JP3565242B2 - Electrophotographic carrier coating agent and electrophotographic carrier - Google Patents

Description

【００１２】
ここで、上記式（２）において、Ｒ^１としては、メチル基、エチル基、プロピル基、ブチル基、オクチル基、ヘキシル基等のアルキル基、フェニル基等のアリール基、ベンジル基等のアラルキル基、ビニル基、アリル基、プロペニル基、ブテニル基等のアルケニル基や、これら基の炭素原子に結合した水素原子の一部をフッ素原子、塩素原子等のハロゲン原子で置換した基、例えばトリフロロプロピル基等のハロゲン化アルキル基が挙げられ、好ましくはメチル基である。なお、ｎは典型的には３であることが好ましい。また、ｍはジオルガノシロキサン単位の繰り返し数を表わし、１〜１２０の整数、好ましくは１〜８０の整数である。ｍの値が１２０を超えると、ポリイミド樹脂が溶剤に対して十分な溶解性を示さなくなる。
【００１３】
上記式（２）の単位の量は、全Ｙ基に対して２〜５０モル％、好ましくは３〜３０モル％である。この単位の量が２モル％未満であると可撓性が失われ、キャリアとした時にスペント化が起る。また、５０モル％を超えるとフィルム強度が低下し、キャリアとした時に耐久性がなくなる。他方、残余の基である芳香環含有単位の割合は、全Ｙ基に対して９８〜５０モル％、好ましくは９７〜７０モル％である。
【００１４】
ポリイミド樹脂の重量平均分子量は、５，０００〜１５０，０００であることが好ましく、より好ましくは２０，０００〜１００，０００である。この重量平均分子量が小さすぎると、得られる硬化皮膜が十分な強度を示さず、逆に大きすぎると、ポリイミド樹脂の分子末端に存在するアミノ基、カルボン酸又は酸無水物基が加水分解して生成するカルボキシル基の量が減り、エポキシ樹脂と反応させることができず、硬化性及び耐溶剤性が低下する場合がある。
【００１５】
このポリイミド樹脂は、ポリイミド樹脂を合成するのに採用される従来公知の方法によればよく、例えば次のようにして製造することができる。
【００１６】
例えば、原料のテトラカルボン酸二無水物として下記のものを使用することができる。
【００１７】
【化５】

【００１８】
また、ジアミンとして、下記のジアミノシロキサン及び芳香族ジアミンを用いることができる。
【００１９】
【化６】

【００２０】
上記原料をシクロヘキサノン等の溶剤中に仕込み、低温、例えば２０〜４０℃程度で反応させてポリイミド樹脂の前駆体であるポリアミック酸を合成する。ここで、テトラカルボン酸二無水物成分に対するジアミン成分の割合は、ポリイミド樹脂の分子量の調整等に応じて適宜決められ、通常モル比で０．９５〜１．０５、好ましくは０．９８〜１．０２の範囲である。なお、ポリイミド樹脂の分子量を調整するために、無水フタル酸、アニリン等の一官能の原料を添加することも可能である。この場合の添加量はポリイミド樹脂の量に対して２モル％以下が好ましい。引き続き、得られたポリアミック酸溶液を、通常８０〜２００℃、好ましくは１４０〜１８０℃の温度範囲に昇温することにより、ポリアミック酸の酸アミド部分に脱水閉環反応を進行させ、ポリイミド樹脂を溶液として得ることができる。また、無水酢酸／ピリジン混合溶液をポリアミック酸溶液に添加し、次いで得られた溶液を５０℃前後に昇温し、イミド化を行う方法もある。
【００２１】
１分子中に２個以上のエポキシ基を含有する化合物
本発明に用いられる化合物としては、例えばエポキシ樹脂が挙げられる。エポキシ樹脂としては、特に下記式（３）で示されるビスフェノール型エポキシ樹脂及び下記式（４）で示されるエポキシ樹脂が挙げられ、これらは単独で用いても併用してもよい。
【００２２】
【化７】

【００２３】
上記エポキシ樹脂成分は、本発明のポリイミド樹脂成分と良好な相溶性を示す。また、触媒の存在下、比較的低温で該ポリイミド樹脂成分と反応硬化させることができ、キャリアとした時に良好な耐久性、環境安定性を示す。
【００２４】
エポキシ基含有化合物の配合量は、ポリイミド樹脂１００重量部に対して、通常０．１〜７０重量部であり、好ましくは５〜５０重量部である。エポキシ基含有化合物が少なすぎると、得られる硬化皮膜の耐溶剤性が十分には得られない。逆に多すぎると、該硬化皮膜の耐熱性がかえって低下する。
【００２５】
本発明のコーティング剤には、触媒を配合することができる。触媒としては、イミダゾール化合物が好ましく、特に下記一般式（５）で示されるイミダゾール化合物が好ましい。
【００２６】
【化８】

