JP3987214B2 - Electrostatic latent image developer and image forming method - Google Patents

Description

【０１４６】
前記各着色粒子に、ヘキサメチルジシラザン（以下、「ＨＭＤＳ」と略す場合がある）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Ａ〜Ｇをそれぞれ作製した（得られた各トナーに付されたＡ〜Ｇの記号は、用いた着色粒子の各符号Ａ〜Ｇに対応する）。
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。
【０１４７】
また、メタチタン酸とイソブチルトリメトキシシランとの反応条件は以下の通りである。メタチタン酸スラリーに４Ｎ水酸化ナトリウム水溶液を加え、ｐＨ９．０に調整し攪拌後、６Ｎ塩酸を加え中和した。これを濾過して濾紙上に得られた物質を水洗後、該物質に再度水を加えてスラリーとし、６Ｎ塩酸を加え、ｐＨ１．２にして一定時間攪拌して解膠した。該解膠スラリーにイソブチルトリメトキシシランを加え、一定時間攪拌後、８Ｎ水酸化ナトリウム水溶液を加えて中和した。これを濾過して濾紙上に得られた物質を水洗し、１５０℃で乾燥後、ジェットミルで微粉砕した後粗大粒子を取り除いて、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を得た。
【０１４８】
＜キャリア製造例１＞
フルオロエチルメタクリレート／メチルメタクリレート共重合体（共重合比７０：３０）２．５重量部と、カーボンブラック０．５重量部と、メラミン微粒子（粒径０．３μｍ）０．３重量部とをトルエン２０重量部に溶解分散して被覆溶液を調製し、これにフェライト粒子（平均粒子径３５μｍ）１００重量部を投入し、真空脱気型ニーダーを使用して、８０℃で３０分間攪拌後、減圧してトルエンを留去し、体積平均粒子径３５μｍのキャリアａを製造した。キャリアａの体積固有電気抵抗を測定したところ、２．３×１０¹⁰Ω／ｃｍであった。
【０１４９】
＜キャリア製造例２＞
フルオロエチルメタクリレート／メチルメタクリレート共重合体（共重合比７０：３０）２．５重量部と、カーボンブラック０．８重量部と、メラミン微粒子（粒径０．３μｍ）０．３重量部とをトルエン２０重量部に溶解分散して被覆溶液を調製し、これにフェライト粒子（平均粒子径３５μｍ）１００重量部を投入し、真空脱気型ニーダーを使用して、８０℃で３０分間攪拌後、減圧してトルエンを留去し、体積平均粒子径３５μｍのキャリアｂを製造した。キャリアｂの体積固有電気抵抗を測定したところ、４．１×１０⁸ Ω／ｃｍであった。
【０１５０】
＜キャリア製造例３＞
フルオロエチルメタクリレート／メチルメタクリレート共重合体（共重合比７０：３０）２．５重量部と、カーボンブラック０．３重量部と、メラミン微粒子（粒径０．３μｍ）０．３重量部とをトルエン２０重量部に溶解分散して被覆溶液を調製し、これにフェライト粒子（平均粒子径３５μｍ）１００重量部を投入し、真空脱気型ニーダーを使用して、８０℃で３０分間攪拌後、減圧してトルエンを留去し、体積平均粒子径３５μｍのキャリアｃを製造した。キャリアｃの体積固有電気抵抗を測定したところ、５．３×１０¹⁴Ω／ｃｍであった。
【０１５１】
＜キャリア製造例４＞
フルオロエチルメタクリレート／メチルメタクリレート共重合体（共重合比７０：３０）２．５重量部と、カーボンブラック０．７重量部と、メラミン微粒子（粒径０．３μｍ）０．３重量部とをトルエン２０重量部に溶解分散して被覆溶液を調製し、これにフェライト粒子（平均粒子径３５μｍ）１００重量部を投入し、真空脱気型ニーダーを使用して、８０℃で３０分間攪拌後、減圧してトルエンを留去し、体積平均粒子径３５μｍのキャリアｄを製造した。キャリアｄの体積固有電気抵抗を測定したところ、２．０×１０⁹ Ω／ｃｍであった。
【０１５２】
＜キャリア製造例５＞
フルオロエチルメタクリレート／メチルメタクリレート共重合体（共重合比７０：３０）２．０重量部と、カーボンブラック２．０重量部と、メラミン微粒子（粒径０．３μｍ）０．３重量部とをトルエン２０重量部に溶解分散して被覆溶液を調製し、これにフェライト粒子（平均粒子径３５μｍ）１００重量部を投入し、真空脱気型ニーダーを使用して、８０℃で３０分間攪拌後、減圧してトルエンを留去し、体積平均粒子径３５μｍのキャリアｅを製造した。キャリアｅの体積固有電気抵抗を測定したところ、３．２×１０⁵ Ω／ｃｍであった。
【０１５３】
＜キャリア製造例６＞
カーボンブラックを添加しないこと以外は、キャリア製造例１と同様にして、体積平均粒子径３５μｍのキャリアｆを製造した。キャリアｆの体積固有電気抵抗を測定したところ、１．２×１０¹⁵Ω／ｃｍであった。
【０１５４】
〔実施例１〕
以上で得られたキャリアａ；１００重量部と、静電潜像現像用トナーＡ；４重量部とを混合し、実施例１の二成分現像剤（シアン）を作製した。得られた二成分現像剤を使用して、後述の各種評価試験を行った。
【０１５５】
〔実施例２〕
以上で得られたキャリアｂ；１００重量部と、静電潜像現像用トナーＡ；４重量部とを混合し、実施例２の二成分現像剤（シアン）を作製した。得られた二成分現像剤を使用して、後述の各種評価試験を行った。
【０１５６】
〔実施例３〕
以上で得られたキャリアｃ；１００重量部と、静電潜像現像用トナーＡ；４重量部とを混合し、実施例３の二成分現像剤（シアン）を作製した。得られた二成分現像剤を使用して、後述の各種評価試験を行った。
【０１５７】
〔実施例４〕
以上で得られたキャリアｄ；１００重量部と、静電潜像現像用トナーＢ；４重量部とを混合し、実施例４の二成分現像剤（マゼンタ）を作製した。得られた二成分現像剤を使用して、後述の各種評価試験を行った。
【０１５８】
〔実施例５〕
以上で得られたキャリアｄ；１００重量部と、静電潜像現像用トナーＣ；４重量部とを混合し、実施例５の二成分現像剤（イエロー）を作製した。得られた二成分現像剤を使用して、後述の各種評価試験を行った。
【０１５９】
〔実施例６〕
以上で得られたキャリアｄ；１００重量部と、静電潜像現像用トナーＤ；４重量部とを混合し、実施例６の二成分現像剤（ブラック）を作製した。得られた二成分現像剤を使用して、後述の各種評価試験を行った。
【０１６０】
〔実施例７〕
以上で得られたキャリアａ；１００重量部と、静電潜像現像用トナーＥ；４重量部とを混合し、実施例７の二成分現像剤（シアン）を作製した。得られた二成分現像剤を使用して、後述の各種評価試験を行った。
【０１６１】
〔比較例１〕
以上で得られたキャリアｆ；１００重量部と、静電潜像現像用トナーＡ；４重量部とを混合し、比較例１の二成分現像剤（シアン）を作製した。得られた二成分現像剤を使用して、後述の各種評価試験を行った。
【０１６２】
〔比較例２〕
以上で得られたキャリアｅ；１００重量部と、静電潜像現像用トナーＡ；４重量部とを混合し、比較例２の二成分現像剤（シアン）を作製した。得られた二成分現像剤を使用して、後述の各種評価試験を行った。
【０１６３】
〔比較例３〕
以上で得られたキャリアａ；１００重量部と、静電潜像現像用トナーＦ；６重量部とを混合し、比較例３の二成分現像剤（シアン）を作製した。得られた二成分現像剤を使用して、後述の各種評価試験を行った。
【０１６４】
〔比較例４〕
以上で得られたキャリアａ；１００重量部と、静電潜像現像用トナーＧ；６重量部とを混合し、比較例４の二成分現像剤（シアン）を作製した。得られた二成分現像剤を使用して、後述の各種評価試験を行った。
【０１６５】
実施例１〜７および比較例１〜４の各二成分現像剤の構成を一覧表にして、下記表２に示す。
【０１６６】
【表２】

【０１６７】
［評価試験］
実施例１〜７および比較例１〜４において得られた、各二成分現像剤を使用して、後述する各種評価試験を行った。該各種評価試験においては、転写材として通常の非コートフルカラー専用紙を使用し、画像形成装置として富士ゼロックス社製Ａｃｏｌｏｒ９３５改造機（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）を用いた。
画像形成は、ＤＭＡおよびＴＭＡが下記表３に示す値となるよう調整して行った。
【０１６８】
【表３】

【０１６９】
また、現像設定は、Ａ／Ｃ電位をピーク間電圧１．５ｋＶ、周波数９ｋＨｚで、Ｄｕｔｙ比５０％の矩形波とし、Ｄ／Ｃ電位を現像バイアスが５５０Ｖ、現像コントラスト４００Ｖとした。また、クリーニングの電位は１００Ｖとした。
【０１７０】
なお、ＤＭＡおよびＴＭＡの測定方法は、以下に示す通りである。
＜潜像担持体上に形成されるトナー画像のトナー重量ＤＭＡ＞
画像面積率１００％のベタ画像を潜像担持体上に作成し、当該画像部分の単位面積当たりのトナーの重量（ＤＭＡ：ｍｇ／ｃｍ² ）を測定した。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潜像担持体上に作成し、秤量したメンディングテープを用いて、潜像担持体上に形成された未定着トナー画像にメンディングテープを貼り剥がし、トナーを移行させこれを秤量し、これを未定着トナー画像のトナーが無くなるまで繰り返して、メンディングテープに移行したトナーの総重量をＤＭＡとした。
【０１７１】
＜転写材上に転写されるトナー画像のトナー重量ＴＭＡ＞
画像面積率１００％のベタ画像を転写材上に作成し、当該画像部分の単位面積当たりのトナーの重量（ＴＭＡ：ｍｇ／ｃｍ² ）を測定した。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を算出した。
【０１７２】
［各種評価試験方法］
各種評価試験の具体的方法について、以下に説明する。
＜画像濃度＞
画像面積率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した。
【０１７３】
＜細線再現性評価試験＞
感光体上に線幅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５００倍で観察した。具体的な評価基準は、以下の通りである。
○：細線のエッジ乱れが、観察されない。
△：細線のエッジ乱れが、若干観察される。
×：細線のエッジ乱れが、目立つ。
【０１７４】
＜階調再現性評価試験＞
ｉｎ−ｐｕｔ時の階調画像の濃度と、転写材上に形成された（ｏｕｔ−ｐｕｔされた）階調画像の濃度を測定し、階調性の変化を評価した。画像濃度は、Ｘ−Ｒｉｔｅ４０４（Ｘ−Ｒｉｔｅ社製）により測定した。具体的な評価基準は、以下の通りである。
○：１７５線オフセット印刷による印刷物と比較して、同等以上の階調再現性である。
△：１７５線オフセット印刷による印刷物と比較して、やや劣る階調再現性である。
×：１７５線オフセット印刷による印刷物と比較して、大きく劣る階調再現性である。
【０１７５】
＜ソリッド画像の均一性評価試験＞
転写材表面と、画像濃度１．２以上の画像領域の画像光沢の差、および、フルカラープリントの場合には、画像濃度１．２以上の一次色の画像領域の画像光沢と、画像濃度１．２以上の三次色の画像領域の画像光沢の差、をそれぞれ官能評価した。具体的な評価基準は、以下の通りである。
○：１７５線オフセット印刷による印刷物と比較して、同等以上の均一性である。
△：１７５線オフセット印刷による印刷物と比較して、やや劣る均一性である。
×：１７５線オフセット印刷による印刷物と比較して、大きく劣る均一性である。
【０１７６】
＜ソリッド画像端部抜け＞
画像濃度１．５で、大きさ１５ｍｍ×２０ｍｍの矩形のソリッド画像を作成し、画像の端部の白抜けの程度を目視にて評価した。具体的な評価基準は、以下の通りである。
○：目視で認識できない。
△：目視でわずかに認識できる。
×：目視でかなり目立つ。
【０１７７】
＜ハイライト部粒状性評価試験＞
ハイライト部の粒状性を目視にて評価した。具体的な評価基準は、以下の通りである。
◎：１７５線オフセット印刷による印刷物よりも優れた均一性である。
○：１７５線オフセット印刷による印刷物と比較して、同等の均一性である。
△：１７５線オフセット印刷による印刷物と比較して、やや劣る均一性である。
×：１７５線オフセット印刷による印刷物と比較して、大きく劣る均一性である。
【０１７８】
＜キャリア飛翔評価試験＞
キャリアの感光体への移行による画質の低下の有無、あるいはその程度について、評価した。具体的な評価基準は、以下の通りである。
○：問題ないレベル。
△：初期にやや発生。
×：顕著に発生して使用が困難。
【０１７９】
＜連続プリントテスト時の画質安定性評価試験＞
１万枚のプリントテストを実施し、カブリ、細線再現性、階調再現性、ハイライト部の粒状性、ソリッド画像の端部抜けについて、初期プリントサンプルと１万枚プリント後のプリントサンプルとを、既述の評価基準を参考にして評価した。具体的な評価基準は、以下の通りである。
○：１万枚プリントした後にも、画質レベルが初期と変わらず。
△：１万枚プリントした後に、やや画質レベルが悪化。
×：１万枚プリント以前に、画質レベルが大きく悪化。
【０１８０】
実施例１〜７および比較例１〜４の各現像剤の評価結果を下記表４にまとめる。
【０１８１】
【表４】

【０１８２】
〔実施例８〕
実施例１、４、５および６で作製したシアン、マゼンタ、イエローおよびブラックの各二成分現像剤を使用してフルカラーのコピーテストを行った。コピーテストは、画像形成装置としてＡｃｏｌｏｒ９３５改造機を用いた。上記実施例１〜７および比較例１〜４と同様の各評価項目について評価したところ、いずれも結果が○であり、良好であった。
【０１８３】
【発明の効果】
本発明によれば、カブリのない画像形成が可能で、転写効率が高く、耐久性に優れた小粒径のトナーと、適切に電気抵抗値が調整されたキャリアとの組み合わせにより、細線再現性および階調性が良好で、ソリッド画像端部抜けが生じず、オフセット印刷によって形成される画像と同等またはそれ以上の画質を達成することが可能な静電潜像現像剤および画像形成方法を提供することができる。
また、本発明によれば、小粒径のトナーを用いトナーの外添剤の添加量を多くした場合にも、トナーの消費量が少なく、キャリアの劣化が進みにくい画像形成方法を提供することができる。
【図面の簡単な説明】
【図１】着色粒子表面に対する外添剤の被覆率を説明するための、着色粒子表面の一部の拡大平面図である
【図２】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
２２、２２ａ〜２２ｆ：外添剤[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrostatic latent image developer and an image forming method applied to an electrophotographic method, an electrostatic recording method, an electrostatic printing method, and the like, and in particular, an electrostatic image for obtaining an image from a digital electrostatic latent image. The present invention relates to a latent image developer and an image forming method.
