JP3987237B2 - Image forming method and image forming apparatus - Google Patents

Description

【０１１２】
上記成分をバンバリーミキサーにより溶融混錬し、冷却後ジェットミルによる微粉砕と風力分級機による分級を行い、粉砕および分級の条件を変えて後記表１に示す各粒度分布の着色粒子Ｍ１、Ｍ２を得る。
【０１１３】
＜着色粒子の作製例２＞
マゼンタフラッシング顔料をシアンフラッシング顔料に代えた他は、着色粒子の作製例１と同様にして後記表１に示す着色粒子Ｃ１、Ｃ２を得る。なお、粉砕および分級の条件は、後記表１に示す粒度分布となるように調整する。
【０１１４】
＜着色粒子の作製例３＞
ポリエステル樹脂を５０重量部とし、マゼンタフラッシング顔料２５重量部をイエローフラッシング顔料５０重量部に代えた他は、着色粒子の作製例１と同様にして、後記表１に示す着色粒子Ｙ１、Ｙ２を得る。なお、粉砕および分級の条件は、後記表１に示す粒度分布となるように調整する。
【０１１５】
＜着色粒子の作製例４＞
ポリエステル樹脂を９０重量部とし、マゼンタフラッシング顔料２５重量部をカーボンブラック（一次粒子平均径４０ｎｍ）１０重量部に代えた他は、着色粒子の作製例１と同様にして、後記表１に示す着色粒子Ｋ１、Ｋ２を得る。なお、粉砕および分級の条件は、後記表１に示す粒度分布となるように調整する。
【０１１６】
以上のようにして得られた各着色粒子について、粒度分布、顔料粒子平均分散粒径、およびａＤＣをまとめて、後記表１に示す。
【０１１７】
３）トナーの作製
前記Ｍ１、Ｃ１、Ｙ１、Ｋ１の各着色粒子に、ヘキサメチルジシラザンで表面疎水化処理した一次粒子平均粒径４０ｎｍのシリカ（ＳｉＯ₂）微粒子と、メタチタン酸とイソブチルトリメトキシシランの反応生成物である一次粒子平均粒径２０ｎｍのメタチタン酸化合物微粒子とを、それぞれの着色粒子の表面に対する被覆率が４０％となるように添加し、ヘンシェルミキサーで混合し、トナーを作製する。また、Ｍ２、Ｃ２、Ｙ２、Ｋ２の各着色粒子には、それぞれの着色粒子の表面に対する被覆率が３０％となるように添加した。得られた各トナーは、使用した各着色粒子の番号をそのまま使用して表記することとする。
【０１１８】
なお、ここでいう着色粒子の表面に対する被覆率とは、前述の式（１）により求められる値Ｆ（％）をいう。
得られた各トナーについて、全外添剤被覆率と、ｑ／ｄのピーク値およびボトム値を既述の方法により測定した値と、をまとめて、下記表１に示す。
【０１１９】
【表１】

【０１２０】
▲２▼キャリア製造例
体積平均粒子径４０μｍのＣｕ−Ｚｎフェライト微粒子１００重量部にγ−アミノプロピルトリエトキシシラン０．１重量部を含有するメタノール溶液を添加し、ニーダーで被覆した後、メタノールを留去し、さらに１２０℃で２時間加熱して上記シラン化合物を完全に硬化させる。この粒子に、パーフルオロオクチルエチルメタクリレート−メチルメタクレート共重合体（共重合比４０：６０）をトルエンに溶解させたものを添加し、真空減圧型ニーダーを使用してパーフルオロオクチルエチルメタクリレート−メチルメタクレート共重合体のコーティング量が０．５重量％となるように樹脂被覆し、以下の実施例および比較例で用いる樹脂被覆型キャリアを製造する。
【０１２１】
〔現像剤の作製〕
樹脂被覆型キャリア；１００重量部に対して、前記得られた各トナー；４重量部をＶ型混合機により混合し、実施例および比較例で用いる各二成分現像剤を得る。
【０１２２】
［各種評価試験方法］
上記得られた各二成分現像剤を使用して、以下に示すトナーの各種評価試験を行った。ここで、用いた各二成分現像剤において、含まれるトナーの番号がＭ１、Ｃ１、Ｙ１、およびＫ１のものを順に実施例１、２、３、および４と、含まれるトナーの番号がＭ２、Ｃ２、Ｙ２、およびＫ２のものを順に比較例１、２、３、および４とする。
【０１２３】
なお、下記各種評価試験においては、転写材として富士ゼロックス社製Ｊコート紙を使用し、画像形成装置として富士ゼロックス社製Ａｃｏｌｏｒ９３５改造機（潜像担持体及び露光装置を改造し、外部電源により、現像時に電圧を調整できるように改造したもの（以下、単に「Ａｃｏｌｏｒ９３５改造機」という））を用い、全て温度２２℃、湿度５５％の環境条件にて行う。また、画像形成は、画像濃度１．６〜２．０の範囲内になるように適宜調整しつつ行う。
【０１２４】
帯電装置は、導電性基体の外周面を順次被覆する導電性ゴム層、ブリード防止層、分子内にイオン性セグメントを有するポリウレタンアイオノマーに電解質を含有させた抵抗制御層、および表面層から構成される。イオン性セグメントとしては、スルホン酸基を有する。また、上記ポリウレタンアイオノマーのガラス転移温度は２５℃、体積固有抵抗率は１０⁷Ωｃｍである。電解質としては、過塩素酸リチウムを用いた。この帯電部材がロールとして構成され、感光体に接触して配置されている。該帯電装置を用いて、有機感光体を−５００Ｖに帯電する。
【０１２５】
＜ＴＭＡ＞
面積率１００％のベタ画像を作成し、当該画像部分の単位面積当たりのトナーの重量（ＴＭＡ：ｍｇ／ｃｍ²）を測定する。具体的な測定方法としては、１０ｃｍ²の面積の未定着ベタ画像を転写材上に作成し、これを秤量し、次いでエアブローにより転写材上の未定着トナーを除去した後、転写材のみの重量を測定し、未定着トナー除去前後の重量差からＴＭＡを算出する。
【０１２６】
＜画像濃度＞
面積率１００％のベタ画像を作成し、Ｘ−Ｒｉｔｅ４０４（Ｘ−Ｒｉｔｅ社製）を用いて、当該画像部分の画像濃度を測定する。
【０１２７】
＜細線再現性評価試験＞
潜像担持体上に線幅５０μｍになるように細線の画像を形成し、それを転写材に転写および定着した。転写材上の定着像の細線の画像をＶＨ−６２００マイクロハイスコープ（キーエンス社製）を用いて倍率１７５倍で観察する。具体的な評価基準は以下の通りである。
◎：細線がトナーにより均一に埋まり、エッジ部での乱れもない。
×：細線がトナーにより均一に埋まっていない。エッジ部でぎざつきが非常に目立つ。
【０１２８】
＜階調再現性評価試験＞
画像面積率１０％、２０％、３０％、４０％、５０％、６０％、７０％、８０％、９０％、および１００％の各水準の階調画像を作成し、Ｘ−Ｒｉｔｅ４０４（Ｘ−Ｒｉｔｅ社製）により画像濃度を測定し、階調性を判断する。具体的な評価基準は以下の通りである。
◎：低画像面積率部から高画像面積率部まで、全ての階調画像について階調性が非常に良好である。
×：高／低画像面積率部で階調再現領域が狭く、階調性が不安定である。
【０１２９】
＜画像欠陥＞
画像面積率５％および１０％の水準の階調画像を作成し、得られた画像を目視にて観察し、濃度ムラを評価する。具体的な評価基準は以下の通りである。
◎：５％、１０％ともに濃度ムラがない。
×：５％、１０％ともにやや濃度ムラが観察される。
【０１３０】
以上の各評価結果を下記表２にまとめる。
【０１３１】
【表２】

【０１３２】
また、上記実施例１〜４で得られた４色の二成分現像剤を使用して、フルカラー画像を形成したところ、中間色の発色性に優れ、濃度ムラのない高画質の画像を繰り返し得ることができた。これに対し、上記比較例１〜４で得られた４色の二成分現像剤を使用して、フルカラー画像を形成したところ、得られた画像は中間色の発色性が劣り、鮮鋭度の低いものであった。
【０１３３】
【発明の効果】
以上のように本発明の画像形成方法あるいは画像形成装置によれば、接触方式の帯電を行うことによっても、濃度ムラのない、中間調の再現に優れた高画質の画像を得ることができる。
【図面の簡単な説明】
【図１】 ＣＳＧ法によりｑ／ｄ値の度数分布を測定するための測定装置の概略斜視図である。
【符号の説明】
１０：測定装置
１２：胴部
１４：フィルター
１６：メッシュ
１８：サンプル供給筒
２０：サンプル出口[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming method and an image forming apparatus, and more particularly to an image forming method and an image forming apparatus applied to electrophotography, electrostatic recording, electrostatic printing, and the like.
