JP2014016586A - Antireflection article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antireflection article having an excellent adhesion between an acrylic resin base material and a fine projection layer which comprises a hardened material of an acrylic resin composition formed on the surface, even if the acrylic resin base material and the acrylic resin composition forming the fine projection layer are used as a combination of arbitrary materials.SOLUTION: An antireflection article 10 is configured by having a fine projection group which comprises a collection of fine projections 2a for antireflection, and also, by forming a fine projection layer 2 which comprises a hardened material of an acrylic resin composition on the surface of an acrylic resin base material 1. The fine projections 2a have a relation of dmax≤Λmin, where a minimum wavelength of a light wavelength band for antireflection is defined as Λmin, and an interval of the fine projections is defined as dmax. The interface between the acrylic resin base material 1 and the fine projection layer 2 is formed in such a shape that it is rugged alternately on the acrylic resin base material 1 side and on the fine projection layer 2 side.

Description

The present invention relates to an antireflection article that prevents reflection of light on a surface and can be used in various applications such as protection of information display sections of equipment and exhibits.

Information displays such as mobile phones and digital cameras, and exhibits such as works of art and merchandise are exposed to the outside and may become dirty or broken, protecting them from water, dust, external forces, etc. There is a need to. However, if a transparent plastic plate or the like is placed outside so that they are not exposed to the outside as they are, there is a problem that external light is reflected on both the front and back surfaces of the plate, which reduces the visibility of the display. Articles are being used.

  In recent years, as an antireflection treatment technique, a technique has been proposed in which surface reflectance is reduced by providing extremely fine irregularities with a repetition period equal to or less than the wavelength of light on the surface. An antireflection article having a fine uneven layer has been developed. For example, Patent Document 1 discloses an antireflection article in which a fine uneven layer made of a cured product of an ionizing radiation curable resin is formed on one surface of a transparent acrylic resin plate by a 2P method (Photo-polymerization method). Yes.

As the base material used in the antireflection article, an acrylic resin base material is often used because of its excellent transparency, and the material of the fine uneven layer formed on the base material is acrylic. In many cases, a resin composition mainly composed of an acrylic resin such as an ionizing radiation curable resin is used.
However, when forming a fine uneven layer made of an acrylic resin composition on an acrylic resin substrate, depending on the combination of the resin contained in the substrate and the resin contained in the fine uneven layer, a copolymerization component Depending on the composition, grade, etc., the adhesion between the substrate and the fine uneven layer may be inferior.

JP 2003-240904 A

  The present invention has been made to solve the above-described problems, and is a case where an acrylic resin base material and an acrylic resin composition for forming a microprojection layer are used in any combination of materials. However, an object of the present invention is to provide an antireflection article having excellent adhesion between the acrylic resin substrate and a microprojection layer made of a cured product of the acrylic resin composition formed on the surface thereof.

The antireflective article according to the present invention comprises a surface of an acrylic resin base material with a group of microprojections formed by aggregation of antireflection microprojections, and is made of a cured product of an acrylic resin composition. An antireflection article formed with a microprojection layer,
When the shortest wavelength of the wavelength band of light for preventing reflection is Λmin and the distance between the small protrusions is dmax,
dmax ≦ Λmin
Have the relationship
The interface between the acrylic resin substrate and the microprojection layer is characterized by being formed in a shape that interleaves alternately with the acrylic resin substrate side and the microprojection layer side.

  In the antireflection article according to the present invention, the interface between the acrylic resin substrate and the microprojection layer has an average projection spacing Sm defined in JIS B0601 1994 of 0.1 to 4 μm, and in JIS B0601 1994. It is preferable from the point which is excellent in the adhesiveness of the said acrylic resin base material and the said microprotrusion layer that 10 point average roughness Rz prescribed | regulated is 0.1-4 micrometers.

  According to the present invention, the adhesion between the acrylic resin substrate and the microprojection layer made of a cured product of the acrylic resin composition formed on the surface thereof is excellent, and basic characteristics such as optical characteristics and mechanical characteristics are provided. It is possible to provide an antireflection article that also satisfies the required performance.

It is sectional drawing which shows typically an example of the anti-reflective article which concerns on this invention. It is sectional drawing which shows typically another example of the antireflection article which concerns on this invention. It is a figure which shows a Delaunay figure. It is a frequency distribution diagram used for measurement of the distance between adjacent protrusions. It is a frequency distribution figure with which it uses for description of minute height. It is a figure explaining the cutting location for obtaining the cross-sectional sample of the antireflection article used for measurement of average protrusion space | interval Sm and ten-point average roughness Rz. It is a figure explaining an example of the manufacturing method of the antireflection article concerning the present invention. It is a figure explaining another example of the manufacturing method of the antireflection article concerning the present invention.

Next, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the spirit thereof.
In the present invention, (meth) acrylic resin represents acrylic resin and / or methacrylic resin, and (meth) acrylate represents acrylate and / or methacrylate.
In the present invention, the resin is a concept including a polymer in addition to a monomer and an oligomer.

The antireflection article according to the present invention has a surface of a microprojection formed by collecting microprojections for antireflection on the surface of an acrylic resin base material (hereinafter sometimes simply referred to as “base material”). And an antireflection article in which a microprojection layer made of a cured product of an acrylic resin composition is formed,
When the shortest wavelength of the wavelength band of light for preventing reflection is Λmin and the distance between the small protrusions is dmax,
dmax ≦ Λmin
Have the relationship
The interface between the acrylic resin substrate and the microprojection layer is characterized by being formed in a shape that interleaves alternately with the acrylic resin substrate side and the microprojection layer side.