[0002]
[Prior art]
In electrophotography, toner in a developer is attached to an electrostatic latent image formed on a photoreceptor, transferred onto paper or plastic film as a transfer material, and fixed by heating or the like to form an image. 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, colorization has progressed in the past several years in printers and copiers using electrophotography, and electrostatic latent images have become finer due to improvements in the 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]
However, in order to realize future demands for higher resolution (improvement of fine line reproducibility, improvement in gradation, etc.), it is necessary to further reduce the toner particle size and provide an appropriate particle size distribution. If the particle size of the toner is further reduced, the non-electrostatic adhesion force represented by van der Waals force increases, and the cohesive force between the toners increases, so that the powder fluidity is greatly deteriorated, or the carrier and photosensitive Since the adhesion force of the toner to the surface of the body is increased, developability and transferability are deteriorated, the image density is lowered, and further, the cleaning property of the toner remaining on the surface of the photoreceptor is greatly lowered.
[0005]
In addition, since the charge exchange between the toner and the carrier decreases due to the decrease in the powder characteristics accompanying the reduction in the diameter of the toner, the rising of the charge decreases, resulting in a wide charge distribution and image quality defects such as fogging. . Further, by reducing the particle size of the toner, a phenomenon that the chargeability is lowered under high temperature and high humidity and the rise of charging under low temperature and low humidity becomes remarkable. In addition, since the thickness of the toner layer on the transfer material is reduced in the small particle size full color toner, it is necessary to increase the concentration of the colorant in the toner. However, the effect on the chargeability of the colorant contained in the toner is required. Has become more prominent, and there are major problems to be solved, such as differences in charge amount, rise of charge, and temperature and humidity dependency of charge among cyan, magenta, yellow, and black toners. The actual situation is that high image quality with the following small-diameter toner has not been realized.
[0006]
Furthermore, in order to achieve a high image density with a two-component developer, in order to achieve a sufficient image density, the peripheral speed of the developer carrying member (developing sleeve) is made faster than the peripheral speed of the photosensitive member, so that A method of supplying sufficient developer is generally adopted. However, the development defect caused by the relative speed difference between the developing sleeve and the photosensitive member, for example, the image missing at the rear end of the solid image, or the front end of the solid image and the halftone when the halftone portion and the solid image are mixed. It is known that rear end image omission occurs at the boundary with the image. In the development process, when the developer layer potential change due to toner movement in the development nip area depends on the latent image structure, or when developing with a speed difference, the area where development is actually performed In this case, the development is performed with a developer that has received an electric field history immediately before the latent image to be developed, for example, because of the discontinuity of the latent image structure, for example, the boundary between the solid image portion and the non-image portion In addition, these image omissions appear to be remarkable at the boundary with the halftone portion.
[0007]
For these improvements, it has been proposed to keep the resistance of the developer or carrier low. On the other hand, if the developer or carrier resistance is kept too low in order to improve the above-mentioned defect, the effect of the proximity of the development effective electrode to the extreme photoreceptor is reduced, and the ability to supply toner to the photoreceptor is reduced, and So-called brush marks are generated due to the occurrence of latent image leakage. In order to suppress this phenomenon, proposals have been made to define the lower limit value of the resistance of the developer layer (Japanese Patent Publication Nos. 5-40309 and 6-29992). The carrier resistance needs to be adjusted to a certain range.
[0008]
In general, from the viewpoint of easy control of charging characteristics and charge maintenance, a coated carrier in which a resin is coated on the surface of magnetic particles that are core particles is often used. At this time, the carrier resistance also includes the type of coating resin coated on the surface of the magnetic particles, the coating amount, the coating state, and the conductive particles appropriately dispersed in the coating resin, in addition to the resistance control of the magnetic particles themselves used. In many cases, it is adjusted as appropriate.
[0009]
Constituent materials such as external additives, binder resins, and colorants migrate to the coating resin layer of the coat carrier, contaminating the surface and changing the charge imparting property (in this case, the charge amount of the toner is usually reduced) Or the transfer amount increases, as in the case where the thickness of the coating resin layer of the carrier is increased, the resistance of the carrier is increased and the image quality is deteriorated.
[0010]
On the other hand, in the developing device, peeling or abrasion of the coating resin layer on the carrier surface occurs due to the shearing force applied to the carrier surface that is generated when the toner and the carrier are mixed. This peeling or abrasion depends on the type and amount of the external additive used in the toner, and further on the consumption of the entire toner. When the amount of the external additive is increased or the consumption amount of the entire toner is increased, the coating resin layer on the carrier surface tends to be peeled off or worn. The wear of the coating resin layer changes the structure of the coating resin layer on the carrier surface, changing the chargeability of the toner, or the resistance of the entire carrier approaches the resistance of the core particles, resulting in deterioration in image quality. Will arise.
