Optical devices, imaging devices

Abstract

To provide a light controlling element, such as variable ND filter, intensively inhibiting substantial light source influence on color reproducibility.SOLUTION: A light controlling element 1001 includes a plurality of compounds having optical absorption properties changeable due to external stimulus. The plurality of compounds each have different absorption wavelengths. The light controlling element 1001 has variable transmittance VT(λ) obtained by combining the optical absorption properties of the plurality of compounds, and satisfies NWDMax<NWDMaxFP, where NWDMax represents a maximum value of a ratio between a reference light source and a target light source (reference light source / target light source or target light source / reference light source) of a signal intensity ratio of transmitted light in each detection light wavelength region of a photodetector 1002, in a transmission state and a light-reduced state of the light controlling element 1001; NWDMaxFP represents NWDMax in concentration ratio of the plurality of compounds in which a wavelength flat TF of the VT(λ) in the detection light wavelength region is a minimum value TFFP.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a light control element, and an optical device, an imaging device, and a lens unit using the same. [Background technology]

[0002] ND (Neutral Density) filters, a type of light-adjusting element, reduce the amount of light while minimizing the impact on color, and are widely used in still and video photography. In recent years, variable ND filters that can electrically change the light attenuation of ND filters have been put into practical use, enabling previously impossible image expression. These variable ND filters use multiple compounds whose light absorption characteristics change in response to external stimuli (especially electrically), and the combination of the light absorption of these multiple compounds enables control of light attenuation while minimizing the impact on color. One of the important characteristics of ND filters is that they have little effect on color reproducibility due to the light source. An ideal ND filter has a constant transmittance independent of the wavelength of the transmitted light (maximum wavelength flatness), and such an ND filter can eliminate the effect of the light source on color. For this reason, conventional ND filters have reduced the effect of the light source on color reproducibility by improving wavelength flatness. Patent Document 1 describes an ND filter that uses a multilayer film with high wavelength flatness and has a constant light attenuation (fixed light attenuation). An ND filter with such high wavelength flatness can reduce the effect of the light source on color reproducibility. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-175225 Summary of the Invention [Problem to be solved by the invention]

[0004] Some variable ND filters use multiple compounds whose light absorption characteristics change in response to external stimuli, and exhibit ND properties through the combination of the absorption spectra of the multiple compounds. In this case, there is a limit to how much control can be given to the absorption wavelengths of the multiple compounds, making it difficult to achieve a highly flat spectrum like an ND filter whose attenuation does not change (a conventional ND filter with a fixed attenuation). The inventors have made repeated efforts to improve wavelength flatness, but it has been difficult to achieve a variable ND filter that highly suppresses the influence of the light source on color reproducibility. The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a light control element such as a variable ND filter that highly suppresses the substantial influence of the light source on color reproducibility, and a device that uses the light control element. [Means for solving the problem]

[0005] A first aspect of the present invention is an optical device including a photodetector and a photochromic element having a plurality of compounds whose light absorption characteristics change in response to an external stimulus, the plurality of compounds are compounds having different absorption wavelengths, the light-adjusting element has a variable transmittance VT(λ) that is a combination of the light absorption characteristics of the plurality of compounds; the photodetector has a detection light wavelength range of x bar: 580 nm to 680 nm, y bar: 500 nm to 580 nm, and z bar: 425 nm to 500 nm in a CIE color matching function; The reference illuminants are CIE D65, D55, D50, Illuminant B, and Illuminant C. Source? are selected from The contrast light source is 、C IE A light source is time, NWD Max <NWD MaxFP An optical device characterized by: NWD Max The maximum value of the ratio of the signal intensity of the transmitted light for each wavelength region of the detected light incident on the photodetector in the transmission state and the dimming state of the dimming element between the reference light source and the reference light source (reference light source / reference light source or reference light source / reference light source). NWD MaxFPThe wavelength flatness TF of the VT(λ) in the detection light wavelength region is the minimum value TF FP NWD at the concentration ratio of the plurality of compounds Max It is characterized in that: A second aspect of the present invention is an imaging device having an optical system with a plurality of lenses and the optical device of the present invention, characterized in that the imaging element receives light that has passed through the optical system, and the dimming element is arranged between the optical system and the imaging element as an optical filter. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a light-adjusting element such as a variable ND filter that highly suppresses the substantial influence of the light source on color reproducibility, and an optical device, an imaging device, and a lens unit that use the light-adjusting element. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram schematically illustrating an example of an optical device including a light-adjusting element according to the present invention. [Figure 2] FIG. 10 is a diagram illustrating an example of the spectral sensitivity of a photodetector. [Figure 3] FIG. 2 is a diagram illustrating an example of the spectrum of a light source. [Figure 4] 1 shows the spectrum of the change in extinction coefficient of the EC compound used in the examples. [Figure 5] 1 shows the variable absorbance spectrum and variable transmittance spectrum of the EC element of Example 1. [Figure 6] 1 shows the variable absorbance spectrum and variable transmittance spectrum of the EC element of Comparative Example 1. [Figure 7] 1 shows transmission spectra of the EC elements of Example 1 and Comparative Example 1 in a transmitted state and a dimmed state. [Figure 8] FIG. 1 is a diagram showing the evaluation results of the influence of light sources on the color reproducibility of the EC elements of Example 1 and Comparative Example 1. [Figure 9] FIG. 1 is a diagram showing the evaluation results of the influence of light sources on the color reproducibility of the EC elements of Example 1 and Comparative Example 1. [Figure 10]1 shows variable transmittance spectra of the EC elements of Examples 2 and 3. [Figure 11] FIG. 10 is a diagram showing the evaluation results of the influence of light sources on the color reproducibility of the EC elements of Examples 2 and 3. [Figure 12] 1 shows variable transmittance spectra of the EC elements of Examples 4 and 5 and Comparative Examples 2 and 3. [Figure 13] FIG. 10 is a diagram showing the evaluation results of the influence of light sources on the color reproducibility of the EC elements of Examples 4 and 5 and Comparative Examples 2 and 3. [Figure 14] FIG. 2 is a diagram illustrating an example of the spectrum of a light source. [Figure 15] 10 is a variable transmittance spectrum of the EC element of Example 6. [Figure 16] FIG. 10 is a diagram showing the evaluation results of the influence of light sources on the color reproducibility of the EC elements of Example 6 and Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0008] The photochromic element of the present invention has multiple compounds whose light absorption characteristics change in response to external stimuli, and exhibits variable light absorption in the visible light range by superimposing the multiple absorption spectra of the compounds. When the transmission spectrum of the photochromic element is plotted with wavelength on the horizontal axis and transmittance on the vertical axis, the absorption spectrum can be made closer to flat by adjusting the concentration ratio of the multiple compounds. The photochromic element of the present invention is an element that places more importance on suppressing the substantial light source effect on color reproducibility than on the flatness of the absorption spectrum, and the parameter NWD Max It is evaluated using

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following embodiments, and appropriate modifications and improvements to the following embodiments based on the ordinary knowledge of those skilled in the art are also included in the scope of the present invention, provided that they do not deviate from the spirit of the present invention.

[0010] <Optical device equipped with a light-adjusting element> Fig. 1 is a schematic diagram showing an example of an optical device equipped with a photochromic element of the present invention. In Fig. 1, the optical device 1000 has a photochromic element 1001 such as a variable ND filter, and a photodetector 1002 such as an image sensor having a plurality of detection light wavelength regions such as R (red), G (green), and B (blue). Note that if a photodetector is provided separately from the optical device 1000, the optical device 1000 does not need to have the photodetector 1002. Examples of optical devices according to this embodiment include a camera system (including a camera and a lens) with a variable ND filter, a variable transmittance window, variable transmittance glasses, and a variable reflectance mirror.

[0011] <Photodetector> The photochromic element of the present invention is intended for use with a specific photodetector. In other words, the photochromic element of the present invention is designed to function in combination with a specific photodetector. Examples include a combination of an imaging device such as a camera system with a CMOS sensor, a combination of a variable transmittance window with a human eye, a combination of variable transmittance eyeglasses with a human eye, and a combination of a variable reflectance mirror with a human eye. The photodetector has multiple detection wavelength ranges. Specifically, in the case of an imaging CMOS sensor, the detection wavelength ranges are R, G, and B, while in the case of a human eye, the detection wavelength ranges are the x-bar, y-bar, and z-bar CIE color matching functions. Examples of CIE color matching functions include CIE(1931), CIE(1964), and CIE(2006), and functions for a 2-degree or 10-degree field of view can be selected. While any value can be used to calculate RRGAC, the 2-degree field of view of CIE(1931) is particularly preferred.

[0012] The photochromic element of the present invention can also be used as a component of an optical filter in an imaging device that includes an optical system having multiple lens systems, an optical filter, and an imaging element that receives light that has passed through the optical filter. Furthermore, the photochromic element of the present invention can be combined with an imaging optical system having multiple lenses to form a lens unit. Such a lens unit can be connected to an optical device that includes a photodetector, and the lens unit is positioned so that, when connected to the optical device, transmitted light that has passed through the lens unit enters the photodetector. The photodetector has multiple detection light wavelength ranges and may be an imaging element.

