JP3918554B2 - Ink composition - Google Patents

Description

〔式中、Ｒは、場合により（好ましくはヒドロキシ基で）置換されていることのある炭素原子数１〜２０（好ましくは炭素原子数１〜１２）の飽和又は不飽和炭化水素基（好ましくはアルキル基）である〕
で表されるメタクリル酸エステル少なくとも１種５〜７０重量％（好ましくは１０〜５０重量％）と、（ｃ）炭素原子２〜１１（好ましくは炭素原子２〜７）の飽和脂肪族カルボン酸少なくとも１種とビニル化合物との重合体５〜８０重量％（好ましくは２０〜６０重量％）とのポリマー粘性調整剤が記載されており、このポリマー粘性調整剤は、本発明のインク組成物においても好適に使用することができる。前記のメタクリル酸エステル（Ｂ）としては、例えば、メチルメタクリレート、エチルメタクリレート、プロピルメタクリレート、イソプロピルメタクリレート、ブチルメタクリレート、ｎ−アミルメタクリレート、ｓｅｃ−アミルメタクリレート、ヘキシルメタクリレート、ラウリルメタクリレート、ステアリルメタクリレート、エチルヘキシルメタクリレート、クロチルメタクリレート、シンナミルメタクリレート、オレイルメタクリレート、リシノレイルメタクリレート、ヒドロキシエチルメタクリレート、又はヒドロキシプロピルメタクリレートなどを挙げることができ、メチルメタクリレートが好ましい。
【００７２】
脂肪族カルボン酸ビニルエステルとしては、例えば、酢酸ビニル、プロピオン酸ビニル、酪酸ビニル、ｔｅｒｔ−酪酸ビニル、カプリン酸ビニル、ステアリン酸ビニル、ラウリン酸ビニル、又はオレイン酸ビニルなどを挙げることができ、酢酸ビニルが好ましい。
【００７３】
前記のポリマー粘性調整剤は十分な量のカルボン酸基を含んでおり、ポリマーを水溶性にして水溶性塩基で中和させることから、しばしばアルカリ膨潤性又はアルカリ可溶性ラテックス共重合性濃化剤と呼ばれており、市販もされている〔例えば、レオックス・インターナショナル・インコーポレイディド社（米国）のレオレート（ＲＨＥＯＬＡＴＥ）３５０〕。
【００７４】
前記のアルカリ膨潤性又はアルカリ可溶性ポリマー粘性調整剤のポリマー主鎖に疎水性基を導入したポリマー粘性調整剤も知られており、例えば、米国特許第４，３８４，０９６号明細書には、炭素原子数３〜８のα，β−エチレン性不飽和カルボン酸モノマーと、非イオン性ビニルモノマーと、ある特定のビニルエステル界面活性剤〔例えば、一方の末端がＣ₈〜Ｃ₁₆アルキルフェニル基で終わっているアルキルフェノキシポリ（エチレンオキシ）エチルアクリレート〕１〜３０％とのポリマー反応生成物が記載されている。また、米国特許第４，１３８，３８１号明細書には、炭素原子数３〜６の不飽和カルボン酸と，アルキルアクリレート又はアルキルメタクリレートと、アルキルフェニル基（ただし、アルキル基は８〜２０個の炭素原子を有する）を含むエステルとの反応生成物が記載されている。これらのポリマー粘性調整剤も、本発明のインク組成物に好適に使用することができる。
【００７５】
更に、アクリル酸又はメタクリル酸、アルキルアクリレート又はアルキルメタアクリレート、疎水性基を有するアクリル酸又はメタクリル酸のエトキシ化エステル、及びポリエチレン性不飽和モノマーを乳化重合して形成されるアクリルエマルジョンコポリマー粘性調整剤（例えば、ヨーロッパ特許第１３，８３６号明細書参照）も、本発明のインク組成物に好適に使用することができる。また、アルキルポリエチレンオキシエーテル界面活性剤を、溶媒和により、ポリアクリルアミド主鎖を有する会合性ポリマーに加えた生成物〔「プロシーディングズ・オブ・ジ・エーシーエスディビジョン・オブ・ポリメリック・マテリアルズ（Proceedings of the ACS Division of Polymeric Materials）」，第５７巻４７６〜４８１頁（１９８７年）参照〕も本発明のインク組成物に好適に使用することができる。
【００７６】
メタクリル酸、エチルアクリレート、共重合性エチレン性不飽和モノマー、及び少量のポリエチレン性不飽和モノマーを含む各種モノマーの反応生成物であるコポリマー（例えば、米国特許第４，４２１，９０２号明細書参照）も本発明のインク組成物に好適に使用することができる。
【００７７】
更に最近では、鉱物油を含まない水溶性コポリマーを用いてその系の粘性を調節することが知られている（例えば、米国特許第４，６６８，４１０号明細書参照）。前記米国特許第４，６６８，４１０号明細書に記載のポリマーは、６つの成分の反応生成物であり、その成分はメタクリル酸、アルコール類のメタクリル酸エステル又はアクリル酸エステル、ビニルエステル及び表面活性不飽和エステルである。このポリマーを部分的に又は完全に中和すると、水溶性又は水にコロイド状に分散して、濃化剤として使用することができる。多価アルコールをモノエチレン性不飽和モノイソシアネートで縮合して得られる同様のコポリマーも知られており（例えば、米国再発行特許第３３，００８号明細書参照）、しかも市販されている〔例えば、レオックス・インターナショナル・インコーポレイディド社（米国）のレオレート（ＲＨＥＯＬＡＴＥ）２１０及び２１６〕。
【００７８】
更に、炭素原子数３〜８のα，β−エチレン性不飽和カルボン酸モノマー（例えば、アクリル酸又はメタクリル酸）の一種またはそれ以上（約１５〜８０重量％）、共重合可能なビニル非イオン性エチレン性不飽和モノマー（例えば、エチルアクリレート、ビニルアセテート、又はメチルメタクリレート）の一種またはそれ以上（約１５〜８５重量％）、及び疎水性フェノールモノマー、即ち、アラルキル置換フェノール系疎水性基で終わる非イオン性ポリ（アルキレンオキシ）ビニルモノマー（約０．５〜２５重量％）を反応して形成される水性組成物用粘性調整剤（特開平８−２２５６１８号公報参照）も、本発明のインク組成物において好適に使用することができる。
【００７９】
本発明のインク組成物においては、前記の粘性調整剤の１種又は２種以上の組み合わせを用いることができる。
【００８０】
本発明のインク組成物において、前記粘性調整剤の含有量は、インク組成物の全重量に対して、０．０１〜１重量％程度が好ましく、より好ましくは０．０５〜０．５重量％程度である。
【００８１】
本発明のインク組成物は、溶媒として水を含み、更に、水溶性有機溶媒を含むことができる。
【００８２】
水溶性有機溶媒の例としては、メタノール、エタノール、ｎ−プロピルアルコール、ｉｓｏ−プロピルアルコール、ｎ−ブタノール、Ｓｅｅ−ブタノール、ｔｅｒｔ−ブタノール、ｉｓｏ−ブタノール、ｎ−ペンタノール、エチレングリコール、プロピレングリコール、ジエチレングリコール、ペンタメチレングリコール、トリメチレングリコール、２−ブチン−１，４−ジオール、２−エチル−１，３−へキサンジオール、２−メチル−２，４−ペンタンジオール、Ｎ−メチル−２−ピロリドン、１，３−ジメチル−２−イミダゾリジノン、２−ピロリドン、グリセリン、トリプロピレングリコールモノメチルエーテル、ジプロピレングリコールモノエチルグリコール、ジプロピレングリコールモノメチルエーテル、ジプロピレングリコール、トリエチレングリコールモノメチルエーテル、テトラエチレングリコール、トリエチレングリコール、ジ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エチルエーテル、ジエチレングリコールモノメチルエーテル等が挙げられる。
【００８３】
本発明のインク組成物において、水溶性有機溶媒を用いる場合の含有量は、インク組成物の全重量に対して、好ましくは１０〜４０重量％程度であり、より好ましくは１０〜２０重量％である。
【００８４】
本発明の好ましい態様のインク組成物は、更に界面活性剤を含有することができる。本発明において用いられる界面活性剤は、アニオン界面活性剤、ノニオン界面活性剤、及び両性界面活性剤からなる群から選択される１種以上の界面活性剤である。
【００８５】
界面活性剤の例としては、アニオン界面活性剤（例えばドデシルベンゼルスルホン酸ナトリウム、ラウリル硫酸ナトリウム、ポリオキシエチレンアルキルエーテルサルフェートのアンモニウム塩など）、ノニオン界面活性剤（例えば、ポリオキシエチレンアルキルエーテル、ポリオキシエチレンアルキルエステル、ポリオキシエチレンソルビタン脂肪酸エステル、ポリオキシエチレンアルキルフェニルエーテル、ポリオキシエチレンアルキルアミン、ポリオキシエチレンアルキルアミドなど）及び、アセチレングリコール等が挙げられる。これらは単独使用又は２種以上を併用することができる。
【００８６】
更に、本発明の好ましい態様によるインク組成物は、ｐＨ調整剤として三級アミンを含有する。
【００８７】
本発明によるインク組成物に添加することができる三級アミンは、トリメチルアミン、トリエチルアミン、トリエタノールアミン、ジメチルエタノールアミン、ジエチルエタノールアミン、トリイソプロペノールアミン、ブチルジエタノールアミン等が挙げられる。これらは、単独で使用しても併用しても構わない。これら三級アミンの本発明のインク組成物への添加量は、０．１〜１０重量％、より好ましくは、０．５〜５重量％である。
【００８８】
また、本発明によるインク組成物には、浸透促進剤、糖、及び／又はアルギン酸誘導体を含有させることもできる。
【００８９】
前記浸透促進剤としては、例えば、多価アルコールの炭素数３以上のアルキルエーテル誘導体、例えば、ジエチ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、プロピレングリコールモノブチルエーテル、又はジプロピレングリコールモノブチルエーテル等を挙げることができ、これらの１種又は２種以上を用いることができる。
【００９０】
糖の例としては、単糖類、二糖類、オリゴ糖類（三糖類及び四糖類を含む）及び多糖類を挙げることができ、好ましくはグルコース、マンノース、フルクトース、リボース、キシロース、アラビノース、ガラクトース、アルドン酸、グルシトール、（ソルビット）、マルトース、セロビオース、ラクトース、スクロース、トレハロース、マルトトリオース、などを挙げることができる。ここで、多糖類とは広義の糖を意味し、アルギン酸、α−シクロデキストリン、セルロースなど自然界に広く存在する物質を含む意味に用いることとする。また、これらの糖類の誘導体としては、前記した糖類の還元糖［（例えば、糖アルコール（一般式ＨＯＣＨ₂（ＣＨＯＨ）_nＣＨ₂ＯＨ（ここで、ｎは２〜５の整数を表す）で表される］、酸化糖（例えば、アルドン酸、ウロン酸など）、アミノ酸、チオ糖などを挙げることができる。特に糖アルコールが好ましく、具体例としてはマルチトール、ソルビットなどを挙げることができる。これら糖類の添加量は０．１〜４０重量％程度が好ましく、より好ましくは１〜３０重量％程度である。
【００９１】
アルギン酸誘導体の好ましい例としては、アルギン酸アルカリ金属塩（例えば、ナトリウム塩、カリウム塩）、アルギン酸有機塩（例えば、トリエタノールアミン塩）、アルギン酸アンモニウム塩、等を挙げることができる。このアルギン酸誘導体のインク組成物への添加量は、好ましくは０．０１〜１重量％程度であり、より好ましくは０．０５〜０．５重量％程度である。
【００９２】
アルギン酸誘導体の添加により良好な画像が得られる理由は明確ではないが、反応液に存在する多価金属塩が、インク組成物中のアルギン酸誘導体と反応し、着色剤の分散状態を変化させ、着色剤の記録媒体への定着が促進されることに起因するものと考えられる。
【００９３】
本発明によるインク組成物には、その他、必要に応じて、防腐剤、防かび剤、及び／又はりん系酸化防止剤等を添加することもできる。
【００９４】
