JP4830461B2 - Manufacturing method of antireflection material - Google Patents

Description

  The present invention relates to an antireflective composition having a high transmittance and a low refractive index, which is applied on an optical film substrate, and an antireflective material and a display using the composition.

Antireflection coating layers for various displays such as liquid crystal displays (LCD), cathode ray tube displays (CRT), plasma displays (PDP), electroluminescent displays (EL), lenses for optical components, screens, etc. Thin films are known.
Low reflection thin films and antireflection thin films are generally known to be composed of multilayer films and have low residual reflectance. In the case of a multilayer film, the manufacturing method uses a method such as a vacuum vapor deposition method, a dip coating method, etc., which is complicated, low in productivity, high in cost, and economically problematic.

  On the other hand, a configuration composed of two or one coating layer is also known, and this configuration has the disadvantage that the cost is low and mass production is easy but the residual reflectance is high.

  In order to solve this problem, various low refractive index coating layers have been developed. Silica is a material having a relatively low refractive index, has excellent light transmittance in a wide wavelength range, and can obtain a lower refractive index material by introducing voids in silica. There is an example of a method for producing a low refractive index thin film using porous silica fine particles (see Patent Documents 1, 2, and 3).

Japanese Patent Laid-Open No. 2001-115028 JP-A-6-299091 JP-A-3-199043

  However, the above method example has the following problems. In the said patent document 1, the high temperature heating is required in the case of post-processing, and preparation of a low refractive index thin film with respect to a film is difficult. In Patent Document 2, the stability of the system is poor by mixing an acidic hydrolyzate of silica and a salt hydrolyzate, and a precipitate may be deposited if left to stand. In Patent Document 3, there is a problem that the thin film swells or peels off from the substrate when the pore-opening agent is extracted.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art and provide a stable silica composition capable of forming a low refractive index and low reflection layer on a substrate such as a transparent film. Moreover, it aims at setting it as the anti-reflective material using it.

The invention of claim 1 is: (1) Centrifugating a transparent silica precursor obtained by acidic hydrolysis of an alkoxysilane having two or more hydrolyzable functional groups in an organic solvent. Removing the supernatant liquid;
(2) centrifuging the acidic silica particle dispersion and removing the supernatant;
(1) stirring the supernatant of the silica precursor and (2) the supernatant of the acidic silica particle dispersion to obtain a low refractive index composition;
A step of coating and heating the low refractive index composition on a substrate to form a low refractive index layer;
In order, the manufacturing method of the antireflective material characterized by the above-mentioned.

The invention according to claim 2 is the method for producing an antireflection material according to claim 1 , wherein the refractive index of the low refractive index layer is within 1.2 to 1.3.

A third aspect of the present invention is the method for producing an antireflection material according to the first or second aspect, wherein a hard coat layer is provided between the substrate and the low refractive index layer .

  The low refractive index composition of the present invention can easily and efficiently form a thin film having a low absolute reflectance by coating, and the obtained thin film has a low refractive index of 1.2 to 1.3. The silica composition of the present invention is characterized in that no precipitate is deposited when left for a long time (one week). That is, the stability of the silica composition of the present invention is good. For this reason, when applied to an antireflection coating agent, a stable low refractive index film can be obtained.

  The alkoxysilane in the transparent silica precursor obtained by acidic hydrolysis of an alkoxysilane having two or more hydrolyzable functional groups in an organic solvent according to the present invention (1) is bifunctional. Those having a group or a trifunctional group or higher functional group can be used.

  Examples of trifunctional alkoxysilanes include trimethoxylane, triethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, and isobutyltrimethoxy. Examples include silane, isobutyltriethoxysilane, cyclohexyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, and allyltriethoxysilane. In the present invention, incomplete hydrolysis products of trifunctional alkoxysilanes may be used as raw materials.

  Bifunctional alkoxysilanes include dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, dimethyldi (n-propoxy) silane, dimethyldi (iso-propoxy) silane, and dimethyldi (n-propoxy) silane. , Dimethyldi (sec-butoxy) silane, dimethyldi (tert-butoxy) silane, dimethyldi (sec-butoxy) silane, diethyldi (n-propoxy) silane, diethyldi (iso-propoxy) silane, diethyldi (n-propoxy) silane, diethyldi Examples include (sec-butoxy) silane, diethyldi (tert-butoxy) silane, diethyldi (sec-butoxy) silane, and the like, but not limited thereto.

  As the organic solvent for acidic hydrolysis, alcohols such as methanol, ethanol and isopropyl alcohol, ethers such as ethyl ether, esters such as ethyl acetate, and ketones such as methyl ethyl ketone can be used.

  Moreover, an acidic catalyst can be included. Examples of the acidic catalyst include inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, tripolyphosphoric acid, and phosphonic acid. Organic acids include acetic acid, butanoic acid, pentanoic acid, hexanoic acid, octanoic acid, meritic acid, nonanoic acid, maleic acid, sebamic acid, stearic acid, methylmalonic acid, shikimic acid, linoleic acid, salicylic acid, benzoic acid, p -Aminobenzoic acid, p-toluenesulfonic acid, benzenesulfonic acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, trifluoroacetic acid, formic acid, sulfonic acid, phthalic acid, citric acid, succinic acid, tartaric acid, isonicotinic acid, etc. be able to.

