JP3546075B2 - Infrared fluorescent pigment and infrared fluorescent pigment ink composition - Google Patents
Infrared fluorescent pigment and infrared fluorescent pigment ink composition Download PDFInfo
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Description
【０００１】
【産業上の利用分野】
本発明は、赤外蛍光体および赤外蛍光体インク組成物に関するもので、特に赤外線に対する応答速度が速く、高速で読み取るのに充分な発光出力を有する赤外蛍光体および赤外蛍光顔料インク組成物に関するものである。
【０００２】
【従来の技術】
従来、赤外蛍光体顔料としては、ネオジムとイッテルビウムからなる無機蛍光体が知られている（特公昭５３ー６０８８８号）。
【０００３】
しかしながら、このような無機粉末の蛍光体顔料は、樹脂などで固めて使用に供する場合には問題が無いが、インクとして印刷するような場合には、粒子の径をできるだけ小さくしておかなければ高い分解能が得られないが、その反面、粒子を細かくすると極端に発光出力が低下するという不都合があった。
【０００４】
従って、事実上一定以上の粒子径を確保することが必要になるが、この場合、インク化するに際し、バインダとの比重がかけはなれていることもあって、インク中での沈降が激しく、その印刷物は、蛍光体顔料がバインダの被膜の奥深くに隠れてしまい、赤外線が容易に透過することが困難となり、この点からも発光出力が低下することが認められた。
【０００５】
しかし、本発明者らの知見によれば、この無機蛍光体顔料はそれ自体はもともと発光出力は大きく、事実、８００ｎｍにおいて放射するＧａＡｌＡｓ発光ダイオードを用いて、この無機蛍光体の発光を測定すると、発光の最大ピークは９８０ｎｍ付近であることが確認された。これは励起されたＮｄからエネルギー伝達を受けたＹｂの発光であり、近赤外波長で最も普通に用いられているシリコン光検出器（例えば、ＳｉーＰＩＮ光検出器）との波長のマッチングが良好である。但、本発明者らの実験によれば、この無機蛍光体顔料は、上記の特有の問題点の他にも、応答速度も著しく遅く、高速読み取りにも問題があるという新しい事実を見出したのである。
【０００６】
【発明が解決しようとする課題】
そこで、本発明では、ネオジムとイッテルビウムからなる蛍光体のもつ上記の特徴を活かしながら、その固有の問題を解決し、特に、高速読み取りを行う時に、充分な発光出力を満足するような赤外蛍光体を提供することを目的とするものである。
【０００７】
【課題を解決するための手段】
そのためには、まず、無機材料をそのままで使用するのではなく、有機物と結合させて、ネオジムおよびイッテルビウムと有機物とからなる全く新規の蛍光体を開発したのである。なかでも、桂皮酸とネオジムおよびイッテルビウムからなるカルボン酸複合塩が本発明の目的を最もよく達成できることを見いだした。
【０００８】
ネオジムの含有モル分率（Ｎｄ）およびイッテルビウムの含有モル分率（Ｙｂ）については、９５：５≦Ｎｄ：Ｙｂ≦３０：７０とすること、より望ましくは９０：１０≦Ｎｄ：Ｙｂ≦５０：５０とすることが、発光強度の点から特に望ましい。
【０００９】
また、本発明の赤外蛍光体顔料は、赤外線で励起後、発光強度が９０％に達するまでの立上りが時間が１００μｓｅｃ以下であり、特に赤外線に対する応答速度が速く，高速で読み取るのに充分な発光出力を有する。
【００１０】
本発明の赤外蛍光体は、如何なる方法により合成してもよいが、Ｍ．Ｄ．Ｔａｙｌｏｒらが報告した水溶液中でのイオン交換反応（Ｊ．Ｉｎｏｒｇ．Ｎｕｃｌ．Ｃｈｅｍ．，３０，１５０３−１５１１（１９６８））、あるいはＰ．Ｎ．Ｋａｐｏｏｒらが報告した非極性溶媒中でのイソプロポキシドの脱離反応（Ｓｙｎｔｈ．Ｒｅａｃｔ．Ｉｎｏｒｇ．Ｍｅｔ．−Ｏｒｇ．Ｃｈｅｍ．，Ｖｏｌ．１７，５０７−５２３（１９８７））により合成することが可能である。
