高田俊二発表論文の要旨

  

1.　Ionic conduction of silver bromide emulsion grains by the measurements of dielectric loss：

　　Shunji TAKADA : Jap. J. Appl. Phys., 12, 190 (1973) 

 

The photographic emulsion consists of the conductive silver halides and the insulating gelatin, and such a heterogeneous medium shows the dielectric dispersion, called Maxwell-Wagner effect. From the dielectric measurement, the ionic conductivity of small silver bromide crystals is measured for both pure and cadmium containing emulsions. The ionic conductivity of the pure silver bromide grains is 1.0×10^-6 Ω^-1 cm^-1 with an activation energy of 0.42 eV and the conductivity is proportional to the surface-volume ratio of the grains. The origin of the high conductivity here seems due to the nature of the surface. The conductivity decreases as the cadmium concentration is increased and by adding 0.08 mol of cadmium per mol silver bromide, it decreases by the factor of about 10^-2 with an activation energy of 0.78 eV. 

 

2.　Ionic conduction and space charge layer in silver halide photographic emulsion grains：

　　Shunji TAKADA : Photogr. Sci. Eng., 18, 500 (1974) 

 

 The ionic conductivity of the AgCl and AgBr microcrystals in the photographic emulsion has been studied with the aid of the dielectric loss measurements. It is found that the formation energy of an interstitial silver ion at the surface in AgBr and AgCl grains is 0.27 and 0.46 eV, respectively. Since the formation energy of interstitials is less than that of vacancies in both microcrystals, a positive space charge layer would be created in the sub-surface region. The conductivity of the microcrystal is one or two orders of magnitude greater than that of bulk crystals, because the concentration of interstitials in the space charge layer becomes a significant factor in small crystals. 

 

3.　Ionic conduction of silver bromide emulsion grains as affected by dye adsorption：

　　Shunji TAKADA and Tadaaki TANI : J. Appl. Phys., 45, 4767 (1974) 

 

The effects of various dyes upon the electrical conductivity of cubic silver bromide grains with edge lengths of 0.9 μm in a photographic emulsion have been studied with the aid of dielectric loss measurements. The conductivity of the grains was increased by 3,3′‐diethyl‐9‐methylthiacarbocyanine bromide (dye 1) and 1,1′‐diethyl–2,2′‐quinocyanine iodide (dye 2), and decreased by erythrosin (dye 3) and a merocyanine (dye 4). Based on the knowledge that dyes 1 and 2 are tightly attached to positively charged surface sites composed of silver ions, and that dyes 3 and 4 to negatively charged surface sites, the results are considered to provide evidence for the view on the formation of interstitial silver ions through the positively charged surface sites on silver bromide microcrystals.

 

4.　Effects of dye adsorption upon ionic conduction of silver bromide emulsion grains and discussion on dye adsorption：　　

　　Tadaaki TANI and Shunji TAKADA : Photogr. Sci. Eng., 18, 620 (1974) 

 

 The ionic conductivities obtained by dielectric loss method of cubic silver bromide emulsion grains (～1.0μm) which adsorbed various dyes and the adsorptivities of the dyes to the grains have been measured and compared. The ionic conductivity of the grains was increased by a positively charged dye with strong adsorptivity to the grains (3,3′‐diethyl‐9‐methylthiacarbocyanine bromide), and decreased by a negatively charged dye with strong adsorptivitiy (erythrosin). The conductivity of the grains was similarly affected to a smaller extent by the dyes with weak adsorptivities (phenosafranine and eosin). These observations have been interpreted as a result of the physical adsorption of the dyes to the grains with both coulombic and van der Waals’ forces between them, and is inconsistent with their chemical adsorption. Discussion is also given of the distribution of ionization energy of adsorbed dyes in emulsions. 

 

5.　Distribution of interstitial silver ions in silver bromide microcrystals：

　　Shunji TAKADA : Photogr. Sci. Eng., 19, 214 (1975) 

 

It has been pointed out that positive space charges consisting of an excess of interstitials and a deficiency of vacancies would exist in AgBr photographic emulsion grains, since the formation energy for interstitials is less than that for vacancies. Effects of iridium ions, whose distribution in a grain was varied for each sample, upon the ionic conductivity of AgBr microcrystals were studied with the aid of the dielectric loss method. The incorporation of iridium ions into AgBr grains would decrease the concentration of interstitial silver ions. A greater decrease of the conductivity was observed in the case that iridium ions were distributed densely in the vicinity of the grain surface. It was concluded that interstitials which were predominant ionic carrier, were distributed non-uniformly in a grain. Interstitials exist with higher concentration in the vicinity of surface than in the core of a grain and they are distributed densely to about 0.1 μm from surface. The calculated distribution of interstitials is qualitatively consistent with the experimental results. 

