JP3988479B2 - Ink composition - Google Patents

Description

（上記式中、Ｒ^１〜Ｒ^９は、独立して、Ｃ_１−６アルキル基を表し、ｊ及びｋは、独立して１以上の整数を表し、ＥＯはエチレンオキシ基を表し、ＰＯはプロピレンオキシ基を表し、ｍ及びｎは０以上の整数を表すが、但しｍ＋ｎは１以上の整数を表し、ＥＯ及びＰＯは、［ ］内においてその順序は限定されず、ランダムであってもブロックであってもよい）で表されるポリシロキサン系界面活性剤を含むことができる。
【００８９】
式（Ｉ）において、Ｒ^１〜Ｒ^９は、独立して、Ｃ_１−６アルキル基、好ましくはメチル基を表す。ｊ及びｋは、独立して、１以上の整数を表すが、より好ましくは１〜２である。また、ｍ及びｎは０以上の整数を表すが、但しｍ＋ｎは１以上の整数を表す。好ましくはｍ＋ｎは２〜４である。
【００９０】
本発明の好ましい態様によれば、式（Ｉ）の化合物として、Ｊ＝Ｋ＋１を満足するものが好ましい。また別の本発明の好ましい態様によれば、式（Ｉ）の化合物として、Ｒ^１〜Ｒ^９が全てメチル基を表し、ｊが２を表し、ｋが１を表し、ｌが１を表し、ｍが１以上の整数を表し、ｎが０を表すものが好ましい。
【００９１】
式（Ｉ）の化合物の添加量は適宜決定することができ、インク組成物の全重量に対して、０．０３〜３重量％が好ましく、より好ましくは０．１〜２重量％程度であり、更に好ましくは０．３〜１重量％程度である。
【００９２】
式（Ｉ）の化合物は市販されており、それを利用することが可能である。例えば、ビッグケミー・ジャパン株式会社より、シリコン系界面活性剤ＢＹＫ−３４５、ＢＹＫ−３４６、又はＢＹＫ−３４８が利用可能である。
【００９３】
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。
【００９４】
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。
【００９５】
また、本発明によるインク組成物には、浸透促進剤を含有させることもできる。
【００９６】
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。
【００９７】
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。
【００９８】
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）、糖類、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。
【００９９】
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。
【０１００】
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）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。
【０１０１】
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。
【０１０２】
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。
【０１０３】
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。
【０１０４】
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。
【０１０５】
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。
【０１０６】
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。
【０１０７】
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／ｍ^２、更に好ましくは１８０〜２６０ｇ／ｍ^２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／ｍ^２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。
【０１０８】
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。
【０１０９】
【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、以下の調整例で得られた共重合体の酸価は、ＪＩＳ Ｋ ００７０に従い測定した。
【０１１０】
＜調整例＞
《ｐＨ調整樹脂Ａの調整》
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部を撹拌混合して、単量体混合物の分散物を調整した。別の撹拌機付き反応器に、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。
【０１１２】
＜実施例及び比較例＞
《インク組成物の調整》
下記の各組成からなるインク組成物を調整し、それらの組み合わせからインクセットＡ〜インクセットＤとした。各インク組成物の調整は下記の手順でおこなった。
【０１１３】
すなわち、以下に具体的に示す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、顔料分散液を調整した。得られた分散液と、以下に具体的に示す成分とを混合し、２５℃で６０分間攪拌した。混合液を５μｍのメンブランフィルターでろ過し、インク組成物を得た。なお、以下の成分に記載の［ＢＹＫ３４８］はビッグケミー・ジャパン社製シリコン系界面活性剤である。
【０１１４】
＜実施例１＞
インクセットＡ
（ａ）ブラックインク組成物Ａ
カーボンブラックＭＡ７（三菱化学（株）製） 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Ａ ０．２重量％
ＨＳ−５００
