Protective material for display panels

Abstract

To provide a protective material for display panels that has excellent anti-reflective and anti-fogging properties. [Solution] A protective material 1A for a display panel, provided on the front side of the display panel 100, comprises a transparent substrate 2, a hydrophilic layer 3 provided on one side of the transparent substrate 2, and an anti-reflective layer 4 provided on the other side of the transparent substrate 2. The hydrophilic layer 3 is arranged between it and the display panel 100 via a gap layer G, and a fine uneven structure 5 having hydrophilic and anti-reflective functions is provided on the side of the hydrophilic layer 3 facing the gap layer G.

Description

Technical Field

[0001] The present invention relates to a protective material for a display panel.

Background Art

[0002] Generally, on the front side of a display panel such as a liquid crystal panel or a touch panel, a protective material for the display panel is provided to protect the display panel from external impacts. This protective material for the display panel is arranged with a gap (air gap layer) provided between it and the display panel. As a result, when the protective material is damaged by an external impact, it has a structure (air gap structure) that does not affect the display panel.

[0003] However, in a display device having such an air gap structure, when exposed to an environment of high temperature and high humidity such as in summer or during the rainy season, or an environment with large temperature changes, condensation occurs inside the protective material for the display panel, causing clouding and reducing the visibility of the display panel.

[0004] In addition, a general protective material for a display panel is formed only of a transparent base material such as tempered glass or an acrylic plate, and since it strongly reflects external light on its surface, there is a problem that the visibility of the display panel deteriorates.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention has been proposed in view of such conventional circumstances, and an object thereof is to provide a protective material for a display panel having excellent antireflection properties and antifogging properties.

Means for Solving the Problems

[0007] To achieve the above objective, the present invention provides the following means. [1] A protective material for a display panel provided on the front side of the display panel, Transparent substrate and A hydrophilic layer provided on one side of the transparent substrate, The transparent substrate is provided with an anti-reflective layer on the other side, The hydrophilic layer is arranged between it and the display panel with a gap layer in between. A protective material for a display panel, characterized in that a fine uneven structure having hydrophilic and anti-reflective properties is provided on the side of the hydrophilic layer facing the void layer. [2] The protective material for a display panel according to [1], characterized in that the water contact angle of the hydrophilic layer is 20° or less. [3] The protective material for display panels according to [1], characterized in that the anti-reflective layer consists of a cured film of a composition mainly composed of alkoxysilane, and its reflectivity is 3% or less. [4] The protective material for a display panel according to [1], characterized in that the hydrophilic layer having the fine uneven structure is directly provided on one side of the transparent substrate. [5] The protective material for a display panel according to [1], characterized in that the hydrophilic layer having the fine uneven structure is provided on one side of the transparent substrate via an adhesive layer. [Effects of the Invention]

[0008] As described above, the present invention provides a protective material for display panels that is excellent in anti-reflective properties and anti-fogging properties. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing an example of a protective material for a display panel according to one embodiment of the present invention. [Figure 2] This is a cross-sectional view showing an example of a protective material for a display panel according to one embodiment of the present invention. [Figure 3]This is a cross-sectional view showing an example of a protective material for a display panel according to one embodiment of the present invention. [Figure 4] This is a cross-sectional view showing an example of a protective material for a display panel according to one embodiment of the present invention. [Figure 5] This is a cross-sectional view showing an example of a protective material for a display panel according to one embodiment of the present invention. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below with reference to the drawings. Please note that the drawings used in the following description may schematically represent key features for ease of understanding, and the dimensional ratios of each component may not necessarily be the same as those in reality. Furthermore, the materials, dimensions, etc., exemplified in the following description are merely examples, and the present invention is not necessarily limited to them. It can be implemented with appropriate modifications without altering its essence.

[0011] (Protective material for display panels) In this embodiment, for example, protective materials 1A to 1E for display panels, as shown in Figures 1 to 5, can be exemplified.

[0012] Specifically, the protective materials 1A to 1D for the display panel shown in Figures 1 to 5 are provided on the front side of the display panel 100 to protect the display panel 100 from external impacts, and are arranged with a gap (void layer) G between them and the display panel 100.

[0013] Of these, the protective material 1A for the display panel shown in Figure 1 comprises a transparent substrate 2, a hydrophilic layer 3 provided on one side (back side) of the transparent substrate 2, and an anti-reflective layer 4 including a low refractive index layer 41 provided on the other side (front side) of the transparent substrate 2.

[0014] Furthermore, a fine uneven structure 5 having hydrophilic and anti-reflective properties is provided on the side of the hydrophilic layer 3 facing the void layer G. The hydrophilic layer 3 having the fine uneven structure 5 is directly provided on one side of the transparent substrate 2.

[0015] On the one hand, the protective material 1B for a display panel shown in FIG. 2 includes a transparent substrate 2, a hydrophilic layer 3 provided on one surface (back surface) side of the transparent substrate 2, and an antireflection layer 4 including a low refractive index layer 41 provided on the other surface (front surface) side of the transparent substrate 2.

