CN110622061A

CN110622061A - Light control device for infrared light region and visible light region

Info

Publication number: CN110622061A
Application number: CN201880032295.7A
Authority: CN
Inventors: 望月典明
Original assignee: Baolai Technology Co Ltd; Nippon Kayaku Co Ltd
Current assignee: Baolai Technology Co Ltd; Nippon Kayaku Co Ltd
Priority date: 2017-06-02
Filing date: 2018-05-30
Publication date: 2019-12-27
Anticipated expiration: 2038-05-30
Also published as: TW201908780A; TWI763860B; JPWO2018221598A1; CN110622061B; WO2018221598A1; JP7111703B2

Abstract

The present application provides a light control device which can emit light in an infrared light region and light in a visible light region at the time of incidence, respectively, with different polarized lights on the side to be detected, and can control the light quantity by the polarized lights. Specifically, the light control device includes at least one polarizing plate having a polarizing property for light in an infrared light region, at least one polarizing plate having a polarizing property for light in a visible light region, and a medium having a phase or a medium capable of controlling a phase, wherein transmitted light in the infrared light region and transmitted light in the visible light region are controlled by converting incident light in the infrared light region and incident light in the visible light region into light of different polarizations.

Description

Light control device for infrared light region and visible light region

Technical Field

The present invention relates to a light control device that controls light in an infrared region and a visible light region.

Background

A polarizing plate having a light transmission/shielding function is used in a Display device such as a Liquid Crystal Display (LCD) together with a Liquid Crystal having a light switching function. The LCD can be applied to small-sized devices such as early-stage computers and clocks, notebook computers, document processors, liquid crystal projectors, liquid crystal televisions, car navigation systems, information display devices inside and outside houses, measuring devices, and the like. Further, the present invention is also applicable to lenses having a polarizing function, and is applicable to sunglasses with improved visibility, and in recent years, polarizing glasses for 3D televisions and the like.

A general polarizing plate is manufactured by dyeing or containing iodine or a dichroic dye as a polarizing element to a polarizing film substrate such as a polyvinyl alcohol film or a derivative thereof oriented by stretching, or a polyvinyl film substrate in which polyvinyl is produced by dehydrochlorination of a polyvinyl chloride film or dehydration of a polyvinyl alcohol film and oriented by polymerization. Of the above, an iodine-based polarizing film using iodine as a polarizing element has a problem in durability when used for a long time under high temperature and high humidity conditions because it is weak to water and heat although it has excellent polarizing performance. On the other hand, a dye-based polarizing film using a dichroic dye as a polarizing element is generally insufficient in polarizing performance, although it is superior in moisture resistance and heat resistance compared to an iodine-based polarizing film. In other words, the polarizing plate has a polarizing function for wavelengths targeted for the visible light wavelength region, and is not a polarizing plate targeted for the infrared light wavelength region.

In recent years, for applications such as identification light sources for touch panels, crime prevention monitoring cameras, sensors, forgery prevention, and communication equipment, polarizing plates for use in the infrared region as well as visible light region wavelengths have been required. In order to meet such a demand, an infrared polarizing plate obtained by polyalkyleneizing an iodine polarizing plate as in patent document 1, an infrared polarizing plate using a wire grid as in patent document 2 or 3, an infrared polarizing plate obtained by extending a glass containing fine particles as in patent document 4, and a type using a cholesteric liquid crystal as in patent document 5 or 6 have been reported. In patent document 1, the durability is poor, and the heat resistance, the moist heat resistance and the light resistance are poor, so that the method is not practical. Like the wire grid type of patent document 2 or 3, it is possible to process it into a thin film type and is stable as a product, and thus it has been gradually popularized. However, since the optical characteristics cannot be maintained without the nano-scale unevenness on the surface, the surface cannot be contacted, and thus the use thereof is limited, and anti-reflection and anti-glare (anti-glare) processing is difficult. The glass drawn type containing fine particles, such as patent document 4, has high durability and high dichroism, and is therefore useful. However, since the glass contains fine particles and is stretched, the element itself is easily broken and fragile, and is not as flexible as a conventional polarizing plate, and therefore, there is a problem that surface processing and bonding to other substrates are difficult. The techniques of patent documents 5 and 6 use circular polarization as disclosed in the prior art, but since the color changes depending on the viewing angle and basically a reflective polarizing plate is used, stray light and absolutely polarized light are not easily formed. In other words, there is no polarizing plate corresponding to the infrared wavelength region, which is a thin film type polarizing element and has flexibility and high durability, unlike a general iodine-based polarizing plate, belonging to an absorption-type polarizing element. In addition, even a polarizing plate having only an infrared region functions, not a polarizing plate that can control polarization in a visible light region.

Therefore, even though polarization in the infrared region and polarization in the visible region can be controlled separately, there is no polarizing plate that can control polarization of light in each region at the same time.

Further, elements that can switch between visible light and infrared light and switch independently from each other do not exist.

[ patent document 1] specification No. US 2,494,686

[ patent document 2] Japanese patent laid-open publication No. 2016-148871

[ patent document 3] Japanese Kokai publication No. 2006-507517

[ patent document 4] Japanese patent application laid-open No. 2004-86100

[ patent document 5] International publication No. 2015/087709

[ patent document 6] Japanese patent laid-open publication No. 2013-064798

[ non-patent document 1] polarization and its application, Co-Press, Chapter 2 (p 14-30).

Disclosure of Invention

[ problems to be solved by the invention ]

The present application aims to provide a light control device capable of controlling light having a wavelength in the infrared region and light having a wavelength in the visible region to be polarized light different from each other at the same time.

The present application is also directed to provide optical control of light in which incident polarization in the infrared region and incident polarization in the visible region are controlled to be polarized in each region at the same time. In addition, an object is to provide an optical system that can switch and control the amount of light in each of the infrared region and the visible region on the side of detection from light in the infrared region and light in the visible region of the same light source, that is, an element that can switch between visible light and infrared light dynamically.

[ means for solving problems ]

The present inventors have continued intensive studies to solve the above-described problems, and as a result, have found that by using a medium having a phase or a medium whose phase is controllable and controlling light in the infrared region and light in the visible region to be polarized differently, polarization of light in the infrared region at the time of incidence and polarization of light in the visible region at the time of incidence can be emitted to the side to be detected with different polarizations in the infrared region and the visible region.

The present inventors have also found that a light control device which uses light in the visible light region and light in the infrared light region simultaneously and includes at least 1 polarizing plate having a polarizing property for light in the infrared light region and at least 1 polarizing plate having a polarizing property for light in the visible light region, wherein the amount of transmitted light in the infrared light region and the amount of transmitted light in the visible light region can be controlled by a medium capable of dynamically controlling a phase, and the light control device can function as a switching element for light in the infrared light region and light in the visible light region. Further, it has been found that an optical system capable of controlling the amount of light by switching between the infrared region and the visible region on the side to be detected, even when the same light source is used, the amount of light in the infrared region and the amount of light in the visible region when light is incident on the optical system.

