KR20220093895A - A light diffusing bead, method of producing the same, and light diffusing sheets comprising thereof - Google Patents

Abstract

The present invention relates to light diffusing beads, and more particularly, to a light diffusion bead having improved thermal properties, excellent optical properties, and high strength properties, and a light diffusion sheet comprising the same. More specifically, the dispersion stabilizer and the light diffusion beads of the present invention are prepared by using the same monomer so that light transmittance can be significantly improved and light diffusion beads having a specific average particle diameter and uniform particle size distribution can be provided. In addition, the light diffusion sheet prepared comprising the light diffusion beads has high light transmittance and low haze, exhibits improved optical properties, and has improved heat resistance so that the light diffusion sheet is suitable for application to a backlight for a liquid crystal display used for a long time, a lighting device, a signboard, or a glass display case.

Description

Light diffusion bead, manufacturing method thereof, and light diffusion sheet comprising the same

The present invention relates to a light-diffusion bead having improved thermal properties and excellent optical properties and high-strength properties, a method for manufacturing the same, and a light-diffusion sheet manufactured using the same.

In the backlight method, the light generated from the light source of the backlight unit attached to the back of the display element reaches the opposite side through the light guide plate, and reflects it on a reflective plate such as a metal deposition plate or an opaque white plate so that the light is emitted to the front of the display screen. It is an indirect lighting method that improves the brightness of

As one type of such technology, a light diffusion sheet having a function of uniformly diffusing while passing light emitted from a light source lamp without loss has been developed. In the conventional light-diffusion sheet, in order to uniformly diffuse the light, there have been many related to the technical configuration of distributing the light-diffusion granular material inside the light-diffusion sheet.

As described in Japanese Patent Application Laid-Open No. Hei 1-172801, the conventionally used light-diffusion sheet uses a conventional inorganic material as a light-diffusing agent and has a high degree of blurring but low light transmittance. Although diffusion beads are used, the improvement of light transmittance is not sufficient, and there is a risk of adhesion of dust due to generation of static electricity. In addition, the light-diffusing sheet has a weak impact strength, so it is limited in the shape of a molded article during processing, and there are still disadvantages in that the haze is high and the thermal stability is low.

Therefore, there is a need to develop a light diffusion sheet that maintains mechanical strength and heat resistance even when the backlight is used for a long time while simultaneously increasing light transmittance and diffusivity.

Japanese Laid-Open Patent Publication No. 1-172801

In order to solve the problems of the prior art, the present invention aims to provide a light-diffusion bead, a method for manufacturing the same, and a light-diffusion bead and a light-diffusion sheet having excellent optical properties and low haze, manufactured using the same .

Another object of the present invention is to provide light-diffusion beads with easy particle size control through a simple process by polymerizing light-diffusion beads using a specific dispersion stabilizer, and having a specific average particle diameter and uniform particle size distribution using a specific dispersion stabilizer. An object of the present invention is to provide a light-diffusing bead.

An object of the present invention is to provide a light-diffusion sheet with significantly improved light transmittance by preparing the light-diffusion beads and the dispersion stabilizer using the same type of monomer.

Another object of the present invention is to provide a light-diffusion bead having excellent thermal properties having a high glass transition temperature and a 2% weight loss temperature.

Another object of the present invention is to provide a light-diffusing sheet having excellent optical properties such as low yellowness, low haze, and good matte properties.

Another object of the present invention is to provide a light-diffusion bead suitable for application to a backlight for a liquid crystal display, a lighting device, a signboard, or a glass showcase, a method for manufacturing the same, and a light-diffusion sheet manufactured using the light-diffusion bead.

One aspect of the present invention for achieving the above object is a light-diffusion bead polymerized including a monomer, a crosslinking agent and a dispersion stabilizer, wherein the monomer uses a methyl methacrylate monomer alone, and the dispersion stabilizer is represented by the following Chemical Formula 1, It is prepared by polymerizing a mixture for a dispersion stabilizer containing Chemical Formula 2 and an alkyl (meth)acrylate-based monomer, and the light diffusion beads have an average particle diameter of 10 to 100 μm and a particle size distribution of 1 to 3 Provides light diffusion beads do.

[Formula 1]

In Formula 1, R ₁ is hydrogen or C1 to C3 alkyl, n is an integer selected from 1 to 3, and M is any one selected from lithium, sodium, potassium and ammonium salts.

[Formula 2]

In Formula 2, R ₂ is hydrogen or C1 to C3 alkyl, and M is any one selected from lithium, sodium, potassium and ammonium salts.

