JP4123776B2 - Image recording method and inkjet printer - Google Patents

Description

【０１６４】
〔熱可塑性樹脂塗布液１の調製〕
ノニオン系界面活性剤を乳化剤として乳化重合したスチレン−アクリル系ラテックスポリマー（Ｔｇ７８℃、平均粒径０．３μｍ、固形分濃度４０％）を、６％硝酸水溶液でｐＨ４．７に調整し、これを熱可塑性樹脂塗布液１とした。
【０１６５】
〔塗布液の調製〕
【０１６６】
以下に記載の様にして塗布液を調製した後、塗布液を市販のフィルタ（東洋濾紙株式会社製ＴＣＰ１０あるいはＴＣＰ３０）を用いて濾過した。
【０１６７】
（下層塗布液１の調製）
４０℃で攪拌しながら、前記調製したシリカ分散液２の７１０ｍｌに、以下の添加剤を順次混合して、下層塗布液１を調製した。
【０１６８】
ポリビニルアルコール（クラレ工業株式会社製：ＰＶＡ２０３）の１０％水溶液・・・３ｍｌ
ポリビニルアルコール（クラレ工業株式会社製：ＰＶＡ２３５）４．８％及び ポリビニルアルコール（クラレ工業株式会社製：ＰＶＡ２４５）の１．８４％を含む水溶液・・・２７３ｍｌ
純水で全量を１０００ｍｌに仕上げた。
【０１６９】
（上層塗布液１の調製）
前記調製した熱可塑性樹脂塗布液１及び前記下層塗布液１を用いて、熱可塑性樹脂と無機顔料の固形分比率が４０：６０となるように混合した後、４３℃での粘度が４５ｍＰａ・ｓとなるように水を添加して、これを上層塗布液１とした。
【０１７０】
（上層塗布液２の調製）
上記上層塗布液１の調製において、熱可塑性樹脂と無機顔料の固形分比率を５０：５０に変更した以外は同様にして、上層塗布液２を調製した。
【０１７１】
〔記録媒体の作製〕
【０１７２】
両面をポリエチレンで被覆した紙支持体（ＲＣ紙ともいい、厚みが２２０μｍであり、インク吸収層面のポリエチレン中にはポリエチレンに対して１３質量％のアナターゼ型酸化チタンを含有する）に、支持体側から順に、第１層として下層塗布液１を湿潤膜厚１７２μｍで、第２層として上層塗布液１（熱可塑性樹脂の平均粒径：０．３μｍ）を湿潤膜厚６０μｍで熱可塑性樹脂の固形分量として３．０ｇ／ｍ^２となる条件で、スライドホッパーを用いて２層同時塗布及び乾燥を行った。なお、各塗布液は、４０℃に加温して塗布し、塗布直後に０℃に保たれた冷却ゾーンで２０秒冷却した後、２５℃の風（相対湿度１５％）で６０秒間、４５℃の風（相対湿度が２５％）で６０秒間、５０℃の風（相対湿度が２５％）で６０秒間順次乾燥し、２０〜２５℃、相対湿度が４０〜６０℃の雰囲気下で２分間調湿した後、試料を巻き取って、試料Ｆ１を作製した。この後、試料Ｆ１をポリエチレン袋に封入して、５５℃で３日間のエージング処理を施した
【０１７３】
また、第１層の湿潤膜厚を１８４ｍμｍとし、第２層で上層塗布液２を使用し、湿潤膜厚を４０μｍ、熱可塑性樹脂の固形分率を２．５ｇ／ｍ^２となる条件に変更した以外は、上述の試料Ｆ１と同様にして試料Ｆ２を作製し、その後同等のエージング処理を施した。
【０１７４】
《インクの作製》
水系顔料インクを次の手順で作製した。
【０１７５】
〔水系顔料インクの調製〕
【０１７６】
（顔料分散液の調製）
〈イエロー顔料分散体１の調製〉
Ｃ．Ｉ．ピグメントイエロー７４・・・２０質量％
スチレン−アクリル酸共重合体（分子量１０，０００、酸価１２０）・・・１２質量％
ジエチレングリコール・・・１５質量％
イオン交換水・・・５３質量％
上記各添加剤を混合し、０．３ｍｍのジルコニアビーズを体積率で６０％充填した横型ビーズミル（アシザワ社製 システムゼータミニ）を用いて分散し、イエロー顔料分散体１を得た。得られたイエロー顔料の平均粒径は１１２ｎｍであった。
【０１７７】
〈マゼンダ顔料分散体１の調製〉
Ｃ．Ｉ．ピグメントレッド１２２・・・２５質量％
ジョンクリル６１（アクリル−スチレン系樹脂、ジョンソン社製） ・・・固形分で１８質量％
ジエチレングリコール・・・１５質量％
イオン交換水・・・４２質量％
上記各添加剤を混合し、０．３ｍｍのジルコニアビーズを体積率で６０％充填した横型ビーズミル（アシザワ社製 システムゼータミニ）を用いて分散し、マゼンダ顔料分散体１を得た。得られたマゼンダ顔料の平均粒径は１０５ｎｍであった。
【０１７８】
〈シアン顔料分散体１の調製〉
Ｃ．Ｉ．ピグメントブルー１５：３・・・２５質量％
ジョンクリル６１（アクリル−スチレン系樹脂、ジョンソン社製）・・・固形分として１５質量％
グリセリン・・・１０質量％
イオン交換水・・・５０質量％
上記各添加剤を混合し、０．３ｍｍのジルコニアビーズを体積率で６０％充填した横型ビーズミル（アシザワ社製 システムゼータミニ）を用いて分散し、シ ン顔料分散体１を得た。得られたシアン顔料の平均粒径は８７ｎｍであった。
【０１７９】
〈ブラック顔料分散体１の調製〉
カーボンブラック・・・２０質量％
スチレン−アクリル酸共重合体（分子量７，０００、酸価１５０） ・・・１０質量％
グリセリン・・・１０質量％
イオン交換水・・・６０質量％
上記各添加剤を混合し、０．３ｍｍのジルコニアビーズを体積率で６０％充填した横型ビーズミル（アシザワ社製 システムゼータミニ）を用いて分散し、ブラック顔料分散体１を得た。得られたブラック顔料の平均粒径は７５ｎｍであった。
【０１８０】
（顔料インクの調製）
【０１８１】
〈イエローインクの調製〉
イエロー顔料分散体１・・・１５質量％
エチレングリコール・・・２０質量％
ジエチレングリコール・・・１０質量％
界面活性剤（サーフィノール４６５ 日信化学工業社）・・・０．１質量％
イオン交換水・・・５４．９質量％
以上の各組成物を混合、攪拌し、１μｍフィルターでろ過し、水性顔料インクであるイエローインクを調製した。インク中の顔料の平均粒径は１２０ｎｍであり、表面張力γは３６ｍＮ／ｍであった。
【０１８２】
〈マゼンダインクの調製〉
マゼンダ顔料分散体１・・・１５質量％
エチレングリコール・・・２０質量％
ジエチレングリコール・・・１０質量％
界面活性剤（サーフィノール４６５ 日信化学工業社）・・・０．１質量％
イオン交換水・・・５４．９質量％
以上の各組成物を混合、攪拌し、１μｍフィルターでろ過し、水性顔料インクであるマゼンダインクを調製した。インク中の顔料の平均粒径は１１３ｎｍであり、表面張力γは３５ｍＮ／ｍであった。
【０１８３】
〈シアンインクの調製〉
シアン顔料分散体１・・・１０質量％
エチレングリコール・・・２０質量％
ジエチレングリコール・・・１０質量％
界面活性剤（サーフィノール４６５ 日信化学工業社）・・・０．１質量％
イオン交換水・・・５９．９質量％
以上の各組成物を混合、攪拌し、１μｍフィルターでろ過し、水性顔料インクであるシアンインクを調製した。インク中の顔料の平均粒径は９５ｎｍであり、表面張力γは３６ｍＮ／ｍであった。
【０１８４】
〈ブラックインクの調製〉
ブラック顔料分散体１・・・１０質量％
エチレングリコール・・・２０質量％
ジエチレングリコール・・・１０質量％
界面活性剤（サーフィノール４６５ 日信化学工業社）・・・０．１質量％
イオン交換水・・・５９．９質量％
以上の各組成物を混合、攪拌し、１μｍフィルターでろ過し、水性顔料インクであるブラックインクを調製した。インク中の顔料の平均粒径は８５ｎｍであり、表面張力γは３５ｍＮ／ｍであった。
【０１８５】
次に、上述した記録媒体の各試料Ｆ１，Ｆ２について、上述の各色の水系顔料インクを用いて実施例及び比較例として図１のインクジェットプリンタを用いて以下の条件で画像を形成した。なお、定着部は図１３のベルト方式を用いた。
【０１８６】
（１）噴射インクの着弾時間間隔を次のようにして種々に変えた。図１，図８で、記録媒体の移動速度をＶ（ヘッドが移動する場合はヘッドの移動速度）とすると、図８（ｂ）でノズル列６ａが１ライン分のドットを形成してからノズル列６ｂが手前の１ライン分のドットを形成するまでの時間Ｔは、次の式（１）で表すことができる。
【０１８７】
Ｔ＝（Ｌ−ｎ）／Ｖ （１）
但し、Ｌ：各ノズル列の間隔（図８）、ｎ：ドット間隔（図８）
【０１８８】
記録媒体の通常の移動速度Ｖ（０．１〜１ｍ／ｓ程度）ではＬ≫ｎであるので、時間Ｔは次の近似式（２）で表すことができる。
【０１８９】
Ｔ＝Ｌ／Ｖ （２）
【０１９０】
ここで、例えば、Ｖ≦０．１ｍ／ｓ、Ｌ≧１ｍｍの組み合わせで、インクの着弾時間間隔は１０ｍｓ以上となる。このように、記録媒体の移動速度Ｖ及び／又はノズル列の間隔Ｌを変えることでインクの着弾時間間隔を変えることができる。この場合、ラインヘッドの駆動周波数も同じ着弾位置間隔になるように変える。
【０１９１】
本実施例及び比較例では、ラインヘットのノズル列間隔Ｌを１ｍｍとし、記録媒体の移動速度Ｖを１ｍ／ｓ〜０．０５ｍ／ｓの範囲で５通りに変えることにより、インクの着弾時間間隔を、１．０，２．０，５．０，１０．０，２０．０ｍｓとし、それぞれ画像を形成し、各々の画像のざらつき感の良否を測定した。各インクの液滴量は１乃至５ｐｌとした。なお、液滴量は、図３，図４のようにノズルに対する駆動電圧、ノズル径を変えることで調整した。その結果を次の表１に示す。
【０１９２】
（２）図３，図４のようにノズルに対する駆動電圧を変えて液滴速度を４，５，６，７，８ｍ／ｓと変えてドットによる画像を形成し、画質を評価した。
【０１９３】
（３）本実施例では、図１０（ａ）のようなラインヘッドを用いて図１２のように画素ピッチの約半分ずらして各ラインを形成したが、ずらさない場合についても画像を形成し、画質を比較した。
【０１９４】
【表１】

【０１９５】
表１から分かるように、隣り合う画素の着弾時間間隔が１０ｍｓ未満の比較例ではざらつき感が大きい（特に液滴量が３〜５ｐｌの場合）のに対し、着弾間隔が１０ｍｓ、２０ｍｓの実施例では、液滴量１〜５ｐｌの範囲でざらつき感が何れも良好または良のよい結果であった。
【０１９６】
また、液滴速度に関し、インクの滴液速度が４，５ｍ／ｓの各比較例では、画像を形成するドットが一様に分布せずに疎密を生じ画像にむらができたり、ざらつき感がでたり、また、直線が曲がったりギザギザ状になり等の画像のひずみが生じた。このように、インク滴の噴射から着弾までの時間が長くなり、滴液速度の変動が滴液の着弾位置に大きな変動をもたらすことで画質が低下する。これに対し、滴液速度が６，７，８ｍ／ｓの各実施例では、比較例のような画質の低下はなく、良好な画質を得ることができた。なお、インクの滴液速度が１０ｍ／ｓを越えると、記録媒体面上でインクが飛び散ってしまい画質が低下する。
【０１９７】
また、図９のように画素ピッチの約半分ずらして各ラインを形成した実施例では、ずらしていない場合に比べてざらつき感が減少し画質が向上し、また同一液滴量のインクで画像濃度がすれていない場合の画像に比べて向上し、特に、髪の毛や影の部分などの最高濃度部の画質が向上した。
【０１９８】
以上のように本発明を実施の形態及び実施例により説明したが、本発明はこれらに限定されるものではなく、本発明の技術的思想の範囲内で各種の変形が可能である。例えば、記録部におけるヘッドの構成は、ラインヘッドに限定されずに、キャリッジと一体に移動するように構成されたシリアルヘッドであってもよい。シリアルヘッドの場合のインク噴射の制御の例を図１４により説明すると、例えば、図８（ｂ）の複数のライン６０ｅのように、ノズル７１，７３で各ドット○（図中、丸印）を形成してから、記録媒体を１ライン分移動し、次に、ノズル７２，７４でにドット◎（図中、二重丸印）を形成してから、記録媒体を１ライン分移動する。同様にして、ノズル７１，７３でドット●（図中、黒丸印）を各ドット○間に形成し、記録媒体を１ライン分移動し、次に、ノズル７２，７４でドット×（図中、罰点印）を各ドット◎間に形成する。このようにして、図８（ｂ）の複数のライン６０ｅと同様のラインを形成ができるが、この場合、各ドット○◎●×による１ライン分の記録時にキャリッジによるシリアルヘッドの１往復動が必要となるので、各ラインの各画素において隣り合う全ての画素に対しインクの着弾時間は１０ｍｓよりもかなり長くなる。
【０１９９】
【発明の効果】
本発明によれば、写真と同程度の画質と保存性を有する画像形成が可能な画像記録方法及びインクジェットプリンタを提供できる。
【図面の簡単な説明】
【図１】本実施の形態によるインクジェットプリンタを概略的に示す側面図である。
【図２】図１のラインヘッドの概略的構成を示す斜視図である。
【図３】図２のラインヘッドのノズルを部分的に示す斜視図（ａ）、ノズルの電極の作動を説明するための正面図（ｂ），（ｃ）、及びノズルの噴射・非噴射の各駆動状態を説明するための正面図（ｄ），（ｅ），（ｆ）である。
【図４】図４は図３の各ノズルの駆動波形を示す図である。
【図５】図１のインクジェットプリンタの定着部を更に詳しく示す側面図である。
【図６】図１のインクジェットプリンタの制御系を示すブロック図である。
【図７】本実施の形態における記録媒体の積層構成を示す断面図である。
【図８】図２のノズル構成及びインク噴射の時間間隔制御の第１例を示す図であり、ラインヘッド１１の各ノズル列６ａ〜６ｄの配置を示す平面図（ａ）及び記録媒体上のインク着弾位置を図８（ａ）の各ノズル列の各ノズル位置に対応して示す平面図（ｂ）である。
【図９】図２のノズル構成及びインク噴射の時間間隔制御の第２例を示す図であり、ラインヘッド１１の各ノズル列６ａ〜６ｄの配置を示す平面図（ａ）及び記録媒体上のインク着弾位置を図９（ａ）の各ノズル列の各ノズル位置に対応して示す平面図（ｂ）である。
【図１０】図２のノズル構成及びインク噴射の時間間隔制御の第３例を示す図であり、ラインヘッド１１の各ノズル列６ａ〜６ｄの配置を示す平面図（ａ）及び記録媒体上のインク着弾位置を図１０（ａ）の各ノズル列の各ノズル位置に対応して示す平面図（ｂ）である。
【図１１】図２のノズル構成及びインク噴射の時間間隔制御の第４例を示す図であり、ラインヘッド１１の各ノズル列６ａ〜６ｄの配置を示す平面図（ａ）及び記録媒体上のインク着弾位置を図１１（ａ）の各ノズル列の各ノズル位置に対応して示す平面図（ｂ）である。
【図１２】図１０（ｂ）及び図１１（ｂ）において記録媒体に千鳥状に形成された各画素（ドット）の配置を示す平面図である。
【図１３】図１の定着部の別の構成例を詳細に示す側面図である。
【図１４】図１のヘッド構成の変形例を示すシリアルヘッドのノズル配置を示す平面図である。
【符号の説明】
９ ロール体
１０ 記録部
１１ ラインヘッド
６ａ〜６ｄ ノズル列
１ａ ノズル
２０ 制御部
２３ ヘッド駆動回路
２６ 定着部駆動機構
４０ カット部
５０ 定着部
５１ 加熱ローラ
５２ 圧着ローラ
５３ 発熱体
５５ 温度センサ
６１ 支持体
６２ 記録媒体Ｆのインク吸収層
６３ 記録媒体Ｆの表層
４１０ 加熱ローラ
４５０ 発熱体
４４０ 加圧ローラ
４３０ 加熱ベルト
４７０ 付勢手段
Ｆ 記録媒体
Ｓ 搬送方向
Ｌ ノズル列間隔
Ｘ 図８，図１０におけるノズル間隔
Ｘ／２ 図９，図１１におけるノズル間隔
ｐ 画素ピッチ
ｎ ドット（画素）間隔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image recording method and an ink jet printer capable of forming an image having image quality and storability comparable to those of photographs.