That is, the main configuration of the present invention is as follows.

1)

A light control device comprising at least one polarizing plate (IR polarizing plate) having a polarizing property for light in an infrared light region, at least one polarizing plate (VIS polarizing plate) having a polarizing property for light in a visible light region, and a medium having a phase or a medium capable of controlling a phase, wherein transmitted light in the infrared light region and transmitted light in the visible light region are controlled by converting incident light in the infrared light region and incident light in the visible light region into light of different polarizations.

2)

The light control device according to 1), wherein an angle θ i between an angle at which the phase difference value R λ is displayed for the phase-having medium or the phase-controllable medium and an angle at which the infrared light region exhibits linear polarization is in a range of 0 ≦ θ i < 180 °.

3)

The light control device according to 1) or 2), wherein an angle θ v between an angle at which the phase difference value R λ is displayed in the phase-having medium or the phase-controllable medium and an angle at which the linearly polarized light appears in the visible light region is in a range of-90 ° < θ v < 180 °.

4)

The light control device according to any one of claims 1) to 3), wherein a relationship of the following expression (1) or expression (2) is satisfied when a wavelength of light in an infrared light region is represented by I λ, a wavelength of light in a visible light region is represented by V λ, an error in a phase difference value is represented by RD, and a phase difference value of a phase-having medium or a phase-controllable medium is represented by R λ;

v lambda-RD R lambda is less than or equal to V lambda + RD mathematical formula (1)

(however, RD represents 0 to 40nm)

I lambda/2-RD R lambda is less than or equal to I lambda/2 + RD mathematical formula (2)

(however, RD represents 0 to 40 nm).

5)

The light control device according to any one of claims 1) to 3), wherein a relationship of the following expression (3) or expression (4) is satisfied when a wavelength of light in an infrared light region is represented by I λ, a wavelength of light in a visible light region is represented by V λ, an error in a phase difference value is represented by RD, and a phase difference value of a phase-having medium or a phase-controllable medium is represented by R λ;

v lambda/2-RD R lambda is less than or equal to V lambda/2 + RD mathematical formula (3)

(however, RD represents 0 to 40nm)

I lambda/4-RD R lambda is less than or equal to I lambda/4 + RD mathematical formula (4)

(however, RD represents 0 to 40 nm).

6)

The light control device according to any one of claims 1) to 3), wherein a relationship of the following expression (5) or expression (6) is satisfied when a wavelength of light in an infrared light region is represented by I λ, a wavelength of light in a visible light region is represented by V λ, an error in a phase difference value is represented by RD, and a phase difference value of a phase-having medium or a phase-controllable medium is represented by R λ;

v lambda is multiplied by 3/2-RD lambda is not less than R lambda is not less than V lambda is multiplied by 3/2+ RD mathematic formula (5)

(however, RD represents 0 to 40nm)

I lambda x 1/2-RD R lambda is less than or equal to I lambda x 1/2+ RD mathematic formula (6)

(however, RD represents 0 to 40 nm).

7)

A light control device for controlling light in a visible light region and light in an infrared light region simultaneously, as described in any one of 1) to 6), wherein the phase-controllable medium is a medium capable of dynamically controlling the phase.

8)

The light control device according to claim 7), wherein the medium whose phase is dynamically controllable is a liquid crystal panel (liquid crystal cell).

9)

The light control device according to claim 8), wherein the liquid crystal used in the liquid crystal panel (liquid crystal cell) is a twisted nematic liquid crystal (TN liquid crystal; twisted Nematic liquid crystal) or super Twisted Nematic liquid crystal (STN liquid crystal; SuperTwisted Nematic liquid crystal).

10)

The light control device according to any one of claims 7) to 9), wherein a contrast ratio of transmission to non-transmission of light in a visible light region and light in an infrared light region is 10 or more.

11)

The light control device according to any one of claims 7) to 9), which comprises 1 polarizing plate (VIS-IR polarizing plate) having polarizing properties for light in a visible light region and light in an infrared light region.

12)

The light control device according to claim 11), wherein the difference between the orthogonal transmittance of light in the infrared region and the orthogonal transmittance of light in the visible region in the VIS-IR polarizing plate is 1% or less.

13)

The light control device according to any one of claims 1) to 12), wherein the IR polarizing plate has a difference of 10% or more between a perpendicular transmittance of light in an infrared region and a perpendicular transmittance of light in a visible region.

14)

The light control device according to any one of 1) to 13), comprising: a polarizing plate in which the orthogonal transmittance of light in the infrared region is 1% or less and the difference in transmittance from light in the visible region is 10% or more; and at least 1 polarizing plate which has a high transmittance in an infrared region, is less likely to affect the transmittance of light in the infrared region, and has a cross transmittance of light in a visible region of 1% or less.

15)

The light control device according to any one of claims 1) to 14), wherein the IR polarizing plate or the VIS-IR polarizing plate is an absorptive polarizing plate.

16)

The light control device according to any one of claims 1) to 15), wherein the IR polarizing plate or the VIS-IR polarizing plate is a film.

17)

The light control device according to any one of 1) to 16), which is laminated with a medium having a phase difference or a phase-controllable medium and at least 1 polarizing plate.

18)

A liquid crystal display device, a forgery prevention device, or a sensor, which is provided with the light control device as described in any one of 1) to 17).

[ Effect of the invention ]

According to the present invention, light in the infrared light region and light in the visible light region when incident can be emitted at the detection side with different polarized lights, and the amount of light can be controlled by the polarized lights.

In one aspect, according to the present invention, the amount of light in the infrared region and the amount of light in the visible region when the light is incident from the same light source are switched to be transmitted or not transmitted in each region on the side to be detected, and the respective amounts of light can be controlled.

Detailed Description

The light control device of the present invention includes at least one polarizing plate (IR polarizing plate) having a polarizing property for light in an infrared light region, at least one polarizing plate (VIS polarizing plate) having a polarizing property for light in a visible light region, and a medium having a phase or a medium capable of controlling a phase, wherein transmitted light in the infrared light region and transmitted light in the visible light region are controlled by converting incident light in the infrared light region and incident light in the visible light region into light of different polarizations.

In one aspect, a light control device according to the present invention includes a medium that can dynamically control a phase when light in a visible light region and light in an infrared light region enter simultaneously, wherein transmitted light in the infrared light region and transmitted light in the visible light region are controlled by controlling the light in the infrared light region and the light in the visible light region to be light of different polarizations.

The IR polarizing plate is not particularly limited as long as it is a polarizing plate capable of controlling polarization in the wavelength of the infrared region. Examples of the polarizing plate include: a polyolefin type using an iodine-based polarizing plate as in patent document 1, a wire grid type polarizing plate as in patent documents 2 and 3, a glass polarizing plate extended by mixing metal particles in glass as in patent document 4, a dye-based polarizing plate containing a dye, and the like. The dye-based polarizing plate can be formed into a film form, can be easily laminated with other polarizing plates, retardation plates, and the like, and has the characteristics of flexibility and easy optical control.

