JP2000180259A - Integral type optical sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To qualitatively or quantatively measure the dose of light by providing irradiation and non-irradiation regions of light to be measured on a thin film containing aggregate of luminescence fine particles having TDLM (memorizing) function. SOLUTION: An optical sensor is provided with a thin film having aggregate of luminescence fine particles having TDLM function capable of increasing and memorizing luminescence strength as a function of the irradiation time of exciting light or the dose, and a mask constituted of the irradiation regions and the non-irradiation region of light to be measured on the thin film. By the TDLM function, when a thin film having aggregate of super fine particles of nanometer size (nanoparticles) is used under the condition in which the thin film contacts with air at room temperature, fluorescent intensity from the region irradiated by exciting light on the thin film of nanoparicles increases up to several times the initial strength as the function of the dose. Hereby from the contrast of photoluminescence intensity in the exciting light irradiation region and the non-irradiation region on the thin film of nanoparticles, an optional image can be formed on the nanoparticle thin film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrating optical sensor. Specifically, the photoluminescence intensity increases when irradiated with excitation light, and the photoluminescence intensity before storage (hereinafter referred to as “emission intensity”) when stored for a long time in a dark place without light irradiation and then irradiated again with light. Function that indicates, that is, memorizes (hereinafter referred to as “TDLM”
(Referred to as Time Dependent Luminescence and Memory). By comparing the light emission intensity between the light-irradiated part and the non-irradiated part, the irradiation amount (light energy x irradiation time) can be measured. The present invention relates to an integrating optical sensor having a function of:

[0002]

2. Description of the Related Art The main function of a conventional optical sensor is to measure instantaneous energy of light at the time of measurement. When measuring the amount of light irradiation (light energy × irradiation time), continuous measurement is required. In this case, it was necessary to perform measurements such as taking measurements at each time and taking in instantaneous values at each time as data. In addition, since optical-electrical conversion is basically the principle of measurement, the configuration of the apparatus itself is complicated, and it is not advantageous in terms of cost.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to apply the collective function of an aggregate of ultra-fine particles which are densely integrated and arranged this time, that is, the above-mentioned TDLM function, and to apply a light irradiation amount (light energy × light energy). Irradiation time) can be qualitatively or quantitatively measured in the form of a photoluminescence intensity ratio (contrast) between an irradiated area and a non-irradiated area, and the apparatus can be manufactured with a very simple and low-cost apparatus. An object of the present invention is to provide an integral type optical sensor that can be used.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, the light to be measured was formed on the thin film containing the aggregate of luminescent fine particles having the TDLM function. It has been found that the above object can be achieved by providing the irradiation region and the non-irradiation region of the present invention, and reached the present invention. That is, the gist of the present invention is to provide a thin film containing an aggregate of luminescent fine particles having a function of increasing, or increasing and memorizing, the emission intensity as a function of the irradiation time or the irradiation amount of the excitation light, and a coating on the thin film. An integral-type optical sensor having a mask including a measurement light irradiation area and a non-irradiation area.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The integral type optical sensor of the present invention can increase, or increase and memorize the light emission intensity as a function of the irradiation time or irradiation amount of the excitation light (TDL).
M) a thin film having an aggregate of luminescent fine particles having a function;
And a mask comprising a light irradiation area and a non-irradiation area to be measured on the thin film. The above TDLM function is a function of ultra-fine particles of nanometer size
In some cases, a thin film having an aggregate of (i.e., referred to as) is used at room temperature and in contact with air, and the photoluminescence (fluorescence) intensity from a region of the nanoparticle thin film irradiated with excitation light is exposed. Increases several times with respect to the initial intensity as a function of the irradiation time (irradiation dose). Thus, an arbitrary image (image) can be formed on the nanoparticle thin film from the difference (contrast) in the photoluminescence intensity between the excitation light irradiation region and the non-irradiation region on the nanoparticle thin film. Such an optical memory effect is an essential physical property of a multi-particle system in which nanoparticles are close to each other in a nano-particle thin film formed on a solid substrate by various coating methods.

