JP2009228001A - Display window protection plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin display window protection plate having excellent visibility of a display screen, impact resistance, rigidity, and surface smoothness, high surface hardness, and good appearance (few fish-eyes). <P>SOLUTION: The display window protection plate is constructed of a methacrylic resin composition, wherein 1-80 pts.mass of a block copolymer (B) as a dispersed phase is contained in 100 pts.mass of a continuous phase consisting of a methacrylic resin (A) containing 50 mass% or more of a repeating unit derived from a methyl methacrylate, and the block copolymer (B) comprises 30-65 mass% of a polymer block (a) consisting of a repeating unit derived from (meth)acrylic acid alkyl ester and having a glass transition temperature 23°C or lower, and 35-70 mass% of a polymer block (b) consisting of a repeating unit derived from a conjugated diene compound and having a glass transition temperature 0°C or lower. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a display window protection plate. More specifically, the present invention is a thin-walled display window protection plate that has excellent visibility of the display screen, as well as excellent impact resistance, rigidity, and surface smoothness, high surface hardness, and excellent appearance (low flutter). About.

In recent years, thin display devices such as a liquid crystal display, a plasma display, and an electroluminescence display have been actively developed. These display devices are used in mobile phones, mobile laptop computers, portable information terminals, and the like.
In order to protect the display screen in front of these displays, a protective plate is fitted to the display window.
The display window protection plate is required to have excellent display screen visibility, as well as excellent impact resistance, rigidity, and surface smoothness, high surface hardness, and a beautiful appearance. For this reason, display window protection plates such as mobile phones are often made of methacrylic resin.

In recent years, as represented by mobile phones, there is an increasing demand for downsizing and thinning of devices. For this reason, the display window protection plate is also becoming thinner.
However, methacrylic resins themselves are fragile and have low impact resistance, so they are not suitable for thinning. Therefore, Patent Document 1 and Patent Document 2 have proposed using a methacrylic resin composition obtained by blending multilayer structure acrylic rubber particles produced by an emulsion polymerization method with a methacrylic resin. This multilayer structure acrylic rubber particle is composed of two or more layers, and a hard layer mainly composed of methyl methacrylate and a soft layer mainly composed of an acrylate ester such as n-butyl acrylate are substantially And have a spherical structure that overlaps alternately. However, the effect of improving the impact resistance of the methacrylic resin by this resin composition is still insufficient, and it cannot fully meet the recent demand for thinning. Moreover, multilayer structure acrylic rubber particles may aggregate and a lump (gel colony) may be produced. When the thickness is reduced, the lump (fish eye) resulting from this lump becomes prominent, which may impair the appearance and reduce the commercial value.

  As another method for improving the impact resistance of a methacrylic resin, a method of polymerizing a monomer mainly composed of methyl methacrylate in the presence of a butadiene-butyl acrylate copolymer rubber (Patent Document 3). And a method of polymerizing a monomer mainly composed of methyl methacrylate in the presence of a partially hydrogenated conjugated diene polymer rubber (Patent Document 4). However, in these methods, it is difficult to control the dispersibility of the rubber component, and it may still cause poor appearance.

  Patent Document 5 proposes a composition comprising a methacrylic resin blended with a block copolymer obtained by grafting a methyl methacrylate copolymer and a vinyl acetate copolymer. However, this composition has low transparency and is not suitable for a display window protection plate.

JP 2006-232879 A JP 2007-190794 A Japanese Examined Patent Publication No. 45-26111 WO96 / 032440 Japanese Patent Laid-Open No. 06-345933

  An object of the present invention is to provide a thin display window protection plate which is excellent in visibility of a display screen, at the same time, excellent in impact resistance, rigidity and surface smoothness, high in surface hardness and excellent in appearance (low roughness). There is.

  As a result of intensive investigations to achieve the above object, the present inventors have found that 100 parts by mass of a continuous phase composed of a methacrylic resin (A) having a repeating unit derived from methyl methacrylate of 50% by mass or more ( 30 to 65% by mass of the polymer block (a) having a glass transition temperature of 23 ° C. or less and a repeating unit derived from a conjugated diene compound is 0 ° C. When a plate is molded using a methacrylic resin composition containing 1 to 80 parts by mass of a block copolymer (B) having a polymer block (b) of 35 to 70% by mass as a dispersed phase, the display is as follows. A thin-walled display window with excellent screen visibility, impact resistance, rigidity, and surface smoothness, high surface hardness, and excellent appearance (low roughness). It was found to be suitable to the plate. The present invention has been further studied and completed based on this finding.

  That is, the present invention is a glass comprising a repeating unit derived from a (meth) acrylic acid alkyl ester in 100 parts by mass of a continuous phase consisting of a methacrylic resin (A) having 50% by mass or more of a repeating unit derived from methyl methacrylate. 30 to 65% by mass of polymer block (a) having a transition temperature of 23 ° C. or less and 35 to 70% by mass of polymer block (b) having a glass transition temperature of 0 ° C. or less consisting of repeating units derived from a conjugated diene compound. It is a display window protective plate which consists of a methacrylic-type resin composition which 1-80 mass parts of block copolymers (B) which have these contain as a dispersed phase.

  Since the display window protection plate of the present invention has a high total light transmittance, the display screen has excellent visibility. Even if it is made thinner, it has excellent impact resistance and rigidity, and has a high surface hardness. Therefore, even when it is applied to a portable device or the like, problems such as scratches and cracks are unlikely to occur. In addition, since it has low surface roughness and excellent surface smoothness and surface glossiness, it is also suitable for devices that require design and fashionability.

Hereinafter, the present invention will be described in more detail.
The display window protection board of this invention consists of a resin composition which a block copolymer (B) contains as a dispersed phase in the continuous phase which consists of methacrylic resin (A).

(Continuous phase)
The methacrylic resin (A) constituting the continuous phase is a resin having 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more of repeating units derived from methyl methacrylate.
As repeating units derived from vinyl monomers other than repeating units derived from methyl methacrylate, alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate; ethyl methacrylate, butyl methacrylate, etc. Methacrylic acid alkyl esters excluding methyl methacrylate; acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, etc .; repeating derived from a non-crosslinkable monomer having only one alkenyl group in one molecule Units are listed.
The mass ratio of methyl methacrylate / other vinyl monomer is 50/50 to 100/0, preferably 80/20 to 99/1, more preferably 90/10 to 98/2.

The weight average molecular weight of the methacrylic resin (A) measured by GPC (gel permeation chromatography) is preferably 70,000 to 200,000, more preferably 80,000 to 150,000, and particularly preferably 90,000 to 120,000. . When the weight average molecular weight is less than 70,000, the impact resistance of the display window protection plate tends to decrease. When the weight average molecular weight exceeds 200,000, the fluidity of the methacrylic resin composition is lowered and the surface smoothness of the display window protection plate tends to be lowered.
Furthermore, the molecular weight distribution (= weight average molecular weight / number average molecular weight) measured by GPC of the methacrylic resin (A) is preferably 3.0 or less, more preferably 2.5 or less, and particularly preferably 2.3 or less. It is. If the molecular weight distribution exceeds 3.0, the impact resistance of the display window protection plate tends to decrease. The molecular weight and molecular weight distribution of the methacrylic resin (A) can be controlled by adjusting the types and amounts of the polymerization initiator and the chain transfer agent.

(Dispersed phase)
The block copolymer (B) contained in the dispersed phase has a glass transition temperature of 23 ° C. or lower, preferably 0 ° C. or lower, more preferably −10 ° C. or lower, consisting of repeating units derived from alkyl (meth) acrylate. And a polymer block (b) having a glass transition temperature composed of repeating units derived from a conjugated diene compound of 0 ° C. or lower, preferably −10 ° C. or lower. The lower the glass transition temperature, the more suitable for use in cold regions.

The repeating unit derived from the (meth) acrylic acid alkyl ester constituting the polymer block (a) is obtained by addition polymerization of (meth) acrylic acid alkyl ester. “(Meth) acryl” means methacryl or acrylic.
Examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate and the like, and examples of the acrylic acid alkyl ester include methyl acrylate, ethyl acrylate, n-butyl acrylate, and acrylic acid. i-butyl, 2-ethylhexyl acrylate, and the like. These may be polymerized individually by 1 type, and may be copolymerized combining 2 or more types. Among these, a monomer or a combination of monomers giving a polymer block (a) having a glass transition temperature (Tg) of 23 ° C. or lower is preferable, and a monomer giving a polymer block (a) having a Tg of 0 ° C. or lower is preferable. A monomer or a combination of monomers is more preferable, and a monomer or a combination of monomers giving a polymer block (a) having a Tg of −10 ° C. or lower is still more preferable. As such a monomer, n-butyl acrylate and / or 2-ethylhexyl acrylate are preferable, and n-butyl acrylate is more preferable.

The repeating unit derived from the conjugated diene compound constituting the polymer block (b) is obtained by addition polymerization of the conjugated diene compound.
Examples of the conjugated diene compound include 1,3-butadiene, isoprene, pentadiene, 2,3-dimethylbutadiene and the like. These may be polymerized individually by 1 type, and may be copolymerized combining 2 or more types. Among these, a monomer or a combination of monomers giving a polymer block (b) having a glass transition temperature (Tg) of 0 ° C. or lower is preferable, and a polymer block (b) having a Tg of −10 ° C. or lower is given. A monomer or a combination of monomers is more preferred. Moreover, 1,3-butadiene and / or isoprene are preferable from the viewpoint of versatility, economy, and handleability, and 1,3-butadiene is more preferable.