本発明のインク組成物は、常法によって調製することができ、例えば、前記の各成分を適当な方法で分散、及び混合することによって製造することができる。好ましくは、まず、顔料と高分子分散剤とイオン交換水とを適当な分散機（例えば、ボールミル、サンドミル、アトライター、ロールミル、アジテータミル、ヘンシェルミキサー、コロイドミル、超音波ホモジナイザー、ジェットミル、オングミルなど）で混合し、均一な顔料分散液を調製する。次いで、前記のｐＨ調整樹脂液（例えば、ｐＨ調整樹脂水溶液）、前記の粘性調整剤、イオン交換水、水溶性有機溶媒、防腐剤、及び／又は防黴剤等を常温で充分に攪拌してインク溶媒を調製する。このインク溶媒を適当な分散機で攪拌した状態のところに前記顔料分散液を徐々に滴下して充分に攪拌する。充分に攪拌した後に、目詰まりの原因となる粗大粒子及び異物を除去するために濾過を行って目的のインク組成物を得ることができる。
【００９５】
本発明のインク組成物は、任意の印刷方法に用いることができ、例えば、水性グラビアインク、水性フレキソインク、又は特にインクジェット記録用水性インクとして好適に使用することができる。また、水性塗料として使用することも可能である。
【００９６】
本発明のインク組成物は、記録媒体として、前記インク組成物に含まれるｐＨ調整樹脂と前記着色剤（特に顔料）とを表面上に実質的に残留させるが、前記インク組成物の液体成分を実質的に吸収する記録媒体に利用するのが特に好ましい。こうした記録媒体は、例えば、表面の平均孔径が、前記顔料の平均粒径よりも小さい。好ましい記録媒体は、前記顔料の平均粒径よりもそれぞれ小さい平均孔径を有するインク受容層を含む記録媒体である。
【００９７】
好ましい記録媒体として、多孔質顔料を含有するインク受容層を、基材上に設けた記録媒体を使用することができる。インク受容層は、記録媒体の最上層であるか、あるいはその上に、例えば、光沢層を有する中間層であることもできる。このような記録媒体としては、そのインク受容層中に多孔質顔料及びバインダー樹脂を含有する、いわゆる吸収型（空隙型ともいう）の記録媒体と、前記インク受容層中にカゼイン、変性ポリビニルアルコール（ＰＶＡ）、ゼラチン、又は変性ウレタン等の樹脂を更に含有する、いわゆる膨潤型の記録媒体とが知られており、本発明のインク組成物はいずれの記録媒体にも使用することができる。
【００９８】
吸収型記録媒体のインク受容層に含有される前記多孔質顔料としては、例えば、沈殿法、ゲルタイプ、又は気相法等のシリカ系、擬ベーマイト等のアルミナ水和物、シリカ／アルミナハイブリッドゾル、スメクタイト粘土、炭酸カルシウム、硫酸カルシウム、硫酸バリウム、二酸化チタン、カオリン、白土、タルク、珪酸マグネシウム、又は珪酸カルシウム等を挙げることができ、これらの１種又は２種以上を用いることができる。
【００９９】
また、吸収型記録媒体のインク受容層に含有される前記バインダー樹脂としては、結着能力を有し、インク受容層の強度を高めることのできる化合物であれば特に限定されず、例えば、ポリビニルアルコール、シラノール変性ポリビニルアルコール、酢酸ビニル、澱粉、カルボキシメチルセルロース等のセルロース誘導体、カゼイン、ゼラチン、スチレン−ブタジエン共重合体等の共役ジエン系共重合体ラテックス、エチレン−酢酸ビニル共重合体等のビニル系共重合体ラテックス、アクリル酸及びメタクリル酸の重合体等のアクリル系共重合体ラテックス等を挙げることができる。
【０１００】
前記インク受容層には、吸収型記録媒体のインク受容層の場合も、膨潤型の記録媒体のインク受容層の場合も、必要に応じ、定着剤、蛍光増白剤、耐水化剤、防かび剤、防腐剤、分散剤、界面活性剤、増粘剤、ｐＨ調整剤、消泡剤、及び／又は保水剤等の各種添加剤を含有させることもできる。
【０１０１】
前記の各インク受容層が設けられる前記基材としては、紙（サイズ処理紙を含む）；ポリエチレン、ポリプロピレン、又はポリエステル等を紙にコートしたレジンコート紙；バライタ紙；ポリエチレンテレフタレート、ポリエチレン、又はポリプロピレン等の熱可塑性樹脂フィルム；合成紙；合成繊維で形成されたシート状物等を挙げることができる。
【０１０２】
特に好ましい態様の記録媒体は、前記基材と、その上に設けた最上層としての前記インク受容層とを有する記録媒体であり、それらの基材及びインク受容層も、例えば、以下の物性を有するものが好ましい。
【０１０３】
前記基材としては、紙（木材パルプを含有するもの）が好ましく、その坪量は、好ましくは１００〜３５０ｇ／ｍ²、更に好ましくは１８０〜２６０ｇ／ｍ²である。また、厚みは、好ましくは１００〜４００μｍ、更に好ましくは１８０〜２６０μｍである。前記インク受容層は、インク受容層全体の重量を基準として、固形分換算で、前記多孔質顔料として湿式法シリカゲルを５０〜６０重量％の量で含有し、前記バインダー樹脂としてポリビニルアルコールを３０〜４０重量％の量で含有することが、インク吸収性、及び印字堅牢性等の点で好ましい。また、前記インク受容層の塗工量は、固形分換算で、５〜５０ｇ／ｍ²であることが、インク吸収性の点で好ましい。なお、インク受容層自体の厚みとしては、好ましくは１０〜４０μｍ、更に好ましくは２０〜３０μｍである。
【０１０４】
本発明のインク組成物を印刷する記録媒体は、前記記録媒体の表面（特には、インク受容層）の平均孔径が５０ｎｍ以下であることが好ましく、３０ｎｍ以下であることがより好ましい。平均孔径が３００ｎｍを超えると、顔料がインク受容層内部まで浸透し、発色性が低下することがある。
【０１０５】
【実施例】
以下に実施例によって本発明を更に具体的に説明するが、これらは本発明の範囲を限定するものでない。なお、実施例中の「％」及び「部」は特に断りのない限り、重量基準である。また、以下の調製例で得られた共重合体の酸価は、ＪＩＳ Ｋ ００７０に従い測定した。
【０１０６】
＜調製例１＞
《ｐＨ調整樹脂の調製》
メタクリル酸エチル６０部、メタクリル酸メチル３６部、メタクリル酸４部、分子量調整剤としてチオグリコール酸オクチル３部、ポリビニルアルコール１部及びイオン交換水２８０部を攪拌混合して、単量体混合物の分散物を調製した。
【０１０７】
別の攪拌機付き反応器に、イオン交換水１３０部及び過硫酸カリウム２部を仕込み、８０℃に昇温し、そして前記単量体混合物の分散物を４時間かけて連続添加して重合させた。連続添加終了後、８０℃にて、３０分間後反応を行った。重合転化率は、９９％以上であった。
【０１０８】
次いで、仕込みのメタクリル酸と当モル量の水酸化ナトリウムに相当する量の１０％水酸化ナトリウム水溶液を反応器に添加し、更に８０℃にて、１時間熱処理した後に、適量のイオン交換水を加えて、固形分濃度１５％のｐＨ調整樹脂溶液Ａを得た。このｐＨ調整樹脂溶液Ａの酸価は３０であった。
【０１０９】
＜調製例２＞
アクリル酸エチル５６部、メタクリル酸メチル３６部、メタクリル酸８部、分子量調整剤としてチオグリコール酸オクチル３部、ラウリル硫酸ナトリウム２．５部及びイオン交換水８０部を攪拌混合して、単量体混合物の分散物を調製した。
【０１１０】
別の攪拌機付き反応器に、エチレンジアミン四酢酸０．０５部を溶解したイオン交換水９０部を仕込み、８０℃に昇温し、５％過硫酸カリウム水溶液４０部を添加した後、前記単量体混合物の分散物を２時間かけて連続添加して重合させた。連続添加終了後、８０℃にて、３０分間後反応を行った。重合転化率は９９％以上であった。
【０１１１】
次いで、仕込みのメタクリル酸と当モル量のアンモニアに相当する量の２８％アンモニア水溶液と５％過硫酸ナトリウム水溶液２部を反応器に添加し、更に８０℃にて、１時間後処理した後、適量のイオン交換水を加えて、固形分２５％のｐＨ調整樹脂溶液Ｂを得た。このｐＨ調整樹脂溶液Ｂの酸価は、５０であった。
【０１１２】
＜インクの調製実施例及び比較例＞
顔料と分散剤と水とを混合し、サンドミル（安川製作所製）中でガラスビーズ〔直径１．７ｍｍ，混合物の１．５倍量（重量）〕とともに２時間分散させた後に、ガラスビーズを取り除き、顔料分散液を調製した。
【０１１３】
次いで、顔料及び分散剤を除く溶剤及び粘性調整剤を混合してインク溶媒とし、上記の顔料分散液及び上記調製例で製造したｐＨ調整樹脂溶液Ａ又はＢを攪拌しながら、前記のインク溶媒を徐々に滴下し、常温で２０分間攪拌した。５μｍのメンブランフィルターでろ過し、インクジェット記録用インクを得た。
【０１１４】
＜実施例１＞
（１）ブラック顔料インク
カーボンブラックＭＡ７（三菱化学（株）） ３重量％
スチレン−アクリル酸共重合体（分散剤） １重量％
ｐＨ調整樹脂溶液Ａ ２重量％
ＲＨＥＯＬＡＴＥ ３５０（粘性調整剤） ０．２重量％
（有効成分５０％，レオックス・インターナショナル・インコーポレイティド社製）
グリセリン １０重量％
イオン交換水 残量
（２）シアンインク
Ｃ．Ｉ．ピグメントブルー １５：３ ２重量％
スチレン−アクリル酸共重合体（分散剤） １重量％
ｐＨ調整樹脂溶液Ａ ２重量％
ＲＨＥＯＬＡＴＥ ３５０（粘性調整剤） ０．２重量％
（有効成分５０％，レオックス・インターナショナル・インコーポレイティド社製）
トリエチレングリコールモノブチルエーテル １０重量％
ジエチレングリコール １０重量％
イオン交換水 残量
（３）マゼンタインク
Ｃ．Ｉ．ピグメントレッド １２２ ３重量％
スチレン−アクリル酸共重合体（分散剤） １重量％
ｐＨ調整樹脂溶液Ａ ２重量％
ＲＨＥＯＬＡＴＥ ３５０（粘性調整剤） ０．２重量％
（有効成分５０％，レオックス・インターナショナル・インコーポレイティド社製）
トリエチレングリコールモノブチルエーテル １０重量％
グリセリン ５重量％
ジエチレングリコール ５重量％
イオン交換水 残量
（４）イエローインク
Ｃ．Ｉ．ピグメントイエロー ７４ ３．５重量％
スチレン−アクリル酸共重合体（分散剤） １重量％
ｐＨ調整樹脂溶液Ａ ２重量％
ＲＨＥＯＬＡＴＥ ３５０（粘性調整剤） ０．２重量％
（有効成分５０％，レオックス・インターナショナル・インコーポレイティド社製）
トリエチレングリコールモノブチルエーテル １０重量％
グリセリン ８重量％
イオン交換水 残量
【０１１５】
＜比較例１＞
（１）ブラック顔料インク
カーボンブラックＭＡ７（三菱化学（株）） ３重量％
スチレン−アクリル酸共重合体（分散剤） １重量％
ｐＨ調整樹脂溶液Ｂ ２重量％
ＲＨＥＯＬＡＴＥ ２１０（粘性調整剤） ０．４重量％
（有効成分２５％，レオックス・インターナショナル・インコーポレイティド社製）
グリセリン １５重量％
イオン交換水 残量
（２）シアンインク
Ｃ．Ｉ．ピグメントブルー １５：３ ２重量％
スチレン−アクリル酸共重合体（分散剤） １重量％
ｐＨ調整樹脂溶液Ｂ ２重量％
ＲＨＥＯＬＡＴＥ ２１０（粘性調整剤） ０．４重量％
（有効成分２５％，レオックス・インターナショナル・インコーポレイティド社製）
トリエチレングリコールモノブチルエーテル １０重量％
ジエチレングリコール １０重量％
イオン交換水 残量
（３）マゼンタインク
Ｃ．Ｉ．ピグメントレッド １２２ ３重量％
スチレン−アクリル酸共重合体（分散剤） １重量％
ｐＨ調整樹脂溶液Ｂ ２重量％
ＲＨＥＯＬＡＴＥ ２１０（粘性調整剤） ０．４重量％
（有効成分２５％，レオックス・インターナショナル・インコーポレイティド社製）
トリエチレングリコールモノブチルエーテル １０重量％
グリセリン ５重量％
ジエチレングリコール ５重量％
イオン交換水 残量
（４）イエローインク
Ｃ．Ｉ．ピグメントイエロー ７４ ３．５重量％
スチレン−アクリル酸共重合体（分散剤） １重量％
ｐＨ調整樹脂溶液Ｂ ２重量％
ＲＨＥＯＬＡＴＥ ２１０（粘性調整剤） ０．４重量％
（有効成分２５％，レオックス・インターナショナル・インコーポレイティド社製）
トリエチレングリコールモノブチルエーテル １０重量％
グリセリン ８重量％
イオン交換水 残量
【０１１６】
＜比較例２＞
（１）ブラック顔料インク
カーボンブラックＭＡ７（三菱化学（株）） ３重量％
スチレン−アクリル酸共重合体（分散剤） １重量％
ＲＨＥＯＬＡＴＥ ２１６（粘性調整剤） ２重量％
（有効成分２０％，レオックス・インターナショナル・インコーポレイティド社製）
グリセリン １０重量％