【００１１】
さらに、本発明の赤外蛍光体顔料の一次粒子径は、好都合なことにおよそ赤外線波長の８０％以下となる。というのは、本発明の赤外蛍光体は無機蛍光体のような強固な一次粒子を形成しているのではなく、蛍光体の結晶に損傷を加えることが無いので、粉砕も容易であり、バインダとの分散時に赤外蛍光体顔料の粒径がより細かくなるという特徴も併せ持っているためである。すなわち、インク化の際にバインダ中に安定して分散し、印刷時にも高い分解能が得られるが、粒子径が小さくても、発光出力が低下することはない。
【００１２】
本発明の赤外蛍光体顔料の密度は、およそ１．８ｇ／ｃｍ３程度であり、赤外蛍光体の密度（ρ１）と有機バインダの密度（ρ２）との間で、ρ１／ρ２≦１．８の関係を満たすため、インク中での沈降も少なく、その印刷物も、蛍光体顔料がバインダの被膜の奥深くに隠れてしまい、赤外線が容易に透過することが困難となるというような問題が排除できる。バインダとしては、如何なるものでも良いが、特に望ましいのはアクリル樹脂が挙げられる。また、溶媒は必要に応じて使用すれば良い。溶剤としては，水、アルコール、ケトン、エステル、エーテル、芳香族炭化水素系溶剤、脂肪族炭化水素系溶剤が単独もしくは混合して用いられる。
【００１３】
また、赤外蛍光顔料インク組成物を種々の印刷方式で適用する場合に応じて、分散剤、消泡剤、界面活性剤および電導性付与剤等を用いても良い。必要に応じて、各種整色染料、蛍光染料等を併用しても良い。
【００１４】
【作用】
本発明では、第一に、無機材料をそのままで使用するのではなく、有機物と結合させて、粒子径を小さくし、インク中での沈降を防止し、赤外線で高速読み取りを行う際に、充分な発光出力を得ることができる。第二にネオジムおよびイッテルビウムとを共存させることで、赤外線に対する応答速度が速く，高速で読み取るのに充分な発光出力をもたせることができる。
【００１５】
本発明の蛍光体はＧａＡｌＡｓ発光ダイオードで発光測定を行うと、９８０ｎｍ付近に発光ピークが最大となった。これは上記の無機蛍光体の発光形態と類似している。しかし、応答速度が無機蛍光体の２０倍以上も速く、高速読み取りを行う際には、特に本発明の蛍光体が有効となってくる。
【００１６】
無機蛍光体と異なって、有機物を分子中に配置させており、この有機物としては、カルボン酸、β−ジケトンの中から選ばれる少なくとも１種が用いられる。特にカルボン酸の一種としての桂皮酸が、化学的安定性に優れている。
【００１７】
更に、桂皮酸以外のカルボン酸についても検討を行ったところ、ほぼ同等の応答速度を得た。但し、これとの関係で、桂皮酸はとくに発光出力が他の物よりも２倍以上あり、読み取りの出力がきわだって大きい。この原因については、詳細は不明であるが、桂皮酸との結合により、蛍光体中の希土類金属のイオン間距離が、赤外領域での吸収・発光に適合するように、調整されるためと考えられる。
【００１８】
【実施例】
以下，本発明の具体的な実施例について説明するが，本発明はこれら実施例に限定されるものではない。
【００１９】
実施例１
桂皮酸１．２４ｇ（８．３７ｍｏｌ）と水酸化ナトリウムＯ．３７ｇ（８．３７ｍｏｌ）を各々１２Ｏｍｌのイオン交換水に撹拌しながら加えて，桂皮酸ナトリウム水溶液を得た。この水溶液をＯ．１Ｎ水酸化ナトリウム水溶液でｐＨ１Ｏに調整し，次に塩化ネオジム６水和物Ｏ．５Ｏｇ（１．３９ｍｏｌ）と塩化イッテルビウム６水和物Ｏ．５４ｇ（１．３９ｍｏｌ）をイオン交換水５Ｏｍｌに完全に溶解させて得た水溶液を，上記桂皮酸ナトリウム水溶液に室温で撹拌しながら，添加していくと桂皮酸ネオジム・イッテルビウム（１／１）複合塩が沈殿生成物として得られた。その後Ｏ．１Ｎ塩酸で反応液をｐＨ５になるように調整し２時間撹拌を行った。得られた沈殿生成物は，濾過・洗浄後１２Ｏ℃で５時間乾燥し，桂皮酸ネオジム・イッテルビウム（１／１）複合塩を得た。収量は１．６２ｇ（収率：９３．１％）であった。
【００２０】
図１に桂皮酸ネオジム・イッテルビウム（１／１）複合塩の発光スペクトルを示す。
【００２１】