[0002]
[Prior art]
In electrophotography, the toner in the developer is attached to the electrostatic latent image formed on the latent image carrier, transferred onto paper or plastic film as a transfer material, and then fixed by heating or the like to form an image. To do. The developer used here includes a two-component developer composed of a toner and a carrier, and a one-component developer such as a magnetic toner. The two-component developer is a carrier that stirs, conveys, and charges the developer. Since it has functions such as good controllability to share functions, it is widely used at present.
[0003]
On the other hand, in printers and copiers using electrophotography, colorization has progressed over the past few years, and electrostatic latent images have become finer due to improved resolution of the apparatus. Along with this, in order to develop the electrostatic latent image faithfully and obtain a higher quality image, the diameter of the toner has been decreasing in recent years. In particular, in a full-color copying machine that develops, transfers, and fixes a digital latent image with chromatic toner, a small particle size toner of 7 to 8 μm is used to achieve a certain level of high image quality.
[0004]
Various improvements have been proposed as full-color toners. For example, in JP-A-6-75430 and JP-A-7-77825, in order to obtain an image excellent in highlight reproduction and fine line reproduction at a high image density, the weight average particle diameter of toner particles is 3 to 3. The amount of toner having a particle size of 7 μm and 5.04 μm or less is more than 40% by number, the toner having a particle size of 4 μm or less is 20 to 70% by number, and the toner having a particle size of 8 μm or more is 2 to 20 A proposal has been made to use a toner containing 6% by volume or less of toner having a particle size of 10% by volume or less.
[0005]
JP-A-7-146589 discloses that the toner particles have a weight average particle diameter of 3.5 to 7.5 μm in order to obtain an image having high image density and excellent highlight reproduction and fine line reproduction. More than 35% by number of toner having a particle size of 5.04 μm or less, more than 15% by number of toner having a particle size of 4 μm or less, and 2 to 20% by volume or less of toner having a particle size of 8 μm or more. A proposal has been made to use a toner containing 6 vol% or less of toner having a particle size of 0.08 μm or more.
[0006]
Further, Japanese Patent Application Laid-Open No. 8-227171 discloses a toner having a weight average particle diameter of 1 to 9 μm with a specified shape factor in order to improve transferability and cleaning properties, and to improve deterioration of toner characteristics due to external additive deterioration. There is a proposal to add 10-90 nm inorganic powder and 30-120 nm hydrophobized silicon compound fine powder.
[0007]
In the small particle size toners studied in these documents, the weight average particle size of the toner particles is 3 to 7 μm, but the proportion of the toner having a particle size of 5 μm or less is not necessarily large. However, there are limits to improving image quality. Furthermore, the relationship between the content of toner having a particle diameter of 1 μm or less and various toner characteristics has not been studied at all.
[0008]
Further, in these toners, the particle size distribution of the external additive is wide, and the idea regarding the coverage of the toner particles is not clearly shown. Therefore, when the toner has a volume average particle diameter of 5 μm or less, the toner Therefore, it is impossible to provide appropriate powder flowability, powder adhesion, and chargeability, and image quality improvement with a small particle size toner cannot be achieved. In fact, the weight average particle size of the toner particles listed in these examples is at least 6 μm.
[0009]
In addition, due to the decrease in powder characteristics accompanying the reduction in toner diameter, the charge exchange between the toner and carrier decreases, leading to a decrease in the rise of charging, resulting in a broader charge distribution and image quality defects such as fogging. As a matter of fact, it has been difficult to achieve high image quality with a toner having a small particle diameter of 6 μm or less.
[0010]
As the toner particle size is reduced, it becomes difficult to secure the toner charge amount necessary for development, and in some cases, the toner may be charged to a reverse polarity. If a toner with an insufficient charge amount or a toner charged to a reverse polarity is used, image dropout or fogging of non-image areas is likely to occur. On the other hand, if the charge amount is too high, the electrostatic adhesive force becomes too large, resulting in a decrease in density and non-uniform image structure. That is, when the toner particle size is reduced, the charged state of each toner particle greatly affects the resulting image, and therefore it is extremely important to make the frequency distribution of the charge amount appropriate. However, the proposal of each toner listed in the above document has not been studied at all regarding the frequency distribution of the charge amount.
[0011]
[Problems to be solved by the invention]
Furthermore, when charging with a charging roll is performed, variations in charging are likely to occur, and image defects due to variations in charging are likely to occur when a high-definition image is to be formed. In particular, the conventional small-diameter toner has an image defect because the charge distribution is not sharp.
Accordingly, an object of the present invention is to provide an image forming method and an image forming apparatus capable of forming a high quality image.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present inventors have examined the charge distribution of toner for developing a latent image. As a result, when the charge amount of the toner in a temperature 20 ° C. and humidity 50% environment is expressed as q (fC) and the toner particle size is expressed as d (μm), the peak value in the frequency distribution of the q / d value is It was found that when the contact charging method is used, a high-quality image having no density unevenness can be obtained when the bottom value is not more than 1.0 and the bottom value is not less than 0.005.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a charging step of charging a latent image carrier with a charging member, a latent image forming step of forming a latent image on the latent image carrier using coherent light, and a latent image carrier using a developer containing toner. In the image forming method, comprising: a developing step of developing the electrostatic latent image above to obtain a toner image; and a transfer step of transferring the formed toner image onto a transfer material, the charging step includes the charging member A step of charging the latent image carrier in contact with the latent image carrier, and the developer is a two-component electrostatic latent image developer comprising a toner and a carrier, The volume average particle diameter of the carrier is 50 μm or less, the toner is composed of colored particles containing at least a binder resin and a colorant, and the volume average particle diameter of the colored particles is 2.0 to 5.0 μm. 20 pieces of colored particles of 1.0 μm or less The number of colored particles exceeding 5.0 μm is 10% by number or less, the charge amount of the toner in an environment of a temperature of 20 ° C. and a humidity of 50% is represented by q (fC), and the particle diameter of the toner is represented by d (μm). In the frequency distribution of q / d values Both peak and bottom values are positive or both negative The absolute value of the peak value is 1.0 or less and the bottom value Absolute value of Is an image forming method characterized in that the value is 0.005 or more.
[0014]
(Image forming method)
The image forming method of the present invention comprises a charging step of charging a latent image carrier with a charging member, a latent image forming step of forming an electrostatic latent image on the latent image carrier, and an electrostatic on the latent image carrier with toner. A developing process for developing the latent image; and a transferring process for transferring the developed toner image onto the transfer material.
[0015]
For the charging step, a charging member as described in JP-A-10-161393 may be used. The charging member includes, for example, a conductive rubber layer that sequentially covers the outer peripheral surface of the conductive base, a bleed prevention layer, a resistance control layer in which an electrolyte is contained in a polyurethane ionomer having an ionic segment in the molecule, and a surface layer. Composed. The ionic segment is selected from sulfonic acid groups, carboxyl groups and tertiary amino groups, or salts thereof. The polyurethane ionomer has a glass transition temperature of 30 ° C. or lower and a volume resistivity of 10 ° C. ⁶ -10 ⁹ It is in the range of Ωcm. As the electrolyte, lithium perchlorate, lithium thiocyanate, sodium tetraphenylborate, sodium dodecylbenzenesulfonate, or the like is preferably used. This charging member is configured as a roll, and is disposed in contact with the electrostatic latent image carrier (photoconductor).
[0016]
Conventional coherent light (laser) is used as an exposure light source for forming a latent image. Although any exposure light source can be used, a semiconductor laser that can be remarkably reduced in size with respect to a gas laser is preferably used.
Furthermore, the transfer process may include a transfer process using an intermediate transfer member.
[0017]
(A) Particle size and particle size distribution of colored particles
As described above, the volume average particle diameter of the colored particles is used to improve the reproducibility and gradation of fine lines of the latent image having a coherent light wavelength of 600 nm or less used in the latent image forming step. Is at least 5.0 μm or less. If it exceeds 5.0 μm, the ratio of coarse particles increases, and the fine line reproducibility and gradation are deteriorated. The “reproducibility of fine lines” as used in the present invention means mainly whether or not fine lines with a width of 30 to 60 μm, preferably 30 to 40 μm can be faithfully reproduced, and further reproduce dots of the same diameter. This is also taken into consideration.