[0013] <Compounds whose light absorption properties change in response to external stimuli> The light-adjusting element of the present invention absorbs light by combining multiple compounds whose light-absorption properties change in response to external stimuli. Examples of such external stimuli include electrical, thermal, optical, and pH stimuli. Examples of compounds whose light-absorption properties change in response to external stimuli include electrochromic (EC) compounds, liquid crystal compounds (including guest-host liquid crystals), thermochromic compounds, photochromic compounds, and pH-responsive compounds. Among these, compounds whose light-absorption properties change electrically are preferred in terms of stability, ease of external control, and response speed. Among compounds whose light-absorption properties change electrically, electrochromic compounds (EC compounds) and liquid crystal compounds are preferred. In particular, light-adjusting elements using EC compounds are preferred because they can achieve both a high-transmittance light-transmitting state and a low-transmittance dimming state.

[0014] In order to fabricate a light-controlling element using compounds whose light absorption characteristics change in response to these external stimuli, it is not easy to obtain high color reproducibility by changing the light absorption characteristics of a single compound alone, and it is preferable to utilize changes in the light absorption characteristics of multiple compounds. In order to effectively utilize changes in the light absorption characteristics of multiple compounds, it is useful to select compounds with different light absorption wavelengths as these multiple compounds and combine their strong and weak absorptions to improve color reproducibility.

[0015] The light control element of the present invention absorbs light by combining multiple compounds whose light absorption characteristics change in response to an external stimulus, thereby substantially suppressing the effect of the light source on the color reproducibility of the variable ND filter. The reason for using multiple compounds is that if only one compound is used, the spectral shape that constitutes the spectrum of the variable ND filter is determined by that compound, and color reproducibility greater than the color reproducibility of the spectrum of that compound cannot be expected, making it impossible to substantially suppress the effect of the light source on color reproducibility.

[0016] The number of compounds to be combined is preferably three or more, for the reasons described below. (1) When forming a variable transmittance spectrum by combining compounds with different variable absorption spectra, the more types of compounds there are, the more detailed the absorption wavelengths can be complemented. As a result, higher color reproducibility and the substantial light source effect on color reproducibility can be suppressed. Specifically, this can be explained as follows: In terms of concentration ratio, when there are two types of compounds, once the concentration ratio of one compound is determined, there is no flexibility in the concentration ratio of the other two compounds. When there are three or more types of compounds, even if the concentration ratio of one type of compound is determined, there is flexibility in the concentration ratio of the other two compounds, making it possible to complement more detailed absorption wavelengths.

[0017] (2) The spectrometers targeted by ND filters have three or more detection wavelength ranges, as typified by the human eye and RGB sensors. Therefore, if there are three or more types of compounds, the degree of light absorption corresponding to each detection wavelength range can be set relatively freely with respect to other compounds, and NWD Max Specifically, the number of compounds is preferably 4 or more, and more preferably 6 or more.

[0018] From the above viewpoint, it is preferable that at least one compound selected from the plurality of compounds has a peak of a variable absorption spectrum in each of the plurality of detection light wavelength ranges of the photodetector. This allows for greater flexibility in setting the optical absorption corresponding to the detection light wavelength range of the photodetector for other compounds. In this case, each of the plurality of detection light wavelength ranges of the photodetector is a wavelength range of the detection wavelength range that is maximum in the normalized sensitivity spectrum of the photodetector. For example, in FIG. 2(b), the detection light ranges of the plurality of detection light wavelength ranges (x bar, y bar, z bar) are x bar: 580 nm to 680 nm, y bar: 500 nm to 580 nm, and z bar: 425 nm to 500 nm. It is preferable that at least one compound selected from the plurality of compounds has a peak of a variable absorption spectrum in each of these ranges.

[0019] <Principles of improving color reproducibility> In conventional photochromic devices, the influence of light sources on color reproducibility has been suppressed by improving wavelength flatness. In the photochromic device of the present invention, the substantial influence of light sources on color reproducibility is suppressed by prioritizing reducing the ratio of the detection signal ratio change between the reference light source and the control light source in each of the multiple detection light wavelength ranges of the photodetector, rather than improving wavelength flatness. The principle of improving color reproducibility in the photochromic device of the present invention is described in detail below.

[0020] The amount of light that passes through the photochromic element and enters the image sensor (photodetector) or the human eye is proportional to the transmittance of the photochromic element. For this reason, when discussing color reproducibility, the transmittance normalized by the amount of light is used. If the spectrum of this normalized transmittance does not change, the influence of the light source on color reproducibility can be eliminated by correction. However, the photochromic element of the present invention is a light absorbing element, and multiple compounds are combined to form an absorbance (absorption) spectrum with a specific shape. In this case, the shape of the absorbance spectrum is basically (ideally) constant regardless of concentration (in other words, the normalized absorbance spectrum does not basically change). On the other hand, the relationship between absorbance Abs and transmittance T is T=10 -AbsTherefore, even if the shape of the absorbance spectrum is constant, the normalized transmittance spectrum will not be constant, and the deviation from the average value will increase as the absorbance increases. As a result, it becomes difficult to eliminate the influence of the light source on color reproducibility through correction.

[0021] Therefore, in the present invention, the light source influence on color reproducibility is suppressed mainly by the relationship between the photodetector and the light source. Specifically, in the relationship between the sensitivity of the photodetector and the intensity of the light source, the deviation of the normalized transmittance from the average value in the wavelength region with high signal intensity is suppressed. For example, photodetectors used in image sensors typically have wavelength sensitivity characteristics as described above in the <Photodetector> section, and the main light source has a relatively continuous intensity spectrum, as described in the light source section (described later). As such, the sensitivity of the detector and the intensity of the light source each have characteristic wavelength dependence. In the wavelength region where the signal intensity is high, which is proportional to the product of this sensitivity and intensity, if the transmittance of the photochromic element deviates significantly compared to other wavelength regions, the impact of a change in the light source is significant. Conversely, in the wavelength region where the signal intensity is low, the impact is relatively small even if the deviation in the transmittance of the photochromic element is large. The photochromic element of the present invention utilizes this concept to suppress the deviation of the normalized transmittance from the average value in the wavelength region with the greatest impact, thereby substantially suppressing the light source influence on color reproducibility.

[0022] Here, we will explain the term "substantially." For example, if we try to suppress the light source effect of any light source, or in an extreme case, a light source with a uniform wavelength such as laser light, we would improve wavelength flatness. However, the light used in environments where photochromic elements are mainly used is often natural light or light that mimics natural light, and has a fairly continuous spectrum with a wide wavelength distribution. If we can support the light source used in such environments where photochromic elements are used, we can substantially suppress the light source effect.

[0023] <Variable transmittance VT(λ)> The variable transmittance VT(λ) is a combination of the light absorption characteristic changes (for example, the change in extinction coefficient Δε(λ)) of each of the compounds whose light absorption characteristics change, which are included in the photochromic element of the present invention. Here, the change in extinction coefficient Δε(λ) is the change component of the molar extinction coefficient obtained by subtracting the molar extinction coefficient of the compound whose light absorption characteristics change in the transmitted state from the molar extinction coefficient of the compound whose light absorption characteristics change in the dimmed state. Also, the variable transmittance VT(λ) is the change component obtained by dividing the transmittance of the photochromic element in the dimmed state by the transmittance of the photochromic element in the transmitted state. The change in extinction coefficient of a compound m whose light absorption characteristics change is Δε m (λ), and the concentration of the dimmed state is C m If the optical path length of the photochromic element is L, VT(λ) can be expressed by the following formula: where m is a number greater than or equal to 1 and less than or equal to the total number of compounds used in the photochromic element whose light absorption characteristics change.

[0024]

number

[0025] The above optical path length L, and the concentration C in the dimmed state m Examples of the optical path length L are described below. In the case of a transmissive ND filter, the thickness of the layer containing the compound that changes the light absorption characteristics can be cited as an example. Also, when light is reflected on the back surface of the ND filter and travels back and forth inside the ND filter, twice the thickness of that layer can be cited as an example. Concentration C mis the average concentration of the compound whose light absorption characteristics change in the dimming state in the thickness of the layer in which the compound whose light absorption characteristics change is retained. Here, being in the dimming state means that the variable state of the compound whose light absorption characteristics change is more prevalent when the light-adjusting element is in the dimming state than when it is in the transmitting state. Specific examples include EC compounds whose light absorption characteristics change in the visible light region and dichroic dyes whose light absorption characteristics change in the visible light region.

[0026] <Wavelength flatness TF> The wavelength flatness of VT(λ) in the wavelength range of the photodetector is defined as TF. The wavelength range of the photodetector is the wavelength range in which the photodetector has significant spectral sensitivity. The spectral sensitivity of a photodetector is the spectral sensitivity when used in its normal configuration. Specifically, when the photodetector is used as part of a camera system, it refers to the spectral sensitivity including other optical elements normally used in the camera system, such as UV and IR cut filters and low-pass filters. Figure 2(a) shows an example of the spectral sensitivity of an RGB image sensor, including the effects of the transmittance of UV and IR cut filters and low-pass filters when the photodetector is used as part of a camera system. When the photodetector is the human eye, the CIE color matching functions are used.

