JP6254768B2 - Detection system and detection method using light - Google Patents

Description

  The present invention relates to a detection system and a detection method using light.

A detection system using polarized light in the infrared region is conventionally known. For example, in Patent Document 1, a silicon substrate is irradiated with polarized infrared light through a first linear polarization filter, and reflected or transmitted light from the silicon substrate is received through a second linear polarization filter. The crack of the silicon substrate is detected. This technique means that the reflected light or transmitted light in a place where there is no crack is linearly polarized light, and the amount of light that can be sensed is reduced except when a specific condition is satisfied through the second linearly polarizing filter. In the reflected light or transmitted light, the fact that light that can be sensed through the second linear polarization filter is generated by irregular reflection is utilized. In Patent Document 2, in an automatic water faucet device that detects a human hand or object using infrared light, a first polarizing means that transmits a linearly polarized component of infrared light to be projected, and infrared light that is received An apparatus is disclosed in which erroneous detection is prevented by using a second polarizing means that transmits a linearly polarized component of light.
Patent Document 3 discloses a technique using circularly polarized light in the technique of Patent Document 1. The use of circularly polarized light eliminates the need to adjust the polarization direction of the second linear polarizing filter.

JP 2008-58270 A JP 2003-96850 A JP 2013-36888 A

  A detection system using polarized light in the infrared light wavelength range may be used in various light environments. It is an object of the present invention to provide a detection system using polarized light in the infrared wavelength region, which has high sensitivity regardless of the surrounding environment and has few false detections. Another object of the present invention is to provide a detection method using polarized light in the infrared light wavelength range, which has high sensitivity regardless of the surrounding environment and has few false detections.

  In order to solve the above problems, the present inventors have studied a detection system using polarized light in the infrared wavelength region. And even if it is a case where it detects using the sensor which has a light receiving element which detects infrared rays, it discovered that the light receiving element might also detect the light of visible region, and has caused the false detection. Based on this finding, the inventors have further studied and completed the present invention. That is, the present invention provides the following [1] to [12].

[1] A system for detecting the object by irradiating the object with light and detecting reflected light or transmitted light of the object derived from the light irradiation,
A light source, a circularly polarized light separating film 1, a circularly polarized light separating film 2, and a light receiving element that detects light having a wavelength in the near-infrared light wavelength region,
Both the circularly polarized light separating film 1 and the circularly polarized light separating film 2 selectively transmit either the right circularly polarized light or the left circularly polarized light in at least a part of the near infrared wavelength region,
The circularly polarized light separating film 1 may also serve as the circularly polarized light separating film 2,
In the light source, the circularly polarized light separating film 1, the circularly polarized light separating film 2, and the light receiving element, the light supplied from the light source passes through the circularly polarized light separating film 1 and is irradiated on the object, and the object is The transmitted or reflected light is arranged so as to pass through the circularly polarized light separating film 2 and be detected by the light receiving element,
The system in which the circularly polarized light separating film 2 includes a visible light blocking layer 2 that reflects or absorbs light in at least a part of the visible light wavelength range.

[2] The system according to [1], wherein the circularly polarized light separating film 1 includes a visible light blocking layer 1 that reflects or absorbs light in at least a part of the visible light wavelength range.
[3] The system according to [1] or [2], wherein the circularly polarized light separating film 1 includes a layer in which the cholesteric liquid crystal phase is fixed as the circularly polarized light separating layer 1.
[4] The system according to any one of [1] to [3], wherein the circularly polarized light separating film 2 includes a layer in which the cholesteric liquid crystal phase is fixed as the circularly polarized light separating layer 2.
[5] The system according to any one of [1] to [4], wherein the light source is a near-infrared light source.
[6] A system for detecting the object through glass,
The light source, the circularly polarized light separating film 1, the circularly polarized light separating film 2, and the light receiving element detect the reflected light of the object derived from the light of the light source through the circularly polarized light separating film 2 and detected by the light receiving element. The system according to any one of [1] to [5], which is arranged as described above.

[7] The object is a transparent film,
The light source, the circularly polarized light separating film 1, the circularly polarized light separating film 2, and the light receiving element detect the transmitted light of the object derived from the light of the light source through the circularly polarized light separating film 2 and detected by the light receiving element. The system according to any one of [1] to [5], which is arranged as described above.
[8] Any one of [1] to [7], wherein an optical axis of reflected light or transmitted light of the object derived from the light source forms an angle of 70 ° to 89 ° with the circularly polarized light separating film 2. The system described in.

[9] A method of irradiating an object with light and detecting the object by reflected light or transmitted light of the object derived from the light irradiation,
(1) irradiating the object with circularly polarized light in a near-infrared light wavelength region that selectively includes either right circularly polarized light or left circularly polarized light;
(2) The light in which at least a part of the light generated by the circularly polarized light reflected by the object or transmitted through the object is transmitted through the circularly polarized light separating layer 2 and the visible light blocking layer 2 is near infrared. Sensing with a light receiving element that detects light of a wavelength in the light wavelength range,
The circularly polarized light separating layer 2 selectively transmits either the right circularly polarized light or the left circularly polarized light in at least a part of the near infrared wavelength region,
The visible light blocking layer 2 is a method of reflecting or absorbing light in at least a part of the visible light wavelength range.

[10] The method according to [9], wherein the circularly polarized light separating layer 2 and the visible light blocking layer 2 are layers constituting the same film.
[11] In (2), at least a part of the light generated by being reflected by the object or transmitted through the object passes through the circularly polarized light separating layer 2 and the light blocking layer 2 in this order [9] ] Or the method according to [10].
[12] The circularly polarized light in the near infrared wavelength region of (1) is light formed by transmitting light through the visible light blocking layer 1 and the circularly polarized light separating layer 1,
The circularly polarized light separating layer 1 is a layer that selectively transmits either right circularly polarized light or left circularly polarized light in at least a part of the near-infrared light wavelength region, and may also serve as the circularly polarized light separating layer 2 ,
The visible light blocking layer 1 is a layer that reflects or absorbs light in at least a part of the visible light wavelength range, and may also serve as the visible light blocking layer 2. Any of [9] to [11] The method according to claim 1.

  The present invention provides a detection system and a detection method using polarized light in the infrared wavelength region, which have high sensitivity regardless of the surrounding environment and are less susceptible to erroneous detection.

It is a figure which shows the example of arrangement | positioning of a light source, a light receiving element, and a circularly polarized light separation film for the detection of the target object by the method of this invention.

Hereinafter, the present invention will be described in detail.
In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

In this specification, “selective” for circularly polarized light means that the amount of light of either the right circularly polarized component or the left circularly polarized component of the irradiated light is greater than that of the other circularly polarized component. Specifically, when referred to as “selective”, the degree of circular polarization of light is preferably 0.3 or more, more preferably 0.6 or more, and even more preferably 0.8 or more. More preferably, it is substantially 1.0. Table In _{/ (I R + I L)} | Here, the degree of circular polarization, the intensity of the right circularly polarized light component of the light I _R, when the strength of the left-handed circularly polarized light component and I _L, | I _R -I _L Is the value to be In this specification, the degree of circular polarization is sometimes used to represent the ratio of circularly polarized light components.

  In this specification, “sense” for circularly polarized light means right circularly polarized light or left circularly polarized light. The sense of circularly polarized light is right-handed circularly polarized light when the electric field vector tip turns clockwise as time increases when viewed as the light travels toward you, and left when it turns counterclockwise. Defined as being circularly polarized.

  In this specification, the term “sense” may be used for the twist direction of the spiral of the cholesteric liquid crystal. The selective reflection by the cholesteric liquid crystal reflects right circularly polarized light when the twist direction (sense) of the cholesteric liquid crystal spiral is right, transmits left circularly polarized light, and reflects left circularly polarized light when the sense is left, Transmits circularly polarized light.

  Visible light is light having a wavelength visible to the human eye among electromagnetic waves, and indicates light having a wavelength range of 380 nm to 780 nm.

  Infrared rays (infrared light) are electromagnetic waves in the wavelength range that are longer than visible rays and shorter than radio waves. Near-infrared light is generally an electromagnetic wave having a wavelength range of 700 nm to 2500 nm. As near-infrared light, a wavelength range of 780 nm to 1500 nm or 800 nm to 1500 nm is preferable. Typically, any wavelength range corresponding to the wavelength range of near-infrared light used in an infrared camera, an infrared photoelectric sensor, or infrared communication may be used.

  In this specification, the measurement of the light intensity required in connection with the calculation of the light transmittance may be performed by using, for example, a normal visible and near infrared spectrum meter and measuring the reference as air.

