JP2011107618A - Anti-reflection sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anti-reflection sheet capable of exhibiting stable anti-reflection performance over a long period by preventing the deterioration of adhesion of an anti-reflection film to a base sheet even under a severe environment including outdoor. <P>SOLUTION: The anti-reflection sheet 1 is structured by successively laminating a first layer (Si-Sn alloy layer) 3 having >1 nm and <10 nm thickness as the anti-reflection film and a second layer (low refractive index layer) 4 comprising organopolysiloxane on one surface of a base sheet 2 comprising an ultraviolet curing type acrylic resin. The second layer 4 is formed by applying sol prepared by hydrolyzing organosiloxane by a wet coat method and curing by heating. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an antireflection sheet, and more particularly to a technique for improving the adhesion between an antireflection film and a plastic sheet.

  In recent years, various displays such as a liquid crystal display (LCD), a plasma display panel (PDP), a cathode ray tube (CRT), an organic light emitting display (OLED), and electronic paper have been developed. In addition to television, these are also used as mobile phones, personal digital assistants (PDAs), notebook computers, OA / medical devices, POS registers, ticket machines, car navigation systems, FA devices, digital signage, etc. Widely used regardless of organization, school, hospital, etc.

In addition, touch panels arranged as input means on the surfaces of various displays are widely used.
An antireflection film is placed on the top surface of the display or touch panel on a plastic or glass substrate as a means to prevent external light such as sunlight or room lighting from being reflected and image display performance to deteriorate. The light reflection preventing means may be used (see Patent Documents 1 and 2). By such light reflection preventing means, the reflectance of external light (total light reflectance) can be reduced by about 3 to 4%. It can be said that the light reflection preventing means is essential for improving the visibility of the display.

An antireflection sheet, which is one of the light reflection preventing means, usually has several tens of nm thin films alternately composed of inorganic materials such as SiO ₂ and TiO _{2 on} the surface of a base sheet (resin sheet) serving as a base material. It is configured to be laminated. A pressure-sensitive adhesive layer and an adhesive layer are formed on the surface opposite to the surface on which the antireflection film is formed, and the entire surface can be bonded to each surface of a display or a touch panel.

  The base sheet is required to have transparency and sufficient durability (for example, durability against light and temperature change during outdoor use). Therefore, transparent film materials such as cyclic olefin resins such as polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA) and norbornene are used. Usually, in order to ensure the surface hardness of the base sheet, a hard coat layer made of UV-curable acrylic resin or thermosetting silicone resin (sol / gel method) is formed on the surface of the film material by dip coating or roll coating method. Is done. The antireflection film is formed on the surface of the hard coat layer.

  On the other hand, the structure which formed the base sheet itself with the thickness of about 0.1-0.5 mm using the ultraviolet curable acrylic resin is also considered. A resin sheet obtained using an ultraviolet curable acrylic resin as a starting material has a very high characteristic (for example, 3H to 9H or more in pencil hardness). Therefore, if this resin sheet is used as a base sheet, a separate step of performing a hard coat process on the surface of the film becomes unnecessary. Further, by introducing a siloxane component into the resin, for example, an effect of reducing yellowing can be expected even when a temperature around 200 ° C. is applied.

Furthermore, a base sheet made of an ultraviolet curable acrylic resin has an advantage that it can be efficiently manufactured by forming a continuous sheet by casting and curing it by irradiation with ultraviolet rays.
Furthermore, according to such a roll-to-roll method, it is possible to continuously form a thin film by sputtering or vapor deposition or a thick film by wet coating on the surface of the base sheet cured by ultraviolet rays. Therefore, a dramatic improvement in the production efficiency of the antireflection sheet can be expected.

Japanese Patent No. 42089881 Japanese Patent No. 3098926

However, when a base sheet made of an ultraviolet curable acrylic resin is used, the adhesion between the base sheet and the antireflection film decreases due to the deterioration of the base sheet with the passage of use period, and the antireflection film peels off. .
That is, generally, when the antireflection sheet is exposed to the atmosphere, oxygen and water vapor in the atmosphere enter and diffuse near the interface between the antireflection film and the base sheet. This oxygen and water vapor cause a reaction (oxidation reaction or hydrolysis reaction) that deteriorates the base sheet in the extreme surface region (a depth region of about 10 nm or less from the surface) of the base sheet in contact with the antireflection film. .

