JP3728085B2 - Image forming method - Google Patents

Description

（式中、Ｒはエチレンまたはプロピレン基であり、ｘ，ｙは各々１以上の正の整数であり、かつｘ＋ｙの平均値は２〜１０である。）で代表されるビスフェノール誘導体またはその置換体をジオール成分とし、２価以上のカルボン酸またはその酸無水物またはその低級アルキルエステルとからなるカルボン酸成分（例えばフマル酸、マレイン酸、無水マレイン酸、フタル酸、テレフタル酸、トリメリット酸、ピロメリット酸等）とを少なくとも共縮重合したポリエステル樹脂がシャープな溶融特性を有するのでより好ましい。
【００２６】
シャープメルト性ポリエステル樹脂の軟化点は６０〜１２０℃が好ましい。このシャープメルト性のポリエステル樹脂をバインダー樹脂として含有するトナーの軟化点特性を図２に示す。
【００２７】
フローテスターＣＦＴ−５００形（島津製作所製）を使用し、ダイ（ノズル）の直径０．５ｍｍ、厚さ１．０ｍｍとして５０ｋｇの押出荷重を加え初期設定温度８０℃で、予熱時間３００秒の後、５℃／分の速度で等速昇温した時描かれるトナーのプランジャー降下量−温度曲線（以後軟化Ｓ字曲線という）を求める。試料となるトナーは１〜３ｇ精秤した微粉末を用い、プランジャー断面積は１０ｃｍ² とする。軟化Ｓ字曲線は図２のようなカーブとなる。等速昇温するに従い、トナーは徐々に加熱され流出が開始される（プランジャー降下Ａ→Ｂ）。更に昇温すると溶融状態となったトナーは大きく流出し（Ｂ→Ｃ→Ｄ）プランジャー降下が停止し終了する（Ｄ→Ｅ）。
【００２８】
Ｓ字曲線の高さＨは全流出量を示し、Ｈ／２のＣ点に対応する温度Ｔ₀ はそのトナーの軟化点を示す。
【００２９】
このようなシャープメルト性のトナーまたは樹脂とは、溶融粘度が１０⁵ ｃｐを示す時の温度をＴ₁ 、５×１０⁴ ｃｐを示す時の温度をＴ₂ としたとき、
Ｔ₁ ＝９０〜１５０℃ ｜ΔＴ｜＝｜Ｔ₁ −Ｔ₂ ｜＝５〜３０℃
の条件を満たす樹脂のことをいう。
【００３０】
これらの温度−溶融粘度特性を有するシャープメルト性のトナーまたは樹脂は加熱されることにより極めてシャープに粘度低下を起こすことが特徴である。このような粘度低下が最上部トナー層と最下部トナー層との適度な混合を生じせしめ、更にトナー層自体の透明性を急激に増加させ、良好な減色混合を起こすものである。
【００３１】
次に、本発明に係わる転写媒体側に用いられる樹脂について詳述する。この樹脂は、カラー画像を形成するトナーと同じ、あるいは同程度の表面張力であることが必要である。トナーと同程度の表面張力をもつということは、表面のぬれと接着の理論（Ｚｉｓｍａｎ）からトナーが転写材の表面の樹脂に引っ付き易いということを意味する。
【００３２】
選択の範囲としては、例えばトナーの結着樹脂にポリエステル樹脂を用いた場合、表面張力は２０ｄｙｎｅ／ｃｍである。それに対して転写材側の表面に用いる樹脂としては、表面張力が２０±１０ｄｙｎｅ／ｃｍのポリエステル樹脂、ポリトリフルオロエチレン樹脂、ポリビニルフロライド樹脂、アクリル樹脂、エポキシ樹脂、シリコン樹脂、フッ素樹脂等のうち、室温もしくは加熱により硬化可能な樹脂等が使用できる。
【００３３】
転写材側に設けられる樹脂層の厚さは、用いられるトナーの粒径によって異なるが、画像上トナー粒子が転写するためには、トナー粒径の１／２の厚さであることがが好ましく、これより薄くなるとトナーが転写しにくくなる。但し、トナー粒径の３倍より厚くなると逆に転写材とトナーと樹脂層とのが別々に分かれてしまい易い。
【００３４】
本発明において、トナーの平均粒径は下記方法に基づいて測定した値をいう。
【００３５】
測定装置としてコールターカウンターＴＡ−II型（コールター社製）を用い、個別分布、体積分布、個数平均及び体積平均を出力するインターフェイス（日科機製）及びＣＸ−１パーソナルコンピューター（キヤノン製）を接続し電解液は１級塩化ナトリウムを用いて１％ＮａＣｌ水溶液を調製する。
【００３６】
測定法としては前記電界水溶液１００〜１５０ｍｌ中に分散剤として界面活性剤、好ましくはアルキルベンゼンスルホン酸塩を０．１〜５ｍｌ加え、更に測定試料を０．５〜５０ｍｇ、好ましくは２〜２０ｍｇ加える。
【００３７】
