JP3624545B2 - Inkjet recording medium - Google Patents

Description

【００１４】
【数４】

【００１５】
配向度の値が１であればベーマイトは無配向である。この値が小さいほど配向の度合いが高く、０であれば完全なｂ軸配向、すなわちすべてのベーマイト結晶粒子のｂ軸がシート面に対し垂直であることを示す。ベーマイトの配向度が０．５を超える場合は、ベーマイト層の透明性が不足するので不適当である。ベーマイト層の透明性が不足すると、透明シートの場合にはヘイズが高くなるので好ましくない。本発明の記録媒体ではベーマイト層は色素の担持層となる、基材として紙のように不透明なものを用いたような場合にも、透明性の高い層に色素が担持されている方が、発色が良好で色濃度の高い記録が可能になる。ベーマイトの配向度が０．３以下の場合は、さらに好ましい。
【００１６】
このように配向したベーマイトを含む多孔質層は、ベーマイトゾルを含む塗工液を塗布し乾燥することにより形成される。これは主としてベーマイト結晶の異方性に起因するもので、ベーマイトゾル塗工液の乾燥過程で、基材上にｂ軸が垂直になるように配向するものとみられる。ベーマイトゾルにおいてベーマイト結晶粒子が単分散している場合だけでなく、ゾル粒子がある程度二次凝集している場合も同様である。しかし、ベーマイトキセロゲルを粉砕して得られた粉末をバインダとともに基材上に塗布することによっては、このように配向したベーマイト層を得ることはできない。
【００１７】
ベーマイトゾルは、上記の細孔容積の多孔質層を形成するものを選択する必要があるが、一般のベーマイトゾルは細孔半径が１０〜３０ｎｍの範囲にある細孔の細孔容積が不足するのでこの細孔容積を大きくする必要がある。たとえばアルコキシドの加水分解法によるベーマイトゾルの場合、従来のベーマイトゾルに比べて加水分解時間を長時間にするなどして結晶一次粒子がより成長したものを用いるのが好ましい。
【００１８】
基材としては特に限定されず、種々のものを使用できる。具体的には、ポリエチレンテレフタレートなどのポリエステル系樹脂、ポリカーボネート系樹脂、エチレン−テトラフルオロエチレン共重合体などのフッ素系樹脂のようなプラスチック類や紙類を好適に使用できる。プラスチック類のフィルムやシートあるいは各種ガラスなどの透明体の他、布、紙、金属等の不透明体、エチレン−テトラフルオロエチレン共重合体などのフッ素樹脂フィルムなどの半透明体を適宜用い得る。これらの基材には、ベーマイト多孔質層の接着強度を向上させるなどの目的で、コロナ放電処理や各種アンダーコートを行うこともできる。
【００１９】
基材として紙などのようにインク吸収性のある材料も使用できるし、ポリエステルフィルムなどの吸収性のない材料も使用できる。基材とベーマイトを含む多孔質層の中間に、インク吸収性の樹脂層やシリカ質の多孔質層などを設けてもよい。ベーマイトを含む多孔質層の上層にさらに他の層を設けてもよい。
【００２０】
ベーマイトを含む多孔質層の厚さは、基材のインク吸収特性にも依存するが、１〜５０μｍの範囲にあることが好ましい。厚さが１μｍ未満の場合には、インクの吸収性が不足したり発色が不充分となるおそれがあるので好ましくない。厚さが５０μｍを超える場合には、多孔質層の機械的強度が低下したり、記録物の色彩を阻害されるおそれがあるので好ましくない。ベーマイトを含む多孔質層の厚さが５〜３０μｍである場合はさらに好ましい。
【００２１】
ベーマイトを含む多孔質層を記録媒体の最上層に設ける場合は、鮮やかな発色を得る意味で好ましい。記録物の光沢性や耐擦傷性をさらに付与するために、表面に保護層を設けてもよい。表面保護層としてはシリカの球状一次粒子が相互に結合した構造を有し、シリカの二次粒子からなる粉末が実質的に層中に含まれない、厚さ０．１〜３０μｍのシリカゲル層を用いることが好ましい。
【００２２】
ベーマイトを含む多孔質層としては、５０重量％以上がベーマイトであることが好ましい。さらに、８０重量％以上がベーマイトである場合は、鮮やかな発色が得られるので特に好ましい。ベーマイトを含む多孔質層において、ベーマイト以外にバインダを含む場合は、多孔質層の強度が向上するので好ましい。ベーマイトおよびバインダ成分以外にも、多孔質層の特性を損なわない範囲で、シリカなどの無機顔料や各種の添加剤を含有することができる。
【００２３】
