JP2004168794A - Ink composition, recording method and recorded image using it, and ink set and ink head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition which, when used in an inkjet recording method, shows an excellent ejection stability and gives a high-quality recorded image, to provide a recording method and a recorded image using it, and to provide an ink set and an ink head. <P>SOLUTION: The ink composition 60 is produced by the addition of a surfactant in which the difference d (=σ<SB>10</SB>-γ) between the dynamic surface tension (σ<SB>10</SB>) of a solution obtained by dissolving 0.1 wt.% surfactant in deionized water measured at 24 to 26°C by a maximum bubble pressure method at a bubble frequency of 10 Hz and the static surface tension γ measured at 24-26°C is 0-15 mN/m. The image is recorded by adhering liquid drops of the ink composition to a recording substrate by pressurizing the ink composition 60, fed from the ink tank 50 of an ink head to an ink chamber 40, by applying a voltage to a diaphragm 12 made of a piezoelectric material to thereby eject the liquid drops from an ejection port 31. <P>COPYRIGHT: (C)2004,JPO

Description

【００７５】
【化２】

【００７６】
【化３】

【００７７】
【化４】

【００７８】
【化５】

【００７９】
【化６】

【００８０】
前記一般式（Ｉ）において、ｍは０〜３０の整数または小数を示し、ｎは０〜３０の整数または小数を示す。ただし、ｍとｎとの和（ｍ＋ｎ）は、０〜３０の整数または小数である。
【００８１】
前記一般式（ＩＩ）において、ｋは１１〜１３の整数または小数を示し、ｌは３〜３０の整数または小数を示す。
【００８２】
前記一般式（ＩＩＩ）において、ｈは０〜１１の整数または小数を示し、ｉは０〜１１の整数または小数を示し、ｊは３〜５０の整数または小数を示す。ただし、ｈとｉとの和（ｈ＋ｉ）は、９〜１１の整数または小数である。
【００８３】
前記一般式（ＩＶ）において、ｗは０〜１１の整数または小数を示し、ｘは５〜９の整数または小数を示し、ｙは２．５〜５の整数または小数を示し、ｚは０〜９の整数または小数を示す。ただし、ｗとｚとの和（ｗ＋ｚ）は、９〜１１の整数または小数である。
【００８４】
前記一般式（Ｖ）において、ｐは０〜７８の整数または小数を示し、ｑは２〜１５の整数または小数を示し、ｒは０〜１８の整数または小数を示す。
【００８５】
前記一般式（ＶＩ）において、ｓは０〜３０の整数または小数を示し、ｔは０〜３０の整数または小数を示す。ただし、ｓとｔとの和（ｓ＋ｔ）は、０〜３０の整数または小数である。また、ｕは０〜１０の整数または小数を示し、ｖは０〜１０の整数または小数を示す。ただし、ｕとｖとの和（ｕ＋ｖ）は、０〜１０の整数または小数である。
【００８６】
前述の界面活性剤の中でも、非イオン系界面活性剤は、共存する電解質の影響を受けにくく、インク組成物に電解質が添加されるか否かに関わらず、界面活性剤によって制御される前述のインク組成物の動的表面張力と静的表面張力との関係を好適なものにすることができるので、これを界面活性剤に用いることが好ましい。
【００８７】
前述の条件を満足する界面活性剤は、インク組成物中に臨界ミセル濃度以上含まれることが好ましい。界面活性剤を含有する溶液の表面張力は、臨界ミセル濃度までは界面活性剤の増加に伴って低下するけれども、臨界ミセル濃度以上ではほぼ一定である。したがって、前述のように界面活性剤を臨界ミセル濃度以上含有させることによって、界面活性剤の効果を充分に発揮させ、界面活性剤によって制御される前述のインク組成物の動的表面張力および静的表面張力をそれぞれほぼ一定の値にすることができるので、均一な性質を有するインク組成物を得ることができる。
【００８８】
臨界ミセル濃度は、各界面活性剤で異なるけれども、非イオン系界面活性剤、アニオン系界面活性剤、カチオン系界面活性剤および両性界面活性剤のいずれの場合にも、２５℃において、０．００１重量％〜３重量％程度である。
【００８９】
本実施の形態のインク組成物は、前述の条件を満足する界面活性剤だけでなく、前述の条件を満足しない他の界面活性剤を含有してもよい。
【００９０】
また、本実施の形態のインク組成物は、前述のように水を含有する。このことによって、吸収性の被記録材上における滲みを抑え、乾燥性を向上させることができる。
【００９１】
インク組成物中の水の含有量は、３０重量％以上９５重量％以下であることが好ましく、より好ましくは３０重量％以上８５重量％以下である。水の含有量が３０重量％未満であると、インク組成物中の有機溶媒の含有量が多くなり過ぎるので、水に溶解または分散するような添加剤をインク組成物中に安定に存在させることが困難になる。また粘度の上昇が著しく、インク組成物としての適正粘度から外れることがある。水の含有量が９５重量％を超えると、有機溶媒の含有量が少なくなり過ぎるので、インク組成物の湿潤性を保つことができなくなる。したがって、３０重量％以上９５重量％以下とした。
【００９２】
有機溶媒の具体例としては、たとえば、ジメチルホルムアミドおよびジメチルアセトアミドなどのアミド類、ポリエチレングリコール、ポリプロピレングリコール、エチレングリコール、ジエチレングリコール、チオジグリコール、プロピレングリコール、トリエチレングリコール、１，５−ペンタンジオール、１，４−ブタンジオール、１，２−ヘキサンジオール、１，３−プロパンジオール、グリセリンおよび１，２，６−ヘキサントリオールなどの多価アルコール類、エチレングリコールモノメチルエーテル、エチレングリコールモノブチルエーテル、ジエチレングリコールモノメチルエーテル、ジエチレングリコールモノエチルエーテル、トリエチレングリコールモノブチルエーテル、プロピレングリコールモノエチルエーテル、テトラエチレングリコールモノメチルエーテルおよびエチレングリコールモノフェニルエーテルなどのグリコールエーテル類などの多価アルコールのエーテル類、スルホランおよびジメチルスルホキシドなどの硫黄含有化合物、２−ピロリドン、Ｎ−メチルピロリドンおよびε−カプロラクタムなどの窒素含有化合物、γ−ブチロラクトンなどの酸素含有化合物、ならびにジメチルアミノエタノール、ジエチルアミノエタノール、トリエタノールアミンおよびモルホリンなどの多官能化合物などが挙げられるけれども、有機溶媒はこれに限定されるものではない。これらの有機溶媒は、１種が単独で使用されてもよく、また２種以上が混合されて使用されてもよい。
【００９３】
前述した有機溶媒の中でも、グリコールエーテル類および多価アルコール類は、蒸気圧が低く、インク組成物中に含有させることによって、湿潤効果が得られ、吐出安定性を向上させることができるので、有機溶媒は、グリコールエーテル類および多価アルコール類のうちの少なくとも一方を含むことが好ましい。グリコールエーテル類および多価アルコール類の中でも、グリコールエーテル類であるジエチレングリコールモノブチルエーテル、プロピレングリコールモノブチルエーテル、トリエチレングリコールモノブチルエーテルもしくはテトラエチレングリコールモノブチルエーテル、または多価アルコール類であるグリセリン、１，２−ヘキサンジオールもしくは１，５−ペンタンジオールは、２５℃における蒸気圧が０．０５ｍｍＨｇ以下であり、湿潤効果に優れるので、これらを有機溶媒に用いることがより好ましい。
【００９４】
インク組成物中の有機溶媒の含有量は、３重量％以上７０重量％以下であることが好ましく、より好ましくは３重量％以上５０重量％以下である。有機溶媒の含有量が３重量％未満であると、インク組成物の乾燥が速く、湿潤性を保つことが困難である。有機溶媒の含有量が７０重量％を超えると、水溶性または水分散性の添加剤をインク組成物中に安定に存在させることができない場合が生じる。また用いる有機溶媒の種類によっては粘度の上昇が著しく、インク組成物としての適正粘度を越えることがある。したがって、３重量％以上７０重量％以下とした。ただし、インク組成物中の有機溶媒の含有量は、インク組成物が水を主成分とする場合には、３重量％以上４０重量％以下であることが好ましく、より好ましくは３重量％以上３０重量％以下である。インク組成物が水を主成分とする場合に、有機溶媒の含有量が４０重量％を超えると、用いる色材の種類にもよるけれども、得られる記録画像の品質の低下およびインク組成物の乾燥時間の遅延が起こる。したがって、３重量％以上４０重量％以下とした。
【００９５】
色材には、染料、顔料またはこれらの混合物が用いられる。染料および顔料は、これらが含有されたものであってもよく、またこれらが被着されたものであってもよい。
【００９６】
色材に染料を用いることによって、目詰まりの発生を抑え、吐出安定性を向上させることができる。また色材に顔料を用いることによって、耐光性および耐水性に優れる記録画像を得ることができる。
【００９７】
フルカラーのインクジェット記録法における各色の再現には、シアン（Ｃｙａｎ；略称：Ｃ）、マゼンタ（Ｍａｇｅｎｔａ；略称：Ｍ）およびイエロー（Ｙｅｌｌｏｗ；略称：Ｙ）の３色のインク組成物が用いられ、これらのインク組成物を混色することによって、各色が表現される。ただし、前記３色の混色では黒色の再現が難しいので、黒色の表現には一般的にブラック（Ｂｌａｃｋ；略称：Ｂ）のインク組成物が用いられる。含有させる色材の色を変えることによって、シアン、マゼンタ、イエローまたはブラックのインク組成物を得ることができる。
【００９８】
染料としては、酸性染料、直接染料、反応性染料および食品用色素などの水溶性染料が好適に用いられる。これらの中でも、耐水性、耐光性または安全性に優れるものを用いることが好ましい。
【００９９】
染料の具体例としては、以下に示す染料が挙げられるけれども、染料はこれに限定されるものではない。なお、以下では、染料をカラーインデックス（Ｃｏｌｏｒ Ｉｎｄｅｘ；略称：Ｃ．Ｉ．）ナンバーで示す。
【０１００】
シアンのインク組成物に用いられる染料としては、たとえば、酸性染料であるＣ．Ｉ．アシッドブルー７，９，２９，４５，９２および２４９、直接染料であるＣ．Ｉ．ダイレクトブルー１，２，６，１５，２２，２５，７１，７６，７９，８６，９０，９８，１６３，１６５，１９９および２０２、ならびに反応性染料であるＣ．Ｉ．リアクティブブルー１，２，７，１４，１５，２３，３２，３８，４１，６３，８０および９５などが挙げられる。これらの中でも、Ｃ．Ｉ．アシッドブルー７および９、ならびにＣ．Ｉ．ダイレクトブルー１９９からなる群から選ばれる少なくとも１つの染料を用いることが好ましい。
【０１０１】
マゼンタのインク組成物に用いられる染料としては、たとえば、酸性染料であるＣ．Ｉ．アシッドレッド１，８，１３，１４，１８，２６，２７，３５，３７，４２，５２，８２，８７，８９，９２，９７，１０６，１１１，１１４，１１５，１３４，１８６，２４９，２５４および２８９、直接染料であるＣ．Ｉ．ダイレクトレッド１，４，９，１３，１７，２０，２８，３１，３９，８０，８１，８３，８９，２２５および２２７、Ｃ．Ｉ．ダイレクトオレンジ２６，２９，６２および１０２、ならびに反応性染料であるＣ．Ｉ．リアクティブレッド１，１４，１７，２５，２６，３２，３７，４４，４６，５５，５８，６０，６６，７４，７９，９６，９７，１４１，１４７，１８０および１８１などが挙げられる。これらの中でも、Ｃ．Ｉ．アシッドレッド５２および２８９、ならびにＣ．Ｉ．リアクティブレッド５８，１４１および１８０からなる群から選ばれる少なくとも１つの染料を用いることが好ましい。
【０１０２】
イエローのインク組成物に用いられる染料としては、たとえば、酸性染料であるＣ．Ｉ．アシッドイエロー１，７，１７，２３，４２，４４，７９および１４２、直接染料であるＣ．Ｉ．ダイレクトイエロー１，１２，２４，２６，３３，４４，５０，８６，１２０，１３２，１４２および１４４、ならびに反応性染料であるＣ．Ｉ．リアクティブイエロー１，５，１１，１３，１４，２０，２１，２２，２５，４０，４７，５１，５５，６５および６７などが挙げられる。これらの中でも、Ｃ．Ｉ．アシッドイエロー１７および２３、ならびにＣ．Ｉ．ダイレクトイエロー８６からなる群から選ばれる少なくとも１つの染料を用いることが好ましい。
【０１０３】
ブラックのインク組成物に用いられる染料としては、たとえば、食品用色素であるＣ．Ｉ．フードブラック２、直接染料であるＣ．Ｉ．ダイレクトブラック１９，２２，３２，３８，５１，５６，７１，７４，７５，７７，１５４，１６８および１７１、ならびに反応性染料であるＣ．Ｉ．リアクティブブラック３，４，７，１１，１２および１７などが挙げられる。これらの中でも、Ｃ．Ｉ．フードブラック２およびＣ．Ｉ．ダイレクトブラック１５４のうちの少なくとも一方の染料を用いることが好ましい。
【０１０４】
これらの染料は、常温で安定に溶解する範囲内で用いられる。この範囲は各染料で異なるので、インク組成物中の染料の含有量は、特に限定されるものではないけれども、好ましくは０．１重量％〜１０重量％である。
【０１０５】
顔料としては、溶液中に分散可能な顔料であれば、どのような顔料を用いてもよいけれども、耐光性または安全性に優れるものが好適に用いられる。
【０１０６】
顔料の具体例としては、以下に示す顔料が挙げられるけれども、顔料はこれに限定されるものではない。なお、以下では顔料をカラーインデックス（Ｃ．Ｉ．）ナンバーで示す。
