Optical sensor and thermal sensor

Abstract: An optical sensor has a photosensitive portion which has a first layer (12) including oxo metallic phthalocyanine pigment and a second layer (10) consisting of organic polysilane and shows a sensing of light with a change of color. The optical sensor can also be used as a thermal sensor.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical sensor and a thermal sensor. 2. Description of the Prior Arts Many kinds of thermal sensors and optical sensors having a structure where a thermosensitive material and a photosensitive material are applied to the surface of paper, film, etc. have already been put to practical use and are being used. Moreover, there are many types of mediums in the form of thermosensitive paper and photosensitive paper for recording and displaying images such as letters, figures, etc. However, few of the conventional sensors meet a demand for a sensor having an excellent sensitivity, being easily manufactured and whose characteristic is stably maintained. SU-A-501 619 describes for example a thermo sensitive indicator composition consisting of 35-55 wt.-% acylated aromatic amine as thermo sensitive agent, 0.01-1.5 wt.-% pigment (e.g. phthalocyanine blue), 0.86-6.5 wt.-% binder and balance solvent for indicating temperatures in the range of 65-147 °C. SUMMARY OF THE INVENTION An object of the present invention is to provide a plane-type optical sensor and a thermal sensor having an excellent sensitivity, easily manufactured and whose characteristic is stable, where a combination of new materials and a physical and chemical reaction of these materials by adding light energy and heat energy thereto are utilized. A thermal sensor according to the present invention is characterized in comprising a thermosensitive portion or a photosensitive portion (hereinafter referred to as lamination layer portion) composed of a first layer including oxo metallic phthalocyanine pigment and a second layer consisting of organic polysilane, or of a single layer of organic polysilane wherein oxo metallic phthalocyanine pigment is dispersed, and showing a sensing of heat or light with a change of color. BRIEF DESCRIPTION OF THE DRAWINGS This and other objects and features of this invention will become clear from the following description taken in conjunction with the preferred embodiments with reference to the accompanied drawings in which: Figs. 1A to 1C are views showing a thermal and/or optical sensor with a lamination layer portion according to the present invention; Figs. 2A to 2C are views showing a thermal and/or optical sensor of the dispersion-type according to the present invention. Figs. 3A and 3B respectively show the chemical formula of organic polysilane and that of oxo metallic phthalocyanine pigment; Fig. 4 is a graph showing a change in the light absorbance of a (PhMeSi)x/TiO-Pc lamination layer film which is an embodiment by a heating, where a quantity of ultraviolet ray irradiation is the parameter; Fig. 5 is a graph showing a absorption spectrum of the (PhMeSi)x/Tio-Pc lamination layer film after ultraviolet ray irradiation, where a quantity of ultraviolet ray irradiation is the parameter; Fig. 6 is a graph showing a result of an FT-IR measurement of phenylmethylpolysilane which is an embodiment before (the upper) and after (the lower) ultraviolet ray irradiation; Fig. 7 is a graph showing a change in the absorption spectrum when ultraviolet ray is irradiated on a solution where titanylphthalocyanine is dispersed in a toluene solution of phenylmethylpolysilane; Fig. 8 shows the chemical formulae showing a process of decomposition of phenylmethylpolysilane by photon or heat; Fig. 9 is a graph showing a result of an FT-IR measurement of each of (1) only phenylmethylpolysilane (PhMeSi)x, (2) the (PhMeSi)x/TiO-Pc lamination layer film, (3) after ultraviolet ray is irradiated on the (PhMeSi)x/TiO-Pc lamination layer film for two hours, and (4) after the lamination layer film is heated at 250°C and decolored; and Fig. 10 is a graph showing a change in the light absorbance, by heating, of the (PhMeSi)x/TiO-Pc lamination layer film when a first layer is an evaporation film of the simple body of oxo metallic phthalocyanine pigment, where a quantity of ultraviolet ray is the parameter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Figs. 3A and 3B respectively show the chemical formulae of organic polysilane and oxo metallic phthalocyanine pigment which constitute a lamination portion of a sensor according to the present invention. By heating the lamination layer portion to a temperature equal to or higher than the pyrolyzing point of organic polysilane, the organic polysilane of the second layer is decomposed. Since the pyrolyzing point of organic polysilane is higher than its glass transition point, the second and first layers mix by the above heating, which enables a contact of the above-described decomposition product of organic polysilane and oxo metallic phthalocyanine pigment. Thereby, the decomposition