JP2005017851A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce adverse effects due to difference in chargeability while using toner which shares resin. <P>SOLUTION: In a full color image forming method using pulverized toner of a plurality of colors having a wax dispersion diameter of 0.5-2 μm and a volume average particle diameter of 6-10 μm, a volume percentage of particles of ≤5 μm diameter in the toner of each color having a larger charge amount as compared with the color toner having the smallest charge amount is made higher than that in the color toner having the smallest charge amount. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

表中のオフセット開始温度は、表示温度まではオフセットが発生しなかったことを表す。また、未発生とは、２１０ ℃までの評価においてオフセットが発生しなかったことを表す。
【００３０】
〔実施例２〕
実施例１と同様にしてＹＣＭＫ各色のトナーを得た。
得られたトナーで現像器を組立て、印字耐久試験を行ったところ、表２に示すように、トナー飛散、現像ローラヘのトナーフィルミングが発生することなく１２ｋ枚の印字を終了することができた。また、そのトナーで定着試験を行ったところ、何れのトナーも１４５ ℃以上では十分な定着強度が得られ、ＣＫについては１９５ ℃まで、Ｍ については２００ ℃まで高温オフセットが発生することなく定着することができた。また、Ｙ については２１０ ℃までの確認の中では高温オフセットは発生しなかった。
【００３１】
【表２】

〔比較例１〕
実施例１と同様にしてＹＣＭＫ各色のトナーを得た。
得られたトナーで現像器を組立て、印字耐久試験を行ったところ、表３に示すように、ＹＭはトナー飛散、現像ローラヘのトナーフィルミングが発生することなく１２ｋ枚の印字を終了することができたが、Ｃ については、耐久時には８ｋ枚時点でトナー飛翔性不足が発生し、必要な画像濃度が得られなくなった。Ｋ については、組立て時にトナー飛散が発生し、耐久時には８ｋ枚時点で印字の欠落が発生し、現像ローラを確認したところフィルミングが認められた。また、そのトナーで定着試験を行ったところ、何れのトナーも１４５ ℃以上では十分な定着強度が得られ、Ｙ については１９５ ℃まで、ＣＭＫ については２１０ ℃までの確認の中では高温オフセットは発生しなかった。
【００３２】
【表３】

【００３３】
【発明の効果】
樹脂を共通化することにより、ＹＭＣＫ４色の特性を概ね揃えることが可能となるが、顔料等の影響により帯電性に差が生じてしまう。帯電性の高いトナーは現像ローラに対する付着力が強く、現像されにくくなり、現像に必要な電界が大きくなる。そこで、帯電量の最も低い色のトナーに比して、帯電量の高い他色のトナーについては、ワックス主体の微粉を多くすることにより、トナーとワックス主体の微粉の混合系としての現像剤の帯電性を低下させることにより現像に必要な電界を下げられ、現像量も必要量確保することができる。
【図面の簡単な説明】
【図１】本実施形態で使用する画像形成装置の例を説明する図である。
【図２】高温オフセット及びトナー飛散とワックス分散径の関係を説明する図である。
【図３】ワックス主体の微粉量とトナーの粒径分布の関係を示す図である。
【図４】５μｍ径以下の体積割合とトナー飛翔性との関係を示す図である。
【符号の説明】
１…感光体、２…露光器、３…ロータリ式現像器、４…現像ローラ、５…中間転写媒体、６…駆動ローラ、７…従動ローラ、８…１次転写ローラ、９…テンションローラ、１０…用紙トレー、１１…用紙繰り出しローラ、１２…紙搬送路、１３…２次転写ローラ、１４…紙ガイド、１５…定着器、１６…排紙トレー。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a full-color image forming method using a plurality of pulverized toners.
[0002]
[Prior art]
In general, after a toner image obtained by exposing an electrostatic latent image formed on an electrostatic latent image carrier with a toner charged by a developing device is overlaid on an intermediate transfer medium and transferred onto paper in a batch An image forming apparatus that heats and fixes is known. As a toner used in such an image forming apparatus, a binder resin is used so that charging can be applied to the developing roller without filming and fixing can be performed in an appropriate temperature range as the apparatus. The thing which makes a softening point 110-160 degreeC and an acid value 10-40 is proposed (patent document 1).