  Conjugated diene compounds include those that undergo 1,4-addition polymerization and those that undergo 1,2- or 3,4-addition polymerization. When the conjugated diene compound undergoes 1,4-addition polymerization, it has a carbon-carbon double bond in the molecular main chain. When the conjugated diene compound is subjected to 1,2- or 3,4-addition polymerization, the conjugated diene compound has a vinyl group (side chain vinyl bond) bonded to the molecular main chain. The carbon-carbon double bond and / or the vinyl group bonded to the molecular main chain in the molecular main chain is a starting point for the graft reaction or the crosslinking reaction. The proportion of 1,2- or 3,4-addition polymerization of the conjugated diene compound can be increased by adding a polar compound such as ethers to the reaction system.

The amount of side chain vinyl bonds in the polymer block (b) is selected in consideration of the graft reactivity with the methacrylic resin as the continuous phase, the crosslinking reactivity of the dispersed phase, and the impact resistance of the display window protection plate. The The amount of side chain vinyl bonds in the polymer block (b) is preferably 10 mol% to 60 mol%, more preferably 10 mol% to 50 mol%, and still more preferably 10 mol% to 35 mol%. When the side chain vinyl bond content is within this range, transparency, surface smoothness, impact resistance, rigidity, etc. are improved. The amount of the side chain vinyl bond is represented by the ratio [mol%] of 1,2-addition polymerization or 3,4-addition polymerization conjugated diene compound in 1 mol of the conjugated diene compound. For example, in the case of a polymer block (b) composed of repeating units derived from 1,3-butadiene, it is analyzed using ¹ H-NMR, and a chemical shift of 4.7 to 5.2 ppm (hereinafter referred to as signal C ₀ ). )) And 1,2-vinyl protons (= CH ₂ ) and chemical shifts of 5.2 to 5.8 ppm (hereinafter referred to as signal D ₀ ) vinyl protons (= CH-), and the integrated intensity is obtained. The side chain vinyl bond amount V ₀ [%] can be calculated and calculated by the equation.
V ₀ = _{[(C 0/2) / {} C 0/2 + (D 0 -C 0/2) / 2} ] × 100

  The polymer block (b) may be obtained by partially hydrogenating a carbon-carbon double bond in the aforementioned molecular main chain and / or a vinyl group bonded to the molecular main chain. From the viewpoint of maintaining the effects of the present invention, the hydrogenation rate of the polymer block (b) is preferably less than 70 mol%, and more preferably less than 50 mol%. The method of hydrogenation is not particularly limited, and can be achieved by, for example, the method disclosed in Japanese Patent Publication No. 5-20442.

The total number average molecular weight (Mn) of the block copolymer (B) used in the present invention is preferably 5,000 to 1,000,000, more preferably 10,000 to 800,000, and particularly preferably 50. , 000 to 500,000.
The number average molecular weight is a value in terms of polystyrene calculated by gel permeation chromatography (GPC).

  The mass ratio of the polymer block (a) to the polymer block (b) is such that when the total of the polymer block (a) and the polymer block (b) is 100% by mass, the polymer block (a) Is 30 to 65% by mass, preferably 40 to 60% by mass. A polymer block (b) is 35-70 mass%, Preferably it is 40-60 mass%.

The block copolymer (B) may have one each of the polymer block (a) and the polymer block (b), or the polymer block (a) and / or the polymer block (b). ) May be included.
Examples of the bonding mode of the block copolymer include an ab type diblock copolymer, an aba type triblock copolymer, a bb type triblock copolymer, and an aba type. -B-type tetrablock copolymers and linear multi-block copolymers typified by ba-ba-type tetrablock copolymers, (ba-) _n , (ab-) _n, etc. And a star copolymer (radial star) block copolymer, a graft copolymer represented by agb, and the like. Note that n is a value larger than 2. g is a bond symbol indicating a graft bond. The block copolymer (B) may have an inclined connecting part between the polymer block (a) and the polymer block (b). The inclined connecting portion is a portion having a repeating unit composition that gradually changes from the composition of the repeating unit of the polymer block (a) to the composition of the repeating unit of the polymer block (b). These block copolymers may be used individually by 1 type, and may be used in combination of 2 or more type.

The block copolymer (B) has a refractive index of preferably 1.48 to 1.50, more preferably 1.485 to 1.495. When the refractive index is within this range, the transparency of the methacrylic resin is maintained.
The refractive index of the block copolymer (B) can be adjusted by selecting the kind of repeating unit constituting the polymer, the composition ratio, the amount of side chain vinyl bonds in the polymer block (b), and the like. For example, a diblock copolymer comprising a polymer block (a) composed of repeating units derived from n-butyl acrylate and an unhydrogenated polymer block (b) composed of repeating units derived from 1,3-butadiene. Then, when the content of n-butyl acrylate is 30 to 65% by mass and the content of 1,3-butadiene is 70 to 35% by mass with respect to the total mass of the diblock copolymer, the refractive index of polymethyl methacrylate And a transparent display window protection plate can be obtained.

  The block copolymer (B) is a diblock composed of a polymer block composed of repeating units derived from n-butyl acrylate monomers and a polymer block composed of repeating units derived from 1,3-butadiene monomers. Block copolymer, radial star block copolymer, polymer block composed of repeating units derived from 2-ethylhexyl acrylate monomer, and polymer block composed of repeating units derived from 1,3-butadiene monomer A diblock copolymer, a radial star block copolymer, a polymer block composed of repeating units derived from a methyl methacrylate monomer, and a polymer composed of repeating units derived from an n-butyl acrylate monomer A triblock composed of a block and a polymer block composed of repeating units derived from 1,3-butadiene monomer. Lock copolymer or radial star block copolymer.

As the block copolymer (B), a star block copolymer is particularly preferable from the viewpoint of the mechanical strength of the dispersed phase.
The star block copolymer includes a copolymer in which a plurality of arm polymer blocks are linked by a group (coupling agent residue) derived from a polyfunctional monomer, a polyfunctional coupling agent, or the like.

  The arm polymer block constituting the star block copolymer is not limited by the bonding mode as long as it has the polymer block (a) and / or the polymer block (b). As the arm polymer block, an ab type diblock copolymer, an aba type triblock copolymer, a bb type triblock copolymer, an abaa- Examples thereof include a b-type tetrablock copolymer, a multiblock copolymer in which four or more polymer blocks (a) and polymer blocks (b) are bonded. The plurality of arm polymer blocks constituting the star block copolymer may be the same type of block copolymer or may be different types of block copolymers.

In the present invention, the chemical structural formula:
(Polymer block (b) -polymer block (a)-) _n X
A star block copolymer represented by the formula (wherein X represents a coupling agent residue and n represents a number exceeding 2) is particularly preferred.

The star block copolymer has a polystyrene-equivalent number average molecular weight calculated by GPC.
[Number average molecular weight of star block copolymer]> 2 × [Number average molecular weight of arm polymer block]
It is preferable to satisfy.
The ratio of [number average molecular weight of star block copolymer] / [number average molecular weight of arm polymer block] is sometimes referred to as the number of arms.

  By setting the number average molecular weight of the star block copolymer to a range exceeding twice the number average molecular weight of the arm polymer block, the dispersed phase comprising the star block copolymer dispersed in the continuous phase The mechanical strength against shearing is increased, and a desired impact resistance performance can be obtained. Since the number average molecular weight of the star block copolymer is more than 100 times the number average molecular weight of the arm polymer block is difficult to synthesize, the number average molecular weight of the industrially preferable star block copolymer is: The number average molecular weight of the arm polymer block is more than 2 times and 100 times or less, more preferably 2.5 to 50 times, and further preferably 3 to 10 times.

  The block copolymer (B) preferably used in the present invention is mainly composed of a star-shaped block copolymer, but other than this, an arm polymer not linked by a coupling agent residue. Blocks may be included. The mass ratio of the star block copolymer / arm polymer block not linked by the coupling agent residue is preferably 20/80 or more, and more preferably 30/70 or more.

A block copolymer (B) is not specifically limited by the manufacturing method, It can employ | adopt from what was obtained by the method according to a well-known method. In general, as a method for obtaining a block copolymer having a narrow molecular weight distribution, a method of living polymerizing monomers as constituent units is employed.
Living polymerization methods include, for example, a method of polymerizing using an organic rare earth metal complex as a polymerization initiator, an organic alkali metal compound as a polymerization initiator, and in the presence of an alkali metal or alkaline earth metal mineral salt. And an anion polymerization method using an organic alkali metal compound as a polymerization initiator in the presence of an organoaluminum compound, an atom transfer radical polymerization (ATRP) method, and the like.

  Among the above production methods, the method of anionic polymerization using an organoalkali metal compound as a polymerization initiator in the presence of an organoaluminum compound is a narrower molecular weight distribution and a residual monomer under relatively mild temperature conditions. Is preferable in that it can produce a block copolymer with a small amount and has a low environmental load (mainly power consumption of a refrigerator necessary for controlling the polymerization temperature) in industrial production.

