JP2011001525A - Transparent plastic substrate plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent plastic substrate plate having heat resistance and a small birefringence value, and excellent in molding processability and surface smoothness, and concretely, the plastic substrate plate for a liquid crystal touch panel, transparent electroconductive substrate plate and lens array.SOLUTION: This acrylic copolymer and the transparent plastic substrate plate consisting of the same are provided. The copolymer consists of (i) a recurring unit derived from a methacrylate monomer, (ii) a recurring unit derived from a vinylaromatic monomer and (iii) an acid anhydride recurring unit.

Description

  The present invention relates to a transparent plastic substrate. More specifically, the present invention relates to a liquid crystal touch panel plastic substrate, a transparent conductive substrate, and a lens array.

  Touch panels are widely used mainly for car navigation, portable game machines, PDAs and the like. Conventionally, a glass substrate has been used as a substrate for a liquid crystal touch panel, but in recent years, there is an increasing need for a small and portable touch panel substrate. In order to realize this, demands for weight reduction, impact resistance and heat resistance increase have increased, and liquid crystal touch panels using a glass substrate having a thickness of 0.4 to 2.0 mm have been produced. However, there is a problem that the glass substrate has low impact resistance and is easily broken by dropping. Further, reducing the thickness of the glass substrate for the purpose of reducing the weight leads to an increase in the rate of occurrence of cracks in the glass substrate, resulting in a problem in that the production yield and the durability are lowered. In order to reduce the weight and prevent the above-mentioned glass breakage, there is an increasing demand for the development of a liquid crystal touch panel using a transparent plastic substrate as a substrate instead of glass (Patent Document 1).

  A transparent conductive film is widely known as a film having both visible light transmission and electrical conductivity. The transparent conductive film includes, for example, a tin-added indium oxide film (hereinafter referred to as “ITO film”), and a laminate in which this ITO film is laminated on a transparent substrate includes an electrode, a heating element by energization, and an electromagnetic wave shielding material. And widely used as a translucent body. In recent years, zinc oxide (ZnO) based transparent conductive films and the like have been developed as materials to replace expensive ITO films. Conventionally, glass has been mainly used as a base material for a transparent conductive film. However, as demand and applications increase, improvement in workability and productivity has been demanded. Therefore, in recent years, plastics that are lighter than glass and superior in workability and productivity have attracted attention. For example, polyethylene terephthalate, polycarbonate, and cyclic olefin resins have been processed into transparent plastic substrates. (Patent Document 2).

An electrode substrate, for example, an electrode substrate for a liquid crystal display or an electrode substrate for a liquid crystal touch panel, requires a plastic substrate having a smaller birefringence even if the total light transmittance is the same. Furthermore, as a result of the recent increase in size of liquid crystal displays, a transparent plastic substrate having a small change in birefringence caused by bias of external force, that is, a small photoelastic coefficient has been demanded (Patent Documents 3 and 4).
On the other hand, as an illumination / display device, there is a lens array made of a transparent plastic substrate. The lens array is an unevenly molded product. For example, a push button of a mobile phone has a shape in which a plurality of single lenses that are thick portions are arranged and connected by thin portions. The conventional transparent plastic base material has a problem that it undergoes thermal deformation depending on the use environment temperature and leads to uneven brightness (Patent Document 5).

JP 2003-5909 A JP 2007-115657 A JP-A-4-176857 Japanese Patent Laid-Open No. 2003-34860 JP 2008-281728 A Japanese Patent No. 2886893

  As described above, in applications where glass substrates have been used, efforts have been made to replace them with transparent plastic substrates. Acrylic resin typified by PMMA is widely used as a material for transparent plastic substrates because of its high transparency and low birefringence, but it is not sufficient in heat resistance and is subject to dimensional changes. There was a problem and it was not satisfactory for the demands of the market. On the other hand, a terpolymer composed of methyl methacrylate, styrene and maleic anhydride, which is an acrylic resin with improved heat resistance (styrene / maleic anhydride weight ratio ≧ 1), is disclosed. The polymer has a problem that the birefringence is large (Patent Document 5).

Therefore, development of a transparent plastic substrate having heat resistance, a small birefringence value, excellent molding processability and surface smoothness is required.
An object of this invention is to provide the transparent plastic substrate which has heat resistance, a small birefringence value, and is excellent in molding processability and surface smoothness. Specifically, it aims at providing the plastic substrate for liquid crystal touch panels, a transparent conductive substrate, and a lens array.
In the present invention, a transparent plastic substrate made of a specific acrylic copolymer has heat resistance, a small birefringence value, excellent thermal stability during molding, excellent molding processability and surface smoothness. It was made to find out.

That is, the present invention
[1] Repeating unit derived from a methacrylate monomer represented by the following formula (1): 10 to 70% by weight, repeating unit derived from a vinyl aromatic monomer represented by the following formula (2): 5 to 40 A copolymer containing 20% by weight and a cyclic acid anhydride repeating unit represented by the following formula (3) or the following formula (4): 20 to 50% by weight, which is a repeat derived from a vinyl aromatic monomer The molar ratio (B / A) of the unit content (A) to the cyclic acid anhydride repeating unit content (B) is greater than 1 and 10 or less, and 100 parts by weight of the copolymer. The transparent plastic substrate which consists of a copolymer whose sum total of the monomer which remains with respect to is 0.5 weight part or less.

(In the formula: R ¹ represents hydrogen, a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 12 carbon atoms.)