[0016] Also, on the side facing the void layer G of the hydrophilic layer 3, a fine uneven structure 5 having hydrophilic and antireflection functions is provided. The hydrophilic layer 3 having the fine uneven structure 5 is provided on one surface side of the transparent substrate 2 via an adhesive layer 6.

[0017] On the one hand, the protective material 1C for a display panel shown in FIG. 3 includes a transparent substrate 2, a hydrophilic layer 3 provided on one surface (back surface) side of the transparent substrate 2, an antireflection layer 4 including a low refractive index layer 41 provided on the other surface (front surface) side of the transparent substrate 2, and a hard coat layer 7 provided between the transparent substrate 2 and the antireflection layer 4.

[0018] Also, on the side facing the void layer G of the hydrophilic layer 3, a fine uneven structure 5 having hydrophilic and antireflection functions is provided. The hydrophilic layer 3 having the fine uneven structure 5 is provided directly on one surface side of the transparent substrate 2.

[0019] On the one hand, the protective material 1D for a display panel shown in FIG. 4 includes a transparent substrate 2, a hydrophilic layer 3 provided on one surface (back surface) side of the transparent substrate 2, an antireflection layer 4 including a low refractive index layer 41 provided on the other surface (front surface) side of the transparent substrate 2, and a hard coat layer 7 provided between the transparent substrate 2 and the antireflection layer 4.

[0020] Also, on the side facing the void layer G of the hydrophilic layer 3, a fine uneven structure 5 having hydrophilic and antireflection functions is provided. The hydrophilic layer 3 having the fine uneven structure 5 is provided on one surface side of the transparent substrate 2 via an adhesive layer 6.

[0021] On the other hand, the protective material 1E for the display panel shown in Figure 5 has a hydrophilic layer 3 with a fine uneven structure 5 provided on one side (back side) of the transparent substrate 2, and a hard coat layer 7, an anti-reflective layer 4, and a protective layer 8 are laminated in this order on the other side (front side) of the transparent substrate 2.

[0022] Furthermore, the anti-reflective layer 4 consists of a medium refractive index layer 42, a high refractive index layer 43, and a low refractive index layer 41, which are laminated in this order.

[0023] [Transparent base material] The transparent substrate 2 can be any transparent resin substrate or sheet that has excellent impact resistance and does not impair visibility. Specifically, from the viewpoint of transparency and impact resistance, it is preferable to use one made of aromatic polycarbonate resin or polymethyl methacrylate resin. Alternatively, a laminate of aromatic polycarbonate resin and polymethyl methacrylate resin may be used. The thickness of the transparent substrate 2 is appropriately selected and designed based on the required transparency and impact resistance, but is usually 0.3 mm or more and 5 mm or less, and preferably 0.5 mm or more and 5 mm or less.

[0024] [Hydrophilic layer with a finely textured surface] The micro-textured structure 5 is called a moth-eye structure and has a structure in which many nano-level micro-protrusions are arranged in the plane at regular intervals. By having such a micro-textured structure 5, the hydrophilic layer 3 can have high hydrophilicity and anti-reflective properties on the side facing the void layer G of the hydrophilic layer 3.

[0025] The hydrophilic layer 3 having a fine uneven structure 5 may be integrally formed on the surface of the transparent substrate 2 facing the void layer G, as shown in the display panel protective materials 1A and 1C in Figures 1 and 3, or it may be attached to the surface of the transparent substrate 2 facing the void layer G via an adhesive layer 6, as shown in the display panel protective materials 1A and 1C in Figures 2 and 4.

[0026] The water contact angle of the hydrophilic layer 3 is preferably 20° or less. By setting it to 20° or less, hydrophilicity is increased, and high anti-fogging properties can be obtained on the side of the hydrophilic layer 3 facing the void layer G.

[0027] [Hard court layer] The hard coat layer 7 is a layer that contributes to the strength of the display panel protective materials 1C to 1E, as well as to the adhesion between the transparent substrate 2 and the anti-reflective layer 4. The display panel protective materials 1C to 1E have excellent abrasion resistance and hardness due to the improved adhesion provided by this hard coat layer 7.

[0028] The hard coat layer 7 consists of a resin cured body. Specifically, a resin cured body obtained by polymerizing and curing polymerizable polyfunctional acrylates such as dipentaerythritol hexa(meth)acrylate, phenylglycidyl ether (meth)acrylate hexamethylene diisocyanate urethane prepolymer, phenylglycidyl ether (meth)acrylate isophorone diisocyanate urethane prepolymer, phenylglycidyl ether (meth)acrylate tolylene diisocyanate urethane prepolymer; glycerin di(meth)acrylate tolylene diisocyanate urethane oligomer, pentaerythritol tri(meth)acrylate hexamethylene diisocyanate urethane oligomer, glycerin di(meth)acrylate isophorone diisocyanate urethane oligomer, pentaerythritol tri(meth)acrylate tolylene diisocyanate urethane oligomer, and pentaerythritol tri(meth)acrylate isophorone diisocyanate urethane pre-oligomer is used.

