JP2004012559A - Melt transfer method and device for liquid developing electrophotography - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably melt and transfer an image on an intermediate transfer body where carrier is completely removed to a printing medium with good transfer efficiency in a liquid developing electrophotographic device using nonvolatile carrier. <P>SOLUTION: In the melt transfer method, liquid toner (liquid developer) where two kinds of resin having different softening temperature are mixed is used. Melt transfer is performed in a state where the carrier is completely removed by appropriately setting the softening temperature and the melting temperature of each of two kinds of resin and the temperature of an image support. Namely, two kinds of resin are selected to meet the relation of Tg1<Tg3<Tg2<Tm3 and the temperature of the image support is controlled to meet the relation of Tg1<T4<Tg2<Tm3, wherein the softening temperature of either resin is Tg1, the softening temperature of the other resin is Tg2, the softening temperature of the mixed resin is Tg3, the melting temperature thereof is Tm3, and the temperature of the image support is T4. <P>COPYRIGHT: (C)2004,JPO

Description

【００２７】
表１は、それぞれのトナー（トナーＡ〜Ｅ）中のレジンの軟化温度（Ｔｇ１、Ｔｇ２）と、その配合割合、混合トナーとしての軟化温度（Ｔｇ３）と溶融温度（Ｔｍ３）を示している。トナーＡは、１種類のレジンで構成されたトナーである。なお、これ以外に、顔料、その他の助剤を合わせて１００％になる。ここで使用したトナーＡ〜Ｅのそれぞれは、レジンとしてビィスフェノールＡ型エポキシ樹脂を用い、その重合度を変えることによって軟化温度を変化させたサンプルを作成して用いた。また、ポリエステル樹脂などの分子量の違いによって軟化温度が異なるものも知られており、本発明は、軟化温度を変化させることのできる樹脂であれば、ここで用いたエポキシ樹脂に限定されることなく用いることができる。
【００２８】
【表２】

【００２９】
表２は、表１で示した各トナーを用いて、かつ、画像支持体温度Ｔ４とキャリア除去回数を変化させて、中間転写体から印刷用紙への転写効率を調べた結果を示している。転写効率は、最も良いものを○、良いものを△、悪いものを×、最も悪いものを××で、それぞれ示している。一般的に言って、キャリア除去をすればする程、転写効率は悪くなる傾向があるが、しかし、キャリア液の除去が不十分だと、定着におけるトナー層の溶融に影響を与えたり、リビュレッツ（リブ）と呼ばれるまだら模様が発生して画像を乱したりすることがあるのは前述した通りである。
【００３０】
１種類のレジンで構成されたトナーＡを用いた場合、転写効率が良好な条件は存在するが、キヤリア除去回数を増やしたり（転写前の固形分比率をあげる）すると転写効率は悪くなりやすい。また、温度条件にも敏感である。これは、レジンが１種類で構成されていると、温度に対してトナー全体が軟化状態、溶融状態になるために画像支持体に対する接着力が強くなり、転写効率の良好条件が狭くなるためである。
【００３１】
これに対して、２種類のレジンで構成されたトナーＢ〜Ｅでは、画像支持体温度、キャリア除去回数の条件に対して、転写効率の艮好な範囲が広くなっている。これは、２種類のレジンの軟化温度Ｔｇ１、Ｔｇ２に対して、画像支持体温度Ｔ４をＴｇ１＜Ｔ４＜Ｔｇ２、と設定することにより、軟化温度をこえていないレジンが画像支持体への接着力を抑制する役割をするために、温度に対してや、キャリア除去回数に対して、転写効率の良好な範囲が広がると考えられる。
【００３２】
また、混合レジンの構成を変えたそれぞれのトナーの転写効率の結果から以下のように考察できる。
【００３３】
Ｔｇ１＜Ｔ４＜Ｔｇ２、の条件であっても、Ｔｇ１がＴ４に対して低すぎると、溶融状態が進み過ぎて、局所的に転写効率が悪化してしまう。
【００３４】
また、Ｔｇ２がＴ４に近すぎると、溶融を抑制する力が弱くなり転写効率が悪くなる。上の実験結果より、転写効率がより良好な条件は、（Ｔ４−Ｔｇ１）＜２０℃、かつ、（Ｔｇ２−Ｔ４）＞１０℃の条件の時である。（Ｔｇ２−Ｔ４）が高すぎても、溶融が進まず転写効率が悪くなる。よって、３０℃＞（Ｔｇ２−Ｔ４）＞１０℃、が望ましい。
【００３５】
また、媒体温度も今回の実験では、Ｔｇ３＜Ｔ５、の設定であったが、媒体の転写時に溶融状態が進むほど転写効率は良好になる結果になるため、Ｔｍ３＜Ｔ５、の条件が望ましい。
【００３６】
【発明の効果】
本発明は、不揮発性液体現像液に用いられるレジンとして、軟化温度の異なる２種類のレジンを混合して用いると共に、画像支持体の温度を所定条件に設定することにより、
・画像支持体温度に対して転写効率の良好な範囲が広くなる、
・キャリア除去回数に対して転写効率の良好な範囲が広くなる、
などの効果が得られる。
【００３７】
この結果、画像支持体の表面状態、環境変化などに対して安定して印刷媒体に転写できる。これにより、本発明によれば、安定して高画質な画像を得ることができるようになるという効果を生じる。
【図面の簡単な説明】
【図１】本発明を具体化するフルカラー電子写真装置の構成を例示する図である。
【図２】図１に例示したようなキャリア除去ユニットをさらに説明するための図である。[0001]
TECHNICAL FIELD OF THE INVENTION