(In the formula: R ² and R ³ may be the same or different, and each represents hydrogen, halogen, hydroxyl group, alkoxy group, nitro group, linear or branched alkyl group having 1 to 12 carbon atoms. L represents an integer of 1 to 3)

(Wherein R ^{5 to} R ⁸ may be the same or different and each represents hydrogen, a linear or branched alkyl group having 1 to 12 carbon atoms).

[2] The copolymer further comprises a copolymer containing a repeating unit derived from a methacrylate monomer having an aromatic group represented by the following formula (5): 0.1 to 5% by weight [1] ] The transparent plastic substrate of description.

(In the formula: R ⁴ represents hydrogen, halogen, hydroxyl group, alkoxy group, nitro group, linear or branched alkyl group having 1 to 12 carbon atoms, m is an integer of 1 to 3, and n is 0 to 0. Indicates an integer of 2.)

[3] The copolymer has a weight average molecular weight of 10,000 to 400,000 and a molecular weight distribution of 1.8 to 3.0 according to GPC measurement method. [1] or [2] Transparent plastic substrate as described in 1.
[4] The copolymer has a repeating unit derived from a methacrylate monomer as methyl methacrylate, a repeating unit derived from a vinyl aromatic monomer as styrene, a cyclic acid anhydride repeating unit as maleic anhydride, and an aromatic group. The transparent plastic substrate according to any one of [1] to [3], wherein the repeating unit derived from a methacrylate monomer is a copolymer derived from benzyl methacrylate.
[5] A plastic substrate for a liquid crystal touch panel comprising the transparent plastic substrate according to any one of [1] to [4].
[6] A transparent conductive substrate in which a tin-added indium oxide film is directly laminated on at least one surface of the transparent plastic substrate according to any one of [1] to [4].
[7] A transparent conductive film conductive substrate in which a zinc oxide-based transparent conductive film is directly laminated on at least one surface of the transparent plastic substrate according to any one of [1] to [4].
[8] A lens array comprising the transparent plastic substrate according to any one of [1] to [4].
About.

  The present invention provides a transparent plastic substrate made of a specific acrylic resin, having heat resistance, a small birefringence value, excellent thermal stability at the time of molding, molding processability, and surface smoothness. be able to.

[Acrylic copolymer]
A preferred acrylic copolymer for obtaining the transparent plastic substrate of the present invention is:
Repeating unit derived from a methacrylate monomer represented by the following formula (1): 10 to 70% by weight, repeating unit derived from a vinyl aromatic monomer represented by the following formula (2): 5 to 40% by weight, And a cyclic acid anhydride repeating unit represented by the following formula (3) or the following formula (4): a copolymer containing 20 to 50% by weight, containing a repeating unit derived from a vinyl aromatic monomer The molar ratio (B / A) between the amount (A) and the content (B) of the cyclic acid anhydride repeating unit is in the range of more than 1 and 10 or less, and relative to 100 parts by weight of the copolymer It is an acrylic copolymer in which the total of the remaining monomers is 0.5 parts by weight or less.

(In the formula: R ¹ represents hydrogen, a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 12 carbon atoms.)

(In the formula: R ² and R ³ may be the same or different, and each represents hydrogen, halogen, hydroxyl group, alkoxy group, nitro group, linear or branched alkyl group having 1 to 12 carbon atoms. L represents an integer of 1 to 3)

(Wherein R ^{5 to} R ⁸ may be the same or different and each represents hydrogen, a linear or branched alkyl group having 1 to 12 carbon atoms).

  A more preferable acrylic copolymer is an acrylic copolymer containing 0.1 to 5% by weight of a repeating unit derived from a methacrylate monomer having an aromatic group represented by the following formula (5).

(In the formula: R ⁴ represents hydrogen, halogen, hydroxyl group, alkoxy group, nitro group, linear or branched alkyl group having 1 to 12 carbon atoms, m is an integer of 1 to 3, and n is 0 to 0. Indicates an integer of 2.)

In the acrylic copolymer, the repeating unit represented by the formula (1) is derived from methacrylic acid and a methacrylic acid ester monomer. Examples of the methacrylic acid ester used include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid. Cyclohexyl acid; and the like. Methacrylic acid and methacrylic acid ester may be used alone or in combination of two or more.
Among these methacrylic acid esters, methacrylic acid alkyl esters having 1 to 7 carbon atoms in the alkyl group are preferable, and methyl methacrylate is particularly preferable because the resulting acrylic copolymer has excellent heat resistance and transparency. .

The content ratio of the repeating unit represented by the formula (1) is 10 to 70% by mass, preferably 25 to 70% by mass, more preferably 40 to 70% by mass from the viewpoint of transparency.
The repeating unit represented by the formula (2) is derived from an aromatic vinyl monomer. Examples of the monomer used include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, and 2-methyl-4-chlorostyrene. 2,4,6-trimethylstyrene, α-methylstyrene, cis-β-methylstyrene, trans-β-methylstyrene, 4-methyl-α-methylstyrene, 4-fluoro-α-methylstyrene, 4-chloro -Α-methylstyrene, 4-bromo-α-methylstyrene, 4-t-butylstyrene, 2-fluorostyrene, 3-fluorostyrene, 4-fluorostyrene, 2,4-difluorostyrene, 2-chlorostyrene, 3 -Chlorostyrene, 4-chlorostyrene, 2,4-dichlorostyrene, 2,6-dichlorostyrene, 2-bromo Styrene, 3-bromostyrene, 4-bromostyrene, 2,4-dibromostyrene, alpha-bromostyrene, beta-bromostyrene, 2-hydroxystyrene, 4-hydroxy styrene. These aromatic vinyl monomers may be used alone or in combination of two or more.
Of these monomers, styrene and α-methylstyrene are preferable because of easy copolymerization.