(2) The acidic silica particle dispersion is a silica particle dispersion that is stable at a pH of 7.0 or less.
In the present invention, by using this acidic silica particle dispersion, the stability is higher than in the case of using an alkaline silica particle dispersion, and it does not deteriorate even when stored for a long period of time.
This acidic silica particle dispersion contains silica fine particles having a particle diameter of 15 to 80 nm. Examples include acidic nanoporous silica dispersion and acidic silica sol. Specific examples include nanoporous silica manufactured by Sumitomo Osaka Cement Co., Ltd., Snowtex OS manufactured by Nissan Chemical Industries, Ltd., Snowtex PS-MO, Snowtex OUP, and the like.

  The stable low refractive index composition of the present invention comprises a transparent silica precursor obtained by acidic hydrolysis of the alkoxysilane in an organic solvent and an acidic silica particle dispersion, and is stirred at room temperature for 3 to 4 hours. After that, a low refractive index layer can be formed by applying to a substrate, heating and drying at 80 to 120 ° C., and curing.

The refractive index of the low refractive index layer to be formed varies depending on the film thickness, the kind of components used, the ratio of the transparent silica precursor and the acidic silica particle dispersion, and the like. When light is incident vertically, the single layer of the low refractive index layer has the lowest reflectance at the incident wavelength when the condition given by the film thickness = 1/4 wavelength is satisfied.
Usually, the film thickness at this time is preferably about 100 nm in order to design so as to have a minimum value at a wavelength of about 550 nm with high human visibility. As the porosity of the thin film increases, the refractive index decreases. For this reason, in addition to the difference in shrinkage rate, it is preferable that the ratio of the porous acidic silica particles is high, and it is particularly preferable that the ratio of the silica particles is 70 to 90%. Furthermore, since a large amount of solvent is evaporated, a large number of pores are included, and the refractive index of the thin film is lowered. Therefore, the amount of the solid component may be 0.5 to 5.0% ((wt%)). preferable.

Further, a contamination inhibitor may be mixed in the low refractive index composition of the present invention. By using the antifouling agent, when it is provided on the front surface of the display as an antireflection material, it can be easily removed when it is protected or contaminated from dirt.
Although it does not specifically limit as a pollution inhibitor, The compound etc. which contain a fluorine and silicon can be used conveniently.
In particular, an alkoxysilane compound having a perfluoro group can be used.

  In this invention, it can be set as an antireflection material by apply | coating the above-mentioned low refractive index composition on a base material, and forming a low refractive index layer.

The substrate is preferably transparent. Such as cellulose triacetate (TAC) film, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyamide (PA), polycarbonate (PC), polyacryl (PMMA), nylon (Ny), Examples thereof include plastic film base materials such as polyethersulfone (PES), polyvinyl chloride (PVC), and polypropylene (PP), and glass base materials.
In addition, when using it as the antireflection material used for the surface of LCD, it is preferable to use a TAC film in the point of an optical characteristic.

  It is also possible to use an organic polymer constituting the plastic film base material containing a known additive such as an ultraviolet absorber, a plasticizer, a lubricant, a colorant, an antioxidant, a flame retardant and the like. . The film substrate 2 may be a single layer or a laminate of a plurality of organic polymers. Moreover, although the thickness is not specifically limited, 50-200 micrometers is preferable.

A hard coat layer may be provided between the base material and the low refractive index layer.
The hard coat layer is not particularly limited as long as it has high transparency and improves the surface hardness and mechanical strength of the antireflection material, and a known one can be used.

  The hard coat layer can be made of curable resin or thermosetting resin by ionizing radiation or ultraviolet irradiation. An organosilicon resin, a thermosetting polysiloxane resin, or the like is preferable. If the film thickness is in the range of 3 to 20 μm, sufficient mechanical strength is exhibited. However, from the viewpoint of transparency, coating accuracy, and handling, the range of 5 to 15 μm is more preferable.

In addition, a functional additive may be added to the hard coat layer in order to impart functions such as antiglare property and antistatic property.
In order to impart antiglare properties, for example, acrylic resin particles or silica particles having a particle size of about 0.1 to 10 μm can be used.
In order to impart antistatic properties, conductive particles such as zinc oxide-based particles, tin-indium composite oxide (ITO) particles, tin oxide-based particles, and antimony oxide-based particles can be used.

  The antireflection material thus obtained can be used by being attached to the front surface of various displays such as LCD, CRT, PDP and EL.

<Example 1>
(Preparation of transparent silica precursor)
In a sealed glass container, 0.05 mol tetraethoxylane, 20.0 g isopropyl alcohol, 0.12 g 1.0N hydrochloric acid and 0.62 g water were mixed and stirred for 2 days. The obtained liquid was centrifuged at 5000 rpm for 10 minutes, and the supernatant was removed to obtain a transparent silica precursor.