【０１０７】
シアンのインク組成物に用いられる顔料としては、たとえば、Ｃ．Ｉ．ピグメントブルー１，２，１５，１６，１７，２１，２２，６０および６４などが挙げられる。
【０１０８】
マゼンタのインク組成物に用いられる顔料としては、たとえば、Ｃ．Ｉ．ピグメントレッド２，３，５，１６，２３，３１，４９，５７，６３，１２２および２０９、ならびにＣ．Ｉ．ピグメントヴァイオレット１９などが挙げられる。
【０１０９】
イエローのインク組成物に用いられる顔料としては、たとえば、Ｃ．Ｉ．ピグメントイエロー１，２，３，５，１２，７４，１３８，１５０および１８０などが挙げられる。
【０１１０】
ブラックのインク組成物に用いられる顔料としては、たとえば、チャンネルブラック、ファーネスブラック、サーマルブラックおよびランプブラックなどのカーボンブラックなどが挙げられる。
【０１１１】
これらの顔料のうち、シアンのインク組成物には、Ｃ．Ｉ．ピグメントブルー１５：３およびＣ．Ｉ．ピグメントブルー１５：４のうちの少なくとも一方の顔料を用いることが好ましい。またマゼンタのインク組成物には、Ｃ．Ｉ．ピグメントレッド１２２、Ｃ．Ｉ．ピグメントレッド２０９およびＣ．Ｉ．ピグメントヴァイオレット１９からなる群から選ばれる少なくとも１つの顔料を用いることが好ましい。またイエローのインク組成物には、Ｃ．Ｉ．ピグメントイエロー７４、Ｃ．Ｉ．ピグメントイエロー１３８、Ｃ．Ｉ．ピグメントイエロー１５０およびＣ．Ｉ．ピグメントイエロー１８０からなる群から選ばれる少なくとも１つの顔料を用いることが好ましい。またブラックのインク組成物には、前述のカーボンブラックのうちから選ばれる少なくとも１つの顔料を用いることが好ましい。これらの顔料を用いることによって、シアン、マゼンタ、イエローまたはブラックの発色性に優れる記録画像を実現可能なインク組成物を得ることができる。
【０１１２】
また、これらの好ましい顔料を用いたシアン、マゼンタおよびイエローの３色のインク組成物、すなわちＣ．Ｉ．ピグメントブルー１５：３およびＣ．Ｉ．ピグメントブルー１５：４のうちの少なくとも一方の顔料を用いたシアンのインク組成物と、Ｃ．Ｉ．ピグメントレッド１２２、Ｃ．Ｉ．ピグメントレッド２０９およびＣ．Ｉ．ピグメントヴァイオレット１９からなる群から選ばれる少なくとも１つの顔料を用いたマゼンタのインク組成物と、Ｃ．Ｉ．ピグメントイエロー７４、Ｃ．Ｉ．ピグメントイエロー１３８、Ｃ．Ｉ．ピグメントイエロー１５０およびＣ．Ｉ．ピグメントイエロー１８０からなる群から選ばれる少なくとも１つの顔料を用いたイエローのインク組成物との３種類のインク組成物を重ね合せることによって、ブラックのインク組成物を用いて形成された記録画像に近い濃度の濃い黒色の記録画像を得ることができる。すなわち、これらの３種類のインク組成物を含むインクセットは、カラーバランスに優れる。したがって、これらの３種類のインク組成物を含むインクセット、またはこれらの３種類のインク組成物に、カーボンブラックを用いたブラックのインク組成物を加えた４種類のインク組成物を含むインクセットを用いることによって、様々な色を表現することができるので、発色性に優れるフルカラーの記録画像を実現することができる。
【０１１３】
顔料は、たとえばカルボキシル基、ヒドロキシル基、アミノ基およびスルホン酸基などからなる群から選ばれる１種または２種以上の親水基を有することが好ましい。これらの親水基は、顔料表面に化学修飾を行うことによって直接導入されていてもよく、またこれらの親水基を有するポリマーで顔料表面を被覆することによって導入されていてもよい。またこれらの親水基は、塩になっていてもよい。
【０１１４】
親水基を有する顔料は、水を含有するインク組成物中に安定に分散されて存在することができる。したがって、色材に親水基を有する顔料を用いることによって、目詰まりの発生を抑えることができるので、吐出安定性を損なうことなく、耐光性および耐水性に優れる記録画像を得ることができる。
【０１１５】
これらの顔料は、常温で安定に分散する範囲内で用いられる。この範囲は各顔料で異なるので、インク組成物中の顔料の含有量は、特に限定されるものではないけれども、好ましくは０．１重量％〜１０重量％である。
【０１１６】
また本実施の形態のインク組成物は、色材に顔料を用いる場合には、バインダ樹脂を含有することが好ましい。バインダ樹脂を含有させることによって、被記録材上からの顔料の剥離を防ぐことができる。
【０１１７】
バインダ樹脂には、たとえば、ポリエステル樹脂、アクリル樹脂、スチレン−アクリル共重合体樹脂およびポリエステル−アクリル共重合体樹脂などからなる群から選ばれる１種または２種以上が用いられる。
【０１１８】
また本実施の形態のインク組成物は、色材、有機溶媒、水、界面活性剤およびバインダ樹脂以外に、各種添加剤、たとえば防カビ剤、ｐＨ調整剤、キレート化剤、防錆剤または紫外線吸収剤などを含んでもよい。
【０１１９】
防カビ剤には、デヒドロ酢酸ナトリウム、安息香酸ナトリウムまたはソルビタン酸ナトリウムなどが好適に用いられる。
【０１２０】
ｐＨ調整剤には、トリエタノールアミン、水酸化ナトリウム、炭酸ナトリウム、硝酸ナトリウムまたは硝酸カリウムなどが好適に用いられる。
【０１２１】
色材と有機溶媒と水と前述の条件を満足する界面活性剤とを含有する本実施の形態のインク組成物の粘度は、２５℃において、２０ｍＰａ・ｓ以下であることが好ましく、より好ましくは１５ｍＰａ・ｓ以下である。インク組成物の２５℃における粘度が２０ｍＰａ・ｓを超えると、インクジェット記録法に用いた場合、インク組成物の液滴を安定して吐出させることができない。したがって、２０ｍＰａ・ｓ以下とした。
【０１２２】
図１は、本発明の第２の実施形態であるインクヘッド１の構成を簡略化して示す分解斜視図であり、図２は、図１に示すインクヘッド１を構成するヘッドプレート１０の構成の一部を拡大して示す斜視図である。なお、図１では、図２に示す駆動電極１３は、図が錯綜して理解が困難になるので記載を省略する。
【０１２３】
インクヘッド１は、圧電材料で形成される底壁部１１と複数の隔壁部１２とを有するヘッドプレート１０と、隔壁部１２の上面に設けられる天板２０と、複数の吐出口３１を備え隔壁部１２の一方の端部に設けられるノズルプレート３０と、隔壁部１２の他方の端部に設けられる図示しない背面板と、天板２０の上部に設けられ開口部５１を有するインクタンク５０とを含んで構成される。複数の隔壁部１２は、底壁部１１上に所定の間隔で平行に配置されており、複数の隔壁部１２と底壁部１１と天板２０とノズルプレート３０と図示しない背面板とによって複数のインク室４０が形成されている。天板２０には、各インク室４０に連通する共通インク供給路２１と、共通インク供給路２１とインクタンク５０の開口部５１とを連結するインク供給管２２とが形成される。インクタンク５０には実施の第１形態のインク組成物６０が貯留されており、このインク組成物６０は共通インク供給路２１を介して各インク室４０に供給される。
【０１２４】
また図２に示すように、ヘッドプレート１０の底壁部１１および複数の隔壁部１２のインク室４０に臨む表面には、複数の隔壁部１２に電圧を印加する駆動電極１３が形成される。また複数の隔壁部１２を形成する圧電材料は、矢符７０の方向に分極しており、複数の隔壁部１２は圧電素子として機能する。
【０１２５】
このように構成されるインクヘッド１は、圧電素子である複数の隔壁部１２に印加される電圧に応じて、吐出口３１からインク組成物６０の液滴を吐出させることのできるピエゾ方式のインクヘッドである。
【０１２６】
インクヘッド１において、インク室４０からインク組成物６０を吐出させる際の動作原理について説明する。図３は、図１に示すインクヘッド１をインク室４０の延長方向から見た断面図である。ここでは、インク室４０ｂからインク組成物６０を吐出させる場合の動作について説明する。
【０１２７】
インク室４０ｂを構成する隔壁部１２ａおよび１２ｂに電圧が印加されていないとき、すなわちインク室４０ｂの駆動電極１３ｂとインク室４０ｂに隣接するインク室４０ａの駆動電極１３ａとの間、およびインク室４０ｂの駆動電極１３ｂとインク室４０ｂに隣接するインク室４０ｃの駆動電極１３ｃとの間に電位差が生じていないとき、インク室４０ｂは、毛管作用によってインクタンク５０から供給されるインク組成物６０で充填された状態になっている。同様に、インク室４０ａおよび４０ｃもインク組成物６０で充填された状態になっている。
【０１２８】
駆動電極１３ａおよび駆動電極１３ｃに電圧が印加されると、駆動電極１３ｂと駆動電極１３ａとの間、および駆動電極１３ｂと駆動電極１３ｃとの間に電位差が生じ、インク室４０ｂを構成する隔壁部１２ａおよび１２ｂに電圧が印加される。この電圧によって、隔壁部１２ａおよび１２ｂにそれぞれ矢符７１および７２の方向の電界が発生し、この電界の作用によって、インク室４０ｂを構成する隔壁部１２ａおよび１２ｂにひずみが生じ、インク室４０ｂ側に凸になるように変形する。これによって、圧力波が発生し、インク室４０ｂ内に充填されているインク組成物６０に大きな圧力がかかり、インク組成物６０の液滴が前述の図１に示す吐出口３１から吐出する。
【０１２９】
駆動電極１３ａおよび駆動電極１３ｃへの電圧の印加を止めると、隔壁部１２ａおよび１２ｂの形状が元に戻ってインク室４０ｂの体積が元に戻り、復元された体積分のインク組成物６０が前述の図１に示す共通インク供給路２１を介してインクタンク５０から供給され、インク室４０ｂは、インク組成物６０が充填された初期の状態に戻る。
【０１３０】
本実施の形態のインクヘッド１では、前述のようにインクタンク５０は実施の第１形態のインク組成物６０を貯留し、このインク組成物６０がインク室４０に供給されて吐出口３１から液滴として吐出するので、安定して吐出口３１からインク組成物６０の液滴を吐出させることができる。このようなインクヘッドを用いれば、信頼性の高いピエゾ方式のインクジェット記録装置を実現することができ、高品質の記録画像を安定して得ることができる。
【０１３１】
以上に述べたように、本実施の形態では、インク室４０を構成する隔壁部１２を圧電材料で形成し、圧電素子として機能させるけれども、これに限定されることなく、インク室を構成する隔壁を圧電材料以外の材料で形成し、隔壁の内方または外方に圧電素子を設けてもよい。
【０１３２】
図４は、本発明の第３の実施形態であるインクヘッド２の構成を簡略化して示す分解斜視図であり、図５は、図４に示すインクヘッド２の構成の一部を示す平面図である。なお、図５では、図４に示す天板２０およびインクタンク５０は、図が錯綜して理解が困難になるので、記載を省略する。本実施の形態のインクヘッド２は、実施の第２形態のインクヘッド１と類似し、対応する部分については同一の参照符号を付して説明を省略する。
【０１３３】
注目すべきは、ヘッドプレート１００が、基板１０１と、基板１０１上に所定の間隔で平行に配置される複数の隔壁１０２と、基板１０１のインク室４０に臨む表面上に設けられる発熱体であるヒータ１０３と、ヒータ１０３に電圧を印加する駆動電極１０４および１０５とを含んで構成されることである。
【０１３４】
このように構成されるインクヘッド２は、発熱体であるヒータ１０３に印加される電圧に応じて、吐出口３１からインク組成物６０の液滴を吐出させることのできるサーマルインクジェット方式のインクヘッドである。
【０１３５】
インクヘッド２において、インク室４０からインク組成物６０を吐出させる際の動作原理について説明する。図６は、インク室４０からインク組成物６０の液滴６１が吐出する様子を模式的に示す断面図である。図６では、図５に示すインクヘッド２の切断面線Ｉ−Ｉにおける断面構成を示す。
【０１３６】
ヒータ１０３に電圧が印加されていないとき、実施の第２形態のインクヘッド１において隔壁部１２に電圧が印加されていないときと同様に、インク室４０はインク組成物６０が充填された状態になっている。
【０１３７】
駆動電極１０４および１０５によってヒータ１０３に電圧が印加されると、ヒータ１０３が発熱し、インク室４０内に充填されているインク組成物６０が加熱されて、気泡６２が発生する。これによって、圧力波が発生し、インク室４０内に充填されているインク組成物６０に大きな圧力がかかり、インク組成物６０の液滴６１が吐出口３１から吐出する。
【０１３８】
ヒータ１０３への電圧の印加を止めると、インク室４０内のインク組成物６０が冷却されて気泡６２が消滅し、復元された体積分のインク組成物６０が前述の図４に示す共通インク供給路２１を介してインクタンク５０から供給され、インク室４０は、インク組成物６０が充填された初期の状態に戻る。
【０１３９】
本実施の形態のインクヘッド２では、前述の実施の第２形態のインクヘッド１と同様に、インクタンク５０は実施の第１形態のインク組成物６０を貯留し、このインク組成物６０がインク室４０に供給されて吐出口３１から液滴６１として吐出するので、安定して吐出口３１からインク組成物６０の液滴６１を吐出させることができる。このようなインクヘッドを用いれば、信頼性の高いサーマルインクジェット方式のインクジェット記録装置を実現することができ、高品質の記録画像を安定して得ることができる。
【０１４０】
【実施例】
以下、本発明について、実施例を用いてさらに詳細に説明するけれども、本発明は、これに限定されるものではない。なお、本実施例では、画像を記録することを印刷または印字と呼ぶことがある。
【０１４１】
＜界面活性剤の特性評価＞
表１に示す７種類の界面活性剤をそれぞれ純水に０．１重量％溶解させ、界面活性剤溶液を調製した。調整した各界面活性剤溶液について、以下のようにして動的表面張力および静的表面張力を測定した。
【０１４２】
（動的表面張力）
表面張力計（協和界面科学株式会社製：ＢＰ−４）を用い、気泡周波数０．５Ｈｚ〜３５Ｈｚにおいて測定した。
【０１４３】
（静的表面張力）
表面張力計（協和界面科学株式会社製：ＣＢＶＰ−Ａ３）を用いて測定した。
【０１４４】
表１に、各界面活性剤溶液の気泡周波数１０Ｈｚでの動的表面張力（σ_１０）および静的表面張力（γ）の測定値（ｍＮ／ｍ）、そのときの測定温度（℃）、ならびにσ_１０とγとの差ｄ（＝σ_１０−γ）の値（ｍＮ／ｍ）を示す。なお、表１において、一般式（Ｉ）は、前記一般式（Ｉ）で示される界面活性剤を表し、一般式（ＩＩ）は、前記一般式（ＩＩ）で示される界面活性剤を表し、一般式（ＩＩＩ）は、前記一般式（ＩＩＩ）で示される界面活性剤を表し、一般式（ＩＶ）は、前記一般式（ＩＶ）で示される界面活性剤を表し、一般式（Ｖ）は、前記一般式（Ｖ）で示される界面活性剤を表し、フッ素系界面活性剤１は、下記構造式（ＶＩＩ）で示される界面活性剤を表し、フッ素系界面活性剤２は、下記構造式（ＶＩＩＩ）で示される界面活性剤を表す。
【０１４５】
【化７】