The content ratio of the repeating unit represented by the formula (2) is 5 to 40% by mass, preferably 5 to 30% by mass, and more preferably 5 to 20% by mass from the viewpoints of transparency and heat resistance.
The cyclic acid anhydride repeating unit represented by the formula (3) is derived from unsubstituted and / or substituted maleic anhydride. Examples of the monomer used include maleic anhydride, citraconic anhydride, dimethyl maleic anhydride, dichloromaleic anhydride, bromomaleic anhydride, dibromomaleic anhydride, phenylmaleic anhydride, and diphenylmaleic anhydride. Can be mentioned. Of these monomers, maleic anhydride is preferable because of easy copolymerization.
The cyclic acid anhydride repeating unit represented by the formula (4) is derived by a condensation cyclization reaction between the repeating units described later, and examples thereof include glutaric anhydride.

In the copolymer (a) of the present invention, the cyclic acid anhydride repeating unit represented by the formula (3) or the formula (4) can be opened by being partially hydrolyzed by an external environment such as moisture in the air. There is sex. In the copolymer (a) of the present invention, the hydrolysis rate is preferably less than 10 mol% from the viewpoint of optical properties and heat resistance. Furthermore, it is preferable that it is less than 5 mol%, and it is more preferable that it is less than 1 mol%.
Here, the hydrolysis rate (mol%) is obtained by {1- (cyclic acid anhydride amount after hydrolysis (mol)) / cyclic acid anhydride amount (mol) before hydrolysis} × 100.

The content ratio of the cyclic acid anhydride repeating unit represented by the formula (3) or the formula (4) is such that the acrylic copolymer of the present invention has high heat resistance and optical characteristics (particularly, control of retardation described later). In order to achieve a high degree, it is 20-50 mass%, Preferably it is 20-45 mass%. However, in the acrylic copolymer of the present invention, the content (A) of the repeating unit derived from the vinyl aromatic monomer represented by the formula (2) and the formula (3) or the formula (4) The molar ratio (B / A) of the content (B) of cyclic acid anhydride repeating units is preferably more than 1 and 10 or less, more preferably more than 1 and 5 or less.
The repeating unit represented by the formula (5) is derived from a methacrylate monomer having an aromatic group. Examples of the monomer used include phenyl methacrylate, benzyl methacrylate, and 1-phenylethyl methacrylate. These monomers may be used alone or in combination of two or more. Of these monomers, benzyl methacrylate is particularly preferred.
The content of the repeating unit represented by the formula (5) is 0.1 to 5% by mass, preferably 0.1% by mass, preferably the optical properties (particularly minimizing the photoelastic coefficient) that are the effects of the present invention. It is 0.1-4 mass%, More preferably, it is 0.1-3 mass%.

In the copolymer of the present invention, the total amount of the remaining monomers (constituting the copolymer repeating unit) is 0.5 parts by weight or less with respect to 100 parts by weight of the copolymer. 4 parts by weight or less, more preferably 0.3 parts by weight or less. When the total amount of residual monomers exceeds 0.5 parts by weight, there is a problem in that a molded product that is not suitable for practical use is obtained, such as being colored when heated during molding, and the heat resistance and weather resistance of the molded product are reduced. The amount of residual volatile matter referred to in the present invention refers to the total amount of residual monomer, polymerization solvent, by-product water, and by-product alcohol that have not reacted during the above-described polymerization reaction.
The weight average molecular weight (Mw) in terms of PMMA according to the GPC measurement method of the acrylic copolymer of the present invention is 10,000 to 400,000, preferably 40,000 to 300,000, more preferably 70,000 to 200. The molecular weight distribution (Mw / Mn) is 1.8 to 3.0, preferably 1.8 to 2.7, more preferably 1.8 to 2.5.
The glass transition temperature (Tg) of the acrylic copolymer of the present invention can be arbitrarily controlled by the resin composition, but is preferably controlled to 120 ° C. or more from the viewpoint of industrial applicability. More preferably, it is controlled to 130 ° C. or higher, more preferably 135 ° C. or higher.

The method for producing the acrylic copolymer of the present invention can be produced by applying a known polymerization method such as suspension polymerization, solution polymerization or bulk polymerization, and is not particularly limited. For example, methods described in Japanese Patent Publication No. 63-1964, Japanese Patent Application Laid-Open No. 60-147417, Japanese Patent No. 387964, and the like can be used. As the acrylic copolymer, two or more types having different molecular weight, composition and the like can be used at the same time.
The acrylic copolymer of the present invention may use known colorants, stabilizers such as ultraviolet absorbers and antioxidants, and various additives as necessary. For example, inorganic fillers, pigments such as iron oxides, lubricants such as stearic acid, behenic acid, zinc stearate, calcium stearate, magnesium stearate, ethylene bisstearamide, mold release agents, paraffinic process oil, naphthenic process Oils, aromatic process oils, paraffins, organic polysiloxanes, mineralizers and other softeners / plasticizers, hindered phenol antioxidants, phosphorus heat stabilizers and other antioxidants, hindered amine light stabilizers, benzo Examples include triazole-based ultraviolet absorbers, flame retardants, antistatic agents, organic fibers, glass fibers, carbon fibers, reinforcing agents such as metal whiskers, colorants, other additives, or mixtures thereof.
The content of the additive is preferably 0 to 5% by mass, more preferably 0 to 2% by mass, and still more preferably 0 to 1% by mass.