(Pretreatment of acidic silica dispersion)
20.0 g acidic silica dispersion liquid Snowtex OUP manufactured by Nissan Chemical Industries, Ltd. was centrifuged at 5000 rpm for 10 minutes, and the supernatant was taken to obtain a 17.0 g dispersion liquid.

(Preparation of low refractive index composition)
In a sealed glass container, 2.0 g of the transparent silica precursor, 1.5 g of the acidic silica dispersion, and 6.0 g of the solvent isopropyl alcohol were mixed and stirred for 3 hours. The composition was left for 6 hours to obtain a low refractive index composition. The low refractive index composition was stable, and no precipitate was deposited even after being left for 1 week.

(Formation of antireflection material)
1.5 ml of the obtained low refractive index composition was dropped on the surface of a triacetylcellulose film substrate (manufactured by Fuji Film Co., Ltd.), and a film was formed at room temperature under a rotation of 3000 rpm by a spin coating method. An antireflection material was obtained by drying and fixing at 80 ° C. for 15 minutes to form a low refractive index layer. The film thickness of the obtained low refractive index layer was 0.14 μm.

Next, the absolute reflectance of the obtained antireflection material at an incident angle of 8 ° was measured. The absolute reflectance was measured at an incident angle of 8 ° using a UV-Vis spectrophotometer UV-2400 manufactured by Shimadzu Corporation.
As a result of the measurement, the minimum reflectance was shown at 560 nm, and in the case where there was no low refractive index layer, what was 4.3% was suppressed to 0.3%. The refractive index of the low refractive index layer was 1.28.
The chromatic dispersion at this time is shown in FIG.

<Comparative Example 1>
In Example 1, instead of the acidic silica particle dispersion, 5.0 g of tetraethoxysilane, 41.4 g of isopropyl alcohol, and 1.46 g of 25% aqueous ammonia are placed in a sealed glass container and left at room temperature for 4 days. A low refractive index composition was obtained in the same manner as in Example 1 except that the dispersed colloidal silica dispersion was centrifuged at 5000 rpm for 10 minutes, and the supernatant was removed and a transparent colloidal silica dispersion was used.
When the low refractive index composition was allowed to stand for 2 days, a precipitate was observed. The supernatant was taken and 1.5 ml was dropped on the TAC surface, and a film was formed at room temperature by spin coating at 3000 rpm. It was dried and fixed at 80 ° C. for 15 minutes to form a low refractive index layer to obtain an antireflection material.
When the absolute reflectance measurement at an incident angle of 8 ° of the obtained antireflection material was measured in the same manner as in Example 1, it showed a minimum reflectance at 560 nm, which was 0.8%, and the refractive index of the low refractive index layer. Was 1.35.

<Example 2>
In Example 1, the low refractive index composition was obtained by performing the same operation as in Example 1 except that Snowtex PS-MO manufactured by Nissan Chemical Industries, Ltd. was used as the acidic silica particle dispersion. The low refractive index composition solution did not precipitate even after being allowed to stand for 1 week.
Thereafter, an antireflection material was obtained by the same operation as in Example 1, and the absolute reflectance measurement at an incident angle of 8 ° was measured in the same manner as in Example 1. As a result, the minimum reflectance was shown at 560 nm, which was 0.4%. The refractive index of the low refractive index layer was 1.29.

<Example 3>
In Example 1, the same operation as in Example 1 was performed except that Snowtex OS manufactured by Nissan Chemical Industries, Ltd. was used as the acidic silica particle dispersion, and methyl ethyl ketone was used as the solvent. Obtained. The low refractive index composition did not precipitate even after being allowed to stand for 1 week.
Thereafter, an antireflection material was obtained by the same operation as in Example 1, and the absolute reflectance measurement at an incident angle of 8 ° was measured in the same manner as in Example 1. As a result, the minimum reflectance was shown at 560 nm, which was 0.4%. The refractive index of the low refractive index layer was 1.29.

It is a spectrum figure which shows the reflectance of the base material in Example 1, and an antireflection material.

Claims (3)

(1) a step of centrifuging a transparent silica precursor obtained by acidic hydrolysis of an alkoxysilane having two or more hydrolyzable functional groups in an organic solvent and taking a supernatant;
(2) centrifuging the acidic silica particle dispersion and removing the supernatant;
(1) stirring the supernatant of the silica precursor and (2) the supernatant of the acidic silica particle dispersion to obtain a low refractive index composition;
A step of coating and heating the low refractive index composition on a substrate to form a low refractive index layer;
In order. The manufacturing method of the antireflection material characterized by the above-mentioned. The method for producing an antireflection material according to claim 1, wherein the low refractive index layer has a refractive index of 1.2 to 1.3 or less. The method for producing an antireflection material according to claim 1, wherein a hard coat layer is provided between the base material and the low refractive index layer.

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