[0018]
On the other hand, the lower limit of the volume average particle diameter of the colored particles is necessarily 2.0 μm or more. If it is less than 2.0 μm, the powder flowability, developability, or transferability as a toner deteriorates, and the cleaning properties of the toner remaining on the surface of the latent image carrier deteriorate. May cause problems.
[0019]
Considering the above, the range of the volume average particle diameter of the colored particles is 2.0 to 5.0 μm, preferably 2.0 to 4.5 μm, more preferably 2.0 to 4.0 μm, and still more preferably. It is 2.0-3.5 micrometers.
[0020]
In the present invention, the particle size distribution of the colored particles is further defined. Specifically, it is essential to have a particle size distribution in which the colored particles of 1.0 μm or less are 20% by number or less and the colored particles of more than 5.0 μm are 10% by number or less in all the colored particles. .
[0021]
If the number of colored particles of 1.0 μm or less in all the colored particles exceeds 20% by number, the non-electrostatic adhesive force of the colored particles increases, so that cleaning failure tends to occur. More preferably, the number of colored particles of 1.0 μm or less in all colored particles is 10% by number or less. In addition, fog is also improved by setting the number of colored particles of 1.0 μm or less in all the colored particles within the above range.
[0022]
On the other hand, when the number of colored particles exceeding 5.0 μm in all the colored particles exceeds 10% by number, the improvement in fine line reproducibility as the object of the present invention cannot be achieved. More preferably, the number of colored particles exceeding 5.0 μm in all colored particles is 5% by number or less.
[0023]
Further, in the present invention, the number% of colored particles exceeding 5.0 μm was used as a parameter for defining the large particle size side of the particle size distribution of the colored particles, but the reference particle size should be defined by other numerical values. You can also. Specifically, when 4.0 μm is used as a reference particle size, it is preferable that the colored particles of 4.0 μm or less are 75% by number or more in all the colored particles. In view of the volume average particle size and particle size distribution of the colored particles in the present invention, when the number of colored particles of 4.0 μm or less is 75% by number or more in all the colored particles, the colored particles exceeding 5.0 μm. Is generally 10% by number or less.
[0024]
In order to obtain colored particles having such a particle size distribution, conditions for pulverization and classification may be set as appropriate when obtained by a pulverization method, and polymerization conditions may be set as appropriate when obtained by a polymerization method.
[0025]
The particle size distribution of the colored particles can be measured by various methods. In the present invention, the particle size distribution of toner particles of 1 μm or less is measured by using a Coulter Counter TA2 type (manufactured by Coulter Co., Ltd.) with an aperture diameter of 50 μm. Only when the measurement was performed, the aperture diameter was set to 30 μm.
[0026]
Specifically, 2 to 3 drops of a dispersion (surfactant: Triton X100) and a measurement sample are added to an aqueous sodium chloride solution (10 g / liter), and after 1 minute of dispersion treatment with an ultrasonic disperser, the above Measurements were performed using the instrument.
[0027]
(B) Colored particles
In the present invention, the colored particles contain at least a binder resin and a colorant.
The binder resin contained in the colored particles preferably has a glass transition point of 50 to 80 ° C, more preferably 55 to 75 ° C. If the glass transition point is less than 50 ° C, the heat storage stability is lowered, and if it exceeds 80 ° C, the low-temperature fixability is lowered.
[0028]
Moreover, it is preferable that it is 80-150 degreeC as a softening point of binder resin, More preferably, it is 90-150 degreeC, More preferably, it is 100-140 degreeC. When the softening point is less than 80 ° C., the heat storage stability is lowered, and when it exceeds 150 ° C., the low-temperature fixability is lowered.
Furthermore, the number average molecular weight of the binder resin is preferably in the range of 1,000 to 50,000, and the weight average molecular weight is preferably in the range of 7,000 to 500,000. Furthermore, the molecular weight distribution may have two or more peaks.
[0029]
As the binder resin, those conventionally used as a binder resin for toner are used without any particular limitation, but styrene-based polymers, (meth) acrylic acid ester-based polymers, and styrene- (meth) acrylic acid ester-based resins. Polymers, polyester polymers, epoxy resins and the like can be preferably used. Examples of the styrene polymer, (meth) acrylate polymer, and styrene- (meth) acrylate polymer include the following styrene monomers, (meth) acrylate monomers, and other acrylic or methacrylic monomers. Polymers obtained by polymerizing one or more monomers appropriately selected from vinyl ether monomers, vinyl ketone monomers, N-vinyl compound monomers and the like are preferably used.
[0030]
Examples of the styrene monomer include styrene, o-methyl styrene, ethyl styrene, p-methoxy styrene, p-phenyl styrene, 2,4-dimethyl styrene, pn-octyl styrene, pn-decyl styrene, p- Examples thereof include styrene derivatives such as n-dodecylstyrene and butylstyrene.
[0031]
Examples of the (meth) acrylate monomer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, (meth) (N-octyl acrylate, dodecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, phenyl (meth) acrylate, dimethylaminoethyl (meth) acrylate), And (meth) acrylic acid esters.
[0032]
Examples of other acrylic or methacrylic monomers include acrylonitrile, methacrylamide, glycidyl methacrylate, N-methylol acrylamide, N-methylol methacrylamide, and 2-hydroxyethyl acrylate.
[0033]
Examples of vinyl ether monomers include vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, and vinyl isobutyl ether.
[0034]
Examples of the vinyl ketone monomer include vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and methyl isopropenyl ketone.
[0035]
Examples of the N-vinyl compound monomer include N-vinyl compounds such as N-vinyl pyrrolidone, N-vinyl carbazole, and N-vinyl indole.
[0036]
In the present invention, polyester is preferably used as the binder resin from the viewpoint of fixability. As this polyester, what is synthesize | combined by polycondensation of polyhydric carboxylic acid and polyhydric alcohol can be used.
[0037]
Examples of the polyhydric alcohol monomer include ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, 1,5-pentanediol, 1,6-hexanediol, Aliphatic alcohols such as neopentyl glycol, alicyclic alcohols such as cyclohexanedimethanol and hydrogenated bisphenol, bisphenol derivatives such as bisphenol A ethylene oxide adducts and bisphenol A propylene oxide adducts, phthalic acid as the polyvalent carboxylic acid Aromatic carboxylic acids such as terephthalic acid and phthalic anhydride and their anhydrides, saturated and unsaturated carboxylic acids such as succinic acid, adipic acid, sebacic acid, azelaic acid and dodecenyl succinic acid and their anhydrides. It can be.
[0038]
Pigment particles are used as the colorant contained in the colored particles. In the present invention, even if the toner weight per unit area of the image is reduced, a sufficient image density can be achieved, and it is included in the colored particles in order to ensure the water resistance, light resistance, or solvent resistance of the image. As the colorant to be used, it is essential to use pigment particles having high coloring power and excellent water resistance, light resistance, or solvent resistance.
[0039]
Examples of usable pigments include carbon black, nigrosine, graphite, C.I. I. Pigment Red 48: 1, 48: 2, 48: 3, 53: 1, 57: 1, 112, 122, 123, 5, 139, 144, 149, 166, 177, 178, 222, C.I. I. Pigmento Yellow 12, 14, 17, 97, 180, 188, 93, 94, 138, 174, C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment blue 15: 3, 15, 15: 2, 60, C.I. I. Pigment green 7 and the like. Among these, carbon black, C.I. I. Pigment red 48: 1, 48: 2, 48: 3, 53: 1, 57: 1, 112, 122, 123, C.I. I. Pigummet Yellow 12, 14, 17, 97, 180, 188, C.I. I. Pigment Blue 15: 3 is preferable. These pigments can be used alone or in combination of two or more.
[0040]
In order to improve the coloring power and transparency of the color toner, the present inventors have already set the average particle diameter of dispersed particles in the binder resin of the pigment fine particles as the toner colorant to 0 by the equivalent circle diameter by the melt flushing method. However, this method is extremely effective for the toner used in the present invention in which the concentration of the colorant in the colored particles needs to be increased. That is, the melt flushing method as a means for dispersing the pigment particles in the binder resin is a method of replacing the moisture in the pigment-containing water-containing cake in the pigment manufacturing process with a molten binder resin, and according to this method, The average particle diameter of dispersed particles in the binder resin of the pigment fine particles can be easily set to a circle equivalent diameter of 0.3 μm or less, and it is preferable because transparency of the toner can be secured and good color reproduction can be achieved.
[0041]
In the present invention, the average particle diameter of the dispersed particles in the binder resin of the pigment fine particles is equivalent to the circle diameter. After the colored particles are partially taken out and embedded in the resin, the dispersion state of the pigment particles in the colored particles is observed. A thin slice for observation was cut out so that an enlarged photograph at a magnification of 15,000 times was taken with a transmission electron microscope, the area of the pigment particles was measured with an image analyzer, and the diameter of a circle corresponding to the area was calculated. Value.
