JP4048619B2

JP4048619B2 - Liquid crystal optical element and manufacturing method thereof

Info

Publication number: JP4048619B2
Application number: JP29862398A
Authority: JP
Inventors: 慎哉田原; 聡新山
Original assignee: Asahi Glass Co Ltd
Current assignee: AGC Inc
Priority date: 1998-10-20
Filing date: 1998-10-20
Publication date: 2008-02-20
Anticipated expiration: 2018-10-20
Also published as: JP2000122045A

Description

【０００１】
【発明の属する技術分野】
本発明は、電界の印加／非印加により、素子の透過、散乱、反射状態を制御し、調光素子や表示素子、光学シャッター等に利用可能な液晶光学素子に関する。
【０００２】
【従来の技術】
液晶と透明な高分子とを複合して、高分子と液晶、または液晶内部（微小領域間）の屈折率差を生じせしめた透過−散乱型の光学素子が提案された。液晶／高分子複合体素子、液晶／樹脂複合体素子あるいは分散型液晶素子などと呼ばれている。この素子は原理的に偏光板を必要としないので、光の吸収損失が少なく、かつ高い散乱性能が得られ、素子全体における光の利用効率が高いことが大きな利点となっている。
【０００３】
この特性を生かして、調光ガラス、光シャッター、レーザー装置および表示装置などに用いられている。電圧非印加で散乱状態、電圧印加で透明状態のものが商用化された。
【０００４】
さらに、従来例１（ＵＳＰ５１８８７６０）では、液晶と重合性の液晶を用いた素子が開示された。この従来例１は、電圧非印加時において素子内の液晶と重合された液晶とが同じ配向方向を有しているので、素子をどの方向から見ても透明状態を呈する。そして、電圧印加時には、素子内の液晶の配向が電界によって制御され、液晶分子の配列方向が微小領域においてさまざまに変化することにより、素子は散乱状態を呈する。
【０００５】
また、カイラル剤を添加して初期配向にヘリカル構造を設けることで、コントラスト比が向上することが開示された。この素子は、「異方性ゲル」または「液晶ゲル」と呼ばれている。この従来例１ではアクリロイル基を末端に持つメソゲンモノマーが使用された。
【０００６】
また、従来例２（国際特許公開ＷＯ９２／１９６９５）にも同様の構成を持つ素子が開示された。従来例１と同様の動作モードであって、カイラルネマチック液晶中に微量の高分子を分散させ、電圧非印加時に透明状態、電圧印加時に散乱状態を得る。この素子はＰＳＣＴ（ポリマー・スタビライズド・コレステリック・テクスチャー）と呼ばれている。この従来例２にもアクリロイル基を末端に持つメソゲンモノマーが開示された。
【０００７】
【発明が解決しようとする課題】
従来例１において、組成物全体が液晶相を示す状態で硬化せしめて素子を形成することが示された。その製造方法では基板間に未硬化の組成物を挟持してから硬化を行うが、通常基板間にはスペーサーなど基板の間隙を一定に保つための構造が配置される。
【０００８】
このため異物が基板間に存在することになり、組成物を基板間に注入したり滴下して広げる際に配向などの不連続部分の原因となりやすい。硬化性化合物の硬化時にはその不連続部分もそのまま固定されてしまうため、形成後の素子の透過率が低くなるとともに著しく素子の光学特性の均一性を損ねていた。
【０００９】
例えば、組成物を基板間に挟持する際に発生する配向などの不連続部分を減らす方法としては、原因となるスペーサーなどの構造物を減らすこと、あるいは構造物を全く用いないといった方法が考えられる。しかし、基板間隙の保持手段をあまり減らしすぎると大面積を支えきれずに基板と基板が接触してしまうといった問題点がある。
【００１０】
本発明では、これらの問題を解決するものであって、かつ形成後の液晶光学素子の透過率が高く、基板面における均一性が優れた素子を提供することである。また、微小領域の配向が均一であるので高密度表示に適した素子を提供することができる。