（還元分岐オリゴ糖、固形分７０％ 林原商事（株）製） ５重量％
グリセリン １０重量％
１，２−ヘキサンジオール ５重量％
ＢＹＫ３４８ ０．５重量％
イオン交換水 残量
（ｂ）シアンインク組成物Ａ
顔料としてカーボンブラックＭＡ７に替えてピグメントブルー１５：３を使用したこと以外は、ブラックインク組成物Ａの調整法と同様にして、シアンインク組成物Ａを得た。
（ｃ）マゼンタインク組成物Ａ
顔料としてカーボンブラックＭＡ７に替えてピグメントレッド１２２を使用したこと以外は、ブラックインク組成物Ａの調整法と同様にして、マゼンタインク組成物Ａを得た。
（ｄ）イエローインク組成物Ａ
顔料としてカーボンブラックＭＡ７に替えてピグメントイエロー７４を使用したこと以外は、ブラックインク組成物Ａの調整法と同様にして、イエローインク組成物Ａを得た。
【０１１５】
＜実施例２＞
インクセットＢ
（ａ）ライトブラックインク組成物Ｂ
カーボンブラックＭＡ７（三菱化学（株）製） ０．９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Ａ ０．２重量％
ＨＳ−５００
（還元分岐オリゴ糖、固形分７０％ 林原商事（株）製） １０重量％
グリセリン １０重量％
１，２−ヘキサンジオール ５重量％
ＢＹＫ３４８ ０．５重量％
イオン交換水 残量
（ｂ）ライトシアンインク組成物Ｂ
顔料としてカーボンブラックＭＡ７に替えてピグメントブルー１５：３を使用したこと以外は、ライトブラックインク組成物Ｂの調整法と同様にして、ライトシアンインク組成物Ｂを得た。
（ｃ）ライトマゼンタインク組成物Ｂ
顔料としてカーボンブラックＭＡ７に替えてピグメントレッド１２２を使用したこと以外は、ライトブラックインク組成物Ｂの調整法と同様にして、ライトマゼンタインク組成物Ｂを得た。
【０１１６】
＜比較例１＞
インクセットＣ
（ａ）ライトブラックインク組成物Ｃ
カーボンブラックＭＡ７（三菱化学（株）製） ０．９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Ａ ０．２重量％
グリセリン ２０重量％
１，２−ヘキサンジオール ５重量％
ＢＹＫ３４８ ０．５重量％
イオン交換水 残量
（ｂ）ライトシアンインク組成物Ｃ
顔料としてカーボンブラックＭＡ７に替えてピグメントブルー１５：３を使用したこと以外は、ライトブラックインク組成物Ｃの調整法と同様にして、ライトシアンインク組成物Ｃを得た。
（ｃ）ライトマゼンタインク組成物Ｃ
顔料としてカーボンブラックＭＡ７に替えてピグメントレッド１２２を使用したこと以外は、ライトブラックインク組成物Ｃの調整法と同様にして、ライトマゼンタインク組成物Ｃを得た。
【０１１７】
＜比較例２＞
インクセットＤ
（ａ）ライトブラックインク組成物Ｄ
カーボンブラックＭＡ７（三菱化学（株）製） ０．９重量％
スチレン・アクリル酸共重合体（分散剤） １重量％
グリセリン ２０重量％
１，２−ヘキサンジオール ５重量％
ＢＹＫ３４８ ０．５重量％
イオン交換水 残量
（ｂ）ライトシアンインク組成物Ｄ
顔料としてカーボンブラックＭＡ７に替えてピグメントブルー１５：３を使用したこと以外は、ライトブラックインク組成物Ｄの調整法と同様にして、ライトシアンインク組成物Ｄを得た。
（ｃ）ライトマゼンタインク組成物Ｄ
顔料としてカーボンブラックＭＡ７に替えてピグメントレッド１２２を使用したこと以外は、ライトブラックインク組成物Ｄの調整法と同様にして、ライトマゼンタインク組成物Ｄを得た。
【０１１８】
＜印字評価１＞
（１）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、以下の印字評価を行った。印字評価は、インクジェットプリンター〔ＰＭ−９２０Ｃ（セイコーエプソン（株）製）〕を用い、ＭＣ写真用紙（型番：ＫＡ４２０ＭＳＫ）、ＭＣ光沢紙（型番：ＫＡ４２０ＭＫ）〔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。
（２）評価１：にじみ評価
得られた印字物を目視で観察し、にじみを以下の基準で評価し、結果を「評価１」として表１に示す。
◎：両紙においてにじみの発生がなかった。
○：少なくとも一方の用紙においてのみ、わずかなにじみが発生した。
△：両紙にひげ状のにじみが発生した。
×：少なくとも一方の用紙において、文字の輪郭がはっきりしないほどのにじみが発生した。
（３）評価２：カラーブリード評価
評価１と同様の記録紙及び印字条件で印字を行った。但し、単色を隣り合うように印刷し、色境で不均一な色混じり（ブリード）を目視で観察した。その結果を以下の基準で評価し、結果を「評価２」として表１に示す。
◎：両紙において色混じりが全くなく、境界が鮮明であった。
○：少なくとも一方の用紙においてのみ、わずかな色混じりがあった。
△：両紙にひげ状の色混じりが発生した。
×：少なくとも一方の用紙において、色境界がはっきりしないほどの色混じりが発生した。
【０１１９】
＜印字評価２＞
（１）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（耐擦性評価及び光沢度評価）を行った。印字評価は、インクジェットプリンター〔ＰＭ−９２０Ｃ（セイコーエプソン（株）製）〕を用い、ＰＭ写真用紙（型番：ＫＡ４５０ＰＳＫ）〔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。
（２）評価３：耐擦性評価１（指擦りによる評価）
印字後３分間経過した時点で、印字をした記録媒体の表面を指で擦り、色材の剥離により、耐擦性を目視で判断した。評価基準は、以下の通りである。結果を「評価３」として表１に示す。
◎：色材の剥離が全くない。
○：色材の剥離がわずかにある（色材全体の２０％未満）。
△：色材の剥離がある（色材全体の２０％以上８０％未満）。
×：色材がほとんど剥離する（色材全体の８０％以上剥離する）。
（３）評価４：耐擦性評価２（ＪＩＳ Ｋ ５７０１による評価）
印字後４８時間経過した時点で、サウザーランドラブテスターを用い、ＪＩＳＫ ５７０１に準じて耐擦性評価を行った。評価基準は、以下の通りである。結果を「評価４」として表１に示す。
