JP2010271400A - Optical sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sheet which suppresses shrink wrinkles and curls and has excellent hardness. <P>SOLUTION: The optical sheet is obtained by arranging a first HC layer and a second HC layer on one surface side of a TAC base material in this order from the TAC base material side. The first HC layer consists of a cured product of a first composition containing a reactive silica fine particle having a methacryloyl group and a first binder component having three or more acryloyl groups and has 15-70 wt.% content ratio of the reactive silica fine particle to the whole solid of the first composition. The second HC layer consists of the cured product of a second composition containing a second binder component having three or more acryloyl groups. The second composition is applied to the half-cured first HC layer on one surface side of the TAC base material and the half-cured first HC layer and a coating film of the second composition are fully cured to form the first HC layer and the second HC layer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical sheet used for the purpose of protecting the surface of a display or the like.

An image display surface in an image display device such as a liquid crystal display, a CRT display, a projection display, a plasma display, an electroluminescence display, or a reflection screen is required to be provided with scratch resistance so as not to be damaged when handled.
On the other hand, the scratch resistance of the image display surface of the image display device is improved by using a hard coat film or an optical sheet provided with a hard coat (hereinafter sometimes referred to as HC) layer on the base material. It is generally done.

  The hard coat layer in which only the binder component is cured often has insufficient hardness, and as in Patent Document 1, a hard coat layer is formed by curing a composition containing reactive inorganic fine particles in addition to the binder component. In general, the hardness of the hard coat film is improved.

However, in order to obtain an optical sheet having excellent hardness, an HC layer is obtained in an optical sheet in which a thick HC layer of 10 to 20 μm is provided on a triacetyl cellulose (hereinafter sometimes referred to as TAC) substrate. For this reason, the amount of light applied to the coating film of the curable resin composition increases, and the heat generated during curing also increases. Since the TAC base material is easily damaged by heat, there is a problem in that the generated heat causes the TAC base material to be damaged due to heat damage.
If the amount of light applied to the coating is reduced in order to suppress the heat generated during curing, curing proceeds on the irradiation surface side of the thick HC layer, and curing does not occur on the opposite side of the HC layer irradiation surface. This is sufficient, and the degree of curing varies in the film thickness direction of the HC layer. In this way, when the degree of curing varies, the curing shrinkage force on the side with sufficient curing becomes stronger than the force on the side with insufficient curing, which causes curling of the optical sheet including the TAC substrate. There was a problem.

  In addition, instead of forming one thick HC layer, if the two thin HC layers are formed so that the sum of the thickness and thickness of the one layer is the same, the hardness of the optical sheet is reduced. There was a problem.

  Therefore, an optical sheet that hardly causes warpage of the TAC base material when the curable resin composition is cured, warpage of the optical sheet due to curing shrinkage of the hard coat layer (so-called curl), and has excellent hardness. It is requested.

JP 2008-165040 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an optical sheet having excellent hardness while suppressing shrinkage wrinkles and curling.

As a result of intensive studies by the present inventors, it has been found that each component having crosslinking reactivity has a difference in intrinsic reactivity, and the crosslinking reactivity is different even when irradiated with the same amount of light. Moreover, it turned out that a difference arises also in adhesiveness with a base material or an adjacent layer by the reactivity of a binder component.
Accordingly, the present inventors can obtain an optical sheet having excellent hardness by suppressing shrinkage wrinkles and curling by forming a two-layer hard coat layer using a component having specific crosslinking reactivity. As a result, the present invention has been completed.

That is, the optical sheet according to the present invention is an optical in which the first hard coat layer and the second hard coat layer are provided in this order on the one surface side of the triacetyl cellulose base material from the triacetyl cellulose base material side. A sheet,
The first hard coat layer includes a first reactive silica fine particle having an average primary particle diameter of 1 to 100 nm having a methacryloyl group on the particle surface, and a first binder component having three or more acryloyl groups in one molecule. A cured product of the first curable resin composition containing
The ratio of the content of the first reactive silica fine particles to the total solid content of the first curable resin composition is 15 to 70% by weight,
The second hard coat layer comprises a cured product of a second curable resin composition containing a second binder component having 3 or more acryloyl groups in one molecule, and
After applying the first curable resin composition on one side of the triacetylcellulose base material and half-curing, the second curable resin composition is applied on the half-cured first hard coat layer. A first hard coat layer and a second hard coat layer are formed by fully curing the first hard coat layer and the second curable resin composition coated and half-cured. And

  A 1st binder component contributes to the hardness improvement of a 1st hard-coat layer by having 3 or more acryloyl groups in 1 molecule.

The reactive silica fine particle has a methacryloyl group on the particle surface and is contained in an amount of 15 to 70% by weight based on the total solid content of the first curable resin composition. Contributes to improving the adhesion of the hard coat layer.
Further, the reactive silica fine particles are contained in an amount of 15 to 70% by weight with respect to the total solid content of the first curable resin composition, thereby contributing to an improvement in hardness as an underlayer.

  The second binder component contributes to improving the hardness of the second hard coat layer by having three or more acryloyl groups in one molecule.

  The first curable resin composition is prepared using the first curable resin composition and the second curable resin composition containing the binder component having the specific type of reactive functional group and the reactive silica fine particles. Half-curing, then applying the second curable resin composition, combining the half-cured coating film of the first curable resin composition and the coating film of the second curable resin composition, and performing a full cure. As a result, the optical sheet according to the present invention is a TAC base material, but it is an optical sheet that suppresses shrinkage wrinkles and curls and has excellent hardness.

  In the optical sheet according to the present invention, the reactive silica fine particle is a reactive irregular silica having 3 to 20 spherical silica fine particles having an average primary particle diameter of 1 to 100 nm bonded by an inorganic chemical bond and having a methacryloyl group on the surface. Fine particles are preferable from the viewpoint of improving hardness.

  In a preferred embodiment of the optical sheet according to the present invention, the pencil hardness test (4.9 N load) specified in JIS K5600-5-4 (1999) can have a hardness of 5H or more.

In the present invention, the average primary particle size of the fine particles is a 50% particle size (d50 median size) when the fine particles in the solution are measured by a dynamic light scattering method and the particle size distribution is expressed as a cumulative distribution. means. The average primary particle size can be measured using a Microtrac particle size analyzer or a Nanotrac particle size analyzer manufactured by Nikkiso Co., Ltd.
In the definition of film and sheet in JIS-K6900, a sheet is a thin and generally flat product whose thickness is small relative to the length and width. A film has a thickness compared to the length and width. A thin, flat product that is extremely small and has an arbitrarily limited maximum thickness, usually supplied in the form of a roll. Accordingly, it can be said that a sheet having a particularly thin thickness 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, both a thick sheet and a thin sheet are used. Including meaning, it is defined as “sheet”.
In the present invention, the “hard coat layer” refers to a layer having a hardness of “H” or higher in a pencil hardness test (4.9 N load) defined in JIS K5600-5-4 (1999).