試料を懸濁した電解液は超音波分散器で約１〜３分間分散処理を行い、前記コールターカウンターＴＡII型により、アパチャーとして１００μｍアパチャーを用いて２〜４０μｍの粒径を有する粒子の粒度分布を測定して体積平均粒径を求める。
【００３８】
本発明に用いられる、トナーと同程度の表面張力を有する樹脂層の作成方法としては、前述転写材上にメタノール、エタノール等のアルコールまたはメチルエチルケトン、アセトン等のケトン類からなる揮発性有機溶剤に前述のトナーと同程度の表面張力をもつ樹脂層を形成するための樹脂を溶解し、転写材の形状からバーコート法、ディップ法、スプレー法、スピンコート法等の方法から最適に塗布し、乾燥する方法がある。
【００３９】
（実施例１）
家庭用のタイル（ＩＮＡＸ社製）の光沢のある面側に、フローテスターＣＦＴ−５００形（島津製作所社製）で得られる軟化点Ｓ字曲線上のＣ点で規定されている軟化点１１０℃のシャープメルト性のポリエステル樹脂（表面張力約２０ｄｙｎｅ／ｃｍ）をアセトンに溶かした溶液をスプレー法により塗布し、乾燥後の厚さで１０μｍになるように樹脂層を形成した。
【００４０】
次に、図１に示す移し絵転写材１の転写層１４上にキヤノン社製の電子写真装置ＣＬＣ７００で画像を出力し、そのトナー（平均粒径８μｍ、結着樹脂の表面張力２０ｄｙｎｅ／ｃｍ）を載せた転写層１４と接着層１２から容易に剥離できるように設けられた離型層１３とを基材１１から引き剥がし、トナー像を載せた部分を下にして、転写対象物（転写媒体）の転写層側に被せる。その上から約１００℃で１０秒間ホットプレスを行う。その際に、タイルとポリビニルアルコール層の間に空気が入り込むため、表面上のエアー抜きをシルボン紙等で擦って行う。これらの作業を２〜３回繰り返して行う。これらの作業が終ったあと、水約２０％、エチルアルコール約８０％の混合溶液で転写層１４を軟化させる。そうすることで、トナー像Ｔが転写媒体のタイルに約１００％転写され十分に良好な画像を得た。
【００４１】
用いた移し絵転写材の各層の厚さおよび構成材料は次の通りである。

【００４２】
樹脂層の表面張力はトナー像が転写される前における値である。
【００４３】
樹脂層、トナーの結着樹脂及び転写層の各樹脂の表面張力は、ぬれ指数標準液（ダイキンファインケミカル製）を用いて測定された。即ち、測定しようとする樹脂をシート状にし、このシートの上にぬれ指数標準液をスポイトで一滴たらし、液滴の接触角（θ）を測定する。この測定をぬれ指数標準液のナンバーの小さい順、即ち、表面張力の小さい順から行い、その結果を、横軸をぬれ指数標準液の表面張力値、縦軸をｃｏｓθとしてプロットする。得られるグラフは右下がりの直線となる。
この直線グラフから、θ＝０となるときの値、即ち、ｃｏｓθ＝１のときの指数標準液の表面張力値を読み取り樹脂の表面張力とした。
【００４４】
（比較例１）
転写媒体のタイルの上に樹脂層を形成しなかった以外、実施例１と同様に再転写を行った。しかし、転写媒体側にトナーが５０％しか転写されないし、また転写された部分についてもトナーがすぐに剥がれてしまった。
【００４５】
（実施例２）
転写媒体の表面にポリトリフルオロチエン樹脂（表面張力２２ｄｙｎｅ／ｃｍ）の層を形成した以外、実施例１と同様に再転写を行った。そうすることで、トナー像Ｔが転写媒体のタイルに約１００％転写され十分に良好な画像を得た。
【００４６】
（比較例２）
転写媒体の表面にポリエチレンテレフタレート樹脂（表面張力４３ｄｙｎｅ／ｃｍ）を使用する以外、実施例１と同様に再転写を行う。転写側にトナーが８０％しか転写されない。
【００４７】
（実施例３）
転写媒体の表面にスチレン−アクリル樹脂（表面張力３０ｄｙｎｅ／ｃｍ）層を形成し、トナーの結着樹脂にスチレンアクリル樹脂（表面張力３０ｄｙｎｅ／ｃｍ）を用いた以外、実施例１と同様に再転写を行った。そうすることで、トナー像Ｔが転写媒体のタイルに約１００％転写され十分に良好な画像を得た。
【００４８】
（比較例３）
転写媒体の表面にポリヘキサメチレンアジパミド樹脂（表面張力４６ｄｙｎｅ／ｃｍ）層を形成した以外、実施例３と同様に再転写を行う。転写媒体側にトナーが８０％しか転写されなかった。
【００４９】
【表２】

【００５１】
（実施例４）
転写媒体の表面にポリエステル樹脂（表面張力２０ｄｙｎｅ／ｃｍ）を形成し、トナーの結着樹脂にスチレンアクリル樹脂（表面張力３０ｄｙｎｅ／ｃｍ）を用いた以外、実施例１と同様に再転写を行った。そうすることで、トナー像Ｔが転写媒体のタイルに約１００％転写され十分に良好な画像を得た。