（式中、Ｒ^２は水素原子又は炭素数１〜２０の１価炭化水素基であり、ｑは１〜３の整数で、ｑが２又は３の場合、Ｒ^２は互いに同一でも異なっていてもよい。）
【００２７】
ここで、Ｒ^２の１価炭化水素基としては、メチル基、エチル基、プロピル基、ブチル基、ペンチル基、ヘキシル基、オクチル基、デシル基、ラウリル基、ミリスチル基、ステアリル基、ウンデシル基等の炭素数１〜２０のアルキル基、フェニル基等のアリール基を例示することができ、また、上記基の炭素原子に結合した水素原子の一部がヒドロキシ基により置換した基、例えばヒドロキシアルキル基を例示することもできる。
【００２８】
上記イミダゾール化合物の具体例としては、２−メチルイミダゾール、２−エチルイミダゾール、２−ウンデシルイミダゾール、２−エチル−４−メチルイミダゾール及び２−フェニル−４，５−ジヒドロキシメチルイミダゾール等が挙げられ、好ましくは２−メチルイミダゾール、２−エチルイミダゾール及び２−フェニル−４，５−ジヒドロキシメチルイミダゾールである。
【００２９】
該イミダゾール化合物の配合量は、ポリイミド樹脂１００重量部に対して、通常０．０５〜５重量部でよく、好ましくは０．１〜５重量部である。配合量が少なすぎると低温での硬化性が悪化する場合がある。逆に多すぎると本発明の組成物の保存安定性を悪化させたり、耐熱性を低下させたりするおそれがある。
【００３０】
本発明の組成物に使用される溶剤は、該組成物と相溶性のあるものであればよい。溶剤の具体的な例としては、テトラヒドロフラン、アニソール、ジグライム、トリグライム等のエーテル類；シクロヘキサノン、２−ブタノン、メチルイソブチルケトン、２−ヘプタノン、２−オクタノン、アセトフェノン等のケトン類；酢酸ブチル、安息香酸メチル、γ−ブチロラクトン、２−ヒドロキシプロパン酸メチル等のエステル類；ブチルセロソルブアセテート、プロピレングリコールモノメチルエーテルアセテート等のセロソルブ類；Ｎ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジメチルアセトアミド、Ｎ−メチル−２−ピロリドン等のアミド類及びトルエン、キシレン等の芳香族炭化水素類などが挙げられ、好ましくはケトン類、エステル類及びセロソルブ類であり、特に好ましくはシクロヘキサノン、γ−ブチロラクトン、プロピレングリコールモノメチルエーテルアセテート、ｎ−メチル−２−ピロリドンである。これらの溶剤は、１種単独でも２種以上組み合わせて用いてもよい。
【００３１】
本発明の組成物に含まれる溶剤の量は、樹脂の溶解性、塗布時の作業性、皮膜の厚み等を考慮して、通常、ポリイミド樹脂の濃度が１〜４０重量％となる範囲で調整される。保存の際には比較的高濃度で調整しておき、使用の際に適度の濃度に希釈してもよい。
【００３２】
本発明のコーティング剤は、電子写真キャリア用として用いられ、キャリア核粒子の表面に被覆硬化するものである。
【００３３】
ここで、本発明において使用されるキャリア核粒子としては、鉄粉又はフェライト粉が代表的なものであるが、その他、ニッケル、コバルト等の磁性金属又はその酸化物、銅、カーボランダム、ガラスビーズ、二酸化ケイ素等、キャリア核粒子の素材として公知のものの中から選択して用いることができる。
【００３４】
キャリア核粒子の粒子径は、１０〜１，０００μｍ、好ましくは２０〜３００μｍである。
【００３５】
本発明においては、上記コーティング剤を、必要であれば有機溶剤に溶解した後、例えば流動下ベット法、浸漬法、スプレー法等によってキャリア核粒子上に塗布し、次いで乾燥、硬化せしめる。被覆層の膜厚は０．１〜２０μｍであることが好ましい。必要により重ね塗りすることも可能であり、目的によっては各層の成分を変えて重ね塗りすることもできる。
【００３６】
本発明のシリコーンポリイミド樹脂組成物溶液は、従来のポリアミック酸溶液と異なり、塗布後に３００℃以上という高温でかつ長時間の加熱を必要としない。例えば、該ポリイミド樹脂組成物溶液を基材に塗布後、１５０〜２００℃の温度で１０分〜４時間加熱すれば、溶剤を完全に除去し、かつ硬化させ、ポリイミド樹脂硬化皮膜を得ることができる。
【００３７】
本発明のコーティング剤は、低温での硬化で皮膜を得ることができることから、乾燥性に優れるのでキャリアコート剤として使用した場合にブロッキングもなく、作業性に優れる。
【００３８】
なお、現像剤として、キャリアと共に使用されるトナーについては特に制限がなく、天然樹脂、天然及び合成樹脂を組み合わせた改良剤を含む広い材料に、既知の各種合成染料類を分散させて製造したものを使用することができる。
【００３９】
【発明の効果】
本発明の電子写真キャリア用コーティング剤は、従来公知のポリイミドよりも低温硬化可能で乾燥性に優れ、しかも高硬度であり、かつ可撓性に富む。そして、この電子写真キャリア用コーティング剤を用いた電子写真用キャリアは、乾燥性に優れるのでブロッキングもなく、帯電量が高く、チャージアップがなく、安定な帯電特性を有する。また、可撓性に優れるので耐久性、密着性も良好である。
【００４０】
【実施例】
以下、合成例及び実施例と比較例を示し、本発明を具体的に説明するが、本発明は下記の実施例に制限されるものではない。
【００４１】
〔合成例１〕
撹拌機、温度計及び窒素置換装置を備えたフラスコ内に、３，３’，４，４’−ジフェニルスルホンテトラカルボン酸二無水物３５．８ｇ（０．１モル）及びシクロヘキサノン４００ｇを仕込んだ。次いで、下記式（ｉ）で示されるジアミノシロキサン１６．８ｇ（０．０２モル）、４，４’−（３，３’−ジヒドロキシ）ジアミノビフェニル１０．９９ｇ（０．０５モル）及び２，２−ビス［４−（４−アミノフェノキシ）フェニル］プロパン１２．３ｇ（０．０３モル）をシクロヘキサノン１００ｇに溶解した溶液を反応系の温度が５０℃を超えないように調節しながら、上記フラスコ内に滴下した。滴下終了後、更に室温で１０時間撹拌した。
【００４２】
次に、該フラスコに水分受容器付き還流冷却器を取り付けた後、キシレン３０ｇを加え、１５０℃に昇温させてその温度を６時間保持し、シリコーンを含有するポリイミド樹脂溶液（Ｉ）を得た。
【００４３】
【化９】

