Polymethacrylate compositions and optical and display devices formed therefrom - Patents.com

Abstract

To provide a polymethacrylate composition, an optical device formed of the composition, and a display device including the optical device.SOLUTION: The polymethacrylate composition includes 50 to 85 pts.wt. of a methacrylate-based polymer, 15 to 50 pts.wt. of a styrene-maleic acid anhydride-based copolymer, and an aromatic compound having a phosphite group. The methacrylate-based polymer includes a methacrylate-based monomer unit and an acrylate-based monomer unit and has a weight average molecular weight (Mw) in a range between 20,000 and 200,000. The styrene-maleic acid anhydride-based copolymer includes 65 wt.% to 85 wt.% of a styrene-based monomer unit, 15 wt.% to 35 wt.% of a maleic acid anhydride-based monomer unit, and 0 to 20 wt.% of a second copolymerizable monomer unit. The polymethacrylate composition contains 200 ppm to 900 ppm of the aromatic compound having a phosphite group.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to polymer compositions, and more particularly to polymethacrylate compositions and optical and display devices formed therefrom. [Background technology]

[0002] Polymethacrylate is a widely used polymer that is highly regarded for its processability, physical properties, and mechanical properties, and has a transmittance equivalent to that of glass, and excellent appearance of molded products. Therefore, it is currently one of the most excellent polymer transparent materials, and is often applied in various optical devices or consumer products such as camera lenses, lenses, optical films, car taillights, billboards, etc.

[0003] In recent years, with the development of lightweight and thin notebook personal computers, there has been an increasing demand for thinner and more powerful optical devices in display devices such as liquid crystal display devices. In addition, due to the wide range of application environments of liquid crystal display devices, the optical devices are also required to have durability such as heat resistance in high temperature environments and moisture resistance in high humidity environments.

[0004] Therefore, currently, additives that can improve the heat resistance are added to polymethacrylate, but such modifications have been found to affect the optical properties of polymethacrylate.

[0005] To solve this problem, for example, in Patent Document 1, an additive capable of improving optical properties is added to a polymethacrylate composition. However, although this modification has excellent thermal stability, it has poor heat resistance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Taiwan Patent No. I466904 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention provides a polymethacrylate composition, an optical device formed from the composition that can have both the heat resistance and optical properties of the polymethacrylate composition, and a display device that includes the optical device. [Means for solving the problem]

[0008] In order to achieve the above object, the polymethacrylate composition of the present invention includes 50-85 parts by weight of a methacrylate polymer, 15-50 parts by weight of a styrene-maleic anhydride copolymer, and an aromatic compound having a phosphite group. The methacrylate polymer includes a methacrylate monomer unit and an acrylate monomer unit, and has a weight average molecular weight (Mw) in the range of 20,000-200,000. The styrene-maleic anhydride copolymer includes 65 wt%-85 wt% of a styrene monomer unit, 15 wt%-35 wt% of a maleic anhydride monomer unit, and 0-20 wt% of a second copolymerizable monomer unit. The polymethacrylate composition includes 200 ppm-900 ppm of an aromatic compound having a phosphite group.

[0009] In one embodiment of the present invention, the ratio of weight percent of styrene-based monomer units to weight percent of maleic anhydride-based monomer units in the styrene-based-maleic anhydride copolymer is between 1 and 8.5.

[0010] In one embodiment of the present invention, the weight average molecular weight (Mw) of the styrene-maleic anhydride copolymer is between 60,000 and 100,000.

[0011] In one embodiment of the invention, the polymethacrylate composition further comprises 500 ppm to 2,000 ppm of an antioxidant.

[0012] The optical devices of the present invention are formed from the polymethacrylate compositions described above.

[0013] In one embodiment of the invention, the optical device is at least one selected from the group consisting of an optical plate, an optical sheet, and an optical film.

[0014] A display device of the present invention includes the optical device, and is at least one selected from the group consisting of a television, a digital camera, a digital photo frame, a mobile phone, a notebook computer, a mobile computer, a monitor used in a computer, a portable game machine, a portable information terminal, an audio reproducing device, a game machine, and a car display. Effect of the Invention

[0015] As described above, the polymethacrylate composition of the present invention has specific components and ratios, and therefore has heat resistance, thermal stability, and optical properties. Therefore, it can be applied to optical devices and has excellent optical properties such as low haze and low yellow index. Display devices having the above optical devices also have excellent display effects.

[0016] In order to make the above and other objects, features and advantages of the present invention more comprehensible, several embodiments accompanied with drawings are described below. [Brief description of the drawings]

[0017] The accompanying drawings are included to provide a further understanding of the principles of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0018] [Figure 1] Figure 1(a) is a schematic cross-sectional view of an optical device according to one embodiment of the present invention, and Figure 1(b) is a schematic cross-sectional view of an optical device according to another embodiment of the present invention. [Diagram 2]2(a) to (e) are schematic diagrams of display devices according to some embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, embodiments of the present invention will be described in detail. However, these embodiments are merely illustrative and do not limit the disclosure of the present invention.

[0020] In one embodiment of the present invention, the polymethacrylate composition includes 50-85 parts by weight of a methacrylate polymer, 15-50 parts by weight of a styrene-maleic anhydride copolymer, and an aromatic compound having a phosphite group. The methacrylate polymer includes a methacrylate monomer unit and an acrylate monomer unit. The weight average molecular weight (Mw) of the methacrylate polymer is in the range of 20,000-200,000. The styrene-maleic anhydride copolymer includes 65 wt%-85 wt% of a styrene monomer unit, 15 wt%-35 wt% of a maleic anhydride monomer unit, and 0-20 wt% of a second copolymerizable monomer unit. The polymethacrylate composition includes 200 ppm-900 ppm of an aromatic compound having a phosphite group.