SUMMARY OF THE INVENTION The present invention provides a method for liquid development electrophotography using a non-volatile liquid developer configured to melt transfer to a transfer medium after removing excess carrier liquid contained in a toner image on an image support. The present invention relates to a transfer method and apparatus.
[0002]
[Prior art]
An electrophotographic apparatus using a liquid toner composed of a carrier liquid containing toner particles as a developing solution generates an electrostatic latent image on a photosensitive member, forms an image by attaching toner particles to the latent image, and then transfers the image to an intermediate transfer member. And then directly or directly onto paper or the like for fixing. In such an electrophotographic apparatus, when an excessive carrier liquid is present at the time of transfer to an intermediate transfer member or paper, it may affect the melting of the toner layer at the time of fixing, or the toner layer may be broken at the nip exit at the time of transfer. Due to the separation, a mottled pattern called ribulets (ribs) is generated and disturbs the image.
[0003]
For this reason, it is necessary to remove the excess carrier liquid, but when using a non-volatile high-viscosity, high-concentration liquid toner as a developer, it is removed by vaporization as in the case of using a volatile carrier liquid. Therefore, the carrier is removed at the position on the photoreceptor after development and on the intermediate transfer member.
[0004]
Japanese Patent Application Laid-Open No. 2001-60046 discloses that, in order to improve the transfer efficiency, the toner temperature and the transfer medium are set by setting the surface temperature of the image support ≦ the glass transition point of the toner particles <the temperature of the transfer medium. Disclosed is a technique for increasing the adhesive strength between the two.
[0005]
However, when the surface temperature of the image support is set to be lower than the glass transition point of the toner particles, the solid content of the toner easily retains the carrier, the carrier removal efficiency is deteriorated, and the fixing failure occurs after the image is transferred to the medium. Problem arises.
[0006]
Similarly, in order to improve transfer efficiency, Japanese Patent Application Laid-Open No. 2001-92199 sets the temperature of the image support and the temperature of the transfer-receiving body to be higher than the glass transition temperature of the liquid toner.
[0007]
However, when the carrier is removed by setting the surface temperature of the image support to be higher than the glass transition point of the toner particles, the image support and the toner are removed when the carrier is sufficiently removed (solid content ratio: 50% to 90%). Therefore, even if the temperature of the transfer object is higher than the glass transition temperature of the toner, the transfer efficiency is deteriorated.