  In addition, the acrylic copolymer of the present invention is within the range not impairing the object of the present invention, for example, polyolefin resin such as polyethylene and polypropylene, polystyrene, styrene / acrylonitrile copolymer, styrene / maleic anhydride copolymer. , Styrene resins such as styrene / methacrylic acid copolymer, polymethacrylate resin, polyamide, polyphenylene sulfide resin, polyether ether ketone resin, polyester resin, polysulfone, polyphenylene oxide, polyimide, polyetherimide, It is possible to mix at least one kind of thermoplastic resin such as polyacetal, cyclic olefin resin, norbornene resin, and thermosetting resin such as phenol resin, melamine resin, silicone resin, epoxy resin, etc. That.

[Transparent plastic substrate]
When producing transparent plastic substrates in the present invention, dyes, pigments, heat stabilizers such as hindered phenols and phosphates, ultraviolet rays such as benzotriazoles, 2-hydroxybenzophenones, and salicylic acid phenyl esters Absorbent, phthalate ester, fatty acid ester, trimellitic acid ester, phosphate ester, polyester and other plasticizer, higher fatty acid, higher fatty acid ester, higher fatty acid mono-, di- or triglyceride Molding agents, higher fatty acid esters, polyolefin-based lubricants, polyether-based, polyether-ester-based, polyether-ester amide-based, alkyl sulfonates, alkylbenzene sulfonates and other antistatic agents, phosphorus-based, phosphorus / chlorine , Phosphorus / bromine flame retardants, reflected light In order to prevent sticking, organic light diffusing agents such as methyl methacrylate / styrene copolymer beads, inorganic light diffusing agents such as barium sulfate, titanium oxide, calcium carbonate, talc, and acrylics obtained by multistage polymerization as reinforcing agents System rubber or the like may be used.
When these additives are blended, it can be carried out by a known method. For example, a method in which an additive is dissolved in a monomer mixture in advance and polymerized, or an additive is dry-blended with a mixer or the like in a molten state, bead-like or pellet-like resin, and kneaded and granulated using an extruder The method of doing is mentioned.

The transparent plastic substrate of the present invention is preferably a film or a sheet. The film / sheet in the present invention is only a difference in thickness, the film is a thickness of 300 μm or less, and the sheet is more than 300 μm.
A preferred plastic substrate thickness is a film or sheet in the range of 0.01 to 10.0 mm. A film or sheet in the range of 0.01 to 10.0 mm is hard to be deformed during panel processing and easy to handle. Further, deformation due to the load on the substrate is less likely to occur. A more preferable thickness of the plastic substrate is in the range of 0.1 to 5.0 mm.
The film or sheet, which is a transparent plastic substrate in the present invention, preferably has heat resistance. As an index of heat resistance, the film or sheet is warped or deformed when left in an atmosphere at a temperature of 90 ° C. for about 1 hour. Preferably not.
The film or sheet, which is a transparent plastic substrate in the present invention, must have transparency, and it is preferable that the total light transmittance is 80% or more and the haze value is 5% or less as an index of transparency. More preferably, the total light transmittance is 85% or more and the haze value is 2% or less.

  The film or sheet which is a transparent plastic substrate in the present invention preferably has excellent optical isotropy, the retardation value is 30 nm or less, the variation of the slow axis is within 40 degrees, more preferably the retardation value is 20 nm or less, the slow phase A shaft with a variation of 20 degrees or less is preferable. Here, the retardation value is represented by a product Δn · d of a refractive index difference Δn of birefringence at a wavelength of 590 nm and a film thickness d measured using a known measuring apparatus.

The film or sheet which is a transparent plastic substrate in the present invention preferably has an absolute value of the photoelastic coefficient of less than 3.0 × 10 ⁻¹² Pa ⁻¹ . If the photoelastic coefficient is within this range, the change in birefringence due to stress is small, so that the contrast and the uniformity of the screen are excellent when used in a liquid crystal display device or the like.
The photoelastic coefficient is described in various documents (for example, Macromolecules).
2004, 37, 1062-1066), and is defined by the following equation.
| CR | = | Δn | / σR | Δn | = | n1-n2 |
(Where: | CR |: absolute value of photoelastic coefficient, σR: stretching stress, | Δn |: absolute value of birefringence, n1: refractive index in stretching direction, n2: refractive index perpendicular to stretching direction)
The closer the value of the photoelastic coefficient is to zero, the smaller the change in birefringence due to external force, which means that the change in birefringence designed for each application is small.

The transparent plastic substrate of the present invention has heat resistance and a small birefringence value. Furthermore, since it is excellent in molding processability and surface smoothness, it is suitably used for plastic substrates for liquid crystal touch panels, transparent conductive substrates, lens arrays, and the like.
1) Plastic substrate for liquid crystal touch panel A liquid crystal touch panel substrate is obtained, for example, by laminating a plastic substrate via an ultraviolet curable resin on the upper surface of a glass substrate whose surface is processed flat for a liquid crystal touch panel substrate. Specifically, the ultraviolet curable resin is rolled and applied to a predetermined thickness by rotating a rolling roller from the upper side of the plastic substrate.
Then, the surface coat layer (thin film layer) which hardened ultraviolet curable resin is formed by irradiating with an ultraviolet lamp from the lower surface side of a glass substrate. After curing, the plastic substrate is pulled away from the glass substrate together with the surface coat layer (cured ultraviolet curable resin).
As a result, the surface shape of the glass substrate is transferred to the surface of the surface coat layer integrally bonded to the plastic substrate, and the liquid crystal touch panel substrate, which is a plastic substrate having the same surface-coated surface coat layer as the glass substrate, is obtained. Obtainable.