[0042]
In the toner used in the present invention, the colored particles have a volume average particle size of 5 μm or less, and it is necessary to increase the coloring power per colored particle. In particular, in the case of a full-color image in which colored particles are superimposed on a transfer material, the upper layer is used to express secondary colors such as red and green and tertiary colors such as process black unless the transparency of the colored particles is good. The colored particles in the lower layer may alienate the color development in the lower layer, and good color reproduction may not be achieved. However, this problem can occur when the average particle size of dispersed particles in the binder resin is 0.3 μm or less. Can be solved.
[0043]
As described above, the toner used in the present invention has a small particle diameter, and it is difficult to obtain a sufficient image density with the same pigment concentration as that of a conventional toner having a larger particle diameter. Although the toner used in the present invention has a small particle diameter, the volume average particle diameter varies from 2.0 μm to 4.5 μm, and the toner per unit area in a solid image. There is also a big difference in the weight (TMA). Therefore, it is desirable to set the necessary pigment concentration according to TMA.
[0044]
TMA is determined by the volume average particle diameter D (μm) and true specific gravity a of the colored particles, and the pigment concentration C (%) in the colored particles satisfies the following relational expression (1). desirable.
25 ≦ a · D · C ≦ 90 (1)
[0045]
When the value of a · D · C (hereinafter sometimes referred to as “aDC” for short) is less than 25, the coloring power is not sufficient, and it is difficult to obtain a desired image density, and development is performed to obtain a desired image density. If the amount of toner to be formed is increased, it is not preferable because the difference in image gloss occurs, the thickness of the image increases, the reproducibility of fine lines decreases, and the transferability also decreases, although the folding angle is reduced.
[0046]
On the other hand, if the value of aDC exceeds 90, a sufficient image density can be obtained, but background contamination due to scattering of toner to a small amount of non-image area is likely to occur. Then, there is a possibility that the fixing property is deteriorated, which is not preferable.
[0047]
Further, there is a difference in coloring power due to a difference in color, and it is more preferable that the following relational expressions (1-1) to (1-4) are satisfied for each color.
Cyan: 25 ≦ a · D · C ≦ 90 (1-1)
Magenta: 25 ≦ a · D · C ≦ 60 (1-2)
Yellow: 30 ≦ a · D · C ≦ 90 (1-3)
Black: 25 ≦ a · D · C ≦ 60 (1-4)
[0048]
Of course, even in the case of pigments of the same color, the coloring power varies depending on the chemical structural formula and the like. Therefore, the pigment concentration is preferably set appropriately within the above range according to the type of pigment used.
[0049]
The colored particles can be produced by any conventionally known method such as a pulverization method or a polymerization method by suspension polymerization or emulsion polymerization. In the present invention, the pulverization method is desirable. Here, the pulverization method is a method in which a binder resin, a colorant, and other additives as necessary are premixed and then melt-kneaded in a kneader, cooled and pulverized and classified to achieve a specified particle size distribution. It is.
[0050]
[Other additives]
In the present invention, it is preferable to add an external additive for the purpose of charge control.
Inorganic fine powder materials that can be used as external additives include metal oxides such as titanium oxide, tin oxide, zirconium oxide, tungsten oxide, and iron oxide, nitrides such as titanium nitride, silicon oxide, and titanium compounds. It is done. The addition amount of the external additive is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 8 parts by weight with respect to 100 parts by weight of the colored particles.
[0051]
As a method for adding the inorganic fine powder to the toner, for example, a conventionally known method in which the inorganic fine powder and the colored particles are mixed in a Henschel mixer and mixed can be employed.
[0052]
Furthermore, in the present invention, in order to improve powder characteristics such as powder flowability and powder adhesion, to prevent a decrease in transfer efficiency and chargeability, and to reduce environmental dependency, as an external additive It is preferable to contain ultrafine particles having a primary particle average particle diameter of 30 nm or more and 200 nm or less, and ultrafine particles having a primary particle average particle diameter of 5 nm or more and less than 30 nm.
[0053]
The ultrafine particles have a function of reducing adhesion between the colored particles or between the colored particles and the latent image carrier or carrier, and preventing deterioration in developability, transfer property, or cleaning property. The average primary particle diameter of the ultrafine particles is 30 nm to 200 nm, more preferably 35 nm to 150 nm, and still more preferably 35 nm to 100 nm. If it exceeds 200 nm, it will be easily detached from the toner, and the effect of reducing the adhesive force cannot be exhibited. On the other hand, if it is less than 30 nm, it will function as ultra-fine particles described later.
[0054]
The ultra-fine particles improve the fluidity of the toner (colored particles), reduce the degree of aggregation, and contribute to the improvement of environmental stability through effects such as suppression of thermal aggregation. The average primary particle diameter of the ultrafine particles is 5 nm or more and less than 30 nm, more preferably 5 nm or more and less than 29 nm, and still more preferably 10 nm or more and 29 nm or less. When the thickness is less than 5 nm, the toner is easily embedded in the surface of the colored particles due to stress applied to the toner. On the other hand, when it is 30 nm or more, the above-mentioned ultrafine particles function. In the present specification, “primary particle diameter” refers to a primary particle diameter equivalent to a sphere.
[0055]
Ultrafine particles include hydrophobized silicon oxide, titanium oxide, tin oxide, zirconium oxide, tungsten oxide, metal oxides such as iron oxide, nitrides such as titanium nitride, and fine particles made of titanium compounds. It is preferable that the fine particles are made of silicon oxide. Hydrophobization is performed by treating with a hydrophobizing agent, and any of chlorosilane, alkoxysilane, silazane, and silylated isocyanate can be used as the hydrophobizing agent. Specifically, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane, hexamethyldisilazane, ter -Butyldimethylchlorosilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane and the like can be mentioned.
[0056]
Ultra fine particles include hydrophobic titanium compounds, silicon oxide, titanium oxide, tin oxide, zirconium oxide, tungsten oxide, metal oxides such as iron oxide, and fine particles made of nitride such as titanium nitride. The titanium compound fine particles are preferable.
[0057]
In addition, the titanium compound fine particles are highly hydrophobic, are not subjected to a baking treatment, are less likely to generate aggregates, and are a reaction product of metatitanic acid and a silane compound that has good dispersibility during external addition. preferable. Further, as the silane compound at that time, an alkylalkoxysilane compound and / or a fluoroalkylalkoxysilane compound, which can satisfactorily control the charge of the toner and can reduce adhesion to a carrier or a latent image carrier, are preferably used.
[0058]
As the metatitanic acid compound, which is a reaction product of metatitanic acid and an alkylalkoxysilane compound and / or a fluoroalkylalkoxysilane compound, the metatitanic acid synthesized by the sulfuric acid hydrolysis reaction is peptized, and then the base metatitanic acid is used. Those obtained by reacting an alkylalkoxysilane compound and / or a fluoroalkylalkoxysilane compound can be preferably used. Examples of the alkylalkoxysilane to be reacted with metatitanic acid include methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, isobutyltrimethoxysilane, n-butyltrimethoxysilane, n-hexyltrimethoxysilane, and n-octyltrisilane. Examples of the fluoroalkylalkoxysilane compound include trifluoropropyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, and heptadecafluorodecylmethyl. Dimethoxysilane, (Tridecafluoro-1,1,2,2-tetrahydrooctyl) triethoxysilane, (3,3,3-trifluoropropyl) trimethoxysila , (Heptadecafluoro-1,1,2,2-tetrahydrodecyl) triethoxysilane, 3- (heptafluoroisopropoxy) propyltriethoxysilane and the like can be used.
[0059]
By using two types of external additives, ultrafine particles and ultrafine particles, the effects of the addition of both can be obtained.
[0060]
However, when the amount of the external additive added is too large as a whole, free external additive (not attached to the colored particles) is generated, and the latent image carrier and the carrier surface are easily contaminated with the external additive. In addition, if the ultrafine particles and the ultrafine particles are not added to a certain extent, the effect of adding both cannot be obtained. Furthermore, if the amount of ultrafine particles is too large, the effect of improving powder flowability cannot be obtained, and if the amount of ultrafine particles is too large, the effect of improving powder adhesion cannot be obtained. Therefore, it is necessary to appropriately control the amount of external additive added.