[0021] Methacrylate Polymers

[0022] The methacrylate polymer is synthesized from a monomer mixture mainly composed of methacrylate monomers. In one embodiment, the methacrylate polymer is synthesized from a mixture containing a methacrylate monomer and an acrylate monomer; preferably, the methacrylate polymer is synthesized from a mixture containing a methacrylate monomer, an acrylate monomer, and a first copolymerizable monomer. In one embodiment, the weight average molecular weight (Mw) of the methacrylate polymer is in the range of 20,000 to 200,000, for example, in the range of 50,000 to 150,000 or 70,000 to 110,000.

[0023] Methacrylate monomers include, but are not limited to, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, amyl methacrylate, cyclohexyl methacrylate, heptyl methacrylate, n-octyl methacrylate, octadecyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and the like; the above-mentioned monomers may be used alone or in combination.

[0024] The acrylate monomers include, but are not limited to, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, amyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, heptyl acrylate, dodecyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, octadecyl acrylate, etc. The above-mentioned monomers can be used alone or in combination.

[0025] The first copolymerizable monomer is, for example, an unsaturated carboxylic acid monomer such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, citraconic acid, aconitic acid, etc. (but is not limited to these); (2) for example, maleimide, N-methylmaleimide, N-isopropylmaleimide, N-butylmaleimide, N-hexylmaleimide, N-octylmaleimide, N-dodecylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-2,3-toylmaleimide, N-2,4-toylmaleimide, N-2,3-ethylphenylmaleimide, N-2,4-ethylphenylmaleimide, N-2,3-butylmaleimide, etc. (3) maleimide monomers such as, but not limited to, N-2,4-butylphenylmaleimide, N-2,6-toylmaleimide, N-2,3-chlorophenylmaleimide, N-2,4-chlorophenylmaleimide, N-2,3-bromophenylmaleimide, and N-2,4-bromophenylmaleimide; (4) acrylamide, acrylonitrile, α-methacrylonitrile, allyl glycidyl ether, (4) vinyl-containing compound monomers, such as vinyl acetate or chloroethene, but not limited thereto; and (5) styrenic monomers, such as styrene, 2-chlorostyrene, 4-chlorostyrene, bromostyrene, vinyl toluene, α-methylstyrene, p-tert-butylstyrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, etc. The above-mentioned monomers may be used alone or in combination.

[0026] In one embodiment, the methacrylate-based polymer comprises a methacrylate-based monomer unit, an acrylate-based monomer unit, and a first copolymerizable monomer unit. As used herein, the term "monomer unit" refers to a repeating structure formed by a polymerization reaction of the above-mentioned methacrylate-based monomer, acrylate-based monomer, or first copolymerizable monomer.

[0027] In one embodiment, the methacrylate polymer contains 92 wt % to 99 wt % of methacrylate monomer units and 1 wt % to 8 wt % of acrylate monomer units. The methacrylate polymer may further contain 0 to 7 wt % of a first copolymerizable monomer based on the total weight of the methacrylate polymer, if necessary.

[0028] In one embodiment, the weight average molecular weight (Mw) of the methacrylate polymer is in the range of 20,000 to 200,000, for example, in the range of 50,000 to 150,000 or 60,000 to 140,000; preferably in the range of 70,000 to 130,000.

[0029] Methacrylate polymers can be made using solution or bulk polymerization methods, and are preferably carried out in the presence of a solvent to prevent the increase in viscosity of the crude polymer from making the polymerization difficult to control. The viscosity of methacrylate polymers is usually expressed in terms of solids content, and the amount of solvent should be adjusted so that the solids content of the crude polymer is less than 50 wt%, preferably less than 40 wt%.

[0030] When the boiling point of the solvent is similar to that of the main monomer to be polymerized, the mixture of the solvent and the monomer has a relatively narrow boiling range, thereby reducing the probability of mixing contaminants in the regenerated mixture, and the step of intermediate fractionation of the regenerated monomer and the solvent mixture can be omitted. For example, a solvent having a boiling point close to the boiling point of the methacrylate monomer can be selected, and a solvent having a boiling point of 40°C to 225°C is preferred, and a solvent having a boiling point of 60°C to 150°C is more preferred. Specific examples of the above-mentioned solvents include hexane, heptane, octane, benzene, toluene, p-xylene, o-xylene, m-xylene, ethylbenzene, cyclohexane, cyclorodecane, isooctane, or various low boiling point hydrocarbon or aromatic hydrocarbon solvents (although the present invention is not limited thereto). The above-mentioned solvents can be used alone or in combination.

[0031] The polymerization reaction of the methacrylate polymer is initiated by a radical initiator. The radical initiator is not particularly limited, but specific examples include: (1) azo compounds such as 2,2'-azobis-(isobutyronitrile) (ABN), 2,2'-azobis-(2-methylbutyronitrile) (AMBN), and 2,2'-azobis-(2,4-dimethylvaleronitrile) (ADVN); (2) diacyl peroxides such as dilauroyl peroxide, decanoyl peroxide, and dibenzoyl peroxide (BPO); (3) dialkyl peroxide compounds such as 2,5-dimethyl-2,5-di-(t-butylperoxy) hexane, dicumyl peroxide, and 1,3-bis-(t-butylperoxy isopropyl)benzene; (4) peroxyesters such as t-butylperoxypivalate and 2,5-dimethyl-2,5-di(2-ethyl hexanoylperoxy) hexane; (5) peroxyesters such as tert-amylperoxy 2-ethylhexyl carbonate. peroxycarbonate compounds such as tert-butylperoxy 2-ethylhexyl carbonate and tert-butylperoxy 2-ethylhexyl carbonate;(6) Peroxydicarbonate compounds such as dimyristyl peroxydicarbonate and di(4-tert-butylcyclohexyl peroxydicarbonate); (7) Peroxyketal compounds such as 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane and 2,2-di(4,4-di(tert-butylperoxy) cyclohexyl)propane; (8) Peroxyketal compounds such as t-butyl hydroperoxide and isopropylcumyl hydroperoxide. (9) other hydroperoxide compounds such as 2,3-dimethyl-2,3-diphenyl-butane, potassium persulfate, sodium persulfate, ammonium persulfate, etc. (however, the present invention is not limited thereto). In one embodiment, the radical initiator is 2,2'-azobis-(isobutyronitrile). The amount of the radical initiator may be 0.01 to 1 part by weight, for example, 0.03 to 0.5 parts by weight or 0.07 to 0.1 parts by weight, based on 100 parts by weight of the total amount of the monomer mixture supplied;

