JP3909692B2 - Image forming method and image forming apparatus - Google Patents

Description

以上の結果より、紙の粗さ１５μｍ(トナー径の２．３倍)以上で、感光体粗さ３．１μｍ(０．４８倍)以下が良い結果となっている。以上の結果より、感光体の粗さはトナー粒径の１／２以下、転写紙の粗さはトナー粒径の２倍以上の条件で良い結果が得られる。
【００３１】
（実施例２）
トナーＨ（Ｔｇ＝６５℃、 Ｔｍ＝１５０℃)を用いて、評価機は図１のリコーＩｍａｇｉｏ−ＭＦ７０７０の転写ユニット改造機を用いた。現像として一成分非接触方式は図２の現像装置を用いた。転写、一次定着の圧力と、ベルト温度を印加して転写一次定着を行った。二次定着は面圧：９．３Ｎ／ｃｍ^２の加圧力で圧接されて定着ニップ幅：約１０ｍｍを構成し、温度は１７５℃に設定されている。この装置を用いて、６００ｄｐｉの２値ドットから形成されたグレースケールを中心としたテストチャートをプリントアウトして画像を得られるようになっている。感光体の粗さはトナー粒径の１／２以下、転写紙の粗さはトナー粒径の２倍以上の条件で、転写、一次定着に用いる感光体、転写紙間の圧力と与えるベルト温度の条件を確認した。
評価は、実施例と同じく転写率で行った。その結果を表２に示した。
【００３２】
【表２】

以上の結果より、圧力は１０〜１００Ｎ／ｃｍ^２で、加える温度は用いたトナーのガラス転移点温度からトナー軟化点温度内の温度を用いることで良好な結果が得られている。
また、圧力６０Ｎ／ｃｍ^２の条件で感光体の摩擦係数を０．７から０．３に変えて転写性を確認した。感光体の摩擦係数は図１のクリーニング部に設けた感光体の摩擦係数を改善するためにステアリン酸亜鉛のブロックを設け、ブラシを介して感光体に塗布して２条件を得た。その結果を表２の圧力８０Ｎ／ｃｍ^２で印加温度４５から１７０℃で確認した。
上記結果から、ステアリン酸亜鉛を塗布することで、転写率は改善される。
【００３３】
（実施例３）
トナーH（Ｔｇ＝６５℃、 Ｔｍ＝１５０℃)を用いて、評価機は図１のリコーＩｍａｇｉｏ−ＭＦ７０７０の転写ユニット改造機を用いた。現像として一成分非接触方式は図２の現像装置を用いた。転写、一次定着の圧力は面圧で６０Ｎ／ｃｍ^２、ベルト温度は１００℃(Ｔｇ＜１００℃＜Ｔｍ)に設定した。二次定着は面圧：９．３Ｎ／ｃｍ^２の加圧力で圧接されて定着ニップ幅：約１０ｍｍを構成し、温度は１７５℃に設定されている。この装置を用いて、転写ユニットとクリーニングユニットを作像形成時以外は離して置く場合と、常に当接して使用する条件で経時での特性を確認した。
通常の環境では問題は発生しない。室温を３０℃６０％ＲＨに保たれた環境で余裕度テストを確認した。
作像条件は、プリント枚数５００枚プリント（文字部面積６％チャート）を１５分間隔で一日８時間（１６千枚）稼動して１０日間で比較した。
その結果、常に接触して稼動した機械では、クリーニングのブレード先端にトナーは固着し、クリーニング不良が発生し、感光体の汚れ、画像上地肌汚れ、黒スジなどが５０千枚程度からわずかではあるが発生した。
一方、作像時以外は転写ユニットとクリーニングユニットを離して置く条件では、同じテストでも問題の発生は無く、正常な画像が得られた。
【００３４】
（実施例４）
評価機は図１のリコーＩｍａｇｉｏ−ＭＦ７０７０の転写ユニット改造機を用いた。現像として一成分非接触方式の現像装置を用いた。図２は、一成分非接触方式の現像装置の構成を示す概略図である。転写、一次定着の圧力は面圧で６０Ｎ／ｃｍ^２、ベルト温度は１００℃（Ｔｇ＜１００℃＜Ｔｍ）に設定した。二次定着は面圧：９．３Ｎ／ｃｍ^２の加圧力で圧接されて定着ニップ幅：約１０ｍｍを構成し、温度は１７５℃に設定されている。転写同時一次定着で感光体からの剥離を良くして、転写紙にトナーが付着し易くするため、トナー粒径ａとして、感光体粗さをａ／２以下とし、転写紙の表面粗さを３ａ以上にし、６００ｄｐｉの２値ドットから形成されたグレースケールを中心としたテストチャートをプリントアウトして画像を得た。
本実施例で用いたトナーは前記のトナーＡ、Ｂ、Ｃ、Ｈを用いた。
評価は転写一次定着特性（転写率％）、二次定着（スミア濃度）、粒状度の各項目で評価した。結果を表３に示した。
【００３５】
【表３】

以上の結果より、トナー軟化温度で１００〜１６０℃、ガラス転移温度で５５〜７０℃の範囲が好ましい結果となった。
【００３６】
（実施例５）
評価方法は実施例４と同じ方法で行った。本実施例で用いたトナーは前記のトナーＤ、Ｅ、Ｈ、Ｉを用いた。
評価は転写一次定着特性（転写率％）、二次定着（スミア濃度）、粒状度の各項目で評価した。結果を表４に示した。ここで分散度とは（重量平均粒径／個数平均粒径）のことである。
【００３７】
【表４】

以上の結果より、円形度で０．９２以上、分散度で１．４以下が良好な範囲である。
【００３８】
（実施例６）
評価方法は実施例４と同じ方法で行った。本実施例で用いたトナーは前記のトナー処方を用いた。用いた特性値はトナーの溶融粘度が１０００Ｐａ・ｓとなる温度（すなわち、トナー同士が溶けて付着しだす温度）と各特性を確認した。
評価は転写一次定着特性（転写率％）、二次定着（スミア濃度）、粒状度の各項目で評価した。結果を表５に示した。
【００３９】
【表５】