Examples of the antireflection article according to the present invention include a single-layer type in which a single microprojection layer is formed and a multi-layer type in which two or more microprojection layers are formed.
Hereinafter, a one-layer type antireflection article and a two-layer type antireflection article according to the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing a single-layer antireflection article according to the present invention. The antireflection article 10 shown in FIG. 1 is formed by forming on the surface of an acrylic resin substrate 1 a microprojection layer 2 having a microprojection group formed by a collection of microprojections 2a on the surface.
FIG. 2 is a cross-sectional view schematically showing a two-layered antireflection article according to the present invention. The antireflection article 20 shown in FIG. 2 includes, on the surface, a group of microprojections formed by aggregating the first layer 3 and the microprojections 2a on the surface of the acrylic resin substrate 1 in this order from the substrate 1 side. The microprojection layer 2 formed by laminating the second layer 4 is formed.

The antireflective article according to the present invention may be a single layer type as shown in FIG. 1 or a multilayer type such as a double layer type as shown in FIG. And the microprojection layer are formed in a shape that alternately interlaces with the acrylic resin base material side and the microprojection layer side. Thereby, the antireflection article according to the present invention has excellent adhesion between the acrylic resin substrate and the microprojection layer.
In the present invention, “the interface is formed in a shape alternately interlaced with the acrylic resin base material side and the microprojection layer side” means that the resin composition for forming microprojection layers on a flat substrate or This means that the base material surface was deformed in the process of applying and drying the first layer forming resin composition, and as a result, the interface was formed into a shape that was intertwined in the depth direction. It does not mean that the interface has been formed into a concavo-convex shape by applying the resin composition for forming a microprojection layer or the resin composition for forming a first layer after forming the concavo-convex by prior processing such as sandblasting.
In the present invention, as described above, the mechanism of action resulting in the shape in which the interface is formed in the depth direction is not clear at present, but the resin composition for forming a microprojection layer or the first layer is formed. When the resin composition is coated on the base material, the solvent contained in the resin composition penetrates the base material surface, and in the process of drying the resin composition, the base material surface into which the solvent penetrates is At the same time that the resin composition swells and deforms, the resin composition enters a recess on the surface of the substrate formed by the deformation, thereby forming a shape in which the interface enters the depth direction.

(Acrylic resin base material)
The acrylic resin used for the acrylic resin substrate is not particularly limited. For example, poly (meth) methyl acrylate, poly (meth) ethyl acrylate, methyl (meth) acrylate- (meth) acrylic acid. A butyl copolymer etc. are mentioned.
Further, as the acrylic resin, in order to improve heat resistance and the like, a monomer having a cyclic structure such as a lactone ring structural unit having a six-membered ring structure, a glutaric anhydride structural unit and a glutarimide structural unit is a copolymerization component. Used in combination, or imidized by treating a primary amine, specifically, for example, polymethylmethacrylate or polymethylmethacrylate-styrene copolymer treated with a primary amine and imidized. You can also.
In addition, when the said acrylic resin contains a non-acrylic monomer as a copolymerization component, it is preferable that the content rate of an acrylic monomer is 50 mass% or more.

Although the thickness of the said acrylic resin-made base material is not specifically limited, A 20-5000 micrometers thing can be used normally and any of a sheet form and plate shape may be sufficient.
In the definition of film and sheet in JIS-K6900, a sheet is thin and generally refers to a flat product whose thickness is small for the length and width, and the film is extremely thick compared to the length and width. A thin, flat product that is small and has an arbitrarily limited maximum thickness, typically supplied in the form of a roll. Therefore, it can be said that a film having a particularly thin thickness among the sheets is a film, but the boundary between the sheet and the film is not clear and is difficult to distinguish clearly. Therefore, in the present invention, the meaning of both a thick sheet and a thin sheet is meant. Is defined as “sheet”. Further, in the present invention, the “plate-like” is thicker than the sheet-like shape, and does not bend completely, or does not bend enough to be wound, but is bent by applying a load. Including meaning.

(Micro-projection layer)
First, the surface shape of the microprojection layer will be described.
The microprotrusion layer has a microprojection group formed by a collection of antireflection microprotrusions on the surface, and the microprotrusion has Λmin as the shortest wavelength of the wavelength band of light to prevent reflection, and dmax as the microprotrusion interval. And when
dmax ≦ Λmin
Have a relationship.

The microprotrusions are closely arranged so that the distance d (see FIG. 1) between adjacent microprotrusions is equal to or less than the shortest wavelength Λmin (d ≦ Λmin) of the wavelength band for preventing reflection. When the antireflection article according to the present invention is used mainly for the purpose of improving visibility by placing it on an image display panel, this shortest wavelength Λmin is the shortest visible light region considering individual differences and viewing conditions. The wavelength (usually 380 nm) is set, and the interval d is usually 100 to 300 nm in consideration of variation. The height of the fine protrusion is usually 50 to 350 nm.
The adjacent minute protrusions related to the distance d are so-called adjacent minute protrusions, which are in contact with the hem portion of the minute protrusion which is the base portion on the base material side. In the antireflection article according to the present invention, when the microprojections are arranged closely so that a line segment is created so as to sequentially follow the valley portions between the microprojections, a polygonal shape surrounding each microprojection in plan view A mesh-like pattern formed by connecting a large number of regions is produced. The adjacent minute protrusions related to the distance d are protrusions that share a part of the line segments constituting the mesh pattern.

