WO2015122458A1 - 光変調素子 - Google Patents
光変調素子 Download PDFInfo
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- WO2015122458A1 WO2015122458A1 PCT/JP2015/053823 JP2015053823W WO2015122458A1 WO 2015122458 A1 WO2015122458 A1 WO 2015122458A1 JP 2015053823 W JP2015053823 W JP 2015053823W WO 2015122458 A1 WO2015122458 A1 WO 2015122458A1
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- external field
- reactive substance
- light modulation
- modulation element
- light
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/0009—Materials therefor
- G02F1/0045—Liquid crystals characterised by their physical properties
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1343—Electrodes
- G02F1/13439—Electrodes characterised by their electrical, optical, physical properties; materials therefor; method of making
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
- G02F1/139—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on orientation effects in which the liquid crystal remains transparent
Definitions
- the present invention relates to a light modulation element.
- the optical modulation element is an element having a function of spatially modulating and outputting the phase, intensity, amplitude, and the like of input light according to an input external field signal. It has been widely researched and developed, and is expected to be applied to such fields.
- the spatial light modulator for example, an element using an electric field response of liquid crystal is known and widely used as a display device (for example, Patent Documents 1 and 2).
- the liquid crystal can freely control the molecular arrangement by substrate surface treatment or an external field, and the phase and intensity of light can be freely changed by utilizing this feature.
- the light modulation element is required to be stable against external factors such as light and heat.
- the light modulation element constantly functions to modulate and output the input light, the stability to light is particularly important.
- An object of the present invention is to provide a light modulation element that can respond to a physical action from the outside and hardly undergoes photodegradation or light degradation.
- the present invention relates to a light modulation device comprising at least one transparent substrate and a dielectric layer laminated on the transparent substrate, wherein the dielectric layer is made of 90% of an external field reactive substance (A).
- the light-modulating element containing the mol% to 100 mol%, wherein the external field reactive material has an energy level (T 1 ) of a lowest triplet excited state of 2.6 eV to 5.4 eV .
- the external field reactive substance when the energy level of the excited singlet of the external field reactive substance (A) is (S 1 ), the external field reactive substance has a value of S 1 -T 1 of 1.0 eV to It is preferable to have an external field reactive substance (A-1) of 2.0 eV in an amount of 35 mol% to 85 mol%.
- the external field reactive substance may comprise 25 mol% to 65 mol% of the external field reactive substance (A-1-1) having a value of S 1 -T 1 of 1300 meV ⁇ 200 meV. preferable.
- the extrinsic field reactive substance (A) preferably has a molar extinction coefficient ( ⁇ ) at a wavelength of 300 nm to 650 nm of less than 500, and reacts with the magnetic field, electric field, light field, and flow field as the external field. It is preferable.
- a transparent electrode is formed on at least one of the transparent substrates, and the light is modulated in response to an electromagnetic wave generated by an electric signal input to the electrode.
- an optical modulation element that is difficult to photodecompose and has high optical reliability by having an external field reactive substance having a predetermined energy level.
- the light modulation element of the present invention comprises at least one transparent substrate and a dielectric layer laminated on the transparent substrate, the dielectric layer containing an external field reactive substance, and the external field reaction.
- the active material contains 90 mol% to 100 mol% of an external field reactive material (A) having an energy level (T 1 ) in the lowest triplet excited state of 2.6 eV to 5.4 eV. .
- the light modulation element of the present invention modulates incident light and emits it to exhibit an optical function.
- the light modulation element of the present invention includes a liquid crystal display element, a hologram element, a retardation element such as a retardation film, an optical communication element such as a wavelength division multiplexing element, an illumination element such as an electroluminescence element, and a 3D printer element. Can be used as
- the material of the transparent substrate used in the present invention is polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polystyrene (PS), polyethylene (PE), polyarylate (PAR), poly Flexible polymers such as ether ether ketone (PEEK), polycarbonate (PC), polycycloolefin, polypropylene (PP), polyimide (PI), polyamide, polyimide amide, triacetyl cellulose (TAC), glass fiber reinforced plastic, Examples thereof include inorganic materials such as substrates and glass made of a composite material such as cellulose fiber reinforced plastic. Among these, glass is preferable.