【０１４６】
【化８】

【０１４７】
【表１】

【０１４８】
＜インク組成物＞
表１に示す界面活性剤を用いて、純水に０．１重量％を溶解させて得られる溶液の温度２４〜２６℃で最大泡圧法によって測定される気泡周波数１０Ｈｚでの動的表面張力（σ_１０）と温度２４〜２６℃で測定される静的表面張力（γ）との差ｄ（＝σ_１０−γ）が前記式（１）を満足する界面活性剤を含有する実施例１〜７のインク組成物と、ｄが前記式（１）を満足する界面活性剤を含有しない比較例１〜４のインク組成物とを得た。表２に、実施例１〜７および比較例１〜４の各インク組成物に含まれる各成分の含有量を示す。表２において、各欄の値の単位は重量部であり、実施例１〜７および比較例１〜４の各インク組成物の合計量はそれぞれ１００重量部である。また表２において、ＴＥＧＢＥは、トリエチレングリコールモノブチルエーテル（Ｔｒｉｅｔｈｙｌｅｎｅ ｇｌｙｃｏｌ ｍｏｎｏｂｕｔｙｌ ｅｔｈｅｒ）を表し、ＰＥＧ４００は、分子量が４００のポリエチレングリコール（
Ｐｏｌｙｅｔｈｙｌｅｎｅ ｇｌｙｃｏｌ）を表す。
【０１４９】
【表２】

【０１５０】
得られた実施例１〜７および比較例１〜４の各インク組成物について、インクジェット記録法に用いた場合の吐出安定性および得られる記録画像の画質の評価を以下のように行った。
【０１５１】
（吐出安定性）
前述の図１に示すインクヘッド１を装着できるように市販のインクジェット記録装置（シャープ株式会社製：ＡＪ２０００）を改造して得られたインクジェット記録装置のインクタンクに、得られた実施例１〜７および比較例１〜４のインク組成物をそれぞれ充填し、印刷濃度を５％として毎分Ａ４判用紙７枚の印刷速度で、シャープ株式会社製の複写機用普通紙（品番：ＳＦ４ＡＭ３）上に連続的に印刷を行った。試験ではインクタンクが空になった時点でインク組成物を再充填し、ノズルからインク組成物の液滴が吐出せず印刷することができなくなるまで印刷を行い、その時点までに完全に印刷できた枚数を印刷可能枚数として求め、吐出安定性の評価指標とした。印刷可能枚数が２００枚を超える場合を良（○）とし、１５０〜２００枚の場合を可（△）とし、１５０枚未満の場合を不良（×）とした。
【０１５２】
（画質）
前述の図１に示すインクヘッド１を装着できるように市販のインクジェット記録装置（シャープ株式会社製：ＡＪ２０００）を改造して得られたインクジェット記録装置のインクタンクに、得られた実施例１〜７および比較例１〜４のインク組成物をそれぞれ充填し、シャープ株式会社製の複写機用普通紙（品番：ＳＦ４ＡＭ３）上に特定のパターンを印刷し、評価用画像を形成した。前記評価用画像を１日放置した後、設定したパターンの線幅を１００として、これに対する各評価用画像のパターンの線幅の相対値を求め、画質の評価指標とした。線幅の相対値が１５０未満であり滲みがほとんどない場合を良（○）とし、１５０以上２５０以下であり若干の滲みがある場合を可（△）とし、２５０を超え滲みが多い場合を不良（×）とした。
以上の評価結果を表３に示す。
【０１５３】
【表３】

【０１５４】
前述の気泡周波数１０Ｈｚでの動的表面張力（σ_１０）と静的表面張力（γ）との差ｄ（＝σ_１０−γ）が前記式（１）を満足する界面活性剤を含有する実施例１〜７のインク組成物では、吐出安定性および画質のいずれもが良であった。一方、ｄが前記式（１）を満足する界面活性剤を含有せず、ｄが１５より大きく前記式（１）を大きい方に外れる界面活性剤を含有する比較例１〜４のインク組成物では、吐出安定性および画質のいずれもが不良であった。
【０１５５】
以上のように、純水に０．１重量％を溶解させて得られる溶液の温度２４〜２６℃で測定される気泡周波数１０Ｈｚでの動的表面張力（σ_１０）と、温度２４〜２６℃で測定される静的表面張力（γ）との差ｄ（＝σ_１０−γ）が、前記式（１）を満足する界面活性剤を含有させることによって、インクジェット記録法に用いた場合、吐出安定性に優れるとともに、被記録材上における滲みを抑え高品質の記録画像を得ることが可能なインク組成物を得ることができた。
【０１５６】
＜インクセット＞
実施例２〜６および比較例１〜３のインク組成物を、表４に示すようにシアン、マゼンタおよびイエローのインク組成物として組合せることによって、Ｃ．Ｉ．ピグメントブルー１５：３および１５：４のうちの少なくとも一方の顔料を含有するシアンのインク組成物と、Ｃ．Ｉ．ピグメントレッド１２２，２０９およびＣ．Ｉ．ピグメントヴァイオレット１９からなる群から選ばれる少なくとも１つの顔料を含有するマゼンタのインク組成物と、Ｃ．Ｉ．ピグメントイエロー７４，１３８，１５０および１８０からなる群から選ばれる少なくとも１つの顔料を含有するイエローのインク組成物とを含む実施例インクセット１と、シアン、マゼンタおよびイエローのインク組成物のうちのいずれかが前述の顔料と異なる顔料を含有する比較例インクセット１〜３と、シアン、マゼンタおよびイエローのインク組成物のすべてが前述の顔料と異なる顔料を含有する比較例インクセット４とを得た。
【０１５７】
【表４】

【０１５８】
得られた実施例インクセット１および比較例インクセット１〜４をそれぞれ用い、市販のインクジェット記録装置（シャープ株式会社製：ＡＪ２０００）を改造して得られたインクジェット記録装置を使用し、シャープ株式会社製の光沢紙（品番：ＡＪ−Ｋ４ＡＧ）上に、シアン、マゼンタおよびイエローの各インク組成物の印字率を１：１：１として印刷することによって黒色画像を形成した。また、ブラックのインク組成物である実施例７のインク組成物を用い、同一の画像を形成した。
【０１５９】
得られた各黒色画像について、分光測色計（Ｘ−Ｒｉｔｅ社製：Ｘ−Ｒｉｔｅ９３８）を用い、Ｌ^＊ａ^＊ｂ^＊表色系（ＣＩＥ：１９７６）における明度指数Ｌ^＊およびクロマチックネス指数ａ^＊，ｂ^＊を測定した。
【０１６０】
試験結果の評価は、以下のように行った。実施例７のインク組成物を用いて形成された黒色画像のクロマチックネス指数ａ^＊をＡ１、ｂ^＊をＢ２とし、実施例インクセット１および比較例インクセット１〜４をそれぞれ用いて形成された黒色画像のクロマチックネス指数ａ^＊をＡ２、ｂ^＊をＢ２として、下記式（３）で示されるΔａ^＊ｂ^＊の値を求め、黒色再現性の評価指標とした。
Δａ^＊ｂ^＊＝｛（Ａ１−Ａ２）^２＋（Ｂ１−Ｂ２）^２｝^１／２ …（３）
Δａ^＊ｂ^＊の値が、２０以下（Δａ^＊ｂ^＊≦２０）である場合を良（○）とし、２０を超える（Δａ^＊ｂ^＊＞２０）場合を不良（×）とした。評価結果を表５に示す。
【０１６１】
【表５】