バインダとしては、一般にデンプンやその変性物、ポリビニルアルコール（ＰＶＡ）やその変性物、スチレンブタジエンゴム（ＳＢＲ）ラテックス、アクリロニトリルブタジエンゴム（ＮＢＲ）ラテックス、ヒドロキシセルロース、ポリビニルピロリドンなどの有機物を使用できる。これらのうち、ＰＶＡを採用すると擬ベーマイトの好ましい物性を実質的に阻害することなく、またインク受容層の機械的強度を十分にできるので特に好ましい。バインダの含有量は、ベーマイトの５〜５０重量％程度を採用するのが好ましい。バインダの含有量が５重量％未満の場合は多孔質層の強度が不充分となり、逆に５０重量％を超えるとインクの吸収性を阻害するおそれがあるので好ましくない。バインダのより好ましい含有量は１０〜３０重量％である。
【００２４】
ベーマイトを含有した多孔質層を基材上に設ける手段としては、ベーマイトゾルにバインダと溶媒を加えてゾル状塗工液にし、これを基材に塗布したあと乾燥する方法が好ましい。塗布方法は、例えば、ダイコーター、ロールコーター、エアナイフコーター、ブレードコーター、ロッドコーター、バーコーター、コンマコーターなどが採用できる。スラリーの溶媒としては、水系、非水系のいずれも採用できる。
【００２５】
【実施例】
例１（実施例）
容量２リットルのガラス製反応器（セパラブルフラスコ、撹拌羽根・温度計付き）に水９００ｇ（５０モル）とイソプロパノール７５１ｇ（１２．５モル）を仕込み、マントルヒーターにより液温を７５℃に加熱した。撹拌しながらアルミニウムイソプロポキシド２０４．２５ｇ（１モル）を添加し、液温を７５〜７８℃に保持しながら１２０時間加水分解を行った。そのあとイソプロパノールを留去しながら９５℃に昇温し、酢酸６ｇ（０．１モル）を添加して４８時間９５〜９７℃に保持して解膠した。さらにこの液を４００ｇになるまで濃縮し、白色のベーマイトゾルを得た。得られたゾル液の固形分は、１５重量％であった。
【００２６】
このゾルにポリビニルアルコール（ケン化度９９．８％、重合度４０００）をベーマイト固形分に対して１０重量％加え、厚さ１００μｍの白色ポリエチレンテレフタレートフィルム上にバーコーターを用いて塗布し、１４０℃で乾燥して記録媒体を得た。乾燥後の塗工層の厚さは３０μｍであった。この記録媒体の塗工層の細孔分布（細孔半径がそれぞれ１〜３０ｎｍ、１０〜３０ｎｍ、３０〜１００ｎｍの細孔の容積）、配向度を表１に示す。
【００２７】
例２（比較例）
加水分解の時間を１２０時間から２４時間に代えた以外は、すべて例１と同様にして固形分は１５重量％の白色のベーマイトゾルを得た。このゾルを用いて例１と同様に記録媒体を得た。この記録媒体の塗工層の細孔分布、配向度を表１に示す。
【００２８】
例３（比較例）
容量２リットルのガラス製反応器（セパラブルフラスコ、撹拌羽根・温度計付き）に水９００ｇ（５０モル）とイソプロパノール７５１ｇ（１２．５モル）を仕込み、マントルヒーターにより液温を７５℃に加熱した。撹拌しながらアルミニウムイソプロポキシド２０４．２５ｇ（１モル）を添加し、液温を７５〜７８℃に保持しながら９６時間加水分解を行った。そのあとイソプロパノールを留去し、冷却、濾過、１６０℃で乾燥してベーマイトキセロゲルを得た。さらにこれを粉砕して平均粒径３μｍの白色の粉末を得た。
【００２９】
この粉末をポリビニルアルコール（ケン化度９９．８％、重合度４０００）水溶液に固形分換算で粉末１００重量部に対してポリビニルアルコール１０重量部の比で加え、全体の固形分濃度１５重量％の塗工液を調製した。この塗工液を厚さ１００μｍの白色ポリエチレンテレフタレートフィルム上にバーコーターを用いて塗布し、１４０℃で乾燥して記録媒体を得た。乾燥後の塗工層の厚さは２９μｍであった。この記録媒体の塗工層の細孔分布、配向度を表１に示す。
【００３０】
例４（実施例）
例１と同じ固形分１５重量％のベーマイトゾルに、ポリビニルアルコール（ケン化度９６．５％、重合度２６００）をベーマイト固形分に対して１０重量％加え、坪量１２８ｇ／ｍ^２の上質紙上にバーコーターを用いて塗布し、１４０℃で乾燥して記録媒体を得た。乾燥後の塗工層の厚さは２５μｍであった。この記録媒体の塗工層の細孔分布、配向度を表１に示す。ここで細孔分布は、基材を含む記録媒体および基材のみの細孔分布を測定し、基材の分を差し引くことにより塗工層の細孔分布を求めた。
【００３１】
例５（比較例）