以上のような結果から、最適は範囲としては、１２０〜１７０℃である。
【００４０】
（実施例７）
評価方法は実施例４と同じ方法で行った。本実施例で用いたトナーは前記のトナーＨ、Ｊを用いた。用いた特性値はゆるみ見かけ密度（ｇ／ｃｃ）である。
評価は転写一次定着特性（転写率％）、二次定着（スミア濃度）、粒状度の各項目で評価した。結果を表６に示した。
【表６】

以上の結果より、トナーのゆるみ見かけ密度が０．３ｇ／ｃｃ以上であることが好ましい。ここで従来の評価で用いていない「◎」がつけられた。今回最も良い０．２１の値が得られた。
【００４１】
（実施例８）
評価方法は実施例4と同じ方法で行った。本実施例で用いたトナーは前記のトナー処方を用いた。用いた特性値は体積固有抵抗である。
評価は転写一次定着特性(転写率％)、二次定着(スミア濃度)、粒状度の各項目で、結果を表７に示した。
【表７】

以上の結果より、体積固有抵抗で１×１０^９Ωｃｍ以上が良好な範囲である。
【００４２】
【発明の効果】
以上の説明より、本発明の画像形成方法及び画像形成装置では、トナーは変形してトナー間の表面は軽く固着し、転写紙の凹部に詰められアンカー効果でトナーが転写と一次定着することで、静電的な転写における画像の劣化を防ぐことができる。
また、本発明の画像形成方法及び画像形成装置では、作像時以外は熱源である転写一次定着ユニットを離す事で、感光体等の温度上昇が防止でき画像上、システム上の問題は低減でき、設計上の余裕度を上げることができる。
また、本発明の画像形成方法及び画像形成装置では、表面が硬く摩擦係数の低い感光体にしてトナーの離型性を良くして転写率を向上させることができる。
また、本発明の画像形成方法及び画像形成装置では、転写率を向上させることで、粒状性のない高品位の画像を得ることができる。
また、本発明の画像形成方法及び画像形成装置では、ホットオフセットの発生が少なくすることができる。
【図面の簡単な説明】
【図１】本発明の画像形成方法を用いる画像形成装置全体の概略図である。
【図２】一成分非接触方式の現像装置の構成を示す概略図である。
【符号の説明】
１ 感光体
２ 帯電器
３ 露光手段
３１ スキャナー
３２ ポリゴンモータ
３３ ミラー
４ 現像手段
５ 転写手段
５２ 一次定着ローラ
５３ 転写ベルト
５４ テンションローラ
５５ クリーニング装置
５６ ヒーター
５７ 温度検知手段
６ クリーニング手段
７ 定着手段
７１ 定着ローラ
７２ 加圧ローラ
７３、７４ 加熱手段（ヒーター）
１０１、１０６ 転写紙バンク
１０２、１０７ 給紙ローラ
１０３、１０８ 給紙[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming method using an electrophotographic system such as a copying machine, a printer, and a facsimile. More specifically, the present invention relates to an image forming apparatus using the image forming method, and further using a toner having characteristics optimal for this method.
[0002]
[Prior art]
An electrophotographic image forming method requires many steps. In the case of copying, the document is converted into an electrical signal by a scanner or an optical system. By writing this electric signal with a laser or the like, the photosensitive member is irradiated as an optical image, and an electrostatic latent image is formed on the charged photosensitive member. A colored fine powder represented by toner is electrostatically attached to the latent image in the development process. Further, it is electrostatically transferred to transfer paper in the transfer process. Recently, in the color field, a system in which toner images of 3 to 4 colors are transferred onto an intermediate transfer member and transferred onto a transfer paper is often used. Then, the toner is melted and fixed on the transfer paper by heat or the like to form an image.
In recent years, however, fine line reproducibility is high, and high-quality images with little graininess in a halftone portion are demanded particularly in color images. When image quality is considered, image quality degradation factors are included in all steps of the image forming method. As is well known, image deterioration is particularly significant in the development, transfer, and fixing steps.
For example, in the developing process, the toner is electrostatically attached to the latent image of the photosensitive member by the electric field formed between the photosensitive member and the developing roller, so that the toner is developed over a wider range than the latent image or the carrier is rubbed. As a result, it is difficult to form a toner image that is faithful to the electrostatic latent image because the toner on the photosensitive member is moved, and the image is deteriorated. Recent techniques have been improved by reducing the diameter of the toner, making it spherical, reducing the diameter of the carrier, reducing the resistance, and alternating current bias.
[0003]
  On the other hand, in the transfer process, the transfer sheet conveyed in synchronism with the developed photoreceptor on which toner is adhered is brought into contact and electrostatically transferred from the photoreceptor to the transfer sheet by an electric field. However, in this transfer process, the toner is transferred from the photoconductor to the transfer paper by the electric field formed between the photoconductor and the transfer bias roller. In the process, toner flying occurs, and it is difficult to faithfully transfer the toner image on the photoconductor. Deterioration due to dust or blemishes occurs on the image, and so far no solution has been made.
  There is also a problem in the fixing process. Completely add toner to improve fixabilityMeltingWhen melted, the toner image spreads. When there is a variation in the amount of toner adhering to the transfer paper or when there is transfer dust or the like, the variation in dot diameter and line width after fixing often results in image degradation.
  As described above, the image quality deterioration phenomenon is particularly large in the transfer process. As a result, image quality such as image blurring, sharpness, and resolution is degraded.
[0004]
Therefore, it has been conventionally proposed to simultaneously perform the transfer process and the fixing process. As a well-known system, Patent Document 1 has been proposed as a system for performing heat-fixing simultaneously with transfer. However, since the heat generating body comes into contact with the photoconductor to perform transfer and complete fixing at the same time, even if a cooling device is provided, it is caused by heat to the photoconductor, toner on the photoconductor, developing device, etc. Damage cannot be avoided.
In order to eliminate the adverse effect on the system due to heat, a method of performing simultaneous transfer and fixing only by pressure without heating has been proposed. For example, in Patent Document 2, 1470 to 2450 N / cm²There has been proposed a method of fixing with the pressure. Patent Documents 3 and 4 propose a method for simultaneously fixing the toner image-formed on the photosensitive member by a transfer fixing device facing the photosensitive member using an amorphous silicon photosensitive member and a capsule toner. Yes. In any case, the pressure is large, and the mechanism becomes large as a system, which has become a practical problem and has not been put into practical use.
[Patent Document 1]
JP-A-55-87156
[Patent Document 2]
Japanese Patent Laid-Open No. 03-186879
[Patent Document 3]
JP-A-5-216354
[Patent Document 4]
JP-A-6-35841
[0005]
[Problems to be solved by the invention]
As described above, the method of fixing at the same time as transfer with heat or pressure has been proposed as a technique for complete fixing. In a system in which transfer and fixing are performed simultaneously with heat, the area around the photosensitive member becomes a temperature higher than the melting point of the toner, and a large stress is applied to the toner in a developing and cleaning device, which causes a large problem in practical use. In addition, in the method in which transfer fixing is performed only by pressure, 980 N / cm from the viewpoint of transfer fixing property.²There are disadvantages such as an increase in the size of the apparatus, generation of weight and transfer paper fixing wrinkles.
In Patent Document 4, capsule toner is used. However, capsule toner has many problems in practical use. In particular, there is a problem in that development and fixing are not compatible and the cost is too high. It is currently not used for
[0006]
