JP4470335B2 - Liquid crystal display spacer - Google Patents

Description

体積平均粒子径:
【数２】

粒子径分布指数：
【数３】

ここで、Ｘｉ；個々の粒子径、ｎは測定数である。
【００１９】
また、本発明のポリアミド多孔質球状粒子のＢＥＴ比表面積は１００〜８００００ｍ^２／ｋｇ、好ましくは、１０００〜６００００ｍ^２／ｋｇ、さらに好ましくは、３０００〜４００００ｍ^２／ｋｇであることが望ましい。比表面積が１００ｍ^２／ｋｇより小さいと液晶表示用スペーサー粒子としては、耐衝撃性が劣るから好ましくない。また比表面積が８００００ｍ^２／ｋｇであると取り扱いにくい。
【００２０】
また、本発明のポリアミド多孔質球状粒子の多孔度指数（ＲＩ）は、５〜１００が好ましい。さらに好ましくは、多孔度指数が５〜７０である。ここで多孔度指数（ＲＩ）とは、同じ直径の平滑な球状粒子の比表面積に対し、多孔質の球状粒子の比表面積の比で表示したものと定義する。次式で表せる。多孔度指数が５より小さければ、多孔質の程度が低すぎて、本発明のスペーサー粒子の耐衝撃性の効果が少なくなる。多孔度が１００より大きければ形状が不安定となるから、液晶用スペーサーには上記の範囲が好ましい。
【００２１】
【数４】

ここで、ＲＩ；多孔度指数、Ｓ；多孔粒子の比表面積[ｍ^２/kg]、
Ｓ_０；同一粒子径の円滑な球状粒子の比表面積[ｍ^２/kg]である。
Ｓ_０は、次式に従って求めることができる。
すなわち、観測された数平均球状粒子径ｄ_obs[m]、ポリアミドの密度ρ[ｋｇ／ｍ³]とすると、円滑な球の比表面積Ｓ_０は次式で表すことができる。
【数５】

ここでは、ポリアミド６ならびにポリアミド６６の密度を結晶相１２３０ｋｇ／ｍ^３、非晶相１１００ｋｇ／ｍ^３とし、その結晶化度から密度を算出した。
【００２２】
また、本発明のポリアミド多孔質球状粒子は結晶性であって、融点が１１０〜３２０℃である。好ましくは、１４０〜２８０℃である。融点が１１０℃より低くなると、熱安定性が低くなって好ましくない。
【００２３】
さらに、本発明のポリアミド多孔質球状粒子は、ＤＳＣで測定された結晶化度が４０％以上であることが好ましい。ポリアミドの結晶化度は、Ｘ線解析より求める方法、ＤＳＣ測定法により求める方法、密度から求める方法があるが、ＤＳＣ測定法により求める方法が好適がである。結晶化度が４０％以上であることが好ましい。特に結晶化度が５０％より高いのが特に好ましい。普通溶融物から結晶化させたポリアミドの結晶化度は高いものでせいぜい３０％程度である。本発明のポリアミドは結晶化度が４０％より高いことが好ましい。特に好ましくは、結晶化度４５％より高いことが好ましい。結晶化度が４０％より低いと、多孔質粒子が熱的に形状的に不安定になるから好ましくない。
【００２４】
ポリアミドの結晶化度は、 Ｒ．Ｖｉｅｗｅｇら、ｋｕｎｓｔｓｔｏｆｆｅ IV ｐｏｌｙａｍｉｄｅ、２１８頁、Ｃａｒｌ Ｈａｎｇｅｒ Ｖｅｒｌａｇ、１９６６年の記載により、ポリアミド６、ポリアミド６６の融解熱はそれぞれ４５ｃａｌ／ｇとして算出した。結晶化度は次の式から算出される。
【数６】