As the organic alkali metal compound used for the anionic polymerization, an organic lithium compound is preferable.
Specific examples of the organic lithium compound include methyl lithium, ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, isobutyl lithium, tert-butyl lithium, n-pentyl lithium, and n-hexyl lithium. Alkyllithium and alkyldilithium such as tetramethylenedilithium, pentamethylenedilithium and hexamethylenedilithium; aryllithium and aryldilithium such as phenyllithium, m-tolyllithium, p-tolyllithium, xylyllithium and lithium naphthalene Lithium; benzyl lithium, diphenylmethyl lithium, trityl lithium, 1,1-diphenyl-3-methylpentyl lithium, α-methylstyryl lithium, diisopropenyl benzene Aralkyllithium and aralkyldilithium such as dilithium produced by the reaction of butyllithium with lithium; lithium amides such as lithium dimethylamide, lithium diethylamide and lithium diisopropylamide; methoxylithium, ethoxylithium, n-propoxylithium, isopropoxylithium, n -Butoxylithium, sec-butoxylithium, tert-butoxylithium, pentyloxylithium, hexyloxylithium, heptyloxylithium, octyloxylithium, phenoxylithium, 4-methylphenoxylithium, benzyloxylithium, 4-methylbenzyloxylithium, etc. Lithium alkoxide of the following. These may be used alone or in combination of two or more.

Examples of the organoaluminum compound used in the above anionic polymerization include the following general formula:
AlR ¹ R ² R ³
(In the formula, R ¹ , R ² and R ³ may each independently have an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, or a substituent. A good aryl group, an aralkyl group which may have a substituent, an alkoxyl group which may have a substituent, an aryloxy group which may have a substituent or an N, N-disubstituted amino group; Or R ¹ represents any of the groups described above, and R ² and R ³ together represent an aryleneoxy group which may have a substituent.) Is mentioned.

  Among organoaluminum compounds, isobutylbis (2,6-di-tert-butyl-4-methylphenoxy) aluminum, isobutylbis (2,6-di-tert-butylphenoxy) aluminum, isobutyl [2,2′-methylenebis (4-Methyl-6-tert-butylphenoxy)] aluminum is particularly preferred in that it is easy to handle and allows an anionic polymerization reaction to proceed without deactivation under relatively mild temperature conditions. .

  In the above anionic polymerization, if necessary, an ether such as dimethyl ether, dimethoxyethane, diethoxyethane, 12-crown-4-ether; triethylamine, N, N, N ′, N′— Including tetramethylethylenediamine, N, N, N ′, N ″, N ″ -pentamethyldiethylenetriamine, 1,1,4,7,10,10-hexamethyltriethylenetetramine, pyridine, 2,2′-dipyridyl, etc. Nitrogen compounds can further coexist for stabilization of the polymerization reaction.

The star block copolymer can be obtained by adding a polyfunctional monomer to the block copolymer reaction solution obtained by the above-mentioned anionic polymerization or the like and copolymerizing it, or by adding the block copolymer reaction solution to the reaction solution of the block copolymer. It can be obtained by adding a polyfunctional coupling agent to cause a coupling reaction.
The polyfunctional monomer is a compound having two or more ethylenically unsaturated groups, and specifically includes allyl methacrylate, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, divinylbenzene, 1 , 6-hexanediol diacrylate and the like.
The polyfunctional coupling agent is a compound having 3 or more reactive groups, specifically, trichloromethylsilane, tetrachlorosilane, butyltrichlorosilane, bis (trichlorosilyl) ethane, tetrachlorotin, butyltrichlorotin, Examples include tetrachlorogermanium.

  The methacrylic resin composition used in the present invention is usually 1 to 80 parts by mass, preferably 2 to 30 parts by mass of the block copolymer (B) with respect to 100 parts by mass of the methacrylic resin (A). More preferably, it contains in 4-20 mass parts. When the block copolymer (B) is small, the effect of improving the impact resistance of the display window protection plate is small. When there are many block copolymers (B), it will become difficult for a block copolymer (B) to form a dispersed phase. Further, the surface hardness and rigidity of the display window protection plate tend to decrease. In addition, it is easy to generate lumps and the appearance may be impaired.

  The average diameter of the dispersed phase comprising the block copolymer (B) is usually 0.05 to 2 μm, preferably 0.05 to 1 μm, more preferably 0.1 to 0.5 μm. When the average diameter of the dispersed phase is small, the impact resistance tends to decrease, and when the average diameter of the dispersed phase is large, transparency and surface smoothness tend to decrease.

  The dispersed phase preferably contains a sea-island structure composed of a sea phase composed of the block copolymer (B) and an island phase composed of the methacrylic resin (A). The sea-island structure of the dispersed phase is obtained by cutting a molded plate of a methacrylic resin composition with a diamond knife, obtaining an ultrathin section, staining the section with osmium tetroxide, and observing it with a transmission electron microscope. I can confirm.

In dyeing with osmium tetroxide, the polymer block (b) in the block copolymer (B) is dyed. The dispersed phase of the sea-island structure is composed of a sea phase composed of a dyed portion (block copolymer (B)) and an island phase composed of an undyed portion (methacrylic resin (A)).
The average diameter of the island phase is usually 0.01 to 0.2 μm, preferably 0.05 to 0.1 μm.
The area ratio of the island phase / sea phase observed in the molded product section is preferably 20/80 or more, more preferably 30/70 to 70/30.
Moreover, it is preferable that the ratio of the dispersed phase which comprised the sea-island structure is 20 mass% or more of all the dispersed phases, and it is more preferable that it is 30-100 mass%.

The methacrylic resin composition used in the present invention is not particularly limited by the production method. For example, it can be obtained by adding the block copolymer (B) constituting the dispersed phase to the methacrylic resin (A) constituting the continuous phase and melt-kneading in a uniaxial or biaxial melt extruder or the like. However, the block copolymer (B) is dissolved in a monomer mixture (A _m ) containing 50% by mass or more of methyl methacrylate, and the monomer mixture (A _m ) is polymerized under shear to polymerize. It is preferable to obtain by a method in which the solution phase of the polymer of the monomer mixture (A _m ) and the solution phase of the block copolymer (B) are reversed in the middle.

In a preferred method for producing the methacrylic resin composition, first, the block copolymer (B) is mixed with 50 to 100% by mass of methyl methacrylate and other vinyl monomers 0 to 50 copolymerizable with methyl methacrylate. A raw material liquid is prepared by dissolving in a monomer mixture (A _m ) composed of mass% and, if necessary, a solvent (C).

The methyl methacrylate and other vinyl monomers copolymerizable with methyl methacrylate used in the monomer mixture (A _m ) are the same as those described above.
The solvent (C) used in the present invention includes a monomer mixture (A _m ), a polymer of the monomer mixture (A _m ) (that is, a methacrylic resin (A)), and a block copolymer (B). As long as it has the ability to dissolve in water, it is not particularly limited. For example, aromatic hydrocarbons such as benzene, toluene, and ethylbenzene are desirable. Moreover, you may mix and use 2 or more types of solvents as needed. When using a mixed solvent, the monomer mixture (A _m), if the mixed solvent can dissolve the methacrylic resin (A) and the block copolymer (B), the monomer mixture (A _m), methacrylic A solvent that cannot dissolve the resin (A) and the block copolymer (B) may be contained in the mixed solvent. For example, the mixed solvent may contain alcohols such as methanol, ethanol and butanol; ketones such as acetone and methyl ethyl ketone; hydrocarbons such as hexane; alicyclic hydrocarbons such as cyclohexane and the like.

The amount of the block copolymer (B) in the raw material liquid is usually 1 to 80 parts by mass, preferably 2 to 30 parts by mass, and more preferably 4 parts per 100 parts by mass of the monomer mixture (A _m ). ˜20 parts by mass. When the amount of the block copolymer (B) is less than 1 part by mass, the effect of improving the impact resistance of the display window protection plate is small. When the amount of the block copolymer (B) is more than 80 parts by mass, the block copolymer (B) is difficult to form a dispersed phase. In addition, the elastic modulus of the display window protection plate is reduced, and the excellent rigidity inherent in the methacrylic resin is lost.

  Dissolution of the block copolymer (B) is promoted by stirring, and further promoted by heating to about 30 to 60 ° C. Moreover, when preparing a raw material liquid, the said solvent (C) can be used as needed.

The quantity of the solvent (C) in a raw material liquid is 0-100 mass parts normally with respect to 100 mass parts of monomer mixtures ( _Am ), Preferably it is 0-90 mass parts. The larger the amount of the solvent, the lower the viscosity of the raw material liquid and the better the handling properties, but it may cause side reactions such as chain transfer reaction and inhibit graft reaction and cross-linking reaction, and the productivity tends to decrease. .

Next, the raw material liquid is polymerized. Simultaneously with the polymerization of the raw material liquid, the polymerization reaction of the monomer mixture (A _m ) proceeds, and at the same time, the graft reaction and / or crosslinking between the block copolymer (B) and the monomer mixture (A _m ). The reaction proceeds.
For polymerization of the raw material liquid, a radical polymerization initiator is usually used. Moreover, a chain transfer agent is used as needed.

  The polymerization initiator is not particularly limited as long as it generates a reactive radical. As polymerization initiators, azo compounds such as azobisisobutyronitrile and azobiscyclohexylcarbonitrile; benzoyl peroxide, t-butylperoxy 2-ethylhexanoate, t-butylperoxybenzoate, di-t- Butyl peroxide, dicumyl peroxide, 1,1-di (t-butylperoxy) 3,3,5-trimethylcyclohexane, t-butylperoxyisopropyl carbonate, 1,1-di (t-butylperoxy) Examples thereof include organic peroxides such as cyclohexane and t-hexylperoxyisopropyl monocarbonate. These polymerization initiators may be used alone or in combination of two or more. Further, the addition timing and the addition method of the polymerization initiator are not particularly limited as long as the predetermined polymerization reaction proceeds, but the pre-stage polymerization is performed with the polymerization initiator charged at the start of the polymerization, and during the reaction It is preferable to add a polymerization initiator and perform post-stage polymerization.

