Sensor and bandpass filter

Abstract

The present application provides a sensor capable of high-precision measurement with high SN ratio even when the ambient temperature changes, and a bandpass filter for the sensor. The sensor has a light source, a bandpass filter that extracts light of a peak wavelength of the light source, and a light-receiving element that receives the light extracted by the bandpass filter. The bandpass filter has a bandpass layer and a support that supports the bandpass layer. When the thermal expansion coefficient of the bandpass layer is α1, the elastic modulus is E1, the thermal expansion coefficient of the support is α2, and the elastic modulus is E2, α1 > α2 and E1 < E2 are satisfied.

Description

Technical Field

[0001] The present invention relates to a sensor and a bandpass filter used in ranging devices, etc. Background Technology

[0002] Distance sensors (depth sensors) are used to determine the distance to objects in motion capture, autonomous driving of automobiles, and automatic control of robots.

[0003] For example, Patent Document 1 describes a method for calculating the distance to a distance-measuring object in a so-called time-of-flight type distance sensor (optical distance sensor) based on the phase shift between the flashing infrared light and the reflected light from the distance-measuring object.

[0004] Specifically, Patent Document 1 describes the following: infrared light is emitted as a flashing light corresponding to the emission signal and directed to the distance measuring object; the reflected infrared light is received from the distance measuring object to generate a light-receiving signal; the time difference, i.e., the phase difference, between the waveforms (e.g., pulse waveforms) of the emission signal and the light-receiving signal is calculated; and the distance between the optical distance sensor and the distance measuring object is calculated based on the phase difference.

[0005] Previous technical documents

[0006] Patent documents

[0007] Patent Document 1: U.S. Patent Publication No. 2010 / 0118123 Summary of the Invention

[0008] The technical problem to be solved by the invention

[0009] Not only this kind of distance measuring sensor, but also optical measurement sensors emit measuring light from a light source, measure the measuring light reflected by the object through a light receiving element, analyze the measurement results, and thus perform various measurements.

[0010] However, various types of light, such as sunlight and illumination, exist within the space where the sensor performs measurements. This light, known as external light, is incident on the light-receiving element. In many cases, external light includes light in the wavelength range emitted by the light source and light to which the light-receiving element is sensitive. If this external light is incident on the sensor's light-receiving element, it becomes noise, reducing the sensor's signal-to-noise ratio (SNR) and consequently decreasing the sensor's measurement accuracy. Therefore, a narrow-bandwidth bandpass filter is used to extract the light emitted by the light source at its wavelength, blocking other wavelengths and cutting off external light incident on the light-receiving element, thereby suppressing noise. The narrower the half-width at half-maximum (WHM) of the bandpass filter's transmission peak, the more effectively it can suppress external light incident on the light-receiving element, thus further improving the SNR.

[0011] Here, the emission wavelength of the light source changes with the ambient temperature. Specifically, the higher the temperature, the longer the emission wavelength of the light source. On the other hand, narrow-band bandpass filters made of ordinary inorganic materials show almost no change in the transmitted wavelength relative to temperature changes. Therefore, when using a bandpass filter with a narrow half-peak width (HWHM), a shift occurs between the emission wavelength of the light source and the transmitted wavelength of the bandpass filter when the ambient temperature changes. This results in less light of the transmitted wavelength incident on the light-receiving element, thus reducing the signal-to-noise ratio (SN ratio). If a bandpass filter with a wide HWHM is used, the shift between the emission wavelength of the light source and the transmitted wavelength of the bandpass filter can be suppressed even when the ambient temperature changes. However, if the HWHM of the bandpass filter is wide, the amount of external light that cannot be blocked increases, thus failing to adequately suppress noise and leading to a lower SN ratio.

[0012] In particular, when using light sources with narrow half-widths of the emission peak wavelength, such as laser light sources and LED (light-emitting diode) light sources used in ranging sensors, the effect of the emission wavelength shift caused by changes in ambient temperature becomes greater, resulting in a significant decrease in the SN ratio when the ambient temperature changes.

[0013] The objective of this invention is to solve the problems of the prior art and to provide a sensor that can achieve a high SN ratio and perform high-precision measurements even when the ambient temperature changes in sensors such as range sensors, as well as a bandpass filter for the sensor.

[0014] means for solving technical problems

[0015] To address this issue, the present invention has the following structure.

[0016] [1] A sensor having:

[0017] light source;

[0018] A bandpass filter extracts light at its peak emission wavelength from the light source; and

[0019] The light-receiving element receives the light extracted by the bandpass filter.

[0020] A bandpass filter has a bandpass layer and a support structure that supports the bandpass layer.

[0021] When the thermal expansion coefficient of the bandpass layer is set to α1, the elastic modulus is set to E1, the thermal expansion coefficient of the support is set to α2, and the elastic modulus is set to E2, the conditions are met: α1 > α2 and E1 < E2.

[0022] [2] According to the sensor described in [1], wherein,

[0023] The half-width at half-peak of the emission peak of the light source is less than 30 nm.

[0024] [3] According to the sensor described in [1] or [2], wherein,

[0025] The light source is a laser or a light-emitting diode.

[0026] [4] The sensor according to any one of [1] to [3], wherein,

[0027] The bandpass layer contains organic materials.

[0028] [5] The sensor according to any one of [1] to [4], wherein,

[0029] A bandpass filter transmits light at its peak emission wavelength from a light source and extracts the light at that peak emission wavelength.

[0030] The half-width at half maximum (WHM) of the transmission peak in the bandpass layer is less than 20 nm.

[0031] [6] The sensor according to any one of [1] to [4], wherein,

[0032] The bandpass filter reflects light at its emission peak wavelength from the light source and extracts light at the emission peak wavelength from the light source.

[0033] The half-width at half maximum (WHM) of the reflection peak in the bandpass layer is less than 20 nm.

[0034] [7] The sensor according to any one of [1] to [6], wherein,

[0035] The difference between the thermal expansion coefficient α1 of the bandgap layer and the thermal expansion coefficient α2 of the support is greater than 30 (ppm / ℃).

[0036] [8] The sensor according to any one of [1] to [7], wherein,

[0037] The coefficient of thermal expansion α2 of the support is less than 0 ppm / ℃.

[0038] [9] The sensor according to any one of [1] to [8], wherein,

[0039] The elastic modulus E1 of the bandpass layer is less than 10 GPa.

[0040]

[10] The sensor according to any one of [1] to [9], wherein,

[0041] The bandpass layer is an organic dielectric multilayer film.

[0042]

[11] The sensor according to any one of [1] to

[10] , wherein,

[0043] The bandpass layer is a layer formed by fixing a cholesterol-type liquid crystal phase, namely a cholesterol-type liquid crystal layer.

[0044] Cholesterol-type liquid crystal layers have regions where the in-plane refractive index nx along the slow axis and the refractive index ny along the fast axis satisfy nx > ny.

[0045] When the selective reflection center wavelength of the cholesterol-type liquid crystal layer is set to λ, the cholesterol-type liquid crystal layer has a second selective reflection peak at wavelength λ / 2, and the half-width of the second selective reflection peak at λ / 2 is less than 20 nm.

[0046]

[12] A bandpass filter having a bandpass layer and a support for supporting the bandpass layer.

[0047] The coefficient of thermal expansion α2 of the support is less than 0 ppm / ℃.

[0048]

[13] The sensor according to any one of [1] to [9], wherein,

[0049] The bandpass layer is a layer formed by fixing a cholesterol-type liquid crystal phase, namely a cholesterol-type liquid crystal layer.

[0050] The half-width at half-maximum (WHM) of the selective reflection peak in cholesterol-type liquid crystal layers is below 45 nm.

[0051]

[14] The sensor according to any one of [1] to [9] and

[13] , wherein,

[0052] The bandpass layer is a layer formed by fixing a cholesterol-type liquid crystal phase, namely a cholesterol-type liquid crystal layer.

[0053] The cholesterol-type liquid crystal layer is formed by immobilizing a cholesterol-type liquid crystal phase with a Δn of less than 0.06.

[0054]

[15] The sensor according to any one of [1] to [9],

[11] ,

[13] and

[14] , wherein,

[0055] The bandpass layer is a layer formed by fixing a cholesterol-type liquid crystal phase, namely a cholesterol-type liquid crystal layer.

[0056] The thickness of the cholesterol-type liquid crystal layer is 10 μm or more.

[0057]

[16] The sensor according to any one of [1] to [9],

[11] ,

[13] to

[15] , wherein,

[0058] The bandpass layer is a layer formed by fixing a cholesterol-type liquid crystal phase, namely a cholesterol-type liquid crystal layer.

[0059] Cholesterol-type liquid crystal layers are formed by stacking a cholesterol-type liquid crystal layer with a right-handed helical structure and a cholesterol-type liquid crystal layer with a left-handed helical structure.

[0060] Invention Effects

[0061] According to the present invention, a sensor capable of achieving a high signal-to-noise ratio and high-precision measurement even when the ambient temperature changes in a sensor such as a ranging sensor, and a bandpass filter for the sensor, can be provided. Attached Figure Description

[0062] Figure 1 This is a diagram that conceptually illustrates an example of the sensor of the present invention.

[0063] Figure 2 This is a diagram that conceptually illustrates another example of the sensor of the present invention.

[0064] Figure 3 This is a diagram conceptually illustrating the function of an example of the bandpass filter in the sensor of the present invention.

[0065] Figure 4 This is a diagram conceptually illustrating the function of another example of the bandpass filter in the sensor of the present invention.

[0066] Figure 5 This diagram conceptually illustrates the function of a conventional bandpass filter.

[0067] Figure 6 It is a graph showing the relationship between temperature and wavelength.

[0068] Figure 7 It is a conceptual representation Figure 1 The diagram shows the cholesterol-type liquid crystal layer with a bandpass filter in the sensor shown.

[0069] Figure 8 Viewed from the direction of the helical axis Figure 7 A diagram showing a portion of the liquid crystal compound in the cholesterol-type liquid crystal layer of the bandpass filter.

[0070] Figure 9 This is a diagram showing a portion of multiple liquid crystal compounds oriented in a twisted manner along the helical axis, viewed from the direction of the helical axis.

[0071] Figure 10 This is a conceptual diagram showing the probability of the presence of liquid crystal compounds in a cholesterol-type liquid crystal layer when viewed from the helical axis direction.

[0072] Figure 11 This is a diagram that conceptually illustrates an example of the light reflection characteristics of a typical cholesterol-type liquid crystal layer.

[0073] Figure 12 This is a diagram that conceptually illustrates an example of the light reflection characteristics of the bandpass filter possessed by the sensor of the present invention.

[0074] Figure 13This is a conceptual diagram illustrating an example of a light-shielding component used in the sensor of the present invention.

[0075] Figure 14 This is a diagram that conceptually illustrates an example of a wavelength selection element having the sensor of the present invention. Detailed Implementation

[0076] The sensor and bandpass filter of the present invention will now be described in detail with reference to the preferred embodiments shown in the accompanying drawings.

[0077] In this specification, the numerical range indicated by “~” refers to the range including the lower and upper limits of the values ​​recorded before and after “~”.

[0078] In this specification, "(meth)acrylate" is used to mean "any one or both of acrylate and methacrylate".

[0079] In this specification, terms such as "same" and "equal" encompass the range of error typically permissible in the technical field.

[0080] In this specification, when the minimum transmittance in the object (part) to be targeted is set as Tmin (%), the selected reflection center wavelength refers to the average of two wavelengths representing the half-value transmittance T1 / 2 (%) as expressed by the following formula.

[0081] The formula for calculating half-value transmittance is: T1 / 2 = 100 - (100 - Tmin) ÷ 2

[0082] [sensor]

[0083] The sensor of the present invention has:

[0084] light source;

[0085] A bandpass filter extracts light at its peak emission wavelength from the light source; and

[0086] The light-receiving element receives the light extracted by the bandpass filter.

[0087] A bandpass filter has a bandpass layer and a support structure that supports the bandpass layer.

[0088] When the thermal expansion coefficient of the bandpass layer is set to α1, the elastic modulus is set to E1, the thermal expansion coefficient of the support is set to α2, and the elastic modulus is set to E2, the conditions are met: α1 > α2 and E1 < E2.

[0089] Figure 1 The image below conceptually illustrates an example of the sensor of the present invention.

[0090] Figure 1The sensor 10a shown has a light source 12, a light-receiving element 14, and a bandpass filter 16a. Figure 1 In the sensor 10a shown, the bandpass filter 16a is a reflective bandpass filter that extracts light in a specified wavelength range by reflecting only light in that range. Specifically, the bandpass filter 16a is a bandpass filter that extracts light in the peak emission wavelength range of the light source by reflecting light in the wavelength range containing the emission peak wavelength of the light source and transmitting light in other wavelength ranges.

[0091] like Figure 1 As shown, the light source 12 is arranged to illuminate the measurement light I0 towards the outside (object O). The bandpass filter 16a is arranged to reflect the measurement light I1 incident at a predetermined angle towards the light-receiving element 14 from the measurement light I1 reflected by the object O. The light-receiving element 14 is arranged to receive the measurement light I2 reflected by the bandpass filter 16a.

[0092] The measurement of object O based on the sensor 10 of the present invention can be performed using various known measurements performed by optical sensors. Therefore, object O is not limited and can be a person, an animal, or an object.

[0093] As an example of measuring an object O, this can include measuring the distance to the object O (distance measurement), measuring the shape of the object O, measuring the movement of the object O, and identifying the object O.

[0094] These measurements can all be performed using known methods. For example, sensor 10 measures the distance to object O using time-of-flight (ToF) method.

[0095] This sensor 10a emits a light source 12, which, via a bandpass filter 16a, is used by a light-receiving element 14 to measure the light reflected from the object O. The light measurement result is analyzed, and thus the distance to the object O, etc., is measured (hereinafter, also referred to as the object measurement). At this time, external light such as sunlight and illumination incident on the sensor... z Since it is not reflected by the bandpass filter 16a, it can block the external light I incident on the light-receiving element 14. z Furthermore, it can suppress noise. At this time, the external light I in the reflection wavelength band (hereinafter also referred to as the pass range) of the bandpass filter 16a... z The light does not pass through the bandpass filter 16a and is incident on the light-receiving element 14. Therefore, if the bandpass filter 16a has a wide passing range, the external light I incident on the light-receiving element 14 will be... z Increasing the SN ratio cannot sufficiently improve the signal-to-noise ratio. Therefore, the bandpass filter 16a is required to have a narrow pass range (narrow bandwidth).

[0096] As mentioned earlier, the emission wavelength of the light source changes with ambient temperature. Specifically, the higher the temperature, the longer the emission wavelength of the light source. On the other hand, narrow-band bandpass filters made of ordinary inorganic materials show almost no change in the transmitted wavelength relative to temperature changes. Therefore, when using a narrow-band bandpass filter, a shift occurs between the emission wavelength of the light source and the transmitted wavelength of the bandpass filter when the ambient temperature changes. This results in less light of the emission wavelength incident on the light-receiving element, thus reducing the signal-to-noise ratio (SN ratio). If a bandpass filter with a wide half-width at half-maximum (HWHM) is used, the shift between the emission wavelength of the light source and the transmitted wavelength of the bandpass filter can be suppressed even when the ambient temperature changes. However, if the HWHM of the bandpass filter is wide, the amount of external light that cannot be blocked increases, thus failing to adequately suppress noise and leading to a lower SN ratio.

[0097] In contrast, the sensor of the present invention has the following structure: the bandpass filter has a bandpass layer and a support for supporting the bandpass layer. The thermal expansion coefficient of the bandpass layer is set as α1 and the elastic modulus is set as E1. The thermal expansion coefficient of the support is set as α2 and the elastic modulus is set as E2. Then, α1 > α2 and E1 < E2 are satisfied.

[0098] By employing this structure, the wavelength transmitted through the bandpass filter changes with variations in ambient temperature. Specifically, if the ambient temperature increases, the transmitted wavelength shifts to a longer wavelength range. Therefore, when the emission wavelength of the light source changes according to the ambient temperature, the transmitted wavelength of the bandpass filter also changes. For example, if the ambient temperature increases and the emission wavelength of the light source becomes longer, the transmitted wavelength of the bandpass filter also becomes longer. Thus, even with a narrow-bandwidth bandpass filter, both the emission wavelength of the light source and the transmitted wavelength of the bandpass filter change in the same way when the ambient temperature changes. Therefore, light of the emitted wavelength of the light source can pass through the bandpass filter, reducing the amount of light of the transmitted wavelength incident on the light-receiving element and preventing a decrease in the signal-to-noise ratio (SN ratio). Consequently, even with changes in ambient temperature, the sensor can achieve a high SN ratio and perform high-precision measurements.

[0099] The effect of changes in the wavelength of the bandpass filter when the ambient temperature changes will be discussed in detail later.

[0100] Here, in Figure 1 In the sensor 10a shown, the bandpass filter 16a is a reflective bandpass filter, but it is not limited to this.

[0101] Figure 2 Another example of the sensor of the present invention is shown conceptually.