◎：色材の剥離が全くない。
○：色材の剥離がわずかにある（色材全体の２０％未満）。
△：色材の剥離がある（色材全体の２０％以上８０％未満）。
×：色材がほとんど剥離する（色材全体の８０％以上剥離する）。
（４）評価５：光沢度評価
インク組成物を、ＰＭ写真用紙に２０％、４０％、６０％、８０％、又は１００％の印字デューティー（ｄｕｔｙ）で印刷した。目視で様々な角度から観察し、以下の判断基準に従って評価した。結果を「評価５」として表１に示す。
◎：異なる印字ｄｕｔｙであっても光沢の違いがほとんど気にならない。
○：異なる印字ｄｕｔｙでの光沢の違いが認められるが、目立たない。
△：異なる印字ｄｕｔｙでの光沢の違いが気になる。
×：異なる印字ｄｕｔｙでの光沢の違いが気になり、表面がくすんでみえる。
【０１２０】
＜評価結果＞
前記実施例及び比較例で製造したインクセットＡ〜Ｄの評価１〜５に関する結果を以下の表に示す。
【０１２１】
【表１】

【０１２２】
【発明の効果】
本発明のインク組成物によれば、特に淡色インク組成物におけるにじみ、カラーブリード、凝集ムラの発生を防止し、専用紙に対する耐擦性や光沢性を向上させることができる。[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 effective for improving the abrasion resistance, particularly for eliminating gloss unevenness of a recorded image printed on a special paper for ink jet recording, or particularly for eliminating aggregation unevenness in light ink.
[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, use of ink sets containing light color inks is widely performed.
[0003]
For example, a six-color ink set obtained by adding light cyan ink and light magenta ink, which are representative light color inks, to an ink set consisting of four colors of cyan ink, magenta ink, yellow ink, and black ink, A seven-color ink set obtained by adding light black ink to the ink jet recording method is used.
[0004]
Since these light-colored ink compositions have a low colorant concentration, it is necessary to increase the content of organic solvents such as glycerin and ethylene glycol in order to align the ejection characteristics with those of other dark ink compositions. . However, when the content of these organic solvents is high, the drying speed on the recording medium becomes slow, and various defects appear. For example, when two or more kinds of light color inks are mixed with each other on a recording medium, there is a disadvantage that uneven mixing occurs and aggregation unevenness occurs.
[0005]
On the other hand, in the ink jet recording method, an ink jet recording medium having high gloss comparable to photographic paper or art paper used in the fields 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.
[0006]
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.
[0007]
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 fixability of the printed image on the dedicated paper as described above has been increased, and a high level of abrasion resistance has been demanded. 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.
[0008]
However, since the light color ink composition has a low colorant concentration, the resin content decreases as the colorant concentration decreases. Accordingly, there is a drawback that the glossiness on the recording medium is lowered.