【００４４】
この溶液（Ｉ）に、該溶液（Ｉ）中の固形分１００ｇに対して下記式（ｉｉ）のエポキシ樹脂１８ｇを混合し、ヘキサノンで固形分２重量％に調整し、電子写真キャリア用コーティング剤（１）を得た。
【００４５】
【化１０】

【００４６】
〔合成例２〕
合成例１で得られたシリコーンを含有するポリイミド樹脂溶液（Ｉ）に、この溶液中の固形分１００ｇに対して、下記式（ｉｉｉ）で示されるエポキシ樹脂５８ｇ、２−メチルイミダゾール１ｇを混合し、シクロヘキサノンで固形分２重量％に調整し、シリコーンを含有する電子写真キャリア用コーティング剤（２）を得た。
【００４７】
【化１１】

【００４８】
〔合成例３〕
撹拌機、温度計及び窒素置換装置を備えたフラスコ内に、３，３’，４，４’−ジフェニルスルホンテトラカルボン酸二無水物３５．８ｇ（０．１モル）及びシクロヘキサノン４００ｇを仕込んだ。次いで、上記式（ｉ）のジアミノシロキサン１６．８ｇ（０．０２モル）、４，４’−（３，３’−ジヒドロキシ）ジアミノビフェニル５．５ｇ（０．０２５モル）及び２，２−ビス［４−（４−アミノフェノキシ）フェニル］プロパン２２．６ｇ（０．０５５モル）をシクロヘキサノン１００ｇに溶解した溶液を反応系の温度が５０℃を超えないように調節しながら、上記フラスコ内に滴下した。滴下終了後、更に室温で１０時間撹拌した。
【００４９】
次に、該フラスコに水分受容器付き還流冷却器を取り付けた後、キシレン３０ｇを加え、１５０℃に昇温させてその温度を６時間保持し、シリコーンを含有するポリイミド樹脂溶液（ＩＩ）を得た。
【００５０】
この溶液（ＩＩ）に、その固形分１００ｇに対して上記式（ｉｉ）のエポキシ樹脂９ｇを混合し、シクロヘキサノンで固形分２重量％に調整し、電子写真キャリア用コーティング剤（３）を得た。
【００５１】
〔合成例４〕
合成例１で得られたシリコーンを含有するポリイミド樹脂（Ｉ）をシクロヘキサノンで固形分２重量％に調整し、電子写真キャリア用コーティング剤（４）（比較例）を得た。
【００５２】
〔合成例５〕
撹拌機、温度計及び窒素置換装置を備えたフラスコ内に、メチルトリメトキシシラン４０８ｇ（３．０モル）を入れ、１０℃以下でトルエン１５４．７ｇ、メタンスルホン酸１０．１ｇを加え、よく混合させた。そこに、水９７．２ｇを６０分間で滴下し、加水分解を行った。滴下終了後、室温で５時間撹拌した。メタンスルホン酸を中和後、加水分解で生成したメタノールを留去した。水洗、脱水を経て、無色透明のシリコーン溶液を得た。この溶液中の固形分４０ｇに対して、メチルトリス（メチルエチルケトオキシム）シラン１２重量部、ジブチルスズジオクトエートの５０％キシレン溶液０．４重量部を混合し、溶剤揮発油、トルエンで不揮発分２重量％に調整し、電子写真キャリア用コーティング剤（５）（比較例）を得た。
【００５３】
〔実施例，比較例〕
合成例で得られたコーティング剤を、キャリア核粒子として平均粒子径１００μｍのフェライト１ｋｇを流動床を用いて９０℃で３０分間かけて塗布した。その後、２００℃で３０分間加熱して、キャリア材を調製した。
【００５４】
キャリア材９５重量部に負帯電型トナー（黒）５重量部を加えてポリビン中で振盪（振盪幅５０ｍｍ，振盪速度２００回／ｍｉｎ）帯電させた後、ブローオフ粉体帯電量測定装置（東芝ケミカル（株）製）によりトナー帯電量を測定した。その結果を表１に示す。
【００５５】
【表１】