[0029] In particular, to improve the adhesion between the transparent substrate 2 and the anti-reflective layer 4, as well as the hardness of the hard coat layer 7 itself, a cured resin body of the following composition is preferably used. Specifically, a curable composition preferably used for forming the hard coat layer 7 consists of a cured body of a curable composition comprising (A) a polymerizable monomer, (B-1) silica fine particles, (C) a silane coupling compound or its hydrolysate, and (D) a metal chelate compound, wherein the composition is 1500 to 2000 parts by mass of (A) polymerizable monomer and 300 to 500 parts by mass of (B-1) silica fine particles, for a total of 100 parts by mass of 95 to 99 parts by mass of (C) silane coupling compound or its hydrolysate and 1 to 5 parts by mass of (D) metal chelate compound.

[0030] <(A) Polymerizable monomers> Polymerizable monomers are components that form the base material of the hard coat layer 7 after polymerization and curing, but they are used in combination with other essential components, and there are no particular restrictions on their type. Examples of polymerizable monomers include the following compounds.

[0031] Monofunctional acrylate monomers include acrylate monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, lauryl (meth)acrylate, and hydroxyethyl (meth)acrylate.

[0032] Examples of difunctional acrylate monomers include difunctional acrylate compounds such as ethylene glycol (meth)acrylate, or difunctional urethane acrylate compounds obtained by a polyaddition reaction between a diisocyanate compound and a (meth)acrylate compound having multiple hydroxyl groups, and in which the number of (meth)acryloyl groups is controlled to two. Conventional known methods can be used without any limitations for the conditions of the polymerization addition reaction and the raw materials.

[0033] 3-4 functional acrylate monomers include 3-4 functional acrylate compounds such as pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, and trimethylolpropane tri(meth)acrylate, or 3-4 functional urethane acrylate compounds obtained by polyaddition reactions of diisocyanate compounds with (meth)acrylate compounds having multiple hydroxyl groups, and in which the number of (meth)acryloyl groups is controlled to 3-4. Conventional known methods can be used without any limitations for the conditions of the polymerization addition reaction and the raw materials.

[0034] Hexafunctional acrylate monomers include (meth)acrylate compounds having six (meth)acryloyl groups, such as dipentaerythritol hexaacrylate. Preferably, a hexafunctional urethane acrylate compound obtained by a polyaddition reaction between a diisocyanate compound and a (meth)acrylate compound having multiple hydroxyl groups, and in which the number of (meth)acryloyl groups is controlled to six, is preferred for forming a dense layer with high surface hardness. Conventional known methods can be used without any limitations for the conditions of the polymerization addition reaction and the raw materials.

[0035] In addition to the monofunctional, difunctional, tertiary-tetrafunctional, and hexafunctional acrylate monomers mentioned above, polyfunctional acrylate monomers such as octafunctional and daphnofunctional monomers may also be used.

[0036] The polymerizable monomers mentioned above are commercially available and therefore generally accessible. Various urethane acrylate monomers are also commercially available from companies such as Shin-Nakamura Chemical Industry Co., Ltd., Kyoeisha Chemical Co., Ltd., KSM Co., Ltd., Negami Kogyo Co., Ltd., Nippon Synthetic Chemical Industry Co., Ltd., Tomoe Kogyo Co., Ltd., and Toyo Chemicals Co., Ltd.

[0037] The polymerizable monomers described above are used in combination as appropriate, taking into consideration not only the hardness of the cured product after curing, but also impact resistance, adhesion to the anti-reflective layer 4, and the viscosity of the monomers. In particular, when (A) the polymerizable monomer is a mixed composition containing 5.0 to 15.0 parts by mass of a 3- to 4-functional urethane acrylate monomer and 5.0 to 10.0 parts by mass of a 2-functional acrylate monomer per 100 parts by mass of a 6- or more-functional urethane acrylate monomer, it is highly preferable in terms of adhesion to the anti-reflective layer 4, light resistance, flexibility, and hardness.

[0038] Furthermore, it is possible to use not only monomers such as polymerizable monomers, but also oligomers.

[0039] <(B-1) Silica microparticles> Silica nanoparticles are particles that contribute to improved adhesion and coating properties. While the properties of silica nanoparticles are not particularly limited, they are typically spherical, with an average particle diameter of 5-30 nm and a refractive index of 1.44-1.50. When the average particle diameter falls outside this range, crack resistance tends to deteriorate.

[0040] Silica nanoparticles are single-particle, dense, non-hollow particles without internal cavities, and typically have a density of 1.9 g / cm³. 3 That concludes the explanation. Since silica nanoparticles are publicly known and commercially available, one can simply select and use a commercially available product that satisfies the above average particle size and refractive index. Silica nanoparticles are usually supplied dispersed in a solvent. The solvent inevitably becomes mixed into the solution of the curable composition for forming the hard coat layer 7 and behaves like other solvents.