[0009]
[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. ), While preventing the occurrence of bleeding, color bleed and aggregation unevenness in the light-colored ink composition as described above, and further researching means for improving the abrasion resistance and glossiness of the special paper. The present inventors have found that the above-mentioned problems can be solved by including a specific resin and saccharide together in the ink composition. In particular, in the light-color ink composition containing the specific resin described above, the above-mentioned drawbacks can be solved by adding saccharides without increasing the amount of organic solvent such as glycerin or ethylene glycol for adjusting discharge characteristics. I found out that I can.
[0010]
The present invention is based on these findings.
[0011]
[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 The present invention relates to 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-adjusting resin), water, a colorant, and a saccharide.
[0012]
According to a preferred aspect of the present invention, the saccharide comprises a monosaccharide, an oligosaccharide (particularly, a reducing branched oligosaccharide), or a mixture thereof (particularly, a monosaccharide, a disaccharide, and a trisaccharide. Mixture).
[0013]
According to another preferred embodiment of the present invention, the colorant is a pigment.
[0014]
According to still another preferred aspect of the present invention, the colorant is contained at a concentration of 1.3% by weight or less based on the total weight of the ink composition.
[0015]
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.
[0016]
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.
[0017]
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.
[0018]
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.
[0019]
According to still another preferred embodiment of the present invention, the resin has a pH of 8 to 11 (more preferably 9 to 10).
[0020]
The ink composition of the present invention is preferably for inkjet recording.
[0021]
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.
[0022]
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.
[0023]
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.
[0024]
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.
[0025]
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.
[0026]
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. .
[0027]
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.
[0028]
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.
[0029]
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.
[0030]
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 these, 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.
[0031]
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.
[0032]
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.
[0033]
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.
[0034]
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.
[0035]
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.
[0036]
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.
[0037]
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; diisopropylbenzene hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, 1 , 1,3,3-tetramethylbutyl hydroperoxide, di-t-butyl peroxide, isobutyryl peroxide, benzoyl peroxide, and the like; azobisisobutyronitrile, azobis-2,4- Examples include azo compounds such as 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.
[0038]
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.
[0039]
Moreover, these polymerization initiators can also be used as a redox polymerization initiator in combination with a reducing agent.
[0040]
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.
[0041]
These reducing agents can be used alone or in combination of two or more.
[0042]
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.
[0043]
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.
[0044]
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.
[0045]
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.
[0046]
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.
[0047]
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.
[0048]
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.
[0049]
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.
[0050]
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.
[0051]
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.
[0052]
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.
[0053]
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.
[0054]
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.
[0055]
Examples of the saccharide contained in the ink composition of the present invention include monosaccharides, oligosaccharides, and polysaccharides, and monosaccharides, oligosaccharides, or mixtures thereof are preferable.
[0056]
In the present specification, the monosaccharide is a saccharide that cannot be decomposed into a simpler saccharide by hydrolysis, and is preferably a tricarbon sugar (monosaccharide having 3 carbon atoms) to a decasaccharide (monocarbon having 10 carbon atoms). Sugars), more preferably hexoses (monosaccharides having 6 carbon atoms).
[0057]
In the present specification, oligosaccharides preferably have 2 to 10 monosaccharide units, more preferably 2 to 5 in number. That is, it is preferably disaccharide to decasaccharide, more preferably disaccharide to pentasaccharide. The oligosaccharide may be a homo-oligosaccharide or a hetero-oligosaccharide, and is preferably a homo-oligosaccharide. The oligosaccharide can be a reducing oligosaccharide (ie, maltose-type oligosaccharide) or a non-reducing oligosaccharide (ie, a trehalose-type oligosaccharide), and a reducing oligosaccharide is preferred. Furthermore, the oligosaccharide is preferably a branched oligosaccharide. Here, branching means, for example, a state in which glucose molecules are bound by α-1,6-glucoside bonds. Examples of reducing branched oligosaccharides include isomaltose, panose, and isomaltotriose.
[0058]
The oligosaccharide can be prepared from one or a mixture of two or more preferably selected from the group consisting of starch, amylopectin, or glycogen. The reducing branched oligosaccharide can be obtained from these starches, amylopectin, or glycogen using well-known and conventional means. A well-known and commonly used means is preferably hydrolysis of polysaccharides, or alternatively, a glucoside bond of glucose or an isomerization reaction of maltose can be used.
[0059]
Polysaccharide means saccharide in a broad sense, and is used to mean a substance that exists widely in nature, such as alginic acid, α-cyclodextrin, and cellulose. In addition, the derivatives of these saccharides include reducing sugars of the saccharides described above (for example, sugar alcohol (general formula HOCH ₂ (CHOH) _s CH ₂ OH (where s represents an integer of 2 to 5)). ), Oxidized sugars (for example, aldonic acid, uronic acid, etc.), amino acids, thio sugars, etc. Particularly preferred are sugar alcohols, and specific examples thereof include maltitol, sorbit and the like.