  The first curable resin composition containing the binder component having the specific type of reactive functional group and the reactive silica fine particles, and the second curable property containing the binder component having the specific type of reactive functional group. Using the resin composition, the first curable resin composition is half-cured, then the second curable resin composition is applied, and the half-cured first curable resin composition coating film, The optical sheet according to the present invention, which is a TAC substrate, suppresses shrinkage wrinkles and curls, and is excellent in adhesion and hardness by combining the two curable resin composition coatings and fully curing. It becomes.

FIG. 1 is a diagram schematically illustrating an example of a layer configuration of an optical sheet according to the present invention.

  Hereinafter, the optical sheet according to the present invention will be described first, and then the method for producing the optical sheet will be described.

In the present invention, (meth) acrylate represents acrylate and / or methacrylate.
The light of the present invention includes not only electromagnetic waves having wavelengths in the visible and non-visible regions, but also particle beams such as electron beams, and radiation or ionizing radiation that collectively refers to electromagnetic waves and particle beams.
In the present invention, unless otherwise specified, the film thickness means the film thickness during drying (dry film thickness).
In the present invention, the molecular weight means a weight average molecular weight which is a polystyrene equivalent value measured by gel permeation chromatography (GPC) when having a molecular weight distribution, and when having no molecular weight distribution, Mean molecular weight.
The spherical shape is a concept including not only a true sphere but also a shape that can approximate a sphere including a spheroid and a polyhedron.

(Optical sheet)
The optical sheet according to the present invention is an optical sheet in which a first hard coat layer and a second hard coat layer are provided in this order from the triacetyl cellulose base material side to the one surface side of the triacetyl cellulose base material. There,
The first hard coat layer includes a first reactive silica fine particle having an average primary particle diameter of 1 to 100 nm having a methacryloyl group on the particle surface, and a first binder component having three or more acryloyl groups in one molecule. A cured product of the first curable resin composition containing
The ratio of the content of the first reactive silica fine particles to the total solid content of the first curable resin composition is 15 to 70% by weight,
The second hard coat layer comprises a cured product of a second curable resin composition containing a second binder component having 3 or more acryloyl groups in one molecule, and
After applying the first curable resin composition on one side of the triacetylcellulose base material and half-curing, the second curable resin composition is applied on the half-cured first hard coat layer. A first hard coat layer and a second hard coat layer are formed by fully curing the first hard coat layer and the second curable resin composition coated and half-cured. And

FIG. 1 is a diagram schematically illustrating an example of a layer configuration of an optical sheet according to the present invention.
In the optical sheet 1, the first hard coat layer 20 and the second hard coat layer 30 are laminated in this order on the one surface side of the triacetyl cellulose base material 10 from the triacetyl cellulose base material side.

The first curable resin composition is prepared using the first curable resin composition and the second curable resin composition containing the binder component having the specific type of reactive functional group and the reactive silica fine particles. Half-curing, then applying the second curable resin composition, combining the half-cured coating film of the first curable resin composition and the coating film of the second curable resin composition, and performing a full cure. As a result, the optical sheet according to the present invention is a TAC base material, but it is an optical sheet that suppresses shrinkage wrinkles and curls and has excellent adhesion and hardness. Especially, the optical sheet which concerns on this invention is excellent in the pencil hardness and adhesiveness after a durability test, and is especially excellent in adhesiveness.
The reason for this is not clear, but when the reactive functional group of the reactive silica fine particles contained in the first curable resin composition is a methacryloyl group, an epoxy group other than the methacryloyl group, a hydroxyl group, a carboxyl group, and an amino group. It is presumed that the reactivity with the binder component is higher than that of the base and the like, and the adhesion with the adjacent TAC base material and the second HC layer is increased, contributing to the improvement of the hardness of the first HC layer. The
In addition, when the reactive functional group of the first binder component and the second binder component is an acryloyl group, compared to an epoxy group other than the acryloyl group, a hydroxyl group, a carboxyl group, an amino group, etc. It is presumed that the reactivity is high and the adhesion with the adjacent layer is enhanced. In particular, in the case of the first HC layer, the adhesion with the adjacent TAC substrate is also increased and contributes to the improvement of the hardness of the optical sheet. .

  In a preferred embodiment of the optical sheet according to the present invention, the pencil hardness test (4.9 N load) specified in JIS K5600-5-4 (1999) can have a hardness of 5H or more.

  Hereinafter, the triacetyl cellulose base material, the first hard coat layer, the second hard coat layer, and other layers that can be appropriately provided as necessary will be described in order.

(Triacetyl cellulose base material)
The triacetyl cellulose base material used in the present invention is a triacetyl cellulose sheet having a high light transmittance, and is not particularly limited as long as it satisfies the physical properties that can be used as the light transparent base material of the optical laminate. A conventionally known hard coat film or TAC substrate of an optical sheet can be appropriately selected and used. A surface treatment such as saponification treatment or provision of a primer layer may be applied to the TAC substrate. In addition, additives such as an antistatic agent may be added.

  The thickness of the TAC substrate is not particularly limited, and is usually about 30 μm to 200 μm, preferably 40 μm to 200 μm. In the present invention, since curling can be suppressed, curling can be suppressed even if the thickness of the TAC substrate is thin, and even a thickness of about 40 μm to 80 μm can be suitably used.

  In the present invention, rather than forming one thick HC layer, by forming two relatively thin HC layers, the coating of the curable resin composition is cured (hereinafter simply referred to as HC layer curing). It is possible to suppress the occurrence of shrinkage wrinkles such as a tatami pattern due to thermal damage of the TAC base material due to the heat of polymerization that occurs at times.

(First hard coat layer)
The first hard coat layer of the present invention comprises a reactive silica fine particle having an average primary particle diameter of 1 to 100 nm having a methacryloyl group on the particle surface, and a first binder component having three or more acryloyl groups in one molecule. The reactive silica fine particles are composed of a cured product of the first curable resin composition contained in a proportion of 15 to 70% by weight with respect to the total solid content of the curable resin composition, and are formed through a half cure. Has been.