In addition, the polarization state of each wavelength of light can be measured using a spectral radiance meter or a spectrometer equipped with a circularly polarizing plate. In this case, the intensity of light measured through the right circularly polarizing plate corresponds to I _R , and the intensity of light measured through the left circularly polarizing plate corresponds to I _L. In addition, ordinary light sources such as incandescent bulbs, mercury lamps, fluorescent lamps, and LEDs emit almost natural light, but the characteristics that are attached to these to produce the polarization of the polarization state control member are, for example, a polarization phase difference manufactured by AXOMETRICS. It can be measured using an analyzer AxoScan or the like.
Moreover, even if a circularly polarizing plate is attached to an illuminance meter or an optical spectrum meter, it can be measured. The ratio can be measured by attaching a right circular polarized light transmission plate, measuring the right circular polarized light amount, attaching a left circular polarized light transmission plate, and measuring the left circular polarized light amount.

(Object detection)
In the present invention, infrared light, particularly light in the near-infrared light wavelength region is used for detecting an object. And polarized light is used as infrared rays. By using polarized light as infrared light for detection, the optical properties of the object as a contrast to the background in the detection of reflected and transmitted light from the object through a film that is selective in polarization transmission Can be reflected, and an object having a specific optical property can be detected, or a detection with few malfunctions can be performed. In this specification, “reflected light and transmitted light” are used to mean scattered light and diffracted light. Further, in the present invention, circularly polarized light is used as polarized light for detection. When circularly polarized light is used to detect reflected light and transmitted light from an object, it becomes easier to adjust the orientation of the film for polarization detection than when linearly polarized light is used as polarized light.

  Examples of objects that can be detected by the method of the present invention include transparent (birefringent) films, cracks or scratches on a specular reflector (such as a metal plate), and foreign matters on the specular reflector. Security applications include use as human sensors such as pedestrians at night and human sensors in automatic doors and elevators.

FIG. 1 shows an arrangement example of a light source, a light receiving element, and a circularly polarized light separating film for detecting an object.
In the arrangement 1, the light source, the circularly polarized light separating film on the light source side (sometimes referred to as the circularly polarized light separating film 1 in this specification), the object, the circularly polarized light separating film on the light receiving element side (in this specification, the circularly polarized light separating film). The light receiving element is arranged in this order, and the transmitted light of the object is detected. As the object at this time, a transparent film (particularly, one having birefringence) or the like can be considered. For example, it can be used to detect the passage of a film in a film production line. In the arrangement 1, glass is arranged between the object and the circularly polarized light separating film 1 (1 in the figure) and between the object and the circularly polarized light separating film 2 (1 in the figure). Depending on the use of the polarization separation film, the influence of the reflected light from the glass can be greatly reduced.
In the arrangement 1, the circularly polarized light separating film 2 is preferably arranged so that the visible light blocking layer is on the light source side and the circularly polarized light separating layer is on the object side. When the circularly polarized light separating film 1 has a visible light blocking layer, it is preferable that the visible light blocking layer is disposed on the light receiving element side and the circularly polarized light separating layer is on the object side.

  Arrangements 2 to 4 are configurations for detecting reflected light, and the circularly polarized light separating film 1 also serves as the circularly polarized light separating film 2, that is, the circularly polarized light separating film 1 and the circularly polarized light separating film 2 are the same. It is. In the arrangements 2 to 4, the light source and the light receiving element are arranged on the same side of the circularly polarized light separating film (1 in the figure) as viewed from the object. In this configuration, the light receiving element may be provided with a light blocking layer or the like between the light receiving element and the light source as shown in the figure so that the light receiving element is not affected by the direct light from the light source.

In the arrangement 2, an example is shown in which a transparent film (particularly one having birefringence) is an object. Glass is disposed between the object and the circularly polarized light separating film, but depending on the use of the circularly polarized light separating film, the influence of the reflected light from the glass can be greatly reduced.
In the arrangement 3, the paper on the specular reflector is detected. In this example, since the light that has become circularly polarized light of one sense through the circularly polarized light separating film (1 in the figure) is reflected as circularly polarized light of the other sense by the specular reflector, Although the light cannot be transmitted through the separation film and reach the light receiving element, the light irregularly reflected by the paper contains the light component that can be transmitted through the circularly polarized light separation film.
In the arrangement 4, an example in which a foreign object or a crack of a specular reflector is detected as an object is shown, but the principle of detection (sensing) is the same as that in the arrangement 3.

  Arrangement 5 is a configuration for detecting reflected light, and is an example in which different films are used for circularly polarized light separating film 1 and circularly polarized light separating film 2. In such an example of use, the light source (2 in the figure) and the circularly polarized light separating film 1 (1 in the figure) may be integrated to form a light source device, and the light receiving element (3 in the figure) and The circularly polarized light separating film 2 (1 in the figure) may be integrated to form a sensor. In the example shown in the figure, the human is detected at the arrangement 5. For example, a pedestrian at night or a person in an elevator can be preferably detected with such an arrangement.

  In the arrangements 2 to 4, the circularly polarized light separating film is preferably arranged so that the visible light blocking layer is on the light source and light receiving element side and the circularly polarized light separating layer is on the object side. In the arrangement 5, it is preferable that the visible light blocking layer of the circularly polarized light separating film 2 is disposed so that the light receiving element side and the circularly polarized light separating layer side are the object side, and the circularly polarized light separating film 1 is the visible light blocking layer. It is preferable that the visible light blocking layer is disposed on the light receiving element side and the circularly polarized light separating layer is on the object side.

For example, as shown in the arrangements 2 to 5, it is preferable that the optical path (optical axis) of the reflected light or transmitted light of the object derived from the light source forms an angle with the normal direction of the circularly polarized light separating film 2. For example, the angle of the optical path (optical axis) of the light with respect to the circularly polarized light separating film 2 may be about 70 ° to 89 °, 80 ° to 89 °, or 85 °. With such an arrangement, for example, the circularly polarized light reflected by the circularly polarized light separating film 2 after reflecting or transmitting a specular reflector or the like corresponding to the background of the object is not derived from the object by reflecting the background again. Light detection can be reduced.

(Optical properties of circularly polarized light separating film)
The circularly polarized light separating film that can be used in the system and method of the present invention will be described below.
The circularly polarized light separating film is a film that selectively transmits either right circularly polarized light or left circularly polarized light in at least a part of the near-infrared light wavelength region. A circularly polarized light separating film separates light (natural light, non-polarized light) in a specific near-infrared wavelength region incident from one side into right-handed circularly polarized light and left-handed circularly polarized light, and selectively selects either one on the other side. It is preferable that it can permeate. At this time, the other circularly polarized light may be reflected or absorbed.

  The circularly polarized light separating film may selectively transmit either right circularly polarized light or left circularly polarized light with respect to light incident from any surface, and light incident from either surface. Only the right circularly polarized light or the left circularly polarized light may be selectively transmitted only with respect to the light, and the same selective transmission may not be exhibited with respect to the light incident from the other side surface. In the latter case, the arrangement may be such that a desired circular polarization selectivity can be obtained in use. Further, the circularly polarized light separating film may be separated into right circularly polarized light and left circularly polarized light, and either one of the light incident from any surface may be selectively transmitted to the other side surface. Only light incident from one side is separated into right circularly polarized light and left circularly polarized light, either one is selectively transmitted to the other side, and such light is separated from light incident from the other side. May not be shown. In the latter case, the arrangement may be such that a desired circular polarization selectivity can be obtained in use.

  The circularly polarized light separating film has a light transmittance {(transmitted) of circularly polarized light having the same sense as the incident light when either the right or left circularly polarized light is incident in a region of 50 nm width or more in the wavelength range of 800 to 1500 nm. If the light intensity of circularly polarized light) / (light intensity of incident circularly polarized light) × 100} is 70% or more, 80% or more, 90% or more, 95% or more, 99% or more, preferably substantially 100%. Good. At the same time, in the same wavelength range as described above, when the other sense circularly polarized light is incident, the light transmittance of the same sense circularly polarized light {(light intensity of transmitted circularly polarized light) / (incident circularly polarized light is incident) Light intensity) × 100} is 30% or less, 20% or less, 10% or less, 5% or less, 1% or less, preferably substantially 0%.

  The circularly polarized light separating film preferably has a low light transmittance in the visible light wavelength region. In particular, the circularly polarized light separating film 2 used on the light receiving element side preferably has a low light transmittance in the visible light wavelength region. In general, the transmittance of natural light (non-polarized light) may be low, and the transmittance of circularly polarized light and / or linearly polarized light is also preferably low. Moreover, the light transmittance may be low in a part of the visible light wavelength region, and the light transmittance may be low in the entire visible light wavelength region. Specifically, the average light transmittance in the wavelength region of 380 nm to 780 nm may be 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less.

  The low light transmittance in the visible light wavelength range can significantly reduce light that is unnecessary for sensing (light that hinders sensing) reaching the light receiving element in a system using a circularly polarized light separating film. , The S / N ratio can be increased and the minimum light intensity detected by the light receiving element can be decreased.