イオン交換水 残量
（２）シアンインク
Ｃ．Ｉ．ピグメントブルー １５：３ ２重量％
スチレン−アクリル酸共重合体（分散剤） １重量％
ＲＨＥＯＬＡＴＥ ２１６（粘性調整剤） ２重量％
（有効成分２０％，レオックス・インターナショナル・インコーポレイティド社製）
トリエチレングリコールモノブチルエーテル １０重量％
ジエチレングリコール １０重量％
イオン交換水 残量
（３）マゼンタインク
Ｃ．Ｉ．ピグメントレッド １２２ ３重量％
スチレン−アクリル酸共重合体（分散剤） １重量％
ＲＨＥＯＬＡＴＥ ２１６（粘性調整剤） ２重量％
（有効成分２０％，レオックス・インターナショナル・インコーポレイティド社製）
トリエチレングリコールモノブチルエーテル １０重量％
グリセリン ５重量％
ジエチレングリコール ５重量％
イオン交換水 残量
（４）イエローインク
Ｃ．Ｉ．ピグメントイエロー ７４ ３．５重量％
スチレン−アクリル酸共重合体（分散剤） １重量％
ＲＨＥＯＬＡＴＥ ２１６（粘性調整剤） ２重量％
（有効成分２０％，レオックス・インターナショナル・インコーポレイティド社製）
トリエチレングリコールモノブチルエーテル １０重量％
グリセリン ８重量％
イオン交換水 残量
【０１１７】
＜印字評価＞
前記の実施例及び比較例で製造した各インク組成物を用いて印字評価を行った。印字評価は、インクジェットプリンター〔ＰＭ−９００Ｃ（セイコーエプソン（株）製〕を用い、ＰＭ写真用紙〔インクジェット専用紙：セイコーエプソン（株）製〕に印字を行った。
【０１１８】
（１）光沢度評価
印字後の画像について、印字デューティー（duty）３０％部での光沢度を光沢度計（ＰＧ-１Ｍ；日本電色工業株式会社製）で測定した。光沢度は、２０°、６０°、又は８５°での正反射を測定することで各々の角度での光沢度とした。
【０１１９】
評価結果は以下の表１に示す通りであった。
【０１２０】
【表１】

【０１２１】
上記結果より明らかなように、実施例１の方が比較例１及び比較例２に比べ、全体の光沢度が上昇し、かつ光沢度の角度依存性も低減し、より良好な画像が得られた。
【０１２２】
【発明の効果】
本発明のインク組成物によれば、光沢性に優れた記録物を得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink composition, and more particularly to an aqueous pigment ink composition suitable for printing on dedicated paper for inkjet recording. According to the ink composition of the present invention, it is possible to improve the glossiness of a recorded image printed on a dedicated paper for inkjet recording.
[0002]
[Prior art]
The ink jet recording method is a printing method in which printing is performed by causing ink droplets to fly and adhere to a recording medium such as paper. Due to recent advances in inkjet recording technology, inkjet recording methods have been used in the field of high-definition printing that has been realized only by silver salt photography and offset printing. Accordingly, an ink jet recording medium having high gloss comparable to photographic paper or art paper used in the field of silver salt photography and offset printing has been developed. As a recording medium for such a high gloss inkjet recording method, a recording medium in which an ink receiving layer containing a porous pigment such as silica is provided on a substrate such as paper or a film is mainly used.
[0003]
Further, the ink used when recording characters and / or images on the recording medium for the high gloss ink jet recording method contains water as a main component, and contains a coloring material, a resin emulsion, and other various additives. Water-based ink is common. As the coloring material, dyes or pigments can be used. However, since the pigments are excellent in terms of weather resistance such as light resistance, gas resistance, water resistance, and moisture resistance, the demand has been increasing in recent years. Development of pigment inks that take advantage of the properties of pigments is underway. In addition, water-based pigment ink containing a resin emulsion is used to improve the fixability of the pigment to the recording medium.
[0004]
There is an increasing demand for image quality even in an ink jet recording method using an ink jet exclusive paper having an ink receiving layer as described above as a recording medium and using an aqueous pigment ink composition containing a resin emulsion as described above as an ink. It has become more sophisticated. For example, the demand for the gloss of the printed image on the dedicated paper as described above is increasing, and a high level of gloss is required. That is, in the dedicated paper as described above, the ink receiving layer absorbs the solvent component, and the pigment particles and the polymer fine particles of the resin emulsion remain on the surface of the recording medium. Since the solvent component decreases on the surface of the recording medium, the density of the polymer fine particles increases, and a film formation reaction by the polymer fine particles proceeds to form a film, and the pigment is fixed on the surface of the recording medium by the film. However, although the conventional pigment ink for inkjet recording can obtain a certain degree of gloss, it is insufficient from the viewpoint of gloss comparable to silver salt photography.
[0005]
In addition, an ink composition containing a water-soluble resin has been proposed for the inkjet recording. For example, JP-A-4-18467 discloses an aqueous ink containing a specific carbon black and a water-soluble resin having an acid value of 100 or more and a weight average molecular weight of 3,000 to 7,000 in an aqueous medium. Yes. This water-based ink has the advantage that precipitates are not easily generated even after long-term storage, but it is not only inferior in halftone dot reproducibility of the obtained image but also in abrasion resistance. Further, JP-A-7-70254 discloses a high acid value obtained by copolymerizing 21 to 99% by weight of an ethylenically unsaturated carboxylic acid monomer with other monomers in the presence of polyvinyl alcohol. A water-soluble resin obtained by neutralizing the above copolymer with a basic compound is described. The water-based ink composed of the water-soluble resin and the colorant has a drawback in that the viscosity change during long-term storage is large and the resulting image has poor abrasion resistance.