  The film thickness of the first HC layer only needs to be 10 to 20 μm in terms of the total film thickness with the second HC layer to be described later, and within that range, the film thickness is appropriately adjusted according to the required performance of the optical sheet. That's fine. The film thickness of the first HC layer is preferably 3 to 17 μm, more preferably 5 to 15 μm. If it is 3 μm or more, it is easy to obtain a sufficient hardness as an underlayer. If it is thicker than 17 μm, the curl of the optical sheet becomes tight and cracks are likely to occur. In addition, the cost increases. In addition, when manufacturing a liquid crystal display, if the film thickness of the first HC layer is greater than 17 μm, when the polarizing plate and the optical sheet are bonded, drying of the solvent used for the adhesive is deteriorated. May adversely affect

  Hereinafter, the 1st curable resin composition which hardens | cures and becomes the 1st HC layer of this invention is demonstrated.

(First curable resin composition)
The curable resin composition for a hard coat layer of the present invention includes a reactive silica fine particle having an average primary particle diameter of 1 to 100 nm having a methacryloyl group on the surface of the silica fine particle, and a first having three or more acryloyl groups in one molecule. The binder component is included.
In addition, an antiglare agent, an antifouling agent and an antistatic agent may be contained for the purpose of imparting functionality, a leveling agent, a solvent for controlling coating suitability, and an easy lubricant for the purpose of preventing blocking.

(Reactive silica fine particles)
The reactive silica fine particles have a methacryloyl group having cross-linking reactivity with acryloyl groups of the first and second binder components described later on the surface of the silica fine particles having an average primary particle diameter of 1 to 100 nm. The reactive silica fine particles are contained in a proportion of 15 to 70% by weight with respect to the total solid content of the first curable resin composition. Accordingly, the reactive silica fine particles undergo a crosslinking reaction with the first and second binder components when the first curable resin composition is cured to form the first HC layer, and the first HC layer and the first HC layer This contributes to improving the adhesion between the two HC layers and the hardness of the optical sheet.

  The average primary particle size of the reactive silica fine particles is 1 to 100 nm, preferably 10 to 80 nm, and more preferably 12 to 50 nm. If the average primary particle diameter of the reactive silica fine particles is less than 1 nm, it cannot contribute to the improvement of the hardness of the HC layer. When the average primary particle size exceeds 100 nm, haze increases.

  In addition, the reactive silica fine particles have a narrow particle size distribution from the viewpoint of improving the hardness while maintaining the restoration rate when only the first binder component described later is used without impairing the light transmittance. More preferably, it is dispersed.

  The ratio of the content of reactive silica fine particles to the total solid content of the first curable resin composition is 15 to 70% by weight. The content may be appropriately adjusted according to the required physical properties of the optical sheet as long as the content is within this range, more preferably 35 to 65% by weight, and still more preferably 50 to 65% by weight. If it is less than 15% by weight, sufficient hardness cannot be imparted to the first HC layer. When the fine particles are closely packed, the content of the fine particles with respect to the curable resin composition is 70% by weight. When the fine particle content exceeds 70% by weight, the filling rate is excessively increased, and the silica fine particles, the first and second binder components, The adhesiveness of the optical sheet deteriorates, and the hardness of the optical sheet is reduced.

  The reactive silica fine particles may be used not only having a single average primary particle size but also a combination of two or more types having different average primary particle sizes. When two or more types are used in combination, the average primary particle size of each particle may be within 1 to 100 nm.

  The reactive silica fine particles of the present invention do not exclude the use of particles having pores or porous structures inside the particles, such as hollow particles, but are solid having no pores or porous structures inside the particles. It is more preferable to use particles from the viewpoint of improving hardness.

  The reactive silica fine particles may further impart a function to the HC layer, and are appropriately selected and used according to the purpose.

The methacryloyl group of the reactive silica fine particle has a higher reactivity with the binder component than other epoxy groups, hydroxyl groups, carboxyl groups, amino groups, etc., and the TAC base material and the second HC layer are adjacent to each other. Adhesion increases, contributing to the improvement of the hardness of the first HC layer.
When the methacryloyl group is used as the functional group of the reactive silica fine particles, the reactivity is low and the TAC substrate is not easily fouled by the reaction heat compared to the case where the acryloyl group is used, and it is adjacent to the first HC layer. Excellent adhesion to the second HC layer provided. Further, when the methacryloyl group is used, there is an advantage that the hardness after sufficiently curing is higher than that when the acryloyl group is used. Furthermore, when the coating film of the first curable resin composition is half cured, the curing of the coating film surface proceeds, but the methacryloyl group whose reactivity is lower than that of the acryloyl group is the second curing after that. Crosslinking reaction at the boundary portion with the second HC layer during full curing combined with the coating film of the conductive resin composition, and contributes to the improvement of the adhesion between the first HC layer and the second HC layer.
In addition, the first binder component easily undergoes a growth reaction due to polymerization of acryloyl groups. However, if a methacryloyl group is present on the surface of the reactive silica fine particles, the growth reaction is likely to be inhibited, and an unreacted functional group at the time of half-curing. There is an advantage that the number of groups increases as compared with the case where both the binder component and the reactive silica fine particles are acryloyl groups, and the number of components contributing to cross-linking between layers by full cure increases.

  Preparation of the reactive silica fine particles used in the present invention (introduction of a methacryloyl group on the surface of the silica fine particles) may be performed by a known method. For example, the method described in Patent Document 1 can be used.

  Commercially available reactive silica fine particles having a methacryloyl group on the surface of the silica fine particles include MIBK-SD, MIBK-SDMS, MIBK-SDL, MIBK-SDZL, manufactured by Nissan Chemical Industries, Ltd., and JGC Catalysts & Chemicals, Inc. DP1021, DP1022, DP1032, DP1037, DP1041, DP1042, DP1044, and the like can be given.

  In the present invention, the reactive silica fine particles are reactive deformed silica fine particles having 3 to 20 spherical silica fine particles having an average primary particle diameter of 1 to 100 nm bonded by an inorganic chemical bond and having a methacryloyl group on the surface. However, it is preferable because the hardness of the first HC layer can be further improved.

Hereinafter, the reactive irregularly shaped silica fine particles will be described.
In the reactive irregularly shaped silica fine particles, 3 to 20 spherical silica fine particles having an average primary particle diameter of 1 to 100 nm are bonded by an inorganic chemical bond to form irregularly shaped silica fine particles. A methacryloyl group is formed on the surface of the irregularly shaped silica fine particles. Have. By the methacryloyl group, the reactive irregularly shaped silica fine particles and the first and second binder components can be cross-linked, which contributes to improving the hardness of the first HC layer.

  When the reactive irregularly shaped silica fine particles are viewed as aggregated particles, the aggregated reactive silica fine particles having a particle size comparable to that of the reactive irregularly shaped silica fine particles have higher strength as the aggregated particles. Also excellent in hardness.