χ ；結晶化度（％）
ΔＨ_obs；サンプルの融解熱 （ｃａｌ／ｇ）
ΔＨ_ｍ；ポリアミドの融解熱 （ｃａｌ／ｇ）
【００２５】
本発明の液晶表示用スペーサー粒子は、特定の比表面積と、特定の粒子径およびシャープな粒子径分布をもつ衝撃性に強い多孔質ポリアミド粒子からなる。
これは微細なフィブリル構造を単位として、フィブリルの方向が球状粒子の中心から伸びていて放射線状に成長している。この構造により球状粒子が圧縮を受けた場合、フィブリルが衝撃エネルギーを吸収して、その結果、液晶表示板の耐衝撃性がでると思われる。
【００２６】
本発明の液晶表示用スペーサー粒子の製造方法について述べる。
ポリアミド多孔質粒子は、ポリアミド溶液と、ポリアミドの非溶媒および水を混合することにより、一時的に均一な溶液を形成した後、ポリマーを析出することにより製造される。
【００２７】
ポリアミド溶液に用いられる溶媒としては、蟻酸、芳香族アルコール系溶媒などが好ましい。
芳香族アルコール系溶媒として、具体的には、０−クレゾール、ｍ−クレゾール、ｐ−クレゾール、クロロフェノール、フェノール等が好ましい。これらは水と部分的に相溶するから好ましい。
【００２８】
ポリアミド溶液は、ポリアミドが０．１〜３０重量％、好ましくは、０．２〜２５重量％と溶媒が９９．９〜７０重量％、好ましくは、９９．８〜７５重量％であって、合計１００重量％ある。である。ポリアミドの割合が３０重量％を越えると溶解しにくくなったり、均一な溶液にならないことがある。また、溶解しても溶液の粘度が高くなり、扱いにくくなるので好ましくない。ポリアミドの割合が０．１重量％より低くなると、ポリマー濃度が低く、製品の生産性が低くなるから好ましくない。
【００２９】
ポリアミドの非溶媒は、該溶媒と水が少なくとも部分的に相溶するものが好ましい。沸点１００℃以下の脂肪族アルコール、ケトンなどが好ましい。また、水とは相溶することが重要である。例えば、メタノール、エタノール、プロパノール、イソプロパノール、アセトン、メチルエチルケトンまたはそれらの混合物などが好ましい。
【００３０】
ポリマーの非溶媒の添加割合は、非溶媒と水の合計の割合が、ポリマー溶液の添加割合より大きいことが好ましい。
ポリアミドの非溶媒と水の添加割合が、ポリマー溶液の割合より小さければ、ポリマーが十分析出しないことがあるので好ましくない。また極端に多すぎる時は、仕上げ工程の溶媒量が増えすぎて経済的でない。
【００３１】
ポリアミドの非溶媒と水の重量％は、合計１００重量％に対して、水の割合が２〜９０重量％が好ましい。好ましくは、５〜８５重量％である。水の割合が２重量％より少ない場合は、球状粒子にならない。また水の割合が９０重量％より大きいならば、芳香族アルコールを溶媒に使った場合には、水が相分離するから好ましくない。
【００３２】
溶液の添加順序は、ポリアミド溶液に、ポリアミド非溶媒を添加し、次に水を加えてもよい。または、ポリアミド非溶媒と水を混合した後、ポリマー溶液を加えてもよい。また、ポリマー溶液に水を混合した後でポリマー非溶媒を加えてもよい。ポリマー非溶媒と水を混合した後、ポリマー溶液を加えるのが好ましい。ポリマー溶液系の均一性が保たれればいずれの方法でもよい。
【００３３】
ポリマー溶液、ポリマー非溶媒と水の、それぞれの割合は、３者が相溶系になることが重要である。均一な溶液を形成させて、時間的な経過を得て、ポリマー粒子を析出させる。均一な溶液を形成する時間は、たとえば、０．１秒〜１２０分程度の時間である。一時的にも、均一な溶液を形成することが重要である。必要ならば、適当な撹拌を加えてもよい。
【００３４】
均一な溶液になるまでの溶液において均一になるまでの撹拌方法は、混合溶液が迅速に均一になるような方法がよい。思いがけなく、撹拌の方法に依存して得られる多孔質球状粒子の大きさが変わることが見られる。
例えば、マグネチックスターラーのような回転式撹拌機の場合、粒径が５〜１５μｍの多孔質球状粒子が生成する。
【００３５】
この撹拌方法の異なるものでも、均一な粒径分布は均一であって、ＰＤＩは１〜１．２さらに１〜１．１程度まで小さくなるのである。溶液が均一になるまでの期間の撹拌方法の違いで多孔質球状粒子の大きさに依存するものであって、肉眼で見て、析出が始まった以降は撹拌の方法には依存しない。
【００３６】
均一な溶液を形成したならば、撹拌の必要はなく、ポリアミド粒子が析出し始める時以降は、静置しておくことが好ましい。撹拌してもよいがポリアミド粒子の形状、大きさには影響がないと思われる。
【００３７】
前記の均一な溶液からポリマー粒子を析出させる温度は、５〜７０℃が好ましい。温度によっては、溶液が均一になる組成範囲が広くなることがある。温度が５℃より低いと、均一になる領域が狭くなる溶媒組成の範囲が場合がある。温度が７０℃より高いと、溶媒の蒸気圧が高くなり好ましくない。
【００３８】
析出したポリアミド粒子は、溶液から遠心分離、濾過、デカンテイションなどの通常の方法で単離することができる。例えば、縣濁した溶液を、メタノールで希釈して、遠心分離に掛けてもよい。数回メタノールで洗浄して遠心分離に掛けてもよい。次に熱風乾燥、真空乾燥に供してもよい。
【００３９】
このようにして製造されたポリマー粒子は、均一な粒径の多孔質球状ポリアミド粒子となる。さらに、粒子径分布が狭くしたい時は、アルコール系、または水径で分級してもよい。
【００４０】
このようにして製造されたポリマー粒子は、また、ポリアミドの結晶化度は、ＤＳＣ測定より４０％以上である。
【００４１】
本発明の液晶表示用スペーサー粒子は、特定の比表面積と、特定の粒子径およびシャープな粒子径分布をもつ衝撃性に強い多孔質ポリアミド粒子からなる。
この多孔質粒子は、微細なフィブリル構造を単位として、フィブリルの方向が球状粒子の中心から伸びていて放射線状に成長している。この構造により球状粒子が圧縮を受けた場合、軸方向のフィブリルが衝撃エネルギーを吸収して、液晶表示板スペーサーとしての耐衝撃性が発現すると思われる。
【００４２】
【実施例】
以下、実施例により本発明を具体的に説明するが、本発明はこれらの実施例に限定されるものではない。また、粒子径、比表面積、結晶化度などの測定は次のように行った。
【００４３】
（平均粒子径、粒子径分布指数）
走査型電子顕微鏡で観察して、粒子形状と大きさとを観察した。球形粒子は粒子径を読みとった。１００個の数平均粒子径と体積平均粒子径とを観測し、粒子径分布指数（ＰＤＩ）を前出の式を用いて算出した。また、参考値として、標準偏差を算出し、次式により変動係数を求めた。
【数７】

