WO2019181882A1 - 液晶表示素子 - Google Patents
液晶表示素子 Download PDFInfo
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- WO2019181882A1 WO2019181882A1 PCT/JP2019/011259 JP2019011259W WO2019181882A1 WO 2019181882 A1 WO2019181882 A1 WO 2019181882A1 JP 2019011259 W JP2019011259 W JP 2019011259W WO 2019181882 A1 WO2019181882 A1 WO 2019181882A1
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- liquid crystal
- carbon atoms
- crystal display
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- display element
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Classifications
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K19/00—Liquid crystal materials
- C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
- C09K19/38—Polymers
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K19/00—Liquid crystal materials
- C09K19/52—Liquid crystal materials characterised by components which are not liquid crystals, e.g. additives with special physical aspect: solvents, solid particles
- C09K19/54—Additives having no specific mesophase characterised by their chemical composition
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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
- G02F1/1334—Constructional arrangements; Manufacturing methods based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
Definitions
- the present invention relates to a transmission / scattering liquid crystal display element.
- a TN (Twisted Nematic) mode As a liquid crystal display element, a TN (Twisted Nematic) mode has been put into practical use. In this mode, it is necessary to use a polarizing plate in order to switch light using the optical rotation characteristics of the liquid crystal. When a polarizing plate is used, the light use efficiency is lowered.
- a liquid crystal display element that does not use a polarizing plate there is an element that performs switching between a liquid crystal transmission state (also referred to as a transparent state) and a scattering state.
- PDLC Polymer Dispersed Liquid Crystal
- PNLC Polymer Network Liquid Crystal
- liquid crystal display elements In these liquid crystal display elements, a liquid crystal composition containing a polymerizable compound that is polymerized by ultraviolet rays is placed between a pair of substrates provided with electrodes, and the liquid crystal composition is cured by irradiation with ultraviolet rays, whereby the liquid crystal and the polymerizable compound are polymerized. Forms a complex with a cured product of the compound (eg, a polymer network).
- the scattering state and the transmission state of the liquid crystal are controlled by applying a voltage.
- liquid crystal display elements using PDLC or PNLC when no voltage is applied, the liquid crystal is in a random direction, so it becomes cloudy (scattering).
- voltage is applied, the liquid crystal is aligned in the electric field direction and transmits light.
- a liquid crystal display element that is in a transmissive state also referred to as a normal element.
- the electrode and the liquid crystal layer are in direct contact (see Patent Documents 1 and 2).
- liquid crystal display element using PDLC also referred to as a reverse type element
- PDLC also referred to as a reverse type element
- the present invention improves the adhesion between the liquid crystal layer and the electrode, and even in a harsh environment exposed to high temperature, high humidity and light irradiation for a long time, the device is peeled off, the generation of bubbles, and the optical
- An object of the present invention is to provide a liquid crystal display element capable of suppressing deterioration of characteristics.
- the present invention has a liquid crystal layer that is cured by irradiating ultraviolet rays to a liquid crystal composition containing a liquid crystal and a polymerizable compound disposed between a pair of substrates provided with electrodes, and in a scattering state when no voltage is applied.
- a liquid crystal display element that becomes transparent when a voltage is applied, wherein the liquid crystal composition contains a compound represented by the following formula [1].
- X 1 represents the following formula [1-a] or [1-b]:
- X 2 represents an alkylene group having 2 to 24 carbon atoms, and is an arbitrary group not adjacent to X 1 and O of the alkylene group.
- —CH 2 — may be substituted with —O—, —CO—, —COO—, —OCO—, —CONH—, —NHCO—, —NH— or —CON (CH 3 ) —, where Xm is Represents an integer of 1 or 2.
- Xn represents an integer of 1 or 2. However, Xm + Xn is 3.
- the adhesion between the liquid crystal layer and the electrode is improved, and even in a harsh environment exposed to high temperature and high humidity or light irradiation for a long time, the device is peeled off, bubbles are generated, and the optical characteristics are deteriorated.
- a liquid crystal display element that is in a scattering state when no voltage is applied and in a transparent state when a voltage is applied can be obtained. Therefore, the element of the present invention can be used for a liquid crystal display for display purposes, a dimming window for controlling blocking and transmission of light, an optical shutter element, and the like.
- the mechanism by which the liquid crystal display device having the above-described excellent characteristics is obtained by the present invention is not necessarily clear, but is estimated as follows.
- the liquid crystal composition used in the present invention contains a liquid crystal, a polymerizable compound, and a compound represented by the formula [1] (also referred to as a specific compound).