[0027] Figure 2(b) shows the CIE color matching functions. A typical example of the detection light wavelength range of these photodetectors is the range from 425 nm to 680 nm. Another example is a wavelength range with a sensitivity of 10% or more of the maximum spectral sensitivity of the photodetector. The wavelength flatness TF can be calculated by dividing the difference between the maximum and minimum values ​​of VT(λ) in the detection light wavelength range of the photodetector by the average value, as shown in the following formula.

[0028]

number

[0029] <Light source> The light source of the light incident on the photochromic element (the light that ultimately enters the photodetector through the photochromic element) is described below. The photochromic element of the present invention is a photochromic element that substantially suppresses the influence of the light source on color reproducibility. The light source includes the source of the light incident on the photochromic element (light source) itself and light emitted from the light source that has passed through a filter or the like. For example, when using artificial light source lighting, it includes not only the artificial light source but also the filter or the like when the artificial light source is used for lighting or the like with a filter or the like attached. For example, when considering sunlight on Earth, it includes sunlight that has passed through the Earth's atmosphere and reached the Earth's surface. Light sources can be classified by color temperature into three types: low color temperatures of 4000K or less, medium color temperatures of 4000K to 7000K, and high color temperatures of 7000K or higher.

[0030] The photochromic element of the present invention suppresses the substantial light source effect on color reproducibility by prioritizing reducing the ratio between the reference light source and the reference light source in the change in the detection signal ratio in each of the multiple detection light wavelength ranges of the photodetector. There are two methods for selecting the reference light source and the reference light source. For ease of understanding, an example will be described in which the photochromic element is used as an optical filter for an imaging device. One method involves performing the settings (correction) of the imaging device without changing them depending on the light source, while the other involves changing the settings (correction) of the imaging device depending on the light source. Each method will be described below.

[0031] In the former case, natural daylight, which is frequently used with dimming devices, is preferably selected as the reference light source, and a light source with a corresponding medium color temperature is preferably selected. Figure 3(a) shows examples of the spectrum of natural daylight and a pseudo-sunlight source with a color temperature of approximately 5000 K. Examples of defined light sources include CIE D65, D55, D50, illuminant B, and illuminant C.

[0032] For the reference light source, selecting a light source that is important (used relatively frequently) in the environment in which the photochromic element is used can highly enhance the neutral density properties of the photochromic element. An example of the color temperature of the reference light source is a color temperature of 2000K to 9000K. Figure 3(b) shows examples of light sources corresponding to each color temperature, including the spectra of light sources with color temperatures of 3200K, 5600K, and 8000K. Light sources with low color temperatures are important as traditionally commonly used artificial light, such as sunlight at low altitudes, incandescent lamps, and halogen lamps. Light sources with medium color temperatures are important as artificial light that simulates natural daylight as a reference light source. Light sources with high color temperatures are important, for example, when expressing colors in the shade. In particular, light sources with color temperatures of 2000K to 4000K or 7000K to 9000K are important as reference light sources, from the perspective of compatibility with a medium color temperature reference light source.

[0033] Furthermore, in addition to compatibility with the above-mentioned standard light source, it is important to use a light source with a color temperature of 2000 K to 4000 K as commonly used artificial light. Specific light sources include those listed in the low color temperature light source section above, and an example of a defined light source is the CIE A illuminant.

[0034] The light control element of the present invention is preferably compatible with light sources of a plurality of color temperatures. It is more preferable that the light control element is compatible with a plurality of color temperatures including a medium color temperature. For example, it is preferable that the light control element is compatible with a medium color temperature and a low color temperature, a medium color temperature and a high color temperature, and a medium color temperature, a low color temperature and a high color temperature. Here, being compatible with a light source of a certain color temperature means that even when that light source is used, the NWD Max <NWD MaxFP This means that it is possible to achieve this. Being able to handle light sources with multiple color temperatures expands the range of application of dimming elements. Specifically, dimming elements can achieve high color reproducibility regardless of the color temperature of the light source. For example, a camera can achieve high color reproducibility without having to distinguish the color temperature of the light source.

[0035] An example of the latter (changing the image capture device settings (correction) depending on the light source) is estimating the color temperature of the light source and changing the image capture device settings (correction values) for each color temperature. An example of this correction value is the white balance correction value. In this case, changes in the correction value based on the color temperature of the light source are compensated for by correction based on the estimated color temperature of the light source. Therefore, it is preferable to be able to accommodate multiple light sources in a single color temperature range (although it is possible to accommodate light sources with multiple color temperatures). Specifically, this would involve a combination of a reference light source with a medium color temperature and a control light source with a medium color temperature. Generally, when different light sources selected from the same color temperature range are used, the light source's influence on color reproducibility is often smaller than when light sources selected from different color temperature ranges are used, but exceptions do occur frequently. When different light sources selected from the same color temperature range are used, the most common issue regarding the influence of light sources on color reproducibility is the influence of light sources with spectra with large intensity fluctuations. Specific examples include fluorescent lamps and LED light sources. Figure 14 shows an example of the spectrum of a daylight fluorescent lamp (color temperature 5000K). This shows that there are large changes in spectral intensity. Fluorescent lamps, in particular, have a large influence of emission lines, which can easily cause issues with light source influence on color reproducibility. When using such light sources, it is preferable to select a reference light source and a control light source that have a continuous spectrum as the reference light source, and a light source with a spectrum with large intensity fluctuations as the control light source. Light sources with a continuous spectrum include natural daylight, simulated sunlight, D65, D55, D50, B light source, and C light source as light sources with medium color temperatures. Furthermore, halogen lamps and A light source are examples of light sources with low color temperatures.

[0036] Furthermore, to improve the color reproducibility of photochromic elements, it is desirable to faithfully reproduce a variety of colors. Therefore, it is preferable to assume that the light from the above-mentioned light source is reflected by samples of various colors as the light incident on the photochromic element. A specific example of a color sample is a color checker (e.g., x-rite ColorChecker).

[0037] <NWD Max > In the photochromic element of the present invention, the substantial influence of the light source on color reproducibility is suppressed by prioritizing the reduction of the ratio of the detection signal ratio change between the reference light source and the control light source in each of the multiple detection light wavelength ranges of the photodetector rather than improving wavelength flatness. Max This will be explained using the schematic diagram of the optical device in FIG.

[0038] The variable transmittance of the dimming element 1001 is VT(λ), the transmission spectrum in the transmission state is T0(λ), and the spectral sensitivity of the photodetector (RGB image sensor) 1002 is D for each of R, G, and B. R (λ), D G (λ), D B (λ). In this optical device 1000, I n When incident light 1003 having a spectrum of (λ) is incident and passes through the dimming element 1001, the signal intensity obtained from the photodetector 1002 is expressed as S Rn ,S Gn ,S Bn Here, n=0 means the reference light source (I0), and n=1 means the reference light source (I1). At this time, the signal intensity S RTn (S RT0 or S RT1 ),S GTn (S GT0 or S GT1 ),S BTn (S BT0 or S BT1 ) is described by the following formula:

[0039]

number

[0040] Similarly, the signal strength S of the dimming element (the variable transmittance from the transmitting state is VT(λ)) RCn (S RC0 or S RC1),S GCn (S GC0 or S GC1 ),S BCn (S BC0 or S BC1 ) is described by the following formula:

[0041]

number

[0042] The transmittance of a photochromic element in the dimming state functions as the transmittance multiplied by the variable transmittance VT(λ). A photochromic element in this transmissive state has higher transmittance than a photochromic element in the dimming state. This is typically the photochromic element's highest transmittance state. If the spectrum of the photochromic element in the highest transmittance state provides poor color reproduction, it is preferable to select a transmissive state within the range in which the photochromic element can be effectively used. The dimming ratio between the transmissive state and the dimming state of this photochromic element (the ratio of the amount of light emitted when the same amount of light is incident (transmissive state / dimming state)) is preferably 8 (ND8) or greater, and more preferably 32 (ND32) or greater. There are two reasons for this:

[0043] (1) Usefulness as a dimming element If the dimming ratio is 8 or less, the adjustable range of the dimming element is limited, and the range of applications as a dimming element is severely restricted. On the other hand, if the dimming ratio is 32 or more, the applicability as a dimming element expands dramatically.

[0044] (2) The greater the dimming ratio, the more difficult it becomes to achieve high color reproducibility. A photochromic element that absorbs light by combining multiple compounds with variable light absorption properties is a light absorbing element, and by combining multiple compounds, it forms an absorbance (absorption) spectrum with a specific shape. The shape of this absorbance spectrum is basically (ideally) constant regardless of concentration. On the other hand, the amount of light that enters the image sensor, which is a photodetector, and the human eye is determined by "amount of incident light x transmittance." For this reason, when discussing the reproducibility of colors normalized by the amount of light, normalized transmittance is used. Here, the relationship between absorbance Abs and transmittance T is T=10 -Abs Therefore, the effect of variations in absorbance due to wavelength increases exponentially as the absorbance increases. Therefore, when the extinction ratio is small, at 8 or less, the effect of changes in the extinction ratio of the photochromic element on color reproducibility is relatively small. On the other hand, when the extinction ratio is 8 or more, the effect of changes in the extinction ratio of the photochromic element on color reproducibility becomes large, and when the extinction ratio is 32 or more, the effect becomes extremely large. By using the photochromic element technique of the present invention, it is possible to provide the photochromic element with high color reproducibility even in such a large extinction ratio range.