  On the other hand, the antireflection sheet may be exposed to severe temperature / humidity changes and high-intensity light irradiation depending on the use situation and use environment together with the touch panel and display to which the antireflection sheet is applied. In particular, in outdoor applications and applications such as navigation systems mounted in a vehicle, they are easily affected by sunlight, ultraviolet irradiation, high temperature and humidity environment, etc. over a long period of time. Even when used in factories or public facilities, there are cases in which light of a specific wavelength is continuously irradiated by various illumination light sources such as mercury lamps.

  Here, ultraviolet light and light on the short wavelength side of visible light (wavelength 300 to 550 nm) are acceleration factors that cause the deterioration reaction of the base sheet. Therefore, when an antireflection sheet is used in such a light irradiation environment, the base sheet deteriorates. The antireflection film cannot withstand the stress exerted on the base sheet, and the base sheet may peel off from the antireflection film within a relatively short period of time.

Such a problem of peeling due to stress is currently a problem that is difficult to avoid in forming an antireflection film. For example, when considering the case where an antireflection film is formed by laminating a plurality of lamination units composed of a low refractive index layer (such as SiO ₂ ) and a high refractive index layer (such as TiO ₂ ), the interface of each layer is proportional to the film thickness. The stress acting on the surface also increases. For this reason, the adhesiveness between the base sheet and the antireflection film is always easily lowered, and peeling is likely to occur.

When the antireflection sheet is disposed on the touch panel surface and used, in addition to the above-mentioned problems, durability is also required so as not to cause peeling due to being pressed with a sharp pen tip at the time of input. .
Such a peeling problem is a problem to be solved by all means in order to continue to use the antireflection sheet satisfactorily.

  The present invention has been made in view of the above problems, and prevents deterioration of the adhesion between the antireflection film and the base sheet even under harsh environments including the outdoors, and stable antireflection performance over a long period of time. An object is to provide an antireflection sheet that can be expected to exhibit the above.

  In order to solve the above problems, the present invention provides an antireflection sheet in which an antireflection film is formed on at least one surface of a base sheet made of an ultraviolet curable acrylic resin. The first layer and the second layer are sequentially stacked, and the first layer is formed of a silicon-tin (Si-Sn) alloy layer having a thickness of more than 1 nm and less than 10 nm. Was composed of organopolysiloxane.

Here, the first layer is desirably set to have a film thickness of 2 nm or more and 7 nm or less. Among these, when the film thickness is further set to 3 nm or more and 6 nm or less, it is preferable because excellent characteristics can be obtained for both the adhesion effect and the antireflection effect.
The second layer may be formed by heat curing after applying a sol prepared by hydrolyzing organosiloxane by wet coating.

In addition, the antireflection film may have a structure in which a third layer made of a fluorosilane compound or a fluorine compound is laminated on the second layer.
Alternatively, a transparent conductive film can be formed on one uppermost surface of the base sheet.
The present invention also relates to an antireflection sheet that undergoes a base sheet forming step of forming a base sheet using an external line curable acrylic resin and an antireflection film forming step of forming an antireflection film on at least one surface of the base sheet. In the manufacturing method, the antireflection film forming step includes steps for sequentially forming the first layer and the second layer from the base sheet side. In the first layer forming step, a sputtering method, a vacuum evaporation method, a CVD method are included. The first layer is formed with a Si—Sn alloy layer having a film thickness of more than 1 nm and less than 10 nm using any one of the ion plating method and the electron beam method, and in the second layer forming step, an organosiloxane is formed. A sol prepared by hydrolyzing was applied by a wet coating method and then heat-cured to form a second layer made of organopolysiloxane.

The antireflection film forming step may further include a step of forming a third layer made of a fluorosilane compound or a fluorine compound on the second layer after the second layer forming step.
Or the process of forming a transparent conductive film in one uppermost surface of a base sheet can also be passed.
Moreover, it is also possible to implement at least one of the base sheet forming step, the first layer forming step, and the second layer forming step by a roll-to-roll method.

As a result of intensive studies by the inventors of the present application, when a Si—Sn alloy layer is used as a constituent layer of an antireflection film, both a base sheet made of an ultraviolet curable acrylic resin and a low refractive index layer containing an organopolysiloxane are used. It was confirmed that it exhibits good adhesion.
The present invention has been made based on this finding, and the antireflection film is composed of a first layer made of a Si—Sn alloy and a second layer (low refractive index layer) using organosiloxane as a starting material, The first layer is formed by directly laminating a base sheet made of an ultraviolet curable acrylic resin.