Accordingly, the object of the present invention has been made in view of such problems, and by having a transfer process without image deterioration, it is possible to obtain a high-quality image without deteriorating the image quality. An image forming method and an image forming apparatus using the image forming method are provided.
[0007]
[Means for Solving the Problems]
  In order to achieve the above object, the invention described in claim 1 uses a latent image forming step for forming a latent image on a photosensitive member, a developing step for developing the latent image, and a transfer roller pressed against the photosensitive member. An image forming method having a transfer step of transferring and a fixing step of fixing toner by a heat roller, wherein the transfer step is performed on the toner and transfer paper via the transfer roller.Without static electricityTransfer and primary fixing are performed simultaneously by applying heat and pressure, and the fixing step is a secondary fixing in which the primary fixing transfer paper separated from the photoreceptor is fixed again.Develop the latent image without contact with the photoconductorUsing a non-contact development method, the transfer process is 10 to 100 N / cm between the transfer roller and the photosensitive member.²In this image forming method, the pressure applied to the transfer paper is in the range from the toner glass transition temperature to the toner softening temperature.
  According to a second aspect of the present invention, in the image forming method according to the first aspect, the photoreceptor surface roughness has a ten-point average roughness Rz of a / 2 or less (where a represents a toner particle size). The transfer paper surface roughness is an image forming method having a ten-point average roughness Rz of 2a or more.
  Claim3The invention described in claim 11 or 2In the image forming method described in 1.
  The transfer / cleaning unit is an image forming method in which a contact / separation mechanism with the photosensitive member is provided and separated from the photosensitive member except during image formation.
  The invention according to claim 4 is the claim1 to 3In the image forming method according to any one of the above,tonerGlass transitiontemperature(Tg) is 55 to 70 ° C., and toner softening temperature (Tm) is 100 to 160 ° C.IsAn image forming method.
[0008]
  Claim5An image forming apparatus having a photosensitive member having a latent image, a developing device, a transfer device using a transfer roller pressed against the photosensitive member, and a heat roller fixing device,The transfer deviceThe transfer roller in the transfer device applies toner and transfer paper.Without static electricityApply heat and pressure, perform transfer and primary fixing at the same time,The pressure between the transfer roller and the photoconductor is 10 to 100 N / cm. ² The temperature applied to the transfer paper is in the range from the toner glass transition temperature to the toner softening temperature, and the fixing device isSecondary fixing is performed to fix the transfer paper separated from the photoconductor on the primary fixing side again.Yes,Development deviceDevelop the latent image without contact with the photoconductorAn image forming apparatus.
  Claim6The invention described in claim 15The image forming apparatus according to claim 1, wherein the image forming apparatus includes:Any of 2 to 4An image forming apparatus using the image forming method described in 1 above.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The present invention includes an amorphous photosensitive drum, transfer means including a transfer conveyance belt, and the like. The toner image formed on the photoconductor drum is transferred to a transfer paper sandwiched between the photoconductor and the transfer unit, and a temperature in the range from the toner glass transition temperature to the toner softening temperature is 10 to 100 N / cm.²When the pressure is applied, the toner is primarily fixed on the transfer paper simultaneously with the transfer. The toner image on the transfer paper that is primarily fixed at the same time as the transfer with low-temperature heat and pressure is fixed by transporting the transfer paper by a transfer belt and passing through heat fixing means provided in a downstream process. In this way, it is possible to obtain a high quality image without electrostatic image degradation that occurs during transfer.
Here, the primary fixing means a state in which the toner is fixed by biting into the transfer paper due to heat deformation of the toner, and is not transferred or deteriorated due to conveyance of the transfer paper in the machine or vibration.
As described above, image degradation occurs in each process of latent image formation, development, transfer, separation, and fixing. According to the present invention, toner is primarily fixed onto a transfer paper simultaneously with transfer by a transfer means having the greatest deterioration, thereby preventing image deterioration such as dust and blur due to the influence of electrostatic discharge. A method and apparatus for conveying a transfer sheet to a fixing device and obtaining a final fixed image are provided.
[0010]
Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic view of an entire image forming apparatus using the image forming method of the present invention.
The drum-shaped photosensitive member 1 is provided inside using an electrophotographic system. Around the photosensitive member 1, a charger 2, an exposure unit 3, a developing unit 4, a transfer unit 5, a cleaning unit 6, and a fixing unit 7 are disposed along the rotational direction indicated by the arrow. Yes.
The exposure means 3 converts the data read by the scanner 31 and the image signal sent from the PC (not shown), scans the laser beam with the polygon motor 32 and reads the image signal read through the mirror 33 on the photosensitive member 1. An electrostatic latent image is formed on the surface. The photoreceptor 1 uses amorphous silicon.
The electrostatic latent image formed on the photoreceptor 1 is formed with a toner image by the non-contact developing unit 4, and the toner image is fed from the transfer paper banks 101 and 106 in which the transfer paper is stored to the paper feed roller 102. , 107 and is fed by paper feed rollers 103, 108. A roller 104 is a resist roller 104 for conveying the transfer paper in synchronization with the toner image on the photosensitive member. The transfer paper is sent to the transfer means 5 and thermally transferred. The transfer paper on which the toner image is placed is conveyed by the transfer belt 53, conveyed and fixed to the fixing means 7, and then discharged outside the apparatus.
On the other hand, the untransferred portion and the photosensitive member 1 with dirt are cleaned by the cleaning means 6 arranged so as to be able to contact and separate, and then enters the next image forming step. In the present invention, since the heat application method is used as the transfer, it is advantageous to arrange the units that are in contact with the photoconductor so that they can come in contact with and away from each other, and to control the unit so that it does not come into contact with the photoconductor except during image creation. .