ただし、σは標準偏差である。
【００４４】
（比表面積・多孔度指数）
ポリアミド粒子の比表面積は、窒素吸着によるＢＥＴ法で３点測定でおこなった。この値から、前に述べた式に従って多孔度指数を求めた。
【００４５】
（結晶化度）
ポリアミドの結晶化度は、ＤＳＣ（示差走査熱量計）で測定した。前述の方法で行った。
【００４６】
参考例１
ポリアミド６（分子量１３，０００）を、濃度５．０重量％ｍ−クレゾール溶液１４．３重量％とし、メタノール７１．４重量％と水１４．３重量％を混合し、ポリアミド溶液に、マグネチックスターラーで撹拌した。１分攪拌後、溶液は均一になった。撹拌を止め、静置して２分後に、ポリマーが析出してきた。さらに２４時間静置して、析出終了させた。その後遠心分離でポリマーを単離した。粒子特性結果を表１に示す。
【００４７】
参考例２
ポリアミド６（分子量１３，０００）を、濃度５．０重量％ｍ−クレゾール溶液１４．３重量％とし、メタノール７８．４重量％と水１４．３重量％を温度５℃で混合し、ポリアミド溶液に、マグネチックスターラーで撹拌した。１分攪拌後、溶液は均一になった。温度は室温で行った。撹拌を止め、静置して１分後に、ポリマーが析出してきた。さらに２４時間静置して、析出終了させた。その後遠心分離でポリマーを単離した。粒子結果を表１に示す。
【００４８】
【表１】