  The size of the reactive deformed silica fine particles in which 3 to 20 spherical silica fine particles having an average primary particle diameter of 1 to 100 nm are bonded by an inorganic chemical bond, that is, the length of the major axis may be appropriately adjusted. It is preferable that it is 20-300 nm. If it is this range, it will be easy to give hardness to the 1st HC layer, and it will be easy to maintain the light transmittance of HC layer.

  The size of the reactive deformed silica fine particles can be measured in the first curable resin composition by the same method as that for the reactive silica fine particles. In the cured HC layer, the cross section of the HC layer is shown by an SEM photograph. Alternatively, the number of hardened deformed silica fine particles observed using a TEM photograph was counted as 100, and the average value of particles observed with an aspect ratio of less than 1.3 was defined as the primary particle diameter, and the aspect ratio was 5 near the maximum value. The average of the points is obtained as the major axis length.

The deformed silica fine particles of the present invention are formed by bonding 3-20, preferably 3-10, of the silica fine particles by inorganic chemical bonds.
If the number of the fine particles in which the silica fine particles are bonded by an inorganic chemical bond is 3 to 20, the effect of improving the hardness can be obtained.

Examples of the inorganic chemical bond include an ionic bond, a metal bond, a coordination bond, and a covalent bond. Among these, bonds that do not disperse the bonded fine particles even when the deformed silica fine particles are added to a polar solvent, specifically, metal bonds, coordinate bonds, and covalent bonds are preferable, and covalent bonds are more preferable. In a conventional aggregate having no covalent bond, there is a possibility that the aggregate is separated by a physical external force (for example, a shear in stirring at the ink stage, a shear received during application of a doctor knife or the like). Chemically, there is a possibility that the aggregate is separated by an additive such as a solvent that breaks the aggregation, a binder component, or a surfactant. In addition, even when the optical sheet is formed, the aggregate is separated by a physical external force (contact by a pointed object or the like), which may cause scratches on the optical sheet. On the other hand, a covalent bond is stable because it is difficult to decompose due to physical and chemical forces.
Examples of the polar solvent include water, methanol, and lower alcohols such as ethanol and isopropanol.

The deformed silica fine particles of the present invention are superior in hardness to those obtained by binding the reactive silica fine particles via a binder component with methacryloyl groups, and surface-treat the deformed silica particles to obtain reactive deformed silica fine particles having a methacryloyl group. When used, the optical sheet according to the present invention exhibits excellent hardness.
The reason why the deformed silica fine particles are superior in hardness than those obtained by bonding 3 to 20 methacryloyl groups of the reactive silica fine particles is not clear, but the inorganic chemical bonds of the deformed silica fine particles are bonded by methacryloyl groups that are organic components. It is presumed that the rigidity is higher than that.

  The method for producing irregular shaped silica fine particles is not particularly limited as long as the silica fine particles are bonded by an inorganic chemical bond, and a conventionally known method can be appropriately selected and used. For example, it can be obtained by adjusting the concentration or pH of the monodispersed silica fine particle dispersion and performing hydrothermal treatment at a high temperature of 100 ° C. or higher. At this time, if necessary, a binder component can be added to promote the binding of the silica fine particles. Further, ions may be removed by passing the silica fine particle dispersion used through an ion exchange resin. Such ion exchange treatment can promote the binding of silica fine particles. After the hydrothermal treatment, the ion exchange treatment may be performed again.

As a method for introducing a methacryloyl group into the surface of the irregular shaped silica fine particle to obtain a reactive irregular shaped silica fine particle, a method of introducing a methacryloyl group into the silica fine particle of the reactive silica fine particle can be used.
When spherical reactive silica fine particles and reactive deformed silica fine particles are used in combination as the reactive silica fine particles, the reactive functional groups of the spherical reactive silica fine particles and the reactive functional groups of the reactive deformed silica fine particles are the same. It may be different.

  When spherical reactive silica fine particles and reactive irregularly shaped silica fine particles are used in combination, it is preferable that the reactive irregularly shaped silica fine particles are contained in an amount of 50% by weight or more based on the total amount of the two types of reactive silica fine particles. It is more preferable that it is contained by weight% or more from the viewpoint of improving hardness.

  Commercially available products of the above-mentioned reactive deformed silica fine particles include DP1039, DP1040, DP1071, DP1072, DP1073 manufactured by JGC Catalysts and Chemicals.

(First binder component)
The first binder component used in the first curable resin composition has three or more acryloyl groups in one molecule, and the first binder component is crosslinked with each other at the time of curing. It is the ingredient which becomes. In addition, since the acryloyl group has cross-linking reactivity with the methacryloyl group of the reactive silica fine particles and the acryloyl group of the second binder component contained in the second curable resin composition described later, the acryloyl group is crosslinked with these components. Thus, a network structure is formed, and the adhesion between the first HC layer and the second HC layer and the hardness of the optical sheet are further increased.

The acryloyl group has higher reactivity than the functional groups used in conventional binder components such as epoxy groups, hydroxyl groups, carboxyl groups, and amino groups, and contributes to improvement in hardness.
When an acryloyl group is used as the binder component, the reactivity is higher than when a methacryloyl group is used, so even with a small amount of light irradiation such as a half cure (even if the production rate is high), the crosslinking density is high and the second layer becomes the upper layer Hardness is further increased by full cure when forming the HC layer. In addition, the difference in hardness between methacryloyl group and acryloyl group is small if the amount of light irradiation is so large that wrinkles are generated on the TAC substrate, but acryloyl group is used in the range of moderate light irradiation amount that suppresses wrinkles on the TAC substrate. The case where the methacryloyl group is used is superior to the case where the methacryloyl group is used.
Furthermore, since the reaction reaches the region on the TAC substrate side of the first HC layer, there is also an advantage that the adhesiveness with the TAC substrate is excellent.

  The first binder component is preferably a light-transmitting material that transmits light when formed into a coating film, and a known curable resin or the like is required as long as it has three or more acryloyl groups in one molecule. What is necessary is just to employ | adopt suitably according to etc.

The molecular weight of the first binder component is not particularly limited and can be appropriately selected and used. In addition, when the molecular weight of the first binder component is 1000 or less, it is preferable to have 3 to 6 acryloyl groups in one molecule. When the molecular weight of the first binder component is more than 1000, acryloyl groups are contained in one molecule. 6 or more are preferable. These may be used alone or in combination.
As the first binder component, one or more of the above binder components can be used.

Examples of the binder component having three or more acryloyl groups include pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, dipentaerythritol pentaacrylate, trimethylolpropane triacrylate, trimethylolpropane hexaacrylate, and these The modified body is mentioned.
Examples of modified products include EO (ethylene oxide) modified products, PO (propylene oxide) modified products, CL (caprolactone) modified products, and isocyanuric acid modified products.