[0011]
The fixing unit 7 is a necessary configuration in the present invention in order to completely fix the toner primarily fixed by the transfer unit 5. The basic configuration includes a fixing roller 71 having heating means 74 (hereinafter referred to as “heater”) such as a halogen lamp, and a pressure roller 72 that is in pressure contact. The fixing roller 71 is provided with an elastic layer made of silicone rubber or the like having a rubber hardness of about 42 Hs (using an Asuka C hardness meter) on the surface of a core metal (not shown) having an outer diameter of 50 mm and having a thickness of 100 to 500 μm, preferably 400 μm. Further, for the purpose of preventing adhesion due to the viscosity of the toner, a resin surface layer having good releasability such as a fluororesin is formed. The resin surface layer is composed of a PFA tube or the like, and its thickness is preferably about 10 to 50 μm in consideration of mechanical deterioration. A temperature detecting means is provided on the outer peripheral surface of the fixing roller 71, and the heater 74 is controlled so as to keep the surface temperature of the fixing roller 71 substantially constant within a range of about 160 to 200 (165) ° C. . The pressure roller 72 has a core metal surface covered with an offset prevention layer such as tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA) or polytetrafluoroethylene (PTFE). Similar to the fixing roller 71, an elastic layer such as silicone rubber may be provided on the surface of a core metal (not shown), or a heater 73 may be provided.
In the fixing device having such a configuration, the fixing roller 71 and the pressure roller 72 have a surface pressure of 5 to 10 (9.3) N / cm.²The fixing nip width is about 10 mm and is controlled to a predetermined temperature, and when the toner image on the transfer paper passes between both rollers, it is thermally melted while receiving pressure. By leaving the roller pair and being cooled, it is fixed on the transfer paper as a permanent image.
[0012]
Next, the configuration of the present invention will be described.
The present invention resides in that transfer is performed using low-temperature heat in an electrophotographic system. Pressure is applied between the photoconductor and the transfer roller so that heat transfer is performed more efficiently. A new transfer system using heat and a combination of weak pressure is provided.
As an example, the transfer device includes a belt, a primary fixing roller 52, and a tension roller 54. The transfer roller 52 is made of an iron, aluminum, stainless steel or other metal core having an outer diameter of 40 mm, and is made of an elastic body having a hardness of 60 Hs (as Ask C hardness tester). The contact width is about 1.5 mm, and the pressing force is a surface. 11-100 N / cm in pressure²To. Considering the contact between the transfer paper and the photoconductor, the surface pressure is determined by the hardness of the roller and the contact width, but is about 20 to 50 N / cm.²Is a preferred range. The transfer roller 52 is an important roller for primary fixing transfer. Here, the transfer roller 52 has an elastic structure having the above-described hardness, and obtains a necessary surface pressure and contact width. Furthermore, in order not to lower the heat for supplying heat to the belt, the surface of the metal cylinder is 3 mm thick with a silicone rubber having a thermal conductivity of 0.5 × (1/1000) (cal / cm · sec · ° C.) or less. And has a hardness of 60 Hs. A heater 56 for heating is provided therein, and a belt (described later) is stretched. A temperature detecting means 57 is provided on the outer peripheral surface of the transfer roller 52, and the heater 56 is controlled so as to be kept substantially constant within the range of the glass transition temperature of the toner using the surface temperature of the transfer roller 52 to the toner softening temperature. Has been. As an example, a temperature of 70 to 120 ° C. is used for a normal toner.
[0013]
The transfer belt 53 includes a base material made of a seamless polyimide film. A fluororesin layer is provided on the outside. Further, if necessary, a silicone rubber layer may be provided on the fill layer and a fluororesin layer may be provided thereon. Belt driving and tensioning rollers 54 are provided inside the transfer belt. Various heat-resistant materials can be selected for the belt material. It is preferable to provide a fluororesin layer on the outside of the substrate. This does not reduce the heat of the belt.
[0014]
Although a technique for transferring using heating is disclosed, the difference from the present invention is that the heating temperature is as low as possible. If the temperature is high, the transferability is improved, but on the other hand, the photoconductor, the developing means 4 and the cleaning means 6 are thermally destroyed. In order to peel the toner on the photoconductor from the photoconductor, the temperature is about 140 ° C. or higher. Further, since transfer is not efficiently performed at a low temperature, the temperature is set to about 80 ° C. or higher even at a low temperature. The belt is heated at a temperature ranging from the glass transition temperature of the toner to the softening temperature of the toner (for example, 70 to 120 ° C.) and the above-described pressure is used in combination to produce a stable primary fixing toner and achieve transfer. . As a result, thermal stress is not applied to the above-mentioned photosensitive member, developing means 4 and cleaning means 6 and sufficient transfer performance is achieved.
The photoconductor may be selenium, amorphous silicon, or an organic compound, but an amorphous silicon photoconductor is preferred. Compared to other materials, the temperature dependence of photoconductivity is low.
[0015]
In order to obtain a semi-fixed toner stably, by adding the temperature from the glass transition point to the softening point of the toner to the toner, the toner deforms and adheres to the irregularities on the surface of the transfer paper having poor releasability by the anchor effect. Transfer from the photoconductor to transfer paper completes primary fixing and transfer. Furthermore, the surface roughness of the photoreceptor and the surface roughness of the transfer paper are important in order to obtain primary fixing stably at a low temperature. As the conditions, in the case of the toner particle diameter a, the roughness Rz of the photoreceptor is a / 2 or less, and the roughness Rz of the transfer paper is 2a or more, and particularly preferably 3a or more.
[0016]
Below, the toner has the characteristics that achieve the present invention.
<Evaluation method>
The toner evaluation method will be described. The evaluation machine was made by modifying the transfer unit of Ricoh Imagio-MF7070. The unit configuration is the same as the schematic diagram of the apparatus of FIG. As the development, the one-component non-contact method uses the developing device shown in FIG. The pressure for transfer and primary fixing is 60 N / cm in surface pressure.²The belt temperature was set to 100 ° C. Secondary fixing is surface pressure: 9.3 N / cm²The fixing nip width is about 10 mm, and the temperature is set to 175 ° C. Using this apparatus, a test chart centered on a gray scale formed from 600 dpi binary dots was printed out to obtain an image.