[0002]
[Prior art]
In recent years, image processing technology using an ink jet printer has improved the sharpness and graininess of pixels by reducing the size of ink droplets to be printed, scanning the head, and increasing the accuracy of recording paper transport, bringing the image quality closer to that of photographs. Efforts are made. For example, by recording an image with dye ink using a special paper provided with an ink absorbing layer on resin-coated paper used for photographic printing paper, it has become possible to obtain image quality comparable to silver salt photography. .
[0003]
However, when an image is recorded with a dye ink, the storability of the image, which is an important function of photography, may be inferior. In addition, when an image is recorded with pigment ink, the image storability is good, but an image quality comparable to a silver salt photograph may not be obtained. Image quality is an important performance for traditional photographs as a means of expressing images, but the texture of images cannot be expressed by evaluation scales such as sharpness, graininess, and glossiness. However, the texture was different from the silver halide photograph, and it looked strange. A photograph is also a means for recording an image, and the storability of the image is also an important performance.
[0004]
Therefore, in order to achieve both high image quality and storability of the image, an image is formed with a pigment ink on a recording paper containing latex on the surface of the image receiving layer, and then the image is fixed by heating and pressing. There is a printing method. According to this method, an image similar to a silver salt photograph was obtained in terms of image storage stability, sharpness, glossiness, etc., but color reproducibility and granularity were inferior, and the texture could be different.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide an image recording method and an ink jet printer that have image storability and can obtain the same image quality as a photograph.
[0006]
[Means for Solving the Problems]
  In order to achieve the above object, an image recording method according to the present invention comprises an ink absorption layer on a support, and a thermoplastic resin and an inorganic pigment on the surface layer. The solid content mass ratio of thermoplastic resin / inorganic pigment is 90 / While the pigment ink is ejected onto the recording medium contained at 10 to 10/90 at a droplet speed of 6 to 10 m / s, each pixel is formed with respect to the adjacent pixels at a time interval of at least 10 ms, and then the recording medium is heated. The temperature is in the range of Tg ± 10 ° C. (Tg: glass transition point (° C.) of the thermoplastic resin of the surface layer) and the pressure applied to the recording medium is 9.8 × 10^Four~ 4.9 × 10⁶By controlling in the range of Pa, the image formed on the recording mediumObtained based on JIS standard H8866-2Image recording is performed by heating and pressurizing the recording medium so that the image clarity value is 60% or more and 95% or less.
[0007]
According to this image recording method, since a recording medium containing a thermoplastic resin in the surface layer is used, the image clarity value can be improved by heating and pressurizing after ink ejection. Although the image clarity value of the surface of the recording medium on which an image is formed with the pigment ink tends to be lowered, the image clarity value is improved because the thermoplastic resin is melted by heat and pressure to cover the surface of the recording medium.
[0008]
In addition, when the ink droplet speed is 6 m / s or less, the time from ejection to landing becomes long, and fluctuations in the droplet speed cause large fluctuations in the landing position of the liquid droplets, resulting in a decrease in image quality. When the liquid speed is 10 m / s or more, the ink is scattered on the surface of the recording medium and the image quality is deteriorated. From the above, by setting the ink droplet speed to 6 to 10 m / s, the color reproduction range is widened, and an image with good image quality can be formed.
[0009]
In addition, when each pixel is formed, the ink is landed on the recording medium so that the time interval of ink landing is at least 10 ms with respect to adjacent pixels, whereby the pigment ink is absorbed by the recording medium. Since the ink of the adjacent pixels is landed, the graininess is improved and the image quality is improved. If the time is less than 10 ms, the ink droplets coalesce and the pigments aggregate to form an image with an apparently large droplet, resulting in a decrease in graininess.
[0010]
  Further, by heating and pressurizing the recording medium so that the image clarity value is 60% to 95%, the glossiness of the image quality resembles that of a photograph and a photograph-like texture can be obtained. The image clarity value includes, for example, the configuration of the recording medium, the type and content of the thermoplastic resin particles, the heating temperature, the pressing pressure, the heating and pressing time, the heating and pressing method, and the smoothness of the surface that contacts the medium during heating and pressing. It can be controlled by the degree. In the present invention, the heating temperature of the recording medium is in the range of Tg ± 10 ° C. (Tg: glass transition point (° C.) of the thermoplastic resin of the surface layer) and the applied pressure to the recording medium is 9.8 × 10.^Four~ 4.9 × 10⁶By controlling within the range of Pa,Obtained based on JIS standard H8866-2The image clarity value can be controlled within 60% to 95%. Further, it is preferable to further control the heating and pressing time during heating and pressing of the recording medium.
[0011]
Further, by using a pigment ink as an ink, it is possible to realize long-term image quality preservation such as a photograph without a fading due to light or oxygen in a recording medium after image recording, as compared with a dye ink. In addition, pigment ink has a larger diameter than dye ink, and its image clarity value tends to decrease due to the characteristics that it is difficult to absorb into the recording medium. However, the thermoplastic resin particles are melted by heating and pressurizing the recording medium after ink ejection. In addition, since it becomes a transparent thermoplastic resin layer and covers the pigment ink layer of the pigment ink, the image clarity value is improved and a glossy and high-quality image can be formed. Further, since the pigment ink layer is absorbed by the image receiving layer of the recording medium and covered with the thermoplastic resin layer, an image with high storage stability can be formed.
[0012]
Further, since each pixel is formed with a shift of approximately half of the pixel pitch (about half a pixel) for each line, the ink landing interval of each pixel is increased for each line as compared with a conventional image. The number of adjacent pixels on the upper side is reduced, the ink droplets coalesce, the pigment is aggregated and the granularity is reduced, and the image quality can be improved. Further, the coverage of the recording medium with ink droplets is improved and the color reproduction range is widened.
[0013]
  Further, the surface layer of the recording mediumIs a thermoplastic resinInorganic pigmentWhenTheThe solid content mass ratio of thermoplastic resin / inorganic pigment is 90/10 to 10/90.contains. Further, the Young's modulus of the rubber coating layer of the pressure roller for pressing the recording medium is 10 ⁶ -10 ⁷ A range of Pa is preferred.
[0014]
  In addition, an ink jet printer according to the present invention includes an ink head that ejects ink onto a recording medium, and a heating and pressurizing unit that heats and pressurizes the recording medium after the ink ejection, and records an image on the recording medium. An ink-jet printer having an ink-absorbing layer on a support, and a thermoplastic resin and an inorganic pigment on the surface layer, the thermoplastic resin / inorganic pigment solid content ratio being 90/10 to 10/90 The pigment ink is ejected from the ink head at a droplet velocity of 6 to 10 m / s so that each pixel is formed on the recording medium at a time interval of at least 10 ms with respect to adjacent pixels, and the heating temperature of the recording medium is set to Tg ±. The range of 10 ° C. (Tg: glass transition point (° C.) of the thermoplastic resin of the surface layer) and the pressure applied to the recording medium are 9.8 × 10^Four~ 4.9 × 10⁶By controlling in the range of Pa, the image formed on the recording mediumObtained based on JIS standard H8866-2The recording medium is heated and pressurized by the heating and pressing unit so that the image clarity value is 60% or more and 95% or less.
[0015]
  According to this ink jet printer, the above-described image recording method according to the present invention can be executed. In this case, the ink head is preferably composed of a line head. In addition, the heating and pressurizing means canFurther heating and pressing timeIt is preferably configured to control. Further, the surface layer of the recording mediumIs a thermoplastic resinInorganic pigmentWhenTheThe solid content mass ratio of thermoplastic resin / inorganic pigment is 90/10 to 10/90.contains. Further, the heating and pressing means has a pressure roller for pressing the recording medium, and the Young's modulus of the rubber coating layer of the pressure roller is 10 ⁶ -10 ⁷ A range of Pa is preferred.
[0016]
  In addition, image clarity is an important characteristic value that determines the aesthetic elements of an image as an indicator of how clear and distorted the image is when an object is reflected on the coating surface. It is. Examples of the method for measuring the image clarity value include JIS.standardH8686-2There is a method of obtaining image clarity as image clarity from a light intensity waveform obtained through an optical comb using an optical device. There are various types of optical combs in which the ratio of dark part to bright part is 1: 1 and the width is 0.125, 0.5, 1.0 and 2.0 mm. In the measurement, the optical comb is moved, the highest waveform (M) and the lowest waveform (m) on the recording paper are read, and the image definition is obtained by the following equation.
[0017]
C = (M−m) / (M + m) × 100
Here, C: image definition (%), M: highest waveform, m: lowest waveform.
[0018]
The image clarity C is an index indicating that image clarity is good when the value is large, and that there is “blur” or “distortion” when the value is small. Even when the gloss values are the same, the glossiness by appearance becomes strong.
[0019]
The ink head of the above-described inkjet printer may be an on-demand system or a continuous system. In addition, as a discharge (injection) method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method ( Specific examples include, for example, a thermal ink jet type, a bubble jet type, and the like, an electrostatic attraction method (for example, an electric field control type, a slit jet type, etc.), and a discharge method (for example, a spark jet type). However, any discharge method may be used.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. 1 is a conceptual diagram of an ink jet printer according to an embodiment of the present invention, FIG. 2 is a perspective view schematically showing the ink head of FIG. 1, and FIG. 3 is a partial view of nozzles of the line head of FIG. (A), front views (b), (c) for explaining the operation of the electrode of the nozzle, and front views (d), for explaining the respective drive states of nozzle injection / non-injection, (E), (f), and FIG. 4 is a figure which shows the drive waveform of each nozzle of FIG.
[0021]
As shown in FIG. 1, the ink jet printer according to the present embodiment includes a roll body 9 in which a sheet-like long recording medium F is wound in a roll shape, and a recording medium drawn from the roll body 9 in the transport direction S. A recording unit 10 having a line head 11 for jetting YMCK four-color ink onto F and a platen 12 arranged to face the line head 11 via the recording medium F, and an image is written A cutting unit 40 for cutting the recording medium F into a predetermined size, a fixing unit 50 for fixing the image by heating and pressurizing the cut recording medium F, and discharging the recording medium F on which the image is fixed. A discharge storage unit 60 for storage is arranged from the upstream side in the transport direction S.
[0022]
An accumulating unit 18 is provided between the recording unit 10 and the cutting unit 40 so as to adjust the cutting timing in the cutting unit 40, and conveyance for conveying the recording medium F is performed upstream and downstream of the accumulating unit 18. Roller pairs 15a and 15b are arranged. The accumulator 18 is provided with a sensor 19 for detecting the amount of accumulation of the recording medium F. Further, conveyance roller pairs 16 a and 16 b for conveying the cut recording medium F are disposed on the upstream side and the downstream side of the fixing unit 50.