[0006]
Furthermore, ink compositions for ink jet recording containing various viscosity modifiers for the main purpose of improving ejection stability are also known. For example, Japanese Patent Publication No. 10-502957 discloses an aqueous ink composition containing a colorant in which a pigment or a dye insoluble in water is dispersed in water and a rheology modifier. However, this aqueous ink composition is suitable for continuous ink jet printing, but has a drawback that it is unsuitable for ordinary on-demand ink jet recording methods from the viewpoint of clogging characteristics and the like.
[0007]
[Problems to be solved by the invention]
The inventor of the present invention has various characteristics (for example, ejection stability, storage stability, weather resistance, and color developability) required for an ink composition for an inkjet recording method in the aqueous emulsion ink composition containing a resin emulsion as described above. In particular, the inventors have eagerly studied the means for improving the glossiness of the special paper as described above. As a result, the ink composition contains a specific resin and a viscosity modifier together with the above-mentioned problem. I found out that it can be solved.
[0008]
The present invention is based on these findings.
[0009]
[Means for Solving the Problems]
Therefore, the present invention
Acid value obtained by polymerizing ethylenically unsaturated carboxylic acid monomer and other monomers copolymerizable therewith in the presence of alcoholic hydroxyl group-containing water-soluble polymer compound or copolymerizable surfactant An ink composition comprising: a copolymer having a pH of 40 or less, a resin whose pH is adjusted with an inorganic base (hereinafter referred to as a pH adjustment resin), water, a colorant, and a viscosity modifier. About.
[0010]
According to a preferred aspect of the present invention, the viscosity modifier is a synthetic polymer viscosity modifier. The synthetic polymer-based viscosity modifier is preferably a synthetic polymer-based viscosity modifier formed by a reaction of (a) methacrylic acid, (b) methacrylic acid ester, and (c) saturated aliphatic carboxylic acid vinyl ester.
[0011]
According to another preferred embodiment of the present invention, the colorant is a pigment.
[0012]
According to still another preferred embodiment of the present invention, the inorganic base used for the preparation of the pH adjusting resin is an alkali metal hydroxide or an alkaline earth metal hydroxide.
[0013]
According to still another preferred embodiment of the present invention, the alcoholic hydroxyl group-containing water-soluble polymer compound used for the preparation of the pH adjusting resin is a vinyl alcohol polymer.
[0014]
According to still another preferred embodiment of the present invention, the ethylenically unsaturated carboxylic acid monomer used for the preparation of the pH adjusting resin is acrylic acid or methacrylic acid.
[0015]
According to still another preferred embodiment of the present invention, the monomer copolymerizable with the ethylenically unsaturated carboxylic acid monomer used for the preparation of the pH adjusting resin is an ethylenically unsaturated carboxylic acid ester monomer. It is.
[0016]
According to still another preferred embodiment of the present invention, the resin has a pH of 8 to 11 (more preferably 9 to 10).
[0017]
The ink composition of the present invention is preferably for inkjet recording.
[0018]
In the present invention, the ink composition is used, and the pH adjusting resin and the colorant contained in the ink composition are substantially left on the surface, but the liquid component of the ink composition is substantially reduced. It also relates to a method of recording on an absorbing recording medium.
[0019]
Furthermore, the present invention uses the ink composition described above and causes the pH adjusting resin and the colorant contained in the ink composition to substantially remain on the surface, but the liquid component of the ink composition is substantially reduced. The present invention also relates to a recorded image formed on a recording medium that absorbs light.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
The ink composition used in the present invention comprises an ethylenically unsaturated carboxylic acid monomer and another monomer copolymerizable therewith, an alcoholic hydroxyl group-containing water-soluble polymer compound or copolymerizable surfactant. Resin produced by adjusting the pH of a copolymer having an acid value of 40 or less (hereinafter referred to as “alkali-soluble copolymer”) obtained by polymerization in the presence of an inorganic base (that is, pH adjusting resin) Containing.
[0021]
The alcoholic hydroxyl group-containing water-soluble polymer compound used for producing the alkali-soluble copolymer includes, for example, 5 to 25 alcoholic hydroxyl groups per 1,000 molecular weights of the water-soluble polymer compound. For example, vinyl alcohol polymers such as polyvinyl alcohol and various modified products thereof; saponified products of copolymers of vinyl acetate and acrylic acid, methacrylic acid or maleic anhydride; alkyl cellulose, hydroxyalkyl cellulose, Examples thereof include cellulose derivatives such as alkylhydroxyalkyl cellulose; starch derivatives such as alkyl starch, carboxymethyl starch and oxidized starch; gum arabic, tragacanth gum; polyalkylene glycol and the like. Of these, vinyl alcohol polymers are preferred from the viewpoint of easy availability of industrially stable products.
[0022]
The weight average molecular weight of the alcoholic hydroxyl group-containing water-soluble polymer compound is not particularly limited, but is usually 1,000 to 500,000, preferably 2,000 to 300,000. When the molecular weight is less than 1,000, the dispersion stabilizing effect may be lowered. On the other hand, when the molecular weight is more than 500,000, the viscosity when polymerized in the presence of the polymer compound becomes high and the polymerization becomes difficult. Sometimes.
[0023]
The amount of the alcoholic hydroxyl group-containing water-soluble polymer compound used in the production of the alkali-soluble copolymer is usually 0.05 to 20 parts by weight, preferably 1 to 100 parts by weight of the monomer. 10 parts by weight. If the amount is less than 0.05 parts by weight, the dispersion stabilizing effect is lowered, so that aggregates are generated at the time of polymerization. .
[0024]
In the production of an alkali-soluble copolymer, it is preferable not to use a surfactant that is usually used in emulsion polymerization. However, when a surfactant is used in combination, the amount of the surfactant is an alkali-soluble copolymer. The amount is usually less than 0.05 parts by weight with respect to 100 parts by weight of all the monomers used for the synthesis. When the amount of the surfactant is increased, the obtained image tends to be inferior in water resistance.
[0025]
The ethylenically unsaturated carboxylic acid monomer used for the production of the alkali-soluble copolymer is not particularly limited, and examples thereof include ethylenically unsaturated monocarboxylic acid monomers such as acrylic acid and methacrylic acid; itaconic acid and maleic acid. Ethylenically unsaturated polyvalent carboxylic acid monomers such as acid, fumaric acid and butenetricarboxylic acid; ethylenically unsaturated polyvalent carboxylic acid moieties such as monobutyl fumarate, monobutyl maleate and mono-2-hydroxypropyl maleate And ester monomers; polyhydric carboxylic acid anhydrides such as maleic anhydride and citraconic anhydride; and the like. These monomers can be used individually or in combination of 2 or more types. Of these ethylenically unsaturated acid monomers, ethylenically unsaturated monocarboxylic acids such as (meth) acrylic acid are preferred, and methacrylic acid is more preferred.
[0026]
The amount of the ethylenically unsaturated carboxylic acid monomer used is an amount calculated such that the acid value of the alkali-soluble copolymer is 40 or less, preferably 10 to 40, more preferably 30 to 40. When this amount is converted and the acid value of the alkali-soluble copolymer exceeds 40 or less than 10, the quality of the obtained image may be inferior.
[0027]
Other monomers that can be used for the production of the alkali-soluble copolymer and copolymerizable with the ethylenically unsaturated carboxylic acid monomer are not particularly limited. For example, styrene, α-methylstyrene, vinyl Aromatic vinyl monomers such as toluene and chlorostyrene; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, (meth ) Acrylic acid-n-amyl, (meth) acrylic acid isoamyl, (meth) acrylic acid-n-hexyl, (meth) acrylic acid-2-ethylhexyl, (meth) acrylic acid-n-octyl, (meth) acrylic acid Ethylenically unsaturated carboxylic acids such as 2-hydroxyethyl, hydroxypropyl (meth) acrylate, and glycidyl (meth) acrylate Ester monomers; ethylenically unsaturated nitrile monomers such as (meth) acrylonitrile; ethylenically unsaturated glycidyl ether monomers such as allyl glycidyl ether; (meth) acrylamide, N-methylol (meth) acrylamide, N -Ethylenically unsaturated amide monomers such as butoxymethyl (meth) acrylamide; conjugated diene monomers such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene A carboxylic acid vinyl ester such as vinyl acetate; These monomers can be used alone or in combination of two or more. Among them, an ethylenically unsaturated carboxylic acid ester monomer is preferable, and methyl methacrylate and ethyl acrylate are more preferable in terms of excellent light resistance and gloss of the obtained image.
[0028]
The alkali-soluble copolymer can be obtained by polymerizing the monomer mixture, preferably in an aqueous medium, in the presence of an alcoholic hydroxyl group-containing water-soluble polymer compound. At this time, the alcoholic hydroxyl group-containing water-soluble polymer compound and the monomer mixture are added all at once to the reactor before the polymerization is started, or a part is charged before the polymerization is started, and after the polymerization is started. The remaining portion can be added in portions, or the remaining portion can be added continuously. In the case of divided addition or continuous addition, the addition amount can be made uniform or constant, and can be changed according to the progress of polymerization.
[0029]
Even if the alcoholic hydroxyl group-containing water-soluble polymer compound and the monomer mixture are added separately, the monomer obtained by mixing the alcoholic hydroxyl group-containing water-soluble polymer compound, the monomer mixture and water It may be added in the form of a dispersion. When the alcoholic hydroxyl group-containing water-soluble polymer compound and the monomer are added separately, it is desirable that the addition of both be started almost simultaneously. Aggregates are likely to occur when only a large amount of the monomer mixture is added first, and conversely, when only a large amount of the alcoholic hydroxyl group-containing water-soluble polymer compound is added first, the polymerization system thickens. Or problems such as the occurrence of aggregates are likely to occur. The addition of both does not necessarily have to be the same, but it is desirable that the addition be almost the same.
[0030]
Among the methods of adding the alcoholic hydroxyl group-containing water-soluble polymer compound and the monomer mixture, the alcoholic hydroxyl group-containing water-soluble polymer compound is mixed with the monomer mixture and water to disperse, and the polymerization is started in the reactor. The addition method is preferable because the chain distribution of the ethylenically unsaturated acid monomer in the polymer chain of the alkali-soluble copolymer becomes uniform.
[0031]
The alkali-soluble copolymer used for the production of the pH adjusting resin is obtained by polymerizing an ethylenically unsaturated carboxylic acid monomer and other monomers copolymerizable therewith in the presence of a copolymerizable surfactant ( Preferably, it can be produced by emulsion polymerization.
