JPS6240695B2 - - Google Patents

Description

[Detailed description of the invention]

Photosensitive films made of silver halide have been the main subject of photographic research. Although research has been primarily concerned with photoreduction reactions that produce latent silver photographic images, research has also focused on the reverse reaction in which silver halide is regenerated from metallic silver by the action of light or heat. . An early paper on the changes in absorption that occur in blackened photographic plates upon exposure to red light was published by Cameron and Taylor in ``Photophysical Changes in the Silver-Silver Chloride System'' [Journal of the Optical Society
of America, vol. 24, pp. 316-330 (1934)]. In this paper, the authors demonstrate that optically or chemically blackened silver halide-containing emulsions are selectively bleached, especially by red light, and become more transparent to light at bleaching wavelengths.
This effect is called color adaptation. Furthermore, it was noted that polarized bleaching light creates a dichroic birefringence image in the blackened film. Optically induced dichroism is also observed in polycrystalline silver halide layers produced by vapor deposition techniques. VP Cheerkashin is Soviet Physics―
Solid State, Vol. 13, No. 1, pp. 264-265 (1971)
reported enhanced dichroism exhibited in silver halide films containing vacuum-deposited silver adducts. It has been believed that the anisotropic absorption effect of silver halide films is due to elongated metal film colloids. This hypothesis is consistent with some absorption properties observed for granular metal layers. Optical properties of isolated gold and silver layers provided by sputtering are described by R.H. Doremus, J. Chem. Phys., vol. 42,
pp. 414-417 (1964), by R.W. Cohen et al.
Physical Review B. Vol. 8, No. 8, pp. 3689-3701 (1973), and other publications. The present inventors have invented a photosensitive thin film that can photographically record color images (natural colors) by a single exposure using ordinary white light, and a method for producing the same.
The photosensitive film of the present invention is also capable of recording images with optical anisotropy if polarized light is used to project the image to be recorded onto the film.
The image thus produced has dichroism (polarization) and birefringence. The photosensitive thin film of the present invention is of the additively-colored type. Additively colored type refers to photosensitive thin films that, when first formed, contain metallic colored centers and therefore absorb visible light over a wide wavelength range. The photosensitive thin film of the invention comprises not only a polycrystalline dielectric layer but also an underlying metal layer, preferably deposited by sputtering or vacuum deposition techniques, which causes additional coloration. The photosensitive thin films of the present invention are photosensitive as formed and record optical information through bleaching, in which the alignment of the metallic colored centers is altered by exposure to light of a selected wavelength. This change in the arrangement of the metal coloring centers makes the photosensitive film substantially more transparent to light at the wavelength used for exposure, but less transparent to light at other wavelengths. Furthermore, when polarized light is used as the bleaching light, the increase in transmittance caused by bleaching is primarily limited to light polarized in the same direction as the bleaching light. In either case, the degree of bleaching is determined by the bleaching light intensity and exposure time. The photosensitive thin film of the present invention is capable of accurately recording the intensity and polarization direction of light projected onto it, and moreover retaining most of the color information of the projected light.