[0023]
The cut unit 40 moves the recording medium F in a predetermined position to a predetermined size by moving the recording medium F in a predetermined position and a detection sensor 41 arranged on the upstream side in order to detect the leading end of the conveyed recording medium F. And a cutting member 42 to be cut. The cutting member 42 is driven in the direction B and the opposite direction by the cut portion driving mechanism 25 (FIG. 6).
[0024]
Next, the line head 11 of FIG. 1 will be described. As shown in FIGS. 1 and 2, the line head 11 is separated so that the nozzle surface 6 faces the recording medium F, and the nozzle surface 6 in FIG. 2 is orthogonal to the conveyance direction S of the recording medium F in FIG. 1. It is arranged to extend in the direction.
[0025]
A plurality of nozzles 1a for ejecting ink are formed on the nozzle surface 6 of the line head 11 in FIG. 2, and a plurality of nozzle rows 6a, 6b, 6c, and 6d are formed to extend in one row. . A large number of nozzles 1a in each of the nozzle arrays 6a, 6b, 6c, 6d are composed of piezo elements that are shear-deformed by the application of a drive signal, and are subjected to shear deformation according to the voltage level of the input drive signal, respectively. By jetting, an image can be written on the recording medium. The recording unit 10 includes the line heads 11 shown in FIG. 2 for each color of YMCK. By ejecting each pigment ink onto the recording medium F from a total of 16 nozzle rows of each line head 11, the recording unit F is applied to the recording medium F. A color image can be formed.
[0026]
With reference to FIG. 3, the structure of the nozzle 1a formed in large numbers on the nozzle surface 6 of the line head 11 of FIG. 2 will be described. As shown in FIG. 3A, the nozzle 1a is formed on the nozzle surface 6 so as to be surrounded by the piezo elements 31 and 32 and the piezo elements 33 and 34 arranged in the vertical direction in the drawing so as to form a pressure chamber. . As shown in FIG. 3B, the piezo element 31 includes a pair of electrodes 31a and 31b provided on both wall surfaces of the pressure chamber, and the other piezo elements 32 to 34 also include similar electrodes. When the drive voltage of the drive signal as shown in FIG. 4 is applied from the head drive circuit 23 to the electrodes 31a and 31b, the piezo element 31 changes from the undeformed state shown in FIG. 3B, for example, as shown in FIG. Shear deformation. The mode of the shear deformation changes depending on the positive / negative polarity applied to the electrodes 31a and 31b, and the degree of deformation changes depending on the voltage level.
[0027]
When the positive drive voltage V1 of FIG. 4 is applied to each electrode in the nozzle 1a, the piezo elements 31 to 34 change from the undeformed state of FIG. 3 (f) where the drive signal is zero to the solid line of FIG. Then, when the negative pressure V2 of each electrode is applied, the pressure chamber is sheared so as to be contracted as a whole as shown in FIG. 3 (e). . As shown in FIG. 3D, the pressure chamber expands as a whole to suck ink from the ink tank (not shown), and as shown in FIG. 3E, the pressure chamber contracts as a whole to draw ink from the pressure chamber. The ink can be continuously ejected by repeating such operations.
[0028]
Further, when a positive drive voltage V1 ′ smaller than the drive voltage V1 is applied as shown in FIG. 4, the expansion amount of the pressure chamber is smaller than that at the drive voltage V1 as shown by the broken line in FIG. If a negative driving voltage V2 ′ having an absolute value smaller than that of the driving voltage V2 is added to the driving voltage V2, the amount of contraction of the pressure chamber becomes smaller than that at the driving voltage V2, as indicated by a broken line in FIG. For this reason, the amount of ink droplets ejected from the nozzle 1a varies depending on the ratio (V1 / V2) between the positive drive voltage V1 and the negative drive voltage V2 in FIG. 4, and the positive drive voltage V1 and the negative drive voltage are negatively driven. The amount of ink droplets and the velocity of ink droplets ejected from the nozzles 1a vary depending on the sum (V1 + | V2 |) of the absolute value of the voltage V2, and therefore the ink ejected from each nozzle 1a can be controlled appropriately. The droplet volume and droplet velocity can be adjusted. It should be noted that the adjustment range of the ink droplet amount can be increased by changing the nozzle diameter.
[0029]
Next, the fixing unit 50 in FIG. 1 will be described with reference to FIGS. 1 and 5. FIG. 5 is a front view showing the fixing unit of FIG. 1 in detail. 1 and 5 includes a heating roller 51 that heats the recording medium F, a pressure roller 52 that can press the recording medium F between the heating roller 51, and a surface of the heating roller 51. And a temperature sensor 55 disposed in the vicinity.
[0030]
The heating roller 51 incorporates a heating element 53 such as a halogen lamp heater which is a heat source along the axial direction in a hollow roller, and the control unit 20 (FIG. 6) based on the temperature detected by the temperature sensor 55. Thus, by controlling the heat generation amount of the heating element 53, the temperature of the heating roller 51 can be adjusted to be maintained within a predetermined temperature range, and the heating temperature of the recording medium F can be adjusted appropriately.
[0031]
The heating roller 51 has a gear (not shown) provided at an end thereof meshed with a gear of the driving motor included in the fixing unit driving mechanism 26 (FIG. 6), so that the driving force of the driving motor is transmitted. , And rotationally driven in the rotational direction R. The heating roller 51 is preferably formed of a material having high thermal conductivity, whereby the recording medium F can be efficiently heated by the heat from the heating element 53, and for example, a metal roller is preferable. The surface of the heating roller 51 preferably has a fluororesin layer, which can prevent contamination by ink when the recording medium F is heated and pressurized.
[0032]
The pressure roller 52 is made of a metal roller such as stainless steel having a rubber coating layer 52c having elasticity on the outer periphery, and roller shafts 52b at both ends thereof are rotatably attached to and supported by support members 58 via bearings 52a. ing. The support member 58 can move in the vertical direction in the figure integrally with the pressure roller 52, and the pressure roller 52 presses the recording medium F against the heating roller 51 with a predetermined pressure to form a nip portion 59. As shown, the biasing members 56 and 57 formed of coil springs or the like are biased upward in FIG. 5 with a substantially constant biasing force. The pressure sensor 27 is disposed so as to contact the upper surface of the support member 58 in the figure, and the pressure sensor 27 measures the pressure applied to the recording medium F between the heating roller 51 and the pressure roller 52.
[0033]
The longitudinal elastic modulus (Young's modulus) of the rubber coating layer 52c of the pressure roller 52 is 10⁶-10⁷A range of Pa is preferred, 1.0 × 10⁶~ 4.0 × 10⁶A range of Pa is more preferable. As a result, the pressure applied to the recording medium F between the heating roller 51 and the pressure roller 52 is controlled within a predetermined range as will be described later, so that the width of the nip portion 59 is reduced to the heating roller 51 and the pressure roller. Thus, it is possible to obtain a pressing force and a pressurizing time with a simple configuration.
[0034]
In addition, instead of the rubber coating layer 52 c of the pressure roller 52, the outer periphery of the heating roller 51 may be coated with heat-resistant silicon rubber or the like so as to have a longitudinal elastic modulus in the above range. You may comprise so that both the rollers 52 may become the longitudinal elastic modulus of the said range.
[0035]
Further, the support member 58 of the pressure roller 52 is driven by the fixing unit driving mechanism 26 (FIG. 6) so as to pressurize the heating roller 51 in the arrow direction A in FIG. 5 and release the pressure in the opposite direction A ′. It has become so. The pressing force of the pressure roller 52 in the arrow direction A is applied to a substantially constant urging force by the urging members 56 and 57, whereby a pressure force on the recording medium F between the heating roller 51 and the pressure roller 52 is obtained. However, the control unit 20 controls the pressure applied to the recording medium F by controlling the pressure applied to the pressure roller 52 in the arrow directions A and A ′ via the fixing unit driving mechanism 26 based on the measurement result of the pressure sensor 27. Can be adjusted. In this case, the pressure applied to the recording medium F is 9.8 × 10⁴~ 4.9 × 10⁶A range of Pa is preferred. As a result, it is possible to obtain a pressure sufficient and sufficient to make the ink receiving layer described later of the recording medium F transparent.
[0036]
Further, the control unit 20 controls the number of rotations of the heating roller 51 and the number of rotations of the conveyance roller pairs 16a and 16b, and controls the moving speed of the recording medium F in the conveyance direction S, whereby the recording medium F in the fixing unit 50 is controlled. The heating and pressing time can be adjusted as appropriate.
[0037]
Next, the control system of the ink jet printer of FIG. 1 will be described with reference to FIG. FIG. 6 is a block diagram showing a control system of the ink jet printer of FIG. As shown in FIG. 6, the inkjet printer of FIG. 1 has, as its control system, a control unit 20 for controlling the entire apparatus, an image memory 21 for storing image data signals input from an external device such as a personal computer, and the like. An operation panel 22 that allows the user to input various control information, a head drive circuit 23 that generates a drive signal to the line head 11, a cut unit drive mechanism 25 that drives the cut unit 40, and a fixing unit And a fixing unit driving mechanism 26 for driving 50.
[0038]
Based on the image data signal from the image memory 21, the control unit 20 outputs a drive signal for driving the line head 11 so that ink is ejected from each nozzle of the nozzle rows 6 a to 6 d of the line head 11. And the application timing of the drive signal from the head drive circuit 23 to each nozzle is controlled.
[0039]
Further, the control unit 20 controls the movement of the cutting member 42 by the cutting unit driving mechanism 25 based on the position information of the recording medium F from the detection sensor 41, and the heating element 53 of the heating element 53 based on the temperature information from the temperature sensor 55. The heating temperature of the recording medium F is adjusted by controlling the temperature of the heating roller 51 by adjusting the amount of heat generation, and further controlling the rotation speed of the heating roller 51 and the like in the directions A and A ′ by the fixing unit driving mechanism 26. The pressing force and heating / pressurizing time can be adjusted.
[0040]
Next, the recording medium F will be described. FIG. 7 is a cross-sectional view schematically showing a cross-sectional configuration of the recording medium F. As shown in FIG. 7, the recording medium F includes a support 61, a surface layer 63 containing thermoplastic resin particles (latex particles), an ink solvent component after the coloring material and the ink solvent component are separated on the surface of the surface layer 63. And an ink absorbing layer 62 formed between the surface layer 63 and the support 61, and is used as an ink jet recording sheet.
[0041]
The ink absorption capacity in the recording medium F is 22 to 60 ml / m.²Preferably 25-60 ml / m²And more preferably 25-35 ml / m²It is.
[0042]
Here, the above-described ink absorption capacity can be obtained as follows. That is, a recording medium having a certain area is conditioned for 24 hours or more in an atmosphere of 25 ° C. and 50% RH, and then immersed in pure water for 10 seconds. At this time, with the absorption of water, the air in the gap of the recording medium adheres to the surface as bubbles and prevents water absorption, so that the recording medium is vibrated appropriately to remove the bubbles. After 10 seconds, the recording medium is pulled up from the water, the water content on the surface is quickly removed with a water-absorbing material such as filter paper, and the ink absorption can be determined from the mass change before and after the immersion.
[0043]
Next, the ink absorption layer 62 of the recording medium F will be described. In general, the ink absorbing layer is roughly divided into a swelling type and a void type. As the swelling type, a water-soluble binder is used, for example, gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide or the like is applied alone or in combination, and this is used as an ink absorbing layer.
[0044]
As the void type, a mixture of fine particles and a water-soluble binder is applied, and a glossy one is particularly preferable. As the fine particles, alumina or silica is preferable, and those using silica having a particle size of 0.1 μm or less are particularly preferable. As the water-soluble binder, gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide or the like is preferably used alone or in combination.
[0045]
Of the above two types, in order to adapt to continuous high-speed printing, a higher ink absorption speed in the recording medium is suitable. From this point, the void type can be used particularly preferably.
[0046]
Hereinafter, the void type ink absorbing layer will be described in more detail. The void layer is mainly formed by soft aggregation of a hydrophilic binder and inorganic fine particles. Conventionally, various methods for forming voids in a film are known. For example, a uniform coating solution containing two or more kinds of polymers is coated on a support, and these polymers are phase-separated from each other in the drying process. A method of forming voids by applying a coating liquid containing solid fine particles and a hydrophilic or hydrophobic resin on a support, and after drying, the inkjet recording paper is immersed in water or a liquid containing an appropriate organic solvent. , A method of creating voids by dissolving solid fine particles, a method of forming voids in a film by applying a coating liquid containing a compound having a property of foaming during film formation, and then foaming this compound in the drying process, porous A coating solution containing a porous solid fine particle and a hydrophilic binder on a support to form voids in the porous fine particles or between the fine particles, and having a volume approximately equal to or larger than the hydrophilic binder Solid particles and or a coating solution containing a particulate oil and a hydrophilic binder is coated on a support, and a method of forming an air gap between the solid particles are known. In the present embodiment, it is particularly preferable that the void layer is formed by containing various inorganic solid fine particles having an average particle diameter of 100 nm or less.
[0047]
Examples of the inorganic fine particles used for the above purpose include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide. , Zinc carbonate, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, magnesium hydroxide, etc. A white inorganic pigment etc. can be mentioned.
[0048]
The average particle size of the inorganic fine particles is determined by observing the particles themselves or the particles appearing on the cross section or surface of the void layer with an electron microscope, measuring the particle size of 1,000 arbitrary particles, and calculating the simple average value (number average). ). Here, the particle diameter of each particle is represented by a diameter assuming a circle equal to the projected area.
[0049]
As the inorganic fine particles, it is preferable to use solid fine particles selected from silica and alumina or alumina hydrate.