In the present invention, the time for increasing the emission intensity
In other words, the measurement time of the light irradiation amount is preferably 1 minute or more.
1 to 10 hours.
The light intensity is usually 1.1 times or more, preferably 2 to 10 times.
It is about 0 times. In addition, sustaining, holding or memorizing the emission intensity
The time is 1 second or more at a temperature of 77 K or more, preferably
1 minute to 24 hours. Nano targeted in the present invention
The size of the particles is usually 0.5 to 100 nm, preferably
Preferably 0.5 to 50 nm, more preferably 1 to 10
nm. If the particle size is too large, it will have bulk properties.
If it is too small, it becomes an atom or molecule itself.
I will. The type of the nanoparticles is not particularly limited.
Any fine particles having a predetermined size may be used.
l-VII group compound semiconductors such as CdS, CdSe, etc.
II-VI compound semiconductor, III-V compound semiconductor, IV semiconductor
Semiconductor crystal such as conductor, TiO _Two, SiO, SiO_TwoEtc.
Inorganic compounds such as metal oxides and phosphors, fullerenes, den
Organic compounds such as drimers, phthalocyanines and azo compounds
Or composite materials thereof.
You.

[0007] In addition, as long as the object of the present invention is not impaired,
The surface of these nanoparticles may be chemically or physically modified, and additives such as a surfactant, a dispersion stabilizer and an antioxidant may be added. Such nanoparticles can be obtained by colloidal chemistry, such as the reverse micelle method (Lianos, P. et a).
l., Chem. Phys. Lett., 125, 299 (1986)) and the hot soap method (Peng, X. et al., J. Am. Chem. Soc., 119,
7019 (1997)).

In the present invention, the thickness of the thin film containing the nanoparticles (hereinafter sometimes referred to as “TDLM film”) is not particularly limited. Is about 100 μm in diameter of nanoparticles. Further, it is preferable that the nanoparticles exist in the TDLM film at a certain density or higher. In that sense, the average interparticle distance between individual nanoparticles in the aggregate of nanoparticles is usually within 10 times the particle diameter,
More preferably, it is within a range of twice the particle diameter. If the average interparticle distance is too large, the nanoparticles will not exhibit collective function.

[0009] Such patterned or uncoated (uniform) nanoparticle thin films exhibit significant TDLM effects as described above. By exciting the nanoparticle thin film (continuously or intermittently) with light of a suitable wavelength, the photoluminescence intensity from the film increases as a function of the excitation light irradiation time. The increased photoluminescence intensity of the excitation light irradiation area on the film without any special treatment is maintained at room temperature for at least several hours. It is also possible to reduce (erase) the increased photoluminescence intensity by applying a light, thermal, electrical, chemical, magnetic or mechanical external field. The photoluminescence intensity from the nanoparticle film can be controlled by changing the film thickness, the material of the solid substrate, the intensity of the excitation light, the irradiation method (continuous or intermittent), and the like. Such a thin film containing nanoparticles can be obtained, for example, by applying and drying a suspension in which nanoparticles are dispersed in a solvent on a solid substrate.

[0010] The concentration of the nanoparticles in the suspension is not particularly limited, and varies depending on the coating method and the desired film (layer) structure or particle arrangement structure and film (layer) thickness. For example, in the case of a spin coating method, the thickness of the nanoparticle thin film can be changed by changing the concentration and the rotation speed of the nanoparticles. The target solvent used here is usually water, aliphatic alcohols such as methanol and ethanol, aromatic hydrocarbons such as toluene and hexane, and mixtures thereof, and liquids such as pyridine and chloroform. Those having properties that can be dispersed are preferred. It is desirable that the dried solid be volatile in order to efficiently exhibit the TDLM function. The coating methods include casting, die coating, spin coating, dip coating (immersion coating), wetting film (liquid film), spray coating,
Ink jet method, Langmuir Blodget (L
B) method or the like can be used.

It should be noted that within a range not to impair the object of the present invention,
Additives such as surfactants, dispersion stabilizers and antioxidants, or binders such as polymers and materials that gel during the coating and drying process may be added to the suspension. The solid substrate is usually an organic solid such as a polymer or paper, or an inorganic solid material such as glass, a metal, a metal oxide, an alloy, silicon, or a compound semiconductor. For the purpose of retaining the original light emission of the TDLM function, it is preferable that the material be a material that does not show significant light emission in or near the emission wavelength band of the light-emitting fine particle aggregate. Note that the surface of the solid substrate can be modified to be hydrophobic or hydrophilic as long as the object of the present invention is not impaired. For the purpose of erasing an image stored or held by the TDLM function, a solid substrate provided with a film made of a photoconductive material may be used as the substrate.
In addition, it is possible to arbitrarily control the geometric shape of the nanoparticle thin film as described above by performing patterning (for example, a pattern with a hydrophilic / hydrophobic surface) on the solid substrate in advance. Further, a protective film or the like made of an insulating material such as SiO ₂ may be provided on the nanoparticle thin film.