ＧａＡｌＡｓ発光ダイオードを励起源とした。発光の最大ピークは９８０ｎｍ付近でブロードな発光を示した。
【００２２】
図２に上記蛍光体のＮｄ／Ｙｂの組成比と発光強度の関係を示す。Ｎｄ／Ｙｂ（モル比）＝７／３で発光が最大を示した。
【００２３】
実施例２
実施例１において、桂皮酸を安息香酸に変更した以外は同様の方法で行い、安息香酸ネオジム・イッテルビウム（１／１）を合成した。
【００２４】
比較例１
Ｎｄ２Ｏ３１７ｇと、Ｙｂ２Ｏ３２０ｇと、Ｌｉ２Ｏ３１１ｇと（ＮＨ４）Ｈ２ＰＯ４１４０ｇとを充分良く混合し、石英製のフタ付きルツボに充填した後、電気炉に入れ、室温から７００℃迄、一定昇温速度で２時間で昇温し、しかる後７００℃で２時間焼成した。焼成終了後、ただちに電気炉から取り出し空気中で冷却した。蛍光体は、ルツボごと水で煮沸し、冷却後、１Ｎ−硝酸で洗浄し、その後水洗して乾燥し、ＬｉＮｄ０．５Ｙｂ０．５Ｐ４Ｏ１２を得た。これをボ−ルミルにより、平均粒径が２μｍになるまで粉砕した。
【００２５】
比較例２
実施例１において、塩化ネオジム６水和物Ｏ．５Ｏｇ（１．３９ｍｏｌ）と塩化イッテルビウム６水和物Ｏ．５４ｇ（１．３９ｍｏｌ）を塩化ネオジム６水和物１．０ｇ（２．７８ｍｏｌ）に変更した以外は同様の方法で行い、桂皮酸ネオジム（１／１）を合成した。｛過渡現象測定｝
図３に実施例１および比較例１の蛍光体の過渡現象を示す。２ｍｓｅｃ間隔でＧａＡｌＡｓ発光ダイオードを照射し、Ｓｉ−ＰＩＮ光検出器で検出した。その結果、実施例１の蛍光体は比較例１の蛍光体に比べ、立ち上がり速度が２０倍以上速いことがわかる。
【００２６】
｛高速読み取り試験｝
実施例１〜２および比較例１〜２の蛍光体を各々直径５ｍｍ、厚み２ｍｍの円盤上に成形した。高速読み取り試験方法は、試料を２０ｍ／ｓｅｃの速度で走査して、ＧａＡｌＡｓ発光ダイオードを照射し、Ｓｉ−ＰＩＮ光検出器で検出した。その結果、実施例１〜２の蛍光体の発光出力は検知できたが、比較例１〜２の蛍光体の発光出力は検知できなかった。
【００２７】
実施例３
実施例１で合成した赤外蛍光体を用いて、赤外蛍光体１重量部と、ポリビニルアルコ−ル４重量部と、水／エチルアルコ−ル（５／５）２０重量部とを、混合し、ボールミルで２４時間分散し、インクを作製した。このインクを１０μｍの厚さでスクリーン印刷により紙に塗布した。得られた印刷物はＧａＡｌＡｓ発光ダイオードを照射し、Ｓｉ−ＰＩＮ光検出器で検出できた。
【００２８】
【発明の効果】
上記から明かなように，実施例１〜２で得られた赤外蛍光体は，比較例１〜２で得られた蛍光体に比較し，高速読み取りにおいて、充分な発光出力を提供する。また、実施例３からインク組成物としても有用であることがわかる。このことからこの発明によって得られる赤外蛍光体および赤外蛍光体インク組成物は，高速読み取りにおいて、充分な発光出力を提供することが可能である。
【図面の簡単な説明】
【図１】本発明の実施例１で示す蛍光体の発光スペクトルを示した図である。
【図２】実施例１と同様のネオジムおよびイッテルビウムと有機物からなる赤外蛍光体のネオジムとイッテルビウムとの比率と発光強度との関係を示す図である。
【図３】実施例１と比較例１の各蛍光体につきパルス光励起後の蛍光強度の過渡的状況を示す図である。[0001]
[Industrial applications]
The present invention relates to an infrared fluorescent substance and an infrared fluorescent substance ink composition, and particularly to an infrared fluorescent substance and an infrared fluorescent pigment ink composition, which have a fast response speed to infrared light and have a light emission output sufficient for high-speed reading. It is about things.