[0041] <(C) Silane coupling compound or its hydrolysate> Silane coupling compounds or their hydrolysates undergo hydrolysis themselves to form a dense siliceous film. Known silane coupling compounds can be used without limitation. Specifically, examples include γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, p-styryltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, γ-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2(aminoethyl)3-aminopropylmethyldimethoxysilane, N-2(aminoethyl)3-aminopropyltriethoxysilane, N-2(aminoethyl)3-aminopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-isocyanatetopropyltriethoxysilane.

[0042] Depending on the type, silane coupling compounds are preferably pre-hydrolyzed with a dilute acid or the like to improve their solubility in water or solvents. There are no particular restrictions on the pre-hydrolysis method; however, a common method involves hydrolyzing a portion of the compound using an acid catalyst such as acetic acid.

[0043] <(D) Metal Chelate Compounds> The metal chelate compound is a component that functions as a crosslinking agent, and it contributes to making the formed hard coat layer 7 a denser hardened body.

[0044] Metal chelate compounds are compounds in which a chelating agent, typically a bidentate ligand, is coordinated to a metal ion such as a tetravalent titanium metal ion, a tetravalent zirconium metal ion, or a trivalent aluminum metal ion. Specifically, titanium chelate compounds such as triethoxy-mono(acetylacetonate)titanium, diethoxy-bis(acetylacetonate)titanium, monoethoxy-tris(acetylacetonate)titanium, tetrakis(acetylacetonate)titanium, triethoxy-mono(ethylacetoacetate)titanium, diethoxy-bis(ethylacetoacetate)titanium, monoethoxy-tris(ethylacetoacetate)titanium, mono(acetylacetonate)tris(ethylacetoacetate)titanium, bis(acetylacetonate)bis(ethylacetoacetate)titanium, tris(acetylacetonate)mono(ethylacetoacetate)titanium; triethoxy-mono(acetylacetonate)zirconium, diethoxy-bis(acetylacetonate)zirconium, monoethoxy-tris(acetylacetonate)zirconium, tetrakis(acetylacetonate)zirconium, Examples include zirconium chelate compounds such as triethoxy mono(ethyl acetate) zirconium, diethoxy bis(ethyl acetate) zirconium, monoethoxy tris(ethyl acetate) zirconium, tetrakis(ethyl acetate) zirconium, mono(acetylacetonate) tris(ethyl acetate) zirconium, bis(acetylacetonate) bis(ethyl acetate) zirconium, and tris(acetylacetonate) mono(ethyl acetate) zirconium; and aluminum chelate compounds such as diethoxy mono(acetylacetonate) aluminum, monoethoxy bis(acetylacetonate) aluminum, di-i-propoxy mono(acetylacetonate) aluminum, monoethoxy bis(ethyl acetate) aluminum, and diethoxy mono(ethyl acetate) aluminum.

[0045] The above curable composition preferably contains (A) a polymerizable monomer, (B-1) silica fine particles, (C) a silane coupling compound or its hydrolysate, and (D) a metal chelate compound in the following specific ratios.

[0046] In other words, it is preferable that (A) the polymerizable monomer be in an amount of 1500 to 2000 parts by mass per 100 parts by weight of the total amount of (C) the silane coupling compound or its hydrolysate and (D) the metal chelate compound. If the amount is less than 1500 parts by mass, the formation of the hard coat layer 7 will be insufficient, and if it exceeds 2000 parts by mass, it will result in a poor appearance.

[0047] On the other hand, (B-1) silica fine particles are preferably present in an amount of 300 to 500 parts by mass per 100 parts by weight of the total amount of (C) silane coupling compound or its hydrolysate and (D) metal chelate compound. If the amount is less than 300 parts by mass, the appearance will be unsatisfactory, and if it exceeds 500 parts by mass, the impact resistance tends to deteriorate.

[0048] On the other hand, the amount of (C) silane coupling compound or its hydrolysate is preferably 95 to 99 parts by mass per 100 parts by weight of the total amount with (D) metal chelate compound. If the amount is less than 95 parts by mass, the film adhesion will be poor, and if it exceeds 99 parts by mass, the smoothness of the hard coat layer tends to be poor.

[0049] On the other hand, the amount of (D) metal chelate compound is preferably 1 to 5 parts by mass per 100 parts by weight of the total amount of (C) silane coupling compound or its hydrolysate. If the amount is outside this range, the adhesion between the hard coat layer 7 and the anti-reflective layer 4 formed on top of the hard coat layer 7 will be poor, or the density will be insufficient, and the hardness will tend to decrease.

[0050] The above curable composition may contain any additives for viscosity adjustment or ease of application, provided that these additives do not impair its original purpose. Conventionally known ultraviolet absorbers may also be added. In particular, to cure the above curable composition on a transparent substrate 2 to form a hard coat layer 7, a thermal polymerization initiator or photopolymerization initiator is usually added in a catalytic amount, typically 0.01 to 20% by mass based on the total solid content in the composition. This polymerization initiator does not essentially affect the properties of the hard coat layer 7 obtained by curing the curable composition.

