高感乳剂颗粒增感机理

本文着重讨论了高速负性乳剂的化学增感和表面潜影形成机理,尤其是核壳乳剂体系的内部和表面增感对颗粒感光特性的影响。     

对高感微粒乳剂的一点探讨

“高感微粒”乳剂与多层薄后挤压、高速涂布工艺构成了当前感光胶片工业生产的新技术。富士彩底FⅡ-400的商品化引起了广泛的注意。这种新型的高感微粒乳剂采用了“集中潜影技术”,使乳剂感光度大幅度提高。根据现代对潜影形成机理的认识:有多少光量子投射到卤化银晶体表面,就会产生     

感光胶片的压力效应

本文探讨了压力对照相性能的影响。一般认为,在多种曝光条件下,胶片受压之后的灰雾总是增大的。由于AgX颗粒中会产生许多新的浅电子陷阱,引起潜影中心的分散,导致感光度的下降。实验证明,在压力作用下,晶体表面感光中心确实向内部移动,但光谱增感染料可以引起压力增感。     

过度化学成熟引起减感

对六面晶体乳剂所做的感光测定试验指出:在过度化学成熟时,潜影分散是感光度降低的主要原因。在化学成熟适度和过度的情况下,分别计量乳剂在闪光曝光时每个颗粒所形成的显影中心数,就能证实这点。但是,并非所有的感光度降低都是源于此因。本文提出再化合作用同样也会导致感光度降低。     

几种黑白负片在不同曝光量下形成的潜影中心分布

一、前言潜影中心的形成,无疑是银盐感光材料的根本性问题,是制造条件与曝光条件共同形成的结果。胶片涂层中乳剂颗粒潜影中心生成条件的综合表现,决定了该胶片的感光特性和画面质量。对潜影的研究引起了人们的很大兴趣,并形成了不同的理论观点。关于潜影中心几何尺寸的测定也作了不少工作。Hillson 等人应用 Thomson 效应,确定了潜影中心几何尺寸与氧化还原电位的关     

彩色负片利用排列结构提高感光度

本文综述了近些年来，在采用改变多层彩色胶片乳剂层排列结构的新途径，以提高彩色负片的感光度。着重介绍了通过在分色感光层的下面，再涂一层卤化银颗粒较细小的乳剂层，引起漫反射光提高该分色感光层感光度的原理和实效。文中详细地阐明了下层乳剂层的厚度和卤化银颗粒大小对上层乳剂层感光度的影响。     

影响照相感光度的因素

本文讨论了潜影的分散、再结合及光电子扩散长度等影响潜影生成效率的各种因素。大量试验表明,对于实用乳剂凭借改进φ_r来提高其感光度的余地是很少的。但是,许多研究小组指出,抑制染料减感和改善染料的光吸收不完全来增加感光度却有较大的潜力。     

国外文摘

AgBr乳剂中含金的次潜影中心H.E.Speneer,A.Bunysviroch J.Photogr.Sci.,37:202～206(1989) 硫加金增感的AgBr乳剂经高照度曝光,大部分次潜影中心都含金。该中心是将已曝光颗粒用低照度潜影增强后经标准显影检测出来的。用稀KCN溶液从潜影中心中溶解出金来。并提出了高强度曝光生成的双原子次潜影中心是AgAu的理论。这个中心的特性,对中心形成时的高效率至关紧要。     

用乳剂表面灰化法制备直接正性照相材料

一、引言直接正性照相材料,即预灰化的直接正性光漂白材料,是基于光生正穴漂白表面灰雾中心而使颗粒失去可显影性的原理。本文研究了不同表面感光度与内部感光度之比(s/i)的乳剂表面和内部灰化习性,以了     