[0002]
[Prior art]
Conventionally, an inorganic phosphor composed of neodymium and ytterbium has been known as an infrared phosphor pigment (Japanese Patent Publication No. 53-60888).
[0003]
However, such an inorganic powder phosphor pigment has no problem when it is hardened with a resin or the like to be used, but in the case of printing as ink, the particle diameter must be as small as possible. Although a high resolution cannot be obtained, on the other hand, there is a disadvantage that when the particles are made finer, the light emission output is extremely reduced.
[0004]
Therefore, it is necessary to secure a particle diameter of a certain level or more in practice, but in this case, when the ink is formed, the specific gravity with the binder may be too large, and the sedimentation in the ink is severe. In the printed matter, it was recognized that the phosphor pigment was hidden deep in the binder film, making it difficult for infrared rays to easily pass therethrough, and from this point, the emission output was also reduced.
[0005]
However, according to the findings of the present inventors, this inorganic phosphor pigment itself has a large luminous output by itself, and in fact, when the emission of this inorganic phosphor is measured using a GaAlAs light emitting diode emitting at 800 nm, It was confirmed that the maximum peak of light emission was around 980 nm. This is the emission of Yb that receives energy transfer from the excited Nd, and its wavelength matching with the most commonly used silicon photodetector (for example, Si-PIN photodetector) at the near infrared wavelength. Good. However, according to the experiments of the present inventors, this inorganic phosphor pigment has a new fact that, besides the above-mentioned specific problems, the response speed is extremely slow and there is also a problem in high-speed reading. is there.
[0006]
[Problems to be solved by the invention]
In view of the above, the present invention solves the inherent problem of the phosphor composed of neodymium and ytterbium while taking advantage of the above-mentioned features, and particularly, an infrared fluorescent material that satisfies a sufficient emission output when performing high-speed reading. It is intended to provide the body.
[0007]
[Means for Solving the Problems]
For that purpose, first, an inorganic material was not used as it is, but was combined with an organic substance, and a completely new phosphor composed of neodymium, ytterbium, and an organic substance was developed. Among them, it has been found that a carboxylic acid complex salt composed of cinnamic acid, neodymium and ytterbium can best achieve the object of the present invention.
[0008]
The molar fraction of neodymium (Nd) and the molar fraction of ytterbium (Yb) should be 95: 5 ≦ Nd: Yb ≦ 30: 70, more preferably 90: 10 ≦ Nd: Yb ≦ 50: A value of 50 is particularly desirable in terms of emission intensity.
[0009]
In addition, the infrared phosphor pigment of the present invention has a rise time of 100 μsec or less until the emission intensity reaches 90% after being excited by infrared rays, and particularly has a fast response speed to infrared rays, which is sufficient for high-speed reading. It has a light emission output.
[0010]
The infrared phosphor of the present invention may be synthesized by any method. D. An ion exchange reaction in an aqueous solution reported by Taylor et al. (J. Inorg. Nucl. Chem., 30, 1503-1511 (1968)), N. It can be synthesized by the elimination reaction of isopropoxide in a nonpolar solvent reported by Kapoor et al. (Synth. React. Inorg. Met.-Org. Chem., Vol. 17, 507-523 (1987)). It is.