【０１６２】
表５から、実施例インクセット１に含まれる３種類のインク組成物を重ね合わせて得られる黒色画像は、比較例インクセット１〜４にそれぞれ含まれる３種類のインク組成物を重ね合わせて得られる黒色画像に比べ、実施例７のインク組成物を用いて形成された黒色画像に近い濃い濃度の黒色画像であることが判った。すなわち、実施例インクセット１は、比較例インクセット１〜４に比べ、黒色再現性が良好であり、カラーバランスに優れることが判った。
【０１６３】
以上のように、Ｃ．Ｉ．ピグメントブルー１５：３および１５：４のうちの少なくとも一方の顔料を含有するシアンのインク組成物と、Ｃ．Ｉ．ピグメントレッド１２２，２０９およびＣ．Ｉ．ピグメントヴァイオレット１９からなる群から選ばれる少なくとも１つの顔料を含有するマゼンタのインク組成物と、Ｃ．Ｉ．ピグメントイエロー７４，１３８，１５０および１８０からなる群から選ばれる少なくとも１つの顔料を含有するイエローのインク組成物とを組合せることによって、カラーバランスに優れるインクセットを得ることができた。
【０１６４】
【発明の効果】
以上のように本発明によれば、純水に０．１重量％を溶解させて得られる溶液の温度２４〜２６℃で最大泡圧法によって測定される気泡周波数１０Ｈｚでの動的表面張力と、温度２４〜２６℃で測定される静的表面張力との差が、ある一定の範囲内にある界面活性剤を含有するので、インク組成物の動的表面張力と静的表面張力との関係を好適なものにすることができ、インクジェット記録法に用いた場合、吐出安定性に優れるとともに、被記録材上における滲みを抑え高品質の記録画像を得ることが可能なインク組成物を得ることができる。
【０１６５】
また本発明によれば、純水に０．１重量％を溶解させて得られる溶液の温度２４〜２６℃で最大泡圧法によって測定される気泡周波数１０Ｈｚでの動的表面張力および温度２４〜２６℃で測定される静的表面張力が好適な範囲に選択されるので、インクジェット記録法に用いた場合、吐出安定性に優れるとともに、被記録材上における滲みを抑え高品質の記録画像を得ることが可能なインク組成物を得ることができる。
【０１６６】
また本発明によれば、有機溶媒は、蒸気圧の低いグリコールエーテル類および多価アルコール類のうちの少なくとも一方を含むので、湿潤効果が得られ、吐出安定性を向上させることができる。
【０１６７】
また本発明によれば、色材は染料を含むので、目詰まりの発生を抑え、吐出安定性を向上させることができる。
【０１６８】
また本発明によれば、色材は顔料を含むので、耐光性および耐水性に優れる記録画像を得ることができる。
【０１６９】
また本発明によれば、顔料は親水基を有するので、目詰まりの発生を抑えることができ、吐出安定性を損なうことなく、耐光性および耐水性に優れる記録画像を得ることが可能なインク組成物を得ることができる。
【０１７０】
また本発明によれば、界面活性剤は、共存する電解質の影響を受けにくい非イオン系界面活性剤を含むので、インク組成物に電解質が添加されるか否かに関わらず、界面活性剤によって制御されるインク組成物の動的表面張力と静的表面張力との関係を好適なものにすることができる。
【０１７１】
また本発明によれば、界面活性剤は臨界ミセル濃度以上含まれるので、界面活性剤の効果を充分に発揮させ、界面活性剤によって制御されるインク組成物の動的表面張力および静的表面張力をそれぞれほぼ一定の値にすることができ、均一な性質を有するインク組成物を得ることができる。
【０１７２】
また本発明によれば、シアンの発色性に優れる記録画像を実現可能なインク組成物を得ることができる。
【０１７３】
また本発明によれば、マゼンタの発色性に優れる記録画像を実現可能なインク組成物を得ることができる。
【０１７４】
また本発明によれば、イエローの発色性に優れる記録画像を実現可能なインク組成物を得ることができる。
【０１７５】
また本発明によれば、ブラックの発色性に優れる記録画像を実現可能なインク組成物を得ることができる。
【０１７６】
また本発明によれば、高品質の記録画像を安定して提供することができる。
また本発明によれば、安定した吐出が可能であるとともに、高品質の記録画像を安定して提供することができる。
【０１７７】
また本発明によれば、様々な色を表現することができるので、発色性に優れるフルカラーの記録画像を提供することができる。
【０１７８】
また本発明によれば、高品質の記録画像を得ることができる。
また本発明によれば、カラーバランスに優れるインクセットを得ることができるので、様々な色を表現することができ、発色性に優れるフルカラーの記録画像を実現することができる。
【０１７９】
また本発明によれば、圧電素子に印加される電圧に応じて、吐出口からインク組成物の液滴を吐出させることのできるピエゾ方式のインクヘッドにおいて、安定して吐出口からインク組成物の液滴を吐出させることができる。
【０１８０】
また本発明によれば、発熱体に印加される電圧に応じて、吐出口からインク組成物の液滴を吐出させることのできるサーマルインクジェット方式のインクヘッドにおいて、安定して吐出口からインク組成物の液滴を吐出させることができる。
【０１８１】
また本発明によれば、記録画像は、安定してインク組成物の液滴を吐出させることのできるピエゾ方式のインクヘッドによって吐出されるインク組成物の液滴が、被記録材上に付着されることによって記録されるので、高品質の記録画像を安定して得ることができる。
【０１８２】
また本発明によれば、記録画像は、安定してインク組成物の液滴を吐出させることのできるサーマルインクジェット方式のインクヘッドによって吐出されるインク組成物の液滴が、被記録材上に付着されることによって記録されるので、高品質の記録画像を安定して得ることができる。
【図面の簡単な説明】
【図１】本発明の第２の実施形態であるインクヘッド１の構成を簡略化して示す分解斜視図である。
【図２】図１に示すインクヘッド１を構成するヘッドプレート１０の構成の一部を拡大して示す斜視図である。
【図３】図１に示すインクヘッド１をインク室４０の延長方向から見た断面図である。
【図４】本発明の第３の実施形態であるインクヘッド２の構成を簡略化して示す分解斜視図である。
【図５】図４に示すインクヘッド２の構成の一部を示す平面図である。
【図６】インク室４０からインク組成物６０の液滴６１が吐出する様子を模式的に示す断面図である。
【符号の説明】
１，２ インクヘッド
１０ ヘッドプレート
１１ 底壁部
１２，１２ａ，１２ｂ 隔壁部
１３，１３ａ，１３ｂ，１３ｃ 駆動電極
２０ 天板
２１ 共通インク供給路
２２ インク供給管
３０ ノズルプレート
３１ 吐出口
４０，４０ａ，４０ｂ，４０ｃ インク室
５０ インクタンク
５１ 開口部
６０ インク組成物
６１ 液滴
６２ 気泡
１００ ヘッドプレート
１０１ 基板
１０２ 隔壁
１０３ ヒータ
１０４，１０５ 駆動電極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink composition suitably used in an ink jet recording method, a recording method and a recorded image using the ink composition, an ink set, and an ink head.
[0002]
[Prior art]
In the ink jet recording method, droplets of an ink composition (hereinafter also simply referred to as “ink”) are ejected and flying using mechanical energy or thermal energy, and the droplets are deposited on a recording material such as paper. This is a method for recording an image.
[0003]
Conventionally, characteristics of inks used in ink jet recording methods (hereinafter also simply referred to as “ink jet inks”) are indicated by physical property values such as surface tension and viscosity. By defining these physical property values, adjustment of the drying property of the ink and improvement of the quality of the formed image are achieved.
[0004]
For example, an ink jet recording method using ink droplets defined by the product of the Weber number including surface tension as a factor and the Reynolds number including viscosity as a factor has been proposed. A high-quality image is realized by setting the product of the Weber number and the Reynolds number within a specific range (see Patent Document 1). Further, an ink jet recording method using an ink having a surface tension within a specific range has been proposed (see Patent Document 2).
[0005]
The surface tension handled by the techniques described in Patent Document 1 and Patent Document 2 are both surface tension when the liquid surface reaches an equilibrium state, that is, static surface tension. Further, the surface tension generally used as an index of the characteristics of the ink jet ink is also a static surface tension (see, for example, Non-Patent Document 1). As described above, the characteristics of the ink-jet ink are often indicated by the static surface tension among the surface tensions.
[0006]
However, it is difficult to sufficiently show the characteristics of ink-jet ink only by static surface tension.
[0007]
In an ink jet recording apparatus that records an image using an ink jet recording method, ink is filled in an ink chamber in an ink head, and ink droplets are continuously ejected and ejected from an ejection port provided at the tip of the ink chamber. Then, an image is recorded by being deposited on the recording material. When ink is ejected continuously, ink droplets are ejected at the ejection port, and at the same time, a new surface of the ink, that is, a new meniscus is formed. Therefore, the surface tension of the ink causes a new surface to be formed at the ejection port. When starting, immediately before ejection, at the moment of ejection, at the time of flight, at the moment of landing on the recording material, when it penetrates into the recording material such as paper, it differs. In particular, the surface tension in a state that can be regarded as static, such as when a new surface starts to form at the discharge port or when it penetrates into a recording material such as paper, and the moment when it is discharged Thus, it is greatly different from the surface tension in the dynamic state where the movement is fast. Therefore, when evaluating the characteristics of the inkjet ink, it is necessary to consider not only the static surface tension but also the dynamic surface tension, which is the surface tension in a dynamic state.
[0008]
The importance of dynamic surface tension is described in many documents. For example, Schwartz, J evaluates the static and dynamic surface tensions of water-based paints, and dynamic surface tension is an important factor in film formation with water-based paints, reducing the dynamic surface tension. It shows that it is effective for forming a uniform excellent coating film (see Non-Patent Document 2).
[0009]
Medina, S .; W. And Sutovich, M .; N. Discusses the importance of dynamic surface tension in high-speed printing, and the static surface tension, which is the surface tension when the liquid surface reaches equilibrium, is static as it moves slowly into paper. This suggests that it is effective as an indicator of the properties of ink in a state that can be regarded as an ink, but is not effective as an indicator of the properties of ink that is in a particularly fast-moving state as in high-speed printing. (See Non-Patent Document 3).
[0010]
In addition, an ink composition suitable for an ink jet recording method in which the relationship between dynamic surface tension and viscosity is defined, and a recording method using the ink composition have been proposed. This technique shows that the ink composition can provide good printing characteristics within a range satisfying the condition of [dynamic surface tension (dyne / cm) of lifetime 0 msec] + [viscosity (cP)] = 42 to 49. (See Patent Document 3).
[0011]
[Patent Document 1]
Japanese Patent No. 2968010
[Patent Document 2]
Japanese Patent Publication No. 63-65034
[Patent Document 3]
Japanese Patent No. 2516218
[Non-Patent Document 1]
Kinoshita Ikuo, “Actual Technology of Special Function Ink”, first edition of popular edition, CMC Co., Ltd., November 15, 1999, p. 4
[Non-Patent Document 2]
Schwartz, J.A. , "The Importance of Low Dynamic Surface Tension in
Waterborne Coatings ", Journal of Coatings Technology, USA, vol. 64, no. 812 (1992), p. 65-74
[Non-Patent Document 3]
Medina, S .; W. and Sutovic, M .; N. , “Using Surfactants to Format VOC Commuter Water based Inks”, American Ink Maker, USA, vol. 72, no. 2 (1994), p. 32-38
[0012]
[Problems to be solved by the invention]
However, in the technique described in Patent Document 3, the dynamic surface tension is defined using a conditional expression obtained by adding the value of the dynamic surface tension and the value of the viscosity. However, the dynamic surface tension and the viscosity are in units. Are different, that is, the dimensions are different, so the value of the conditional expression itself has no meaning.
[0013]
In this technique, the dynamic surface tension is specified, but the static surface tension is not specified. As described above, in the ink jet recording method, the surface tension of the ink is largely different between a state that can be regarded as static with slow motion and a dynamic state with fast motion, and thus sufficiently shows the characteristics of the ink for ink jet. This requires both static and dynamic surface tension.
[0014]
This technique also shows that surfactants do not contribute to the reduction of dynamic surface tension. However, surfactants are generally known to greatly contribute to the wettability of the ink-jet ink to the inner wall of the ink chamber and the properties on the recording material. It is also important for control. For example, Schwartz, J, in the aforementioned Non-Patent Document 2, uses several surfactants to change the static surface tension and dynamic surface tension, evaluates the effects of these on film formation, It has been shown that lowering the surface tension is effective in reducing shrinkage of the coating film, generation of craters in the coating film, and reduction of bubble entrapment. Medina, S .; W. And Sutovich, M .; N. In the above-mentioned Non-Patent Document 3, the dynamic surface tension is such that the surfactant contained in the ink adheres one after another to the new surface of the ink that is newly formed one after another or the recording material. This suggests that it is an index of the ability to move to the interface between the ink droplet and the recording material. That is, the surfactant lowers the surface tension of the ink by adsorbing to the nascent surface of the ink or the interface between the ink droplet and the recording material, and therefore moves to the nascent surface of the ink or the interface between the ink droplet and the recording material. The higher the ability to perform, the higher the effect of lowering the surface tension of the ink in the dynamic state, and the lower the dynamic surface tension of the ink. Thus, the properties of the surfactant greatly affect the dynamic surface tension and static surface tension of the ink.
[0015]
The object of the present invention is to control the relationship between the dynamic surface tension and the static surface tension of the ink composition by defining the properties of the surfactant to be contained, and when used in the ink jet recording method, the ejection stability And an ink composition capable of obtaining a high-quality recorded image, a recording method and a recorded image using the ink composition, an ink set, and an ink head.
[0016]
[Means for Solving the Problems]
The present invention relates to a color material, an organic solvent, water, and a solution obtained by dissolving 0.1% by weight in pure water at a temperature of 24 to 26 ° C. and a bubble frequency of 10 Hz measured by the maximum bubble pressure method. Surface tension (σ ₁₀ ) And the static surface tension (γ) measured at a temperature of 24-26 ° C. d (= σ ₁₀ -Γ) contains a surfactant satisfying the following formula (1):
0 mN / m ≦ d ≦ 15 mN / m (1)
[0017]
According to the present invention, the ink composition is obtained by a maximum bubble pressure method at a temperature of 24 ° C. to 26 ° C. of a solution obtained by dissolving 0.1% by weight in a color material, an organic solvent, water, and pure water. Dynamic surface tension (σ ₁₀ ) And the static surface tension (γ) measured at a temperature between 24 ° C. and 26 ° C. ₁₀ -Γ) contains a surfactant within a certain range. The dynamic surface tension and static surface tension of the ink composition are most affected by the surfactant, although they vary depending on the type and content of the organic solvent contained in the ink composition. That is, the dynamic surface tension and static surface tension of the ink composition can be controlled by the surfactant. In an ink jet recording apparatus that records an image using an ink jet recording method, when ink composition droplets are continuously ejected, a new ink composition is formed at an ejection port provided at the tip of an ink chamber in the ink head. Since the surface is constantly generated, the ink composition moves quickly and is greatly affected by the dynamic surface tension. On the other hand, in the ink chamber, after the ink composition is ejected, the volume of the ink composition that is ejected and reduced is supplied from the ink tank by capillary action, so that the ink composition moves slowly and is in a static state. It can be considered that the effect of static surface tension is great. In other words, since both the dynamic surface tension and the static surface tension of the ink composition affect the ejection, the dynamic surface tension and the static surface tension are required to stably eject the ink composition droplets. It is necessary to balance the surface tension. In addition, the movement of the ink composition when an ink composition droplet is deposited on a recording material to record an image is fast at the moment the droplet lands on the recording material, but then gradually decreases. In the case of an absorbent recording material, the ink composition slowly penetrates into the recording material. That is, since the surface tension of the ink composition changes from a dynamic one to a static one, if the difference between the dynamic surface tension and the static surface tension is large, the ink composition dries on the recording material. It takes time and bleeding occurs. Moreover, it penetrates too much and causes a strike through. Thus, in the ink jet recording method, the relationship between the dynamic surface tension and the static surface tension of the ink composition is important. As described above, since the dynamic surface tension and static surface tension of the ink composition can be controlled by the surfactant, the ink composition is defined by defining the properties of the surfactant contained in the ink composition. The relationship between the dynamic surface tension and the static surface tension can be controlled. Therefore, as described above, the dynamic surface tension (σ at the bubble frequency of 10 Hz) of a solution obtained by dissolving 0.1% by weight in pure water. ₁₀ ) And the static surface tension (γ) d (= σ) ₁₀ -Γ) contains a surfactant within a certain range, whereby the relationship between the dynamic surface tension and the static surface tension of the ink composition can be made suitable. When used in the method, it is possible to obtain an ink composition that is excellent in ejection stability and can suppress bleeding on a recording material and obtain a high-quality recorded image.
[0018]
The present invention also provides a dynamic surface tension (σ at the bubble frequency of 10 Hz). ₁₀ ) And the static surface tension (γ) is 20 to 70 mN / m.
[0019]
According to the present invention, the dynamic surface tension (σ ₁₀ ) And the static surface tension (γ) are 20 mN / m or more and 70 mN / m or less. σ ₁₀ And γ of less than 20 mN / m, the dynamic surface tension and static surface tension of the ink composition become too low, so that the permeability of the ink composition to the absorbent recording material becomes too high, and the absorptivity. When the ink composition adheres to the recording material, the ink composition spreads from the landing point to the periphery, and the outline of the formed recorded image becomes unclear. Also σ ₁₀ When γ exceeds 70 mN / m, the dynamic surface tension and static surface tension of the ink composition become too high, so that the permeability of the ink composition to the absorbent recording material becomes too low, and the absorbency Dryability on the recording material decreases. Further, the wettability between the ink composition and the inner wall of the ink chamber is deteriorated, the supply of the ink composition to the ink chamber is delayed, and the ink chamber is hardly filled with the ink composition. Drops cannot be ejected. In addition, it is difficult to form a new surface of the ink composition in a desired shape at the discharge port provided at the tip of the ink chamber, that is, to control the meniscus, so that the ink composition droplets can be continuously formed at high speed. Cannot be discharged. Therefore, as described above, the dynamic surface tension (σ at the bubble frequency of 10 Hz) of a solution obtained by dissolving 0.1% by weight in pure water. ₁₀ ) And the static surface tension (γ) is 20 mN / m or more and 70 mN / m or less, and σ ₁₀ And γ difference d (= σ ₁₀ -Γ) contains a surfactant within a certain range, so that when used in an ink jet recording method, it has excellent ejection stability and suppresses bleeding on a recording material, thereby producing a high-quality recorded image. An obtainable ink composition can be obtained.
[0020]
In the invention, it is preferable that the organic solvent contains at least one of glycol ethers and polyhydric alcohols.
[0021]
According to the present invention, the organic solvent contains at least one of glycol ethers and polyhydric alcohols having a low vapor pressure, so that a wetting effect can be obtained and discharge stability can be improved.
[0022]
In the invention, it is preferable that the coloring material contains a dye.
According to the invention, since the color material contains a dye, it is possible to suppress the occurrence of clogging and improve the discharge stability.
[0023]
In the invention, it is preferable that the color material includes a pigment.
According to the invention, since the color material contains a pigment, a recorded image having excellent light resistance and water resistance can be obtained.
[0024]
In the invention, it is preferable that the pigment has a hydrophilic group.
According to the invention, since the pigment has a hydrophilic group, it can be stably dispersed in the ink composition containing water. Therefore, since the occurrence of clogging can be suppressed, an ink composition capable of obtaining a recorded image having excellent light resistance and water resistance without impairing ejection stability can be obtained.
[0025]
In the invention, it is preferable that the surfactant includes a nonionic surfactant.
[0026]
According to the present invention, the surfactant includes a nonionic surfactant that is not easily affected by the coexisting electrolyte. Therefore, the surfactant is used regardless of whether an electrolyte is added to the ink composition. The relationship between the dynamic surface tension and the static surface tension of the ink composition controlled by the agent can be made favorable.
[0027]
Further, the present invention is characterized in that the surfactant is contained in a critical micelle concentration or more.
[0028]
According to the present invention, the surfactant is contained in a critical micelle concentration or more. The surface tension of the solution containing the surfactant decreases with the increase of the surfactant up to the critical micelle concentration, but is almost constant above the critical micelle concentration. Therefore, as described above, by containing the surfactant at a critical micelle concentration or more, the surface effect of the surfactant is sufficiently exerted, and the dynamic surface tension of the ink composition controlled by the surfactant is controlled. In addition, since the static surface tension can be set to a substantially constant value, an ink composition having uniform properties can be obtained.
[0029]
In the present invention, the pigment may be C.I. I. Pigment blue 15: 3 and C.I. I. It contains at least one pigment of CI Pigment Blue 15: 4.
[0030]
According to the invention, the pigment is C.I. I. Pigment blue 15: 3 and C.I. I. Since it contains at least one pigment of CI Pigment Blue 15: 4, an ink composition capable of realizing a recorded image having excellent cyan color developability can be obtained.
[0031]
In the present invention, the pigment may be C.I. I. Pigment red 122, C.I. I. Pigment red 209 and C.I. I. And at least one pigment selected from the group consisting of CI Pigment Violet 19.
[0032]
According to the invention, the pigment is C.I. I. Pigment red 122, C.I. I. Pigment red 209 and C.I. I. Since it contains at least one pigment selected from the group consisting of CI Pigment Violet 19, an ink composition capable of realizing a recorded image with excellent magenta color developability can be obtained.
[0033]
In the present invention, the pigment may be C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 150 and C.I. I. And at least one pigment selected from the group consisting of CI Pigment Yellow 180.
[0034]
According to the invention, the pigment is C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 150 and C.I. I. Since at least one pigment selected from the group consisting of CI Pigment Yellow 180 is contained, an ink composition capable of realizing a recorded image with excellent yellow color developability can be obtained.
[0035]