[0061]
The appearance of the effect by adding the external additive and the fluctuation of various powder characteristics do not depend on the absolute amount of the external additive to be added, but depend on the coverage on the surface of the colored particles. . Here, the covering ratio of the external additive to the colored particle surface is a case where the covering ratio is 100% as an ideal state in which the external additive having the same diameter is closely packed in a single layer on the colored particle surface. In addition, the percentage of how much the actual external additive covers the surface of the actual colored particles is expressed in%. This can be expressed by the following formula (2).
[0062]
F = √3 ・ D ・ ρ _t ・ (2π ・ d ・ ρ _a ) ^-1 ・ C × 100 (2)
(In the above formula, F is the coverage (%), D is the volume average particle diameter (μm) of the colored particles, ρ _t Is the true specific gravity of the colored particles, d is the average primary particle diameter (μm) of the external additive, ρ _a Represents the true specific gravity of the external additive, and C represents the ratio (x / y) of the weight x (g) of the external additive to the weight y (g) of the colored particles. )
[0063]
In the present invention, the coverage of the external additive on the colored particle surface obtained by the above formula (2) is 20% or more for both the ultrafine particles Fa and the ultrafine particles Fb, and the coverage of all external additives Is preferably 100% or less. The “total of the coverage ratios of all external additives” refers to the sum of the coverage ratios of the respective external additives obtained by individually calculating the coverage ratios of the respective external additives to be added.
[0064]
When the coverage Fa of the ultrafine particles is less than 20%, the effect of adding the ultrafine particles cannot be obtained. The coverage Fa of the ultrafine particles is preferably 20 to 80%, more preferably 30 to 60%.
[0065]
When the coverage Fb of the ultrafine particles is less than 20%, the effect of adding the ultrafine particles cannot be obtained. The coverage Fb of the ultrafine particles is preferably 20 to 80%, more preferably 30 to 60%.
[0066]
If the total coverage of all the external additives exceeds 100%, a large amount of free external additives are generated, so that the latent image carrier and the carrier surface are easily contaminated with the external additives. The total coverage of all external additives is preferably 40 to 100%, more preferably 50 to 90%.
[0067]
The relationship between the ultrafine particle coverage Fa (%) and the ultrafine particle coverage Fb (%) more preferably satisfies the following expression (3).
0.5 ≦ Fb / Fa ≦ 4.0 (3)
Outside this range, the effect of adding ultrafine particles or ultrafine particles becomes difficult to obtain, which is not preferable. In order to optimize the effect of adding ultrafine particles or ultrafine particles, it is more preferable to satisfy the following formula (3 ′).
0.5 ≦ Fb / Fa ≦ 2.5 (3 ′)
[0068]
As a method for adding the ultrafine particles and the ultrafine particles to the toner, for example, a conventionally known method in which ultrafine particles, ultrafine particles, and colored particles are mixed in a Henschel mixer and mixed can be employed.
[0069]
To the toner used in the present invention, a charge control agent, a release agent, and the like may be added as necessary within a range that does not affect color reproducibility and transparency. Examples of the charge control agent include chromium azo dyes, iron azo dyes, aluminum azo dyes, salicylic acid metal complexes, and organic boron compounds. Examples of the release agent include polyolefins such as low molecular weight propylene and low molecular weight polyethylene, natural waxes such as paraffin wax, candelilla wax, carnauba wax, and montan wax, and derivatives thereof.
[0070]
(D) Relationship between charge quantity q and particle diameter d (q / d value)
In the toner used in the present invention, it is preferable to appropriately control the charged state of individual colored particles. That is, not the charge amount of the toner as a whole but the charged state of each toner particle has a great influence on the obtained image. On the other hand, since the particle size of each toner particle has a great influence on the image quality, the relationship with the image quality cannot be sufficiently explained only by specifying the frequency distribution of the charge amount of each toner particle. Therefore, in the toner according to the present invention, it is preferable that the relationship between the charge amount of each toner particle and the particle size is regulated appropriately.
[0071]
That is, when the charge amount of the toner is expressed as q (fC) and the particle diameter of the toner is expressed as d (μm) in an environment where the temperature is 20 ° C. and the humidity is 50%, Both peak and bottom values are positive or both negative The absolute value of the peak value is 1.0 or less and the bottom value Absolute value of Must be 0.005 or more is necessary . As for the q / d value, in the case of a positively charged toner, the above numerical value rule is applied as it is, but in the case of a negatively charged toner, the value of the toner charge amount q (fC) is reversed positively and negatively. Later, the above numerical rules will apply.
[0072]
The measurement environment of the charge amount in the environment of temperature 20 ° C. and humidity 50% is that the charge amount in a standard environment, which is generally set to room temperature, defines various performances targeted by the present invention. This is because it is optimal above. That is, a toner satisfying the above conditions in such a standard environment has a large charge amount distribution suitable for obtaining the high image quality as the object of the present invention even when the environmental conditions are somewhat different. It does not come off, and can exhibit high performance extremely stably. Of course, it is needless to say that the toner having the above-mentioned charge amount distribution is preferable in a higher temperature, high humidity and low temperature, low humidity environment.
[0073]
When the q / d value is measured for each toner and the frequency distribution is graphed, it becomes a substantially normal distribution with an upper limit value and a lower limit value. In the present invention, the q / d value of the point that becomes the apex of this graph is the peak value, and the q / d value of the point that becomes the lower limit value (in the case of negatively charged toner, the lower limit value after reverse rotation) Value.
[0074]
In the toner used in the present invention, in the frequency distribution of the q / d value, Both peak and bottom values are positive or both negative The peak value is 1.0 or less Is necessary More preferably, it is 0.80 or less, More preferably, it is 0.70. If the peak value exceeds 1.0, even if the frequency distribution is set to be narrow, the adhesion of the toner to the carrier and the surface of the photoreceptor increases, so the developability and transferability deteriorate, and the image density decreases. Furthermore, there is a possibility that the cleaning property of the toner remaining on the surface of the photoreceptor may be deteriorated, which is not preferable. In addition, when the peak value is set to exceed 1.0 and the charge distribution is set to be wide, in addition to the same problem as described above, the variation in chargeability of individual toners increases, so that developability and transferability are increased. May be non-uniform.
[0075]
On the other hand, if the q / d value is too close to 0 or has a positive or negative value (that is, reverse polarity toner), the image area may be lost or the non-image area may be fogged. Therefore, the bottom value in the frequency distribution of q / d values Absolute value of Is desired to be maintained at a certain value or more, specifically, 0.005 or more Is necessary More preferably, it is 0.01 or more, More preferably, it is 0.02 or more, Most preferably, it is 0.025 or more.
[0076]
The value that is the upper limit (the upper limit of the absolute value in the case of negatively charged toner) in the frequency distribution of the q / d value need not be specified. This is because the frequency distribution of the q / d value shows a substantially normal distribution as described above, and if the peak value and the bottom value are defined, the upper limit value is naturally determined.
[0077]
The frequency distribution of the q / d value can be measured by, for example, a charge spectrograph method (hereinafter referred to as “CSG method”) disclosed in JP-A-57-79958. Hereinafter, a specific measurement method will be described.
[0078]
FIG. 1 is a schematic perspective view of a measuring apparatus 10 for measuring a frequency distribution of q / d values by the CSG method. The measuring apparatus 10 includes a cylindrical body 12, a filter 14 that closes the lower opening thereof, a mesh 16 that closes the upper opening, and a sample supply projecting from the center of the mesh 16 into the body 12. The cylinder 18 includes a suction pump (not shown) that sucks air from the lower opening of the body 12, and an electric field generator (not shown) that applies an electric field E from the side surface of the body 12.
[0079]
The suction pump is set so as to suck air inside the barrel 12 uniformly over the entire surface of the filter 14 through the filter 14 in the lower opening of the barrel 12. Along with this, air flows from the mesh 16 of the upper opening, and a laminar flow having a constant air flow rate Va is generated in the vertically downward direction inside the trunk 12. Further, the electric field generator provides a uniform and constant electric field E in a direction orthogonal to the air flow.
[0080]
The toner particles to be measured are gradually dropped (dropped) from the sample supply cylinder 18 into the barrel 12 in the above state. If the toner particles coming out of the sample outlet 20 at the tip of the sample supply cylinder 18 are not affected by the electric field E, they fly vertically downward while reaching the center O of the filter 14 while being influenced by the laminar air flow. (At this time, the distance k between the sample outlet 20 and the filter 14 is the straight flight distance of the toner). The filter 14 is composed of a coarse polymer filter or the like, and allows air to pass therethrough sufficiently, but the toner particles remain on the filter 14 without being transmitted. However, in the case of charged toner, the toner is affected by the electric field E, and the position is shifted in the traveling direction of the electric field E from the center O and reaches the filter 14 (point T in FIG. 1). By measuring the distance (displacement) x between the point T and the center O and obtaining the frequency distribution, the frequency distribution of the q / d value can be obtained (in the present invention, the peak is actually obtained by image analysis). The value and the bottom value were obtained directly.)