[0045] At this time, the signal intensity ratio W of the R and B detection wavelength ranges of the photodetector in the transmitted state, with G as the reference, is RTn (W RT0 or W RT1 ), W BTn (W BT0 or W BT1 ) is expressed as a gain (inverse) based on G as shown in the following equation. W RTn =S GTn / S RTn W BTn =S GTn / S BTn

[0046] Similarly, the signal intensity ratio W of the R and B detection light wavelength regions of the photodetector in the dimmed state with G as the reference RCn (W RC0 or W RC1 ), W BCn (W BC0 or W BC1 ) is expressed as a gain (inverse) based on G as shown in the following equation. W RCn =S GCn / S RCn W BCn =S GCn / S BCn

[0047] NW used as the degree of change in the detection signal ratio Rn (N.W. R0 or NW R1 ), N.W. Bn (N.W. B0 or NW B1 ) is expressed as the change in the signal intensity ratio between the transmission state and the dimming state (dimming state / transmission state) as shown in the following equation: NW Rn =W RCn / W RTn NW Bn =W BCn / W BTn

[0048] And the ratio of the detected signal change between the reference light source and the control light source NWD Max is the above NW Rn , N.W. Bn The ratio between each reference illuminant and the reference illuminant (reference illuminant / reference illuminant or reference illuminant / reference illuminant) is the largest. In other words, the largest of the following four ratios is the NWD: Max is. NW R1 / NW R0 NW R0 / NW R1 NW B1 / NW B0 NW B0 / NW B1

[0049] The minimum wavelength flatness of the transmission spectrum, which is a combination of the optical absorption characteristic change spectra of multiple compounds, is defined as TF. FP , NWD at that time Max NWD MaxFP This minimum value TF FP And, TF FPVariable transmittance VT FP (λ) can be calculated by performing a minimization calculation using the optical absorption characteristic change spectra of multiple compounds. MaxFP VT FP Calculate using (λ) and the above formula.

[0050] In the photochromic element of the present invention, priority is given to reducing the ratio of the change in the detection signal ratio between the reference light source and the control light source in each of the multiple detection light wavelength regions of the photodetector rather than improving the wavelength flatness. Therefore, the wavelength flatness TF of the photochromic element of the present invention is TF > TF FP and NWD Max <NWD MaxFP is.

[0051] NWD Max The preferred values ​​of NWD are listed below. Max Since the value of changes depending on the amount of change in the variable transmittance VT(λ), it is preferable to evaluate it using a normalized value. Therefore, it is evaluated using a normalized value so that the average change in the variable transmittance VT(λ) in multiple detection light wavelength regions of the photodetector is 1 / 64 (ND64). Since the shape of the variable transmittance spectrum changes depending on the change in transmittance, normalization is performed by converting the variable transmittance spectrum to a variable absorbance spectrum (given by -log(VT(λ))), normalizing, and then converting it back to a variable transmittance spectrum. NWD Max When simulated images of different filter values ​​were evaluated, the images were perceived as natural compared to images of the same filters in their transmission state. Max The range of NWD was 1.03 or less. Max The value is 1.03 or less when the variable transmittance VT(λ) is normalized so that the average change is ND64.

[0052] <Electrochromic element (EC element)> The photochromic element of the present invention absorbs light by combining multiple compounds whose light absorption properties change in response to external stimuli. EC elements using EC compounds are most preferably used because they can achieve both a high light transmission state and a low light transmission state. Photochromic elements using EC elements are described in detail below.

[0053] EC devices include those using inorganic materials and those using organic materials, with an example of the former being one using tungsten oxide. Organic materials include polymer-type and low-molecular-weight EC devices, with an example of the former being one using polythiophene. In order to produce a light-controlling device with high color reproducibility, it is necessary to precisely control the light absorption characteristics, and from this perspective, low-molecular-weight EC devices are preferably used. Specifically, it is preferable to select low-molecular-weight EC compounds with different light absorption wavelengths and combine their strong and weak absorptions to improve color reproducibility.

[0054] A typical EC device consists of two transparent conductive electrodes, one of which is transparent, facing each other, an EC layer containing an EC compound placed in the space between them, and a sealant sealing the periphery. By controlling the voltage between the electrodes, the EC device can be changed from a transparent state to a dimming state.

[0055] <Electrode> The electrodes are preferably made of a material that can stably exist in the operating environment of the EC device and rapidly undergo a redox reaction in response to the application of an external voltage. Examples of materials that can be used for the electrodes include transparent conductive materials such as tin-doped indium oxide (ITO) and fluorine-doped tin oxide (FTO), as well as metals. By using a transparent electrode for at least one of the electrodes, light can be efficiently captured from outside the EC device, allowing it to interact with the EC compound in the EC layer, thereby reflecting the optical properties of the EC compound in the emitted light.

[0056] <Sealing material> The sealing material is preferably composed of a material that is chemically stable, impermeable to gases and liquids, and does not inhibit the redox reaction of the EC compound. For example, inorganic materials such as glass frit, organic materials such as epoxy and acrylic resins, and metals can be used. The sealing material may also contain a spacer material to maintain the distance between the two electrodes. This allows the distance between the electrodes to be determined, thereby defining the optical path length. The spacer material can be inorganic materials such as silica beads and glass fiber, or organic materials such as polyimide, polytetrafluoroethylene, polydivinylbenzene, fluororubber, and epoxy resin.

[0057] <Electrochromic layer (EC layer)> EC devices include unipolar EC devices in which an electrochemical reaction occurs at one electrode, and complementary EC devices in which an electrochemical reaction occurs at both electrodes. While either type of EC device can be used as the photochromic device of the present invention, complementary EC devices are preferred in order to increase the extinction ratio between the transmissive and dimmed states of the photochromic device. A typical complementary EC device contains an anodic EC compound that changes from the transmissive state to the dimmed state through an oxidation reaction, and a cathodic EC compound that changes from the transmissive state to the dimmed state through a reduction reaction. Among typical complementary EC devices, EC devices that highly suppress electrochemical reactions other than the electrochemical reaction of the EC compound exhibit minimal color change in the dimmed state even after repeated operation, making them a preferred form of photochromic device of the present invention.

[0058] In a complementary EC device that highly suppresses electrochemical reactions other than those of the EC compound, the charge consumed during the reaction of the anodic EC compound is approximately equal to the charge consumed during the reaction of the cathodic EC compound. Therefore, in such a complementary EC device, when configuring a variable transmittance VT(λ) that combines changes in the light absorption characteristics of multiple compounds, it is necessary to distinguish between changes in the light absorption characteristics of the anodic EC compound and changes in the light absorption characteristics of the cathodic EC compound. Specifically, the device is configured so that the sum of the charge concentrations of the anodic EC compound in the dimmed state is approximately equal to the sum of the charge concentrations of the cathodic EC compound in the dimmed state.

[0059] Here, the charge concentration in the dimmed state refers to the charge required to produce a concentration of the EC compound in the dimmed state, and can be expressed as n × c, where n is the number of reactive electrons used in the reaction that changes the EC material from a transparent state to a dimmed state, and c is the concentration of the EC compound in the dimmed state. Furthermore, "approximately equal total charge concentrations" means that the difference in total charge concentrations is within 10%, preferably within 5%.

[0060] As described above, in a complementary EC device, when configuring a variable transmittance spectrum, there are limitations on the total charge concentration in the dimmed state of the anodic EC compounds and the charge concentration in the dimmed state of the cathodic EC compounds. As described above, it is preferable that the number of compounds is three or more. In a complementary EC device, in order to ensure the degree of freedom in configuring a variable transmittance spectrum under this charge concentration limitation, it is preferable to further include multiple anodic EC compounds and multiple cathodic EC compounds. This is because, even if there is the above-mentioned charge concentration limitation, the concentration ratio in the dimmed state between anodic EC compounds and between cathodic EC compounds can be freely set. This allows the NWD of the present invention to be realized. Max This can dramatically increase the effectiveness of optimization.

[0061] The EC compound in the EC element may be dissolved in a solvent or the like to form an EC layer, or may be immobilized on an electrode. When immobilized on an electrode, the extinction ratio between the transmissive state and the dimming state can be increased by increasing the concentration of the adsorbed EC compound by using a porous electrode. In this case, the thickness of the EC layer is the range in which the EC compound exists where the transmittance changes, and the concentration is the average concentration throughout the thickness of the EC layer.

[0062] EC compounds are compounds whose light absorption characteristics change repeatedly in the target light wavelength range of the EC element due to redox reactions. Some EC compounds have a relatively small change in extinction coefficient. Even compounds with a relatively small change in extinction coefficient change their light absorption characteristics, albeit small, and contribute to the reaction charge. Therefore, when calculating the charge concentration described above, compounds with a small change in extinction coefficient are included as EC compounds.