[0060]
As the saccharide contained in the ink composition of the present invention, a mixture mainly composed of monosaccharide, disaccharide, and trisaccharide is particularly preferable. Here, the main component means that monosaccharides, disaccharides, and trisaccharides occupy about 60% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more of the entire saccharide component.
[0061]
Examples of sugars that can be used in the ink composition of the present invention include glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol, sorbitol, maltose, cellobiose, lactose, sucrose, trehalose, maltotri Aus, etc. Moreover, HS-500 or HS-300 (made by Hayashibara Biochemical Laboratories) etc. can be used as a commercial item. The HS-500 or HS-300 (produced by Hayashibara Biochemical Laboratories) is a saccharide mixture obtained by treating starch with an enzyme, and its main component is a monosaccharide (about 40% by weight), two It consists of saccharides (about 25% by weight) and trisaccharides (about 20% by weight), and also contains a small amount of tetrasaccharides or more. Moreover, said HS-500 or HS-300 contains a reducible branched oligosaccharide.
[0062]
In the ink composition of the present invention, the saccharide content is preferably about 0.1 to 30% by weight, more preferably about 3 to 20% by weight, based on the total weight of the ink composition.
[0063]
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.
[0064]
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.
[0065]
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.
[0066]
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 .
[0067]
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.
[0068]
Examples of pigments used for magenta ink include C.I. I. Pigment Red 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.
[0069]
Examples of pigments used for cyan ink include C.I. I. Pigment Blue1, C.I. I. Pigment Blue 2, C.I. I. Pigment Blue 3, C.I. I. Pigment Blue 15: 3, C.I. I. PigmentBlue 15: 4, 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.
[0070]
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.
[0071]
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.
[0072]
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.
[0073]
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.
[0074]
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.
[0075]
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.
[0076]
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 0.01 to 4, more preferably 0.1 to 0.1. 2.
[0077]
The ink composition of the present invention is particularly preferably applied to a light color ink composition. The content of the colorant in the light color ink composition is not particularly limited, but is generally 1.3% by weight or less, preferably 1.2% by weight with respect to the total weight of the ink composition. % Or less, more preferably 1.1% by weight or less. The content of the colorant in a typical light color ink composition is about 1.0% by weight with respect to the total weight of the ink composition.
[0078]
Here, the light-color ink composition is, for example, each ink composition such as light magenta and light cyan. Generally, for the purpose of improving the image quality of a printed image by density modulation, the magenta ink composition and the cyan ink are respectively used. This is an ink composition in which the colorant concentration of the composition is lowered. These magenta ink composition and cyan ink composition are prepared by lowering the concentration of the same pigment as the pigment used in the magenta ink composition and cyan ink composition described above, and appropriately changing the composition of other components. be able to. Furthermore, the present invention can be applied to light color ink compositions for “yellow”, “red”, “orange”, “green”, “blue”, or “violet” ink compositions that are commonly used in color ink sets.
[0079]
In addition, a light black ink composition can be used as the light color ink composition. This light black ink composition improves the color reproducibility for dark colors such as shadow areas and the gray gradation and improves the granularity. In order to reduce the color density, the color material (pigment) concentration of the black ink composition is lowered.
[0080]
The ink composition of the present invention contains water as a solvent and can further contain a water-soluble organic solvent.
[0081]
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.
[0082]
According to a preferred embodiment of the present invention, the ink composition according to the present invention preferably further comprises 1,2-alkanediol. The 1,2-alkanediol is preferably 1,2-C _1-6 alkanediol, and most preferably 1,2-hexanediol. The amount of 1,2-alkanediol added can be determined as appropriate, and is preferably about 1 to 15% by weight, more preferably about 2 to 10% by weight, based on the total weight of the ink composition.
[0083]
In general, in the light-color ink composition of the color ink set, the content of the water-soluble organic solvent is usually increased more than the content in the dark-color ink composition for adjusting ejection characteristics. There is. However, since the ink composition of the present invention contains the above-mentioned saccharides, the content of the water-soluble organic solvent is increased with respect to the light-color ink composition as compared with the content of the dark-color ink composition. There is no need and the content can be the same as that of a normal dark ink composition.
[0084]
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.