The light-diffusion bead according to an embodiment of the present invention is close to a spherical shape, and the particle diameter ratio (major axis/minor axis) may be in the range of 1.0 to 1.2.

The light-diffusion beads according to an embodiment of the present invention may contain 0.001 to 10 parts by weight of a dispersion stabilizer based on 100 parts by weight of the methyl (meth)acrylate-based monomer.

The light-diffusion beads according to an embodiment of the present invention may contain 0.1 to 10 parts by weight of a crosslinking agent based on 100 parts by weight of the methyl (meth)acrylate-based monomer.

The glass transition temperature (Tg) of the light-diffusion bead according to an embodiment of the present invention is 120° C. or higher, and the temperature at which a 2% weight loss occurs (2% Td) may be 285° C. or higher.

A method of manufacturing a light-diffusion bead according to an embodiment of the present invention

(a) stirring a reaction mixture in which a monomer, a crosslinking agent, and a dispersion stabilizer are added to water at room temperature;

(b) raising the reaction temperature to perform a polymerization reaction;

The monomer is a methyl (meth) acrylate-based monomer is used alone,

The dispersion stabilizer is prepared by polymerizing a mixture for a dispersion stabilizer including the following Chemical Formulas 1 and 2 and an alkyl (meth)acrylate-based monomer,

The light diffusion beads may have an average particle diameter of 10 to 100 μm and a particle size distribution of 1 to 3, preferably 1 to 2.

[Formula 1]

In Formula 1, R ₁ is hydrogen or C1 to C3 alkyl, n is an integer selected from 1 to 3, and M is any one selected from lithium, sodium, potassium and ammonium salts.

[Formula 2]

In Formula 2, R ₂ is hydrogen or C1 to C3 alkyl, and M is any one selected from lithium, sodium, potassium and ammonium salts.

The present invention may provide a light-diffusion sheet prepared including the above-described light-diffusing beads.

The light-diffusion sheet according to an embodiment of the present invention may have a light transmittance of 80% or more, and a yellowness (YI) of 0.01 to 1, measured according to ASTM D1003.

The light diffusion sheet according to an embodiment of the present invention may have a haze measured according to ISO 14782 of 60 or less.

In the light diffusion sheet according to an embodiment of the present invention, the yellowing time measured according to ISO 13468-1 may be 6 hours or more.

The present invention may provide a light-diffusion sheet prepared by further comprising the above-described light-diffusion beads and polymethyl methacrylate resin.

The light-diffusion sheet according to an embodiment of the present invention may include 1 to 50 parts by weight of light-diffusion beads based on 100 parts by weight of the polymethacrylate resin.

In the light diffusion sheet according to an embodiment of the present invention, the weight average molecular weight of the polymethyl methacrylate resin may be 20,000 to 300,000 g/mol.

The present invention may provide a master batch chip (Mater Batch Chip) manufactured including the above-described light diffusion beads.

The present invention can provide light-diffusion beads with easy particle size control through a simple process by polymerizing the light-diffusion beads using a specific dispersion stabilizer.

In addition, the dispersion stabilizer and the light-diffusion bead of the present invention can be prepared by using the same type of monomer to provide a light-diffusion bead that significantly improves the light transmittance and has a specific average particle diameter and a uniform particle size distribution.

The light-diffusion sheet manufactured including the light-diffusion bead has high light transmittance and low haze, exhibiting improved optical properties, and excellent heat resistance, so it is applied to backlights for liquid crystal displays, lighting devices, signboards, or glass showcases that are used for a long time. suitable for

Hereinafter, the present invention will be described in more detail through embodiments or examples including the accompanying drawings. However, the following specific examples or examples are only a reference for describing the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

Also, unless defined otherwise, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description herein is for the purpose of effectively describing particular embodiments only and is not intended to limit the invention.

Also, the singular forms used in the specification and appended claims may also be intended to include the plural forms unless the context specifically dictates otherwise.

Also, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

Hereinafter, a preferred embodiment and a method for measuring physical properties of a light-diffusion bead prepared using the dispersion stabilizer of the present invention, a method for manufacturing the same, and a light-diffusion sheet prepared using the light-diffusion bead will be described in detail.

The present invention may be better understood by the following examples, which are for illustrative purposes of the present invention and are not intended to limit the scope of protection defined by the appended claims.

The present invention can provide a light-diffusion bead prepared by using methyl methacrylate alone as a monomer, using a specific dispersion stabilizer, and a light-diffusion sheet prepared using the same.