  As the first binder component, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, pentaerythritol tetraacrylate, and dipentaerythritol pentaacrylate are preferably used. Dipentaerythritol hexaacrylate, pentaerythritol tetraacrylate And dipentaerythritol pentaacrylate are most preferably used.

Urethane acrylates and epoxy acrylates having 6 or more acryloyl groups in one molecule and a molecular weight of more than 1000 can also be preferably used.
As such commercially available products of urethane acrylate, Nippon Synthetic Chemical Industry Co., Ltd .: UV1700B, Nippon Kayaku Co., Ltd .: DPHA40H, Negami Kogyo Co., Ltd .: Art Resin UN904, Art Resin UN3320HS, Arakawa Chemical Industries Product: Co., Ltd .: Beam set 577, Shin-Nakamura Chemical Co., Ltd .: U15HA, U6HA.

As commercial products of epoxy acrylate, Arakawa Chemical Industries, Ltd .: Beam Set 371,
Examples thereof include a beam set 371MLV, a beam set DK1, a beam set DK2, and a beam set DK3.

(Other ingredients)
In addition to the above components, a solvent, a polymerization initiator, an antistatic agent, an antiglare agent, and the like can be appropriately added to the first curable resin composition. Furthermore, various additives, such as a reactive or non-reactive leveling agent and various sensitizers, may be mixed. When an antistatic agent and / or an antiglare agent are included, antistatic properties and / or antiglare properties can be further imparted to the HC layer.

(Solvent of the first curable resin composition)
Specific examples of the solvent include isopropanol (IPA), methyl ethyl ketone (MEK), and methyl isobutyl ketone (MIBK).
From the viewpoint of improving the hardness of the optical sheet, non-permeable solvents such as MIBK and isopropanol are preferred. By using the non-permeable solvent, the first binder component does not penetrate into the triacetyl cellulose base material, so that the hardness of the first HC layer can be increased.
In addition, in this invention, osmosis | permeation means dissolving or swelling a triacetylcellulose base material.

(Polymerization initiator)
If necessary, radicals and cationic polymerization initiators may be appropriately selected and used. These polymerization initiators are decomposed by light irradiation and / or heating to generate radicals or cations to advance radical polymerization and cationic polymerization.

(Antistatic agent)
As specific examples of the antistatic agent, conventionally known antistatic agents such as a quaternary ammonium salt, a conductive polymer, and conductive fine particles can be used.

(Anti-glare agent)
As the antiglare agent, a conventionally known antiglare agent such as a fine particle antiglare agent such as styrene beads (refractive index 1.59) may be used. When a fine particle antiglare agent is used, the addition amount is preferably 2 to 30 parts by weight, more preferably 10 to 25 parts by weight, with respect to 100 parts by weight of the curable resin composition.

(Leveling agent)
A leveling agent can be added to the first curable resin composition of the present invention, and among them, it is preferable to add a fluorine or silicone leveling agent. The first curable resin composition to which the leveling agent is added can impart coating stability, slipperiness, antifouling property, and scratch resistance to the coating film surface during application or drying.
The addition amount of the leveling agent is preferably 0 to 0.5% by weight, more preferably 0 to 0.2% by weight, and more preferably 0.01 to 0. 2% by weight is more preferred.

  As a leveling agent, ionizing radiation curing such as X22-163A manufactured by Shin-Etsu Chemical Co., Ltd., a leveling agent having no ionizing radiation curable group, such as a conventionally known DIC Corporation MegaFac series (MCF350-5). Any leveling agent having a sex group can be used.

(Second hard coat layer)
The second hard coat layer of the present invention comprises a cured product of a second curable resin composition containing a second binder component having three or more acryloyl groups in one molecule and is half-cured. It is fully cured together with the HC layer.

  The second binder component used in the second curable resin composition has three or more acryloyl groups in one molecule, and is crosslinked between the second binder components at the time of curing. Is a component. Moreover, since the acryloyl group has cross-linking reactivity with the methacryloyl group of the reactive silica fine particles contained in the first curable resin composition and the acryloyl group of the first binder component, the acryloyl group crosslinks with these components, A network structure is formed to further enhance the adhesion between the first HC layer and the second HC layer and the hardness of the optical sheet.

The acryloyl group of the second binder component has higher reactivity than the functional group such as an epoxy group as described in the first binder component, and contributes to the improvement of hardness. In addition, when an acryloyl group is used as a binder component, the hardness when using an acryloyl group is superior to that when using a methacryloyl group even in a moderate light irradiation range in which wrinkles are prevented from occurring on the TAC substrate. .
When the functional group of the binder of the second HC layer, which is the upper layer, is a methacryloyl group, the reactivity of the second HC layer is insufficient, so that sufficient hardness cannot be obtained, as well as an antifouling agent and an antistatic agent. When the functional additive such as is added to the second curable resin composition and used, the functional additive is hardly fixed on the surface of the second HC layer, and the functional additive is easily The desired functionality may not be sufficiently imparted due to peeling off.
Moreover, since the reactivity is insufficient when the functional group of the second binder component is a methacryloyl group, when the optical sheet is rolled up, it sticks to the TAC substrate in contact with the second HC layer (blocking). May occur. In addition, when an optical sheet is attached to a polarizing plate for use in a liquid crystal display, the optical sheet may be saponified, but the functional additive such as an antifouling agent is peeled off by the saponification process, There is also a risk that the hardness of the optical sheet is reduced and haze is deteriorated.

As the second binder component, the first binder component mentioned in the first HC layer can be used. When the molecular weight of the second binder component is 1000 or less, it is preferable to have 3 to 6 acryloyl groups in one molecule, and when the molecular weight of the second binder component is larger than 1000, acryloyl groups are contained in one molecule. 6 or more are preferable. These may be used alone or in combination.
As the second binder component, one or more of the above binder components can be used.

For the second curable resin composition, the second reactive silica having an average primary particle size of 1 to 100 nm having a methacryloyl group on the particle surface as in the case of the first curable resin composition, depending on the required performance. Fine particles may be included.
The second reactive silica fine particles are preferably reactive deformed silica fine particles.

  When the second reactive silica fine particles are contained in the second curable resin composition, the content ratio of the second reactive silica fine particles is the first curable resin composition from the viewpoint of ensuring appropriate flexibility. It is preferably more than 0% by weight and less than 30% by weight with respect to the total solid content of the product.

  Similarly to the first curable resin composition, a solvent, a polymerization initiator, an antistatic agent, an antiglare agent, a leveling agent, and the like can be appropriately added to the second curable resin composition.