[0003]
In addition, the number distribution of toner particles having a particle size of 4 μm or less is 30% by number or less and the charge amount is from | 5 | to | 50 | μC / g so that high transfer efficiency, cleaning properties, and toner scattering are improved. Has also been proposed (Patent Document 2).
[0004]
[Patent Document 1] Japanese Patent Publication No. 6-42081
[Patent Document 2] Japanese Patent No. 2925431
[Problems to be solved by the invention]
By the way, Y, M, C, and K toners used in recent full-color image forming apparatuses are prepared from a kneading method in which resin, pigment, wax, CCA (Charge Control Agent), etc. are kneaded and then classified, or from a solution. Manufactured by a polymerization process that produces particles. However, when created under the same manufacturing conditions, color differences occur in the thermal characteristics, charging characteristics, fluidity, etc., so the developer configuration such as toner charge amount and development amount is made as similar as possible. There is a problem in that it is necessary to cope with each color, etc., and the parts cannot be shared, and high-precision adjustment is necessary. Also, the secondary transfer from the intermediate transfer medium to the paper and the subsequent fixing are performed in a batch on the toner with the colors overlaid. Therefore, if there is a difference between colors, the characteristics overlap. Since it is necessary to set the conditions, there is a problem that the favorable range of the conditions to be set becomes very narrow. The toner having a common resin causes a difference in chargeability due to the influence of pigments and the like, and there is a problem in that the assembling conditions of the developing device are different. Is not touched.
[0007]
[Means for Solving the Problems]
An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to alleviate the harmful effects caused by the difference in chargeability by using a toner having a common resin.
Therefore, the present invention provides a toner having the lowest charge amount in a full-color image forming method using a plurality of pulverized toners having a wax dispersion diameter of 0.5 to 2 μm and a volume average particle diameter of 6 to 10 μm. The toner of other colors having a relatively high charge amount is characterized by increasing the volume ratio of 5 μm diameter or less.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 1 is a diagram illustrating an example of an image forming apparatus used in the present embodiment.
The photoreceptor 1 is uniformly charged by a charger (not shown), and an electrostatic latent image is formed by image exposure from the exposure device 2. A rotary developing unit 3 for developing toner on an electrostatic latent image has developing units of four colors Y, M, C, and K, and the developing roller 4 of each unit is positioned on the photosensitive member by intermittent rotation of the rotary developing unit. In this position, toner development is performed facing the photoreceptor 1 at that position. An intermediate transfer medium 5 stretched by a driving roller 6, a driven roller 7, a primary transfer roller 8, a tension roller 9 and the like is separated from and abutted on the photosensitive member 1 at the position of the primary transfer roller 8, and is placed on the photosensitive member. The formed toner image is transferred to the intermediate transfer medium 5 (primary transfer), and four colors are superimposed on the intermediate transfer medium.
[0009]
A secondary transfer roller 13 that is in contact with the intermediate transfer medium 5 is provided at a position facing the drive roller 6 (also serving as a secondary transfer backup roller), and four color toner images on the intermediate transfer medium are provided at this position. Are collectively transferred (secondary transfer). That is, the paper fed from the paper tray 10 by the paper feed roller 11 is conveyed to the position of the secondary transfer roller 13 through the paper conveyance path 12. While the color transfer is being performed on the intermediate transfer medium (during the primary transfer), the secondary transfer roller 13 is separated from the intermediate transfer medium. When applied, a four-color toner image is collectively transferred from the intermediate transfer medium to the paper (secondary transfer). The sheet after the secondary transfer passes through a paper guide 14 and is introduced into a fixing device 15 including a heating roller 15a and a pressure roller 15b, and is discharged to a discharge tray 16 on the upper surface of the apparatus.