In addition, by adding the light-diffusing beads to a light-diffusing plate made of the same type of monomer as the light-diffusion beads and made of polymethyl methacrylate homopolymer, they have high light transmittance and low haze, resulting in improved optical properties and excellent heat resistance It is possible to manufacture a light-diffusion sheet having the characteristics.

That is, as a result of repeated research to solve the problems of the prior art, the present inventors prepared a specific light-diffusion bead with an easy polymerization process, a uniform particle size distribution, and an improved glass transition temperature, The present invention was completed by discovering that a light diffusion sheet having excellent light transmittance, low yellowness and haze, high heat resistance, and improved matte properties can be manufactured using diffusion beads.

Hereinafter, an embodiment of the present invention will be described in more detail.

The light-diffusion beads according to an embodiment of the present invention are light-diffusion beads polymerized including a monomer, a crosslinking agent, and a dispersion stabilizer, and the monomer is a methyl methacrylate monomer alone, and the dispersion stabilizer is It is prepared by polymerizing a mixture for a dispersion stabilizer containing Formula 2 and an alkyl (meth)acrylate-based monomer, and the average particle diameter of the light-diffusion beads is 10 to 100 μm, and the particle size distribution is 1 to 3, preferably 1 It may be a light-diffusion bead of 2 to 2.

[Formula 1]

[Formula 2]

In Formula 1, R ₁ is hydrogen or C1 to C3 alkyl, n is an integer selected from 1 to 3, and M is any one selected from lithium, sodium, potassium and ammonium salts. More specifically, the compound represented by [Formula 1] is 3-sulfopropyl acrylate potassium salt, 3-sulfopropyl methacrylate potassium salt, 2-sulfoethyl methacrylate sodium salt, and 2-sulfoethyl acrylate sodium salt It may be selected from one type or two or more types, etc., but is not limited thereto. As a more specific example, it may be 2-sulfoethyl methacrylate potassium salt.

In Formula 2, R ₂ is hydrogen or C1 to C3 alkyl, and M is any one selected from lithium, sodium, potassium and ammonium salts.

The alkyl (meth)acrylate-based monomer used in the preparation of the dispersion stabilizer is not limited as long as it is a compound clearly known in the art. More specifically, the alkyl (meth) acrylate-based monomer is methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, benzyl One or two or more types may be selected from the group consisting of methacrylate, methoxyethyl methacrylate, ethoxyethyl methacrylate, butoxymethyl methacrylate and hydroxyethyl methacrylate, but limited thereto it is not going to be More preferably, it may be methyl methacrylate. When the dispersion stabilizer is prepared with methyl methacrylate, which is the same monomer as the monomer from which the light-diffusion bead was prepared, the light transmittance of the light-diffusion bead can be improved, which is better.

The content range of the dispersion stabilizer mixture may consist of 10 to 85 wt% of the monomer of Formula 1, 5 to 45 wt% of the monomer of Formula 2, and 10 to 45 wt% of the alkyl (meth)acrylate monomer, and the dispersion The stabilizer may be a copolymer obtained by uniformly polymerizing the monomer mixture in the above range in an aqueous solution.

The weight average molecular weight of the dispersion stabilizer may be 20,000 to 300,000 g/mol. Specifically, it may be 50,000 to 200,000 g/mol, and more specifically, 60,000 to 80,000 g/mol, but is not particularly limited thereto.

In the case of the light-diffusion beads prepared using the dispersion stabilizer, control of particle size and inter-particle agglomeration may be facilitated, matt properties may be remarkably improved, and yellowness may be reduced.

The content of the dispersion stabilizer according to an embodiment of the present invention is not limited, but may be included in an amount of 0.001 to 10 parts by weight based on 100 parts by weight of the above-described methyl methacrylate monomer mixture. More preferably 0.01 to 5 parts by weight may be included, and polymerization stability may be maintained within the above range, and the average particle diameter and particle size distribution of the light-diffusion bead particles may be controlled, but is not limited thereto.

In addition, when the above range is satisfied, uniform cross-linked polymer particles can be obtained, polymerization stability can be improved, loss can be prevented in washing and drying processes, and economic efficiency can be improved due to improved workability. Even better.

In addition, if necessary, it may further include a dispersing aid, and any dispersing aid clearly known in the art may be used without limitation. Specific examples include magnesium sulfate, sodium sulfate, ammonium sulfate, and the like.