【００５２】
【発明の効果】
以上説明したように、支持体上にポリビニルアルコール層を有する転写材に電子写真方式で転写された画像を一度定着させ、再度別の転写媒体に転写するカラー画像形成方法において、該転写媒体の表面に、ポリビニルアルコールの表面張力より、定着されるべきトナーの結着樹脂の表面張力に近い表面張力を有する樹脂層を設けることで、再転写時の転写不良を防ぎ、十分に良好な画像を転写媒体に形成できる。
【図面の簡単な説明】
【図１】本発明で用いる移し絵転写材の概略断面図である。
【図２】本発明に好ましく用いられるトナーの溶解特性図である。
【符号の説明】
１ 移し絵転写材
１１ 基材
１２ 接着層
１３ 離型層
１４ 転写層
Ｔ トナー像[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming method capable of retransferring a powder image obtained in an apparatus for forming an image using charged powder such as an electrophotographic apparatus or an electrostatic recording apparatus to another final transfer material. About.
[0002]
[Prior art]
Conventionally, it is widely known to transfer an image to a three-dimensional object using a technique called transfer picture. For example, a water-soluble paste typified by dextrin is coated on a substrate such as paper, The required image using acrylic ink is formed by screen printing etc., the paper with this image is dipped in water to dissolve dextrin, and the acrylic ink image floating in water is transferred to a three-dimensional object such as pottery by water pressure The hydraulic transfer method is widely known. An example of direct application of the transfer paper used in this method to electrophotography is Denpu, manufactured by Muto Kogyo. This transfer material is prepared by forming a dextrin film on rice paper as a transfer material, applying this to an electrophotographic apparatus to form a toner image on the surface of the dextrin, and then softening the resin in the toner. After passing the transfer material through a solvent and giving the toner image an adhesive force to the retransfer body to be retransferred, the transfer material and the toner image are brought into close contact with the retransfer body, Water is applied from the back of the paper to dissolve the dextrin film, and only the toner image is transferred.