[0102] Figure 2 The sensor 10b shown has a light source 12, a light-receiving element 14, and a bandpass filter 16b. Figure 2 In the sensor 10b shown, the bandpass filter 16b is a transmissive bandpass filter that extracts light in a specified wavelength range by transmitting light only through the specified wavelength range. Specifically, the bandpass filter 16b is a bandpass filter that extracts light in the peak emission wavelength range of the light source by transmitting light in the wavelength range containing the emission peak wavelength of the light source and absorbing and / or reflecting light in other wavelength ranges.

[0103] like Figure 2 As shown, the light source 12 is configured to illuminate the measurement light I0 towards the outside (object O). The bandpass filter 16b is configured to transmit the measurement light I1 reflected by the object O towards the light-receiving element 14. The light-receiving element 14 is positioned to receive the measurement light I3 transmitted through the bandpass filter 16a.

[0104] This sensor 10b emits a light source 12, which, via a bandpass filter 16b, is used by a light-receiving element 14 to measure the light reflected from the object O. The light measurement result is analyzed, and thus the distance to the object O, etc., is measured (hereinafter, also referred to as the object measurement). At this time, external light such as sunlight and illumination incident on the sensor... z The non-transmissive bandpass filter 16b can therefore block external light I incident on the light-receiving element 14. z It can also suppress noise.

[0105] In this type of transmissive bandpass filter, when a narrow-band bandpass filter is used, the emission wavelength of the light source and the transmission wavelength band (hereinafter also referred to as the transmission range) of the bandpass filter also shift when the ambient temperature changes. As a result, the amount of light of the emission wavelength of the light source incident on the light receiving element decreases, which leads to a problem of reduced SN ratio.

[0106] In contrast, when the sensor of the present invention is a transmissive bandpass filter, it also has the following structure: it has a bandpass layer and a support for supporting the bandpass layer. The thermal expansion coefficient of the bandpass layer is set to α1, the elastic modulus is set to E1, the thermal expansion coefficient of the support is set to α2, and the elastic modulus is set to E2, then α1 > α2 and E1 < E2 are satisfied.

[0107] By employing this structure, the wavelength transmitted through the bandpass filter changes with variations in ambient temperature. Therefore, even with a narrow-bandwidth bandpass filter, both the emitted wavelength of the light source and the transmitted wavelength change in the same way with changes in ambient temperature. Consequently, light of the emitted wavelength can pass through the bandpass filter, reducing the amount of light of the emitted wavelength that reaches the light-receiving element and preventing a decrease in the signal-to-noise ratio (SN ratio). Thus, even with changes in ambient temperature, the sensor can achieve a high SN ratio and perform high-precision measurements.

[0108] Furthermore, in the following description, without needing to distinguish between the reflective bandpass filter 16a and the transmissive bandpass filter 16b, they will be collectively referred to as bandpass filter 16.

[0109] 〔light source〕

[0110] There are no restrictions on the light source 12; any known light source used as a light source in an optical sensor can be utilized.

[0111] Examples of light sources include light bulbs such as mercury lamps, fluorescent lamps, halogen lamps, LEDs (Light Emitting Diodes), and semiconductor lasers.

[0112] Furthermore, the emitted light from the light source 12 can be diffused light or parallel light, such as a calibrated beam. Also, the sensor 10 can perform one-dimensional or two-dimensional scanning of the light emitted from the light source 12, as needed.

[0113] From the viewpoint of improving the sensor's signal-to-noise ratio, lasers such as LEDs (Light Emitting Diodes) and semiconductor lasers, which are capable of illuminating narrow-band light, are preferably used as the light source 12.

[0114] Furthermore, from the viewpoint of improving the SN ratio of the sensor, the half-width of the emission peak of the light source 12 is preferably 30 nm or less, more preferably 15 nm or less, and even more preferably 10 nm or less.

[0115] Here, when the light source 12 is a laser such as an LED (Light Emitting Diode) or a semiconductor laser, the change in emission wavelength (peak wavelength) based on temperature is approximately 0.1 nm / ℃ to 0.7 nm / ℃.

[0116] The wavelength of the light emitted by the light source 12 is not limited; it can be visible light, or non-visible light such as infrared and ultraviolet light. Among these, infrared light, which is non-visible light, is preferably used as the light emitted by the light source 12.

[0117] Furthermore, the light emitted from the light source 12 can be either unpolarized or polarized. When the light source 12 emits polarized light, the emitted light can be either linearly polarized or circularly polarized.

[0118] [Light receiving element]

[0119] There are no restrictions on the light-receiving element 14; various known light-receiving elements (photodetectors) used as light-receiving elements in optical sensors can be used.

[0120] As a light-receiving element 14, examples include CMOS (Complementary Metal Oxide Semiconductor) sensors and CCD (Charge-Coupled Device) sensors.

[0121] The light-receiving element 14 may not have spatial resolution, and is preferably a line sensor for detecting light in a linear manner or a region sensor for detecting light in two dimensions, with a region sensor being particularly preferred.

[0122] The light receiving element 14 measures the measurement light emitted from the light source 12 and reflected by the object O via the bandpass filter 16.

[0123] [Bandpass filter]

[0124] There are no special restrictions on a bandpass filter as long as it has the following characteristics: it has a bandpass layer and a support for the bandpass layer. The thermal expansion coefficient of the bandpass layer is set as α1 and the elastic modulus is set as E1. The thermal expansion coefficient of the support is set as α2 and the elastic modulus is set as E2. Then, α1 > α2 and E1 < E2 are satisfied.

[0125] <Bandpass Layer>

[0126] As a bandpass layer whose coefficient of thermal expansion and elastic modulus relative to the support satisfy the above formula, it is preferable to use a bandpass layer containing organic materials.

[0127] Specifically, examples of bandpass layers include organic dielectric multilayer films and cholesterol-type liquid crystal layers.

[0128] As is well known, dielectric multilayer films have a structure in which transparent films with high refractive index and transparent films with low refractive index are alternately stacked. By adjusting the thickness and refractive index of the high-refractive-index and low-refractive-index layers, light in the desired wavelength region can be reflected or transmitted, while light in other wavelength regions can be transmitted or reflected. That is, in dielectric multilayer films, the wavelength depends on the thickness of the high-refractive-index and low-refractive-index layers.

[0129] By using organic materials (polymers) to form the layers of a dielectric multilayer film, the thermal expansion coefficient α1 of the bandpass layer can be made greater than the thermal expansion coefficient α2 of the support, and the elastic modulus E1 can be made less than the elastic modulus E2 of the support.

[0130] As is well known, a cholesterol-type liquid crystal layer is a layer formed by fixing a cholesterol-type liquid crystal phase in which a liquid crystal compound is oriented in a helical manner. The cholesterol-type liquid crystal layer has a selective reflection center wavelength determined by the helical pitch of the cholesterol-type liquid crystal phase, reflecting light in a wavelength region containing the selective reflection center wavelength and transmitting light in other wavelength regions. That is, in a cholesterol-type liquid crystal layer, light passes through a wavelength dependent on the helical pitch of the cholesterol-type liquid crystal phase.

[0131] Thus, in dielectric multilayer films and cholesterol-type liquid crystal layers, the size of the structure formed in the thickness direction within the layer depends on the wavelength.

[0132] There are no particular restrictions on the thickness of the bandpass layer, as long as it is thinner than the thickness of the support. When the bandpass layer is reflective, its thickness should be sufficient to reflect light of the transmitted wavelength without reflecting light of other wavelengths. Similarly, when the bandpass layer is transmissive, its thickness should be sufficient to transmit light of the transmitted wavelength without transmitting light of other wavelengths.

[0133] As an example, the thickness of the bandpass layer is preferably 0.5 to 100 μm, more preferably 1 to 50 μm, and even more preferably 5 to 30 μm.

[0134] <Support>

[0135] The support structure supports the through layer.

[0136] If the support body is capable of supporting the bandpass layer and its coefficient of thermal expansion, elastic modulus, and thickness relative to the bandpass layer satisfy the above formula, then various sheet-like materials (films, plates) can be used.

[0137] Furthermore, when the bandpass filter is reflective, the support is preferably a bandpass filter that does not reflect light in wavelength regions other than the reflected wavelength region in the bandpass layer. And, when the bandpass filter is transmissive, the support is preferably a support that has sufficient transmittance in the transmitted wavelength region of the bandpass layer.

[0138] There is no limit to the thickness of the support, which is sufficient to support the bandpass layer. The thickness of the support can be appropriately set to maintain the bandpass layer, depending on the application of the bandpass filter and the material of the support.

[0139] The thickness of the support is preferably 1 to 2000 μm, more preferably 3 to 500 μm, and even more preferably 5 to 250 μm.

[0140] The support structure can be a single layer or multiple layers.

[0141] Examples of single-layer supports include supports made of glass, triacetyl cellulose (TAC), polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, acrylic acid, and polyolefins. Examples of multi-layer supports include supports comprising any of the aforementioned single-layer supports as a substrate, with other layers of supports disposed on the surface of the substrate.

[0142] Furthermore, the support can be made of a material with a negative coefficient of thermal expansion. That is, the material used as the support can be a material whose length decreases with increasing temperature.

[0143] As materials with a negative thermal expansion factor, they have various physical origins such as transverse vibration modes or rigid unit modes, and phase transitions. For example, cubic zirconium tungstate, rubber elastomers, quartz, zeolite, high-purity silicon, cubic scandium fluoride, high-strength polyethylene fiber, bismuth / nickel / iron oxide, etc. are known to have such origins. They are also described in detail in Sci. Technol. Adv. Mater. 13 (2012) 013001.

[0144] The following uses Figures 3-6 The effect of changes in the wavelength of a bandpass filter when the ambient temperature changes is explained.

[0145] Figure 3 This is a conceptual diagram illustrating the function of an example of a bandpass filter used in the sensor of the present invention. Furthermore, in the example diagram, the thickness and size of each layer and region are appropriately adjusted to clearly represent the structure of the present invention, differing from an actual bandpass filter.

[0146] Figure 3 The bandpass filter 16 shown has a bandpass layer 42 and a support 40a supporting the bandpass layer 42. Figure 3 The example shown is an example where the coefficient of thermal expansion α2 of the glass, etc., of the support 40a is approximately 0.

[0147] The coefficient of thermal expansion α1 of the bandpass layer 42 is greater than that of the support 40a. This means that during thermal expansion, the dimensional change of the bandpass layer 42 is greater than that of the support 40a. Furthermore, the elastic modulus E1 of the bandpass layer 42 is less than that of the support 40a. Typically, the support 40a is thicker than the bandpass layer 42; therefore, the fact that the elastic modulus E1 of the bandpass layer 42 is less than that of the support 40a indicates that the rigidity of the support 40a is higher than that of the bandpass layer 42.

[0148] exist Figure 3In the bandpass filter 16 shown, when the ambient temperature increases, the coefficient of thermal expansion α2 of the support 40a is approximately 0, so it hardly expands, but the bandpass layer 42 expands. At this time, the rigidity of the support 40a is higher than the rigidity of the bandpass layer 42, therefore the bandpass layer 42 expands in the planar direction (…). Figure 3 The bandpass layer 42 is constrained by the support 40a in the left-right direction, thus inhibiting stretching. Therefore, the bandpass layer 42 elongates in the thickness direction, from... Figure 3 The state shown above changes to the state shown below.

[0149] Here, as described above, the transmission wavelength of the bandpass layer 42 depends on the size of the structure formed in the thickness direction. Therefore, if the bandpass layer 42 is elongated in the thickness direction, the size of the structure formed in the thickness direction is elongated, and thus the transmission wavelength is correspondingly lengthened. Specifically, for example, if the bandpass layer 42 is a cholesterol-type liquid crystal layer, if the bandpass layer 42 is elongated in the thickness direction, the direction in which the helical pitch of the cholesterol-type liquid crystal layer becomes longer changes. If the helical pitch of the cholesterol-type liquid crystal layer becomes longer, the reflected wavelength is selected for lengthening. Furthermore, if the bandpass layer 42 is a dielectric multilayer film, if the bandpass layer 42 is elongated in the thickness direction, the direction in which the thickness of each high-refractive-index layer and low-refractive-index layer of the dielectric multilayer film increases changes. If the thickness of each high-refractive-index layer and low-refractive-index layer increases, the transmission wavelength (reflected wavelength or transmitted wavelength) is lengthened.

[0150] Figure 4 This is a conceptual diagram illustrating the function of another example of the bandpass filter used in the sensor of the present invention.

[0151] Figure 4 The bandpass filter 16 shown has a bandpass layer 42 and a support 40b supporting the bandpass layer 42. Figure 4 The example shown is an example of support 40b using a material with a negative coefficient of thermal expansion.

[0152] exist Figure 4 In the bandpass filter 16 shown, when the ambient temperature increases, the coefficient of thermal expansion α2 of the support 40b becomes negative, thus causing it to shrink. On the other hand, the bandpass layer 42 expands. At this time, the rigidity of the support 40b is higher than the rigidity of the bandpass layer 42, therefore the bandpass layer 42 expands in the planar direction (…). Figure 4 The bandpass layer 42 is constrained by the support 40b in the left-right direction, thus its stretching is suppressed and it contracts. Therefore, the bandpass layer 42 elongates in the thickness direction, from... Figure 4 The state shown above changes to the state shown below. If the bandpass layer 42 elongates in the thickness direction, the size of the structure formed in the thickness direction elongates, and thus the wavelength is correspondingly increased.

[0153] Thus, when a material with a negative coefficient of thermal expansion is used as the support 40b, the amount of elongation of the bandpass layer 42 in the thickness direction increases, thereby enabling a greater change in the transmission wavelength of the bandpass filter.

[0154] On the other hand, using Figure 5 The case where the thermal expansion coefficient α2 of the support is greater than the thermal expansion coefficient α1 of the bandpass layer is explained.

[0155] exist Figure 5 In the bandpass filter 116 shown, when the ambient temperature increases, the support 140 expands in the planar direction according to the coefficient of thermal expansion α2. Figure 5 The bandpass layer 42 extends horizontally (in the left-right direction). On the other hand, the bandpass layer 42 also expands. At this time, the coefficient of thermal expansion α1 of the bandpass layer 42 is less than the coefficient of thermal expansion α2 of the support 140, therefore the amount of elongation of the bandpass layer 42 in the planar direction is small. However, the bandpass layer 42 is constrained by the support 140 in the planar direction, and therefore extends as the support 140 elongates. Therefore, the bandpass layer 42 hardly elongates in the thickness direction. Figure 5 The state shown above changes to the state shown below. The bandpass layer 42 does not elongate in the thickness direction, therefore the transmission wavelength of the bandpass layer 42 remains unchanged.

[0156] Furthermore, in conventional narrow-band bandpass filters made of ordinary inorganic materials, the bandpass layer hardly expands thermally, so it does not elongate in the thickness direction, and the transmission wavelength of the bandpass layer does not change.

[0157] above, Figure 6 The diagram shows a conceptual representation of the relationship between ambient temperature and the wavelength transmitted by a bandpass filter. Furthermore, Figure 6 The diagram also shows the relationship between the wavelength of light emitted by the light source and the ambient temperature.

[0158] like Figure 6 As shown, the emission wavelength of the light source becomes longer as the ambient temperature increases.

[0159] On the other hand, in the case of conventional inorganic bandpass filters and bandpass layers where the coefficient of thermal expansion α1 is smaller than the coefficient of thermal expansion α2 of the support (α1 < α2), the transmitted wavelength of the bandpass filter does not change even if the ambient temperature increases. Therefore, as Figure 6 As shown, when the ambient temperature increases, a shift occurs between the emission wavelength of the light source and the transmission wavelength of the bandpass filter. This results in a decrease in the amount of light emitted at the emission wavelength of the light source incident on the light-receiving element, thus leading to a decrease in the SN ratio.

[0160] In contrast, such as Figure 6As shown, when the coefficient of thermal expansion α1 of the bandpass layer is greater than the coefficient of thermal expansion α2 of the support (α1 > α2), the transmitted wavelength of the bandpass filter increases with increasing ambient temperature. Therefore, even with a narrow-band bandpass filter, both the emission wavelength of the light source and the transmitted wavelength of the bandpass filter change in the same way when the ambient temperature changes. Thus, light of the emission wavelength of the light source can pass through the bandpass filter, reducing the amount of light of the transmitted wavelength incident on the light-receiving element and preventing a decrease in the signal-to-noise ratio (SN ratio).

[0161] In addition, Figure 3 In the example shown, the coefficient of thermal expansion of the support is set to approximately 0. Figure 4 In the example shown, the coefficient of thermal expansion of the support is set to negative, but this is not a limitation; the coefficient of thermal expansion of the support can be positive. When the coefficient of thermal expansion of the support is positive, if the coefficient of thermal expansion α1 of the bandpass layer is greater than the coefficient of thermal expansion α2 of the support, then the elongation of the bandpass layer in the planar direction when the ambient temperature increases is greater than the elongation of the support in the planar direction. However, the bandpass layer is constrained by the support in the planar direction, thus suppressing the stretching in the planar direction. Therefore, the bandpass layer elongates in the thickness direction.