【００４９】
実施例１〜２
参考例１〜２で得られたポリアミド多孔質粒子を、ガラス基板上にほぼ均一に散布し （散布密度約２，５００個／ｃｍ² ）、この上に同じサイズのガラス基板を重ねた。このガラス基板の上から、重さ２００ｇの鋼球を高さ２０cmから落球させた後、破損した粒子の割合を光学顕微鏡により観測した。結果を表２に示す。
【００５０】
液晶表示セルの評価エポキシ系のシール用樹脂１００ｇに、参考例１〜２で得られたポリアミド多孔質粒子１ｇを分散させてインキ用組成物を調製した。得られたインキ組成物を、液晶表示装置用研磨ガラス基板上に透明電極、配向膜が形成された積層体の配向膜の周縁にスクリーン印刷機で印刷して、液晶表示装置用基板を得た。次に、エチルアルコール１リットルに、上記のようにして得られた参考例の粒子０．０１ｇを分散させ、この分散液を前記の液晶表示装置用基板上のシール用樹脂が設けられていない部分に参考例で得た粒子の分散密度が約２，５００個／ｃｍ² となるように噴霧した。次いで、この液晶表示装置用基板と、ガラス基板上に透明電極および配向膜が設けられてなる別の液晶表示装置基板とを、相互の透明電極が対向し、かつ上述したようにして分散された粒子１個当たりに約０．２ｇの荷重がかかるように加圧しながら約１５０℃の温度で貼り合わせ、セルを作成した。
【００５１】
このようにして得られたセルに、STN 液晶（メルク社製）を注入して、液晶表示パネルを得た。この得られた液晶表示パネルについてセルギャップ、色むらを評価した。セルギャップ干渉式膜厚計により複数箇所のセルギャップを測定して平均セルギャップおよびバラツキ（３σ）を求めた。また、色むら目視観察により色むらの有無を判定した。結果を表２に示す。
【００５２】
比較例１
平均粒子径５μｍの球状シリカを５倍量のエタノール−水−アンモニア水の混合液でシード粒子分散液を調製し、１％水酸化ナトリウム水溶液を加えた後、オートクレーブ中で１２０℃で保持した。さらに、ケイ酸液とエチルシリケートとアンモニアアルコール溶液を加えて溶液に分散させた後、徐々にケイ酸溶液とエチルシリケートを加えて、さらに１５０℃で１時間後保持した。さらに水力分級した。温度２００℃で乾燥してシリカ粒子を調製した。得られたシリカ粒子を実施例１と同様にスペーサー粒子としての評価を行った。結果を表２に示す。
【００５３】
【表２】