[0050]
As silica that can be used in the present embodiment, silica synthesized by an ordinary wet method, colloidal silica, silica synthesized by a gas phase method, or the like is preferably used, but is particularly preferably used in the present embodiment. As the fine particle silica, colloidal silica or fine particle silica synthesized by a gas phase method is preferable. Among them, fine particle silica synthesized by a gas phase method is used not only for obtaining a high porosity but also for immobilizing a dye. When added to the cationic polymer, it is preferable because coarse aggregates are hardly formed. Alumina or alumina hydrate may be crystalline or amorphous, and any shape such as amorphous particles, spherical particles, and acicular particles can be used.
[0051]
The inorganic fine particles are preferably in a state where the fine particle dispersion before mixing with the cationic polymer is dispersed to the primary particles.
[0052]
The inorganic fine particles preferably have a particle size of 100 nm or less. For example, in the case of the above vapor phase method fine particle silica, the average particle size of primary particles of inorganic fine particles dispersed in a primary particle state (particle size in a dispersion state before coating) is preferably 100 nm or less, More preferably, it is 4-50 nm, Most preferably, it is 4-20 nm.
[0053]
As the silica synthesized by the vapor phase method in which the average particle diameter of primary particles is 4 to 20 nm, which is most preferably used, for example, Aerosil manufactured by Nippon Aerosil Co., Ltd. is commercially available. The vapor phase fine particle silica can be dispersed to primary particles relatively easily by being sucked and dispersed in water, for example, by a jet stream inductor mixer manufactured by Mitamura Riken Kogyo Co., Ltd.
[0054]
The ink absorbing layer preferably contains a water-soluble binder. Examples of the water-soluble binder include polyvinyl alcohol, gelatin, polyethylene oxide, polyvinyl pyrrolidone, polyacrylic acid, polyacrylamide, polyurethane, dextran, and dextrin. , Color ginnan (κ, ι, λ, etc.), agar, pullulan, water-soluble polyvinyl butyral, hydroxyethyl cellulose, carboxymethyl cellulose and the like. These water-soluble binders can be used in combination of two or more.
[0055]
The water-soluble binder preferably used in the present embodiment is polyvinyl alcohol. This polyvinyl alcohol includes, in addition to ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, modified polyvinyl alcohol such as polyvinyl alcohol having a cation-modified terminal and anion-modified polyvinyl alcohol having an anionic group.
[0056]
The polyvinyl alcohol obtained by hydrolyzing vinyl acetate preferably has an average degree of polymerization of 1,000 or more, and particularly preferably has an average degree of polymerization of 1,500 to 5,000. The degree of saponification is preferably 70 to 100%, particularly preferably 80 to 99.5%.
[0057]
Examples of the cation-modified polyvinyl alcohol have primary to tertiary amino groups and quaternary ammonium groups in the main chain or side chain of the polyvinyl alcohol as described in JP-A-61-110483. Polyvinyl alcohol, which is obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate.
[0058]
Examples of the ethylenically unsaturated monomer having a cationic group include trimethyl- (2-acrylamido-2,2-dimethylethyl) ammonium chloride and trimethyl- (3-acrylamido-3,3-dimethylpropyl) ammonium chloride. N-vinylimidazole, N-vinyl-2-methylimidazole, N- (3-dimethylaminopropyl) methacrylamide, hydroxylethyltrimethylammonium chloride, trimethyl- (2-methacrylamidopropyl) ammonium chloride, N- (1, 1-dimethyl-3-dimethylaminopropyl) acrylamide and the like.
[0059]
The ratio of the cation-modified group-containing monomer of the cation-modified polyvinyl alcohol is 0.1 to 10 mol%, preferably 0.2 to 5 mol%, relative to vinyl acetate.
[0060]
Anion-modified polyvinyl alcohol is, for example, polyvinyl alcohol having an anionic group as described in JP-A-1-2060888, as described in JP-A-61-237681 and JP-A-63-330779, Examples thereof include a copolymer of vinyl alcohol and a vinyl compound having a water-soluble group, and modified polyvinyl alcohol having a water-soluble group as described in JP-A-7-285265.
[0061]
Nonionic modified polyvinyl alcohol is, for example, a polyvinyl alcohol derivative obtained by adding a polyalkylene oxide group to a part of vinyl alcohol as described in JP-A-7-9758, and described in JP-A-8-25595. And a block copolymer of a vinyl compound having a hydrophobic group and vinyl alcohol. Polyvinyl alcohol can be used in combination of two or more types such as the degree of polymerization and the type of modification.
[0062]
The amount of inorganic fine particles used in the ink absorption layer depends largely on the required ink absorption capacity, the void ratio of the void layer, the type of inorganic pigment, and the type of water-soluble binder.²Usually, it is 5-30 g, preferably 10-25 g.
[0063]
The ratio of the inorganic fine particles and the water-soluble binder used in the ink absorbing layer is usually 2: 1 to 20: 1 by mass ratio, and particularly preferably 3: 1 to 10: 1.
[0064]
In addition, a cationic water-soluble polymer having a quaternary ammonium base in the molecule may be contained, and the inkjet recording paper 1 m²Usually, it is used in the range of 0.1 to 10 g, preferably 0.2 to 5 g.
[0065]
In the void layer, the total amount of voids (void volume) is 1 m of recording paper.²It is preferably 20 ml or more per unit. The void volume is 20ml / m²If the amount of ink is less, the ink absorptivity is good when the amount of ink at the time of printing is small, but if the amount of ink increases, the ink is not completely absorbed, resulting in a decrease in image quality or a delay in drying. The problem is likely to occur.
[0066]
In the void layer having ink retention ability, the void volume relative to the solid content volume is referred to as a void ratio. In this embodiment, it is preferable to set the porosity to 50% or more because the voids can be efficiently formed without unnecessarily increasing the film thickness.
[0067]
As another type of void type, in addition to forming an ink absorbing layer using inorganic fine particles, a polyurethane resin emulsion, a water-soluble epoxy compound and / or an acetoacetylated polyvinyl alcohol, and an epichlorohydrin polyamide resin are used in combination. The ink absorbing layer may be formed using the applied coating liquid. The polyurethane resin emulsion in this case is preferably a polyurethane resin emulsion having a polycarbonate chain, a polycarbonate chain and a polyester chain and a particle diameter of 3.0 μm, and the polyurethane resin of the polyurethane resin emulsion is a polyol having a polycarbonate polyol, a polycarbonate polyol and a polyester polyol. And the polyurethane resin obtained by reacting the aliphatic isocyanate compound with a sulfonic acid group in the molecule, and further having an epichlorohydrin polyamide resin, a water-soluble epoxy compound and / or an acetoacetylated vinyl alcohol. preferable. In the ink absorption layer using the polyurethane resin, it is estimated that weak cations of anions and anions are formed, and accordingly, voids having an ink absorption capability are formed, so that an image can be formed.
[0068]
In the present embodiment, it is preferable to use a curing agent. The curing agent can be added at any time during the preparation of the inkjet recording paper. For example, the curing agent may be added to the coating liquid for forming the ink absorbing layer, but after the ink absorbing layer is formed, the water-soluble binder is cured. It is preferable to supply an agent.
[0069]
In the present embodiment, a method of supplying a water-soluble binder curing agent after forming the ink absorbing layer may be used alone, but preferably the above-described curing agent is used in the coating liquid for forming the ink absorbing layer. It is to be used in combination with the method of adding.
[0070]
The curing agent that can be used in this embodiment is not particularly limited as long as it causes a curing reaction with a water-soluble binder, but boric acid and its salts are preferable, but other known ones can be used. In general, a compound having a group capable of reacting with a water-soluble binder or a compound that promotes the reaction between different groups of the water-soluble binder, and is appropriately selected and used depending on the type of the water-soluble binder . Specific examples of the curing agent include, for example, epoxy curing agents (diglycidyl ethyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidyl cyclohexane, N, N-diglycidyl- 4-glycidyloxyaniline, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, etc.), aldehyde curing agents (formaldehyde, glioxal, etc.), active halogen curing agents (2,4-dichloro-4-hydroxy-1,3,5) , -S-triazine, etc.), active vinyl compounds (1,3,5-trisacryloyl-hexahydro-s-triazine, bisvinylsulfonylmethyl ether, etc.), aluminum alum and the like.
[0071]
Boric acid or a salt thereof refers to an oxygen acid having a boron atom as a central atom and a salt thereof, specifically, orthoboric acid, diboric acid, metaboric acid, tetraboric acid, pentaboric acid, and octaboron. Examples include acids and their salts.
[0072]
Boric acid having a boron atom and a salt thereof as a curing agent may be used alone or in combination of two or more. Particularly preferred is a mixed aqueous solution of boric acid and borax.
[0073]
The aqueous solutions of boric acid and borax can be added only in relatively dilute aqueous solutions, respectively, but by mixing them both can be made into a concentrated aqueous solution and the coating solution can be concentrated. Further, there is an advantage that the pH of the aqueous solution to be added can be controlled relatively freely.
[0074]
The total amount of the curing agent used is preferably 1 to 600 mg per 1 g of the water-soluble binder. The supply amount is preferably 100 to 600 mg per 1 g of the water-soluble binder.
[0075]
In the recording medium F according to the present embodiment, the surface layer 63 contains a thermoplastic resin, and preferably contains an inorganic pigment together with the thermoplastic resin.
[0076]
The surface layer referred to in the present embodiment is not limited to the outermost surface layer, and is not particularly limited as long as the effect of the present embodiment is exhibited. The recording medium of the present embodiment exhibits many of the effects of the present embodiment by melting and forming a film of the thermoplastic resin contained in the surface layer by heating after image recording, for example. For example, if printing is performed with pigment ink and image quality is improved with or without heat treatment after image recording, for example, glossiness, abrasion resistance is improved, or the degree of bronzing is improved, a thermoplastic resin, or Even if the layer containing the inorganic pigment and the thermoplastic resin is not the outermost layer, the configuration corresponds to this embodiment.
[0077]
Preferred configuration examples for clearly indicating the surface layer in the present embodiment are listed below, but the layer configuration of the recording medium according to the present invention is not limited to these.
1: A structure in which a void-type ink absorbing layer 62 is provided on a support 61 and a layer 63 containing a thermoplastic resin or an inorganic pigment and a thermoplastic resin is the outermost layer.
2: On the support 63, which has a void-type ink absorbing layer 62, on which a thermoplastic resin, or a layer 63 containing an inorganic pigment and a thermoplastic resin, is intended to improve surface properties. A configuration with a thin layer.
3: For the purpose of cutting harmful light on a layer 63 having a void-type ink absorbing layer 62 on a support 61 and containing a thermoplastic resin or an inorganic pigment and a thermoplastic resin thereon, A structure provided with a thin layer having an ultraviolet absorbing function.
4: A void-type ink absorbing layer 62 is provided on the support 61, and a layer containing a matting agent is provided on the layer 63 containing a thermoplastic resin or an inorganic pigment and a thermoplastic resin. Constitution.
5: A structure in which a void-type ink absorbing layer 62 is provided on a support 61, and a peelable layer is provided on a layer 63 containing a thermoplastic resin or an inorganic pigment and a thermoplastic resin. .
[0078]
The most preferable configuration among the configuration examples described above is a case where the layer containing the inorganic pigment and the thermoplastic resin is the outermost layer. The surface layer containing the thermoplastic resin or the inorganic pigment and the thermoplastic resin may contain an inorganic pigment, a thermoplastic resin, and a binder component if necessary.
[0079]
The inorganic pigment can be selected from inorganic fine particles that can be used for the above-mentioned void layer. For example, light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate, hydrotalcite, aluminum silicate, diatomaceous earth Examples thereof include white inorganic pigments such as earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, and magnesium hydroxide.
[0080]
As the preferable inorganic pigment, solid fine particles selected from silica and alumina or alumina hydrate are preferably used, and silica is more preferable.
[0081]
As silica, silica synthesized by an ordinary wet method, colloidal silica, silica synthesized by a gas phase method, or the like is preferably used, but particularly preferably used fine particle silica is colloidal silica or a gas phase method. Particulate silica is preferred.Particularly, fine silica synthesized by the vapor phase method not only provides a high porosity, but also forms coarse aggregates when added to a cationic polymer used to immobilize the dye. It is preferable because it is difficult. Alumina or alumina hydrate may be crystalline or amorphous, and any shape such as amorphous particles, spherical particles, and acicular particles can be used.
[0082]
The inorganic pigment is preferably in a state where the fine particle dispersion before mixing with the cationic polymer is dispersed to the primary particles. The inorganic pigment preferably has a particle size of 100 nm or less. For example, in the case of vapor phase method fine particle silica, the average particle size (particle size in the dispersion state before coating) of the inorganic pigment dispersed in the primary particle state is preferably 100 nm or less, more Preferably it is 4-50 nm, Most preferably, it is 4-20 nm.
[0083]
Examples of the thermoplastic resin that can be used in this embodiment include polycarbonate, polyacrylonitrile, polystyrene, polyacrylic acid, polymethacrylic acid, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyester, polyamide, poly Examples include ethers, copolymers thereof, and salts thereof. Among them, styrene-acrylic acid ester copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-acrylic acid ester copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, SBR latex preferable. The thermoplastic resin may be used by mixing a plurality of polymers having different monomer compositions, particle sizes, and polymerization degrees.
[0084]
In selecting the thermoplastic resin, the ink acceptability of the recording medium, the glossiness of the image after fixing by heating and pressing, the image fastness, and the releasability should be taken into consideration.
[0085]
Regarding the ink receptivity, when the particle size of the thermoplastic resin is less than 0.05 μm, the separation of the pigment particles and the ink solvent in the pigment ink is slowed, resulting in a decrease in the ink absorption rate. On the other hand, if it exceeds 10 μm, it is not preferable from the viewpoint of the film strength and gloss deterioration of the ink jet recording medium after coating and drying. For this reason, the preferred thermoplastic resin diameter is preferably 0.05 to 10 μm, more preferably 0.1 to 5 μm. More preferably, it is 0.1-1 micrometer.