[0010]
The present embodiment is intended for an image forming apparatus using non-contact development using a non-magnetic one-component toner. Y, M, C, and K toners are manufactured by a pulverization method in which pigments, waxes, CCA, external additives, and the like are added to a common negatively charged thermoplastic polyester resin, kneaded, and then pulverized and classified. A negatively charged toner having a particle diameter of 6 to 10 μm (measured by Coulter Multisizer II (aperture diameter: 100 μm) manufactured by Coulter, Inc.) is used. The softening point of each color toner is proportional to the molecular weight and varies depending on the kneading conditions.
[0011]
By making the resin common, it is possible to make the characteristics of the Y, M, C, and K4 colors substantially uniform, but a difference in chargeability occurs due to the influence of pigments and the like. Highly chargeable toner has strong adhesion to the developing roller due to mirror image force, etc., and in non-contact development, the flying property from the developing roller to the photosensitive member is reduced and development becomes difficult, and the electric field required for development increases. End up. When the electric field between the developing roller and the photosensitive member becomes large, problems such as the occurrence of discharge occur, causing image deterioration.
[0012]
By the way, in full-color image formation, toner transfer images formed with Y, M, C, and K color toners are collectively fixed by a fixing device. For this reason, the set temperature of the fixing device is determined by the toner having the narrowest fixing temperature range among the Y, M, C, and K color toners. The upper limit of the good fixing temperature range is high temperature offset that causes the toner to melt into the heat roller and the paper side, paper wrapping around the heat roller caused by the effect, and the toner does not cry clearly It is determined by gloss (glossiness) unevenness or the like where the surface layer of the toner image is rough, but all are determined due to high temperature offset.
[0013]
FIG. 2 is a diagram for explaining the relationship between high temperature offset, toner scattering, and wax dispersion diameter.
As a method for improving the high temperature offset, there is a method in which a wax is added to the toner so that a peeling effect by the wax is expressed between the heat roller and the toner layer at the time of fixing. The dispersion diameter of the wax (the diameter of the wax particles dispersed in the toner). ) Of 0.5 to 2 μm improves the high temperature offset of fixing.
[0014]
As shown in the figure, the effect of improving the high temperature offset was obtained by setting the wax dispersion diameter to 0.5 μm or more. If the dispersion diameter of the wax exceeds 2 μm, the effect of high temperature offset can be obtained, but the wax is likely to fall off from the resin particles constituting the toner, and the wax-based fine powder (wax fine powder) is more likely to be generated. . When the fine powder having a diameter of about 1 μm mainly composed of wax adheres to the developing roller, it inhibits the frictional charging of the toner with the developing roller, the toner chargeability is lowered, the toner layer cannot be formed, and fogging and toner scattering occur. . Accordingly, when the wax dispersion diameter is in the range of 0.5 to 2 μm, the effect of improving the high temperature offset can be obtained, and a toner with less scattering from the developing device can be obtained.
[0015]
In this embodiment, the wax dispersion diameter is set to 0.5 to 2 μm to improve the high temperature offset of fixing, and the fact that the chargeability of the toner is reduced by the fine wax powder makes it possible to obtain a toner having the lowest charge amount. For other color toners having a higher charge amount, the chargeability is lowered by increasing the amount of fine wax powder, and the adhesion to the developing roller is weakened to improve the flying property from the developing roller to the photoreceptor.
[0016]
FIG. 3 is a graph showing the relationship between the amount of fine powder mainly composed of wax and the particle size distribution of the toner.
The control of the amount of fine wax powder can be confirmed directly by enlarging with a microscope or the like and counting the actual number. Moreover, as mentioned above, since the diameter is around 1 μm, it can be confirmed by the particle size ratio of the fine powder amount measured by a particle size measuring device such as a Coulter counter. As shown in the figure, it was found that a strong correlation was obtained between the volume ratio of the toner having a diameter of 5 μm or less and the amount of fine wax powder, and the amount of the wax powder could be controlled by the volume ratio of the toner having a diameter of 5 μm or less. It was. Therefore, for a toner with high chargeability, the amount of wax fine powder can be increased and the chargeability can be lowered by increasing the volume ratio of 5 μm diameter or less.