In the invention, it is preferable that the pigment contains carbon black.
According to the invention, since the pigment contains carbon black, it is possible to obtain an ink composition capable of realizing a recorded image having excellent black color developability.
[0036]
Further, the present invention is a recording method for recording an image by attaching an ink composition onto a recording material,
Any one of the ink compositions of the present invention is used as the ink composition.
[0037]
According to the present invention, since any one of the ink compositions of the present invention is used in a recording method for recording an image by depositing an ink composition on a recording material, a high-quality recorded image can be stabilized. Can be provided.
[0038]
Further, the present invention is a recording method for recording an image by ejecting droplets of the ink composition by applying pressure to the ink composition and attaching the droplets on a recording material,
Any one of the ink compositions of the present invention is used as the ink composition.
[0039]
According to the present invention, a recording method for recording an image by applying a pressure to an ink composition, ejecting droplets of the ink composition, and depositing the droplets on a recording material, that is, an inkjet recording method. Since any one of the ink compositions of the present invention is used, stable ejection is possible and a high-quality recorded image can be stably provided.
[0040]
In the ink composition, at least the pigment may include C.I. I. Pigment blue 15: 3 and C.I. I. Pigment Blue 15: 4, an ink composition containing at least one pigment, and the pigment includes C.I. I. Pigment red 122, C.I. I. Pigment red 209 and C.I. I. An ink composition containing at least one pigment selected from the group consisting of CI Pigment Violet 19; I. Pigment yellow 74, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 150 and C.I. I. And an ink composition containing at least one pigment selected from the group consisting of CI Pigment Yellow 180.
[0041]
According to the present invention, the ink composition includes at least an ink composition capable of realizing a recorded image excellent in cyan color developability, an ink composition capable of realizing a recorded image excellent in magenta color developability, and yellow And an ink composition capable of realizing a recorded image having excellent color developability. By superimposing these three types of ink compositions, a dark black recorded image can be obtained. Therefore, since various colors can be expressed by using the above-described three kinds of ink compositions, a full-color recorded image having excellent color developability can be provided.
[0042]
In the ink composition, at least the pigment may include C.I. I. Pigment blue 15: 3 and C.I. I. Pigment Blue 15: 4, an ink composition containing at least one pigment, and the pigment includes C.I. I. Pigment red 122, C.I. I. Pigment red 209 and C.I. I. An ink composition containing at least one pigment selected from the group consisting of CI Pigment Violet 19; I. Pigment yellow 74, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 150 and C.I. I. An ink composition containing at least one pigment selected from the group consisting of CI Pigment Yellow 180 and an ink composition containing carbon black as the pigment are used.
[0043]
According to the present invention, the ink composition includes at least an ink composition capable of realizing a recorded image excellent in cyan color developability, an ink composition capable of realizing a recorded image excellent in magenta color developability, and yellow An ink composition capable of realizing a recorded image having excellent color developability and an ink composition capable of realizing a recorded image excellent in black color developability are used. Ink composition capable of realizing a recording image having excellent cyan color development, an ink composition capable of realizing a recording image excellent in magenta color development, and an ink composition capable of realizing a recording image excellent in yellow color development By superimposing three kinds of ink compositions on the object, a dark black recorded image can be obtained. Therefore, various colors can be expressed by using four types of ink compositions obtained by adding the above-described three types of ink compositions to the above-described ink composition capable of realizing a recorded image having excellent black color development. Therefore, it is possible to provide a full-color recorded image having excellent color developability.
[0044]
The present invention is a recorded image recorded by the recording method.
[0045]
According to the present invention, since the recorded image is recorded by the recording method, a high-quality recorded image can be obtained.
[0046]
In the present invention, the pigment may be C.I. I. Pigment blue 15: 3 and C.I. I. An ink composition comprising at least one pigment of CI Pigment Blue 15: 4;
The pigment is C.I. I. Pigment red 122, C.I. I. Pigment red 209 and C.I. I. An ink composition comprising at least one pigment selected from the group consisting of CI Pigment Violet 19;
The pigment is C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 150 and C.I. I. And an ink composition containing at least one pigment selected from the group consisting of CI Pigment Yellow 180.
[0047]
According to the present invention, the ink set has an ink composition capable of realizing a recorded image excellent in cyan color developability, an ink composition capable of realizing a recorded image excellent in magenta color developability, and excellent yellow color developability. And an ink composition capable of realizing a recorded image. By superimposing these three types of ink compositions, a dark black recorded image can be realized. That is, an ink set including the above-described three types of ink compositions is excellent in color balance. Accordingly, since various colors can be expressed by using an ink set including the above-described three types of ink compositions, a full-color recorded image having excellent color developability can be realized.
[0048]
In the present invention, the pigment may be C.I. I. Pigment blue 15: 3 and C.I. I. An ink composition comprising at least one pigment of CI Pigment Blue 15: 4;
The pigment is C.I. I. Pigment red 122, C.I. I. Pigment red 209 and C.I. I. An ink composition comprising at least one pigment selected from the group consisting of CI Pigment Violet 19;
The pigment is C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 150 and C.I. I. An ink composition comprising at least one pigment selected from the group consisting of CI Pigment Yellow 180;
An ink set, wherein the pigment contains an ink composition containing carbon black.
[0049]
According to the present invention, the ink set has an ink composition capable of realizing a recorded image excellent in cyan color developability, an ink composition capable of realizing a recorded image excellent in magenta color developability, and excellent yellow color developability. An ink composition capable of realizing a recorded image, and an ink composition capable of realizing a recorded image excellent in black color developability. Ink composition capable of realizing a recording image having excellent cyan color development, an ink composition capable of realizing a recording image excellent in magenta color development, and an ink composition capable of realizing a recording image excellent in yellow color development By superimposing three kinds of ink compositions on the object, a dark black recorded image can be realized. That is, an ink set including the above-described three types of ink compositions is excellent in color balance. Accordingly, various colors can be obtained by using an ink set including four ink compositions obtained by adding the above-described three ink compositions to the above-described ink composition capable of realizing a recorded image excellent in black color developability. Therefore, it is possible to realize a full-color recorded image having excellent color developability.
[0050]
The present invention also includes an ink tank for storing any of the ink compositions of the present invention,
An ink chamber having a discharge port for discharging droplets of the ink composition, and the ink composition being supplied from the ink tank;
A piezoelectric element that generates strain in response to an applied voltage, the piezoelectric element being provided in at least a part of the ink chamber and applying pressure to the ink composition housed in the ink chamber;
And an electrode provided for applying a voltage to the piezoelectric element.
[0051]
According to the present invention, the ink head stores any one of the ink compositions of the present invention by an ink tank, and is ejected from the ink tank by an ink chamber having an ejection port for ejecting droplets of the ink composition. A piezoelectric element that accommodates the supplied ink composition and generates distortion in response to an applied voltage, the ink being accommodated in the ink chamber by a piezoelectric element provided in at least a part of the ink chamber A pressure is applied to the composition, and a voltage is applied to the piezoelectric element by an electrode. Accordingly, it is possible to obtain a piezo-type ink head capable of ejecting droplets of the ink composition from the ejection port in accordance with the voltage applied to the piezoelectric element. Further, since the ink tank stores any one of the ink compositions of the present invention, the ink composition droplets can be stably discharged from the discharge port. By using such an ink head, a highly reliable piezo-type ink jet recording apparatus can be realized.
[0052]
The present invention also includes an ink tank for storing any of the ink compositions of the present invention,
An ink chamber having a discharge port for discharging droplets of the ink composition, and the ink composition being supplied from the ink tank;
A heating element that is provided in at least a part of the ink chamber and applies pressure to the ink composition by generating bubbles by heating the ink composition housed in the ink chamber;
An ink head comprising: an electrode provided for applying a voltage to the heating element.
[0053]
According to the present invention, the ink head stores any one of the ink compositions of the present invention by an ink tank, and is ejected from the ink tank by an ink chamber having an ejection port for ejecting droplets of the ink composition. The ink composition is stored in the ink composition by heating the ink composition stored in the ink chamber by a heating element provided in at least a part of the ink chamber and generating bubbles. A pressure is applied to the heating element to apply a voltage to the heating element. This makes it possible to obtain a thermal ink jet type ink head capable of discharging droplets of the ink composition from the discharge port in accordance with the voltage applied to the heating element. Further, since the ink tank stores any one of the ink compositions of the present invention, the ink composition droplets can be stably discharged from the discharge port. If such an ink head is used, a highly reliable thermal ink jet recording apparatus can be realized.
[0054]
According to another aspect of the present invention, there is provided a recorded image in which droplets of an ink composition ejected by the piezo-type ink head are recorded by being deposited on a recording material.
[0055]
According to the present invention, as described above, the recording image is formed by the ink composition droplets ejected by the piezo-type ink head capable of stably ejecting the ink composition droplets on the recording material. Therefore, a high-quality recorded image can be stably obtained.
[0056]
According to another aspect of the present invention, there is provided a recorded image in which droplets of an ink composition ejected by the thermal ink jet type ink head are recorded by adhering onto a recording material.
[0057]
According to the present invention, a recording image is a recording material in which a droplet of an ink composition discharged by an ink head of a thermal ink jet system capable of stably discharging a droplet of the ink composition as described above. Since it is recorded by adhering to the top, a high-quality recorded image can be stably obtained.
[0058]
DETAILED DESCRIPTION OF THE INVENTION
The ink composition according to the first embodiment of the present invention has a temperature of 24 ° C. or higher and 26 ° C. or lower of a solution obtained by dissolving 0.1% by weight in a coloring material, an organic solvent, water, and pure water. Dynamic surface tension (σ at a bubble frequency of 10 Hz measured by the maximum bubble pressure method ₁₀ ) And the static surface tension (γ) measured at a temperature between 24 ° C. and 26 ° C. ₁₀ -Γ) contains a surfactant that satisfies the following formula (1).
0 mN / m ≦ d ≦ 15 mN / m (1)
[0059]
Here, pure water is 0.1 × 10 5 at 25 ° C. ⁶ It is water having an electrical resistivity of Ω · cm or more. The “0.1 × 10” used in the definition of the pure water. ⁶ “Electrical resistivity of Ω · cm or higher” is expressed as “electrical conductivity of 10 μS / cm or lower”.
[0060]
The maximum bubble pressure method, which is a method for measuring dynamic surface tension, will be described.
The maximum bubble pressure method inserts a thin tube into the liquid and generates bubbles from the tip of the thin tube to form an interface between the liquid and gas in the liquid. That is, the pressure difference (ΔP) is measured when the bubble radius becomes equal to the radius (r) of the narrow tube, and the surface tension (σ) is obtained from the measured value. The surface tension (σ) is obtained from the following formula (2).
σ = ΔP · r / 2 (2)
[0061]
By changing the bubble frequency, which is the number of bubbles generated per unit time, from surface tension in a state that can be regarded as static with slow motion, to surface tension in dynamic state with fast movement, that is, dynamic surface tension Can be requested. In addition, by determining the surface tension from a state that can be regarded as static with slow motion to a dynamic state with fast motion, it is possible to evaluate the change in the dynamic properties of the liquid.
[0062]
As a method for measuring the static surface tension, for example, an annular method or a hanging plate method known as the Di Nui method can be used. In the present embodiment, the static surface tension is measured by the hanging plate method.
[0063]
The ink composition of the present embodiment is used in a recording method for recording an image by adhering the ink composition onto a recording material, for example, an inkjet recording method or a recording method using a writing instrument such as a pen. By using the ink composition of the present embodiment, it is possible to stably provide a high-quality recorded image.
[0064]
Among the recording methods described above, the ink composition of the present embodiment is suitably used for the ink jet recording method. In the ink jet recording method, a pressure is applied to an ink composition to eject droplets of the ink composition, and an image is recorded by depositing the droplets on a recording material. By using the ink composition of the present embodiment in the ink jet recording method, stable ejection can be achieved and a high-quality recorded image can be stably provided.
[0065]
In an ink jet recording apparatus that records an image using an ink jet recording method, when ink composition droplets are continuously ejected, a new ink composition is formed at an ejection port provided at the tip of an ink chamber in the ink head. Since the surface is constantly generated, the ink composition moves quickly and is greatly affected by the dynamic surface tension. On the other hand, in the ink chamber, after the ink composition is ejected, the volume of the ink composition that is ejected and reduced is supplied from the ink tank by capillary action, so that the ink composition moves slowly and is in a static state. It can be considered that the effect of static surface tension is great. In other words, since both the dynamic surface tension and the static surface tension of the ink composition affect the ejection, the dynamic surface tension and the static surface tension are required to stably eject the ink composition droplets. It is necessary to balance the surface tension. In addition, the movement of the ink composition when an ink composition droplet is deposited on a recording material to record an image is fast at the moment the droplet lands on the recording material, but then gradually decreases. In the case of an absorbent recording material, the ink composition slowly penetrates into the recording material. That is, since the surface tension of the ink composition changes from a dynamic one to a static one, if the difference between the dynamic surface tension and the static surface tension is large, the ink composition dries on the recording material. It takes time and bleeding occurs. Moreover, it penetrates too much and causes a strike through. Thus, in the ink jet recording method, the relationship between the dynamic surface tension and the static surface tension of the ink composition is important.
[0066]
The dynamic surface tension and static surface tension of the ink composition are most affected by the surfactant, although they vary depending on the type and content of the organic solvent contained in the ink composition. That is, since the dynamic surface tension and static surface tension of the ink composition can be controlled by the surfactant, the dynamic properties of the ink composition can be determined by defining the properties of the surfactant contained in the ink composition. The relationship between surface tension and static surface tension can be controlled. Therefore, as described above, the dynamic surface tension (σ at a bubble frequency of 10 Hz) of a solution obtained by dissolving 0.1% by weight in pure water. ₁₀ ) And the static surface tension (γ) difference d (= σ ₁₀ -Γ) contains a surfactant that satisfies the above formula (1), whereby the relationship between the dynamic surface tension and the static surface tension of the ink composition can be made suitable. When used in a recording method, it is possible to obtain an ink composition that is excellent in ejection stability and can suppress bleeding on a recording material and obtain a high-quality recorded image.
[0067]
The reason for limiting the range in selecting the surfactant in the ink composition of the present embodiment will be described below.
[0068]
σ ₁₀ And γ difference d (= σ ₁₀ When -γ) exceeds 15 mN / m, the balance between the dynamic surface tension and the static surface tension of the ink composition is deteriorated, and droplets cannot be ejected stably. Further, since drying takes time on the recording material and bleeding occurs, the image quality deteriorates. Therefore, it was set to 15 mN / m or less.
[0069]
σ ₁₀ And γ difference d (= σ ₁₀ -Γ) is less than 0 mN / m, the static surface tension of the ink composition is increased, the wettability of the ink composition with respect to the members constituting the ink head is reduced, and the ink composition is filled in the ink chamber. It becomes difficult. Therefore, it was set to 0 mN / m or more.
[0070]
Dynamic surface tension (σ ₁₀ ) And static surface tension (γ) are preferably 20 mN / m or more and 70 mN / m or less, and more preferably 20 mN / m or more and 45 mN / m or less.
[0071]
σ ₁₀ And γ of less than 20 mN / m, the dynamic surface tension and static surface tension of the ink composition become too low, so that the permeability of the ink composition to the absorbent recording material becomes too high, and the absorptivity. When the ink composition adheres to the recording material, the ink composition spreads from the landing point to the periphery, and the outline of the formed recorded image becomes unclear. Also σ ₁₀ When γ exceeds 70 mN / m, the dynamic surface tension and static surface tension of the ink composition become too high, so that the permeability of the ink composition to the absorbent recording material becomes too low, and the absorbency Dryability on the recording material decreases. Further, the wettability between the ink composition and the inner wall of the ink chamber is deteriorated, the supply of the ink composition to the ink chamber is delayed, and the ink chamber is hardly filled with the ink composition. Drops cannot be ejected. In addition, it is difficult to form a new surface of the ink composition in a desired shape at the discharge port provided at the tip of the ink chamber, that is, to control the meniscus, so that the ink composition droplets can be continuously formed at high speed. Cannot be discharged. Therefore, it is set to 20 mN / m or more and 70 mN / m or less.
[0072]
The surfactant that satisfies the above-described conditions may be any of a nonionic surfactant, an anionic surfactant, a cationic surfactant, and an amphoteric surfactant. The type of surfactant such as nonionic, anionic and cationic is selected according to the type of electrolyte contained in the ink composition. For example, when the ink composition contains an anionic substance, a nonionic or anionic surfactant is used. These surfactants may be used in combination. At this time, the types of surfactants such as nonionic, anionic and cationic may be the same or different.
[0073]
Specific examples of the surfactant that satisfies the above-described conditions include surfactants represented by the following general formula (I), (II), (III), (IV), (V), or (VI). However, the surfactant satisfying the above-mentioned conditions is not limited to this.
[0074]
[Chemical 1]