[0011]
Further, the primary particle size of the infrared phosphor pigments of the present invention is advantageously less than about 80% of the infrared wavelength. This is because the infrared phosphor of the present invention does not form strong primary particles such as an inorganic phosphor, and does not damage crystals of the phosphor. This is because it also has a feature that the particle size of the infrared fluorescent pigment becomes finer when dispersed with a binder. That is, the ink is stably dispersed in the binder at the time of ink conversion, and high resolution can be obtained even during printing, but the light emission output does not decrease even if the particle diameter is small.
[0012]
The density of the infrared phosphor pigment of the present invention is about 1.8 g / cm 3 , and between the density of the infrared phosphor (ρ1) and the density of the organic binder (ρ2), ρ1 / ρ2 ≦ 1. .8, there is little sedimentation in the ink, and the printed matter also has the problem that the phosphor pigment is hidden deep in the binder coating, making it difficult for infrared rays to easily pass through. Can be eliminated. Although any binder may be used, an acrylic resin is particularly preferable. Further, a solvent may be used as needed. As the solvent, water, alcohol, ketone, ester, ether, aromatic hydrocarbon solvent, or aliphatic hydrocarbon solvent is used alone or in combination.
[0013]
In addition, a dispersant, an antifoaming agent, a surfactant, a conductivity-imparting agent, and the like may be used depending on the case where the infrared fluorescent pigment ink composition is applied by various printing methods. If necessary, various coloring dyes, fluorescent dyes and the like may be used in combination.
[0014]
[Action]
In the present invention, first, the inorganic material is not used as it is, but is combined with an organic substance to reduce the particle size, prevent sedimentation in the ink, and perform high-speed reading with infrared light. Light emission output can be obtained. Second, the coexistence of neodymium and ytterbium has a high response speed to infrared rays, and can provide a sufficient light emission output for high-speed reading.
[0015]
When the emission of the phosphor of the present invention was measured by using a GaAlAs light emitting diode, the emission peak became maximum around 980 nm. This is similar to the emission form of the inorganic phosphor described above. However, the response speed is more than 20 times faster than the inorganic phosphor, and the phosphor of the present invention is particularly effective for high-speed reading.
[0016]
Unlike an inorganic phosphor, an organic substance is arranged in a molecule. As the organic substance, at least one selected from carboxylic acids and β-diketones is used. In particular, cinnamic acid as a kind of carboxylic acid has excellent chemical stability.
[0017]
Furthermore, when carboxylic acids other than cinnamic acid were examined, almost the same response speed was obtained. However, in connection with this, cinnamic acid has a light emission output more than twice that of other substances, and the read output is extremely large. Although the details of this cause are unknown, it is because the bond between the phosphor and the rare earth metal in the phosphor is adjusted to be compatible with absorption and emission in the infrared region by bonding with cinnamic acid. Conceivable.
[0018]
【Example】
Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.
[0019]
Example 1
1.24 g (8.37 mol) of cinnamic acid and sodium hydroxide O.I. 37 g (8.37 mol) of each was added to 120 ml of ion-exchanged water with stirring to obtain an aqueous solution of sodium cinnamate. This aqueous solution was added to O.D. The pH was adjusted to 10 with a 1N aqueous sodium hydroxide solution, and then neodymium chloride hexahydrate O.D. 5Og (1.39 mol) and ytterbium chloride hexahydrate An aqueous solution obtained by completely dissolving 54 g (1.39 mol) in 50 ml of ion-exchanged water was added to the above-mentioned aqueous solution of sodium cinnamate with stirring at room temperature to obtain a neodymium cinnamate-ytterbium (1/1) composite. The salt was obtained as a precipitation product. Then O. The reaction solution was adjusted to pH 5 with 1N hydrochloric acid and stirred for 2 hours. The resulting precipitate was filtered, washed and dried at 120 ° C. for 5 hours to obtain neodymium cinnamate-ytterbium (1/1) complex salt. The yield was 1.62 g (yield: 93.1%).
[0020]
FIG. 1 shows the emission spectrum of neodymium cinnamate-ytterbium (1/1) complex salt.
[0021]
A GaAlAs light emitting diode was used as the excitation source. The maximum peak of light emission showed broad light emission at around 980 nm.