(Visible light blocking layer)
The circularly polarized light separating film 2 used on the light receiving element side is a visible light blocking layer that reflects or absorbs light in at least a part of the visible light wavelength range and a right circularly polarized light or a left circularly polarized light in at least a part of the near infrared wavelength range. And a circularly polarized light separating layer that selectively transmits any one of the above. The circularly polarized light separating film 1 used on the light source side only needs to include a circularly polarized light separating layer that selectively transmits either right circularly polarized light or left circularly polarized light in at least a part of the near-infrared light wavelength region. Furthermore, it is preferable to include a visible light blocking layer that reflects or absorbs light in at least a part of the visible light wavelength region. In the present specification, the visible light blocking layer used on the light source side may be referred to as the visible light blocking layer 1, and the visible light blocking layer used on the light receiving element side may be referred to as the visible light blocking layer 2. The circularly polarized light separating film may contain other layers as necessary. Hereinafter, each layer will be described.

(Visible light blocking layer)
The visible light blocking layer functions so that light in a specific visible light wavelength region does not pass through the film. The visible light blocking layer preferably blocks natural light. Moreover, it is preferable to block any of non-polarized light, circularly polarized light, and linearly polarized light. The circularly polarized light separating film only needs to achieve a low light transmittance in the visible light wavelength region mainly by the visible light reflecting layer or the visible light absorbing layer. Examples of the visible light blocking layer include a visible light reflecting layer and a visible light absorbing layer.

  At least a part of the visible light wavelength range in which the visible light blocking layer reflects or absorbs light may be in the wavelength range of 380 nm to 780 nm. The wavelength band width of at least a part of the visible light wavelength band may be 10 nm or more, 20 nm or more, 30 nm or more, 40 nm or more, or 50 nm or more. The visible light wavelength range in which light is reflected or absorbed by the visible light blocking layer includes a wavelength range in which light unnecessary for sensing (light that hinders sensing) is easily detected in the sensor (light receiving element). preferable. Moreover, it is also preferable that the wavelength range of light other than the desired near-infrared light wavelength range defined according to the light emission wavelength etc. from a light source is included. At least a part of the visible light wavelength region may be 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more of the wavelength region of 380 nm to 750 nm, and is substantially 100%. Also good.

The visible light blocking layer only needs to have a high light reflectivity or light absorption property in at least a part of the wavelength range excluding the detection wavelength range of the sensor (light receiving element) to be used. Or what is necessary is just to have a light reflectivity or high light absorptivity in at least one part except the light emission wavelength range of the light source to be used, normally an infrared light source. In general, a silicon photodiode used as a light receiving element (photodetector) has a sensitivity up to a visible light region which is the most present in the use environment and is a main cause of noise. A material that reflects or absorbs light is preferred. In addition, it is preferable that the visible light blocking layer substantially does not reflect or absorb light in a near-infrared wavelength region that allows the circularly polarized light separating layer to selectively transmit either right circularly polarized light or left circularly polarized light.
The thickness of the visible light blocking layer is preferably 2 μm to 500 μm, more preferably 5 μm to 300 μm, and still more preferably 10 μm to 150 μm.
Hereinafter, the visible light reflection layer and the visible light absorption layer that can be used as the visible light blocking layer will be described.

(Visible light reflection layer)
Depending on the use of a visible light reflecting layer that reflects light to block light, the temperature of the film does not increase, so that the film durability is improved and the film performance is easily maintained. In addition, the visible light reflecting layer usually has a mirror-like appearance, has a positive effect on the appearance of the film, and is easy to use on a portion that is touched by human eyes even when used as a sensor component.
Examples of the visible light reflecting layer include a dielectric multilayer film and a layer in which a cholesteric liquid crystal phase is fixed.

(Dielectric multilayer film)
The dielectric multilayer film is formed by laminating transparent dielectric layers having different refractive indexes of inorganic oxides and organic polymer materials. At least one of these transparent dielectric layers has a product (n × d) of the thickness (d) and the refractive index (n) of the transparent dielectric layer, which is a quarter of the wavelength (λ) of the light to be reflected. Thus, the light in the region of the reflection bandwidth determined by the difference in the refractive index of the dielectric layer with the central wavelength of reflection being λ can be reflected. With ordinary material combinations, it is difficult to reflect the entire visible light region with a dielectric multilayer film of one period, so there are several types with different center wavelengths of reflected light with different nxd values. Lamination can be adjusted to increase the reflection bandwidth. The transparent dielectric layer is not particularly limited as long as it is transparent in the infrared light wavelength region to be used.

Usually, TiO ₂ , SiO ₂ , Ta ₂ O ₅ or the like can be suitably used as the inorganic oxide in the dielectric multilayer film. The inorganic oxide layer can be formed by sputtering or the like on the surface of glass or heat-resistant polymer film, for example. On the other hand, examples of the organic polymer material include polycarbonate, acrylic resin, polyester, epoxy resin, polyurethane, polyamide, polyolefin, silicone (including modified silicone such as silicone polyurea), and the like, and Japanese National Publication No. 9-507308 It can be produced according to the method disclosed in the publication.

(Layer with fixed cholesteric liquid crystal phase: visible light reflection layer)
It is known that the cholesteric liquid crystal phase exhibits circularly polarized light selectively reflecting either right circularly polarized light or left circularly polarized light and transmitting the other circularly polarized light. Many cholesteric liquid crystal compounds that exhibit circularly polarized light selective reflection and films formed from cholesteric liquid crystal compounds have been known, and when using a layer in which a cholesteric liquid crystal phase is fixed in a circularly polarized light separating film, those conventional techniques are used. Can be referred to.

The layer in which the cholesteric liquid crystal phase is fixed may be a layer in which the alignment of the liquid crystal compound in the cholesteric liquid crystal phase is maintained, and typically, the polymerizable liquid crystal compound is in the alignment state of the cholesteric liquid crystal phase. In addition, any layer that is polymerized and cured by ultraviolet irradiation, heating, or the like to form a layer having no fluidity, and at the same time, has been changed to a state in which the orientation form is not changed by an external field or an external force. . In the layer in which the cholesteric liquid crystal phase is fixed, it is sufficient that the optical properties of the cholesteric liquid crystal phase are maintained in the layer, and the liquid crystalline compound in the layer may no longer exhibit liquid crystallinity. . For example, the polymerizable liquid crystal compound may have a high molecular weight due to a curing reaction and may no longer have liquid crystallinity.
In the present specification, the layer in which the cholesteric liquid crystal phase is fixed may be referred to as a cholesteric liquid crystal layer or a liquid crystal layer.

  The layer in which the cholesteric liquid crystal phase is fixed exhibits circularly polarized light reflection derived from the helical structure of the cholesteric liquid crystal. The central wavelength λ of the reflection depends on the pitch length P (= spiral period) of the helical structure in the cholesteric phase, and follows the relationship between the average refractive index n of the cholesteric liquid crystal layer and λ = n × P. Therefore, by adjusting the pitch length of this helical structure, the wavelength exhibiting circularly polarized reflection can be adjusted. That is, in order to form a visible light reflecting layer that reflects light in at least a part of the visible light wavelength range, the n value and the P value are adjusted so that the center wavelength λ is in the wavelength range of 380 nm to 780 nm. That's fine. Since the pitch length of the cholesteric liquid crystal phase depends on the kind of chiral agent used together with the polymerizable liquid crystal compound or the concentration of the chiral agent, the desired pitch length can be obtained by adjusting these. For the method of measuring the spiral sense and pitch, the method described in “Introduction to Liquid Crystal Chemistry Experiments” edited by the Japanese Liquid Crystal Society, Sigma Publishing 2007, 46p, and “Liquid Crystal Handbook”, Liquid Crystal Handbook Editorial Committee Maruzen 196p can be used. it can.

In addition, the sense of the reflected circularly polarized light of the cholesteric liquid crystal layer coincides with the sense of the spiral.
The reflectivity at the reflection wavelength increases as the cholesteric liquid crystal layer becomes thicker. However, with normal liquid crystal materials, it is saturated at a thickness of 2 to 8 μm in the visible light wavelength range, and it is reflected only on one side of circularly polarized light. Therefore, the maximum reflectance is 50%. In order to reflect light regardless of the sense of circularly polarized light and the reflectance of natural light to be 50% or more, the visible light reflecting layer has the same period P, the spiral sense is the right cholesteric liquid crystal layer and the left cholesteric A layer of liquid crystal layers, or a cholesteric liquid crystal layer having the same period P and the same spiral sense, and a half-wavelength relative to the central wavelength of circularly polarized reflection of the cholesteric liquid crystal layer disposed therebetween A laminate comprising a retardation film having a phase difference can be used.

  Further, the half width of the selective reflection (circular polarization reflection) band is such that Δλ depends on the birefringence Δn of the liquid crystal compound and the pitch length P, and follows the relationship of Δλ = Δn × P. Therefore, the width of the selective reflection band can be controlled by adjusting Δn. Δn can be adjusted by adjusting the kind of the polymerizable liquid crystal compound and the mixing ratio thereof, or by controlling the temperature at the time of fixing the alignment.

In the visible light region, the width of the circularly polarized reflection wavelength region is 50 nm to 100 nm for ordinary materials. Therefore, by reflecting several layers of cholesteric liquid crystal layers having different center wavelengths of reflected light with a different period P, reflection can be achieved. Bandwidth can be increased. Further, in one cholesteric liquid crystal layer, the reflection band can be widened by gradually changing the period P in the film thickness direction.
Specific materials and methods for producing the cholesteric liquid crystal layer will be described later.