  In the antireflection sheet of the present invention having such a configuration, the stress exerted by the antireflection film on the interface of the base sheet is reduced as much as possible, so that the adhesion between them can be improved. That is, since the first layer made of the Si—Sn alloy layer is superior in malleability and flexibility compared to conventionally used metal oxides (including ceramics), the stress exerted on the base sheet side is also small. . For this reason, even if the base sheet receives intrusion of oxygen or water vapor in the atmosphere and receives ultraviolet irradiation or the like, the deterioration progresses, and the adhesion between the antireflection film and the base sheet is kept good.

Moreover, the 1st layer has the adhesiveness excellent also with respect to the 2nd layer, and both peeling has been reduced.
On the other hand, the second layer is composed of organosiloxane as a starting material, and can contain an organic group and a fluorocarbon group in a polymer network forming a molecular structure. For this reason, compared with the conventional layer (low refractive index layer) made of SiO ₂ or the like, the second layer also reduces the generation of stress as much as possible and improves the followability to the first layer.

Furthermore, each of the first layer and the second layer has characteristics that are superior to conventional ones as antireflection characteristics.
For this reason, the anti-reflection sheet of the present invention can be used in a harsh environment, the base sheet deteriorates due to relatively high intensity light irradiation or ultraviolet irradiation, and the pressing force at the time of input in a touch panel application is reduced. Even when receiving repeatedly, the stress which generate | occur | produces between a 1st layer and a base sheet or a 1st layer and a 2nd layer is reduced as much as possible, and these each layer does not peel easily. Therefore, according to the present invention, excellent antireflection characteristics can be expected with high reliability over a long period of time.

The antireflection sheet of the present invention can be composed of only two layers, a first layer and a second layer. For this reason, since it is not necessary to comprise as a laminated body of many layers unlike the past, the problem of peeling which arises in the interface of each layer in a multilayer laminated body can also be avoided.
In addition, paragraph 0005 of Patent Document 1 states that “a titanium oxynitride film having a geometric film thickness of 5 to 25 nm and silica having a geometric film thickness of 70 to 130 nm are mainly formed on the substrate from the substrate side. A light-absorbing antireflective body that reduces reflection of incident light from the side of the film mainly composed of silica, the atomic ratio of oxygen to titanium in the titanium oxynitride Is a light-absorptive antireflective body having an A of 0.11 or more and less than 0.33. This light-absorbing antireflective body has the same point as the antireflective sheet of the present invention in that it has an external light reflecting function, but is different from the present invention in any of the problems, configurations, and manufacturing methods.

It is sectional drawing which shows the laminated structure of the antireflection sheet in this Embodiment 1. It is sectional drawing which shows another structural example of an antireflection sheet. It is sectional drawing which shows another structural example of an antireflection sheet. It is a graph which shows the measurement result of the reflectance of Si film. It is a graph which shows the measurement result of the reflectance of Ti film. It is a graph which shows the measurement result of the reflectance of ST film | membrane (Si-Sn alloy layer).

Embodiments of the present invention will be described below, but the present invention is naturally not limited to these embodiments, and can be appropriately modified and implemented without departing from the technical idea of the present invention. .
<Embodiment 1>
(Configuration of antireflection sheet)
FIG. 1 is a schematic cross-sectional view showing the configuration of the antireflection sheet 1 of the first embodiment. The antireflection sheet 1 is configured by forming an antireflection film on one surface of a base sheet 2. The antireflection film has a configuration in which a first layer (Si—Sn alloy layer) 3 and a second layer (low refractive index layer) 4 are sequentially laminated from the base sheet 2 side.

The base sheet 2 is a transparent plastic sheet (base material) made of an ultraviolet curable acrylic resin having a thickness of 200 μm, and has sufficient hardness and excellent transparency without performing a hard coat treatment or the like on the surface. . The surface of the base sheet 2 where the antireflection film is not formed (the lower surface in the figure) is used as a laminated surface with a touch panel or various displays.
The first layer 3 is a thin film layer composed of an ST film (Si—Sn alloy layer), which can reduce the generation of stress as much as possible with respect to the base sheet 2 and the second layer 4 and is excellent with respect to the base sheet 2. Excellent follow-up performance. In addition, here, by combining the first layer 3 with the second layer 4, an excellent antireflection effect can be exhibited over an optical wavelength region of at least 300 nm to 800 nm (see FIG. 6 described later). In addition, by setting the film thickness of the first layer 3 to be more than 1 nm and less than 10 nm, it is possible to achieve both good transparency and antireflection effect.