- the specific compound has a site that undergoes a polymerization reaction by ultraviolet rays represented by X 1 in formula [1] and a phosphate group. Therefore, when a specific compound is included in the liquid crystal composition, an interaction between a phosphoric acid group and an inorganic electrode such as an ITO electrode works, and the X1 site in the formula [1] reacts with the polymerizable compound. This is considered to increase the adhesion between the polymer network in the liquid crystal layer and the electrode.
- the liquid crystal display element using the liquid crystal composition of the present invention improves the adhesion between the liquid crystal layer and the electrode, and even in harsh environments exposed to high temperature and high humidity and light irradiation for a long time. It becomes a liquid crystal display element which can suppress peeling of an element, generation
- it can be suitably used for a normal element that is in a scattering state when no voltage is applied and is in a transparent state when a voltage is applied.
- the liquid crystal composition in the present invention contains a liquid crystal, a polymerizable compound, and a specific compound represented by the formula [1].
- a liquid crystal nematic liquid crystal, smectic liquid crystal, or cholesteric liquid crystal can be used.
- a liquid crystal having positive dielectric anisotropy is preferable for the normal type element, and a liquid crystal having negative dielectric anisotropy is preferably used for the reverse type element.
- those having a large dielectric anisotropy and a large refractive index anisotropy are preferred.
- two or more kinds of liquid crystals can be mixed and used according to the respective physical property values of the phase transition temperature, dielectric anisotropy and refractive index anisotropy.
- liquid crystal display element As an active element such as a TFT (Thin Film Transistor), it is required that the liquid crystal has a high electric resistance and a high voltage holding ratio (also referred to as VHR). For this reason, it is preferable to use a fluorine-based or chlorine-based liquid crystal that has high electrical resistance and does not lower VHR by active energy rays such as ultraviolet rays.
- active energy rays such as ultraviolet rays.
- the liquid crystal display element can be made into a guest-host type element by dissolving a dichroic dye in a liquid crystal composition.
- a dichroic dye in the case of a normal type element, an element that is absorbed (scattered) when no voltage is applied and is transparent when a voltage is applied can be obtained.
- the direction of the liquid crystal director in this element, changes by 90 degrees depending on the presence or absence of voltage application. Therefore, this element can obtain a higher contrast than the conventional guest-host type element that switches between random alignment and vertical alignment by utilizing the difference in light absorption characteristics of the dichroic dye.
- a guest-host type element in which a dichroic dye is dissolved is colored when the liquid crystal is aligned in the horizontal direction, and is opaque only in the scattering state. Therefore, as the voltage is applied, it is possible to obtain an element that switches from colored and opaque when no voltage is applied to colored and colorless and transparent.
- the polymerizable compound in the liquid crystal composition is for forming a polymer network (also referred to as a curable resin) by a polymerization reaction by irradiation with ultraviolet rays at the time of producing a liquid crystal display element. Therefore, a polymer obtained by polymerizing a polymerizable compound in advance may be introduced into the liquid crystal composition. However, even when a polymer is used, it is necessary to have a site that undergoes a polymerization reaction upon irradiation with ultraviolet rays.
- a liquid crystal composition containing a polymerizable compound is preferably used from the viewpoint of handling of the liquid crystal composition, that is, suppressing the increase in viscosity of the liquid crystal composition and solubility in the liquid crystal.
- the polymerizable compound is not particularly limited as long as it dissolves in the liquid crystal, but when the polymerizable compound is dissolved in the liquid crystal, it is necessary that a temperature at which a part or the whole of the liquid crystal composition exhibits a liquid crystal phase exists. Even when a part of the liquid crystal composition exhibits a liquid crystal phase, it is sufficient that the liquid crystal display element is confirmed with the naked eye and the entire element has substantially uniform transparency and scattering characteristics.
- the polymerizable compound is not particularly limited as long as it is a compound that is polymerized by ultraviolet rays. At that time, the polymerization may proceed in any reaction form to form a curable resin.
- Specific reaction formats include radical polymerization, cationic polymerization, anionic polymerization, or polyaddition reaction. Among these, radical polymerization is preferable as the reaction mode of the polymerizable compound from the viewpoint of the optical characteristics of the liquid crystal display element. In that case, the following radical type polymerizable compounds or oligomers thereof can be used as the polymerizable compound. Further, as described above, a polymer obtained by polymerizing these polymerizable compounds can also be used. Specific examples of the radical type polymerizable compound or oligomer thereof include the radical type polymerizable compounds described on pages 69 to 71 of International Publication No. WO2015 / 146987.
- the use ratio of the radical type polymerizable compound or oligomer thereof is preferably 70 to 150 parts by mass with respect to 100 parts by mass of the liquid crystal in the liquid crystal composition from the viewpoint of adhesion between the liquid crystal layer and the electrode of the liquid crystal display element. . More preferred is 80 to 110 parts by mass.