国际照相科学大会将于1982年召开

国际照相科学委员会将于1982年9月6～10日召开国际照相科学大会,会议将由英国皇家摄影协会主持。地点在英国剑桥大学。这次大会的重点是卤化银照相,预计有下列内容:(1)卤化银的性能。(2)光解作用,潜影形成和潜影效应,增感剂聚集体的性能。(3)乳剂技术,如卤化物的沉淀及作用;各种乳剂附加物及其机械效应;化学增感;光谱增感以及感光度标准和前景展望。     

含内部调变剂的卤化银颗粒的感光乳剂

本文概述了柯达公司近年来提出的在对辐射光敏感的卤化银颗粒中,具有一个面心的立方晶体点阵结构。内部含有一种亚硝酰基配位体和一个过渡金属,如Ru(钌),Re(铼)、Os(锇)所组成的六配位体的络合物,对卤化银颗粒进行内部调变。这种乳剂颗粒用于印刷制版明室片时,可获得优良的对辐射光的感光度,提高反差;用于对辐射光敏感的彩纸,可减少低照度的互易律失效。     

The Present Status of Photographic Sensitivity

Photographic sensitivity, an intrinsically practical concept related to the smallest exposure yielding a usable result, can be considered in various ways. For the photographic scientist it depends essentially on the formation of a stable latent image by the impact of a minimum of radiant energy and on its capacity to trigger the development reaction, while technical users of photography attempt to find means, however involved, for the extraction of the requested information from recordings unavoidably made unsatisfactory by the conditions prevailing during exposure.

As to the first approach, the principle of the absorption of at least four quanta per silver halide crystal to form a stable latent image, first demonstrated in 1960, is now quite generally accepted. The practical aspect of photographic sensitivity, on the other hand, is at present strongly influenced by the techniques of image evaluation and restoration, i.e. by pattern recognition and image processing. Ultimate sensitivity does indeed not only depend on the sheer presence of exposed and developed grains, but it is judged rather by the information transmitted to the observer by the recording.     

A Contribution to Interpretation of the Photographic Characteristic Curve

The problem of the photon sensitivity of emulsion crystals is reviewed and is seen to rest on interpretation of the characteristic curve. A partial-development technique for the identification of grains hearing latent image is used to determine characteristic curves for effectively mono-sized classes of grains in a fast medical X-ray film given monochromatic exposure. The characteristic curve of a pure-bromide nominally monodisperse emulsion is also shown for monochromatic exposure. Characteristic curves of the two emulsions are analyzed according to models which assume, respectively, a unique photon sensitivity and efficiency factor, and the existence of a spread of effective photon sensitivities. Conclusions are drawn concerning the success of the partial development technique and of the analytical methods, the photon sensitivities found and the minimum size of latent image.     

The Eleventh Renwick Memorial Lecture: The Nature Of Photographic Sensitivity

This paper reviews the work on photographic sensitivity which has been carried out by the author and his colleagues, and presents the conclusions which have been drawn from it. The earlier concept of the sensitivity speck has been replaced by that of the sensitivity centre. The sensitivity speck was assumed to consist of silver or of silver sulphide and to have the function of concentrating silver atoms: the sensitivity centre is a region of enhanced reactivity associated with a crystal imperfection. The conclusion is now that the principal function of the silver sulphide is to trap positive holes and thus to prevent the regression of latent image specks. The theory of dye sensitization has been extended and a number of new features introduced. According to present ideas, the latent image is formed in two stages. In the primary stage, electrons and positive holes are liberated and the positive holes are trapped with the production of interstitial silver ions. In the secondary stage these combine with the conduction electrons to form first latent pre-image specks, then latent sub-image specks, and finally stable latent image specks. A discussion of reciprocity failure is given. The new approach to the theory of photographic sensitivity, in which the role of kink sites Is emphasized throughout, leads to the enunciation of four basic principles which must be satisfied by any theory of the formation of the latent image. Of these, only the Gurney-Mott principle has previously been recognized.     