[0075]
[Chemical formula 2]

[0076]
[Chemical 3]

[0077]
[Formula 4]

[0078]
[Chemical formula 5]

[0079]
[Chemical 6]

[0080]
In the said general formula (I), m shows the integer or decimal of 0-30, n shows the integer or decimal of 0-30. However, the sum (m + n) of m and n is an integer of 0 to 30 or a decimal.
[0081]
In the general formula (II), k represents an integer or decimal of 11 to 13, and 1 represents an integer or decimal of 3 to 30.
[0082]
In the general formula (III), h represents an integer or decimal of 0 to 11, i represents an integer or decimal of 0 to 11, and j represents an integer or decimal of 3 to 50. However, the sum (h + i) of h and i is an integer or a decimal number of 9 to 11.
[0083]
In the general formula (IV), w represents an integer or decimal of 0 to 11, x represents an integer or decimal of 5 to 9, y represents an integer or decimal of 2.5 to 5, and z represents 0 to Indicates an integer or decimal of 9. However, the sum (w + z) of w and z is an integer or a decimal number of 9 to 11.
[0084]
In the said general formula (V), p shows the integer or decimal of 0-78, q shows the integer or decimal of 2-15, r shows the integer or decimal of 0-18.
[0085]
In the said general formula (VI), s shows the integer or decimal of 0-30, and t shows the integer or decimal of 0-30. However, the sum (s + t) of s and t is an integer of 0 to 30 or a decimal. U represents an integer or decimal of 0 to 10, and v represents an integer or decimal of 0 to 10. However, the sum (u + v) of u and v is an integer of 0 to 10 or a decimal.
[0086]
Among the above-mentioned surfactants, the nonionic surfactant is not easily affected by the coexisting electrolyte, and is controlled by the surfactant regardless of whether the electrolyte is added to the ink composition. Since the relationship between the dynamic surface tension and the static surface tension of the ink composition can be made suitable, it is preferable to use this for the surfactant.
[0087]
The surfactant that satisfies the above-mentioned conditions is preferably contained in the ink composition at a critical micelle concentration or more. The surface tension of the solution containing the surfactant decreases with the increase of the surfactant up to the critical micelle concentration, but is almost constant above the critical micelle concentration. Therefore, as described above, by containing the surfactant at a critical micelle concentration or more, the effect of the surfactant is sufficiently exerted, and the dynamic surface tension and static of the ink composition controlled by the surfactant are controlled. Since the surface tension can be set to a substantially constant value, an ink composition having uniform properties can be obtained.
[0088]
Although the critical micelle concentration is different for each surfactant, it is 0.001 at 25 ° C. in any case of a nonionic surfactant, an anionic surfactant, a cationic surfactant and an amphoteric surfactant. It is about 3 to 3% by weight.
[0089]
The ink composition of the present embodiment may contain not only a surfactant that satisfies the above-described conditions, but also other surfactants that do not satisfy the above-described conditions.
[0090]
Further, the ink composition of the present embodiment contains water as described above. Accordingly, it is possible to suppress bleeding on the absorbent recording material and improve the drying property.
[0091]
The water content in the ink composition is preferably 30% by weight or more and 95% by weight or less, and more preferably 30% by weight or more and 85% by weight or less. If the water content is less than 30% by weight, the content of the organic solvent in the ink composition is excessively increased. Therefore, an additive that dissolves or disperses in water should be stably present in the ink composition. Becomes difficult. In addition, the viscosity is remarkably increased and may deviate from the proper viscosity as the ink composition. If the water content exceeds 95% by weight, the content of the organic solvent becomes too small, so that the wettability of the ink composition cannot be maintained. Therefore, the content is set to 30% by weight or more and 95% by weight or less.
[0092]
Specific examples of the organic solvent include amides such as dimethylformamide and dimethylacetamide, polyethylene glycol, polypropylene glycol, ethylene glycol, diethylene glycol, thiodiglycol, propylene glycol, triethylene glycol, 1,5-pentanediol, 1 Polyhydric alcohols such as 1,4-butanediol, 1,2-hexanediol, 1,3-propanediol, glycerin and 1,2,6-hexanetriol, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether Diethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monoethyl ether, Ethers of polyhydric alcohols such as glycol ethers such as raethylene glycol monomethyl ether and ethylene glycol monophenyl ether, sulfur-containing compounds such as sulfolane and dimethyl sulfoxide, nitrogen such as 2-pyrrolidone, N-methylpyrrolidone and ε-caprolactam Examples of the organic solvent include, but are not limited to, an oxygen-containing compound such as γ-butyrolactone and a polyfunctional compound such as dimethylaminoethanol, diethylaminoethanol, triethanolamine, and morpholine. One of these organic solvents may be used alone, or two or more thereof may be mixed and used.
[0093]
Among the organic solvents described above, glycol ethers and polyhydric alcohols have low vapor pressure, and can be incorporated into the ink composition to obtain a wetting effect and improve discharge stability. The solvent preferably contains at least one of glycol ethers and polyhydric alcohols. Among glycol ethers and polyhydric alcohols, diethylene glycol monobutyl ether which is glycol ether, propylene glycol monobutyl ether, triethylene glycol monobutyl ether or tetraethylene glycol monobutyl ether, or glycerin which is polyhydric alcohol, 1,2- Hexanediol or 1,5-pentanediol has a vapor pressure at 25 ° C. of 0.05 mmHg or less and is excellent in the wetting effect, so that these are more preferably used as the organic solvent.
[0094]
The content of the organic solvent in the ink composition is preferably 3% by weight or more and 70% by weight or less, and more preferably 3% by weight or more and 50% by weight or less. When the content of the organic solvent is less than 3% by weight, the ink composition is quickly dried and it is difficult to maintain wettability. When the content of the organic solvent exceeds 70% by weight, a case where the water-soluble or water-dispersible additive cannot be stably present in the ink composition may occur. Depending on the type of organic solvent used, the viscosity increases remarkably and may exceed the appropriate viscosity for the ink composition. Therefore, the content is 3% by weight or more and 70% by weight or less. However, the content of the organic solvent in the ink composition is preferably 3% by weight or more and 40% by weight or less, more preferably 3% by weight or more and 30% or less when the ink composition is mainly composed of water. % By weight or less. When the ink composition contains water as a main component and the content of the organic solvent exceeds 40% by weight, the quality of the recorded image is deteriorated and the ink composition is dried, depending on the type of color material used. A time delay occurs. Therefore, the content is 3% by weight or more and 40% by weight or less.
[0095]
As the coloring material, a dye, a pigment, or a mixture thereof is used. The dyes and pigments may contain them, or may be those to which they are attached.
[0096]
By using a dye for the color material, the occurrence of clogging can be suppressed and the ejection stability can be improved. Further, by using a pigment as the color material, a recorded image having excellent light resistance and water resistance can be obtained.
[0097]
For reproduction of each color in the full-color inkjet recording method, ink compositions of three colors of cyan (abbreviation: C), magenta (abbreviation: M), and yellow (abbreviation: Y) are used. Each color is expressed by mixing the ink compositions. However, since it is difficult to reproduce black in the mixed colors of the three colors, a black ink composition is generally used for black expression. By changing the color of the color material to be contained, an ink composition of cyan, magenta, yellow or black can be obtained.
[0098]
As the dye, water-soluble dyes such as acid dyes, direct dyes, reactive dyes and food colorings are preferably used. Among these, it is preferable to use a material excellent in water resistance, light resistance or safety.
[0099]
Specific examples of the dye include the following dyes, but the dye is not limited thereto. In the following, the dye is indicated by a color index (abbreviation: CI) number.
[0100]
Examples of the dye used in the cyan ink composition include acid dyes such as C.I. I. Acid Blue 7, 9, 29, 45, 92 and 249, a direct dye C.I. I. Direct Blue 1, 2, 6, 15, 22, 25, 71, 76, 79, 86, 90, 98, 163, 165, 199 and 202, and the reactive dye C.I. I. Reactive blue 1, 2, 7, 14, 15, 23, 32, 38, 41, 63, 80 and 95 can be mentioned. Among these, C.I. I. Acid Blue 7 and 9, and C.I. I. It is preferable to use at least one dye selected from the group consisting of Direct Blue 199.
[0101]
Examples of the dye used in the magenta ink composition include acid dyes such as C.I. I. Acid Red 1, 8, 13, 14, 18, 26, 27, 35, 37, 42, 52, 82, 87, 89, 92, 97, 106, 111, 114, 115, 134, 186, 249, 254 and 289, a direct dye C.I. I. Direct Red 1, 4, 9, 13, 17, 20, 28, 31, 39, 80, 81, 83, 89, 225 and 227, C.I. I. Direct Orange 26, 29, 62 and 102 and the reactive dye C.I. I. Reactive Red 1,14,17,25,26,32,37,44,46,55,58,60,66,74,79,96,97,141,147,180,181 etc. are mentioned. Among these, C.I. I. Acid Red 52 and 289, and C.I. I. It is preferable to use at least one dye selected from the group consisting of Reactive Red 58, 141 and 180.
[0102]
Examples of the dye used in the yellow ink composition include acid dyes such as C.I. I. Acid Yellow 1, 7, 17, 23, 42, 44, 79 and 142, C.I. I. Direct yellow 1,12,24,26,33,44,50,86,120,132,142 and 144, and the reactive dye C.I. I. Reactive yellow 1,5,11,13,14,20,21,22,25,40,47,51,55,65,67 etc. are mentioned. Among these, C.I. I. Acid Yellow 17 and 23, and C.I. I. It is preferable to use at least one dye selected from the group consisting of direct yellow 86.
[0103]
Examples of the dye used in the black ink composition include C.I. I. Food Black 2, a direct dye C.I. I. Direct Black 19, 22, 32, 38, 51, 56, 71, 74, 75, 77, 154, 168 and 171 and the reactive dye C.I. I. Reactive black 3, 4, 7, 11, 12, 17 and the like can be mentioned. Among these, C.I. I. Food Black 2 and C.I. I. It is preferable to use at least one dye of direct black 154.
[0104]
These dyes are used within a range that dissolves stably at room temperature. Since this range is different for each dye, the content of the dye in the ink composition is not particularly limited, but is preferably 0.1% by weight to 10% by weight.
[0105]
As the pigment, any pigment that can be dispersed in a solution may be used, but a pigment that is excellent in light resistance or safety is preferably used.
[0106]
Specific examples of the pigment include the following pigments, but the pigment is not limited thereto. Hereinafter, the pigment is indicated by a color index (CI) number.
[0107]
Examples of the pigment used in the cyan ink composition include C.I. I. Pigment Blue 1, 2, 15, 16, 17, 21, 21, 22, 60 and 64.
[0108]
Examples of the pigment used in the magenta ink composition include C.I. I. Pigment Red 2, 3, 5, 16, 23, 31, 49, 57, 63, 122 and 209, and C.I. I. Pigment violet 19 and the like.
[0109]
Examples of the pigment used in the yellow ink composition include C.I. I. Pigment yellow 1, 2, 3, 5, 12, 74, 138, 150 and 180.
[0110]
Examples of the pigment used in the black ink composition include carbon black such as channel black, furnace black, thermal black, and lamp black.
[0111]
Among these pigments, cyan ink compositions include C.I. I. Pigment blue 15: 3 and C.I. I. It is preferable to use at least one pigment of CI Pigment Blue 15: 4. The magenta ink composition includes C.I. I. Pigment red 122, C.I. I. Pigment red 209 and C.I. I. It is preferable to use at least one pigment selected from the group consisting of CI pigment violet 19. The yellow ink composition includes C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 150 and C.I. I. It is preferable to use at least one pigment selected from the group consisting of CI Pigment Yellow 180. In addition, it is preferable to use at least one pigment selected from the aforementioned carbon blacks for the black ink composition. By using these pigments, it is possible to obtain an ink composition capable of realizing a recorded image having excellent color developability of cyan, magenta, yellow or black.
[0112]
Also, cyan, magenta and yellow ink compositions using these preferred pigments, that is, C.I. I. Pigment blue 15: 3 and C.I. I. A cyan ink composition using at least one pigment of CI Pigment Blue 15: 4; I. Pigment red 122, C.I. I. Pigment red 209 and C.I. I. Magenta ink composition using at least one pigment selected from the group consisting of CI Pigment Violet 19; I. Pigment yellow 74, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 150 and C.I. I. Similar to a recorded image formed using a black ink composition by superimposing three types of ink compositions with a yellow ink composition using at least one pigment selected from the group consisting of CI Pigment Yellow 180 A dark black recorded image can be obtained. That is, an ink set including these three types of ink compositions is excellent in color balance. Accordingly, an ink set including these three types of ink compositions, or an ink set including four types of ink compositions obtained by adding a black ink composition using carbon black to these three types of ink compositions. By using it, various colors can be expressed, so that it is possible to realize a full-color recorded image having excellent color developability.
[0113]