- the light modulation element may have at least one transparent substrate, but preferably has two sheets. In the case of having two or more substrates, they may be made of the same material or different materials.
- the dielectric layer contains an external field reactive substance.
- the external field reactive substance refers to a substance that can control the function in response to physical and chemical stimuli from the external field.
- the external field of the external field reactive substance include a magnetic field, an electric field, a light field such as polarized light (laser or a large light amount lamp), a flow of shearing force (flow field), and the like.
- examples of the external field reactive material include dielectric materials such as pyroelectric materials, piezoelectric materials, ferroelectric materials, fluorescent materials, phosphorescent materials, dyes, and liquid crystalline materials.
- the liquid crystalline substance is mainly composed of an assembly of liquid crystalline molecules, and has a feature that the molecular arrangement can be freely controlled by an external field.
- an electric field is used in the external field, by applying a voltage between a plurality of electrodes, the liquid crystal molecules aligned perpendicular to the substrate change in orientation parallel to the substrate, The orientation of the liquid crystal molecules that are approximately parallel to each other is changed so that only the orientation of the molecules changes while leaving the orientation parallel to the substrate, so that the electric field control of the dynamic orientation of the liquid crystal molecules is possible.
- the degree of order of the liquid crystal phase can be changed by giving the liquid crystal substance an effect of adding or removing temperature as an external field.
- the liquid crystalline substance has a feature that light modulation can be performed with respect to various external fields.
- the external field reactive substance is preferably a liquid crystal molecule.
- the external field reactive substance is an external field reactive substance (A) in which the energy level (T 1 ) of the lowest triplet excited state of the external field reactive substance is 2.6 eV to 5.4 eV. Is contained in an amount of 90 mol% to 100 mol%.
- the light modulation element is an element that modulates light and is assumed to be irradiated with light. Therefore, sufficient light stability is required so that the performance does not change even if light irradiation is continued for a long time.
- the light modulation element of the present invention has peripheral members such as a substrate, electrodes, wiring, inorganic protective film, organic protective film, polarizing plate, and retardation film. Light irradiation sometimes causes deterioration of the light modulation element. This is because the constituent material of the light modulation element undergoes photolysis or photodegradation due to light irradiation energy.
- the present inventors after the external field reactive material or the peripheral member is photoexcited to generate an excited singlet, a deactivation process after a part of the intersystem crossing to generate the lowest triplet I paid attention to. This is because the lowest triplet state generally has a very long excitation lifetime as compared with the excited singlet, and thus has a high probability of occurrence of a photoreaction that causes photodegradation.
- the external field reactive material or the peripheral member it is necessary that the material either absorbs light or causes a transfer of excitation energy from the excited molecule. Even if either one of the externally reactive substance or the peripheral member is photoexcited by light irradiation, they are independently deactivated and return to the ground state without causing a photochemical reaction. Is believed to be preserved. This is the first light stability mechanism.
- the light stability of the light modulation element can be maintained without being excessively light-degraded by being deactivated through a moderate energy relaxation process due to energy transfer.
- the dielectric layer constituting the light modulation element contains 90 mol% to 100 mol% of an external field reactive material having an energy level (T 1 ) of 2.6 eV to 5.4 eV
- the present inventors have found that it can be deactivated through a moderate energy relaxation step to suppress photodegradation and maintain photostability.
- the transfer of excitation energy occurs from a substance having a high energy level toward a substance having a low energy level. Therefore, the relative relationship between the energy level of the excited substance and the energy level of the substance that receives energy is an important factor.
- the energy level (T 1 ) of the lowest triplet excited state of the external field reactive substance is 2.6 eV or more, it is considered that deactivation due to decomposition of the external field reactive substance is difficult to occur.
- the energy level is 2.6 eV or more, the energy level of the external field reactive substance is not too low and becomes an appropriate height, and the peripheral energy of the lower energy level is appropriately released while appropriately releasing the excitation energy. It is because it is thought that it can deactivate.
- the energy level (T 1 ) of the lowest triplet excited state of the external field reactive substance is less than 2.6 eV, there are many compounds in which the light stability of the external field reactive substance itself is not good in the first place. Deactivation accompanied by decomposition of the compound itself is likely to occur. In addition, the energy level of the external field reactive substance is often relatively lower than the energy level of the peripheral member, and it is considered that the probability of deactivation through a relaxation process that releases energy to the peripheral member is lowered.