  The second layer 4 is a low refractive index layer and is a layer made of organopolysiloxane. Specifically, it is a layer obtained by hydrolysis and dehydration condensation polymerization using organosiloxane as a starting material in accordance with a sol-gel method so as to form a polymer network having a three-dimensional network structure based on a siloxane (Si—O) skeleton. It is configured. Fluorocarbon groups, methyl groups, and the like are present in the side chain of the organopolysiloxane skeleton, and adhesion to both the base sheet 2 and the first layer 3 and good followability to the base sheet 2 are ensured. The refractive index of the second layer 4 is set in the range of 1.30 to 1.45. The film thickness is adjusted in the range of 50 nm to 200 nm in consideration of transparency and antireflection characteristics.

(About the effect of the sheet)
The Si—Sn alloy layer constituting the first layer 3 is very excellent in malleability and flexibility compared to conventional antireflection film materials (SiO ₂ , TiO ₂ , other inorganic oxide materials, etc.). Material. Therefore, the antireflection sheet 1 uses the first layer 3 made of the Si—Sn alloy layer, so that deformation stress accompanying thermal expansion, thermal contraction, etc. from the first layer 3 reaches the base sheet 2 as much as possible during use. Can be reduced. Thereby, the outstanding adhesiveness of the 1st layer 3 with respect to the base sheet 2 can be maintained.

Furthermore, the Si—Sn alloy layer forming the first layer 3 has good adhesion to the second layer 4. The second layer 4 contains a large number of organic groups and fluorine groups in a polymer network having a three-dimensional network structure based on a siloxane skeleton as a main bond, and these functional groups cause stress generated in the second layer 4. It works to reduce. Further, since the polymer network structure has good flexibility, the followability to the base sheet 2 is improved as compared with the layer (low refractive index layer) of the second layer 4 made of conventional SiO ₂ or the like, Even if the base sheet 2 is bent or changed, it is not easily peeled off.

For these reasons, in the antireflection sheet 1, the laminated structure of the base sheet 2, the first layer 3, and the second layer 4 is maintained well, and an effective peeling prevention effect is exhibited.
Therefore, even if water vapor or oxygen in the atmosphere enters into the antireflection sheet 1 as it is used and the deterioration reaction of the base sheet 2 proceeds due to light irradiation such as ultraviolet rays, the base sheet 2 and the first The layer 3 maintains a stable form over a long period of time without excessively losing adhesion. In addition to this, adhesion between the first layer 3 and the second layer 4 is also exhibited, and an excellent antireflection effect is realized by the combination of these three and four.

  Each of these effects is particularly effective when the antireflection sheet is used in an environment where light irradiation or ultraviolet irradiation with relatively high intensity is performed outdoors or in a factory. In addition, since the antireflection film and the base sheet are firmly adhered to each other, troubles such as falling off of the antireflection film even when the antireflection sheet is applied to the touch panel are reduced, and excellent input durability (keystroke durability) ).

In addition, although the Si-Sn alloy layer is used as the first layer 3 in the antireflection sheet 1, due to the complex refractive index of the alloy layer, there is an absorption effect on light having a certain wavelength in the visible light wavelength region. can get. This property is particularly effective when the antireflection sheet 1 is disposed on the image display surface of a self-luminous high-brightness display, so that reflection from the periphery of the display (reflection of external light) can be efficiently reduced. There is an effect that performance is exhibited.
(Consideration of peeling of antireflection film)
In general, an antireflective film containing an inorganic material such as SiO ₂ or TiO ₂ as a main component and formed by a sputtering method, a vacuum deposition method, or the like hardly undergoes a chemical change even by light irradiation. Accordingly, the deterioration of the antireflection sheet tends to occur due to the base sheet made of an organic material.

  Further, in the antireflection sheet, a certain stress accompanying thermal expansion and contraction generated in the antireflection film immediately after manufacture acts on the base sheet side. In the antireflection sheet in which the base sheet immediately after manufacture is not deteriorated, the base sheet generates a reaction against the internal stress of the antireflection film, and thus is difficult to peel off from each other. However, as the base sheet gradually deteriorates and becomes weaker as the antireflection sheet is used, the reaction of the base sheet is reduced. As a result, the stress of the antireflection film becomes relatively large, and breakage occurs near the interface between the base sheet and the antireflection film, resulting in peeling. It should be noted that such anti-reflection sheet peeling actually occurs not in the interface between the anti-reflection film and the base sheet, but in a depth region of about several nm from the surface layer of the base sheet. It is revealed by confirmation.