[0003]
However, a transfer material in which a water-soluble coating film is formed on such opaque paper is not only difficult to align during retransfer, but also due to the influence of moisture in the atmosphere, the transfer material before image formation. The surface is softened, which causes a problem that the softened dextrin adheres to a photosensitive drum or the like in the electrophotographic apparatus. Further, as described above, since it is sensitive to the moisture in the air, the expansion and contraction with respect to the amount of moisture is severe, causing the transfer material to be left unnecessarily curled, and the paper transportability in the apparatus is significantly deteriorated.
[0004]
In response to the above two problems, JP-A-4-36186 proposes a retransfer material using polyvinyl alcohol, which is a saponified product of vinyl acetate, instead of dextrin. The transfer material proposed here is the one in which a silicone resin is coated on paper, and a mixture of Casezol O-5 manufactured by Nikka Chemical Co., Ltd. and a silicone antifoaming agent is applied. After forming a toner image on this coating film with an electrophotographic apparatus, the caseol film is peeled off from the base material, and the toner image is superimposed on the retransfer medium so as to face each other.
[0005]
By applying heat and pressure, the resin in the toner image described above is softened to obtain an adhesive force to the retransfer body, and after cooling, an 80% aqueous solution of ethyl alcohol is applied from the back surface of the caseol film to form the caseose film and the toner. This reduces the adhesive strength of the image and terminates the retransfer.
[0006]
According to this method, since the thin film having the toner image is peeled off from the base material, it becomes a substantially transparent film, and there is an advantage that the alignment becomes easy.
[0007]
[Problems to be solved by the invention]
However, in the above conventional example, when the transfer medium is not well compatible with the toner, such as metal or tile ceramics or glass, the method of heating and pressurization at the time of retransfer is very difficult. As a result, it was difficult to transfer the toner or the toner after retransfer could be easily removed.
[0008]
An object of the present invention is to provide an image forming method for preventing a transfer failure and toner peeling at the time of retransfer and forming a sufficiently good image on a transfer medium.
[0009]
[Means for Solving the Problems]
That is, in the present invention, an image transferred by an electrophotographic method is once fixed on a transfer material having a polyvinyl alcohol layer on a support, and the toner image formed on the polyvinyl alcohol layer is placed with the image side down. In a color image forming method in which only a toner image is transferred to a transfer medium by applying heat and pressure on another transfer medium and then softening the polyvinyl alcohol layer by applying a liquid, the surface of the transfer medium is coated with polyvinyl A resin layer having a surface tension closer to that of the binder resin of the toner to be fixed than the surface tension of the alcohol is provided, and the surface tension of the binder resin of the toner and the resin of the surface of the transfer medium The image forming method is characterized in that the difference from the surface tension of the layer is within 10 dyne / cm.
[0010]
In the present invention, by having a resin layer compatible with the toner on the surface of the transfer medium, transfer failure and toner peeling during retransfer are prevented, and a sufficiently good image is formed on the transfer medium.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0012]
FIG. 1 is a schematic sectional view showing a layer structure of an electrophotographic transfer picture transfer material 1 used in the present invention. Reference numeral 11 denotes a base material on which the transfer material 1 is coated, which is a medium or high-quality plain paper, a coated paper obtained by applying a resin coating to one or both sides of these papers, and polyethylene terephthalate (PET). ) Or the like is used. In the case of paper, the basis weight is preferably 30 g / m ² or more, and more preferably 45 g / m ² or more. With paper of less than 30 g / m ² , it is difficult to ensure transportability in the electrophotographic apparatus even if the coating resin film is thickened. The basis weight is preferably from 200 g / m ² or less, more preferably 150 g / m ² or less. If it exceeds 200 g / m ² , the rigidity of the base paper is too high, and the transportability tends to be poor. In addition, in order to maintain good image transferability in an electrophotographic apparatus, 0.2 to 4% by weight of an inorganic salt such as sodium chloride is added to the base paper, and its volume resistance value is 20 ° C. and 65% RH environment. It is preferably adjusted to 10 ⁹ to 10 ¹⁴ Ω · cm after being left for 24 hours. Also, when a film material is used for the base, the thickness is preferably 50 μm or more, more preferably 75 μm or more and 150 μm or less in the case of a biaxially stretched heat resistant type PET film from the viewpoint of transportability. Further, for this film, an antistatic layer made of a cationic or nonionic surfactant is applied to the B surface on the drawing, and the surface resistivity is 10 ⁸ to 10 ¹² Ω / □ (20 ° C., 65% RH). It is preferable to be adjusted to.