[0017]
FIG. 4 is a diagram for explaining the relationship between the volume ratio of 5 μm diameter or less and the toner flightability, where the horizontal axis indicates the volume ratio of 5 μm diameter or less and the vertical axis indicates the toner flight performance.
In the figure, toner represented by a solid line (high charge amount) and a broken line (low charge amount) indicate toner pulverized from the same kneaded material for each line. For example, the solid line toner has a high chargeability due to the effect of the pigment as a kneaded product, and plots the results of evaluating the toner flying performance based on the volume ratio difference of 5 μm diameter or less after pulverization / classification. It is a thing. The toner flying property can be evaluated, for example, by developing with non-contact development by applying a development bias and confirming the development efficiency. The development efficiency is a development position toner supply amount indicating how much toner is supplied to the development position which is a position where the photosensitive member and the developing roller are opposed to each other (the amount of toner on the developing roller × the linear speed ratio of the developing roller to the photosensitive member). ) And the ratio supplied to the development of the toner on the developing roller. The higher the development efficiency, the higher the toner flying property.
[0018]
In the case of a color toner, the chargeability of each color toner varies depending on the difference in pigments and the like, and therefore, the difference in flightability, which is also called the ease of development, occurs. Compared to the toner of the color with the lowest charge amount, the toner of other colors with a high charge amount will have insufficient flying properties, so by increasing the volume ratio of 5 μm diameter or less (that is, increasing the amount of fine wax powder). Reduce chargeability and improve flight performance. As described above, the difference in flying property due to the difference in toner charge amount can be adjusted by the volume ratio of the toner having a diameter of 5 μm or less.
[0019]
Examples will be described below.
The toner used in the present invention contains at least a colorant, a wax, and a binder resin, and may contain others as necessary.
[0020]
(Binder resin)
Examples of the binder resin contained in the toner include styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butadiene, and isoprene; vinyl esters such as vinyl acetate, vinyl propionate, and vinyl benzoate. , Acrylic monomers such as methyl acrylate, ethyl acrylate and butyl acrylate; α-methylene aliphatic monocarboxylic esters such as methyl methacrylate, ethyl methacrylate and butyl methacrylate; vinyl methyl ether and vinyl ethyl Homopolymers of monomers such as vinyl ethers such as ether and vinyl butyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone, and combinations of two or more of these monomers Such as copolymers or mixtures thereof. Butter, and the like. Among these resins, typical examples include polystyrene resins, styrene-alkyl acrylate alkyl copolymers, styrene-alkyl methacrylate copolymers, styrene-acrylonitrile copolymers, polyethylene resins, and polypropylene resins. A preferred example of the resin is a resin. Furthermore, a polyester resin, a polyurethane resin, an epoxy resin, a silicon resin, a polyamide resin and the like are also preferable.
[0021]
Of these, polyester resins are particularly preferred. The polyester resin uses an alcohol component and a carboxylic acid component such as a carboxylic acid, a carboxylic acid ester, and a carboxylic acid anhydride as raw material monomers. The polyester resin can be usually produced by polycondensation of an alcohol component and a carboxylic acid component in an inert gas atmosphere at a temperature of 180 ° C to 250 ° C.
The acid value of the polyester resin is desirably 10 (KOHmg / g) or more, preferably 15 (KOHmg / g) or more in order to improve the dispersibility of the colorant, so as not to deteriorate the environmental resistance of the toner. It is 30 (KOHmg / g) or less, preferably 25 (KOHmg / g) or less.
[0022]
The acid value can be measured by a method according to JISK0070.
The glass transition point of the polyester resin is 55 ° C. or higher, preferably 60 ° C. or higher, from the viewpoint of toner durability. The glass transition point is raised to 100 ° C. using a differential scanning calorimeter (DSC10 manufactured by Seiko Denshi Kogyo Co., Ltd.), left at that temperature for 3 minutes, and then cooled to room temperature at a cooling rate of 10 ° C./min. When the sample was heated at a heating rate of 10 ° C / min and the thermal history was measured, the maximum slope between the extension of the baseline below the glass transition point and the peak rising portion to the peak apex was obtained. The temperature at the intersection with the indicated tangent.