【００５４】
【発明の効果】
本発明は、大きな荷重、衝撃に耐える液晶用スペーサーに適したポリアミド球状多孔質粒子からなることを特徴とするものである。特定の粒子径および狭い粒子径分布を有し、電極間ギャップを保持し、耐熱性にも安定である液晶用スペーサー粒子を供給することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention has a specific particle size, has a narrow particle size distribution, can maintain a constant gap between electrodes, and is a polyamide porous spherical particle having a large specific surface area. The present invention relates to an excellent liquid crystal display spacer.
[0002]
[Prior art]
In a liquid crystal display device, a liquid crystal cell having a structure in which liquid crystal is sealed between a pair of transparent electrodes formed on a transparent substrate is used. The thickness of the liquid crystal layer is required to be as uniform as possible.
[0003]
For this reason, a spacer made of an insulator is interposed between the electrodes to maintain the uniformity of the gap between the electrodes. As such spacers, spherical, columnar, and fibrous materials made of inorganic compounds such as silica and alumina are known.
[0004]
Among these, when spherical particles are used as spacers, uniformity of particle size is required. For example, Japanese Patent Application Laid-Open No. 62-269933 discloses that a silica particle group having a coefficient of variation of 10% or less indicating the uniformity of particle diameter is used as a spacer.
[0005]
Japanese Patent Laid-Open No. 5-53122 discloses a spacer characterized in that a certain amount or more of agglomerated particles aggregated in a plane are mixed so that the spacer particles do not break even when a large load or impact is applied locally. Particles are disclosed.
[0006]
However, the mixture of aggregated particles and single particles increases non-uniformity and may cause color unevenness. Therefore, the spacer particles are spherical with no anisotropy, and there is no group of particles such as aggregates. Is preferred. Therefore, it is considered optimal for the spacer particles to have an even distribution of particle diameters and the ability to withstand impact on the particles themselves.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to supply spacer particles for liquid crystal display that do not break even under a large load and impact.
[0008]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventors have used a polyamide porous spherical particle having a specific particle size, a narrow particle size distribution, and a large specific surface area. Thus, the present inventors have found that liquid crystal display spacer particles having excellent impact properties can be obtained.
That is, the present invention relates to a spacer for liquid crystal display characterized by comprising polyamide porous spherical particles having a number average particle size of 1 to 30 μm and a ratio of the volume average particle size to the number average particle size of 1 to 1.2.
[0009]
The present invention is a liquid crystal display spacer characterized by having a BET specific surface area of 100 to 80,000 m ² / kg.
[0010]
The present invention is also a liquid crystal display spacer having a porosity index of 5 to 100.
[0011]
The present invention also provides a liquid crystal display spacer having a crystallinity measured by DSC of 40% or more.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the polyamide used in the present invention include various known ones. For example, it can be obtained by ring-opening polymerization of a cyclic amide or polycondensation of a dicarboxylic acid and a diamine. As monomers, polycondensation of amino acids such as crystalline polyamide obtained by ring-opening polymerization of cyclic amides such as ε-caprolactam and ω-laurolactam, ε-aminocaproic acid, ω-aminododecanoic acid, ω-aminoundecanoic acid, etc. Or dicarboxylic acids and derivatives such as succinic acid, adipic acid, sebacic acid, terephthalic acid, isophthalic acid, 1,4-cyclohexyldicarboxylic acid, and ethylenediamine, hexamethylenediamine, 1,4-cyclohexyldiamine, m-xylylenediamine, penta Those obtained by polycondensation of diamines such as methylenediamine and decamethylenediamine.
[0013]
The crystalline polyamide of the present invention is a crystalline polyamide comprising a homopolymer or a copolymer thereof or a derivative thereof. Specifically, polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 610, polyamide 66 / 6T (T represents a terephthalic acid component), and the like. Moreover, the mixture of the said polyamide may be sufficient. Particularly preferred are polyamide 6 and polyamide 66.
[0014]
The polyamide of the present invention has a molecular weight of 2,000 to 100,000. Preferably it is 5,000-40,000.
[0015]
The polyamide porous particles of the present invention are spherical particles. Preferably at least 90% by weight of the porous particles are spherical particles. More preferably, at least 98% by weight are spherical particles. If the amount of spherical particles is less than 90% by weight, the gap between the electrodes as a liquid crystal display spacer may not be constant, and density unevenness or color unevenness may occur in the display image.
[0016]
The spacer for liquid crystal display of the present invention is a polyamide porous spherical particle having a number average particle diameter of 1 to 30 μm. The number average particle diameter is preferably 1 to 25 μm. When the number average particle diameter is smaller than 1 μm, the handling operation becomes worse. If the number average particle size is larger than 30 μm, it is too large for a liquid crystal display spacer, which is inappropriate.
[0017]
The polyamide porous particle of the present invention relates to a polyamide porous spherical particle having a volume average particle diameter ratio to a number average particle diameter of 1 to 1.2. In the particle size distribution of the porous polyamide of the present invention, the ratio of the volume average particle size (or volume reference average particle size) to the number average particle size (or number reference average particle size) is 1 to 1.2. The ratio of the volume average particle diameter to the number average particle diameter is preferably 1 to 1.1. When the ratio of the volume average particle diameter to the number average particle diameter (particle size distribution index PDI) is larger than 1.2, the particle diameter distribution becomes wide and spacer particles having a uniform particle diameter cannot be obtained.
[0018]
The particle size distribution index is expressed by the following equation.
Number average particle size:
[Expression 1]

Volume average particle size:
[Expression 2]

Particle size distribution index:
[Equation 3]

Here, Xi: individual particle diameter, n is the number of measurements.
[0019]
Further, BET specific surface area of the polyamide porous spherical particles of the present invention is 100~80000m ² / kg, preferably, 1000~60000m ² / kg, more preferably, it is desirable that 3000~40000m ² / kg. If the specific surface area is less than 100 m ² / kg, the liquid crystal display spacer particles are not preferable because the impact resistance is poor. Moreover, it is difficult to handle when the specific surface area is 80000 m ² / kg.
[0020]
The porosity index (RI) of the polyamide porous spherical particles of the present invention is preferably 5 to 100. More preferably, the porosity index is 5 to 70. Here, the porosity index (RI) is defined as the ratio of the specific surface area of the porous spherical particles to the specific surface area of the smooth spherical particles having the same diameter. It can be expressed by the following formula. If the porosity index is less than 5, the degree of porosity is too low and the impact resistance effect of the spacer particles of the present invention is reduced. Since the shape becomes unstable if the porosity is larger than 100, the above range is preferable for the spacer for liquid crystal.
[0021]
[Expression 4]