[0086]
Moreover, a glass transition point (Tg) is mentioned as a reference | standard of selection of a thermoplastic resin. When Tg is lower than the coating / drying temperature, for example, the coating / drying temperature at the time of manufacturing the recording medium is already higher than Tg and the ink solvent permeates, so the voids due to the thermoplastic resin disappear. Further, when Tg is higher than the temperature at which the support is denatured by heat, in order to melt and form a film after ink jet recording with a pigment ink, a fixing operation at high temperature is required. There is a problem with the thermal stability and the like. A preferable Tg of the thermoplastic resin is 50 to 150 ° C. Moreover, as minimum film-forming temperature (MFT), the thing of 50-150 degreeC is preferable.
[0087]
The thermoplastic resin is preferably dispersed in an aqueous system from the viewpoint of environmental suitability, and an aqueous latex obtained by emulsion polymerization is particularly preferable. At this time, a type obtained by emulsion polymerization using a nonionic dispersant as an emulsifier is a form that can be preferably used. The thermoplastic resin to be used is preferably less residual monomer component from the viewpoint of odor and safety, preferably 3% by mass or less, more preferably 1% by mass or less, based on the solid content of the polymer. Preferably it is 0.1 mass% or less.
[0088]
In the case of a surface layer containing an inorganic pigment and a thermoplastic resin, the mass ratio of the solid content of the thermoplastic resin / inorganic pigment can be selected from the range of 90/10 to 10/90, preferably the range of 70/30 to 30/70. More preferably, it is the range of 60 / 40-40 / 60.
[0089]
The solid content of the thermoplastic resin contained in the surface layer 63 is 2 g / m.²20 g / m²The following, but preferably 2 to 15 g / m², More preferably 2.5 to 10 g / m²Range. When the solid content of the thermoplastic resin is too small, a sufficient film cannot be formed, and the pigment cannot be sufficiently dispersed in the film. For this reason, image quality and gloss are not sufficiently improved. On the other hand, if the amount of the solid content of the thermoplastic resin is too large, the thermoplastic resin cannot be completely formed into a film in a short heating process, and the fine particles remain as they are, and the opacity is changed and the image quality is lowered. In addition, the ink absorption speed is also lowered, causing blurring at the boundary, which becomes a problem.
[0090]
The surface layer coating liquid containing the inorganic pigment and the thermoplastic resin may be obtained by dispersing the inorganic pigment and the thermoplastic resin at the same time, or may be a method of mixing each dispersion prepared at the time of preparing the coating liquid.
[0091]
As the support 61 of the recording medium F, a support conventionally used for an inkjet recording medium, for example, a paper support such as plain paper, art paper, coated paper and cast coated paper, a plastic support, and a polyolefin on both sides A paper support coated with, a composite support obtained by laminating these, and the like can be appropriately selected and used.
[0092]
Further, in the recording medium F, for the purpose of increasing the adhesive strength between the support 61 and the ink absorption layer 63, the support is subjected to corona discharge treatment, subbing treatment, etc. prior to the application of the ink absorption layer 62. Is preferred. Further, the recording medium F is not necessarily colorless, and may be a colored recording paper.
[0093]
In the recording medium F, it is particularly preferable to use a paper support obtained by laminating both surfaces of a base paper support with polyethylene or the like because a recorded image is close to photographic image quality and a high-quality image can be obtained at low cost. A paper support laminated with such polyethylene will be described below.
[0094]
The base paper used for the paper support is made from wood pulp as a main raw material, and if necessary, paper is made using synthetic pulp such as polypropylene or synthetic fibers such as nylon or polyester in addition to wood pulp. As wood pulp, any of LBKP, LBSP, NBKP, NBSP, LDP, NDP, LUKP, and NUKP can be used, but it is preferable to use more LBKP, NBSP, LBSP, NDP, and LDP with a large amount of short fibers. . However, the ratio of LBSP and / or LDP is preferably 10% by mass or more and 70% by mass or less.
[0095]
As the above-mentioned pulp, chemical pulp (sulfate pulp or sulfite pulp) with few impurities is preferably used, and a pulp whose whiteness is improved by performing a bleaching treatment is also useful. In the base paper, sizing agents such as higher fatty acids and alkyl ketene dimers, white pigments such as calcium carbonate, talc and titanium oxide, paper strength enhancing agents such as starch, polyacrylamide and polyvinyl alcohol, fluorescent whitening agents, polyethylene glycols A water retaining agent such as a dispersant, a softening agent such as a quaternary ammonium, and the like can be appropriately added.
[0096]
The freeness of the pulp used for papermaking is preferably 200 to 500 ml as defined by CSF, and the fiber length after beating is 24% by mass as defined in JIS-P-8207, and 42 mesh residue. 30 to 70% of the sum with the mass% of is preferable. In addition, it is preferable that the mass% of 4 mesh remainder is 20 mass% or less. The basis weight of the base paper is 30 to 250 g / m²In particular, 50 to 200 g / m²Is preferred. The thickness of the base paper is preferably 40 to 250 μm. The base paper can be given a high smoothness by calendering at the paper making stage or after paper making. Base paper density is 0.7-1.2g / m²(JIS-P-8118) is common. Furthermore, the base paper stiffness is preferably 20 to 200 g under the conditions specified in JIS-P-8143. A surface sizing agent may be applied to the surface of the base paper. As the surface sizing agent, a sizing agent similar to the size that can be added to the base paper can be used. The pH of the base paper is preferably 5 to 9 when measured by a hot water extraction method defined in JIS-P-8113.
[0097]
The polyethylene that covers the front and back of the base paper is mainly low-density polyethylene (LDPE) and / or high-density polyethylene (HDPE), but in addition, some LLDPE (linear low-density polyethylene), polypropylene, etc. should be used. Can do. In particular, the polyethylene layer on the ink absorbing layer side preferably has an improved opacity and whiteness by adding rutile or anatase type titanium oxide to the polyethylene, as widely used in photographic paper. The titanium oxide content is usually 3 to 20% by mass, preferably 4 to 13% by mass, based on polyethylene.
[0098]
Polyethylene-coated paper can be used as glossy paper, or when the polyethylene is melt-extruded and coated on the surface of the base paper, a so-called molding process is performed to provide a matte surface or silky surface as obtained with ordinary photographic printing paper. The thing which formed the surface can also be used.
[0099]
The amount of polyethylene used on the front and back of the base paper is selected so as to optimize curling under low and high humidity after providing a void layer and a back layer. The range is 40 μm and the back layer side is 10 to 30 μm.
[0100]
Furthermore, the polyethylene-coated paper support preferably has the following characteristics.
1. Tensile strength: strength defined by JIS-P-8113, preferably 20 to 300N in the vertical direction and 10 to 200N in the horizontal direction.
2. Tear strength: 0.1 to 20N in the longitudinal direction and 2 to 20N in the lateral direction are preferred as defined in JIS-P-8116.
3. Compression modulus ≧ 98.1 MPa
4). Surface Beck smoothness: 20 seconds or more is preferable as a glossy surface under the conditions specified in JIS-P-8119, but it may be less than this for a so-called molded product.
5. Surface roughness: The surface roughness specified in JIS-B-0601 preferably has a maximum height of 10 μm or less per reference length of 2.5 mm.
6). Opacity: When measured by the method defined in JIS-P-8138, 80% or more, particularly 85 to 98% is preferable.
7. Whiteness: L *, a *, and b * defined by JIS-Z-8729 are preferably L * = 80 to 95, a * = − 3 to +5, and b * = − 6 to +2.
8). Surface glossiness: The 60-degree specular glossiness specified in JIS-Z-8741 is preferably 10 to 95%.
9. Clark stiffness: Clark stiffness in the recording medium transport direction S is 50 to 300 cm.²A support that is / 100 is preferred.
10. Water content of middle paper: usually 2 to 100% by weight, preferably 2 to 6% by weight, based on the middle paper
[0101]
For the above-mentioned recording medium F, any of dye ink, pigment ink, water-based ink, oil-based ink, and hot-melt ink can be used, but water-based pigment ink and oil-based pigment ink are suitable, and water-based pigment ink is most suitable. ing.
[0102]
Next, a method for manufacturing the recording medium F will be described. As a method for producing this recording medium, each of the constituent layers including the ink absorbing layer can be suitably selected from known coating methods, either alone or simultaneously, and coated and dried on a support. Examples of the coating method include a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method, or a slide bead coating using a hopper described in US Pat. Nos. 2,761,419 and 2,761,791. A method, an extrusion coating method or the like is preferably used.
[0103]
When the slide bead coating method is used, the viscosity of each coating solution at the time of simultaneous multilayer coating is preferably in the range of 5 to 100 mPa · s, more preferably in the range of 10 to 50 mPa · s. Moreover, when using a curtain application | coating system, the range of 5-1200 mPa * s is preferable, More preferably, it is the range of 25-500 mPa * s.
[0104]
Further, the viscosity at 15 ° C. of the coating solution is preferably 100 mPa · s or more, more preferably 100 to 30,000 mPa · s, further preferably 3,000 to 30,000 mPa · s, and most preferably 10 , 30,000 to 30,000 mPa · s.
[0105]
As a coating and drying method, the coating liquid is heated to 30 ° C. or more, and after simultaneous multi-layer coating, the temperature of the formed coating film is once cooled to 1 to 15 ° C. and dried at 10 ° C. or more. Is preferred. It is preferable to prepare, apply, and dry the coating liquid at a temperature equal to or lower than Tg of the thermoplastic resin so that the thermoplastic resin contained in the surface layer does not form a film at the time of preparing the coating liquid, at the time of coating, and at the time of drying. More preferably, the drying conditions are a wet bulb temperature of 5 to 50 ° C. and a film surface temperature of 10 to 50 ° C. Moreover, as a cooling method immediately after application | coating, it is preferable to carry out by a horizontal set system from a viewpoint of the formed coating-film uniformity.
[0106]
The recording medium manufacturing process preferably includes a step of supplying a water-soluble binder curing agent after the ink absorption layer is formed. The method for supplying the curing agent is not particularly limited. For example, after forming the ink absorbing layer, a method of applying a solution containing the curing agent, and a method of spraying the solution containing the curing agent on the surface of the recording medium on which the ink absorbing layer has been formed. Etc., and can be appropriately selected and used.
[0107]
Moreover, it is preferable to have the process preserve | saved 24 hours or more and 60 days or less on the conditions of 35 degreeC or more and 70 degrees C or less in the manufacture process. The heating condition is not particularly limited as long as it is stored at a temperature of 35 ° C. or higher and 70 ° C. or lower for 24 hours or longer and 60 days or shorter, but a preferable example is, for example, 36 ° C. for 3 days to 4 weeks. , 40 ° C. for 2 days to 2 weeks, or 55 ° C. for 1 to 7 days. By performing this heat treatment, the curing reaction of the water-soluble binder can be promoted or the crystallization of the water-soluble binder can be promoted, and as a result, preferable ink absorbability can be achieved.
[0108]
A pigment ink is ejected from the line head 11 shown in FIGS. 1 and 2 to the recording medium F configured as described above, and an image is written and recorded. The ink includes a water-based ink composition and an oil-based ink. Although a composition, a solid (phase change) ink composition, or the like can be used, a water-based ink composition (for example, a water-based inkjet recording liquid containing 10% by mass or more of water per total ink mass) is preferable.
[0109]
A pigment ink is preferably used as the colorant used in the ink from the viewpoint of image storage stability. As the pigment used in the pigment ink, insoluble pigments, organic pigments such as lake pigments, carbon black and the like can be preferably used.
[0110]
The insoluble pigment is not particularly limited. Dioxazine, thiazole, phthalocyanine, diketopyrrolopyrrole and the like are preferable.
[0111]
Further, specific pigments that can be preferably used include the following pigments. Examples of the magenta or red pigment include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.
[0112]
Examples of the pigment for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. And CI Pigment Yellow 138.
[0113]
Examples of green or cyan pigments include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.
[0114]
For these pigments, a pigment dispersant may be used as necessary. Examples of pigment dispersants that can be used include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates. Acid salt, naphthalene sulfonate, alkyl phosphate, polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, amine Activators such as oxides, or styrene, styrene derivatives, vinyl naphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives Block copolymer comprising a monomer of the above, a random copolymer and can be exemplified salts thereof.
[0115]
As a method for dispersing the pigment, for example, various dispersing machines such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, and a paint shaker can be used. It is also preferable to use a centrifugal separator or a filter for the purpose of removing the coarse particles of the pigment dispersion.
[0116]
The average particle size of the pigment particles in the pigment ink is selected in consideration of the stability in the ink, image density, glossiness, light resistance, etc. In addition, the particle size is also from the viewpoint of improving glossiness and improving texture. Is preferably selected as appropriate. The reason why the glossiness or texture is improved is not clear at this stage, but in the formed image, the pigment is preferably dispersed in the film in which the thermoplastic resin is melted. It is speculated that For the purpose of high-speed processing, the thermoplastic resin must be melted and formed into a film in a short time, and the pigment must be sufficiently dispersed in the film. At this time, it is considered that the surface area of the pigment has a large influence, and therefore there is an optimum region for the average particle diameter.
[0117]
The water-based ink composition which is a preferable form as the pigment ink preferably uses a water-soluble organic solvent in combination. Examples of water-soluble organic solvents that can be used include alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc.) Polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc.), Polyhydric alcohol ethers (for example, ethylene glycol monomethyl ether, ethylene glycol Ethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol Ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.), amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, -Ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethylformamide, N, N- Dimethylacetamide, etc.), heterocycles (eg, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.), sulfoxides (eg, dimethyl) Sulfoxide and the like), sulfones (for example, sulfolane and the like), urea, acetonitrile, acetone and the like. Preferable water-soluble organic solvents include polyhydric alcohols. Furthermore, it is particularly preferable to use a polyhydric alcohol and a polyhydric alcohol ether in combination.
[0118]
The water-soluble organic solvent may be used alone or in combination. The total amount of the water-soluble organic solvent added to the ink is 5 to 60% by mass, preferably 10 to 35% by mass.