[0008]
[Problems to be solved by the invention]
The present invention solves such a problem, and removes a carrier liquid of an image on an image support by a carrier removing device, and then melts and transfers the liquid to a print medium, using a non-volatile carrier liquid. In a developing electrophotographic apparatus, an object is to stably transfer an image on an intermediate transfer body from which a carrier has been sufficiently removed to a printing medium with high transfer efficiency.
[0009]
[Means for Solving the Problems]
The present invention uses a liquid toner (liquid developer) in which two kinds of resins having different softening temperatures are mixed. By appropriately setting the softening temperature, the melting temperature, and the image support temperature of each of the two types of resins, the melt transfer can be performed in a state where the carrier has been sufficiently removed.
[0010]
The melt transfer method and apparatus for liquid development electrophotography using the non-volatile liquid developer according to the present invention is a method for removing excess carrier liquid contained in a toner image on an image support by a carrier removal device and then performing printing. It is configured to be melt-transferred to a medium. As a resin used in this nonvolatile liquid developer, two kinds of resins having different softening temperatures are mixed and used. When the softening temperature of one resin is Tg1, the softening temperature of the other resin is Tg2, the softening temperature of the mixed resin is Tg3, the melting temperature is Tm3, and the temperature of the image support is T4, Tg1 <Tg3 It is characterized in that two types of resins are selected so as to satisfy the relationship of <Tg2 <Tm3, and the temperature of the image support is controlled so as to satisfy the relationship of Tg1 <T4 <Tg2 <Tm3.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a diagram illustrating a configuration of a full-color electrophotographic apparatus embodying the present invention. The non-volatile liquid toner used in the present device uses a non-volatile silicone oil as a carrier and has a viscosity of 10 cSt to 200 cSt, preferably 50 cSt to 100 cSt. In this silicone oil, toner particles of a resin (resin) and a pigment having a particle size of about 1 to 2 μm are dispersed at a ratio of about 10 to 30%, preferably 10 to 20%.
[0012]
A photosensitive drum (photoreceptor) corresponding to each color of yellow, magenta, cyan, and black is arranged in contact with the intermediate transfer member exemplified as the drum configuration to constitute a tandem type full-color electrophotographic apparatus. I have. During one rotation of the intermediate transfer body, the intermediate transfer body comes into contact with the photoconductor corresponding to each color, and images are sequentially superimposed on the intermediate transfer body to form a color image.
[0013]
On each photoconductor, a charger, an exposure unit, a static eliminator, and the like, which are not shown, are provided. After the charger charges the photoconductor to, for example, about 700 V, the exposure unit exposes the charged photoconductor to a laser beam having a wavelength of, for example, 780 nm based on the image data. As a result, an electrostatic latent image is formed on the photosensitive drum in which the potential of the exposed portion is, for example, about 100 V. Further, the static eliminator eliminates the residual potential on the photoconductor.
[0014]
The developing roller of the developing unit is biased to a predetermined voltage such as about 400 V to 600 V, and supplies a positively charged toner particle on the developing roller to the photoconductor according to an electric field between the photoconductor and the developing roller. As a result, toner particles adhere to exposed portions on the photoconductor charged to about 100 V, and the electrostatic latent image on the photoconductor is developed to form an image.
[0015]
The intermediate transfer member transfers the toner particles attached to the photoconductor in accordance with an electric field between each of the photoconductors. The carrier liquid is removed by the carrier removal unit from the toner layer containing the toner particles forming the four-color image superimposed on the intermediate transfer member. The image formed by the toner particles on the intermediate transfer member contains a carrier liquid, and the carrier removal unit removes excess carrier oil. One or more exemplary carrier removal units are located downstream of the process for each photoreceptor and upstream of the next photoreceptor. In the example shown, two carrier removal units are arranged on the intermediate transfer member, one after each photoreceptor, after the last photoreceptor (and therefore before the first photoreceptor) as finishing. I have.
[0016]
Thereafter, the four-color image is transferred to the print medium by applying pressure by a pressure roller at a contact portion with the print medium, and then subjected to a fixing process using a fixing unit.