- the radical type polymerizable compound may be used alone or in combination of two or more depending on each characteristic.
- a radical initiator that generates radicals by ultraviolet rays also referred to as a polymerization initiator
- a radical initiator that generates radicals by ultraviolet rays
- a radical initiator that generates radicals by ultraviolet rays
- Specific examples include radical initiators described on pages 71 to 72 of International Publication No. 2015/146987.
- the use ratio of the radical initiator is preferably 0.01 to 20 parts by mass with respect to 100 parts by mass of the liquid crystal in the liquid crystal composition from the viewpoint of adhesion between the liquid crystal layer and the electrode of the liquid crystal display element. More preferred is 0.05 to 10 parts by mass.
- a radical initiator can also be used 1 type or in mixture of 2 or more types according to each characteristic.
- the specific compound is a compound represented by the formula [1].
- X 1 , X 2 , Xm and Xn are as defined above, and among them, the following are preferable.
- X 1 is preferably the formula [1-a] or the formula [1-b].
- X 2 is preferably an alkylene group having 2 to 12 carbon atoms, and any —CH 2 — not adjacent to X 1 and O may be substituted with —O—, —COO— or —OCO—.
- Xm is preferably an integer of 1 or 2.
- Xn is preferably an integer of 1 or 2. However, Xm + Xn is 3.
- Specific examples of the specific compound include compounds selected from the group consisting of the following formulas [1a-1] to [1a-3], and these are preferably used.
- Xa represents the formula [1-a] or the formula [1-b].
- X b represents an alkylene group having 2 to 18 carbon atoms.
- X c represents —COO— or —OCO—.
- X d represents an alkylene group having 2 to 12 carbon atoms.
- p1 represents an integer of 1 or 2.
- p2 represents an integer of 1 or 2.
- p1 + p2 is 3.
- p3 represents an integer of 2 to 8.
- the liquid crystal composition in the present invention preferably contains a compound represented by the following formula [2] (also referred to as a second specific compound).
- Y 1 represents the following formulas [2-a] to [2-j]. Of these, the formula [2-a], the formula [2-b], the formula [2-c], the formula [2-d], the formula [2-e], or the formula [2-f] is preferable. Formula [2-a], formula [2-b], formula [2-c] or formula [2-e] is more preferred, and formula [2-a] or formula [2-b] is most preferred.
- Y A represents a hydrogen atom or a benzene ring.
- Y 2 is a single bond, —O—, —NH—, —N (CH 3 ) —, —CH 2 O—, —CONH—, —NHCO—, —CON (CH 3 ) —, —N (CH 3 ) CO—, —COO— or —OCO— is shown.
- a single bond, —O—, —CH 2 O—, —CONH—, —COO— or —OCO— is preferable, and a single bond, —O—, —COO— or —OCO— is more preferable.
- Y 3 represents a single bond or — (CH 2 ) a — (a is an integer of 1 to 15). Among these, a single bond or — (CH 2 ) a — (a is an integer of 1 to 10) is preferable, and — (CH 2 ) a — (a is an integer of 1 to 10) is particularly preferable.
- Y 4 represents a single bond, —O—, —OCH 2 —, —COO— or —OCO—. Of these, a single bond, —O— or —COO— is preferable, and —O— is particularly preferable.
- Y 5 represents a divalent cyclic group selected from a benzene ring, a cyclohexane ring and a heterocyclic ring, or a divalent organic group having 17 to 51 carbon atoms having a steroid skeleton, and any hydrogen atom on the cyclic group is It may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxy group having 1 to 3 carbon atoms, or a fluorine atom.
- a divalent organic group having 17 to 51 carbon atoms having a benzene ring, a cyclohexane ring, or a steroid skeleton is preferable. More preferred is a C 17-51 divalent organic group having a benzene ring or a steroid skeleton.
- Y 6 represents a single bond, —O—, —CH 2 —, —OCH 2 —, —CH 2 O—, —COO— or —OCO—.
- a single bond, —O—, —COO— or —OCO— is preferable, and a single bond, —COO— or —OCO— is more preferable.
- Y 7 represents a cyclic group selected from a benzene ring, a cyclohexane ring and a heterocyclic ring, and any hydrogen atom on these cyclic groups is an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, carbon It may be substituted with a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxy group having 1 to 3 carbon atoms, or a fluorine atom. Of these, a benzene ring or a cyclohexane ring is preferable.