Regarding the image quality, the generation of toner dust and blemishes in the toner image transfer process, the volume and area after fixing change, and the image quality deteriorates. This phenomenon is particularly remarkable in the case of digital development, and the reproducibility of independent dots is greatly affected.
[0017]
The density of the halftone should be uniform, but if there is micro-density unevenness, it gives a rough impression when viewed with the naked eye. The quality of an image is represented by granularity, which is a physical evaluation value of roughness. The granularity can be measured by a Wiener Spectrum which is a frequency characteristic of a minute area density variation.
If the density fluctuation component whose average value is 0 is f (x)
F (u) = ∫f (x) exp (-2πiux) dx …… Equation 1
WS (u) = F (u)²... Formula 2 (where u represents the spatial frequency)
The granularity (GS) is a value obtained by integrating the product of WS and visual frequency characteristics (Visual Transfer Function: VTF), and is expressed by the following equation.
GS = exp (-1.8 <D>) ∫WS (u)^1/2 VTF (u) du …… Formula 3
Here, exp (−1.8 <D>) is a coefficient for correcting the difference between the density and the brightness perceived by the person, and <D> represents the average value of the density.
The granularity has a high correlation with the subjective evaluation of the smoothness of the image. The smaller the granularity value, the smoother the image quality becomes, and vice versa.
[0018]
In addition to the granularity described above, transferability (primary fixability) and fixability were evaluated and evaluated as evaluation items.
Transferability is determined by heat and pressure without using static electricity, and the rate at which the amount of black solid portion (2 × 2 cm) on the photoconductor has moved to the transfer body is determined. Judgment, the same 60-79% is indicated as “Δ”, and 59% or less is indicated as “x”. The allowable level is “Δ” or more.
Next, the fixing property was evaluated by the smear method (the density on the cloth when the cloth attached to the weight of 8.8 N / 15φ was placed on the transfer paper and rubbed five times). An acceptable level of 0.3 or lower was indicated by “◯”, an allowable level was indicated by 0.5 or lower “Δ”, and a level of 0.51 or higher was evaluated as “x”.
Furthermore, the evaluation of typical granularity as a high-quality item is an acceptable range of “◯” when the granularity is 0.29 or less, and “Δ” when 0.3 to 0.39. Furthermore, 0.4 or more was evaluated as "x".
[0019]
The toner production method and carrier used in the experiment will be described below.
Toner A
(Toner prescription)
82 parts by weight of polyester resin (weight average molecular weight: 52000, Tg: 54)
Polyethylene wax (molecular weight 900) 5 parts by weight
Carbon black (Mitsubishi Kasei # 44) 12 parts by weight
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part by weight
With the above formulation, after kneading at 80 ° C. using a biaxial extruder, pulverized and classified with an airflow pulverizer to give a weight average particle size of 9.5 μm (weight average particle size / number average particle size 1.45). Thereafter, using a Henschel mixer, 0.25% by weight of silica (R-972 Nippon Aerosil) was mixed to obtain a toner.
The toner has a softening temperature of 98 ° C. and a volume resistivity of 9.5 × 10.⁸The average circularity was 0.91, the Tg was 53 ° C., the temperature at which the melt viscosity was 1000 Pa · s was 115 ° C., and the loose apparent density was 0.28 g / cc.
[0020]
Toner B
(Toner prescription)
Polyester resin (weight average molecular weight: 182500, Tg: 71) 82 parts by weight
Polyethylene wax (molecular weight 1200) 5 parts by weight
Carbon black (Mitsubishi Kasei # 44) 12 parts by weight
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part by weight
With the above formulation, after kneading at 160 ° C. using a biaxial extruder, pulverized and classified with an airflow pulverizer to give a weight average particle size of 9.5 μm (weight average particle size / number average particle size 1.42). Thereafter, using a Henschel mixer, 0.25% by weight of silica (R-972 Nippon Aerosil) was mixed to obtain a toner.
The toner has a softening temperature of 165 ° C. and a volume resistivity of 8.5 × 10⁸The average circularity was 0.91, the Tg was 71 ° C., the temperature at which the melt viscosity was 1000 Pa · s was 175 ° C., and the loose apparent density was 0.29 g / cc.
[0021]
Toner C
(Toner prescription)
45 parts by weight of polyester resin (weight average molecular weight: 52000, Tg: 54)
40 parts by weight of styrene-butyl acrylate copolymer
(Weight average molecular weight: 105000, Tg: 58)
Polypropylene wax (Biscol 550P: Sanyo Chemical Industries) 4 parts by weight
Carbon black (Mitsubishi Kasei # 44) 10 parts by weight
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part by weight
With the above formulation, after kneading at 100 ° C. using a biaxial extruder, pulverized and classified with an airflow pulverizer to give a weight average particle size of 8.5 μm (weight average particle size / number average particle size 1.45). Thereafter, 0.50% by weight of silica (R-972 Nippon Aerosil) was mixed using a Henschel mixer to obtain a toner.
This toner has a softening temperature of 105 ° C. and a volume resistivity of 9.5 × 10.⁸The average circularity was 0.91, the Tg was 56 ° C., the temperature at which the melt viscosity was 1000 Pa · s was 118 ° C., and the loose apparent density was 0.29 g / cc.
[0022]
Toner D
(Toner prescription)
65 parts by weight of polyester resin (weight average molecular weight: 182500, Tg: 71)
20 parts by weight of styrene-butyl acrylate copolymer
(Weight average molecular weight: 105000, Tg: 58)
Polypropylene wax (Biscol 550P: Sanyo Chemical Industries) 4 parts by weight
Carbon black (Mitsubishi Kasei # 44) 10 parts by weight
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part by weight
With the above formulation, after kneading at 150 ° C. using a biaxial extruder, pulverized and classified with an airflow pulverizer to give a weight average particle size of 8.5 μm (weight average particle size / number average particle size 1.43). Thereafter, 0.50% by weight of silica (R-972 Nippon Aerosil) was mixed using a Henschel mixer to obtain a toner.
The toner has a softening temperature of 155 ° C. and a volume resistivity of 7.5 × 10⁸The average circularity was 0.90, the Tg was 68 ° C., the temperature at which the melt viscosity was 1000 Pa · s was 172 ° C., and the loose apparent density was 0.29 g / cc.
[0023]
Toner E
(Toner prescription)
35 parts by weight of polyester resin (weight average molecular weight: 182500, Tg: 71)
49 parts by weight of styrene-butyl acrylate copolymer
(Weight average molecular weight: 105000, Tg: 58)
Polypropylene wax (Biscol 550P: Sanyo Chemical Industries) 5 parts by weight
Carbon black (Mitsubishi Kasei # 44) 10 parts by weight