Although somewhat less sensitive to blue and green light than to red light, the photosensitive thin films of the present invention are sufficient to record color optical images. The reason why the photosensitive thin films of the present invention have such a broad color sensitivity is not completely understood, but is believed to be due to the thin film microstructure provided by the manufacturing method. A further advantage of the photosensitive thin film of the present invention is that very high resolution of about 1-10 microns can be obtained. This value is comparable to the resolving power of high-resolution photographic film. The photosensitive thin film of the present invention includes at least one layer consisting of a metal layer and a transparent dielectric coating layer covering the metal layer (hereinafter referred to as a "metal-dielectric layer"). Depending on the degree of resolution or color reproducibility required, one or several metal-dielectric layers are provided. The method of making photosensitive thin films of the present invention includes the initial step of depositing a discontinuous isolated metal layer on a suitable substrate. The metal used to deposit the discrete isolated metal layer must be such a metal that exhibits plasma absorption of light when the isolated layer is surrounded by a suitable dielectric receptor. The absorption peak wavelength and peak half-width are determined by the refractive index of the dielectric as well as the size and shape of the isolated metal. Suitable metals for making the isolated metal layer are Ag, Pb, Cu, Al, Cr and Ge. The absorption properties of the metal phase of a photosensitive thin film are determined by the size and shape of the metal particles. The size and shape of the particles is determined by the structure of the initially deposited isolated metal layer, although this is significantly influenced by subsequent manufacturing steps. In order to obtain good imaging properties, the isolated layer must consist primarily of isolated metals in the size range of approximately 100-1000 Å, with approximately 15-150 Å
It must have an apparent thickness in the range of . Figure 3 is an electron micrograph of a discontinuous silver isolated layer deposited on a glass substrate, with the white band representing 0.5 microns. Following the deposition of the discrete isolated metal layer described above, a transparent coating layer consisting primarily of a suitable dielectric receptor is deposited over the isolated layer. This dielectric receptor layer must accomplish at least two functions: First of all, the dielectric receptor layer must be able to receive and conduct electrons released from the metal by the action of light from the metal colored center. Second, the dielectric receptor layer must allow diffusion of metal cations generated by photoemission from the metal colored center into the dielectric receptor layer. Dielectric receptors suitable for this purpose are
AgCl, AgBr, AgI and _PbI2 . Although the dielectric receptor is intended to form a transparent coating layer on the discrete isolated metal layer, the thickness of the transparent coating layer also affects the color image properties of the photosensitive thin film. Generally, for good results, the thickness of the continuous transparent coating layer should be at least approximately 300 mm
It is preferable that it is Å. Although resolution tends to worsen with thicker transparent coating layers, the maximum thickness of the layer is limited only by the need for transparency. Layers as thick as 1 micron or more can also be used, although no particular benefit is gained by doing so. By using the above-described method, a photosensitive material useful for recording optical information can be easily obtained. The photosensitive material includes a support means in the form of a substrate and a photosensitive film deposited on the support means.
The photosensitive thin film includes at least one metal-dielectric layer consisting of a metal layer and a transparent electric coating layer covering the metal layer. FIG. 1 is a schematic front sectional view of a specific example of the photosensitive material of the present invention comprising a glass substrate and a photosensitive thin film.
The photosensitive thin film consists of a single metal-dielectric layer including a discontinuous metal layer of isolated metal (Me) and a transparent cover layer of a dielectric receptor covering the metal layer. FIG. 2 is a schematic front sectional view of another specific example of the photosensitive material of the present invention, in which the photosensitive thin film is composed of five metal-dielectric layers. Generally, a recording material having a photosensitive thin film consisting of only a single metal-dielectric layer has high resolution. However, the intensified color image has several layers, e.g. 2-6
This is obtained when the metal-dielectric layers of the layers are provided on a single substrate. Photosensitive thin films containing two or more metal-dielectric layers are made by successively repeating the isolated layer deposition process and the dielectric layer deposition process described above. When photographically recording a color optical image using the photosensitive material of the present invention, a color real image is projected onto a photosensitive thin film containing at least one metal-dielectric layer prepared as described above. The real image is projected onto the photosensitive film by any suitable method including lenses, mirrors or similar focusing means. A prerecorded image, such as a color slide or the like, can be projected onto a photosensitive film or by contact printing, i.e. by directly exposing the photosensitive film through a transparency in contact with the film. transcribed. The exposure time required to record an image on a photosensitive thin film is determined primarily by the intensity of the recording light and secondly by the particular configuration of the film selected for processing. However, for any particular film and exposure conditions, it is easy to determine the optimal exposure time by observing the appearance of a positive image during exposure and terminating the exposure when the optimal image is obtained. Can be done. The ability of the photosensitive thin films of the present invention to record information regarding the polarization state of light enables the recording of dichroic images. Dichroic images are created by projecting a color real image onto a thin film with linearly polarized light along a selected axis. Note that the above-mentioned axis will be referred to as the "recording axis" hereinafter. Images formed using linearly polarized light are dichroic, so they exhibit good transmittance for light polarized in a direction parallel to the recording axis and can be easily observed; In contrast, viewing vertically polarized light reduces transmittance and reduces contrast and coloration. Dichroic images created by recording with polarized light have two distinct advantages over normally recorded images. First of all, the color quality of the recorded dichroic image is superior to that of a normally recorded image when viewed with white light linearly polarized in the direction of the recording axis. Second, the contrast of the dichroic image is determined by the optical axis of each polarizer (the axis where the light transmittance is maximum).
can be easily increased by placing a thin film between two crossed polarizers arranged at an angle of 45° to the recording axis of the dichroic image and viewing the recorded image with transmitted light. Both of the above two advantages come at the cost of sacrificing the intensity of the transmitted observation light to some extent.