The ultraviolet curable resin used for forming the surface coat layer has advantages such as easy peeling from the glass and less foaming problem due to a small amount of volatile components.
A thermosetting resin may be used in place of the ultraviolet curable resin, or an ultraviolet curable resin and a thermosetting resin may be used in combination, but the ultraviolet curable resin is preferably used because of the above advantages.
In the case of using a thermosetting resin, after mixing using a two-component mixed thermosetting resin, the pot life is used to peel from the glass after curing is started and thermoset. Note that ultraviolet rays and heat rays may be irradiated from the lower side of the glass substrate, or may be irradiated from the upper side of the plastic substrate or from both sides.

2) Transparent conductive substrate The transparent conductive substrate is obtained, for example, by laminating a tin-added indium oxide film and a zinc oxide film on a plastic substrate. The obtained laminate is widely used as an electrode, a heating element by energization, an electromagnetic shielding material or a translucent body.
For example, the material used for the zinc oxide-based transparent conductive film is at least one selected from aluminum, gallium, boron, silicon, tin, indium, germanium, antimony, iridium, rhenium, cerium, zirconium, scandium, and yttrium. A zinc oxide film containing is used.

The content of aluminum, gallium, boron, silicon, tin, indium, germanium, antimony, iridium, rhenium, cerium, zirconium, scandium, yttrium added to the zinc oxide film, when adding one of these, The atomic ratio of these materials to zinc oxide is preferably in the range of 0.05 to 15. When added at such a ratio, the conductivity and transparency of the film can be maintained well.
Moreover, when adding multiple types of these materials, the range of 15% or less of the total addition amount of the material to add with respect to zinc oxide is preferable.
Among these materials, zinc oxide to which digallium trioxide is added is more suitable for the conductivity and transparency of the film.
The film thickness of the zinc oxide-based transparent conductive film is preferably in the range of 10 nm to 1000 nm. In this film thickness range, although it varies depending on the application, it is possible to obtain a continuous film in which flexibility is maintained.
Furthermore, the film thickness of the transparent conductive film of the present invention is desirably 20 to 500 nm depending on the application.

Although the sheet resistance value of a transparent conductive substrate changes with uses, the thing of the range of 5-10000 ohms / square is preferable as an electroconductive material. More preferably, the range of 10 to 300Ω / □ is preferable.
In the method for producing a transparent conductive substrate formed by forming a transparent conductive film, the film forming method is not particularly limited, and a sputtering method, a vacuum deposition method, a CVD method, or an ion plating method is used. In the ion plating method, zinc oxide containing a dopant is disposed as a film forming material on a hearth as an electrode portion disposed in a film forming chamber, and the zinc oxide is irradiated with, for example, argon plasma to form zinc oxide. Each particle of zinc oxide that has been heated and evaporated and passed through the plasma is deposited on a transparent resin film or sheet placed at a position facing the hearth or the like. In this ion plating method, for example, the kinetic energy of the particles is smaller than that of the sputtering method. Therefore, when the particles collide, damage to the substrate or the zinc oxide-based transparent conductive film formed on the substrate is deposited. It is known that a small film with good crystallinity can be obtained.
As the outermost layer of the transparent conductive substrate, one or two or more layers of any resin or inorganic compound may be laminated. Such an outermost layer can have a role of a protective film, an antireflection film, a filter, or the like, or functions such as adjustment of the viewing angle of liquid crystal and anti-fogging.

3) Lens array The lens array referred to in the present invention is a lens in which a plurality of single lenses are arranged, for example, a lens having a continuous continuous lens shape, and the single lens is in the X direction or in the XY direction as a surface. Included are integrated types. There is no restriction | limiting in the shape of a single lens, For example, a general uneven | corrugated R lens shape, a prism shape, a pyramid shape, a saddle-shaped lens shape, a Fresnel lens shape, a moth-eye lens shape, a lenticular lens, a fly eye lens etc. are mentioned. Further, the size of the lens is not limited, and includes a microlens to a gentle R shape.
An example of a lens array is a push button of a mobile phone. In this case, a plurality of single lenses that are thick portions are arranged, and portions other than the single lenses are connected by thin portions to form an integral molded product, which is generally called a connected lens. Mobile phone push buttons are built in a fixed location, and considering the efficiency of assembly, it is a great merit that all buttons are connected.

Depending on the design, single lenses are regularly arranged in a plane in the XY direction, aligned in the straight line only in the X direction, or randomly arranged in the design, and the shape, thickness, and size of the single lens are the functions of each lens. Although various shapes can be envisaged depending on the type of lens, various shapes can be assumed, but the lens array of the present invention includes any of them. In addition to mobile phone push buttons, display indicators are also included.
Furthermore, in particular, as a lens for LED light sources that has spread rapidly in recent years, in order to efficiently pick up the light of the LED, a hole for putting the LED into the apex of the inverted triangular pyramid is formed so as to enclose one LED. In addition, a lens for an LED light source is also included in which a single lens is covered with each LED in which LEDs are spread in the XY directions as surface light sources at intervals of 10 mm, and this is formed into an integral molded product.

It is also suitable for lens arrays composed of single lenses, such as convex lenses, concave lenses, pickup lenses, projector lenses, uneven-thickness lenses, prisms, and mirror lenses, where sink marks tend to cause problems depending on the product shape.
Examples of the method for producing the lens array of the present invention include injection molding, extrusion molding, blow molding, vacuum molding, pressure forming, and stretch molding. The heat resistance of the lens array of the invention is preferably 100 ° C. or higher, more preferably 103 ° C. or higher in terms of Vicat softening temperature.