[0013]
An adhesive layer 12 is provided to prevent the release layer 13 and the transfer layer 14 to be applied later from being easily peeled off in the electrophotographic apparatus. Examples of the material used include water-based acrylic emulsion, water-soluble acrylic, water-soluble polyester, 6.6 nylon, polyacrylonitrile and the like. When paper is a base material, all of the above materials can be used. However, in the case of a resin film such as PET, it should be selected according to the base material to obtain a sufficient adhesive force. In the case of PET or the like, a water-soluble polyester is preferable, and a type in which water resistance after drying of the coating film is improved by adding ammonium chloride at the time of coating film formation is preferable.
[0014]
Next, reference numeral 13 denotes a release layer which is mainly composed of polyvinyl alcohol which is a saponified product of polyvinyl acetate, and preferably has a saponification degree of 90% or more. When polyvinyl alcohol having a saponification degree of less than 90% is used, it is possible to use a mixture of a small amount of a water-soluble silicone resin as a release agent. However, polyvinyl alcohol having a saponification degree of less than 60% is difficult to use in terms of water resistance.
[0015]
Further, the mutual material selection of the release layer 13 and the adhesive layer 12 is also influenced by the adhesive force, and the adhesive strength is 1.5 g / cm at 90 ° peeling so as not to be peeled off at least by the conveying force in the electrophotographic apparatus. The above is preferable, and 4 g / cm or less is preferable so that the film is not torn when the retransfer film layer composed of the transfer layer 14 and the release layer 13 described later is peeled off from the substrate.
[0016]
Next, the transfer layer 14 will be described. This layer receives the toner image T by the electrophotographic apparatus, holds the toner image at least until it enters the retransfer process by heating, and has sufficient toner at the time of retransfer. It is required to have peeling performance. In addition, it is required to have sufficient water resistance as compared with the prior art. That is, it is necessary to have excellent water resistance while ensuring solvent permeability during retransfer. Specifically, polyvinyl alcohol obtained by saponifying 95% or more of polyvinyl acetate and polyvinyl alcohol saponified by 90% or less of polyvinyl acetate are mixed to form a transfer layer. The mixing ratio is preferably such that the content of polyvinyl alcohol with a high saponification degree of 95% or more is 10% by weight or more, more preferably 25% by weight or more, as a solid fraction. If it is less than 10% by weight, the water-soluble property, which is the property of low-degree polyvinyl alcohol of 90% or less, appears strongly, and the surface layer may melt out in a high-temperature environment, possibly contaminating the members in the electrophotographic apparatus. There is sex. Further, when the polyvinyl alcohol content of the high saponification degree exceeds 75% by weight, the arrangement of the linear polymer forming the film itself becomes more regular like the cellulose film, so that the film shrinks with respect to the change in the moisture content in the air. May become large. That is, the high saponification degree polyvinyl alcohol is more preferably 25 to 75% by weight as a solid content ratio. In addition, an inorganic white pigment such as silica powder may be added to the transfer layer 14 to ensure electrophotographic transferability.
[0017]
Regarding the film thickness of each layer, the adhesive layer 12 is preferably a thin layer so that split separation does not occur, and preferably 2 to 10 μm. If it is less than 2 μm, unevenness tends to occur, and if it exceeds 10 μm, delamination within the layer tends to occur.
[0018]
The release layer 13 has a role as a primer layer of the transfer layer 14 and a role of achieving sufficient peeling at the interface between this layer and the adhesive layer 12, and the thickness is preferably 2 to 6 μm. When the thickness exceeds 6 μm, the shrinkage due to moisture in this layer appears strongly and tends to cause curling, and when the thickness is less than 2 μm, unevenness tends to occur.