【００５６】
表１の結果より、本発明にかかるシリコーンを含有するポリイミドとエポキシ樹脂からなるコーティング剤を塗布したものは、負帯電性トナーに対して高帯電を示した。これに対し、エポキシ樹脂を含まない比較例１やシリコーン樹脂からなる比較例２は帯電しなかった。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a coating agent for an electrophotographic carrier and an electrophotographic carrier using the same.
[0002]
Problems to be solved by the prior art and the invention
The developer of a two-component dry copying machine is composed of two components, a fine toner and a larger carrier, and the toner and the carrier are electrostatically charged to different signs by friction caused by mixing and stirring the two. . A visible image is formed by electrostatically attaching the charged toner to the electrostatic latent image formed on the photoreceptor, and copying is achieved by transferring and fixing this image to a transfer sheet. You. As the carrier in this case, oxidized or unoxidized iron powder is usually used. However, if this is used as it is when mixed with the toner, the triboelectric charging characteristics for the toner are insufficient, and The toner adheres to the surface of the carrier to form a toner film (spent), so that the charging characteristics of the carrier change with time, resulting in a short life of the developer. Further, there is a disadvantage that the difference in the charging characteristics of the carrier is large between dry and wet conditions.
[0003]
In order to prevent such defects, the carrier surface is coated with a resin such as an acrylic resin, a styrene-acryl copolymer, a silicone resin, a polyester, and a fluororesin. Among them, silicone resins, fluororesins, and the like have attracted attention because they have a low surface energy and can reduce the spent phenomenon. In particular, in the case of silicone resin, since it can be dissolved in various solvents and various molecular structures can be formed by selecting a monomer, a carrier having various charge amount levels depending on the selection, the third component, and the processing conditions. There is an advantage that can be made. For example, charging is performed by a method of curing a room-temperature moisture-curable silicone resin at a high temperature (Japanese Patent Publication No. 62-61948) or a silicone resin containing a tin compound (Japanese Patent Publication No. 2-3181, Japanese Patent Publication No. 6-1392). Methods for controlling the amount have been proposed. However, these methods have a problem that although a high charge amount can be obtained for a positively chargeable toner, a sufficient charge amount cannot be obtained for a negatively chargeable toner.
[0004]
In order to solve such a problem, a silicone resin containing a nitrogen-containing resin or an aminosilane (Japanese Patent Application Laid-Open No. 55-127569), or a silicone resin reacted or mixed with an organic resin (Japanese Patent Publication No. 59-8827, Japanese Patent Publication No. 62-23308, JP-A-56-140358 and JP-A-59-228261) have been proposed. However, these have a problem that the charge amount is not stable and the durability is poor.
[0005]
Further, a method using a special silicone polyimide has been proposed (JP-A-61-231566). When this method is used, the stability and durability of the charge amount are superior to those of a nitrogen-containing resin, a silicone resin containing an aminosilane, or a silicone resin reacted or mixed with an organic resin, but are still sufficient. I can't say. In addition, this silicone polyimide uses an inexpensive norbornane-terminated polydiorganosiloxane as a raw material and is difficult to industrialize. Further, there is a problem that the curability, especially the drying property at a low temperature is poor, blocking occurs, and coating is difficult.
[0006]
The present invention is an improvement over the above circumstances, and has a high charge level, prevents charge-up (change in charge amount with time), does not cause spent, stabilizes the charge amount, and is particularly suitable for negatively chargeable toner. An object of the present invention is to provide an electrophotographic carrier coating agent capable of providing an electrophotographic carrier having a high charge level and an electrophotographic carrier using the same.
[0007]
Means for Solving the Problems and Embodiments of the Invention