[0119]
The ink composition may be prepared by adding various known additives such as viscosity according to the purpose of improving ejection stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performances as necessary. Adjusting agents, surface tension adjusting agents, specific resistance adjusting agents, film forming agents, dispersants, surfactants, ultraviolet absorbers, antioxidants, anti-fading agents, anti-fouling agents, rust inhibitors, etc. are appropriately selected and used. For example, polystyrene, polyacrylic acid esters, polymethacrylic acid esters, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, or a copolymer thereof, urea resin, melamine resin, etc. Organic latex fine particles, liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil and other oil droplet fine particles, Thion or nonionic surfactants, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, JP-A-57-74192, JP-A-57-87989, 60-72785, 61-146591, anti-fading agents described in JP-A-1-95091 and 3-13376, JP-A-59-42993, 59-52689, 62- 280069, 61-242871, and JP-A-4-219266, etc., optical brighteners, pH adjusters such as sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate, etc. Can be mentioned.
[0120]
The ink composition has a flying viscosity of preferably 40 mPa · s or less, and more preferably 2 to 20 mPa · s. The ink composition has a surface tension during flight of preferably 20 mN / m or more, and more preferably 30 to 45 mN / m.
[0121]
Next, when a large number of dots (pixels) are formed by ejecting ink from the line head 11 onto the recording medium F, each pixel is controlled to be formed at a time interval of 10 ms or more with respect to all adjacent pixels. However, in this case, it is necessary not to decrease the overall printing speed. Regarding the control of the nozzle configuration of the line head and the time interval (landing time interval) of ink ejection, FIGS. This will be described with reference to FIG.
[0122]
FIG. 8 is a diagram illustrating a first example of nozzle configuration and time interval control of ink ejection, and FIG. 8A is a plan view schematically illustrating the arrangement of the nozzle rows 6a to 6d of the line head 11. FIG. 8B is a plan view schematically showing the ink landing position on the recording medium corresponding to each nozzle position of each nozzle row in FIG.
[0123]
As shown in FIG. 8A, the nozzle rows 6a to 6d of the line head 11 in FIG. 2 are arranged in a line at a constant interval L in this order. Each nozzle of the group of nozzle rows 6a and 6b is at the same position in the nozzle extending direction, and each nozzle of another group of the nozzle rows 6c and 6d is at the same position between the nozzles of the nozzle rows 6a and 6b. is there. That is, if the nozzle interval between a nozzle and the adjacent nozzle is X, each nozzle in the group of nozzle arrays 6a and 6b and each nozzle in another group in the nozzle arrays 6c and 6d It is shifted by half of the nozzle interval X so that another dot is formed between the nozzle and the other nozzle.
[0124]
The interval L between the nozzle rows 6a to 6d is wider than the dot interval n formed on the recording medium F shown below in FIG. 8B, and the nozzle rows 6a and 6b and the nozzle rows 6c and 6d are respectively The dots are spaced apart by an odd multiple of n, so that, for example, 50 lines of lines are formed between them. The nozzle rows 6a and 6c and the nozzle rows 6b and 6d are spaced apart by an even multiple of the dot interval n, and are separated so that, for example, 101 lines of dots are formed between them. In FIGS. 8A and 8B, the vertical direction of the figure is shortened (the same applies to FIGS. 9 to 11 below).
[0125]
Image recording is performed while repeating ejection of ink from each nozzle of the nozzle rows 6a to 6d of the line head 11 and then transporting the recording medium F downward in FIG. 8B. As shown in FIG. 8B, the ink on the recording medium F is ejected from each nozzle of the nozzle rows 6a to 6d, and each dot ○ (circle mark in the figure, the same applies hereinafter) is formed by the nozzle row 6a. At the same time, each dot ◎ (double circle mark in the figure, the same applies hereinafter) in the nozzle row 6b, each dot ● (in the figure, black circle mark, the same applies hereinafter) in the nozzle row 6c, and each dot in the nozzle row 6d. X (in the figure, punishment mark, the same applies hereinafter) is formed. In this case, lines 60a and 60b are formed by the nozzle rows 6a and 6b, respectively, while each dot ● and each dot × by the nozzle rows 6c and 6d are each dot of the line by the dot ○ and dot ◎ formed before that. Formed in between to form lines 60c and 60d, respectively.
[0126]
Next, since the recording medium F is transported downward in the figure by a distance (twice the dot interval n) that is one line apart, each dot line is formed by each nozzle in the nozzle rows 6a to 6d. As shown in FIG. 8 (b), each line formed by each dot ○ ◎ ● x is formed by one line.
[0127]
In other words, in FIG. 8B, the dot circle line 60a is formed one line after the formation of the line 61a, and the dot circle line 62a is formed after the formation of 25 lines in terms of time. Is done. Since the line 60b by the dot 形成 is formed at the same time as the line 60a as a line adjacent to the line 62a of the dot ◯, it is formed after forming 25 lines from the line 62a. Similarly, since the ink landing time interval between each line and the adjacent line is a time for forming 25 lines, even if ink is ejected every 0.4 ms (= drive frequency 2.5 kHz). 10 ms.
[0128]
As described above, an image can be formed by forming a plurality of lines 60e made up of each pixel on the recording medium F as shown in FIG. 8B. For example, even if it is controlled to 10 ms or less, such as 0.4 ms, each pixel in each line can be controlled to be formed at a time interval of 10 ms or more for all adjacent pixels. In this way, it is possible to lengthen only the ink landing time interval without increasing the ejection time interval, that is, without reducing the printing speed.
[0129]
Next, a second example of nozzle configuration and ink ejection time interval control will be described with reference to FIG. The second example of FIG. 9 can reduce the drive frequency of the line head 11 more than the first example of FIG. FIG. 9A is a plan view schematically showing the arrangement of the nozzle rows 6a to 6d of the line head 11, and FIG. 9B shows the ink landing position on the recording medium. It is a top view shown typically corresponding to each nozzle position of a row.
[0130]
As shown in FIG. 9A, in the nozzle rows 6a to 6d of the line head 11, the nozzle (1) (in the figure, 1 circled letters, the same applies hereinafter) and the nozzle (2) (in the figure, 2 Circled letters (hereinafter the same) are alternately arranged, the interval between the nozzle (1) and the adjacent nozzle (2) is half (X / 2) of FIG. 8 (a), and the nozzle density is doubled. It has become. The interval L between the nozzle rows 6a to 6d is the same as that in FIG. As shown in FIG. 9B, the line 60a is formed by the dots ◯ with the nozzle {circle around (1)} of the nozzle row 6a. The line 61a formed one line away immediately before that is the nozzle {circle around (2)} of the nozzle row 6a. It is to be formed with. Similarly, the line 62a is formed by the nozzle {circle around (1)} of the nozzle row 6a before the formation of 25 lines of the line 60a, and the line 60b by the dot ◎ is adjacent to the line 62a by the nozzle {circle around (1)} of the nozzle row 6b. It is formed. Further, in the lines 60c and 60d, each dot ● by the nozzle {circle around (1)} of the nozzle rows 6c and 6d, and each dot × by the dot ○ and dot ◎ previously formed by the nozzle {circle around (2)} of the nozzle rows 60c and 60d. It is formed between each dot of the line.
[0131]
As described above, nozzles 6a to 6d are used to alternately form the nozzles (1) and (2), and the ink ejection time interval is set to 0.4 ms (each of which is the same as in FIG. 8B). When image formation is performed at an ink ejection time interval of 0.8 ms per nozzle), the drive frequency of the line head 11 is halved compared to FIG. According to the configuration of FIG. 9, as in the case of FIG. 8, even if the time interval of ink ejection is controlled to be 10 ms or less, for example, 0.4 ms, each pixel of each line is 10 ms or more for all adjacent pixels. It can control so that it may form in the time interval of.
[0132]
Next, a third example of nozzle configuration and ink ejection time interval control will be described with reference to FIG. In the third example of FIG. 10, each pixel (dot) formed on the recording medium F is shifted by half the pixel pitch p (about half a pixel) for each line as compared with the first example of FIG. Is. FIG. 10A is a plan view schematically showing the arrangement of the nozzle rows 6a to 6d of the line head 11, and FIG. 10B shows the ink landing positions on the recording medium shown in FIG. It is a top view typically shown corresponding to each nozzle position of a nozzle row.
[0133]
As shown in FIG. 10A, in the nozzle rows 6a to 6d of the line head 11, the nozzle interval between the nozzle and the adjacent nozzle is the same (X) as in FIG. The nozzles 6d are shifted in order by a quarter of the nozzle interval X with respect to the nozzles of the nozzle row 6a. That is, the interval between each nozzle in the nozzle row 6a and each nozzle in the nozzle row 6b is shifted by X / 4. Similarly, the nozzle row 6b and the nozzle row 6c are also shifted by X / 4. Even 6d is shifted by X / 4.
[0134]
10A, dots are formed on the recording medium F in the same manner as in the first example of FIG. 8, and finally a plurality of lines 60f are formed as shown in FIG. 10B. Each line is formed in the same way as in FIG. 8, but each pixel of the line is shifted by p / 2 (= X / 4), which is half the pixel pitch p (= X / 2), with respect to each pixel of the adjacent line. . This relationship is shown in FIG. 12 (each circle corresponds to one pixel), but the shortest distance d between the pixel and the adjacent pixel between the lines is larger than the shortest distance d ′ when the pixels are not shifted. Since the ink landing interval is widened, compared to the case where the pixels are not shifted, the ink droplets coalesce and the pigments aggregate and the graininess is reduced, and the image quality is improved. Further, according to the configuration of FIG. 10, similarly to the case of FIG. 8, even if the time interval of ink ejection is controlled to 10 ms or less, for example, 0.4 ms, each pixel of each line is compared to all adjacent pixels. It can be controlled to be formed at a time interval of 10 ms or more.
[0135]
Next, a fourth example of nozzle configuration and ink ejection time interval control will be described with reference to FIG. In the fourth example of FIG. 11, each pixel is shifted by half the pixel pitch p for each line as in FIG. 10, and the drive frequency of the line head 11 can be reduced as in FIG. FIG. 11A is a plan view schematically showing the arrangement of the nozzle rows 6a to 6d of the line head 11, and FIG. 11B shows the ink landing positions on the recording medium shown in FIG. It is a top view typically shown corresponding to each nozzle position of a nozzle row.
[0136]
As shown in FIG. 11A, similarly to FIG. 9A, in the nozzle rows 6a to 6d of the line head 11, the nozzle (1) and the nozzle (2) are alternately arranged, and the nozzle (1). And the adjacent nozzle (2) is half (X / 2) of FIG. 8A, and the nozzle density is doubled. The interval L between the nozzle rows 6a to 6d is the same as that in FIG.
[0137]
Further, the nozzles of the nozzle row 6a and the nozzles of the nozzle row 6b of the line head 11 are shifted by X / 4 which is a half of the nozzle interval X / 2. Similarly, the nozzles of the nozzle row 6c and the nozzles of the nozzle row 6d are shifted by X / 4, which is half of the nozzle interval X / 2. The nozzles 6a and 6d are arranged in the same position.
[0138]
When dots are formed on the recording medium F in the same manner as in the second example of FIG. 9 by the line head 11 of FIG. 11A, a plurality of lines similar to FIG. 10B are obtained as shown in FIG. 60f can be formed. Accordingly, as shown in FIG. 12, since the shortest distance d between the pixel between each line and the adjacent pixel is larger than the shortest distance d ′ when the pixels are not shifted, the ink landing interval is widened. As compared with the case where the pixels are not shifted, the ink droplets coalesce and the pigments aggregate and the graininess is reduced, and the image quality is improved. Similarly to FIG. 9, since the dots (1) and (2) are alternately used in the nozzle rows 6a to 6d to form dots, the driving frequency of the line head 11 is halved compared to FIG. According to the configuration of FIG. 11, as in the case of FIG. 8, even if the time interval of ink ejection is controlled to 10 ms or less, for example, 0.4 ms, each pixel of each line is 10 ms or more for all adjacent pixels. It can control so that it may form in the time interval of.
[0139]
10 and 11, the nozzle positions of the nozzle rows 6a to 6d of the line head 11 are staggered by shifting from line to line, but ink landing is performed by changing the ink ejection angle of each nozzle. You may comprise a nozzle so that a position may become zigzag like FIG.10 (b) and FIG.11 (b).
[0140]
Next, an operation of recording an image on the recording medium F with the ink jet printer of FIG. 1 will be described. First, the recording unit 10 ejects ink from the line head 11 onto the recording medium F transported from the roll body 9 in FIG. 1 to form a large number of pixels, and image recording is performed. At this time, since each pixel formed on the recording medium F as described above is formed at a time interval of at least 10 ms with respect to all adjacent pixels, the pigment ink droplets are adjacent to each other after being absorbed by the recording medium. Pixel ink droplets land. For this reason, the granularity is improved, the image quality is improved, the pigment ink droplets are not coalesced and the pigments are not aggregated, and there is no problem that is the same as when printing with apparently large droplets.
[0141]
Further, as described above, it is desirable that the ink droplet velocity when ejecting ink from each nozzle of the ink head 11 is 6 m / s or more and 10 m / s or less. As described in FIGS. 3 and 4 by the control unit 20 in FIG. 6, the droplet velocity is determined by adding the positive and negative drive voltages V1 and V2 (V1 + | V2 |) applied to the piezo elements constituting each nozzle. ) To adjust to a desired value.
[0142]
When the droplet speed of the ink ejected from each nozzle of the line head 11 is 6 m / s or less, the time from the ejection of the ink to the landing becomes long, and the fluctuation of the droplet speed causes a large fluctuation in the landing position, and the recording medium F The edge of the image formed on the recording medium becomes indistinct or the fine line is bent, so that the image quality is likely to be deteriorated. Further, when the droplet velocity is 10 m / s or more, the pigment ink is scattered on the surface of the recording medium F. As a result, the recording medium F is easily soiled and the image quality is lowered. Therefore, by controlling the ink droplet velocity to 6 m / s or more and 10 m / s or less, high-quality printing is possible.