[0017]
FIG. 2 is a diagram for further explaining the carrier removal unit as exemplified in FIG. Although the configuration shown in the figure illustrates that excess carrier liquid on the intermediate transfer member is removed by using a carrier removal roller, the present invention is not limited to the intermediate transfer member but includes a general image supporting member including a photosensitive member. It is applicable when transferring from a body to a print medium. Further, the present invention is characterized in that the temperature of the image support and the temperature of the printing medium at the time of transfer are appropriately controlled and the mixed toner is used, but the carrier removing unit itself has a conventionally known configuration. can do.
[0018]
As illustrated, the carrier removing unit is realized by a carrier removing roller for contacting the image support and recollecting toner while removing excess carrier liquid, and applying a bias voltage to the roller. can do. By rotating the carrier removing roller in the direction opposite to the image support, it is possible to remove many carriers. Here, the opposite direction means the direction in which the contact surfaces of both rollers move in opposite directions.
[0019]
The carrier removal roller applies a bias voltage having the same polarity as that of the toner particles on the image support using a metal roller, for example, so that the toner image is pressed against the image support and the toner particles aggregate. Thereby, a purer carrier liquid is present in the outer toner layer and is removed by rotation of the carrier removing roller. The carrier liquid removed by the carrier removal roller is collected by a blade that contacts the carrier removal roller. Note that the carrier removal unit itself can be variously modified, for example, a carrier removal belt can be used instead of the carrier removal roller.
[0020]
In the present invention, a non-volatile liquid toner in which toner particles composed of a resin (resin) and a pigment are dispersed in silicone oil is used. As the resin, two kinds of resins having different softening temperatures are mixed and used. Assuming that the softening temperature of one resin is Tg1, the softening temperature of the other resin is Tg2, the softening temperature of the mixed resin is Tg3, and the melting temperature is Tm3, the relation is such that Tg1 <Tg3 <Tg2 <Tm3. In the present invention, when the temperature of the image support is T4 and the print medium temperature at the time of transfer is T5, the temperature of the image support is adjusted so as to satisfy the relationship of Tg1 <T4 <Tg2 <Tm3 <T5. And, in addition, controls the temperature of the print medium during transfer. As for the temperature of the image support, the temperature at or near the surface is detected by a temperature sensor as shown in FIG. 2, and the detected temperature is set as the temperature T4 of the image support so as to satisfy the above relationship. The current can be controlled by controlling the current flowing through the heater. Further, the temperature of the print medium at the time of transfer can be determined by providing a heater inside the pressure roller shown in FIG. 1 and heating by the pressure roller. Alternatively, it can be performed by heating the print medium in advance before the print medium is sent to the transfer unit. Alternatively, it can be performed using both of these heating means. In any case, by heating the print medium, the temperature is controlled so that the print medium temperature T5 satisfies the above relationship at the time of transfer.
[0021]
When the temperature of the image support is set between the softening temperatures of the two resins and carrier removal is performed, one of the resins exceeds the softening temperature, so that the carrier can be efficiently removed and the other resin is removed. Does not exceed the softening temperature and plays a role of suppressing the adhesive force on the image support. As a result, the carrier is sufficiently removed (solid content ratio: 50% to 90% or more). Adhesion to the body can be low. Further, by setting the medium temperature higher than the melting temperature of the mixed toner, a stronger adhesive force is generated and transferred. At this time, since the adhesive force to the image support is low, the image can be transferred with good transfer efficiency.
[0022]
Desirably, the mixed toner is set at (T4−Tg1) <20 ° C. and (Tg2−T4)> 10 ° C. When (T4−Tg1) <20 ° C., the adhesive force of the Tg1 resin does not become too strong, and the adhesive force of the Tg2 resin to the image support is suppressed, so that the transfer efficiency is good. On the other hand, when (T4−Tg1) ≧ 20 ° C., the melting force of the resin of Tg1 is excessively advanced, so that the adhesive force to the image support locally increases and cannot be completely suppressed by Tg2. Transfer loss occurs in
[0023]
When (Tg2−T4)> 10 ° C., the transfer efficiency is good because the Tg2 resin suppresses the adhesive force of the Tg1 resin to the image support, whereas (Tg2−T4) At ≦ 10 ° C., the ability to suppress the adhesive force of Tg2 is weak, so that the adhesive force to the image support increases, and transfer loss occurs.