The time taken for the antireflection film and the base sheet to peel from each other depends on the amount of stress that the antireflection film exerts on the interface with the base sheet, and varies depending on the material, manufacturing method, thickness, etc. of the antireflection film. . Therefore, it can be said that it is desirable that the internal stress of the antireflection film is as small as possible in order to ensure and maintain good adhesion between the antireflection film and the base sheet.
<Other embodiments>
The antireflection sheet of the present invention may have a configuration in which the first layer 3 and the second layer 4 are sequentially laminated on both surfaces of the base sheet 2 sequentially as shown in 1A shown in the sectional view of FIG. With such a configuration, a good antireflection function can be imparted to both surfaces of the sheet. Moreover, the improvement of the transparency of an antireflection sheet can also be expected by forming such a multilayer laminated structure.

As another embodiment, an antireflection film having a three-layer structure can be formed by laminating a predetermined third layer 5 on the second layer 4 as shown in 1B shown in the cross-sectional view of FIG. If the third layer 5 is made of, for example, a fluorosilane compound or a fluorine compound, the antireflection property can be further improved.
In the antireflection sheet 1B, the transparent conductive film 6 is formed on the other surface of the base sheet 2 using a known transparent conductive material (ITO, ZnO, etc.). This transparent conductive film 6 assumes that the antireflection sheet 1B is applied to a touch panel or the like, and the presence or absence of appropriate arrangement can be selected according to the application. Such a transparent conductive film may be applied to other antireflection sheets.

In any antireflection sheet, a pressure-sensitive adhesive layer or adhesive layer for adhering to a display or the like can be formed at a predetermined position on the outermost surface.
<Example of manufacturing process>
Here, the manufacturing process example of the antireflection sheet 1 will be mainly described.
(Preparation of base sheet)
For ultraviolet curable acrylic resin materials and polymerization initiators, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), isobutyl alcohol (IBA), ethyl alcohol, methyl alcohol, normal butyl alcohol (NBA), cyclohexanone (CAN), di A paint (volatile solution) is prepared by adding a solvent such as acetylacetone (DAA), butyl acetate, ethyl acetate, or isopropyl alcohol (IPA). Further, a nano-oxide particle material containing an inorganic oxide component such as SiO ₂ , ZrO ₂ , SnO ₂ may be added. As these particulate materials, various commercially available products that are uniformly dispersed in powder or an organic solvent can be used.

However, for reasons of manufacturing, it may be preferable not to use an organic solvent for the base sheet. In that case, the monomer described below can be used as a reactive diluent instead of the organic solvent.
In the ultraviolet curable acrylic resin material, the hardness and rollability (easy to break) of the base sheet after photocuring are determined by monomers and oligomers in the molecular structure. Therefore, selection of the ultraviolet curable acrylic resin material is important. Specifically, a monomer or oligomer component containing a vinyl group in the skeleton is used. Among them, the monomer is also called a reactive diluent, and an acrylic monomer, for example, trimethylolpropane triacrylate (TMPT) or its EO-modified, PO-modified product, pentaerythritol triacrylate (PET-3A) as a trifunctional monomer, 4 Examples of the functional monomer include pentaerythritol tetraacrylate, and examples of the hexafunctional monomer include dipentaerythritol hexaacrylate (DPE-6A). On the other hand, as the oligomer, a urethane-based or epoxy-based oligomer component containing a vinyl group is appropriately selected and introduced.

  About introduction | transduction of these monomer components and oligomer components, in order to make flexibility and hardness compatible, it is preferable to obtain | require optimal amount beforehand. In general, when the ratio of the oligomer component is high (including the case where the monomer component is zero), roll-to-roll molding becomes easier as the flexibility increases, but the hardness decreases. On the contrary, if the ratio of the oligomer component is reduced (including the case where the oligomer component is zero), the flexibility can be reduced but the hardness can be increased.

Examples of the polymerization initiator for the monomer component and oligomer component include Irgacure 907 (2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one) manufactured by Ciba Specialty Chemicals Co., Ltd. A general photopolymerization initiator such as Irgacure 184 may be used.
A sheet molding (base sheet) is obtained by performing a known casting method and an ultraviolet irradiation process using the coating material. Here, the radical initiator contained in the coating material generates radicals upon irradiation with ultraviolet rays, and a crosslinking reaction (polymerization reaction) proceeds in a three-dimensional manner with the generated radicals as starting points. Thereby, since the base sheet has a three-dimensional network polymer structure, it has excellent mechanical strength (hardness, scratch resistance, etc.), and there is an advantage that a separate hard coat treatment is unnecessary.