(Visible light absorption layer)
As a visible light absorbing layer, a dispersion liquid in which a colorant such as a pigment or a dye is dispersed in a solvent containing a dispersant, a binder or a monomer is used as a base material (having sufficient light transmittance in the infrared wavelength region detected by the light receiving element) A layer formed by coating on the surface of the polymer substrate, a layer formed by directly dyeing the surface of the polymer substrate with a dye, and a layer formed from a polymer material containing the dye.
As the pigment, those that do not absorb or scatter in the infrared wavelength region detected by the light receiving element are preferably used. Therefore, cyan, magenta, yellow, and black inks for color printing that require transparency, and pigments used in red, green, and blue color filters such as liquid crystal display devices and organic LED display devices are preferably used. be able to. By mixing these pigments having different absorption maximum wavelengths, it is possible to form a layer that absorbs the entire light in the visible light wavelength region widely and sufficiently.
As the dye, a dye which does not absorb in the infrared wavelength region detected by the light receiving element and is robust against exposure to visible light is preferably used. General direct dyes, acid dyes, basic dyes, mordant dyes, disperse dyes, reactive dyes, and the like can be used. As this dye-type absorbing layer, commercially available photographic filters IR-80, IR-82, IR-84, etc. (manufactured by Fuji Film Co., Ltd.) can also be used.

(Circularly polarized light separating layer)
The circularly polarized light separating film includes a circularly polarized light separating layer that selectively transmits either the right circularly polarized light or the left circularly polarized light in at least a part of the near-infrared light wavelength region. In this specification, the circularly polarized light separating layer used on the light source side may be referred to as the circularly polarized light separating layer 1, and the circularly polarized light separating layer used on the light receiving element side may be referred to as the circularly polarized light separating layer 2. The circularly polarized light separating film includes a circularly polarized light separating layer so that the function of selectively transmitting either the right circularly polarized light or the left circularly polarized light of the circularly polarized light separating layer is not lost by the other layers, thereby allowing near infrared light It has a function of selectively transmitting either right circularly polarized light or left circularly polarized light in at least a part of the wavelength range. That is, for example, a circularly polarized light separating film has the same sense in the same wavelength region together with a circularly polarized light separating layer that selectively transmits either right circularly polarized light or left circularly polarized light in a specific near infrared light wavelength region. By including a circularly polarized light separating layer that reflects circularly polarized light simultaneously, or by including a layer that reflects or absorbs light (natural light) in the corresponding near-infrared light wavelength region, either right circularly polarized light or left circularly polarized light It is preferable that the functions of the individual circularly polarized light separating layers that selectively transmit one of them are not offset.

  The near-infrared light wavelength range in which the circularly polarized light separating layer selectively transmits one of right-handed circularly polarized light and left-handed circularly-polarized light may be in the range of 780 nm to 1500 nm, preferably 800 nm to 1500 nm. It may be 5 nm or more, 10 nm or more, 20 nm or more, 30 nm or more, 40 nm or more, or 50 nm or more. The near-infrared light wavelength range in which the circularly polarized light separating layer selectively transmits either right-handed circularly polarized light or left-handed circularly-polarized light is combined with the usage form of the circularly polarized light separating film, for example, the wavelength of light necessary for sensing. It may be included, and may be 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more, or substantially 100% of the wavelength region of 800 nm to 1500 nm.

The circularly polarized light separating layer may transmit, reflect, or absorb light other than the wavelength region that selectively transmits either right circularly polarized light or left circularly polarized light. The circularly polarized light separating layer selectively transmits either right circularly polarized light or left circularly polarized light, and may reflect or absorb the other circularly polarized light.
As the circularly polarized light separating layer, for example, a layer in which the cholesteric liquid crystal phase is fixed or a layer made of a laminate including a linearly polarized light separating layer and a λ / 4 retardation layer can be used.

(Layer with fixed cholesteric liquid crystal phase: circularly polarized light separating layer)
As the circularly polarized light separating layer, a layer in which the cholesteric liquid crystal phase is fixed as described above can be used. However, the cholesteric liquid crystal layer used as the circularly polarized light separating layer described above so as to selectively transmit (reflect) either the right circularly polarized light or the left circularly polarized light in at least a part of the near infrared light wavelength region, The n value and the P value may be adjusted so that the center wavelength λ is in the wavelength range of 780 nm to 1500 nm, preferably 800 nm to 1500 nm.

  As the circularly polarized light separating layer, a cholesteric liquid crystal layer whose spiral sense is either right or left may be used. When laminating for the purpose of increasing the circularly polarized light selectivity at a specific wavelength, A plurality of cholesteric liquid crystal layers having the same period P and the same spiral sense may be stacked. In this case, it is preferable to apply a liquid crystal composition containing a polymerizable liquid crystal compound or the like directly on the surface of the previous cholesteric liquid crystal layer formed by the method described later, and repeat the alignment and fixing steps. By such a process, the orientation direction of the liquid crystal molecules on the air interface side of the cholesteric layer formed earlier and the orientation direction of the liquid crystal molecules on the lower side of the cholesteric liquid crystal layer formed thereon coincide with each other. The polarization characteristics are improved.

Similarly to the case where a cholesteric liquid crystal layer is used for the visible light reflection layer, a plurality of layers may be laminated in order to widen the selective reflection (transmission) bandwidth. In this case, a cholesteric liquid crystal layer having the same spiral sense is laminated. It is preferable to do.
The cholesteric liquid crystal layer selectively transmits either right circularly polarized light or left circularly polarized light with respect to light incident from any surface, and right circularly polarized light and light incident from any surface Any one of them can be selectively transmitted to the other side by separating into left circularly polarized light.
A material and a manufacturing method of the cholesteric liquid crystal layer will be described later.

(Laminated body including linearly polarized light separating layer and λ / 4 retardation layer)
In a circularly polarized light separating layer composed of a laminate including a linearly polarized light separating layer and a λ / 4 retardation layer, light incident from the surface of the linearly polarized light separating layer is converted into linearly polarized light by reflection or absorption, and thereafter λ / 4. By passing through the retardation layer, it is converted into right or left circularly polarized light. On the other hand, in the case of light incidence from the λ / 4 retardation layer, linearly polarized light is converted into linearly polarized light by the linearly polarized light separating layer that finally passes through any polarization state. Since it is converted into linearly polarized light that is parallel or orthogonal to the transmission axis of the linearly polarizing layer by the phase difference layer, it is preferable to enter light from the λ / 4 phase difference layer side in order to use it for identification of incident circularly polarized light sense, In the case where outgoing circularly polarized light is used, it is preferable that light is incident from the linearly polarized light separating layer side.
As the linearly polarized light separating layer, a linear polarizer can be used as long as it is a polarizer corresponding to light in the infrared region.

(Linear polarizer)
Infrared linear polarizers that can be suitably used include multilayer dielectric reflective polarizers in which a plurality of resins having different refractive indexes and different refractive indexes are laminated, and the thickness and retardation value are controlled by stretching, and a number of parallel conductor wires Examples thereof include a grit polarizer constituted by an array (grit), a polarizer in which metal nanoparticles having shape anisotropy are arrayed and fixed, and a polarizer in which dichroic dyes are arrayed and fixed. Any of these can be easily formed into a thin layer, a film, or a plate, and can be formed by simply laminating a sheet-like retardation layer described later in the step of forming the circularly polarized light separating layer. Alternatively, a retardation layer can be formed by coating a composition for forming a retardation layer directly on an infrared linear polarizer, and a thinner circularly polarized light separating layer can be produced.

  The multilayer dielectric reflective polarizer is a polarizing film that transmits only light in a vibration direction parallel to the in-plane transmission axis and reflects other light. An example of such a film is a multilayer film disclosed in JP-T-9-507308. This is obtained by alternately laminating a layer consisting of a transparent dielectric layer 1 having no birefringence in the film plane and a layer consisting of a transparent dielectric layer 2 having birefringence in the plane. The refractive index of the layer 1 is formed so as to coincide with either the ordinary light refractive index or the extraordinary light refractive index of the transparent dielectric layer 2. Furthermore, in at least one of these transparent dielectric layers, the product (n × d) of the thickness (d) and the refractive index (n) of the transparent dielectric layer is a quarter of the wavelength of light to be reflected. It is configured to become. The material for forming the transparent dielectric layer may be any material that is light transmissive at the infrared wavelength used. Examples include polycarbonate, acrylic resin, polyester, epoxy resin, polyurethane, polyamide, polyolefin, cellulose derivative, Examples thereof include silicone (including modified silicone such as silicone polyurea).

  A grid polarizer is a submicron pitch (based on the wavelength of incident light) made of a thin film of a good conductor such as aluminum, silver, or gold on one side of a glass film or silicon (Si) substrate that is transparent to the infrared wavelength used. A plurality of parallel conductor line arrangement structures (grit) with a short pitch) are provided, and examples thereof include a polarizer disclosed in JP-A-2002-328234. This polarizer functions as a polarizer by reflecting a polarized light component parallel to the grid of incident light and transmitting a perpendicular polarized light component. If necessary, this can be sandwiched between glasses or an antireflection layer can be provided.