 

6.　Low-temperature triboluminescence of silver halide microcrystals：

　　Shunji TAKADA : Photogr. Sci. Eng., 21, 139 (1977)  

 

When a silver halide powder is mechanically abraded at liquid nitrogen temperature, a green emission peak centered at 550 nm and a red emission peak centered at 600 nm are observed, respectively, for silver iodobromide and silver bromide. The emission band positions are the same under blue or ultraviolet excitation. These phenomena give direct evidence that electrons can be excited to conduction bands by mechanical abrasion. The excitation of the electrons seems to be due to thermal effects associated with the movement of dislocations. Based on these observations, a mechanism for photographic pressure effects is proposed. Since the electrons are generated by the application of pressure, the effect of pressure can be considered to be similar to the effects of exposure. The pressure-induced fog would be caused by developable silver specks formed by the same process as latent image formation. The mechanism proposed to explain the desensitization by high-intensity pre-exposure (Clayden effect) can be applied at least partially to the pressure-induced desensitization. 

 

7.　硫黄増感乳剤の高照度相反則不軌と乳剤粒子のｲｵﾝ伝導度の関係：

　　高田　俊二：日本写真学会誌，42，112（1979） 

 

Relation between the ionic conductivity of silver halide emulsion grains and the sensitivity of sulfur-sensitized emulsions at high-intensity exposure was studied by using mono-dispersed fine grain emulsions (0.2 μm). The emulsions containing grains of high ionic conductivity (σ～10^-5 Ω^-1 cm^-1) exhibited no high-intensity reciprocity-law failure (HIRF) at the primitive stage, but they showed strong HIRF due to the dispersion of latent image when they were sulfur sensitized. The addition of CdCl₂ to emulsions decreased the ionic conductivity and improved this HIRF. The emulsions containing the grains of low ionic conductivity (σ～10^-8 Ω^-1 cm^-1) showed HIRF due to the limited rate of the ionic step both in primitive and sulfur-sensitized emulsions. 

The electron residence time in traps, which depends on the trap depth, and the time for the ionic step in latent image formation, which depends on the ionic conductivity, will influence the nucleation and growth processes of silver specks formation. If the time for the ionic step is shorter than the electron residence time, the dispersion of latent image will occur as the result of the increased nucleation probability. It is thought that the above situation is achieved when the emulsion of high ionic conductivity is sulfur sensitized. 

 

8.　Sensitization by photographic stabilizer as related to their influence upon ionic conduction of silver bromide emulsion 　

　　grains：

　　T.TANI, Y.SANO, S.TAKADA and M.SAITO : J. Photog. Sci., 28, 28, (1980)  

 

  The interaction of photographic stabilizers with the surface of silver bromide grains was studied to clarify the

mechanism of sensitization caused by the stabilizer. The dielectric loss and Dember effect methods were applied to

the measurement of the ionic conductivity of cubic silver bromide emulsions to which photographic stabilizers and

their related compounds were added. The compounds with adsorptivity to silver bromide grains decreased the ionic

conductivity of the emulsion grains, and increased the photographic sensitivity of the emulsions. It is considered

that sensitization by the stabilizers arises from the interaction of their anions with silver ions at kink sites, which

results in a decrease in the concentration of interstitial silver ions. 

 

9.　写真乳剤粒子のイオン伝導と空間電荷層の研究－ハロゲン化銀の感光性と物性の関係，

　　高田俊二：日本写真学会誌，44(2)，81-95，（1981）  

 

In this review, physical properties of the silver halide crystals that would be closely related to high efficiency of the latent image formation were discussed from the general point of view and then discussions were concentrated on the ionic process that was indispensable to the latent image formation. 

Ionic conductivity of the silver halide microcrystals dispersed in gelatin was measured by the dielectric loss method based on the Maxwell-Wagner-Sillars theory. It was shown that the ionic conductivity of the microcrystals was larger by several orders of magnitude than that of the large pure crystals, being proportional to the surface-to-volume ratio of the microcrystals and that the incorporation of divalent cadmium ions into the emulsions grains markedly decreased ionic conductivity. These results indicated that interstitial silver ions were the predominant charge carriers in ionic conduction, and that surface sites were responsible for the formation of the positive space-charge layer resulting in the existence of interstitial silver ions with high concentration in the microcrystals. Since the ionic carries were controlled by the surface process, the ionic conductivity was influenced by many emulsion variables, such as the grain size, surface structure of the grains and adsorption of the photographic addenta (for example, antifoggant, stabilizer and sensitizing dye). Effects of sulfur and reduction sensitization and emulsion pAg on the ionic conductivity were also examined in relation to the photographic effects. Distribution of Frenkel defects in a grain was studied theoretically and was examined experimentally by using iridium-doped AgBr grains. Further discussions were made on the effects of the space-charge layer upon the electronic process of the latent image formation. 