[0162] From the viewpoint that the transmission wavelength of the bandpass filter can be changed more appropriately with respect to changes in ambient temperature, the coefficient of thermal expansion α1 of the bandpass layer is preferably 20 to 200 ppm / ℃, more preferably 30 to 150 ppm / ℃, and even more preferably 40 to 100 ppm / ℃.

[0163] Furthermore, from the viewpoint that the transmission wavelength of the bandpass filter can be changed more appropriately with respect to changes in ambient temperature, the coefficient of thermal expansion α2 of the support is preferably -500 to 20 ppm / ℃, more preferably -300 to 10 ppm / ℃, and even more preferably -200 to 5 ppm / ℃.

[0164] Furthermore, the coefficient of thermal expansion α2 of the support is preferably less than 0 ppm / ℃, i.e., it has a negative coefficient of thermal expansion.

[0165] Furthermore, from the viewpoint that the transmission wavelength of the bandpass filter can be changed more appropriately relative to changes in ambient temperature, the difference between the thermal expansion coefficient α1 of the bandpass layer and the thermal expansion coefficient α2 of the support is preferably 30 ppm / ℃ or more, more preferably 35 to 200 ppm / ℃, and even more preferably 40 to 200 ppm / ℃.

[0166] The coefficient of thermal expansion is determined as follows.

[0167] For example, it can be determined using known methods such as JIS K 7197.

[0168] For example, the thermomechanical properties are determined using a thermomechanical analysis apparatus (NETZSCH TMA4000SE). The measurement conditions are as follows: sample size is set to 5mm × 20mm, clamp spacing is set to 15mm, and clamp length is set to 2.5 ± 0.5mm both vertically. The temperature is changed at a rate of 5℃ / min within the range of -20℃ to 60℃, and the displacement of the clamp spacing is measured. Furthermore, a specified weight of 3g is applied to the sample for measurement. Next, the slope of the approximate straight line of displacement data from -20℃ to 60℃ is calculated, and the displacement per 1℃ temperature change is determined. Furthermore, by dividing this slope by the clamp spacing of 15mm when the sample is set, the coefficient of thermal expansion can be calculated.

[0169] Furthermore, from the viewpoint that the transmission wavelength of the bandpass filter can be changed more appropriately with respect to changes in ambient temperature, the elastic modulus E1 of the bandpass layer is preferably less than 10 GPa, more preferably 1 to 8 GPa, and even more preferably 2 to 6 GPa.

[0170] Furthermore, from the viewpoint that the transmission wavelength of the bandpass filter can be changed more appropriately with respect to changes in ambient temperature, the elastic modulus E2 of the support is preferably 10 to 200 GPa, more preferably 20 to 150 GPa, and even more preferably 40 to 100 GPa.

[0171] Furthermore, from the viewpoint that the transmission wavelength of the bandpass filter can be changed more appropriately with respect to changes in ambient temperature, the ratio of the elastic modulus E2 of the support to the elastic modulus E1 of the bandpass layer is preferably 2 or more, more preferably 5 or more, and even more preferably 10 or more.

[0172] The elastic modulus is measured as follows. Unless otherwise specified, the elastic modulus is the elastic modulus at room temperature (25°C).

[0173] The elastic modulus can be determined, for example, by known methods such as JIS K 7127.

[0174] Here, the half-width at half-maximum (WHM) of the peak at the transmitted wavelength of the bandpass filter is preferably 20 nm or less. That is, when the bandpass filter is a transmission type bandpass filter, the WHM of the transmission peak of the bandpass layer is preferably 20 nm or less, more preferably 1 to 18 nm, and even more preferably 2 to 15 nm. Furthermore, when the bandpass filter is a reflection type bandpass filter, the WHM of the reflection peak of the bandpass layer is preferably 20 nm or less, more preferably 1 to 18 nm, and even more preferably 2 to 15 nm.

[0175] By setting the half-peak width (FWHM) of the bandpass filter's transmitted wavelength to 20 nm or less, it is more effective to cut off external light incident on the sensor and further improve the signal-to-noise ratio (SN ratio). Furthermore, in this invention, the transmitted wavelength of the bandpass filter changes with ambient temperature; therefore, when the FWHM of the bandpass filter is small, it is preferable to suppress the shift between the emission wavelength of the light source and the transmitted wavelength of the bandpass filter when the ambient temperature changes.

[0176] Here, the bandpass layer has a layer formed by fixing a cholesterol-type liquid crystal phase, namely a cholesterol-type liquid crystal layer. Therefore, the cholesterol-type liquid crystal layer has a region in which the refractive index nx in the slow axis direction and the refractive index ny in the fast axis direction satisfy nx > ny. When the selective reflection center wavelength of the cholesterol-type liquid crystal layer is set to λ, the cholesterol-type liquid crystal layer has a second selective reflection peak at wavelength λ / 2. The half-width of the second selective reflection peak at λ / 2 is preferably less than 20 nm.

[0177] By configuring the cholesterol-type liquid crystal layer to have a region where the in-plane refractive index nx along the slow axis and the refractive index ny along the fast axis satisfy nx > ny, it is possible to configure the cholesterol-type liquid crystal layer to have a second selective reflection peak with a narrow half-width at half the wavelength of the selective reflection center. Utilizing the narrow half-width second selective reflection peak of the cholesterol-type liquid crystal layer, a narrow-band bandpass filter that allows only narrow-band light to pass through can be fabricated. By using such a bandpass filter, the sensor of the present invention can further reduce the influence of external light and perform higher-precision measurements with a high signal-to-noise ratio (SN ratio).

[0178] The following describes a cholesteric liquid crystal layer that has a region satisfying nx > ny and has a second selective reflection peak at wavelength λ / 2.

[0179] Figure 7 The image shows a conceptual example of such a cholesterol-type liquid crystal layer.

[0180] Figure 7 The cholesterol-type liquid crystal layer 26 shown is formed on an alignment film 24 formed on a support 20.

[0181] In the following description, the side of the support 20 is referred to as the lower surface, and the side of the cholesterol-type liquid crystal layer 26 is referred to as the upper surface. Therefore, in the support 20, the side of the cholesterol-type liquid crystal layer 26 is referred to as the upper surface, and the opposite side is referred to as the lower surface. Furthermore, in the alignment film 24 and the cholesterol-type liquid crystal layer 26, the surface of the support 20 side is referred to as the lower surface, and the opposite side is referred to as the upper surface.

[0182] <Support>

[0183] The support 20 supports the cholesterol-type liquid crystal layer 26 during its formation.

[0184] Alternatively, when using the cholesterol-type liquid crystal layer 26 as a bandpass layer, the support 20 and alignment film 24 can be peeled off and transferred to the support of the bandpass filter for use. That is, the support 20 can be a dummy support. Or, the support 20 can be used as the support of the bandpass filter. That is, the cholesterol-type liquid crystal layer 26 can be formed on the support of the bandpass filter.

[0185] When the support 20 is used as a support for a bandpass filter, the support described above can be used as the support 20.

[0186] Furthermore, when the support 20 is a dummy support, various dummy supports used in the fabrication of cholesterol-type liquid crystal layers can be exemplified. For example, thin-film components made of glass, triacetyl cellulose (TAC), polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, acrylic acid, and polyolefins can be exemplified as dummy supports. Moreover, a multilayer support having multiple layers made of these materials can be used.

[0187] <Orientation film>

[0188] The orientation film 24 is formed on the surface (upper surface) of the support 20.

[0189] The alignment film 24 is an alignment film used to orient the liquid crystal compound 32 to a specified orientation state when forming the cholesterol-type liquid crystal layer 26.

[0190] The orientation film 24 utilizes various known orientation films.

[0191] Examples include friction-treated films made of organic compounds such as polymers, tilted vapor-deposited films of inorganic compounds, films with microgrooves, films that accumulate organic compounds such as ω-trisanoic acid, dioctadecylmethylammonium chloride and methyl stearate based on the Langmuir-Blodgett process, and photo-aligned films that are prepared by emitting polarized or unpolarized light from materials with optical orientation properties.

[0192] The alignment film 24 can be formed by a known method corresponding to the forming material of the alignment film.

[0193] For example, orientation films based on friction processing are formed by repeatedly rubbing the surface of a polymer layer with paper or cloth in a specified direction.

[0194] As materials used in the alignment film, polyimide, polyvinyl alcohol, polymers with polymerizable groups as described in Japanese Patent Application Publication No. 9-152509, and materials used in the formation of alignment films as described in Japanese Patent Application Publication Nos. 2005-97377, 2005-99228, and 2005-128503 are preferred.

[0195] Furthermore, even if the alignment film 24 is not formed, the support 20 can be treated by friction processing and laser processing to function as an alignment film.

[0196] The alignment film 24 is preferably prepared by irradiating polarized or unpolarized light with a material that is photo-oriented, thus forming a so-called photo-alignment film. That is, the alignment film 24 is preferably prepared by coating a photo-alignment material onto a support 20.

[0197] It can irradiate the optical alignment film with polarized light from a vertical or inclined direction, and can also irradiate the optical alignment film with unpolarized light from an inclined direction.

[0198] As preferred examples of photoalignment materials that can be used in the alignment film of the present invention, examples include Japanese Patent Application Publication Nos. 2006-285197, 2007-76839, 2007-138138, 2007-94071, 2007-121721, 2007-140465, and 2007... Azo compounds described in Japanese Patent Publication No. -156439, Japanese Patent Application Publication No. 2007-133184, Japanese Patent Application Publication No. 2009-109831, Japanese Patent Publication No. 3883848 and Japanese Patent Publication No. 4151746, aromatic ester compounds described in Japanese Patent Application Publication No. 2002-229039, Japanese Patent Application Publication No. 2002-265541 and Japanese Patent Application Publication No. 2002-317013 The photocrosslinking polyimide and / or alkenyl-substituted nadicimide compounds with photooriented units described in the publications, the photocrosslinking silane derivatives described in Japanese Patent Nos. 4205195 and 4205198, the photocrosslinking polyimide, photocrosslinking polyamide, and photocrosslinking polyamide described in Japanese Patent Nos. 2003-520878, 2004-529220, and 4162850, are all examples of such products. Crosslinked polyesters and photodimerizable compounds, particularly cinnamic acid ester compounds, chalcone compounds and coumarin compounds, as described in Japanese Patent Application Publication Nos. 9-118717, 10-506420, 2003-505561, International Publication No. 2010 / 150748, 2013-177561 and 2014-012823.

[0199] Among them, azo compounds, photocrosslinked polyimides, photocrosslinked polyamides, photocrosslinked polyesters, cinnamic acid ester compounds and chalcone compounds can be preferentially utilized.

[0200] There is no limit to the thickness of the alignment film 24. The thickness can be appropriately set according to the forming material of the alignment film to obtain the necessary alignment function.

[0201] The thickness of the alignment film is preferably 0.01 to 5 μm, more preferably 0.05 to 2 μm.

[0202] <Cholesterol-type liquid crystal layer>

[0203] A cholesterol-type liquid crystal layer 26 is formed on the surface of the alignment film 24.

[0204] in addition, Figure 7In order to simplify the accompanying drawings and clearly illustrate the structure of the cholesterol-type liquid crystal layer 26, the cholesterol-type liquid crystal layer 26 is only conceptually shown with two rotations (720° rotations) of the twisted orientation of the liquid crystal compound 32 in the cholesterol-type liquid crystal phase. That is, in Figure 7 Only two pitches of the helical structure in the cholesterol-type liquid crystal phase are shown.

[0205] However, the cholesterol-type liquid crystal layer 26, like the cholesterol-type liquid crystal layer formed by fixing a cholesterol-type liquid crystal phase, has a spiral structure in which the liquid crystal compound 32 is stacked in a spiral rotation along the spiral axis in the thickness direction. The structure in which the liquid crystal compound 32 is stacked in a spiral rotation once (360° rotation) is set as a spiral period of 1 pitch, and the liquid crystal compound 32 rotating in a spiral has a stacked structure of more than 1 pitch.

[0206] That is, in this invention, the helical structure of the cholesterol-type liquid crystal phase (cholesterol-type liquid crystal layer) is formed by stacking more than one pitch. The helical structure of the liquid crystal compound 32, which is stacked by more than one pitch of cholesterol-type liquid crystal layer, exhibits wavelength-selective reflectivity as described later.

[0207] Therefore, in this invention, even if a layer with a spiral structure in which the liquid crystal compound 32 is stacked in a spiral shape along the spiral axis in the thickness direction is not a cholesterol-type liquid crystal layer, the layer with a spiral period of less than 1 pitch is not a cholesterol-type liquid crystal layer.

[0208] The cholesterol-type liquid crystal layer 26 is formed by fixing a cholesterol-type liquid crystal phase. That is, the cholesterol-type liquid crystal layer 26 is a layer formed by orienting the liquid crystal compound 32 (liquid crystal material) in a cholesterol-type manner.

[0209] As is well known, cholesterol-type liquid crystal layers formed by fixing a cholesterol-type liquid crystal phase have wavelength-selective reflectivity.

[0210] Although detailed later, the selective reflection wavelength region of the cholesterol-type liquid crystal layer depends on the thickness length of the aforementioned helical pitch. Figure 7 The pitch P shown.

[0211] In this invention, the first embodiment in which the bandpass layer has a layer formed by fixing a cholesterol-type liquid crystal phase, namely a cholesterol-type liquid crystal layer, is as follows:

[0212] Cholesterol-type liquid crystal layers have regions where the in-plane refractive index nx along the slow axis and the refractive index ny along the fast axis satisfy nx > ny.

[0213] When the selective reflection center wavelength of the cholesterol-type liquid crystal layer is set to λ, the cholesterol-type liquid crystal layer has a second selective reflection peak at wavelength λ / 2, and the half-width of the second selective reflection peak at λ / 2 is less than 20 nm.

[0214] In this case, the second selected reflection peak at λ / 2 is used as the bandpass.

[0215] In this invention, the second embodiment where the bandpass layer has a layer formed by fixing a cholesterol-type liquid crystal phase, i.e., a cholesterol-type liquid crystal layer, is as follows:

[0216] The half-width at half-maximum (WHM) of the selective reflection peak in cholesterol-type liquid crystal layers is below 45 nm.

[0217] In this case, the first selective reflection peak is used as the bandpass instead of the second selective reflection peak.

[0218] In the first embodiment where the bandpass layer is a layer formed by fixing a cholesterol-type liquid crystal phase, i.e., a cholesterol-type liquid crystal layer, the in-plane refractive index nx in the slow axis direction and the refractive index ny in the fast axis direction of the cholesterol-type liquid crystal layer 26 satisfy nx > ny.

[0219] In this invention, such as Figure 8 As shown, the cholesterol-type liquid crystal layer 26 has a structure in which the angle between the molecular axes of adjacent liquid crystal compounds 32 gradually changes when viewed from the helical axis direction. In other words, the probability of the presence of liquid crystal compounds 32 is different when viewed from the helical axis direction. Thus, the cholesterol-type liquid crystal layer 26 has a structure in which the refractive index nx in the slow axis direction and the refractive index ny in the fast axis direction satisfy nx > ny.

[0220] Additionally, in the following explanation, such as Figure 8 As shown, when the arrangement of liquid crystal compounds 32 is observed from the direction of the helical axis, the structure of the cholesterol-type liquid crystal layer 26 having a gradually changing angle between the molecular axes of adjacent liquid crystal compounds 32 is also called an ellipsoid with refractive index.

[0221] By configuring the cholesteric liquid crystal layer 26 such that the refractive index nx along the slow axis and the refractive index ny along the fast axis satisfy nx > ny, primary and secondary light are obtained as reflected light reflected through the cholesteric liquid crystal layer 26. In this case, the secondary light is obtained as a wavelength with a very narrow frequency band compared to the primary light. Furthermore, the selective center reflection wavelength of the secondary light is half that of the selective center reflection wavelength of the primary light. The function of this cholesteric liquid crystal layer 26 (bandpass filter) will be described in detail later. The primary light corresponds to the selective reflection peak (hereinafter also referred to as the first selective reflection peak) of the selective reflection center wavelength of the cholesteric liquid crystal layer. The secondary light corresponds to the second selective reflection peak.

[0222] <<Cholesterol-type liquid crystal phase>>

[0223] It is known that cholesterol-type liquid crystal phases exhibit selective reflectivity at specific wavelengths.

[0224] In typical cholesterol-type liquid crystal phases, the selective reflection center wavelength λ depends on the pitch P of the helical coil in the cholesterol-type liquid crystal phase and follows the relationship between the average refractive index n of the cholesterol-type liquid crystal phase and λ = n × P. Therefore, by adjusting this helical pitch, the selective reflection center wavelength can be adjusted. Furthermore, in this invention, light reflected according to the relationship λ = n × P is primary light.

[0225] In the selective reflection center wavelength of cholesterol-type liquid crystal phases, the longer the pitch P, the longer the wavelength.

[0226] In addition, as mentioned above, the pitch P of the helix is ​​one pitch (the period of the helix) of the helical structure of the cholesterol-type liquid crystal phase, in other words, the number of turns of the helix once, that is, the length of the helical axis direction of the direction vector (or the long axis direction if it is a rod-shaped liquid crystal) of the liquid crystal compound constituting the cholesterol-type liquid crystal phase rotating 360°.