The material of the mask constituting the integral type optical sensor of the present invention is not particularly limited, but it is necessary that the material has an irradiated area portion and a non-irradiated area portion of the light to be measured. The portion forming the irradiation region may be a simple hole, and examples thereof include an inorganic material such as glass and quartz, and a polymer material such as polyethylene, polypropylene, polycarbonate, and polyester. Further, the portion is N
A filter such as a D (neutral density) filter, a sharp cut filter, a polarizing filter, or a composite material thereof may be used.

The material of the portion forming the non-irradiation region is not particularly limited as long as it does not transmit the light to be measured and is solid at normal temperature. For example, stainless steel, aluminum,
Examples thereof include materials made of alloys or metals such as iron and duralumin, and high molecular compounds such as polycarbonate, polystyrene, polyethylene, vinyl chloride, polyester, Teflon, and nylon. In addition, a pigment, a pigment, and the like may be contained in each of the above materials as long as the object of the present invention is not impaired.

In the present invention, the integral type means the total irradiation amount from the measurement start time (t = 0) to the end time (t = t _f ) when the light intensity at a certain time t is I (t). ,
That is, it means that the amount obtained by integrating I (t) with respect to t from 0 to t _f can be measured. (Formula (1) below)

[0015]

(Equation 1)

As described above, the integral type optical sensor of the present invention forms an excitation light irradiation region and a non-irradiation region by irradiating excitation light, ie, light to be measured, onto the integral type optical sensor through a mask, The TDLM function increases the photoluminescence intensity of the irradiated area, and the intensity ratio (contrast) to the non-irradiated area is measured visually or by using a detector such as a photodiode, so that the light irradiation amount (light energy × irradiation time) ) Can be grasped qualitatively or quantitatively. In this case, the wavelength of the light to be measured needs to be higher than the excitation energy of the nanoparticle thin film, that is, shorter than the absorption edge of the nanoparticle thin film. For example, when CdSe having a particle size of 3.7 nm is used as the nanoparticles, the light has a wavelength of 550 nm or less.

That is, the wavelength range of the light to be measured can be changed (adjusted) by appropriately selecting the particle size and the material of the nanoparticles to be used. When the light to be measured includes a plurality of wavelengths (for example, white light or sunlight), the light is converted into monochromatic light having a desired wavelength by using a filter, or into a light of a desired wavelength range. Irradiation method. As an example of the embodiment of the integration type optical sensor of the present invention as described above, a thin film composed of an aggregate of the nanoparticles is formed on an arbitrary solid substrate, and a detachable lid-shaped cover is further formed on the nanoparticle thin film. Or a structure in which the above-mentioned or sheet-shaped mask is fixed by a metal fitting such as a hinge, a clasp, an adhesive, a magic tape, a button, a screw, a clip, a magnet, or the like.

The integral type optical sensor of the present invention has a very simple device configuration and is not costly.
It can be applied to an exposure dose sensor, a UV exposure sensing sticker for preventing sunburn, and the like. In addition, by monitoring the photoluminescence from the nanoparticle thin film in combination with a photodetector, the door lock and up of the light irradiation amount sensing type that the lock cannot be released unless the light of a specific wavelength is irradiated for a certain period of time or more. It can also be applied to fire alarms by sensing the amount of infrared irradiation by conversion.

[0019]

EXAMPLES Specific examples of the present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the present invention.