This may not be a problem depending on the application. The plain and dichroic images produced as described above are optionally altered by further exposure to bleaching light. Of course, if it is desired to preserve the recorded image for a long period of time, care must be taken to prevent the recorded image from being exposed to stray light. However, in the absence of stray light, the recorded image is completely stable and preserved forever. The photosensitive thin films of the present invention are not only useful for recording color photographic images, but are also useful for preserving information regarding the color and polarization state of the projected light. Although the exact mechanism for the broad spectral photosensitivity of the photosensitive thin film of the present invention has not been clearly established, it is believed that the metal-dielectric layer is photosensitive as follows. When light is projected onto the structure, the light excites the metal's electrons. This may be due to internal band transitions or transfer of plasma mode energy to single electronic states. These plasma modes correspond to the collective excitation of many electrons and exhibit free electron or near-free electron characteristics. When the energy level of the excited electron exceeds an energy corresponding to the difference between the fundamental energy of the dielectric and the Fermi energy of the metal, the electron can escape from the metal to the conducting state of the dielectric. This process corresponds to photoemission, in which the effective work function of the metal (the energy required to remove an electron from the metal) is lowered due to the approach of a dielectric with appropriate conduction band energy. The nature of the dielectric layer also plays a role in the proposed mechanism. In addition to providing a path for electrons to escape through the conduction band, the dielectric must also have the ability to incorporate metal ions into the lattice. In order for the metal dissolution process to proceed quickly, the diffusion of metal ions must be relatively fast. When the diffusion coefficient of metal ions at room temperature is low, heating the structure improves its sensitivity to light. Isolated metals lose atoms by a combination of two processes: electron emission from the metal and diffusion of metal cations into the dielectric lattice. As photoemission and diffusion of metal cations continues, the lone metal finally dissolves. If an isolated metal with n atoms is represented by (M) _o , then this reaction is It is expressed as As exposure continues, the isolated metals dissolve while the light passes through the photosensitive film, thus reducing absorption and making the photosensitive film more transparent in the exposed areas. The coloring in the above process is caused by the fact that when an excited electronic state is generated by the attenuation of plasma oscillations, the peak absorption of plasma oscillations depends on the optical constants of the metal and the refractive index of the dielectric surrounding the isolated metal, as well as the size and size of the isolated metal colloid. This is due to the fact that it is strictly determined by the shape. If a discontinuous isolated metal layer is provided such that the isolated metal has a distribution in size and shape, then exposure of the thin film structure with light at a particular visible wavelength will produce a size and shape that will produce a peak absorption corresponding to the wavelength of the irradiated light. selectively removes isolated metal colloids. This selective removal of isolated metal colloids makes a portion of the structure more transparent to that particular visible wavelength than to other visible wavelengths. In this way a color image is created. The dichroic effect is well explained by the hypothesized coloration mechanism described below. When the shape of the isolated metal colloid is not spherical, its optical absorption also has anisotropy. For example, if the shape of a metal particle is represented by a wide ellipsoid, absorption in the length direction (principal axis) of this particle will be stronger for light polarized parallel to the length direction than for light polarized perpendicular to it. It will be larger than that. It is believed that the non-spherical metal particles are randomly oriented. However, if polarized light is projected, an isolated metal colloid oriented approximately parallel to the polarization direction of the projected light will dissolve at a faster rate than an isolated metal colloid oriented approximately perpendicular to the direction of polarization of the projected light. . Therefore, by projecting polarized light, the thin film structure becomes dichroic. Of course, the above explanation is just a hypothesis,