Here, if the above casting and ultraviolet irradiation processes are carried out continuously based on a roll-to-roll method, energy loss is less than conventional single wafer processing in which the surface of a plastic sheet is dip coated. The base sheet can be produced with high manufacturing efficiency.
When it is desired to impart both high hardness and heat resistance to the base sheet, a siloxane skeleton can be introduced into the molecular chain, or silica fine particles (so-called nano silica) having a particle size of 100 nm or less can be dispersed. In this case, examples of the siloxane skeleton include a method in which an acrylic monomer and siloxane are addition-polymerized using a sol-gel method (hybridization), and a method in which silsesquioxane is introduced and incorporated into a monomer or oligomer molecular skeleton. . As this specific method, for example, “the latest technology of plastic hard coat material” (CMC Publishing Co., Ltd., 2008) can be referred to.

Further, the surface of the base sheet may be subjected to a surface treatment such as shape forming (embossing forming) by pressing a carrier having a predetermined surface roughness.
(Production of the first layer)
A first layer (ST film) made of a Si—Sn alloy having a film thickness of more than 1 nm and less than 10 nm is formed on one side of the formed base sheet by sputtering or vacuum deposition. When the film thickness is set within this range, the first layer becomes almost transparent, and can satisfy the transparency required as an antireflection sheet, and can also ensure excellent antireflection characteristics.

In addition, when forming a 1st layer into a film by sputtering method or a vacuum evaporation method, the said layer may be oxidized or nitrided by the residual gas in a vacuum chamber somewhat in an actual process. However, with such a slight oxidation or nitridation, unnecessary stress acting on the interface between the base sheet and the first layer is considered to be sufficiently small, and there is no problem that causes the performance of the antireflection sheet to deteriorate. .
(Production of the second layer)
Next, a second layer which is a low refractive index layer made of polyorganosiloxane is formed on the first layer.

  Specifically, organic silane materials such as diethyldiethoxysilane, ethyltriethoxysilane, and tetraethoxysilane partially hydrolyzed and dehydrated and condensed with a predetermined volume of fluorosilane compound, methyl group, or ethyl group An organosilane material (organosiloxane material) is prepared. A paint prepared by blending this material with an alcohol-based organic solvent such as methanol, ethanol, isopropanol, or butanol, water, and hydrochloric acid to prepare a sol is used.

This paint is applied based on a sol-gel method so as to have a predetermined final film thickness by a roll coating method such as a gravure coating method. When the applied paint is dried, a second layer is obtained.
Alternatively, the organosiloxane as a starting material, may be used a solution obtained by dispersing the SiO ₂ component.
Specifically, as described above, a predetermined volume of a fluorosilane compound or an organosilane material having a methyl group, an ethyl group, or the like is prepared, and a sol obtained by dispersing a SiO ₂ component is used as a paint. By applying and drying this paint based on the sol-gel method, a second layer having a low refractive index made of organopolysiloxane is formed. The refractive index of the second layer obtained by this method is generally lower than the refractive index value of bulk SiO ₂ (1.46).

  Here, the thickness of the second layer is required to be adjusted so that sufficient antireflection characteristics can be obtained. The characteristics of the antireflection film (spectral spectrum of light reflection) vary depending on the material and thickness of the first layer and the refractive index and thickness of the second layer. For this reason, it is practically difficult to obtain an optimized antireflection characteristic without specific examination. Accordingly, it is preferable to examine the film thicknesses of the first layer and the second layer by calculating numerical values in advance.

Here, as an example, the second layer is obtained by applying on the first layer so that the final thickness is in the range of 50 to 100 nm and passing through a drying step.
A third layer made of a fluorosilane compound or a fluorine compound (for example, “OPTOOL ^TM DSX” manufactured by Daikin Industries, Ltd.) is formed on the uppermost surface of the second layer 4 in order to further improve the antireflection characteristics. You can also This third layer can also be laminated by a roll coating method.

Hereinafter, specific effects of the present invention will be described based on performance confirmation experiments.
<Performance confirmation experiment>
[Sample preparation]
Samples of Examples and Comparative Examples were prepared according to the following procedure.
As an ultraviolet curable acrylic resin material, a mixture prepared by mixing 25 parts by weight of trifunctional urethane acrylate (New Frontier R1302 manufactured by Daiichi Kogyo Seiyaku) with 75 parts by weight of pentaerythritol triacrylate (PET-3A) was prepared. By mixing 5 parts by weight of this with a photopolymerization initiator (Irgacure 184 manufactured by Ciba Specialty Chemicals Co., Ltd.), an ultraviolet curable coating was prepared.
(Preparation of base sheet)
A base sheet was produced by the following procedure.