[0085]
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.
[0086]
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, etc.), acetylene glycol, and polysiloxane surfactants. These can be used alone or in combination of two or more.
[0087]
According to a preferred embodiment of the present invention, the ink composition according to the present invention has the formula (I):
[0088]
[Chemical 1]

(In the above formula, R ^{1 to} R ⁹ independently represent a C _1-6 alkyl group, j and k independently represent an integer of 1 or more, EO represents an ethyleneoxy group, and PO represents Represents a propyleneoxy group, and m and n represent an integer of 0 or more, provided that m + n represents an integer of 1 or more, and EO and PO are not limited in the order in [], and even if they are random, they are blocked. May be included).
[0089]
In formula (I), R ^{1 to} R ⁹ independently represent a C _1-6 alkyl group, preferably a methyl group. j and k independently represent an integer of 1 or more, and more preferably 1 or 2. M and n represent an integer of 0 or more, provided that m + n represents an integer of 1 or more. Preferably m + n is 2-4.
[0090]
According to a preferred embodiment of the present invention, compounds satisfying J = K + 1 are preferred as the compound of formula (I). According to another preferred embodiment of the present invention, as the compound of formula (I), R ^{1 to} R ⁹ all represent a methyl group, j represents 2, k represents 1, l represents 1, It is preferable that m represents an integer of 1 or more and n represents 0.
[0091]
The addition amount of the compound of the formula (I) can be appropriately determined, and is preferably 0.03 to 3% by weight, more preferably about 0.1 to 2% by weight with respect to the total weight of the ink composition. More preferably, it is about 0.3 to 1% by weight.
[0092]
Compounds of formula (I) are commercially available and can be used. For example, silicon surfactant BYK-345, BYK-346, or BYK-348 can be used from Big Chemie Japan Co., Ltd.
[0093]
Furthermore, the ink composition according to a preferred embodiment of the present invention contains a tertiary amine as a pH adjuster.
[0094]
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.
[0095]
Further, the ink composition according to the present invention may contain a penetration enhancer.
[0096]
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.
[0097]
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.
[0098]
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, an ink solvent is prepared by sufficiently stirring the pH adjusting resin liquid (for example, pH adjusting resin aqueous solution), saccharides, ion exchange water, water-soluble organic solvent, preservative, and / or antifungal agent at room temperature. To do. 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.
[0099]
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.
[0100]
In the ink composition of the present invention, the pH adjusting resin and the colorant (particularly the pigment) contained in the ink composition are substantially left on the surface as a recording medium, but the liquid component of the ink composition is substantially eliminated. It is particularly preferable to use it for a recording medium that absorbs light. 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.
[0101]
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.
[0102]
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.
[0103]
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.
[0104]
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.
[0105]
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.
[0106]
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.
[0107]
The substrate is preferably paper (containing wood pulp), and the basis weight thereof is preferably 100 to 350 g / m ² , more preferably 180 to 260 g / m ² . 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 preferably 5 to 50 g / m ² in terms of solid content from the viewpoint of ink absorbability. The thickness of the ink receiving layer itself is preferably 10 to 40 μm, more preferably 20 to 30 μm.
[0108]
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.
[0109]
【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 adjustment examples was measured according to JIS K0070.
[0110]
<Example of adjustment>
<< Adjustment of pH adjustment resin A >>
Dispersion of the 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, 1 part of polyvinyl alcohol and 280 parts of ion-exchanged water as molecular weight regulators I adjusted things. 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. It was. After completion of the continuous addition, the reaction was carried out at 80 ° C. for 30 minutes. The polymerization conversion rate was 99% or more.
[0111]
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.
[0112]
<Examples and Comparative Examples>
<Preparation of ink composition>
Ink compositions having the following compositions were prepared, and ink sets A to D were obtained from combinations thereof. Each ink composition was adjusted according to the following procedure.
[0113]
That is, a pigment, a dispersant, and water specifically described below are mixed and dispersed in a sand mill (manufactured by Yaskawa Seisakusho) with glass beads (diameter 1.7 mm, 1.5 times the weight (weight) of the mixture) for 2 hours. Then, the glass beads were removed to prepare a pigment dispersion. The obtained dispersion and the components specifically shown below were mixed and stirred at 25 ° C. for 60 minutes. The mixture was filtered through a 5 μm membrane filter to obtain an ink composition. In addition, [BYK348] described in the following components is a silicon-based surfactant manufactured by Big Chemie Japan.