It is not intended to limit the scope of the invention. The choice of substrate used as a support means for the photosensitive film of the present invention is not critical. Any material may be used that is not detrimental to the overlying dielectric layer components and metal layer components. For example, an inert porcelain body, a glass porcelain body, treated paper, etc. are used as the substrate material. Although light-reflecting materials can also be used, it is preferable to use a light-transmissive substrate, preferably a transparent substrate, since it is easier to retrieve the information stored in the thin film. A particularly preferred substrate is glass. In some cases, it is desirable to provide a base layer on the substrate to ensure compatibility with the photosensitive thin film. Organic substrates, such as paper, for example, are provided with a base layer of SiO, and glass substrates, for example, are provided with a base layer of dielectric receptor. Deposition of the discrete discrete metal layer onto the substrate is preferably accomplished using sputtering or vacuum deposition techniques. However, other metal deposition methods such as plating methods can also be used. Although the equipment used for the deposition may be any conventional equipment, the deposition conditions used have an important effect on the imaging properties of the resulting thin film. Direct current or radio frequency sputtering
It is used to precipitate any of Ag, Pb, Cu, Cr, Ge and Al. Control of the thickness of the discontinuous metal layer and the size of the isolated metal layers is achieved by varying the sputtering voltage, substrate temperature, and bias voltage between the substrate and target. The condition of the target underlying the metal of the discrete isolated metal layer is also important. For example, partially oxidized silver targets provide better results in some cases than clean, unoxidized silver targets. Vacuum deposition techniques are also used to create discrete isolated metal layers and are particularly convenient methods for depositing Ag, Ge, Pb and Cu. The thickness of the isolated metal layer and the size distribution of the isolated metal are controlled by varying the substrate temperature, deposition temperature, evaporation temperature, and base pressure of the vacuum system. Table 1 below provides example vacuum deposition conditions used to create isolated metal layers that exhibit good imaging properties for several metals. The table shows the base pressure of the system, substrate temperature and deposition rate. Of course, these conditions are only examples of the variety of precipitation conditions that can be used.

[Table] When a photosensitive thin film consisting of multiple layers is provided,
Conditions similar to those stated in Table 1 above are used not only for the deposition of the first isolated metal layer, but also for the deposition of subsequent isolated metal layers. Following the deposition of the isolated metal layer, a dielectric receptor is vacuum deposited directly onto the isolated metal layer and a transparent overcoat layer is provided. The imaging properties of the resulting metal-dielectric layer are influenced by the deposition rate of the dielectric, the thickness of the dielectric layer, and the composition of the dielectric layer. The dielectric cover layer must consist "primarily" of at least one dielectric acceptor selected from the group consisting of AgCl, AgBr, AgI and _PbI2 . In this specification, a coating layer will be said to consist "primarily" of dielectric receptors when the dielectric receptors constitute at least approximately 50% by weight of the layer. The coating layer may consist entirely of these dielectric receptors, but a small amount, for example up to about 30% by weight, of a dopant selected from the group consisting of CuCl, CuCl ₂ and CdCl ₂ may be included in the layer. In some cases, the color imaging properties of the metal-dielectric layer are improved if the color imaging characteristics of the metal-dielectric layer are improved. Whether or not these impurities are included is determined depending on the intended use of the thin film. Of course, the coating layer may contain other components that do not interfere with the imaging properties. Table 2 below shows typical vacuum deposition conditions used to deposit a transparent dielectric coating layer on an isolated metal layer to obtain a metal-dielectric layer with good imaging properties. The table shows the system base pressure, dielectric deposition rate, and substrate temperature for several different dielectric receptors. These conditions are also just examples of the range of conditions that can be used.