The thickness of the microprojection layer is not particularly limited, but is usually 10 to 300 μm. In the present invention, the thickness of the microprojection layer means a distance (for example, t in FIG. 1) from the top of the highest convex portion to the lowest vertex of the interface with the substrate.
When the microprojection layer is a multilayer type, the thickness of the microprojection layer means the total thickness (for example, t in FIG. 2) obtained by adding the thicknesses of the respective layers.

  In the present invention, the structure of the microprojection group may be a so-called “moth eye structure”. The “moth-eye structure” is a structure having a regular protrusion arrangement like a moth-eye, and continuously changes the refractive index with respect to the incident light in the thickness direction of the substrate, thereby discontinuous interface of the refractive index. Is eliminated to prevent reflection. Each micro-projection constituting the moth-eye structure is produced so that the cross-sectional area gradually decreases toward the tip side from the base material so as to be planted on the base material (to be tapered). Examples of the shape include a hemisphere, a semicircular shape of a spheroid, and a cone such as a cone or a quadrangular pyramid.

The antireflection article of the present invention exhibits an antireflection effect by a group of microprojections formed by a collection of microprojections formed on the surface of the microprojection layer. The microprojection group has an antireflection effect for the following reason.
That is, the microprojection group comprises the microprojection layer constituting the surface of the antireflection article and the outside (usually air. However, depending on the usage of the antireflection article, water, vacuum, or resin such as an adhesive, etc. This is because a sudden and discontinuous change in refractive index between the change and the change in refractive index can be changed into a continuous and gradually changing refractive index change. Since light reflection is a phenomenon caused by a sudden and rapid change in the refractive index of the material interface, the refractive index change on the surface of the article is changed spatially and continuously. Light reflection on the surface of the article is reduced.
The microprojection layer is normally transparent and allows light to pass therethrough, but even an opaque material can provide an antireflection effect that reduces surface reflection.

  When the microprojections of the microprojection group are regularly arranged at a constant period, in order to obtain the antireflection effect, for example, as disclosed in JP-A-50-70040, Japanese Patent No. 4632589, etc. An interval d between adjacent minute protrusions is a period P (d = P) of the protrusion arrangement. Thus, when the longest wavelength in the visible light band is λmax and the shortest wavelength is λmin, the minimum necessary condition that can exhibit an antireflection effect at the longest wavelength in the visible light band is Λmin = λmax. P ≦ λmax, and the necessary and sufficient condition for exhibiting the antireflection effect for all wavelengths in the visible light band is Λmin = λmin, and therefore P ≦ λmin.

  On the other hand, recent anti-reflective articles have a complicated structure of microprojections, and have a simple periodicity or a completely irregular arrangement. As described above, when the minute protrusions of the minute protrusion group are irregularly arranged, the distance d between adjacent minute protrusions varies. Therefore, in such a case, the interval d is calculated as follows.

  (1) First, an in-plane arrangement of projections (planar shape of the projection arrangement) is detected using an atomic force microscope (AFM) or a scanning electron microscope (SEM).

  (2) Subsequently, a maximum point of the height of each protrusion (hereinafter simply referred to as a maximum point) is detected from the obtained in-plane arrangement. There are various methods for obtaining the maximum point, such as a method of sequentially comparing the planar view shape and the enlarged photograph of the corresponding cross-sectional shape to obtain the maximum point, and a method of obtaining the maximum point by image processing of the plan view enlarged photo. Can be applied.

  (3) Next, a Delaunay diagram with the detected maximum point as a generating point is created. Here, Delaunay diagram is obtained by dividing the Voronoi region adjacent to the Voronoi region when the Voronoi division is performed with each local maximum as the generating point, and connecting the adjacent generating points with line segments. This is a net-like figure made up of triangular aggregates. Each triangle is called a Delaunay triangle, and a side of each triangle (a line segment connecting adjacent generating points) is called a Delaunay line. FIG. 3 is a diagram in which a Delaunay diagram (a diagram represented by a white line segment) is superimposed on the original image.

  (4) Next, the frequency distribution of the line segment length of each Delaunay line, that is, the frequency distribution of the distance between adjacent maximum points (hereinafter referred to as the distance between adjacent protrusions) is obtained. FIG. 4 is a histogram of the frequency distribution created from the Delaunay diagram of FIG.

(5) The average value d _AVG and the standard deviation σ are obtained from the frequency distribution of the distance d between adjacent protrusions thus obtained. Here, when the frequency distribution obtained in this manner is regarded as a normal distribution and the average value d _AVG and the standard deviation σ are obtained, the average value d _AVG = 158 nm and the standard deviation σ = 38 nm are obtained in the example of FIG. As a result, the maximum value of the distance d between adjacent protrusions is set to dmax = d _AVG + 2σ, and in this example, dmax = 234 nm.

The same method is applied to define the height of the protrusion. In this case, the relative height difference of each local maximum point position from a specific reference position is acquired from the local maximum point obtained by the above (2), and is histogrammed. FIG. 5 is a diagram showing a histogram of the frequency distribution of the protrusion height H with the protrusion root position obtained in this way as a reference (height 0). The average value _HAVG of the protrusion height and the standard deviation σ are obtained from the frequency distribution based on the histogram. Here in the example of FIG. 5, the mean value _H AVG = 178 nm, the standard deviation sigma = 30 nm. Thus in this example, the height of the projections is an average value _H AVG = 178 nm.

