knob nut, and the vibration intensity was adjusted to a feed width of 1 mm. After vibration was applied for 10 seconds, the mass [g] of the toner on the sieve was measured.

[0323] The toner cohesion rate [%] was calculated using the following formula. Toner cohesion rate [%] = toner mass on sieve [g] / 0.5g x 100

[0324] The heat-resistant storage stability of the toner was evaluated according to the following criteria, and the evaluation results are shown in Table II. ○: Toner cohesion rate is less than 15% (good heat-resistant storage properties of toner) △: Toner cohesion rate is 15% or more (the toner has poor heat resistance and is not suitable for use)

[0325] [8. Evaluation of color development] A two-component developer containing each toner was prepared by adding and mixing a ferrite carrier coated with acrylic resin and having a volume average particle size of 32 μm to each of the toners prepared above so that the toner particle concentration was 6 mass %.

[0326] The fixing device of a commercially available multifunction printer, full-color copier "bizhub PRO C6501" (manufactured by Konica Minolta Business Technologies, Inc.), was modified so that the surface temperature of the fixing heat roller could be changed within the range of 100 to 210°C.

[0327] Using a modified full-color copier and a two-component developer containing each toner, A4 size (80g / m2) was printed. 2 ) Plain paper was fed lengthwise, and a 5 mm wide solid band image extending in a direction perpendicular to the feeding direction was fixed. The fixing temperature was set to 180°C.

[0328] Three subjects were asked to evaluate the desirable color development of the solid image. The evaluation results were ranked as follows: Good: Color development is good. △: There are some problems with color development. ×: Problems with color development.

[0329] [9. Evaluation of fixation] The prepared toners were combined as shown in Table II to form toner sets 1 to 12 each containing a first toner and a second toner.

[0330] A two-component developer containing each toner was prepared by adding and mixing an acrylic resin-coated ferrite carrier with a volume average particle size of 32 μm to each toner contained in the toner set so that the toner particle concentration was 6 mass %.

[0331] The fixing device of a commercially available multifunction printer, full-color copier "bizhub PRO C6501" (manufactured by Konica Minolta Business Technologies, Inc.), was modified so that the surface temperature of the fixing heat roller could be changed within the range of 100 to 210°C.

[0332] Using a modified full-color copier and a two-component developer containing each toner, a price of 152 g / m was measured under normal temperature and humidity conditions (20°C and 50% RH). 2 (Nippon Paper Industries Co., Ltd.) with a top layer adhesion weight of 2.5g / m 2 , and the coating weight of the lower layer is 20 g / m 2 An unfixed solid image was formed so that the upper layer was formed with the second toner and the lower layer was formed with the first toner.

[0333] Next, the surface temperature of the pressure roller of the fixing device was set to 140°C, and the surface temperature of the heating roller was changed in 2°C increments within the range of 140 to 180°C, and fixing was performed. At this time, the minimum fixing temperature of the upper fixing belt at which under-offset did not occur was measured. The measurement of the minimum fixing temperature was performed for both toners stored under the different conditions described above.

[0334] The fixability was evaluated according to the following evaluation criteria, with ◯ and Δ being considered as acceptable. The evaluation results are shown in Table II. ◯: The minimum fixing temperature is 148° C. or less. △: The minimum fixing temperature is 150 to 154°C. x: The minimum fixing temperature is 156°C or higher.

[0335] [Table 2]

[0336] From the above evaluation results, it is clear that the toner set of the present invention has good color development, heat-resistant storage stability, and fixability. In Table II, "the present invention" in the remarks column for Toner Sets Nos. 5 to 7 should be read as "Reference Example." [Explanation of symbols]

[0337] 31 Photosensitive drum 32 Charger 33 Exposure optical system as an image writing means 34 Developing device 34a Developing roller 36 Intermediate transfer body 36a Tension roller 36B Backup Roller 37 Primary transfer roller 37A Secondary transfer member 38 Detection Sensor 47 Fixing device 47a Heating roller 47b Compression belt 50A, 50B, 50C paper cassettes 51 Feed roller 52 Transport path 52A Paper feed roller 52B, 52C, 52D Conveyor rollers 53 Resist Roller 54 Paper ejection roller 55 Paper output tray 70 Secondary transfer device 100 Yellow (Y), Magenta (M), Cyan (C), Black (K) and White (W) process units 190 Photosensitive body cleaning device as image carrier cleaning means 190A Intermediate transfer body cleaning device GS Image Forming System SC image reader CCD line image sensor P Recording medium

Claims

1. A toner set for developing an electrostatic image, comprising a first toner and a second toner, the toner base particles of which contain different types of pigments, the first toner base particles contained in the first toner and the second toner base particles contained in the second toner each contain at least the pigment and a crystalline resin; the first toner and the second toner satisfy the following formulas (1A) and (2A), the peak endothermic heat ΔH C2 attributed to the crystalline resin of the second toner base particles is within a range of 8 to 15 J / g; The pigment content W P1 of the first toner base particles is 30% by mass or more and 60% by mass or less. A toner set for developing electrostatic images, comprising: Equation (1A) 10≦W Ｐ１ -W Ｐ２ Formula (2A) ΔH Ｃ１ / ΔH Ｃ２ ≤0.15 W Ｐ１ : Pigment content of first toner base particles [mass %] W Ｐ２ : Pigment content of second toner base particles [mass %] ΔH Ｃ１ : Peak endothermic heat amount [J / g] derived from the crystalline resin of the first toner base particles ΔH Ｃ２ : Peak endothermic heat amount [J / g] derived from the crystalline resin of the second toner base particles

2. The first toner and the second toner satisfy the following formula (2B):

2. The toner set for developing electrostatic images according to claim 1. Formula (2B) ΔH Ｃ１ / ΔH Ｃ２ ≤0.08 ΔH Ｃ１ : Peak endothermic heat amount [J / g] derived from the crystalline resin of the first toner base particles ΔH Ｃ２ : Peak endothermic heat amount [J / g] derived from the crystalline resin of the second toner base particles

3. The crystalline resin content W of the second toner base particles Ｃ２ is in the range of 5 to 10 mass % 2. The toner set for developing electrostatic images according to claim 1.

4. The pigment content W of the second toner base particles Ｐ２ is in the range of 2 to 10 mass % 2. The toner set for developing electrostatic images according to claim 1.

5. The pigment contained in the second toner base particles is an organic pigment.

2. The toner set for developing electrostatic images according to claim 1.

6. The pigment contained in the first toner base particles is an inorganic pigment.

2. The toner set for developing electrostatic images according to claim 1.

7. An image forming system using a toner set for developing electrostatic images, comprising: The toner set for developing an electrostatic image according to any one of claims 1 to 6, An image forming system comprising:

8. An image forming method using a toner set for developing an electrostatic image, comprising: The toner set for developing an electrostatic image according to any one of claims 1 to 6, An image forming method comprising:

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