[Table] Of course, if the layer thickness and size and size distribution of the isolated metal layer necessary for good image formation are obtained,
Other methods may be used to provide the discontinuous isolated metal layer and dielectric cover layer. Next, the present invention will be explained with reference to Examples. Example 1 A clean glass slide with a flat surface suitable for layer deposition was placed in a vacuum deposition chamber with a large amount of AgCl. Chamber 5x
While evacuating to 10 ^-6 Torr and keeping the slide at approximately 25°C, heat the AgCl to evaporate it to approximately
Deposition was performed on the slide at a rate of 10 Å/sec. This deposition was continued until the AgCl layer on the glass substrate was approximately 400 Å thick. Following the deposition of the AgCl base layer described above, a discrete isolated metal layer of Pb was vacuum deposited on the AgCl base layer by heating a large amount of Pb introduced into the chamber. The chamber pressure was maintained at approximately 5 x 10 ^-6 Torr during the deposition. Pb precipitation occurs at a rate of approximately 1 Å/sec, and this precipitation
This process was continued until it became Å thick. Thereafter, an approximately 400 Å thick AgCl transparent overcoat layer was vacuum deposited on the Pb layer in the same manner as the AgCl base layer deposition described above. The precipitation of Pb and the subsequent precipitation of AgCl were repeated three times, and the AgCl base layer and the four layers stacked on top of it were
A photosensitive thin film structure consisting of a Pb gold-AgCl dielectric layer was placed on a glass slide. The slides were removed from the vacuum deposition chamber and tested. A transparent film was observed on the glass surface that showed a bright purple coloration when light was transmitted through it. A portion of the thin film structure thus obtained was irradiated with visible bleaching light of several different wavelengths at an intensity of approximately 10-20 milliwatts/cm ² for approximately 1 minute to test its optical properties. The results of this bleaching are shown in FIGS. 4 and 5. FIG. 4 is a graph showing the effect on the transmittance of a thin film caused by bleaching using four different wavelengths of unpolarized light. Different wavelengths 4
Each species of light produces bleaching and different coloring effects at its wavelength and in the wavelength range near its wavelength. FIG. 5 is a graph showing dichroism caused by bleaching using three types of polarized light having different wavelengths. The bleached area not only exhibits coloration, but also substantially higher polarization for light polarized parallel to the bleaching light polarization direction (solid line) than for light polarized perpendicular to it (dashed line) near the bleaching wavelength. Indicates transmittance. Example 2 A clean glass slide with a flat surface suitable for layer deposition was placed in the substrate holder of a triode radio frequency sputtering apparatus with a silver target. The chamber was evacuated to 10 ^-6 Torr with the substrate holder maintained at approximately 25°C. After that, introduce argon gas into the chamber and increase the atmospheric pressure by 5x.
The voltage was 10 ^-3 Torr, and an rf voltage of 400 V was applied to the target, and at the same time, a DC bias voltage of 45 V was applied between the target and the substrate. Depending on this condition
Ag was deposited on the glass slide at a sputtering rate of approximately 9 Å/min. on glass slide
Sputtering was continued until the Ag layer was 100 Å thick. After the deposition of the Ag layer described above, the glass slide was removed from the sputtering apparatus and placed in a vacuum evaporator with a large amount of AgCl. 1 chamber
While evacuating to ×10 ^-6 Torr and keeping the glass slide at approximately -70°C, AgCl was heated to evaporate, and the glass slide was heated at a rate of approximately 50 Å/s.
It was deposited on the Ag layer. This precipitation was continued until the AgCl layer was approximately 1500 Å thick. The imaging properties of the photosensitive thin film thus obtained were tested by irradiating the surface of the photosensitive thin film thus obtained with a real image of a photographic slide using a 100 watt tungsten iodide lamp using a photographic lens. Images with excellent color reproduction, contrast, and resolution were obtained with approximately 15 seconds of exposure. Example 3 A clean glass slide with a flat surface suitable for layer deposition was placed in a vacuum deposition chamber with a large amount of Ag. Chamber 5x
Evacuate to 10 ^-6 Torr and press the glass slide to approx.
Ag was evaporated by heating at 50°C and deposited on the surface of the glass slide at a rate of approximately 1 Å/sec. This precipitation was continued until the Ag layer was approximately 50 Å thick. After the above-mentioned precipitation of the Ag layer, AgCl containing a small amount of CdCl ₂ is introduced into the chamber and heated to form an AgCl layer containing approximately 10% by weight of CdCl ₂ .
It was deposited onto the Ag layer of a glass slide at a rate of 100 Å/sec. This precipitation is covered by a transparent coating layer with a thickness of approximately 1500Å.
I continued until. The photosensitive thin film consisting of a single Ag metal-AgCl dielectric layer prepared by the method described above exhibited very good imaging properties in terms of color reproducibility, contrast, and resolution. It is clear that in all of the cases of photosensitive thin film fabrication of the invention described above, substantial interaction between the metal and the dielectric occurs during the deposition of one layer over another. For this reason, it is doubtful whether the isolated structure of the metal layer will remain intact during the deposition process. Unfortunately, analysis of the final structure of photosensitive thin films is currently not possible due to volatile components that interfere with electron microscopy. Nevertheless, the use of deposition conditions to form an isolated layer of the structure detailed above is essential in producing the photosensitive thin films of the present invention with sensitivity over a suitably broad wavelength range. It is clear that there is.