  In addition, the reference position when measuring the height of the protrusion described above is based on the valley bottom (minimum point of height) between the adjacent minute protrusions as a reference of height 0. However, when the height of the valley bottom itself varies depending on the location (for example, when the height of the valley bottom has undulation with a period larger than the distance between adjacent projections of the microprojections), (1) First, The average value of the height of each valley bottom measured from the front surface or the back surface is calculated within an area sufficient for the average value to converge. (2) Next, a plane having the average height and parallel to the front surface or the back surface of the base material is considered as a reference surface. (3) Then, the height of each microprotrusion from the reference surface is calculated by setting the reference surface to a height of 0 again.

If the protrusions are irregularly arranged, when this way the maximum value of the adjacent protrusions distance obtained by dmax = d AVG ₊ 2σ, average H _AVG height of projections are arranged regularly It is necessary to satisfy the above conditions. Specifically, the condition of the distance between the microprotrusions that exhibits the antireflection effect is dmax ≦ Λmin. At a minimum, the minimum necessary condition that can exhibit the antireflection effect at the longest wavelength in the visible light band is Λmin = λmax, so dmax ≦ λmax, and the antireflection effect can be achieved for all wavelengths in the visible light band. The necessary and sufficient condition is dmax ≦ λmin because Λmin = λmin. A preferable condition that can more reliably exhibit the antireflection effect for all wavelengths in the visible light band is dmax ≦ 300 nm, and a more preferable condition is dmax ≦ 200 nm. Also, dmax ≧ 50 nm is usually satisfied and dmax ≧ 100 nm is preferable because of the antireflection effect and ensuring the isotropic (low angle dependency) of the reflectance. The height of the protrusion is set to _HAVG ≧ 0.2 × λmax = 156 nm (λmax = 780 nm) in order to exhibit a sufficient antireflection effect.

  The surface shape of the microprojection layer is not particularly limited. For example, in the embossing method, the 2P method, etc., it can be formed by shaping using a replication mold.

Next, a material for forming the microprojection layer will be described.
The microprojection layer is made of a cured product of an acrylic resin composition. The acrylic resin composition used to form a layer that is in direct contact with the substrate, such as the micro-projection layer of the above-mentioned single-layer type antireflection article and the first layer of the above-mentioned multilayer type antireflection article, It contains an acrylic curable resin and a solvent, and can contain an acrylic non-curable resin, a non-acrylic resin, and other additives as necessary.
When the acrylic resin composition used for forming the layer in direct contact with the substrate contains a solvent, the acrylic resin composition is coated on the substrate when the antireflection article according to the present invention is produced. When processed, the solvent contained in the resin composition penetrates the substrate surface. And in the process of drying the resin composition, the base material surface infiltrated with the solvent swells and deforms, and at the same time, the resin composition enters the concave portion of the base material surface formed by the deformation, whereby the interface is formed. It is considered that an intricate shape is formed in the depth direction.

On the other hand, an acrylic resin composition used for forming a layer that forms a microprojection layer other than the first layer of the multilayer type antireflection article described above, that is, used for forming a layer that does not directly contact the substrate. The obtained acrylic resin composition preferably contains almost no solvent, and more preferably is a non-solvent type containing no solvent. If the acrylic resin composition contains a solvent, the solvent contained in the acrylic resin composition may penetrate into the first layer after drying when the antireflection article is produced. Therefore, when the resin composition is cured in forming the microprojection layer, there may be a problem that bubbles are generated in the resin composition in which the solvent remains.
In order to prevent such a problem from occurring, the resin composition for forming a microprojection layer of a single-layer antireflection article and the resin composition for forming a first layer of a multilayer antireflection article should be cured before curing. It must be thoroughly dried to remove the solvent.

The acrylic resin composition used for forming the layer that does not directly contact the base material is the same as the acrylic resin composition used for forming the layer that directly contacts the base material, except for the solvent. Ingredients can be included.
In addition, the acrylic resin composition used for formation of the layer which does not contact a base material directly can be prepared in a liquid state by containing a dilution monomer instead of a solvent.

The acrylic curable resin contained in the acrylic resin composition is cured by a reaction between a carbon-carbon double bond of a (meth) acryl group. As the acrylic curable resin, it is preferable that a carbon-carbon double bond of a (meth) acryl group reacts and cures by at least one treatment selected from ionizing radiation and heating.
The ionizing radiation means electromagnetic waves or charged particles having energy that can be cured by polymerizing molecules. For example, all ultraviolet rays (UV-A, UV-B, UV-C), visible rays, gamma rays , X-rays, electron beams and the like. Among these, it is preferable to use ultraviolet rays (UV) or electron beams (EB).

Examples of the acrylic curable resin include urethane (meth) acrylate, ester (meth) acrylate, epoxy (meth) acrylate, silicon (meth) acrylate, and the like. Can be used.
The acrylic curable resin is not particularly limited, but is preferably a bifunctional or higher (meth) acrylate having two or more (meth) acryl groups from the viewpoint of excellent reactivity.