【００１１】
【課題を解決するための手段】
すなわち本発明は、少なくとも一方が透明な２枚の電極付き基板間に液晶および硬化性化合物を含有する組成物とスペーサーとを挟持し、組成物の一部または全体が液晶相を示す温度で硬化を行う液晶光学素子の製造方法において、２枚の電極付き基板間に組成物を注入し、未硬化の組成物全体が等方相を示す温度をＴ _C （℃）としたときにおけるＴ _C ＋１８（℃）以上Ｔ _C ＋４８（℃）以下の温度で加熱処理を行い、その後、組成物を硬化させることを特徴とする液晶光学素子の製造方法を提供する。
【００１２】
また、上記の製造方法において、組成物を硬化させるときの温度を２５℃にする液晶光学素子の製造方法を提供する。
また、上記の製造方法において、組成物中にカイラル剤を含有する液晶光学素子の製造方法を提供する。
【００１３】
【発明の実施の形態】
本発明では組成物を基板間に挟持した後に組成物に熱エネルギーを加えることにより分子の運動性を高め、不連続構造を減らすことにより均一性を高める手法を採用する。この構造均一化手法は組成物全体が等方相を示す温度以下でも有効であるが、ほぼ等方相を示す温度付近の温度に加熱する方がより短時間かつ効果的に不連続構造を減らすことができる。
【００１４】
加熱時間が長すぎる場合、または加熱温度が高すぎる場合には白濁を生じることがある。このようなときには加熱処理の時間を短くするか、加熱処理の温度を低くすることによって最適条件を選択することができる。特に組成物のカイラルピッチが小さい場合や基板間隙の大きい場合にはより精密に温度制御を行う必要があるからである。
【００１５】
この加熱処理の後に重合硬化を行うことで、均一性がよく、透過率の高い液晶光学素子を形成できる。
【００１６】
液晶と未硬化の硬化性化合物の組成物は、混合後均質な溶液であることが好ましい。この組成物は、電極付き基板に挟持される時、液晶相でも等方相でもよい。硬化されるときには、一部または全体が液晶相を示す温度に設定する。
【００１７】
組成物を挟持する電極付き基板の電極表面を直接研磨したり、樹脂の薄膜を設けそれをラビングするなどして、電極表面に液晶を配向させる機能を付与することもでき、それにより、液晶と未硬化の硬化性化合物の組成物を挟持する際のむらを低減させることもできる。
【００１８】
また、一対の配向処理済み基板の配向方向の組み合わせとしては、平行、直交、その他どのような角度でもよく、組成物挟持時のむらが最小となるよう角度を設定すればよい。
【００１９】
電極間隙は、スペーサー等で保持することができ、４〜５０μｍが好ましく、さらに５〜３０μｍが好ましい。この電極間隙は小さすぎるとコントラスト比が低下し、大きすぎると駆動電圧が上昇する。
【００２０】
電極を支持する基板は、ガラス基板でも樹脂基板でもよく、またガラス基板と樹脂基板の組み合わせでもよい。また、片方の基板にアルミニウムなどの金属や誘電体多層膜が設けられてもよい。
【００２１】
フィルム基板の場合、連続で供給される電極付き基板を２本のゴムロール等で挟み、その間に、スペーサーを含有分散させた液晶と未硬化の硬化性化合物との組成物を供給し、挟み込み、連続で熱処理および硬化をさせることができ生産性が高い。
【００２２】
ガラス基板の場合、電極面内に微量のスペーサーを散布し、対向させた基板の４辺をエポキシ樹脂等のシール剤で封止セルとし、２カ所以上の設けたシールの切り欠きの一方を液晶と未硬化の硬化性化合物の組成物に浸し、他方より吸引することでセル内に組成物を満たし、硬化させ液晶光学素子を得ることができる。また、通常の真空注入法を用いることもできる。以下、実施例について説明を行う。
【００２３】
【実施例】
（実施例１）
カイラル剤（メルク社製Ｓ−８１１とメルク社製Ｃ１５の重量比１：１の混合物）を２．５ｗｔ％溶解したシアノ系ネマチック液晶（メルク社製ＢＬ−００９）９５部、式（１）の未硬化の硬化性化合物５部、２，２−ジメトキシ−２−フェニルアセトフェノン０．１５部の組成物を調製した。組成物全体が等方相となる温度（Ｔ_C ）を測定したところ１０２℃であった。
【００２４】
【化１】