product of organic polysilane reacts on oxo metallic phthalocyanine pigment to decolor the oxo metallic phthalocyanine pigment. Therefore, a thermal sensor having the above-described type of lamination layer portion can be used as a sensor for detecting whether or not the temperature has risen to a temperature equal to or higher than the pyrolyzing point of organic polysilane. Next, when ultraviolet ray is irradiated on the above lamination layer portion, organic polysilane of the second layer is decomposed (photon decomposition) by the light energy of the ultraviolet ray. At this point of time, however, the decomposition product remains in the second layer, so that nothing is changed externally. Thereafter, by heating the lamination layer portion on which ultraviolet ray is irradiated to a temperature equal to or higher than the glass transition point of organic polysilane, similarly to the above-described case, the second and first layers mix, so that the decoloring reaction of oxo metallic phthalocyanine pigment is caused by a contact of organic polysilane with the oxo metallic phthalocyanine pigment. Therefore, an optical sensor having the above-described type of lamination layer portion can be used as a sensor for detecting whether or not ultraviolet ray has been irradiated. As described above, in the lamination layer portion according to the present invention, the decoloring of oxo metallic phthalocyanine pigment is caused by two kinds of processes (heating to a temperature equal to or higher than the pyrolyzing point of organic polysilane, and irradiating ultraviolet ray plus heating to a temperature equal to or higher than the glass transition point). Therefore, by conducting the above-described processes, that is, the [heating] or the [irradiating ultraviolet ray plus heating], selectively on the lamination layer portion, the laminated portion can be used for selectiv thermal and/or optical sensing. The following is a more detailed description of the selectiv thermal and/or optical sensing method: i) Fig. 1A shows a cross sectional view of the thermal and/or optical sensor. On a base layer 14 made of paper, film, etc., the lamination layer consisting of an oxo metallic phthalocyanine pigment layer 12 (which may include binder polymer) and an organic polysilane layer 10 is formed. Although the entire lamination layer serves as a sensing layer, only a portion can be used for selective sensing. Firstly, thermal selective sensing will be explained. When temperature of a portion of the lamination layer rises above the pyrolyzing point of polysilane by selective heating, decoloration of the oxo metallic phthalocyanine pigment at the portion occurs. This portion can be distinguished from the remaining portion which has not been heated, since colors are different between these portions. Because the decoloration reaction of the oxo metallic phthalocyanine pigment is irreversible, the heated portion is recorded on the lamination layer after the sensing. For the selective heating, laser beam and thermal head can be used. ii) Fig. 1B shows how optical selective sensing is performed. When the lamination layer is irradiated with an ultraviolet ray 18 with a mask 16 being placed over a part of the surface thereof, as shown in the figure, the photon decomposition reaction of the organic polysilane is caused at the irradiated portion 20. This decomposition cannot be viewed by the eye. Then, by heating the entire surface of the irradiated portion to a temperature equal to or higher than the glass transition point of organic polysilane, both of the layers mix, so that the oxo metallic phthalocyanine pigment is decolored only in a portion 22 where there is the organic polysilane decomposed by the irradiation of ultraviolet ray (Fig. 1C). When binder polymer is used for the first layer 12, it is required that the heating after the irradiation of ultraviolet ray is to a temperature equal to or higher than the glass transition point of the binder polymer. Moreover, when a dispersion-type layer 30 (where oxo metallic phthalocyanine pigment is dispersed in organic polysilane) is formed on the base layer 14 by mixing organic polysilane and oxo metallic phthalocyanine pigment as shown in Figs. 2A to 2C, the dispersion-type layer can in the same manner as shown in Fig. 1B serve as a sensing layer. This is because even if ultraviolet ray is irradiated, there is no sufficient chance for organic polysilane and oxo metallic phthalocyanine pigment to contact with each other unless the layer is heated, so that a satisfactory decoloring reaction is not caused. Therefore, this dispersion-type structure can also be used as an optical sensor and a thermal sensor in the same manner as that of the above-described lamination-layer-type structure. A more detailed description of the embodiment of the present invention will hereinafter be given with reference to the drawings. <Formation of a Lamination Layer Film> Firstly, phenylmethylpolysilane (PhMeSi)x was produced as an embodiment of the organic