- the energy level of the external field reactive substance By setting the energy level (T 1 ) of the lowest triplet excited state of the external field reactive substance to 5.4 eV or less, the energy level of the external field reactive substance can be set to an appropriate level without being too high. Therefore, it is difficult for photoreactions accompanying various photolysis to occur.
- the energy level of the peripheral members is relatively low compared to the energy level of the externally reactive substance, and moderate and gradual energy transfer occurs between them, without excessive photoreaction. It can be deactivated through an energy relaxation step. Therefore, the light stability of the light modulation element can be increased.
- the energy level (T 1 ) of the lowest triplet excited state of the external field reactive substance is higher than 5.4 eV, the energy level of the excited molecule is very high.
- the energy level (T 1 ) of the lowest triplet excited state of the external field reactive substance (A) contained in the dielectric layer of the present embodiment is preferably 3.0 to 4.9 eV. More preferably, it is 5 to 4.1 eV.
- the energy level of the external field reactive substance can be measured by emission spectrum measurement such as phosphorescence measurement. More specifically, the measurement is preferably carried out according to the method described in ⁇ "Fluorescence measurement-application to biological science", Kazuhiko Kinoshita and Satoshi Mihashi, Academic Publishing Center, Tokyo, 1983>.
- the energy level is determined by the compound and the surrounding environment.
- the energy level of the compound can be measured by phosphorescence measurement or the like, and the energy level of the composition using the compound can be further measured.
- an excited molecule can be used for energy transfer, excimer formation, etc.
- a certain technique and know-how are required to take a complicated linear behavior and to take a simple linear value.
- the content of the external field reactive substance (A) contained in the dielectric layer of the present embodiment is 90 mol% to 100 mol%, preferably 93 mol% to 100 mol%.
- the excitation energy deactivation route can be controlled, and the light stability can be improved.
- the external field reactive substance when the excited singlet energy level of the external field reactive substance (A) is (S 1 ), the external field reactive substance has a value of S 1 -T 1 of 1. It is preferable that the externally reactive substance (A-1) having a concentration of 0.0 eV to 2.0 eV is 35 mol% to 85 mol%.
- Molecules in the lowest triplet state are important for photochemical reactions because of their long excitation lifetimes, but next we need to consider excited singlets with short excitation lifetimes.
- the concept of the deactivation path of excitation energy related to photodegradation is handled by the relative relationship of the energy level between the external field reactive substance and the constituent material of the light modulation element, as in the case of the lowest triplet.
- the energy level of the excited singlet is an appropriate height, so that the energy is deactivated while appropriately releasing energy between the peripheral member and the liquid crystal molecules. can do.
- the value of S 1 -T 1 is less than 1.0 eV, light absorption tends to occur because the energy level of the excited singlet is low.
- a photochemical reaction starting from this occurs.
- a photochemical reaction is caused directly from an excited singlet, and a photochemical reaction based on the lowest triplet through intersystem crossing is also included.
- the value of S 1 -T 1 is larger than 2.0 eV, the excited singlet energy level is high, and it is difficult to form excited molecules by light absorption.
- peripheral member absorbs light and an excited singlet is generated due to the high energy level, energy transfer from the peripheral member to the external field reactive substance does not occur, and a gentle relaxation process cannot be performed. Therefore, there is a high possibility that the peripheral member will cause a photoreaction accompanied by photolysis.
- the value of S 1 -T 1 of the external field reactive substance (A-1) contained in the dielectric layer of this embodiment is preferably 1.2 to 1.9 eV, and 1.1 to 1. More preferably, it is 7 eV.
- the content of the external field reactive substance (A-1) contained in the dielectric layer of this embodiment is preferably 35 mol% to 85 mol%, and preferably 40 mol% to 80 mol%. preferable. In the present invention, when the content of the external field reactive substance (A-1) is in the above range, the light stability can be improved.
- the external field reactive substance (A-1-1) having a value of S 1 -T 1 of 1300 meV ⁇ 200 meV is contained in an amount of 25 mol% to 65 mol%.
- the energy level is an appropriate height, so that moderate energy is generated between the peripheral member and the liquid crystal molecules. Can be inactivated while letting go.