Hereinafter, the present invention will be described more specifically with reference to examples.
The measuring method of each measured value used for this invention is as follows.
(A) Analysis of acrylic copolymer (1) Repeating unit
^{From 1} H-NMR measurement, (i) a repeating unit derived from a methacrylate monomer, (ii) a repeating unit derived from a vinyl aromatic monomer, (iii) a repeating unit derived from a methacrylate monomer having an aromatic group, And (iv) an acid anhydride repeating unit was identified and its abundance was calculated.
Measuring instrument: DPX-400 manufactured by Blue Car Co., Ltd.
Measurement solvent: CDCl ₃ or d ⁶ -DMSO
Measurement temperature: 40 ° C

(2) Glass transition temperature The glass transition temperature (Tg) is JIS-K-7121 using a differential scanning calorimeter (Diamond DSC, manufactured by PerkinElmer Japan Co., Ltd.) under a nitrogen gas atmosphere and α-alumina as a reference. Based on the DSC curve obtained by heating about 10 mg of the sample from room temperature to 200 ° C. at a rate of temperature increase of 10 ° C./min, it was calculated by the midpoint method.
(3) Molecular weight The weight average molecular weight and the number average molecular weight were determined using a gel permeation chromatograph (HLC-8220 manufactured by Tosoh Corporation), the solvent being tetrahydrofuran, at a set temperature of 40 ° C., in terms of commercial standard PMMA.

(B) Optical characteristic evaluation (1) Production of optical film sample (a) Molding of press film Using a vacuum compression molding machine (SFV-30 type, manufactured by Kamito Metal Industries Co., Ltd.) at 260 ° C under atmospheric pressure, After preheating for 25 minutes, the film was compressed under vacuum (about 10 kPa) at 260 ° C. and about 10 MPa for 5 minutes to form a press film.
(B) Molding of stretched film A stretched film was molded by uniaxial free stretching at a stretching temperature (Tg + 20) ° C. and a stretching speed (500 mm / min) using an Instron 5t tensile tester. The draw ratio was drawn at 100%, 200%, and 300%.
(2) Measurement of birefringence Measurement was performed by a rotating analyzer method using RETS-100 manufactured by Otsuka Electronics. The value of birefringence is a value of light having a wavelength of 550 nm. Birefringence (Δn) was calculated by the following formula.
Δn = nx-ny
(Δn: birefringence, nx: refractive index in the stretching direction, ny: refractive index perpendicular to the stretching direction)
The absolute value (| Δn |) of birefringence (Δn) was determined as follows.
| Δn | = | nx−ny |

(3) Phase difference measurement <In-plane phase difference>
Using a RETS-100 manufactured by Otsuka Electronics Co., Ltd., measurement was performed in the wavelength range of 400 to 800 nm by the rotary analyzer method.
The absolute value of birefringence (| Δn |) and the phase difference (Re) have the following relationship.
Re = | Δn | × d
(| Δn |: absolute value of birefringence, Re: phase difference, d: thickness of sample)
The absolute value (| Δn |) of birefringence is a value shown below.
| Δn | = | nx−ny |
(Nx: refractive index in the stretching direction, ny: refractive index perpendicular to the stretching direction in the plane)

<Thickness direction retardation>
Using a phase difference measuring device (KOBRA-21ADH) manufactured by Oji Scientific Instruments, the phase difference at a wavelength of 589 nm was measured, and the obtained value was converted to a film thickness of 100 μm to obtain a measured value.
The absolute value of birefringence (| Δn |) and the phase difference (Rth) have the following relationship.
Rth = | Δn | × d
(| Δn |: absolute value of birefringence, Rth: phase difference, d: thickness of sample)
The absolute value (| Δn |) of birefringence is a value shown below.
| Δn | = | (nx + ny) / 2−nz |
(Nx: refractive index in the stretching direction, ny: refractive index in the plane perpendicular to the stretching direction, nz: refractive index in the thickness direction out of the plane perpendicular to the stretching direction)
(In an ideal film that is completely isotropic in the three-dimensional direction, both in-plane retardation (Re) and thickness direction retardation (Rth) are zero.)

(4) Measurement of photoelastic coefficient A birefringence measuring apparatus described in detail in Polymer Engineering and Science 1999, 39, 2349-2357 was used. A film tensioning device was placed in the laser beam path, and birefringence was measured while applying an extensional stress at 23 ° C. The strain rate during stretching was 50% / min (between chucks: 50 mm, chuck moving speed: 5 mm / min), and the test piece width was 6 mm. From the relationship between the absolute value of birefringence (| Δn |) and the extensional stress (σ _R ), the slope of the straight line was obtained by least square approximation, and the photoelastic coefficient (C _R ) was calculated. For the calculation, data with a tensile stress between 2.5 MPa ≦ σ _R ≦ 10 MPa was used.
C _R = | Δn | / σ _R
| Δn | = | nx−ny |
(C _R : photoelastic coefficient, σ _R : stretching stress, | Δn |: absolute value of birefringence, nx: refractive index in the stretching direction, ny: vertical refractive index in the stretching direction)