例３と同じベーマイト粉末をポリビニルアルコール（ケン化度９６．５％、重合度２６００）水溶液に固形分換算で粉末１００重量部に対してポリビニルアルコール１２重量部の比で加え、全体の固形分濃度１５重量％の塗工液を調製した。この塗工液を坪量１２８ｇ／ｍ^２の上質紙上にバーコーターを用いて塗布し、１４０℃で乾燥して記録媒体を得た。乾燥後の塗工層の厚さは２５μｍであった。この記録媒体の塗工層の細孔分布、配向度を表１に示す。細孔分布は例４と同様にして測定した。
【００３２】
【表１】

【００３３】
評価
例１〜５の記録媒体について、セイコーエプソン株式会社製カラーインクジェットプリンタＭＪ−７００Ｖ２Ｃを用いて、ブラック、および、グリーン（シアンとイエローの混合色）で５ｃｍ×５ｃｍのテストパターンを印字した。印字したシートのブラックパターンの反射色濃度をコニカ株式会社製サクラデンシトメータＰＤＡ４５で測定した。印字したシートのグリーンパターンから、ビーディングの程度を０〜３の４段階（０：最良、３：最悪）で相対評価した。
【００３４】
【表２】

【００３５】
本発明の実施例である例１および例４では、色濃度が高く、かつ、ビーディングの生じない記録媒体が得られた。これに対し、比較のために挙げた例２では、色濃度については例１より良好であったが、ややビーディングが生じやすかった。また、比較のために挙げた例３および例５では、ビーディングは生じなかったが、色濃度がやや低かった。
【００３６】
【発明の効果】
本発明の記録媒体は、インクの吸収性が良好で、優れた発色を示し、かつ、インクを速やかに吸収することが可能である。このため、インクジェットプリンタの記録媒体として用いた場合にも、ビーディングなどの問題が発生しない。基材として透明なものを用いた場合には、透明性の良好な記録媒体となる。[0001]
BACKGROUND OF THE INVENTION
The present invention, such as Lee inkjet method, an inkjet recording medium which can clear the recording by printing method using a dye as a coloring material (hereinafter, referred to simply recording medium) related.
[0002]
[Prior art]
In recent years, in order to obtain a small amount of printed matter such as a sheet for an overhead projector, a method of editing a manuscript using a personal computer or a word processor and printing with a printer is widely used. As such a printer, an ink jet system is becoming popular because it is easy to make full color and is relatively inexpensive.
[0003]
As the recording medium in this case, since it is necessary to sufficiently absorb a large amount of ink, a coated paper or film having an inorganic porous powder or a water-absorbing resin provided on the surface as an ink receiving layer has been developed. For example, an ink jet recording medium having porous alumina xerogel having pores with a radius of 4 to 100 nm in the ink receiving layer (see Japanese Patent Application Laid-Open No. 60-245588) has been developed.