  The urethane (meth) acrylate is not particularly limited, but a preferred chemical structure is (A) a compound having an isocyanate group (preferably a plurality) in the molecule and a hydroxyl group in the molecule (preferably Is obtained by reacting a diisocyanate compound or a triisocyanate compound with a compound having a structure obtained by reacting a compound having a plurality of (meth) acrylic groups, and (B) a compound having a plurality of hydroxyl groups. Examples thereof include those having a structure obtained by reacting a compound having a hydroxyl group and a (meth) acryl group in the molecule, such as hydroxyethyl (meth) acrylate, with the unreacted isocyanate group of the compound.

  Moreover, as said urethane (meth) acrylate, it can use individually by 1 type or in mixture of 2 or more types. Especially, as said urethane (meth) acrylate, it is preferable to contain the tetrafunctional or more urethane (meth) acrylate which has a 4 or more (meth) acryl group, and it is a hexafunctional or more urethane (meth) acrylate. It is particularly preferable that the resin contains a urethane (meth) acrylate having 10 or more functional groups. Moreover, the upper limit of the number of (meth) acryl groups contained in the urethane (meth) acrylate is not particularly limited, but is preferably 15 or less. If the number of (meth) acrylic groups in the urethane (meth) acrylate is too small, the curability and reaction rate of the obtained microprojection layer may be reduced, and scratch resistance and mechanical strength may be reduced. On the other hand, if the number of (meth) acryl groups in the urethane (meth) acrylate is too large, the reaction rate of the carbon-carbon double bond of the (meth) acryl group by polymerization may not be sufficiently increased.

  When the urethane (meth) acrylate is contained in the acrylic resin composition, the curability and reaction rate of the obtained microprojection layer are increased, the storage elastic modulus is increased, and the flexibility is excellent. Thus, it is possible to achieve both optical characteristics such as antireflection performance and light transmittance and mechanical characteristics such as surface scratch resistance and physical strength.

Although it does not specifically limit as said ester (meth) acrylate, A bifunctional or more thing is preferable.
Examples of the bifunctional ester (meth) acrylate include linear alkanediol di (meth) acrylate, alkylene glycol di (meth) acrylate, trivalent or higher alcohol partial (meth) acrylate ester, and bisphenol di (meth) acrylate. ) Acrylate and the like. Among these, a bifunctional ester (meth) acrylate having an alkylene glycol chain and having one (meth) acryl group at each of both ends of the molecule is preferable from the viewpoint of excellent curability.

Examples of the trifunctional ester (meth) acrylate include glycerin PO-modified tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane EO-modified tri (meth) acrylate, and trimethylolpropane PO-modified tri (meth). ) Acrylate, isocyanuric acid EO modified tri (meth) acrylate, isocyanuric acid EO modified ε-caprolactone modified tri (meth) acrylate, 1,3,5-triacryloylhexahydro-s-triazine, pentaerythritol tri (meth) acrylate, Examples include dipentaerythritol tri (meth) acrylate tripropionate.
Examples of tetrafunctional or higher functional ester (meth) acrylates include pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate monopropionate, dipentaerythritol hexa (meth) acrylate, tetramethylolethanetetra (meth) ) Acrylate, oligoester tetra (meth) acrylate and the like.

  When the ester (meth) acrylate is contained in the acrylic resin composition, the flexibility of the microprojection layer is improved and the mechanical strength of the surface of the microprojection layer is improved. Moreover, when the said acrylic resin composition contains urethane (meth) acrylate in order to improve sclerosis | hardenability etc., the softness | flexibility of a microprotrusion layer deteriorates by containing ester (meth) acrylate further. Can be prevented.

The epoxy (meth) acrylate is not particularly limited. For example, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, tripropylene glycol Diglycidyl ethers of alkylene glycol such as diglycidyl ether; Glycerin glycidyl ethers such as glycerin diglycidyl ether; Bisphenol A diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, PO modified diglycidyl ether of bisphenol A, bisphenol Diglycidyl ethers of bisphenol compounds such as F diglycidyl ether, Such as those having a structure obtained by adding acrylic acid and the like. Moreover, what has the structure which added (meth) acrylic acid to the polycondensation epoxy resin is mentioned. Furthermore, those having a structure in which (meth) acrylic acid is added to an epoxy resin having a structure obtained by reacting, for example, epichlorohydrin with a polycondensation product such as phenol novolak or cresol novolak Is mentioned.
When the epoxy (meth) acrylate is contained in the acrylic resin composition, the microprojection layer is further toughened, and mechanical strength such as scratch resistance on the surface of the microprojection layer is further improved.

  In order to obtain sufficient physical properties, the content of the acrylic curable resin in the acrylic resin composition is preferably 60% by mass or more based on the total solid content (nonvolatile component).

As the solvent contained in the acrylic resin composition used for forming the layer in direct contact with the substrate, a solvent having a boiling point not higher than the heat resistance temperature of the acrylic resin substrate used can be appropriately selected and used. Although not particularly limited, for example, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), methanol, ethanol, isopropyl alcohol (IPA), butanol, ethyl acetate, methyl acetate, butyl acetate, cyclohexanone, acetone, γ-butyl lactone, Examples thereof include n-methylpyrrolidone (NMP) and propylene glycol monomethyl ether acetate (PMA).
In the acrylic resin composition used for forming a layer that is in direct contact with the substrate, the content of the solvent in the acrylic resin composition is not particularly limited, but is usually 20 to 80% by mass, preferably 40 to 40%. It can be 70 mass%.

  The additive that can be contained in the acrylic resin composition is not particularly limited. For example, a release agent, a photopolymerization initiator, a photosensitizer, an antioxidant, a polymerization inhibitor, a crosslinking agent, and an infrared ray. Examples thereof include an absorbent and an antistatic agent.