[Acrylic copolymer]
Methyl methacrylate / styrene / maleic anhydride
[Synthesis Example 1]
A jacketed glass reactor (capacity: 1 L) equipped with a stirrer, a temperature sensor, a cooling pipe, a nitrogen gas introduction nozzle, a raw material solution introduction nozzle, an initiator solution introduction nozzle, and a polymerization solution discharge nozzle was used. The pressure in the polymerization reactor was slightly pressurized, and the reaction temperature was controlled at 100 ° C.
After mixing 518 g of methyl methacrylate (MMA), 48 g of styrene (St), 384 g of maleic anhydride (MAH), 240 g of methyl isobutyl ketone and 1.2 g of n-octyl mercaptan, a raw material solution was prepared by replacing with nitrogen gas. . An initiator solution was prepared by dissolving 0.364 g of 2,2′-azobis (isobutyronitrile) in 12.96 g of methyl isobutyl ketone and then substituting with nitrogen gas.
The raw material solution was introduced from the raw material solution introduction nozzle at 6.98 ml / min using a pump. The initiator solution was introduced from the initiator solution introduction nozzle at 0.08 ml / min using a pump. After 30 minutes, the polymer solution was discharged at a constant flow rate of 425 ml / hr using a pump extracted from the polymerization solution discharge nozzle.

The polymer solution was collected separately in the initial flow tank for 1.5 hours after discharge. The polymer solution was collected for 2.5 hours after 1.5 hours from the start of discharge. The obtained polymer solution was dropped into methanol, which is a poor solvent, and precipitated and purified. It was dried at 130 ° C. for 2 hours under vacuum to obtain a desired acrylic copolymer.
Composition: MMA / St / MAH = 61/11/27 wt%
Molecular weight: Mw = 19.5 × 10 ⁴ ; Mw / Mn = 2.23
Tg: 141 ° C
Methyl methacrylate / styrene / maleic anhydride / benzyl methacrylate

[Synthesis Example 2]
A jacketed glass reactor (capacity: 1 L) equipped with a stirrer, a temperature sensor, a cooling pipe, a nitrogen gas introduction nozzle, a raw material solution introduction nozzle, an initiator solution introduction nozzle, and a polymerization solution discharge nozzle was used. The pressure in the polymerization reactor was slightly pressurized, and the reaction temperature was controlled at 100 ° C.
After mixing 518 g of methyl methacrylate (MMA), 48 g of styrene (St), 9.6 g of benzyl methacrylate (BzMA), 384 g of maleic anhydride (MAH), 240 g of methyl isobutyl ketone and 1.2 g of n-octyl mercaptan, nitrogen was mixed. A raw material solution was prepared by replacing with gas. An initiator solution was prepared by dissolving 0.364 g of 2,2′-azobis (isobutyronitrile) in 12.96 g of methyl isobutyl ketone and then substituting with nitrogen gas.
The raw material solution was introduced from the raw material solution introduction nozzle at 6.98 ml / min using a pump. The initiator solution was introduced from the initiator solution introduction nozzle at 0.08 ml / min using a pump. After 30 minutes, the polymer solution was discharged at a constant flow rate of 425 ml / hr using a pump extracted from the polymerization solution discharge nozzle.

The polymer solution was collected separately in the initial flow tank for 1.5 hours after discharge. The polymer solution was collected for 2.5 hours after 1.5 hours from the start of discharge. The obtained polymer solution was dropped into methanol, which is a poor solvent, and precipitated and purified. It was dried at 130 ° C. for 2 hours under vacuum to obtain a desired acrylic copolymer.
Composition: MMA / St / BzMA / MAH = 61/12/1/27 wt%
Molecular weight: Mw = 18.8 × 10 ⁴ ; Mw / Mn = 2.08
Tg: 142 ° C

[Synthesis Example 3]
An acrylic copolymer was obtained in the same manner as in Synthesis Example 2 except that the synthesis was changed to 499 g of methyl methacrylate, 42 g of styrene, 48 g of benzyl methacrylate, and 371 g of maleic anhydride.
Composition: MMA / St / BzMA / MAH = 60/11/5/24 wt%
Molecular weight: Mw = 20.2 × 10 ⁴ ; Mw / Mn = 2.36
Tg: 138 ° C
Methyl methacrylate / styrene / methacrylic acid / glutaric anhydride

[Synthesis Example 4]
A jacketed glass reactor (capacity: 1 L) equipped with a stirrer, a temperature sensor, a cooling pipe, a nitrogen gas introduction nozzle, a raw material solution introduction nozzle, an initiator solution introduction nozzle, and a polymerization solution discharge nozzle was used. The pressure in the polymerization reactor was slightly pressurized, and the reaction temperature was controlled at 100 ° C.
After mixing 900 g of methyl methacrylate, 36 g of styrene, 48 g of benzyl methacrylate, 216 g of methacrylic acid (MAA), 240 g of methyl isobutyl ketone and 1.2 g of n-octyl mercaptan, the mixture was replaced with nitrogen gas to prepare a raw material solution. An initiator solution was prepared by dissolving 0.364 g of 2,2′-azobis (isobutyronitrile) in 12.96 g of methyl isobutyl ketone and then substituting with nitrogen gas.
The raw material solution was introduced from the raw material solution introduction nozzle at 6.98 ml / min using a pump. The initiator solution was introduced from the initiator solution introduction nozzle at 0.08 ml / min using a pump. After 30 minutes, the polymer solution was discharged at a constant flow rate of 425 ml / hr using a pump extracted from the polymerization solution discharge nozzle.