[0004]
Furthermore, in order to improve the color density of the image and obtain a higher quality image, the total volume of pores having a radius of 10 to 100 nm is 0.1 cc / g or less, mainly from pseudo boehmite. A recording sheet provided with a highly transparent adsorption layer has been developed (see JP-A-2-276670).
[0005]
[Problems to be solved by the invention]
A recording sheet provided with an adsorption layer composed of pseudoboehmite having a total pore volume of 0.1 cc / g or less having a radius of 10 to 100 nm is printed in an appropriate environment using an appropriate inkjet printer. Although a high-quality full-color image can be obtained, depending on the ink jet printer used and the use environment, the ink absorption speed is insufficient, so-called beading occurs, and a high-quality image may not be obtained. Beading is a phenomenon in which dots are distorted by joining droplets on the surface of a recording medium. An object of the present invention is to obtain a recording medium having an ink receiving layer having a sufficient absorption rate without impairing transparency.
[0006]
[Means for Solving the Problems]
The present invention relates to a porous layer containing boehmite on a substrate, wherein the pore volume is 1 to 30 nm and the pore volume is 0.3 to 1.2 cc / g, and the pore radius is 10 to 30 nm. The volume of 0.2 to 1.0 cc / g, the pore volume of 30 to 100 nm and the pore volume of 0.3 cc / g or less, and the [020] plane and [200] of boehmite obtained by X-ray diffraction Provided is a recording medium having at least one porous layer having an orientation degree defined by Formula 2 of 0.5 or less based on a peak height ratio (Formula 1) due to surface reflection .
[0007]
Boehmite is a crystal of alumina hydrate represented by the composition formula Al ₂ O ₃ .nH ₂ O (n = 1 to 1.5), and the colloidal aggregate of boehmite is also called pseudoboehmite. Since boehmite is excellent in ink absorbability, dye fixing, and the like, a porous layer containing boehmite is suitable as an ink receiving layer. In particular, the recording medium of the present invention is suitable as a recording sheet for an ink jet printer because it exhibits high adsorptivity to water-soluble anionic dyes often used in ink jet printers.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The porous layer containing boehmite needs to have a pore volume of 0.3 to 1.2 cc / g of pores having a pore radius in the range of 1 to 30 nm. When the pore volume having a pore radius in the range of 1 to 30 nm is less than 0.3 cc / g, the ink absorbability and the dye fixing property are insufficient, which is inappropriate. When the pore volume in this range exceeds 1.2 cc / g, light scattering in the porous layer containing boehmite increases, and the transparency of the porous layer is impaired, or the dye is adsorbed on this layer. The formed image becomes whitish and is inappropriate. More preferably, the pore volume of pores having a pore radius in the range of 1 to 30 nm is 0.5 to 1.2 cc / g.
[0009]
The porous layer containing boehmite needs to have a pore volume of 0.2 to 1.0 cc / g of pores having a pore radius in the range of 10 to 30 nm. If the pore volume having a pore radius in the range of 10 to 30 nm is less than 0.2 cc / g, the ink absorption rate is slow, which is not suitable. When the pore volume in this range exceeds 1.0 cc / g, light scattering in the porous layer containing boehmite increases, and the transparency of the porous layer is impaired, or the dye is adsorbed on this layer. The formed image becomes whitish and is inappropriate. More preferably, the pore volume of pores having a pore radius in the range of 10 to 30 nm is 0.3 to 0.5 cc / g.
[0010]
The porous layer containing boehmite needs to have a pore volume of 30 to 100 nm and a pore volume of 0.3 cc / g or less. When the pore volume with a pore radius of 30 to 100 nm exceeds 0.3 cc / g, light scattering in the porous layer containing boehmite increases, and the transparency of the porous layer is impaired. An image formed by adsorbing a dye on the surface becomes whitish, which is inappropriate. It is preferable that pores having a pore radius of more than 30 nm are not substantially present, and it is more preferable that the pore volume of pore radius of 30 to 100 nm is 0.1 cc / g or less.