[0143]
Next, the recording medium F is transported in the transport direction S by the transport roller pair 15a and 15b via the accumulator unit 18 and cut to a predetermined size at an appropriate position by the cutting unit 40, and then is transported by the transport roller pair 16a. It is conveyed to the fixing unit 50 and enters between the heating roller 51 and the pressure roller 52 of the fixing unit 50. Then, under the control of the control unit 20, the heating roller 51 is heated to a predetermined temperature and driven so that the pressure applied by the pressure roller 52 becomes a predetermined pressure on the recording medium F, whereby the recording medium F on which an image is written is recorded. Is heated and pressurized at the nip 59 formed between the heating roller 51 and the pressure roller 52 at a predetermined temperature and a predetermined pressure as described above, and the time for passing through the nip 59 is controlled.
[0144]
By heating and pressurizing the recording medium F at the fixing unit 50 as described above, the latex particles contained in the outermost surface layer 63 of the recording medium F in FIG. The ink is absorbed by the ink absorbing layer 62 to fix the image on the recording medium F. At this time, at least one of the heating temperature, pressing force, and heating and pressing time of the recording medium F is formed on the recording medium F. Control is performed so that the image clarity value of the generated image is in the range of 60% to 95%.
[0145]
That is, the heating temperature T of the recording medium F is controlled to be T = Tg ± ΔT = 50 to 150 ° C. ± 10 ° C., and the pressure applied to the recording medium F by the heating roller 51 is 9.8 × 10.⁴~ 4.9 × 10⁶By controlling the image clarity value to be within 60% to 95% by controlling to Pa, latex particles contained in the surface layer 63 of the recording medium F in FIG. 7 are melted to smooth the surface layer 63. By making the thermoplastic resin layer transparent, it is excellent in appearance and glossiness comparable to that of a photograph can be obtained, and a high-quality image can be formed. In addition, the pigment ink is taken into the ink absorption layer 62 to become a pigment ink layer, and this pigment ink layer is covered with a thermoplastic resin layer, and an image having excellent storability is combined with the original good storability of the pigment ink. Can be formed.
[0146]
If the image clarity value is 60% or less, the gloss unique to the photograph is reduced and the image quality is lowered. If the image clarity value is 95% or more, abnormal image formation occurs and the image quality is liable to be lowered. Therefore, the range of 60% to 95% is preferable.
[0147]
Next, another configuration example of the fixing unit 50 in FIG. 1 will be described with reference to FIG. FIG. 13 is a side view showing in detail an endless belt type fixing unit.
[0148]
The fixing unit in FIG. 13 is configured to press and heat the recording medium F while being conveyed by the endless belt, and sandwiches the heating roller 410 and the recording medium F between the heating roller 410 as shown in the figure. The pressure roller 440, the driven roller 420 disposed downstream, the endless heating belt 430 stretched between the heating roller 410 and the driven roller 420, and the recording medium F to the heating belt 430. A pressing means 470 for pressing, a temperature sensor 480 for detecting the surface temperature of the heating belt 430, a conveyance sensor 490 for detecting the recording medium F on the upstream side of the heating roller 410 and the pressure roller 440, and a heating belt And cleaning means 600 for removing ink stains adhering to the surface of 430.
[0149]
The heating roller 410 is a hollow roller, and includes a heating element 450 such as a halogen heater as a heat source along the axial direction thereof. The heating roller 410 is heated by the heating element 450 and is further suspended on the heating belt. By also heating 430, the recording medium F pressed by the heating belt 430 is heated, and the thermoplastic resin particles on the surface layer are melted. The heating roller 410 is preferably formed of a material having a high thermal conductivity so that the recording medium F can be efficiently heated by the heat generated from the heating element 450, and is preferably composed of a metal roller.
[0150]
The temperature sensor 480 is disposed in the vicinity of the heating roller 410, detects the surface temperature of the heating belt 430, and based on this detected temperature, the control unit 20 in FIG. Is controlled so that the surface temperature of the heating belt 430 is maintained within a predetermined temperature range. The heating element 450 may be provided near the outside of the heating roller 410.
[0151]
The heating belt 430 is suspended from the heating roller 410 and the driven roller 420, and is heated to a predetermined temperature range by the heating element 450, and then presses the recording medium F on which the image has been formed. The thermoplastic resin particles contained in the surface layer are melted, and the surface roughness of the recording medium F becomes approximately the same as the surface roughness of the heating belt 430.
[0152]
Therefore, the outer surface (the recording medium side) of the heating belt 430 is required to have a small surface roughness. Specifically, Ra = 0.5 μm or less and 0.01 μm or more (preferably Ra = 0). .1 μm or less). Here, the incidental effect of reducing the surface roughness of the belt will be described. Generally, in the same material, the smaller the surface roughness, the higher the wear resistance and the higher the durability. Are known. Further, it is known that the smaller the surface roughness is, the more excellent the antistatic property and the prevention of offset are. Therefore, such an effect can also be obtained in FIG.
[0153]
The heating belt 430 is basically a metal belt or resin belt whose surface is coated. The following materials are used in consideration of releasability from the recording medium F, surface roughness when coated, and the like. Is preferred.
・ Nickel belt + silicon rubber + PFA
・ Nickel belt + PFA
・ Nickel belt + silicone rubber
・ Nickel belt + fluorine coating
・ Nickel belt + silicone rubber + curable silicone
・ Nickel belt + hardened silicone
・ Stainless steel belt + silicon rubber + PFA
・ Stainless steel belt + PFA
・ Stainless steel belt + silicone rubber
・ Stainless steel belt + fluorine coating
・ Stainless steel belt + silicone rubber + hardened silicone
・ Stainless steel belt + hardened silicone
・ Polyimide belt + silicone rubber + PFA
・ Polyimide belt + PFA
・ Polyimide belt + silicone rubber
・ Polyimide belt + fluorine coating
・ Polyimide belt + silicone rubber + curable silicone
・ Polyimide belt + curable silicone
[0154]
The pressure roller 440 is composed of a metal roller such as stainless steel or a metal roller such as stainless steel having an elastic coating on the outer periphery, and is always pressed against the heating roller 410 side by an urging means (not shown). Has been. When the conveyance sensor 490 provided on the upstream side of the heating roller 410 and the pressure roller 440 detects the conveyance of the recording medium F, the urging means presses the pressure roller 440 against the heating roller 410 in the control unit 20 of FIG. Control is performed to reduce the pressure. This prevents the surface of the heating belt 430 and the pressure roller 440 from being damaged by the end surface protrusion of the recording medium F.
[0155]
The pressing unit 470 includes a plate-like member 471 that contacts the lower surface of the recording medium F in the figure, and a biasing unit 472 for biasing the plate-like member 471 and the recording medium F toward the heating belt 430. The plate-like member 471 is preferably made of metal, and its surface roughness is required to be as small as that of the heating belt. Specifically, Ra = 0.5 μm or less and 0.01 μm or more ( Preferably, Ra = 0.1 μm or less) is required. The urging means 472 is constituted by a spring or the like, and a plurality of urging means 472 may be provided, and the urging means 472 may be configured to adjust the pressing force (pressing force) against the recording medium F. In order to detect this applied pressure, it is preferable to arrange a pressure sensor as in FIG.
[0156]
Further, the auxiliary heating body 451 and the temperature sensor 452 therefor are arranged between the heating roller 410 and the driven roller 420 and inside the heating belt 430, thereby controlling the heating temperature for the recording medium F with higher accuracy. be able to.
[0157]
In FIG. 13, when the recording medium F on which an image is recorded with ink is conveyed from the conveyance direction S, the conveyance sensor 490 detects the recording medium F and weakens the pressing force of the pressure roller 440 against the heating roller 410. After that, the recording medium F enters between the heating belt 430 and the pressure roller 440 and is conveyed between the heating belt 430 moving in the conveyance direction S and the plate member 471. During the conveyance, the recording medium F receives pressure from the spring 472 of the urging means 470 via the plate-like member 471 while being heated by the heating belt 430. At least one of the heating temperature and the applied pressure is controlled by the control unit 20 in FIG. 6 so that the image clarity value of the image formed on the recording medium F is in the range of 60% to 95% as in FIG. To do. Further, the endless belt system of FIG. 13 is preferable in this respect because the heating time and the pressurization time can be secured longer than the rotating roller system of FIG.
[0158]
【Example】
Next, the present invention will be further described with reference to examples and comparative examples.
[0159]
<Production of recording medium>
Samples F1 and F2 of recording media as ink jet recording papers were prepared by the following procedure.
[0160]
[Preparation of inorganic fine particle dispersion]
[0161]
(Preparation of silica dispersion 1)
125 kg of gas phase method silica (Tokuyama: QS-20) having an average primary particle size of about 0.012 μm was mixed with nitric acid using a jet stream inductor mixer TDS manufactured by Mitamura Riken Kogyo Co., Ltd. Was dispersed in 620 L of pure water adjusted to 2.5 at room temperature, and then the total amount was finished to 694 L with pure water to prepare silica dispersion 1.
[0162]
(Preparation of silica dispersion 2)
The silica dispersion prepared above was added to 18 L of an aqueous solution (pH = 2.3) containing 1.14 kg of the cationic polymer (P-1) shown in the following [Chemical Formula 1], 2.2 L of ethanol, and 1.5 L of n-propanol. 69.4 L of No. 1 was added with stirring, 7.0 L of an aqueous solution containing 260 g of boric acid and 230 g of borax were added, and 1 g of an antifoaming agent SN381 (manufactured by San Nopco Co., Ltd.) was added. This mixed solution was dispersed with a high-pressure homogenizer manufactured by Sanwa Kogyo Co., Ltd., and the entire amount was finished to 97 L with pure water to prepare silica dispersion 2.
[0163]
[Chemical 1]

[0164]
[Preparation of thermoplastic resin coating solution 1]
A styrene-acrylic latex polymer emulsion-polymerized using a nonionic surfactant as an emulsifier (Tg 78 ° C., average particle size 0.3 μm, solid content concentration 40%) was adjusted to pH 4.7 with a 6% nitric acid aqueous solution. A thermoplastic resin coating solution 1 was obtained.
[0165]
(Preparation of coating solution)
[0166]
After preparing a coating solution as described below, the coating solution was filtered using a commercially available filter (TCP10 or TCP30 manufactured by Toyo Roshi Kaisha, Ltd.).
[0167]
(Preparation of lower layer coating solution 1)
While stirring at 40 ° C., the following additives were sequentially mixed in 710 ml of the silica dispersion 2 prepared above to prepare a lower coating solution 1.
[0168]
10% aqueous solution of polyvinyl alcohol (Kuraray Industrial Co., Ltd .: PVA203) 3 ml
An aqueous solution containing 4.8% of polyvinyl alcohol (Kuraray Industrial Co., Ltd .: PVA235) and 1.84% of polyvinyl alcohol (Kuraray Kogyo Co., Ltd .: PVA245) 273 ml
The whole amount was finished to 1000 ml with pure water.
[0169]
(Preparation of upper layer coating solution 1)
Using the prepared thermoplastic resin coating liquid 1 and the lower layer coating liquid 1, the thermoplastic resin and the inorganic pigment were mixed so that the solid content ratio was 40:60, and then the viscosity at 43 ° C. was 45 mPa · s. Water was added so that the upper coating solution 1 was obtained.
[0170]
(Preparation of upper layer coating solution 2)
In the preparation of the upper layer coating solution 1, an upper layer coating solution 2 was prepared in the same manner except that the solid content ratio of the thermoplastic resin and the inorganic pigment was changed to 50:50.
[0171]
[Production of recording medium]
[0172]
A paper support coated with polyethylene on both sides (also referred to as RC paper, having a thickness of 220 μm and containing 13% by mass of anatase-type titanium oxide based on polyethylene in the polyethylene of the ink absorption layer surface) from the support side In order, the lower layer coating liquid 1 as the first layer has a wet film thickness of 172 μm, and the second layer as the upper layer coating liquid 1 (average particle diameter of the thermoplastic resin: 0.3 μm) has a wet film thickness of 60 μm and the solid content of the thermoplastic resin. As 3.0 g / m²Under the conditions, two layers were simultaneously applied and dried using a slide hopper. Each coating solution was heated to 40 ° C. and then applied, cooled for 20 seconds in a cooling zone maintained at 0 ° C. immediately after application, and then subjected to 45 ° C. wind (relative humidity 15%) for 60 seconds for 45 seconds. Dry sequentially for 60 seconds with air at ℃ (25% relative humidity) and 60 seconds with wind at 50 ℃ (25% relative humidity) for 2 minutes in an atmosphere of 20 to 25 ° C. and relative humidity of 40 to 60 ° C. After adjusting the humidity, the sample was wound up to prepare Sample F1. Thereafter, the sample F1 was sealed in a polyethylene bag and subjected to aging treatment at 55 ° C. for 3 days.
[0173]
Further, the wet film thickness of the first layer is 184 mμm, the upper layer coating liquid 2 is used in the second layer, the wet film thickness is 40 μm, and the solid content rate of the thermoplastic resin is 2.5 g / m.²A sample F2 was prepared in the same manner as the sample F1 except that the conditions were changed to the conditions described above, and then the same aging treatment was performed.
[0174]
<Production of ink>
A water-based pigment ink was prepared by the following procedure.
[0175]
[Preparation of water-based pigment ink]
[0176]
(Preparation of pigment dispersion)
<Preparation of Yellow Pigment Dispersion 1>
C. I. Pigment Yellow 74 ... 20% by mass
Styrene-acrylic acid copolymer (molecular weight 10,000, acid value 120) ... 12% by mass
Diethylene glycol: 15% by mass
Ion exchange water: 53% by mass
The above additives were mixed and dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 60% by volume of 0.3 mm zirconia beads to obtain Yellow Pigment Dispersion 1. The average particle size of the obtained yellow pigment was 112 nm.