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part by weight
With the above formulation, after kneading at 120 ° C. using a biaxial extruder, pulverized and classified with an airflow pulverizer to give a weight average particle size of 7.0 μm (weight average particle size / number average particle size 1.46). Thereafter, 0.75% by weight of silica (R-972 Nippon Aerosil) was mixed using a Henschel mixer to obtain a toner.
The toner has a softening temperature of 150 ° C. and a volume resistivity of 5.5 × 10.⁸The average circularity was 0.90, the Tg was 65 ° C., the temperature at which the melt viscosity was 1000 Pa · s was 125 ° C., and the loose apparent density was 0.29 g / cc.
[0024]
Toner F
(Toner prescription)
60 parts by weight of polyester resin (weight average molecular weight: 182500, Tg: 71)
Styrene-butyl acrylate copolymer 24 parts by weight
(Weight average molecular weight: 105000, Tg: 58)
Polypropylene wax (Biscol 550P: Sanyo Chemical Industries) 5 parts by weight
Carbon black (Mitsubishi Kasei # 44) 10 parts by weight
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part by weight
With the above formulation, after kneading at 140 ° C. using a biaxial extruder, pulverized and classified with an airflow type pulverizer to give a weight average particle size of 7.0 μm (weight average particle size / number average particle size 1.46). Thereafter, 0.75% by weight of silica (R-972 Nippon Aerosil) was mixed using a Henschel mixer to obtain a toner.
The softening temperature of this toner is 150 ° C., and the volume resistivity is 7.5 × 10.⁸The average circularity was 0.90, the Tg was 65 ° C., the temperature at which the melt viscosity was 1000 Pa · s was 165 ° C., and the loose apparent density was 0.29 g / cc.
[0025]
Toner G
(Toner prescription)
Polyester resin (weight average molecular weight: 182500, Tg: 71) 58 parts by weight
26 parts by weight of styrene-butyl acrylate copolymer
(Weight average molecular weight: 105000, Tg: 58)
Polypropylene wax (Biscol 550P: Sanyo Chemical Industries) 5 parts by weight
Carbon black (Mitsubishi Kasei # 44) 10 parts by weight
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part by weight
With the above formulation, after kneading at 140 ° C. using a biaxial extruder, pulverized and classified with a mechanical pulverizer to give a weight average particle size of 7.5 μm (weight average particle size / number average particle size of 1.41). Thereafter, 0.75% by weight of silica (R-972 Nippon Aerosil) was mixed using a Henschel mixer to obtain a toner.
The toner has a softening temperature of 153 ° C. and a volume resistivity of 8.5 × 10⁸The average circularity was 0.95, the Tg was 65 ° C., the temperature at which the melt viscosity was 1000 Pa · s was 152 ° C., and the loose apparent density was 0.29 g / cc.
[0026]
Toner H
(Toner prescription)
60 parts by weight of polyester resin (weight average molecular weight: 182500, Tg: 71)
Styrene-butyl acrylate copolymer 24 parts by weight
(Weight average molecular weight: 105000, Tg: 58)
Carnauba wax 5 parts by weight
Carbon black (Mitsubishi Kasei # 44) 10 parts by weight
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part by weight
With the above formulation, after kneading at 135 ° C. using a biaxial extruder, pulverized and classified with a mechanical pulverizer to give a weight average particle size of 6.5 μm (weight average particle size / number average particle size 1.35). Then, using a Henschel mixer, 1.00% by weight of silica (R-972 Nippon Aerosil) was mixed to obtain a toner.
The toner has a softening temperature of 150 ° C. and a volume resistivity of 9.5 × 10.⁸The average circularity was 0.98, the Tg was 65 ° C., the temperature at which the melt viscosity was 1000 Pa · s was 145 ° C., and the loose apparent density was 0.29 g / cc.
[0027]
Toner I
(Toner prescription)
60 parts by weight of polyester resin (weight average molecular weight: 182500, Tg: 71)
27 parts by weight of styrene-butyl acrylate copolymer
(Weight average molecular weight: 105000, Tg: 58)
Carnauba wax 5 parts by weight
Carbon black (Mitsubishi Kasei # 44) 7 parts by weight
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part by weight
With the above formulation, after kneading at 130 ° C. using a biaxial extruder, pulverized and classified with a mechanical pulverizer to give a weight average particle size of 6.5 μm (weight average particle size / number average particle size 1.35). Then, using a Henschel mixer, 1.00% by weight of silica (R-972 Nippon Aerosil) was mixed to obtain a toner.
The toner has a softening temperature of 150 ° C. and a volume resistivity of 2.5 × 10⁹The average circularity was 0.97, the Tg was 62 ° C., the temperature at which the melt viscosity was 1000 Pa · s was 145 ° C., and the loose apparent density was 0.29 g / cc.
[0028]
toner J
(Toner prescription)
60 parts by weight of polyester resin (weight average molecular weight: 182500, Tg: 71)
27 parts by weight of styrene-butyl acrylate copolymer
(Weight average molecular weight: 105000, Tg: 58)
Carnauba wax 5 parts by weight
Carbon black (Mitsubishi Kasei # 44) 7 parts by weight
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part by weight
With the above formulation, after kneading at 130 ° C. using a biaxial extruder, pulverized and classified with a mechanical pulverizer to give a weight average particle size of 6.5 μm (weight average particle size / number average particle size 1.35). Thereafter, 1.50% by weight of silica (R-972 Nippon Aerosil) was mixed using a Henschel mixer to obtain a toner.
The toner has a softening temperature of 150 ° C. and a volume resistivity of 2.5 × 10⁹The average circularity was 0.97, the Tg was 62 ° C., the temperature at which the melt viscosity was 1000 Pa · s was 145 ° C., and the loose apparent density was 0.35 g / cc.
[0029]
【Example】
Example 1
The toner H (Tg = 65 ° C., Tm = 150 ° C.) was used, and the Ricoh Imagio-MF7070 transfer unit remodeling machine shown in FIG. As the development, the one-component non-contact method uses the developing device shown in FIG. The pressure for transfer and primary fixing is 60 N / cm in surface pressure.²The belt temperature was set to 100 ° C. (Tg <100 ° C. <Tm). Secondary fixing is surface pressure: 9.3 N / cm²The fixing nip width is about 10 mm, and the temperature is set to 175 ° C. By using this apparatus, an image can be obtained by printing out a test chart centered on a gray scale formed from binary dots of 600 dpi.
An experiment for optimizing simultaneous transfer was performed under the following conditions.
The toner particle size (weight average) is 6.5 μm (denoted as a). Three levels of photoreceptor roughness Rz: 2.5 μm, 3.1 μm, and 4.8 μm. The photoreceptor was made of amorphous silicon, and the surface roughness condition was determined by feather polishing using a metal oxide powder. As the transfer paper, transfer paper having three levels of surface roughness (Rz) of 8 μm, 15 μm, and 24 μm was used. The roughness was selected from coated paper and plain paper. The surface roughness was measured using an ultra-deep shape measurement microscope VK8500 manufactured by Keyence Corporation using a line roughness measurement mode. The results are shown in Table 1.
[0030]
[Table 1]