  As the chain transfer agent, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, 1,4-butanedithiol, 1,6-hexanedithiol, ethylene glycol bisthiopropionate, butanediol bisthioglycolate, Alkyl mercaptans such as butanediol bisthiopropionate, hexanediol bisthioglycolate, hexanediol bisthiopropionate, trimethylolpropane tris- (β-thiopropionate), pentaerythritol tetrakisthiopropionate; α-methylstyrene dimer; terpinolene and the like can be mentioned. These can be used alone or in combination of two or more.

In the polymerization of the raw material liquid, it is important to give a shearing force to the raw material liquid from the initial stage of polymerization until phase inversion occurs. At the initial stage of polymerization, the polymerization of the monomer mixture (A _m ) mainly proceeds to produce a methacrylic resin. As the polymerization conversion increases, the proportion of the solution phase of the methacrylic resin produced by the polymerization of the monomer mixture (A _m ) increases, and the solution phase of the methacrylic resin and the solution phase of the block copolymer (B) Phase separates.

Along with the progress of the polymerization reaction, an action for stabilizing the whole phase works. By the shearing force by stirring, the solution phase of the methacrylic resin and the solution phase of the block copolymer (B) are phase-inverted, The solution phase of the system resin becomes a continuous phase, and the solution phase of the block copolymer (B) becomes a dispersed phase. When phase inversion occurs, the viscosity decreases. The polymerization conversion rate of the monomer mixture (A _m ) when this phase inversion occurs is the volume ratio of the solution phase of the methacrylic resin to the solution phase of the block copolymer (B), the block copolymer (B) When the molecular weight, the graft ratio to the block copolymer (B) before phase inversion, and a solvent are used, it varies depending on the amount of solvent and the solvent type.

  Examples of the apparatus for performing polymerization while applying a shearing force to the raw material liquid include a tank reactor with a stirrer, a cylindrical reactor with a stirrer, a cylindrical reactor having a static stirring ability, and the like. One or more of these apparatuses may be used, or a combination of two or more different reactors may be used. The polymerization reactor may be either a batch type or a continuous type. The polymerization of the raw material liquid is preferably performed by a bulk polymerization method or a solution polymerization method from the initial stage of polymerization until phase inversion occurs.

  The diameter of the dispersed phase depends on factors such as the number of stirring revolutions in the case of a reactor equipped with a stirrer; the linear velocity of the reaction liquid, the viscosity of the polymerization system, and the phase inversion in the case of a static stirring reactor represented by a tower reactor It can be controlled by various factors such as the graft ratio to the previous block copolymer (B).

  A bulk polymerization method or a solution polymerization method can be applied to the polymerization after the phase inversion occurs, but a suspension polymerization method and a cast polymerization method can also be applied in addition to these.

In the present invention, the polymerization conversion rate of the monomer mixture (A _m ) is preferably 70% by mass or more, and more preferably 80% by mass or more. If the polymerization conversion rate is lower than this, the crosslinking reaction and graft reaction in the dispersed phase containing the block copolymer (B) formed by phase inversion hardly proceed sufficiently. When the crosslinking reaction and graft reaction are not sufficiently advanced, the dispersed phase in the methacrylic resin composition is easily broken by mechanical shearing such as an extruder or a kneader, and the impact strength is sufficient. At the same time, the mechanical strength may change depending on the molding method. In order to further advance the crosslinking reaction and graft reaction and increase the impact strength, it is preferable to add a polymerization initiator during the reaction. On the other hand, the polymerization conversion rate is preferably 95% by mass or less. When it exceeds 95% by mass, the molecular weight distribution of the polymer of the monomer mixture (A _m ) becomes wide, and the impact resistance tends to decrease.

  The presence or absence of a dispersed phase comprising the block copolymer (B) in the middle of polymerization and the diameter of the dispersed phase were determined by extracting a part of the raw material liquid during polymerization and subjecting it to suspension polymerization. A method of observing the morphology of a resin-based resin composition with a scanning electron microscope, or removing a part of a raw material liquid in the middle of polymerization and drying and devolatilizing it to remove unreacted monomers and solvents, and its composition The morphology of the product can be confirmed by a method of observing with a scanning electron microscope.

After the polymerization conversion rate of the monomer mixture (A _m ) reaches 70% by mass to 95% by mass, devolatilization is performed to remove the unreacted monomer and the solvent. Examples of the devolatilization method include an equilibrium flash method and an adiabatic flash method. In particular, in the adiabatic flash method, devolatilization is preferably performed at a temperature of 200 to 300 ° C, more preferably 220 to 270 ° C. Below 200 ° C., devolatilization takes time, and when devolatilization is insufficient, appearance defects such as silver may occur on the display window protection plate. On the other hand, when the temperature exceeds 300 ° C., the display window protection plate may be colored due to oxidation, burning or the like. Examples of the apparatus used for devolatilization include a flash drum, a biaxial devolatilizer, a thin film evaporator, and an extruder. The residual volatile content is preferably 0.5% by mass or less, more preferably 0.4% by mass or less, and still more preferably 0.3% by mass or less.

  For methacrylic resin compositions, known antioxidants, UV absorbers, light stabilizers, lubricants, mold release agents, antistatic agents, polymer processing aids, flame retardants, dyes and pigments, as needed A diffusing agent, an impact resistance modifier, a phosphor or the like can be added. Moreover, a methacrylic resin composition can also be diluted with a normal methacrylic resin (D) and used. In addition, other resins such as AS resin, ABS resin, AES resin, AAS resin, MS resin, MBS resin, styrene resin, high-impact polystyrene resin, and vinyl chloride resin can be used.

Examples of the ultraviolet absorber include benzophenones, benzotriazoles, triazines, benzoates, salicylates, cyanoacrylates, oxalic anilides, malonic esters, formamidines, and the like. These can be used alone or in combination of two or more. Among these, from the viewpoint of suppressing the yellowness of the display window protection plate, an ultraviolet absorber having a maximum value ε _max of a molar extinction coefficient at a wavelength of 380 to 450 nm of 1200 dm ³ · mol ⁻¹ cm ⁻¹ or less is preferable, Ultraviolet absorbers having 600 dm ³ · mol ⁻¹ cm ⁻¹ or less are more preferable, and ultraviolet absorbers having 300 dm ³ · mol ⁻¹ cm ⁻¹ or less are particularly preferable.

In addition, the measurement of the maximum value ε _max of the molar extinction coefficient of the ultraviolet absorber is performed by sufficiently dissolving 10.00 mg of the ultraviolet absorber (molecular weight (Mw)) in 1 L of cyclohexane so that there is no undissolved substance by visual observation. This solution was poured into a 1 cm × 1 cm × 3 cm quartz glass cell, and the absorbance at a wavelength of 380 to 450 nm was measured using a U-3410 type spectrophotometer manufactured by Hitachi, Ltd. From the maximum value (A _max ), molar absorption was measured. The maximum coefficient ε _max was calculated by the following equation.
ε _max = [A _max / (10 × 10 ⁻³ )] × Mw
As an ultraviolet absorber having a maximum molar extinction coefficient ε _{max at a} wavelength of 380 to 450 nm of 1200 dm ³ · mol ⁻¹ cm ⁻¹ or less, 2-ethyl-2′-ethoxy-oxalanilide (Clariant Japan, Inc .; product) Name Sundeyuboa VSU).

  The amount of the ultraviolet absorber is preferably 0.001 to 1 part by mass, more preferably 0.005 to 0.5 part by mass, and still more preferably 0.01 to 0 part per 100 parts by mass of the methacrylic resin composition. .2 parts by mass. When the amount of the ultraviolet absorber is less than 0.001 part by mass, the effect of suppressing the resin deterioration due to ultraviolet rays tends not to be exhibited sufficiently. If the amount exceeds 1 part by mass, the mold tends to become dirty during molding, so that it is easy to cause a decrease in yield and productivity due to mold cleaning, etc., and to cause the occurrence of silver and to the eyes.

In the present invention, a light stabilizer such as a hindered amine such as a compound having a 2,2,6,6-tetraalkylpiperidine skeleton may be further contained.
Examples of hindered amines include dimethyl succinate / 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, poly ((6- (1,1,3 , 3-tetramethylbutyl) imino-1,3,5-triazine-2,4-diyl) ((2,2,6,6-tetramethyl-4-pipedyl) imino) hexamethylene ((2,2, 6,6-tetramethyl-4-pipedyl) imino)), 2- (2,3-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2, 6,6-pentamethyl-4-piperidyl), 2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2,6,6-pentamethyl) -4-piperidyl), N, N′-bis (3-a Nopropyl) ethylenediamine / 2,4-bis (N-butyl-N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino) -6-chloro-1,3,5-triazine condensate, Examples thereof include bis (2,2,6,6-tetra-methyl-4-pipedyl) sebacate and bis (2,2,6,6-tetramethyl-4-piperidyl) succinate.
The amount of the light stabilizer is preferably 0.001 to 0.5 parts by mass with respect to 100 parts by mass of the methacrylic resin composition with respect to 100 parts by mass of the methacrylic resin composition.