[0227] If the cross-section of a cholesterol-type liquid crystal layer is observed using a scanning electron microscope (SEM), a stripe pattern originating from the cholesterol-type liquid crystal phase and alternating bright lines (bright areas) and dark lines (dark areas) is observed in the thickness direction. The helical periodic pitch, or pitch P, is equal to the length of two bright lines and two dark lines in the thickness direction.

[0228] When forming a cholesterol-type liquid crystal layer, the helical pitch of the cholesterol-type liquid crystal phase depends on the type and concentration of the chiral reagent used with the liquid crystal compound. Therefore, by adjusting these factors, the desired helical pitch can be obtained.

[0229] Furthermore, the adjustment of the pitch is described in detail in FUJIFILM Research Report No. 50 (2005), pp. 60-63. The methods for determining the direction of the helix and the pitch can be found in "Introduction to Liquid Crystal Chemistry Experiments," edited by the Japan Liquid Crystal Society and published by Sigma in 2007, page 46, and in "Liquid Crystal Handbook," edited by Maruzen of the Liquid Crystal Handbook Editorial Committee, page 196.

[0230] Cholesterol-type liquid crystal phases exhibit selective reflectivity for either right- or left-handed circularly polarized light at specific wavelengths. Whether the reflected light is right-handed or left-handed circularly polarized depends on the direction of helical twist (rotation) of the cholesterol-type liquid crystal phase. In the selective reflection of circularly polarized light based on cholesterol-type liquid crystal phases, right-handed circularly polarized light is reflected when the helix of the cholesterol-type liquid crystal layer is twisted to the right, and left-handed circularly polarized light is reflected when the helix is ​​twisted to the left. Therefore, the direction of helical twist in the cholesterol-type liquid crystal phase can be determined by incident right-handed and / or left-handed circularly polarized light onto the cholesterol-type liquid crystal layer.

[0231] Furthermore, the rotation direction of the cholesterol-type liquid crystal phase can be adjusted by the type of liquid crystal compound forming the cholesterol-type liquid crystal layer and / or the type of chiral reagent added.

[0232] Furthermore, the half-peak width Δλ (nm) of the selective reflection wavelength region (circularly polarized reflection wavelength region), representing the first-order light half-peak width, depends on the pitch P of the cholesterol-type liquid crystal phase (Δn) and the helix, and follows the relationship Δλ = Δn × P. Therefore, the width of the selective reflection wavelength region (selective reflection wavelength region) of the first-order light can be controlled by adjusting Δn. Δn can be adjusted according to the type and mixing ratio of the liquid crystal compound forming the cholesterol-type liquid crystal layer, as well as the temperature at which the orientation is fixed.

[0233] The full width at half maximum (FWHM) of the primary light can be adjusted according to the application of the bandpass filter. For example, a FWHM of 30 nm or higher is acceptable.

[0234] In cholesterol-type liquid crystal layers, there are no restrictions on the selection of the reflection center wavelength; it can be set appropriately according to the application of the sensor using the bandpass filter.

[0235] Specifically, in the cholesterol-type liquid crystal layer, the selective reflection center wavelength can be appropriately set according to the wavelength of the measurement light used by the sensor. Although described later, in this embodiment, the sensor receives light in the wavelength region of the second selective reflection peak of the bandpass filter through a light-receiving element. The wavelength of the second selective reflection peak is half the wavelength of the selective reflection center wavelength λ of the cholesterol-type liquid crystal layer. Therefore, the wavelength of the second selective reflection peak is set to the selective reflection center wavelength of the cholesterol-type liquid crystal layer in a manner that includes the wavelength region of the measurement light.

[0236] As mentioned above, the selective reflection center wavelength of the cholesterol-type liquid crystal layer depends on the pitch P of the helical structure. Therefore, the wavelength of the second selective reflection peak can be set by including the pitch P of the helical structure in the wavelength region of the measurement light. The pitch P of the helical structure can be confirmed by observing the cross-section of the cholesterol-type liquid crystal layer using SEM to resolve the stripe pattern originating from the cholesterol-type liquid crystal phase, which alternates between bright and dark lines in the thickness direction.

[0237] <<Methods for forming cholesterol-type liquid crystal layers>>

[0238] Cholesterol-type liquid crystal layers can be formed by fixing the cholesterol-type liquid crystal phase in a layered manner.

[0239] The structure formed by fixing the cholesterol-type liquid crystal phase only needs to be a structure that maintains the orientation of the liquid crystal compound that is a cholesterol-type liquid crystal phase. Typically, the following structure is preferred: the polymerizable liquid crystal compound is set in the orientation state of the cholesterol-type liquid crystal phase, and then polymerized and cured by ultraviolet irradiation, heating, etc., to form a non-flowing layer, and at the same time change it to a state in which the orientation morphology will not change by external field or external force.

[0240] Furthermore, in structures formed by fixing a cholesterol-type liquid crystal phase, it is sufficient to retain the optical properties of the cholesterol-type liquid crystal phase; in a cholesterol-type liquid crystal layer, the liquid crystal compound may not exhibit liquid crystal properties. For example, polymerizable liquid crystal compounds can lose their liquid crystal properties by undergoing a curing reaction to increase their molecular weight.

[0241] As an example of materials used in the formation of a cholesterol-type liquid crystal layer formed by fixing a cholesterol-type liquid crystal phase, a liquid crystal composition comprising a liquid crystal compound can be cited. The liquid crystal compound is preferably a polymerizable liquid crystal compound.

[0242] Furthermore, the liquid crystal composition used in the formation of the cholesterol-type liquid crystal layer may also contain surfactants and chiral reagents.

[0243] <<Polymerizable Liquid Crystal Compounds (Rod-shaped Liquid Crystal Compounds)>>

[0244] Polymerizable liquid crystal compounds can be rod-shaped or disc-shaped.

[0245] Examples of rod-shaped polymerizable liquid crystal compounds that form cholesterol-type liquid crystal phases include rod-shaped nematic liquid crystal compounds. Preferably, rod-shaped nematic liquid crystal compounds are methylimine derivatives, azo derivatives, cyanobiphenyl derivatives, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexane derivatives, cyano-substituted phenylpyrimidine derivatives, alkoxy-substituted phenylpyrimidine derivatives, phenyl dioxane derivatives, diphenylacetylene derivatives, and alkenylcyclohexylbenzonitrile derivatives. Not only low-molecular-weight liquid crystal compounds but also high-molecular-weight liquid crystal compounds can be used.

[0246] Polymerizable liquid crystal compounds are obtained by introducing polymerizable groups into liquid crystal compounds. Examples of polymerizable groups include unsaturated polymerizable groups, epoxy groups, and acridine groups; unsaturated polymerizable groups are preferred, and olefinic unsaturated polymerizable groups are more preferred. Polymerizable groups can be introduced into the molecules of liquid crystal compounds by various methods. The number of polymerizable groups in the polymerizable liquid crystal compound is preferably 1 to 6, more preferably 1 to 3.

[0247] Examples of polymerizable liquid crystal compounds include those described in Makromol. Chem., Vol. 190, pp. 2255 (1989), Advanced Materials, Vol. 5, pp. 107 (1993), U.S. Patent No. 4,683,327, U.S. Patent No. 5,622,648, U.S. Patent No. 5,770,107, International Publications Nos. 95 / 22586, 95 / 24455, 97 / 00600, 98 / 23580, 98 / 52905, Japanese Patent Application Publications Nos. 1-272,551, 6-16616, 7-110,469, 11-080081, and 2001-328,973. Two or more polymerizable liquid crystal compounds can be used together. Using two or more polymerizable liquid crystal compounds together can lower the orientation temperature.

[0248] Furthermore, as polymerizable liquid crystal compounds other than those mentioned above, cyclic organopolysiloxane compounds having a cholesterol phase, such as those disclosed in Japanese Patent Application Publication No. 57-165480, can be used. Additionally, as the aforementioned polymeric liquid crystal compounds, polymers with mesocrystalline groups for displaying liquid crystals incorporated into the main chain, side chain, or both the main chain and side chain, cholesteric liquid crystals with cholesterol groups incorporated into the side chains, liquid crystal polymers such as those disclosed in Japanese Patent Application Publication No. 9-133810, and liquid crystal polymers such as those disclosed in Japanese Patent Application Publication No. 11-293252 can be used.

[0249] <<Disc-shaped Liquid Crystal Compounds>>

[0250] As a disc-shaped liquid crystal compound, the disc-shaped liquid crystal compound described in Japanese Patent Application Publication No. 2007-108732 and Japanese Patent Application Publication No. 2010-244038 are preferred, for example.

[0251] Furthermore, the amount of polymerizable liquid crystal compound added to the liquid crystal composition is preferably 75 to 99.9% by mass relative to the mass of the solid components of the liquid crystal composition (mass after removing the solvent), more preferably 80 to 99% by mass, and even more preferably 85 to 90% by mass.

[0252] <<Surfactants>>

[0253] The liquid crystal composition used to form a cholesterol-type liquid crystal layer may contain a surfactant.

[0254] The surfactant is preferably a compound that can function as an orientation control agent, which helps to stabilize or rapidly orient a cholesterol-type liquid crystal phase. Examples of surfactants include siloxane surfactants and fluorinated surfactants, with fluorinated surfactants being a preferred example.

[0255] Specific examples of surfactants include compounds described in paragraphs

[0082] to

[0090] of Japanese Patent Application Publication No. 2014-119605, compounds described in paragraphs

[0031] to

[0034] of Japanese Patent Application Publication No. 2012-203237, compounds exemplified in paragraphs

[0092] and

[0093] of Japanese Patent Application Publication No. 2005-099248, compounds exemplified in paragraphs

[0076] to

[0078] and

[0082] to

[0085] of Japanese Patent Application Publication No. 2002-129162, and fluoro(meth)acrylate polymers described in paragraphs

[0018] to

[0043] of Japanese Patent Application Publication No. 2007-272185.

[0256] In addition, a single surfactant can be used alone, or two or more surfactants can be used in combination.

[0257] As a fluorinated surfactant, the compounds described in paragraphs

[0082] to

[0090] of Japanese Patent Application Publication No. 2014-119605 are preferred.

[0258] The amount of surfactant added to the liquid crystal composition relative to the total mass of the liquid crystal compound is preferably 0.01 to 10% by mass, more preferably 0.01 to 5% by mass, and even more preferably 0.02 to 1% by mass.

[0259] Here, in the second embodiment where the bandpass layer is a layer formed by fixing a cholesterol-type liquid crystal phase, i.e., a cholesterol-type liquid crystal layer, the liquid crystal compound is preferably represented by the following formula (I) in terms of having a small Δn and narrowing the half-width of the selective reflection of the cholesterol-type liquid crystal layer.

[0260] When mc is defined as the number of trans-1,4-cyclohexyl groups that can have substituents represented by A divided by m, liquid crystal compounds that satisfy mc > 0.1 are preferred, and liquid crystal compounds that satisfy 0.4 ≤ mc ≤ 0.8 are more preferred.

[0261] In addition, the above mc is a number represented by the following formula.

[0262] mc = (the number of trans-1,4-cyclohexyl groups that can have substituents represented by A) ÷ m

[0263]

[0264] In the formula,

[0265] A represents a phenylene group that may have substituents or a trans-1,4-cyclohexylene group that may have substituents, wherein at least one of A represents a trans-1,4-cyclohexylene group that may have substituents.

[0266] L represents a single bond or a linker group selected from the group consisting of -CH2O-, -OCH2-, -(CH2)2OC(=O)-, -C(=O)O(CH2)2-, -C(=O)O-, -OC(=O)-, -OC(=O)O-, -CH=NN=CH-, -CH=CH-, -C≡C-, -NHC(=O)-, -C(=O)NH-, -CH=N-, -N=CH-, -CH=CH-C(=O)O-, and -OC(=O)-CH=CH-.

[0267] m represents an integer from 3 to 12.

[0268] Sp 1 and Sp 2 Each of these groups independently represents a linker selected from the group consisting of a single bond or a group selected from straight-chain or branched alkylene groups having 1 to 20 carbon atoms, in which one or more -CH2- groups are substituted with -O-, -S-, -NH-, -N(CH3)-, -C(=O)-, -OC(=O)-, or C(=O)O-.

[0269] Q 1 and Q 2 Each independently represents a hydrogen atom or a polymeric group selected from the group represented by the following formulas (Q-1) to (Q-5), wherein Q 1 and Q 2 Any one of them represents a polymerizable group;

[0270]

[0271] A is a phenylene group that may have substituents or a trans-1,4-cyclohexylene group that may have substituents. In this specification, when referred to as phenylene, 1,4-phenylene is preferred.

[0272] In addition, at least one of A is a trans-1,4-cyclohexyl group that can have substituents.

[0273] The m A's can be the same or different from each other.

[0274] m represents an integer from 3 to 12, preferably an integer from 3 to 9, more preferably an integer from 3 to 7, and even more preferably an integer from 3 to 5.

[0275] In formula (I), the substituents that can have phenylene and trans-1,4-cyclohexene are not particularly limited. Examples include substituents selected from the group consisting of alkyl, cycloalkyl, alkoxy, alkyl ether, amide, amino, and halogen atoms, as well as groups composed of two or more of the above substituents. Furthermore, as an example of a substituent, -C(=O)-X (described later) can be included. 3 -Sp 3 -Q 3 The substituents are indicated. Phenylidene and trans-1,4-cyclohexylene can also have 1 to 4 substituents. When there are two or more substituents, the two or more substituents can be the same or different from each other.

[0276] In this specification, the alkyl group can be either straight-chain or branched. Preferably, the alkyl group has 1 to 30 carbon atoms, more preferably 1 to 10, and even more preferably 1 to 6. Examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, 1,1-dimethylpropyl, n-hexyl, isohexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl. The description of alkyl groups in alkoxy groups is the same as that related to the above-mentioned alkyl groups. Furthermore, in this specification, as specific examples of alkylene groups when they are alkylene compounds, divalent groups obtained by removing one arbitrary hydrogen atom from each of the above-mentioned alkyl groups can be given. Examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms.

[0277] In this specification, the cycloalkyl group preferably has 3 or more carbon atoms, more preferably 5 or more, and more preferably 20 or less, more preferably 10 or less, even more preferably 8 or less, and particularly preferably 6 or less. Examples of cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl.

[0278] The substituents that can be present in the phenylene and trans-1,4-cyclohexene groups are preferably selected from alkyl, alkoxy, and -C(=O)-X groups. 3 -Sp 3 -Q 3 The substituents in the group. Where X 3 Indicates a single bond, -O-, -S-, or -N (Sp 4 -Q 4 - or indicates the relationship with Q 3 and Sp 3 Together, they form nitrogen atoms with a ring structure. 3 and Sp 4Each of these groups independently represents a single bond or a linker selected from the group consisting of one or more -CH2- groups substituted with -O-, -S-, -NH-, -N(CH3)-, -C(=O)-, -OC(=O)- or C(=O)O-, including straight-chain or branched alkylene groups having 1 to 20 carbon atoms.

[0279] Q 3 and Q 4 Each of the following groups independently represents a polymerizable group selected from the group consisting of hydrogen atoms, cycloalkyl groups, one or more of the cycloalkyl groups whose -CH2- is replaced by -O-, -S-, -NH-, -N(CH3)-, -C(=O)-, -OC(=O)- or -C(=O)O-, or groups represented by formulas (Q-1) to (Q-5).

[0280] As a group in a cycloalkyl group where one or more -CH2- are replaced by -O-, -S-, -NH-, -N(CH3)-, -C(=O)-, -OC(=O)-, or -C(=O)O-, examples include tetrahydrofuranyl, pyrrolidinyl, imidazolidinyl, pyrazolidineyl, piperidinyl, piperazinyl, and morpholinyl. Among these, tetrahydrofuranyl is preferred, and 2-tetrahydrofuranyl is more preferred.

[0281] In formula (I), L represents a single bond or a linker selected from the group consisting of -CH2O-, -OCH2-, -(CH2)2OC(=O)-, -C(=O)O(CH2)2-, -C(=O)O-, -OC(=O)-, -OC(=O)O-, -CH=CH-C(=O)O-, and -OC(=O)-CH=CH-. L is preferably -C(=O)O- or OC(=O)-. The m L's can be the same or different from each other.

[0282] Sp 1 and Sp 2 Sp represents independently a single bond or a linker group selected from the group consisting of one or more -CH2- groups substituted with -O-, -S-, -NH-, -N(CH3)-, -C(=O)-, -OC(=O)- or -C(=O)O-, including straight-chain or branched alkylene groups having 1 to 20 carbon atoms. 1 and Sp 2The linking group is preferably composed of a straight-chain alkylene group with 1 to 10 carbon atoms, which is selected from the group consisting of -O-, -OC(=O)- and -C(=O)O-, and is independently and independently bonded to both ends. Alternatively, it may be composed of one or more groups selected from the group consisting of -OC(=O)-, -C(=O)O-, -O- and straight-chain alkylene groups with 1 to 10 carbon atoms. More preferably, it may be a straight-chain alkylene group with 1 to 10 carbon atoms, which is bonded to both ends with -O-.