[0032]
A copolymerizable surfactant is a surfactant having one or more polymerizable vinyl groups in its molecule. Specific examples thereof include propenyl-2-ethylhexyl sulfosuccinate sodium salt, (meth) acrylic acid polyoxyethylene sulfate ester, polyoxyethylene alkylpropenyl ether sulfate ammonium salt, (meth) acrylic acid polyoxyethylene ester phosphate ester, etc. Nonionic polymerizable surfactants such as polyoxyethylene alkylbenzene ether (meth) acrylic acid ester and polyoxyethylene alkyl ether (meth) acrylic acid ester. Among these copolymerizable surfactants, polyoxyethylene alkylpropenyl ether ammonium sulfate is preferable because of its excellent balance between the emulsifying and dispersing performance of the monomer and the copolymerizability with the monomer.
[0033]
The amount of the copolymerizable surfactant is usually 0.01 to 5.0 parts by weight, preferably 0.05 to 100 parts by weight based on 100 parts by weight of all monomers used for the synthesis of the alkali-soluble copolymer. 5.0 parts by weight, more preferably 0.1 to 3.0 parts by weight. If it is less than 0.01 part by weight, the emulsion stability becomes low, and a large amount of aggregates may be generated during the polymerization. On the other hand, when the amount exceeds 5.0 parts by weight, the problem that the pH-adjusting resin composition tends to foam may occur. In the polymerization of the alkali-soluble copolymer, it is preferable not to use a non-polymerizable surfactant. However, when a non-polymerizable surfactant is used in combination, the amount of the non-polymerizable surfactant is the amount of the alkali-soluble copolymer. The amount is usually less than 0.05 parts by weight with respect to 100 parts by weight of all monomers used for the synthesis of the polymer. When the amount of the non-polymerizable surfactant is increased, the obtained image tends to be inferior in water resistance.
[0034]
The polymerization initiator that can be used for the production of the alkali-soluble copolymer is not particularly limited. Specific examples include inorganic peroxides such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium perphosphate, and hydrogen peroxide; diisofuropylbenzene hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide , 1,1,3,3-tetramethylbutyl hydroperoxide, di-t-butyl peroxide, isobutyryl peroxide, benzoyl peroxide, and other organic peroxides; azobisisobutyronitrile, azobis-2, Examples include azo compounds such as 4-dimethylvaleronitrile and methyl azobisisobutyrate. These polymerization initiators can be used alone or in combination of two or more. Of these, persulfates such as potassium persulfate and ammonium persulfate are preferable.
[0035]
The amount of the polymerization initiator used varies depending on the type, but is preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the total monomer mixture used in the production of the aqueous dispersion of the alkali-soluble copolymer. More preferably, it is 0.8-4 weight part.
[0036]
Moreover, these polymerization initiators can also be used as a redox polymerization initiator in combination with a reducing agent.
[0037]
The reducing agent of the redox polymerization initiator is not particularly limited. Specific examples thereof include compounds containing metal ions in a reduced state such as ferrous sulfate and cuprous naphthenate; sulfones such as sodium methanesulfonate. Acid compounds; amine compounds such as dimethylaniline; and the like.
[0038]
These reducing agents can be used alone or in combination of two or more.
[0039]
Although the usage-amount of a reducing agent changes with reducing agents, it is preferable that it is 0.03-10 weight part with respect to 1 weight part of polymerization initiators.
[0040]
In order to adjust the weight average molecular weight of the alkali-soluble copolymer, a chain transfer agent can be used at the time of polymerization, if necessary. Examples of chain transfer agents include mercaptans such as t-dodecyl mercaptan and n-dodecyl mercaptan; α-methylstyrene dimer; sulfides such as dimethylxanthogen disulfide and diisopropylxanthogen disulfide; 2-methyl-3-butynenitrile, 3- Nitrile compounds such as pentenenitrile; thioglycolic acid esters such as methyl thioglycolate, propyl thioglycolate, and octyl thioglycolate; β-mercaptopropionic acid esters such as methyl β-mercaptopropionate and octyl β-mercaptopropionate; These can be used alone or in combination of two or more. Of these chain transfer agents, thioglycolate is preferable, and octyl thioglycolate is more preferable.
[0041]
When a chain transfer agent is used, the addition amount is usually 0.1 to 5 parts by weight, preferably 0.5 to 4 parts per 100 parts by weight of the monomer used for the production of the alkali-soluble copolymer. Parts by weight. When the amount of the chain transfer agent used is too small, the viscosity after neutralization becomes high and handling may be difficult, and when too large, the molecular weight may be remarkably lowered. The method for adding the chain transfer agent is not particularly limited, and the whole amount may be added all at once, or may be added to the polymerization system intermittently or continuously in small amounts.
[0042]
The polymerization temperature when producing the alkali-soluble copolymer is usually 0 to 100 ° C, preferably 30 to 90 ° C. The polymerization conversion is usually 90% by weight or more, preferably 95% by weight or more.
[0043]
The neutralization degree in the neutralized product of the alkali-soluble copolymer used in the present invention (the molar equivalent of the inorganic base relative to the molar equivalent of the ethylenically unsaturated carboxylic acid monomer) is not particularly limited, but the neutralization degree is usually 70% or more, preferably 95% or more.
[0044]
The inorganic base used to neutralize the alkali-soluble copolymer is not particularly limited, and examples thereof include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; calcium hydroxide and magnesium hydroxide. Examples thereof include hydroxides of alkaline earth metals such as these, and these can be used alone or in combination of two or more. Of these inorganic bases, sodium hydroxide is preferred. Ammonia may be used as the inorganic base, but it may cause a decrease in ink aging stability (for example, pH reduction) and ejection stability.
[0045]
Among the above-mentioned alkali-soluble copolymers used in the present invention, those obtained by polymerization in the presence of an alcoholic hydroxyl group-containing water-soluble polymer compound can be obtained when the pH-adjusted resin composition is stored for a long time. It is preferable in that it hardly changes in viscosity and is excellent in its dot reproducibility.
[0046]
The weight average molecular weight of the pH adjusting resin used in the present invention is not particularly limited, but if it is too large (for example, more than 50,000), the viscosity of the pH adjusting resin aqueous solution becomes high, and its handling is difficult. It can be difficult. On the other hand, if it is too low (for example, less than 8,000), the abrasion resistance may deteriorate. The weight average molecular weight of the pH adjusting resin is, for example, preferably 8,000 or more, more preferably 9,000 to 100,000, and still more preferably 10,000 to 50,000.
[0047]
The glass transition temperature of the pH adjusting resin used in the present invention can be arbitrarily set, but is preferably 5 to 50 ° C., more preferably 20 to 40 ° C. When the glass transition temperature of the pH adjusting resin is within this range, an image excellent in bending resistance and blocking resistance can be obtained. In addition, even if the glass transition temperature of the pH adjusting resin used in the present invention is somewhat high, the film forming temperature of the ink composition of the present invention is generally kept low.
[0048]
The pH adjusting resin used in the present invention can be added to the ink composition in any form of a water-soluble resin, a resin emulsion, or a polymer fine particle.
[0049]
In the ink composition of the present invention, the water-soluble pH adjusting resin is usually used in the form of an aqueous solution. The solid content concentration in this case is usually 1 to 40% by weight, preferably 20 to 30% by weight. This aqueous solution may contain a water-soluble organic solvent described later. Further, when the pH adjusting resin is used in the form of a resin emulsion or polymer fine particles, the solid content concentration is usually 1 to 40% by weight, preferably 20 to 30% by weight, and the resin emulsion is used in the state of an aqueous emulsion. Is done.
[0050]
The pH adjusting resin used in the present invention preferably has a pH of 8 to 11 in an aqueous solution state, and more preferably has a pH of 9 to 11. If the pH is less than 8, there may be a problem in ejection stability, and if it exceeds 11, there may be a problem in dispersion stability.
[0051]
The amount of the alkali-soluble copolymer used in the pH-adjusting resin used in the present invention is preferably 2 to 200 parts by weight, more preferably 5 to 150 parts by weight, particularly preferably 10 to 100 parts by weight of the colorant. ~ 100 parts by weight.
[0052]
The colorant used in the present invention is not particularly limited, and is, for example, a water-soluble dye or a water-insoluble pigment. A water-insoluble pigment is preferable from the viewpoint of excellent image density, light resistance and water resistance.
[0053]
As the colorant used in the present invention, any dye that is a water-soluble dye used in conventional inks and does not change color tone or produce precipitates due to the addition of other ink components can be used. it can.
[0054]
In the present invention, inorganic pigments and organic pigments can be used without particular limitation as pigments that can be used with the pH adjusting resin. As the inorganic pigment, in addition to titanium oxide and iron oxide, carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used. Organic pigments include azo dyes (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazines). Pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (for example, basic dye chelate, acid dye chelate, etc.), nitro pigments, nitroso pigments, aniline black, and the like.
[0055]
In particular, as carbon black used as black ink, No. manufactured by Mitsubishi Chemical Corporation. 2300, no. 900, HCF88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, No2200B, etc. are Raven5750, Raven5250, Raven5000, Raven3500, Raven1255, Raven700, etc. manufactured by Colombia, Regal400R, Regal330R, Regal660R, onchalM900 , Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc. are Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black FW200, Col. 0, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Special Black 6, Special Black 5, Special Black 4A, and Spac 4 .
[0056]
Examples of pigments used in yellow ink include C.I. I. Pigment Yellow 1, C.I. I. Pigment Yellow 2, C.I. I. Pigment Yellow 3, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 14C, C.I. I. Pigment Yellow 16, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 73, C.I. I. Pigment Yellow 74, C.I. I. Pigment Yellow 75, C.I. I. Pigment Yellow 83, C.I. I. Pigment Yellow 93, C.I. I. Pigment Yellow 95, C.I. I. Pigment Yellow 97, C.I. I. Pigment Yellow 98, C.I. I. Pigment Yellow 114, C.I. I. Pigment Yellow 128, C.I. I. Pigment Yellow 129, C.I. I. Pigment Yellow 151, C.I. I. Pigment Yellow 154 and the like.
[0057]
Examples of pigments used for magenta ink include C.I. I. PigmentRed 5, C.I. I. Pigment Red 7, C.I. I. Pigment Red 12, C.I. I. Pigment Red 48 (Ca), C.I. I. Pigment Red 48 (Mn), C.I. I. Pigment Red 57 (Ca), C.I. I. Pigment Red 57: 1, C.I. 1. Pigment Red 112, C.I. I. Pigment Red 123, C.I. I. Pigment Red 168, C.I. I. Pigment Red 184, C.I. I. Pigment Red 202 or the like.