[0019]
The film thickness of the transfer layer 14 is preferably 10 μm or more. If it is thinner than this, insufficient strength such as tearing of the film at the time of peeling from the substrate tends to occur. Moreover, 50 micrometers or less are preferable. If it is thicker than this, the film after peeling becomes hard and the curved surface followability tends to be lowered at the time of retransfer.
[0020]
Next, the electrophotographic toner that can be applied to the transfer picture transfer material used in the present invention will be described in detail. Basically, it is used for electrophotography that contains binder resin mainly composed of resin such as styrene-acrylic copolymer, styrene-butadiene copolymer, epoxy, polyester, etc., in addition to carbon black, and dyes such as yellow, cyan, magenta. Color toner can be used. By using such a color toner, a color image can be formed. Among these, the color toners shown below are those that can bring out the effects of the color image forming method according to the present invention.
[0021]
The toner powder for color electrophotographic apparatus needs to have good meltability and color mixing property when heat is applied, and is preferably a sharp melt toner having a low softening point and a short melting time.
[0022]
By using the sharp melt toner, the color reproduction range of the copy can be widened, and a color copy faithful to the multicolor image of the original can be favorably obtained.
[0023]
Such sharp melt toners are produced by, for example, melt-kneading, pulverizing, and classifying a binder resin such as polyester resin or styrene-acrylic resin, a colorant (dye, sublimation dye), a charge control agent, and the like. . If necessary, an external addition step of adding various external additives to the toner may be added.
[0024]
In consideration of fixing property and sharp melt property, the color toner preferably uses a polyester resin as a binder resin. The sharp melt polyester resin is a polymer compound having an ester bond in the main chain of a molecule synthesized from a diol compound and a dicarboxylic acid. In particular, the following formula:
[Outside 1]

(In the formula, R is an ethylene or propylene group, x and y are each a positive integer of 1 or more, and the average value of x + y is 2 to 10) or a substituted product thereof A diol component and a carboxylic acid component comprising a divalent or higher carboxylic acid or its acid anhydride or its lower alkyl ester (for example, fumaric acid, maleic acid, maleic anhydride, phthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, A polyester resin obtained by cocondensation polymerization with merit acid or the like is more preferable because it has sharp melting characteristics.
[0026]
The softening point of the sharp melt polyester resin is preferably 60 to 120 ° C. FIG. 2 shows the softening point characteristics of a toner containing this sharp-melt polyester resin as a binder resin.
[0027]
After using a flow tester CFT-500 (manufactured by Shimadzu Corporation) with a die (nozzle) diameter of 0.5 mm and a thickness of 1.0 mm, an extrusion load of 50 kg was applied and the initial setting temperature was 80 ° C. and the preheating time was 300 seconds. A toner plunger drop-temperature curve (hereinafter referred to as a softened S-shaped curve) drawn when the temperature is increased at a constant rate of 5 ° C./min is obtained. The toner used as a sample is a fine powder precisely weighed 1 to 3 g, and the plunger cross-sectional area is 10 cm ² . The softened S-shaped curve is as shown in FIG. As the temperature rises at a constant speed, the toner is gradually heated and starts to flow out (plunger lowering A → B). When the temperature is further increased, the melted toner largely flows out (B → C → D), and the plunger lowering stops and ends (D → E).
[0028]
The height H of the S-shaped curve indicates the total outflow amount, and the temperature T ₀ corresponding to the point C of H / 2 indicates the softening point of the toner.
[0029]
Such sharp-melt toner or resin is defined as T ₁ when the melt viscosity is 10 ⁵ cp and T ₂ when the temperature is 5 × 10 ⁴ cp.
T ₁ = 90 to 150 ° C. | ΔT | = | T ₁ −T ₂ | = 5 to 30 ° C.
It means a resin that satisfies the following conditions.
[0030]
These sharp-melting toners or resins having temperature-melt viscosity characteristics are characterized by extremely sharp viscosity reduction when heated. Such a decrease in viscosity causes proper mixing of the uppermost toner layer and the lowermost toner layer, and further increases the transparency of the toner layer itself, thereby causing good subtractive color mixing.
[0031]
Next, the resin used on the transfer medium side according to the present invention will be described in detail. This resin needs to have the same or similar surface tension as the toner for forming a color image. Having the same surface tension as that of the toner means that the toner is easily attracted to the resin on the surface of the transfer material from the theory of surface wetting and adhesion (Zisman).