- the content of the external field reactive substance (A-1-1) in the above range, the light stability can be improved.
- the molar extinction coefficient ( ⁇ ) of the external field reactive substance at a wavelength of 300 nm to 650 nm is less than 500.
- the molar extinction coefficient ( ⁇ ) at a wavelength of 300 nm to 650 nm is less than 500, light degradation can be made difficult.
- examples of the external field of the external field reactive substance include a magnetic field, an electric field, a light field such as polarized light (laser or a large light amount lamp), a flow of shearing force (flow field), and the like. These do not need to be brought into contact with the substrate surface like a rubbing roller, and can be operated remotely, so that even an enormous liquid crystal display panel can be easily aligned.
- a magnetic field is used for the external field
- the anisotropic axes of the liquid crystal molecules can be aligned with the magnetic field direction.
- Even when polarized light is used for the external field the anisotropic axis of the liquid crystal molecules can be aligned with the plane of vibration of the polarized light.
- the light modulation element according to the present invention is a light modulation element having a dielectric layer sandwiched between two opposed transparent substrates, and a transparent electrode is formed on at least one of the transparent substrates. It is preferable that the light is modulated in response to an electromagnetic wave generated by an electric signal input to the electrode.
- the two transparent substrates used for the light modulation element can be made of a transparent material having flexibility such as glass or plastic.
- a transparent substrate having a transparent electrode layer can be obtained, for example, by sputtering indium tin oxide (ITO) on a transparent substrate such as a glass plate.
- the transparent electrode preferably has a higher transmittance and preferably has a lower electrical resistance.
- the sheet resistance is preferably 150 ohms or less, preferably 100 ohms or less, and preferably 50 ohms or less.
- a method of sandwiching a light modulation element having a dielectric layer between two transparent substrates is a normal vacuum injection method or a drop injection (ODF). : One Drop Fill) method or the like can be used.
- ODF drop injection
- a drop mark is not generated, there is a problem that a mark of injection remains, but in the present invention, it can be suitably used for a display element manufactured using the ODF method.
- a sealant such as epoxy photothermal combination curing is drawn on a backplane or front plane substrate using a dispenser in a closed-loop bank shape, and then removed.
- a liquid crystal display element can be manufactured by bonding a front plane and a back plane after dropping a predetermined amount of the liquid crystal composition in the air.
- the liquid crystal composition of the present invention can be preferably used because the liquid crystal composition can be stably dropped in the ODF process.
- the light modulation element according to the present invention has a structure in which a dielectric layer is sandwiched between two opposed substrates.
- the light modulation element according to the present invention may have the same structure as a liquid crystal display element according to the prior art. That is, the orientation of liquid crystal molecules may be controlled by applying electricity to the alignment film provided on the substrate and the electrode provided on the substrate. Further, by providing a polarizing plate, a retardation film, etc., it is possible to display using this orientation state.
- the light modulation element can be applied to TN, STN, VA, IPS, FFS, and ECB, but TN is particularly preferable.
- the energy level (T 1 ) of the lowest triplet excited state and the excited singlet energy level (S 1 ) of the externally reactive substance were measured.
- Examples 1 to 53 were good.
- (A) shows an external field reactive substance (A) whose energy level (T 1 ) in the lowest triplet excited state is 2.6 eV to 5.4 eV
- (A-1) when the energy level of the excited singlet of the external field reactive substance (A) is (S 1 ), the external field reactive substance has a value of S 1 -T 1 of 1.
- the liquid crystal composition has an excited triplet energy level (T 1 ) and an excited singlet energy level (S 1 ), and the liquid crystal composition has T 1 of 2.0 to 5.4 eV and T 1 -S 1 is
- a liquid crystal composition was prepared by mixing liquid crystal compounds so as to be 1.0 to 2.0 eV.
- FIG. 1 shows T 1 and T 1 -S 1 of each liquid crystal composition.
- T 1 vertical axis in FIG. 1, 2.0 to 6.0
- T 1 -S 1 horizontal axis in FIG. 1, 0.8 to 2.2
- FIG. 615 liquid crystal compositions were prepared. All the liquid crystal compositions were evaluated for light stability. The result is shown in FIG. FIG. 1 shows the result of quantifying the light stability by relative evaluation, with “100” being the best light stability.