  The acrylic resin composition has its composition (for example, the type and blending amount of the acrylic curable resin, and the type and amount of the polymerization initiator), and irradiation conditions (intensity and exposure time) of ionizing radiation used for the polymerization. , Wavelength, oxygen removal, etc.), heating conditions during polymerization (temperature, heating time, oxygen removal, etc.), microprojection layer shape (thickness, etc.), etc. are adjusted to improve reaction rate and curability Can be made.

(Interface between acrylic resin substrate and microprojection layer)
In the antireflection article according to the present invention, the interface between the acrylic resin base material and the microprojection layer is formed in a shape that alternately interlaces with the acrylic resin base material side and the microprojection layer side. Yes. Thereby, the antireflection article according to the present invention has excellent adhesion between the acrylic resin base material side and the microprojection layer.
The interface between the acrylic resin substrate and the fine protrusion layer is not particularly limited, but the average protrusion interval Sm is 0.1 to 4 μm, and the ten-point average roughness Rz is 0.1 to 4 μm. Is preferred. Thereby, the adhesiveness of the said acrylic resin-made base material and the said microprotrusion layer improves. In view of further improving the adhesion, the average protrusion spacing Sm is particularly preferably 1 to 2 μm, and the ten-point average roughness Rz is particularly preferably 1 to 2 μm.

  The average projection spacing Sm represents the average spacing of the irregularities of the interface of the microprojection layer (see Sm in FIG. 1), and the ten-point average roughness Rz represents the ten-point average roughness, This corresponds approximately to the average value of the height difference between the top and bottom of the unevenness of the interface (see Rz in FIG. 1). The definitions of these terms are based on JIS B0601 1994.

The average protrusion spacing Sm and the ten-point average roughness Rz are obtained by using a longitudinal section (cut surface in the depth direction) of the antireflection article according to the present invention as SEM (manufactured by Hitachi High-Technologies Corporation, Hitachi ultra-high resolution electric field). It can be measured and evaluated under the following conditions from the uneven profile of the interface between the acrylic resin substrate and the microprojection layer expressed by observation with an emission scanning electron microscope (SU8000) or the like. The Sm value and the Rz value are calculated based on a profile measured for each evaluation length.
Reference length (cutoff value λc of roughness curve): 4 μm
Evaluation length (reference length (cutoff value λc) × 5): 20 μm

The measurement of the Sm value and the Rz value is not particularly limited, but in consideration of intra-interface variation, two or more cut surfaces (cross-section samples) obtained by cutting at least two locations of the antireflection article are used. It is preferable to measure. Among them, it is preferable that the cutting direction of at least one set of cutting points among the cutting points of the antireflection article to be cut when obtaining two or more cross-sectional samples is not a parallel direction, and particularly has a vertical relationship. Is preferred.
The cross-sectional sample used for the measurement is more preferably obtained as follows. First, a reference length and an evaluation length are set in advance. Next, at least two center points are set on the surface of the antireflection article as sampling points. Furthermore, a circle having the center point as the center and the evaluation length as a radius is drawn, and at least four points are set on the circumference of the circle. Then, a cross-section sample is obtained by cutting the antireflection article in the depth direction along a straight line having a predetermined azimuth angle connecting the point on the circumference and the center point. About each obtained cross-sectional sample, a profile is measured for every evaluation length, and Sm value and Rz value based on it are calculated | required.
It is preferable that the straight lines serving as the cut portions are set so that the azimuth angles in the circle are equally spaced. Moreover, the straight line that becomes the cut portion is not particularly limited, but it is preferable that at least one set intersects at 90 °.
Further, it is preferable that at least one of the center points is set at a central portion that occupies 50% of the total area of the surface of the antireflection article, and at least one is set at a portion other than the central portion.
As a specific example of a cut portion for obtaining a cross-sectional sample of the antireflection article, an example in which the center point A is set in a central portion surrounded by a dotted line and the center point B is set in a portion other than the central portion in FIG. Show. In the example shown in FIG. 6, the straight lines that are the cutting points for obtaining the cross-sectional sample are centered at the center points A and B, respectively, and the azimuths are 90 ° apart in a circle with the evaluation length as the radius. Is set. The antireflection article shown in FIG. 6 is a plan view.
In the present invention, the average protrusion interval Sm and the ten-point average roughness Rz are average values when the Sm value and the Rz value are measured for each sample using a plurality of cross-sectional samples as described above. .

(Method for manufacturing antireflection article)
Although the manufacturing method of the antireflection article according to the present invention is not particularly limited, details of an example of a manufacturing method of a one-layer type and a two-layer type will be described below as representative examples of the antireflection article according to the present invention. Explained.

1. Method for Producing Single Layer Type Antireflective Article The single layer type antireflective article according to the present invention, as shown in FIG. 7, for example, first prepares an acrylic resin base material 11 (FIG. 7A), and The fine projection layer-forming coating film 12 ′ is formed by applying the resin composition for forming the microprojection layer on the surface of the base resin substrate 11 (FIG. 7B), and the coating film 12 ′ is heated. After drying (FIG. 7C), the surface of the coating film 12 ′ is shaped using a replication mold 15 to form a group of micro protrusions formed by assembling the micro protrusions 12 a (FIG. 7D )), By irradiating with ionizing radiation, the acrylic resin composition is cured to form the microprojection layer 12 (FIG. 7 (e)), the replica mold 15 is removed, and the antireflection article 10 is removed. Can be manufactured (FIG. 7F).