polysilane. The following is the method. Under the existence of 13g metallic sodium, 50g phenylmethyldichlorosilane (0.28mol) was heated to 135°C in 200ml dry toluene, and was reacted for approximately 11 hours while being agitated. After a cooling, ethanol was added to the solution where dark violet precipitation had been deposited to make the sodium which had not reacted into ethoxide. After the precipitation was filtered out, the solution was dried, and was dissolved in toluene. The solution was dropped into ethanol and re-precipitated to obtain phenylmethylpolysilane. The yield of the phenylmethylpolysilane was 10.2g and 34%. In Fig. 3A showing the phenylmethylpolysilane, R1 represents the phenyl radical and R2 represents the methyl radical. Next, titanylphthalocyanine TiO-Pc (shown in Fig. 3B) as an example of the oxo metallic phthalocyanine pigment where Ti is a metal X. The titanylphthalocyanine used was α type manufactured by Sanyo Shikiso Co., Ltd. The lamination layer film consisting of the α type and phenylmethylpolysilane was produced as hereinafter described. Ninety-mg titanylphthalocyanine was added to 6ml tetrahydrofuran (THF). After kneaded for a whole day and night in a ball mill, it was dispersed. Ninety-mg polyvinyl butyral (S-LEC BM-2 manufactured by Sekisui Chemical Co., Ltd. was used) was added thereto, and it was dispersed in a ball mill for one more hour to be made into coating liquid. This was spin-coated on a transparent glass substrate (silica glass or slide glass) to form a titanylphthalocyanine dispersion film. Next, 35mg phenylmethylpolysilane was dissolved in 0.35ml benzene, and it was spin-coated on the titanylphthalocyanine dispersion film to form a (PhMeSi)x/TiO-Pc lamination layer film. In both of the titanylphthalocyanine dispersion film and the phenylmethylpolysilane film, uniform layers were extremely easily obtained by the spin-coating. <Optical and Thermal Characteristics of the Lamination Layer Film> Fig. 4 shows a change in absorbance, to a 690nm red light, of the (PhMeSi)x/Tio-Pc lamination layer film formed as described above when the lamination layer film was heated to 300°C after ultraviolet rays having intensities of 0 to 39.2J/cm 2 were irradiated at room temperature. From the figure, it is understood that, for example, when the lamination layer film is heated to approximately 240°C, there is a large difference in absorbance between the portion where ultraviolet ray is irradiated (39.2J/cm 2 ) and the portion where ultraviolet ray is not irradiated (OJ/cm 2 ). This indicates that this lamination layer film can be used for an optical sensor for ultraviolet ray. That is, the optical sensor is placed at a place where ultraviolet ray is to be detected, and by heating the sensor to approximately 240°C thereafter, whether or not ultraviolet ray is irradiated is detected by an extremely clear change of color (that is, the difference in absorbance). Further, by previously irradiating ultraviolet ray on a part of the lamination layer and leaving it at a place where temperature rises, the lamination layer can be used as a thermal sensor for detecting whether or not the temperature at the place has risen to a range between 200°C to 300°C. The lamination layer film can also be used for a thermal sensor which can finely detect temperature by previously irradiating a different quantity of ultraviolet ray on each portion of the lamination layer film, respectively. Fig. 4 also shows that by heating the lamination layer film to a temperature equal to or more than approximately 300°C, the absorbance is decreased (that is, decoloring is caused) even if ultraviolet ray is not previously irradiated, which indicates that the lamination layer film can also be used as a thermal sensor. <Principle of the Decoloring> In order to search the cause of such optical and thermal characteristics of the (PhMeSi)x/Tio-Pc lamination layer film, firstly, the decomposition of phenylmethylpolysilane by the irradiation of ultraviolet ray was examined. After 300nm to 400nm ultraviolet rays having intensities of 0J/cm 2 to 5.1J/cm 2 , respectively, were irradiated to a simple component film of phenylmethylpolysilane, the absorbance of the film to 200nm to 400nm ultraviolet rays was measured. Fig. 5 shows the result. A peak of 1 λ MAX =331nm which appears when ultraviolet ray is not irradiated (0J/cm 2 ) rapidly disappears after ultraviolet ray is irradiated. Since the peak of λ MAX =331nm corresponds to an Si-Si compound which is the principal chain of phenylmethylpolysilane, it is understood that the Si-Si compound which is the principal chain is cut off by the irradiation of ultraviolet ray. Moreover, Fig. 6 shows an FT-IR spectrum of phenylmethylpolysilane measured before and after the irradiation of ultraviolet ray (the upper is before the irradiation, and the lower is after the irradiation), where the existence of Si-OH compound and Si-O-Si compound is confirmed. From the above, it is understood that by irradiating ultraviolet ray on phenylmethylpolysilane, the