[0023]
(Coloring agent)
Examples of the colorant used in the present invention include carbon black: C.I. I, Pigment Yellow 1, 3, 3, 74, 97, 98, etc. Acetoacetic acid arylamide monoazo yellow pigments: C.I. I, Pigment Yellow 12, 13, 13, 17, etc. Acetoacetic Arylamide Disazo Yellow Pigment: C.I. I, Solvent Yellow 19, 77, 79, C.I. Yellow dyes such as I, Disperse Yellow 164, etc .: C.I. Pigment Red 48, 49: 1, 53: 1, 57, 57: 1, 81, 122, 5 etc. Red or red pigment: C.I. Red dyes such as I, Solvent Red 49, 52, 58, 8; I. Pigment Blue 15: 3 and other copper phthalocyanines and their blue dyes: C.I. Green pigments such as I, Pigment Green, and 36 (phthalocyanine green) can be used. These dyes and pigments may be used alone or in combination of two or more. The amount of the colorant used is not particularly limited, but it is usually preferably about 2 to 7 with respect to the binder resin 100 1.
[0024]
(Charge control agent; CCA)
Examples of the charge control agent used in the present invention include metal salts of benzylic acid derivatives and metal salts of salicylic acid derivatives.
Both the metal salt of the benzylic acid derivative and the metal salt of the salicylic acid derivative used in the present invention are colorless and can give a high negative charge to the toner. In addition, the metal salt of benzylic acid derivative is very effective in improving the rise of charge, and the metal salt of salicylic acid is very effective in increasing the level of charge. Therefore, by using both in combination, it is possible to improve the image history and supply ability of the non-magnetic one-component development method.
The addition amount of the charge control agent is 3 or less, preferably 2 or less with respect to the binder resin 100 in order to prevent a decrease in the charge amount due to the conductivity of the charge control agent.
[0025]
(wax)
The wax preferably has a melting point of 60 to 120 ° C, more preferably 70 to 110 ° C. When the melting point is 60 ° C. or lower, toner aggregation may occur. When the melting point is higher than 120 ° C., the wax may not ooze out during fixing and offset may occur. The melting point is a value obtained by measuring the endothermic peak temperature with a DSC curve measured by a differential scanning calorimeter.
Examples of the wax include paraffin wax and derivatives thereof, montan wax and derivatives thereof, microcrystalline wax and derivatives thereof, and polyolefin wax and derivatives thereof. Furthermore, alcohol-based and fatty acid-based waxes, animal-based waxes, mineral-based waxes, ester waxes, acid amide-based waxes and the like can also be mentioned. These waxes may be used alone or in combination of two or more.
[0026]
(External additive)
Examples of the external additive include silicon dioxide (silica), titanium dioxide (titania), aluminum oxide, zinc oxide, magnesium oxide, cerium oxide, iron oxide, copper oxide, and tin oxide. Silica fine particles are preferable from the viewpoint of imparting properties and charging properties.
[0027]
The confirmation method of toner physical properties is as follows.
(Confirmation of wax dispersion diameter)
The wax dispersion diameter was quantified by randomly extracting ten toners and measuring the size of the wax dispersed in the toner by observation with a transmission electron microscope.
(Toner softening point)
The softening point temperature of the toner is such that a load of 20 kg / cm ² is applied while heating a sample of about 1 g at a temperature rising rate of 6 ° C./min using a flow tester (CFT-500, manufactured by Shimadzu Corporation), Extrusion was performed from a die having a height of 1 mm, and the temperature corresponding to the midpoint between the descending start temperature and the descending end temperature of the plunger was defined as the softening point temperature.
(Toner charge amount)
The charge amount was measured by mixing the carrier particles and the toner in the same manner as the two-component toner and measuring the blow-off charge amount.
[0028]
[Example 1]
(Production of toner)
Polynistel ... 90 parts Pigment ... 4 parts Wax ... 4 parts CCA ... 2 parts After kneading the mixture of the above composition and pulverizing with a jet type pulverizer, fine particles and coarse particles are classified with a wind classifier, YCMK colored particles were obtained.