  The film thickness of the second HC layer is sufficient if the total film thickness with the first HC layer is 10 to 20 μm, and if it is within this range, it can be appropriately adjusted according to the required performance of the optical sheet. Good.

(Other layers)
The optical sheet according to the present invention is basically composed of the TAC substrate, the first HC layer, and the second HC layer as described above. However, in consideration of the function or application as an optical sheet, the surface of the second HC layer on the side opposite to the first HC layer is not further deviated from the gist of the present invention. One or more layers such as a layer, an antifouling layer, and a low refractive index layer may be provided.
The thicknesses of the other layers vary depending on the lamination conditions, and may be adjusted as appropriate.

(Optical sheet manufacturing method)
The optical sheet of the present invention is obtained by applying the first curable resin composition to one side of the TAC base material to form a coating film, half-curing the coating film, and then forming the coating on the half-cured first HC layer. Apply the second curable resin composition and fully cure the half-cured first HC layer and the second curable resin composition coating to form the first HC layer and the second HC layer. It is obtained by doing.

  The first curable resin composition is usually prepared by mixing and dispersing a reactive silica fine particle, a binder component, a polymerization initiator, and the like in a solvent according to a general preparation method. A paint shaker or a bead mill can be used for mixing and dispersing. When the first binder component has fluidity, the first curable resin composition can be applied to the substrate without using a solvent, and therefore a solvent may be used as necessary. The same applies to the second curable resin composition.

The application method of the curable resin composition is not particularly limited as long as it can uniformly apply the curable resin composition to the application surface of the TAC base material or the half-cured first HC layer. In addition, various methods such as a slide coating method, a bar coating method, and a roll coater method can be used.
The coating amount of the first curable resin composition on the TAC substrate varies depending on the performance required of the obtained optical sheet, but the film thickness after drying is 3 to 17 μm. What is necessary is just to adjust suitably.

As the method of half cure or full cure, a conventionally known method may be used. For example, light irradiation may be performed by ultraviolet irradiation with a high-pressure mercury lamp. The irradiation amount of the energy ray source at the time of half-curing is 5 to 50 mJ / cm ² as an integrated exposure amount at an ultraviolet wavelength of 365 nm. The irradiation amount of the energy ray source at the time of full cure is 50 to 5000 mJ / cm ² as an integrated exposure amount at an ultraviolet wavelength of 365 nm.

(Formation of other layers)
When forming other layers on the second HC layer, before curing the coating film of the second curable resin composition, or after curing, apply the curable resin composition of the other layer, Other layers may be formed by drying, light irradiation and / or heating.

  Hereinafter, the present invention will be described more specifically with reference to examples. These descriptions do not limit the present invention.

As irregular-shaped silica fine particles (1), a long-axis length of 60 nm, solid content of 40%, dispersion medium IPA solvent, irregular-shaped silica fine particles in which an average of 3.5 silica fine particles having an average primary particle size of 20 nm are bonded by inorganic chemical bonds Was used.
As the irregular-shaped silica fine particles (2), a long-axis length of 90 nm, a solid content of 40%, a dispersion medium IPA solvent, and irregular-shaped silica fine particles in which an average of five silica fine particles having an average primary particle size of 20 nm are bonded by inorganic chemical bonds are used. It was.
As the irregular-shaped silica fine particles (3), a long-axis length of 15 nm, solid content of 40%, dispersion medium IPA solvent, irregular-shaped silica fine particles in which an average of three silica fine particles having an average primary particle size of 5 nm are bonded by inorganic chemical bonds are used. It was.

As silica fine particles (1), IPA-ST (L), average primary particle size 44 nm, colloidal silica, 40% solid content liquid (dispersion medium: IPA) manufactured by Nissan Chemical Industries, Ltd. was used.
As the silica fine particles (2), IPA-ST, average primary particle size 12 nm, colloidal silica, 40% solid content liquid (dispersion medium: IPA) manufactured by Nissan Chemical Industries, Ltd. was used.
As the silica fine particles (3), MIBK-SDZL, average primary particle size 80 nm, colloidal silica, 40% solid content liquid (dispersion medium: MIBK) manufactured by Nissan Chemical Industries, Ltd. was used.
As the silica fine particles (4), an average primary particle size of 200 nm, colloidal silica, and a solid content 40% liquid (dispersion medium: MIBK) were used.
As reactive irregularly shaped silica fine particles (1), manufactured by JGC Catalysts & Chemicals Co., Ltd., manufactured by JGC Catalysts & Chemicals Co., Ltd., DP1039SIV (irregular shape, average primary particle size 20 nm, average number of connections 3.5, solid content 40% The liquid (dispersion medium: MIBK) and the functional group were methacryloyl groups) were used.
As the binder component (1), Nippon Kayaku Co., Ltd .: 6-functional dipentaerythritol hexaacrylate (product name: DPHA) was used.
As the binder component (2), Nippon Kayaku Co., Ltd .: trifunctional pentaerythritol triacrylate (product name: PETA) was used.
As the binder component (3), Arakawa Chemical Industries, Ltd. beam set DK1 (30 or more acryloyl groups, weight average molecular weight 20000, solid content 75% by weight, MIBK solvent) was used.
As the binder component (4), Nippon Kayaku Co., Ltd. product: DPMHA (six methacryloyl groups, molecular weight 662) was used.
As the binder component (5), a bifunctional acrylate monomer (product name: M215) manufactured by Toagosei Co., Ltd. was used.

As a polymerization initiator, Ciba Japan Co., Ltd. product: Irgacure 184 was used.
As the leveling agent, DIC Corporation: MegaFac MCF350-5 was used.
As a triacetyl cellulose base material, Konica Corporation product name: KC4UY (thickness 40 μm) was used.
Abbreviations for each compound are as follows.
DPHA: dipentaerythritol hexaacrylate PETA: pentaerythritol triacrylate MIBK: methyl isobutyl ketone IPA: isopropanol TAC: triacetyl cellulose

(Preparation of reactive silica fine particles (1-1))
The silica fine particles (1) were subjected to solvent substitution from IPA to MIBK using a rotary evaporator to obtain a MIBK dispersion having 40% by weight of silica particles. 5 parts by weight of 3-methacryloxypropylmethyldimethoxysilane was added to 100 parts by weight of this MIBK dispersion, and heat treatment was carried out at 50 ° C. for 1 hour, whereby the reactivity with an average primary particle size of 44 nm surface-treated with methacryloyl groups was achieved. A silica fine particle 40 wt% MIBK dispersion was obtained.