[0063] Examples of anodic EC compounds include thiophene derivatives, amines having aromatic rings (e.g., phenazine derivatives and triallylamine derivatives), pyrrole derivatives, thiazine derivatives, triallylmethane derivatives, bisphenylmethane derivatives, xanthene derivatives, fluoran derivatives, and spiropyran derivatives. Among these, low-molecular-weight amines having aromatic rings are preferred as anodic EC compounds, with dihydrophenazine derivatives being the most preferred. This is because the use of these compounds as EC compounds facilitates the provision of EC devices with desired absorption spectra and high durability for repeated use. In their neutral state (reduced form), these compounds have an absorption peak in the ultraviolet region, no absorption in the visible region, and a transparent state with high transmittance in the visible region. When these molecules undergo an oxidation reaction to become radical cations (oxidized forms), the absorption peak shifts to the visible region, resulting in a dimming state. The absorption wavelength of these molecules can be freely designed by adjusting their π-conjugation length or by changing the substituents to modify the π-conjugated system. The term "low molecular weight" used here refers to a molecular weight of 2000 or less.

[0064] Cathodic EC compounds are not particularly limited, but examples include pyridine derivatives and quinone compounds. Among these, pyridine derivatives, particularly viologen derivatives, are most preferred. These compounds typically have an absorption peak in the ultraviolet region in their divalent cationic state (oxidized form), no absorption in the visible light region, and a transparent state with high transmittance in the visible light region. When these molecules undergo a reduction reaction to become radical cations (reduced forms), the absorption peak shifts to the visible light region, resulting in a dimmed state. The absorption wavelength of these molecules can also be freely designed by expanding or contracting their π-conjugation length or by changing the substituents to modify the π-conjugated system. The term "small molecule" as used here refers to a molecular weight of 2000 or less, excluding counterions.

[0065] <Color reproducibility evaluation method> The method for evaluating the color reproducibility of the photochromic element of the present invention is described below. It is desirable that the color change of the photochromic element of the present invention when the dimming level is changed does not change depending on the light source. Therefore, the color of the light incident on the photodetector of the photochromic element is evaluated by evaluating the difference when the reference light source is used as the reference light source and the change (ratio) between the transmitted and dimmed states of the photochromic element. Specifically, since the brightness changes when the dimming level of the photochromic element is changed, the brightness in the transmitted and dimmed states of the photochromic element is made uniform, and the difference in color is evaluated as L. * a * b * a in space * b * It is plotted on a plane and evaluated. Also, numerically, the color difference (CIEDE2000 (ΔE 00 )) is used to evaluate.

[0066] The smaller the color difference, the higher the color reproducibility. The following table, published by Nippon Denshoku Industries Co., Ltd., is a widely known indicator of this. C-class tolerance (ΔE 00 :6.5 to 13.0): Color difference equivalent to one degree on the JIS standard color chart, Munsell color chart, etc. Class B tolerance (ΔE 00:3.2 to 6.5): A color difference that can be treated as the same color at the impression level, but which can lead to complaints about color differences in the paint and plastics industries. A-class tolerance (ΔE 00 : 1.6 to 3.2) A level of color difference that is barely noticeable when comparing colors, and is generally considered to be the same color. AA class tolerance (ΔE 00 :0.8 to 1.6): A level at which slight color differences can be perceived when comparing adjacent colors. This is the range of acceptable color differences, including the errors of general color measurement institutions.

[0067] Effect The photochromic element of the present invention can suppress the substantial influence of light sources on color reproducibility even in an optical device equipped with a photochromic element using multiple compounds, such as multiple compounds whose light absorption characteristics change in response to external stimuli. The present invention prioritizes reducing the ratio of detection signal ratio changes between a reference light source and a control light source in each of multiple detection light wavelength ranges of a photodetector over improving wavelength flatness. This allows the substantial influence of light sources on color reproducibility to be further suppressed than when wavelength flatness is improved.

[0068] Specifically, the following optical devices can be realized. For example, a camera system that adjusts the amount of light using a variable ND filter can exhibit high color reproducibility under various lighting conditions. Other examples include variable transmittance windows and variable transmittance glasses (sunglasses) that display natural colors under various lighting conditions. Furthermore, a variable transmittance mirror (anti-glare mirror) can display natural colors under various lighting conditions. [Example]

[0069] The light-adjusting element of the present invention will be described below with reference to examples. All of the following examples are for reference purposes only. Specifically, an EC element equipped with a variable ND filter using a complementary EC element that absorbs light by combining multiple EC materials whose light absorption characteristics are electrically changed will be described as an example, but the present invention is not limited to these examples.

[0070] [EC compound] <Anodic EC Compound> The anodic EC compounds used in this example are listed below, but the EC compounds used in the present invention are not limited to these.

[0071] [ka]

[0072] The above EC compounds (1) to (5) can be synthesized by the reaction shown in the following formula (A).

[0073] [ka]

[0074] In the above formula (A), R1 is a hydrogen atom, an alkyl group, or a phenoxy group, and R2 is a hydrogen atom, an alkyl group, or an aryl group. EC compounds (1) to (5) can be synthesized by reduction of the phenazine ring and isopropylation.

[0075] For EC compounds (2) to (4), a precursor can be synthesized by a known Pd-catalyzed coupling reaction using a combination of a halogenated substituted phenazine (X is a halogen) represented by the following formula (B) and a phenylboronic acid or boronic acid ester compound having a substituted alkyl group or alkoxy group at the ortho position (R3, R4) prior to the reaction of formula (A) above. The R1 position can also be treated in the same manner as the R2 position.

[0076] [ka]

[0077] For EC compound (3), a phenoxy group is introduced at the 7-position of the phenazine ring prior to the reactions of formulas (A) and (B). The phenoxy group can be introduced by a known Cu-catalyzed coupling reaction using phenol with a halogenated phenazine. The synthesis scheme for EC compound (3), including specific examples of the reactions of formulas (A) and (B), is shown in formula (C) below.

[0078] [ka]

[0079] The EC compound (3) can be synthesized, for example, by the following procedure. First, the first-stage intermediate was synthesized. 2,7-Dibromophenazine and phenol were mixed in DMSO (dimethyl sulfoxide), and dissolved oxygen was removed with nitrogen. Next, CuI / Spartein complex and potassium carbonate were added, and the mixture was refluxed for 8 hours. The reaction solution was concentrated under reduced pressure and purified by silica gel chromatography to obtain the first-stage intermediate as a yellow solid.

[0080] Next, the first-stage intermediate, 2-isopropoxy-6-methoxyphenylboronic acid, was mixed in a toluene / 1,4-dioxane mixed solvent and the dissolved oxygen was removed with nitrogen. Pd(OAc)2, 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (S-Phos), and tripotassium phosphate were added and refluxed for 15 hours. The reaction solution was concentrated under reduced pressure and purified by silica gel chromatography to obtain the second-stage intermediate as a yellow solid.

[0081] Next, the second-stage intermediate, 2-iodopropane, was mixed in an acetonitrile / water mixed solvent, and dissolved oxygen was removed with nitrogen. Sodium hydrosulfite and potassium carbonate were added, and the mixture was refluxed for 10 hours. The reaction solution was concentrated under reduced pressure and purified by silica gel chromatography to obtain the solid EC compound (3). 1H-NMR (heavy acetone) δ(ppm):7.35(m,2H),7.19(t,1H),7.06(t,1H),6.99(d,2H),6.8-6.65(m,6H),6.49(d,1H),6.4 2(dd,1H),4.47(sep,1H),4.17(sep,1H),3.97(sep,1H),3.71(s,3H),1.51(d,6H),1.46(d,6H),1.18(d,6H).

[0082] <Cathodic EC Compound> The cathodic EC compounds used in this example are shown below, but the EC compounds used in the present invention are not limited to these.

[0083] [ka]

[0084] The above EC compounds (6) to (8) can be synthesized by the reaction shown in the following formula (D).

[0085] [ka]

[0086] In the above formula (D), R4 is a hydrogen atom or a methyl group, and R5 is a hydrogen atom or an alkyl group. As an example, a specific synthesis method for the EC compound (7) will be described.

[0087] In the first step, 3-methyl-4-chloropyridine hydrochloride, 4-pyridylboronic acid, tris(dibenzylideneacetone)dipalladium(0), tricyclohexylphosphine, and tripotassium phosphate were added to a dioxane / water solvent and heated under reflux for 8 hours under a nitrogen atmosphere. The reaction mixture was concentrated, extracted with ethyl acetate, and purified by silica gel column chromatography and recrystallization to obtain 3-methyl-4,4'-bipyridine.

[0088] In the second step, 3-methyl-4,4'-bipyridine and 2,4-dinitrobromobenzene were reacted in N,N-dimethylformamide at 100°C for 24 hours, and the precipitated crystals were filtered and washed with acetonitrile to obtain intermediate 1.

[0089] In the third step, intermediate 1, o-toluidine, was refluxed in ethanol for 8 hours. After removing the solvent, ethyl acetate was added and the precipitate was filtered. The resulting crystals were dissolved in water, and an aqueous solution of lithium bis(trifluoromethanesulfonyl)imide was added dropwise. The mixture was stirred at room temperature for 3 hours, and then isopropyl alcohol was added to recrystallize the product, yielding EC compound (7). 1 H-NMR(CD3CN)σ(ppm):9.00(d,2H),8.89(s,1H),8.83(d,1H),8.33(d,2H),8.12(d ,1H),7.76-7.66(m,2H),7.64-7.51(m,6H),2.57(s,3H),2.27(s,3H),2.25(s,3H).