[0032] The polymerization reaction of the methacrylate polymer can be carried out at room temperature, but the polymerization rate can be increased by heating the reaction system. The reaction temperature is usually about 5°C to 200°C, for example, 20°C to 130°C or 30°C to 100°C. During the polymerization process, a chain transfer agent may be added as needed to help control the molecular weight; examples of chain transfer agents include, but are not limited to, n-dodecyl mercaptan (NDM), stearyl mercaptan, t-dodecyl mercaptan (TDM), n-propyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, t-nonyl mercaptan, and terpinolene.

[0033] Styrene-maleic anhydride copolymer (SMA)

[0034] A styrenic-maleic anhydride copolymer is any polymer obtained by copolymerization of a styrenic monomer (SM), a maleic anhydride monomer (MAh), and a second copolymerizable monomer, such as a linear or branched random copolymer, a linear or branched block copolymer, or a mixture thereof.

[0035] In one embodiment, the styrenic-maleic anhydride copolymer is formed by polymerizing a styrenic monomer, a maleic anhydride monomer, and a second copolymerizable monomer.

[0036] The above-mentioned maleic anhydride monomers can be used alone or in combination. The maleic anhydride monomers can be, for example, maleic anhydride, itaconic anhydride, citraconic anhydride, aconitic anhydride, etc., but the present invention is not limited thereto. In one embodiment, the maleic anhydride monomer is maleic anhydride.

[0037] The styrene-based monomers can be used alone or in combination, and examples of the styrene-based monomer include (1) halogen-substituted styrenes such as 2-chlorostyrene, 4-chlorostyrene, and bromostyrene; and (2) alkyl-substituted styrenes such as vinyltoluene, α-methylstyrene, p-tert-butylstyrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, 2,4-dimethylstyrene, and ethylstyrene, but the present invention is not limited thereto. In one embodiment, the styrene-based monomer is at least one selected from the group consisting of styrene and halogen-substituted styrenes, and alkyl-substituted styrenes. In one embodiment, the styrene-based monomer is at least one selected from the group consisting of styrene and α-methylstyrene.

[0038] The second copolymerizable monomer may be used alone or in combination. The second copolymerizable monomer is, for example, selected from the group consisting of the methacrylate monomers and the acrylate monomers used in the methacrylate polymer (however, the present invention is not limited thereto), and therefore a detailed description thereof will be omitted here.

[0039] In one embodiment, the styrenic-maleic anhydride copolymer comprises a styrenic monomer unit, a maleic anhydride monomer unit, and a second copolymerizable monomer unit. As used herein, the term "monomer unit" refers to a repeating structure formed by the polymerization reaction of the above-mentioned styrenic monomer, the maleic anhydride monomer, or the second copolymerizable monomer. Thus, the styrenic monomer unit is derived from the above-mentioned styrenic monomer, the maleic anhydride monomer unit is derived from the above-mentioned maleic anhydride monomer, and the second copolymerizable monomer unit is derived from the above-mentioned second copolymerizable monomer.

[0040] In one embodiment, the styrenic-maleic anhydride copolymer comprises 65 wt % to 85 wt % styrenic monomer units, 15 wt % to 35 wt % maleic anhydride monomer units, and 0 to 20 wt % of a second copolymerizable monomer unit.

[0041] In another embodiment, the content of styrene-based monomer units in the styrene-based maleic anhydride copolymer is 65wt%-85wt%, for example, 65wt%-83wt% or 66wt%-81wt%. When the content of styrene-based monomer units is higher than 65wt%, the polymethacrylate composition having such a content of styrene-based monomer units has favorable transmittance (T%), haze (HAZE), and yellowing index (YI); when the content of styrene-based monomer units is lower than 85wt%, the content of maleic anhydride monomer units in the styrene-based maleic anhydride copolymer is higher than 15wt%. Therefore, the polymethacrylate composition containing such a styrene-based maleic anhydride copolymer can have favorable heat resistance (glass transition temperature, Tg).

[0042] In one embodiment, the content of styrene monomer units in the styrene-maleic anhydride copolymer is 65wt%-83wt%, and the content of maleic anhydride monomer units is 17wt%-35wt%. The polymethacrylate composition having the styrene-maleic anhydride copolymer with the above ratio is applicable to optical devices that require high heat resistance. In one embodiment, the styrene-maleic anhydride copolymer with the above ratio has a molecular weight distribution index (PDI) in the range of 1.5-2.05, so that it can have high heat resistance under the premise of maintaining a preferable transmittance (T%), haze (HAZE) and yellowing index (YI).

[0043] In one embodiment, the weight percent ratio of styrenic monomer units to maleic anhydride monomer units in the styrenic-maleic anhydride copolymer is between 1 and 8.5, such as between 1.3 and 8 or between 1.5 and 7.

[0044] In one embodiment, the weight average molecular weight (Mw) of the styrene-maleic anhydride copolymer is between 60,000 and 100,000, for example, between 65,000 and 95,000 or between 65,000 and 90,000.