- Y 8 represents an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, a fluorine-containing alkyl group having 1 to 18 carbon atoms, an alkoxy group having 1 to 18 carbon atoms, or a fluorine-containing alkoxy group having 1 to 18 carbon atoms. Indicates a group. Of these, an alkyl group having 1 to 18 carbon atoms or an alkoxy group, or an alkenyl group having 2 to 18 carbon atoms is preferable. More preferred is an alkyl group having 1 to 12 carbon atoms or an alkoxy group.
- Ym represents an integer of 0 to 4. Of these, an integer of 0 to 2 is preferable. Preferred combinations of Y 1 to Y 8 and Ym in the formula [2] are shown in Tables 1 to 9 below. In Tables 1 to 9, a in — (CH 2 ) — representing Y 3 represents an integer of 1 to 10.
- More specific examples of the second specific compound include compounds selected from the group consisting of the following formulas [2a-1] to [2a-11], and these are preferably used.
- Y c represents a single bond, —COO— or —OCO—.
- Y d represents an alkyl group or alkoxy group having 1 to 12 carbon atoms.
- q3 represents an integer of 1 to 10.
- q4 represents an integer of 1 or 2.
- Y e represents —O— or —COO—.
- Y f represents a divalent organic group having 17 to 51 carbon atoms and having a steroid skeleton.
- Y g represents an alkyl group having 1 to 12 carbon atoms or an alkenyl group having 2 to 18 carbon atoms.
- q5 represents an integer of 1 to 10.
- the content ratio of the second specific compound is preferably 0.1 to 30 parts by mass with respect to 100 parts by mass of the liquid crystal in the liquid crystal composition in terms of adhesion between the liquid crystal layer and the electrode of the liquid crystal display element. More preferred is 5 to 20 parts by mass, and most preferred is 1 to 10 parts by mass.
- the 2nd specific compound can also be used 1 type or in mixture of 2 or more types according to each characteristic.
- Examples of the method for preparing the liquid crystal composition include a method of mixing a liquid crystal, a polymerizable compound, and a specific compound together, and a method of mixing a polymerizable compound and a specific compound in advance with a liquid crystal. .
- the second specific compound is prepared by adding a polymerizable compound and a specific compound to a liquid crystal, or by previously preparing a liquid crystal in which the second specific compound is added, and adding the polymerizable compound and the specific compound to the liquid crystal.
- the method of adding to the mixture is mentioned.
- it can also heat according to the solubility of a polymeric compound, a specific compound, and a 2nd specific compound.
- the temperature at that time is preferably less than 100 ° C.
- a liquid crystal alignment film for vertically aligning liquid crystal molecules is attached to at least one of the substrates.
- the liquid crystal alignment film is prepared by applying a liquid crystal alignment treatment agent on a substrate and baking it. At that time, an orientation treatment such as rubbing treatment or light irradiation may be performed after firing.
- the liquid crystal composition used in the liquid crystal display element is as described above, and a spacer for controlling the electrode gap (also referred to as a gap) of the liquid crystal display element can be introduced therein.
- the method for injecting the liquid crystal composition is not particularly limited, and examples thereof include the following method. That is, when a glass substrate is used as a substrate, prepare a pair of substrates, apply a sealant to four pieces of the substrate on one side, except for a part, and then place the electrode surface on the inside, An empty cell on which the substrates are bonded is manufactured. And the method of injecting a liquid-crystal composition under reduced pressure from the place where the sealing agent is not apply
- liquid crystal display element of the present invention since the adhesion between the liquid crystal layer and the electrode is high, it is not necessary to apply the sealing agent to the four pieces of the substrate.
- the gap of the liquid crystal display element can be controlled by the above spacers.
- Examples of the method include a method of introducing a spacer having a target size into the liquid crystal composition and a method using a substrate having a column spacer of a target size as described above.
- the gap can be controlled without introducing a spacer.
- the size of the gap of the liquid crystal display element is preferably 1 to 100 ⁇ m, more preferably 1 to 50 ⁇ m, and particularly preferably 2 to 30 ⁇ m. If the gap is too small, the contrast of the liquid crystal display element is lowered. If the gap is too large, the driving voltage of the element is increased.
- the liquid crystal display element is obtained by curing the liquid crystal composition and forming a liquid crystal layer.
- the liquid crystal composition is cured by irradiating the liquid crystal composition injection cell with ultraviolet rays.
- the light source include a metal halide lamp and a high-pressure mercury lamp.
- the wavelength of ultraviolet rays is preferably 250 to 400 nm, more preferably 310 to 370 nm. Further, heat treatment may be performed after irradiation with ultraviolet rays.
- the temperature at that time is preferably 20 to 120 ° C, more preferably 30 to 100 ° C.