[0011]
If the toner has a small particle size, the image quality is improved, but the non-electrostatic adhesion increases, so that the toner that is not developed in the development process remains attached to the carrier surface, and if used as it is, the toner on the carrier surface Adhesion increases or residual toner on the carrier surface is repeatedly stressed and adheres to the carrier surface, so the charge imparting ability of the carrier toner to the toner and the resistance of the carrier itself may increase, and image quality may deteriorate. is there. In particular, since the adhesion force of toner increases under the influence of moisture, such a phenomenon becomes remarkable under high humidity. In addition, in a toner having a small particle size, a large amount of an external additive is often used in the toner in order to improve powder flowability and adhesion, and the carrier surface is contaminated by the external additive, or conversely, the surface of the carrier. Due to the abrasion of the coating resin layer, the charge imparting property and the resistance change greatly, and as a result, the image quality is deteriorated.
[0012]
[Problems to be solved by the invention]
The object of the present invention is to achieve fine line reproducibility by combining a toner having a small particle diameter capable of forming an image without fogging, having high transfer efficiency and excellent durability, and a carrier having an appropriately adjusted electric resistance value. An electrostatic latent image developer and an image forming method capable of achieving an image quality equal to or higher than that of an image formed by offset printing without causing solid image edge omission with good gradation characteristics There is to do.
Another object of the present invention is to provide an image forming method in which toner consumption (weight) is small and carrier deterioration does not easily proceed even when a toner having a small particle size is used and the amount of external additive added to the toner is increased. It is to provide.
[0013]
[Means for Solving the Problems]
The inventors of the present invention have studied the particle size of colored particles (a part excluding external additives in the toner, that is, what is generally called toner particles) required to achieve the above object. As a result, it was found that the volume average particle size of the colored particles is 5.0 μm or less in order to achieve improvement in fine line reproducibility and gradation.
[0014]
Then, in order to prevent the above-mentioned conventional problems using the small colored particles, an electrostatic latent image developer (hereinafter simply referred to as “developer”) composed of A toner and B carrier shown below. And the present invention has been completed. That is, the present invention is an electrostatic latent image developer comprising at least the following A toner and B carrier.
[0015]
A toner
  Consisting of colored particles containing at least a binder resin and a colorant, and
(A) The volume average particle diameter of the colored particles is 2.0 to 5.0 μm, the colored particles of 1.0 μm or less are 20 number% or less, and the colored particles exceeding 5.0 μm are 10 number% or less. ,
(B) When the charge amount of the toner is expressed as q (fC) and the particle size of the toner is expressed as d (μm) in an environment of a temperature of 20 ° C. and a humidity of 50%, Both bottom values are positive or both negative, the absolute value of the peak value is 1.0 or less, the absolute value of the bottom value is 0.005 or more,
(c) Toner where the colorant is pigment particles.
[0016]
B carrier
(d) The volume average particle size is 45 μm or less,
(e) The applied voltage is 10 under the measurement environment of temperature 20 ° C and humidity 50%.^ThreeThe volume specific electrical resistance of the entire carrier particles at V / cm is 1.0 × 10⁸Ω · cm or more 1.0 × 10¹³A carrier having a range of Ω · cm or less.
[0017]
If the colored particles are reduced in size, high image quality can be achieved, but the particle size distribution on the small particle size side in the particle size distribution of the colored particles greatly affects the deterioration of the surface state of the carrier. Especially important. In the present invention, the conventional problems are not solved by making the particle size distribution on the small particle size side appropriate rather than simply reducing the particle size of the colored particles.
[0018]
Specifically, the toner A reduces the amount of the toner having a very small particle size with large non-electrostatic adhesion of the colored particles by suppressing the colored particles of 1.0 μm or less to 20% by number or less. Contamination and adhesion due to the toner of the toner can be suppressed, and an increase in charge imparting ability and resistance of the carrier to the toner can be prevented. Further, the colored particles of 1.0 to 2.5 μm are not as large as the colored particles of 1.0 μm or less, but they should not be too much to suppress the contamination and adhesion of the toner on the carrier surface with 50% by number. It is necessary to: The toner A preferably further contains 5.0 to 50% by number of colored particles of 1.0 to 2.5 μm.
[0019]
In addition, according to the electrostatic latent image developer of the present invention comprising a B carrier having an appropriate volume average particle diameter and an appropriate volume resistivity, and this and the A toner, the deterioration of the B carrier is unlikely to proceed. Therefore, a high-quality image can be obtained over a long period of time. According to such an electrostatic latent image developer of the present invention, fine line reproducibility and gradation are good, solid image edge missing does not occur, and the image quality is equal to or higher than an image formed by offset printing. In particular, the fine line reproducibility is extremely superior to the printed matter obtained by the 175 line offset printing, and is extremely suitable for developing a digital latent image.
[0020]
In order to maintain the electrostatic latent image developer of the present invention containing the above-mentioned toner having a small particle diameter more stably and with high handling properties, it is desirable to add an external additive. In particular, it is preferable that the following conditions are satisfied.
(A) One or more types of ultrafine particles having an average primary particle size of at least 30 nm to 200 nm and one or more types of ultrafine particles having an average primary particle size of 5 nm to less than 30 nm.
(B) The coverage of the external additive on the surface of the colored particles determined by the following formula (1) is 20% or more for both the ultrafine particles Fa and the ultrafine particles Fb, and the total coverage of all external additives is 100% or less
F = √3 ・ D ・ ρ_t・ (2π ・ d ・ ρ_a)^-1・ C × 100 (1)
(In the above formula, F is the coverage (%), D is the volume average particle diameter (μm) of the colored particles, ρ_tIs the true specific gravity of the colored particles, d is the average primary particle diameter (μm) of the external additive, ρ_aRepresents 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. )
[0021]
In the present invention, in order to obtain a sufficiently colored image by using a toner having a small particle size and suppressing the amount of toner used, the pigment concentration of the pigment particles in the colored particles is C (wt%), True specific gravity is a (g / cm^Three), When the volume average particle diameter of the colored particles is D (μm), it is preferable to satisfy the relationship of the following formula (2).
25 ≦ a · D · C ≦ 90 (2)
[0022]
  In the present invention, A toner having a small particle diameter is used, and in order to prevent the fogging of the non-image area, the transfer efficiency, and the rising of the charging, the A toner at a temperature of 20 ° C. and a humidity of 50% is used. In the frequency distribution of the q / d value, when the charge amount is expressed as q (fC) and the particle diameter of the electrostatic latent image developing toner is expressed as d (μm),The peak and bottom values are both positive or negative,Of peak valueAbsolute valueIs 1.0 or less and the bottom value isAbsolute valueIs 0.005 or moreRu.
[0023]
The electrostatic latent image developer of the present invention includes at least a latent image forming step for forming an electrostatic latent image on the latent image carrier, and a development disposed opposite to the latent image carrier by the electrostatic latent image developer. A toner layer forming step of forming a toner layer on the surface of the agent carrier, a developing step of developing an electrostatic latent image on the latent image carrier by the toner layer to form a toner image, and the developed toner image Is preferably used in an image forming method having a transfer step of transferring a toner image onto a transfer material, and a fixing step of heat-fixing a toner image on the transfer material, and particularly at least cyan, magenta and yellow on the transfer material. It is suitably used in an image forming method for forming a full-color image by laminating at least three-color or four-color toner images using a three-color or further black four-color electrostatic latent image developer. .
[0024]
In the development step of such an image forming method, a bias voltage containing an alternating current component having a frequency of 6,000 Hz to 18,000 Hz is applied between the developer carrying member and the latent image carrying member, so that a static image on the latent image carrying member is obtained. It is preferable to develop the electrostatic latent image to form a toner image. By forming an oscillating electric field in an appropriate frequency range in the developing region, it is possible to further improve the image quality of the image formed by the image forming method using the electrostatic latent image developer of the present invention.
[0025]
In the developing step of the image forming method, the toner weight of the toner image formed on the latent image carrier in the developing step is 0.50 mg / cm per color.²By making the following, toner consumption can be reduced, and as a result, carrier deterioration can be suppressed.
Furthermore, the toner weight of the toner image transferred onto the transfer material in the transfer process is 0.40 mg / cm per color.²By suppressing to the following, the thickness of the obtained image is reduced, and an image with good image quality that is visually uncomfortable can be obtained.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
[Electrostatic latent image developer]
The electrostatic latent image developer of the present invention comprises a specific electrostatic latent image developing toner (A toner) and a specific carrier (B toner). First, the present invention will be described by dividing it into A toner and B carrier.
[0027]
A toner
The A toner (colored toner that forms a toner image in the developing process) used in the present invention is a toner having the following configuration.
(1) It consists of colored particles containing at least a binder resin and a colorant, and
(A) The volume average particle diameter of the colored particles is 2.0 to 5.0 μm, the colored particles of 1.0 μm or less are 20 number% or less, and the colored particles exceeding 5.0 μm are 10 number% or less. ,
(B) A toner in which the colorant is pigment particles.
Hereinafter, the A toner will be described in detail by dividing it into a characteristic configuration and a common configuration.
[0028]
<Characteristic configuration of toner A>
(A) Volume average particle diameter of colored particles
As described above, in order to achieve improvement in fine line reproducibility and gradation, it is essential that the volume average particle size of the colored particles 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.
[0029]
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 the particle diameter is less than 2.0 μm, various problems associated with powder characteristics deterioration such as powder flowability, developability, or transferability as toner deteriorate and cleaning performance of toner remaining on the surface of the photoreceptor deteriorates. May occur.
[0030]
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.
[0031]
Further, in the A toner, the particle size distribution of the colored particles is 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. .
[0032]
If the number of colored particles of 1.0 μm or less in all the colored particles exceeds 20% by number, fogging of the non-image area is likely to occur, and defective cleaning of the photoreceptor (latent image carrier) is likely to occur. Further, the colored particles of 1.0 μm or less in all the colored particles increase the non-electrostatic adhesion force of the toner, the toner that is not developed in the development process remains attached to the carrier surface, and then undergoes repeated stress to cause the carrier. In some cases, the toner may adhere to the surface, and in this case, the charge imparting ability and resistance of the carrier to the toner increase. Therefore, the ratio of the colored particles having such a minimum particle size needs to be suppressed to a certain level. Considering these, the colored particles of 1.0 μm or less in all the colored particles are required to be 20% by number or less, preferably 10% by number or less in all the colored particles.