The present inventors have conducted intensive studies to achieve the above object, and as a result, a polyimide resin having a repeating unit containing a diorganosiloxy group, particularly a silicone polyimide comprising a repeating unit represented by the formula (1) described below, When a curable resin composition containing an epoxy compound containing two or more epoxy groups in one molecule as a main component is used as a coating agent for an electrophotographic carrier, the charge amount is stable and low-temperature curing is possible. It has excellent drying properties, high hardness, and high flexibility, and has no problem in industrial production. As it has excellent drying properties, there is no blocking, the charge level is high even for negatively chargeable toner, and there is no charge-up, and it is stable. Has a charging characteristics, environmental characteristics, and finding flexibility, durability, that adhesion is good, the present invention has been accomplished.
[0008]
That is, the present invention
(A) A polyimide resin having a repeating unit containing a diorganosiloxy group represented by the following formula (1) : 100 parts by weight (B) a bisphenol-type epoxy resin represented by the following formula (3), a following formula (4) in is selected from epoxy resins represented, compounds having two or more epoxy groups in one molecule: 0.1 to 70 parts by weight electrophotographic carrier coating agent composed mainly of, and the carrier core the coating agent Provided is an electrophotographic carrier obtained by coating and curing the surface of a particle.
[0009]
Hereinafter, the present invention will be described in more detail.
The electrophotographic carrier coating agent of the present invention, as described above,
(A) A polyimide resin having a repeating unit containing a diorganosiloxy group (B) A compound containing two or more epoxy groups in one molecule as a main component.
[0010]
The polyimide resin of the polyimide resin (A) component is a resin obtained by introducing a diorganosiloxy group into its repeating unit, and specifically, a resin comprising a repeating unit represented by the following general formula (1) is preferable.
[0011]
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[0012]
Here, in the above formula (2), R ¹ represents an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, an octyl group, a hexyl group, an aryl group such as a phenyl group, and an aralkyl group such as a benzyl group. Alkenyl groups such as vinyl group, allyl group, propenyl group and butenyl group, and groups in which some of the hydrogen atoms bonded to carbon atoms of these groups have been substituted with halogen atoms such as fluorine atoms and chlorine atoms, for example, trifluoropropyl And a halogenated alkyl group such as a group, preferably a methyl group. Note that it is typically preferable that n is 3. M represents the number of repeating diorganosiloxane units, and is an integer of 1 to 120, preferably an integer of 1 to 80. If the value of m exceeds 120, the polyimide resin will not show sufficient solubility in a solvent.
[0013]
The amount of the unit of the above formula (2) is 2 to 50 mol%, preferably 3 to 30 mol%, based on all Y groups. When the amount of this unit is less than 2 mol%, flexibility is lost, and spent is caused when used as a carrier. On the other hand, if it exceeds 50 mol%, the film strength is reduced, and the durability of the carrier is lost. On the other hand, the proportion of the aromatic ring-containing unit as the remaining group is 98 to 50 mol%, preferably 97 to 70 mol%, based on all the Y groups.
[0014]
The weight average molecular weight of the polyimide resin is preferably from 5,000 to 150,000, and more preferably from 20,000 to 100,000. If the weight average molecular weight is too small, the cured film obtained does not show sufficient strength, and if it is too large, the amino group, carboxylic acid or acid anhydride group present at the molecular terminal of the polyimide resin is hydrolyzed. The amount of the generated carboxyl group may decrease, and the carboxyl group may not react with the epoxy resin, and the curability and the solvent resistance may decrease.
[0015]
This polyimide resin may be according to a conventionally known method employed for synthesizing the polyimide resin, and can be produced, for example, as follows.
[0016]
For example, the following can be used as the raw material tetracarboxylic dianhydride.
[0017]
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[0018]
Further, the following diaminosiloxane and aromatic diamine can be used as the diamine.
[0019]
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[0020]