- the liquid crystal display element before this treatment was cut with a wavelength of 350 nm or less using a metal halide lamp with an illuminance of 20 mW / cm 2 and irradiated with ultraviolet rays for an irradiation time of 60 seconds. Thereby, a liquid crystal display element (glass substrate) was obtained.
- Table 10 summarizes the measurement results of Haze in the initial stage, after storage in a constant temperature and humidity chamber (constant temperature and humidity) and after irradiation with ultraviolet rays (ultraviolet rays).
- the liquid crystal display element (glass substrate and plastic substrate) is stored in a constant temperature and humidity chamber at a temperature of 80 ° C. and a humidity of 90% RH for 24 hours, and the liquid crystal display element is peeled off and the presence or absence of bubbles is confirmed.
- As a stability test of the liquid crystal display device in a high temperature and high humidity environment Specifically, the case where no peeling of the element (the liquid crystal layer and the resin film or the state where the resin film and the electrode are peeled off) and the case where no bubbles are generated in the element are excellent in this evaluation. (Good indication in the table).
- the liquid crystal display element was confirmed by irradiating it with ultraviolet rays of 5 J / cm 2 in terms of a wavelength of 365 nm using a desktop UV curing device (HCT3B28HEX-1, manufactured by Senlite) (light of the liquid crystal display element).
- a stability test against irradiation Specifically, the case where no peeling of the element occurred and the case where no bubbles were generated in the element were considered to be excellent in this evaluation (good indication in the table).
- Table 11 summarizes the results of adhesion between the liquid crystal layer and the electrode (adhesion) after initial storage in a constant temperature and humidity chamber (constant temperature and humidity) and after ultraviolet irradiation (ultraviolet light).
- Examples 1 to 8 and Comparative Examples 1 and 2 As shown in Table 10 and Table 11 below, using the liquid crystal compositions (1) to (5), liquid crystal display elements were prepared by the above method, and optical characteristics (scattering characteristics and transparency) were evaluated. The adhesion between the liquid crystal layer and the electrode was evaluated. At that time, in Examples 1, 3, 5, 7 and Comparative Example 1, a liquid crystal display element was prepared and evaluated using a glass substrate. In Examples 2, 4, 6, 8 and Comparative Example 2, plastic was used. A substrate was used.
- the liquid crystal display elements of the examples have better optical characteristics than the comparative examples, that is, the Haze of the initial stage after storage in a constant temperature and humidity chamber and after ultraviolet irradiation. Change is small. Furthermore, a liquid crystal display element having high adhesion between the liquid crystal layer and the electrode was obtained, and even after being exposed to these harsh environments, peeling and bubbles were not observed in the liquid crystal display element. In particular, these characteristics were good even when a plastic substrate was used as the substrate of the liquid crystal display element. Specifically, in comparison under the same conditions, the comparison between Examples 1 and 3 and Comparative Example 1, and the comparison between Examples 2 and 4 and Comparative Example 2. Further, when the second specific compound was introduced into the liquid crystal composition, the haze was lowered at a lower voltage. Specifically, in comparison under the same conditions, comparison is made between Example 3 and Example 5, and comparison between Example 4 and Example 6.
- the liquid crystal display element of the present invention can be suitably used for a normal type element that is in a scattering state when no voltage is applied and becomes transparent when a voltage is applied.
- the element can be used for a liquid crystal display for display purposes, as well as a light control window and an optical shutter element for controlling the blocking and transmission of light.
- a substrate can be used.