  Examples of the antioxidant include phosphorus-based antioxidants, hindered phenol-based antioxidants, thioether-based antioxidants, and the like. These can be used alone or in combination of two or more. Among these, phosphorus antioxidants and hindered phenol antioxidants are preferably used from the viewpoint of preventing the deterioration of optical properties due to coloring.

  Examples of phosphorus antioxidants include 2,2-methylenebis (4,6-di-t-butylphenyl) octyl phosphite and bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphos. Phyto, tris (2,4-di-t-butylphenyl) phosphite, tetrakis (2,4-di-t-butylphenyl) [1,1-biphenyl] -4,4′-diylbisphosphonite, bis [ 2,4-bis (1,1-dimethylethyl) -6-methylphenyl] ethyl ester phosphorous acid and the like. Among these, 2,2-methylenebis (4,6-di-t-butylphenyl) octyl phosphite and tris (2,4-di-t-butylphenyl) phosphite are preferable.

  Examples of the hindered phenol antioxidant include triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3 , 5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octyl) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3 , 5-triazine, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,2-thio-diethylenebis [3- (3,5-di- t-butyl-4-hydroxyphenylpropionate), octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N′-hex Methylenebis (3,5-di-tert-butyl-4-hydroxy-hydrocinnamamide), 3,5-di-tert-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1,3,5-trimethyl -2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate, octyl Diphenylamine, 2,4-bis [(octylthio) methyl] -o-cresol, isooctyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, and the like. Among these, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (trade name “IRGANOX1010”, manufactured by Ciba Special Chemicals), octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (trade name “IRGANOX1076”, manufactured by Ciba Special Chemicals) is preferable.

  The amount of the antioxidant is preferably 0.001 to 1 part by mass, more preferably 0.005 to 0.5 part by mass, and still more preferably 0.01 to 0 part per 100 parts by mass of the methacrylic resin composition. 3 parts by mass. If the amount of the antioxidant is less than 0.001 part by mass, the effect of preventing the heat coloring of the molded product at a high temperature tends not to be sufficiently exhibited. On the other hand, when the amount of the antioxidant exceeds 1 part by mass, it causes a decrease in yield due to mold contamination and a decrease in productivity due to mold cleaning, and also causes a defect in the display window protection plate due to silver generation. Or the display window protection plate is burned and the hue is lowered, or foreign matter is generated on the display window protection plate.

  Examples of the mold release agent include higher alcohol and / or glycerin monoester. Examples of higher alcohols include cetyl alcohol and stearyl alcohol. Examples of the glycerin monoester used in the present invention include glycerides of higher fatty acids such as stearic acid monoglyceride and stearic acid diglyceride. When the higher alcohol and glycerol monoester are used in combination, the ratio is not particularly limited, but the mass ratio of higher alcohol / glycerol monoester is preferably 2.5 / 1 to 3.5 / 1, more preferably 2.8. / 1 to 3.2 / 1.

  The amount of the release agent is preferably 0.5 parts by mass or less, more preferably 0.3 parts by mass or less, and more preferably 0.1 parts by mass with respect to 100 parts by mass of the methacrylic resin composition. More preferably, it is as follows. If the amount of the release agent exceeds 0.5 parts by mass, there is a tendency to reduce the yield due to mold contamination and the productivity due to mold cleaning, etc. It becomes easy to cause the eyes and the eyes at the time of extrusion molding.

  The polymer processing aid has an effect on thickness accuracy and thin film properties when the methacrylic resin composition is molded into the display window protection plate. The polymer processing aid can be usually produced as polymer particles having a particle size of 0.05 to 0.5 μm by an emulsion polymerization method. The polymer particles may be so-called single layer particles having a single composition and a single intrinsic viscosity, or may be multi-layer particles having two or more layers having different compositions or intrinsic viscosities. Among these, particles having a two-layer structure having a low intrinsic viscosity layer in the inner layer and a high intrinsic viscosity layer having an intrinsic viscosity of 5 dl / g or more in the outer layer are preferable. The intrinsic viscosity of the polymer processing aid is 3 to 6 dl / g, and if it is less than 3 dl / g, a sufficient improvement effect on the sheet formability is not recognized. If it exceeds 6 dl / g, the melt fluidity tends to be lowered.

  The compounding amount in the case of using the polymer processing aid is 0.05 to 10 parts by mass, preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the methacrylic resin composition. If the polymer processing aid is less than 0.05 parts by mass, a sufficient improvement effect on the thickness accuracy at the time of molding cannot be recognized. On the other hand, if it exceeds 10 parts by mass, the melt fluidity tends to decrease.

Examples of the organic dye include terphenyl having a function of converting ultraviolet rays that are considered harmful to the resin into visible light.
Examples of the light diffusing agent and matting agent include glass fine particles, polysiloxane-based crosslinked fine particles, crosslinked polymer fine particles, talc, calcium carbonate, and barium sulfate.
Examples of the phosphor include fluorescent pigments, fluorescent dyes, fluorescent white dyes, fluorescent brighteners, and fluorescent bleaching agents.

  Moreover, you may use impact resistance modifiers other than a block copolymer (B) for a methacrylic-type resin composition. Examples of other impact resistance modifiers include a core-shell type modifier containing acrylic rubber or diene rubber as a core layer component, and a modifier containing a plurality of rubber particles. Other impact modifiers are preferably added in less than normal amounts to improve some properties.

  The methacrylic resin (D) used for dilution of the methacrylic resin composition is 80% by mass or more of repeating units derived from methyl methacrylate and 20% by mass or less of repeating units derived from a vinyl monomer copolymerizable therewith. Consists of Examples of copolymerizable vinyl monomers include methyl acrylate, ethyl acrylate, butyl acrylate, propyl acrylate, hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, Acrylic acid ester monomers such as benzyl acrylate; Ethyl methacrylate, butyl methacrylate, propyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, methacrylic acid esters such as benzyl methacrylate; vinyl acetate, styrene, Aromatic vinyl compounds such as p-methylstyrene, o-methylstyrene, m-methylstyrene, α-methylstyrene and vinylnaphthalene; nitriles such as acrylonitrile and methacrylonitrile; acrylic acid, methacrylic acid, α such as tons acid, beta-unsaturated carboxylic acid; N- ethylmaleimide, and the like maleimide compounds such N- cyclohexyl maleimide. Two or more of these vinyl monomers can be used in combination.

  The intrinsic viscosity of the methacrylic resin (D) used for dilution is 0.3 to 1.0 dl / g. When the intrinsic viscosity of the methacrylic resin (D) is less than 0.3, the tenacity when melt-molding the resulting methacrylic resin composition tends to decrease. On the other hand, when the intrinsic viscosity is 1.0 dl / g or more, the fluidity during melt molding tends to decrease. The compounding amount of the methacrylic resin (D) is preferably 1 to 100 parts by mass, more preferably 5 to 70 parts by mass with respect to 100 parts by mass of the methacrylic resin composition. When the compounding quantity of a methacryl resin (D) exceeds 100 mass parts, the handleability of the display window protection board which consists of a methacrylic-type resin composition obtained will become a fall tendency.

  The methacrylic resin (D) used for dilution is generally commercially available as methacrylic resin as long as the above conditions are satisfied, and ISO 8257-1: 1997 (E) “Plastic-Poly (methyl methacrylate) (PMMA) Includes materials specified in "Plastics-Poly (Methyl Methacrylate) (PMMA) molding and extrusion material-").

  There is no restriction | limiting in particular about the polymerization method for manufacturing the methacryl resin (D) used for dilution, Well-known polymerization methods, such as emulsion polymerization, suspension polymerization, block polymerization, and solution polymerization, are employable.

The display window protection plate of the present invention may be a single layer plate of the methacrylic resin composition or a multilayer plate having at least one layer of the methacrylic resin composition.
For example, a methacrylic resin layer that does not contain rubber particles may be formed on the surface of a plate made of a methacrylic resin composition. In this case, the thickness of the plate made of the methacrylic resin composition is preferably 50% or more, more preferably 60% or more with respect to the thickness of the entire display window protection plate. In order to manufacture such a display window protective plate having a multilayer structure, for example, a known multilayer having a plurality of extruders and a mechanism such as a multi-manifold system or a feed block system for laminating resins extruded from them. An extruder can be used.

  The display window protection plate of the present invention may have a flat surface, or may have a curved surface such as a convex lens or a concave lens. Further, a fine structure such as fine irregularities may be provided on the surface.

  The display window protective plate of the present invention is preferably subjected to at least one of hard coat treatment, antireflection treatment, and antistatic treatment on one or both sides. The method of hard coat treatment, antireflection treatment, or antistatic treatment is not particularly limited, and is performed by a conventionally known method.

  For example, as a hard coat treatment, a method of applying a hard coat agent in which silica, titanium oxide or the like is mixed with a solvent such as ethanol or toluene or an acrylic curable resin, a method of immersing the plate in the hard coat agent, Examples thereof include a method of applying and curing a curable acrylic resin and a thermosetting silicone resin, a method of bonding a semi-curable acrylic resin sheet and a silicon resin sheet to a plate, and curing.

Examples of the antireflection treatment include a method of laminating a plurality of layers of an inorganic film having a high refractive index and an inorganic film having a low refractive index by vapor deposition or the like, and a method of applying and drying a liquid containing particles having a low refractive index and a binder. It is done.
Examples of the antistatic treatment include a method of applying and drying a liquid containing a surfactant and the like, and a method of applying and drying a liquid containing a conductive substance.