  A polarizer in which metal nanoparticles having shape anisotropy are arrayed and fixed is a silver halide particle having a large aspect ratio or a silver particle oriented and fixed. This polarizing plate is an absorptive linear polarizing plate that absorbs infrared light having an electric field vibration plane in the direction of particle arrangement and transmits infrared light in a direction perpendicular to the infrared light. As those belonging to this, those disclosed in JP-A-59-83951, JP-A-2-248341, and JP-A-2003-139951 can be used.

Examples of the polarizer in which the dichroic dyes are arranged and fixed include an infrared polarizing film in which PVA (polyvinyl alcohol) is adsorbed with iodine or doped with a dichroic dye and stretched to form polyvinylene. This polarizing plate absorbs infrared light having an electric field vibration plane in a stretching method and transmits infrared light in a direction orthogonal thereto.
This is to obtain the orientation of the dichroic dye by passing the PVA film through a dyeable composition tank such as iodine / iodide to dye the PVA layer and then stretching it at a magnification of 4 to 6 times. Can do. Conversion of PVA to polyvinylene can be accomplished by the hydrochloric acid vapor process as described in US Pat. No. 2,445,555. Further, in order to improve the stability of the polarizing material, boration is performed using an aqueous borate bath containing boric acid and borax. Commercially available Edmund Optics Japan Co., Ltd. near-infrared linearly polarizing film can be cited as an equivalent.
The thickness of the linearly polarized light separating layer is preferably 0.05 μm to 300 μm, more preferably 0.2 μm to 150 μm, and still more preferably 0.5 μm to 100 μm.

(Λ / 4 retardation layer)
The in-plane slow axis of the retardation plate is set in an orientation rotated by 45 ° from the absorption axis or transmission axis of the polarizing plate. When a monochromatic light source such as LED or laser is used as the infrared light source, the front phase difference of the retardation plate is ¼ of the center wavelength of the light emission wavelength of the light source, or “center wavelength * n ± center wavelength. For example, if the emission center wavelength of the light source is 1000 nm, the phase difference is preferably 250 nm, 750 nm, 1250 nm, 1750 nm, or the like. Further, the smaller the dependency of the phase difference on the light incident angle is, the more preferable, and a retardation plate having a phase difference of ¼ length of the center wavelength is most preferable in this respect.

  In the detection system or the detection method of the present invention, when a combination of various light sources having different emission wavelengths is used as an infrared light source, a light source having a peak emission intensity of two or more wavelengths, or a light source that emits light over a wide wavelength range In such a case, it is conceivable that the wavelength range showing the circularly polarized light selectivity should be widened. In such a case, the above-described retardation plate can be used, but it is more preferable to use a broadband retardation plate. A broadband retardation plate is a retardation plate having a constant retardation angle over a wide wavelength range. For example, a retardation layer having different birefringence wavelength dispersions can be obtained by making the slow axes orthogonal to each other. Broad-band laminated phase difference plate, polymer film using this principle at the molecular level and oriented with the alignment axes orthogonal to each other with substituents with different birefringence wavelength dispersion, wavelength (λ) in use wavelength range On the other hand, a retardation plate or the like in which a layer having a phase difference of λ / 2 and a layer having a phase difference of λ / 4 are stacked with their slow axes intersecting at 60 degrees can be given.

Examples of the material of the retardation plate include crystalline glass, inorganic crystal, polycarbonate, acrylic resin, polyester, epoxy resin, polyurethane, polyamide, polyolefin, cellulose derivative, silicone (including modified silicone such as silicone polyurea). ) And other polymers, polymerizable liquid crystal compounds, and polymer liquid crystal compounds arranged and fixed.
The thickness of the λ / 4 layer is preferably 0.2 μm to 300 μm, more preferably 0.5 μm to 150 μm, still more preferably 1 μm to 80 μm.

(Method for producing a layer having a fixed cholesteric liquid crystal phase)
Hereinafter, a material and a method for manufacturing a cholesteric liquid crystal layer that can be used for a visible light reflection layer or a circularly polarized light separation layer will be described.
Examples of the material used for forming the cholesteric liquid crystal layer include a liquid crystal composition containing a polymerizable liquid crystal compound and a chiral agent (optically active compound). If necessary, apply the above liquid crystal composition, which is further mixed with a surfactant or polymerization initiator and dissolved in a solvent, onto a substrate (support, alignment film, underlying cholesteric liquid crystal layer, etc.), and then cholesteric. After the alignment aging, the cholesteric liquid crystal layer can be formed by fixing.

Polymerizable liquid crystal compound The polymerizable liquid crystal compound may be a rod-like liquid crystal compound or a disc-like liquid crystal compound, but is preferably a rod-like liquid crystal compound.
Examples of the rod-like polymerizable liquid crystal compound forming the cholesteric liquid crystal layer include a rod-like nematic liquid crystal compound. Examples of the rod-shaped nematic liquid crystal compound include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, and alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. Not only low-molecular liquid crystal compounds but also high-molecular liquid crystal compounds can be used.

  The polymerizable cholesteric liquid crystal compound can be obtained by introducing a polymerizable group into the cholesteric liquid crystal compound. Examples of the polymerizable group include an unsaturated polymerizable group, an epoxy group, and an aziridinyl group, preferably an unsaturated polymerizable group, and particularly preferably an ethylenically unsaturated polymerizable group. The polymerizable group can be introduced into the molecule of the cholesteric liquid crystal compound by various methods. The number of polymerizable groups possessed by the polymerizable cholesteric liquid crystal compound is preferably 1 to 6, more preferably 1 to 3. Examples of polymerizable cholesteric liquid crystal compounds are described in Makromol. Chem. 190, 2255 (1989), Advanced Materials 5, 107 (1993), US Pat. No. 4,683,327, US Pat. No. 95/24455, No. 97/00600, No. 98/23580, No. 98/52905, JP-A-1-272551, No. 6-16616, and No. 7-110469. 11-80081 and JP-A 2001-328773, and the like. Two or more kinds of polymerizable cholesteric liquid crystal compounds may be used in combination. When two or more kinds of polymerizable cholesteric liquid crystal compounds are used in combination, the alignment temperature can be lowered.

  Moreover, it is preferable that the addition amount of the polymeric liquid crystal compound in a liquid-crystal composition is 10-60 mass% with respect to solid content mass (mass except a solvent) of a liquid-crystal composition, 20-50 mass%. It is more preferable that it is, and it is especially preferable that it is 30-40 mass%.

Chiral agent (optically active compound)
The chiral agent has a function of inducing a helical structure of a cholesteric liquid crystal phase. The chiral compound may be selected according to the purpose because the helical sense or helical pitch induced by the compound is different.
The chiral agent is not particularly limited, and known compounds (for example, liquid crystal device handbook, Chapter 3-4-3, TN, chiral agent for STN, page 199, Japan Society for the Promotion of Science, 142nd edition, 1989) Description), isosorbide, and isomannide derivatives can be used.
A chiral agent generally contains an asymmetric carbon atom, but an axially asymmetric compound or a planar asymmetric compound containing no asymmetric carbon atom can also be used as the chiral agent. Examples of the axial asymmetric compound or the planar asymmetric compound include binaphthyl, helicene, paracyclophane, and derivatives thereof. The chiral agent may have a polymerizable group. When the chiral agent and the curable cholesteric liquid crystal compound have a polymerizable group, it is derived from a repeating unit derived from the cholesteric liquid crystal compound and the chiral agent by a polymerization reaction between the polymerizable chiral agent and the polymerizable cholesteric liquid crystal compound. A polymer having repeating units can be formed. In this embodiment, the polymerizable group possessed by the polymerizable chiral agent is preferably the same group as the polymerizable group possessed by the polymerizable cholesteric liquid crystal compound. Therefore, the polymerizable group of the chiral agent is also preferably an unsaturated polymerizable group, an epoxy group or an aziridinyl group, more preferably an unsaturated polymerizable group, and an ethylenically unsaturated polymerizable group. Particularly preferred.
The chiral agent may be a liquid crystal compound.

It is preferable that the chiral agent has a photoisomerizable group because a pattern having a desired reflection wavelength corresponding to the emission wavelength can be formed by irradiation with a photomask such as actinic rays after coating and orientation. The photoisomerization group is preferably an isomerization site of a compound exhibiting photochromic properties, an azo group, an azoxy group, or a cinnamoyl group. Specific examples of the compound include JP 2002-80478, JP 2002-80851, JP 2002-179668, JP 2002-179669, JP 2002-179670, and JP 2002-2002. Use the compounds described in JP-A No. 179681, JP-A No. 2002-179682, JP-A No. 2002-338575, JP-A No. 2002-338668, JP-A No. 2003-313189, and JP-A No. 2003-313292. Can do.
The content of the chiral agent in the liquid crystal composition is preferably 0.01 mol% to 200 mol%, more preferably 1 mol% to 30 mol% of the amount of the polymerizable liquid crystal compound.