Abstract
Description
偏光板を用いない液晶表示素子として、液晶の透過状態(透明状態ともいう。)と散乱状態との間でスイッチングを行う素子がある。一般的には、高分子分散型液晶(PDLC(Polymer Dispersed Liquid Crystal)ともいう。)や高分子ネットワーク型液晶(PNLC(Polymer Network Liquid Crystal)ともいう。)を用いたものが知られている。
一方、電圧無印加時に透過状態となり、電圧印加時には散乱状態になるPDLCを用いた液晶表示素子(リバース型素子ともいう。)も提案されている(特許文献3、4参照)。
即ち、本発明は、電極を備えた一対の基板の間に配置した液晶及び重合性化合物を含む液晶組成物に対し、紫外線を照射して硬化させた液晶層を有する、電圧無印加時に散乱状態となり、電圧印加時には透明状態となる液晶表示素子であって、前記液晶組成物が、下記式[1]で表される化合物を含むことを特徴とする液晶表示素子にある。
本発明に使用される液晶組成物は、液晶、重合性化合物及び前記式[1]で示される化合物(特定化合物ともいう。)を含有する。特定化合物は、式[1]中のX1で示される紫外線により重合反応する部位と、リン酸基を有する。そのため、特定化合物を液晶組成物中に含めると、リン酸基とITO電極などの無機系の電極との相互作用が働き、更に、式[1]中のX1の部位が重合性化合物と反応することで、液晶層中のポリマーネットワークと電極との密着性が高くなると考えられる。
本発明における液晶組成物は、液晶、重合性化合物及び前記式[1]で表される特定化合物を含有する。
液晶には、ネマチック液晶、スメクチック液晶又はコレステリック液晶を用いることができる。なかでも、ノーマル型素子には、正の誘電異方性を有する液晶が好ましく、リバース型には、負の誘電異方性を有する液晶を用いることが好ましい。その際、低電圧駆動及び散乱特性の点からは、誘電率の異方性が大きく、屈折率の異方性が大きいものが好ましい。また、液晶には、前記の相転移温度、誘電率異方性及び屈折率異方性の各物性値に応じて、2種類以上の液晶を混合して用いることができる。
重合性化合物は、液晶に溶解すれば、特に限定されないが、重合性化合物を液晶に溶解した際に、液晶組成物の一部又は全体が液晶相を示す温度が存在することが必要となる。液晶組成物の一部が液晶相を示す場合であっても、液晶表示素子を肉眼で確認して、素子内全体がほぼ一様な透明性と散乱特性が得られていれば良い。
なかでも、重合性化合物の反応形式は、液晶表示素子の光学特性の点から、ラジカル重合が好ましい。その際、重合性化合物としては、下記のラジカル型の重合性化合物、又はそのオリゴマーを用いることができる。また、前記の通り、これらの重合性化合物を重合反応させたポリマーを用いることもできる。
ラジカル型の重合性化合物又はそのオリゴマーの具体例は、国際公開第WO2015/146987の69~71頁に記載されるラジカル型の重合性化合物が挙げられる。
前記硬化性樹脂の形成を促進させるため、液晶組成物中には、重合性化合物のラジカル重合を促進させる目的で、紫外線により、ラジカルを発生するラジカル開始剤(重合開始剤ともいう)を導入することが好ましい。具体的には、国際公開第2015/146987の71~72頁に記載されるラジカル開始剤が挙げられる。
特定化合物は、前記式[1]で表される化合物である。
式[1]中、X1、X2、Xm及びXnは、前記に定義した通りであるが、なかでもそれぞれ、下記のものが好ましい。
X1は前記式[1-a]又は式[1-b]が好ましい。X2は炭素数2~12のアルキレン基が好ましく、X1とOと隣り合わない任意の-CH2-は、-O-、-COO-又は-OCO-で置換されていても良い。Xmは1又は2の整数が好ましい。Xnは1又は2の整数が好ましい。ただし、Xm+Xnは3である。
Xdは、炭素数2~12のアルキレン基を示す。p1は、1又は2の整数を示す。p2は、1又は2の整数を示す。ただし、p1+p2は3である。p3は、2~8の整数を示す。
特定化合物の含有割合は、液晶表示素子の液晶層と電極との密着性の点から、液晶組成物中の液晶100質量部に対して、0.01~20質量部が好ましく、0.05~10質量部がより好ましく、0.1~10質量部が最も好ましい。また、特定化合物は、各特性に応じて、1種又は2種以上を混合して使用することもできる。
Y2は単結合、-O-、-NH-、-N(CH3)-、-CH2O-、-CONH-、-NHCO-、-CON(CH3)-、-N(CH3)CO-、-COO-又は-OCO-を示す。なかでも、単結合、-O-、-CH2O-、-CONH-、-COO-又は-OCO-が好ましく、単結合、-O-、-COO-又は-OCO-がより好ましい。
Y4は単結合、-O-、-OCH2-、-COO-又は-OCO-を示す。なかでも、単結合、-O-又は-COO-が好ましく、-O-が特に好ましい。