[0033]
Furthermore, when the number of colored particles exceeding 5.0 μm exceeds 10% by number in all the colored particles, 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.
[0034]
In addition, as the parameter that defines the large particle size side of the particle size distribution of the colored particles, the number% of colored particles exceeding 5.0 μm was used in the A toner, 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 toner A, 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.
[0035]
In order to faithfully reproduce fine lines having a line width of about 30 to 60 μm and minute dots having the same diameter, it is preferable that colored particles of 1.0 to 2.5 μm are present at a certain ratio, Although the colored particles of 1.0 to 2.5 μm are not as large as the colored particles of 1.0 μm or less, it is preferable that the colored particles are not too many to suppress the contamination and fixing of the carrier surface with the toner. In consideration of these matters, the number of colored particles of 1.0 to 2.5 μm is preferably 5 to 50% by number, more preferably 10 to 45% by number in all the colored particles. When the number of colored particles of 1.0 to 2.5 μm exceeds 50% by number, the same problem as when a large amount of colored particles of 1.0 μm or less is present may occur. If the colored particles are less than 5% by number, filling of fine lines and fine dots may be insufficient.
[0036]
In order to obtain colored particles having such a particle size, the conditions for pulverization and classification may be set appropriately when obtained by a pulverization method, and the polymerization conditions may be appropriately set when obtained by a polymerization method. When trying to make the particle size as small as possible by the method, overgrinding is less likely to occur, and classification is easy. Therefore, the pulverization method is preferred from the viewpoint of easy production and low cost.
[0037]
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.
[0038]
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.
[0039]
(B) Colorant
Pigment particles are used as the colorant contained in the colored particles. In the case of A toner, even if the toner weight per unit area of the image is reduced, 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 preferable to use pigment particles having high coloring power and excellent water resistance, light resistance, or solvent resistance.
[0040]
<Preferred configuration for toner A>
1. External additive
In the case of the A toner, it is preferable to add an external additive for the purpose of improving the deterioration of the powder characteristics and the charging characteristics when the toner is reduced in particle size.
Examples of materials for inorganic fine powders that can be used as external additives include metal oxides such as silicon oxide, titanium oxide, tin oxide, zirconium oxide, tungsten oxide, and iron oxide, nitrides such as titanium nitride, 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.
[0041]
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.
[0042]
In addition, the A toner has good powder properties such as powder flowability and powder adhesion, prevents a decrease in development efficiency in the development process and transfer efficiency in the transfer process, under high humidity One or more types of ultrafine particles having an average primary particle size of at least 30 nm or more and 200 nm or less, and 5 nm as an external additive in order to prevent deterioration of powder characteristics and deterioration of chargeability and alleviate environmental dependency It is preferable to use one or more ultrafine particles having an average primary particle diameter of less than 30 nm.
[0043]
The ultrafine particles have a function of enhancing the effect of controlling the particle size distribution of the colored particles in the present invention, and further reduce the adhesion between the colored particles or between the colored particles and the photoreceptor or carrier, thereby developing, transferring, or cleaning. It works to prevent the decline of sex. 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. When the average primary particle size of the ultrafine particles exceeds 200 nm in the particle size range of the A toner, the difference from the size of the colored particles becomes small, so that the particles are easily detached from the colored particles, 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.
[0044]
The ultrafine particles improve the fluidity of the toner (colored particles), reduce the degree of aggregation, and contribute to the improvement of environmental stability due to the effect of suppressing the thermal aggregation of the powder. 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 29 nm or less, and further preferably 10 nm or more and 29 nm or less. If it is less than 5 nm, the ultra-fine particles tend to be buried in the surface of the colored particles due to the stress that the toner receives in the developing machine. 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.
[0045]
Examples of 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.
[0046]
Examples of ultrafine particles include hydrophobic titanium compounds, metal oxides such as silicon oxide, titanium oxide, tin oxide, zirconium oxide, tungsten oxide, and iron oxide, and fine particles composed of nitrides such as titanium nitride. The titanium compound fine particles are preferable.
[0047]
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 photoreceptor, are preferably used.
[0048]
As a metatitanic acid compound, which is a reaction product of metatitanic acid and an alkylalkoxysilane compound and / or a fluoroalkylalkoxysilane compound, the base metatitanic acid is treated after peptizing the metatitanic acid synthesized by the sulfuric acid hydrolysis reaction. 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.
[0049]
By using two types of external additives, ultrafine particles and ultrafine particles, the effects of the addition of both can be obtained.
[0050]
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 photoreceptor 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.
[0051]
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 coverage with respect to the colored particle surface of the external additive will be described.
[0052]
When the external additive is regarded as a true sphere of a certain size (diameter d) and it is assumed that primary particles without aggregation are attached as a single layer on the surface of the colored particles, The closest packing of the additives (the most closely arranged state) is a hexagonal closest packing in which six external additives 22a to 22f are adjacent to one external additive 22 as shown in FIG. 1 (FIG. 1). Is an enlarged plan view showing only a part of the colored particle surface).
[0053]
In this way, when the state as shown in FIG. 1 is an ideal state covering rate of 100%, how much is the actual weight of the external additive relative to the actual weight of the colored particles? The percentage expressed in terms of% is defined as the coverage referred to in the present invention.
[0054]
That is, in the actual state, the volume average particle diameter of the colored particles is D (μm), and the true specific gravity of the colored particles is ρ._tThe average primary particle diameter of the external additive is d (μm), and the true specific gravity of the external additive is ρ._aWhen the ratio (x / y) between the weight x (g) of the external additive and the weight y (g) of the colored particles is C, the coverage F (%) is
F = C / {2π · d · ρ_a/ (√3 ・ D ・ ρ_t)} × 100
When this is organized, the following formula (1) is obtained.
[0055]
F = √3 ・ D ・ ρ_t・ (2π ・ d ・ ρ_a)^-1・ C × 100 (1)
(In the above formula, F is the coverage (%), D is the volume average particle diameter (μm) of the colored particles, ρ_tIs the true specific gravity of the colored particles, d is the average primary particle diameter (μm) of the external additive, ρ_aRepresents 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. )
[0056]
In the present invention, the coverage of the external additive on the colored particle surface obtained by the above formula (1) 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.
[0057]
If 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%.
[0058]
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%.
[0059]
If the total coverage of all external additives exceeds 100%, a large amount of free external additives are generated, and the photoreceptor and the carrier surface are easily contaminated with external additives. The total coverage of all external additives is preferably 40 to 100%, more preferably 50 to 90%.
[0060]
The relationship between the ultrafine particle coverage Fa (%) and the ultrafine particle coverage Fb (%) more preferably satisfies the following formula (4).
0.5 ≦ Fb / Fa ≦ 4.0 (4)
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 (4 ′).
0.5≤Fb / Fa≤2.5 (4 ')
[0061]
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.
[0062]
2. Relationship between charge quantity q and particle size d (q / d value)
In the toner, not the charge amount of the toner as a whole but the charged state of the toner particles 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 A toner, it is preferable that the relationship between the charge amount of each toner particle and the particle diameter is appropriate.
[0063]
  That is, for the A toner, the charge amount of the electrostatic latent image developing toner at a temperature of 20 ° C. and a humidity of 50% is represented by q (fC), and the particle size of the electrostatic latent image developing toner is represented by d (μm). In the frequency distribution of q / d value,The peak and bottom values are both positive or negative,Of peak valueAbsolute valueIs 1.0 or less and the bottom valueAbsolute value ofIs 0.005 or moreIt is.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.
[0064]
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.
[0065]
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.
[0066]
  In the A toner, the peak value in the frequency distribution of the q / d value is 1.0 or less.YesMore 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. In addition, the cleaning property of the toner remaining on the surface of the photoreceptor may be deteriorated. 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.
[0067]
  Further, when the q / d value is too close to 0 or is a positive or negative value (that is, reverse polarity toner), the image portion may be lost or the non-image portion may be fogged. Therefore, the bottom value in the frequency distribution of q / d values can be kept at a certain value or more.Is necessarySpecifically, 0.005 or moreAndMore preferably, it is 0.01 or more, More preferably, it is 0.02 or more, Most preferably, it is 0.025 or more.
[0068]
In addition, it is not necessary to specify in particular the value which becomes the upper limit value (the upper limit value in the absolute value in the case of negatively charged toner) in the frequency distribution of the q / d value. 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.
[0069]
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. A specific measurement method will be described below.
[0070]
FIG. 2 is a schematic perspective view of the measuring apparatus 10 for measuring the frequency distribution of the q / d value 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.
[0071]
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.
[0072]
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 a charged toner, it is affected by the electric field E, and the position shifts from the center O in the traveling direction of the electric field E to reach the filter 14 (point T in FIG. 2). 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.)
[0073]
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 expressed by equation (3).
q / d = (3πηVa / kE) × x (3)
In equation (2), 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.
[0074]
In the present invention, measurement is performed by setting each condition of the measurement apparatus 10 shown in FIG. 2 so that each condition of the expression (3) 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
[0075]
Substituting the above values into Equation (3) yields:
q (fC) / d (μm) ≒ 0.09 · x
[0076]
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.
[0077]
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).
[0078]
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.
[0079]
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.
[0080]
In order to manufacture the toner as described above, there is a method of adding an external additive for the purpose of charge control to the colored particles.
Examples of inorganic fine powder materials that can be used as external additives include metal oxides such as silicon oxide, titanium oxide, tin oxide, zirconium oxide, tungsten oxide, and iron oxide, nitrides such as titanium nitride, 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.
[0081]
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.
[0082]
In order to produce such a toner having a frequency distribution of q / d values, as described above, as described above, one or more types of ultrafine particles and one or more types of ultrafine particles are used as an external additive. The toner configuration using the toner. With such a toner configuration, the frequency distribution of the q / d value of the toner can be appropriately controlled.
[0083]
[Other composition of toner A]
(I) colored particles
In the A toner, the colored particles contain at least a binder resin and a colorant.
[0084]
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.