From the above results, a paper roughness of 15 μm (2.3 times the toner diameter) or more and a photoreceptor roughness of 3.1 μm (0.48 times) or less are good results. From the above results, good results can be obtained under conditions where the roughness of the photoreceptor is ½ or less of the toner particle diameter and the roughness of the transfer paper is twice or more of the toner particle diameter.
[0031]
(Example 2)
The toner H (Tg = 65 ° C., Tm = 150 ° C.) was used, and the Ricoh Imagio-MF7070 transfer unit remodeling machine shown in FIG. As the development, the one-component non-contact method uses the developing device shown in FIG. Transfer primary fixing was performed by applying a pressure for transfer and primary fixing and a belt temperature. Secondary fixing is surface pressure: 9.3 N / cm²The fixing nip width is about 10 mm, and the temperature is set to 175 ° C. By using this apparatus, an image can be obtained by printing out a test chart centered on a gray scale formed from binary dots of 600 dpi. The pressure between the photoconductor used for transfer and primary fixing and the transfer belt temperature and the applied belt temperature are as follows. The conditions of were confirmed.
The evaluation was performed at the transfer rate as in the examples. The results are shown in Table 2.
[0032]
[Table 2]

From the above results, the pressure is 10 to 100 N / cm.²Thus, good results are obtained by using a temperature within the toner softening temperature from the glass transition temperature of the toner used.
Also, the pressure is 60N / cm²Under these conditions, the coefficient of friction of the photosensitive member was changed from 0.7 to 0.3 to confirm transferability. In order to improve the friction coefficient of the photoconductor provided in the cleaning section of FIG. 1, a zinc stearate block was provided and applied to the photoconductor via a brush to obtain two conditions. The result is shown in Table 2 under the pressure of 80 N / cm.²The application temperature was confirmed at 45 to 170 ° C.
From the above results, the transfer rate is improved by applying zinc stearate.
[0033]
(Example 3)
The toner H (Tg = 65 ° C., Tm = 150 ° C.) was used, and the Ricoh Imagio-MF7070 transfer unit remodeling machine shown in FIG. As the development, the one-component non-contact method uses the developing device shown in FIG. The pressure for transfer and primary fixing is 60 N / cm in surface pressure.²The belt temperature was set to 100 ° C. (Tg <100 ° C. <Tm). Secondary fixing is surface pressure: 9.3 N / cm²The fixing nip width is about 10 mm, and the temperature is set to 175 ° C. Using this apparatus, characteristics over time were confirmed when the transfer unit and the cleaning unit were placed apart from each other except during image formation, and when they were always in contact with each other.
There is no problem in a normal environment. The margin test was confirmed in an environment where the room temperature was maintained at 30 ° C. and 60% RH.
The image forming conditions were 500 prints (character area 6% chart) operated for 8 hours a day (16,000 sheets) at 15 minute intervals and compared over 10 days.
As a result, in a machine that has always been in contact with the toner, the toner adheres to the tip of the cleaning blade, resulting in poor cleaning, and there are only about 50000 sheets of photoconductor stains, image background stains, black streaks, etc. There has occurred.
On the other hand, when the transfer unit and the cleaning unit were placed apart from each other except during image formation, there was no problem even in the same test, and a normal image was obtained.
[0034]
(Example 4)
The evaluation machine used was a modified Ricoh Imagio-MF7070 transfer unit in FIG. As a development, a one-component non-contact developing device was used. FIG. 2 is a schematic diagram showing the configuration of a one-component non-contact developing device. The pressure for transfer and primary fixing is 60 N / cm in surface pressure.²The belt temperature was set to 100 ° C. (Tg <100 ° C. <Tm). Secondary fixing is surface pressure: 9.3 N / cm²The fixing nip width is about 10 mm, and the temperature is set to 175 ° C. In order to improve the peeling from the photoconductor by the simultaneous primary fixing of the transfer so that the toner easily adheres to the transfer paper, the toner particle size a is the photoconductor roughness is a / 2 or less, and the transfer paper has a surface roughness of An image was obtained by printing out a test chart centering on a gray scale formed from binary dots of 600 dpi, with 3a or more.
The toners A, B, C, and H described above were used as toners used in this example.
The evaluation was made for each item of transfer primary fixing characteristics (transfer rate%), secondary fixing (smear density), and granularity. The results are shown in Table 3.
[0035]
[Table 3]