[0051] <Formation of the hard coat layer> Each of the above essential components, and any optional components, is typically mixed and stirred with the following solvents in any order at around room temperature to form a solution of the curable composition. After applying this solution onto the transparent substrate 2, the solvent is dried at 50°C or higher, and then cured by ultraviolet irradiation to form a hard coat layer 7. The thickness of the hard coat layer 7 is set to a range of 1 to 100 μm, preferably 1 to 30 μm, and more preferably 1 to 10 μm.

[0052] Suitable solvents include alcohol-based solvents such as ethyl alcohol and (iso)propyl alcohol; aromatic solvents such as toluene and xylene; acetic acid ester solvents such as (iso)butyl acetate; and ketone-based solvents such as methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK). These solvents are removed by evaporation during the formation of the hard coat layer.

[0053] The method for coating the transparent substrate 2 with the solution is not particularly limited, and methods such as dip coating, roll coating, die coating, flow coating, and spray coating can be used. However, the dip coating method is preferred from the viewpoint of appearance quality and layer thickness control.

[0054] [Anti-reflection layer] The anti-reflective layer 4 has at least a low refractive index layer 41. The low refractive index layer 41 consists of a cured film of a composition mainly composed of alkoxysilane, and has a refractive index of 1.25 to 1.40.

[0055] Since the anti-reflective layer 4 is a cured film of a composition mainly composed of alkoxysilane, it has superior chemical resistance, abrasion resistance, and weather resistance compared to anti-reflective layers with a fine uneven structure. Furthermore, while anti-reflective layers with a fine uneven structure break down when rubbed, the anti-reflective layer 4 of this embodiment is a glassy cured film, so the layer surface does not break even when rubbed, and it has particularly excellent abrasion resistance.

[0056] If the refractive index of the low refractive index layer 41 falls outside this range, it will not function as an anti-reflective layer 4. Furthermore, if the anti-reflective layer 4 consists of multiple layers, the low refractive index layer 41 is located on the outermost layer (viewing side) of the anti-reflective layer 4.

[0057] Furthermore, the reflectance of the low refractive index layer 41 (anti-reflective layer 4) is preferably 3% or less, and more preferably 1.6% or less. This ensures that it has sufficient anti-reflective function against incident external light.

[0058] <(B-2) Hollow silica microparticles> The low refractive index layer 41 contains (B-2) hollow silica nanoparticles as particles that control its refractive index. The hollow silica nanoparticles of the low refractive index layer 41 are hollow inside, with a porosity of 20-70%, preferably 30-50%, a refractive index of typically 1.30 or less, and an average particle diameter of 10-150 nm. It is essential to select a particle diameter smaller than the thickness of the low refractive index layer 41.

[0059] If the average particle size falls outside the above range, not only will the reflectivity decrease and the haze rate increase, but even if the protective layer 8 is provided, the wear resistance, which is an effect of the present invention, will not improve. A more preferable average particle size is 50 to 100 nm, and an even more preferable average particle size is 50 to 70 nm.

[0060] The hollow silica nanoparticles described above can be selected from commercially available products that meet the above average particle size requirement. Since these hollow silica nanoparticles are usually provided dispersed in a solvent, this solvent behaves in the same way as in the case of the (B-1) silica nanoparticles described above.

[0061] <Composition for forming a low refractive index layer> The composition for forming the low refractive index layer 41 is a curable composition comprising (B-2) hollow silica fine particles, (C) a silane coupling compound or its hydrolysate, and (D) a metal chelate compound as essential components.

[0062] Furthermore, the (C) silane coupling compound or its hydrolysate and (D) metal chelate compound in the composition for forming the low refractive index layer 41 are the same as those exemplified in the hard coat layer described above.

[0063] In order to exhibit excellent abrasion resistance in addition to anti-reflective properties, it is important that the protective materials 1A to 1E for the display panel in this embodiment have the following composition.

[0064] In other words, (B-2) the amount of hollow silica fine particles is preferably 50 to 200 parts by mass per 100 parts by weight of the total amount of (C) silane coupling compound or its hydrolysate and (D) metal chelate compound. If the amount is less than 50 parts by mass, a low refractive index cannot be achieved, and if it exceeds 200 parts by mass, the wear resistance decreases and the characteristics of the present invention are impaired.

[0065] On the other hand, it is preferable that (C) the silane coupling compound or its hydrolysate and (D) the metal chelate compound are used in a mass ratio of 90:10 to 98:2 (total 100 parts by mass). If the mixing ratio of the two does not meet this numerical range, the layer strength of the low refractive index layer 41 will decrease, coating defects will occur, and the basic layer characteristics will not be exhibited, resulting in the low refractive index layer 41 not functioning properly.

[0066] In addition to the essential components mentioned above, the composition for forming the low refractive index layer 41 may contain tetraalkoxysilane compounds such as tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane to improve adhesion to the transparent substrate 2 and to densify and increase the strength of the hard coat layer 7.

[0067] Furthermore, in order to promote the hydrolysis and condensation of (C) silane coupling compounds or their hydrolysates or the tetraalkoxysilicon compounds, an appropriate amount of an acidic aqueous solution, such as an aqueous hydrochloric acid solution, can be added to the composition for forming the low refractive index layer 41.