[0024]
Further, it is desirable to use a mixed toner in which the mixing ratio of the resin of Tg1 is 20% or more and 80% or less as the mixing ratio of each resin of the mixed toner. When the mixing ratio of the Tg1 resin is 20% or more and 80% or less, the transfer is performed favorably because the carrier removal efficiency is good and the Tg2 resin can suppress the adhesive force of the Tg1 resin. When the mixing ratio of the resin of Tg1 is 20% or less, the proportion of Tg2 that has not reached the softening temperature increases, so that the carrier removal efficiency is deteriorated and poor fixing occurs. On the other hand, when the mixing ratio of the Tg1 resin is 80% or more, the adhesion of the Tg2 resin to the image support cannot be sufficiently suppressed by the Tg2 resin, resulting in poor transfer.
[0025]
【Example】
[0026]
[Table 1]

[0027]
Table 1 shows the softening temperatures (Tg1, Tg2) of the resins in the respective toners (toners A to E), the mixing ratio thereof, the softening temperature (Tg3) and the melting temperature (Tm3) of the mixed toner. The toner A is a toner composed of one kind of resin. In addition, in addition to this, the total amount of the pigment and other auxiliaries is 100%. Each of the toners A to E used here was prepared by using a bisphenol A type epoxy resin as a resin, and preparing a sample in which the degree of polymerization was changed to change the softening temperature. Also, those having different softening temperatures due to differences in molecular weight of polyester resins and the like are known, and the present invention is not limited to the epoxy resin used here, as long as the resin can change the softening temperature. Can be used.
[0028]
[Table 2]

[0029]
Table 2 shows the results of examining the transfer efficiency from the intermediate transfer body to the printing paper using each of the toners shown in Table 1 and changing the image support temperature T4 and the number of times of carrier removal. The transfer efficiency is indicated by 最 も for the best one, Δ for the good one, × for the bad one, and XX for the worst one. Generally speaking, the more the carrier is removed, the lower the transfer efficiency tends to be. However, if the removal of the carrier liquid is insufficient, it may affect the melting of the toner layer at the time of fixing, or may cause the Liburetz ( As described above, a mottled pattern called “rib” may be generated to disturb the image.
[0030]
When the toner A composed of one type of resin is used, there are conditions under which the transfer efficiency is good, but the transfer efficiency tends to be deteriorated if the number of removal of the carrier is increased (the solid content ratio before transfer is increased). It is also sensitive to temperature conditions. This is because if the resin is composed of one kind, the entire toner is in a softened state and a molten state with respect to the temperature, so that the adhesive force to the image support is increased, and the conditions for good transfer efficiency are narrowed. is there.
[0031]
On the other hand, in the toners B to E composed of two types of resins, the favorable range of the transfer efficiency is wide with respect to the conditions of the image support temperature and the number of times of carrier removal. This is because, by setting the image support temperature T4 to Tg1 <T4 <Tg2 with respect to the softening temperatures Tg1 and Tg2 of the two types of resins, the resin which does not exceed the softening temperature has an adhesive force to the image support. It is considered that the good range of the transfer efficiency is widened with respect to the temperature and the number of times of the carrier removal in order to suppress the transfer.
[0032]
The following can be considered from the results of the transfer efficiencies of the respective toners in which the configuration of the mixed resin is changed.
[0033]
Even if the condition of Tg1 <T4 <Tg2 is satisfied, if Tg1 is too low with respect to T4, the melting state proceeds too much, and the transfer efficiency is locally deteriorated.
[0034]
On the other hand, if Tg2 is too close to T4, the ability to suppress melting is weakened, and transfer efficiency is deteriorated. According to the above experimental results, the conditions under which the transfer efficiency is better are the conditions of (T4−Tg1) <20 ° C. and (Tg2−T4)> 10 ° C. Even if (Tg2-T4) is too high, the melting does not proceed and the transfer efficiency deteriorates. Therefore, it is desirable that 30 ° C.>(Tg2−T4)> 10 ° C.