Polymerization initiator The liquid crystal composition preferably contains a polymerization initiator. In the embodiment in which the polymerization reaction is advanced by ultraviolet irradiation, the polymerization initiator to be used is preferably a photopolymerization initiator that can start the polymerization reaction by ultraviolet irradiation. Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatics. Group acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), combinations of triarylimidazole dimers and p-aminophenyl ketone (US patents) No. 3549367), acridine and phenazine compounds (JP-A-60-105667, US Pat. No. 4,239,850), oxadiazole compounds (US Pat. No. 4,221,970), and the like. .
The content of the photopolymerization initiator in the liquid crystal composition is preferably 0.1 to 20% by mass, and preferably 0.5 to 5% by mass with respect to the content of the polymerizable liquid crystal compound. Further preferred.

Crosslinking agent The liquid crystal composition may optionally contain a crosslinking agent in order to improve the film strength after curing and the durability. As said crosslinking agent, what hardens | cures with an ultraviolet-ray, a heat | fever, moisture, etc. can be used conveniently.
There is no restriction | limiting in particular as a crosslinking agent, According to the objective, it can select suitably, For example, polyfunctional acrylate compounds, such as a trimethylol propane tri (meth) acrylate and pentaerythritol tri (meth) acrylate; Glycidyl (meth) acrylate , Epoxy compounds such as ethylene glycol diglycidyl ether; aziridine compounds such as 2,2-bishydroxymethylbutanol-tris [3- (1-aziridinyl) propionate], 4,4-bis (ethyleneiminocarbonylamino) diphenylmethane; hexa Isocyanate compounds such as methylene diisocyanate and biuret type isocyanate; polyoxazoline compounds having an oxazoline group in the side chain; vinyltrimethoxysilane, N- (2-aminoethyl) 3-aminopropylto Alkoxysilane compounds such as trimethoxysilane and the like. Moreover, a well-known catalyst can be used according to the reactivity of the said crosslinking agent, and productivity can be improved in addition to film | membrane strength and durability improvement. These may be used individually by 1 type and may use 2 or more types together.
3 mass%-20 mass% are preferable, and, as for content of a crosslinking agent, 5 mass%-15 mass% are more preferable. When the content of the crosslinking agent is less than 3% by mass, the effect of improving the crosslinking density may not be obtained. When the content exceeds 20% by mass, the stability of the cholesteric layer may be lowered.

Alignment control agent In the liquid crystal composition, an alignment control agent that contributes to stably or rapidly forming a planar cholesteric liquid crystal layer may be added. Examples of the orientation control agent include fluorine (meth) acrylate polymers described in paragraphs [0018] to [0043] of JP-A-2007-272185, and paragraphs [0031] to [0034] of JP-A-2012-203237. Etc.] and the compounds represented by the formulas (I) to (IV).
In addition, as said orientation control agent, 1 type may be used independently and 2 or more types may be used together.

  The addition amount of the alignment control agent in the liquid crystal composition is preferably 0.01% by mass to 10% by mass, more preferably 0.01% by mass to 5% by mass with respect to the total mass of the cholesteric liquid crystal compound. 02 mass%-1 mass% are especially preferable.

Other additives In addition, the liquid crystal composition contains at least one selected from various additives such as a surfactant for adjusting the surface tension of the coating film and making the film thickness uniform, and a polymerizable monomer. It may be. Further, in the liquid crystal composition, a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a light stabilizer, a colorant, metal oxide fine particles, and the like are added in a range that does not deteriorate the optical performance, if necessary. Can be added.

  The cholesteric liquid crystal layer is formed by applying a liquid crystal composition in which the polymerizable liquid crystal compound and the polymerization initiator, the chiral agent added as necessary, the surfactant, and the like are dissolved in a solvent on a substrate. The film is dried to obtain a coating film, and the coating film is irradiated with actinic rays to polymerize the cholesteric liquid crystalline composition, thereby forming a cholesteric liquid crystal layer in which cholesteric regularity is fixed. In addition, the laminated film which consists of a some cholesteric layer can be formed by repeating the manufacturing process of a cholesteric layer.

There is no restriction | limiting in particular as a solvent used for preparation of a liquid-crystal composition, Although it can select suitably according to the objective, An organic solvent is used preferably.
The organic solvent is not particularly limited and may be appropriately selected depending on the intended purpose. For example, ketones, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, ethers, etc. Can be given. These may be used individually by 1 type and may use 2 or more types together. Among these, ketones are particularly preferable in consideration of environmental load.

  The method of applying the liquid crystal composition on the substrate is not particularly limited and can be appropriately selected depending on the purpose. For example, the wire bar coating method, curtain coating method, extrusion coating method, direct gravure coating method, reverse Examples include gravure coating, die coating, spin coating, dip coating, spray coating, and slide coating. Moreover, it can implement also by transferring the liquid-crystal composition separately coated on the support body to a base material. The liquid crystal molecules are aligned by heating the applied liquid crystal composition. The heating temperature is preferably 200 ° C. or lower, and more preferably 130 ° C. or lower. By this alignment treatment, an optical thin film in which the polymerizable liquid crystal compound is twisted and aligned so as to have a helical axis in a direction substantially perpendicular to the film surface is obtained.

The aligned liquid crystal compound may be further polymerized. The polymerization may be either thermal polymerization or photopolymerization by light irradiation, but photopolymerization is preferred. It is preferable to use ultraviolet rays for the light irradiation. The irradiation energy is preferably ^{20mJ / cm 2 ~50J / cm 2} , 100mJ / cm 2 ~1,500mJ / cm 2 is more preferable. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions or in a nitrogen atmosphere. The irradiation ultraviolet wavelength is preferably 350 nm to 430 nm. The polymerization reaction rate is preferably as high as possible from the viewpoint of stability, preferably 70% or more, and more preferably 80% or more.
The polymerization reaction rate can determine the consumption rate of a polymerizable functional group using an IR absorption spectrum.

  The thickness of the cholesteric liquid crystal layer that is a circularly polarized light separating layer in the near-infrared wavelength region is preferably 1 μm to 150 μm, more preferably 2 μm to 100 μm, and more preferably 5 μm. More preferably, it is ˜50 μm.

(Other layers)
The circularly polarized light separating film may include other layers such as a support, an alignment layer for aligning the liquid crystal compound, and an adhesive layer for bonding the circularly polarized light separating layer and the visible light blocking layer.
The support is not particularly limited, and glass or the like may be used in addition to the plastic film. It is preferable that the optical properties of the visible light blocking layer and the circularly polarized light separating layer are not canceled, and it is generally transparent and preferably has low birefringence. Examples of the plastic film include polyester such as polyethylene terephthalate (PET), polycarbonate, acrylic resin, epoxy resin, polyurethane, polyamide, polyolefin, cellulose derivative, and silicone. The support used for producing the cholesteric liquid crystal layer may be peeled off in the circularly polarized light separating film.

The alignment film is a layer having an organic compound, a rubbing treatment of a polymer (resin such as polyimide, polyvinyl alcohol, polyester, polyarylate, polyamide imide, polyether imide, polyamide, modified polyamide), oblique deposition of an inorganic compound, or a micro groove. Or accumulation of organic compounds (eg, ω-tricosanoic acid, dioctadecylmethylammonium chloride, methyl stearylate) by the Langmuir-Blodgett method (LB film). Furthermore, an alignment film in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known. Among these, an alignment film formed by polymer rubbing treatment is particularly preferable. The rubbing treatment can be performed by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth.
You may apply | coat a liquid-crystal composition to the support body surface without providing an alignment film, or the surface which carried out the rubbing process of the support body.

  Adhesives include hot melt type, thermosetting type, photocuring type, reactive curing type, and pressure-sensitive adhesive type that does not require curing, from the viewpoint of curing method, and the materials are acrylate, urethane, urethane acrylate, epoxy , Epoxy acrylate, polyolefin, modified olefin, polypropylene, ethylene vinyl alcohol, vinyl chloride, chloroprene rubber, cyanoacrylate, polyamide, polyimide, polystyrene, polyvinyl butyral, etc. can do. From the viewpoint of workability and productivity, the photocuring type is preferable as the curing method, and from the viewpoint of optical transparency and heat resistance, the material is preferably an acrylate, urethane acrylate, epoxy acrylate, or the like. .

(Method for producing circularly polarized light separating film)
A circularly polarized light separating film having a visible light blocking layer can be prepared by bonding a visible light blocking layer and a circularly polarized light separating layer, which can be prepared as described above, using an adhesive or the like. The surface to be bonded is not particularly limited. For example, when a support is provided, it may be the support surface side or the opposite side. After bonding both together, the support may or may not be peeled off. When the circularly polarized light separating layer includes a linearly polarized light separating layer and a λ / 4 retardation layer, a visible light blocking layer may be bonded to the surface of the linearly polarized light separating layer as viewed from the λ / 4 retardation layer. preferable.
The circularly polarized light separating film may be formed by forming a circularly polarized light separating layer directly on the visible light blocking layer through a step of applying a composition for forming the circularly polarized light separating layer. The visible light blocking layer may be formed directly through a step of applying a composition for forming a visible light blocking layer.