  The display window protection plate of the present invention has a thickness of usually 0.1 mm to 1.5 mm, preferably 0.2 mm to 1.0 mm. If it is 0.1 mm or less, the rigidity is insufficient and the display screen may not be protected. If it is thicker than 1.5 mm, it will not be possible to meet the demand for thinning cellular phones and the like.

  As a method for producing the display window protection plate of the present invention, a known molding method such as an extrusion molding method using T-die or an injection molding method can be adopted, but an extrusion molding method using T-die is preferable from the viewpoint of economy. .

  Even if the display window protective plate of the present invention is thin, there are few defects due to fish eyes, and the surface smoothness and surface hardness are excellent. The display window protection plate of the present invention includes a display (device) window for a mobile phone, a liquid crystal monitor, a liquid crystal television, etc .; a front plate of the display device, a picture frame, etc .; a window for taking in external light; a display signboard; And the like.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples. In the synthesis of the block copolymer, chemicals dried and purified by a conventional method were used. At that time, measurement of the polymerization conversion rate and analysis of the synthesized block copolymer were carried out by the following methods. Moreover, the analysis, dynamics, and optical measurement of the methacrylic resin composition were performed by the following methods.

(1) Measurement of number average molecular weight (Mn), weight average molecular weight (Mw), molecular weight distribution (Mw / Mn) and block copolymer production rate by gel permeation chromatography (GPC) Apparatus: Gel Perm manufactured by Tosoh Corporation Eation chromatograph (HLC-8020)
Column: Tosoh TSKgel G2000H _HR (1) and GMH _HR- M (2) connected in series Eluent: Tetrahydrofuran Eluent flow rate: 1.0 ml / min Column temperature: 40 ° C
Detection method: differential refractive index (RI) meter Calibration curve: created using standard polystyrene

(2) Measurement of polymerization conversion rate of charged monomer by gas chromatography (GC) Apparatus: Gas chromatograph GC-14A manufactured by Shimadzu Corporation
Column: GL Sciences Inc. INERT CAP 1 (df = 0.4 μm, 0.25 mm ID × 60 m)
Analysis conditions: injection temperature 180 ° C., detector temperature 180 ° C., 60 ° C. (5 minutes hold) → temperature increase rate 10 ° C./min→200° C. (10 minutes hold)

(3) Amount of side chain vinyl bonds The block copolymer was dissolved in deuterated chloroform to obtain a test solution, and the test solution was analyzed using ¹ H-NMR (JEOL nuclear magnetic resonance apparatus (JNM-LA400)). , A chemical shift of 4.7 to 5.2 ppm (hereinafter referred to as signal C ₀ ), 1,2-vinyl proton (= CH ₂ ), and a chemical shift of 5.2 to 5.8 ppm (hereinafter referred to as signal D ₀ ). )) Was determined by calculating the integral intensity of vinyl protons (= CH-) and calculating the side chain vinyl bond amount V ₀ [mol%] by the following equation.
V ₀ = _{[(C 0/2) / {} C 0/2 + (D 0 -C 0/2) / 2} ] × 100

(4) Analysis of molecular structure of block copolymer by nuclear magnetic resonance spectrum ( ¹ H-NMR spectrum) Instrument: JEOL nuclear magnetic resonance apparatus (JNM-LA400)
Solvent: deuterated chloroform

(5) Glass transition temperature (Tg)
The glass transition temperature (Tg) of poly (n-butyl acrylate) used as the polymer block (a) is the value described in “POLYMER HANDBOOK FOURTH Edition, page VI / 199, Wiley Interscience, New York, 1998” (−49 ° C) was used.
The glass transition temperature (Tg) of poly1,3-butadiene used as the polymer block (b) is 1,2-vinyl bond amount described in “ANIONIC POLYMERIZATION, page 434, MARCEL DEKKER, Inc. 1996”. A value derived from the relationship between Tg and Tg was used.

(6) Refractive index (nd)
The block copolymer (B) was uniformly dissolved in toluene so as to be 30% by mass. The density and refractive index of the solution and toluene were measured at room temperature, and the refractive index of the block copolymer (B) was determined using the following formulas (Formula 1) to (Formula 3). Furthermore, polymethyl methacrylate having a known refractive index (nd = 1.492) was measured by the same method, and a refractive index measurement calibration coefficient was obtained by this method to calibrate the refractive index of the block copolymer (B). .
(Nd ² −1) / (nd ² +2) × V = r = constant (Expression 1)
r ₃ = w ₁ r ₁ + w ₂ r ₂ (Formula 2)
V ₂ = 1 / ρ ₁ −1 / w ₂ (1 / ρ ₁ −1 / ρ ₃ ) (Equation 3)
nd: refractive index, V: specific volume, r: molecular refraction, w: mass fraction ρ: density subscript 1: toluene subscript 2: block copolymer (B) subscript 3: solution Actual measurement: V ₃ , nd ₃ , V ₁ , nd ₁
Formula (1) and Formula (2) Source: Polymer Experimental Studies Vol. 12 Thermodynamic, Electrical and Optical Properties 1984 Kyoritsu Publishing Formula (3) Source: Polymer Experimental Studies Vol. 11 Polymer Solution Showa 57 years Kyoritsu Publishing

(7) Morphology The molded product was cut out using a diamond knife to obtain an ultrathin section, this section was stained with osmium tetroxide, and an observation image was photographed using a transmission electron microscope. A dispersed phase comprising 30 block copolymers (B) was selected at random, the diameters of the dispersed phases were measured, and the average value thereof was expressed.
In addition, the polymer block (b) in the block copolymer (B) is dyed by the above dyeing, and the morphology of the methacrylic resin composition can be observed. The methacrylic resin composition of the present invention contains a continuous phase composed of an undyed methacrylic resin (A) and a dispersed phase comprising a dyed block copolymer (B). The thing which made the sea island structure of the dye | stained part (the sea phase which consists of block copolymers (B)) and the part which is not dyed (the island phase which consists of methacrylic resin (A)) is contained.

(8) Evaluation of impact resistance of molded plate Charpy impact strength with a notch was measured according to ISO 179-1eA.

(9) Measurement of flexural modulus of molded plate The flexural modulus was measured according to ISO178.

(10) Evaluation of transparency of molded plate The haze of a molded plate having a thickness of 1 mm was measured in accordance with ISO14782.

(11) Adhesion of cured film of display window protection plate Adhesion of cured film of display window protection plate by the number of eyes peeled per 100 grids provided on the cured film by the cross-cut tape method of JIS K 5400 evaluated.

(12) Appearance evaluation of display window protection plate The number of bumps of 0.01 mm ² or more in the 400 mm × 550 mm size of the display window protection plate was measured by visual observation.
[Evaluation criteria for appearance evaluation]
○: The number per 400 mm × 550 mm is less than 5 Δ: The number per 400 mm × 550 mm is 5 or more and less than 20 ×: The number per 400 mm × 550 mm is 20 or more

(13) Evaluation of surface hardness In accordance with JIS K5600-5-4, the pencil hardness of the molded plate and the display window protection plate obtained with a 0.75 kg load was measured.

<< Synthesis Example 1 >> Production of Block Copolymer (B-1) (1) 801 ml of toluene and 0.007 ml of 1,2-dimethoxyethane were put into a 1.5 liter autoclave vessel equipped with a stirrer and purged with nitrogen for 20 minutes. Went. Thereto was added 1.9 ml of a cyclohexane solution of sec-butyllithium having a concentration of 1.3 mol / l, then 97 ml of 1,3-butadiene was added and reacted at 30 ° C. for 3 hours to obtain a 1,3-butadiene polymer. A reaction mixture containing was obtained.
As a result of sampling analysis of a part of the obtained reaction mixture, the 1,3-butadiene polymer in the reaction mixture has a number average molecular weight (Mn) of 48,700 and a molecular weight distribution (Mw / Mn) of 1.06. The side chain vinyl bond content was 30 mol%, and the glass transition temperature of the 1,3-butadiene polymer (polymer block (b)) was -77 ° C.

(2) The reaction mixture obtained in (1) above is cooled to −30 ° C., and toluene containing 0.45 mol / l isobutylbis (2,6-di-t-butyl-4-methylphenoxy) aluminum 18.1 ml of the solution and 8.1 ml of 1,2-dimethoxyethane were added and stirred for 10 minutes to obtain a homogeneous solution.

(3) Next, 71 ml of n-butyl acrylate was added while vigorously stirring the solution obtained in the above (2), and polymerized at −15 ° C. for 3 hours. A part of the obtained reaction mixture was sampled, and the molecular weight was analyzed by GPC (polystyrene conversion). As a result, the butadiene-n-butyl acrylate diblock copolymer (arm polymer block) in the reaction mixture was a number average molecular weight. The weight average molecular weight / number average molecular weight ratio (Mw / Mn) was 1.02. The glass transition temperature of the polymer block (a) obtained by polymerization of n-butyl acrylate was −49 ° C.

(4) The reaction mixture obtained in the above (3) was kept at −15 ° C., and with vigorous stirring, 2.1 ml of 1,6-hexanediol diacrylate was added and polymerized for 30 minutes. Then about 1 ml of methanol was added to stop the polymerization.

(5) The block copolymer (B-1) was obtained by putting the reaction mixture obtained by said (4) in 8000 ml of methanol, and making it precipitate. The yield of the obtained block copolymer (B-1) was almost 100%.