[0283] Q 1 and Q 2 Each of the following can independently represent a hydrogen atom or a polymeric group selected from the group represented by the following formulas (Q-1) to (Q-5). Wherein, Q 1 and Q 2 Any one of them represents a polymerizable group.

[0284]

[0285] As a polymerizable group, acryloyl (formula (Q-1)) or methacryloyl (formula (Q-2)) is preferred.

[0286] Specific examples of the aforementioned liquid crystal compounds include liquid crystal compounds represented by formula (I-11), liquid crystal compounds represented by formula (I-21), and liquid crystal compounds represented by formula (I-31). In addition to the above, examples include compounds represented by formula (I) in Japanese Patent Application Publication No. 2013-112631, compounds represented by formula (I) in Japanese Patent Application Publication No. 2010-070543, compounds represented by formula (I) in Japanese Patent Application Publication No. 2008-291218, compounds represented by formula (I) in Japanese Patent No. 4725516, compounds represented by general formula (II) in Japanese Patent Application Publication No. 2013-087109, and compounds represented by general formula (II). The compounds described in paragraph

[0043] of Japanese Patent Application Publication No. 7-176927, the compounds represented by formula (1-1) in Japanese Patent Application Publication No. 2009-286885, the compounds represented by general formula (I) in WO2014 / 10325, the compounds represented by formula (1) in Japanese Patent Application Publication No. 2016-081035, and the compounds represented by formulas (2-1) and (2-2) in Japanese Patent Application Publication No. 2016-121339 are known compounds.

[0287] Liquid crystal compounds represented by formula (I-11)

[0288]

[0289] In the formula, R 11 It represents a straight-chain or branched alkyl group with 1 to 12 carbon atoms, or -Z.12 -Sp 12 -Q 12 ,

[0290] L 11 This indicates a single bond, -C(=O)O-, or -O(C=O)-.

[0291] L 12 This represents -C(=O)O-, -OC(=O)-, or -CONR. 2 -,

[0292] R 2 Indicates an alkyl group having 1 to 3 hydrogen atoms or carbon atoms.

[0293] Z 11 and Z 12 Each of these can be used independently to represent a single bond, -O-, -NH-, -N(CH3)-, -S-, -C(=O)O-, -OC(=O)-, -OC(=O)O-, or -C(=O)NR. 12 -,

[0294] R 12 Represents a hydrogen atom or Sp 12 -Q 12 ,

[0295] Sp 11 and Sp 12 Each can independently represent a single bond, and can be Q'd. 11 The substituted straight-chain or branched alkylene groups having 1 to 12 carbon atoms may be Q 11 The -CH2- group of any one or more of the straight-chain or branched alkylene groups having 1 to 12 carbon atoms is substituted with -O-, -S-, -NH-, or -N(Q) 11 The linker base obtained by -C (=O)- or -C(=O)-

[0296] Q 11 This refers to a hydrogen atom, a cycloalkyl group, or a group in which one or more -CH2- atoms are substituted with -O-, -S-, -NH-, -N(CH3)-, -C(=O)-, -OC(=O)-, or -C(=O)O-, or a polymerizable group selected from the group consisting of groups represented by formulas (Q-1) to (Q-5).

[0297] Q 12 Represents a hydrogen atom or a polymeric group selected from the group represented by formulas (Q-1) to (Q-5).

[0298] l 11 Represents integers from 0 to 2.

[0299] m 11 Integers representing 1 or 2

[0300] n 11 Represents integers from 1 to 3.

[0301] Multiple R 11 Multiple L 11 Multiple L 12 Multiple l 11 Multiple Z 11 Multiple Sp 11 and multiple Qs 11 They can be the same as each other or different.

[0302] Furthermore, in the liquid crystal compound represented by formula (I-11), R... 11 It contains at least one Q. 12 -Z is a polymerizable group selected from the group represented by formulas (Q-1) to (Q-5). 12 -Sp 12 -Q 12 .

[0303] Furthermore, the liquid crystal compound represented by formula (I-11) is preferably Z. 11 It is -C(=O)O- or C(=O)NR 12 -and Q 11 -Z is a polymerizable group selected from the group represented by formulas (Q-1) to (Q-5). 11 -Sp 11 -Q 11 Furthermore, in the liquid crystal compound represented by formula (I-11), R... 11 Z is preferred. 12 It is -C(=O)O- or C(=O)NR 12 -and Q 12 -Z is a polymerizable group selected from the group represented by formulas (Q-1) to (Q-5). 12 -Sp 12 -Q 12 .

[0304] All 1,4-cyclohexyl groups contained in the liquid crystal compounds represented by formula (I-11) are trans-1,4-cyclohexyl groups.

[0305] As a preferred embodiment of the liquid crystal compound represented by formula (I-11), L can be cited as an example. 11 For single bond, l 11 It is 1-(dicyclohexyl) and Q 11 A compound selected from the group consisting of polymeric groups represented by formulas (Q-1) to (Q-5).

[0306] As another preferred embodiment of the liquid crystal compound represented by formula (I-11), m 11 For 2, l 11 =0 and 2 R 11 All represent -Z 12 -Sp 12 -Q 12 Q 12 A compound selected from the group consisting of polymeric groups represented by formulas (Q-1) to (Q-5).

[0307] Liquid crystal compounds represented by formula (I-21)

[0308]

[0309] In the formula, Z 21 and Z 22 Each can be independently represented as either trans-1,4-cyclohexylene or phenylene, which may have substituents.

[0310] The substituents mentioned above are each independently selected from -CO-X. 21 -Sp 23 -Q 23 1 to 4 substituents in the group consisting of alkyl and alkoxy groups,

[0311] m21 represents an integer of 1 or 2, and n21 represents an integer of 0 or 1.

[0312] When m21 represents 2, n21 represents 0.

[0313] m21 indicates 2 Z at time 2. 21 They can be the same or different.

[0314] Z 21 and Z 22 At least one of them is a phenylene that may have substituents.

[0315] L 21 L 22 L 23 and L 24 Each of these independently represents a single bond or a linker selected from the group consisting of -CH2O-, -OCH2-, -(CH2)2OC(=O)-, -C(=O)O(CH2)2-, -C(=O)O-, -OC(=O)-, -OC(=O)O-, -CH=CH-C(=O)O-, and OC(=O)-CH=CH-.

[0316] X 21 Indicates -O-, -S-, or -N (Sp 25 -Q 25 - or indicates the relationship with Q 23and Sp 23 Nitrogen atoms that together form a ring structure

[0317] r 21 Represents integers from 1 to 4.

[0318] Sp 21 Sp 22 Sp 23 and Sp 25 Each of these groups independently represents a linker selected from the group consisting of a single bond or a group selected from straight-chain or branched alkylene groups having 1 to 20 carbon atoms, in which one or more -CH2- groups are substituted with -O-, -S-, -NH-, -N(CH3)-, -C(=O)-, -OC(=O)-, or C(=O)O-.

[0319] Q 21 and Q 22 Each of the following can be independently represented as a polymerizable group selected from the group represented by formulas (Q-1) to (Q-5).

[0320] Q 23 This refers to a hydrogen atom, a cycloalkyl group, a group in which one or more -CH2- atoms in a cycloalkyl group are substituted with -O-, -S-, -NH-, -N(CH3)-, -C(=O)-, -OC(=O)-, or -C(=O)O-, a polymerizable group selected from the group represented by formulas (Q-1) to (Q-5), or X. 21 To Q 23 and Sp 23 When nitrogen atoms form a ring structure together, they represent a single bond.

[0321] Q 25 Sp represents a hydrogen atom, a cycloalkyl group, or a group in which one or more -CH2- atoms are substituted with -O-, -S-, -NH-, -N(CH3)-, -C(=O)-, -OC(=O)-, or -C(=O)O-, or any polymerizable group selected from the group group represented by formulas (Q-1) to (Q-5). 25 When it is a single key, Q 25 It is not a hydrogen atom.

[0322] The liquid crystal compound represented by formula (I-21) preferably has a structure in which 1,4-phenylene and trans-1,4-cyclohexylene are alternately present, for example, preferably with the following structure: m21 is 2, n21 is 0 and Z 21 From Q 21 The sides are respectively trans-1,4-cyclohexylene, which can have substituents, arylene, or m21 = 1, n21 = 1, and Z = 1. 21For arylene groups that can have substituents and Z 22 It is an aryl group that can have substituents.

[0323] Liquid crystal compounds represented by formula (I-31);

[0324]

[0325] In the formula, R 31 and R 32 Each independently is selected from alkyl, alkoxy, and -C(=O)-X. 31 -Sp 33 -Q 33 The groups in the group,

[0326] n31 and n32 independently represent integers from 0 to 4.

[0327] X 31 Indicates a single bond, -O-, -S-, or -N (Sp 34 -Q 34 - or indicates the relationship with Q 33 and Sp 33 Together they form nitrogen atoms with a ring structure.

[0328] Z 31 This indicates that phenylene can have substituents.

[0329] Z 32 This indicates either the trans-1,4-cyclohexylene or the phenylene group, which may have substituents.

[0330] Each of the above substituents is independently selected from alkyl, alkoxy, and -C(=O)-X groups. 31 -Sp 33 -Q 33 The group contains 1 to 4 substituents.

[0331] m31 represents an integer of 1 or 2, and m32 represents an integer from 0 to 2.

[0332] m31 and m32 represent two Z values ​​at time 2. 31 Z 32 They can be the same or different.

[0333] L 31 and L 32 Each of these independently represents a single bond or a linker selected from the group consisting of -CH2O-, -OCH2-, -(CH2)2OC(=O)-, -C(=O)O(CH2)2-, -C(=O)O-, -OC(=O)-, -OC(=O)O-, -CH=CH-C(=O)O-, and OC(=O)-CH=CH-.

[0334] Sp 31 Sp 32 Sp 33 and Sp 34 Each of these groups independently represents a linker selected from the group consisting of a single bond or a group selected from straight-chain or branched alkylene groups having 1 to 20 carbon atoms, in which one or more -CH2- groups are substituted with -O-, -S-, -NH-, -N(CH3)-, -C(=O)-, -OC(=O)-, or C(=O)O-.

[0335] Q 31 and Q 32 Each of the following can be independently represented as a polymerizable group selected from the group represented by formulas (Q-1) to (Q-5).

[0336] Q 33 and Q 34 Each of the following groups independently represents a hydrogen atom, a cycloalkyl group, or a group in which one or more -CH2- atoms are substituted with -O-, -S-, -NH-, -N(CH3)-, -C(=O)-, -OC(=O)-, or -C(=O)O-, or a polymerizable group selected from the group represented by formulas (Q-1) to (Q-5). 33 With X 31 and Sp 33 When they form a ring structure together, they can represent a single bond, Sp 34 When it is a single key, Q 34 It is not a hydrogen atom.

[0337] As a liquid crystal compound represented by formula (I-31), Z is a particularly preferred compound. 32 Compounds that are phenylene and compounds with m32 of 0.

[0338] The compound represented by formula (I) also preferably has a partial structure represented by the following formula (II).

[0339]

[0340] In equation (II), the black circles indicate the bonding positions with other parts of equation (I). The partial structure represented by equation (II) may be included as part of the partial structure represented by equation (III) below in equation (I).

[0341]

[0342] In the formula, R 1 and R 2 Each is independently selected from hydrogen atoms, alkyl groups, alkoxy groups, and groups consisting of -C(=O)-X atoms.3 -Sp 3 -Q 3 The group represented is a group within a group. Where X... 3 Indicates a single bond, -O-, -S-, or -N (Sp 4 -Q 4 - or indicates the relationship with Q 3 and Sp 3 Together they form nitrogen atoms with a ring structure. X 3 Preferably, it is a single bond or O-. R 1 and R 2 Preferably -C(=O)-X 3 -Sp 3 -Q 3 Furthermore, R 1 and R 2 Ideally, they should be the same as each other. 1 and R 2 There are no particular restrictions on the bonding positions of each component with the phenylene group.

[0343] Sp 3 and Sp 4 Each independently represents a linker group selected from the group consisting of a single bond or a group selected from straight-chain or branched alkylene groups having 1 to 20 carbon atoms, in which one or more -CH2- groups are substituted with -O-, -S-, -NH-, -N(CH3)-, -C(=O)-, -OC(=O)-, or C(=O)O-. As Sp 3 and Sp 4 Each of the following is preferred independently: a straight-chain or branched alkylene group having 1 to 10 carbon atoms, more preferably a straight-chain alkylene group having 1 to 5 carbon atoms, and even more preferably a straight-chain alkylene group having 1 to 3 carbon atoms.

[0344] Q 3 and Q 4 Each of the following can independently represent a hydrogen atom, a cycloalkyl group, a group in which one or more -CH2- atoms are replaced by -O-, -S-, -NH-, -N(CH3)-, -C(=O)-, -OC(=O)- or -C(=O)O-, or any polymerizable group selected from the group represented by formulas (Q-1) to (Q-5).

[0345] Compounds represented by formula (I) also preferably have a structure represented by the following formula (II-2).

[0346]

[0347] In the formula, A 1 and A 2Each of these can independently represent either a phenylene group that may have substituents or a trans-1,4-cyclohexylene group that may have substituents, wherein each substituent is independently selected from alkyl, alkoxy, and -C(=O)-X groups. 3 -Sp 3 -Q 3 The group contains 1 to 4 substituents.

[0348] L 1 L 2 and L 3 Represents a single bond or a linker group selected from the group consisting of -CH2O-, -OCH2-, -(CH2)2OC(=O)-, -C(=O)O(CH2)2-, -C(=O)O-, -OC(=O)-, -OC(=O)O-, -CH=CH-C(=O)O-, and -OC(=O)-CH=CH-.

[0349] n1 and n2 represent integers from 0 to 9 independently, and n1+n2 is less than or equal to 9.

[0350] Q 1 Q 2 Sp 1 and Sp 2 The definition is the same as the definition of each group in formula (I) above. X 3 Sp 3 Q 3 R 1 and R 2 The definition is the same as the definition of each group in formula (II) above.

[0351] The following compounds can be cited as examples of liquid crystal compounds represented by formula (I) that satisfy 0.4≤mc≤0.8.

[0352] [Chemical Formula 10]

[0353]

[0354] [Chemical Formula 11]

[0355]

[0356] [Chemical Formula 12]

[0357]

[0358] [Chemical Formula 13]

[0359]

[0360] [Chemical Formula 14]

[0361]

[0362] [Chemical Formula 15]

[0363]

[0364] [Chemical Formula 16]

[0365]

[0366] [Chemical Formula 17]

[0367]

[0368] [Chemical Formula 18]

[0369]

[0370] [Chemical Formula 19]

[0371]

[0372] Furthermore, two or more liquid crystal compounds can be used together. For example, two or more liquid crystal compounds represented by formula (I) can be used together.

[0373] Preferably, a liquid crystal compound represented by formula (I) and satisfying 0.1 < mc < 0.3 is used together with a liquid crystal compound represented by formula (I) above and satisfying 0.4 ≤ mc ≤ 0.8.

[0374] The following compounds can be cited as examples of liquid crystal compounds represented by formula (I) that satisfy 0.1 < mc < 0.3.

[0375] [Chemical Formula 20]

[0376]

[0377] [Chemical Formula 21]

[0378]

[0379] [Chemical Formula 22]

[0380]

[0381] [Chemical Formula 23]

[0382]

[0383] <<Chiral Reagents (Optically Active Compounds)>>

[0384] Chiral agents have the function of inducing helical structures in cholesterol-type liquid crystal phases. Since the direction of helical twist or the pitch of the helical period induced by the compound varies, the chiral agent can be selected according to the purpose.

[0385] There are no restrictions on the chiral reagents used; well-known compounds can be used (e.g., as described in the Liquid Crystal Devices Handbook, Chapter 3, Item 4-3, TN (twisted nematic), STN (Super Twisted Nematic) with chiral reagents, page 199, edited by the 142nd Committee of the Japan Society for the Promotion of Science, 1989), isosorbide, and isomannitol derivatives, etc.

[0386] Chiral reagents typically contain asymmetric carbon atoms, but axially asymmetric or surface-asymmetric compounds that do not contain asymmetric carbon atoms can also be used as chiral reagents. Examples of axially asymmetric or surface-asymmetric compounds include naphthalene, helicene, p-xylene dimers, and their derivatives. Chiral reagents may also have polymerizable groups. When both the chiral reagent and the liquid crystal compound have polymerizable groups, a polymer having repeating units derived from the polymerizable liquid crystal compound and repeating units derived from the chiral reagent can be formed through a polymerization reaction between the polymerizable chiral reagent and the polymerizable liquid crystal compound. In this manner, the polymerizable groups possessed by the polymerizable chiral reagent are preferably the same as those possessed by the polymerizable liquid crystal compound. Therefore, the polymerizable groups of the chiral reagent are preferably unsaturated polymerizable groups, epoxy groups, or acridine groups, more preferably unsaturated polymerizable groups, and even more preferably olefinic unsaturated polymerizable groups.

[0387] Furthermore, the chiral reagent can also be a liquid crystal compound.