[0045] In one embodiment, the number average molecular weight (Mn) of the styrene-maleic anhydride copolymer is between 30,000 and 55,000, for example, between 35,000 and 50,000 or between 37,000 and 48,000.

[0046] In one embodiment, the styrene-maleic anhydride copolymer has a molecular weight distribution index (PDI) of 1.5 to 2.05, for example, 1.7 to 2.0 or 1.7 to 1.9. If the styrene-maleic anhydride copolymer has a molecular weight distribution index (PDI) of more than 2.05, the polymethacrylate composition containing the copolymer has poor optical properties (low haze and low yellowing index).

[0047] The polymerization method for the styrene-maleic anhydride copolymer is not particularly limited, and may be radical polymerization using a radical initiator. If suspension polymerization or emulsion polymerization is used, sufficient transparency may not be obtained. The radical initiator used may be selected from the radical initiators used for the methacrylate polymer described above (although the present invention is not limited thereto), and therefore a detailed description thereof will be omitted here.

[0048] The amount of the radical initiator is preferably 0.001 to 5 parts by weight based on 100 parts by weight of the total monomers. A small amount of solvent may be used in the polymerization. Examples of the solvent include aliphatic hydrocarbons such as butane, pentane, hexane, isopentane, heptane, octane, and isooctane; alicyclic hydrocarbons such as cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, and ethylcyclohexane; and aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylene, but the present invention is not limited thereto. Also, a well-known molecular weight modifier such as 4-methyl-2,4-diphenylpent-1-ene, t-dodecylmercaptan, and n-dodecylmercaptan may be added during the polymerization. The polymerization temperature is preferably 80°C to 170°C, more preferably 100°C to 160°C.

[0049] Aromatic compounds containing phosphite groups

[0050] In one embodiment, an aromatic compound having a phosphite group is provided to prevent the styrene-maleic anhydride copolymer from undergoing ring opening of maleic anhydride in high temperature process, which changes the composition of the polymethacrylate composition and thus affects the heat resistance (Tg decrease), thermal stability (Td decrease), and optical properties (haze and yellowing index) of the composition.

[0051] Examples of aromatic compounds having a phosphite group include tris(2,4-di-t-butylphenyl)phosphite, bis[2,4-di(1,1-dimethylethyl)-6-methylphenyl]ethyl phosphite, tetra(2,4-di-t-butylphenol)-4,4'-biphenyldiphosphite, bis(2,4-di-t-butylphenyl) pentaerythritol diphosphite, and bis(2,4-di-t-butylphenyl) pentaerythritol diphosphite. diphosphite, bis(2,6-di-t-butyl-4-methylphenyl) pentaerythritol-diphosphite, bis(2,4-dicumylphenyl)pentaerythritol diphosphite, di-t-butyl m-tolyl phosphite ester, etc. (however, the present invention is not limited thereto), and the above-mentioned compounds can be used alone or in combination.

[0052] In one embodiment, the aromatic compound having a phosphite group is preferably a heterocyclic aromatic phosphite compound containing a pentaerythritol diphosphite group, and includes, for example, a structure represented by the following formula (1).

[0053] [ka] (1)

[0054] In the above formula, R1 and R2 each independently represent a hydrogen atom, a linear alkyl group having 1 to 10 carbon atoms, a branched alkyl group having 1 to 10 carbon atoms, or Cyclic alkyl group having 1 to 10 carbon atoms of For example, R1 and R2 each independently represent hydrogen, methyl, or tert-butyl. Specific examples of aromatic compounds having a phosphite group include, for example, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, or bis(2,4-dicumylphenyl)pentaerythritol diphosphite, but the present invention is not limited thereto.

[0055] In one embodiment, the content of aromatic compounds having phosphite groups in the polymethacrylate composition is 200 ppm to 900 ppm, for example, 250 ppm to 800 ppm or 300 ppm to 800 ppm. When the content of aromatic compounds having phosphite groups is within 200 ppm to 900 ppm, the polymethacrylate composition containing aromatic compounds having phosphite groups can have high Tg (excellent heat resistance), high Td (excellent thermal stability), and favorable optical performance (low yellowing index and low haze). The total amount of the methacrylate polymer and the styrene-maleic anhydride copolymer is 100 parts by weight.

[0056] Furthermore, additives may be mixed according to various purposes within a range that does not significantly impair the effects of the present invention. The types of these additives are not particularly limited as long as they are those that are commonly used in resin compositions or rubber compositions; for example, additives include antioxidants, heat stabilizers, UV absorbers, slip agents, processing aids, fillers, reinforcing agents, colorants, antistatic agents, or other additives, and additives are not limited to being added only during or after the polymerization reaction, or during extrusion and mulling. The content of additives is measured when the total amount of polymers is 100 parts by weight, that is, when the total amount of the methacrylate-based polymer and the styrene-based-maleic anhydride-based copolymer is 100 parts by weight.

[0057] Antioxidants

[0058] The antioxidant is an additive other than the aromatic compound having a phosphite group. In one embodiment, the antioxidant is, for example, pentaerythritol tetrakis[3-(3,5-di-tris-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tertiary-butyl-4-hydroxyphenyl)propionate, octadecyl β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, triethylene glycol bis(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate, bis(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate), 3,5-di-t-butyl-4-hydroxycinnamic acid, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane, 3,9-bis(2-(3-(3-tris-butyl-4-hydroxy-5-methylphenyl) propionyloxy)-2,4,8,10-tetraoxaspiro(5,5)undecane -1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro(5,5)undecane) and the like (however, the present invention is not limited thereto), and the above-mentioned antioxidants can be used alone or in combination.