The above raw materials are charged into a solvent such as cyclohexanone and reacted at a low temperature, for example, at about 20 to 40 ° C. to synthesize a polyamic acid which is a precursor of a polyimide resin. Here, the ratio of the diamine component to the tetracarboxylic dianhydride component is appropriately determined according to the adjustment of the molecular weight of the polyimide resin and the like, and is usually 0.95 to 1.05, preferably 0.98 to 1 in molar ratio. .02. In addition, in order to adjust the molecular weight of the polyimide resin, it is also possible to add a monofunctional raw material such as phthalic anhydride or aniline. In this case, the addition amount is preferably 2 mol% or less based on the amount of the polyimide resin. Subsequently, the resulting polyamic acid solution is heated to a temperature range of usually 80 to 200 ° C., preferably 140 to 180 ° C., so that a dehydration ring-closing reaction proceeds to the acid amide portion of the polyamic acid, and the polyimide resin is dissolved. Can be obtained as There is also a method in which an acetic anhydride / pyridine mixed solution is added to a polyamic acid solution, and then the resulting solution is heated to about 50 ° C. to perform imidization.
[0021]
Compound containing two or more epoxy groups in one molecule Examples of the compound used in the present invention include an epoxy resin. Examples of the epoxy resin include a bisphenol-type epoxy resin represented by the following formula (3) and an epoxy resin represented by the following formula (4), and these may be used alone or in combination.
[0022]
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[0023]
The epoxy resin component shows good compatibility with the polyimide resin component of the present invention. In addition, it can be cured by reacting with the polyimide resin component at a relatively low temperature in the presence of a catalyst, and exhibits good durability and environmental stability when used as a carrier.
[0024]
The compounding amount of the epoxy group-containing compound is usually 0.1 to 70 parts by weight, preferably 5 to 50 parts by weight, based on 100 parts by weight of the polyimide resin. If the amount of the epoxy group-containing compound is too small, the resulting cured film cannot have sufficient solvent resistance. Conversely, if the amount is too large, the heat resistance of the cured film is rather lowered.
[0025]
The coating agent of the present invention may contain a catalyst. As the catalyst, an imidazole compound is preferable, and particularly, an imidazole compound represented by the following general formula (5) is preferable.
[0026]
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(Wherein, R ² is a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms, q is an integer of 1 to 3, and when q is 2 or 3, R ² is the same or different. May be.)
[0027]
Here, the monovalent hydrocarbon group for R ² includes a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a decyl group, a lauryl group, a myristyl group, a stearyl group, an undecyl group, and the like. And an aryl group such as an alkyl group having 1 to 20 carbon atoms and a phenyl group, and a group in which part of the hydrogen atoms bonded to the carbon atoms of the above group is substituted with a hydroxy group, for example, a hydroxyalkyl group Can also be exemplified.
[0028]
Specific examples of the imidazole compound include 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, and the like. Preferred are 2-methylimidazole, 2-ethylimidazole and 2-phenyl-4,5-dihydroxymethylimidazole.
[0029]
The compounding amount of the imidazole compound may be generally 0.05 to 5 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the polyimide resin. If the amount is too small, the curability at low temperatures may deteriorate. Conversely, if the amount is too large, the storage stability of the composition of the present invention may be deteriorated, or the heat resistance may be lowered.
[0030]
The solvent used in the composition of the present invention may be any solvent that is compatible with the composition. Specific examples of the solvent include ethers such as tetrahydrofuran, anisole, diglyme, and triglyme; ketones such as cyclohexanone, 2-butanone, methyl isobutyl ketone, 2-heptanone, 2-octanone, and acetophenone; butyl acetate and benzoic acid Esters such as methyl, γ-butyrolactone, methyl 2-hydroxypropanoate; cellosolves such as butyl cellosolve acetate, propylene glycol monomethyl ether acetate; N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2- Examples thereof include amides such as pyrrolidone and aromatic hydrocarbons such as toluene and xylene. Ketones, esters and cellosolves are preferred, and cyclohexanone, γ-butyrolactone, and Pyrene glycol monomethyl ether acetate, n-methyl-2-pyrrolidone. These solvents may be used alone or in combination of two or more.
[0031]
The amount of the solvent contained in the composition of the present invention is usually adjusted in a range where the concentration of the polyimide resin is 1 to 40% by weight in consideration of the solubility of the resin, the workability at the time of application, the thickness of the film, and the like. Is done. It may be adjusted at a relatively high concentration during storage and diluted to an appropriate concentration at the time of use.