[0388] When the chiral reagent has a photoisomerizing group, it is preferable that a pattern corresponding to the desired reflection wavelength is formed by emitting light through a photomask after coating and orientation. As the photoisomerizing group, isomerization sites of compounds exhibiting photochromic properties, azo groups, oxyazo groups, or cinnamyl groups are preferred. As specific compounds, the compounds described in Japanese Patent Application Publication Nos. 2002-080478, 2002-080851, 2002-179668, 2002-179669, 2002-179670, 2002-179681, 2002-179682, 2002-338575, 2002-338668, 2003-313189, and 2003-313292 may be used.

[0389] The content of the chiral reagent in the liquid crystal composition relative to the molar content of the liquid crystal compound is preferably 0.01 to 200 mol%, more preferably 1 to 30 mol%.

[0390] <<Polymerization Initiators>>

[0391] When the liquid crystal composition contains a polymerizable compound, it preferably contains a polymerization initiator. In the case of polymerization reaction carried out by ultraviolet emission, the polymerization initiator used is preferably a photopolymerization initiator capable of initiating polymerization reaction by ultraviolet emission.

[0392] Examples of photopolymerization initiators include α-carbonyl compounds (described in U.S. Patent Nos. 2,367,661 and 2,367,670), azobin ethers (described in U.S. Patent No. 2,448,828), α-hydrocarbon-substituted aromatic azobin compounds (described in U.S. Patent No. 2,722,512), polynucleoquinone compounds (described in U.S. Patent Nos. 3,046,127 and 2,951,758), combinations of triarylimidazolium dimers and p-aminophenyl ketones (described in U.S. Patent No. 3,549,367), acridine and phenazine compounds (described in Japanese Patent Application Publication No. 60-105,667 and U.S. Patent No. 4,239,850), and oxadiazole compounds (described in U.S. Patent No. 4,212,970).

[0393] The polymerization initiator is preferably a dichroic free radical polymerization initiator.

[0394] Dichroic radical polymerization initiators are free radical polymerization initiators that exhibit absorption selectivity relative to light with a specific polarization direction and generate free radicals through excitation by their polarized light. In other words, dichroic radical polymerization initiators are polymerization initiators that have different absorption selectivity in light with a specific polarization direction and light with a polarization direction orthogonal to the aforementioned specific polarization direction.

[0395] For details and specific examples, please refer to booklet WO2003 / 054111.

[0396] Specific examples of dichroic free radical polymerization initiators include polymerization initiators with the following chemical formulas. Furthermore, as dichroic free radical polymerization initiators, polymerization initiators described in paragraphs

[0046] to

[0097] of Japanese Patent Application Publication No. 2016-535863 can be used.

[0397] [Chemical Formula 24]

[0398]

[0399] The content of the photopolymerization initiator in the liquid crystal composition is preferably 0.1 to 20% by mass relative to the content of the liquid crystal compound, and more preferably 0.5 to 12% by mass.

[0400] <<Cross-linking agent>>

[0401] To improve the strength and durability of the cured film, the liquid crystal composition may contain any crosslinking agent. As a crosslinking agent, crosslinking agents that are cured by ultraviolet light, heat, or moisture are preferred.

[0402] There are no particular limitations on the crosslinking agent; it can be appropriately selected according to the purpose. Examples include polyfunctional acrylate compounds such as trimethylolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate; epoxy compounds such as glycidyl methacrylate and ethylene glycol diglycidyl ether; acridine compounds such as 2,2-dihydroxymethylbutanol-tris[3-(1-acrylidinyl)propionate] and 4,4-bis(ethyleneiminocarbonylamino)diphenylmethane; isocyanate compounds such as hexamethylene diisocyanate and biuret-type isocyanate; polyoxazoline compounds with oxazoline groups on the side chains; and alkoxysilane compounds such as vinyltrimethoxysilane and N-(2-aminoethyl)3-aminopropyltrimethoxysilane. Furthermore, known catalysts can be used depending on the reactivity of the crosslinking agent, which can improve not only film strength and durability but also productivity. One of these can be used alone, or two or more can be used in combination.

[0403] The content of the crosslinking agent relative to the solid component mass of the liquid crystal composition is preferably 3 to 20% by mass, more preferably 5 to 15% by mass. As long as the content of the crosslinking agent is within the above range, it is easy to obtain the effect of increasing the crosslinking density and further improve the stability of the cholesterol-type liquid crystal phase.

[0404] <<Other Additives>>

[0405] Polymerization inhibitors, antioxidants, ultraviolet absorbers, light stabilizers, colorants, and metal oxide particles can be added to the liquid crystal composition as needed, without reducing optical performance, etc.

[0406] When forming a cholesterol-type liquid crystal layer, the liquid crystal composition is preferably used as the liquid.

[0407] The liquid crystal composition may contain a solvent. There are no limitations on the solvent; it can be appropriately selected depending on the purpose, but organic solvents are preferred.

[0408] There are no restrictions on organic solvents; they can be appropriately selected according to the purpose. Examples include ketones, haloalkanes, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, and ethers. One or more of these can be used alone or in combination. Among them, ketones are preferred considering the environmental impact.

[0409] When forming a cholesterol-type liquid crystal layer, it is preferable to coat the liquid crystal composition onto the forming surface of the cholesterol-type liquid crystal layer, orient the liquid crystal compound to a state of cholesterol-type liquid crystal phase, and then cure the liquid crystal compound to form the cholesterol-type liquid crystal layer.

[0410] For example, when forming a cholesterol-type liquid crystal layer 26 on an alignment film 24, it is preferable to coat the liquid crystal composition onto the alignment film 24, align the liquid crystal compound to a cholesterol-type liquid crystal phase, and then cure the liquid crystal compound to form a cholesterol-type liquid crystal layer 26 with a fixed cholesterol-type liquid crystal phase.

[0411] The coating of liquid crystal compositions can be achieved using all printing methods such as inkjet and roll printing, as well as known methods such as spin coating, bar coating, and spray coating, which can similarly coat liquids onto sheets.

[0412] The coated liquid crystal composition is dried and / or heated as needed, and then cured to form a cholesterol-type liquid crystal layer. In this drying and / or heating process, it is sufficient that the liquid crystal compounds in the liquid crystal composition are oriented as a cholesterol-type liquid crystal phase. When heating is performed, the heating temperature is preferably below 200°C, more preferably below 130°C.

[0413] The oriented liquid crystal compound is then polymerized as needed. Polymerization can be either thermal polymerization or photopolymerization based on light emission, but photopolymerization is preferred. Ultraviolet light is preferably used for light emission. The emission energy is preferably 20 mJ / cm². 2 ~50J / cm 2 More preferably, it is 50–1500 mJ / cm². 2 To promote the photopolymerization reaction, light emission can also be carried out under heating conditions or in a nitrogen atmosphere. The wavelength of the emitted ultraviolet light is preferably 250–430 nm.

[0414] There is no limit to the thickness of the cholesterol liquid crystal layer. The thickness can be appropriately set to obtain the necessary light reflectivity, depending on the application of the bandpass filter, the required light reflectivity in the cholesterol liquid crystal layer, and the forming material of the cholesterol liquid crystal layer.

[0415] (Liquid crystal elastomer)

[0416] In this invention, a liquid crystal elastomer can be used for the cholesterol-type liquid crystal layer. The liquid crystal elastomer is a mixture of liquid crystal and elastomer. For example, it has a structure formed by introducing liquid crystal-rigid mesocrystalline groups into a flexible polymer mesh with rubber elasticity. Therefore, it possesses soft mechanical properties and is stretchable. Furthermore, the orientation state of the liquid crystal is closely related to the macroscopic shape of the system; therefore, if the orientation state of the liquid crystal changes in temperature or electric field, a macroscopic deformation corresponding to the change in orientation degree exists. For example, if the liquid crystal elastomer is heated from the nematic phase to a temperature that makes it a randomly oriented isotropic phase, the sample shrinks in the direction of the direction vector, and this shrinkage increases as the temperature rises, i.e., the shrinkage increases as the orientation degree of the liquid crystal decreases. The deformation is thermally reversible; if it is cooled back to the nematic phase, it returns to its original shape. On the other hand, if the cholesterol-type liquid crystal elastomer is heated and the orientation degree of the liquid crystal decreases, macroscopic elongation deformation occurs in the helical axis direction, thus increasing the helical pitch length and shifting the reflection center wavelength of the selective reflection peak to the longer wavelength side. This change is also thermally reversible; as the temperature drops, the reflected center wavelength returns to the shorter wavelength side.

[0417] <<Refractive Index Ellipsoid of Cholesterol-Type Liquid Crystal Layers>>

[0418] As described above, the cholesterol-type liquid crystal layer 26 has a structure in which the angle between the molecular axes of adjacent liquid crystal compounds 32 gradually changes when viewed from the helical axis direction, i.e., a refractive index ellipsoid.

[0419] use Figure 9 and Figure 10 The refractive index ellipsoid is explained.

[0420] Figure 9 This is an image showing a portion (1 / 4 pitch) of multiple liquid crystal compounds twisted and oriented along the helical axis, viewed from the helical axis direction (y-direction). Figure 10 It is a conceptual diagram showing the probability of the presence of a liquid crystal compound when viewed from the direction of the helical axis.

[0421] Figure 9 In this design, the liquid crystal compound with its molecular axis parallel to the y-direction is designated C1, the liquid crystal compound with its molecular axis parallel to the x-direction is designated C7, and the liquid crystal compounds between C1 and C7, moving from the C1 side towards the C7 side, are designated C2 to C6. Liquid crystal compounds C1 to C7 are twisted and oriented along the helical axis, rotating 90° between C1 and C7. If the length between the liquid crystal compounds with a 360° angular change in twisted orientation is defined as one pitch... Figure 7 The “P” in the figure refers to the direction of the helical axis from liquid crystal compound C1 to liquid crystal compound C7. Figure 9The length of the direction perpendicular to the paper is 1 / 4 pitch.

[0422] like Figure 9 As shown, within a 1 / 4 pitch from liquid crystal compound C1 to liquid crystal compound C7, the angles formed by the molecular axes of adjacent liquid crystal compounds when viewed from the z-direction (helical axis direction) are different. Figure 9 In the example shown, the angle θ1 between liquid crystal compound C1 and liquid crystal compound C2 is greater than the angle θ2 between liquid crystal compound C2 and liquid crystal compound C3; the angle θ2 between liquid crystal compound C2 and liquid crystal compound C3 is greater than the angle θ3 between liquid crystal compound C3 and liquid crystal compound C4; the angle θ3 between liquid crystal compound C3 and liquid crystal compound C4 is greater than the angle θ4 between liquid crystal compound C4 and liquid crystal compound C5; the angle θ4 between liquid crystal compound C4 and liquid crystal compound C5 is greater than the angle θ5 between liquid crystal compound C5 and liquid crystal compound C6; the angle θ5 between liquid crystal compound C5 and liquid crystal compound C6 is greater than the angle θ6 between liquid crystal compound C6 and liquid crystal compound C7; and the angle θ6 between liquid crystal compound C6 and liquid crystal compound C7 is the smallest.

[0423] That is, the liquid crystal compounds C1 to C7 are twisted and oriented in such a way that the angle between the molecular axes of the adjacent liquid crystal compounds decreases from the side of liquid crystal compound C1 to the side of liquid crystal compound C7.

[0424] For example, if the spacing between liquid crystal compounds (the spacing in the thickness direction) is set to be approximately constant, then it becomes a structure in which the rotation angle per unit length decreases from the liquid crystal compound C1 side to the liquid crystal compound C7 side in a 1 / 4 pitch.

[0425] In the cholesterol-type liquid crystal layer 26, the structure in which the rotation angle per unit length changes in a 1 / 4 pitch is repeated, and the liquid crystal compound is twisted and oriented.

[0426] Here, with the rotation angle per unit length being constant, the angle between the molecular axes of adjacent liquid crystal compounds is constant, so the probability of the presence of liquid crystal compounds observed from the helical axis direction is the same in any direction.

[0427] In contrast, as described above, by configuring a structure in which the rotation angle per unit length decreases from the liquid crystal compound C1 side towards the liquid crystal compound C7 side within a 1 / 4 pitch from liquid crystal compound C1 to liquid crystal compound C7, the probability of the presence of the liquid crystal compound as viewed from the helical axis direction is as follows: Figure 10Conceptually, the x-direction is higher than the y-direction. Refractive index anisotropy arises because the probability of the liquid crystal compound being present differs in the x and y directions, resulting in different refractive indices in those directions. In other words, refractive index anisotropy occurs in a plane perpendicular to the helical axis.

[0428] The refractive index nx in the x-direction, where the probability of the liquid crystal compound's presence increases, is higher than the refractive index ny in the y-direction, where the probability of the liquid crystal compound's presence decreases. Therefore, the refractive indices nx and ny satisfy nx > ny.

[0429] The x-direction, where the probability of the presence of liquid crystal compounds is high, becomes the in-plane slow axis direction of the cholesterol-type liquid crystal layer 26, while the y-direction, where the probability of the presence of liquid crystal compounds is low, becomes the in-plane fast axis direction of the cholesterol-type liquid crystal layer 26.

[0430] Thus, in the twisted orientation of the liquid crystal compound, a structure in which the rotation angle per unit length changes within a 1 / 4 pitch (a structure with a refractive index ellipsoid) can be formed by irradiating the cholesterol-type liquid crystal phase (composition layer) with polarized light in a direction orthogonal to the helical axis after coating the composition as a cholesterol-type liquid crystal layer.

[0431] Irradiation with polarized light can distort the cholesterol-type liquid crystal phase, resulting in in-plane retardation. That is, the refractive index nx can be set to be greater than the refractive index ny.

[0432] Specifically, polymerization is carried out on liquid crystal compounds having a molecular axis in the same direction as the polarization direction of the irradiated polarized light. In this case, only a portion of the liquid crystal compound is polymerized, thus the chiral reagent present at that location is excluded and moves to other locations.

[0433] Therefore, at positions where the molecular axis of the liquid crystal compound is close to the polarization direction, the amount of chiral reagent decreases, and the rotation angle of the twisted orientation becomes smaller. On the other hand, at positions where the molecular axis of the liquid crystal compound is orthogonal to the polarization direction, the amount of chiral reagent increases, and the rotation angle of the twisted orientation becomes larger.

[0434] Therefore, as Figure 9As shown, the structure can be configured such that, in a liquid crystal compound oriented in a twisted manner along a helical axis, within a 1 / 4 pitch from the liquid crystal compound whose molecular axis is parallel to the direction of polarization to the liquid crystal compound orthogonal to the direction of polarization, the angle between the molecular axes of adjacent liquid crystal compounds decreases as they move from the side parallel to the direction of polarization to the side orthogonal to the direction of polarization. That is, by irradiating the cholesterol-type liquid crystal phase with polarized light, the probability of the presence of liquid crystal compounds differs in the x and y directions, resulting in refractive index anisotropy with different refractive indices in the x and y directions. Therefore, the refractive index nx and refractive index ny of the optical element 10 can be configured to satisfy nx > ny. In other words, the cholesterol-type liquid crystal layer can be configured to have a refractive index ellipsoid structure.

[0435] The polarized light irradiation can be performed simultaneously with the immobilization of the cholesterol-type liquid crystal phase, or polarized light irradiation can be performed first, followed by unpolarized light irradiation for immobilization, or unpolarized light irradiation can be used for pre-immobilization followed by polarized light irradiation for photoorientation. To obtain a greater delay, it is preferable to perform only polarized light irradiation or to perform polarized light irradiation beforehand. Polarized light irradiation is preferably performed in an inert gas atmosphere with an oxygen concentration of 0.5% or less. The irradiation energy is preferably 20 mJ / cm². 2 ~10J / cm 2 Further preferred values ​​are 100–800 mJ / cm². 2 The optimal illuminance is 20–1000 mW / cm². 2 More preferably 50–500 mW / cm 2 More preferably, it is 100–350 mW / cm 2 There are no particular restrictions on the type of liquid crystal compound that can be cured by polarized light irradiation, but liquid crystal compounds with ethylene unsaturated groups as reactive groups are preferred.

[0436] Furthermore, as a method for generating in-plane delay by distorting the cholesterol-type liquid crystal phase through irradiation with polarized light, examples include the method of using a dichroic liquid crystal polymerization initiator (WO03 / 054111A1) or the method of using a rod-shaped liquid crystal compound having photo-orientation functional groups such as cinnamyl groups within the molecule (Japanese Patent Application Laid-Open No. 2002-006138).

[0437] The irradiated light can be ultraviolet, visible, or infrared. In other words, the light source should be chosen appropriately based on the liquid crystal compound and polymerization initiator contained in the coating to polymerize the liquid crystal compound.

[0438] By using a dichroic free radical polymerization initiator as a polymerization initiator, when the composition layer is irradiated with polarized light, it is more preferable to polymerize liquid crystal compounds that have molecular axes in the same direction as the polarized light.