[0035]
In this experiment, the medium temperature was set at Tg3 <T5. However, the transfer efficiency becomes better as the molten state advances during the transfer of the medium. Therefore, the condition of Tm3 <T5 is desirable.
[0036]
【The invention's effect】
The present invention uses a mixture of two resins having different softening temperatures as the resin used in the nonvolatile liquid developer, and sets the temperature of the image support to a predetermined condition.
A good range of transfer efficiency with respect to the temperature of the image support is widened,
・ The good range of transfer efficiency with respect to the number of times of carrier removal is widened,
And the like.
[0037]
As a result, the image can be stably transferred to the print medium against the surface condition of the image support, environmental changes, and the like. Thus, according to the present invention, there is an effect that a high quality image can be stably obtained.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating the configuration of a full-color electrophotographic apparatus embodying the present invention.
FIG. 2 is a diagram for further explaining a carrier removal unit as exemplified in FIG. 1;

Claims (8)

For liquid developed electrophotography using a non-volatile liquid developer configured to remove excess carrier liquid contained in a toner image on an image support by a carrier removing device and then melt-transfer it to a transfer medium. In the melt transfer method,
As a resin used in the non-volatile liquid developer, a mixture of two resins having different softening temperatures is used,
When the softening temperature of one resin is Tg1, the softening temperature of the other resin is Tg2, the softening temperature of the mixed resin is Tg3, the melting temperature is Tm3, and the temperature of the image support is T4,
Selecting the two types of resins so as to satisfy the relationship of Tg1 <Tg3 <Tg2 <Tm3 and controlling the temperature of the image support so as to satisfy the relationship of Tg1 <T4 <Tg2 <Tm3. Melt transfer method for liquid developed electrophotography. 2. The transfer medium temperature according to claim 1, wherein when the medium temperature at the time of transfer is T5, the medium temperature at the time of transfer is controlled in addition to the temperature of the image support so as to satisfy the relationship of Tg1 <T4 <Tg2 <Tm3 <T5. Melt transfer method for liquid developed electrophotography. The fusion transfer method for liquid developed electrophotography according to claim 1, wherein the two types of resins are set at (T4−Tg1) <20 ° C. and (Tg2−T4)> 10 ° C. 4. The fusion transfer for liquid developed electrophotography according to any one of claims 1 to 3, wherein a mixing ratio of the one resin to the other resin is 20% or more and 80% or less as a mixing ratio of the two resins. Method. For liquid developed electrophotography using a non-volatile liquid developer configured to remove excess carrier liquid contained in a toner image on an image support by a carrier removing device and then melt-transfer it to a transfer medium. In the fusion transfer device,
As a resin used in the non-volatile liquid developer, a mixture of two resins having different softening temperatures is used,
When the softening temperature of one resin is Tg1, the softening temperature of the other resin is Tg2, the softening temperature of the mixed resin is Tg3, the melting temperature is Tm3, and the temperature of the image support is T4,
Means for selecting the two kinds of resins so as to satisfy the relation of Tg1 <Tg3 <Tg2 <Tm3 and controlling the temperature of the image support so as to satisfy the relation of Tg1 <T4 <Tg2 <Tm3 A melt transfer device for liquid developed electrophotography. Assuming that the medium temperature at the time of transfer is T5, in addition to the means for controlling the temperature of the image support so that the relationship of Tg1 <T4 <Tg2 <Tm3 <T5, means for controlling the medium temperature at the time of transfer is provided. A fusion transfer device for liquid developed electrophotography according to claim 5. 7. The fusion transfer device for liquid developed electrophotography according to claim 5, wherein the two kinds of resins are set to (T4−Tg1) <20 ° C. and (Tg2−T4)> 10 ° C. The fusion transfer for liquid developed electrophotography according to any one of claims 5 to 7, wherein a mixing ratio of the one resin to the other resin is 20% or more and 80% or less as a mixing ratio of the two resins. apparatus.

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