[0068] <Formation of a low refractive index layer> The low refractive index layer 41 is formed in the same manner as the hard coat layer 7. A solution of the composition for forming the low refractive index layer 41 is applied to the hard coat layer 7, which is a cured body, dried, and then heated and cured at 70-120°C. The thickness of the low refractive index layer 41 is usually set in the range of 50-200 nm from the viewpoint of anti-reflective performance.

[0069] Furthermore, if the anti-reflective layer 4 consists of two layers, a medium refractive index layer 42 and a low refractive index layer 41, the medium refractive index layer 42 is first formed on the hard coat layer 7, and then the low refractive index layer 41 is formed on top of this medium refractive index layer 42.

[0070] Furthermore, if the anti-reflective layer 4 consists of three layers: a medium refractive index layer 42, a high refractive index layer 43, and a low refractive index layer 41, then the medium refractive index layer 42 is first formed on the hard coat layer 7, followed by the high refractive index layer 43 being formed on top of this medium refractive index layer, and then the low refractive index layer 41 being formed on top of this high refractive index layer 43.

[0071] <Intermediate refractive index layer> The medium refractive index layer 42 is a layer with a higher refractive index than the low refractive index layer 41, which is provided on the transparent substrate 2 side of the low refractive index layer 41, in order to further enhance the anti-reflective effect of the anti-reflective layer 4.

[0072] The intermediate refractive index layer 42 preferably has a refractive index of 1.50 to 1.75 and a thickness of 50 to 200 nm.

[0073] <Composition for forming the intermediate refractive index layer> The composition for forming the intermediate refractive index layer 42 is a curable composition containing 100 parts by mass of (F) an organic-inorganic composite compound and 150 to 300 parts by mass of (G) metal oxide particles, in addition to a total of 100 parts by mass of (C) a silane coupling compound or its hydrolysate and (D) a metal chelate compound of 90 to 95 parts by mass.

[0074] <(F) Organic / inorganic composite compound> Organic-inorganic composite compounds are used to improve the adhesion and alkali resistance of the intermediate refractive index layer 42. Organic-inorganic composite compounds are compounds that combine the advantages of organic and inorganic materials, with no glass transition temperature (Tg) like glass, due to crosslinking of epoxy groups between compounds and the generation of silica particles through sol-gel curing of alkoxysilyl groups.

[0075] Organic-inorganic composite compounds exist in a variety of types. For example, composite compounds in which an alkoxysilyl group is bonded to bisphenol A epoxy compounds, novolacphenol compounds, or polyamic acid compounds are examples of such compounds.

[0076] Among these, a composite compound in which an alkoxysilyl group is bonded to a bisphenol A type epoxy compound is preferably used as an organic-inorganic composite compound, given that it does not impair the hardness of the intermediate refractive index layer 42 and is readily available.

[0077] <(G) Metal oxide particles> Metal oxide particles are included to satisfy the requirement that the refractive index of the intermediate refractive index layer 42 be between 1.50 and 1.75. The metal oxide particles have an average particle diameter of 10 to 100 nm and a refractive index between 1.70 and 2.80.

[0078] Examples of metal oxide particles used include zirconium oxide particles (refractive index = 2.40); composite zirconium metal oxide particles obtained by molecularly compounding zirconium oxide with other oxides such as silicon oxide to adjust the refractive index; titanium oxide particles (refractive index = 2.71); composite titanium metal oxide particles obtained by molecularly compounding titanium oxide with other oxides such as silicon oxide or zirconium oxide to adjust the refractive index; and silica particles (refractive index = 1.55). These metal oxide particles are selected or appropriately combined to create layers with the desired refractive index. Such particles are publicly known and commercially available.

[0079] <Formation of a medium refractive index layer> The formation of the intermediate refractive index layer 42 is carried out in the same manner as the formation of the low refractive index layer 41. The thickness of the intermediate refractive index layer 42 is set in the range of 50 to 200 nm from the viewpoint of anti-reflective performance.

[0080] <High refractive index layer> The high refractive index layer 43 is a layer with a higher refractive index than the medium refractive index layer 42, and is provided between the low refractive index layer 41 and the medium refractive index layer 42 in order to further enhance the anti-reflective effect of the anti-reflective layer 4.

[0081] The high refractive index layer 43 preferably has a refractive index of 1.60 to 2.00 and a thickness of 50 to 200 nm.

[0082] <Composition for forming a high refractive index layer> The composition for forming the high refractive index layer 43 is a curable composition containing 100 parts by mass of (G) metal oxide particles in a total of 100 parts by mass of (C) silane coupling compound or hydrolysate thereof and (D) metal chelate compound (75 to 95 parts by mass).

[0083] (G) The metal oxide particles are selected from the above metal oxide particles, or used in appropriate combinations, so that the refractive index of the high refractive index layer 43 is 1.60 to 2.00.

[0084] <Formation of a high refractive index layer> The formation of the high refractive index layer 43 is carried out in the same manner as the formation of the low refractive index layer 41 and the medium refractive index layer 42 described above.