[0177]
<Preparation of magenta pigment dispersion 1>
C. I. Pigment Red 122 ... 25% by mass
Jonkrill 61 (acrylic-styrene resin, manufactured by Johnson) ··· 18% by mass in solid content
Diethylene glycol: 15% by mass
Ion exchange water: 42% by mass
Each of the above additives was mixed and dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 0.3 mm zirconia beads at a volume ratio of 60% to obtain a magenta pigment dispersion 1. The average particle size of the obtained magenta pigment was 105 nm.
[0178]
<Preparation of Cyan Pigment Dispersion 1>
C. I. Pigment Blue 15: 3 ... 25% by mass
Jonkrill 61 (acrylic-styrene resin, manufactured by Johnson): 15% by mass as solid content
Glycerin ... 10% by mass
Ion exchange water: 50% by mass
The above additives were mixed and dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 0.3% zirconia beads at a volume ratio of 60% to obtain a thin pigment dispersion 1. The average particle diameter of the obtained cyan pigment was 87 nm.
[0179]
<Preparation of Black Pigment Dispersion 1>
Carbon black: 20% by mass
Styrene-acrylic acid copolymer (molecular weight 7,000, acid value 150) ... 10% by mass
Glycerin ... 10% by mass
Ion-exchanged water ... 60% by mass
The above additives were mixed and dispersed using a horizontal bead mill (System Zeta Mini manufactured by Ashizawa Co., Ltd.) filled with 0.3% zirconia beads at a volume ratio of 60% to obtain a black pigment dispersion 1. The average particle size of the obtained black pigment was 75 nm.
[0180]
(Preparation of pigment ink)
[0181]
<Preparation of yellow ink>
Yellow pigment dispersion 1 ... 15% by mass
Ethylene glycol: 20% by mass
Diethylene glycol: 10% by mass
Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) ... 0.1% by mass
Ion exchange water ... 54.9% by mass
The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare a yellow ink that was an aqueous pigment ink. The average particle diameter of the pigment in the ink was 120 nm, and the surface tension γ was 36 mN / m.
[0182]
<Preparation of magenta ink>
Magenta pigment dispersion 1 ... 15% by mass
Ethylene glycol: 20% by mass
Diethylene glycol: 10% by mass
Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) ... 0.1% by mass
Ion-exchanged water: 54.9% by mass
The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare a magenta ink that was an aqueous pigment ink. The average particle size of the pigment in the ink was 113 nm, and the surface tension γ was 35 mN / m.
[0183]
<Preparation of cyan ink>
Cyan pigment dispersion 1 ... 10% by mass
Ethylene glycol: 20% by mass
Diethylene glycol: 10% by mass
Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) ... 0.1% by mass
Ion-exchanged water ... 59.9% by mass
Each of the above compositions was mixed, stirred, and filtered through a 1 μm filter to prepare a cyan ink as an aqueous pigment ink. The average particle size of the pigment in the ink was 95 nm, and the surface tension γ was 36 mN / m.
[0184]
<Preparation of black ink>
Black pigment dispersion 1 ... 10% by mass
Ethylene glycol: 20% by mass
Diethylene glycol: 10% by mass
Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) ... 0.1% by mass
Ion-exchanged water ... 59.9% by mass
The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare a black ink that was an aqueous pigment ink. The average particle diameter of the pigment in the ink was 85 nm, and the surface tension γ was 35 mN / m.
[0185]
Next, for each sample F1 and F2 of the recording medium described above, an image was formed under the following conditions using the above-described aqueous pigment ink of each color and using the inkjet printer of FIG. 1 as an example and a comparative example. The fixing unit uses the belt system shown in FIG.
[0186]
(1) The landing time interval of the ejected ink was variously changed as follows. 1 and 8, assuming that the moving speed of the recording medium is V (the moving speed of the head when the head moves), the nozzle row 6a forms dots for one line in FIG. The time T until the row 6b forms a dot for the previous line can be expressed by the following equation (1).
[0187]
T = (L−n) / V (1)
However, L: interval between nozzle rows (FIG. 8), n: dot interval (FIG. 8)
[0188]
Since L >> n at a normal moving speed V (about 0.1 to 1 m / s) of the recording medium, the time T can be expressed by the following approximate expression (2).
[0189]
T = L / V (2)
[0190]
Here, for example, in a combination of V ≦ 0.1 m / s and L ≧ 1 mm, the ink landing time interval is 10 ms or more. As described above, the ink landing time interval can be changed by changing the moving speed V of the recording medium and / or the interval L of the nozzle rows. In this case, the drive frequency of the line head is also changed so as to have the same landing position interval.
[0191]
In this embodiment and the comparative example, the ink head landing interval is set by changing the nozzle row interval L of the line head to 1 mm and changing the moving speed V of the recording medium in five ways within the range of 1 m / s to 0.05 m / s. Were set to 1.0, 2.0, 5.0, 10.0, and 20.0 ms, images were formed, and the quality of the rough feeling of each image was measured. The droplet amount of each ink was 1 to 5 pl. The droplet amount was adjusted by changing the drive voltage and nozzle diameter for the nozzle as shown in FIGS. The results are shown in Table 1 below.
[0192]
(2) As shown in FIGS. 3 and 4, the drive voltage for the nozzle was changed to change the droplet velocity to 4, 5, 6, 7, and 8 m / s to form an image with dots, and the image quality was evaluated.
[0193]
(3) In this embodiment, each line is formed by shifting about half of the pixel pitch as shown in FIG. 12 using a line head as shown in FIG. 10A. The image quality was compared.
[0194]
[Table 1]

[0195]
As can be seen from Table 1, in the comparative example in which the landing time interval between adjacent pixels is less than 10 ms, the feeling of roughness is large (particularly in the case where the droplet amount is 3 to 5 pl), while the landing interval is 10 ms and 20 ms. Then, in the range of 1 to 5 pl of droplets, the rough feeling was good or good.
[0196]
In addition, with respect to the droplet velocity, in each comparative example in which the droplet velocity of the ink is 4, 5 m / s, the dots forming the image are not uniformly distributed, resulting in sparseness and unevenness in the image. In addition, the image was distorted such that the straight line was bent or jagged. As described above, the time from the ejection of the ink droplet to the landing becomes long, and the variation in the droplet speed causes a large variation in the landing position of the droplet, thereby degrading the image quality. In contrast, in each of the examples where the droplet speed was 6, 7, and 8 m / s, there was no deterioration in image quality as in the comparative example, and good image quality could be obtained. When the ink droplet speed exceeds 10 m / s, the ink splatters on the recording medium surface and the image quality deteriorates.
[0197]
Further, in the embodiment in which each line is formed by shifting about half of the pixel pitch as shown in FIG. 9, the feeling of roughness is reduced and the image quality is improved as compared with the case where the lines are not shifted, and the image density is increased with the same droplet amount of ink. Compared to the image without blurring, the image quality of the highest density part such as the hair and shadows was improved.
[0198]
As described above, the present invention has been described by the embodiments and examples. However, the present invention is not limited to these, and various modifications can be made within the scope of the technical idea of the present invention. For example, the configuration of the head in the recording unit is not limited to the line head, and may be a serial head configured to move integrally with the carriage. An example of ink ejection control in the case of a serial head will be described with reference to FIG. 14. For example, as shown in a plurality of lines 60e in FIG. After the formation, the recording medium is moved by one line. Next, dots ◎ (double circles in the figure) are formed by the nozzles 72 and 74, and then the recording medium is moved by one line. Similarly, dots ● (black circles in the figure) are formed between the dots ○ by the nozzles 71 and 73, the recording medium is moved by one line, and then dots × (in the figure, A punishment mark) is formed between each dot. In this way, a line similar to the plurality of lines 60e in FIG. 8B can be formed. In this case, one reciprocating motion of the serial head by the carriage is performed at the time of recording for one line by each dot ○ ◎ ● ×. Therefore, the ink landing time is considerably longer than 10 ms for all adjacent pixels in each pixel of each line.
[0199]
【The invention's effect】
According to the present invention, it is possible to provide an image recording method and an ink jet printer capable of forming an image having image quality and storability comparable to those of photographs.
[Brief description of the drawings]
FIG. 1 is a side view schematically showing an ink jet printer according to an embodiment.
FIG. 2 is a perspective view showing a schematic configuration of the line head of FIG. 1;
3 is a perspective view partially showing a nozzle of the line head of FIG. 2, front views (b) and (c) for explaining the operation of the nozzle electrode, and nozzle injection / non-injection. It is a front view (d), (e), (f) for demonstrating each drive state.
FIG. 4 is a diagram illustrating driving waveforms of the nozzles in FIG. 3;
FIG. 5 is a side view showing the fixing unit of the ink jet printer of FIG. 1 in more detail.
6 is a block diagram showing a control system of the ink jet printer of FIG. 1. FIG.
FIG. 7 is a cross-sectional view showing a laminated structure of a recording medium in the present embodiment.
8 is a diagram showing a first example of the nozzle configuration and ink ejection time interval control of FIG. 2; FIG. 8A is a plan view showing the arrangement of the nozzle rows 6a to 6d of the line head 11 and the recording medium; It is a top view (b) which shows an ink landing position corresponding to each nozzle position of each nozzle row of Fig.8 (a).
9 is a diagram illustrating a second example of the nozzle configuration and the time interval control of ink ejection in FIG. 2, and is a plan view (a) illustrating the arrangement of the nozzle rows 6a to 6d of the line head 11 and the recording medium. It is a top view (b) which shows an ink landing position corresponding to each nozzle position of each nozzle row of Fig.9 (a).
10 is a diagram showing a third example of the nozzle configuration and ink ejection time interval control of FIG. 2, and is a plan view (a) showing the arrangement of the nozzle rows 6a to 6d of the line head 11 and on the recording medium. It is a top view (b) which shows an ink landing position corresponding to each nozzle position of each nozzle row of Fig.10 (a).
11 is a diagram showing a fourth example of the nozzle configuration and the time interval control of ink ejection in FIG. 2, and is a plan view (a) showing the arrangement of the nozzle rows 6a to 6d of the line head 11 and the recording medium. It is a top view (b) which shows an ink landing position corresponding to each nozzle position of each nozzle row of Fig.11 (a).
12 is a plan view showing the arrangement of pixels (dots) formed in a staggered pattern on the recording medium in FIGS. 10 (b) and 11 (b). FIG.
13 is a side view showing another detailed configuration example of the fixing unit in FIG. 1; FIG.
14 is a plan view showing a nozzle arrangement of a serial head showing a modification of the head configuration in FIG. 1. FIG.
[Explanation of symbols]
9 Roll body
10 Recording section
11 Line head
6a-6d Nozzle row
1a Nozzle
20 Control unit
23 Head drive circuit
26 Fixing part drive mechanism
40 cut part
50 Fixing part
51 Heating roller
52 Pressure roller
53 Heating element
55 Temperature sensor
61 Support
62 Ink absorbing layer of recording medium F
63 Surface layer of recording medium F
410 Heating roller
450 Heating element
440 Pressure roller
430 Heating belt
470 Energizing means
F Recording medium
S Transport direction
L Nozzle row spacing
X Nozzle spacing in FIGS. 8 and 10
X / 2 Nozzle spacing in FIGS. 9 and 11
p Pixel pitch
n dot (pixel) interval

Claims (9)

Pigment ink is dropped on a recording medium having an ink absorbing layer on a support and containing a thermoplastic resin and an inorganic pigment in a thermoplastic resin / inorganic pigment solid mass ratio of 90/10 to 10/90 on the surface layer. Each pixel is formed at a time interval of at least 10 ms with respect to adjacent pixels while jetting at a speed of 6 to 10 m / s, and then the heating temperature of the recording medium is within a range of Tg ± 10 ° C. (Tg: thermoplasticity of the surface layer) The glass transition point (° C.) of the resin and the pressure applied to the recording medium are controlled in the range of 9.8 × 10 ^{4 to} 4.9 × 10 ⁶ Pa, and the JIS standard H8686 for images formed on the recording medium. A method of recording an image by heating and pressurizing the recording medium so that the image clarity value obtained based on -2 is 60% or more and 95% or less.   2. The image recording method according to claim 1, wherein each of the pixels is formed so as to be shifted by approximately half of the pixel pitch for each line.   3. The image recording method according to claim 1, wherein the image clarity value is set to 60% or more and 95% or less by further controlling a heating and pressing time during heating and pressing of the recording medium. 4. The image recording method according to claim 1, wherein the Young's modulus of the rubber coating layer of the pressure roller that pressurizes the recording medium is in the range of 10 ⁶ to 10 ⁷ Pa. 5. An ink jet printer comprising: an ink head that ejects ink onto a recording medium; and a heating and pressurizing unit that heats and pressurizes the recording medium after the ink is ejected, and performs image recording on the recording medium.
Each pixel is adjacent to a recording medium having an ink absorbing layer on the support and containing a thermoplastic resin and an inorganic pigment on the surface layer and a thermoplastic resin / inorganic pigment solid mass ratio of 90/10 to 10/90. Pigment ink is ejected from the ink head at a droplet velocity of 6 to 10 m / s so as to be formed at a time interval of at least 10 ms with respect to a matching pixel, and the heating temperature of the recording medium is in the range of Tg ± 10 ° C. (Tg: An image formed on the recording medium by controlling the glass transition point (° C.) of the thermoplastic resin of the surface layer and the pressure applied to the recording medium in the range of 9.8 × 10 ^{4 to} 4.9 × 10 ⁶ Pa. An ink jet printer, wherein the recording medium is heated and pressurized by the heating and pressing means so that the image clarity value obtained based on JIS standard H8866-2 is 60% or more and 95% or less.   6. The ink jet printer according to claim 5, wherein each of the pixels is formed so as to be shifted by approximately half of the pixel pitch for each line.   7. The ink jet printer according to claim 5, wherein the ink head is composed of a line head.   The inkjet printer according to claim 5, wherein the heating and pressing unit is configured to further control a heating and pressing time when the recording medium is heated and pressed. 9. The heating and pressurizing unit includes a pressure roller for pressing the recording medium, and a Young's modulus of a rubber coating layer of the pressure roller is in a range of 10 ⁶ to 10 ⁷ Pa. The inkjet printer of any one of Claims.

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