(Light receiving element, sensor)
As a light receiving element used in the detection system or detection method of the present invention, a photodiode type sensor using a semiconductor such as Si, Ge, HgCdTe, PtSi, InSb, PbS, a detector in which light detection elements are arranged in a line, Includes CCDs and CMOSs that can capture images.
In the detection system or the detection method of the present invention, the circularly polarized light separating film serves as a sensor component, and the circularly polarized light separating film selectively transmits light having a wavelength that selectively transmits either right circularly polarized light or left circularly polarized light. It may be used in combination with a light receiving element that can be detected. For example, a circularly polarized light separating film can be disposed on the light receiving surface of the sensor.

  It is preferable that the sensor has a light receiving element inside the housing, and a circularly polarized light separating film is disposed in the light capturing portion so that light other than light passing through the circularly polarized light separating film does not reach the light receiving element. . The circularly polarized light separating film is preferably arranged so that the circularly polarized light separating layer is on the outer side and the visible light blocking layer is on the light receiving element side. When the circularly polarized light separating layer includes a linearly polarized light separating layer and a λ / 4 phase difference layer, the circularly polarized light separating layer may be arranged so that the λ / 4 phase difference layer is outside and the linearly polarized light separating layer is on the light receiving element side. preferable.

(Light source, light source device)
Any light source can be used as long as it emits light of the photosensitive wavelength of the light receiving element, such as a halogen lamp, tungsten lamp, LED, LD, xenon lamp, and meta-hara lamp. LED or LD is preferable in terms of modulation suitability.

  In the detection system or the detection method of the present invention, the light source device may be configured by combining a light source and the circularly polarized light separating film. The light source device has, for example, a light source inside the housing, and a circularly polarized light separating film is disposed in a portion that emits light so that light other than light passing through the circularly polarized light separating film is not emitted from the light source. It is preferable. The circularly polarized light separating film is preferably arranged so that the circularly polarized light separating layer is on the outside and the visible light blocking layer is on the light source side. In the case where the circularly polarized light separating layer includes a linearly polarized light separating layer and a λ / 4 phase difference layer, it is preferable that the λ / 4 phase difference layer is disposed outside and the linearly polarized light separating layer is on the light source side. .

  The present invention will be described more specifically with reference to the following examples. The materials, reagents, amounts and ratios of substances, operations, and the like shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention is not limited to the following examples.

[Production of Circularly Polarized Separation Film A]
The coating solution A-2 shown in Table 1 was applied to a rubbing treated surface of Fujifilm PET subjected to rubbing treatment using a wire bar at room temperature so that the dry film thickness after drying was 5 μm. . The coating layer is dried at room temperature for 30 seconds, heated in an atmosphere of 85 ° C. for 2 minutes, and then irradiated with UV light at 60 ° C. for 6 to 12 seconds with a fusion D bulb (lamp 90 mW / cm). A liquid crystal layer was obtained. On this liquid crystal layer, coating solution A-3 shown in Table 1 was applied at room temperature so that the thickness of the dried film after drying was 5 μm, and then dried, heated, and UV-irradiated in the same manner as described above. An eye liquid crystal layer was formed to obtain a circularly polarized light separating layer.

  The coating liquid B-1 shown in Table 2 was applied to a rubbing-treated surface of Fujifilm PET subjected to rubbing treatment using a wire bar at room temperature so that the dry film thickness after drying was 2 μm. The coating layer is dried at room temperature for 30 seconds, heated in an atmosphere of 85 ° C. for 2 minutes, and then irradiated with UV light at 60 ° C. for 6 to 12 seconds with a fusion D bulb (lamp 90 mW / cm). A liquid crystal layer was obtained. On this liquid crystal layer, coating liquid B-2 shown in Table 2 was applied at room temperature so that the thickness of the dried film after drying was 2 μm, and then dried, heated, and UV-irradiated in the same manner as described above. The liquid crystal layer was formed. Using the coating liquids B-3 to B-16 shown in Table 2 on the second liquid crystal layer, the third to sixteenth liquid crystal layers were formed in the same process to obtain a visible light reflecting layer. .

  On the surface of the circularly polarized light separating layer prepared above on the liquid crystal layer side, a UV curable adhesive Exp. U12034-6 was applied using a wire bar at room temperature so that the dry film thickness after drying was 5 μm. The coated surface and the liquid crystal layer side surface of the visible light reflecting layer prepared above were bonded together so as not to contain bubbles, and then heated at 30 ° C. with a Fusion D bulb (lamp 90 mW / cm) at an output of 60% and 6%. UV irradiation for ˜12 seconds. Thereafter, Fujifilm PET, which was a support for the circularly polarized light separating layer and the visible light reflecting layer, was peeled off to obtain a circularly polarized light separating film A.

[Preparation of circularly polarized light separating film B]
The coating liquid A-2 shown in Table 1 was applied to a rubbing-treated surface of Fujifilm PET subjected to rubbing treatment using a wire bar at room temperature so that the dry film thickness after drying was 5 μm. The coating layer is dried at room temperature for 30 seconds, heated in an atmosphere of 85 ° C. for 2 minutes, and then irradiated with UV light at 60 ° C. for 6 to 12 seconds with a fusion D bulb (lamp 90 mW / cm). A liquid crystal layer was obtained. On this liquid crystal layer, coating solution A-3 shown in Table 1 was applied at room temperature so that the thickness of the dried film after drying was 5 μm, and then dried, heated, and UV-irradiated in the same manner as described above. An eye liquid crystal layer was formed to obtain a circularly polarized light separating layer.

  On the IR80 manufactured by FUJIFILM Corporation as the visible light absorbing layer, the UV curable adhesive Exp. U12034-6 was applied using a wire bar at room temperature so that the dry film thickness after drying was 5 μm. The coated surface and the surface on the liquid crystal layer side of the circularly polarized light separating layer prepared above were bonded together so that no bubbles would enter, and then 6 ° C. with a fusion D bulb (lamp 90 mW / cm) at 30 ° C. with an output of 60%. UV irradiation for ˜12 seconds. Thereafter, Fujifilm PET, which was a support for the circularly polarized light separating layer, was peeled off to obtain a circularly polarized light separating film B.

[Production of Circularly Polarized Separation Film C]
The coating liquid A-1 shown in Table 1 was applied to a rubbing-treated surface of Fujifilm PET subjected to rubbing treatment using a wire bar at room temperature so that the dry film thickness after drying was 5 μm. The coating layer is dried at room temperature for 30 seconds, heated in an atmosphere of 85 ° C. for 2 minutes, and then irradiated with UV light at 60 ° C. for 6 to 12 seconds with a fusion D bulb (lamp 90 mW / cm). A liquid crystal layer was obtained. On this liquid crystal layer, the coating solution A-2 shown in Table 1 was applied at room temperature so that the thickness of the dried film after drying was 5 μm, and then dried, heated and irradiated with UV in the same manner as described above. An eye liquid crystal layer was formed. Apply the coating liquid A-3 shown in Table 1 on the second liquid crystal layer at room temperature so that the thickness of the dry film after drying is 5 μm, and then dry, heat, and UV-irradiate as described above. A third liquid crystal layer was formed to obtain a circularly polarized light separating layer.

  The circularly polarized light separating layer produced above was bonded by the same method as IR80 manufactured by Fujifilm Co., Ltd. and the circularly polarized light separating film B to obtain a circularly polarized light separating film C.

[Preparation of circularly polarized light separating film D]
The coating liquid A-15 shown in Table 1 was applied to the rubbing treated surface of Fujifilm PET subjected to rubbing treatment using a wire bar at room temperature so that the dry film thickness after drying was 5 μm. The coating layer is dried at room temperature for 30 seconds, heated in an atmosphere of 85 ° C. for 2 minutes, and then irradiated with UV light at 60 ° C. for 6 to 12 seconds with a fusion D bulb (lamp 90 mW / cm). A liquid crystal layer was obtained. On this liquid crystal layer, the coating solution A-16 shown in Table 1 was applied at room temperature so that the dry film thickness was 5 μm, and then dried, heated and irradiated with UV in the same manner as above. An eye liquid crystal layer was formed to obtain a circularly polarized light separating layer.

  The circularly polarized light separating layer produced above was bonded by the same method as IR80 manufactured by Fuji Film Co., Ltd. and the circularly polarized light separating film B to obtain a circularly polarized light separating film D.

[Production of circularly polarized light separating film E]
The coating solution A-2 shown in Table 1 was applied to a rubbing-treated surface of Fujifilm PET subjected to rubbing treatment using a wire bar at room temperature so that the dry film thickness after drying was 5 μm. The coating layer is dried at room temperature for 30 seconds, heated in an atmosphere of 85 ° C. for 2 minutes, and then irradiated with UV light at 60 ° C. for 6 to 12 seconds with a fusion D bulb (lamp 90 mW / cm). Thus, a circularly polarized light separating layer was obtained.
The circularly polarized light separating layer produced above was bonded in the same manner as IR80 manufactured by Fuji Film Co., Ltd. and the circularly polarized light separating film B to obtain a circularly polarized light separating film E.