[0085] [Protective layer] The protective layer 8 is an additional layer added to the protective material 1E for the display panel in this embodiment to provide abrasion resistance, and the shape, particle size, and content of the silica fine particles used, as well as the layer thickness, are important requirements.

[0086] In other words, it is preferable to include 7.5 to 35 parts by mass of (B-3) spherical silica fine particles having an average particle diameter of 10 nm or less in a total of 100 parts by mass of (C) silane coupling compound or its hydrolysate and (D) metal chelate compound, with a total of 90 to 98 parts by mass of (C) silane coupling compound or its hydrolysate and 10 to 2 parts by mass of (D) metal chelate compound.

[0087] (C) The mixing ratio of the silane coupling compound or its hydrolysate to (D) the metal chelate compound is in the range of 90:10 to 98:2 parts by mass (100 parts by mass in total), which is necessary to improve the wear resistance of the protective materials 1B to 1D for the display panel.

[0088] <(B-3) Spherical silica microparticles> The silica fine particles in protective layer 8 are preferably spherical and have an average particle diameter of 10 nm or less. If this condition is not met, high abrasion resistance will not be achieved. Although there is no particular lower limit to the average particle diameter of the silica fine particles, it is preferable that it be 5 nm or more for ease of availability.

[0089] The amount of silica fine particles is preferably 7.5 to 35 parts by weight per 100 parts by weight of the total of (C) silane coupling compound or its hydrolysate and (D) metal chelate compound. If the amount is less than 7.5 parts by weight, the refractive index of the protective layer 8 will increase, the abrasion resistance effect will not be achieved, and the film-forming ability will decrease, resulting in an inability to form a uniform protective layer 8 on the anti-reflective layer 4. On the other hand, if the amount exceeds 35 parts by weight, the protective layer 8 will become brittle and the appearance will be poor.

[0090] (C) Silane coupling compounds or their hydrolysates and (D) Metal chelate compounds can be used without limitation as exemplified in the hard coat layer 7 described above.

[0091] The refractive index of the protective layer 8 is preferably 1.45 to 1.50. If this range is not satisfied, the anti-reflective performance will decrease.

[0092] The thickness of the protective layer 8 is preferably 10 to 15 nm. If it is less than 10 nm, it will not function as a protective layer 8, and if it exceeds 15 nm, the reflectivity will increase and the anti-reflective performance will decrease.

[0093] Silica nanoparticles are single-particle, dense, non-hollow, spherical particles without internal cavities. Their average particle size is 5-10 nm, and their density is typically 1.9 g / cm³. 3 That concludes the explanation. Since silica nanoparticles are publicly known and commercially available, one can simply select and use a commercially available product that satisfies the above-mentioned average particle size and refractive index. Silica nanoparticles are usually supplied dispersed in a solvent. The solvent inevitably becomes mixed into the curable composition solution for forming the protective layer 8 and behaves like any other solvent.

[0094] The preparation of the curable composition for forming the protective layer 8 and the method for forming the protective layer 8 may be carried out in the same manner as the anti-reflective layer 4 described above.

[0095] In the protective materials 1A to 1E for display panels of this embodiment, which have the above configuration, by providing a hydrophilic layer 3 having a fine uneven structure 5 on the side of the transparent substrate 2 facing the void layer G, it is possible to obtain excellent anti-fogging and anti-reflective properties on the side of the hydrophilic layer 3 facing the void layer G.

[0096] Therefore, in a display device using the protective materials 1A to 1E for the display panel of this embodiment, the display panel 100 is protected from external impacts, and even when exposed to high temperature and high humidity environments or environments with large temperature fluctuations, condensation is prevented from occurring inside the protective materials 1A to 1E, while also preventing reflection of external light, thereby maintaining high visibility of the display panel 100.

[0097] It should be noted that the present invention is not necessarily limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention.

[0098] There are no limitations on the display devices that use the protective material for display panels of the present invention. For example, it can be used by placing the protective material for display panels of the present invention on the front side of display panels used in display devices equipped with display panels such as CRTs, LCDs, and PDPs, as well as in automobile instrument panels, center information displays (CIDs), head-up displays, car navigation systems, personal computers, picture frames, photo frames, smartphones, tablets, ATMs, automatic ticket vending machines, SLR cameras, medical panels, and car navigation systems. [Examples]

[0099] The effects of the present invention will be made clearer by the following examples. However, the present invention is not limited to the following examples and can be modified as appropriate without altering its essence.

[0100] (Example 1) In Example 1, a transparent acrylic substrate with a thickness of 2 mm was first prepared, and a masking film was applied to the entire surface of one side of this transparent substrate.

[0101] Next, a transparent substrate was dipped in a solution of a curable composition containing a polyfunctional urethane acrylate and a mixture of polyfunctional acrylates, dried at 60°C for 5 minutes, and UV cured to form a 1.5 μm thick hard coat layer on the other side of the transparent substrate.