(Preparation of reactive silica fine particles (1-2))
The silica fine particles (1) were subjected to solvent substitution from IPA to MIBK using a rotary evaporator to obtain a MIBK dispersion having 40% by weight of silica particles. 5 parts by weight of 3-acryloxypropylmethyldimethoxysilane was added to 100 parts by weight of this MIBK dispersion, and the mixture was heat-treated at 50 ° C. for 1 hour, whereby the reactivity with an average primary particle size of 44 nm surface-treated with acryloyl groups was obtained. A silica fine particle 40 wt% MIBK dispersion was obtained.

(Preparation of reactive silica fine particles (2))
Silica fine particles (2) were surface-treated in the same manner as silica fine particles (1) to obtain a 40 wt% solid dispersion MIBK dispersion of reactive silica fine particles having an average primary particle size of 12 nm.

(Preparation of reactive silica fine particles (3))
Average primary particles surface-treated with methacryloyl groups by adding 5 parts by weight of 3-methacryloxypropylmethyldimethoxysilane to 100 parts by weight of MIBK dispersion of silica fine particles (3) and heat-treating at 50 ° C. for 1 hour. A 40 wt% MIBK dispersion of reactive silica fine particles having a diameter of 80 nm was obtained.

(Preparation of reactive silica fine particles (4))
Silica fine particles (4) were surface-treated in the same manner as silica fine particles (3) to obtain a 40 wt% MIBK dispersion of reactive silica fine particles having an average primary particle size of 200 nm.

(Preparation of first curable resin composition)
The components of the composition shown below were blended to prepare first curable resin compositions 1-1 to 1-8, respectively.

(First curable resin composition 1-1)
Reactive silica fine particles (1-1): 125 parts by weight (solid content: 50 parts by weight)
Binder component (1): 50 parts by weight Polymerization initiator: 4 parts by weight MIBK: 100 parts by weight

(First curable resin composition 1-2)
Reactive silica fine particles (1-1): 125 parts by weight (solid content: 50 parts by weight)
Binder component (2): 50 parts by weight Polymerization initiator: 4 parts by weight MIBK: 100 parts by weight

(First curable resin composition 1-3)
Reactive silica fine particles (1-1): 100 parts by weight (solid content: 40 parts by weight)
Binder component (1): 60 parts by weight Polymerization initiator: 4 parts by weight MIBK: 100 parts by weight

(First curable resin composition 1-4)
Reactive silica fine particles (1-1): 150 parts by weight (solid content: 60 parts by weight)
Binder component (1): 40 parts by weight Polymerization initiator: 4 parts by weight MIBK: 100 parts by weight

(First curable resin composition 1-5)
Reactive silica fine particles (2): 125 parts by weight (solid content: 50 parts by weight)
Binder component (1): 50 parts by weight Polymerization initiator: 4 parts by weight MIBK: 100 parts by weight

(First curable resin composition 1-6)
Reactive silica fine particles (3): 125 parts by weight (solid content: 50 parts by weight)
Binder component (1): 50 parts by weight Polymerization initiator: 4 parts by weight MIBK: 100 parts by weight

(First curable resin composition 1-7)
Reactive modified silica fine particles (1): 125 parts by weight (solid content: 50 parts by weight)
Binder component (1): 50 parts by weight Polymerization initiator: 4 parts by weight MIBK: 100 parts by weight

(First curable resin composition 1-8)
Reactive modified silica fine particles (1): 125 parts by weight (solid content: 50 parts by weight)
Binder component (1): 25 parts by weight Binder component (3): 25 parts by weight Polymerization initiator: 4 parts by weight MIBK: 100 parts by weight

(First curable resin composition 1-9)
Reactive silica fine particles (1-2): 125 parts by weight (solid content: 50 parts by weight)
Binder component (1): 50 parts by weight Polymerization initiator: 4 parts by weight MIBK: 100 parts by weight

(First curable resin composition 1-10)
Reactive silica fine particles (1-1): 125 parts by weight (solid content: 50 parts by weight)
Binder component (4): 50 parts by weight Polymerization initiator: 4 parts by weight MIBK: 100 parts by weight

(First curable resin composition 1-11)
Reactive silica fine particles (1-2): 125 parts by weight (solid content: 50 parts by weight)
Binder component (4): 50 parts by weight Polymerization initiator: 4 parts by weight MIBK: 100 parts by weight

(First curable resin composition 1-12)
Silica fine particles (1): 125 parts by weight (solid content: 50 parts by weight)
Binder component (1): 50 parts by weight Polymerization initiator: 4 parts by weight MIBK: 100 parts by weight

(First curable resin composition 1-13)
Silica fine particles (4): 125 parts by weight (solid content: 50 parts by weight)
Binder component (1): 50 parts by weight Polymerization initiator: 4 parts by weight MIBK: 100 parts by weight

(First curable resin composition 1-14)
Reactive silica fine particles (1-1): 25 parts by weight (solid content: 10 parts by weight)
Binder component (1): 90 parts by weight Polymerization initiator: 4 parts by weight MIBK: 100 parts by weight

(First curable resin composition 1-15)
Reactive silica fine particles (1-1): 200 parts by weight (solid content: 80 parts by weight)
Binder component (1): 20 parts by weight Polymerization initiator: 4 parts by weight MIBK: 100 parts by weight

(First curable resin composition 1-16)
Reactive silica fine particles (1-2): 125 parts by weight (solid content: 50 parts by weight)
Binder component (5): 50 parts by weight Polymerization initiator: 4 parts by weight MIBK: 100 parts by weight

(Preparation of second curable resin composition)
Components of the composition shown below were blended to prepare second curable resin compositions 2-1, 2-2, respectively.

(Second curable resin composition 2-1)
Reactive irregularly shaped silica fine particles (1-2): 25 parts by weight (solid content: 10 parts by weight)
Binder component (1): 45 parts by weight Binder component (3): 45 parts by weight Polymerization initiator: 4 parts by weight Leveling agent: 4 parts by weight (solid content: 0.2 parts by weight)
MIBK: 100 parts by weight

(Second curable resin composition 2-2)
Binder component (1): 50 parts by weight Binder component (3): 50 parts by weight Polymerization initiator: 4 parts by weight Leveling agent: 4 parts by weight (solid content: 0.2 parts by weight)
MIBK: 100 parts by weight

  Binder numbers, reactive silica fine particle numbers, and reactive silica fine particle surfaces of the first curable resin composition 1-1 to 1-16 and the second curable resin composition 2-1, 2-2 Table 1 summarizes the types of functional groups.

