JP3545445B2 - Light diffusion film - Google Patents
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- JP3545445B2 JP3545445B2 JP01695694A JP1695694A JP3545445B2 JP 3545445 B2 JP3545445 B2 JP 3545445B2 JP 01695694 A JP01695694 A JP 01695694A JP 1695694 A JP1695694 A JP 1695694A JP 3545445 B2 JP3545445 B2 JP 3545445B2
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Description
【０００１】
【産業上の利用分野】
本発明は、光拡散フィルムに関し、特に液晶表示のバックライト用に適する高拡散性で安価な光拡散フィルムに関するものである。
【０００２】
【従来の技術】
従来、液晶表示のバックライト用光拡散板としては、ポリメチルメタクリレート樹脂、ポリカーボネート樹脂等の光透過性樹脂の表面に凹凸を形成することによって得られている。しかしながらこれらの処理だけでは充分な光拡散性を得ることは困難であった。
また光拡散剤に炭酸カルシウムを用いた光拡散板として、特開昭５０−１４６６４６号公報、特開昭６０−１７５３０３号公報、特開昭６１−４７６２号公報、特開平３−７８７０１号公報と数多く提案されており、これらは全て光透過性樹脂中に炭酸カルシウム等の光拡散剤を配合分散させた組成物でシートを形成するものである。
しかしながら、本発明のような光透過性樹脂中に炭酸カルシウム等の光拡散剤を配合分散させた組成物を基材表面に塗布した光拡散フィルムについてはなにも提案されていない。
【０００３】
【発明が解決しようとする課題】
従来の光透過性樹脂中に炭酸カルシウム等の拡散剤を配合分散させた組成物でシートを形成する光拡散板では、支持体が無いために厚みを薄く出来ないという問題があった。また拡散剤をあまり多く配合すると光拡散板の強度が著しく小さくなるので、高拡散性を得るためにもある一定以上の厚さが必要となってしまうという問題があった。
また、従来のものの中には、たとえば特開平１−１７２８０１に提案されているシリコーン樹脂粒子を光拡散剤として配合分散させた組成物をフィルム基材に塗布したものでは光学特性や耐候性が劣るという問題がある。
本発明はかかる問題点を克服し、薄型で、高拡散性があり、低コストで、耐候性に優れた光拡散フィルムを提供することを目的とする。
【０００４】
【課題を解決するための手段】
本発明は上記目的を達成せんと鋭意研究を行った結果、一定範囲の適合量の炭酸カルシウム等の光拡散剤を光透過性樹脂中に配合分散した組成物をフィルム基材上に塗布することにより上記目的を達成できることを見いだした。その手段は次のとおりである。
（１）基材上の片面ないしは両面に光拡散層をコーティングした構成からなり、該光拡散層はポリエステル系重合体５０重量部に対して塩化ビニル−酢酸ビニル共重合体を１０〜１００重量部含むバインダー中に、微粉状炭酸カルシウムあるいは微粉状シリカのいずれか一方ないしは混合物からなる拡散剤を、該バインダー１００重量部に対して１０〜１５０重量部配合分散した組成物からなり、該基材はポリエステルからなる、ことを特徴とする液晶表示のバックライト用光拡散フィルム。
（２）前記基材において、該基材の片面ないしは両面にエンボス処理があることを特徴とする光拡散フィルム。
（３）前記基材において、該基材がポリエチレンテレフタレートであることを特徴とする光拡散フィルム。
【０００５】
【作用】
本発明によれば、ポリエチレンテレフタレート等のフィルム基材に炭酸カルシウムやシリカといった比較的安価な光拡剤を用いて、光拡散層がコーティング方式によって形成されるため、拡散板の強度を下げることなく拡散剤の濃度を高く設定することが可能となり、ヘイズが８５％以上を目標とする光拡散フィルムを比較的低コストで得ることができる。且つ拡散層の厚みを拡散板の中に光拡散剤を練り込むタイプに比べて薄くできる。
以上から、単位面積当たりの光の拡散効率が良くなり、また拡散層の厚さをコントロールすることによって光の全光透過率を容易に変えることができる。
【０００６】
【構成】
本発明の要旨は透明なフィルム基材に高い光拡散性のあるコート層を設けることであり、基材と光拡散層について説明する。
本発明における光拡散層としてポリエステル系共重合体５０重量部に対して塩化ビニル−酢酸ビニル共重合体０〜１００重量部を含むバインダーを用いるのは基材にコーティングし易い樹脂であるためである。特にポリエステル基材に用いる時には、ポリエステル系重合体を含んでいると密着しやすいためである。また、塩化ビニル−酢酸ビニル共重合体はブロッキング防止のためである。