[0032]
The coating agent of the present invention is used for an electrophotographic carrier, and coats and cures the surface of carrier core particles.
[0033]
Here, as the carrier core particles used in the present invention, iron powder or ferrite powder is a typical one, but in addition, nickel, a magnetic metal such as cobalt or an oxide thereof, copper, carborundum, glass beads , Silicon dioxide and the like can be used by selecting from known materials for carrier core particles.
[0034]
The particle diameter of the carrier core particles is 10 to 1,000 μm, preferably 20 to 300 μm.
[0035]
In the present invention, the coating agent is dissolved in an organic solvent, if necessary, and then applied on carrier core particles by, for example, a fluidized bed method, an immersion method, a spray method, and the like, and then dried and cured. The thickness of the coating layer is preferably 0.1 to 20 μm. If necessary, over-coating is possible, and depending on the purpose, it is also possible to change the components of each layer and over-coat.
[0036]
Unlike the conventional polyamic acid solution, the silicone polyimide resin composition solution of the present invention does not require heating at a high temperature of 300 ° C. or more after coating for a long time. For example, if the polyimide resin composition solution is applied to a substrate and heated at a temperature of 150 to 200 ° C. for 10 minutes to 4 hours, the solvent can be completely removed and cured to obtain a cured polyimide resin film. it can.
[0037]
Since the coating agent of the present invention can obtain a film by curing at a low temperature, it is excellent in drying property, so that when used as a carrier coating agent, there is no blocking and excellent workability.
[0038]
There is no particular limitation on the toner used with the carrier as a developer, and the toner is manufactured by dispersing various known synthetic dyes in a wide range of materials including a natural resin, a modifier combining natural and synthetic resins. Can be used.
[0039]
【The invention's effect】
The coating agent for an electrophotographic carrier of the present invention can be cured at a lower temperature, has better drying properties, has higher hardness, and is more flexible than conventionally known polyimides. An electrophotographic carrier using the coating agent for an electrophotographic carrier has excellent drying properties, has no blocking, has a high charge amount, has no charge-up, and has stable charging characteristics. In addition, since it is excellent in flexibility, durability and adhesion are also good.
[0040]
【Example】
Hereinafter, the present invention will be described specifically with reference to Synthesis Examples, Examples, and Comparative Examples, but the present invention is not limited to the following Examples.
[0041]
[Synthesis Example 1]
In a flask equipped with a stirrer, a thermometer and a nitrogen purging apparatus, 35.8 g (0.1 mol) of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride and 400 g of cyclohexanone were charged. Next, 16.8 g (0.02 mol) of diaminosiloxane represented by the following formula (i), 10.99 g (0.05 mol) of 4,4 ′-(3,3′-dihydroxy) diaminobiphenyl and 2,2 A solution prepared by dissolving 12.3 g (0.03 mol) of bis [4- (4-aminophenoxy) phenyl] propane in 100 g of cyclohexanone was adjusted so that the temperature of the reaction system did not exceed 50 ° C. Was dropped. After completion of the dropwise addition, the mixture was further stirred at room temperature for 10 hours.
[0042]
Next, after attaching a reflux condenser with a water receiver to the flask, 30 g of xylene was added, the temperature was raised to 150 ° C., and the temperature was maintained for 6 hours to obtain a polyimide resin solution (I) containing silicone. Was.
[0043]
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[0044]
To this solution (I), 18 g of an epoxy resin of the following formula (ii) was mixed with 100 g of the solid content in the solution (I), and the solid content was adjusted to 2% by weight with hexanone. (1) was obtained.
[0045]
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[0046]
[Synthesis Example 2]
To the silicone-containing polyimide resin solution (I) obtained in Synthesis Example 1, 58 g of an epoxy resin represented by the following formula (iii) and 1 g of 2-methylimidazole were mixed with 100 g of a solid content in the solution. The solid content was adjusted to 2% by weight with cyclohexanone to obtain a coating agent (2) for an electrophotographic carrier containing silicone.