[0058]
Examples of pigments used for cyan ink include C.I. I. Pigment Blue 1, C.I. I. Pigment Blue 2, C.I. I. Pigment Blue 3, C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 15:34, C.I. I. Pigment Blue 16, C.I. I. Pigment Blue 22, C.I. I. Pigment Blue 60, C.I. I. Vat Blue 4, C.I. I, Vat Blue 60 and the like. However, it is not limited to these.
[0059]
The particle size of the pigment is preferably 10 μm or less, more preferably 1 μm or less, and still more preferably 0.1 μm or less.
[0060]
In the present invention, according to a preferred embodiment of the pigment that can be used together with the pH adjusting resin, these pigments are added to the ink as a pigment dispersion obtained by dispersing the pigment in an aqueous medium. Is preferred. As the dispersant used for preparing the pigment dispersion, a dispersant generally used for preparing the pigment dispersion, for example, a polymer dispersant or a surfactant can be used. Examples of the surfactant used as the dispersant include various anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants described later.
[0061]
Preferable examples of the polymer dispersant include natural polymers. Specific examples thereof include proteins such as glue, gelatin, casein, and albumin, natural rubbers such as gum arabic and tragacanth, glucosides such as saponin, Examples include alginic acid and propylene glycol alginate, alginic acid derivatives such as triethanolamine alginate and ammonium alginate, and cellulose derivatives such as methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, and ethylhydroxycellulose.
[0062]
Further, preferred examples of the polymer dispersant include synthetic polymers, such as polyvinyl alcohols, polyvinylpyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymer, potassium acrylate-acrylonitrile copolymer, vinyl acetate. -Acrylic resin such as acrylic acid ester copolymer, acrylic acid-acrylic acid ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer Styrene-acrylic resins such as styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride Copolymer, vinyl naphthalene-acrylic acid copolymer , Vinyl naphthalene-maleic acid copolymer, and vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-crotonic acid copolymer, vinyl acetate -Vinyl acetate copolymers such as acrylic acid copolymers and their salts.
[0063]
Of these, a copolymer of a monomer having a hydrophobic group and a monomer having a hydrophilic group, and a polymer comprising a monomer having both a hydrophobic group and a hydrophilic group in the molecular structure are particularly preferred.
[0064]
According to another preferred embodiment of the pigment that can be used together with the pH adjusting resin in the present invention, it is preferable to use carbon black whose surface is oxidized. In this embodiment, the dispersant described above may not be used. The oxidation treatment can be performed by a known method. By the oxidation treatment, hydrophilic groups such as a carbonyl group, a carboxyl group, a hydroxyl group, and a sulfone group can be introduced on the surface of the carbon black. The above carbon black is used.
[0065]
In the ink composition of the present invention, the content of the pH adjusting resin and the colorant is about 0.5 to 50% by weight as the total amount of the pH adjusting resin and the colorant with respect to the total weight of the ink composition. Preferably, it is about 2 to 30% by weight. In the ink composition of the present invention, the content ratio of the pH adjusting resin and the colorant (pH adjusting resin / colorant) is not particularly limited, but is preferably 0.05 to 1, and more preferably 0.1 to 0.1. 0.5.
[0066]
Any viscosity adjusting agent can be used in the ink composition of the present invention. Viscosity modifiers are generally widely used as additives in ink compositions and paints, and the rheological properties of ink compositions and paints, i.e., viscosity, leveling, sag, settling, and / or It is a chemical substance that changes fluidity and is called a viscosity modifier, rheology imparting agent, thickener, viscosity improver, gelling agent, thixotropic additive, suspending agent, rheology improving agent It is also called a thickening agent. Also in the ink composition of the present invention, the above general viscosity adjusting agent (in particular, an aqueous viscosity adjusting agent) can be used as it is.
[0067]
Examples of known viscosity modifiers that can be used in the ink composition of the present invention include clay-based viscosity modifiers and organic polymerizable viscosity modifiers. These viscosity modifiers are described, for example, by Van der Watt and Goodman, “Clay and Clay Material”, Vol. 9, page 568 (1960), and McCormick ( McCormick, Gok and Schulz, “Encyclopedia of Polymer Science and Engineering”, Vol. 17, page 730 (1989). Clay minerals are a group of minerals consisting essentially of hydrous aluminum silicate, and specifically include montmorillonite, kaolin, illite, saponite, bentonite, hectorite, beidellite, stevensite, attapulgite, or sepiolite. In particular, bentonite and hectorite used for the aqueous viscosity modifier can be mentioned. For example, hectorite is supplied to the US market as an aqueous thickener.
[0068]
Examples of the organic polymerizable viscosity modifier for an aqueous system include guar gum, tragacanth gum, pectin, xanthan, or alginate. These are often called natural organic thickeners. In addition, there are modified cellulose derivatives hydroxyethylcellulose (HEC thickener) and methylcellulose, as well as synthetic polymers and copolymers.
[0069]
Various synthetic polymer thickeners (ie, synthetic polymer viscosity modifiers) are known and can be used in the ink compositions of the present invention. For example, polymer thickeners based on polyurethane are described in US Pat. No. 5,023,309. Also known is a polymer thickening agent formed by copolymerizing two or more monomers (one or more of the monomers contains a carboxyl group). Such a polymer thickener has a linear structure, a branched structure, or a three-dimensional network structure formed by crosslinking.
[0070]
As one such polymer, a polymer viscosity modifier formed by the reaction of (a) methacrylic acid, (b) methacrylic acid ester, and (c) saturated aliphatic carboxylic acid vinyl ester is known. For example, JP-A-55-23180 (US Pat. No. 4,226,754) includes (a) 15 to 40% by weight (preferably 20 to 35% by weight) of methacrylic acid, and (B) General formula:
[0071]
[Chemical 1]

[Wherein R is a saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms (preferably 1 to 12 carbon atoms) which may be optionally substituted (preferably with a hydroxy group) (preferably Alkyl group)]
5 to 70% by weight (preferably 10 to 50% by weight) of at least one methacrylic acid ester represented by: (c) at least a saturated aliphatic carboxylic acid having 2 to 11 carbon atoms (preferably 2 to 7 carbon atoms) A polymer viscosity modifier of 5 to 80% by weight (preferably 20 to 60% by weight) of a polymer of one kind and a vinyl compound is described, and this polymer viscosity modifier is also used in the ink composition of the present invention. It can be preferably used. Examples of the methacrylic acid ester (B) include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, n-amyl methacrylate, sec-amyl methacrylate, hexyl methacrylate, lauryl methacrylate, stearyl methacrylate, ethylhexyl methacrylate, Examples include crotyl methacrylate, cinnamyl methacrylate, oleyl methacrylate, ricinoleyl methacrylate, hydroxyethyl methacrylate, or hydroxypropyl methacrylate, and methyl methacrylate is preferred.
[0072]
Examples of aliphatic carboxylic acid vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, tert-vinyl butyrate, vinyl caprate, vinyl stearate, vinyl laurate, and vinyl oleate. Vinyl is preferred.
[0073]
Such polymer viscosity modifiers contain a sufficient amount of carboxylic acid groups and make the polymer water-soluble and neutralized with a water-soluble base, which often results in alkali-swellable or alkali-soluble latex copolymerizable thickeners and It is called and commercially available [for example, RHEOLATE 350 from Leox International Inc. (USA)].
[0074]
A polymer viscosity modifier having a hydrophobic group introduced into the polymer main chain of the alkali swellable or alkali-soluble polymer viscosity modifier is also known. For example, US Pat. No. 4,384,096 discloses carbon An α, β-ethylenically unsaturated carboxylic acid monomer having 3 to 8 atoms, a nonionic vinyl monomer, a specific vinyl ester surfactant [for example, one end is C ₈ ~ C ₁₆ Polymer reaction products with 1 to 30% of alkylphenoxypoly (ethyleneoxy) ethyl acrylate] terminated with alkylphenyl groups are described. In addition, US Pat. No. 4,138,381 discloses an unsaturated carboxylic acid having 3 to 6 carbon atoms, an alkyl acrylate or an alkyl methacrylate, and an alkylphenyl group (provided that the alkyl group has 8 to 20 carbon atoms). Reaction products with esters containing (with carbon atoms) are described. These polymer viscosity modifiers can also be suitably used in the ink composition of the present invention.
[0075]
Furthermore, an acrylic emulsion copolymer viscosity modifier formed by emulsion polymerization of acrylic acid or methacrylic acid, alkyl acrylate or alkyl methacrylate, acrylic acid or methacrylic acid ethoxylated ester having a hydrophobic group, and a polyethylenically unsaturated monomer (For example, see European Patent No. 13,836) can also be suitably used in the ink composition of the present invention. In addition, a product obtained by adding an alkyl polyethylene oxyether surfactant to an associative polymer having a polyacrylamide main chain by solvation [“Proceedings of the ASC Division of Polymeric Materials ( Proceedings of the ACS Division of Polymeric Materials ”, 57, 476-481 (1987)] can also be suitably used for the ink composition of the present invention.
[0076]
Copolymers that are reaction products of various monomers including methacrylic acid, ethyl acrylate, copolymerizable ethylenically unsaturated monomers, and small amounts of polyethylenically unsaturated monomers (see, for example, US Pat. No. 4,421,902) Can also be suitably used in the ink composition of the present invention.
[0077]
More recently, it has been known to adjust the viscosity of the system using water-soluble copolymers that do not contain mineral oil (see, for example, US Pat. No. 4,668,410). The polymer described in U.S. Pat. No. 4,668,410 is a reaction product of six components, which include methacrylic acid, methacrylic or acrylate esters of alcohols, vinyl esters and surface activity. Unsaturated ester. When this polymer is partially or completely neutralized, it can be used as a thickener by being dispersed in water or colloidally in water. Similar copolymers obtained by condensation of polyhydric alcohols with monoethylenically unsaturated monoisocyanates are also known (see, for example, US Reissue Pat. No. 33,008) and are commercially available [eg, RHEOLATE 210 and 216 from Leox International Inc. (USA).
[0078]
Further, one or more (about 15 to 80% by weight) of an α, β-ethylenically unsaturated carboxylic acid monomer having 3 to 8 carbon atoms (for example, acrylic acid or methacrylic acid), a copolymerizable vinyl nonion Ends with one or more (about 15-85% by weight) of an ethylenically unsaturated monomer (eg, ethyl acrylate, vinyl acetate, or methyl methacrylate) and a hydrophobic phenol monomer, ie, an aralkyl-substituted phenolic hydrophobic group A viscosity modifier for an aqueous composition formed by reacting a nonionic poly (alkyleneoxy) vinyl monomer (about 0.5 to 25% by weight) (see JP-A-8-225618) is also used in the ink of the present invention. It can be suitably used in the composition.