[0085]
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 property and long-term storage property of the image after being fixed on the transfer material are deteriorated, and when it exceeds 150 ° C., the low-temperature fixability is deteriorated.
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.
[0086]
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. Examples of the polymer include one or two types appropriately selected from the following styrene monomers, (meth) acrylate monomers, other acrylic or methacrylic monomers, vinyl ether monomers, vinyl ketone monomers, N-vinyl compound monomers, and the like. A polymer obtained by polymerizing the above monomers is preferably used.
[0087]
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.
[0088]
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.
[0089]
Examples of other acrylic or methacrylic monomers include acrylonitrile, methacrylamide, glycidyl methacrylate, N-methylol acrylamide, N-methylol methacrylamide, and 2-hydroxyethyl acrylate.
[0090]
Examples of vinyl ether monomers include vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, and vinyl isobutyl ether.
[0091]
Examples of the vinyl ketone monomer include vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and methyl isopropenyl ketone.
[0092]
Examples of the N-vinyl compound monomer include N-vinyl compounds such as N-vinyl pyrrolidone, N-vinyl carbazole, and N-vinyl indole.
[0093]
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.
[0094]
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.
[0095]
A conventionally known pigment or dye can be used as the colorant contained in the colored particles. However, if the amount of the colorant added is too large, the charging characteristics of the toner will be affected. Therefore, it is preferable in the present invention to use a pigment that exhibits high color developability in a small amount.
[0096]
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.
[0097]
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. Although a method of using it at a thickness of 3 μm or less has been proposed (Japanese Patent Laid-Open No. Hei 4-242752), this method is very effective for the A toner which needs to increase the colorant concentration in the colored particles. 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, It is easy to make the average particle size of the dispersed particles in the binder resin of pigment fine particles 0.3 mm or less in terms of equivalent circle diameter. If pigment fine particles with such small particle size are used in this way, the transparency of the toner can be secured. It is preferable because good color reproduction is possible.
[0098]
In the toner A, the colored particles have a volume average particle size of 5.0 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 exclude the color development of the lower layer and good color reproduction may not be achieved. However, the average particle diameter of the dispersed particles of the pigment particles in the binder resin should be 0.3 μm or less in terms of equivalent circle diameter. It becomes possible to solve this problem.
[0099]
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.
[0100]
As described above, the A toner has a small particle diameter, and a sufficient image density cannot be obtained with the same pigment concentration as that of the conventional toner having a larger particle diameter. Further, even though the toner A has a small particle size, the volume average particle size varies from 1.0 μm to 5.0 μm, and the toner weight per unit area (= transfer) in the solid image. A large difference also appears in the toner weight of the toner image transferred onto the material = TMA). Therefore, it is desirable to set the necessary pigment concentration according to TMA. A preferable range of TMA will be described later.
[0101]
Assuming that the toner is formed in a single layer on the transfer material, TMA is determined by the volume average particle diameter D (μm) and specific gravity a of the colored particles, and the pigment concentration C (%) in the colored particles is It is desirable to satisfy the following relational expression (2).
25 ≦ a · D · C ≦ 90 (2)
[0102]
When the value of a · D · C (hereinafter 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 it is formed during development to obtain a desired image density. Increasing the amount of toner is not preferable because the glossiness of the image is increased, the thickness of the image is increased, the reproducibility of the fine lines is reduced, and the transferability is also lowered, although the folding angle is reduced.
[0103]
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, and the melt viscosity of the colored particles increases due to the reinforcing effect of the pigment. Then, there is a possibility that the fixing property is deteriorated, which is not preferable.
[0104]
Further, there is a difference in coloring power due to a difference in color, and it is more preferable that the following relational expressions (2-1) to (2-4) are satisfied for each color.
Cyan: 25 ≦ a · D · C ≦ 90 (2-1)
Magenta: 25 ≦ a · D · C ≦ 60 (2-2)
Yellow: 30 ≦ a · D · C ≦ 90 (2-3)
Black: 25 ≦ a · D · C ≦ 60 (2-4)
[0105]
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.
[0106]
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 as described above. 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.
[0107]
(Ii) Other additives
To the A toner, 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 organoboron 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.
[0108]
(iii) Toner aggregation degree
The toner A preferably has a degree of aggregation of 30 or less, more preferably 25 or less, and still more preferably 20 or less. Here, the cohesion degree is an index representing the cohesive force between toners, and when the value is large, the cohesive force between toners is large.
[0109]
By setting the degree of aggregation to 30 or less, it is possible to suppress a decrease in fluidity due to a reduction in the particle size of the toner and a decrease in agitation with the carrier, poor toner replenishment, a decrease in charge rising property, a deterioration in charge distribution, and It is possible to improve scumming and density reduction resulting from a decrease in the amount of charge, and storage stability. When the degree of aggregation of the toner is greater than 30, it causes scumming due to poor fluidity and stirrability with the carrier, density unevenness due to density reduction, and storage stability also deteriorates. In particular, if two types of external additives, ultrafine particles and ultrafine particles, are added as described above, the degree of agglomeration becomes a very low value due to the balance of the particle size and coverage of the external additive.
[0110]
The aggregation degree can be measured by using a powder tester (manufactured by Hosokawa Micron). Specifically, it is as follows.
Place sieves with openings of 45, 38 and 26 in series, put 2 g of toner accurately weighed onto the top 45 μm sieve, give vibration of 1 mm amplitude for 90 seconds, and lift each sieve after shaking The toner weight is measured, the values of 0.5, 0.3, and 0.1 are sequentially added to the respective weights and added, and the obtained numerical value is multiplied by 100. In the present invention, the sample was left for about 24 hours in an environment of 22 ° C./50% RH, and the measurement was performed in an environment of 22 ° C./50% RH.
[0111]
B carrier
The A toner is mixed with the B carrier and used as a two-component electrostatic latent image developer. The B carrier in the present invention has a volume specific electrical resistance of 1.0 × 10⁸Ω · cm or more 1.0 × 10¹³Ω · cm or less, preferably 1.0 × 10⁸~ 1.0 × 10¹²It is in the range of Ω · cm. Electric resistance value is 1.0 × 10⁸If it is less than Ω · cm, fog may occur in the non-image area or the carrier may move from the developer carrying member to the photosensitive member.¹³If it exceeds Ω · cm, these image omission problems may occur at discontinuous points of the latent image structure, for example, at the boundary between the solid image portion and the non-image portion, or at the boundary between the halftone portion.
[0112]
Here, a method for measuring the volume specific electric resistance (Ω · cm) of the carrier will be described. In the present invention, the measurement environment for the volume specific electrical resistance of the carrier was set to a temperature of 20 ° C. and a humidity of 50%.
20cm²The carrier to be measured is placed flat on a circular jig provided with the electrode plate so as to have a thickness of about 1 to 3 mm to form a carrier layer. The same 20cm as above²The electrode plate is placed and the carrier layer is sandwiched. In order to eliminate the gap between the carriers, the thickness (mm) of the carrier layer is measured after a load of 4 kg is applied on the electrode plate placed on the carrier layer. Both electrodes above and below the carrier layer are connected to an electrometer and a high-voltage power generator. By applying a high voltage (1000 V in the present invention) to both electrodes and reading the current value (A) flowing at this time, the volume specific electrical resistance (Ω · cm) of the carrier is calculated. The calculation formula of the volume specific electric resistance (Ω · cm) of the carrier is as shown in the following formula (5).
R = E × 20 / (I−I₀) / L (5)
In the above formula, R is a volume specific electric resistance (Ω · cm), E is an applied voltage (V), that is, E = 1000, I is a current value (A), I₀Represents a current value (A) at an applied voltage of 0 V, and L represents a thickness (mm) of the carrier layer. The coefficient of 20 is the area of the electrode plate (cm²).
[0113]
As a particle size of B carrier, it is essential that it is 45 micrometers or less as a volume average particle diameter, Preferably it is 10-40 micrometers, More preferably, it is 15-40 micrometers. By setting the volume average particle diameter of the carrier to 45 μm or less, it is possible to suppress the rise of charge and the spread of the charge distribution due to the toner (colored particles) having a small particle diameter.
[0114]
The B carrier used in the present invention is not particularly limited as long as the volume specific electric resistance is within the above range, and magnetic particles such as iron powder, copper, nickel, cobalt, ferrite, magnetite, etc. A resin-coated carrier in which the magnetic metal oxide particle or the like is used as a core particle, and the surface thereof is formed with a resin coating layer such as polyolefin resin, vinyl resin, silicone resin, fluororesin, polyester resin, or the like, or Examples include a magnetic material-dispersed carrier in which magnetic fine particles made of the same material as the core particles are dispersed in a binder resin, and a resin-coated layer formed on the magnetic material-dispersed carrier. Can do.
[0115]
Among these, a resin-coated carrier having a resin coating layer is particularly preferable because the chargeability of the toner and the electric resistance value 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.
[0116]
Specifically, polyolefin resins, such as polyethylene, polypropylene; polyvinyl and polyvinylidene resins, such as polystyrene, acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether and polyvinyl. Ketone; Vinyl chloride-vinyl acetate copolymer; Styrene-acrylic acid copolymer; Straight silicone resin composed of organosiloxane bond or its modified product; Fluororesin such as polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, poly Polyester; Polyurethane; Polycarbonate; Phenol resin; Amino resin such as urea-formaldehyde Fat, melamine resins, benzoguanamine resins, urea resins, polyamide resins, epoxy resins and the like. Moreover, the kind of resin may be individual or may be 2 or more types.
[0117]
The volume specific electrical resistance of the B carrier used in the present invention can be adjusted by dispersing carbon black in the resin coating layer. It can be adjusted to a desired value by adjusting the amount and particle size of carbon black to be dispersed. The particle size of the carbon black that can be used is 5 to 50 nm, and preferably within the range of 1 to 30% by weight, more preferably within the range of 5 to 25% by weight, based on the entire resin coating layer. It can add so that the volume specific electrical resistance of a carrier may become a desired value.