[0090] The above EC compounds (9) and (10) can be synthesized by the reaction shown in the following formula (E).

[0091] [ka]

[0092] In the above formula (E), R6 and R7 are hydrogen atoms or alkyl groups (forming a ring through R6 and R7). As an example, a specific synthesis method for EC compound (9) is described in formula (F).

[0093] [ka]

[0094] First, we describe the synthesis of the intermediate 9,9-dimethyl-2,7-diazafluorene. The synthesis was performed with reference to technical literature (E. Botana, et al., Angew. Chem. Int. Ed. 46, 198-201 (2007)). 3,8-phenanthroline, potassium hydroxide, and water were added to a reaction vessel and heated to 90°C. A solution of water and potassium permanganate heated to 90°C was then added dropwise to the reaction solution. After reacting for one hour, the precipitated solid was filtered, extracted with chloroform, washed with water and saturated brine, dried, and concentrated to obtain a brown powder. This was then separated and purified by silica gel chromatography to obtain the first intermediate, a yellow solid.

[0095] The first intermediate, diethylene glycol, and hydrazine monohydrate were added to a reaction vessel and reacted at 100°C for 12 hours. Water was added to the resulting black-red suspension, which was then extracted with dichloromethane, washed with water and saturated brine, dried, and concentrated to obtain a black-yellow solid. This was then separated and purified by silica gel chromatography to obtain the second intermediate, a yellow-brown solid.

[0096] The second intermediate, DMF (dimethylformamide), was added to the reaction vessel and cooled in an ice bath. Potassium tert-butoxide was then added and stirred at the same temperature for 30 minutes, after which iodomethane diluted in DMF was added dropwise. After stirring at the same temperature for another 30 minutes, the reaction was allowed to proceed at room temperature for 3 hours. The resulting reddish-brown suspension was added to saturated aqueous sodium bicarbonate, extracted with ethyl acetate, washed with water and saturated brine, dried, and concentrated to obtain a black-yellow solid. This was separated and purified by silica gel chromatography to obtain 9,9-dimethyl-2,7-diazafluorene as a beige solid.

[0097] 9,9-Dimethyl-2,7-diazafluorene and an excess amount of 1-bromoheptane were added to a reaction vessel, and the mixture was reacted in DMF as a solvent for 19 hours at 110° C. The precipitate was collected and dissolved in water, and an excess amount of lithium bis(trifluoromethanesulfonyl)imide was added. The precipitate was collected by filtration and dried to obtain EC compound (9).

[0098] [Fabrication of EC device] Two sheets of transparent conductive glass coated with indium-doped tin oxide (ITO) films were prepared and placed so that the ITO films faced each other. The two sheets of transparent conductive glass were then bonded together around their outer peripheries using a sealant containing spacer beads with a particle size of 50 μm. A solution containing a specific EC compound was injected through a pre-formed injection port in the transparent conductive glass, filling the space formed by the two sheets of transparent conductive glass and the sealant with the solution. The injection port was then sealed with a sealant to obtain an EC device.

[0099] [Change in extinction coefficient Δε(λ) of EC compound] The absorbance spectrum of a single EC compound (absorbance in the dark state minus absorbance in the transmitted state) was obtained. Specifically, the EC compound was dissolved at a concentration of 1 mmol / L in a 0.1 mol / L propylene carbonate solution of tetrabutylammonium hexafluorophosphate. A platinum mesh electrode was used as the working electrode, a platinum wire electrode as the counter electrode, and an Ag / Ag + The electrode was used as a reference electrode, and a potential was applied for 120 seconds in a cuvette with an optical path length of 1 mm so that the EC compound was in a dimmed state, and the change absorbance spectrum was obtained.

[0100] Next, one anodic EC compound and one cathodic EC compound were each dissolved in propylene carbonate at a concentration of 0.05 mol / L, and an EC device was fabricated using this solution. In a complementary EC device, in which electrochemical reactions other than those of the EC compounds are highly suppressed, the amount of charge used to create the dimmed state for the anodic and cathodic EC compounds is equal. Taking advantage of this, the extinction coefficient of the reference compound was used to determine the extinction coefficient of the EC compound with the opposite polarity. The reference compound used here was 5,10-diisopropyl-5,10-dihydrophenazine (Δε (480 nm) = 6.5 × 10 3 mol -1 Lcm -1 ) was used as the standard.

[0101] Figure 4(a) shows the spectra of the change in extinction coefficient Δε(λ) for EC compounds (1) to (5), and Figure 4(b) shows the spectra of the change in extinction coefficient Δε(λ) for EC compounds (6) to (10). Note that in this example, because the EC element is of a complementary type, the change in extinction coefficient Δε(λ) is determined before the variable transmittance VT(λ), but it is also possible to directly calculate the variable transmittance VT(λ) and its wavelength flatness TF from the change in absorbance (without determining Δε(λ)).

[0102] (Example 1, Comparative Example 1) An EC device with variable transmittance VT(λ) was constructed using anodic EC compounds (1), (2), and (3) and cathodic EC compounds (6), (7), and (9), which have the Δε(λ) spectra shown in Figure 4. The wavelength range of the photodetector used was the 425 nm to 680 nm range of the photodetector shown in Figure 2(a). The EC compounds (6), (7), and (9) have peaks in the R region of the photodetector, the EC compounds (2) and (3) have peaks in the G region of the photodetector, and the EC compounds (1) and (6) have peaks in the B region of the photodetector. The extinction ratio between the transmitting and attenuating states of this EC device was 64 (= average variable transmittance of 1.56%).

[0103] Figure 5 shows the NWD characteristics of the EC compounds (1), (2), (3), (6), (7), and (9) with various light sources shown in Figure 3. Max The figure shows a spectrum configured to minimize the difference in wavelength between the EC compounds. An EC element having this EC compound composition is designated Example 1, and the concentration (unit: mmol / L) of each EC compound in the dimmed state and the sum of the charge concentrations of the anodic EC compound and cathodic EC compound are shown in Table 1. FIG. 6 also shows a spectrum obtained by combining the same EC compounds as in Example 1 to minimize the wavelength flatness of the variable transmittance. An EC element having an EC compound with this composition is designated Comparative Example 1, and the concentration (unit: mmol / L) of each EC compound in the dimmed state and the sum of the charge concentrations of the anodic EC compound and cathodic EC compound are shown in Table 1.

[0104] [Table 1]

[0105] From Table 1, it can be seen that the total charge concentration in the dimmed state of the anodic EC compound and the total charge concentration in the dimmed state of the cathodic EC compound are approximately equal, at 68.5 mmol / L in Example 1 and 66.2 mmol / L and 66.3 mmol / L in Comparative Example 1.

[0106] Fig. 5(a) shows the variable absorbance spectrum VA(λ) of the EC element of Example 1, and Fig. 5(b) shows the variable transmittance VT(λ) obtained by converting VA(λ) of the EC element of Example 1 into transmittance. Fig. 6(a) shows the variable absorbance spectrum VA(λ) of the EC element of Comparative Example 1, and Fig. 6(b) shows the variable transmittance VT of the EC element of Comparative Example 1 by converting VA(λ) into transmittance. FP (λ) is shown.

[0107] The wavelength flatness TF in the detection light wavelength region was 103% for Example 1 and 67.6% for Comparative Example 1, and the wavelength flatness TF of Comparative Example 1 was the lowest among the combinations of EC compounds used. FP It was.

[0108] In addition, the NWD was calculated using the spectrum of natural daylight in the daytime shown in Figure 3(a) as the reference light source, and the five types of light sources ranging from low to high color temperatures shown in Figure 3(b) as control light sources. Max The values ​​are shown in Table 2.

[0109] [Table 2]

[0110] From the comparison in Table 2, it was confirmed that the EC element of Example 1 is more adaptable to medium, low and high color temperatures than the EC element of Comparative Example 1.

[0111] Figure 7(a) shows the transmission spectrum of the EC element in the transmitting state (ND0) and the dimming state (ND64) of Example 1, and Figure 7(b) shows the transmission spectrum of the EC element in the comparative example 1. Figure 8(a) shows the results of evaluating the influence of the light source on color reproducibility under the following conditions for the EC element in Example 1, and Figure 8(b) shows the results of evaluating the influence of the light source on color reproducibility for the EC element in the comparative example 1, under the following conditions: Transmission spectrum: Figure 7(a) and Figure 7(b) Spectral sensitivity: Figure 2(a) Reference light source: Daytime natural light spectrum shown in Figure 3(a) Reference light source: Illuminant A, halogen lamp, spectrum of color temperature shown in Figure 3(b)

[0112] The evaluation begins with obtaining the white balance change (multiple) when the EC element is changed from a transmission state to a dimming state using the light source light of the reference light source (subject reflectance = 1), and then calculating a correction value to compensate for this (to make the change zero). Next, white balance is performed with the EC element in a transmission state (ND0) for the light source light of the control light source (subject reflectance = 1), and the correction value of the reference light source obtained earlier is applied. The color of the dimming state of the EC element, normalized for the brightness at this time, is called L * a * b * a in space * b * The plot is on a plane. In this diagram, the closer the plot of the dimming state is to the origin (the transmittance state of the EC element after white balancing), the higher the color reproducibility. In other words, the influence of the light source on color reproducibility is small. This means that even if a different light source is used and the dimming level changes, the white image of the subject will still appear white.