The Quantum Sensitivity of Photographic Emulsion Grains

A method is described of obtaining the response curves of individual size classes of a photographic emulsion in which the exposure scale is expressed in absorbed quanta per grain. No assumptions of any significance are involved. The method is applied to the derivation of sensitivity characteristics of grains in modern emulsions of high speed for their average grain size, and to other emulsions not chemically-sensitized to such a high level. It is found that the sensitivity spread among grains of a single size may vary from about 1.0 to 2.0 log units, depending on the emulsion, but does not vary greatly for grains of different size in the same emulsion. The numbers of absorbed quanta involved are such that the greater part of this spread must be attributed to the fact that within a single size class grains differ widely in the numbers of quanta which they must absorb in order to be rendered developable; quantum fluctuations make only a small contribution to the spread in exposures over which grains become developable. Grains of the highest sensitivity encountered become developable after absorption of about 4 quanta, which suggests that a latent image of minimum developable size consists of 4 silver atoms.     

Experiments on Photographic Sensitivity

The methods used for preparing thin sheets of silver chloride, silve r bromide, binary and ternary mixed crystals of silver halides, and mixed crystals of silver bromide with silver sulphide and other metallic bromides are described in detail. The results of expriments on the chemical sensitization of these materials are presented. The conclusion has been reached that, as far as the formation and development of the latent image is concerned, there is no significant increase in the sensitivity of the mixed crystals compared with that of strained crystals of pure silver bromide. Experiments with antifogging agents, antiplumming agents, development accelerators and dye sensitizers and supersensitizers are briefly described , The causes of low intensity reciprocity failure in the formation of the surface and internal latent images in the thin sheets are discussed in detail and methods which may be used to diminish low intensity failure in the formation of the surface latent image are outlined.     

Exclusively Internal Latent Image

The presence of emulsion grains bearing only internal latent image (“exclusively” internal image) can be fairly definitely established by firstly developing fully, in a surface developer, and then either bleaching and developing internally, or observing if there is a further density increase on transferring the surface-developed samples to an internal developer, both methods gave similar results, which indicated that digested emulsions at normal exposure levels form internal image only in grains also bearing a surface image. An undigested emulsion formed much exclusively internal image. Solarization has often been thought to proceed by the destruction of surface image on grains in which build-up of internal silver is continuing. In agreement with this concept, good equivalence was found between solarization density losses as shown by surface development, and density gains shown by development for the exclusively internal image.     

Internal-Image Formation and Related Photographic Effects

In accordance with generally accepted views, it is shown that variations in degree of Clayden and Villard effects and in Solarizability can be broadly correlated with the surface/internal speed ratio. In particular it is shown that increase of surface/internal speed ratio by increase of digestion time, or simply by increase of exposure time, leads to a decrease in the Villard effect, and that solarizability can be greatly enhanced by kinking which increases internal sensitivity without much effect on surface response. However, among collections of commercial emulsions, correlations between surface/internal speed ratio and latent-image effects involving rehalogenation processes are masked by differences in the halogen-accepting properties of the emulsions. Observations on the Villard effect support the view that the grains which do not form surface image readily are the more sensitive ones for internal-image formation, and this should be recognised in attempting to deduce ratios of surface to internal speed.     

Model Investigation of the Effect of Cd- and Cu- Ions on the Photographic Process

The deposition of foreign substances on silver halide single crystals by means of vacuum evaporation mokes it possible to study their effect on the two stages of the photographic process-the latent image formation under exposure to light and the reduction of the exposed parts on development. The effect of cadmium, cuprous and cupric ions on the sensitivity of silver bromide crystals has been investigated. It was established that cadmium and cuprous ions promote the process of development and enhance the latent image formation. Cupric ions have a strong desensitizing effect on both stages of the photographic process. It was found that the metal ions investigated display a certain incompatibility with sulphur sensitizers. In spite of that, an appropriate concentration of cadmium ions was found to increase further the light sensitivity of silver sensitized crystals, promoting only the process of development.