本発明における基材としては、ポリエチレンテレフタレートフィルムやポリカーボネートフィルム等が使用されるが、拡散層のバインダー樹脂との接着性、透明度、機械的強度及びコストの点からポリエチレンテレフタレートが最適である。基材にあらかじめエンボスあるいはサンドブラスト加工を片面あるいは両面に施したものを使用すれば、全光線透過率を一層高めることができる。
基材の厚みは薄いほど全光透過率が小さくなり好ましいが、取扱の点から５０μｍ以上が望ましい。
光拡散剤は上記のようにバインダー樹脂１００重量部中に微粉状炭酸カルシウム或いは微粉状シリカのいずれか一方ないしは混合物を１０〜１５０重量部配合分散するが、拡散剤が１５０重量部以上になると全光線透過率が低くなりすぎてディスプレー画面が暗くなってしまう。逆に１０重量部以下だとヘイズが小さくなり光拡散性が低下してしまい視角が限定されてしまう。バインダー６０重量部に対して光拡散剤４０重量部が望ましい。かかる配合分散によって得られる組成物の基材上へのコーティングはディピング法、カーテンフロー法、ロールコート法、ナイフコート法等が使用できるが、該組成物の粘度、目的とする皮膜厚さ、基材の表面状態等を勘案して最適なものを選んで行う。
【００１１】
【実施例】
（１）光学特性評価
巾３ｃｍ，長さ６ｃｍのサンプルをスガ試験機（株）社製ＳＭカラーコンピューターによって全光線透過率、拡散透過率、平行透過率及びヘイズについて測定した。
（２）実施例及び比較例
以下表１、表２に実施例及び比較例をあげて説明する。
基材には、帝人（株）製ポリエチレンテレフタレートフィルムＨＳタイプ、厚さ、２５〜１００μｍを採用した。
ポリエステル樹脂には東洋紡（株）製バイロン２００を採用した。
基材の厚みは、実施例１〜４に示すように、厚みが増すと吸収により全光線透過率が小さくなる傾向がみられる。
光拡散層のバインダーは、ポリエステル５０重量部に対して、塩化ビニル−酢酸ビニル共重合体を１０−１００重量部含むことが必要であるが、比較例１〜３及び実施例１から、塩化ビニル−酢酸ビニル共重合体が少ないとコーティング時にブロッキングを起こし易く、逆に多いと耐候性等が低下し易いので、ポリエステル５０重量部に対して塩化ビニル−酢酸ビニル共重合体を５０重量部含む事が望ましい。
光拡散剤のバインダー樹脂にたいする配分比Ｐ／Ｖは、実施例１、５、６から上記のように４０／６０が望ましい。
分散剤としては、０．１〜１０μの範囲にある微粉状の炭酸カルシウムとシリカを使用した。実施例７に示すように炭酸カルシウム単独で使用することも可能であるが、実施例１に示すように炭酸カルシウムとシリカを９／１の重量比で併用しても、良好な光拡散性を得ることができる。
光拡散組成物の混練時間は、実施例１、１０に示すように、３０分以上が望ましく、他の実施例では６０分とした。該組成物のコーティングには、３本リバースロールコート法によって行い、溶剤にトルエン／メチルエチルケトンを２／１の比で用い、組成物粘度をザーンカップ＃０３で２０〜３０秒に調整した。
実施例１、８に示すように、コーティング量によっては、ヘイズはほとんど変化が見られないが全光線透過率はコーティング量の少ないほど大きい。
また、光拡散層を基材の片面ないしは両面に設けたが、実施例８、９に示すように、総塗布量が同一の場合、両面のほうが片面よりも全光透過率は低いがヘイズは高い。
【００１２】
【表１】
【表２】
【発明の効果】
本発明により薄型で光拡散性が高く、比較的低コストの光拡散フィルムを得ることが出来、液晶表示のバックライト用として効果的である。[0001]
[Industrial applications]
The present invention relates to a light-diffusing film, and more particularly to a high-diffusion and inexpensive light-diffusing film suitable for a backlight of a liquid crystal display.
[0002]
[Prior art]
BACKGROUND ART Conventionally, a light diffusion plate for a backlight of a liquid crystal display has been obtained by forming irregularities on the surface of a light transmitting resin such as a polymethyl methacrylate resin or a polycarbonate resin. However, it was difficult to obtain sufficient light diffusing properties only by these treatments.