[0081]
More specifically, the relationship between the displacement x (mm) obtained by the measuring apparatus 10 as described above, the toner charge amount q (fC), and the toner particle size d (μm) is as follows. It is represented by equation (4).
q / d = (3πηVa / kE) × x (4)
In equation (4), η is the viscosity of the air (kg / m · sec.), Va is the air flow velocity (m / sec.), K is the straight flight distance (m) of the toner, and E is the electric field (V / m). Respectively.
[0082]
In the present invention, measurement is performed by setting each condition of the measurement apparatus 10 shown in FIG. 1 so that each condition of the equation (4) becomes the following numerical value.
Air viscosity η = 1.8 × 10 ^-Five (Kg / m · sec.)
Air flow rate Va = 1 (m / sec.)
Toner straight flight distance k = 10 (cm)
Electric field E = 190V / cm
[0083]
Substituting the above values into Equation (4) gives the following.
q (fC) / d (μm) ≈0.09 · x
[0084]
When the toner particles to be measured are dropped onto the sample supply cylinder 18, the toner needs to be charged in advance. The q / d value of the toner needs to have the above-mentioned frequency distribution when actually developing the electrostatic latent image. After the toner to be measured is mixed with a carrier, a two-component developer is used. The purpose of the present invention is to perform shaking or the like under conditions similar to the apparatus conditions, and to use this for measurement of the frequency distribution of q / d values.
[0085]
Therefore, in the present invention, the charging conditions of the toner particles to be measured are defined as follows (of course, the toner for actually developing the electrostatic latent image was measured by directly sampling from the apparatus or the like) It is more preferable that the condition of the frequency distribution of the q / d value is satisfied).
[0086]
In the present invention, an electrostatic latent image developer composed of a toner and a carrier, which is actually used, is charged in a glass bottle and stirred for 2 minutes with a tumbler shaker to obtain a frequency distribution of q / d values. We used for measurement.
[0087]
In this way, a frequency distribution of q / d values can be obtained. Of course, in the present invention, the frequency distribution of the q / d value can be obtained by a method other than the CSG method as described above, but according to the CSG method, there are few errors.
[0088]
[Electrostatic latent image developer]
The toner used in the present invention is preferably mixed with a carrier and used as a two-component electrostatic latent image developer. It can also be used as a one-component electrostatic latent image developer that does not use a carrier.
[0089]
The carrier preferably used together with the toner used in the present invention is not particularly limited, and magnetic particles such as iron powder, ferrite, iron oxide powder and nickel, and magnetic particles are used as a core material, and the surface thereof is styrene. In coated resin-type carrier particles or binder resin formed by coating with a known resin such as resin, vinyl resin, ethyl resin, rosin resin, polyester resin, methyl resin, etc., and forming a resin coating layer Examples include magnetic material-dispersed carrier particles in which magnetic fine particles are dispersed.
[0090]
Among these, a coated resin type carrier having a resin coating layer is particularly preferable because the chargeability of the toner and the resistance of the entire carrier can be controlled by the configuration of the resin coating layer. The material for the resin coating layer can be selected from all resins conventionally used as a material for the resin coating layer of the carrier in the industry. Moreover, the kind of resin may be individual or may be 2 or more types.
[0091]
The particle diameter of the carrier is 50 μm or less as the volume average particle diameter. It is necessary . Preferably it is 10-40 micrometers, More preferably, it is 15-35 micrometers. By setting the volume average particle size of the carrier to 50 μm or less, the background of the charge due to the smaller particle size of the toner (colored particles), the deterioration of the charge distribution, and the unevenness of density due to the decrease in the charge amount can be improved. Can do.
[0092]
The mixing ratio of the toner and the carrier is preferably in the range of 1: 100 to 20: 100 by weight, more preferably in the range of 2: 100 to 15: 100, and still more preferably in the range of 3: 100 to 10: 100. It is.
[0093]
Further, in an image forming method for forming a full color image by laminating at least four toner images of cyan, magenta, yellow and black on a transfer material, an image obtained by applying the image forming method of the present invention. Has good fine line reproducibility and gradation, no fog, and small toner particle size, so fine line reproducibility, gradation and highlight part graininess are good, and in colored particles. Even if the pigment concentration is increased, the fine line reproducibility, gradation, and highlight part granularity do not deteriorate, and the unit area of the image formed on the transfer material is increased by increasing the pigment concentration in the colored particles. The toner weight per hit can be reduced, and the thickness of the toner image formed on the transfer material can be suppressed to a small level. There can be to achieve a more high-quality. Further, since the thickness of the toner image on the transfer material is small, the unevenness is small and the external image is not easily damaged, so that the formed image is highly resistant.
[0094]
At this time, in each color toner image to be formed, 1 cm ² It is preferable that the weight (TMA) per toner is 0.40 mg or less, more preferably 0.35 mg or less, and still more preferably 0.30 mg or less. By keeping TMA low as described above, it is possible to reduce the thickness of the toner image on the transfer material, and to achieve high image quality equivalent to that of offset printing without visually uncomfortable feeling. Further, since the thickness of the toner image on the transfer material is small, the unevenness is small and the external image is not easily damaged, so that the formed image is highly resistant.
[0095]
In particular, process black, in which a toner image is laminated with toners of three colors, cyan, magenta, and yellow on a transfer material, tends to increase the thickness of the toner image with normal toner, and the texture of the image is reduced. Although it was easy, by suppressing the TMA of each color low, the thickness of the toner image on the transfer material can be sufficiently reduced, so that high image quality can be achieved. In order to achieve a clear color development of the process black, the TMA of each color when forming the process black in a region where the image area ratio is 100% is preferably 0.10 mg or more, more preferably 0.12 mg. As mentioned above, More preferably, it is 0.15 mg or more.
[0096]
Of course, when using a black toner alone to obtain a black solid image with an area ratio of 100%, or when attempting to obtain a solid image with an area ratio of 100% with a single color toner, the conventional toner has a considerable amount. Although the thickness is increased and the texture is impaired, by suppressing the TMA to a low level, the thickness of the toner image on the transfer material can be sufficiently reduced, so that high image quality can be achieved. Accordingly, the TMA for obtaining a solid image with an area ratio of 100% with black toner is preferably 0.10 mg or more, more preferably 0.12 mg or more, and further preferably 0.15 mg or more. The same applies to the case of a solid image having an area ratio of 100% with other single color toner.
[0097]
As the electrophotographic latent image carrier used in the exposure process of the present invention, any of those conventionally used as a photoreceptor can be used. Specific examples include organic photoreceptors and inorganic photoreceptors. In general, such a photoreceptor has a photosensitive layer formed on a conductive substrate. Examples of the conductive substrate include aluminum, copper, zinc, stainless steel, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, and other metal plates, metal drums, metal belts, or conductive materials. A paper, a plastic film, a belt, or the like coated, vapor-deposited, or laminated with a conductive polymer, a conductive compound such as indium oxide, or a metal or alloy such as aluminum, palladium, or gold is used. Furthermore, if necessary, the surface of the conductive substrate may be subjected to various treatments within a range that does not affect the image quality, such as surface anodic oxide coating treatment, thermal hydroxylation treatment, chemical treatment, coloring treatment, graining, etc. What performed the irregular reflection process etc. can also be used.
[0098]
As the photosensitive layer in the present invention, a latent image carrier having a single-layered photosensitive layer or a latent image carrier having a laminated photosensitive layer can be used. In particular, those in which a photosensitive layer having a laminated structure in which at least a charge generation layer and a charge transport layer are sequentially formed are preferably used. In the charge generation layer, examples of charge generation materials include azo pigments, quinone pigments, perylene pigments, indigo pigments, thioindigo pigments, bisbenzimidazole pigments, phthalocyanine pigments, quinacridone pigments, and quinoline pigments. Various organic pigments such as pigments, lake pigments, azo lake pigments, anthraquinone pigments, oxazine pigments, dioxazine pigments, triphenylmethane pigments, azurenium dyes, squalium dyes, pyrylium dyes, triallylmethane Various dyes such as dyes, xanthene dyes, thiazine dyes, cyanine dyes, and inorganic materials such as amorphous selenium, trigonal selenium, tellurium, selenium-tellurium alloys, cadmium sulfide, antimony sulfide, zinc oxide, zinc sulfide Is used. Ring pigments, perylene pigments, azo pigments, sensitivity, electrical stability, further preferred in terms of photochemical stability against irradiated light. In addition, when using the charge generating substance, the above substances are used alone or in combination of two or more.