The pigment preferably has one or more hydrophilic groups selected from the group consisting of, for example, a carboxyl group, a hydroxyl group, an amino group, and a sulfonic acid group. These hydrophilic groups may be introduced directly by chemically modifying the pigment surface, or may be introduced by coating the pigment surface with a polymer having these hydrophilic groups. These hydrophilic groups may be in the form of a salt.
[0114]
The pigment having a hydrophilic group can be stably dispersed in the ink composition containing water. Therefore, by using a pigment having a hydrophilic group as a coloring material, occurrence of clogging can be suppressed, and a recorded image having excellent light resistance and water resistance can be obtained without impairing ejection stability.
[0115]
These pigments are used within a range in which they are stably dispersed at room temperature. Since this range is different for each pigment, the content of the pigment in the ink composition is not particularly limited, but is preferably 0.1% by weight to 10% by weight.
[0116]
In addition, the ink composition of the present embodiment preferably contains a binder resin when a pigment is used as the color material. By including the binder resin, it is possible to prevent the pigment from peeling off from the recording material.
[0117]
As the binder resin, for example, one or more selected from the group consisting of a polyester resin, an acrylic resin, a styrene-acrylic copolymer resin, a polyester-acrylic copolymer resin, and the like are used.
[0118]
In addition to the colorant, organic solvent, water, surfactant, and binder resin, the ink composition of the present embodiment includes various additives such as a fungicide, a pH adjuster, a chelating agent, a rust inhibitor, and an ultraviolet ray. An absorbent or the like may be included.
[0119]
As the fungicide, sodium dehydroacetate, sodium benzoate or sodium sorbitanate is preferably used.
[0120]
As the pH adjuster, triethanolamine, sodium hydroxide, sodium carbonate, sodium nitrate or potassium nitrate is preferably used.
[0121]
The viscosity of the ink composition of the present embodiment containing a coloring material, an organic solvent, water, and a surfactant that satisfies the above-mentioned conditions is preferably 20 mPa · s or less at 25 ° C., more preferably 15 mPa · s or less. When the viscosity at 25 ° C. of the ink composition exceeds 20 mPa · s, the ink composition droplets cannot be stably ejected when used in the ink jet recording method. Therefore, it was set to 20 mPa · s or less.
[0122]
FIG. 1 is an exploded perspective view showing a simplified configuration of an ink head 1 according to a second embodiment of the present invention. FIG. 2 shows a configuration of a head plate 10 constituting the ink head 1 shown in FIG. It is a perspective view which expands and shows a part. In FIG. 1, the description of the drive electrode 13 shown in FIG. 2 is omitted because the drawing is complicated and difficult to understand.
[0123]
The ink head 1 includes a head plate 10 having a bottom wall portion 11 and a plurality of partition walls 12 formed of a piezoelectric material, a top plate 20 provided on the upper surface of the partition walls 12, and a plurality of ejection ports 31. A nozzle plate 30 provided at one end of the section 12, a back plate (not shown) provided at the other end of the partition section 12, and an ink tank 50 provided on the top plate 20 and having an opening 51. Consists of including. The plurality of partition walls 12 are arranged in parallel at predetermined intervals on the bottom wall 11, and a plurality of partition walls 12, the bottom wall 11, the top plate 20, the nozzle plate 30, and a back plate (not shown). Ink chamber 40 is formed. In the top plate 20, a common ink supply path 21 that communicates with each ink chamber 40 and an ink supply pipe 22 that connects the common ink supply path 21 and the opening 51 of the ink tank 50 are formed. The ink tank 60 stores the ink composition 60 according to the first embodiment, and the ink composition 60 is supplied to each ink chamber 40 via the common ink supply path 21.
[0124]
Further, as shown in FIG. 2, drive electrodes 13 for applying a voltage to the plurality of partition walls 12 are formed on the surface of the bottom wall portion 11 of the head plate 10 and the plurality of partition walls 12 facing the ink chambers 40. The piezoelectric material forming the plurality of partition walls 12 is polarized in the direction of the arrow 70, and the plurality of partition walls 12 function as piezoelectric elements.
[0125]
The ink head 1 configured as described above is a piezo-type ink that can eject droplets of the ink composition 60 from the ejection port 31 according to the voltage applied to the plurality of partition walls 12 that are piezoelectric elements. Head.
[0126]
The operation principle when the ink composition 60 is ejected from the ink chamber 40 in the ink head 1 will be described. FIG. 3 is a cross-sectional view of the ink head 1 shown in FIG. 1 as viewed from the extension direction of the ink chamber 40. Here, the operation when the ink composition 60 is ejected from the ink chamber 40b will be described.
[0127]
When no voltage is applied to the partition walls 12a and 12b constituting the ink chamber 40b, that is, between the drive electrode 13b of the ink chamber 40b and the drive electrode 13a of the ink chamber 40a adjacent to the ink chamber 40b, and the ink chamber 40b. When there is no potential difference between the drive electrode 13b of the ink chamber 40b and the drive electrode 13c of the ink chamber 40c adjacent to the ink chamber 40b, the ink chamber 40b is filled with the ink composition 60 supplied from the ink tank 50 by capillary action. It is in the state that was done. Similarly, the ink chambers 40 a and 40 c are also filled with the ink composition 60.
[0128]
When a voltage is applied to the drive electrode 13a and the drive electrode 13c, a potential difference is generated between the drive electrode 13b and the drive electrode 13a, and between the drive electrode 13b and the drive electrode 13c, so that the partition walls constituting the ink chamber 40b A voltage is applied to 12a and 12b. By this voltage, electric fields in the directions of arrows 71 and 72 are generated in the partition walls 12a and 12b, respectively, and due to the action of this electric field, the partition walls 12a and 12b constituting the ink chamber 40b are distorted, and the ink chamber 40b side. Deforms to become convex. As a result, a pressure wave is generated, a large pressure is applied to the ink composition 60 filled in the ink chamber 40b, and droplets of the ink composition 60 are ejected from the ejection port 31 shown in FIG.
[0129]
When the application of voltage to the drive electrode 13a and the drive electrode 13c is stopped, the shape of the partition walls 12a and 12b returns to the original state, the volume of the ink chamber 40b returns to the original, and the ink composition 60 corresponding to the restored volume is the above-described volume. 1 is supplied from the ink tank 50 via the common ink supply path 21 shown in FIG. 1, and the ink chamber 40 b returns to the initial state in which the ink composition 60 is filled.
[0130]
In the ink head 1 of the present embodiment, as described above, the ink tank 50 stores the ink composition 60 of the first embodiment, and the ink composition 60 is supplied to the ink chamber 40 and is discharged from the ejection port 31. Since it is ejected as a droplet, the droplet of the ink composition 60 can be stably ejected from the ejection port 31. By using such an ink head, a highly reliable piezo ink jet recording apparatus can be realized, and a high-quality recorded image can be stably obtained.
[0131]
As described above, in the present embodiment, the partition wall 12 constituting the ink chamber 40 is formed of a piezoelectric material and functions as a piezoelectric element. However, the present invention is not limited to this, and the partition wall constituting the ink chamber is not limited thereto. May be formed of a material other than the piezoelectric material, and a piezoelectric element may be provided inside or outside the partition wall.
[0132]
FIG. 4 is a simplified exploded perspective view showing the configuration of the ink head 2 according to the third embodiment of the present invention, and FIG. 5 is a plan view showing a part of the configuration of the ink head 2 shown in FIG. It is. In FIG. 5, the top plate 20 and the ink tank 50 shown in FIG. 4 are not shown because they are complicated to understand. The ink head 2 of the present embodiment is similar to the ink head 1 of the second embodiment, and corresponding portions are denoted by the same reference numerals and description thereof is omitted.
[0133]
It should be noted that the head plate 100 includes a substrate 101, a plurality of partition walls 102 arranged in parallel on the substrate 101 at predetermined intervals, and a heating element provided on the surface of the substrate 101 facing the ink chamber 40. The heater 103 is configured to include drive electrodes 104 and 105 that apply a voltage to the heater 103.
[0134]
The ink head 2 configured as described above is a thermal ink jet type ink head capable of discharging droplets of the ink composition 60 from the discharge port 31 in accordance with the voltage applied to the heater 103 which is a heating element. is there.
[0135]
The operation principle when the ink composition 60 is ejected from the ink chamber 40 in the ink head 2 will be described. FIG. 6 is a cross-sectional view schematically showing how the droplets 61 of the ink composition 60 are ejected from the ink chamber 40. FIG. 6 shows a cross-sectional configuration along the cutting plane line II of the ink head 2 shown in FIG.
[0136]
When no voltage is applied to the heater 103, the ink chamber 40 is filled with the ink composition 60 in the same manner as when no voltage is applied to the partition wall 12 in the ink head 1 of the second embodiment. It has become.
[0137]
When a voltage is applied to the heater 103 by the drive electrodes 104 and 105, the heater 103 generates heat, the ink composition 60 filled in the ink chamber 40 is heated, and bubbles 62 are generated. As a result, a pressure wave is generated, a large pressure is applied to the ink composition 60 filled in the ink chamber 40, and the droplet 61 of the ink composition 60 is ejected from the ejection port 31.
[0138]
When the application of voltage to the heater 103 is stopped, the ink composition 60 in the ink chamber 40 is cooled, the bubbles 62 disappear, and the restored volume of the ink composition 60 is supplied to the common ink shown in FIG. The ink chamber 40 is supplied from the ink tank 50 through the path 21 and returns to the initial state in which the ink composition 60 is filled.
[0139]
In the ink head 2 according to the present embodiment, the ink tank 50 stores the ink composition 60 according to the first embodiment, as in the ink head 1 according to the second embodiment described above. Since it is supplied to the chamber 40 and discharged as the droplet 61 from the discharge port 31, the droplet 61 of the ink composition 60 can be stably discharged from the discharge port 31. If such an ink head is used, a highly reliable thermal ink jet recording apparatus can be realized, and a high-quality recorded image can be stably obtained.
[0140]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In the present embodiment, recording an image may be referred to as printing or printing.
[0141]
<Characteristic evaluation of surfactant>
Seven types of surfactants shown in Table 1 were each dissolved in 0.1% by weight in pure water to prepare a surfactant solution. About each adjusted surfactant solution, the dynamic surface tension and the static surface tension were measured as follows.
[0142]
(Dynamic surface tension)
Using a surface tension meter (manufactured by Kyowa Interface Science Co., Ltd .: BP-4), measurement was performed at a bubble frequency of 0.5 Hz to 35 Hz.
[0143]
(Static surface tension)
It measured using the surface tension meter (Kyowa Interface Science Co., Ltd. product: CBVP-A3).
[0144]
Table 1 shows the dynamic surface tension (σ of each surfactant solution at a bubble frequency of 10 Hz. ₁₀ ) And static surface tension (γ) measured value (mN / m), measured temperature (° C.), and σ ₁₀ And γ difference d (= σ ₁₀ -Γ) value (mN / m). In Table 1, the general formula (I) represents the surfactant represented by the general formula (I), the general formula (II) represents the surfactant represented by the general formula (II), The general formula (III) represents a surfactant represented by the general formula (III), the general formula (IV) represents a surfactant represented by the general formula (IV), and the general formula (V) is Represents a surfactant represented by the general formula (V), a fluorosurfactant 1 represents a surfactant represented by the following structural formula (VII), and a fluorosurfactant 2 represents the following structural formula Represents a surfactant represented by (VIII).
[0145]
[Chemical 7]

[0146]
[Chemical 8]

[0147]
[Table 1]

[0148]
<Ink composition>
Dynamic surface tension at a bubble frequency of 10 Hz measured by the maximum bubble pressure method at a temperature of 24-26 ° C. of a solution obtained by dissolving 0.1% by weight in pure water using the surfactant shown in Table 1. σ ₁₀ ) And the static surface tension (γ) measured at a temperature of 24-26 ° C. d (= σ ₁₀ -Γ) Ink compositions of Examples 1 to 7 containing a surfactant satisfying the formula (1), and Comparative Examples 1 to 4 where d does not contain a surfactant satisfying the formula (1) Ink composition was obtained. Table 2 shows the content of each component contained in each ink composition of Examples 1 to 7 and Comparative Examples 1 to 4. In Table 2, the unit of the value in each column is parts by weight, and the total amount of each ink composition of Examples 1 to 7 and Comparative Examples 1 to 4 is 100 parts by weight. In Table 2, TEGBE represents triethylene glycol monobutyl ether, and PEG 400 represents polyethylene glycol having a molecular weight of 400 (
Polyethylene glycol).
[0149]
[Table 2]