[0114]
<Example 1>
Ink set A
(A) Black ink composition A
Carbon black MA7 (Mitsubishi Chemical Corporation) 3% by weight
Styrene / acrylic acid copolymer (dispersant) 1% by weight
pH adjustment resin A 0.2% by weight
HS-500
(Reduced branched oligosaccharide, solid content 70% Hayashibara Shoji Co., Ltd.) 5% by weight
Glycerin 10% by weight
1,2-hexanediol 5% by weight
BYK348 0.5% by weight
Ion exchange water Remaining amount (b) Cyan ink composition A
A cyan ink composition A was obtained in the same manner as the black ink composition A except that Pigment Blue 15: 3 was used instead of carbon black MA7 as a pigment.
(C) Magenta ink composition A
A magenta ink composition A was obtained in the same manner as the preparation method of the black ink composition A, except that Pigment Red 122 was used instead of carbon black MA7 as a pigment.
(D) Yellow ink composition A
A yellow ink composition A was obtained in the same manner as the black ink composition A except that Pigment Yellow 74 was used instead of carbon black MA7 as a pigment.
[0115]
<Example 2>
Ink set B
(A) Light black ink composition B
Carbon black MA7 (Mitsubishi Chemical Corporation) 0.9% by weight
Styrene / acrylic acid copolymer (dispersant) 1% by weight
pH adjustment resin A 0.2% by weight
HS-500
(Reduced branched oligosaccharide, solid content 70% Hayashibara Shoji Co., Ltd.) 10% by weight
Glycerin 10% by weight
1,2-hexanediol 5% by weight
BYK348 0.5% by weight
Ion exchange water Remaining amount (b) Light cyan ink composition B
A light cyan ink composition B was obtained in the same manner as the light black ink composition B except that Pigment Blue 15: 3 was used instead of carbon black MA7 as a pigment.
(C) Light magenta ink composition B
A light magenta ink composition B was obtained in the same manner as the light black ink composition B except that Pigment Red 122 was used instead of carbon black MA7 as a pigment.
[0116]
<Comparative Example 1>
Ink set C
(A) Light black ink composition C
Carbon black MA7 (Mitsubishi Chemical Corporation) 0.9% by weight
Styrene / acrylic acid copolymer (dispersant) 1% by weight
pH adjustment resin A 0.2% by weight
Glycerin 20% by weight
1,2-hexanediol 5% by weight
BYK348 0.5% by weight
Ion exchange water Remaining amount (b) Light cyan ink composition C
A light cyan ink composition C was obtained in the same manner as the light black ink composition C except that Pigment Blue 15: 3 was used instead of carbon black MA7 as a pigment.
(C) Light magenta ink composition C
A light magenta ink composition C was obtained in the same manner as the light black ink composition C except that Pigment Red 122 was used instead of carbon black MA7 as a pigment.
[0117]
<Comparative example 2>
Ink set D
(A) Light black ink composition D
Carbon black MA7 (Mitsubishi Chemical Corporation) 0.9% by weight
Styrene / acrylic acid copolymer (dispersant) 1% by weight
Glycerin 20% by weight
1,2-hexanediol 5% by weight
BYK348 0.5% by weight
Ion exchange water Remaining amount (b) Light cyan ink composition D
A light cyan ink composition D was obtained in the same manner as the light black ink composition D except that Pigment Blue 15: 3 was used instead of carbon black MA7 as a pigment.
(C) Light magenta ink composition D
A light magenta ink composition D was obtained in the same manner as the light black ink composition D except that Pigment Red 122 was used instead of carbon black MA7 as a pigment.
[0118]
<Printing evaluation 1>
(1) The following printing evaluation was performed using each ink composition manufactured in the above-mentioned Examples and Comparative Examples. For printing evaluation, an inkjet printer [PM-920C (manufactured by Seiko Epson Corporation)] is used, MC photo paper (model number: KA420MSK), MC glossy paper (model number: KA420MK) [inkjet paper: manufactured by Seiko Epson Corporation] ] Was printed.
(2) Evaluation 1: Bleeding Evaluation The printed matter obtained was visually observed, and the bleeding was evaluated according to the following criteria. The result is shown in Table 1 as “Evaluation 1”.
A: No bleeding occurred on both papers.
○: Slight bleeding occurred only on at least one paper.
Δ: Whisker-like bleeding occurred on both papers.
X: On at least one of the papers, bleeding occurred so that the outline of the character was not clear.