  Two transparent PET films not subjected to any surface treatment were prepared, and the coating film of the paint was formed on the surface of one PET using a Mayer bar (# 48). Another PET film was placed and bonded to the surface of the obtained coating film (this PET film / coating film / PET film laminate is referred to as “laminate A”). Since the coating film has fluidity, when performing the installation bonding, the coating film was bonded with as low a pressure as possible so that the predetermined thickness of the coating film was maintained. In addition, care was taken so that no bubbles would enter between the PET films.

Subsequently, the coating film was cured by irradiating the laminate A with ultraviolet rays for about 10 seconds from the outside using a high-pressure mercury lamp (tube length: 1200 mm, output power: 15 kW). After the completion of curing, a base sheet used as a sample was obtained by peeling and removing two PET films from the laminate A (this is referred to as “molded body A”). While the molded body A had moderate flexibility, the pencil hardness was 7H, and it was confirmed that the molded body A had a very high hardness.
(Preparation of antireflection film)
Next, using a predetermined sputtering source (any one of Si, Ti, and ST alloy) on one side of the molded body A, a sputtering method is performed, and consists of any one of an Si layer, a Ti layer, and an ST layer. A first layer having a predetermined thickness (either 1, 5, or 10 nm) was formed. As implementation conditions of the sputtering method, the ultimate vacuum before sputtering was set to 2.5 × 10 ⁻⁴ Pa, and the substrate temperature was set to 150 ° C.

  After forming the first layer by performing sputtering, the molded product A with the first layer is taken out from the vacuum into the atmosphere, and a commercially available antireflective agent (Panasonic Electric Works Ltd. The company “AeroCera”, refractive index 1.35) was applied with a thickness of about 100 nm, dried and cured. This formed the 2nd layer and obtained the antireflection sheet of each sample of Examples 1 and 2 and Comparative Examples 1-8 shown in Table 1.

In addition, Comparative Example 9 was obtained by directly forming the second layer on the molded body A.
In addition, when the reflectance of the antireflection film obtained in Examples 1 and 2 was measured, the surface reflectance with respect to light having a wavelength of 550 nm was 0.63%. Thereby, it was confirmed that the reflectance was remarkably reduced as compared with 4.2% of the case where the antireflection film was not formed (molded body A).
[Evaluation of adhesion]
Each of the above prepared samples was subjected to the following two types of treatments after confirming that no peeling occurred at the present time (initial (0 hr)). Thereafter, the adhesion was evaluated by reciprocatingly sliding the surface of the antireflection film with a waste impregnated with ethanol.
(1) Environment; left in a high-temperature and high-humidity environment (light-shielding environment) at 60 ° C. and 90% humidity for a predetermined period of time (2) Environment; for a predetermined period of time using an ultraviolet fade meter manufactured by Suga Test Instruments Co., Ltd. Ultraviolet irradiation treatment When sliding using the ethanol, the load of Wes (“Cotton Seagull” manufactured by Chiyoda Co., Ltd.) was 500 g / cm ^2, and the presence or absence of peeling due to the sliding of the Wes was visually confirmed. In addition, the said evaluation method is set so that it may become a severer evaluation method rather than the tape peeling method which is a general evaluation method so that the effect of this invention can be confirmed easily.

  The results of the evaluation test are shown in Table 1. Moreover, the graph which shows the relationship between each reflectance (%) and film thickness of a comparative example (Si), a comparative example (Ti), a comparative example, and an Example (ST film | membrane) is shown to FIGS. In each figure, the first layer is represented by any one of “Si layer”, “Ti layer”, and “ST layer”, and the second layer is represented by “low refractive index layer”.

［考察］
表１に示される結果が示すように、実施例１及び２では、可視光反射率も１より十分低く抑えられるとともに、密着性試験（１）環境、（２）環境のいずれにおいても良好な剥離耐久性が発揮されることが確認できた。

[Discussion]
As shown in the results shown in Table 1, in Examples 1 and 2, the visible light reflectance is also sufficiently lower than 1, and good peeling in both the adhesion test (1) environment and (2) environment. It was confirmed that the durability was exhibited.

In addition, when viewing the graph of FIG. 6, the antireflection sheet having an ST film having a thickness greater than 1 nm (up to a thickness of 5 nm) as compared with the sample without the ST film (Comparative Example 9) has a wavelength of 300 nm. In the range of ˜800 nm, the reflectivity (%) value was suppressed to about 1% or less, and it was confirmed that a good reflectivity reduction effect was exhibited.
On the other hand, Comparative Examples 1 and 2 each include a first layer using the same Si—Sn alloy as in Examples 1 and 2, but the film thickness (1 nm) of Comparative Example 1 is too thin to cause peeling. On the other hand, it was confirmed that the film thickness (10 nm) of Comparative Example 2 had problems such as being too thick and opaque, leading to an increase in reflectance. In addition, since the transparency of Comparative Example 2 was considerably lowered, the minimum reflectance measurement and the measurement experiment were not performed on the sample.