Example 1 CdSe nanoparticles having an average particle size of 3.4 nm were dispersed in toluene, a suspension having a concentration of 5 wt% was prepared, and then 1 ml of the suspension was spin-coated on a glass substrate to form a nanoparticle thin film. did. The spin coating was performed at a rotation speed of 3000 rpm. The spin coating time (time during which the substrate was rotating) was 10 minutes. Drying was performed in a dark place by air drying for 12 hours and vacuum drying for 48 hours (room temperature). First, C on the glass substrate thus obtained
The initial light emission intensity of the dSe nanoparticle thin film was measured by a fluorometer (broken line in FIG. 1A). Excitation light has wavelength 4
00 nm light was used. The emission wavelength of the CdSe nanoparticle thin film is 570 nm.

Next, the sample (sample 1) was continuously irradiated with sunlight for 90 minutes. FIG. 3 shows the time change of the sunlight intensity at this time. 3 (a), 3 (b) and 3 (c) show the temporal changes in the intensity of light having a wavelength of 400 nm, the illuminance of the sunlight, and the humidity of the atmosphere in the sunlight, respectively. The respective average values are 764.5 μW / cm ² , 8
11.6 lux, 75.3%. The ambient temperature was 24 ° C. The reason why the intensity of the sunlight is considerably weak is that the weather at this time was rainy. 90 of the sunlight
After continuous irradiation for 1 minute, the emission intensity of the nanoparticle thin film was measured by a fluorometer in the same manner as the measurement of the initial emission intensity (solid line in FIG. 1A). The emission intensity of the nanoparticle thin film is TDL
It is increased by the M effect and reaches about 1.7 times the initial light emission intensity (FIG. 1B). The TDLM effect of a sample (sample 2) in which a CdSe nanoparticle thin film was formed on a glass substrate under exactly the same conditions as the above-described thin film formation was measured by a fluorometer (FIG. 2). The excitation light has a wavelength of 40
Light of 0 nm was used. Temperature at measurement 24 ℃, humidity about 70
%. The initial luminescence intensity of Sample 2 was almost the same as the initial luminescence intensity of Sample 1, but the rate of increase thereafter was greater than that during irradiation with sunlight (about 6.4 after 70 minutes of continuous irradiation).
Times). The excitation light intensity of the fluorometer is about 950 μW / cm ²
But monochromatic light, whereas wavelength 4 in sunlight
Although the intensity of the light of 00 nm is slightly weak, light of another wavelength that can be excited is irradiated at the same time. This result suggests that the rate of increase or the rate of increase in the TDLM effect can be controlled by simultaneous irradiation of another appropriate wavelength. In addition, when the sunlight is filtered and converted to monochromatic light of 400 nm and then irradiated to the nanoparticle thin film, the ratio of photoluminescence intensity between the irradiated region and the non-irradiated region on the nanoparticle thin film is at least 6 times at the maximum. It can be seen that it can be obtained.

Application Example 1 UV of an integral type optical sensor capable of measuring the light irradiation amount (light energy × irradiation time) utilizing the TDLM effect
FIG. 4 shows a conceptual diagram of a wristwatch type simple UV exposure sensor as an application example to a sensor or the like. 4A and 4B are a top view and a sectional view from the side of the wristwatch type simple UV exposure sensor, respectively. In FIG. 4B, a structure in which a nanoparticle thin film 6 is applied on a solid substrate 5 is a basic structure. Although not shown in FIG.
A protective film such as SiO ₂ may be provided thereon.

Next, in FIGS. 4A and 4B, a non-irradiated area is formed of a material such as aluminum. A lid-shaped mask (formed of a material such as aluminum in FIG. 4). A non-illuminated area 1 and a window (illuminated area) 2 which is merely a hole or made of any transparent material is formed by a hinge 3 on a solid substrate 5.
, And can be opened and closed as shown in FIG. The (irradiation area) 2 of the lid-shaped mask may be provided with a filter such as an ND filter, a sharp cut filter or a polarizing filter, or may be provided with a plate-like substance made of glass or polymer.
A basic structure in which a nanoparticle thin film 6 is applied on a solid substrate 5, and a window 2 in the center fixed to the solid substrate 5 by a hinge 3
The portion composed of the lid-shaped mask 1 having the
By attaching the band 4 shown in (a), (b) and (c) to the main body, the band 4 can be attached to and detached from the wrist like a wristwatch. Depending on the size of the main body, a ring made of a material such as metal may be attached to the main body instead of the band 4 so as to be a ring type, or a necklace type can be obtained by replacing the chain with a chain. When the nanoparticle thin film 6 is irradiated with UV light through the window 2, an irradiation region by the window 2 and a non-irradiation region shielded by the non-irradiation region 1 of the lid-like mask are formed on the nanoparticle thin film 6. TD
Due to the LM effect, the photoluminescence intensity in the irradiation area increases with an increase in the irradiation amount of UV light. At a certain point, the lid-like mask is opened as shown in FIG. 4 (c), and the entire nanoparticle thin film 6 is uniformly exposed to an appropriate excitation light, so that the photoluminescence intensity ratio between the UV light irradiation region and the non-irradiation region is increased. The mask pattern of the lid-like mask is visible. The total amount of UV light irradiation can be known by measuring the photoluminescence intensity ratio (contrast) from the irradiated region and the non-irradiated region visually or by using a detector such as a photodetector.