[0011]
In the present invention, the pore volume is measured by the nitrogen adsorption / desorption method. According to this method, pore volume exceeding a pore radius of 100 nm cannot be measured, but the porous layer containing boehmite preferably has substantially no pores exceeding a pore radius of 100 nm.
[0012]
In the porous layer containing boehmite, the b-axis of the boehmite crystal needs to be oriented perpendicular to the substrate surface. When the b-axis of boehmite is not oriented perpendicularly to the sheet surface, the transparency of the porous layer is impaired even when the above-mentioned pore characteristics are present, and when the substrate is transparent, haze Is unfavorable because of the high. Here, the degree of orientation is determined by measuring the ratio of the peak heights of the boehmite [020] plane and [200] plane reflection obtained by X-ray diffraction (Equation 1) by thin film X-ray diffraction on the surface of the recording medium. , Defined by comparison with non-oriented boehmite powder. That is, the degree of orientation is defined as in the following formula 2.
[0013]
[Equation 3]

[0014]
[Expression 4]

[0015]
If the orientation value is 1, boehmite is non-oriented. The smaller this value is, the higher the degree of orientation is. If it is 0, it indicates complete b-axis orientation, that is, the b-axis of all boehmite crystal grains is perpendicular to the sheet surface. When the degree of orientation of boehmite exceeds 0.5, the transparency of the boehmite layer is insufficient, which is inappropriate. When the transparency of the boehmite layer is insufficient, haze is increased in the case of a transparent sheet, which is not preferable. In the recording medium of the present invention, the boehmite layer serves as a dye-supporting layer. Even when an opaque material such as paper is used as a base material, the dye is supported in a highly transparent layer. Good color development and high color density recording are possible. More preferably, the degree of orientation of boehmite is 0.3 or less.
[0016]
The porous layer containing the oriented boehmite is formed by applying and drying a coating liquid containing boehmite sol. This is mainly due to the anisotropy of the boehmite crystals, and is considered to be oriented so that the b-axis is perpendicular to the substrate during the drying process of the boehmite sol coating liquid. The same applies not only when the boehmite crystal particles are monodispersed in the boehmite sol, but also when the sol particles are secondarily aggregated to some extent. However, a boehmite layer oriented in this way cannot be obtained by applying a powder obtained by pulverizing boehmite xerogel onto a substrate together with a binder.
[0017]
The boehmite sol needs to be selected to form a porous layer having the above-described pore volume, but a general boehmite sol lacks the pore volume of pores having a pore radius in the range of 10 to 30 nm. Therefore, it is necessary to increase the pore volume. For example, in the case of a boehmite sol by an alkoxide hydrolysis method, it is preferable to use a boehmite sol in which primary crystal particles are further grown by increasing the hydrolysis time as compared with a conventional boehmite sol.
[0018]
It does not specifically limit as a base material, A various thing can be used. Specifically, plastics and papers such as polyester resins such as polyethylene terephthalate, polycarbonate resins, and fluorine resins such as ethylene-tetrafluoroethylene copolymer can be suitably used. In addition to transparent films such as plastic films and sheets or various glasses, opaque materials such as cloth, paper, and metals, and translucent materials such as fluororesin films such as ethylene-tetrafluoroethylene copolymer can be used as appropriate. These substrates can be subjected to corona discharge treatment and various undercoats for the purpose of improving the adhesive strength of the boehmite porous layer.
[0019]
As the base material, an ink-absorbing material such as paper can be used, and a non-absorbing material such as a polyester film can also be used. An ink-absorbing resin layer, a siliceous porous layer, or the like may be provided between the substrate and the porous layer containing boehmite. Another layer may be provided on the upper layer of the porous layer containing boehmite.
[0020]
The thickness of the porous layer containing boehmite is preferably in the range of 1 to 50 μm, although it depends on the ink absorption characteristics of the substrate. If the thickness is less than 1 μm, the ink absorbability may be insufficient or color development may be insufficient. A thickness exceeding 50 μm is not preferable because the mechanical strength of the porous layer may be reduced or the color of the recorded matter may be hindered. More preferably, the thickness of the porous layer containing boehmite is 5 to 30 μm.