From the above results, the toner softening temperature is preferably 100 to 160 ° C., and the glass transition temperature is preferably 55 to 70 ° C.
[0036]
(Example 5)
The evaluation method was the same as in Example 4. The toners used in this example were the toners D, E, H, and I described above.
The evaluation was made for each item of transfer primary fixing characteristics (transfer rate%), secondary fixing (smear density), and granularity. The results are shown in Table 4. Here, the dispersity is (weight average particle diameter / number average particle diameter).
[0037]
[Table 4]

From the above results, the circularity is 0.92 or more and the dispersion is 1.4 or less.
[0038]
(Example 6)
The evaluation method was the same as in Example 4. As the toner used in this example, the above toner formulation was used. As the characteristic values used, the temperature at which the melt viscosity of the toner becomes 1000 Pa · s (that is, the temperature at which the toner melts and starts to adhere) and each characteristic were confirmed.
The evaluation was made for each item of transfer primary fixing characteristics (transfer rate%), secondary fixing (smear density), and granularity. The results are shown in Table 5.
[0039]
[Table 5]

From the above results, the optimum range is 120 to 170 ° C.
[0040]
(Example 7)
The evaluation method was the same as in Example 4. The toners used in this example were the toners H and J described above. The characteristic value used is the loose apparent density (g / cc).
The evaluation was made for each item of transfer primary fixing characteristics (transfer rate%), secondary fixing (smear density), and granularity. The results are shown in Table 6.
[Table 6]

From the above results, it is preferable that the apparent density of loose toner is 0.3 g / cc or more. Here, “◎” not used in the conventional evaluation is given. The best value of 0.21 was obtained this time.
[0041]
(Example 8)
The evaluation method was the same as in Example 4. As the toner used in this example, the above toner formulation was used. The characteristic value used is the volume resistivity.
Evaluation was made for each item of primary transfer characteristics (transfer rate%), secondary fixing (smear density), and granularity, and the results are shown in Table 7.
[Table 7]

From the above results, the volume resistivity is 1 × 10⁹Ωcm or more is a good range.
[0042]
【The invention's effect】
As described above, in the image forming method and the image forming apparatus according to the present invention, the toner is deformed, the surface between the toners is lightly fixed, and the toner is primarily fixed to the transfer with the anchor effect by being packed in the recess of the transfer paper. Further, it is possible to prevent image deterioration during electrostatic transfer.
Further, in the image forming method and the image forming apparatus of the present invention, by separating the transfer primary fixing unit which is a heat source except during image formation, the temperature rise of the photoconductor can be prevented and the problems on the image and the system can be reduced. The design margin can be increased.
Further, in the image forming method and the image forming apparatus of the present invention, it is possible to improve the transfer rate by improving the toner releasability by using a photoconductor having a hard surface and a low friction coefficient.
In the image forming method and the image forming apparatus of the present invention, it is possible to obtain a high-quality image without graininess by improving the transfer rate.
Further, in the image forming method and the image forming apparatus of the present invention, occurrence of hot offset can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic view of an entire image forming apparatus using an image forming method of the present invention.
FIG. 2 is a schematic diagram illustrating a configuration of a one-component non-contact developing device.
[Explanation of symbols]
1 Photoconductor
2 Charger
3 Exposure means
31 Scanner
32 Polygon motor
33 Mirror
4 Development means
5 Transfer means
52 Primary fixing roller
53 Transfer belt
54 Tension roller
55 Cleaning device
56 heater
57 Temperature detection means
6 Cleaning means
7 Fixing means
71 Fixing roller
72 Pressure roller
73, 74 Heating means (heater)
101, 106 Transfer paper bank
102, 107 Paper feed roller
103, 108 paper feed

Claims (6)

A latent image forming step for forming a latent image on the photosensitive member; a developing step for developing the latent image; a transferring step for transferring using a transfer roller in pressure contact with the photosensitive member; and a fixing step for fixing toner by a heat roller. An image forming method comprising:
In the transfer process , heat and pressure are applied to the toner and transfer paper via the transfer roller without applying static electricity to perform transfer and primary fixing at the same time.
The fixing step is an image forming method in which secondary fixing is performed by fixing the transfer paper that has been primarily fixed separately from the photoreceptor.
The development process uses a non-contact development method that develops the latent image in a non-contact state with the photoconductor ,
In the transfer step, an image forming method is characterized in that a pressure of 10 to 100 N / cm ² is applied between the transfer roller and the photosensitive member, and a temperature applied to the transfer paper is in a range from a toner glass transition temperature to a toner softening temperature. The image forming method according to claim 1,
The photoconductor surface roughness is such that the ten-point average roughness Rz is a / 2 or less (where a represents the toner particle size).
The transfer paper surface roughness has a ten-point average roughness Rz of 2a or more. The image forming method according to claim 1 or 2 ,
An image forming method, wherein the transfer / cleaning unit is provided with a contact / separation mechanism with respect to the photosensitive member, and is separated from the photosensitive member except during image formation. The image forming method according to any one of claims 1 to 3 ,
In the toner glass transition temperature (Tg) of 55 to 70 ° C., an image forming method to which the toner softening temperature (Tm) is characterized in that it is a 100 to 160 ° C.. An image forming apparatus having a photosensitive member having a latent image, a developing device, a transfer device using a transfer roller pressed against the photosensitive member, and a heat roller fixing device,
In the transfer device, the transfer roller in the transfer device applies heat and pressure without applying static electricity to the toner and transfer paper, and performs transfer and primary fixing simultaneously.
The pressure between the transfer roller and the photoconductor is 10 to 100 N / cm ² , and the temperature applied to the transfer paper is in the range from the toner glass transition temperature to the toner softening temperature,
Fixing device, a transfer paper having primary fixing separate from the photoreceptor, have rows secondary fixing the fixing again,
An image forming apparatus, wherein the developing device develops the latent image in a non-contact state with the photosensitive member . The image forming apparatus according to claim 5 .
An image forming apparatus using the image forming method according to claim 2 .

Images