Where RI: porosity index, S: specific surface area of porous particles [m ² / kg],
S ₀ : Specific surface area [m ² / kg] of smooth spherical particles having the same particle diameter.
S ₀ can be obtained according to the following equation.
That is, when the observed number average spherical particle diameter d _obs [m] and polyamide density ρ [kg / m ³ ], the specific surface area S ₀ of the smooth sphere can be expressed by the following equation.
[Equation 5]

Here, polyamide 6 and density crystal phase 1230kg / ^{m 3} of polyamide 66, an amorphous phase 1100 kg / ^{m 3,} the density was calculated from the degree of crystallinity.
[0022]
Moreover, the polyamide porous spherical particles of the present invention are crystalline and have a melting point of 110 to 320 ° C. Preferably, it is 140-280 degreeC. When the melting point is lower than 110 ° C., the thermal stability is lowered, which is not preferable.
[0023]
Furthermore, the polyamide porous spherical particles of the present invention preferably have a crystallinity of 40% or more as measured by DSC. There are a method for determining the crystallinity of polyamide by X-ray analysis, a method for determining by a DSC measurement method, and a method for determining from a density, and a method by a DSC measurement method is preferred. The crystallinity is preferably 40% or more. It is particularly preferable that the crystallinity is higher than 50%. The degree of crystallinity of the polyamide crystallized from the ordinary melt is at most about 30%. The polyamide of the present invention preferably has a crystallinity higher than 40%. It is particularly preferable that the crystallinity is higher than 45%. A crystallinity of less than 40% is not preferable because the porous particles become thermally unstable.
[0024]
The crystallinity of the polyamide is The heats of fusion of polyamide 6 and polyamide 66 were each calculated as 45 cal / g according to the description of Vieweg et al., Kunststoff IV polyamide, page 218, Carl Hanger Verlag, 1966. The degree of crystallinity is calculated from the following formula.
[Formula 6]