The IR polarizing plate has a polarizing property for light in a part or all of a wavelength region of 700 to 1400 nm.

The VIS polarizing plate is not particularly limited as long as it can control polarization in a wavelength in the visible light region. The polarizing plate may be, for example, an iodine-based polarizing plate, a dye-based polarizing plate capable of controlling only a specific wavelength to be polarized, a type of polarizing plate using a polyene, or the like, but it is preferable to use a dye-based polarizing plate capable of controlling only a specific wavelength to be polarized, or a combination of a plurality of dye-based polarizing plates capable of controlling only a specific wavelength to be polarized, as a polarizing element capable of controlling only a specific wavelength to be polarized. It is preferable to have a polarizing performance only for light having a specific wavelength, because polarization at a specific wavelength can be detected or controlled.

The VIS polarizing plate has a polarizing property for light in a part or all of a wavelength region of 400 to 700 nm. Preferably, the transmittance in the infrared region is high and no absorption is present if the light is in the infrared region

The transmittance is not particularly limited as long as it is higher than the visible light transmittance. The term "having no absorption" refers to a polarizing plate having high transmittance in the infrared region and hardly affecting the transmittance of light in the infrared region, but a general polarizing plate has a single transmittance of 30 to 45% and thus, when the wavelength in the infrared region has a single transmittance of about the same degree or more, a polarizing plate having a transmittance function of infrared light can be used as a visible light (VIS) polarizing plate of the present application. Specifically, the transmittance in the infrared region is 40% or more, preferably 50% or more, more preferably 60% or more, still more preferably 70% or more, and particularly preferably 80% or more. In particular, the transmittance in the infrared light region when 2 VIS polarizing plates are crossed is 30% or more, preferably 40% or more, more preferably 50% or more, still more preferably 60% or more, and particularly preferably 70% or more, and the VIS polarizing plate can be used as a particularly preferable VIS polarizing plate.

Examples of the medium having a phase include articles called a retardation plate, a wavelength plate, and a retardation film.

Examples of the phase-controllable medium include a liquid crystal panel (liquid crystal cell) in which liquid crystal is sealed and whose phase can be controlled electrically, as used in a general liquid crystal monitor.

Here, the "controllable phase" refers to a phase of light that can be controlled as a wave. When focusing on polarization performance, for example, a wavelength plate, a phase-controllable medium, or the like (wavelength plate or the like) is an optical functional element that gives a predetermined phase difference to linearly polarized light, and polarization may be such that a different phase is provided for light of a specific axis in another axis (for example, 90 °). That is, for light of one polarization, a wavelength plate or the like is provided in the optical path thereof, so that polarization of the opposite axis is obtained, or circular polarization, elliptical polarization or the like can be newly provided. Therefore, a wavelength plate or the like refers to an element that can change the polarization state of incident light by imparting a phase difference to orthogonal 2 polarization components with an aligned birefringent material (for example, an oriented film) or the like. In this wavelength plate, for example, when the wavelength of a specific light is λ, the slow axis of the λ/2 retardation plate is set at 45 ° to the polarization axis, and the linearly polarized light incident on the wavelength plate or the like can be rotated by 90 ° to emit polarized light having a polarization axis in a direction orthogonal (90 °) to the incident polarization axis. Further, by setting the slow axis of the retardation plate of λ/2 to 22.5 ° with respect to the axis of polarization, it is possible to rotate the linear polarization incident on the wavelength plate (retardation plate) by 45 °, and emit light having polarization inclined by 45 ° with respect to the incident polarization axis. In the case where the slow axis of the λ/4 retardation plate is set at 45 ° with respect to the axis of polarization, the linearly polarized light incident on the wavelength plate (retardation plate) can be emitted as circularly polarized light.

The article in which the retardation plate, the wavelength plate, or the retardation film can be used is not particularly limited as long as the slow axis or the fast axis of light of the film can be rotated with respect to the absorption axis of the polarizing plate.

A liquid crystal panel (liquid crystal cell) that can control the phase is a medium that electrically controls the phase. Examples of the liquid crystal driving method to be controlled include various methods such as TN (Twisted Nematic), STN (Super Twisted Nematic), IPS (In-Plane-switching), VA (Vertical Alignment), etc., but the liquid crystal driving method and the control method are not particularly limited as long as the liquid crystal driving method can control the phase of light In the visible light region and the phase of light In the infrared light region. Preferable examples thereof include TN (Twisted Nematic), STN (Super Twisted Nematic), and the like. The above is preferable because the driving voltage is low, the price is low, and the polarization rotation of 0 to 90 ° is easily controlled.

The light control device controls light in the infrared region and light in the visible region to be polarized light having different polarizations by a medium having a phase or a medium capable of controlling a phase. Accordingly, the polarization of the light in the infrared light region at the time of incidence and the polarization of the light in the visible light region at the time of incidence can be sensed as different polarizations on the detection side. Specifically, by simultaneously controlling polarization of light in the visible light region that is visible to the human eye and light in the infrared light region that is difficult to recognize, the amounts of light in the visible light region and light in the infrared light region can be simultaneously adjusted, and light in the infrared light region can be continuously transmitted while controlling light in the visible light region to be transmitted or not transmitted. In other words, the light control device can continuously transmit the light in the visible light region while controlling the light in the infrared light region to be transmitted or not transmitted, and can simultaneously control the polarization and the light amount of each of the light in the visible light region and the light in the infrared light region.

Conventionally, an infrared sensor and a visible light camera have required different types of sensors for sensing light in the infrared region and for sensing light in the visible region, respectively, but by using the device of the present invention, the infrared sensor and the visible light camera can be controlled by 1 light control device. For example, in a camera such as a mobile phone, it is common that a separate light control device is required for an authentication camera for an infrared light region and a camera for a visible light region, but since the light control device can switch between transmission and non-transmission of light in the visible light region and light in the infrared light region, the authentication in the infrared light region and the photographing in the visible light region can be performed using 1 light control device. Further, by applying the light control device, high security and the like can also be applied. Further, since the device can be a light transmission type device, circular polarization control and linear polarization control in the infrared to visible light region, for example, the device can be applied to a device to which a light reflection polarization function is applied, a security application, and the like.

In one aspect, a light control device is preferable in which an angle (phase difference) θ i between an angle (phase of incident light) at which a phase difference R λ is exhibited by a phase medium or a phase controllable medium (phase difference plate) and an angle (phase of emitted light) at which a linear polarization is exhibited (emitted) in an infrared light region is in a range of 0 ≦ θ i < 180 °. When the angle θ i is 0 °, in other words, when the retardation plate is coaxially disposed, the polarization in the infrared region is not affected by the retardation plate or becomes difficult to receive light, and when the retardation plate having a retardation value of λ/2 is disposed, the angle θ i is set to 45 °, whereby the polarization having an opposite axis that is 90 ° opposite to the incident linear polarization can be emitted.