[0113] Comparing Figure 8(a) and Figure 8(b), NWD Max In Example 1, where priority is given to wavelength flatness, the plot of the dimming state is closer to the origin (transmission state) than in Comparative Example 1, where priority is given to wavelength flatness. Max It can be seen that the EC element of Example 1, which prioritizes wavelength flatness, is able to reduce the influence of the light source on color reproducibility more than the EC element of Comparative Example 1, which prioritizes wavelength flatness. Table 5 shows the color difference (ΔE00 ) value.

[0114] [Table 3]

[0115] From this, it can be seen that even when the same EC compounds are combined, the NWD of the present invention is superior to the case where wavelength flatness is prioritized. Max It was found that the light source effect can be suppressed more effectively when priority is given to the reference light source. Specifically, it was found that the light source effect can be suppressed by 2.8 to 11 times for all five types of reference light source, from low to high color temperature. In addition, when the EC element of the example was installed as a variable ND filter in a camera having an image sensor, a sensory evaluation of simulated images when the light source was changed was carried out. The EC element of the example was recognized as having less discomfort when comparing images in the element's transmission state and dimming state, for both the reference light source and the reference light source. From this, it was found that the NWD Max It was found that good color reproducibility can be obtained by setting the value of 1.03 or less using the variable transmittance VT(λ) normalized so that the average change is ND64.

[0116] NWD in the EC elements of Example 1 and Comparative Example 1 when the reference light source and the control light source are changed Max The values ​​are shown in Table 4, and FIG. 9 shows the results of evaluating the influence of the light source on color reproducibility in the same manner as above.

[0117] [Table 4]

[0118] From the comparison in Table 4, it was confirmed that the EC element of Example 1 is more adaptable to medium and low color temperatures than the EC element of Comparative Example 1. Also, from FIG. 9, it can be seen that the plot of Example 1 in the dimmed state of the reference light source is closer to the origin (transmitted state) than the plot of Comparative Example 1. This shows that the EC element of Example 1 is able to reduce the influence of the light source on color reproducibility more than the EC element of Comparative Example 1. Table 7 shows the color difference (ΔE 00 ) value.

[0119] [Table 5]

[0120] From this, it can be seen that even when the same EC compounds are combined, the NWD of the present invention is superior to the case where wavelength flatness is prioritized. Max It was found that the light source effect can be suppressed more effectively when priority is given to the reference light source. Specifically, it was found that the light source effect can be suppressed by 2.1 to 3.2 times for all three types of reference light source. In addition, when the EC element of the example was installed as a variable ND filter in a camera having an image sensor, a sensory evaluation of simulated images when the light source was changed was carried out. The EC element of the example was recognized as having less discomfort when comparing images in the element's transmission state and dimming state, for both the reference light source and the control light source. From this, it was found that the NWD Max It was found that good color reproducibility can be obtained by setting the value of 1.03 or less using the variable transmittance VT(λ) normalized so that the average change is ND64.

[0121] (Examples 2 and 3) Figure 10 shows the VT(λ) of the EC devices of Examples 2 and 3, in which the EC layers were constructed with different compositions (concentration ratios) using the same EC compounds as in Example 1. The wavelength flatness TF in the detection light wavelength range was 110% for Example 2 and 97.5% for Example 3. Table 6 shows the dimmed-state concentration (unit: mmol / L) of each EC compound, as well as the total charge concentration of the anodic EC compound and the cathodic EC compound.

[0122] [Table 6]

[0123] Table 6 shows that the total charge concentration in the dimmed state of the anodic EC compound and the total charge concentration in the dimmed state of the cathodic EC compound in Examples 2 and 3 are approximately equal, at 66.5 mmol / L and 66.6 mmol / L, and 67.6 mmol / L and 67.5 mmol / L, respectively. Table 7 shows the NWD calculated using the spectrum of daytime natural light shown in Figure 3(a) as the reference light source and a halogen lamp as the control light source. Max Table 7 shows the values ​​of wavelength flatness TF and wavelength uniformity TF. Max NWD of Comparative Example 1 (wavelength flatness priority) Max The value and wavelength flatness are also shown.

[0124] From Table 7, it was confirmed that the EC elements of Examples 1 to 3 were more adaptable to medium and low color temperatures than the EC element of Comparative Example 1.

[0125] Figure 11 shows the results of evaluating the influence of light source on color reproducibility for each EC element of Examples 1 to 3 and Comparative Example 1, when natural daylight shown in Figure 3(a) was used as the reference light source and a halogen lamp was used as the control light source. From Figure 11, it can be seen that the plots of the dimmed state of the control light source are closer to the origin (transmitted state) for Examples 1 to 3 than for Comparative Example 1. From this, NWD Max It can be seen that the EC elements of Examples 1 to 3, which prioritize wavelength flatness, are able to reduce the influence of the light source on color reproducibility more than the EC element of Comparative Example 1, which prioritizes wavelength flatness. Table 7 shows the color difference (ΔE 00 ) value.

[0126] [Table 7]

[0127] From Table 7, even when the same EC compounds are combined, the wavelength flatness is prioritized compared to the composition of the present invention, which prioritizes NWD. Max It was found that a composition that prioritizes this can suppress the light source effect. Specifically, it was found that the light source effect can be suppressed by approximately three times or more for all three concentration ratios. Furthermore, when the EC element of the example was installed as a variable ND filter in a camera having an image sensor, a sensory evaluation of simulated images when the light source was changed was carried out. The EC element of the example was recognized as having less discomfort when comparing images in the element's transmission state and dimming state, for both the standard light source and the control light source. From this, it was found that the NWD Max It was found that good color reproducibility can be obtained by setting the value of 1.03 or less using the variable transmittance VT(λ) normalized so that the average change is ND64.

[0128] EC devices in Examples 4 and 5 and Comparative Examples 2 and 3 were fabricated by varying the combination and composition of EC compounds with the spectra shown in Figure 4. In Example 4 and Comparative Example 2, the EC layer was constructed using anodic EC compounds (1), (4), and (5) and cathodic EC compounds (6), (7), and (9). In Example 5 and Comparative Example 3, the EC layer was constructed using anodic EC compounds (1), (2), and (3) and cathodic EC compounds (8), (9), and (10). EC compounds (6) to (10) have tunable absorption spectrum peaks in the R region of the photodetector, EC compounds (2) to (4) have tunable absorption spectrum peaks in the G region of the photodetector, and EC compounds (1), (5), (6), and (8) have tunable absorption spectrum peaks in the B region of the photodetector. The extinction ratio between the transmission state and the extinction state of each EC device was 64 (= average tunable transmittance of 1.56%). The detection light wavelength range of the photodetector was the range of 425 nm to 680 nm of the photodetector shown in FIG. 2(a).

[0129] Figure 12 shows the variable transmittance VT(λ) spectra of Examples 4 and 5 and Comparative Examples 2 and 3. Table 8 shows the dimmed state concentration (unit: mmol / L) of each EC compound, and the total charge concentration of each anodic EC compound and cathodic EC compound.

[0130] [Table 8]

[0131] Table 8 confirms that the total dimmed charge concentration of the anodic EC compounds and the total dimmed charge concentration of the cathodic EC compounds in Examples 4 and 5 were approximately equal to 68.3 mmol / L and 63.5 mmol / L, respectively. It also confirms that the total dimmed charge concentration of the anodic EC compounds and the total dimmed charge concentration of the cathodic EC compounds in Comparative Examples 2 and 3 were approximately equal to 66.6 mmol / L, 66.7 mmol / L, and 61.3 mmol / L, respectively.

[0132] In addition, the NWD was calculated using the spectrum of natural daylight shown in Figure 3(a) as the reference light source and a halogen lamp as the control light source. Max The values ​​are shown in Table 9. From Table 9, it can be seen that Examples 1, 4, and 5 are compatible with medium and low color temperatures.

[0133] Figure 13 shows the results of evaluating the influence of light sources on the color reproducibility of each EC element of Examples 1, 4, and 5 and Comparative Examples 1, 2, and 3. From Figure 13, it can be seen that the plots of the dimmed state of the control light source are closer to the origin (transmitted state) for Examples 1, 4, and 5 than for Comparative Examples 1, 2, and 3. From this, NWD Max It can be seen that the EC elements of Examples 1, 4, and 5, which prioritize wavelength flatness, are able to reduce the influence of the light source on color reproducibility more than the EC elements of Comparative Examples 1, 2, and 3, which prioritize wavelength flatness. Table 9 shows the color difference (ΔE 00 ) value.

[0134] [Table 9]

[0135] From Table 12, even when the EC compound was different, the NWD of the present invention was superior to the case where wavelength flatness was prioritized. MaxIt was found that the influence of the light source on color reproducibility can be suppressed more effectively when the above-mentioned combination is given priority. Specifically, it was found that the influence of the light source can be suppressed by more than 2.4 times for all combinations of the three types of compounds. Furthermore, when the EC element of the example was installed as a variable ND filter in a camera having an image sensor, a sensory evaluation of simulated images was carried out when the light source was changed. The EC element of the example was recognized as having less discomfort when comparing images in the element's transmission state and dimming state, for both the standard light source and the control light source. From this, it was found that the NWD Max It was found that good color reproducibility can be obtained by setting the value of 1.03 or less using the variable transmittance VT(λ) normalized so that the average change is ND64.