The drying temperature in the heat drying is not particularly limited as long as it is not higher than the heat-resistant temperature of the acrylic resin substrate 11 and can be removed by evaporating the solvent contained in the resin composition for forming a microprojection layer. For example, it can be set to 80-130 degreeC. Especially, it is preferable that the said drying temperature is the glass transition temperature (Tg) vicinity of the base material 11 made from acrylic resin. Thereby, substrate defects such as severing, distortion, and deformation of the acrylic resin substrate 11 do not occur, and the adhesion between the acrylic resin substrate 11 and the microprojection layer 12 can be further improved. it can. The glass transition temperature (Tg) can be measured by DSC method.
By the heating and drying step, it is considered that the interface between the acrylic resin substrate 11 and the microprojection layer forming coating film 12 ′ is formed in an alternating shape.

  As the acrylic resin substrate 11, for example, a transparent acrylic resin substrate having a thickness of 20 to 50 μm and a glass transition temperature (Tg) of 100 to 130 ° C. can be used.

As the resin composition for forming a microprojection layer used for forming the coating film 12 ′ for forming the microprojection layer, for example, an acrylic resin composition containing an acrylic ionizing radiation curable resin and a solvent can be used. .
The acrylic ionizing radiation curable resin is not particularly limited, but for example, urethane (meth) acrylate is preferable because it has excellent balance between the adhesion between the microprojection layer and the substrate and the optical and mechanical properties of the microprojection layer. , One containing at least one selected from the group consisting of ester (meth) acrylate, epoxy (meth) acrylate and silicon (meth) acrylate can be used.

  As the solvent, one having a boiling point lower than 130 ° C. is used, for example, at least one selected from methyl ethyl ketone (MEK) (boiling point 79.5 ° C.) and methyl isobutyl ketone (MIBK) (boiling point 116.2 ° C.). Can do.

  In the production of a single-layer antireflection article according to the present invention, when the ionizing radiation is irradiated, the replica mold 15 is laminated on the microprojection layer forming coating film 12 'as shown in FIG. Irradiation can be performed from the material 11 side, and the coating film 12 ′ for forming the microprojection layer is dry and relatively excellent in shape retention. After peeling from 12 ', it can also irradiate from the coating film 12' side for microprojection layer formation. Note that the method of irradiating ionizing radiation after the replica mold 15 is peeled from the coating film 12 'for forming the microprojection layer is excellent in terms of high productivity.

2. Method for Producing Two-Layer Type Antireflection Article As shown in FIG. 8, for example, the two-layer type antireflection article according to the present invention first prepares an acrylic resin base material 21 (FIG. 8 (a)), A first layer-forming coating film 23 ′ is formed by applying at least the first layer-forming resin composition on the surface of the acrylic resin substrate 21 (FIG. 8B), and the first layer After the coating film 23 ′ for forming is heated and dried (FIG. 8C), the coating film 24 for forming the second layer made of the resin composition for forming the second layer is formed on the coating film 23 ′ for forming the first layer. 'Is formed (FIG. 8D). Thereafter, the surface of the coating film 24 ′ for forming the second layer is shaped using the replication mold 25 to form a group of minute protrusions formed by assembling the minute protrusions 22a (FIG. 8 (e)). By irradiating with radiation, the microprojection layer composition is cured to form a microprojection layer 22 composed of a first layer 23 and a second layer 24 (FIG. 8 (f)). It can remove and can manufacture the antireflection article 20 (Drawing 8 (g)).

The drying temperature at the time of heating and drying the first layer forming coating film 23 ′ is equal to or lower than the heat resistance temperature of the acrylic resin substrate 21, and the solvent in the first layer forming coating film 23 ′ is removed. If it is the temperature which can be removed by evaporation, it will not specifically limit, From the point which the adhesiveness of the said acrylic resin base material 21 and said 1st layer 23 improves further, it is the same as the case of the said one-layer type antireflection article. For example, it can be set to 80-130 degreeC. The drying temperature is preferably in the vicinity of the glass transition temperature (Tg) of the acrylic resin substrate 21.
It is considered that the interface between the acrylic resin base material 21 and the first layer forming coating film 23 ′ is formed in an alternating shape by the heating and drying step.

  As the acrylic resin base material 21, the same one as the acrylic resin base material 11 used for the single layer type can be used.

As said 1st layer forming resin composition, the acrylic resin composition containing acrylic ionizing radiation curable resin and a solvent can be used, for example.
Moreover, as a resin composition for 2nd layer formation, the thing containing acrylic type ionizing radiation curable resin and not containing a solvent can be used, for example.
The acrylic ionizing radiation curable resin contained in the first layer forming resin composition and the second layer forming resin composition is not particularly limited, and the one-layer type resin composition for forming a microprojection layer is not particularly limited. The thing similar to what was mentioned as an acrylic ionizing radiation-curable resin contained in can be used.
In addition, by changing the type and blending ratio of the acrylic ionizing radiation curable resin, the resin composition for forming the first layer can be particularly excellent in adhesion to the substrate, The resin composition for forming a second layer is particularly excellent in moldability and excellent in mechanical properties such as surface scratch resistance and physical strength after curing.
As the solvent contained in the resin composition for forming the first layer, the same solvents as those used for the resin composition for forming a single-layer microprojection layer can be used.