[0059] In one embodiment, the antioxidant is preferably a phenolic compound containing a 2,4,8,10-tetraoxaspiro(5,5)undecyl group, for example, having a structure represented by the following formula (2):

[0060] [ka] (2)

[0061] In the above formula, R a and R b each independently represents an alkyl group having 6 to 12 carbon atoms, an ether group having 6 to 12 carbon atoms, an ester group having 6 to 12 carbon atoms, or a combination thereof; R3 and R4 each independently represent a hydrogen atom, or a linear, branched, or cyclic alkyl group having 1 to 10 carbon atoms. A specific example of the antioxidant is 3,9-bis(2-(3-(3-tris-butyl-4-hydroxy-5-methylphenyl)propionyloxy)-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro(5,5)undecane, but the present invention is not limited thereto.

[0062] The content of the antioxidant in the polymethacrylate composition is 500 ppm to 2,000 ppm, for example, 700 ppm to 1,700 ppm or 850 ppm to 1,600 ppm. In one embodiment, when the polymethacrylate composition contains an antioxidant and an organic phosphorus compound, and the ratio of the content of the antioxidant to the organic phosphorus compound is within the range of 1.1 to 10, for example, within the range of 1.2 to 8.5 or 1.5 to 8, the polymethacrylate composition has a high Tg (excellent heat resistance) and a high Td (excellent thermal stability), and shows relatively excellent optical performance with low haze. In one embodiment, the polymethacrylate composition contains 500 ppm to 2,000 ppm of the antioxidant and 200 ppm to 900 ppm of the organic phosphorus compound.

[0063] Heat stabilizer

[0064] In one embodiment, a common heat stabilizer can be used in the present invention. In another embodiment, the present invention can use a heat stabilizer represented by the following formula (3):

[0065] [ka] (3)

[0066] In the above formula, R5 and R8 are each independently hydrogen or a methyl group, and R6 and R7 are each independently a linear, branched, or cyclic alkyl group having 1 to 9 carbon atoms. R6 is, for example, selected from tertiary butyl or tertiary amyl; R7 is, for example, selected from tertiary butyl, tertiary amyl, or tertiary octyl.

[0067] The content of the heat stabilizer in the polymethacrylate composition is 500 ppm to 2,000 ppm. When the content of the heat stabilizer is within this range, the balance between thermal stability and processability can be maintained, and production costs can be controlled. In one embodiment, the content of the heat stabilizer in the polymethacrylate composition is 700 ppm to 1,800 ppm, and in another embodiment, the content of the heat stabilizer in the polymethacrylate composition is 900 ppm to 1,600 ppm.

[0068] UV absorbers

[0069] In one embodiment, an ultraviolet (UV) absorber can be used in the present invention. In one embodiment, the flash point of the UV absorber is higher than the processing temperature. For example, the flash point of the UV absorber is 240° C. or higher to prevent the UV absorber from precipitating during the high temperature process of forming the optical device. Precipitation usually causes serious mold contamination.

[0070] Examples of the ultraviolet absorber include 2-(4,6-bis-(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-(octyloxy)phenol, 2,2'-methylenebis[6-(benzotriazol-2-yl)-4-tert-octylphenol], 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]phenol, and the like. triazin-2-yl)-5-[(hexyl)oxy]-phenol), 2,2',4,4'-tetrahydroxybenzophenone, 3-[(2-Cyano-3,3-diphenylacryloyl)oxy]-2,2-bis{[(2-cyano-3,3-diphenylacryloyl)oxy]methyl}propyl2-cyano-3,3-diphenylacrylate(uvinul 3030), 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol, 2-(2'-hydroxy-3',5'-dipentylphenyl)benzotriazole, and the like. The above-mentioned UV absorbers can be used alone or in combination.

[0071] The content of the ultraviolet absorber in the polymethacrylate composition is 10,000 ppm to 50,000 ppm, for example, 15,000 ppm to 40,000 ppm or 20,000 ppm to 35,000 ppm. When the content of the ultraviolet absorber is within this range, the ultraviolet absorber and the composition can be mixed uniformly, so that the ultraviolet absorber does not precipitate during subsequent hot working, causing mold contamination, and the composition can have excellent ultraviolet light stability. In one embodiment, when the polymethacrylate composition contains an ultraviolet absorber and an aromatic compound having a phosphite group, and the ratio of the content of the ultraviolet absorber to the aromatic compound having a phosphite group is within the range of 10 to 300, for example, within the range of 15 to 200 or 20 to 180, the polymethacrylate composition can have high Tg (excellent heat resistance) and high Td (excellent thermal stability) performance, and shows relatively excellent optical performance with a low yellowing index. In one embodiment, the polymethacrylate composition comprises 10,000 ppm to 50,000 ppm of an ultraviolet absorber and 200 ppm to 900 ppm of an aromatic compound having a phosphite group.

[0072] Slip Agent

[0073] Examples of slip agents include, but are not limited to, metal soaps such as calcium stearate, magnesium stearate, and lithium stearate; compounds such as ethylene distearylamine, methylene distearylamine, decyl palmitate, butyl stearate, palmitate stearate, polypropionate tristearate, n-docosanoic acid, hard fatty acids, and stearyl alcohol; polyethylene wax, octadecanoic acid wax, carnuba wax, and petroleum wax; and the above-mentioned slip agents may be used alone or in combination.

[0074] The content of the slip agent in the polymethacrylate composition is 300 ppm to 50,000 ppm.

[0075] Processing Aids

[0076] The processing aid can improve extrusion moldability, thermoformability, etc., by, for example, including but not limited to, a core-shell acrylate having a weight average molecular weight (Mw) of 500,000 or more.

[0077] Antistatic Agent

[0078] The antistatic agent may include, but is not limited to, low molecular weight compounds such as tertiary amine compounds or quaternary ammonium salt compounds; or polyamine polyethers such as 3-chloro-3-1,2-epoxypropane polymers, and the above-mentioned antistatic agents may be used alone or in combination.