Y7はベンゼン環、シクロヘキサン環及び複素環から選ばれる環状基を示し、これらの環状基上の任意の水素原子が、炭素数1~3のアルキル基、炭素数1~3のアルコキシ基、炭素数1~3のフッ素含有アルキル基、炭素数1~3のフッ素含有アルコキシ基又はフッ素原子で置換されていてもよい。なかでも、ベンゼン環又はシクロヘキサン環が好ましい。
Ymは0~4の整数を示す。なかでも、0~2の整数が好ましい。
式[2]における好ましいY1~Y8及びYmの組み合わせは、下記の表1~9に示される。表1~9中、Y3を示す-(CH2)-におけるaは、1~10の整数を表す。
また、第2の特定化合物は、重合性化合物及び特定化合物を混合した液晶に加える方法や、予め、液晶に第2の特定化合物を加えたものを調製し、それに重合性化合物と特定化合物とを混合したものに加える方法が挙げられる。
前記のように液晶組成物を調製する場合、重合性化合物、特定化合物及び第2の特定化合物の溶解性に応じて、加熱することもできる。その際の温度は100℃未満が好ましい。
液晶表示素子に用いる基板としては、透明性の高い基板であれば特に限定されず、ガラス基板の他、アクリル基板、ポリカーボネート基板、PET(ポリエチレンテレフタレート)基板などのプラスチック基板、更には、それらのフィルムを用いることができる。特に、調光窓などに用いる場合には、プラスチック基板やフィルムが好ましい。また、プロセスの簡素化の観点からは、液晶駆動のためのITO電極、IZO(Indium Zinc Oxide)電極、IGZO(Indium Gallium Zinc Oxide)電極、有機導電膜などが形成された基板が好ましい。また、反射型の液晶表示素子とする場合には、片側の基板のみにならば、シリコンウエハやアルミニウムなどの金属や誘電体多層膜が形成された基板を使用できる。
液晶表示素子に用いる液晶組成物は、前記の通りであるが、そのなかに、液晶表示素子の電極間隙(ギャップともいう。)を制御するためのスペーサーを導入することもできる。
<特定化合物>
X1:ホスマ―PE(DAP社製)
X2:KAYAMER PM-21(日本化薬社製)
R1:IBXA(大阪有機化学工業社製)
R2:2-ヒドロキシエチルメタクリレート
R3:KAYARAD FM-400(日本化薬社製)
R4:EBECRYL 230(ダイセル・オルネクス社製)
R5:EBECRYL 4858(ダイセル・オルネクス社製)
R6:カレンズMT PE1(昭和電工社製)
P1:IRGACURE 184(BASF社製)
<液晶>
L1:MLC-3018(メルク社製)
R1(1.35g)、R2(0.20g)、R3(1.00g)、R4(0.80g)、R5(0.20g)及びR6(0.30g)を混合し、60℃で2時間撹拌した。その後、X1(0.05g)を加え、重合性化合物の溶液を作製した。重合性化合物の溶液、L1(6.00g)及びP1(0.10g)を混合し、25℃で6時間撹拌して、液晶組成物(1)を得た。
R1(1.30g)、R2(0.20g)、R3(1.00g)、R4(0.80g)、R5(0.20g)及びR6(0.30g)を混合し、60℃で2時間撹拌した。その後、X2(0.10g)を加え、重合性化合物の溶液を作製した。重合性化合物の溶液、L1(6.00g)及びP1(0.10g)を混合し、25℃で6時間撹拌して、液晶組成物(2)を得た。
R1(1.40g)、R2(0.20g)、R3(1.00g)、R4(0.80g)、R5(0.20g)及びR6(0.30g)を混合し、60℃で2時間撹拌した。その後、X2(0.10g)を加え、重合性化合物の溶液を作製した。その一方で、S1(0.20g)及びL1(5.80g)を混合し、25℃で2時間撹拌して第2の特定化合物を含む液晶を作製した。重合性化合物の溶液、第2の特定化合物を含む液晶、及びP1(0.10g)を混合し、25℃で6時間撹拌して、液晶組成物(3)を得た。
R1(1.20g)、R2(0.20g)、R3(1.00g)、R4(0.80g)、R5(0.20g)及びR6(0.30g)を混合し、60℃で2時間撹拌した。その後、X2(0.20g)を加え、重合性化合物の溶液を作製した。その一方で、S1(0.20g)、S2(0.20g)及びL1(5.60g)を混合し、25℃で2時間撹拌して第2の特定化合物を含む液晶を作製した。重合性化合物の溶液、第2の特定化合物を含む液晶、及びP1(0.10g)を混合し、25℃で6時間撹拌して、液晶組成物(4)を得た。
R1(1.40g)、R2(0.20g)、R3(1.00g)、R4(0.80g)、R5(0.20g)及びR6(0.30g)を混合し、60℃で2時間撹拌して、重合性化合物の溶液を作製した。重合性化合物の溶液、L1(6.00g)及びP1(0.10g)を混合し、25℃で6時間撹拌して、液晶組成物(5)を得た。