- the liquid crystal composition having T 1 of 2.6 to 5.4 eV had a good light stability of 33.3 or more.
- a liquid crystal composition having a T 1 of less than 2.6 or greater than 5, 4 had a light stability of 25 or less, which was not good.
- T 1 is 3.0 to 4.9 eV
- the light stability is excellent
- T 1 is 3.5 to 4.1 eV
- the light stability is particularly excellent.
- a liquid crystal composition having a T 1 -S 1 of 1.0 to 2.0 eV (within the double encircled line in FIG. 1) has an excellent light stability of 50 or more, and in particular, T 1 -S 1
- the liquid crystal composition having 1.2 to 1.9 eV was particularly excellent in light stability.
Abstract
Description
本発明は、外部からの物理的作用に対して応答可能な、光分解や光劣化し難い光変調素子の提供を課題とする。
本発明において、前記外場反応性物質(A)の励起一重項のエネルギー準位を(S1)としたとき、前記外場反応性物質が、S1-T1の値が1.0eV~2.0eVである外場反応性物質(A-1)を35モル%~85モル%有することが好ましい。
本発明において、前記外場反応性物質が、前記S1-T1の値が1300meV±200meVである外場反応性物質(A-1-1)を、25モル%~65モル%有することが好ましい。
本発明において、前記外場反応性物質(A)の波長300nm~650nmにおけるモル吸光係数(ε)が500未満であることが好ましく、該外場として磁場、電場、光場、流動場に反応することが好ましい。
本発明の光変調素子は、前記透明性基板の少なくとも1枚には透明電極が形成されており、当該電極に入力された電気信号によって生じる電磁波に応答して光を変調することが好ましい。
本発明の光変調素子は、少なくとも1枚以上の透明性基板と該透明性基板に積層されている誘電体層からなり、前記誘電体層が外場反応性物質を含有し、前記外場反応性物質が、最低三重項励起状態のエネルギー準位(T1)が2.6eV~5.4eVである外場反応性物質(A)を90モル%~100モル%含有することを特徴とする。
る。これらのなかでも、ガラスが好ましい。
本発明において、外場反応性物質とは、外場からの物理的・化学的刺激に反応して機能制御できる物質をいう。
外場反応性物質の外場としては、磁場、電場、偏光(レーザー又は大光量ランプ)等の光場、せん断力等の流動(流動場)などが挙げられる。
本発明において、外場反応性物質としては、例えば焦電性物質、圧電性物質、強誘電性物質、蛍光物質、燐光物質、色素、液晶性物質等の誘電性物質が挙げられる。液晶性物質は主に液晶性分子の集合体からなっており、外場によって分子配列を自在に制御することができるという特徴を有している。例えば、外場に電界を用いた場合、複数の電極間に電圧を印加することにより、基板に対して垂直に並んでいた液晶分子が、基板に対して平行に配向変化したり、基板に対しておよそ平行に並んでいた液晶分子が、基板に対して平行な配向を残したまま分子の向きだけ変えるように配向変化したりするので、液晶分子の動的な配向の電界制御が可能である。また、液晶性物質に外場として温度を加えたり奪ったりする作用を与えることにより、液晶相の秩序度に変化を与えることができる。さらに、液晶性分子と色素あるいは蛍燐光物質とを含有する液晶性物質においては、外場として光照射により光エネルギーを与えることによって、液晶相の秩序に変化を与えることが可能である。いずれの作用においても、入力光を変調して出射光として取り出すことができる。このように、液晶性物質には、いろいろな外場に対して光変調を行うことが可能であるという特長を持つ。本発明において、外場反応性物質は液晶分子であることが好ましい。