[0439] Furthermore, the directions of the slow axis and fast axis, as well as the refractive index nx and refractive index ny, can be measured using the JAWoollam M-2000UI spectrometer. Additionally, the refractive index nx and refractive index ny can be obtained from the measured values ​​of the phase difference Δn×d and using the average birefringence n ave It is calculated using the measured value of the thickness d. Here, Δn = nx - ny and the average refractive index n is... ave = (nx + ny) / 2. The average refractive index of liquid crystals is typically around 1.5, so this value can also be used to calculate nx and ny. Furthermore, when measuring the in-plane slow axis direction, fast axis direction, refractive index nx, and refractive index ny of the cholesterol-type liquid crystal layer used in this invention, a wavelength greater than the selective reflection wavelength (in this invention, the selective reflection wavelength of primary light) (for example, a wavelength 100 nm larger than the longer-wavelength end of the selective wavelength) is set as the measurement wavelength. In this way, the influence of the delayed optical rotation component originating from cholesterol-type selective reflection is minimized, thus enabling high-precision measurements.

[0440] Furthermore, a cholesteric liquid crystal layer having a refractive index ellipsoid can also be formed by extending the cholesteric liquid crystal layer after coating a composition that forms a cholesteric liquid crystal layer, or after immobilizing a cholesteric liquid crystal phase, or while the cholesteric liquid crystal phase is semi-immobilized.

[0441] When forming a cholesteric liquid crystal layer with a refractive index ellipsoid by stretching, either uniaxial stretching or biaxial stretching can be performed. Furthermore, the stretching conditions can be appropriately set according to the material, thickness, desired refractive index nx, and refractive index ny of the cholesteric liquid crystal layer. In the case of uniaxial stretching, the elongation ratio is preferably set to 1.1 to 4. In the case of biaxial stretching, the ratio of the elongation ratio in one stretching direction to the elongation ratio in the other stretching direction is preferably set to 1.1 to 2.

[0442] <<The Role of Cholesterol-Type Liquid Crystal Layers>>

[0443] Next, the function of the cholesterol-type liquid crystal layer 26 having the above structure will be explained.

[0444] If light of a selectively reflected wavelength (primary light) is incident on the cholesterol-type liquid crystal layer 26, it will be reflected through the cholesterol-type liquid crystal phase.

[0445] Here, in the case where the cholesterol-type liquid crystal layer 26 has the aforementioned refractive index ellipsoid, it reflects light twice in addition to the first light.

[0446] The center wavelength of the secondary light is approximately half the length of the selective reflection center wavelength λ of the primary light. Furthermore, the bandwidth (half-width at half maximum) of the reflected secondary light is smaller than that of the reflected primary light. The primary light is either right-handed or left-handed circularly polarized light corresponding to the rotation direction of the cholesterol-type liquid crystal phase, but the secondary light also includes either right-handed or left-handed circularly polarized light.

[0447] Figure 11 The concept illustrates the reflective properties of a typical cholesterol-type liquid crystal layer that does not have a refractive index ellipsoid. Figure 11 And then Figure 12 It is a chart that conceptually shows the reflection characteristics with the horizontal axis as wavelength and the vertical axis as reflectivity.

[0448] Typical cholesterol-type liquid crystal layers exhibit wavelength selectivity in reflection, such as... Figure 11 As shown, light in the wavelength region surrounding the selective reflection center wavelength λ is reflected with approximately the same high reflectivity. Reflected light having a selective reflection peak in the wavelength region containing the selective reflection center wavelength λ is primary light. Furthermore, the reflectivity is lower for light in wavelength regions other than the periphery of the selective reflection center wavelength λ.

[0449] On the other hand, such as Figure 12 As shown, a cholesteric liquid crystal layer with a refractive index ellipsoid, in addition to selectively reflecting light in the wavelength region surrounding the central wavelength λ (first-order light), also reflects light in the wavelength region surrounding wavelength λ / 2 (second-order light) with high reflectivity. Figure 12 As shown, the half-width at half-maximum (WHM) of the second selective reflection peak at wavelength λ / 2 is narrower than that of the first selective reflection peak at wavelength λ, being less than 30 nm.

[0450] Therefore, in the sensor of the present invention, if a bandpass filter comprising a cholesterol-type liquid crystal layer 26 having a refractive index ellipsoid is used, when the measurement light reflected by the object O is reflected by the bandpass filter and incident on the light receiving element, the light incident on the light receiving element can only be the narrow-band light reflected by the bandpass filter.

[0451] Therefore, by reducing the external light component reflected by the bandpass filter, only the specified narrow-band light can be incident on the light-receiving element 14, thus greatly reducing noise caused by external light and achieving a high SN ratio, enabling high-precision measurement.

[0452] In the sensor, if the measurement light is reflected by the second selective reflection peak of the cholesterol-type liquid crystal layer 26 at wavelength λ / 2 and incident on the light-receiving element, then a light source that irradiates light at wavelength λ / 2 can be used as the light source.

[0453] Here, as Figure 12As shown, the cholesteric liquid crystal layer 26, which has a refractive index ellipsoid, selectively reflects light in the wavelength region surrounding the central wavelength λ (first-order light) and the wavelength region surrounding wavelength λ / 2 (second-order light), and also reflects light in the wavelength region surrounding wavelength λ / 3 (third-order light) with high reflectivity. The half-width at half-maximum (WHM) of the third-order light is also narrower than that of the first-order light, less than 30 nm. Therefore, the sensor 10 can utilize the third selective reflection peak of the cholesteric liquid crystal layer 26 at wavelength λ / 3. Specifically, the light source can be structured as follows: irradiating the measurement light at wavelength λ / 3, reflecting the measurement light at wavelength λ / 3 reflected by the object O using a bandpass filter (cholesteric liquid crystal layer 26), and incident on the light-receiving element.

[0454] Furthermore, the cholesteric liquid crystal layer 26, which has a refractive index ellipsoid, exhibits higher-order selective reflection peaks, such as a fourth selective reflection peak at wavelength λ / 4 and a fifth selective reflection peak at wavelength λ / 5. Therefore, the sensor can utilize these higher-order selective reflection peaks of the cholesteric liquid crystal layer 26. However, the higher the order, the lower the reflectivity in the selective reflection peak; therefore, it is preferable to use a second or third selective reflection peak, and more preferably, a second selective reflection peak.

[0455] From the viewpoint of being able to further reduce the bandwidth (half-peak width) of the second light, the absolute value of the in-plane retardation Re = (nx - ny) × d of the cholesterol-type liquid crystal layer 26 is preferably 10 nm or more.

[0456] As mentioned above, there is no limitation on the thickness of the cholesteric liquid crystal layer 26 in the bandpass filter. Therefore, the thickness of the cholesteric liquid crystal layer 26 can be appropriately set according to the selective reflection wavelength region of the bandpass filter and the required reflectivity of the bandpass filter.

[0457] In the sensor of the present invention, for example, when measuring object O using the wavelength of the second selective reflection peak, the bandpass filter reflects light from the selective reflection wavelength region (the wavelength region of the first selective reflection peak) and the wavelength region of the third selective reflection peak, in addition to the wavelength region of the second selective reflection peak of the cholesterol-type liquid crystal layer. Therefore, if light from the selective reflection wavelength region and the wavelength region of the third selective reflection peak is incident on the bandpass filter, it is reflected by the bandpass filter and measured by the light-receiving element, resulting in noise and a decrease in the signal-to-noise ratio (SN ratio).

[0458] To prevent this inconvenience, in this invention, such as Figure 13 As conceptually shown by the diagonal lines, it is preferable to provide at least one of a light-shielding component for the wavelength region of the first selective reflection peak of the light-shielding bandpass filter with wavelength λ-100nm or higher, and a light-shielding component for the wavelength region of the second selective reflection peak with wavelength λ / 2-50nm or lower; more preferably, two light-shielding components are provided.

[0459] Therefore, by preventing light outside the wavelength region of the second selective reflection peak from entering the light-receiving element, the SN ratio can be prevented from decreasing.

[0460] Furthermore, various known filters can be used as light-shielding components. Therefore, light shading based on light-shielding components can be either absorption or reflection.

[0461] The placement of the light-shielding component is not particularly limited as long as it is within the optical path from the light source 12, which is reflected by the object O and then by the bandpass filter before reaching the light-receiving element. The light-shielding component is preferably placed close to the light-receiving element.

[0462] In this invention, when a structure with a cholesteric liquid crystal layer 26 having a refractive index ellipsoid is used as the bandpass layer, the thermal expansion coefficient α1 and elastic modulus E1 of the bandpass layer and the thermal expansion coefficient α2 and elastic modulus E2 of the support satisfy the above-mentioned relationship, so that the wavelength of the light source that changes according to the change of ambient temperature is consistent with the wavelength of the second selective reflection peak (higher-order selective reflection peak) of the bandpass filter.

[0463] The sensor of this invention can be used for applications such as sensors that select only wavelengths containing necessary information. For example, it can be used as a wavelength selection element for optical communication in the field of communications, as described in International Publication No. 2018 / 010675. For example, as... Figure 14 The example shown can be used as a wavelength selection element to selectively acquire light of multiple arbitrary wavelengths by means of a structure consisting of multiple bandpass filters 16 with different wavelengths having selective reflection peaks and multiple light-receiving elements 14.

[0464] [Bandpass filter]

[0465] The bandpass filter of the present invention has a bandpass layer and a support for supporting the bandpass layer.

[0466] The coefficient of thermal expansion α2 of the support is less than 0 ppm / ℃.

[0467] The bandpass filter in this embodiment is a bandpass filter whose support has a negative coefficient of thermal expansion.

[0468] As mentioned above, if the support has a negative coefficient of thermal expansion, then when the ambient temperature increases, the support contracts while the bandpass layer expands. However, the bandpass layer is constrained by the support in the planar direction, so its stretching is suppressed and it contracts, thus elongating in the thickness direction (see reference). Figure 4 As a result, the dimensions of the structure formed in the thickness direction of the bandpass layer, for example in the case of a cholesterol-type liquid crystal layer, are lengthened, and thus the transmission wavelength of the bandpass filter is correspondingly increased to a longer wavelength.

[0469] Thus, by using a support with a negative coefficient of thermal expansion as the support for the bandpass layer, it is possible to produce a bandpass filter whose wavelength changes according to changes in ambient temperature.

[0470] The sensor and bandpass filter of the present invention have been described in detail above. However, the present invention is not limited to the above examples. Various improvements or modifications can be made without departing from the spirit of the present invention.

[0471] Example

[0472] The following examples further illustrate the features of the present invention. The materials, reagents, dosages, quantities, ratios, processing methods, and processing order shown in the following examples can be appropriately modified without departing from the spirit of the invention. Therefore, the scope of the present invention should not be interpreted as limited by the specific examples shown below.

[0473] A bandpass filter was fabricated by using a glass substrate as a support and forming a cholesteric liquid crystal layer as a bandpass layer.

[0474] (Formation of the orientation film)

[0475] A glass substrate was prepared as a support. The coefficient of thermal expansion α2 of the support was measured using a laser dilatometer (LIX-2: manufactured by ULVAC, Inc.), and the result was 4 ppm / ℃ (measurement temperature range 100–700 K). Furthermore, the elastic modulus E2 was measured using the same method, and the result was 75 GPa. The thickness of the support was 1100 μm.

[0476] The following alignment film forming coating solution is applied to a support by spin coating. The support with the coating solution is then dried on a hot plate at 60°C for 60 seconds to form alignment film P-1.

[0477] Coating solution for oriented film formation

[0478]

[0479] -Raw materials for photoorientation-

[0480] [Chemical Formula 25]

[0481]

[0482] (Exposure of the alignment film)

[0483] The obtained alignment film P-1 was irradiated with polarized ultraviolet light (50 mJ / cm²). 2 The orientation film was exposed using an ultra-high pressure mercury lamp.

[0484] (Formation of a cholesterol-type liquid crystal layer)

[0485] As a liquid crystal composition, the following composition A-1 was prepared. Composition A-1 is a liquid crystal composition that forms a cholesterol-type liquid crystal layer (cholesterol-type liquid crystal phase) that selectively reflects a center wavelength of 1280 nm and reflects right-handed circularly polarized light.

[0486] Composition A-1

[0487]

[0488] Rod-shaped liquid crystal compound L-1

[0489] [Chemical Formula 26]

[0490]

[0491] Polymerization initiator

[0492] [Chemical Formula 27]

[0493]

[0494] Chiral reagent Ch-1

[0495] [Chemical Formula 28]

[0496]

[0497] Leveling agent T-1

[0498] [Chemical Formula 29]

[0499]

[0500] (Polarized UV irradiation device)

[0501] As a UV (ultraviolet) light source, a microwave-emitting ultraviolet irradiation device (Light Hammer 10, 240 W / cm², manufactured by Fusion UV Systems) was constructed using a D-Bulb equipped with a microwave emission mode and a D-Bulb that has a strong emission spectrum in the 350–400 nm range. A linear grid polarizing filter (ProFlux PPL02 (high transmittance type), manufactured by Moxtek) was placed at a position 10 cm away from the irradiated surface. The maximum illuminance of this device is 400 mW / cm². 2 .

[0502] The above composition A-1 was coated onto the alignment film P-1. After heating the coated film to 95°C on a hot plate and cooling it to 80°C, it was then subjected to polarized UV irradiation at 200 mW / cm² in a nitrogen environment. 2Illuminance, 300mJ / cm 2 The irradiation dose is 365nm ultraviolet light irradiated onto the coating, thereby immobilizing the orientation of the liquid crystal compound and forming a cholesterol-type liquid crystal layer.

[0503] The cross-section of the cholesterol-type liquid crystal layer was confirmed using SEM, revealing that the cholesterol-type liquid crystal phase has a pitch of 6. Furthermore, the thickness of the cholesterol-type liquid crystal layer is 5 μm.

[0504] Furthermore, the coefficient of thermal expansion α1 of the cholesterol-type liquid crystal layer was measured using the above method, and the result was 50 ppm / ℃. Also, the elastic modulus E1 was measured using the above method, and the result was 5 GPa.

[0505] (Evaluation of bandpass filters)

[0506] The reflection (transmission) characteristics of the bandpass filter prepared in Example 1 were measured using a spectrophotometer (UV-3150 (manufactured by SHIMADZU)). Measurements were performed after the filter was placed at ambient temperatures of 25°C, 45°C, and 65°C for one hour. At 25°C, a first selective reflection peak with a reflection center wavelength of 1268 nm and a half-width at half-maximum (HWHM) of 110 nm and a second selective reflection peak with a reflection center wavelength of 634 nm and a HWHM of 12 nm were observed. At 45°C, the reflection center wavelength of the second selective reflection peak was confirmed to be 639 nm and the HWHM to 12 nm. At 65°C, the reflection center wavelength of the second selective reflection peak was confirmed to be 644 nm and the HWHM to 12 nm.

[0507] (Sensor fabrication: reflective type)

[0508] A laser light source, an LED light source (a light source with a yellow phosphor formed on a blue LED), and a light-receiving element were prepared to irradiate light with a center wavelength of 633 nm. The laser light source is equivalent to the light source irradiating the measuring light in this invention, and the LED light source is set as the light source irradiating light equivalent to external light.

[0509] A sensor was fabricated by illuminating a white plate (the object) with light from various light sources, reflecting the reflected light from the white plate using a bandpass filter, and then directing the light onto a light-receiving element. The bandpass filter was configured such that reflected light from the laser source reflected by the white plate was incident at a 5° angle relative to the vertical line of the bandpass filter surface. The light-receiving element was configured such that the reflected light from the bandpass filter was incident perpendicularly onto the light-receiving surface.

[0510] Furthermore, the center wavelength of the laser source is 641nm at 45℃ and 648nm at 65℃ when the ambient temperature increases.

[0511] As a support, a support fabricated as described below was used. In addition, a bandpass filter was fabricated in the same manner as in Example 1, thereby fabricating the sensor.

[0512] (Formation of the support structure)

[0513] β-Cu was prepared using a solid-state reaction method. 1.8 Zn 0.2 Polycrystalline sintered (ceramic) samples of V₂O₇ were obtained. Specifically, CuO, ZnO, and V₂O₅ were mixed in stoichiometric proportions in a mortar and heated in atmosphere at 873–953 K for 10 hours. The powder obtained was sintered using a spark plasma sintering (SPS) furnace (manufactured by Fuji Electronic Industrial Co., Ltd.) to obtain oxide sintered bodies. Regarding sintering, the process was carried out under vacuum (<10 K). -1 The sample was subjected to a process at 723 K for 5 minutes using a graphite mold. A support was formed using this sample.

[0514] The coefficient of thermal expansion α2 of the formed support was measured, and the result was α = -14 ppm / ℃. Furthermore, the elastic modulus E2 was measured, and the result was 75 GPa. The thickness of the support was 1000 μm.

[0515] (Formation of the orientation film)

[0516] Similar to Example 1, an orientation film P-1 was formed on the support.

[0517] (Exposure of the alignment film)

[0518] Similar to Example 1, the alignment film P-1 was exposed using a polarized UV irradiation device.

[0519] The coefficient of thermal expansion α1 of the formed cholesterol-type liquid crystal layer was measured and found to be 50 ppm / ℃. Furthermore, the elastic modulus E1 was measured and found to be 5 GPa. The thickness of the cholesterol-type liquid crystal layer was 5 μm.