[0118]
In addition, it is also possible to add conductive powder in the resin coating layer of the carrier in combination with carbon black or alone. Examples of the conductive powder that can be used include metals such as gold, silver, and copper, and semiconductive oxides such as titanium oxide and zinc oxide; titanium oxide, zinc oxide, barium sulfate, aluminum borate, and titanic acid. The surface of the potassium powder or the like is covered with tin oxide, carbon black, or metal.
[0119]
Furthermore, when it is desired to impart various functions to the carrier, resin fine particles corresponding to those functions can be added to the resin coating layer of the carrier. For example, when it is desired to impart negative charge imparting property and charge maintaining property to the toner, the charge maintaining property can be significantly improved by using nitrogen-containing resin fine particles as the charge control agent. Further, in order to improve the mechanical strength of the carrier by the resin fine particles, it is preferable to use thermosetting resin particles that are relatively easy to increase the hardness. Since the thermosetting resin particles are already in the form of fine particles in the solvent / kneading, they are easy to disperse during coating and kneading, do not aggregate in the resin coating layer of the carrier, and maintain the shape of the primary particles. be able to.
[0120]
The resin fine particles may be appropriately selected from various resins according to the desired function.
Specific examples of thermoplastic resins that can be used for the resin fine particles include polyolefin resins such as polyethylene and polypropylene; polyvinyl and polyvinylidene resins such as polystyrene, acrylic resins, polyacrylonitrile, polyvinyl acetate, and polyvinyl alcohol. , Polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether and polyvinyl ketone; vinyl chloride-vinyl acetate copolymer; styrene-acrylic acid copolymer; straight silicone resin comprising an organosiloxane bond or a modified product thereof; fluorine resin, Examples thereof include polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene; polyester; polycarbonate and the like.
[0121]
The volume average particle diameter of the core particles used for the resin-coated carrier is preferably 45 μm or less, more preferably 10 to 40 μm, and even more preferably 15 to 40 μm.
On the other hand, the volume average particle diameter of the magnetic fine particles used in the magnetic material dispersed carrier is preferably in the range of 0.05 to 2 μm, more preferably in the range of 0.1 to 1 μm.
[0122]
The amount of the resin film coated on the core particles in the resin-coated carrier is in the range of 0.2 to 5.0% by weight as the weight ratio of the entire carrier in consideration of the carrier charge maintenance property, environmental stability, and the like. Preferably, it is in the range of 0.5 to 3.0% by weight. If it is less than 0.2% by weight, the environmental stability and charge maintenance of the charge will be reduced, and if it exceeds 5.0% by weight, it will be difficult to obtain the volume specific electrical resistance of the carrier required in the present invention. . When the amount of resin coating is large, conductive resistance powder such as carbon black is dispersed in the resin coating layer to control the resistance so that the volume specific electrical resistance of the carrier required in the present invention can be obtained. Therefore, the B carrier according to the present invention can be obtained without any problem.
[0123]
Examples of the method for producing a resin-coated carrier include a method of using a raw material solution for forming a resin coating layer in which a resin to be coated on core particles is dissolved (and dispersed) in a solvent. Specifically, a dipping method in which a core particle is immersed in a raw material solution for forming a resin coating layer to form a resin coating layer, a spray method in which a raw material solution for forming a resin coating layer is sprayed on the surface of the core particle, a core Fluidized bed method in which the raw material solution for forming the resin coating layer is sprayed in a state where the particles are suspended by flowing air, and the kneader coater for removing the solvent by mixing the core particles and the raw material solution for forming the resin coating layer in the kneader coater Law. Among these, the kneader coater method is preferably used in the present invention.
[0124]
In the electrostatic latent image developer of the present invention, the mixing ratio of the A toner and the B carrier is preferably in the range of 1: 100 to 20: 100, more preferably 2: 100 to 15: 100. The range is more preferably 3: 100 to 10: 100.
[0125]
[Image forming method]
The toner for developing an electrostatic latent image of the present invention is disposed at least in a latent image forming step for forming an electrostatic latent image on the latent image carrier and facing the latent image carrier by an electrostatic latent image developer. A toner layer forming step of forming a toner layer on the surface of the developer carrying member, a developing step of developing an electrostatic latent image on the latent image carrying member by the toner layer to form a toner image, and the developed toner It is suitably used in an image forming method having a transfer step of transferring an image onto a transfer material and a fixing step of heating and fixing a toner image on the transfer material.
[0126]
In particular, if the development is performed using the electrostatic latent image developer of the present invention including the A toner having a particle size range and particle size distribution in the present invention, the development efficiency can be remarkably improved. Therefore, by using the electrostatic latent image developer of the present invention, the image obtained has good fine line reproducibility and gradation, no fog, and non-fogging of the latent image structure such as a solid image portion. These image omission problems do not occur at the boundary with the image portion and the boundary with the halftone portion.
[0127]
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 electrostatic latent image developer containing these four color toners If the electrostatic latent image developer of the present invention is used, the resulting image has good fine line reproducibility and gradation, no fogging, no solid image edge missing, and a small toner particle size. Therefore, the thickness of the toner image on the transfer material can be reduced, and a high image quality equivalent to or higher than that of offset printing can be achieved with no visual discomfort. 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. In particular, in a full-color image forming method in which solid images and halftone images are often mixed, by using the electrostatic latent image developer of the present invention, discontinuous points of the latent image structure, for example, solid image portions and These image omission problems do not occur at the boundary with the non-image portion or the halftone portion.
[0128]
In the image forming method using the electrostatic latent image developer of the present invention, in the development step, the developer carrying member and the latent image are secured in order to ensure a sufficient supply amount of toner to obtain a sufficient image density in the development step. It is preferable to apply a bias voltage containing an AC component between the carrier and the electrostatic latent image on the latent image carrier to develop a toner image. By applying a bias voltage containing an AC component, the toner effectively adheres to the electrostatic latent image on the latent image carrier by the oscillating electric field formed in the development region. At this time, by setting the frequency of the AC component of the bias voltage within an appropriate range, the image quality of the obtained image can be improved.
[0129]
The frequency of the AC component of the bias voltage applied in the development step is preferably in the range of 6,000 Hz to 18,000 Hz, more preferably in the range of 8,000 Hz to 15,000 Hz. If it is less than 6,000 Hz, fogging of the resulting image is likely to occur, and the reproducibility of the edge portion of the fine line may be deteriorated, or the filling of the fine line may be deteriorated. And the image quality improvement effect will be saturated.
[0130]
In the image forming method of the present invention, the toner weight (development weight, hereinafter referred to as “DMA”) of the toner image formed on the latent image carrier in the development step is 0.50 mg / cm per color.²Or less, more preferably 0.45 mg / cm.²Or less, more preferably 0.40 mg / cm²It is as follows. By reducing the DMA, the amount of toner consumed per unit area can be reduced. When a large number of copies are made, contamination of the carrier surface is reduced, and deterioration in image quality due to carrier deterioration can be suppressed. The upper limit value of the DMA here indicates the upper limit value at an image area ratio of 100% for each color. Of course, the toner image formed on the latent image carrier varies in image area ratio depending on each part, and DMA of course is 0 mg / cm at a part where the image area ratio is 0%.²Therefore, it is not necessary to specify the lower limit value. However, in order to ensure sufficient color development of the toner in the obtained image, the lower limit of DMA at an image area ratio of 100% for each color is 0.10 mg / cm.²Or more, more preferably 0.15 mg / cm.²That's it.
[0131]
The toner image formed on the latent image carrier is transferred onto a transfer material in a transfer process. If the transfer efficiency is 100%, DMA and TMA have the same value, but the transfer efficiency is slightly smaller than 100%, so TMA has a smaller value. In order to reduce the thickness of the obtained image and form an image having a good image quality equivalent to offset printing without visually uncomfortable, TMA is 0.40 mg / cm per color.²Or less, more preferably 0.35 mg / cm.²Or less, more preferably 0.30 mg / cm²It is as follows. The upper limit value of TMA here indicates the upper limit value at an image area ratio of 100% for each color. As a matter of course, the toner image transferred onto the transfer material varies in image area ratio depending on each part, and TMA is of course 0 mg / cm at the part where the image area ratio is 0%.²Therefore, it is not necessary to specify the lower limit value. However, in order to ensure sufficient color development of the toner in the obtained image, the lower limit value of TMA at an image area ratio of 100% for each color is 0.10 mg / cm.²Or more, more preferably 0.15 mg / cm.²That's it.
[0132]
The transfer efficiency here is the ratio of the toner weight (TMA) of the toner image transferred onto the transfer material to the toner weight (DMA) of the toner image formed on the latent image carrier in%. In the present invention, the transfer efficiency is preferably 80% or more, more preferably 90% or more, and the closer to 100%, the more the latent image carrier can be cleaned and the toner consumption can be reduced. This is preferable from the viewpoint.
[0133]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.
<Example of production of electrostatic latent image developer>
(1) Preparation of colored 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) was placed in a kneader-type kneader, mixed, and gradually heated. Kneading was continued at 120 ° C. to separate the water phase and the resin phase, and then water was removed. Further, the resin phase was kneaded to remove water and dehydrated to obtain a magenta flushing pigment.
[0134]
<Cyan flushing pigment>
A cyan flushing pigment was obtained in the same manner as the magenta flushing pigment except that the magenta pigment containing paste was replaced with a cyan pigment (CI Pigment Blue 15: 3) containing paste (pigment content 40 wt%).
[0135]
<Yellow flushing pigment>
A yellow flushing pigment was obtained in the same manner as the magenta flushing pigment except that the magenta pigment-containing paste was replaced with a yellow pigment (CI Pigment Yellow 17) water-containing paste (pigment content 40 wt%).
[0136]
2) Preparation of colored particles
<Preparation Example 1 of Colored Particles>
・ Polyester resin (Bisphenol A type polyester:
Bisphenol A ethylene oxide adduct-cyclohexanedimethanol-terephthalic acid, weight average molecular weight: 11,000, number average molecular weight: 3500, Tg: 65 ° C.) 66.7 parts by weight
-33.3 parts by weight of the above-mentioned cyan flushing pigment (pigment content 30% by weight)
The above components were melted and kneaded with a Banbury mixer, and after cooling, finely pulverized with a jet mill and classified with an air classifier to obtain colored particles A. The conditions for pulverization and classification were adjusted so that the particle size distribution shown in Table 1 below was obtained.