Si-Si compound which is the principal chain is cut off to form a polymer having a bond in siloxane. The formation of the siloxane chain (Si-O-Si) which is a loose compound by the decomposition of phenylmethylpolysilane shows that the phenomenon that the degree of freedom of polymer movement at the ultraviolet-ray-irradiated portion is improved (that is, a glass transition point Tg is decreased) is one of the causes of a shift (see Fig. 4) of the decoloring reaction toward a low temperature side. Next, in order to examine the decoloring reaction of titanylphthalocyanine TiO-Pc, an examination was made with a dispersion solution of titanylphthalocyanine. Titanylphthalocyanine was dispersed in a toluene solution of phenylmethylpolysilane, and after ultraviolet ray was irradiated thereon for 0 to 60 minutes, the absorption spectra of the solution were measured. Fig. 7 shows the result. It is understood that in a dispersion solution where a free contact of phenylmethylpolysilane and titanylphthalocyanine is possible, the decoloring reaction is caused only by the irradiation of ultraviolet ray. As a result of the above research, it is considered that the decoloring phenomenon of the (PhMeSi)x/TiO-Pc lamination layer film is caused in the following process. Firstly, by the irradiation of ultraviolet ray, the Si-Si compound of phenylmethylpolysilane is cut off as shown in Fig. 8, so that decomposition products such as silyl radical, siloxane compound, Si-H compound, etc. are produced. When the temperature is not high, however, the decoloring reaction of titanylphthalocyanine pigment is not caused, since these decomposition products cannot move from the phenylmethylpolysilane layer to the titanylphthalocyanine layer. When the lamination layer film is heated to a temperature equal to or higher than the glass transition point temperature Tg of phenylmethylpolysilane, phenylmethylpolysilane having the silyl radical and siloxane compound moves to the titanylphthalocyanine layer, and decomposes a phthalocyanine ring to decolor the titanylphthalocyanine pigment. Fig. 9 shows the result of the FT-IR measurement in each of the following conditions: (1) only phenylmethylpolysilane (PhMeSi)x; (2) the (PhMeSi)x/TiO-Pc lamination layer film; (3) after ultraviolet ray is irradiated on the (PhMeSi)x/TiO-Pc lamination layer film for two hours; and (4) after, further to the condition (3), the lamination layer film is heated at 250°C and decolored. By comparing (1) and (2), it is confirmed that absorption peaks 1330, 1280, 1120, 1060 and 890cm -1 shown by a mark ○ in (2) are those of titanylphthalocyanine pigment. These peaks still remain after the irradiation of ultraviolet ray (3), although it is hidden in a large absorption band of 1000 to 1100cm -1 showing the formation of the Si-O-Si compound by the photon oxidation of the organic polysilane. After the heating (4), however, these peaks shown by the mark ○ disappear, and instead, the peak (approximately 920cm -1 ) of Si-O-Ti compound that is speculated to be a reaction product of Si-OH compound, which is a decomposition product of phenylmethylpolysilane after the irradiation of ultraviolet ray (3) and titanylphthalocyanine pigment, is generated. As described above, by this embodiment, it has been clarified that by heating the (PhMeSi)x/TiO-Pc lamination layer film to an appropriate temperature after the irradiation of ultraviolet ray, images can be recorded with extremely high contrast. Moreover, as its mechanism, it was clarified that the Si-Si principal chain of the organic polysilane is decomposed by the previous ultraviolet ray irradiation, and active species such as silyl radical, etc. which is the decomposition product thereof reacts on the oxo metallic phthalocyanine pigment to decolor the oxo metallic phthalocyanine pigment. Fig. 4 further shows that even after a large amount of ultraviolet ray (39.2J/cm 2 ) is irradiated, the decoloring does not occur until the temperature reaches 200°C. Therefore, the recording portion where an image is once recorded is extremely stable in a normal condition (at room temperature), so that a high contrast at the time of the recording is maintained for a long period of time. In the above-described embodiment, a mixture of oxo metallic phthalocyanine pigment with a binder (phenylmethylpolysilane) whose glass transition point is relatively low was used as the first layer of the lamination layer film. Fig. 10 is a graph showing a change (the conditions are the same as those in Fig. 4 of the above-described embodiment) in the light absorbance according to the heating temperature when the first layer of the lamination film is an evaporation layer consisting of only oxo metallic phthalocyanine pigment and the second layer consists of phenylmethylpolysilane, where a quantity of ultraviolet irradiation is the parameter. The relation nearly the same as that shown in Fig. 4 is obtained, from which it is understood that quantitatively, the above-described examination applies to this case. The temperature