[Preparation of circularly polarized light separating film F]
A circularly polarized light separating film F was obtained in the same manner as the method for producing the circularly polarized light separating film A except that the visible light reflecting layer was not formed.
[Preparation of circularly polarized light separating film G]
A circularly polarized light separating film G was obtained in the same manner as the method for producing the circularly polarized light separating film C except that no visible light absorbing layer was formed.
[Preparation of circularly polarized light separating film H]
A circularly polarized light separating film H was obtained in the same manner as the method for producing the circularly polarized light separating film D except that no visible light absorbing layer was formed.

[Preparation of circularly polarized light separating film I]
The coating liquid A-1 shown in Table 1 was applied to a rubbing-treated surface of Fujifilm PET subjected to rubbing treatment using a wire bar at room temperature so that the dry film thickness after drying was 5 μm. The coating layer is dried at room temperature for 30 seconds, heated in an atmosphere of 85 ° C. for 2 minutes, and then irradiated with UV light at 60 ° C. for 6 to 12 seconds with a fusion D bulb (lamp 90 mW / cm). A liquid crystal layer was obtained. On this liquid crystal layer, the coating solution A-2 shown in Table 1 was applied at room temperature so that the thickness of the dried film after drying was 5 μm, followed by drying, heating and UV irradiation in the same manner as above. The liquid crystal layer was formed. Using the coating liquids A-3 to A-12 shown in Table 1 on the second liquid crystal layer, the third to twelfth liquid crystal layers are formed in the same process to obtain a circularly polarized light separating film I. It was.

[Preparation of circularly polarized light separating film J]
A visible light absorbing layer was formed on the circularly polarized light separating film I in the same manner as the circularly polarized light separating film B, and a circularly polarized light separating film J was obtained.

[Preparation of circularly polarized light separating film K]
The coating liquid A-1 shown in Table 1 was applied to a rubbing-treated surface of Fujifilm PET subjected to rubbing treatment using a wire bar at room temperature so that the dry film thickness after drying was 5 μm. The coating layer is dried at room temperature for 30 seconds, heated in an atmosphere of 85 ° C. for 2 minutes, and then irradiated with UV light at 60 ° C. for 6 to 12 seconds with a fusion D bulb (lamp 90 mW / cm). A liquid crystal layer was obtained. On this liquid crystal layer, the coating solution A-2 shown in Table 1 was applied at room temperature so that the thickness of the dried film after drying was 5 μm, followed by drying, heating and UV irradiation in the same manner as above. The liquid crystal layer was formed. Using the coating liquids A-3 to A-14 shown in Table 1 on the second liquid crystal layer, the third to fourteenth liquid crystal layers were formed in the same process to obtain a circularly polarized light separating film K. It was.

[Preparation of circularly polarized light separating film L]
A visible light absorbing layer was formed on the circularly polarized light separating film K in the same manner as the circularly polarized light separating film B, and a circularly polarized light separating film L was obtained.

  The circularly polarized light separating films A to L produced as described above were used on the light source side (circularly polarized light separating film 1) and the light receiving element side (circularly polarized light separating film 2) as shown in Table 3, and the numbers shown in Table 3 were used. It arrange | positioned according to the arrangement | positioning figure of FIG. 1, and the target of Examples 1-11 shown in Table 3 and the comparative examples 1-5 was detected. When a film including a visible light blocking layer and a circularly polarized light separating layer is used as the circularly polarized light separating film 1, the visible light blocking layer is disposed on the light source side and the circularly polarized light separating layer is on the object side, When a film including a visible light blocking layer and a circularly polarized light separating layer was used as the circularly polarized light separating film 2, the films were arranged so that the visible light blocking layer was on the light receiving element side and the circularly polarized light separating layer was on the object side.

Evaluation Method Evaluation is performed under the bright room conditions in Examples 1-6, 10, and 11 and Comparative Example 1-3, when the detection target is inserted into the optical path and when the signal intensity ratio of the detector is not inserted, In Examples 7 and 8 and Comparative Example 4, it is performed by comparing the signal intensity ratio of the detector when a detection target having cracks and an intact detection target are inserted in the optical path. In Example 9 and Comparative Example 5, Water was sprayed onto the kappa in the dark, and it was photographed with a camera. When the virtual image was captured, it was judged as “impossible”, and when the virtual image was not recognized as “possible”.
The evaluation criteria are as follows.
A: 4 or more B: 2 or more and less than 4 C: 1.4 or more and less than 2 D: Less than 1.4

The measurement was performed in a dark place where light was completely blocked and in a bright room with an incandescent lamp. The results are shown in Table 3.

1 circularly polarized light separating film 2 light source 3 light receiving element (detector)
4 Object 5 Transparent glass

Claims (12)

A system for detecting the object by irradiating the object with light and detecting reflected light or transmitted light of the object derived from the light irradiation,
A light source, a circularly polarized light separating film 1, a circularly polarized light separating film 2, and a light receiving element that detects light having a wavelength in the near-infrared light wavelength region,
Both the circularly polarized light separating film 1 and the circularly polarized light separating film 2 selectively transmit either the right circularly polarized light or the left circularly polarized light in at least a part of the near infrared wavelength region,
The circularly polarized light separating film 1 may also serve as the circularly polarized light separating film 2,
In the light source, the circularly polarized light separating film 1, the circularly polarized light separating film 2, and the light receiving element, the light supplied from the light source passes through the circularly polarized light separating film 1 and is irradiated on the object, and the object is The transmitted or reflected light is arranged so as to pass through the circularly polarized light separating film 2 and be detected by the light receiving element,
The system in which the circularly polarized light separating film 2 includes a visible light blocking layer 2 that reflects or absorbs light in at least a part of the visible light wavelength range. The system according to claim 1, wherein the circularly polarized light separating film 1 includes a visible light blocking layer 1 that reflects or absorbs light in at least a part of the visible light wavelength range. The system according to claim 1, wherein the circularly polarized light separating film 1 includes a layer in which the cholesteric liquid crystal phase is fixed as the circularly polarized light separating layer 1. The system according to any one of claims 1 to 3, wherein the circularly polarized light separating film 2 includes a layer in which the cholesteric liquid crystal phase is fixed as the circularly polarized light separating layer 2. The system according to claim 1, wherein the light source is a near-infrared light source. A system for detecting the object through glass;
The light source, the circularly polarized light separating film 1, the circularly polarized light separating film 2, and the light receiving element detect the reflected light of the object derived from the light of the light source through the circularly polarized light separating film 2 and detected by the light receiving element. 6. The system according to any one of claims 1 to 5, wherein the system is arranged as described above. The object is a transparent film;
The light source, the circularly polarized light separating film 1, the circularly polarized light separating film 2, and the light receiving element detect the transmitted light of the object derived from the light of the light source through the circularly polarized light separating film 2 and detected by the light receiving element. 6. The system according to any one of claims 1 to 5, wherein the system is arranged as described above. The system according to any one of claims 1 to 7, wherein an optical axis of reflected light or transmitted light of the object derived from the light source forms an angle of 70 ° to 89 ° with the circularly polarized light separating film 2. A method of irradiating an object with light and detecting the object by reflected light or transmitted light of the object derived from the light irradiation,
(1) irradiating the object with circularly polarized light in a near-infrared light wavelength region that selectively includes either right circularly polarized light or left circularly polarized light;
(2) The light in which at least a part of the light generated by the circularly polarized light reflected by the object or transmitted through the object is transmitted through the circularly polarized light separating layer 2 and the visible light blocking layer 2 is near infrared. Sensing with a light receiving element that detects light of a wavelength in the light wavelength range,
The circularly polarized light separating layer 2 selectively transmits either the right circularly polarized light or the left circularly polarized light in at least a part of the near infrared wavelength region,
The visible light blocking layer 2 is a method of reflecting or absorbing light in at least a part of the visible light wavelength range. The method according to claim 9, wherein the circularly polarized light separating layer 2 and the visible light blocking layer 2 are layers constituting the same film. The said (2) WHEREIN: At least one part of the light which reflected by the said target object or permeate | transmitted the said target object permeate | transmits the circularly polarized light separation layer 2 and the light shielding layer 2 in this order. The method described in 1. The circularly polarized light in the near-infrared light wavelength region of (1) is light formed by transmitting light through the visible light blocking layer 1 and the circularly polarized light separating layer 1,
The circularly polarized light separating layer 1 is a layer that selectively transmits either right circularly polarized light or left circularly polarized light in at least a part of the near-infrared light wavelength region, and may also serve as the circularly polarized light separating layer 2 ,
The visible light blocking layer 1 is a layer that reflects or absorbs light in at least a part of the visible light wavelength range, and may also serve as the visible light blocking layer 2. The method according to item.