[0102] Next, a transparent substrate was dipped into a solution of a composition for forming a low refractive index layer (anti-reflective layer), prepared by mixing 95 parts by mass of 3-glycidoxypropyltrimethoxylane and 5 parts by mass of aluminum trisacetylcetonate (total 100 parts by mass), 95 parts by mass of hollow silica sol (solid content 20%), hydrochloric acid (45% relative to 3-glycidoxypropyltrimethoxylane), and an organic solvent to a total of 1000 g. The solution was then dried at 90°C for 20 minutes to form a low refractive index layer (anti-reflective layer) with a thickness of 85 nm and a refractive index of 1.35 on top of the hard coat layer.

[0103] Next, a transparent substrate was dipped into a solution of a protective layer-forming composition prepared by mixing 94 parts by mass of 3-glycidoxypropyltrimethoxylane and 4 parts by mass of aluminum trisacetylcetonate (totaling 100 parts by mass), 5 parts by mass of hollow silica sol (solid content 20%), hydrochloric acid (45% relative to 3-glycidoxypropyltrimethoxylane), and an organic solvent to a total of 1000 g. The solution was then dried at 90°C for 20 minutes to form a protective layer with a thickness of 15 nm and a refractive index of 1.50 on top of a low refractive index layer (anti-reflective layer).

[0104] Next, after peeling the masking film from the transparent substrate, a moth-eye film ("Mosmite" manufactured by Mitsubishi Chemical Corporation) with a fine uneven structure was applied to one side of the transparent substrate using a film laminating machine as a hydrophilic layer. This produced the protective material for the display panel of Example 1.

[0105] (Comparative Example 1) In Comparative Example 1, the protective material for the display panel of Comparative Example 1 was prepared in the same manner as in Example 1, except that a moth-eye film was not attached to one side of the transparent substrate.

[0106] Then, evaluation tests were conducted on the anti-reflective, hydrophilic, and anti-fogging properties of the protective materials for display panels in Example 1 and Comparative Example 1. The evaluation results are shown in Table 1 below.

[0107] [Table 1]

[0108] (Anti-reflective property) Regarding anti-reflective properties, the reflectance was measured at wavelengths of 380 to 780 nm using a "V-650" tester manufactured by JASCO Corporation at a scanning speed of 1000 nm / min. The luminous mean reflectance was then calculated by multiplying this reflectance by a weighting factor in accordance with "JIS Z 8722". As a result, the luminous mean reflectance was 0.91% for Example 1 and 6.7% for Comparative Example 1.

[0109] (hydrophilic) Regarding hydrophilicity, the water contact angle on one side of the protective material for the display panel was measured using the droplet method with "DMs-401" manufactured by Kyowa Interface Chemical Co., Ltd., under constant temperature and humidity conditions. As a result, the angle was 11.3° in Example 1 and 68.0° in Comparative Example 1.

[0110] (Anti-fog properties) Regarding anti-fogging properties, the protective material for the display panel was thoroughly cooled in a food refrigerator (approximately -15°C), and then the surface condition was visually observed when it was removed and placed in a space with a temperature of 25°C and a humidity of 60%. As a result, no fogging occurred in Example 1 (○). On the other hand, fogging occurred across the entire surface in Comparative Example 1 (×).

[0111] On the other hand, a test piece cut from a protective material for a display panel was held approximately 50 mm above the surface of 85°C hot water in a cup, and the time it took for the water to become cloudy or frosted due to the steam was measured. The results showed that it took approximately 3 seconds in Example 1 and approximately 0.5 seconds in Comparative Example 1.

[0112] As described above, as shown in Table 1, the protective material for display panels in Example 1 showed better results in evaluation tests for anti-reflective properties, hydrophilicity, and anti-fogging properties compared to the protective material for display panels in Comparative Example 1. [Explanation of Symbols]

[0113] 1A~1D…Protective material for display panel 2…Transparent substrate 3…Hydrophilic layer 4…Anti-reflective layer 5…Fine uneven structure 6…Adhesive layer 7…Hard coat layer 8…Protective layer 41…Low refractive index layer 42…Medium refractive index layer 43…High refractive index layer G…Void layer 100…Display panel

Claims

1. A protective material for a display panel, provided on the front side of the display panel, Transparent substrate and A hydrophilic layer provided on one side of the transparent substrate, The transparent substrate is provided with an anti-reflective layer on the other side, The hydrophilic layer is arranged between it and the display panel with a gap layer in between. A protective material for a display panel, characterized in that a fine uneven structure having hydrophilic and anti-reflective properties is provided on the side of the hydrophilic layer facing the void layer.

2. The protective material for a display panel according to claim 1, characterized in that the water contact angle of the hydrophilic layer is 20° or less.

3. The protective material for display panels according to claim 1, characterized in that the anti-reflective layer consists of a cured film of a composition mainly composed of alkoxysilane, and its reflectivity is 3% or less.

4. The protective material for a display panel according to claim 1, characterized in that the hydrophilic layer having the fine uneven structure is directly provided on one side of the transparent substrate.

5. The protective material for a display panel according to claim 1, characterized in that the hydrophilic layer having the fine uneven structure is provided on one side of the transparent substrate via an adhesive layer.

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