As light diffusing plates using calcium carbonate as a light diffusing agent, JP-A-50-146646, JP-A-60-175303, JP-A-61-4762, and JP-A-3-78701 disclose a light-diffusing plate. Many proposals have been made, all of which are to form a sheet with a composition in which a light diffusing agent such as calcium carbonate is mixed and dispersed in a light transmitting resin.
However, there is no proposal for a light-diffusing film in which a composition in which a light-diffusing agent such as calcium carbonate is mixed and dispersed in a light-transmitting resin as in the present invention is applied to the surface of a substrate.
[0003]
[Problems to be solved by the invention]
A conventional light diffusing plate which forms a sheet with a composition in which a diffusing agent such as calcium carbonate is mixed and dispersed in a light transmissive resin has a problem that the thickness cannot be reduced due to the lack of a support. Also, if too much diffusing agent is mixed, the strength of the light diffusing plate is significantly reduced, so that a certain thickness or more is required to obtain high diffusivity.
Further, among conventional products, for example, when a composition prepared by mixing and dispersing silicone resin particles as a light diffusing agent proposed in Japanese Patent Application Laid-Open No. 1-172801 is applied to a film substrate, optical properties and weather resistance are inferior. There is a problem.
An object of the present invention is to provide a light diffusion film which is thin, has high diffusivity, is low in cost, and has excellent weather resistance, overcoming such problems.
[0004]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present invention applies a composition in which a light diffusing agent such as calcium carbonate in a certain range is mixed and dispersed in a light transmitting resin onto a film substrate. It has been found that the above purpose can be achieved by the above. The means are as follows.
(1) A light diffusion layer is coated on one or both surfaces of a substrate, and the light diffusion layer is composed of 50 to 100 parts by weight of a polyester polymer and 10 to 100 parts by weight of a vinyl chloride-vinyl acetate copolymer. in a binder containing part, a diffusing agent composed of either one or a mixture of finely powdered calcium carbonate or finely divided silica, consist composition 10 to 150 parts by weight blended dispersion with respect to the binder 100 parts by weight, the substrate Is a light diffusion film for a backlight of a liquid crystal display, comprising polyester .
(2) The light diffusing film, wherein the substrate has an embossing treatment on one or both sides of the substrate.
(3) The light diffusing film, wherein the substrate is polyethylene terephthalate.
[0005]
[Action]
According to the present invention, a relatively inexpensive light spreader such as calcium carbonate or silica is used for a film base such as polyethylene terephthalate, and the light diffusion layer is formed by a coating method, without reducing the strength of the diffusion plate. It becomes possible to set the concentration of the diffusing agent to be high, and it is possible to obtain a light diffusing film having a haze of 85% or more at a relatively low cost. In addition, the thickness of the diffusion layer can be made smaller than that of a type in which a light diffusing agent is kneaded in a diffusion plate.
As described above, the light diffusion efficiency per unit area is improved, and the total light transmittance of light can be easily changed by controlling the thickness of the diffusion layer.
[0006]
【Constitution】
The gist of the present invention is to provide a transparent film substrate with a coat layer having a high light diffusion property. The substrate and the light diffusion layer will be described.
The reason why the binder containing 0 to 100 parts by weight of the vinyl chloride-vinyl acetate copolymer with respect to 50 parts by weight of the polyester copolymer is used as the light diffusion layer in the present invention is because the resin is easily coated on the base material. . In particular, when used for a polyester base material, it is easy to adhere to a polyester-based polymer if it contains a polyester-based polymer. The vinyl chloride-vinyl acetate copolymer is for preventing blocking.
As the substrate in the present invention, a polyethylene terephthalate film, a polycarbonate film, or the like is used, and polyethylene terephthalate is most suitable from the viewpoints of adhesion to the binder resin of the diffusion layer, transparency, mechanical strength, and cost. If the substrate is preliminarily embossed or sandblasted on one or both sides, the total light transmittance can be further increased.
As the thickness of the substrate is smaller, the total light transmittance is preferably smaller, but it is preferably 50 μm or more from the viewpoint of handling.
The light diffusing agent disperses 10 to 150 parts by weight of one or a mixture of fine powdered calcium carbonate and fine powdered silica in 100 parts by weight of the binder resin as described above. The light transmittance becomes too low and the display screen becomes dark. Conversely, if the amount is less than 10 parts by weight, the haze is reduced, the light diffusivity is reduced, and the viewing angle is limited. 40 parts by weight of the light diffusing agent is desirable for 60 parts by weight of the binder. The composition obtained by such compounding and dispersion can be coated on a substrate by a dipping method, a curtain flow method, a roll coating method, a knife coating method, etc., and the viscosity of the composition, the intended film thickness, The best thing is selected by considering the surface condition of the material.