χ: Crystallinity (%)
ΔH _obs ; heat of fusion of sample (cal / g)
ΔH _m : heat of fusion of polyamide (cal / g)
[0025]
The spacer particles for liquid crystal display of the present invention are composed of porous polyamide particles having a specific specific surface area, a specific particle size, and a sharp particle size distribution and having high impact properties.
This is based on a fine fibril structure, and the fibril direction extends from the center of the spherical particle and grows in a radial pattern. When the spherical particles are compressed by this structure, the fibrils absorb the impact energy, and as a result, the impact resistance of the liquid crystal display panel is expected.
[0026]
The manufacturing method of the spacer particle | grains for liquid crystal displays of this invention is described.
The polyamide porous particles are produced by mixing a polyamide solution, a non-solvent of polyamide and water to form a uniform solution temporarily, and then depositing a polymer.
[0027]
As the solvent used for the polyamide solution, formic acid, aromatic alcohol solvents and the like are preferable.
Specifically, as the aromatic alcohol solvent, 0-cresol, m-cresol, p-cresol, chlorophenol, phenol and the like are preferable. These are preferable because they are partially compatible with water.
[0028]
The polyamide solution has a polyamide content of 0.1 to 30% by weight, preferably 0.2 to 25% by weight and a solvent of 99.9 to 70% by weight, preferably 99.8 to 75% by weight. 100% by weight. It is. If the proportion of polyamide exceeds 30% by weight, it may be difficult to dissolve or a uniform solution may not be obtained. Moreover, even if it melt | dissolves, since the viscosity of a solution will become high and it will become difficult to handle, it is unpreferable. If the proportion of polyamide is lower than 0.1% by weight, the polymer concentration is low and the productivity of the product is low, which is not preferable.
[0029]
The polyamide non-solvent is preferably one in which the solvent and water are at least partially compatible. Preferred are aliphatic alcohols and ketones having a boiling point of 100 ° C. or lower. In addition, it is important to be compatible with water. For example, methanol, ethanol, propanol, isopropanol, acetone, methyl ethyl ketone, or a mixture thereof is preferable.
[0030]
The addition ratio of the polymer non-solvent is preferably such that the total ratio of the non-solvent and water is greater than the addition ratio of the polymer solution.
If the addition ratio of the non-solvent of polyamide and water is smaller than the ratio of the polymer solution, the polymer may not be sufficiently precipitated, which is not preferable. On the other hand, when the amount is too large, the amount of the solvent in the finishing process increases too much, which is not economical.
[0031]
The weight percentage of the non-solvent of polyamide and water is preferably 2 to 90% by weight with respect to 100% by weight in total. Preferably, it is 5 to 85% by weight. When the proportion of water is less than 2% by weight, spherical particles are not formed. On the other hand, if the ratio of water is larger than 90% by weight, when aromatic alcohol is used as a solvent, water is not preferable because of phase separation.
[0032]
The addition order of the solution may be that the polyamide non-solvent is added to the polyamide solution, and then water is added. Alternatively, the polymer solution may be added after mixing the polyamide non-solvent and water. Further, after mixing water with the polymer solution, the polymer non-solvent may be added. It is preferred to add the polymer solution after mixing the polymer non-solvent and water. Any method may be used as long as the uniformity of the polymer solution system is maintained.
[0033]
It is important that the ratio of the polymer solution, the polymer non-solvent, and water is three. A uniform solution is formed and a time course is obtained to precipitate the polymer particles. The time for forming a uniform solution is, for example, about 0.1 second to 120 minutes. Even temporarily, it is important to form a uniform solution. If necessary, suitable stirring may be added.
[0034]
As a stirring method until the solution is uniform until it becomes a uniform solution, a method that makes the mixed solution uniform quickly is good. Unexpectedly, it can be seen that the size of the porous spherical particles obtained depends on the stirring method.
For example, in the case of a rotary stirrer such as a magnetic stirrer, porous spherical particles having a particle size of 5 to 15 μm are generated.
[0035]
Even with this different stirring method, the uniform particle size distribution is uniform, and the PDI is reduced to about 1 to 1.2 and further about 1 to 1.1. It depends on the size of the porous spherical particles depending on the difference in the stirring method during the period until the solution becomes uniform, and does not depend on the stirring method after the precipitation has started.
[0036]
If a uniform solution is formed, it is not necessary to stir, and it is preferable to leave it standing after the polyamide particles start to precipitate. Although it may be stirred, it does not seem to affect the shape and size of the polyamide particles.
[0037]
The temperature at which the polymer particles are precipitated from the uniform solution is preferably 5 to 70 ° C. Depending on the temperature, the composition range in which the solution becomes uniform may be widened. When the temperature is lower than 5 ° C., there may be a range of the solvent composition in which the uniform region becomes narrow. If the temperature is higher than 70 ° C., the vapor pressure of the solvent becomes high, which is not preferable.
[0038]
The precipitated polyamide particles can be isolated from the solution by usual methods such as centrifugation, filtration, and decantation. For example, a suspended solution may be diluted with methanol and centrifuged. It may be washed several times with methanol and centrifuged. Next, you may use for hot air drying and vacuum drying.
[0039]
The polymer particles thus produced become porous spherical polyamide particles having a uniform particle size. Furthermore, when the particle size distribution is desired to be narrowed, classification may be performed by alcohol or water size.
[0040]
The polymer particles thus produced also have a polyamide crystallinity of 40% or more based on DSC measurement.
[0041]
The spacer particles for liquid crystal display of the present invention are composed of porous polyamide particles having a specific specific surface area, a specific particle size, and a sharp particle size distribution and having high impact properties.
The porous particles have a fine fibril structure as a unit, and the fibril direction extends from the center of the spherical particles and grows in a radial pattern. When the spherical particles are compressed by this structure, the fibrils in the axial direction absorb the impact energy, and the impact resistance as the liquid crystal display panel spacer appears.
[0042]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. The particle diameter, specific surface area, crystallinity and the like were measured as follows.
[0043]
(Average particle size, particle size distribution index)
The particle shape and size were observed with a scanning electron microscope. The spherical particle size was read. 100 number average particle diameters and volume average particle diameters were observed, and a particle size distribution index (PDI) was calculated using the above formula. In addition, a standard deviation was calculated as a reference value, and a coefficient of variation was obtained by the following equation.
[Expression 7]