Further, a part of the region where the nanoparticle thin film 6 is irradiated with UV light through the window 2 is sufficiently pre-excited with light of an appropriate wavelength (the photoluminescence intensity is saturated), and When the UV light is applied to the nanoparticle thin film 6 through the window 2 from above, the photoluminescence intensity of the pre-excitation section is not changed because the photoluminescence intensity is saturated, and the photoluminescence intensity of the remaining portion increases. At this time, the photoluminescence intensity ratio (contrast) between the pre-excitation portion and the non-pre-excitation portion in the UV light irradiation region may be measured.

Application Example 2 UV of an integral type optical sensor capable of measuring a light irradiation amount (light energy × irradiation time) utilizing the TDLM effect
FIG. 5 shows a conceptual diagram of a UV exposure sensing seal for preventing sunburn as an example of application to a sensor or the like. FIG. 5 (a) and (b)
3A and 3B are a top view and a sectional view, respectively, of the sun exposure preventing UV exposure sensing seal. In FIG. 5B, a nanoparticle thin film 10 is applied on a solid substrate 11 made of a polymer, paper, or the like, and a protective film 9 made of a material such as a polymer, vinyl, or SiO ₂ is provided on the nanoparticle thin film 10. The basic structure is the structure described. A layer 12 made of an adhesive or a pressure-sensitive adhesive is provided on the lower side of the solid substrate 11 (the surface opposite to the surface on which the nanoparticle thin film 10 is applied). Can also.

Next, referring to FIGS. 5A and 5B, a sheet-like mask (a non-irradiation region 7 formed of a material such as aluminum in FIG. 5 and a mere hole or any transparent material) is used. A window (irradiation area) 8 made of a material is fixed on the protective film 9 with an adhesive or an adhesive, and can be opened and closed or detachable as shown in FIG. It has become. The sheet mask has a window 8 at the center thereof, and the window 8 may be provided with a filter such as an ND filter, a sharp cut filter, a polarizing filter, or a plate-like substance made of glass or polymer. May be attached. By selecting a filter, it is possible to irradiate only light having a wavelength to be measured, or to adjust the absorption wavelength band to a desired range by changing the size or material of the nanoparticles in the nanoparticle thin film 10. By selecting the size of the filter and the nanoparticles and / or the material, it is possible to measure the irradiation amount of light having a wavelength related to sunburn.

When sunlight is irradiated to the nanoparticle thin film 10 through the window 8, an irradiation region and a non-irradiation region shielded by the sheet mask 7 are formed on the nanoparticle thin film 10. Due to the TDLM effect, the photoluminescence intensity in the irradiation area increases with an increase in the irradiation amount of UV light in sunlight. At some point, as shown in FIG. 5 (c), the sheet-shaped mask 7 is opened or removed, and the entire nanoparticle thin film 10 is uniformly exposed to sunlight, so that photoluminescence from a solar irradiation area and a non-irradiation area is obtained. The mask pattern of the sheet-like mask 7 according to the intensity ratio can be seen.
By comparing the photoluminescence intensity ratio (contrast) from the irradiated region and the non-irradiated region visually, the total amount of UV light irradiation can be known, and sunburn can be prevented.

Even when the sheet-shaped mask 7 is not provided, a part of the nanoparticle thin film 10 is sufficiently pre-excited with light having an appropriate wavelength (photoluminescence intensity is saturated) beforehand. From nanoparticle thin film 10
When the whole is irradiated with sunlight, the pre-excitation section does not change because the photoluminescence intensity is saturated, and the photoluminescence intensity of the remaining portion increases. The total amount of UV light irradiation can be known from the luminescence intensity ratio (contrast).