[0150]
For each of the obtained ink compositions of Examples 1 to 7 and Comparative Examples 1 to 4, the ejection stability when used in the inkjet recording method and the evaluation of the image quality of the obtained recorded image were performed as follows.
[0151]
(Discharge stability)
Examples 1 to 7 obtained in ink tanks of an ink jet recording apparatus obtained by remodeling a commercially available ink jet recording apparatus (manufactured by Sharp Corporation: AJ2000) so that the ink head 1 shown in FIG. 1 can be mounted. In addition, each of the ink compositions of Comparative Examples 1 to 4 was filled, and the printing density was 5%, and the printing speed was 7 sheets of A4 size paper per minute, on a plain paper for copying machines (product number: SF4AM3) manufactured by Sharp Corporation. Printing was performed continuously. In the test, the ink composition was refilled when the ink tank was emptied, and printing was performed until no ink composition droplets were ejected from the nozzles and printing could not be performed. Was determined as the number of printable sheets and used as an evaluation index for ejection stability. The case where the number of printable sheets exceeded 200 was judged as good (◯), the case where it was 150 to 200 was judged as acceptable (Δ), and the case where it was less than 150 was judged as bad (x).
[0152]
(image quality)
Examples 1 to 7 obtained in ink tanks of an ink jet recording apparatus obtained by remodeling a commercially available ink jet recording apparatus (manufactured by Sharp Corporation: AJ2000) so that the ink head 1 shown in FIG. 1 can be mounted. Each of the ink compositions of Comparative Examples 1 to 4 was filled, and a specific pattern was printed on plain paper for copying machines (product number: SF4AM3) manufactured by Sharp Corporation to form an image for evaluation. After the evaluation image was left for one day, the line width of the set pattern was set to 100, and the relative value of the line width of the pattern of each evaluation image was obtained as an evaluation index for image quality. The case where the relative value of the line width is less than 150 and there is almost no bleeding is judged as good (◯), the case where it is 150 or more and 250 or less and there is a slight bleeding is judged as acceptable (△), and the case where there is much bleeding exceeding 250 is bad. (X).
The above evaluation results are shown in Table 3.
[0153]
[Table 3]

[0154]
Dynamic surface tension (σ ₁₀ ) And the static surface tension (γ) difference d (= σ ₁₀ In the ink compositions of Examples 1 to 7 in which -γ) contains a surfactant satisfying the formula (1), both the ejection stability and the image quality were good. On the other hand, the ink compositions of Comparative Examples 1 to 4 in which d does not contain a surfactant satisfying the above formula (1), and d contains a surfactant greater than 15 and deviating from the formula (1). However, both ejection stability and image quality were poor.
[0155]
As described above, dynamic surface tension (σ at a bubble frequency of 10 Hz measured at a temperature of 24-26 ° C. of a solution obtained by dissolving 0.1% by weight in pure water. ₁₀ ) And the static surface tension (γ) measured at a temperature of 24-26 ° C. d (= σ ₁₀ -Γ) contains a surfactant satisfying the above formula (1), so that when used in an ink jet recording method, the discharge stability is excellent, and bleeding on the recording material is suppressed and a high quality recorded image is obtained. An ink composition capable of obtaining
[0156]
<Ink set>
By combining the ink compositions of Examples 2-6 and Comparative Examples 1-3 as cyan, magenta and yellow ink compositions as shown in Table 4, C.I. I. A cyan ink composition containing at least one pigment of CI Pigment Blue 15: 3 and 15: 4; I. Pigment red 122,209 and C.I. I. A magenta ink composition containing at least one pigment selected from the group consisting of CI Pigment Violet 19; I. Example Ink set 1 comprising a yellow ink composition containing at least one pigment selected from the group consisting of CI Pigment Yellow 74, 138, 150 and 180, and any of cyan, magenta and yellow ink compositions Comparative Example Ink Sets 1 to 3 containing a pigment different from the above-mentioned pigment, and Comparative Ink Set 4 containing all the cyan, magenta and yellow ink compositions different from the above-described pigment were obtained. .
[0157]
[Table 4]

[0158]
Using the obtained Example Ink Set 1 and Comparative Ink Sets 1 to 4, respectively, and using an inkjet recording apparatus obtained by modifying a commercially available inkjet recording apparatus (manufactured by Sharp Corporation: AJ2000), Sharp Corporation A black image was formed by printing on a glossy paper (product number: AJ-K4AG) at a printing ratio of 1: 1: 1 for each ink composition of cyan, magenta and yellow. Further, the same image was formed using the ink composition of Example 7 which is a black ink composition.
[0159]
For each obtained black image, a spectrocolorimeter (manufactured by X-Rite: X-Rite 938) was used. ^* a ^* b ^* Lightness index L in the color system (CIE: 1976) ^* And chromaticness index a ^* , B ^* Was measured.
[0160]
The test results were evaluated as follows. Chromaticness index a of a black image formed using the ink composition of Example 7 ^* A1, b ^* Is B2, and the chromaticness index a of the black image formed using each of the example ink set 1 and the comparative ink sets 1 to 4 ^* A2, b ^* Is represented by the following formula (3) with B2 ^* b ^* Was obtained and used as an evaluation index for black reproducibility.
Δa ^* b ^* = {(A1-A2) ² + (B1-B2) ² } ^1/2 ... (3)
Δa ^* b ^* Of 20 or less (Δa ^* b ^* ≦ 20) is determined to be good (◯) and exceeds 20 (Δa ^* b ^* > 20) The case was regarded as defective (x). The evaluation results are shown in Table 5.
[0161]
[Table 5]

[0162]
From Table 5, the black image obtained by superimposing the three types of ink compositions contained in Example ink set 1 is obtained by superimposing the three types of ink compositions contained in Comparative Example ink sets 1 to 4, respectively. It was found that the black image had a dark density close to that of the black image formed using the ink composition of Example 7 as compared with the black image obtained. That is, it was found that Example Ink Set 1 has better black reproducibility and excellent color balance than Comparative Ink Sets 1 to 4.
[0163]
As described above, C.I. I. A cyan ink composition containing at least one pigment of CI Pigment Blue 15: 3 and 15: 4; I. Pigment red 122,209 and C.I. I. A magenta ink composition containing at least one pigment selected from the group consisting of CI Pigment Violet 19; I. By combining with a yellow ink composition containing at least one pigment selected from the group consisting of CI Pigment Yellow 74, 138, 150 and 180, an ink set excellent in color balance could be obtained.
[0164]
【The invention's effect】
As described above, according to the present invention, the dynamic surface tension at a bubble frequency of 10 Hz measured by the maximum bubble pressure method at a temperature of 24-26 ° C. of a solution obtained by dissolving 0.1% by weight in pure water, Since the difference between the static surface tension measured at a temperature of 24-26 ° C. contains a surfactant within a certain range, the relationship between the dynamic surface tension of the ink composition and the static surface tension is It is possible to obtain an ink composition that is excellent in ejection stability when used in an ink jet recording method and that can suppress bleeding on a recording material and obtain a high-quality recorded image. it can.
[0165]
According to the present invention, the dynamic surface tension at a bubble frequency of 10 Hz measured at a temperature of 24-26 ° C. and a temperature of 24-26 ° C. of a solution obtained by dissolving 0.1% by weight in pure water and a temperature of 24-26 Since the static surface tension measured at ℃ is selected within a suitable range, when used in the ink jet recording method, it has excellent ejection stability and suppresses bleeding on the recording material to obtain a high-quality recorded image. Can be obtained.
[0166]
According to the invention, since the organic solvent contains at least one of glycol ethers and polyhydric alcohols having a low vapor pressure, a wetting effect can be obtained and the ejection stability can be improved.
[0167]
Further, according to the present invention, since the coloring material contains a dye, it is possible to suppress the occurrence of clogging and improve the ejection stability.
[0168]
Further, according to the present invention, since the color material contains a pigment, a recorded image having excellent light resistance and water resistance can be obtained.
[0169]
Further, according to the present invention, since the pigment has a hydrophilic group, it is possible to suppress the occurrence of clogging, and an ink composition capable of obtaining a recorded image having excellent light resistance and water resistance without impairing ejection stability. You can get things.
[0170]
Further, according to the present invention, since the surfactant includes a nonionic surfactant that is not easily affected by the coexisting electrolyte, the surfactant is used regardless of whether the electrolyte is added to the ink composition. The relationship between the dynamic surface tension and the static surface tension of the controlled ink composition can be made favorable.
[0171]
Further, according to the present invention, since the surfactant is contained in a critical micelle concentration or more, the dynamic surface tension and the static surface tension of the ink composition that fully exerts the effect of the surfactant and is controlled by the surfactant. Can be set to a substantially constant value, and an ink composition having uniform properties can be obtained.
[0172]
Further, according to the present invention, it is possible to obtain an ink composition capable of realizing a recorded image having excellent cyan color developability.
[0173]
Further, according to the present invention, an ink composition capable of realizing a recorded image having excellent magenta color developability can be obtained.
[0174]
Further, according to the present invention, it is possible to obtain an ink composition capable of realizing a recorded image excellent in yellow color developability.
[0175]
Further, according to the present invention, it is possible to obtain an ink composition capable of realizing a recorded image having excellent black color developability.
[0176]
Further, according to the present invention, it is possible to stably provide a high-quality recorded image.
Further, according to the present invention, it is possible to stably discharge and to provide a high-quality recorded image stably.
[0177]
Further, according to the present invention, since various colors can be expressed, it is possible to provide a full-color recorded image having excellent color developability.
[0178]
Further, according to the present invention, a high-quality recorded image can be obtained.
In addition, according to the present invention, an ink set with excellent color balance can be obtained, so that various colors can be expressed, and a full-color recorded image with excellent color development can be realized.
[0179]
Further, according to the present invention, in a piezo-type ink head capable of ejecting droplets of an ink composition from an ejection port in accordance with a voltage applied to a piezoelectric element, the ink composition can be stably ejected from the ejection port. Droplets can be ejected.
[0180]
Further, according to the present invention, in a thermal ink jet type ink head capable of ejecting droplets of an ink composition from an ejection port in accordance with a voltage applied to a heating element, the ink composition can be stably ejected from the ejection port. Liquid droplets can be discharged.
[0181]
Further, according to the present invention, a recording image has ink composition droplets ejected by a piezo-type ink head capable of stably ejecting ink composition droplets adhered to a recording material. Therefore, a high-quality recorded image can be stably obtained.
[0182]
In addition, according to the present invention, a recording image has a droplet of an ink composition ejected by a thermal ink jet ink head capable of stably ejecting the droplet of the ink composition on the recording material. As a result, the high-quality recorded image can be stably obtained.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a simplified configuration of an ink head 1 according to a second embodiment of the present invention.
FIG. 2 is an enlarged perspective view showing a part of the configuration of a head plate 10 constituting the ink head 1 shown in FIG.
3 is a cross-sectional view of the ink head 1 shown in FIG. 1 as viewed from the extension direction of the ink chamber 40. FIG.
FIG. 4 is an exploded perspective view showing a simplified configuration of an ink head 2 according to a third embodiment of the present invention.
5 is a plan view showing a part of the configuration of the ink head 2 shown in FIG. 4. FIG.
6 is a cross-sectional view schematically showing a state in which droplets 61 of the ink composition 60 are ejected from the ink chamber 40. FIG.
[Explanation of symbols]
1, 2 Ink head
10 Head plate
11 Bottom wall
12, 12a, 12b Bulkhead
13, 13a, 13b, 13c Drive electrode
20 Top plate
21 Common ink supply path
22 Ink supply pipe
30 Nozzle plate
31 Discharge port
40, 40a, 40b, 40c Ink chamber
50 ink tank
51 opening
60 Ink composition
61 droplets
62 bubbles
100 head plate
101 substrate
102 Bulkhead
103 Heater
104,105 Drive electrode

Claims (23)

Color materials,
An organic solvent,
water and,
A dynamic surface tension (σ ₁₀ ) at a bubble frequency of 10 Hz measured by a maximum bubble pressure method at a temperature of 24-26 ° C. of a solution obtained by dissolving 0.1% by weight in pure water, and a temperature of 24-26 ° C. An ink composition comprising a surfactant having a difference d (= σ ₁₀ −γ) from a measured static surface tension (γ) satisfying the following formula (1):
0 mN / m ≦ d ≦ 15 mN / m (1) The ink composition according to claim 1, wherein the dynamic surface tension (σ ₁₀ ) and the static surface tension (γ) at the bubble frequency of 10 Hz are 20 to 70 mN / m. The ink composition according to claim 1, wherein the organic solvent contains at least one of glycol ethers and polyhydric alcohols. The ink composition according to claim 1, wherein the coloring material includes a dye. The ink composition according to claim 1, wherein the color material includes a pigment. The ink composition according to claim 5, wherein the pigment has a hydrophilic group. The ink composition according to claim 1, wherein the surfactant includes a nonionic surfactant. The ink composition according to claim 1, wherein the surfactant is contained in a critical micelle concentration or more. The pigment is C.I. I. Pigment blue 15: 3 and C.I. I. The ink composition according to claim 5, comprising at least one pigment of CI Pigment Blue 15: 4. The pigment is C.I. I. Pigment red 122, C.I. I. Pigment red 209 and C.I. I. The ink composition according to claim 5, comprising at least one pigment selected from the group consisting of CI pigment violet 19. The pigment is C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 150 and C.I. I. The ink composition according to claim 5, comprising at least one pigment selected from the group consisting of CI Pigment Yellow 180. The ink composition according to claim 5, wherein the pigment contains carbon black. A recording method for recording an image by attaching an ink composition onto a recording material,
A recording method, wherein the ink composition according to claim 1 is used as the ink composition. A recording method of recording an image by ejecting droplets of the ink composition by applying pressure to the ink composition and attaching the droplets on a recording material,
A recording method, wherein the ink composition according to claim 1 is used as the ink composition. The ink composition according to claim 9, at least the ink composition according to claim 10, and the ink composition according to claim 11 are used as the ink composition. 14. The recording method according to 14. For the ink composition, at least the ink composition according to claim 9, the ink composition according to claim 10, the ink composition according to claim 11, and the ink composition according to claim 12 are used. 15. The recording method according to claim 13, wherein the recording method is performed. A recorded image recorded by the recording method according to claim 13. An ink composition according to claim 9,
An ink composition according to claim 10;
An ink set comprising the ink composition according to claim 11. An ink composition according to claim 9 and an ink composition according to claim 10,
An ink composition according to claim 11;
An ink set comprising the ink composition according to claim 12. An ink tank for storing the ink composition according to claim 1;
An ink chamber having a discharge port for discharging droplets of the ink composition, and the ink composition being supplied from the ink tank;
A piezoelectric element that generates strain in response to an applied voltage, the piezoelectric element being provided in at least a part of the ink chamber and applying pressure to the ink composition housed in the ink chamber;
An ink head comprising: an electrode provided for applying a voltage to the piezoelectric element. An ink tank for storing the ink composition according to claim 1;
An ink chamber having a discharge port for discharging droplets of the ink composition, and the ink composition being supplied from the ink tank;
A heating element that is provided in at least a part of the ink chamber and applies pressure to the ink composition by generating bubbles by heating the ink composition housed in the ink chamber;
An ink head comprising: an electrode provided for applying a voltage to the heating element. 21. A recorded image recorded by depositing droplets of an ink composition ejected by the ink head according to claim 20 on a recording material. 23. A recorded image, wherein the ink composition droplets ejected by the ink head according to claim 21 are recorded by being deposited on a recording material.

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