Where σ is a standard deviation.
[0044]
(Specific surface area / Porosity index)
The specific surface area of the polyamide particles was measured by three-point measurement by the BET method using nitrogen adsorption. From this value, the porosity index was determined according to the previously described equation.
[0045]
(Crystallinity)
The crystallinity of the polyamide was measured by DSC (differential scanning calorimeter). Performed in the manner described above.
[0046]
Reference example 1
Polyamide 6 (molecular weight: 13,000) was adjusted to a concentration of 5.0 wt% m-cresol solution 14.3 wt%, methanol 71.4 wt% and water 14.3 wt% were mixed, and the polyamide solution was magnetically mixed. Stir with a stirrer. After stirring for 1 minute, the solution became homogeneous. Stirring was stopped and the polymer was precipitated after 2 minutes of standing. Further, the mixture was allowed to stand for 24 hours to complete the precipitation. The polymer was then isolated by centrifugation. The particle characteristic results are shown in Table 1.
[0047]
Reference example 2
Polyamide 6 (molecular weight 13,000) was adjusted to a concentration of 5.0% by weight of m-cresol solution 14.3% by weight, 78.4% by weight of methanol and 14.3% by weight of water were mixed at a temperature of 5 ° C. to obtain a polyamide solution. The mixture was stirred with a magnetic stirrer. After stirring for 1 minute, the solution became homogeneous. The temperature was room temperature. Stirring was stopped and the polymer was deposited one minute after standing. Further, the mixture was allowed to stand for 24 hours to complete the precipitation. The polymer was then isolated by centrifugation. The particle results are shown in Table 1.
[0048]
[Table 1]

[0049]
Examples 1-2
The polyamide porous particles obtained in Reference Examples 1 and 2 were dispersed almost uniformly on a glass substrate (dispersion density of about 2,500 particles / cm ² ), and a glass substrate of the same size was stacked thereon. After dropping a steel ball having a weight of 200 g from a height of 20 cm on the glass substrate, the ratio of broken particles was observed with an optical microscope. The results are shown in Table 2.
[0050]
Evaluation of Liquid Crystal Display Cell An ink composition was prepared by dispersing 1 g of the polyamide porous particles obtained in Reference Examples 1 and 2 in 100 g of an epoxy-based sealing resin. The obtained ink composition was printed on the periphery of the alignment film of the laminate in which the transparent electrode and the alignment film were formed on the polishing glass substrate for the liquid crystal display device, and a liquid crystal display device substrate was obtained. . Next, 0.01 g of the particles of the reference example obtained as described above are dispersed in 1 liter of ethyl alcohol, and the dispersion liquid is a portion where the sealing resin on the liquid crystal display device substrate is not provided. The particles obtained in Reference Example were sprayed so that the dispersion density of the particles was about 2,500 particles / cm ² . Next, this liquid crystal display device substrate and another liquid crystal display device substrate in which a transparent electrode and an alignment film are provided on a glass substrate were dispersed with the transparent electrodes facing each other and as described above. The cells were made by bonding at a temperature of about 150 ° C. while applying pressure so that a load of about 0.2 g per particle was applied.
[0051]
STN liquid crystal (manufactured by Merck & Co., Inc.) was injected into the cell thus obtained to obtain a liquid crystal display panel. The obtained liquid crystal display panel was evaluated for cell gap and color unevenness. The cell gap at a plurality of locations was measured with a cell gap interference type film thickness meter to determine the average cell gap and variation (3σ). Moreover, the presence or absence of color unevenness was determined by visual observation. The results are shown in Table 2.
[0052]
Comparative Example 1
A seed particle dispersion was prepared with a 5 times amount of ethanol-water-ammonia water mixture of spherical silica having an average particle size of 5 μm, 1% aqueous sodium hydroxide solution was added, and the mixture was kept at 120 ° C. in an autoclave. Further, a silicic acid solution, ethyl silicate, and an ammonia alcohol solution were added and dispersed in the solution, and then the silicic acid solution and ethyl silicate were gradually added, and further maintained at 150 ° C. for 1 hour. Furthermore, the hydro classification was performed. Silica particles were prepared by drying at a temperature of 200 ° C. The obtained silica particles were evaluated as spacer particles in the same manner as in Example 1. The results are shown in Table 2.
[0053]
[Table 2]

[0054]
【The invention's effect】
The present invention is characterized by comprising polyamide spherical porous particles suitable for a spacer for liquid crystal that can withstand a large load and impact. It is possible to supply liquid crystal spacer particles having a specific particle size and a narrow particle size distribution, maintaining a gap between electrodes, and being stable in heat resistance.

Claims (4)

A spacer for liquid crystal display, comprising a porous polyamide spherical particle having a number average particle size of 1 to 30 μm and a ratio of a volume average particle size to a number average particle size of 1 to 1.2. The spacer for liquid crystal display according to claim 1, which has a BET specific surface area of 100 to 80,000 m ² / kg. The spacer for liquid crystal display according to claim 1 or 2, wherein the porosity index is 5 to 100. 4. The liquid crystal display spacer according to claim 1, wherein the degree of crystallinity measured by DSC is 40% or more.