[0032]
As a selection range, for example, when a polyester resin is used as the binder resin of the toner, the surface tension is 20 dyne / cm. On the other hand, as the resin used on the surface of the transfer material side, a polyester resin having a surface tension of 20 ± 10 dyne / cm, a polytrifluoroethylene resin, a polyvinyl fluoride resin, an acrylic resin, an epoxy resin, a silicon resin, a fluorine resin, etc. Of these, resins that can be cured at room temperature or by heating can be used.
[0033]
The thickness of the resin layer provided on the transfer material side varies depending on the particle size of the toner used, but in order for the toner particles on the image to be transferred, the thickness is preferably ½ of the toner particle size. If it is thinner than this, the toner becomes difficult to transfer. However, when the toner particle diameter is larger than 3 times, the transfer material, the toner and the resin layer are easily separated separately.
[0034]
In the present invention, the average particle diameter of the toner is a value measured based on the following method.
[0035]
Using a Coulter Counter TA-II type (manufactured by Coulter) as a measuring device, connect an interface (manufactured by Nikka) and an CX-1 personal computer (manufactured by Canon) that output individual distribution, volume distribution, number average and volume average. As the electrolytic solution, a 1% NaCl aqueous solution is prepared using primary sodium chloride.
[0036]
As a measurement method, 0.1 to 5 ml of a surfactant, preferably alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the electric field aqueous solution, and 0.5 to 50 mg, preferably 2 to 20 mg of a measurement sample is further added.
[0037]
The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the particle size distribution of particles having a particle size of 2 to 40 μm is obtained using the 100 μm aperture as an aperture by the Coulter Counter TAII type. Measure to determine the volume average particle size.
[0038]
As a method for producing a resin layer having a surface tension comparable to that of the toner used in the present invention, a volatile organic solvent composed of alcohols such as methanol and ethanol or ketones such as methyl ethyl ketone and acetone on the transfer material is used. Dissolve the resin to form a resin layer with the same surface tension as that of the toner, apply it optimally from the shape of the transfer material, such as bar coating, dipping, spraying, and spin coating, and then dry There is a way to do it.
[0039]
(Example 1)
The softening point 110 ° C. defined by the point C on the softening point S-shaped curve obtained with the flow tester CFT-500 type (manufactured by Shimadzu Corporation) on the glossy surface side of the household tile (manufactured by INAX). A solution of a sharp melt polyester resin (surface tension of about 20 dyne / cm) dissolved in acetone was applied by spraying to form a resin layer having a thickness of 10 μm after drying.
[0040]
Next, an image is output by a Canon electrophotographic apparatus CLC700 onto the transfer layer 14 of the transfer picture transfer material 1 shown in FIG. 1, and the toner (average particle diameter 8 μm, binder resin surface tension 20 dyne / cm). The transfer layer 14 on which the toner image is placed and the release layer 13 provided so as to be easily peeled off from the adhesive layer 12 are peeled off from the base material 11, and the transfer object (transfer medium) is placed with the portion on which the toner image is placed facing down. ) On the transfer layer side. Then, hot pressing is performed at about 100 ° C. for 10 seconds. At that time, since air enters between the tile and the polyvinyl alcohol layer, the air on the surface is rubbed with sylbon paper or the like. These operations are repeated 2-3 times. After these operations are completed, the transfer layer 14 is softened with a mixed solution of about 20% water and about 80% ethyl alcohol. By doing so, about 100% of the toner image T was transferred to the tile of the transfer medium, and a sufficiently good image was obtained.
[0041]
The thickness and constituent materials of each layer of the transfer picture transfer material used are as follows.

[0042]
The surface tension of the resin layer is a value before the toner image is transferred.
[0043]
The surface tension of each resin of the resin layer, the toner binder resin and the transfer layer was measured using a wetting index standard solution (manufactured by Daikin Fine Chemical). That is, the resin to be measured is formed into a sheet, and a wetting index standard solution is dropped on the sheet with a dropper, and the contact angle (θ) of the droplet is measured. This measurement is performed in ascending order of the number of the wetting index standard solution, that is, in ascending order of the surface tension, and the results are plotted with the horizontal axis representing the surface tension value of the wetting index standard solution and the vertical axis representing cos θ. The resulting graph is a straight line that descends to the right.