[0079] Filler

[0080] Examples of fillers include, but are not limited to, calcium carbonate, bauxite, mica, and the like, and the above-mentioned fillers may be used alone or in combination.

[0081] Reinforcing agent

[0082] Examples of reinforcing agents include, but are not limited to, glass fibers, carbon fibers, various whiskers, and the like, and the reinforcing agents described above can be used alone or in combination.

[0083] Coloring agent

[0084] Examples of colorants include, but are not limited to, titanium oxide, iron oxide, graphite, phthalocyanine dye, and the like, and the above-mentioned colorants may be used alone or in combination.

[0085] The use of the polymethacrylate composition of the present invention is not particularly limited, and can be applied to various molding processes such as injection molding, compression molding, extrusion molding, blow molding, thermoforming, vacuum molding, hollow molding, etc., and various final products such as plates and film molded products produced by the above-mentioned molding processes, etc. The polymethacrylate composition can be formed according to the needs such as high fluidity and high thermal stability.

[0086] The polymethacrylate composition can be obtained by a common mixing muller such as a Brabender plastometer, a Banbury mixer, a kneading-mixer, a roller, a single-screw or twin-screw extruder, etc. Usually, after mixing and kneading in an extruder, the extrudate is cooled and granulated. The polymethacrylate composition is usually kneaded at 160°C to 280°C, preferably 180°C to 250°C. Furthermore, the order of mixing and kneading each component is not particularly limited.

[0087] The optical device according to another embodiment of the present invention is formed by the polymethacrylate composition described above, and has excellent optical properties of low haze and low yellowing index. In one embodiment, the optical device may be an optical material having a planar structure, such as an optical plate, an optical sheet, or an optical film. In one embodiment, the method of preparing the optical material having a planar structure is not particularly limited here, and the polymethacrylate composition may be melted in an extruder, and then extruded into a plate-, sheet-, or film-shaped unstretched optical plate, optical sheet, or optical film. In another embodiment, a tenter may be used to transversely or biaxially stretch the unstretched optical plate, optical sheet, or optical film at a temperature higher than its glass transition temperature.

[0088] In one embodiment, the optical device is an optical plate having a planar structure, for example, including a sheet-shaped body, the body including a planar surface, the body having a rectangular shape and made of the polymethacrylate composition described above.

[0089] In another embodiment, the optical device is, for example, an optical plate having a microstructure. Referring to FIG. 1(a), an optical plate 10 having a microstructure is shown. The optical plate 10 includes a body 12, the body 12 has a surface 122, and a plurality of first microstructures 132 are disposed on the surface 122. As shown in FIG. 1(a), each of the first microstructures 132 in this embodiment is a concave pit structure, but the present invention is not limited thereto. In another embodiment, each of the first microstructures 132 may be a bump structure or a structure having other shapes.

[0090] Referring to FIG. 1(b), yet another embodiment of the optical device is shown, in which in addition to the first microstructure 132 in FIG. 1(a), a plurality of second microstructures 134 are further arranged on other surfaces, such as a surface 124 facing the surface 122 or a side surface 126 perpendicular to the surface 122, and the second microstructures 134 are, for example, microlenses, arranged on the surface 124. In this embodiment, each second microstructure 134 has a semicircular shape, but the present invention is not limited thereto. In another embodiment, each second microstructure 134 may be a suitable protruding structure, such as a prism or a corner pillar. The optical device may also be an optical plate having the second microstructure 134 alone.

[0091] In some embodiments, the optical device can be applied to various display devices. The display devices can be, for example, a television (also called a TV or a TV receiver) (as shown in FIG. 2(a)), a digital camera (as shown in FIG. 2(b)), a digital video camera (as shown in FIG. 2(c)), a digital photo frame (as shown in FIG. 2(d)), a mobile phone (as shown in FIG. 2(e)), a notebook computer, a mobile computer, a monitor used in a computer, a portable game machine, a portable information terminal, an audio reproduction device, a game machine, and a car display.

[0092] The polymethacrylate composition of the present invention will be described in more detail with reference to some experimental examples. The following experimental examples will be described, but the materials, amounts and ratios used, processing contents, processing procedures, etc. can be appropriately changed within the scope of the present invention. Therefore, the present invention should not be interpreted as being limited by the experimental examples described below.

[0093] <Materials used in the Examples and Comparative Examples>

[0094] 1. PMMA: Methacrylate polymer

[0095] 1.1.Preparation of PMMA1

[0096] First, 95 parts by weight of methyl methacrylate, 5 parts by weight of methyl acrylate, 0.4 parts by weight of n-dodecyl mercaptan, 0.08 parts by weight of 2,2'-azobis-(isobutyronitrile), and 66 parts by weight of toluene were mixed and continuously fed into a reaction tank to carry out a continuous solution polymerization reaction. The reaction tank described above was a sandwiched bed with a heat medium oil circulation, and the reaction temperature was maintained at 100°C and the pressure was 600 torr. The components in the reaction tank were thoroughly stirred and mixed uniformly, and the resulting polymer solution was heated to 265°C. Then, the polymer solution was devolatilized under reduced pressure using a devolatilizer, and then fabricated into strips using an extruder. The strips were cooled and granulated to obtain polymethyl methacrylate resin pellets. The polymethyl methacrylate resin pellets contained 97 wt% of methyl methacrylate monomer units and 3 wt% of methyl acrylate monomer units. The weight average molecular weight (Mw) of the polymethyl methacrylate resin pellets (weight average molecular weight measured using GPC and converted into standard polystyrene) was 100,000, and the melt flow rate (MVR) was (230°C*3.8 kg)=1.9.