The phase difference in the visible light region can also be controlled by a light control device in which the angle (phase difference) θ v between the angle at which the phase difference R λ appears (the phase of the incident light) and the angle at which the linear polarization appears in the visible light region (the phase of the emitted light) is in the range of-90 ° < θ v < 180 °. θ v and θ i may be the same or different, and the polarization state of light having a specific wavelength may be controlled by the phase difference plate. In other words, the number of retardation plates used is not limited to 1, and a plurality of retardation plates can be used in the light control device of the present invention, for example, a combination of 1/4 λ plates and 1/2 λ plates is used in a general liquid crystal display.

A light control device satisfying the relationship of the following expression (1) or expression (2) is provided in which the wavelength of light in the infrared region is represented by I lambda, the wavelength of light in the visible region is represented by V lambda, the error of the phase difference value is represented by RD (Retard dispersion), and the phase difference value of the phase difference plate is represented by R lambda, and functions as a phase difference plate capable of providing V lambda in the visible region and functions as a phase difference plate capable of providing I lambda/2 in the infrared region.

(however, RD represents 0 to 40nm)

(however, RD represents 0 to 40 nm).

In the light control device, when the slow axis of the retardation plate having R λ is set to 45 ° with respect to the incident linearly polarized light, the retardation plate continuously functions as a retardation plate capable of maintaining the polarized light at the time of incidence in the visible light region, and functions as a λ/2 polarizing plate in the infrared light region, thereby allowing the reverse polarization axis of the incident polarization axis to be emitted. In the case where the slow axis of the retardation plate having R λ is set to 45 ° with respect to the incident linearly polarized light, and the polarizing plate having an absorption axis orthogonal to the incident axis is provided on the emission side, a light control device that can transmit light in the visible light region but can absorb light in the infrared light region can be provided. In a case where it is desired that both light in the visible light region and light in the infrared light region do not transmit (absorb), the slow axis of the retardation plate having R λ may be set to 0 ° instead of 45 °. In this way, by controlling the slow axis of the retardation plate having R λ that satisfies the relationship of the above equation (1) or equation (2), the axis of linear polarization, elliptical polarization, and the like can be controlled. The RD is more preferably in the range of 0 to 40nm, still more preferably in the range of 0 to 25nm, still more preferably in the range of 0 to 15nm, particularly preferably in the range of 0 to 5 nm. The control of the polarization axis using the phase can be performed with reference to non-patent document 1 and the like.

The light control device satisfying the relationship of the following expression (3) or expression (4) functions as a phase difference plate capable of providing λ/2 in the visible light region and functions as a phase difference plate capable of providing λ/4 in the infrared light region. Further, I λ, V λ, RD and R λ are as defined above.

(however, RD represents 0 to 40nm)

(however, RD represents 0 to 40 nm).

In the light control device, when the slow axis of the retardation plate having R λ is set to 45 ° to which linearly polarized light enters, the retardation plate functions as a λ/2 polarizing plate in the visible light region and can emit the reverse polarization of the incident polarized light, and functions as a retardation plate that functions as a λ/4 polarizing plate in the infrared light region and can emit the incident polarized light as circularly polarized light. Accordingly, in the case where a polarizing plate having an absorption axis orthogonal to the incident axis is provided on the emission side, the visible light region can control polarization while maintaining linearly polarized light, whereas the infrared light region can control circularly polarized light. In a case where it is desired that both light in the visible light region and light in the infrared light region do not transmit (absorb), the slow axis of the retardation plate having R λ may be set to 0 ° instead of 45 °. In this way, by controlling the slow axis of the retardation plate having R λ that satisfies the above-described equations (3) and (4), the axis of linear polarization, elliptical polarization, and the like can be controlled. In the case of the above configuration, reflection in the visible light region and transmission in the infrared light region can be controlled. The preferable configuration may be, for example, a configuration of a polarizing plate that can control the visible light region and the infrared region, a medium having a phase or a medium that can control a phase, or a polarizing plate that can control the visible light region and the infrared region, and examples thereof include, but are not limited to, a configuration of a polarizing plate that can control the visible light region and the infrared region, a medium having a phase or a medium that can control a phase, a polarizing plate that can control the visible light region, and a polarizing plate that can control the infrared region. In addition, when the method is used, polarization control in which light reflected in an infrared region has polarization can be applied. For example, in the case where reflection control is performed by one polarizing plate, in the infrared region, the polarizing plate, the λ/4 phase difference plate, and the reflecting plate are laminated in this order, and in the case where the slow axis of the phase difference plate is set to 45 ° with respect to the absorption axis of the polarizing plate, the linearly polarized light incident from the polarizing plate is changed to circularly polarized light by the phase difference plate, and the light reflected by the reflecting plate is changed to inversely circularly polarized light, so that an antireflection function can be exhibited. However, in this case, since the light in the visible light region is continuously maintained in the linearly polarized state, the light is reflected, and the reflected light can be detected. In addition, even in the case of the reflective use, the slow axis of the retardation plate is set to 0 ° with respect to the absorption axis of the infrared polarizing plate, and the polarization in the infrared region is maintained in a linearly polarized state, so that the light control device functions as a light control device in which both light in the visible region and light in the infrared region can be reflected. In the case of the present light control device, RD is preferably in the range of 0 to 40nm, more preferably 0 to 25nm, still more preferably 0 to 15nm, particularly preferably 0 to 5 nm.

The light control device satisfying the relationship of the following expression (5) or expression (6) functions as a phase difference plate that can provide 3/2 λ in the visible light region and 1/2 λ in the infrared light region. Further, I λ, V λ, RD and R λ are as defined above.

(however, RD represents 0 to 40nm)

(however, RD represents 0 to 40 nm).

In the light control device, the slow axis of the retardation plate having R λ is set to 45 ° to which linearly polarized light enters, and the retardation plate functions as an 3/2 λ polarizing plate in the visible light region, thereby emitting circularly polarized light of the incident polarized light, and functions as a λ/2 polarizing plate in the infrared light region, thereby emitting light of the incident polarized light in the opposite axis. Accordingly, in the case where a polarizing plate having an absorption axis orthogonal to the incident axis is provided on the emission side, the polarized light in the visible light region can be controlled to be circularly polarized light, whereas the infrared light region can be controlled to be linearly polarized light. In a case where it is desired that both light in the visible light region and light in the infrared light region do not transmit (absorb), the slow axis of the retardation plate having R λ may be set to 0 ° instead of 45 °. In this way, by controlling the slow axis of the retardation plate having R λ that satisfies the above-described equations (5) and (6), the axis of linear polarization, elliptical polarization, and the like can be controlled. The preferable configuration may be, for example, a configuration of a polarizing plate that can control the visible light region and the infrared region, a medium having a phase or a medium that can control a phase, or a polarizing plate that can control the visible light region and the infrared region, and examples thereof include, but are not limited to, a configuration of a polarizing plate that can control the visible light region and the infrared region, a medium having a phase or a medium that can control a phase, a polarizing plate that can control the visible light region, and a polarizing plate that can control the infrared region. In addition, when the method is used, polarization control in which light reflected in an infrared region has polarization can be applied. In the case of the above configuration, reflection in the visible light region can be controlled, and transmission in the infrared light region can be controlled. For example, in the case of performing reflection control with one polarizing plate, the polarizing plate, 3/4 λ polarizing plate, and reflecting plate are laminated in this order in the visible light region, and the slow axis of the retardation plate is set to 45 ° with respect to the absorption axis of the polarizing plate on the reflecting plate, whereby the linearly polarized light incident from the polarizing plate is changed to circularly polarized light by the retardation plate, and the light reflected by the reflecting plate is changed to inversely circularly polarized light, resulting in the development of an antireflection function. However, in this case, since the light in the infrared light region continues to be linearly polarized, the light is reflected, and the reflected light can be detected. Even in the case of the reflective use, the retardation plate is set to have a slow axis of 0 °, and thus functions as a light control device capable of reflecting both light in the visible light region and light in the infrared light region. In the case of the present light control device, RD is preferably in the range of 0 to 40nm, more preferably 0 to 25nm, still more preferably 0 to 15nm, particularly preferably 0 to 5 nm.