[0022]
FIG. 2 shows the relationship between the Nd / Yb composition ratio of the phosphor and the emission intensity. Light emission showed the maximum at Nd / Yb (molar ratio) = 7/3.
[0023]
Example 2
Example 1 Neodymium ytterbium benzoate (1/1) was synthesized in the same manner as in Example 1 except that cinnamic acid was changed to benzoic acid.
[0024]
Comparative Example 1
17 g of Nd 2 O 3 , 20 g of Yb 2 O 3, 11 g of Li 2 O 3 and 140 g of (NH 4 ) H 2 PO 4 are sufficiently mixed and filled into a quartz crucible with a lid, and then placed in an electric furnace. Then, the temperature was raised from room temperature to 700 ° C. at a constant rate for 2 hours, followed by firing at 700 ° C. for 2 hours. Immediately after the completion of the firing, it was taken out of the electric furnace and cooled in air. The phosphor was boiled with water together with the crucible, cooled, washed with 1N-nitric acid, then washed with water and dried to obtain LiNd 0.5 Yb 0.5 P 4 O 12 . This was pulverized by a ball mill until the average particle size became 2 μm.
[0025]
Comparative Example 2
In Example 1, neodymium chloride hexahydrate O.D. 5Og (1.39 mol) and ytterbium chloride hexahydrate Neodymium cinnamate (1/1) was synthesized by the same method except that 54 g (1.39 mol) was changed to 1.0 g (2.78 mol) of neodymium chloride hexahydrate. ｛Transient measurement｝
FIG. 3 shows the transient phenomena of the phosphors of Example 1 and Comparative Example 1. The GaAlAs light emitting diode was irradiated at an interval of 2 msec and detected by a Si-PIN photodetector. As a result, it can be seen that the phosphor of Example 1 has a rising speed that is at least 20 times faster than the phosphor of Comparative Example 1.
[0026]
｛High-speed reading test｝
The phosphors of Examples 1 and 2 and Comparative Examples 1 and 2 were each formed on a disk having a diameter of 5 mm and a thickness of 2 mm. In the high-speed reading test method, the sample was scanned at a speed of 20 m / sec, irradiated with a GaAlAs light emitting diode, and detected with a Si-PIN photodetector. As a result, the emission outputs of the phosphors of Examples 1 and 2 could be detected, but the emission outputs of the phosphors of Comparative Examples 1 and 2 could not be detected.
[0027]
Example 3
Using the infrared fluorescent substance synthesized in Example 1, 1 part by weight of the infrared fluorescent substance, 4 parts by weight of polyvinyl alcohol, and 20 parts by weight of water / ethyl alcohol (5/5) were mixed. And dispersed in a ball mill for 24 hours to prepare an ink. This ink was applied to paper by screen printing in a thickness of 10 μm. The obtained printed matter was irradiated with a GaAlAs light emitting diode and could be detected by a Si-PIN photodetector.
[0028]
【The invention's effect】
As is clear from the above, the infrared phosphors obtained in Examples 1 and 2 provide a sufficient emission output in high-speed reading as compared with the phosphors obtained in Comparative Examples 1 and 2. Example 3 also shows that the composition is useful as an ink composition. Accordingly, the infrared phosphor and the infrared phosphor ink composition obtained by the present invention can provide a sufficient light emission output in high-speed reading.
[Brief description of the drawings]
FIG. 1 is a diagram showing an emission spectrum of a phosphor shown in Example 1 of the present invention.
FIG. 2 is a diagram showing the relationship between the ratio of neodymium and ytterbium of the same infrared phosphor made of neodymium and ytterbium and an organic substance and the emission intensity as in Example 1.
FIG. 3 is a diagram showing a transient state of fluorescence intensity after excitation of pulsed light for each phosphor of Example 1 and Comparative Example 1.
Claims (7)
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| JP12696294A JP3546075B2 (en) | 1994-05-16 | 1994-05-16 | Infrared fluorescent pigment and infrared fluorescent pigment ink composition |
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| JP12696294A JP3546075B2 (en) | 1994-05-16 | 1994-05-16 | Infrared fluorescent pigment and infrared fluorescent pigment ink composition |
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