[0079]
In the ink composition of the present invention, one or a combination of two or more of the above viscosity modifiers can be used.
[0080]
In the ink composition of the present invention, the content of the viscosity modifier is preferably about 0.01 to 1% by weight, more preferably 0.05 to 0.5% by weight, based on the total weight of the ink composition. Degree.
[0081]
The ink composition of the present invention contains water as a solvent and can further contain a water-soluble organic solvent.
[0082]
Examples of water-soluble organic solvents are methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butanol, See-butanol, tert-butanol, iso-butanol, n-pentanol, ethylene glycol, propylene glycol, Diethylene glycol, pentamethylene glycol, trimethylene glycol, 2-butyne-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, N-methyl-2-pyrrolidone 1,3-dimethyl-2-imidazolidinone, 2-pyrrolidone, glycerin, tripropylene glycol monomethyl ether, dipropylene glycol monoethyl glycol, dipropylene glycol monomethyl ether, dipropylene glycol , Triethylene glycol monomethyl ether, tetraethylene glycol, triethylene glycol, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, and the like.
[0083]
In the ink composition of the present invention, the content when a water-soluble organic solvent is used is preferably about 10 to 40% by weight, more preferably 10 to 20% by weight, based on the total weight of the ink composition. is there.
[0084]
The ink composition according to a preferred embodiment of the present invention can further contain a surfactant. The surfactant used in the present invention is one or more surfactants selected from the group consisting of anionic surfactants, nonionic surfactants, and amphoteric surfactants.
[0085]
Examples of surfactants include anionic surfactants (eg, sodium dodecyl benzene sulfonate, sodium lauryl sulfate, ammonium salt of polyoxyethylene alkyl ether sulfate), nonionic surfactants (eg, polyoxyethylene alkyl ether, Polyoxyethylene alkyl ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, polyoxyethylene alkylamide and the like) and acetylene glycol. These can be used alone or in combination of two or more.
[0086]
Furthermore, the ink composition according to a preferred embodiment of the present invention contains a tertiary amine as a pH adjuster.
[0087]
Examples of the tertiary amine that can be added to the ink composition according to the present invention include trimethylamine, triethylamine, triethanolamine, dimethylethanolamine, diethylethanolamine, triisopropenolamine, and butyldiethanolamine. These may be used alone or in combination. The amount of these tertiary amines added to the ink composition of the present invention is 0.1 to 10% by weight, more preferably 0.5 to 5% by weight.
[0088]
In addition, the ink composition according to the present invention may contain a penetration enhancer, a sugar, and / or an alginic acid derivative.
[0089]
Examples of the penetration enhancer include alkyl ether derivatives of polyhydric alcohols having 3 or more carbon atoms, such as diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monobutyl ether, or dipropylene glycol monobutyl ether. 1 type, or 2 or more types of these can be used.
[0090]
Examples of sugars include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides) and polysaccharides, preferably glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid. , Glucitol, (sorbitol), maltose, cellobiose, lactose, sucrose, trehalose, maltotriose, and the like. Here, the polysaccharide means a saccharide in a broad sense, and is used to include a substance that exists widely in nature, such as alginic acid, α-cyclodextrin, and cellulose. In addition, derivatives of these saccharides include reducing sugars of the saccharides described above [(for example, sugar alcohol (general formula ₂ (CHOH) _n CH ₂ OH (wherein n represents an integer of 2 to 5)], oxidized sugar (eg, aldonic acid, uronic acid, etc.), amino acid, thiosaccharide, and the like. Sugar alcohol is particularly preferable, and specific examples include maltitol and sorbit. The addition amount of these saccharides is preferably about 0.1 to 40% by weight, more preferably about 1 to 30% by weight.
[0091]
Preferable examples of the alginic acid derivative include alginic acid alkali metal salts (for example, sodium salt and potassium salt), alginic acid organic salts (for example, triethanolamine salt), and alginic acid ammonium salt. The amount of the alginic acid derivative added to the ink composition is preferably about 0.01 to 1% by weight, more preferably about 0.05 to 0.5% by weight.
[0092]
The reason why a good image can be obtained by adding an alginic acid derivative is not clear, but the polyvalent metal salt present in the reaction solution reacts with the alginic acid derivative in the ink composition, changes the dispersion state of the colorant, This is considered due to the fact that the fixing of the agent to the recording medium is promoted.
[0093]
In addition to the ink composition according to the present invention, a preservative, a fungicide, and / or a phosphorus-based antioxidant may be added as necessary.
[0094]
The ink composition of the present invention can be prepared by a conventional method. For example, it can be produced by dispersing and mixing the above-described components by an appropriate method. Preferably, first, a pigment, a polymer dispersant, and ion exchange water are appropriately dispersed (for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator mill, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a jet mill, an ang mill). Etc.) to prepare a uniform pigment dispersion. Next, the pH adjusting resin liquid (for example, pH adjusting resin aqueous solution), the viscosity adjusting agent, ion exchange water, a water-soluble organic solvent, an antiseptic, and / or an antifungal agent are sufficiently stirred at room temperature. An ink solvent is prepared. The pigment dispersion is gradually added dropwise to a state where the ink solvent is stirred by a suitable dispersing machine, and the ink solvent is sufficiently stirred. After sufficiently stirring, the target ink composition can be obtained by performing filtration in order to remove coarse particles and foreign matters that cause clogging.
[0095]
The ink composition of the present invention can be used in any printing method, and can be suitably used as, for example, a water-based gravure ink, a water-based flexographic ink, or particularly a water-based ink for inkjet recording. It can also be used as a water-based paint.
[0096]
In the ink composition of the present invention, the pH adjusting resin and the colorant (particularly pigment) contained in the ink composition are substantially left on the surface as a recording medium. It is particularly preferable to use it for a recording medium that substantially absorbs. In such a recording medium, for example, the average pore diameter on the surface is smaller than the average particle diameter of the pigment. A preferable recording medium is a recording medium including an ink receiving layer having an average pore diameter smaller than the average particle diameter of the pigment.
[0097]
As a preferred recording medium, a recording medium in which an ink receiving layer containing a porous pigment is provided on a substrate can be used. The ink receiving layer may be the uppermost layer of the recording medium, or may be an intermediate layer having, for example, a glossy layer thereon. As such a recording medium, a so-called absorption type (also referred to as a void type) recording medium containing a porous pigment and a binder resin in the ink receiving layer, and casein, modified polyvinyl alcohol (in the ink receiving layer) A so-called swelling type recording medium further containing a resin such as PVA), gelatin, or modified urethane is known, and the ink composition of the present invention can be used for any recording medium.
[0098]
Examples of the porous pigment contained in the ink receiving layer of the absorption-type recording medium include silica-based such as precipitation method, gel type, or gas-phase method, alumina hydrate such as pseudoboehmite, and silica / alumina hybrid sol. , Smectite clay, calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, kaolin, clay, talc, magnesium silicate, calcium silicate, and the like, and one or more of these can be used.
[0099]
Further, the binder resin contained in the ink receiving layer of the absorption type recording medium is not particularly limited as long as it is a compound that has a binding ability and can increase the strength of the ink receiving layer. For example, polyvinyl alcohol Silanol-modified polyvinyl alcohol, cellulose derivatives such as vinyl acetate, starch, carboxymethyl cellulose, casein, gelatin, conjugated diene copolymer latex such as styrene-butadiene copolymer, vinyl copolymer such as ethylene-vinyl acetate copolymer, etc. An acrylic copolymer latex such as a polymer latex and a polymer of acrylic acid and methacrylic acid can be used.
[0100]
The ink receiving layer may be a fixing agent, a fluorescent whitening agent, a water-proofing agent, a fungicide, if necessary, in the case of an ink receiving layer of an absorption type recording medium or an ink receiving layer of a swelling type recording medium. Various additives such as an agent, an antiseptic, a dispersant, a surfactant, a thickener, a pH adjuster, an antifoaming agent, and / or a water retention agent can also be contained.
[0101]
Examples of the substrate on which each of the ink receiving layers is provided include paper (including sized paper); resin-coated paper obtained by coating polyethylene, polypropylene, or polyester on paper; baryta paper; polyethylene terephthalate, polyethylene, or polypropylene. And a thermoplastic resin film such as synthetic paper; a sheet-like material formed of synthetic fibers.
[0102]
A particularly preferable recording medium is a recording medium having the base material and the ink receiving layer as the uppermost layer provided thereon, and the base material and the ink receiving layer also have the following physical properties, for example. What has is preferable.
[0103]
The base material is preferably paper (containing wood pulp), and its basis weight is preferably 100 to 350 g / m. ² More preferably, 180 to 260 g / m ² It is. The thickness is preferably 100 to 400 μm, more preferably 180 to 260 μm. The ink receiving layer contains 50-60% by weight of wet silica gel as the porous pigment in terms of solid content, based on the weight of the entire ink receiving layer, and 30-30% polyvinyl alcohol as the binder resin. A content of 40% by weight is preferred from the standpoints of ink absorptivity and printing fastness. The coating amount of the ink receiving layer is 5 to 50 g / m in terms of solid content. ² It is preferable in terms of ink absorbability. The thickness of the ink receiving layer itself is preferably 10 to 40 μm, more preferably 20 to 30 μm.
[0104]
In the recording medium for printing the ink composition of the present invention, the average pore diameter of the surface of the recording medium (particularly, the ink receiving layer) is preferably 50 nm or less, and more preferably 30 nm or less. When the average pore diameter exceeds 300 nm, the pigment may penetrate into the ink receiving layer and color developability may deteriorate.
[0105]
【Example】
The present invention will be described more specifically with reference to the following examples. However, these examples do not limit the scope of the present invention. In the examples, “%” and “parts” are based on weight unless otherwise specified. Moreover, the acid value of the copolymer obtained by the following preparation examples was measured according to JIS K0070.
[0106]
<Preparation Example 1>
<< Preparation of pH adjusting resin >>
Dispersion of monomer mixture by stirring and mixing 60 parts of ethyl methacrylate, 36 parts of methyl methacrylate, 4 parts of methacrylic acid, 3 parts of octyl thioglycolate as molecular weight regulator, 1 part of polyvinyl alcohol and 280 parts of ion-exchanged water A product was prepared.
[0107]
In another reactor equipped with a stirrer, 130 parts of ion-exchanged water and 2 parts of potassium persulfate were charged, the temperature was raised to 80 ° C., and the dispersion of the monomer mixture was continuously added over 4 hours for polymerization. . After completion of the continuous addition, a post-reaction was performed at 80 ° C. for 30 minutes. The polymerization conversion rate was 99% or more.