[0021]
When a porous layer containing boehmite is provided on the uppermost layer of the recording medium, it is preferable in terms of obtaining a vivid color. A protective layer may be provided on the surface in order to further impart gloss and scratch resistance of the recorded matter. As the surface protective layer, a silica gel layer having a thickness of 0.1 to 30 μm having a structure in which spherical primary particles of silica are bonded to each other, and a powder composed of secondary particles of silica is substantially not included in the layer. It is preferable to use it.
[0022]
As the porous layer containing boehmite, 50% by weight or more is preferably boehmite. Further, it is particularly preferable that 80% by weight or more is boehmite because vivid color development is obtained. In the porous layer containing boehmite, a binder other than boehmite is preferable because the strength of the porous layer is improved. In addition to the boehmite and binder components, inorganic pigments such as silica and various additives can be contained as long as the properties of the porous layer are not impaired.
[0023]
As the binder, starch, modified products thereof, polyvinyl alcohol (PVA) and modified products thereof, styrene butadiene rubber (SBR) latex, acrylonitrile butadiene rubber (NBR) latex, hydroxy cellulose, polyvinyl pyrrolidone, and other organic materials can be used. Of these, the use of PVA is particularly preferable because it does not substantially impair the preferred physical properties of pseudoboehmite and can sufficiently increase the mechanical strength of the ink receiving layer. The binder content is preferably about 5 to 50% by weight of boehmite. When the binder content is less than 5% by weight, the strength of the porous layer becomes insufficient. On the other hand, when it exceeds 50% by weight, the ink absorbability may be hindered. A more preferable content of the binder is 10 to 30% by weight.
[0024]
As a means for providing the porous layer containing boehmite on the substrate, a method of adding a binder and a solvent to boehmite sol to form a sol-like coating liquid, applying this to the substrate, and then drying is preferable. As a coating method, for example, a die coater, a roll coater, an air knife coater, a blade coater, a rod coater, a bar coater, a comma coater or the like can be adopted. As the solvent for the slurry, both aqueous and non-aqueous solvents can be adopted.
[0025]
【Example】
Example 1 (Example)
A glass reactor (separable flask with stirring blade and thermometer) with a capacity of 2 liters was charged with 900 g (50 mol) of water and 751 g (12.5 mol) of isopropanol, and the liquid temperature was heated to 75 ° C. with a mantle heater. . While stirring, 204.25 g (1 mol) of aluminum isopropoxide was added, and hydrolysis was performed for 120 hours while maintaining the liquid temperature at 75 to 78 ° C. Thereafter, the temperature was raised to 95 ° C. while distilling off isopropanol, 6 g (0.1 mol) of acetic acid was added, and the mixture was held at 95 to 97 ° C. for 48 hours to peptize. The liquid was further concentrated to 400 g to obtain a white boehmite sol. The solid content of the obtained sol solution was 15% by weight.
[0026]
Polyvinyl alcohol (saponification degree 99.8%, polymerization degree 4000) was added to this sol by 10% by weight with respect to the boehmite solid content, and it was coated on a white polyethylene terephthalate film having a thickness of 100 μm using a bar coater. And dried to obtain a recording medium. The thickness of the coating layer after drying was 30 μm. Table 1 shows the pore distribution (volume of pores having pore radii of 1 to 30 nm, 10 to 30 nm, and 30 to 100 nm, respectively) and the degree of orientation of the coating layer of this recording medium.
[0027]
Example 2 (Comparative example)
A white boehmite sol having a solid content of 15% by weight was obtained in the same manner as in Example 1 except that the hydrolysis time was changed from 120 hours to 24 hours. Using this sol, a recording medium was obtained in the same manner as in Example 1. Table 1 shows the pore distribution and orientation degree of the coating layer of this recording medium.