[0099]
The charge generation layer is formed by forming the charge generation material by vacuum vapor deposition or by applying a coating liquid in which the charge generation material is dispersed in a binder resin in an organic solvent. At the time of coating, as a binder resin in the charge generation layer coating solution, polyvinyl butyral resin, polyvinyl formal resin, polyvinyl acetal such as partially acetalized polyvinyl acetal resin in which a part of butyral is modified with formal, acetoacetal or the like Resin, polyamide resin, polyester resin, modified ether type polyester resin, polycarbonate resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate copolymer, silicone resin Phenolic resin, phenoxy resin, melamine resin, benzoguanamine resin, urea resin, polyurethane resin, poly-N-vinylcarbazole resin, polyvinylanthracene resin, polyvinylpyrene, etc. are used. But it is not limited thereto. Moreover, these binder resins are used alone or in admixture of two or more. The mixing ratio of the charge generation material and the binder resin is preferably in the range of 5: 1 to 1: 2 by volume.
[0100]
The thickness of the charge generation layer is usually from 0.01 to 5 μm, preferably from 0.1 to 2.0 μm. If the thickness is less than 0.01 μm, it is difficult to form the charge generation layer uniformly. On the other hand, if the thickness exceeds 5 μm, the electrophotographic characteristics tend to be remarkably deteriorated.
[0101]
Further, a stabilizer such as an antioxidant or a light stabilizer can be added to the charge generation layer as necessary. Examples of the antioxidant include antioxidants such as phenol-based, sulfur-based, phosphorus-based, and amine-based compounds. Examples of the light stabilizer include bis (dithiobenzyl) nickel and nickel di-n-butylthiocarbamate.
[0102]
In the present invention, an undercoat layer may be provided between the charge generation layer and the conductive substrate. Examples of the binder resin used for the undercoat layer include the following. Polyamide resin, vinyl chloride resin, vinyl acetate resin, phenol resin, polyurethane resin, melamine resin, benzoguanamine resin, polyimide resin, polyethylene resin, polypropylene resin, polycarbonate resin, acrylic resin, methacrylic resin, vinylidene chloride resin, polyvinyl acetal resin, chloride Vinyl-vinyl acetate copolymer, polyvinyl alcohol resin, water-soluble polyester resin, nitrocellulose, casein, gelatin, polyglutamic acid, starch, starch acetate, amino starch, polyacrylic acid, polyacrylamide, zirconium chelate compound, titanyl chelate compound, Known materials such as a titanyl alkoxide compound, an organic titanyl compound, and a silane coupling agent can be used. These materials can be used alone or in admixture of two or more. Furthermore, fine particles such as titanium oxide, aluminum oxide, silicon oxide, zirconium oxide, barium titanate, and silicone resin can be mixed. As a coating method for forming the undercoat layer, a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, a curtain coating method, or the like is employed. The thickness of the undercoat layer is 0.01 to 10 μm, preferably 0.05 to 2 μm.
[0103]
As a charge transport material in the charge transport layer, for low molecular weight compounds, for example, pyrene, carbazole, hydrazone, oxazole, oxadiazole, pyrazoline, arylamine, arylmethane, benzidine, thiazole Various organic compounds such as stilbene, butadiene, and aromatic polycyclic are used. Examples of the polymer compound include poly-N-vinylcarbazole, halogenated poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, pyrene-formaldehyde resin, ethylcarbazole-formaldehyde resin, and triphenylmethane. A polymer or polysilane is used. Among them, in the triphenylamine compound and the triphenylmethane compound, those having no unsaturated bond or aromatic ring conjugated with the phenyl group are preferable because they do not easily emit fluorescence, and other than the aromatic ring directly connected to the nitrogen element Further, those containing at least one halogen element as a substituent are preferable because the quantum yield of fluorescence emission can be effectively reduced by the heavy atom effect. Furthermore, you may use the polymer containing these.
[0104]
Further, the polymer charge transport material may be formed alone or may be formed by dispersing in a known binder resin. A polymer charge transport material and a hydrazone charge transport material, a triarylamine charge transport material, a stilbene charge transport material, or the like may be mixed and used.
[0105]
Moreover, stabilizers, such as a deactivator, can be added in a charge transport layer as needed. Examples of the quenching agent include bis (dithiobenzyl) nickel and nickel di-n-butylcarbamate.
[0106]
When the binder resin is used for forming the charge transport layer in the present invention, a high molecular polymer capable of forming an electrically insulating film is preferable. Examples of such high molecular polymers include polycarbonate, polyester, methacrylic resin, acrylic resin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile polymer, and chloride. Vinyl-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N-vinylcarbazole, polyvinyl butyral, polyvinyl Formal, polysulfone, casein, gelatin, polyvinyl alcohol, ethyl cellulose, phenol resin, polyamide, carboxy-methyl cellulose, vinylidene chloride polymer latex And polyurethane, but not limited thereto. These binder resins are used singly or in combination of two or more. In particular, polycarbonate, polyester, methacrylic resin, and acrylic resin are excellent in compatibility with charge transport materials, solubility in solvents, and strength. Therefore, it is preferable.
[0107]
In addition to the binder resin, additives such as a plasticizer, a surface modifier, an antioxidant, and a photodegradation inhibitor can also be used. Examples of the plasticizer include biphenyl, biphenyl chloride, terphenyl, dibutyl phthalate, diethylene glycol phthalate, dioctyl phthalate, triphenyl phosphate, methyl naphthalene, benzophenone, chlorinated paraffin, polypropylene, polystyrene, and various fluorohydrocarbons. Examples of the antioxidant include antioxidants such as phenol-based, sulfur-based, phosphorus-based, and amine-based compounds. Examples of the photodegradation inhibitor include benzotriazole compounds, benzophenone compounds, hindered amine compounds, and the like.
[0108]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.
(1) Preparation of toner
1) Preparation of flushing pigment
<Magenta flushing pigment>
70 parts by weight of a polyester resin (bisphenol A type polyester: bisphenol A ethylene oxide adduct-cyclohexanedimethanol-terephthalic acid, weight average molecular weight: 11,000, number average molecular weight: 3,500, Tg: 65 ° C.) and magenta pigment ( CI Pigment Red 57: 1) 75 parts by weight of a water-containing paste (pigment content: 40% by weight) is placed in a kneader-type kneader and mixed and heated gradually. The kneading is continued at 120 ° C. to separate the water phase and the resin phase, and then the water is removed. Further, the resin phase is kneaded to remove the water and dehydrated to obtain a magenta flushing pigment.
[0109]
<Cyan flushing pigment>
A cyan flushing pigment is obtained in the same manner as the magenta flushing pigment except that the magenta pigment hydrous paste is replaced with a cyan pigment (CI pigment blue 15: 3) hydrous paste (pigment content 40 wt%).
[0110]
<Yellow flushing pigment>
A yellow flushing pigment is obtained in the same manner as the magenta flushing pigment except that the magenta pigment hydrous paste is replaced with a yellow pigment (CI Pigment Yellow 17) hydrous paste (pigment content: 40% by weight).
[0111]
2) Preparation of colored particles
<Preparation Example 1 of Colored Particles>

[0112]
The above components are melt-kneaded with a Banbury mixer, and after cooling, finely pulverized by a jet mill and classified by an air classifier, and the pulverization and classification conditions are changed to change the colored particles M1 and M2 of each particle size distribution shown in Table 1 below. obtain.
[0113]
<Preparation Example 2 of Colored Particles>
Colored particles C1 and C2 shown in Table 1 below are obtained in the same manner as in Colored Particle Production Example 1 except that the magenta flushing pigment is replaced with a cyan flushing pigment. The pulverization and classification conditions are adjusted so that the particle size distribution shown in Table 1 below is obtained.
[0114]
<Preparation Example 3 of Colored Particles>
Colored particles Y1 and Y2 shown in Table 1 below are obtained in the same manner as in Colored Particle Production Example 1 except that the polyester resin is 50 parts by weight and the magenta flushing pigment 25 parts by weight is replaced with the yellow flushing pigment 50 parts by weight. . The pulverization and classification conditions are adjusted so that the particle size distribution shown in Table 1 below is obtained.
[0115]
<Preparation Example 4 of Colored Particles>
The coloring shown in Table 1 below is the same as in Preparation Example 1 of colored particles, except that the polyester resin is 90 parts by weight and the magenta flushing pigment 25 parts by weight is replaced with 10 parts by weight of carbon black (average primary particle diameter 40 nm). Particles K1 and K2 are obtained. The pulverization and classification conditions are adjusted so that the particle size distribution shown in Table 1 below is obtained.