The obtained block copolymer (B-1) was a mixture of a star block copolymer and an arm polymer block. In the block copolymer (B-1), the ratio of the star block copolymer calculated from the area ratio of GPC was 92% by mass.
The star block copolymer had a number average molecular weight (Mn) of 310,000 (number of arms = 3.88) and an Mw / Mn of 1.16. The block copolymer (B-1) is a polymer block (b) consisting of 49% by mass of a repeating unit derived from 1,3-butadiene and a polymer block consisting of a repeating unit derived from n-butyl acrylate ( a) A diblock copolymer comprising 51% by mass was contained as an arm polymer block.
The refractive index of the block copolymer (B-1) was 1.492. Table 1 shows the characteristics of the block copolymer (B-1). In the table, BA means n-butyl acrylate, and Bd means 1,3-butadiene.

<< Synthesis Example 2 >> Production of Block Copolymer (B-2) (1) 801 ml of toluene was put into a 1.5 liter autoclave vessel equipped with a stirrer and purged with nitrogen for 20 minutes. Then, 1.9 ml of a cyclohexane solution of sec-butyllithium having a concentration of 1.3 mol / l was added, and then 105 ml of 1,3-butadiene was added and reacted at 30 ° C. for 3 hours to obtain a 1,3-butadiene polymer. A reaction mixture containing was obtained.
As a result of sampling analysis of a part of the obtained reaction mixture, the 1,3-butadiene polymer in the reaction mixture has a number average molecular weight (Mn) of 46,700 and a molecular weight distribution (Mw / Mn) of 1.06. The side chain vinyl bond content was 10 mol%, and the glass transition temperature of the 1,3-butadiene polymer (polymer block (b)) was -95 ° C.

(2) The reaction mixture obtained in (1) above is cooled to −30 ° C., and toluene containing 0.45 mol / l isobutylbis (2,6-di-t-butyl-4-methylphenoxy) aluminum 18.1 ml of the solution and 8.1 ml of 1,2-dimethoxyethane were added and stirred for 10 minutes to obtain a homogeneous solution.

(3) Next, while vigorously stirring the solution obtained in the above (2), 65 ml of n-butyl acrylate was added and polymerized at −15 ° C. for 3 hours. A part of the obtained reaction mixture was sampled, and the molecular weight was analyzed by GPC (polystyrene conversion). As a result, the butadiene-n-butyl acrylate diblock copolymer (arm polymer block) in the reaction mixture was a number average molecular weight. The weight average molecular weight / number average molecular weight ratio (Mw / Mn) was found to be 1.02. The glass transition temperature of the polymer block (a) obtained by polymerization of n-butyl acrylate was −49 ° C.

(4) The reaction mixture obtained in the above (3) was kept at −15 ° C., and with vigorous stirring, 2.1 ml of 1,6-hexanediol diacrylate was added and polymerized for 30 minutes. Then about 1 ml of methanol was added to stop the polymerization.

(5) A block copolymer (B-2) was obtained by putting the reaction mixture obtained in the above (4) into 8000 ml of methanol and precipitating it. The yield of the obtained block copolymer (B-2) was almost 100%.

The obtained block copolymer (B-2) was a mixture of a star block copolymer and an arm polymer block. In the block copolymer (B-2), the ratio of the star block copolymer calculated from the area ratio of GPC was 93% by mass.
The star block copolymer had a number average molecular weight (Mn) of 308,000 (number of arms = 3.88) and an Mw / Mn of 1.16. The block copolymer (B-2) is a polymer block (b) consisting of 53% by mass of a repeating unit derived from 1,3-butadiene and a polymer block consisting of a repeating unit derived from n-butyl acrylate ( a) It contained a diblock copolymer consisting of 47% by mass as an arm polymer block.
The refractive index of the block copolymer (B-2) was 1.492. Table 1 shows the characteristics of the block copolymer (B-2).

<< Synthesis Example 3 >> Production of Diblock Copolymer (B-3) (1) To a 1.5 liter autoclave vessel equipped with a stirrer, 801 ml of toluene and 0.007 ml of 1,2-dimethoxyethane were charged and nitrogen was added for 20 minutes. Purging was performed. Then, 1.9 ml of a cyclohexane solution of sec-butyllithium having a concentration of 1.3 mol / l was added, and then 95 ml of 1,3-butadiene was added and reacted at 30 ° C. for 3 hours to obtain a 1,3-butadiene polymer. A reaction mixture containing was obtained.
As a result of sampling analysis of a part of the obtained reaction mixture, the 1,3-butadiene polymer in the reaction mixture has a number average molecular weight (Mn) of 48,700 and a molecular weight distribution (Mw / Mn) of 1.06. The side chain vinyl bond content was 30 mol%, and the glass transition temperature of the 1,3-butadiene polymer (polymer block (b)) was -77 ° C.

(2) The reaction mixture obtained in (1) above is cooled to −30 ° C., and toluene containing 0.45 mol / l isobutylbis (2,6-di-t-butyl-4-methylphenoxy) aluminum 18.1 ml of the solution and 8.1 ml of 1,2-dimethoxyethane were added and stirred for 10 minutes to obtain a homogeneous solution.

(3) Next, while vigorously stirring the solution obtained in the above (2), 72 ml of n-butyl acrylate was added and polymerized at −15 ° C. for 3 hours. A part of the obtained reaction mixture was sampled, and the molecular weight was analyzed by GPC (polystyrene conversion). As a result, the butadiene-n-butyl acrylate diblock copolymer (arm polymer block) in the reaction mixture was a number average molecular weight. The weight average molecular weight / number average molecular weight ratio (Mw / Mn) was 1.02. The glass transition temperature of the polymer block (a) obtained by polymerization of n-butyl acrylate was −49 ° C.

(4) The block copolymer (B-3) was obtained by putting the reaction mixture obtained by said (3) in 8000 ml of methanol, and precipitating. The yield of the obtained block copolymer (B-3) was almost 100%.

<< Synthesis Example 4 >> Production of Block Copolymer (B-4) The amount of 1,2-dimethoxyethane was changed to 0.014 ml, the amount of 1,3-butadiene was changed to 87 ml, and the amount of n-butyl acrylate Was changed to 78 ml, and the block copolymer (B-4) was obtained by the same method as in Synthesis Example 1 except that the amount of 1,6-hexanediol diacrylate was changed to 2.6 ml. The block copolymer (B-4) is mainly composed of a star block copolymer composed of 44% by mass of repeating units derived from 1,3-butadiene and 56% by mass of repeating units derived from n-butyl acrylate. The polymer block (b) made of 1,3-butadiene has a vinyl bond content of 49 mol%, a glass transition temperature of −60 ° C., and a polymer block made of n-butyl acrylate (a ) Had a glass transition temperature of -49 ° C. The butadiene-n-butyl acrylate diblock copolymer (arm polymer block) had a number average molecular weight of 78,000 and a weight average molecular weight / number average molecular weight ratio (Mw / Mn) of 1.02. It was. The number average molecular weight (Mn) of the star block copolymer is 400,000 (number of arms = 5.13), and its Mw / Mn is 1.14. The star block copolymer calculated from the area ratio of GPC is used. The proportion of the polymer was 90% by mass. The refractive index of the block copolymer (B-4) is 1.492. Table 1 shows the characteristics of the block copolymer (B-4).

Synthesis Example 5 Production of Block Copolymer (B-5) The same method as Synthesis Example 1 except that the amount of 1,3-butadiene was changed to 158 ml and the amount of n-butyl acrylate was changed to 28 ml. As a result, a block copolymer (B-5) was obtained. The block copolymer (B-5) is mainly composed of a star block copolymer comprising 80% by mass of repeating units derived from 1,3-butadiene and 20% by mass of repeating units derived from n-butyl acrylate. The polymer block (b) made of 1,3-butadiene has a vinyl bond content of 30 mol%, a glass transition temperature of −46 ° C., and a polymer block made of n-butyl acrylate (a ) Had a glass transition temperature of -49 ° C. The butadiene-n-butyl acrylate diblock copolymer (arm polymer block) has a number average molecular weight of 69,000 and a weight average molecular weight / number average molecular weight ratio (Mw / Mn) of 1.02. It was. The number average molecular weight (Mn) of the star block copolymer is 270,000 (number of arms = 3.91), and its Mw / Mn is 1.16, and the star block copolymer calculated from the area ratio of GPC is used. The proportion of the polymer was 90% by mass. The refractive index of the block copolymer (B-5) is 1.507. Table 1 shows the properties of the block copolymer (B-5).

<< Synthesis Example 6 >> Production of Block Copolymer (B-6) The same method as Synthesis Example 1 except that the amount of 1,3-butadiene was changed to 40 ml and the amount of n-butyl acrylate was changed to 111 ml. As a result, a block copolymer (B-6) was obtained. The block copolymer (B-6) is mainly composed of a star block copolymer comprising 20% by mass of repeating units derived from 1,3-butadiene and 80% by mass of repeating units derived from n-butyl acrylate. The polymer block (b) made of 1,3-butadiene has a vinyl bond content of 30 mol%, a glass transition temperature of −77 ° C., and a polymer block made of n-butyl acrylate (a ) Had a glass transition temperature of -49 ° C. The butadiene-n-butyl acrylate diblock copolymer (arm polymer block) has a number average molecular weight of 69,000 and a weight average molecular weight / number average molecular weight ratio (Mw / Mn) of 1.02. It was. The number average molecular weight (Mn) of the star block copolymer is 272,000 (number of arms = 3.94), and its Mw / Mn is 1.15, and the star block copolymer calculated from the area ratio of GPC is used. The proportion of the polymer was 90% by mass. The refractive index of the block copolymer (B-6) is 1.473. Table 1 shows the characteristics of the block copolymer (B-6).