  Moreover, as said 2nd layer formation resin composition, the liquid thing containing the dilution monomer instead of the solvent can also be used, and a film-form thing can also be used. When a liquid resin composition is used as the second layer forming resin composition, the second layer forming coating film 24 is formed by coating the liquid resin composition on the first layer forming coating film 23 '. 'Can be formed. When a film-like resin composition is used as the second layer-forming resin composition, the second-layer-forming resin composition is applied by sticking the film-like resin composition onto the first-layer-forming coating film 23 ′. A film 24 'can be formed.

  In the production of the two-layer type antireflection article according to the present invention, when ionizing radiation is applied, when the liquid composition having a high fluidity is used as the second layer forming resin composition, FIG. As shown to e), it can irradiate from the base-material 21 side, making the replication type | mold 25 laminated | stack on coating film 24 'for 2nd layer formation (FIG.8 (e)). When the resin composition for forming the second layer is excellent in shape retention such as a film-like one, although not shown, the replication mold 25 is removed from the coating film 24 ′ for forming the second layer. After peeling, the second layer-forming coating film 24 ′ can be irradiated from the side, or as shown in FIG. 8 (e), the replication mold 25 is laminated on the second layer-forming coating film 24 ′. It is also possible to irradiate from the substrate 21 side. The method of irradiating ionizing radiation after the replication mold 25 is peeled from the second layer forming coating film 24 ′ is excellent in terms of high productivity.

The single-layer type antireflection article is excellent in productivity because the microprojection layer is formed of only one layer, but the adhesion between the microprojection layer and the acrylic resin substrate, and the light of the microprojection layer are excellent. In order to remarkably improve both the characteristics and the mechanical characteristics, it is necessary to relatively carefully select the composition of the resin composition for forming the microprojection layer.
On the other hand, the antireflection article of the two-layer type is formed with two layers of microprojection layers, so the productivity is inferior to that of the single-layer type, but the adhesion between the microprojection layer and the acrylic resin base material Since different materials can be used for the first layer that improves the properties and the second layer that improves the optical properties and mechanical properties of the microprojection layer, it is relatively easy to improve both properties.

1, 11, 21 Acrylic resin substrate 2, 12, 22 Minute protrusion layer 2a, 12a, 22a Minute protrusion 12 'Minute protrusion layer forming coating 3, 23 First layer 23' First layer forming coating 4, 24 Second layer 24 ′ Second layer forming coating film 15, 25 Duplicate type 10 Antireflection article 20 Antireflection article

The antireflective article according to the present invention comprises a surface of an acrylic resin base material with a group of microprojections formed by aggregation of antireflection microprojections, and is made of a cured product of an acrylic resin composition. An antireflection article formed with a microprojection layer,
When the shortest wavelength of the wavelength band of light for preventing reflection is Λmin and the distance between the small protrusions is dmax,
dmax ≦ Λmin
Have the relationship
The interface between the acrylic resin base material and the microprojection layer is formed in a shape alternately interleaved with the acrylic resin base material side and the microprojection layer side, and the intricate shape is JIS B0601 1994. The average protrusion interval Sm defined in JIS B0601 1994 is 0.1 to 4 μm, and the ten-point average roughness Rz defined in JIS B0601 1994 is 0.1 to 4 μm .

Antireflection article according to the present invention, the surface of the acrylic resin substrate, a reflection preventing article comprising formed microprotrusion layer comprising a cured product of A acrylic-based resin composition,
The microprojection layer contains, on the surface of the acrylic resin substrate, at least one acrylic curable resin selected from urethane acrylate and urethane methacrylate, and a solvent consisting of at least one selected from methyl ethyl ketone and methyl isobutyl ketone. It is a layer formed by applying, drying and curing an acrylic resin composition, provided on the surface with a group of microprojections formed by aggregation of antireflection microprojections,
When the shortest wavelength of the wavelength band of light for preventing reflection is Λmin and the distance between the small protrusions is dmax,
dmax ≦ Λmin
Have the relationship
In the process of applying and drying the acrylic resin composition , the interface between the acrylic resin substrate and the microprojection layer is alternately interleaved with the acrylic resin substrate side and the microprojection layer side. The complicated shape is formed in such a shape that the average protrusion interval Sm defined in JIS B0601 1994 is 0.1 to 4 μm and the ten-point average roughness Rz defined in JIS B0601 1994 is 0.1 to 4 μm. It is characterized by being.
In the antireflection article according to the present invention, the acrylic resin composition used for forming the microprojection layer contains urethane acrylate as the acrylic curable resin and methyl ethyl ketone as the solvent. be able to.

Claims (2)

Reflection formed on the surface of a base made of acrylic resin with a microprojection group consisting of aggregated microprojections for reflection prevention and a microprojection layer made of a cured product of an acrylic resin composition. Prevention articles,
When the shortest wavelength of the wavelength band of light for preventing reflection is Λmin and the distance between the small protrusions is dmax,
dmax ≦ Λmin
Have the relationship
The interface between the acrylic resin base material and the microprojection layer is formed in a shape that is alternately interlaced with the acrylic resin base material side and the microprojection layer side. Goods.   The interface between the acrylic resin substrate and the microprojection layer has an average projection spacing Sm defined in JIS B0601 1994 of 0.1 to 4 μm and a ten-point average roughness Rz defined in JIS B0601 1994. The antireflection article according to claim 1, wherein is 0.1 to 4 μm.