[0028]
Example 3 (Comparative example)
A glass reactor (separable flask with stirring blade and thermometer) with a capacity of 2 liters was charged with 900 g (50 mol) of water and 751 g (12.5 mol) of isopropanol, and the liquid temperature was heated to 75 ° C. with a mantle heater. . While stirring, 204.25 g (1 mol) of aluminum isopropoxide was added, and hydrolysis was performed for 96 hours while maintaining the liquid temperature at 75 to 78 ° C. Thereafter, isopropanol was distilled off, cooling, filtration, and drying at 160 ° C. to obtain boehmite xerogel. Further, this was pulverized to obtain a white powder having an average particle diameter of 3 μm.
[0029]
This powder was added to a polyvinyl alcohol (saponification degree 99.8%, polymerization degree 4000) aqueous solution in a ratio of 10 parts by weight of polyvinyl alcohol to 100 parts by weight of the powder in terms of solid content, and the total solid content concentration was 15% by weight. A coating solution was prepared. This coating solution was applied onto a white polyethylene terephthalate film having a thickness of 100 μm using a bar coater and dried at 140 ° C. to obtain a recording medium. The thickness of the coating layer after drying was 29 μm. Table 1 shows the pore distribution and orientation degree of the coating layer of this recording medium.
[0030]
Example 4 (Example)
Polyvinyl alcohol (saponification degree: 96.5%, polymerization degree: 2600) was added to boehmite sol having the same solid content of 15% by weight as in Example 1 with respect to boehmite solid content, and on a fine paper having a basis weight of 128 g / m ² . A recording medium was obtained by coating at a temperature of 140 ° C. using a bar coater. The thickness of the coating layer after drying was 25 μm. Table 1 shows the pore distribution and orientation degree of the coating layer of this recording medium. Here, the pore distribution was determined by measuring the pore distribution of only the recording medium containing the base material and the base material, and subtracting the amount of the base material.
[0031]
Example 5 (Comparative example)
The same boehmite powder as in Example 3 was added to an aqueous solution of polyvinyl alcohol (saponification degree: 96.5%, polymerization degree: 2600) at a ratio of 12 parts by weight of polyvinyl alcohol to 100 parts by weight of the powder in terms of solid content, and the total solid content concentration A coating solution of 15% by weight was prepared. This coating solution was applied onto high quality paper having a basis weight of 128 g / m ² using a bar coater and dried at 140 ° C. to obtain a recording medium. The thickness of the coating layer after drying was 25 μm. Table 1 shows the pore distribution and orientation degree of the coating layer of this recording medium. The pore distribution was measured in the same manner as in Example 4.
[0032]
[Table 1]

[0033]
For the recording media of Evaluation Examples 1 to 5 , a test pattern of 5 cm × 5 cm was printed in black and green (mixed color of cyan and yellow) using a color inkjet printer MJ-700V2C manufactured by Seiko Epson Corporation. The reflection color density of the black pattern of the printed sheet was measured with a Sakura Densitometer PDA45 manufactured by Konica Corporation. From the green pattern of the printed sheet, the degree of beading was relatively evaluated in four stages (0: best, 3: worst) from 0 to 3.
[0034]
[Table 2]

[0035]
In Examples 1 and 4 which are examples of the present invention, a recording medium having a high color density and no beading was obtained. On the other hand, in Example 2 given for comparison, the color density was better than Example 1, but beading was somewhat likely to occur. In Examples 3 and 5 given for comparison, no beading occurred, but the color density was slightly low.
[0036]
【The invention's effect】
The recording medium of the present invention has good ink absorbability, exhibits excellent color development, and can absorb ink quickly. For this reason, problems such as beading do not occur even when used as a recording medium for an inkjet printer. When a transparent material is used as the substrate, the recording medium has good transparency.

Claims (1)

A porous layer containing boehmite on a substrate, the pore volume having a pore radius of 1 to 30 nm is 0.3 to 1.2 cc / g, and the pore volume having a pore radius of 10 to 30 nm is 0.00. 2 to 1.0 cc / g, pore volume of 30 to 100 nm in pore volume is 0.3 cc / g or less, and by reflection of [020] plane and [200] plane of boehmite obtained by X-ray diffraction An ink jet recording medium having at least one porous layer having an orientation degree defined by Formula 2 of 0.5 or less based on the peak height ratio (Formula 1) .