Thus, it was found that the reflectance of each sample used for the experiment tends to increase as the thickness of the first layer increases.
Furthermore, from the results of Comparative Examples 3 to 5 in which the first layer is composed of a Si film, the first layer is thin (1 nm) and easily peels off. When the film thickness is thick (5 to 10 nm), the transparency is high. It was confirmed that the reflectance was extremely increased. The characteristics relating to the reflectance can also be confirmed from the graph of FIG. 4, and in Comparative Examples 4 and 5 having a relatively thick film thickness, the tendency of the reflectance to rise abruptly can be confirmed in the wavelength range of 500 nm or less and the wavelength of 600 nm or less.

  In the results of Comparative Examples 6 to 8 in which the first layer was made of Ti, there were some that could greatly reduce the reflectivity with respect to the measurement light (Comparative Example 7). The reflectance increases rapidly (see graph in FIG. 5). As described above, Comparative Examples 6 to 8 including the first layer made of the Ti film have points to be improved in chemical resistance and moisture and heat resistance, and currently do not have durability and adhesion required as an antireflection film. It was revealed.

  From the above experimental results, the superiority of the present invention over the prior art was confirmed.

In the antireflection sheet of the present invention, the constituent elements are not easily peeled off and can exhibit high reliability over a long period of time.
For this reason, it can be used for a wide range of applications. For example, it can be used outdoors (public facilities display devices) where the amount of light irradiation is relatively large, and in high temperature and high humidity environments (such as car navigation systems). Applicable. Moreover, since excellent input durability can also be exhibited, it is also possible to apply to touch panels provided on various display surfaces.

1, 1A, 1B Antireflection sheet 2 Base sheet (base film)
3 First layer (Si-Sn alloy layer)
4 Second layer (low refractive index layer)
5 Third layer 6 Transparent conductive film

Claims (10)

An antireflection sheet having an antireflection film formed on at least one surface of a base sheet made of an ultraviolet curable acrylic resin,
The antireflection film has a structure in which a first layer and a second layer are sequentially laminated from the base sheet side,
The first layer is made of a Si—Sn alloy layer having a thickness of more than 1 nm and less than 10 nm,
The antireflection sheet, wherein the second layer is composed of organopolysiloxane. The antireflection sheet according to claim 1, wherein the first layer has a film thickness set to 2 nm or more and 7 nm or less. The antireflection sheet according to claim 1, wherein the first layer has a film thickness set to 3 nm or more and 6 nm or less. The said 2nd layer is formed by heat-curing, after apply | coating the sol adjusted by hydrolyzing organosiloxane by the wet-coating method, The any one of Claims 1-3 characterized by the above-mentioned. Antireflection sheet. 5. The antireflection film according to claim 1, wherein the antireflection film has a structure in which a third layer made of a fluorosilane compound or a fluorine compound is laminated on the second layer. Sheet. The transparent conductive film is formed in one uppermost surface of the said base sheet. The antireflection sheet in any one of Claims 1-5 characterized by the above-mentioned. A base sheet forming step of forming a base sheet using an ultraviolet curable acrylic resin;
A method for producing an antireflection sheet that undergoes an antireflection film forming step of forming an antireflection film on at least one surface of a base sheet,
The antireflection film forming step has each step of sequentially forming the first layer and the second layer from the base sheet side,
In the first layer formation step, a Si—Sn alloy layer having a film thickness of more than 1 nm and less than 10 nm is formed by using any one of the thin film forming methods of sputtering, vacuum deposition, CVD, ion plating, and electron beam. Forming the first layer,
In the second layer forming step, a sol prepared by hydrolyzing organosiloxane is applied by a wet coating method, and then heat-cured to form a second layer made of organopolysiloxane. Manufacturing method. The antireflection film forming step further includes a step of forming a third layer made of a fluorosilane compound or a fluorine compound on the second layer after the second layer forming step. Manufacturing method of antireflection sheet. The method for producing an antireflection sheet according to claim 7, wherein a process of forming a transparent conductive film on one uppermost surface of the base sheet is performed. The antireflection according to any one of claims 7 to 9, wherein at least one of the base sheet forming step, the first layer forming step, and the second layer forming step is performed by a roll-to-roll method. Sheet manufacturing method.

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