In the IR polarizing plate of the light control device of the present invention, it is preferable that the difference between the transmittance of light in the infrared region (the orthogonal transmittance of light in the infrared region) when 2 polarizing plates are stacked so that the absorption axes are orthogonal to each other and the transmittance of light in the visible region (the orthogonal transmittance of light in the visible region) when 2 polarizing plates are stacked so that the absorption axes are orthogonal to each other (the wavelength of 400 to 700 nm) is 10% or more, and therefore, the polarization control of light in the visible region and light in the infrared region is facilitated. For example, in the case where a polarizing plate has a polarizing performance for light in the infrared region and a polarizing performance for light in the visible region, the polarization of light in each region can be controlled by the retardation plate, but when one polarizing plate has a polarization degree of 100% of light of 400 to 1400nm, it is difficult to impart the polarizing performance only to light in the infrared region or to light in the visible region. On the other hand, by using polarizing plates having polarizing properties for light in each wavelength region, polarization control can be performed at various wavelengths by selecting suitable polarizing plates depending on the wavelength. In other words, a polarizing plate using wavelength control of light only in the infrared region and a polarizing plate using wavelength control of light only in the visible region are preferable because polarization control and transmittance control can be performed at various wavelengths. However, a polarizing plate having a polarizing performance in the infrared light region may have a polarizing performance in the visible light region, and thus the polarizing plate does not necessarily have a polarizing performance only in the infrared light region. However, in terms of the function of the light control device of the present invention, it is important to emit light in which the phase of light (polarized light) given to the infrared region is different from that of light in the visible region, and therefore the magnitude (S/N ratio) of the amount of detected light (energy) is sufficient if it is clear. Therefore, in the IR polarizing plate, the difference between the transmittance of light of 700 to 1400nm when 2 polarizing plates are stacked with their absorption axes orthogonal to each other and the transmittance of light of 400 to 700nm when 2 polarizing plates are stacked with their absorption axes orthogonal to each other is 10% or more, and the polarization control of light in the visible light region and light in the infrared light region is facilitated, and therefore, the difference in transmittance is preferably 20% or more, more preferably 30% or more, and still more preferably 40% or more, instead of giving 100% polarization performance to all wavelengths.

The light control device including the IR polarizing plate having an orthogonal transmittance of 1% or less in the wavelength range of light in the infrared region and at least 1 VIS polarizing plate having no absorption of light in the wavelength range of light in the infrared region and having an orthogonal transmittance of 1% or less in the polarizing plate is preferable because the polarization performance with respect to light in the infrared region and the polarization performance with respect to light in the visible region can be controlled separately. The light control device is preferably configured to increase the contrast between light in the infrared region and light in the visible region. In addition, the polarizing plates may be used in different axes, and the wavelengths of the polarized lights to be controlled may be controlled in the axis direction, so that the light in the visible light region and the light in the infrared light region may be separated in the wavelength axis to perform the light control. The orthogonal transmittances of the light in the infrared region and the light in the visible region are each independently 1% or less, whereby sufficient light control can be performed, but are preferably 0.3% or less, more preferably 0.1% or less, still more preferably 0.01% or less, and particularly preferably 0.005% or less. For example, when the parallel transmittance is 40% and the orthogonal transmittance is 0.1%, the ratio is 40: 0.1, in other words 400: contrast of 1. In other words, the contrast of the polarizing plate has a large influence on the optical control device of the present invention, and therefore, it is preferable to control the contrast within the above range.

In the control of light in the infrared region and light in the visible region in the light control device of the present invention, the contrast of the amount of light required for switching between transmission and non-transmission (light blocking) needs to be a ratio of the contrast of a general paper medium. In other words, the contrast between transmission and light shielding may be 10 to 1 or more, preferably 100 to 1 or more, and more preferably 1000 to 1 or more.

When the light control device is constructed, it is preferable that at least 1 of the IR polarizing plates is an absorption type polarizing plate. The absorption type polarizing plate has the characteristic of not generating stray light. The IR polarizing plate is generally a wire grid type, but in the case of a polarizing plate that exhibits a polarizing function by controlling refraction and reflection of light, light having an intensity other than the original wavelength and light having an intensity are exhibited by reflection, refraction, resonance, phase modulation, and the like of light due to scattering light, light collection, a highly bright object, an unspecified shape, light overlapping, a positional shift of light, and the like. In this case, light having an intensity other than the original wavelength becomes stray light. In order to prevent false detection, it is important to prevent such stray light from being generated. In other words, a polarizing plate that does not generate stray light is preferably used. For example, when the IR polarizing plate is an absorption type polarizing plate, it is preferably used because it is less likely to cause stray light and is easy to control the optical properties.

The polarizing plates are easily laminated and can be flexible, and at least one of the IR polarizing plates is preferably a film for flexibility. In particular, since the phase-controllable dielectric can be laminated, the phase-controllable dielectric is preferably laminated with the phase-controllable dielectric. By stacking, the transmittance is less likely to be lowered by the influence of interface reflection or the like, and it is preferable in terms of light control.

The polarizing plates, the phase medium, or the phase-controllable medium may be rotated by optical or electrical signals, and may be set to a desired angle or changed.

The light control device can simultaneously control the polarization of light in the visible light region which can be recognized by human eyes and the polarization of light in the infrared light region which is difficult to be recognized, because the light control device can simultaneously control the polarization of light in the infrared light region and the light in the visible light region. Therefore, the light control device can be applied to various applications such as a liquid crystal display device capable of switching detection of light in an infrared light region and light in a visible light region, a camera such as a camera capable of controlling polarization of light in the infrared light region and light in the visible light region, a highly secure forgery prevention device, a sensor capable of functioning as light in the infrared light region and light in the visible light region, and the like, and can also be used as a system in which various applications are combined with the light control device.