[0116]
Regarding the colored particles obtained as described above, the particle size distribution, the pigment particle average dispersed particle size, and the aDC are collectively shown in Table 1 below.
[0117]
3) Preparation of toner
Each of the colored particles of M1, C1, Y1, and K1 is subjected to surface hydrophobization treatment with hexamethyldisilazane and silica having a primary particle average particle size of 40 nm (SiO 2 ₂ ) The fine particles and the metatitanic acid compound fine particles having a primary particle average particle size of 20 nm, which is a reaction product of metatitanic acid and isobutyltrimethoxysilane, are added so that the coverage of each colored particle surface is 40%. Mix with a Henschel mixer to make a toner. Moreover, it added so that the coverage with respect to the surface of each colored particle might become 30% to each colored particle of M2, C2, Y2, and K2. Each obtained toner is described using the number of each colored particle used as it is.
[0118]
In addition, the coverage with respect to the surface of a colored particle here means the value F (%) calculated | required by above-mentioned Formula (1).
Table 1 below summarizes the total external additive coverage and the values obtained by measuring the q / d peak value and bottom value by the above-described method for each toner obtained.
[0119]
[Table 1]

[0120]
(2) Carrier production example
A methanol solution containing 0.1 part by weight of γ-aminopropyltriethoxysilane was added to 100 parts by weight of Cu—Zn ferrite fine particles having a volume average particle diameter of 40 μm and coated with a kneader. The silane compound is completely cured by heating at 0 ° C. for 2 hours. To this particle, a perfluorooctylethyl methacrylate-methyl methacrylate copolymer (copolymerization ratio 40:60) dissolved in toluene was added, and perfluorooctylethyl methacrylate-methyl was added using a vacuum reduced pressure kneader. A resin-coated carrier used in the following Examples and Comparative Examples is manufactured by coating with a resin so that the coating amount of the methacrylate copolymer is 0.5% by weight.
[0121]
(Development of developer)
Resin-coated carrier: 100 parts by weight of each toner obtained above; 4 parts by weight of the toner are mixed by a V-type mixer to obtain each two-component developer used in Examples and Comparative Examples.
[0122]
[Various evaluation test methods]
Each of the two-component developers obtained above was used for various toner evaluation tests described below. Here, in each of the two-component developers used, the toner numbers included are M1, C1, Y1, and K1 in the order of Examples 1, 2, 3, and 4, and the toner number included is M2. C2, Y2, and K2 are referred to as Comparative Examples 1, 2, 3, and 4 in this order.
[0123]
In the following various evaluation tests, Fuji Xerox J-coated paper was used as a transfer material, and Fuji Xerox Acolor 935 remodeling machine (latent image carrier and exposure device was remodeled as an image forming apparatus, Using a device modified so that the voltage can be adjusted during development (hereinafter, simply referred to as “Acolor 935 modified machine”), all are performed under environmental conditions of a temperature of 22 ° C. and a humidity of 55%. Further, image formation is performed while appropriately adjusting so that the image density is in the range of 1.6 to 2.0.
[0124]
The charging device includes a conductive rubber layer that sequentially covers the outer peripheral surface of the conductive substrate, a bleed prevention layer, a resistance control layer in which an electrolyte is contained in a polyurethane ionomer having an ionic segment in the molecule, and a surface layer. . The ionic segment has a sulfonic acid group. The polyurethane ionomer has a glass transition temperature of 25 ° C. and a volume resistivity of 10 ° C. ⁷ Ωcm. As the electrolyte, lithium perchlorate was used. This charging member is configured as a roll and is disposed in contact with the photoreceptor. The organic photoreceptor is charged to −500 V using the charging device.
[0125]
<TMA>
A solid image having an area ratio of 100% was prepared, and the toner weight per unit area of the image portion (TMA: mg / cm ² ). As a specific measurement method, 10 cm ² An unfixed solid image having an area of 1 mm is prepared on a transfer material, and this is weighed. Then, the unfixed toner on the transfer material is removed by air blow, and then the weight of only the transfer material is measured. TMA is calculated from the weight difference.
[0126]
<Image density>
A solid image having an area ratio of 100% is created, and the image density of the image portion is measured using X-Rite 404 (manufactured by X-Rite).
[0127]
<Thin wire reproducibility evaluation test>
A fine line image was formed on the latent image carrier so as to have a line width of 50 μm, and this was transferred and fixed onto a transfer material. The image of the fine line of the fixed image on the transfer material is observed at a magnification of 175 using a VH-6200 micro high scope (manufactured by Keyence Corporation). Specific evaluation criteria are as follows.
A: The fine line is uniformly filled with toner, and there is no disturbance at the edge.
X: The fine line is not uniformly filled with toner. Jaggedness is very noticeable at the edges.
[0128]
<Tone reproducibility evaluation test>
A gradation image of each level of image area ratio 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% is created, and X-Rite404 (X- Rite) is used to measure the image density and determine the gradation. Specific evaluation criteria are as follows.
(Double-circle): The gradation property is very favorable about all the gradation images from a low image area rate part to a high image area rate part.
X: The gradation reproduction region is narrow in the high / low image area ratio portion, and the gradation property is unstable.
[0129]
<Image defect>
A gradation image having a level of 5% and 10% of the image area ratio is created, and the obtained image is visually observed to evaluate density unevenness. Specific evaluation criteria are as follows.
A: There is no density unevenness in both 5% and 10%.
X: Slight density unevenness is observed in both 5% and 10%.
[0130]
The above evaluation results are summarized in Table 2 below.
[0131]
[Table 2]

[0132]
Moreover, when the full-color image was formed using the four-color two-component developer obtained in Examples 1 to 4, it was possible to repeatedly obtain a high-quality image having excellent intermediate color development and no density unevenness. I was able to. On the other hand, when the four-color two-component developer obtained in Comparative Examples 1 to 4 was used to form a full-color image, the obtained image was inferior in neutral color development and low in sharpness. Met.
[0133]
【The invention's effect】
As described above, according to the image forming method or the image forming apparatus of the present invention, it is possible to obtain a high-quality image excellent in halftone reproduction without density unevenness even by performing contact-type charging.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view of a measuring apparatus for measuring a frequency distribution of q / d values by a CSG method.
[Explanation of symbols]
10: Measuring device
12: Torso
14: Filter
16: Mesh
18: Sample supply tube
20: Sample outlet

Claims (2)

A charging step of charging the latent image carrier with a charging member, a latent image forming step of forming a latent image on the latent image carrier using coherent light, and electrostatic on the latent image carrier with a developer containing toner. In an image forming method comprising: a development step of developing a latent image to obtain a toner image; and a transfer step of transferring the formed toner image onto a transfer material.
The charging step is a step of charging the latent image carrier in a state where the charging member and the latent image carrier are in contact with each other;
The developer is a two-component electrostatic latent image developer comprising a toner and a carrier;
The volume average particle diameter of the carrier is 50 μm or less,
The toner is composed of colored particles containing at least a binder resin and a colorant, and the colored particles have a volume average particle diameter of 2.0 to 5.0 μm, and 20% by number of colored particles of 1.0 μm or less. The number of the colored particles exceeding 5.0 μm is 10% by number or less,
When the charge amount of the toner in a temperature of 20 ° C. and a humidity of 50% environment is expressed as q (fC) and the toner particle size is expressed as d (μm), both the peak value and the bottom value in the frequency distribution of the q / d value are An image forming method characterized by being either positive or negative, an absolute value of a peak value being 1.0 or less, and an absolute value of a bottom value being 0.005 or more. A charging unit that charges the latent image carrier with a charging member, a latent image forming unit that forms a latent image on the latent image carrier using coherent light, and an electrostatic image on the latent image carrier by a developer containing toner. In an image forming apparatus comprising: a developing unit that develops a latent image to obtain a toner image; and a transfer unit that transfers the formed toner image onto a transfer material.
The charging means is means for charging the latent image carrier in a state where the charging member and the latent image carrier are in contact with each other;
The developer is a two-component electrostatic latent image developer comprising a toner and a carrier;
The volume average particle diameter of the carrier is 50 μm or less,
The toner is composed of colored particles containing at least a binder resin and a colorant, and the colored particles have a volume average particle diameter of 2.0 to 5.0 μm, and 20% by number of colored particles of 1.0 μm or less. The number of the colored particles exceeding 5.0 μm is 10% by number or less,
When the toner has a charge amount of q (fC) and a toner particle size of d (μm) in an environment of a temperature of 20 ° C. and a humidity of 50%, the peak value in the frequency distribution of q / d value and An image forming apparatus, characterized in that both bottom values are positive or negative, the absolute value of the peak is 1.0 or less, and the absolute value of the bottom value is 0.005 or more.

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