[0137]
The particle size and particle size distribution of the particles were measured using a Coulter Counter TA-II type manufactured by Coulter Counter. At this time, when the average particle diameter of the toner (colored particles) exceeds 5 μm, a 100 μm aperture tube is used. When the average particle diameter is 5 μm or less, the aperture diameter is 50 μm, and the number distribution of particles of 1 μm or less is measured. Occasionally, the measurement was performed with an aperture diameter of 30 μm (the same applies to the following examples and comparative examples).
[0138]
<Preparation Example 2 of Colored Particles>
Colored particles B shown in Table 1 below were obtained in the same manner as in Colored Particle Production Example 1 except that the cyan flushing pigment was replaced with a magenta flushing pigment. The conditions for pulverization and classification were adjusted so that the particle size distribution shown in Table 1 below was obtained.
[0139]
<Preparation Example 3 of Colored Particles>
Colored particles C shown in Table 1 below were obtained in the same manner as in Colored Particle Preparation Example 1 except that the polyester resin was changed to 50 parts by weight and the cyan flushing pigment was changed to 33.3 parts by weight with the yellow flushing pigment. It was. The conditions for pulverization and classification were adjusted so that the particle size distribution shown in Table 1 below was obtained.
[0140]
<Preparation Example 4 of Colored Particles>
Table 1 below shows the same procedure as in Colored Particle Production Example 1 except that 90 parts by weight of the polyester resin and 33.3 parts by weight of the cyan flushing pigment were replaced with 10 parts by weight of carbon black (average primary particle diameter: 40 nm). The colored particles D shown were obtained. The conditions for pulverization and classification were adjusted so that the particle size distribution shown in Table 1 below was obtained.
[0141]
<Preparation Example 5 of Colored Particles>
Colored particles E shown in Table 1 below were obtained in the same manner as in Colored Particle Production Example 1 except that the polyester resin was 86.7 parts by weight and the cyan flushing pigment was 13.3 parts by weight. The conditions for pulverization and classification were adjusted so that the particle size distribution shown in Table 1 below was obtained.
[0142]
<Preparation Example 6 of Colored Particles>
Colored particles F shown in Table 1 below were obtained in the same manner as in Colored Particle Production Example 5 except that the polyester resin was 80 parts by weight and the cyan flushing pigment was 20 parts by weight. The conditions for pulverization and classification were adjusted so that the particle size distribution shown in Table 1 below was obtained.
[0143]
<Preparation Example 7 of Colored Particles>
Colored particles G shown in Table 1 below were obtained in the same manner as in Colored Particle Production Example 3, except that the polyester resin was 73.3 parts by weight and the cyan flushing pigment was 26.7 parts by weight. The conditions for pulverization and classification were adjusted so that the particle size distribution shown in Table 1 below was obtained.
[0144]
In the following Table 1, in addition to the description regarding the particle size of each colored particle obtained above, the pigment concentration C (%) in each colored particle, the true specific gravity a of each colored particle, these values and the volume average particle diameter D The aDC calculated from (μm) and the average particle diameter of the dispersed particles in the binder resin of pigment fine particles (equivalent circle diameter: μm) are also shown.
[0145]
[Table 1]

[0146]
Each colored particle was subjected to surface hydrophobization treatment with hexamethyldisilazane (hereinafter sometimes abbreviated as “HMDS”), and silica (SiO 2) having an average primary particle diameter of 40 nm.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%. The toners A to G were prepared by mixing with a Henschel mixer (the symbols A to G attached to the obtained toners correspond to the symbols A to G of the colored particles used).
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).
[0147]
The reaction conditions between metatitanic acid and isobutyltrimethoxysilane are as follows. A 4N sodium hydroxide aqueous solution was added to the metatitanic acid slurry to adjust the pH to 9.0, and after stirring, 6N hydrochloric acid was added to neutralize. This was filtered and the material obtained on the filter paper was washed with water. Then, water was added to the material again to form a slurry, 6N hydrochloric acid was added, the pH was adjusted to 1.2, and the mixture was stirred for a certain time to peptize. Isobutyltrimethoxysilane was added to the peptized slurry, and after stirring for a certain period of time, an 8N aqueous sodium hydroxide solution was added for neutralization. The material obtained on the filter paper by filtration is washed with water, dried at 150 ° C., finely pulverized with a jet mill, and then coarse particles are removed to obtain primary particles which are reaction products of metatitanic acid and isobutyltrimethoxysilane. Metatitanic acid compound fine particles having an average particle diameter of 20 nm were obtained.
[0148]
<Carrier production example 1>
Fluoroethyl methacrylate / methyl methacrylate copolymer (copolymerization ratio 70:30) 2.5 parts by weight, carbon black 0.5 parts by weight, melamine fine particles (particle size 0.3 μm) 0.3 parts by weight in toluene A coating solution is prepared by dissolving and dispersing in 20 parts by weight, and 100 parts by weight of ferrite particles (average particle size 35 μm) are added thereto, followed by stirring at 80 ° C. for 30 minutes using a vacuum degassing kneader, and then reducing the pressure. Then, toluene was distilled off to produce carrier a having a volume average particle diameter of 35 μm. When the volume specific electrical resistance of the carrier a was measured, it was 2.3 × 10.^TenIt was Ω / cm.
[0149]
<Carrier production example 2>
Fluoroethyl methacrylate / methyl methacrylate copolymer (copolymerization ratio 70:30) 2.5 parts by weight, carbon black 0.8 parts by weight, melamine fine particles (particle size 0.3 μm) 0.3 parts by weight in toluene A coating solution is prepared by dissolving and dispersing in 20 parts by weight, and 100 parts by weight of ferrite particles (average particle size 35 μm) are added thereto, followed by stirring at 80 ° C. for 30 minutes using a vacuum degassing kneader, and then reducing the pressure. Then, toluene was distilled off to produce carrier b having a volume average particle diameter of 35 μm. When the volume specific electric resistance of the carrier b was measured, 4.1 × 10⁸It was Ω / cm.
[0150]
<Carrier Production Example 3>
Fluoroethyl methacrylate / methyl methacrylate copolymer (copolymerization ratio 70:30) 2.5 parts by weight, carbon black 0.3 parts by weight, melamine fine particles (particle size 0.3 μm) 0.3 parts by weight in toluene A coating solution is prepared by dissolving and dispersing in 20 parts by weight, and 100 parts by weight of ferrite particles (average particle size 35 μm) are added thereto, followed by stirring at 80 ° C. for 30 minutes using a vacuum degassing kneader, and then reducing the pressure. Then, toluene was distilled off to produce a carrier c having a volume average particle diameter of 35 μm. When the volume specific electric resistance of the carrier c was measured, it was 5.3 × 10.¹⁴It was Ω / cm.
[0151]
<Carrier Production Example 4>
Fluoroethyl methacrylate / methyl methacrylate copolymer (copolymerization ratio 70:30) 2.5 parts by weight, carbon black 0.7 parts by weight, melamine fine particles (particle size 0.3 μm) 0.3 parts by weight in toluene A coating solution is prepared by dissolving and dispersing in 20 parts by weight, and 100 parts by weight of ferrite particles (average particle size 35 μm) are added thereto, followed by stirring at 80 ° C. for 30 minutes using a vacuum degassing kneader, and then reducing the pressure. Then, toluene was distilled off to produce a carrier d having a volume average particle diameter of 35 μm. The volume specific electrical resistance of the carrier d was measured and found to be 2.0 × 10⁹It was Ω / cm.
[0152]
<Carrier Production Example 5>
Fluoroethyl methacrylate / methyl methacrylate copolymer (copolymerization ratio 70:30) 2.0 parts by weight, carbon black 2.0 parts by weight and melamine fine particles (particle size 0.3 μm) 0.3 parts by weight in toluene A coating solution is prepared by dissolving and dispersing in 20 parts by weight, and 100 parts by weight of ferrite particles (average particle size 35 μm) are added thereto, followed by stirring at 80 ° C. for 30 minutes using a vacuum degassing kneader, and then reducing the pressure. Then, toluene was distilled off to produce a carrier e having a volume average particle diameter of 35 μm. The volume specific electrical resistance of the carrier e was measured and found to be 3.2 × 10^FiveIt was Ω / cm.
[0153]
<Carrier Production Example 6>
A carrier f having a volume average particle diameter of 35 μm was produced in the same manner as in Carrier Production Example 1 except that carbon black was not added. When the volume specific electrical resistance of the carrier f was measured, 1.2 × 10¹⁵It was Ω / cm.
[0154]
[Example 1]
100 parts by weight of the carrier a obtained above and 4 parts by weight of toner A for developing electrostatic latent images were mixed to prepare a two-component developer (cyan) of Example 1. Various evaluation tests described below were performed using the obtained two-component developer.
[0155]
[Example 2]
100 parts by weight of the carrier b obtained above and 4 parts by weight of toner A for developing an electrostatic latent image were mixed to prepare a two-component developer (cyan) of Example 2. Various evaluation tests described below were performed using the obtained two-component developer.
[0156]
Example 3
100 parts by weight of the carrier c obtained above and 4 parts by weight of the electrostatic latent image developing toner A were mixed to prepare a two-component developer (cyan) of Example 3. Various evaluation tests described below were performed using the obtained two-component developer.
[0157]
Example 4
100 parts by weight of the carrier d obtained above and 4 parts by weight of the electrostatic latent image developing toner B were mixed to prepare a two-component developer (magenta) of Example 4. Various evaluation tests described below were performed using the obtained two-component developer.
[0158]
Example 5
100 parts by weight of the carrier d obtained above and 4 parts by weight of the electrostatic latent image developing toner C were mixed to prepare a two-component developer (yellow) of Example 5. Various evaluation tests described below were performed using the obtained two-component developer.
[0159]
Example 6
100 parts by weight of the carrier d obtained above and 4 parts by weight of the electrostatic latent image developing toner D were mixed to prepare a two-component developer (black) of Example 6. Various evaluation tests described below were performed using the obtained two-component developer.