[0520] Similar to Example 1, the center wavelength and half-width at half-maximum (WHM) of the bandpass filter were measured by varying the ambient temperature. At an ambient temperature of 25°C, the center wavelength of the second selective reflection peak was confirmed to be 635 nm and the WHM to be 12 nm. At an ambient temperature of 45°C, the center wavelength of the second selective reflection peak was confirmed to be 642 nm and the WHM to be 12 nm. At an ambient temperature of 65°C, the center wavelength of the second selective reflection peak was confirmed to be 650 nm and the WHM to be 12 nm.

[0521] Referring to IDW / AD, 12, pp. 985-988 (2012), an organic dielectric multilayer film was formed on a glass substrate to fabricate a bandpass filter. Using this bandpass filter, a sensor was fabricated in the same manner as in Example 1, except that the same substrate was used.

[0522] The coefficient of thermal expansion α1 of the organic dielectric multilayer film was measured and found to be 60 ppm / ℃. The elastic modulus E1 was also measured and found to be 4 GPa. The thickness of the organic dielectric multilayer film was 10 μm.

[0523] Similar to Example 1, the ambient temperature was varied, and the reflection center wavelength and half-width at half-maximum (HWHM) of the bandpass filter were measured. At an ambient temperature of 25°C, the reflection center wavelength of the selected reflection peak was confirmed to be 634 nm, and the HWHM was 20 nm. At an ambient temperature of 45°C, the reflection center wavelength of the selected reflection peak was confirmed to be 638 nm, and the HWHM was 20 nm. At an ambient temperature of 65°C, the reflection center wavelength of the selected reflection peak was confirmed to be 642 nm, and the HWHM was 20 nm.

[0524] An acrylic sheet (CLAREX manufactured by Nitto Jushi Kogyo Co., Ltd.) was used as the support. A bandpass filter was fabricated in the same manner as in Example 1, thereby fabricating the sensor. The coefficient of thermal expansion α2 of the support was measured and found to be 70 ppm / ℃. Furthermore, the elastic modulus E2 was measured and found to be 3 GPa. The thickness of the support was 700 μm.

[0525] Similar to Example 1, the center wavelength and half-width at half-maximum (WHM) of the bandpass filter were measured by varying the ambient temperature. At an ambient temperature of 25°C, the center wavelength of the second selective reflection peak was confirmed to be 634 nm and the WHM to be 12 nm. At an ambient temperature of 45°C, the center wavelength of the second selective reflection peak was confirmed to be 634 nm and the WHM to be 12 nm. At an ambient temperature of 65°C, the center wavelength of the second selective reflection peak was confirmed to be 635 nm and the WHM to be 12 nm.

[0526] In Example 1, a sensor without a bandpass filter is used as the reference example 1.

[0527] (Sensor Evaluation)

[0528] Light was shone onto a white board using both laser and LED light sources, and the light reflected from the board was measured using a light-receiving element. Measurements were taken at ambient temperatures of 25°C, 45°C, and 65°C. The results were evaluated using the following criteria.

[0529] • A: Compared with the sensor in the reference example, the noise caused by the LED light source is reduced and the SN ratio is high. Even when the ambient temperature increases, the SN ratio hardly changes compared to the case of 25°C.

[0530] • B: Compared with the sensor in the reference example, the noise caused by the LED light source is reduced and the SN ratio is increased. However, if the ambient temperature increases, the SN ratio decreases compared with the case of 25°C.

[0531] • C: Compared with the sensor in the reference example, the noise caused by the LED light source is reduced and the SN ratio is increased. However, if the ambient temperature increases, the noise is higher than B and the SN ratio is the same as that of the sensor in the reference example.

[0532] The results are shown in Table 1.

[0533] [Table 1]

[0534]

[0535] As shown in Table 1, compared with the comparative example, the embodiments of the present invention can suppress the decrease in SN ratio even when the ambient temperature increases.

[0536] As can be seen from Examples 1 and 2, the difference between the thermal expansion coefficient of the through layer and the thermal expansion coefficient of the support is preferably 30 ppm / ℃ or more.

[0537] As the cholesterol-type liquid crystal layer, a cholesterol-type liquid crystal layer prepared as described below was used. Apart from this, a bandpass filter was prepared in the same manner as in Example 1, thereby fabricating the sensor. The glass substrate used was the same as in Example 1.

[0538] (Formation of a cholesterol-type liquid crystal layer)

[0539] As a liquid crystal composition, composition A-4 was prepared. Composition A-4 is a liquid crystal composition that forms a cholesterol-type liquid crystal layer (cholesterol-type liquid crystal phase) that selectively reflects a central wavelength of 905 nm and reflects right-handed circularly polarized light.

[0540] Composition A-4

[0541]

[0542] Rod-shaped liquid crystal compound L-2

[0543] [Chemical Formula 30]

[0544]

[0545] Rod-shaped liquid crystal compound L-3

[0546] [Chemical Formula 31]

[0547]

[0548] (Polarized UV irradiation device)

[0549] The above composition A-4 was coated onto orientation P-1. The coated film was heated at 100°C for 1 minute on a hot plate. Then, under nitrogen conditions at 100°C, an ultraviolet irradiation device (EXECURE 3000-W, HOYA SCHOTT) was used with an irradiation of 25 mW / cm² at a wavelength of 365 nm. 2 500mJ / cm 2 The amount of irradiation applied to the coating film immobilizes the orientation of the liquid crystal compound, forming a cholesterol-type liquid crystal layer.

[0550] The cross-section of the cholesterol-type liquid crystal layer was confirmed using SEM, revealing that the cholesterol-type liquid crystal phase has a pitch of approximately 10. Furthermore, the thickness of the cholesterol-type liquid crystal layer is 6 μm.

[0551] The coefficient of thermal expansion α1 of the formed cholesterol-type liquid crystal layer was measured and found to be 69 ppm / ℃. Furthermore, the elastic modulus E1 was measured and found to be 4.5 GPa.

[0552] (Evaluation of bandpass filters)

[0553] Similar to Example 1, the center wavelength and half-width at half-maximum (WHM) of the bandpass filter were measured by varying the ambient temperature. At an ambient temperature of 25°C, the center wavelength of the first selective reflection peak was confirmed to be 905 nm and the WHM to be 34 nm. At an ambient temperature of 45°C, the center wavelength of the first selective reflection peak was confirmed to be 911 nm and the WHM to be 34 nm. At an ambient temperature of 65°C, the center wavelength of the first selective reflection peak was confirmed to be 916 nm and the WHM to be 34 nm.

[0554] (Sensor fabrication: reflective type (2))

[0555] A laser source, an LED source (a light source with a yellow phosphor formed on a blue LED), and a light-receiving element were prepared to irradiate light with a center wavelength of 905 nm at 25°C. The laser source is equivalent to the light source irradiating the measurement light in this invention, and the LED source is set as the light source irradiating light equivalent to external light.

[0556] A sensor was fabricated by illuminating a white plate (the object) with light from various light sources, reflecting the reflected light from the white plate using a bandpass filter, and then directing the light onto a light-receiving element. The bandpass filter was configured such that reflected light from the laser source reflected by the white plate was incident at a 5° angle relative to the vertical line of the bandpass filter surface. The light-receiving element was configured such that the reflected light from the bandpass filter was incident perpendicularly onto the light-receiving surface.

[0557] Furthermore, the center wavelength of the laser source is 911 nm at 45°C and 916 nm at 65°C when the ambient temperature increases.

[0558] As the cholesterol-type liquid crystal layer, a cholesterol-type liquid crystal layer prepared as described below was used. In addition, a bandpass filter was prepared in the same manner as in Example 1, and a sensor was prepared in the same manner as in Example 4. The glass substrate used was the same as that in Example 1.

[0559] (Formation of a cholesterol-type liquid crystal layer)

[0560] As a liquid crystal composition, the following composition A-5 was prepared. Composition A-5 is a liquid crystal composition that forms a cholesterol-type liquid crystal layer (cholesterol-type liquid crystal phase) that selectively reflects a central wavelength of 905 nm and reflects left-handed circularly polarized light.

[0561] Composition A-5

[0562]

[0563] Chiral reagent Ch-2

[0564] [Chemical Formula 32]

[0565]

[0566] The above composition A-5 was coated onto orientation P-1. The coated film was heated at 100°C for 1 minute on a hot plate. Then, under nitrogen conditions at 100°C, an ultraviolet irradiation device (EXECURE 3000-W, HOYA SCHOTT) was used with an irradiation of 25 mW / cm² at a wavelength of 365 nm. 2 500mJ / cm 2 The amount of irradiation applied to the coating film immobilizes the orientation of the liquid crystal compound, forming a cholesterol-type liquid crystal layer.

[0567] The cross-section of the cholesterol-type liquid crystal layer was confirmed using SEM, revealing that the cholesterol-type liquid crystal phase has a pitch of approximately 10. Furthermore, the thickness of the cholesterol-type liquid crystal layer is 6 μm.

[0568] The coefficient of thermal expansion α1 of the formed cholesterol-type liquid crystal layer was measured and found to be 66 ppm / ℃. Furthermore, the elastic modulus E1 was measured and found to be 4.7 GPa.

[0569] (Evaluation of bandpass filters)

[0570] Similar to Example 1, the center wavelength and half-width at half-maximum (WHM) of the bandpass filter were measured by varying the ambient temperature. At an ambient temperature of 25°C, the center wavelength of the first selective reflection peak was confirmed to be 905 nm and the WHM to be 34 nm. At an ambient temperature of 45°C, the center wavelength of the first selective reflection peak was confirmed to be 911 nm and the WHM to be 34 nm. At an ambient temperature of 65°C, the center wavelength of the first selective reflection peak was confirmed to be 916 nm and the WHM to be 34 nm.

[0571] As the cholesterol-type liquid crystal layer, a cholesterol-type liquid crystal layer prepared as described below was used. In addition, a bandpass filter was prepared in the same manner as in Example 1, and a sensor was prepared in the same manner as in Example 4. The glass substrate used was the same as that in Example 1.

[0572] (Formation of a cholesterol-type liquid crystal layer)

[0573] The above composition A-4 was coated onto the cholesterol-type liquid crystal layer of Example 4, and the liquid crystal compound was fixed by heating and UV irradiation in the same manner as in Example 4, thus forming a cholesterol-type liquid crystal layer. By repeating this operation once, a cholesterol-type liquid crystal layer consisting of three layers of composition A-4 stacked on orientation P-1 was formed.

[0574] Next, the above composition A-5 was coated onto a cholesterol-type liquid crystal layer, and heated and irradiated with UV in the same manner as in Example 5 to fix the orientation of the liquid crystal compound, thus forming a cholesterol-type liquid crystal layer. By repeating this operation twice, a cholesterol-type liquid crystal layer was formed in which three layers of cholesterol-type liquid crystal layer composed of composition A-4 were stacked on orientation P-1, and three layers of cholesterol-type liquid crystal layer composed of composition A-5 were stacked on top of it.

[0575] The cross-section of the cholesterol-type liquid crystal layer was confirmed using SEM, revealing that the cholesterol-type liquid crystal phase has approximately 62 pitches. Furthermore, the thickness of the cholesterol-type liquid crystal layer is 36 μm.

[0576] The coefficient of thermal expansion α1 of the formed cholesterol-type liquid crystal layer was measured and found to be 68 ppm / ℃. Furthermore, the elastic modulus E1 was measured and found to be 4.6 GPa.

[0577] (Evaluation of bandpass filters)

[0578] Similar to Example 1, the center wavelength and half-width at half-maximum (WHM) of the bandpass filter were measured by varying the ambient temperature. At an ambient temperature of 25°C, the center wavelength of the first selective reflection peak was confirmed to be 905 nm, and the WHM was 34 nm. At an ambient temperature of 45°C, the center wavelength of the first selective reflection peak was confirmed to be 911 nm, and the WHM was 34 nm. At an ambient temperature of 65°C, the center wavelength of the first selective reflection peak was confirmed to be 916 nm, and the WHM was 34 nm. Furthermore, the reflectance relative to natural light from the bandpass filter was measured, and the reflectance was found to be 98%.

[0579] In Example 4, a sensor without a bandpass filter is used as the sensor in Reference Example 2.

[0580] (Sensor Evaluation)

[0581] Using the sensors fabricated in Examples 4-6, light was shone onto a white board from a laser light source and an LED light source, and the light reflected from the white board was measured by a light-receiving element. Measurements were performed at ambient temperatures of 25°C, 45°C, and 65°C, and the results were evaluated using the following criteria.

[0582] •AA: Compared with the sensor in Reference Example 2, the noise caused by the LED light source is reduced and the SN ratio is very high. Even when the ambient temperature increases, the SN ratio hardly changes compared to the case of 25°C.

[0583] • A: Compared with the sensor in Reference Example 2, the noise caused by the LED light source is reduced and the SN ratio is high. Even if the ambient temperature increases, the SN ratio hardly changes compared with the case of 25°C.

[0584] • B: Compared with the sensor in Reference Example 2, the noise caused by the LED light source is reduced and the SN ratio is increased. However, if the ambient temperature increases, the SN ratio decreases compared with the case of 25°C.

[0585] • C: Compared with the sensor of Reference Example 2, the noise caused by the LED light source is reduced and the SN ratio is increased. However, if the ambient temperature increases, the noise is higher than B and the SN ratio is the same as that of the sensor of Reference Example 2.

[0586] The results are shown in Table 2.

[0587] [Table 2]

[0588]

[0589] As shown in Table 2, in the embodiments of the present invention, even if the ambient temperature increases, the decrease in the SN ratio can be suppressed.

[0590] The above results demonstrate that the present invention is highly effective.

[0591] Industrial availability

[0592] It can be used to select various sensors for optical measurement such as distance measuring sensors.

[0593] Symbol Explanation

[0594] 10a, 10b - Sensor; 12 - Light source; 14 - Light receiving element; 16, 16a, 16b, 116 - Bandpass filter; 20 - Support; 24 - Alignment film; 26 - Cholesterol-type liquid crystal layer; 32 - Liquid crystal compound; 40, 40a, 40b, 140 - Support; 42 - Bandpass layer; O - Object; P - Helical pitch; I1~I3 - Measurement light; I z -Exterior light.

Claims

1. A sensor having: light source; A bandpass filter is used to extract the light with the peak emission wavelength of the light source; and The light-receiving element receives the light extracted by the bandpass filter. The bandpass filter has a bandpass layer and a support for supporting the bandpass layer. When the coefficient of thermal expansion of the bandpass layer is set to α1 and the elastic modulus is set to E1, and the coefficient of thermal expansion of the support is set to α2 and the elastic modulus is set to E2, the following conditions are met: α1 > α2 and E1 < E2. The bandpass layer has a layer formed by fixing a cholesterol-type liquid crystal phase, namely a cholesterol-type liquid crystal layer. The half-width at half-maximum (WHM) of the selective reflection peak in the cholesterol-type liquid crystal layer is less than 45 nm.

2. The sensor according to claim 1, wherein, The half-width at half-peak of the emission peak of the light source is less than 30 nm.

3. The sensor according to claim 1 or 2, wherein, The light source is a laser or a light-emitting diode.

4. The sensor according to claim 1 or 2, wherein, The bandpass layer contains organic materials.

5. The sensor according to claim 1 or 2, wherein, The bandpass filter transmits light at the peak emission wavelength of the light source and extracts light at the peak emission wavelength of the light source. The half-width at half maximum (WHM) of the transmission peak in the bandpass layer is less than 20 nm.

6. The sensor according to claim 1 or 2, wherein, The bandpass filter reflects and extracts light at the peak emission wavelength of the light source. The half-width at half maximum (WHM) of the reflection peak in the bandpass layer is less than 20 nm.

7. The sensor according to claim 1 or 2, wherein, The difference between the thermal expansion coefficient α1 of the bandpass layer and the thermal expansion coefficient α2 of the support is greater than 30 ppm / ℃.

8. The sensor according to claim 1 or 2, wherein, The coefficient of thermal expansion α2 of the support is less than 0 ppm / ℃.

9. The sensor according to claim 1 or 2, wherein, The elastic modulus E1 of the bandpass layer is less than 10 GPa.

10. The sensor according to claim 1 or 2, wherein, The cholesterol-type liquid crystal layer has a region in which the in-plane refractive index nx along the slow axis and the refractive index ny along the fast axis satisfy nx > ny. When the selective reflection center wavelength of the cholesterol-type liquid crystal layer is set to λ, the cholesterol-type liquid crystal layer has a second selective reflection peak at wavelength λ / 2, and the half-width of the second selective reflection peak at λ / 2 is less than 20 nm.

11. The sensor according to claim 1 or 2, wherein, The cholesterol-type liquid crystal layer is formed by immobilizing a cholesterol-type liquid crystal phase with a Δn of less than 0.

06.

12. The sensor according to claim 1 or 2, wherein, The thickness of the cholesterol-type liquid crystal layer is 10 μm or more.

13. The sensor according to claim 1 or 2, wherein, The cholesterol-type liquid crystal layer is formed by stacking a cholesterol-type liquid crystal layer with a right-handed helical structure and a cholesterol-type liquid crystal layer with a left-handed helical structure.

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