[0029]

According to the integral type optical sensor of the present invention, the phenomenon that the photoluminescence intensity increases when the excitation light is irradiated,
It uses the function of indicating the photoluminescence intensity before storage, that is, memorizing it when stored for a long time in a dark place without light irradiation and then irradiated again with light. Time) can be qualitatively or quantitatively measured in the form of the emission intensity ratio between the irradiated area and the non-irradiated area, and the apparatus configuration is simple, which is advantageous in terms of manufacturing cost.

[Brief description of the drawings]

FIG. 1A shows an emission spectrum of a CdSe nanoparticle thin film formed on a glass substrate by spin coating.
The broken line in the figure is the emission spectrum before irradiation with sunlight. The solid line shows the emission spectrum after continuous irradiation with sunlight for 90 minutes. TD
An increase in emission intensity due to the LM effect is observed. (B) A graph obtained by correcting the emission intensity of FIG. 1a with a baseline and normalizing the emission intensity before sunlight irradiation (initial emission intensity).

FIG. 2 is a graph showing the time change (TDLM phenomenon) of the emission intensity at a wavelength of 570 nm after continuously irradiating a CdSe nanoparticle thin film produced on a glass substrate by spin coating with excitation light having a wavelength of 400 nm and measuring. The emission intensity is normalized by the initial emission intensity.

FIG. 3 (a) is a graph showing a temporal change in the intensity of light having a wavelength of 400 nm in sunlight when the CdSe nanoparticle thin film is irradiated with sunlight. (B) A graph showing the time change of the illuminance of sunlight when irradiating the CdSe nanoparticle thin film with sunlight. (C) A graph showing a temporal change in the humidity of the atmosphere when the CdSe nanoparticle thin film is irradiated with sunlight.

FIG. 4 is a conceptual diagram of a wristwatch-type simple UV exposure sensor as one of application examples of the integrating optical sensor. (A) The figure which looked at the wristwatch type simple UV exposure sensor from above. (B) A sectional view from the side of the wristwatch-type simple UV exposure sensor. (C) Sectional view of the wristwatch-type simple UV exposure sensor from the side when the lid-shaped mask 1 is opened.

FIG. 5 is a conceptual diagram of a UV exposure amount detecting seal for preventing sunburn as one of application examples of the integral type optical sensor. (A) The figure which looked at the UV exposure dose sensing seal for sun protection from the upper side. (B) A sectional view from the side of the UV exposure dose sensing seal for preventing sunburn. (C) A cross-sectional view of the UV exposure dose sensing seal for preventing sunburn from the side when the sheet-shaped mask 7 is peeled off.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Non-irradiation area in lid mask 2 Window (irradiation area in lid mask) 3 Hinge 4 Band 5 Solid substrate 6 Nanoparticle thin film 7 Non-irradiation area in sheet mask 8 Window (irradiation area in sheet mask) 9 Protective film Reference Signs List 10 Nanoparticle thin film 11 Solid substrate 12 Adhesive (or adhesive) layer

Claims (8)

[Claims] 1. An aggregate of light-emitting fine particles having a function of increasing or memorizing photoluminescence intensity (hereinafter referred to as “emission intensity”) as a function of irradiation time or irradiation amount of excitation light. An integrated optical sensor, comprising: a thin film to be formed; 2. The integration type optical sensor according to claim 1, wherein the excitation light has an intensity of 1 nW / cm ² or more. 3. The integral type optical sensor according to claim 1, wherein the rate of increase of the light emission intensity is 1.1 times or more the initial light emission intensity. 4. The integral type optical sensor according to claim 1, wherein the increase time of the emission intensity at a temperature of 77 K or more is 1 second or more. 5. An average distance between light-emitting fine particles in a thin film is within 10 times the diameter of the fine particles.
The optical memory device according to any one of the above. 6. The optical memory device according to claim 1, wherein the luminescent fine particles have a particle size of 0.5 to 100 nm. 7. The optical memory device according to claim 1, wherein the luminescent fine particles are an inorganic compound. 8. The optical memory device according to claim 1, wherein the luminescent fine particles are an organic compound.