To 100 parts of the obtained YCMK colored particles, 2.5 parts of negatively chargeable silica and 1.0 part of negatively chargeable titania were added as external additives and surface-treated to obtain a toner.
When the developer was assembled with the obtained toner and subjected to a printing durability test, as shown in Table 1, printing of 12k sheets could be completed without causing toner scattering and toner filming on the working roller. It was. Further, when a fixing test was conducted with the toner, all the toners had a sufficient fixing strength at 145 ° C. or higher, and YCK could be fixed up to 195 ° C. without causing a high temperature offset. For M 1, high temperature offset did not occur in the confirmation up to 210 ° C.
[0029]
[Table 1]

The offset start temperature in the table represents that no offset occurred until the display temperature. Further, “not generated” means that no offset occurred in the evaluation up to 210 ° C.
[0030]
[Example 2]
In the same manner as in Example 1, toners of each color of YCMK were obtained.
A developer was assembled with the obtained toner and a printing durability test was conducted. As shown in Table 2, printing of 12k sheets could be completed without causing toner scattering and toner filming on the developing roller. . Further, when a fixing test was performed with the toner, all the toners had a sufficient fixing strength at 145 ° C. or higher, and the toner was fixed to 195 ° C. for CK and 200 ° C. for M 2 without high temperature offset. I was able to. For Y 1, high temperature offset did not occur in the confirmation up to 210 ° C.
[0031]
[Table 2]

[Comparative Example 1]
In the same manner as in Example 1, toners of each color of YCMK were obtained.
When the developer was assembled with the obtained toner and a printing durability test was performed, as shown in Table 3, YM could finish printing 12k sheets without causing toner scattering and toner filming on the developing roller. However, with regard to C 1, the toner flying performance was insufficient at the time of 8k sheets at the end of durability, and the necessary image density could not be obtained. With respect to K 2, toner scattering occurred during assembly, lack of printing occurred at the time of 8k sheets during endurance, and filming was observed when the developing roller was checked. In addition, when a fixing test was performed with the toner, sufficient fixing strength was obtained for all toners at 145 ° C. or higher, and high temperature offset occurred in Y 1 up to 195 ° C. and CMK up to 210 ° C. I did not.
[0032]
[Table 3]

[0033]
【The invention's effect】
By making the resin common, it is possible to substantially align the characteristics of the four colors of YMCK, but there is a difference in chargeability due to the influence of pigments and the like. Highly chargeable toner has strong adhesion to the developing roller, is difficult to develop, and increases the electric field required for development. Therefore, for other color toners with a high charge amount compared to the toner with the lowest charge amount, by increasing the amount of wax-based fine powder, the developer as a mixture system of toner and wax-based fine powder is increased. By reducing the charging property, the electric field necessary for development can be lowered, and the development amount can be secured.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of an image forming apparatus used in the present embodiment.
FIG. 2 is a diagram illustrating the relationship between high temperature offset, toner scattering, and wax dispersion diameter.
FIG. 3 is a graph showing the relationship between the amount of fine powder mainly composed of wax and the particle size distribution of toner.
FIG. 4 is a graph showing a relationship between a volume ratio of a diameter of 5 μm or less and toner flying properties.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Photoconductor, 2 ... Exposure device, 3 ... Rotary developing device, 4 ... Developing roller, 5 ... Intermediate transfer medium, 6 ... Driving roller, 7 ... Driven roller, 8 ... Primary transfer roller, 9 ... Tension roller, DESCRIPTION OF SYMBOLS 10 ... Paper tray, 11 ... Paper feeding roller, 12 ... Paper conveyance path, 13 ... Secondary transfer roller, 14 ... Paper guide, 15 ... Fixing device, 16 ... Paper discharge tray

Claims (1)

In a full-color image forming method using a plurality of pulverized toners having a wax dispersion diameter of 0.5 to 2 [mu] m and a volume average particle diameter of 6 to 10 [mu] m, the charge amount is lower than that of the toner having the lowest charge amount. An image forming method comprising increasing the volume ratio of a diameter of 5 μm or less for high-color toners.

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