Example (embodiment)

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples.

Production of polarizing plate (IR polarizing plate) having polarizing property for light in infrared region

An aqueous solution of azo compound of the following chemical formula (1) at 45 ℃ having a concentration of 0.3% and mirabilite at 0.1% was prepared as a staining solution. A polyvinyl alcohol film having a thickness of 75 μm was immersed in the staining solution for 5 minutes. Then, the film was stretched 5 times in a 50 ℃ solution of a 3% aqueous solution of boric acid, kept in a stretched state, washed with water, and dried to obtain a polarizing element. Both sides of the polarizing element were laminated with an adhesive of an aqueous polyvinyl alcohol solution, and an alkali-treated triacetyl cellulose film (TAC film; manufactured by FUJIFILM corporation; trade name TD-80U) was laminated thereon to obtain a polarizing plate having a high polarizing function centered around 835 nm. The polarizing plate was used as an IR polarizing plate.

Production of polarizing plate (VIS polarizing plate) having polarizing property for light in visible light region

An aqueous solution of Kayarus Supra Orange 2GL (manufactured by japan chemical corporation) at 45 ℃ having a concentration of 0.02%, c.i. direct red 81 at 0.01%, Blue KW (manufactured by japan chemical corporation) at 0.04%, and mirabilite at 0.1% was prepared as a staining solution. A polyvinyl alcohol film having a thickness of 75 μm was immersed in the staining solution for 3 minutes and 30 seconds. Then, the film was stretched 5 times in a 50 ℃ solution of a 3% aqueous solution of boric acid, kept in a stretched state, washed with water, and dried to obtain a polarizing element. Both sides of the polarizer were laminated with an adhesive of an aqueous polyvinyl alcohol solution, and an alkali-treated triacetyl cellulose film (TAC film; manufactured by FUJIFILM corporation; trade name TD-80U) was laminated thereon, to obtain a polarizing plate having a polarizing function in a visible light region of 400 to 650 nm. The polarizing plate was used as a VIS polarizing plate.

Production of polarizing plate capable of controlling light in infrared region and light in visible region (VIS-IR polarizing plate)

An aqueous solution of the azo compound of the formula (1) at 45 ℃ having a concentration of 0.6%, a concentration of 0.02% in Kayarus Supra Orange 2GL (manufactured by Nippon chemical Co., Ltd.), a concentration of 0.01% in C.I. direct Red 81, a concentration of 0.04% in Blue KW (manufactured by Nippon chemical Co., Ltd.), and a concentration of 0.1% in Glauber's salt was prepared as a dyeing liquid. A polyvinyl alcohol film having a thickness of 75 μm was immersed in the staining solution for 5 minutes. Then, the film was stretched 5 times in a 50 ℃ solution of a 3% aqueous solution of boric acid, kept in a stretched state, washed with water, and dried to obtain a polarizing element. Both sides of the polarizer were laminated with an adhesive of an aqueous polyvinyl alcohol solution, and an alkali-treated triacetyl cellulose film (TAC film; manufactured by FUJIFILM corporation; trade name TD-80U) was laminated thereon to obtain a polarizing plate having a polarizing function at 400 to 900 nm. The polarizing plate was used as a VIS-IR polarizing plate.

< measurement of transmittance of polarizing element >

(transmittance measurement of polarizing plate)

The obtained polarizing plates were measured for the transmittance of the monomer (Ts), the parallel transmittance (Tp), the orthogonal transmittance (Tc), and the polarization degree (. rho.) at each wavelength at 380 to 1100nm using a spectrophotometer (U-4100, Hitachi, Ltd.). The single transmittance (Ts) is a transmittance obtained by measuring one polarizing plate, the parallel transmittance (Tp) is a transmittance obtained by measuring the absorption axes of light of 2 polarizing plates in parallel, the orthogonal transmittance (Tc) is a transmittance obtained by measuring the absorption axes of light of 2 polarizing plates in orthogonal, and the polarization degree is a value calculated by the formula (7).

Degree of polarization (%) < 100 × [ (Tp-Tc)/(Tp + Tc)]^1/2Math formula (7)

The monomer transmittances (Ts), parallel transmittances (Tp), and orthogonal transmittances (Tc) at wavelengths of 420nm, 555nm, 830nm, and 840nm of each of the obtained polarizing plates are shown below. The values obtained when the IR polarizing plate was used, the values obtained when the VIS polarizing plate was used, and the values obtained when the VIS-IR polarizing plate was used are shown in table 1, table 2, and table 3, respectively.

[ Table 1]

Wavelength of light	Ts(％)	Tp(％)	Tc(％)	ρ(％)
					420	58.13	39.01	28.58	39.28
555	50.17	34.16	16.17	59.78
					830	38.00	28.68	0.21	99.29
840	38.53	29.42	0.27	99.08

[ Table 2]

Wavelength of light	Ts(％)	Tp(％)	Tc(％)	ρ(％)
					420	38.32	29.13	0.24	99.19
555	43.50	37.62	0.23	99.39
					830	91.95	84.55	84.55	0.08
840	91.38	83.50	83.50	0.43

[ Table 3]

Wavelength of light	Ts(％)	Tp(％)	Tc(％)	ρ(％)
					420	37.56	28.01	0.19	99.31
555	37.62	28.13	0.17	99.39
					830	38.18	28.96	0.18	99.37
840	38.74	29.74	0.28	99.07

< examples A1 to A4>

Production and evaluation of light control device

The light control device, which is constituted by a VIS-IR polarizing plate, a phase difference plate, a VIS polarizing plate and an IR polarizing plate in this order from the light source side, irradiates the light emitted from the light source unit of U-4100 to the light control device and allows the transmitted light to enter the detection unit of U-4100. A polycarbonate-based retardation plate exhibiting a retardation value of 420nm at each of wavelengths of 420nm and 840nm was used as the retardation plate. The transmittance of the retardation plate was measured at 0 ° and 45 ° inclinations of the slow axis with respect to the VIS-IR polarizing plate. At this time, the polarizing axes of the VIS polarizing plate and the IR polarizing plate were measured while being changed variously. The results are shown in Table 4. In table 4, 0 ° means that the slow axis is set to 0 ° in the case of a retardation plate and the absorption axis is set to 0 ° (coaxial) in the case of a VIS or IR polarizing plate, with respect to the absorption axis of the VIS-IR polarizing plate. 45 ° and 90 ° are also the same. St means that the penetration rate detected by U-4100 is high (30 to 50%), Mi means that the penetration rate detected by U-4100 is medium (10 to 25%), and We means that the penetration rate detected by U-4100 is low (0 to 2%).

[ Table 4]

< examples A5 to A8 >

A light control device was evaluated in the same manner as in examples 1 to 4, except that a polycarbonate-based retardation plate exhibiting a retardation value of 210nm at each of wavelengths of 420nm and 840nm was used. The results are shown in Table 5.