(3) Evaluation 2: Color bleed evaluation Printing was performed under the same recording paper and printing conditions as in Evaluation 1. However, a single color was printed so as to be adjacent to each other, and uneven color mixing (bleed) at the color boundary was visually observed. The results were evaluated according to the following criteria, and the results are shown in Table 1 as “Evaluation 2”.
A: There was no color mixing in both papers, and the boundary was clear.
A: There was a slight color mixture only on at least one of the papers.
Δ: A whisker-like color mixture occurred on both papers.
X: At least one of the papers was mixed so that the color boundary was not clear.
[0119]
<Printing evaluation 2>
(1) Printing evaluation (rub resistance evaluation and gloss evaluation) was performed using each of the ink compositions produced in the above Examples and Comparative Examples. For printing evaluation, an inkjet printer [PM-920C (manufactured by Seiko Epson Corporation)] was used, and printing was performed on PM photographic paper (model number: KA450PSK) [inkjet paper: Seiko Epson Corporation].
(2) Evaluation 3: Friction resistance evaluation 1 (Evaluation by finger rubbing)
When 3 minutes had elapsed after printing, the surface of the printed recording medium was rubbed with a finger, and the abrasion resistance was visually judged by peeling off the coloring material. The evaluation criteria are as follows. The results are shown in Table 1 as “Evaluation 3”.
(Double-circle): There is no peeling of a coloring material.
○: There is slight peeling of the coloring material (less than 20% of the whole coloring material).
Δ: There is peeling of the coloring material (20% or more and less than 80% of the whole coloring material).
X: The coloring material is almost peeled off (80% or more of the whole coloring material is peeled).
(3) Evaluation 4: Evaluation of abrasion resistance 2 (Evaluation according to JIS K 5701)
When 48 hours passed after printing, a rust resistance evaluation was performed according to JISK 5701 using a Southerland Love Tester. The evaluation criteria are as follows. The results are shown in Table 1 as “Evaluation 4”.
(Double-circle): There is no peeling of a coloring material.
○: There is slight peeling of the coloring material (less than 20% of the whole coloring material).
Δ: There is peeling of the coloring material (20% or more and less than 80% of the whole coloring material).
X: The coloring material is almost peeled off (80% or more of the whole coloring material is peeled).
(4) Evaluation 5: Glossiness Evaluation The ink composition was printed on a PM photographic paper with a print duty of 20%, 40%, 60%, 80%, or 100%. It observed visually from various angles and evaluated according to the following judgment criteria. The results are shown in Table 1 as “Evaluation 5”.
A: Even if the print duty is different, the difference in gloss is hardly noticed.
◯: A difference in gloss at different print duties is recognized, but is not noticeable.
(Triangle | delta): I am worried about the difference in the glossiness in different printing duty.
X: The difference in gloss at different printing duties is worrisome, and the surface looks dull.
[0120]
<Evaluation results>
The results relating to the evaluations 1 to 5 of the ink sets A to D produced in the examples and comparative examples are shown in the following table.
[0121]
[Table 1]

[0122]
【The invention's effect】
According to the ink composition of the present invention, it is possible to prevent bleeding, color bleeding and aggregation unevenness particularly in a light color ink composition, and to improve the abrasion resistance and glossiness of the special paper.

Claims (13)

  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 saccharide.   The ink composition according to claim 1, wherein the saccharide is a monosaccharide, an oligosaccharide, or a mixture thereof.   The ink composition according to claim 2, wherein the oligosaccharide is a reducing branched oligosaccharide.   The ink composition according to claim 2, wherein the mixture is a mixture mainly composed of monosaccharides, disaccharides, and trisaccharides.   The ink composition according to claim 1, wherein the colorant is a pigment.   The ink composition according to any one of claims 1 to 5, wherein the colorant is contained at a concentration of 1.3% by weight or less with respect to the total weight of the ink composition.   The ink composition according to any one of claims 1 to 6, wherein the inorganic base used for preparing the resin is an alkali metal hydroxide or an alkaline earth metal hydroxide.   The ink composition according to any one of claims 1 to 7, wherein the alcoholic hydroxyl group-containing water-soluble polymer compound used for the preparation of the resin is a vinyl alcohol polymer.   The ink composition according to any one of claims 1 to 8, 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 8. The ink composition as described.   The ink composition according to any one of claims 1 to 9, wherein the pH of the resin is 8 to 11.   The ink composition according to any one of claims 1 to 10, 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 10, but the liquid component of the ink composition is A method of recording on a recording medium that substantially absorbs.