【００２５】
この組成物を、透明電極上に形成したポリイミド薄膜を一方向にラビングした一対の基板をラビング方向が直交するように対向させ、微量の直径１３μｍの樹脂ビーズを介して、四辺に幅約１ｍｍで印刷したエポキシ樹脂により張り合わせて作製した液晶セルに注入した。注入時に配向の不連続部分が発生した。
【００２６】
このセルを１２０℃に温度設定した恒温槽中に１０分間保持したところ、注入に伴う不連続部分は消失した。その後２５℃に保持した状態で、主波長が約３６５ｎｍのＨｇＸｅランプにより、上側より約３ｍＷ／ｃｍ² 、下側より同じく約３ｍＷ／ｃｍ² の紫外線を１０分間照射し、液晶光学素子を得た。
【００２７】
５３０ｎｍを中心波長とした半値幅約２０ｎｍの測定光源を用いた透過率測定系（光学系のＦ値１１．５）で透過率を測定したところ、電圧を印加しない状態で８０．５％であった。硬化後の外観も均一性に問題なく良好なものであった。
【００２８】
（実施例２）
注入後の恒温槽の温度設定条件のみ１５０℃・１０分とした以外は実施例１と同様の条件・材料を用いた。注入後の不均一部分は加熱処理により消滅し、硬化後も均一かつ透明で良好な外観となった。電圧を印加しない状態で透過率は８０．５％（測定の中心波長＝５３０ｎｍ）であった。
【００２９】
（比較例１）
注入後の恒温槽の温度設定条件のみ５０℃・１０分とした以外は実施例１と同様の条件・材料を用いた。注入後の不均一部分は加熱処理を行ってもほとんど変わらず、硬化後も不均一で不適な外観のままであった。電圧を印加しない状態で透過率は７９．７％（測定の中心波長＝５３０ｎｍ）であった。
【００３０】
（比較例２）
注入後の恒温槽の温度設定条件のみ２００℃・１０分とした以外は実施例１と同様の条件・材料を用いた。注入後の不均一部分は加熱処理により白濁が生じ、硬化後も不透明な不適な外観となった。電圧を印加しない状態で透過率は６８．０％（測定の中心波長＝５３０ｎｍ）であった。
【００３１】
【発明の効果】
本発明により、未硬化の組成物の不均一部分を減少させることが可能となった。そして、安定した生産を可能とし、高い歩留で高品位の素子を連続生産できるようになった。本発明は、このほか、本発明の効果を損しない範囲で種々の応用が可能である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal optical element that can be used for a light control element, a display element, an optical shutter, and the like by controlling transmission, scattering, and reflection states of the element by applying / not applying an electric field.
[0002]
[Prior art]
A transmission-scattering type optical element has been proposed in which a liquid crystal and a transparent polymer are combined to cause a difference in refractive index between the polymer and the liquid crystal, or inside the liquid crystal (between microregions). It is called a liquid crystal / polymer composite element, a liquid crystal / resin composite element, or a dispersed liquid crystal element. Since this element does not require a polarizing plate in principle, it has a great advantage that light absorption loss is small, high scattering performance is obtained, and light use efficiency in the entire element is high.
[0003]
Taking advantage of this characteristic, it is used for light control glass, optical shutters, laser devices, display devices and the like. Those in a scattering state when no voltage was applied and in a transparent state when a voltage was applied were commercialized.
[0004]
Furthermore, Conventional Example 1 (USP 5188760) disclosed an element using liquid crystal and polymerizable liquid crystal. In this conventional example 1, since the liquid crystal in the element and the polymerized liquid crystal have the same orientation direction when no voltage is applied, the element is transparent when viewed from any direction. When a voltage is applied, the orientation of the liquid crystal in the element is controlled by an electric field, and the arrangement direction of the liquid crystal molecules changes variously in a minute region, whereby the element exhibits a scattering state.
[0005]
It has also been disclosed that the contrast ratio is improved by adding a chiral agent to provide a helical structure in the initial orientation. This element is called “anisotropic gel” or “liquid crystal gel”. In Conventional Example 1, a mesogenic monomer having an acryloyl group at the terminal was used.
[0006]
Also, a device having the same configuration is disclosed in Conventional Example 2 (International Patent Publication WO92 / 19695). The operation mode is the same as in Conventional Example 1, and a small amount of polymer is dispersed in a chiral nematic liquid crystal to obtain a transparent state when no voltage is applied and a scattering state when a voltage is applied. This element is called PSCT (Polymer Stabilized Cholesteric Texture). This conventional example 2 also disclosed a mesogenic monomer having an acryloyl group at its terminal.
[0007]
[Problems to be solved by the invention]
In Conventional Example 1, it was shown that the entire composition was cured in a state showing a liquid crystal phase to form an element. In the manufacturing method, the uncured composition is sandwiched between the substrates and then cured. Usually, a structure such as a spacer for keeping the gap between the substrates constant is arranged between the substrates.
[0008]
For this reason, foreign matters exist between the substrates, and when the composition is injected between the substrates or dropped and spread, it tends to cause discontinuous portions such as orientation. Since the discontinuous portion is fixed as it is when the curable compound is cured, the transmittance of the formed element is lowered and the uniformity of the optical characteristics of the element is remarkably impaired.
[0009]
For example, as a method of reducing discontinuous portions such as orientation generated when the composition is sandwiched between substrates, a method of reducing the structure such as a spacer causing the composition or not using the structure at all can be considered. . However, if the holding means for the substrate gap is reduced too much, there is a problem that the substrate and the substrate come into contact with each other without supporting a large area.
[0010]
The present invention is to solve these problems and to provide an element in which the liquid crystal optical element after formation has high transmittance and excellent uniformity on the substrate surface. In addition, since the orientation of the minute regions is uniform, an element suitable for high-density display can be provided.