[ Table 5]

< examples A9 to A12 >

A light control device was evaluated in the same manner as in examples 1 to 4, except that a polycarbonate-based retardation plate exhibiting a retardation value of 415nm at each of wavelengths of 555nm and 830nm was used. The results are shown in Table 6.

[ Table 6]

< examples A13 to A14 >

The light control device, which is constituted by a VIS polarizing plate, an IR polarizing plate, a phase difference plate, and a reflecting plate in this order from the light source side, irradiates the light emitted from the light source unit of U-4100 to the light control device and causes the reflected light to enter the detecting unit of U-4100. A polycarbonate-based retardation plate exhibiting a retardation value of 210nm at each of wavelengths of 420nm and 840nm was used as the retardation plate. The transmittance of the retardation plate was measured when the slow axis was tilted at 0 ° and 45 ° with respect to the VIS polarizing plate. At this time, the polarization axes of the IR polarizing plates were variously changed and measured. The results are shown in Table 7. In table 7, 0 ° means that the slow axis is set to 0 ° in the case of a retardation plate and the absorption axis is set to 0 ° (coaxial) in the case of an IR polarizing plate, with respect to the absorption axis of the VIS polarizing plate. 45 ° and 90 ° are also the same. St, (Mi) and We have the same meanings as in Table 4.

[ Table 7]

< examples A15 to A16 >

The light control device, which is constituted by a VIS polarizing plate, an IR polarizing plate, a phase difference plate, and a reflecting plate in this order from the light source side, irradiates the light emitted from the light source unit of U-4100 to the light control device and causes the reflected light to enter the detecting unit of U-4100. A polycarbonate-based retardation plate exhibiting a retardation value of 415nm at each of wavelengths of 555nm and 830nm was used as the retardation plate. The transmittance of the retardation plate was measured when the slow axis was tilted at 0 ° and 45 ° with respect to the VIS polarizing plate. At this time, the polarization axes of the IR polarizing plates were variously changed and measured. The results are shown in Table 8. 0 °, 45 °, 90 °, St, (Mi), and We in table 8 mean the same as those in table 7.

[ Table 8]

Comparative examples A1 to A4

The results of measuring the transmittance using the light control devices (comparative examples 1 to 4) obtained by removing the retardation plates from examples a1 to a4 are shown in table 9. Similarly to a conventional polarizing plate, the transmittance of the polarizing plate decreases when the absorption axes of the polarizing plate are orthogonal to each other and increases when the absorption axes are parallel to each other. Only the transmittance of the parallel bits and the orthogonal bits can be controlled, which is a function of the conventional polarizing plate, and thus the optical device capable of individually controlling the transmittance at each wavelength cannot be obtained.

[ Table 9]

Comparative examples A5 to A6

The results of measuring the transmittance using the light control devices (comparative examples 5 to 6) obtained by removing the retardation plates from examples a13 to a14 are shown in table 10. No change in transmittance was observed at all, and no change was observed between the light in the visible light region and the light in the infrared light region when the conventional 1-sheet polarizing plate was placed on the mirror.

[ Table 10]

From the results of examples a1 to a12, it was found that in each of the light control devices, the amounts of light in the infrared region and light in the visible region were controlled separately for the same light source. Moreover, in the examples a5 to A8 and the examples a13 to a14, and the examples a9 to a12 and the examples a15 to a16, it was found that the results obtained by the light control at the time of light transmission are different from the results obtained by the light control at the time of reflection. As is apparent from the above results, the light control device according to the present invention is effective as a device capable of changing the amount of light in the visible light region and the amount of light in the infrared light region into different amounts of light and polarization, respectively, even when the same light source having light in the visible light region and light in the infrared light region is used.

EXAMPLE B1

The light control device is configured to irradiate the light emitted from the light source unit of U-4100 to the light control device, which is composed of a VIS-IR polarizing plate, an STN type liquid crystal cell, a VIS polarizing plate, and an IR polarizing plate in this order from the light source side, and to irradiate the transmitted light to the detecting unit of U-4100. In this case, the VIS polarizer was laminated such that the absorption axis of the VIS polarizer was parallel to the absorption axis of the VIS-IR polarizer, and the IR polarizer was laminated such that the absorption axis of the IR polarizer was 90 ° to the absorption axis of the VIS-IR polarizer. For the bonding to the liquid crystal cell, an article in which each polarizing plate was bonded so that the visible light region became the lowest transmittance when a voltage was applied to the STN cell was used as the measurement sample of the present application. The STN-type liquid crystal cell is a liquid crystal cell which is arranged to have a slow axis in a 45 ° direction when an initial axis is set to 0 ° when a voltage is applied, and has a phase difference of 1/2 λ at each wavelength of 420nm and 840 nm. In this case, the measurement results of the light having the wavelengths of 420nm and 840nm when the voltage was turned ON and OFF are shown in Table 11. The amount of light (%) entering the detection unit of U-4100 after passing through the light control device is expressed by the amount of light that has passed through only the VIS-IR polarizing plate.

EXAMPLE B2

The light control device is configured to irradiate the light emitted from the light source unit of U-4100 to the light control device, which is composed of a VIS-IR polarizing plate, an STN type liquid crystal cell, a VIS polarizing plate, and an IR polarizing plate in this order from the light source side, and to irradiate the transmitted light to the detecting unit of U-4100. In this case, the VIS polarizer was laminated such that the absorption axis of the VIS polarizer was orthogonal to the absorption axis of the VIS-IR polarizer, and the IR polarizer was laminated such that the absorption axis of the IR polarizer was 0 ° to the absorption axis of the VIS-IR polarizer. For the lamination to the liquid crystal cell, an article in which each polarizing plate was laminated so that the visible light region became the lowest transmittance when no voltage was applied to the STN cell was used as the measurement sample of the present application. When a voltage is applied, the STN-type liquid crystal cell is arranged so as to have a slow axis in the 45 ° direction when the initial axis is set to 0 °, and has a phase difference of 1/2 λ at each wavelength of 420nm and 840 nm. In this case, the measurement results of the light having the wavelengths of 420nm and 840nm when the voltage was turned ON and OFF are shown in Table 11. The amount of light (%) entering the detection unit of U-4100 after passing through the light control device is expressed by the amount of light that has passed through only the VIS-IR polarizing plate.

EXAMPLE B3

The light emitted from the light source unit of U-4100 is incident on a VIS polarizing plate, an IR polarizing plate, an STN type liquid crystal cell, and a reflection plate in this order from the light source side, and the reflected light is incident on the detection unit of U-4100. The IR polarizing plate was bonded at an angle of 45 ° with respect to the absorption axis of the VIS polarizing plate, and for the bonding to the liquid crystal cell, an article in which each polarizing plate was bonded so that the infrared light region had the lowest reflectance when no voltage was applied to the STN cell was used as the measurement sample of the present application. The STN-type liquid crystal cell is a liquid crystal cell which is arranged to have a slow axis in a 45 ° direction when an initial axis is set to 0 ° when a voltage is applied, and has a phase difference of 1/4 λ at each wavelength of 420nm and 840 nm. In this case, the measurement results of the light having the wavelengths of 420nm and 840nm when the voltage was turned ON and OFF are shown in Table 11. The amount of light (%) entering the detection unit of U-4100 after being reflected by the light control device is represented by the amount of light reflected by only the VIS-IR polarizing plate and the reflection plate.