An attempt was made to obtain the relation between photographic sensitivity and the ionic conductivity of the emulsion grains. The emulsions containing the grains with low ionic conductivity showed high-intensity reciprocity-law failure probably due to limited rate of the ionic step. The emulsions containing the grains with high ionic conductivity showed no HIRF when they were chemically unsensitized, but they showed strong HIRF due to the dispersion of latent image when they were sulfur sensitized. These facts were interpreted by the idea that small image centers were apt to be formed dispersedly when the time for the ionic step was comparable to the electron residence time in the temporary traps. 

 

10.　A size effect on the mobility of slow electrons in microcrystalline AgBr：

　　　Akihiko HIRANO, Taizo MASUMI and Shunji TAKADA : J. Appl. Phys., 53, 3093, (1982)  

 

  Measurements of galvanomagnetic effects on AgBr microcrystals dispersed in insulating gelatin layer (photographic

emulsion grains) were performed at 4.2－40K as a function of the grain size (50nm－1.3μm) using a fast pulse technique

with blocking electrodes. The value of the mobility of slow electrons was determined to be about 10³ cm²/Vs for 400 nm 

cubic crystals at 4.2 K, much smaller than that in pure bulk crystals, and decreases with decreasing size of the microcrystals.

Additional results obtained from various specimens eliminate the possibility that this size effect due to differences of impurity

concentration. Possible mechanisms of this size effect on the mobility of slow electrons are discussed from the point of view

of surface effects.

 

11.　Electrochemical and photographic properties of silver specks formed during reduction sensitization on AgBr emulsion 　

　　　grains：

　　　Tadaaki TANI and Shunji TAKADA : Photogr. Sci. Eng., 26, 111, (1982)  

 

  Electronic properties of silver specks formed during reduction sensitization with SnCl2 on cubic and octahedral AgBr grains

were studied by the combination of two different method. The ability of the specks to capture electrons in the interior of the

grains was examined by observing the lifetime of photoelectrons though transient photoconductivity measurement. The ability

of the specks to capture electron from the outside of the grains was examined by observing the growth of the specks in the

redox buffer solution. The results obtained by those two methods were in good agreement with each other, indicating that the

specks formed with moderate reduction sensitization on the cubic grains could not capture electrons, whereas those with

heavy reduction sensitization could capture electrons. In the case of the octahedral grains, the specks which could capture

electrons were formed even with weak and moderate reduction sensitization. The results obtained in this paper indicated the

dependence of the properties of the silver specks upon the condition of their surroundings, which should be considered in the

mechanism of photographic sensitivity.

 

 

２）総説（４報） 

 

1. 超高感度・高画質ｶﾗｰﾈｶﾞﾌｲﾙﾑの開発 

　伊藤　勇，高田　俊二，池上　眞平：日化協月報，37，18（1984）

 

2. 高感度写真ﾌｲﾙﾑ 

　高田　俊二：固体物理，21，835（1986）　

 

3. 超高感度・高画質ｶﾗｰﾈｶﾞﾌｲﾙﾑの開発 

　高田　俊二，平野　積：Dennki Kagaku，56，（1988） 

 

4. 高感度・高画質を支える感光性ﾊﾛｹﾞﾝ化銀結晶の進歩 

　高田　俊二：日本写真学会誌，61，3，（1998） 

 

３）書籍執筆（２報）

 

1. “90年代の光機能材料 － ﾆｭｰﾒﾃﾞｨｱ時代のｷｰﾃｸﾉﾛｼﾞｰ”，大森豊明編，八章 画像記録からみた光機能材料（Ⅰ），

       p.202～225，株式会社工業調査会（1986） 

 

2. “改訂　写真工学の基礎 － 銀塩写真編”，(社）日本写真学会編，3章8　写真乳剤，p.292～320，コロナ社（1998） 

 

 

４）口頭発表（本論文へ引用した発表のみ記載） 

 

1. Photo-conductivity of AgBr Photographic Emulsion Grains with the Dielectric-Loss Method

 　S.Takada, 32th Annual Conference of SPSE（Boston 1979） 

 

2. Review of the Photographic Emulsion Containing Double Structure Grain 

   S.Takada、H.Ayato、S.Ishimaru, Internatinal Congress of Photographic Science（Koln 1986） 

 

3. An Innovative Rapid Access System for Halftone and Line Work 

   S.Moriuchi、N.Inoue、S.Takada, 25^th Fall Symposia ，Imaging（Virginia 1985） 

 

4. The Factors determining the Photographic Sensitivity of Coarse Emulsion Grains 

   S.Takada、N.Ohshima、Y.Nozawa、K.Mihayashi, The International West-East Symposium on the Factor influencing the 

   Photographic Sensitivity (Hawaii 1984)