[0136] Example 6 Figure 15 shows the VT(λ) of the EC device of Example 6, in which the EC layer was constructed with a different composition (concentration ratio) using the same EC compounds as in Comparative Example 3. The wavelength flatness TF in the detection light wavelength range was 130%. Table 10 shows the dimmed concentration (unit: mmol / L) of each EC compound, as well as the total charge concentration of the anodic EC compound and the cathodic EC compound.

[0137] [Table 10]

[0138] From Table 10, it can be seen that the total charge concentration in the dimmed state of the anodic EC compound in Example 6 and the total charge concentration in the dimmed state of the cathodic EC compound are 60.2 mmol / L and 60.2 mmol / L, respectively, and are approximately equal.

[0139] Table 11 shows the NWD calculated using the spectrum of natural daylight shown in Figure 3(a) as the reference light source and the daylight fluorescent lamp shown in Figure 14 as the control light source. Max Table 11 shows the values ​​of wavelength flatness TF and wavelength flatness TF of the NWD of Comparative Example 3 (prioritizing wavelength flatness) constructed using the same compound group. Max The value and wavelength flatness are also shown.

[0140] From Table 11, it was confirmed that the EC elements of Examples 1 to 3 are more adaptable to fluorescent lamps having a spectrum with large intensity fluctuations in the intermediate color temperature range than the EC element of Comparative Example 1.

[0141] Figure 16 shows the results of evaluating the influence of light source on color reproducibility for each EC element of Example 6 and Comparative Example 3, when daytime natural light shown in Figure 3(a) was used as the reference light source and a daylight white fluorescent lamp shown in Figure 14 was used as the control light source. Figure 16 shows that the plot of the dimmed state of the control light source is closer to the origin (transmitted state) for Example 6 than for Comparative Example 3. From this, NWD Max It can be seen that the EC element of Example 6, which prioritizes wavelength flatness, is able to reduce the influence of the light source on color reproducibility more than the EC element of Comparative Example 3, which prioritizes wavelength flatness. Table 11 shows the color difference (ΔE 00 ) value.

[0142] [Table 11]

[0143] From Table 11, it can be seen that even when the same EC compounds are combined, the NWD of the present invention is superior to the composition that prioritizes wavelength flatness. Max It was found that a composition that prioritizes this can suppress the light source effect. Specifically, when the spectrum of daytime natural light, which has a relatively small change in intensity, is used as the reference light source and a fluorescent light source, which has a spectrum with large intensity fluctuations, is used as the control light source, it was found that the light source effect can be suppressed by about 26 times. In addition, when the EC element of the example was installed as a variable ND filter in a camera having an image sensor, a sensory evaluation of simulated images when the light source was changed was carried out. When comparing images in the element's transmission state and dimming state, the EC element of the example was recognized as having less discomfort, regardless of whether it was the reference light source or the control light source. From this, it was found that the NWD Max It was found that good color reproducibility can be obtained by setting the value of 1.03 or less using the variable transmittance VT(λ) normalized so that the average change is ND64.

Claims

1. An optical device having a photodetector and a photochromic element having a plurality of compounds whose light absorption characteristics change in response to an external stimulus, the plurality of compounds are compounds having different absorption wavelengths, the light-adjusting element has a variable transmittance VT(λ) that is a combination of the light absorption characteristics of the plurality of compounds; the photodetector has a detection light wavelength range of x bar: 580 nm to 680 nm, y bar: 500 nm to 580 nm, and z bar: 425 nm to 500 nm in CIE color matching functions; The reference illuminant is selected from CIE D65, D55, D50, Illuminant B, and Illuminant C; When the reference light source is CIE A light source, NWD Max <NWD MaxFP An optical device characterized by: NWD Max : The maximum value of the ratio of the signal intensity ratio of the transmitted light for each wavelength region of the detected light incident on the photodetector in the transmission state and the dimming state of the light modulating element between the reference light source and the reference light source (reference light source / reference light source or reference light source / reference light source) NWD MaxFP : The wavelength flatness TF of the VT(λ) in the detection light wavelength region is the minimum value TF FP NWD at a concentration ratio of the plurality of compounds Max

2. 2. The optical device according to claim 1, wherein the variable transmittance VT(λ) is expressed by the following formula: [Equation 1] Δε m (λ): the change extinction coefficient of compound m (m is 1 to the total number of compounds) C m : concentration of compound m in the dimmed state L: optical path length of the dimming element [m]

3. The NWD Max is NW R1 / N.W. R0 , N.W. R0 / N.W. R1 , N.W. B1 / N.W. B0 , N.W. B0 / N.W. B1 3. The optical device according to claim 1, wherein the maximum value of N.W. R0 : Change in the detection signal ratio in the photodetector in the red wavelength region of transmitted light emitted from the reference light source and transmitted through the dimming element N.W. R1 : A change in the detection signal ratio in the photodetector in the red wavelength region of the transmitted light emitted from the control light source and transmitted through the light control element N.W. B0 : A change in the detection signal ratio in the photodetector in the blue wavelength region of transmitted light emitted from the reference light source and transmitted through the dimming element N.W. B1 : A change in the detection signal ratio in the photodetector in the blue wavelength region of the transmitted light emitted from the control light source and transmitted through the dimming element NW R0 =W RC0 / W RT0 NW R1 =W RC1 / W RT1 NW B0 =W BC0 / W BT0 NW B1 =W BC1 / W BT1 W RC0 =S GC0 / S RC0 W RC1 =S GC1 / S RC1 W RT0 =S GT0 / S RT0 W RT1 =S GT1 / S RT1 W BC0 =S GC0 / S BC0 W BC1 =S GC1 / S BC1 W BT0 =S GT0 / S BT0 W BT1 =S GT1 / S BT1 S RT0 , S RT1 : Detected signal intensity in the photodetector in the red wavelength region of transmitted light emitted from the reference light source and the control light source and transmitted through the light modulating element in the transmitting state S GT0 , S GT1 : Detected signal intensity in the photodetector of the green wavelength region of transmitted light emitted from the reference light source and the control light source and transmitted through the light modulating element in a transmitting state S BT0 , S BT1 : Detected signal intensity in the photodetector of the blue wavelength region of transmitted light emitted from the reference light source and the control light source and transmitted through the light modulating element in the transmitting state S RC0 , S RC1 : Detected signal intensity in the photodetector in the red wavelength region of transmitted light emitted from the reference light source and the control light source and transmitted through the dimming element in a dimmed state S GC0 , S GC1 : Detected signal intensity in the photodetector of the green wavelength region of transmitted light emitted from the reference light source and the control light source and transmitted through the dimming element in the dimming state S BC0 , S BC1 : Detected signal intensity in the photodetector of the blue wavelength region of transmitted light emitted from the reference light source and the control light source and transmitted through the dimming element in the dimming state

4. The NWD Max 4. The optical device according to claim 1, wherein the variable transmittance VT(λ) is normalized so that the amount of change is 1 / 64, and is equal to or less than 1.

03.

5. 5. The optical device according to claim 1, wherein the plurality of compounds are compounds whose light absorption characteristics are electrically changed.

6. 6. The optical device according to claim 1, wherein the plurality of compounds are electrochromic compounds.

7. 7. The optical device according to claim 1, wherein the plurality of compounds is three or more compounds.

8. the plurality of compounds are anodic electrochromic compounds and cathodic electrochromic compounds; 8. The optical device according to claim 1, wherein the sum of the charge densities of the anodic electrochromic compounds in the dimmed state is approximately equal to the sum of the charge densities of the cathodic electrochromic compounds in the dimmed state.

9. 9. The optical device according to claim 8, wherein the optical device comprises a plurality of the anodic electrochromic compounds and a plurality of the cathodic electrochromic compounds.

10. 10. The optical device according to claim 1, wherein at least one of the compounds selected from the plurality of compounds has a peak of a variable absorption spectrum in each of a plurality of detection light wavelength regions of the photodetector.

11. 11. The optical device according to claim 1, wherein the reference illuminant is selected from the group consisting of D50, D55, D65, B illuminant, and C illuminant.

12. 12. The optical device according to claim 1, wherein the dimming element has a dimming ratio, which is a ratio of a transmitting state to a dimming state, of 8 or more.

13. 13. The optical device according to claim 12, wherein the extinction ratio is 32 or greater.

14. The dimming element has a TF>TF FP 14. The optical device according to claim 1, wherein:

15. 15. The optical device according to claim 1, wherein the photodetector is an image sensor.

16. 16. An imaging device comprising an optical system having a plurality of lenses and the optical device according to claim 15, wherein the imaging element receives light that has passed through the optical system, and the dimming element is disposed between the optical system and the imaging element as an optical filter.

17. the imaging optical system further includes a plurality of lenses, and the light control element and the imaging optical system form a lens unit; 16. The optical device according to claim 1, wherein the lens unit is arranged so that light passing through the lens unit is incident on the photodetector.

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