[0097] 1.2.Preparation of PMMA2

[0098] First, 94 parts by weight of methyl methacrylate, 6 parts by weight of methyl acrylate, 0.5 parts by weight of n-dodecyl mercaptan, 0.1 parts by weight of 2,2'-azobis-(isobutyronitrile), and 66 parts by weight of toluene were mixed and continuously fed into a reaction tank to carry out a continuous solution polymerization reaction. The reaction tank described above was a sandwiched bed with a heat medium oil circulation, and the reaction temperature was maintained at 100°C and the pressure was 600 torr. The components in the reaction tank were thoroughly stirred and mixed uniformly, and the resulting polymer solution was heated to 265°C. Then, the polymer solution was devolatilized under reduced pressure using a devolatilizer, and then fabricated into strips using an extruder. The strips were cooled and granulated to obtain polymethyl methacrylate resin pellets. The polymethyl methacrylate resin pellets contained 95.5 wt% of methyl methacrylate monomer units and 4.5 wt% of methyl acrylate monomer units. The weight average molecular weight (Mw) of the polymethyl methacrylate resin pellets (weight average molecular weight measured using GPC and converted into standard polystyrene) was 90,000, and the melt flow rate (MVR) was (230°C*3.8 kg)=3.0.

[0099] 2. SMA: Styrene-maleic anhydride copolymer

[0100] 2.1.Construction of SMA1

[0101] In a 40L stirred reactor, 7,440g of maleic anhydride was added after purging with nitrogen for 10 minutes, and the temperature was raised to 130°C and then kept constant for 30 minutes. Then, while maintaining the temperature at 130°C, a mixed solution containing 22,560g of styrene and 12g of 2,2'-azobis-(isobutyronitrile) was continuously added within 1 hour, and the temperature was lowered to 110°C after the supply was completed. The reaction was carried out at a constant temperature for 4 hours, and first, unreacted maleic anhydride was washed with acetone, and then unreacted styrene was removed in a vacuum oven at 80°C to obtain a bulky styrene-maleic anhydride copolymer.

[0102] 2.2.Construction of SMA2

[0103] The preparation method was the same as that for SMA1, but the amount of maleic anhydride added was adjusted to 9,570 g, and the amount of styrene added was adjusted to 20,430 g.

[0104] 2.3.Construction of SMA3

[0105] The preparation method was the same as that for SMA1, but the amount of maleic anhydride added was adjusted to 8,190 g, the amount of styrene added was adjusted to 21,810 g, and the amount of 2,2'-azobis-(isobutyronitrile) added was adjusted to 14 g.

[0106] Table 1 shows the weight percentages of styrene monomer units (SM), maleic anhydride monomer units (MAh), the ratio of the weight percentage of styrene monomer units to the weight percentage of maleic anhydride monomer units (SM / MAh), the number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution index (PDI) (Q) of SMA1 to SMA3 measured using GPC in terms of standard polystyrene.

[0107] [Table 1]

[0108] 3. Aromatic compounds containing phosphite groups: bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol-diphosphite.

[0109] 4. Heat stabilizer: A heat stabilizer represented by formula (3) (R5 is methyl, R6 and R7 are both tertiary amyl, and R8 is hydrogen).

[0110] 5. Antioxidant: 3,9-bis(2-(3-(3-tris-butyl-4-hydroxy-5-methylphenyl)propionyloxy)-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro(5,5)undecane.

[0111] 6. UV absorber: 2,2'-methylenebis[6-(benzotriazol-2-yl)-4-tert-octylphenol]. Flash point is 420.5℃±35.7℃.

[0112] [Evaluation items]

[0113] Transmittance (T%): The polymethacrylate compositions of Examples 1 to 4 and Comparative Example 1 were cut into disk test pieces with a diameter of 5.5 cm and a thickness of 3 mm, and then measured with a haze meter (Haze Meter NDH 2000N) (unit: %). Based on the requirements of commercially available optical films, it is usually desirable to have a transmittance higher than 90%.

[0114] Haze: The polymethacrylate compositions of Examples 1 to 4 and Comparative Example 1 were cut into disk test pieces with a diameter of 5.5 cm and a thickness of 3 mm, and then measured with a haze meter (Haze Meter NDH 2000N) (unit: %). Based on the requirements of commercially available optical films, it is usually desirable to have a haze of less than 1.5.

[0115] Yellowing index (YI): The polymethacrylate compositions of Examples 1 to 4 and Comparative Example 1 were cut into disk test pieces with a diameter of 5.5 cm and a thickness of 3 mm, and then measured with a computer spectrophotometer SA-2000 manufactured by Nippon Denshoku Industries Co., Ltd.

[0116] Glass transition temperature (Tg): The polymethacrylate compositions of Examples 1 to 4 and Comparative Example 1 were measured by differential scanning calorimetry (DSC) (unit: ° C.).

[0117] Thermal degradation temperature (5% weight loss temperature, Td): 5 mg of the polymethacrylate compositions of Examples 1 to 4 and Comparative Example 1 were used as samples. The samples were placed in a thermogravimetric analyzer (TGA) and analyzed under the following conditions: under a nitrogen atmosphere, the temperature was increased from 100°C to 600°C at a heating rate of 20°C / min, and the temperature at which the weight decreased by 5% was measured.

[0118] Examples 1 to 4

[0119] Examples 1 to 4 are polymethacrylate compositions prepared by mixing PMMA and SMA according to the ratios listed in Table 2, then mixing with a heat stabilizer, an antioxidant, an aromatic compound having a phosphite group, and an ultraviolet absorber, and then mixing and extrusion granulating in an extruder at 240°C. The total amount of the methacrylate polymer (PMMA) and the styrene-maleic anhydride copolymer (SMA) is 100 parts by weight. The amounts of the heat stabilizer, the antioxidant, the aromatic compound having a phosphite group, and the ultraviolet absorber listed in Table 3 are the actual contents measured from the polymethacrylate compositions of Examples 1 to 4 using high performance liquid chromatography (HPLC). The results of the detection of haze, yellowing index (YI), transmittance (T%), and glass transition temperature (Tg) are also recorded in Table 3.