The polymer solution was collected separately in the initial flow tank for 1.5 hours after discharge. The polymer solution was collected for 2.5 hours after 1.5 hours from the start of discharge. The obtained polymer solution was dropped into methanol, which is a poor solvent, and precipitated and purified. The precursor was obtained by drying at 130 ° C. for 2 hours under vacuum. The precursor was heat-treated with a lab plast mill equipped with a devolatilizer (treatment temperature: 250 ° C., vacuum degree: 133 hPa (100 mmHg)) to obtain a target acrylic copolymer.
Composition: MMA / St / BzMA / MAA / glutaric anhydride = 70/5/4/4/21 wt%
Molecular weight: Mw = 11.4 × 10 ⁴ ; Mw / Mn = 2.40
Tg: 128 ° C
The polymerization results are shown in Table 1.

[Comparative Synthesis Example 1]
In Synthesis Example 1, a thermoplastic resin was obtained by performing the same operation as in Synthesis Example 1 except that 960 g of methyl methacrylate was used.
Composition: MMA = 100 wt%
Molecular weight: Mw = 10 × 10 ⁴ ; Mw / Mn = 1.89
Tg: 121 ° C

[Comparative Synthesis Example 2]
In Synthesis Example 1, a thermoplastic resin was obtained by performing the same operation as in Synthesis Example 1 except that benzyl methacrylate was not used and methyl methacrylate was changed to 768 g, styrene 144 g, and maleic anhydride 48 g.
Composition: MMA / St / MAH = 76/17/7 wt%
Molecular weight: Mw = 13.4 × 10 ⁴ ; Mw / Mn = 2.01
Tg: 128 ° C
The polymerization results are shown in Table 1.

[Evaluation Examples 1 to 4, Comparative Evaluation Examples 1 and 2]
Using the acrylic copolymers obtained in Synthesis Examples 1 to 4 and Comparative Synthesis Examples 1 and 2, press films were molded according to the method described above. A 100% stretched film was molded from the press film according to the method described above, and its optical properties were evaluated. The measurement results are shown in Table 2.

[Examples 1 to 4, Comparative Examples 1 and 2]
The pellets obtained by supplying the acrylic copolymers obtained in Examples 1 to 4 and Comparative Examples 1 and 2 to a twin screw extruder with a vent and granulating them at a temperature of 220 to 230 ° C. and a vent vacuum pressure of 700 to 750 mmHg. Was molded by M-70 manufactured by Meiki Seisakusho, and a flat plate molded product of 200 * 200 * 3 mm was obtained at a molding temperature of 220 ° C.
The evaluation results are shown in Table 3.
From Tables 2 and 3, it can be seen that the transparent plastic substrate of the present invention has heat resistance, a small birefringence value, and excellent molding processability and surface smoothness.
These characteristics are suitable for plastic substrates for liquid crystal touch panels, transparent conductive substrates, lens arrays, and the like.

  The transparent plastic substrate is suitable for a liquid crystal touch panel plastic substrate, a transparent conductive substrate, a lens array, and the like. The lens array includes a lens for an LED light source, and is also suitable for a convex lens, a concave lens, a pickup lens, a projector lens, an uneven thickness lens, a prism, a mirror lens, and the like.

Claims (8)

Repeating unit derived from a methacrylate monomer represented by the following formula (1): 10 to 70% by weight, repeating unit derived from a vinyl aromatic monomer represented by the following formula (2): 5 to 40% by weight, And a cyclic acid anhydride repeating unit represented by the following formula (3) or the following formula (4): a copolymer containing 20 to 50% by weight, containing a repeating unit derived from a vinyl aromatic monomer The molar ratio (B / A) between the amount (A) and the content (B) of the cyclic acid anhydride repeating unit is in the range of more than 1 and 10 or less, and relative to 100 parts by weight of the copolymer A transparent plastic substrate made of a copolymer having a total of remaining monomers of 0.5 parts by weight or less.

(In the formula: R ¹ represents hydrogen, a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 12 carbon atoms.)

(In the formula: R ² and R ³ may be the same or different, and each represents hydrogen, halogen, hydroxyl group, alkoxy group, nitro group, linear or branched alkyl group having 1 to 12 carbon atoms. L represents an integer of 1 to 3)

(Wherein R ^{5 to} R ⁸ may be the same or different and each represents hydrogen, a linear or branched alkyl group having 1 to 12 carbon atoms). The copolymer according to claim 1, further comprising a copolymer containing 0.1 to 5% by weight of repeating units derived from a methacrylate monomer having an aromatic group represented by the following formula (5): Transparent plastic substrate.

(In the formula: R ⁴ represents hydrogen, halogen, hydroxyl group, alkoxy group, nitro group, linear or branched alkyl group having 1 to 12 carbon atoms, m is an integer of 1 to 3, and n is 0 to 0. Indicates an integer of 2.)   The transparent plastic according to claim 1 or 2, wherein the copolymer has a weight average molecular weight of 10,000 to 400,000 and a molecular weight distribution of 1.8 to 3.0 by GPC measurement. substrate.   The copolymer has a repeating unit derived from a methacrylate monomer as methyl methacrylate, a repeating unit derived from a vinyl aromatic monomer as styrene, a cyclic acid anhydride repeating unit as maleic anhydride, and a monomer having an aromatic group The transparent plastic substrate according to any one of claims 1 to 3, wherein the repeating unit derived from the body comprises a copolymer derived from benzyl methacrylate.   The plastic substrate for liquid crystal touch panels which consists of a transparent plastic substrate of any one of Claims 1-4.   A transparent conductive substrate in which a tin-added indium oxide film is directly laminated on at least one surface of the transparent plastic substrate according to claim 1.   A transparent conductive film conductive substrate in which a zinc oxide-based transparent conductive film is directly laminated on at least one surface of the transparent plastic substrate according to claim 1.   The lens array which consists of a transparent plastic substrate of any one of Claims 1-4.