Example 1: Production of optical sheet The first curable resin composition 1-1 was applied to one side of a TAC substrate, dried in a heat oven at a temperature of 70 ° C for 60 seconds, and the solvent in the coating film was evaporated. Then, the coating film is half cured by irradiating ultraviolet rays so that the integrated light quantity becomes 50 mJ / cm ² , and the second curable resin composition 2-1 is applied on the half-cured first hard coat layer. The first hard coat layer was applied and dried in a hot oven at a temperature of 70 ° C. for 60 seconds, the solvent in the coating film was evaporated, and the ultraviolet ray was irradiated so that the integrated light amount was 200 mJ / cm ² and half cured. And a second hard coat layer (upper layer) having a thickness of 10 μm and a second hard coat layer (upper layer) having a thickness of 5 μm, by fully curing the coating film of the second curable resin composition, The optical sheet of Example 1 was produced.

As the first and second curable resin compositions, optical sheets of Examples 2 to 9 and Comparative Examples 1 to 8 were produced in the same manner as in Example 1 except that those shown in Table 1 were used.
Further, the optical sheet of Comparative Example 9 was obtained in the same manner as in Example 1 except that the lower layer was fully cured with an integrated light amount of 200 mJ / cm ² without half-curing, and the upper layer was also fully cured with an integrated light amount of 200 mJ / cm ^2. It was.

(Evaluation of optical sheet)
About the produced optical sheet | seat of Examples 1-9 and Comparative Examples 1-9, pencil hardness, adhesiveness, and haze were evaluated as follows. The results are shown in Table 2.

(Evaluation: Pencil hardness)
Pencil hardness test: The hardness of the pencil scratch test was determined by JIS-S-6006 using a test pencil specified in JIS-S-6006 after conditioning the prepared optical sheet for 2 hours at a temperature of 25 ° C. and a relative humidity of 60%. The pencil hardness test (4.9N load) prescribed | regulated to K5600-5-4 (1999) was done, and the highest pencil hardness which becomes (circle) with the following evaluation criteria was evaluated.
○: No damage or 1 line in 5 lines ×: 2 lines or more in 5 lines

(Evaluation: Adhesion)
Put 100 grids with a total of 100 squares in 1mm square, perform 5 continuous peel tests using industrial 24mm cello tape (registered trademark) manufactured by Nichiban Co., Ltd., measure the number of remaining squares, The adhesion was evaluated by measuring the adhesion based on this. In addition, adhesive evaluation was performed about the optical sheet before and behind the following environmental test, respectively.
Adhesion degree (%) = (number of cells not peeled / total number of cells 100) × 100
(Evaluation criteria)
○: 90% or more in all environmental tests 1 to 4 ×: Less than 90% in any of environmental tests 1 to 4

Environmental test 1 (heat resistance test)
Leave at 85 ° C. for 240 hours.

Environmental test 2 (moisture and heat resistance test)
Leave at 65 ° C and 95% humidity for 240 hours.

Environmental test 3 (low temperature resistance test)
Leave at -40 ° C for 240 hours.

Environmental test 4 (light resistance test)
Carbon arc lamp, left in a fade meter (FOM) at a temperature of 63 ° C. for 100 hours.

(Evaluation: Haze)
The haze value (%) of the produced optical sheet was measured according to JIS K-7136 using a haze meter (manufactured by Murakami Color Research Laboratory, product number: HM-150).
○: 1.0% or less ×: larger than 1.0%

(Summary of results)
From Table 2, good results were obtained for Examples 1-9.
In Comparative Example 1 in which the surface functional group of the reactive silica fine particles contained in the first curable resin composition is an acryloyl group, the reactivity of the acryloyl group is high, so that the curing reaction proceeds in the half cure, Since the functional group that improves the adhesiveness is reduced by the curing reaction with the second HC layer, which is the upper layer, the adhesiveness and hardness are reduced.
In Comparative Example 2 and Comparative Example 3 in which the functional group of the first binder component contained in the first curable resin composition is a methacryloyl group, the reactivity of the methacryloyl group is lower than that of the acryloyl group, so that there is little in half cure. The light irradiation dose did not increase the crosslink density but the hardness was low.
In Comparative Example 4 in which the silica fine particles contained in the first curable resin composition were not surface-modified, the adhesion with the second HC layer as the upper layer was insufficient and the hardness was also lowered.
In Comparative Example 5 in which the average primary particle size of the reactive silica fine particles contained in the first curable resin composition was as large as 200 nm, hardness and adhesion were sufficient, but haze was lowered.
In Comparative Example 6 in which the proportion of the reactive silica fine particles contained in the first curable resin composition was less than 15% by weight with respect to the total solid content of the first curable resin composition, the hardness was low.
In Comparative Example 7 in which the proportion of the reactive silica fine particles contained in the first curable resin composition exceeds 70% by weight with respect to the total solid content of the first curable resin composition, there are too many reactive silica fine particles. Therefore, the haze of the first HC layer was deteriorated, the hardness was lowered, and the adhesion was insufficient.
In Comparative Example 8, since the number of functional groups of the first binder component contained in the first curable resin composition is as small as two, crosslinking with the second HC layer, which is the upper layer, does not proceed sufficiently, and adhesion And the hardness decreased.
In Comparative Example 9 in which the second HC layer was formed with full cure after the first HC layer was formed with full cure without using the half cure, the bridge between the first HC layer and the second HC layer was used. Since there was little, adhesiveness and hardness fell.

DESCRIPTION OF SYMBOLS 1 Optical sheet 10 Triacetylcellulose base material 20 1st hard-coat layer 30 2nd hard-coat layer

Claims (3)

An optical sheet in which the first hard coat layer and the second hard coat layer are provided in this order from the triacetyl cellulose substrate side on one side of the triacetyl cellulose substrate,
The first hard coat layer includes a first reactive silica fine particle having an average primary particle diameter of 1 to 100 nm having a methacryloyl group on the particle surface, and a first binder component having three or more acryloyl groups in one molecule. A cured product of the first curable resin composition containing
The ratio of the content of the first reactive silica fine particles to the total solid content of the first curable resin composition is 15 to 70% by weight,
The second hard coat layer comprises a cured product of a second curable resin composition containing a second binder component having 3 or more acryloyl groups in one molecule, and
After applying the first curable resin composition on one side of the triacetylcellulose base material and half-curing, the second curable resin composition is applied on the half-cured first hard coat layer. A first hard coat layer and a second hard coat layer are formed by fully curing the first hard coat layer and the second curable resin composition coated and half-cured. An optical sheet.   The first reactive silica fine particles are reactive deformed silica fine particles having 3 to 20 spherical silica fine particles having an average primary particle diameter of 1 to 100 nm bonded by an inorganic chemical bond and having a methacryloyl group on the surface. The optical sheet according to claim 1, which is characterized.   The optical sheet according to claim 1 or 2, wherein the hardness of a pencil hardness test (4.9 N load) specified in JIS K5600-5-4 (1999) is 5H or more.

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