本発明においては外場反応性物質としては、該外場反応性物質の最低三重項励起状態のエネルギー準位(T1)が2.6eV~5.4eVである外場反応性物質(A)を90モル%~100モル%含有する。
本発明の光変調素子は、後述するように、基板、電極、配線、無機保護膜、有機保護膜、偏光板、位相差フィルム等の周辺部材を有する。
光照射は、時にして光変調素子の劣化を引き起こす。これは、光照射エネルギーにより、光変調素子の構成材料が光分解や光劣化を起こすためである。即ち、光変調素子の光安定性を高めるためには、第一に、光変調素子を構成する外場反応性物質の光安定性を高めることが必要条件と考えられる。
そこで、本発明者らは、外場反応性物質又は周辺部材が光励起して、励起一重項を生成した後、その一部が項間交差をして最低三重項を生成した後の失活過程に注目した。最低三重項状態は一般的に励起一重項と比べて励起寿命が非常に長いため、光劣化を引き起こす原因となる光反応の発生確率が高いためである。
外場反応性物質又は周辺部材が光励起されるためには、物質が光を吸収するか、励起分子から励起エネルギーの移動が起こることのいずれかが必要である。外場反応性物質又は周辺部材のいずれか一方が光照射により光励起されたとしても、それらが光化学反応を起こさずに各々独立して失活して基底状態に戻ることにより、素子の光安定性が保たれると考えられる。これが第一の光安定性の機構である。
本発明者らは、光変調素子を構成する誘電体層が、エネルギー準位(T1)が2.6eV~5.4eVである外場反応性物質を90モル%~100モル%含有する場合に、程よいエネルギー緩和工程を経て失活して光劣化が抑制され、光安定性を保つことができることを見出した。
一方、外場反応性物質の最低三重項励起状態のエネルギー準位(T1)が2.6eV未満であると、そもそも外場反応性物質自体の光安定性が良好ではない化合物が多いため、化合物自体の分解を伴う失活が発生し易い。また、外場反応性物質のエネルギー準位が相対的に周辺部材のエネルギー準位よりも低い場合が多く、周辺部材にエネルギーを逃がす緩和過程を経て失活する確率が低くなると思われる。
外場反応性物質の最低三重項励起状態のエネルギー準位(T1)が5.4eVよりも高い場合には、励起分子のエネルギー準位が非常に高いため、外場反応性物質自体の光反応を誘発するおそれが高まり、これが一つの光安定性不良の原因となる。また、周辺部材のエネルギー準位が外場反応性物質のエネルギー準位と比べて大幅に低い場合が多くなるので、周辺部材から外場反応性物質へのエネルギー移動がおこり難い一方、外場反応性物質から周辺部材へのエネルギー移動が非常に起こりやすくなる。従って、外場反応性物質の励起分子が周辺部材の分解を伴う化学反応を誘起する恐れが高まる。これが第二の光安定性不良の原因となる可能性が高い。
エネルギー準位は化合物とその周辺環境によって定まるものであり、りん光測定等により化合物のエネルギー準位を測定し、さらに該化合物を用いた組成物のエネルギー準位を測定することができる。
また、エネルギー準位が高い化合物と低い化合物とを適宜入れ替え、所望のエネルギー準位を有する組成物とすることは当業者であれば実施可能であるが、励起分子はエネルギー移動、エキシマー形成等の複雑な挙動をとるため単純な線形の値をとることは少なく、組成物において所望のエネルギー準位を得るためには、一定の技術とノウハウを必要とする。
本発明においては、外場反応性物質(A)の含有量を上記の範囲とすることにより励起エネルギーの失活の経路を制御し、光安定性を良好なものとすることができる。
一方、S1-T1の値が1.0eV未満であると、励起一重項のエネルギーレベルが低いため光吸収が起きやすい。光吸収により励起一重項が発生すると、これを起点にした光化学反応が起きる。励起一重項から直接光化学反応を起こす場合もあれば、項間交差を経て最低三重項を基点とした光化学反応も含まれる。
S1-T1の値が2.0eVより大きいと、励起一重項のエネルギーレベルが高いため光吸収による励起分子ができにくい。さらに、エネルギーレベルが高いことにより、周辺部材が光吸収して励起一重項が生じた場合、周辺部材から外場反応性物質へのエネルギー移動が起きず、緩やかな緩和工程を経ることができない。従って、周辺部材が光分解を伴う光反応を起こすおそれが高くなると思われる。
本実施形態の誘電体層に含有される外場反応性物質(A-1)の含有量は、35モル%~85モル%含有することが好ましく、40モル%~80モル%であることが好ましい。