at which the light absorbance decreases, however, is closer to the low temperature side compared with the case shown in Fig. 4, so that the decoloring reaction is caused at a lower temperature. In the above description, only the lamination layer structure was described. From the results of the above-described various experiments, however, it is clear that when a dispersion-type monolayer is formed by mixing the organic polysilane and the oxo metallic phthalocyanine pigment, the monolayer can be used as an optical sensor and as a thermal sensor similar to the above-described embodiment of the lamination layer construction. As described above, the present invention as an optical sensor can be used as a monitor sensor by affixing it on a portion where ultraviolet ray is not to be irradiated, and also can detect whether or not a predetermined amount of ultraviolet ray has correctly been irradiated by affixing it on a portion where ultraviolet ray is to be irradiated. Further, if the temperature in the heating thereafter is uniform, since the discoloring degree of oxo metallic phthalocyanine pigment is varied according to a quantity of ultraviolet irradiation, an approximate quantity of ultraviolet irradiation can be judged. As a thermal sensor, by affixing a thermal sensor according to the present invention on a portion, e.g. a bearing portion, etc. of a rotating machine, where it is dangerous if the operation temperature exceeds a predetermined temperature (or by applying the thermo-sensitive portion of the lamination layer structure directly to the portion), a dangerous condition can be detected at a glance. Furthermore, since the thermal sensor according to the present invention does not return to its original condition if once decolored by being heated to a temperature equal to or higher than a predetermined temperature, a dangerous portion can be found even after an operation of the machine is finished. Moreover, since the degree of the decoloring is varied according to the temperature to which the sensor is heated, approximately how many degrees of temperature the sensor has been heated to can be found by comparing with a predetermined color standard. Since the colors of the lamination layer and the dispersion-type layer 30 do not change as long as the layers are maintained at room temperature in a normal condition, the thermal and/or optical sensor of the present invention is capable of preserving the results of sensing. In any of the above-described cases, the present invention, where a change in the light absorbance of the pigment by light and heat is extremely large, serves as a clear optical sensor and a clear thermal sensor. All of the materials used for the present invention are organic materials, whereby the lamination layer film can easily be produced. Further, since it is stable chemically and thermally at an ordinary temperature, the lamination layer film can be maintained for a long period of time, no deteriorating of characteristics as an optical and thermal sensor being caused.

Claims: An optical sensor characterized in that the photosensitive portion comprises a first layer (12) including oxo metallic phthalocyanine pigment and a second layer (10) consisting of organic polysilane, or a single layer (30) of organic polysilane wherein oxo metallic phthalocyanine pigment is dispersed, and which shows a sensing of light with a change of color. The optical sensor according to claim 1, wherein in said photosensitive portion, an absorbance for red light differs between a portion (22) where light (18) is irradiated and a portion where light is not irradiated when heated after light is irradiated. The optical sensor according to claim 1, wherein in said photosensitive portion, organic polysilane in said second layer (10) is decomposed by light energy at a portion where ultraviolet ray is irradiated when ultraviolet ray is irradiated, and thereafter, the decomposed organic polysilane and oxo metallic phthalocyanine pigment in the first layer (12) react when heated to a temperature equal to or higher than a glass transition point to decolor the oxo metallic phthalocyanine pigment at the portion (22) where ultraviolet ray is irradiated. A thermal sensor containing phthalocyanine pigment and showing a sensing of heat with a change of color, characterized in that the thermosensitive portion comprises a first layer (12) including oxo metallic phthalocyanine pigment and a second layer (10) consisting of organic polysilane, or a single layer (30) of organic polysilane wherein oxo metallic phthalocyanine pigment is dispersed. The thermal sensor according to claim 4, wherein temperature can finely be detected by previously irradiating a different quantity of ultraviolet ray on each portion of said thermosensitive portion, respectively.

Inventors: KAKUI MIKIO, YOKOYAMA MASAAKI, KAKUI, MIKIO, YOKOYAMA, MASAAKI
Applicants: MITA INDUSTRIAL CO LTD, MITA INDUSTRIAL CO. LTD.
Application year: 1991
Main classification: G03C1
IPC codes: G01J1, G01N31, G03C1, G01K11, B41M5