[0011]
【Example】
(1) Evaluation of Optical Properties A sample having a width of 3 cm and a length of 6 cm was measured for total light transmittance, diffuse transmittance, parallel transmittance, and haze by an SM color computer manufactured by Suga Test Instruments Co., Ltd.
(2) Examples and Comparative Examples Tables 1 and 2 show examples and comparative examples.
As the substrate, a polyethylene terephthalate film HS type, manufactured by Teijin Limited, having a thickness of 25 to 100 μm was used.
Byron 200 manufactured by Toyobo Co., Ltd. was used as the polyester resin.
As shown in Examples 1 to 4, the thickness of the base material tends to decrease the total light transmittance due to absorption as the thickness increases.
It is necessary that the binder of the light diffusion layer contains 10 to 100 parts by weight of the vinyl chloride-vinyl acetate copolymer with respect to 50 parts by weight of the polyester. -If the amount of the vinyl acetate copolymer is small, blocking tends to occur at the time of coating, and if the amount is large, the weather resistance and the like are apt to be reduced. Is desirable.
From Examples 1, 5, and 6, the distribution ratio P / V of the light diffusing agent to the binder resin is preferably 40/60 as described above.
As the dispersant, fine powder calcium carbonate and silica in the range of 0.1 to 10 μm were used. Although it is possible to use calcium carbonate alone as shown in Example 7, even if calcium carbonate and silica are used in a weight ratio of 9/1 as shown in Example 1, good light diffusivity is obtained. Obtainable.
As shown in Examples 1 and 10, the kneading time of the light diffusion composition is desirably 30 minutes or more, and is set to 60 minutes in other examples. The coating of the composition was carried out by a triple reverse roll coating method, using toluene / methyl ethyl ketone as a solvent in a ratio of 2/1, and adjusting the composition viscosity to 20 to 30 seconds with Zahn Cup # 03.
As shown in Examples 1 and 8, the haze hardly changes depending on the coating amount, but the total light transmittance increases as the coating amount decreases.
In addition, the light diffusion layer was provided on one side or both sides of the substrate, but as shown in Examples 8 and 9, when the total coating amount was the same, the total light transmittance of both sides was lower than that of one side, but the haze was lower. high.
[0012]
[Table 1]
[Table 2]
【The invention's effect】
According to the present invention, it is possible to obtain a light-diffusing film which is thin, has high light-diffusing properties, and is relatively inexpensive, and is effective for a backlight of a liquid crystal display.
Claims (3)
該光拡散層はポリエステル系重合体５０重量部に対して塩化ビニル−酢酸ビニル共重合体を１０〜１００重量部含むバインダー中に、微粉状炭酸カルシウムあるいは微粉状シリカのいずれか一方ないしは混合物からなる拡散剤を、該バインダー１００重量部に対して１０〜１５０重量部配合分散した組成物からなり、
該基材はポリエステルからなる、
ことを特徴とする液晶表示のバックライト用光拡散フィルム。 It consists of a structure in which a light diffusion layer is coated on one or both sides of the substrate,
Vinyl chloride relative to the light diffusion layer is polyester-based polymer 50 parts by weight - vinyl acetate copolymer in a binder comprising 1 0-100 parts by weight, from either one or a mixture of finely powdered calcium carbonate or finely divided silica the becomes diffusing agent consists 10 to 150 parts by weight of formulation dispersed composition with respect to the binder 100 parts by weight,
The substrate is made of polyester,
A light diffusion film for a backlight of a liquid crystal display , characterized in that:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP01695694A JP3545445B2 (en) | 1994-01-18 | 1994-01-18 | Light diffusion film |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP01695694A JP3545445B2 (en) | 1994-01-18 | 1994-01-18 | Light diffusion film |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH07209502A JPH07209502A (en) | 1995-08-11 |
| JP3545445B2 true JP3545445B2 (en) | 2004-07-21 |
Family
ID=11930570
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP01695694A Expired - Fee Related JP3545445B2 (en) | 1994-01-18 | 1994-01-18 | Light diffusion film |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3545445B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1312942A4 (en) | 2000-07-18 | 2006-10-25 | Omron Tateisi Electronics Co | Light diffusing films |
| JP2010239021A (en) * | 2009-03-31 | 2010-10-21 | Koha Co Ltd | Light source module |
-
1994
- 1994-01-18 JP JP01695694A patent/JP3545445B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH07209502A (en) | 1995-08-11 |
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