[0160]
Example 7
100 parts by weight of the carrier a obtained above and 4 parts by weight of the electrostatic latent image developing toner E were mixed to prepare a two-component developer (cyan) of Example 7. Various evaluation tests described below were performed using the obtained two-component developer.
[0161]
[Comparative Example 1]
100 parts by weight of the carrier f obtained above and 4 parts by weight of toner A for developing an electrostatic latent image were mixed to prepare a two-component developer (cyan) of Comparative Example 1. Various evaluation tests described below were performed using the obtained two-component developer.
[0162]
[Comparative Example 2]
100 parts by weight of the carrier e obtained above and 4 parts by weight of toner A for developing an electrostatic latent image were mixed to prepare a two-component developer (cyan) of Comparative Example 2. Various evaluation tests described below were performed using the obtained two-component developer.
[0163]
[Comparative Example 3]
100 parts by weight of the carrier a obtained above and 6 parts by weight of toner F for developing an electrostatic latent image were mixed to prepare a two-component developer (cyan) of Comparative Example 3. Various evaluation tests described below were performed using the obtained two-component developer.
[0164]
[Comparative Example 4]
100 parts by weight of the carrier a obtained above and 6 parts by weight of the electrostatic latent image developing toner G were mixed to prepare a two-component developer (cyan) of Comparative Example 4. Various evaluation tests described below were performed using the obtained two-component developer.
[0165]
The constitutions of the two-component developers in Examples 1 to 7 and Comparative Examples 1 to 4 are shown in Table 2 below.
[0166]
[Table 2]

[0167]
[Evaluation test]
Various evaluation tests described below were performed using the two-component developers obtained in Examples 1 to 7 and Comparative Examples 1 to 4. In these various evaluation tests, ordinary non-coated full-color dedicated paper was used as a transfer material, and an Acolor 935 remodeling machine manufactured by Fuji Xerox Co., Ltd. (which has been modified so that the voltage can be adjusted during development by an external power source (hereinafter referred to as “the image forming apparatus”) Simply referred to as “Acolor 935 remodeling machine”).
Image formation was performed by adjusting DMA and TMA so as to have values shown in Table 3 below.
[0168]
[Table 3]

[0169]
The development setting was such that the A / C potential was a square wave with a peak-to-peak voltage of 1.5 kV, a frequency of 9 kHz, and a duty ratio of 50%, the D / C potential was a development bias of 550 V, and a development contrast of 400 V. The cleaning potential was 100V.
[0170]
The measurement methods for DMA and TMA are as follows.
<Toner weight DMA of toner image formed on latent image carrier>
A solid image having an image area ratio of 100% is prepared on the latent image carrier, and the toner weight per unit area of the image portion (DMA: mg / cm²) Was measured. As a specific measurement method, 10 cm²Create an unfixed solid image of the area on the latent image carrier and use the weighed mending tape to remove the mending tape from the unfixed toner image formed on the latent image carrier and transfer the toner. This was weighed and repeated until there was no toner in the unfixed toner image, and the total weight of the toner transferred to the mending tape was taken as DMA.
[0171]
<Toner weight TMA of toner image transferred onto transfer material>
A solid image having an image area ratio of 100% is prepared on a transfer material, and the toner weight per unit area of the image portion (TMA: mg / cm²) Was measured. As a specific measurement method, 10 cm²An unfixed solid image of the area is prepared on the transfer material, this is weighed, and then the unfixed toner on the transfer material is removed by air blow, and then the weight of only the transfer material is measured, before and after the unfixed toner is removed. TMA was calculated from the weight difference.
[0172]
[Various evaluation test methods]
Specific methods of various evaluation tests will be described below.
<Image density>
A solid image with an image area ratio of 100% was created, and the image density of the image portion was measured using X-Rite 404 (manufactured by X-Rite).
[0173]
<Thin wire reproducibility evaluation test>
A fine line image was formed on the photoconductor so as to have a line width of 50 μm, and this was transferred and fixed on a transfer material. A fine line image of the fixed image on the transfer material was observed at a magnification of 500 times using a VH-6200 micro high scope (manufactured by Keyence Corporation). Specific evaluation criteria are as follows.
○: Edge irregularities of fine lines are not observed.
Δ: Edge irregularities of fine lines are slightly observed.
X: Disturbance of edge of fine line is conspicuous.
[0174]
<Tone reproducibility evaluation test>
The density of the gradation image at the time of in-put and the density of the gradation image formed on the transfer material (out-put) were measured to evaluate the change in gradation. The image density was measured with X-Rite 404 (manufactured by X-Rite). Specific evaluation criteria are as follows.
A: The gradation reproducibility is equal to or higher than that of a printed material obtained by 175 line offset printing.
Δ: The gradation reproducibility is slightly inferior to that of the printed material by 175 line offset printing.
×: Gradation reproducibility greatly inferior to that of a printed material obtained by 175 line offset printing.
[0175]
<Solid image uniformity evaluation test>
The difference in image gloss between the transfer material surface and an image area having an image density of 1.2 or more, and in the case of full-color printing, the image gloss of the primary color image area of 1.2 or more and the image density of 1. Sensory evaluation was performed on the difference in image gloss between two or more tertiary color image areas. Specific evaluation criteria are as follows.
○: Uniformity equal to or higher than that of printed material by 175 line offset printing.
Δ: Uniformity slightly inferior to that of the printed material obtained by 175 line offset printing.
×: Uniformity greatly inferior to a printed matter obtained by 175 line offset printing.
[0176]
<Solid end of solid image>
A rectangular solid image having an image density of 1.5 and a size of 15 mm × 20 mm was created, and the degree of white spots at the edges of the image was visually evaluated. Specific evaluation criteria are as follows.
○: Cannot be recognized visually.
(Triangle | delta): It can recognize slightly visually.
X: Remarkably visible visually.
[0177]
<Highlight part graininess evaluation test>
The granularity of the highlight portion was visually evaluated. Specific evaluation criteria are as follows.
A: Uniformity superior to a printed material by 175 line offset printing.
○: Uniformity equivalent to that of printed material by 175 line offset printing.
Δ: Uniformity slightly inferior to that of the printed material obtained by 175 line offset printing.
×: Uniformity greatly inferior to a printed matter obtained by 175 line offset printing.
[0178]
<Carrier flight evaluation test>
The presence or absence of image quality degradation due to the transfer of the carrier to the photoreceptor was evaluated. Specific evaluation criteria are as follows.
○: Level with no problem.
Δ: Slightly generated in the initial stage.
X: Remarkably generated and difficult to use.
[0179]
<Image quality stability evaluation test during continuous print test>
A print test of 10,000 sheets was performed, and an initial print sample and a print sample after 10,000 sheets were printed for fogging, fine line reproducibility, gradation reproducibility, highlight graininess, and missing edge of a solid image. The evaluation was made with reference to the aforementioned evaluation criteria. Specific evaluation criteria are as follows.
○ Even after printing 10,000 sheets, the image quality level remains unchanged from the initial level.
Δ: Image quality level slightly deteriorated after printing 10,000 sheets.
×: Image quality level greatly deteriorated before printing 10,000 sheets.
[0180]
The evaluation results of the developers of Examples 1 to 7 and Comparative Examples 1 to 4 are summarized in Table 4 below.
[0181]
[Table 4]

[0182]
Example 8
A full-color copy test was performed using the two-component developers of cyan, magenta, yellow and black prepared in Examples 1, 4, 5 and 6. In the copy test, a modified Acolor 935 machine was used as the image forming apparatus. When the same evaluation items as those in Examples 1 to 7 and Comparative Examples 1 to 4 were evaluated, the results were all good and good.
[0183]
【The invention's effect】
According to the present invention, fine line reproducibility can be achieved by combining a toner having a small particle diameter, which can form an image without fogging, has high transfer efficiency, and is excellent in durability, and a carrier whose electric resistance value is appropriately adjusted. An electrostatic latent image developer and an image forming method capable of achieving an image quality equal to or higher than that of an image formed by offset printing without causing solid image edge omission with good gradation characteristics can do.
In addition, according to the present invention, there is provided an image forming method in which, even when a toner having a small particle diameter is used and the amount of external additive added to the toner is increased, the amount of toner consumption is small and carrier deterioration does not easily proceed. Can do.
[Brief description of the drawings]
FIG. 1 is an enlarged plan view of a part of a colored particle surface for explaining the coverage of an external additive on the colored particle surface.
FIG. 2 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
22, 22a-22f: External additives

Claims (2)

An electrostatic latent image developer comprising at least the following A toner and B carrier.
A toner consisting of colored particles containing at least a binder resin and a colorant, and
(A) The volume average particle diameter of the colored particles is 2.0 to 5.0 μm, the colored particles of 1.0 μm or less are 20 number% or less, and the colored particles exceeding 5.0 μm are 10 number% or less. ,
(B) When the charge amount of the toner is expressed as q (fC) and the particle size of the toner is expressed as d (μm) in an environment of a temperature of 20 ° C. and a humidity of 50%, Both bottom values are positive or both negative, the absolute value of the peak value is 1.0 or less, the absolute value of the bottom value is 0.005 or more,
( C ) A toner in which the colorant is pigment particles.
B carrier ( d ) volume average particle diameter is 45 μm or less,
( E ) The volume specific electric resistance of the entire carrier particle is 1.0 × 10 ⁸ Ω · cm or more and 1.0 × 10 6 at an applied voltage of 10 ³ V / cm in a measurement environment of a temperature of 20 ° C. and a humidity of 50%. ^A carrier having a range of ¹³ Ω · cm or less. At least a latent image forming step for forming an electrostatic latent image on the latent image carrier and a developer layer on the surface of the developer carrier disposed opposite to the latent image carrier by the electrostatic latent image developer. A development process for developing an electrostatic latent image on an image carrier and forming a toner image; a transfer process for transferring the developed toner image onto a transfer material; and a fixing process for heating and fixing the toner image on the transfer material In an image forming method comprising:
The image forming method according to claim 1, wherein the electrostatic latent image developer is the electrostatic latent image developer according to claim 1.

Images