[Brief explanation of the drawing]

FIG. 1 is a schematic front sectional view of a specific example of the photosensitive material of the present invention comprising a glass substrate and a photosensitive thin film.
This is the case when the photosensitive thin film consists of a single metal-dielectric layer. FIG. 2 is a schematic front sectional view of another specific example of the photosensitive material of the present invention, in which the photosensitive thin film is made of five metal layers.
This is the case when it is made of a dielectric layer. Note that in FIGS. 1 and 2, Me represents an isolated metal. Third
The figure is an electron micrograph of a discontinuous silver isolated layer deposited on a glass substrate, with the white band representing 0.5 micron. Figure 4 shows the transmittance at each wavelength of the bleached portion when the photosensitive thin film of the present invention is bleached with four types of unpolarized bleaching light having different wavelengths, and the transmittance at each wavelength of the unbleached photosensitive thin film. It is a graph shown together with. Figure 5 shows the polarized light transmittance of the bleached portion at each wavelength when the photosensitive thin film of the present invention is bleached with three types of polarized bleaching light having different wavelengths, and shows the polarized light transmittance of the bleached portion for light polarized parallel to the polarization direction of the bleaching light (solid line). ) and vertically polarized light (dashed line).

Claims (1)

[Scope of Claims] 1. (a) Support means in the form of a substrate made of a light-transmitting or light-reflecting material; and (b) a metal selected from the group consisting of Ag, Pb, Cu, Al, Cr and Ge. approximately 15-150Å
discontinuous isolated metals, including isolated metals with thicknesses in the range of , and with distributions in the size range of 100-1000 Å, with various shapes to produce peak absorption corresponding to different wavelengths of illuminating light. a transparent coating layer comprising at least one dielectric receptor selected from the group consisting mainly of Ag Cl, Ag Br, AgI and Pb I ₂ and covering said discontinuous isolated metal layer. A photosensitive material for color optical imaging for recording optical information such as color, intensity and polarization state of projected light, comprising at least one dielectric layer and a photosensitive thin film deposited on the support means. 2. The photosensitive material according to claim 1, wherein the supporting means is glass. 3. The photosensitive material according to claim 1, wherein the transparent coating layer has a thickness of at least 300 Å. 4 The transparent coating layer contains Cu Cl, Cu Cl ₂ and Cd
2. The photosensitive material according to claim 1, which contains approximately 30% by weight or less of an impurity selected from the group consisting of Cl ₂ . 5. The photosensitive material according to claim 1, wherein the dielectric receptor is AgCl. 6. The photosensitive material according to claim 1, wherein the discontinuous isolated metal layer is made of Ag or Pb. 7 (a) a support means in the form of a substrate made of a light-transmitting or light-reflecting material; and (b) a metal selected from the group consisting of Ag, Pb, Cu, Al, Cr and Ge, approximately 15-150 Å thick.
discontinuous isolated metals, including isolated metals with thicknesses in the range of , and with distributions in the size range of 100-1000 Å, with various shapes to produce peak absorption corresponding to different wavelengths of illuminating light. a transparent coating layer comprising at least one dielectric receptor selected from the group consisting mainly of Ag Cl, Ag Br, AgI and Pb I ₂ and covering said discontinuous isolated metal layer. a photosensitive film deposited on the support means, comprising at least one dielectric layer; and projecting a color real image onto the photosensitive film of a photosensitive material. 8 (a) a support means in the form of a substrate made of a light-transmitting or light-reflecting material; and (b) a metal selected from the group consisting of Ag, Pb, Cu, Al, Cr and Ge, approximately 15-150 Å thick.
discontinuous isolated metals, including isolated metals with thicknesses in the range of , and with distributions in the size range of 100-1000 Å, with various shapes to produce peak absorption corresponding to different wavelengths of illuminating light. a transparent coating layer comprising at least one dielectric receptor selected from the group consisting mainly of Ag Cl, Ag Br, AgI and Pb I ₂ and covering said discontinuous isolated metal layer. a photosensitive thin film deposited on the support means; and a photosensitive thin film deposited on the support means. A method for photographically recording color optical images to obtain dichroic recorded images exhibiting enhanced color quality and contrast when viewed in linearly polarized transmitted light, comprising the step of projecting.