Example 1
An autoclave equipped with a stirrer and a sampling tube is charged with 59.5 parts by mass of purified methyl methacrylate, 3.1 parts by mass of methyl acrylate and 35 parts by mass of toluene, and 2.4 mass of the block copolymer (B-2). Part was added and stirred at 30 ° C. for 8 hours to uniformly dissolve the block copolymer (B-2). Next, 0.035 parts by mass of 1,1-di (t-butylperoxy) cyclohexane (“Perhexa C” manufactured by NOF Corporation, hydrogen abstraction capacity: 35%, 1 hour half-life temperature: 111.1 ° C.) and n -A 0.1 mass part of octyl mercaptan was added and it was made to melt | dissolve uniformly, and the raw material liquid was obtained. Oxygen in the production apparatus was purged with nitrogen.
The raw material liquid was discharged from the autoclave in a constant amount and supplied to a 3 L tank reactor A controlled at a temperature of 125 ° C. at a constant flow rate. Polymerization was carried out in a tank reactor A with an average residence time of 45 minutes. The reaction solution was collected from the collection tube of the reactor A. The polymerization conversion measured by gas chromatography was 42% by mass.

  In a pipe part equipped with a static mixer manufactured by Noritake Engineering Co., Ltd., 1,1-di (t-butylperoxy) cyclohexane (“Perhexa C” manufactured by Nippon Oil & Fats Co., Ltd., hydrogen drawing capacity: 35%, 1 hour half-life temperature: 111 .1 ° C) is added to 0.003 parts by mass with respect to the whole raw material liquid, mixed with the liquid discharged from the tank reactor A, and 5 L tank reactor B controlled at 135 ° C. At a constant flow rate. Polymerization was carried out in tank reactor B with an average residence time of 90 minutes. The reaction solution was collected from the collection tube of the reactor B. The polymerization conversion measured by gas chromatography was 72% by mass.

  In the piping part equipped with the static mixer manufactured by Noritake Engineering Co., Ltd., t-butyl peroxybenzoate ("Perbutyl Z", hydrogen drawing ability: 56%, 1 hour half-life temperature: 124.7 ° C) is based on the entire raw material liquid. It added so that it might become 0.02 mass part, was mixed with the liquid discharged | emitted from the tank reactor B, and was supplied to the tubular reactor C by which inner wall temperature was controlled to 135 degreeC by fixed flow volume. Polymerization was carried out in tube reactor C with an average residence time of 10 minutes. The internal pressure of the tubular reactor C was 0.7 MPa. The reaction solution was collected from the outlet of the tubular reactor C. The polymerization conversion measured by gas chromatography was 81% by mass.

  The liquid discharged from the tubular reactor C was supplied at a constant flow rate to the tubular reactor D whose inner wall temperature was controlled to 140 ° C. Polymerization was carried out with an average residence time of 50 minutes in the tubular reactor D. The internal pressure of the tubular reactor D was 0.7 MPa. The reaction solution was fractionated from the outlet of the tubular reactor D. The polymerization conversion measured by gas chromatography was 92% by mass.

  The liquid discharged from the tubular reactor D was heated to 230 ° C. and supplied to a twin screw extruder controlled at 260 ° C. at a constant flow rate. In the twin-screw extruder, volatile components mainly composed of unreacted monomers were separated and removed, and the reaction product was extruded in a strand shape. The strand was cut with a pelletizer to obtain a pellet-like methacrylic resin composition. The residual volatile content was 0.1% by mass.

The pellet-like methacrylic resin composition was produced by injection molding to produce a molded plate having a thickness of 3 mm and a molded plate having a thickness of 1 mm, and used as a test piece for evaluation.
The methacrylic resin composition contains n-butyl acrylate in 96 parts by mass of a continuous phase composed of 95% by mass of repeating units derived from methyl methacrylate and 5% by mass of repeating units derived from methyl acrylate. 4 parts by mass of a block copolymer (B-1) having a polymer block (a) composed of a repeating unit derived from a polymer block (a) composed of a repeating unit derived from butadiene and dispersed as a dispersed phase It was.
The dispersed phase observed with an electron microscope has a sea-island structure composed of a dyed sea phase (block copolymer (B)) and an undyed island phase (methacrylic resin (A)). Things were included. The disperse phase having a sea-island structure in which the area of the island phase occupies 20% or more of the area of the disperse phase was 20% by mass or more of the total dispersed phase. The other evaluation results are shown in Table 2.

A plate having a width of 500 mm and a thickness of 0.5 mm was prepared from the pellet-like methacrylic resin composition using a 50 mmφ T-die extruder.
Mixing 50 parts by mass of NK Hard M101 (manufactured by Shin-Nakamura Chemical Co., Ltd.) with a urethane acrylate curable compound as a main component and 50 parts by mass of 1-methoxy-2-propanol as a solvent, a curable paint Was prepared.
The curable paint was applied to one side of the plate with a bar coater and dried. The dried coating film was cured by irradiating with ultraviolet rays to obtain a display window protection plate. The thickness of the cured film was 4 μm.

<< Examples 2-4, Comparative Examples 1-2 >>
Pellets were obtained in the same manner as in Example 1 except that the block copolymer (B-1) used in Example 1 was changed to the block copolymers (B-2) to (B-6) shown in Table 2. A methacrylic resin composition was obtained, and using the obtained pellet-shaped methacrylic resin composition, a molded plate having a thickness of 3 mm and a molded plate having a thickness of 1 mm were prepared and used as test pieces for evaluation. A display window protection plate was obtained in the same manner as in Example 1. Any methacrylic resin composition has a residual volatile content of 0.1% by mass, and the disperse phase having a sea-island structure in which the area of the island phase occupies 20% or more of the area of the dispersed phase is 20% by mass of the total dispersed phase % Or more. The evaluation results are shown in Table 2.

<< Comparative Example 3 >>
Using pellets of a polymer composition in which 30 parts by mass of core-shell polymer particles containing 40% by mass of a styrene-butyl acrylate random copolymer rubber having a particle size of 0.25 μm are mixed with 70 parts by mass of a methacrylic resin, A 3 mm thick molded plate and a 1 mm thick molded plate were produced by injection molding in the same manner as in Example 1, and used as test specimens for evaluation. A display window protection plate was obtained in the same manner as in Example 1. The Charpy impact strength was 3.2 KJ / m ² , the flexural modulus was 2560 MPa, and the haze was 0.2%. The diameter of the dispersed phase was 0.2 μm. Although there was no peeling of the cured film, the surface hardness was 2H and the appearance evaluation was x.

  As shown in Table 2, a polymer block comprising a repeating unit derived from a (meth) acrylic acid alkyl ester in a continuous phase comprising a methacrylic resin (A) having 50% by mass or more of a repeating unit derived from methyl methacrylate. A thin display window protective plate formed using a resin composition in which a block copolymer (B) having (a) and a polymer block (b) comprising a repeating unit derived from a conjugated diene compound is dispersed. It can be seen that (Examples 1 to 4) are superior in rigidity, surface hardness, appearance (low roughness), and transparency as compared with Comparative Examples 1 to 3.

  The display window protection plate of the present invention is excellent in the visibility of the display screen, and at the same time, even if it is thin, it has excellent impact resistance, rigidity, and surface smoothness, high surface hardness, and excellent appearance (low roughness). In addition, it is possible to protect the display screen on the front surface of a thin display device such as a liquid crystal display, a plasma display, and an electroluminescence display. In particular, it is suitable for small and thin electronic devices such as a mobile phone, a mobile notebook computer, and a portable information terminal.

Claims (6)

  100 parts by mass of a continuous phase composed of a methacrylic resin (A) having a repeating unit derived from methyl methacrylate of 50% by mass or more has a glass transition temperature of 23 ° C. or less composed of a repeating unit derived from an alkyl (meth) acrylate. A block copolymer having a polymer block (a) of 30 to 65% by mass and a polymer block (b) of 35 to 70% by mass having a glass transition temperature of 0 ° C. or less composed of repeating units derived from a conjugated diene compound The display window protection board which consists of a methacrylic resin composition which 1-80 mass parts of unions (B) contain as a dispersed phase. The block copolymer (B) is a star block copolymer, the star block copolymer is composed of arm polymer blocks, and the number average molecular weight in terms of polystyrene calculated by gel permeation chromatography (GPC) But the formula:
[Number average molecular weight of star block copolymer]> 2 × [Number average molecular weight of arm polymer block]
The display window protection plate according to claim 1, wherein Star block copolymer has the chemical structural formula:
(Polymer block (b) -polymer block (a)-) _n X
The display window protective plate according to claim 2, wherein X is a coupling residue, and n is a number exceeding 2.   The display window protection plate according to any one of claims 1 to 3, wherein the block copolymer (B) has a refractive index of 1.48 to 1.50.   The display window protection plate according to claim 1, which has a thickness of 0.1 mm to 1.5 mm.   The display window protection plate according to any one of claims 1 to 5, wherein at least one of hard coating, antireflection and antistatic treatment is applied to one side or both sides.