EXAMPLE B4

As an evaluation of the light control device, the light emitted from the light source unit of U-4100 was made incident on the detection unit of U-4100 in a configuration of a VIS-IR polarizing plate, a TN type liquid crystal cell, a VIS polarizing plate and an IR polarizing plate when viewed from the light source side. In this case, the VIS polarizer was laminated such that the absorption axis of the VIS polarizer was parallel to the absorption axis of the VIS-IR polarizer, and the IR polarizer was laminated such that the absorption axis of the IR polarizer was 90 ° to the absorption axis of the VIS-IR polarizer. For the bonding to the liquid crystal cell, an article obtained by bonding a polarizing plate so that the transmittance in the infrared light region is minimized by the polarizing plate for the infrared light region when a voltage is applied to the TN cell was used as the measurement sample of the present application. In this case, the results of the light having the wavelengths of 420nm and 840nm when the voltage was turned ON and OFF are shown in Table 11. As a result, the amount of light (%) entering the detecting section of U-4100 after passing through the light control device was expressed in terms of the amount of light that passed through only the VIS-IR polarizing plate.

[ Table 11]

From the results of examples B1 to B4, it was found that the amounts of light in the infrared region and light in the visible region can be independently and dynamically controlled in each light control device while using the same light source. In particular, it is understood from the examples B1 and B2 that the transmittance of light in the visible light region and the transmittance of light in the infrared light region can be switched by controlling the light in the visible light region and the light in the infrared light region during transmission, that is, by using a medium that dynamically develops a phase. Further, it is understood from embodiment B3 that the light control device is effective in controlling light even when a reflection plate is used. As is apparent from the above results, the light control device according to the present invention is effective as a device capable of easily switching and controlling the transmittances of light in the visible light region and light in the infrared light region, respectively, even when the same light source is used.

[ industrial applicability ]

The present invention can be applied to various applications such as a liquid crystal display device capable of switching detection of light in the infrared region and light in the visible region by controlling polarization of incident light in the infrared region and light in the visible region to be different polarizations at the same time, a camera such as a camera capable of controlling polarization of light in the infrared region and light in the visible region, a highly secure forgery prevention device, and a sensor capable of functioning as both light in the infrared region and light in the visible region.

Claims

1. A light control device comprising at least one polarizing plate (IR polarizing plate) having a polarizing property for light in an infrared light region, at least one polarizing plate (VIS polarizing plate) having a polarizing property for light in a visible light region, and a medium having a phase or a medium capable of controlling a phase, wherein transmitted light in the infrared light region and transmitted light in the visible light region are controlled by converting incident light in the infrared light region and incident light in the visible light region into light of different polarizations.

2. The light control device according to claim 1, wherein an angle θ i between an angle at which the phase-having medium or the phase-controllable medium exhibits the phase difference value R λ and an angle at which the infrared light region exhibits the linear polarization is in a range of 0 ≦ θ i < 180 °.

3. The light control device according to claim 1 or 2, wherein an angle θ v between an angle at which the phase-having medium or the phase-controllable medium exhibits the phase difference value R λ and an angle at which the visible light region exhibits the linear polarization is in a range of-90 ° < θ v < 180 °.

4. The light control device according to any one of claims 1 to 3, wherein a relationship of the following expression (1) or expression (2) is satisfied when the wavelength of light in the infrared light region is represented by l λ, the wavelength of light in the visible light region is represented by V λ, the error in the phase difference value is represented by RD, and the phase difference value of the phase-having medium or the phase-controllable medium is represented by R λ;

(however, RD represents 0 to 40nm)

(however, RD represents 0 to 40 nm).

5. The light control device according to any one of claims 1 to 3, wherein a relationship of the following expression (3) or expression (4) is satisfied when the wavelength of light in the infrared light region is represented by l λ, the wavelength of light in the visible light region is represented by V λ, the error in the phase difference value is represented by RD, and the phase difference value of the phase-having medium or the phase-controllable medium is represented by R λ;

(however, RD represents 0 to 40nm)

(however, RD represents 0 to 40 nm).

6. The light control device according to any one of claims 1 to 3, wherein a relationship of the following expression (5) or expression (6) is satisfied when the wavelength of light in the infrared light region is represented by l λ, the wavelength of light in the visible light region is represented by V λ, the error in the phase difference value is represented by RD, and the phase difference value of the phase-having medium or the phase-controllable medium is represented by R λ;

(however, RD represents 0 to 40nm)

(however, RD represents 0 to 40 nm).

7. The light control device according to any one of claims 1 to 6, configured to control light in the visible light region and light in the infrared light region simultaneously, wherein the phase-controllable medium is a dynamically phase-controllable medium.

8. The light control device of claim 7, wherein the dynamically phase-controllable medium is a liquid crystal panel (liquid crystal cell).

9. The light control device according to claim 8, wherein the liquid crystal used in the liquid crystal panel (liquid crystal cell) is a Twisted Nematic liquid crystal (TN liquid crystal) or a super Twisted Nematic liquid crystal (STN liquid crystal).

10. The light control device according to any one of claims 7 to 9, wherein a contrast ratio of transmission to non-transmission of each of light in a visible light region and light in an infrared light region is 10 or more.

11. The light control device according to any one of claims 1 to 10, comprising 1 polarizing plate (VIS-IR polarizing plate) having a polarizing property for light in a visible light region and light in an infrared light region.

12. The light control device according to claim 11, wherein the difference between the orthogonal transmittance of light in the infrared region and the orthogonal transmittance of light in the visible region in the VIS-IR polarizing plate is 1% or less.

13. The light control device according to any one of claims 1 to 12, wherein the difference between the orthogonal transmittance of light in the infrared region and the orthogonal transmittance of light in the visible region in the IR polarizing plate is 10% or more.

14. The light control device according to any one of claims 1 to 13, comprising: a polarizing plate in which the orthogonal transmittance of light in the infrared region is 1% or less and the difference in transmittance from light in the visible region is 10% or more; and at least 1 polarizing plate which has a high transmittance in an infrared region, is less likely to affect the transmittance of light in the infrared region, and has a cross transmittance of light in a visible region of 1% or less.

15. The light control device of any one of claims 1 to 14, wherein the IR polarizing plate or the VIS-IR polarizing plate is an absorptive polarizing plate.

16. The light control device of any one of claims 1 to 15, wherein the IR polarizing plate or the VIS-IR polarizing plate is a film.

17. The light control device according to any one of claims 1 to 16, which is stacked with a phase-having medium or a phase-controllable medium and at least 1 polarizing plate.

18. A liquid crystal display device, an anti-counterfeiting device or a sensor, provided with the light control device according to any one of claims 1 to 17.