From this straight line graph, the value when θ = 0, that is, the surface tension value of the exponential standard solution when cos θ = 1 was read and used as the surface tension of the resin.
[0044]
(Comparative Example 1)
Retransfer was performed in the same manner as in Example 1 except that the resin layer was not formed on the tile of the transfer medium. However, only 50% of the toner was transferred to the transfer medium side, and the toner was immediately peeled off at the transferred portion.
[0045]
(Example 2)
Retransfer was performed in the same manner as in Example 1 except that a layer of polytrifluorothien resin (surface tension 22 dyne / cm) was formed on the surface of the transfer medium. By doing so, about 100% of the toner image T was transferred to the tile of the transfer medium, and a sufficiently good image was obtained.
[0046]
(Comparative Example 2)
Retransfer is performed in the same manner as in Example 1 except that polyethylene terephthalate resin (surface tension 43 dyne / cm) is used on the surface of the transfer medium. Only 80% of the toner is transferred to the transfer side.
[0047]
(Example 3)
Retransfer was performed in the same manner as in Example 1 except that a styrene-acrylic resin (surface tension 30 dyne / cm) layer was formed on the surface of the transfer medium, and a styrene acrylic resin (surface tension 30 dyne / cm) was used as the toner binder resin. Went. By doing so, about 100% of the toner image T was transferred to the tile of the transfer medium, and a sufficiently good image was obtained.
[0048]
(Comparative Example 3)
Retransfer is performed in the same manner as in Example 3 except that a polyhexamethylene adipamide resin (surface tension 46 dyne / cm) layer is formed on the surface of the transfer medium. Only 80% of the toner was transferred to the transfer medium side.
[0049]
[Table 2]

[0051]
(Example 4)
Retransfer was performed in the same manner as in Example 1 except that a polyester resin (surface tension 20 dyne / cm) was formed on the surface of the transfer medium, and a styrene acrylic resin (surface tension 30 dyne / cm) was used as the toner binder resin. . By doing so, about 100% of the toner image T was transferred to the tile of the transfer medium, and a sufficiently good image was obtained.
[0052]
【The invention's effect】
As described above, in a color image forming method in which an image transferred by an electrophotographic method is once fixed on a transfer material having a polyvinyl alcohol layer on a support, and transferred to another transfer medium again, the surface of the transfer medium In addition, by providing a resin layer that has a surface tension close to that of the binder resin of the toner to be fixed than the surface tension of polyvinyl alcohol, it prevents transfer defects during retransfer and transfers a sufficiently good image. It can be formed on a medium.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a transfer picture transfer material used in the present invention.
FIG. 2 is a dissolution characteristic diagram of a toner preferably used in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Transfer picture transfer material 11 Base material 12 Adhesive layer 13 Release layer 14 Transfer layer T Toner image

Claims (4)

A toner image transferred by an electrophotographic method is once fixed on a transfer material having a polyvinyl alcohol layer on a support, and the toner image formed on the polyvinyl alcohol layer is placed on another transfer medium with the image side down. In an image forming method in which the polyvinyl alcohol layer is softened by applying heat and pressure again, and then the liquid is applied to transfer only the toner image to the transfer medium, on the surface of the transfer medium, the surface tension of the polyvinyl alcohol, A resin layer having a surface tension close to the surface tension of the binder resin of the toner to be fixed is provided, and the surface tension of the binder resin of the toner and the surface tension of the resin layer on the surface of the transfer medium The image forming method, wherein the difference is within 10 dyne / cm.   2. The image forming method according to claim 1, wherein the thickness of the resin layer is not less than half and not more than 3 times the average particle diameter of the toner.   The image forming method according to claim 1, wherein the polyvinyl alcohol layer is divided into a release layer and a transfer layer.   The image forming method according to claim 1, wherein the image transferred by electrophotography is a color image.

Images