純水及びIPA(イソプロピルアルコール)で洗浄したITO電極付きガラス基板(縦:100mm、横:100mm、厚さ:0.7mm)を2枚用意し、その一方の基板のITO面に、粒子径が15μmのスペーサー(商品名:ミクロパール、積水化学社製)を塗布した。その後、その基板のスペーサーを塗布した面に、ODF(One Drop Filling)法にて前記の液晶組成物(1)~(5)を滴下し、次いで、他方の基板のITO面が向き合うように貼り合わせを行い、処理前の液晶表示素子を得た。
この処理前の液晶表示素子に、照度20mW/cm2のメタルハライドランプを用いて、350nm以下の波長をカットし、照射時間60秒で紫外線照射を行った。これにより、液晶表示素子(ガラス基板)を得た。
純水で洗浄したITO電極付きPET基板(縦:150mm、横:150mm、厚さ:0.1mm)を2枚用意し、その一方の基板のITO面に、前記の15μmのスペーサーを塗布した。その後、その基板のスペーサーを塗布したITO面に、ODF法にて前記の液晶組成物(1)~(5)を滴下し、次いで、他方の基板のITO面が向き合うように貼り合わせを行い、処理前の液晶表示素子を得た。なお、ODF法にて、液晶組成物の滴下及び貼り合わせを行う際には、ITO電極付きPET基板の支持基板としてガラス基板を用いた。その後、紫外線を照射する前に、その支持基板を外した。
この処理前の液晶表示素子に、前記の「液晶表示素子の作製(ガラス基板)」と同様の手法で紫外線を照射し、液晶表示素子(プラスチック基板)を得た。
本評価は、液晶表示素子(ガラス基板及びプラスチック基板)の電圧無印加状態(0V)及び電圧印加状態(交流駆動:10V~50V)のHaze(曇り度)を測定することで行った。その際、Hazeは、JIS K 7136に準拠し、ヘーズメータ(HZ-V3,スガ試験機社製)で測定した。なお、本評価では、電圧無印加状態のHazeが高いほど散乱特性に優れ、電圧印加状態でのHazeが低いほど透明性に優れるとした。
更に、液晶表示素子の光の照射に対する安定性試験として、卓上型UV硬化装置(HCT3B28HEX-1、センライト社製)を用いて、波長365nm換算で5J/cm2の紫外線を照射した後の観察も行った。具体的には、初期のHazeに対して、紫外線照射後のHazeの変化が小さいものほど、本評価に優れるとした。
初期、恒温恒湿槽保管後(恒温恒湿)及び紫外線照射後(紫外線)のHazeの測定結果を、表10にまとめて示す。
本評価は、液晶表示素子(ガラス基板及びプラスチック基板)を、温度80℃、湿度90%RHの恒温恒湿槽内に24時間保管し、液晶表示素子の剥離と気泡の有無を確認することで行った(液晶表示素子の高温高湿環境下の安定性試験として)。具体的には、素子の剥離(液晶層と樹脂膜、或いは樹脂膜と電極とが剥がれている状態)が起こっていないもの、及び素子内に気泡が発生していないものを、本評価に優れるとした(表中の良好表示)。
初期、恒温恒湿槽保管後(恒温恒湿)及び紫外線照射後(紫外線)における液晶層と電極との密着性の結果(密着性)を、表11にまとめて示す。
下記の表10及び表11に示されるように、前記の液晶組成物(1)~(5)を用いて、前記の手法で液晶表示素子の作製、光学特性(散乱特性と透明性)の評価、及び液晶層と電極との密着性の評価を行った。
その際、実施例1、3、5、7及び比較例1は、ガラス基板を用いて液晶表示素子の作製と各評価を行い、実施例2、4、6、8及び比較例2では、プラスチック基板を用いた。
また、液晶組成物中に第2の特定化合物を導入した場合、より低い電圧でHazeが低くなった。具体的には、同一の条件での比較において、実施例3と実施例5との比較、及び実施例4と実施例6との比較である。
Claims (8)
- 電極を備えた一対の基板の間に配置した液晶及び重合性化合物を含む液晶組成物に対し、紫外線を照射して硬化させた液晶層を有する、電圧無印加時に散乱状態となり、電圧印加時には透明状態となる液晶表示素子であって、前記液晶組成物が、下記式[1]で表される化合物を含むことを特徴とする液晶表示素子。
- 前記式[1]で表される化合物の導入量が、液晶100質量部に対して、0.05~10質量部である請求項1に記載の液晶表示素子。
- 前記液晶組成物が、下記式[2]で表される化合物を含む請求項1~3のいずれか一項に記載の液晶表示素子。
- 前記式[2]で表される化合物の導入量が、液晶100質量部に対して、0.5~20質量部である請求項4に記載の液晶表示素子。
- 前記式[2]で表される化合物が、下記式[2a-1]~式[2a-11]からなる群から選ばれる少なくとも1種である請求項4又は5に記載の液晶表示素子。
- 前記液晶表示素子の基板が、ガラス基板又はプラスチック基板である請求項1~6のいずれか一項に記載の液晶表示素子。
- 前記液晶表示素子が、調光窓又は光シャッター素子である請求項1~7のいずれか一項に記載の液晶表示素子。
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