The average particle diameter of the light-diffusion beads may be 10 to 100 ㎛. Specifically, it may be 20 to 70 μm, and more specifically, 30 to 60 μm, but is not particularly limited. In the case of the light-diffusion sheet manufactured using the light-diffusion bead satisfying the above range, it may be very good to improve light diffusivity and matte properties and reduce haze, but is not limited thereto.

In addition, the light-diffusion beads satisfying the above range may have a remarkable matte improvement effect, and may prevent agglomeration between particles to improve transmittance. In addition, the problem of surface imbalance due to particle protrusion during the conventional extrusion process can be solved, and mechanical properties such as optical properties deterioration and impact strength can be improved.

The particle size distribution of the light-diffusion beads may be 1 to 3, specifically, 1 to 2. The light-diffusion beads satisfying the above range may have a very uniform particle size distribution, and when a light-diffusion sheet is manufactured using the light-diffusion beads, have a matte effect and constant appearance characteristics, and improve light diffusion and matte properties It is very nice to be able to

The particle size distribution (SPAN) of the light diffusion beads was measured using a light diffraction particle size analyzer (Malvern Mastersizer 2000), and a particle size distribution (SPAN) value expressed by Equation 1 below was derived.

[Equation 1] Particle size distribution (SPAN) = (Dv90 - Dv10) / Dv50

In Equation 1, Dv50 represents a medium particle size among polymers generated through polymerization, and Dv90 represents a particle size corresponding to the top 10% of polymers generated through polymerization (90% from small particle size to large particle size) , and Dv10 represents the particle size (10% from small particle size to large particle size) corresponding to the top 10% of polymers produced through polymerization.

The light-diffusion beads use methyl methacrylate monomer alone, and cross-linked polymer particles having excellent light diffusivity, easy haze control, and excellent polymerization stability and thermal stability can be prepared.

The polymerization method of the light-diffusion beads can be prepared by bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization using the existing free radical polymerization method, but suspension polymerization in minimizing contamination by foreign substances and securing the desired bead particle size This is preferable.

The light-diffusion beads may be prepared using a crosslinking agent to have a light-diffusion bead having a spherical structure. The particle diameter ratio (major axis/minor axis) of the light-diffusion bead may be in the range of 1.0 to 1.2, preferably in the range of 1.0 to 1.1, and may have a very spherical shape.

The crosslinking agent may be included to improve solvent resistance and durability, and polyfunctional monomers, polyfunctional oligomers, or mixtures thereof which are known in the art may be used. More specifically, the polyfunctional monomer is divinylbenzene, ethylene glycol dimethacrylate, 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, ethylene glycol diacrylate, fetaerythritol triacrylate, trimethylene propyl Triacrylate, propoxylated glycerol triacrylate, trimethylopropane ethoxy triacrylate, propoxylated glycerotriacrylate, pentaerythritol tetraacrylate, dipentaerythritol hydroxy pentaacrylate, dipentaerythritol One or two or more types may be selected from the group consisting of hexaatrylate and the like, and may be, for example, ethylene glycol dimethacrylate, but is not limited thereto.

The content of the crosslinking agent according to an embodiment of the present invention may be included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the above-described monomer mixture. More preferably 2 to 8 parts by weight may be included, but is not limited thereto. The higher the content of the crosslinking agent, the higher the glass transition temperature of the light-diffusion sheet manufactured using the light-diffusion bead, so that thermal stability can be improved.

As the polymerization initiator used in the polymerization method of the light-diffusion beads, a commercially available peroxide initiator and an azo-based initiator may be used as a free radical polymerization method, and benzoyl peroxide may be used as an example, but is not particularly limited thereto.

The light-diffusion beads may further include a chain transfer agent to control the molecular weight of the polymer. The chain transfer agent is not limited as long as it is a compound clearly known in the art, and preferably a (C1-C12)alkyl mercaptan having one thiol functional group or polythiol mercaptan having two or more thiol functional groups may be used, and as an example, n-octyl mercaptan may be used, but is not limited thereto.

Light-diffusion beads according to an embodiment of the present invention may further include additives generally used in the art, depending on the purpose and use. For example, it may further include antioxidants, UV stabilizers, heat stabilizers, lubricants, and the like. In this case, the additives may be included in an appropriate amount within a range that does not impair the physical properties of the light-diffusion bead, for example, 0.1 to 5 parts by weight based on 100 parts by weight of the methyl methacrylate monomer.