[0120] Comparative Example 1

[0121] Comparative Example 1 was a polymethacrylate composition prepared by mixing PMMA and SMA based on the component ratios listed in Table 2 in the same manner as in Examples 1 to 4, and then mixing with a heat stabilizer, an antioxidant, an aromatic compound having a phosphite group, and an ultraviolet absorber. The total amount of the methacrylate polymer (PMMA1) and the styrene-maleic anhydride copolymer (SMA1) was 100 parts by weight. The amounts of the heat stabilizer, antioxidant, and ultraviolet absorber listed in Table 3 are the actual contents measured from the polymethacrylate composition of Comparative Example 1 using high performance liquid chromatography (HPLC). The detection results of haze (HAZE), yellowing index (YI), transmittance (T%), and glass transition temperature (Tg) are also recorded in Table 3.

[0122] [Table 2]

[0123] [Table 3]

[0124] As can be seen from the results of Examples 1 to 4 and Comparative Example 1, when the polymethacrylate composition contains 50 to 85 parts by weight of a methacrylate polymer, 15 to 50 parts by weight of a styrene-maleic anhydride copolymer, and an aromatic compound having a phosphite group, and the methacrylate polymer contains a methacrylate monomer unit and an acrylate monomer unit and has a weight average molecular weight (Mw) in the range of 20,000 to 200,000, the styrene-maleic anhydride copolymer contains 65% to 85% of a styrene monomer unit, 15% to 35% of a maleic anhydride monomer unit, and 0 to 20 wt% of a second copolymerizable monomer unit, and the polymethacrylate composition contains 200 ppm to 900 ppm of an aromatic compound having a phosphite group, the polymethacrylate composition can maintain excellent heat resistance (relatively high Tg) and relatively excellent thermal stability (relatively high Td). In other words, the presence of the aromatic compound having a phosphite group increases the thermal degradation temperature of the composition, and high heat resistance can be maintained. In addition, Examples 1 to 4, which contain 200 ppm to 900 ppm of the aromatic compound having a phosphite group and 10,000 ppm to 50,000 ppm of the ultraviolet absorber, have excellent yellowing index (YI).

[0125] In addition, as shown in Table 3, Examples 1 to 4, which contain 200 ppm to 900 ppm of an aromatic compound having a phosphite group and 500 ppm to 2,000 ppm of an antioxidant, have relatively excellent haze performance and high transmittance under the action of the aromatic compound having a phosphite group and the antioxidant. [Industrial Applicability]

[0126] Polymethacrylate compositions find application in a variety of optical devices or consumer products, such as camera lenses, lenses, optical films, car taillights, billboards, and the like. [Explanation of symbols]

[0127] 10, 10' Optical Plate 12 Main unit 122, 124 surface 126 Side 132 First Microstructure 134 Second Microstructure

Claims

1. 50 to 85 parts by weight of a methacrylate polymer containing a methacrylate monomer unit and an acrylate monomer unit and having a weight average molecular weight in the range of 20,000 to 200,000; 15 to 50 parts by weight of a styrene-maleic anhydride copolymer comprising 67.9 wt % to 73.2 wt % of styrene monomer units and 26.8 wt % to 32.1 wt % of maleic anhydride monomer units; The total amount of the methacrylate polymer and the styrene-maleic anhydride copolymer is 100 parts by weight; an aromatic compound having 200 ppm to 900 ppm of a phosphite group; A UV absorber having a flash point of 240° C. or higher and a concentration of 10,000 ppm to 50,000 ppm; A polymethacrylate composition comprising: A polymethacrylate composition, wherein the ratio of the content of the ultraviolet absorber to the content of the aromatic compound having a phosphite group is within the range of 10 to 300.

2. 10. The polymethacrylate composition of claim 1 further comprising from 858 ppm to 1,600 ppm of a heat stabilizer.

3. 2. The polymethacrylate composition of claim 1, wherein the weight average molecular weight of the styrene-maleic anhydride copolymer is between 60,000 and 100,000.

4. The aromatic compound having a phosphite group has a structure represented by the following formula (1): 【Chemistry 1】 (In formula (1), R 1 and R 2 each independently represents hydrogen, a linear alkyl group having 1 to 10 carbon atoms, a branched alkyl group having 1 to 10 carbon atoms, or a cyclic alkyl group having 1 to 10 carbon atoms. Including, The content of the aromatic compound having a phosphite group is 231 ppm to 410 ppm, further comprising 858 ppm to 1,183 ppm of a heat stabilizer, and 586 ppm to 1,191 ppm of an antioxidant; the antioxidant is an additive other than the aromatic compound having a phosphite group, The heat stabilizer includes a structure represented by the following formula (3): 【Chemistry 2】 (In formula (3), R 5 and R 8 are each independently a hydrogen atom or a methyl group, and R 6 and R 7 each independently represents a linear, branched, or cyclic alkyl group having 1 to 9 carbon atoms. The polymethacrylate composition of claim 1.

5. An optical device formed from the polymethacrylate composition of any one of claims 1 to 4, comprising: An optical device, which is at least one selected from the group consisting of an optical plate, an optical sheet, and an optical film.

6. The optical device according to claim 5, A display device which is one selected from the group consisting of a television, a digital camera, a digital photo frame, a mobile phone, a notebook computer, a mobile computer, a monitor used in a computer, a portable game machine, a portable information terminal, an audio reproducing device, a game machine, and a car display.

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