[0108]
Next, 10% aqueous sodium hydroxide solution in an amount corresponding to the charged methacrylic acid and an equimolar amount of sodium hydroxide was added to the reactor, followed by heat treatment at 80 ° C. for 1 hour, and then an appropriate amount of ion-exchanged water was added. In addition, a pH-adjusting resin solution A having a solid content concentration of 15% was obtained. The acid value of this pH adjusting resin solution A was 30.
[0109]
<Preparation Example 2>
A monomer prepared by stirring and mixing 56 parts of ethyl acrylate, 36 parts of methyl methacrylate, 8 parts of methacrylic acid, 3 parts of octyl thioglycolate, 2.5 parts of sodium lauryl sulfate and 80 parts of ion-exchanged water as a molecular weight regulator. A dispersion of the mixture was prepared.
[0110]
In another reactor equipped with a stirrer, 90 parts of ion-exchanged water in which 0.05 part of ethylenediaminetetraacetic acid was dissolved was charged, the temperature was raised to 80 ° C., and 40 parts of a 5% aqueous potassium persulfate solution was added. The dispersion of the mixture was continuously added over 2 hours for polymerization. After completion of the continuous addition, a post-reaction was performed at 80 ° C. for 30 minutes. The polymerization conversion rate was 99% or more.
[0111]
Subsequently, 28 parts ammonia aqueous solution and 2 parts of 5% sodium persulfate aqueous solution in an amount corresponding to the charged methacrylic acid and an equimolar amount of ammonia were added to the reactor, and further post-treated at 80 ° C. for 1 hour, An appropriate amount of ion-exchanged water was added to obtain a pH adjusting resin solution B having a solid content of 25%. The acid value of this pH adjusting resin solution B was 50.
[0112]
<Ink Preparation Examples and Comparative Examples>
A pigment, a dispersant and water are mixed and dispersed in a sand mill (manufactured by Yaskawa Seisakusho) with glass beads (diameter 1.7 mm, 1.5 times the weight of the mixture (weight)) for 2 hours, and then the glass beads are removed. A pigment dispersion was prepared.
[0113]
Next, a solvent other than the pigment and the dispersant and a viscosity modifier are mixed to obtain an ink solvent. While stirring the pigment dispersion and the pH adjusting resin solution A or B produced in the above preparation example, The solution was gradually added dropwise and stirred at room temperature for 20 minutes. Filtration through a 5 μm membrane filter gave an ink for inkjet recording.
[0114]
<Example 1>
(1) Black pigment ink
Carbon black MA7 (Mitsubishi Chemical Corporation) 3% by weight
Styrene-acrylic acid copolymer (dispersant) 1% by weight
pH adjustment resin solution A 2% by weight
RHEOLATE 350 (viscosity modifier) 0.2% by weight
(Active ingredient 50%, manufactured by Leox International Inc.)
Glycerin 10% by weight
Ion exchange water
(2) Cyan ink
C. I. Pigment Blue 15: 3 2% by weight
Styrene-acrylic acid copolymer (dispersant) 1% by weight
pH adjustment resin solution A 2% by weight
RHEOLATE 350 (viscosity modifier) 0.2% by weight
(Active ingredient 50%, manufactured by Leox International Inc.)
10% by weight of triethylene glycol monobutyl ether
Diethylene glycol 10% by weight
Ion exchange water
(3) Magenta ink
C. I. Pigment Red 122 3% by weight
Styrene-acrylic acid copolymer (dispersant) 1% by weight
pH adjustment resin solution A 2% by weight
RHEOLATE 350 (viscosity modifier) 0.2% by weight
(Active ingredient 50%, manufactured by Leox International Inc.)
10% by weight of triethylene glycol monobutyl ether
Glycerin 5% by weight
Diethylene glycol 5% by weight
Ion exchange water
(4) Yellow ink
C. I. Pigment Yellow 74 3.5% by weight
Styrene-acrylic acid copolymer (dispersant) 1% by weight
pH adjustment resin solution A 2% by weight
RHEOLATE 350 (viscosity modifier) 0.2% by weight
(Active ingredient 50%, manufactured by Leox International Inc.)
10% by weight of triethylene glycol monobutyl ether
Glycerin 8% by weight
Ion exchange water
[0115]
<Comparative Example 1>
(1) Black pigment ink
Carbon black MA7 (Mitsubishi Chemical Corporation) 3% by weight
Styrene-acrylic acid copolymer (dispersant) 1% by weight
pH adjustment resin solution B 2% by weight
RHEOLATE 210 (viscosity modifier) 0.4% by weight
(25% active ingredient, manufactured by Leox International Inc.)
Glycerin 15% by weight
Ion exchange water
(2) Cyan ink
C. I. Pigment Blue 15: 3 2% by weight
Styrene-acrylic acid copolymer (dispersant) 1% by weight
pH adjustment resin solution B 2% by weight
RHEOLATE 210 (viscosity modifier) 0.4% by weight
(25% active ingredient, manufactured by Leox International Inc.)
10% by weight of triethylene glycol monobutyl ether
Diethylene glycol 10% by weight
Ion exchange water
(3) Magenta ink
C. I. Pigment Red 122 3% by weight
Styrene-acrylic acid copolymer (dispersant) 1% by weight
pH adjustment resin solution B 2% by weight
RHEOLATE 210 (viscosity modifier) 0.4% by weight
(25% active ingredient, manufactured by Leox International Inc.)
10% by weight of triethylene glycol monobutyl ether
Glycerin 5% by weight
Diethylene glycol 5% by weight
Ion exchange water
(4) Yellow ink
C. I. Pigment Yellow 74 3.5% by weight
Styrene-acrylic acid copolymer (dispersant) 1% by weight
pH adjustment resin solution B 2% by weight
RHEOLATE 210 (viscosity modifier) 0.4% by weight
(25% active ingredient, manufactured by Leox International Inc.)
10% by weight of triethylene glycol monobutyl ether
Glycerin 8% by weight
Ion exchange water
[0116]
<Comparative example 2>
(1) Black pigment ink
Carbon black MA7 (Mitsubishi Chemical Corporation) 3% by weight
Styrene-acrylic acid copolymer (dispersant) 1% by weight
RHEOLATE 216 (viscosity modifier) 2% by weight
(20% active ingredient, manufactured by Leox International Inc.)
Glycerin 10% by weight
Ion exchange water
(2) Cyan ink
C. I. Pigment Blue 15: 3 2% by weight
Styrene-acrylic acid copolymer (dispersant) 1% by weight
RHEOLATE 216 (viscosity modifier) 2% by weight
(20% active ingredient, manufactured by Leox International Inc.)
10% by weight of triethylene glycol monobutyl ether
Diethylene glycol 10% by weight
Ion exchange water
(3) Magenta ink
C. I. Pigment Red 122 3% by weight
Styrene-acrylic acid copolymer (dispersant) 1% by weight
RHEOLATE 216 (viscosity modifier) 2% by weight
(20% active ingredient, manufactured by Leox International Inc.)
10% by weight of triethylene glycol monobutyl ether
Glycerin 5% by weight
Diethylene glycol 5% by weight
Ion exchange water
(4) Yellow ink
C. I. Pigment Yellow 74 3.5% by weight
Styrene-acrylic acid copolymer (dispersant) 1% by weight
RHEOLATE 216 (viscosity modifier) 2% by weight
(20% active ingredient, manufactured by Leox International Inc.)
10% by weight of triethylene glycol monobutyl ether
Glycerin 8% by weight
Ion exchange water
[0117]
<Print evaluation>
Printing evaluation was performed using each of the ink compositions produced in the above Examples and Comparative Examples. For printing evaluation, an ink jet printer [PM-900C (manufactured by Seiko Epson Corporation)] was used, and printing was performed on PM photographic paper [ink jet paper: manufactured by Seiko Epson Corporation].
[0118]
(1) Glossiness evaluation
For the image after printing, the glossiness at a printing duty of 30% was measured with a gloss meter (PG-1M; manufactured by Nippon Denshoku Industries Co., Ltd.). The glossiness at each angle was determined by measuring regular reflection at 20 °, 60 °, or 85 °.
[0119]
The evaluation results were as shown in Table 1 below.
[0120]
[Table 1]

[0121]
As is clear from the above results, the overall glossiness of Example 1 is higher than that of Comparative Example 1 and Comparative Example 2, and the angle dependency of the glossiness is reduced, resulting in a better image. It was.
[0122]
【The invention's effect】
According to the ink composition of the present invention, a recorded matter having excellent gloss can be obtained.

Claims (12)

Acid value obtained by polymerizing ethylenically unsaturated carboxylic acid monomer and other monomers copolymerizable therewith in the presence of alcoholic hydroxyl group-containing water-soluble polymer compound or copolymerizable surfactant An ink composition comprising: a copolymer having a pH of 40 or less, a resin whose pH is adjusted with an inorganic base, water, a colorant, and a viscosity modifier. The ink composition according to claim 1, wherein the viscosity modifier is a synthetic polymer viscosity modifier. The synthetic polymer viscosity modifier is a synthetic polymer viscosity modifier formed by a reaction of (a) methacrylic acid, (b) methacrylic acid ester, and (c) saturated aliphatic carboxylic acid vinyl ester. The ink composition described in 1. The ink composition according to claim 1, wherein the colorant is a pigment. The ink composition according to any one of claims 1 to 4, wherein the inorganic base used for the preparation of the resin is an alkali metal hydroxide or an alkaline earth metal hydroxide. The ink composition according to any one of claims 1 to 5, wherein the alcoholic hydroxyl group-containing water-soluble polymer compound used for preparing the resin is a vinyl alcohol polymer. The ink composition according to any one of claims 1 to 6, wherein the ethylenically unsaturated carboxylic acid monomer used for preparing the resin is acrylic acid or methacrylic acid. The monomer copolymerizable with the ethylenically unsaturated carboxylic acid monomer used for the preparation of the resin is an ethylenically unsaturated carboxylic acid ester monomer according to any one of claims 1 to 7. The ink composition as described. The ink composition according to any one of claims 1 to 8, wherein the pH of the resin is 8 to 11. The ink composition according to any one of claims 1 to 9, which is an ink composition for inkjet recording. A resin and a colorant contained in the ink composition are substantially left on the surface using the ink composition according to any one of claims 1 to 9, but the liquid component of the ink composition is A method of recording on a recording medium that substantially absorbs. A resin and a colorant contained in the ink composition are substantially left on the surface using the ink composition according to any one of claims 1 to 9, but the liquid component of the ink composition is A recorded image formed on a recording medium that substantially absorbs.