[0011]
[Means for Solving the Problems]
That is, in the present invention, a composition containing a liquid crystal and a curable compound and a spacer are sandwiched between two substrates with electrodes, at least one of which is transparent, and the composition is cured at a temperature at which part or all of the composition exhibits a liquid crystal phase. In the method for manufacturing a liquid crystal optical element , the composition is injected between two substrates with electrodes, and the temperature at which the entire uncured composition exhibits an isotropic phase is expressed as T _C T _C when (° C) +18 (℃) or more T _C There is provided a method for producing a liquid crystal optical element, characterized in that a heat treatment is performed at a temperature of +48 (° C.) or less, and then the composition is cured .
[0012]
Moreover, in said manufacturing method, the manufacturing method of the liquid crystal optical element which makes temperature at the time of hardening a composition 25 degreeC is provided.
Further, in the above production method, a method for producing a liquid crystal optical element containing a chiral agent in the composition is provided.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, after sandwiching the composition between the substrates, a technique is adopted in which thermal energy is applied to the composition to increase molecular mobility and discontinuous structure to increase uniformity. Although this structure homogenization method is effective even at a temperature below the temperature at which the entire composition exhibits an isotropic phase, heating to a temperature near the temperature at which the composition is nearly isotropic reduces the discontinuous structure more quickly and effectively. be able to.
[0014]
If the heating time is too long, or if the heating temperature is too high, white turbidity may occur. In such a case, the optimum condition can be selected by shortening the heat treatment time or lowering the heat treatment temperature. This is because, in particular, when the chiral pitch of the composition is small or the substrate gap is large, it is necessary to perform temperature control more precisely.
[0015]
By performing the polymerization curing after this heat treatment may uniformity can be formed with high transmittance liquid crystal optical element.
[0016]
The composition of the liquid crystal and the uncured curable compound is preferably a homogeneous solution after mixing. This composition, when it is sandwiched in the substrate with electrode, may be isotropic phase in the liquid crystal phase. When it is cured, it is set to a temperature at which a part or the whole exhibits a liquid crystal phase.
[0017]
Composition or polished directly electrode surface of the substrates with electrodes for clamping the, such as by rubbing it provided a thin film of resin, it is also possible to impart a function to align the liquid crystal in the electrode surface, whereby the liquid crystal the composition of the curable compound uncured can also reduce unevenness when sandwiched between.
[0018]
Further, the combination of the alignment directions of the pair of alignment-treated substrates may be any angle such as parallel, orthogonal, or the like, and the angle may be set so as to minimize the unevenness when sandwiching the composition.
[0019]
The electrode gap can be held by a spacer or the like, and is preferably 4 to 50 μm, more preferably 5 to 30 μm. If the electrode gap is too small, the contrast ratio decreases, and if it is too large, the drive voltage increases.
[0020]
The substrate that supports the electrodes may be a glass substrate or a resin substrate, or a combination of a glass substrate and a resin substrate. Further, a metal such as aluminum or a dielectric multilayer film may be provided on one substrate.
[0021]
In the case of a film substrate, a substrate with electrodes to be continuously supplied is sandwiched between two rubber rolls and the like, and a composition of a liquid crystal containing a spacer and dispersed therein and an uncured curable compound is supplied and sandwiched between them. Can be heat-treated and cured with high productivity.
[0022]
In the case of a glass substrate, a small amount of spacers are scattered on the electrode surface, and the four sides of the opposed substrate are sealed with a sealing agent such as epoxy resin, and one of the cutouts of the seals provided at two or more locations is liquid crystal And the uncured curable compound composition and suction from the other, the composition is filled in the cell and cured to obtain a liquid crystal optical element. Also, a normal vacuum injection method can be used. Examples will be described below.
[0023]
【Example】
Example 1
Chiral agent: cyano systems was dissolved 2.5 wt% (by weight of Merck S-811 and manufactured by Merck C15 1 mixture of 1) Nema Chi click crystal (manufactured by Merck BL-009) 95 parts of formula ( A composition of 5 parts of the uncured curable compound 1) and 0.15 part of 2,2-dimethoxy-2-phenylacetophenone was prepared. Entire composition was 102 ° C. was measured temperature (T _C) of the isotropic phase.
[0024]
[Chemical 1]