[0047]
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[0048]
[Synthesis Example 3]
In a flask equipped with a stirrer, a thermometer and a nitrogen purging apparatus, 35.8 g (0.1 mol) of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride and 400 g of cyclohexanone were charged. Then, 16.8 g (0.02 mol) of diaminosiloxane of the above formula (i), 5.5 g (0.025 mol) of 4,4 ′-(3,3′-dihydroxy) diaminobiphenyl and 2,2-bis A solution prepared by dissolving 22.6 g (0.055 mol) of [4- (4-aminophenoxy) phenyl] propane in 100 g of cyclohexanone was dropped into the flask while controlling the temperature of the reaction system so as not to exceed 50 ° C. did. After completion of the dropwise addition, the mixture was further stirred at room temperature for 10 hours.
[0049]
Next, after attaching a reflux condenser with a water receiver to the flask, 30 g of xylene was added, the temperature was raised to 150 ° C., and the temperature was maintained for 6 hours to obtain a polyimide resin solution (II) containing silicone. Was.
[0050]
To this solution (II), 9 g of the epoxy resin of the above formula (ii) was mixed with 100 g of the solid content, and the solid content was adjusted to 2% by weight with cyclohexanone to obtain an electrophotographic carrier coating agent (3). .
[0051]
[Synthesis Example 4]
The silicone-containing polyimide resin (I) obtained in Synthesis Example 1 was adjusted to a solid content of 2% by weight with cyclohexanone to obtain an electrophotographic carrier coating agent (4) (Comparative Example).
[0052]
[Synthesis Example 5]
In a flask equipped with a stirrer, a thermometer, and a nitrogen purge device, 408 g (3.0 mol) of methyltrimethoxysilane is added, and at 10 ° C. or lower, 154.7 g of toluene and 10.1 g of methanesulfonic acid are added, and mixed well. I let it. Thereto, 97.2 g of water was added dropwise over 60 minutes to effect hydrolysis. After completion of the dropwise addition, the mixture was stirred at room temperature for 5 hours. After neutralizing methanesulfonic acid, methanol generated by hydrolysis was distilled off. After washing with water and dehydration, a colorless and transparent silicone solution was obtained. 12 parts by weight of methyltris (methylethylketoxime) silane and 0.4 part by weight of a 50% xylene solution of dibutyltin dioctoate were mixed with 40 g of a solid content in this solution, and a 2% by weight of volatile matter in a solvent and 2% by weight of toluene was used. To obtain a coating agent for an electrophotographic carrier (5) (Comparative Example).
[0053]
[Examples and comparative examples]
The coating agent obtained in the synthesis example was applied as carrier core particles by applying 1 kg of ferrite having an average particle diameter of 100 μm at 90 ° C. for 30 minutes using a fluidized bed. Then, it heated at 200 degreeC for 30 minutes, and prepared the carrier material.
[0054]
5 parts by weight of a negatively charged toner (black) was added to 95 parts by weight of a carrier material, and the mixture was shaken (shaking width: 50 mm, shaking speed: 200 times / min) in a polybin, and then a blow-off powder charge amount measuring device (Toshiba Chemical Corporation) (Manufactured by Co., Ltd.). Table 1 shows the results.
[0055]
[Table 1]

[0056]
From the results shown in Table 1, it was found that the coating obtained by applying the coating agent comprising the silicone-containing polyimide and the epoxy resin according to the present invention exhibited high charge to the negatively chargeable toner. In contrast, Comparative Example 1 containing no epoxy resin and Comparative Example 2 consisting of a silicone resin were not charged.

Claims (3)

(A) a polyimide resin having a diorganosiloxy group-containing repeating unit represented by the following formula (1) : 100 parts by weight

(B) a compound containing two or more epoxy groups in one molecule selected from a bisphenol-type epoxy resin represented by the following formula (3) and an epoxy resin represented by the following formula (4) : 0.1 to 70 wt. Department

A coating agent for an electrophotographic carrier, comprising as a main component. As the catalyst, the following general formula (5)

(Wherein, R ² is a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms, q is an integer of 1 to 3, and when q is 2 or 3, even if R ² is the same or different, May be.)
The coating agent according to claim 1 formulated 0.05-5 parts by weight of imidazole compound per 100 weight parts component (A) represented in. Claim 1 or 2 electrophotographic carrier obtained by coating curing a coating agent for electrophotographic carrier according to the surface of the carrier core particles.