本発明においては、外場反応性物質(A-1)の含有量を上記の範囲とすることにより、光安定性を良好なものとすることができる。
外場反応性物質(A-1-1)のS1-T1の値が1300meV±200meVであると、エネルギーレベルが適当な高さであるため、周辺部材と液晶分子間とで適度にエネルギーを逃がしながら失活することができる。
本発明においては、外場反応性物質(A-1-1)の含有量を上記の範囲とすることにより、光安定性を良好なものとすることができる。
波長300nm~650nmにおけるモル吸光係数(ε)が500未満であると、光劣化し難くすることができる。
外場に磁場を用いる場合、液晶分子の異方軸を磁場方向に揃えることができる。外場に偏光を用いる場合も、液晶分子の異方軸を偏光の振動面に揃えることができる。
光変調素子に使用される対抗した2枚の透明性基板はガラス又はプラスチックの如き柔軟性をもつ透明な材料を用いることができる。
透明電極層を有する透明基板は、例えば、ガラス板等の透明基板上にインジウムスズオキシド(ITO)をスパッタリングすることにより得ることができる。
透明電極は、透過率が高い方が好ましく、電気抵抗が小さい方が好ましい。例えば、シート抵抗は150オーム以下が好ましく、100オーム以下が好ましく、50オーム以下が好ましい。
下記表中、
(A)は最低三重項励起状態のエネルギー準位(T1)が2.6eV~5.4eVである外場反応性物質(A)を、
(A-1)は前記外場反応性物質(A)の励起一重項のエネルギー準位を(S1)としたとき、前記外場反応性物質が、S1-T1の値が1.0eV~2.0eVである外場反応性物質(A-1)を、
(A-1-1)は前記外場反応性物質が、前記S1-T1の値が1300meV±200meVである外場反応性物質(A-1-1)を、それぞれ示す。
<「蛍光測定-生物科学への応用」 木下一彦・御橋廣眞編、学会出版センター、東京、1983>に記載の方法に従って測定した。
液晶組成物の励起三重項エネルギー準位(T1)、励起一重項のエネルギー準位を(S1)とし、液晶組成物のT1が2.0~5.4eV、T1-S1が1.0~2.0eVとなるように液晶化合物を混合し、液晶組成物を調製した。各液晶組成物の、T1とT1-S1を図1に示す。本実施例においては、T1(図1の縦軸、2.0~6.0)とT1-S1(図1の横軸、0.8~2.2)を図1に示す値とした、615通りの液晶組成物を調製した。
各液晶組成物のすべてについて、光安定性評価を行った。その結果を図1に示す。
図1は、光安定性が一番良好であったものを「100」とし、光安定性を相対評価で数値化した結果である。
さらに、T1が3.0~4.9eVであると、光安定性に優れ、T1が3.5~4.1eVであると特に光安定性に優れていた。
上記に加え、T1-S1が1.0~2.0eVである液晶組成物(図1中の二重囲線内)は50以上とさらに光安定性に優れ、中でもT1-S1が1.2~1.9eVの液晶組成物は特に光安定性に優れていた。
Claims (6)
- 少なくとも1枚以上の透明性基板と該透明性基板に積層されている誘電体層からなる光変調素子であって、
前記誘電体層が、外場反応性物質(A)を90モル%~100モル%含有し、前記外場反応性物質は、最低三重項励起状態のエネルギー準位(T1)が2.6eV~5.4eVであることを特徴とする光変調素子。 - 前記外場反応性物質(A)の励起一重項のエネルギー準位を(S1)としたとき、前記外場反応性物質が、S1-T1の値が1.0eV~2.0eVである外場反応性物質(A-1)を35モル%~85モル%有する請求項1に記載の光変調素子。
- 前記外場反応性物質が、前記S1-T1の値が1300meV±200meVである外場反応性物質(A-1-1)を、25モル%~65モル%有する請求項2に記載の光変調素子。
- 前記外場反応性物質(A)の波長300nm~650nmにおけるモル吸光係数(ε)が500未満である請求項1に記載の光変調素子。
- 該外場として磁場、電場、光場、流動場に反応することを特徴とする請求項1~4のいずれか1項に記載の光変調素子。
- 対向した2枚の透明性基板の間に狭持された誘電体層を有する光変調素子であって、前記透明性基板の少なくとも1枚には透明電極が形成されており、当該電極に入力された電気信号によって生じる電磁波に応答して光を変調することを特徴とする、請求項1~5のいずれか1項に記載の光変調素子。
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