[0025]
A pair of substrates on which a polyimide thin film formed on a transparent electrode is rubbed in one direction is opposed to each other so that the rubbing directions are orthogonal to each other, and a width of about 1 mm is provided on four sides through a small amount of resin beads having a diameter of 13 μm. It injected into the liquid crystal cell produced by bonding together with the printed epoxy resin. Discontinuous portions of orientation occurred during the implantation.
[0026]
When this cell was held in a thermostatic bath set at 120 ° C. for 10 minutes, the discontinuous portion accompanying the injection disappeared. Thereafter while holding the 25 ° C., the dominant wavelength of about 365nm of HgXe lamp, approximately from the upper 3 mW / cm ^2, the same about 3 mW / cm ² UV than the lower irradiation 10 minutes to obtain a liquid crystal optical element .
[0027]
When the transmittance was measured with a transmittance measurement system (F value 11.5 of the optical system) using a measurement light source with a center wavelength of 530 nm and a half-value width of about 20 nm, it was 80.5% with no voltage applied. It was. The appearance after curing was also good with no problem in uniformity.
[0028]
(Example 2)
The same conditions and materials as in Example 1 were used except that the temperature setting conditions of the thermostat after injection were set at 150 ° C. for 10 minutes. The non-uniform portion after the injection disappeared by the heat treatment, and it became uniform, transparent and good appearance after curing. When no voltage was applied, the transmittance was 80.5% (measurement center wavelength = 530 nm).
[0029]
(Comparative Example 1)
The same conditions and materials as in Example 1 were used except that the temperature setting conditions of the thermostat after the injection were set to 50 ° C. and 10 minutes. The non-uniform portion after the injection hardly changed even when the heat treatment was carried out, and the non-uniform and unsuitable appearance remained after the curing. The transmittance was 79.7% with no voltage applied (measurement center wavelength = 530 nm).
[0030]
(Comparative Example 2)
The same conditions and materials as in Example 1 were used except that the temperature setting conditions of the thermostat after injection were set to 200 ° C. for 10 minutes. The non-uniform portion after the injection became white turbid due to the heat treatment, and became an opaque and inappropriate appearance even after curing. When no voltage was applied, the transmittance was 68.0% (measurement center wavelength = 530 nm).
[0031]
【The invention's effect】
The present invention has made it possible to reduce non-uniform portions of the uncured composition. In addition, stable production is possible, and high-quality elements can be continuously produced with high yield. In addition to the above, the present invention can be applied in various ways as long as the effects of the present invention are not impaired.

Claims

A liquid crystal optical element in which a composition containing a liquid crystal and a curable compound and a spacer are sandwiched between two substrates with electrodes, at least one of which is transparent, and the composition is cured at a temperature at which part or all of the composition exhibits a liquid crystal phase In this manufacturing method, the composition is injected between two substrates with electrodes, and the temperature at which the entire uncured composition exhibits an isotropic phase is expressed as T _C. T _C when (° C) +18 (℃) or more T _C A method for producing a liquid crystal optical element, wherein a heat treatment is performed at a temperature of +48 (° C.) or less, and then the composition is cured .

The method for producing a liquid crystal optical element according to claim 1, wherein the temperature at which the composition is cured is set to 25 ° C.

The method for producing a liquid crystal optical element according to claim 1, wherein the composition contains a chiral agent.

A liquid crystal optical element produced by the production method according to claim 1, 2 or 3.