The glass transition temperature (Tg) of the light-diffusion beads may be 120° C. or higher, and the temperature at which a 2% weight loss occurs (2% Td) may be 285° C. or higher. In the case of a light-diffusion sheet satisfying the above range, it can be applied to a backlight for a liquid crystal display that is used for a long time, a lighting device, a signboard, or a glass showcase, etc. because of its excellent thermal properties.

According to one embodiment of the present invention, it is possible to provide a method of manufacturing a light diffusion bead. The manufacturing method of the light-diffusing sheet is

(a) stirring a reaction mixture in which a monomer, a crosslinking agent, and a dispersion stabilizer are added to water at room temperature;

(b) raising the reaction temperature to perform a polymerization reaction;

includes,

The monomer is a methyl (meth) acrylate-based monomer is used alone,

The dispersion stabilizer is prepared by polymerizing a mixture for a dispersion stabilizer including the following Chemical Formulas 1 and 2 and an alkyl (meth)acrylate-based monomer,

The light-diffusion beads may have an average particle diameter of 10 to 100 μm, and a particle size distribution of 1 to 3, which may be a method of manufacturing the light-diffusion beads.

[Formula 1]

In Formula 1, R ₁ is hydrogen or C1 to C3 alkyl, n is an integer selected from 1 to 3, and M may be any one selected from lithium, sodium, potassium and ammonium salts.

[Formula 2]

In Formula 2, R ₂ is hydrogen or C1 to C3 alkyl, and M may be any one selected from lithium, sodium, potassium and ammonium salts.

Examples of specific compounds of Formulas 1 and 2 are the same as described above.

In step (a), the reaction mixture in which the monomer, crosslinking agent, and dispersion stabilizer are added to water is stirred at room temperature, and dissolved and dispersed for a sufficient time and stirring speed, and the time and stirring speed are not significantly limited thereto. In this case, it may be dispersed by further including a dispersing aid, a chain transfer agent, and an initiator.

The step (a) is performed to sufficiently disperse the mixture, and the droplets of the reaction mixture dispersed in water may be sufficiently stirred so that the droplets are small and evenly spread.

As an example, stirring may be performed at 500 rpm or more based on a 5L reactor, but is not limited thereto, and stirring can be performed to the extent that the particle size of the light-diffusion beads is obtained by satisfying the range of 10 to 100 μm. .

In step (b), the polymerization reaction of the light-diffusion beads is performed through the step of performing a polymerization reaction by raising the reaction temperature.

The polymerization reaction temperature of step (b) may be increased to 60° C. to 90° C., and the time may be performed for 1 hour to 3 hours, but is not limited thereto.

After step (b), an additional polymerization step may be further included, wherein the additional polymerization step is performed by raising the temperature to 100° C. to 130° C. for 30 minutes to 60 minutes, followed by cooling to 30° C. to 50° C. However, the present invention is not limited thereto.

The additional polymerization step may be performed to remove reactivity with respect to monomers, initiators, etc. remaining in the polymerization solution, and then the obtained polymer may be repeatedly washed and dehydrated with distilled water, and then dried to obtain final light-diffusion beads.

According to another embodiment of the present invention, it is possible to provide a light-diffusion sheet manufactured using the above-described light-diffusion beads. The light-diffusion sheet may be a light-diffusion sheet obtained by extruding the above-described light-diffusion beads. Specifically, the light-diffusion sheet may be manufactured to further include a light-diffusion bead or a master batch chip used in the art, depending on the purpose and use, but is not particularly limited thereto. The light-diffusion sheet may be provided by adjusting the type and content of the light-diffusion beads to be mixed so as to have desired light-diffusion performance, light transmittance, and haze according to the intensity and structure of the light source.

The light-diffusion sheet according to an embodiment of the present invention may have a light transmittance of 80% or more, preferably 85% or more, measured according to ASTM D1003. The yellowness (YI) of the light diffusion sheet may be in the range of 0.01 to 1, preferably 0.01 to 0.1. The light diffusion sheet satisfying the above range can be applied as a lighting cover and an exterior material for home appliances due to a remarkably low yellowness, and it is good because it can have an appearance that can be dyed through an organic dye or an inorganic dye. In addition, the light-diffusion sheet can be applied to a light-diffusion lighting device and a backlight for a liquid crystal display.

The light-diffusion sheet according to an embodiment of the present invention may have a haze measured according to ISO 14782 of 60 or less, preferably 55 or less, and the light-diffusion sheet satisfying this has high transmittance, so it can serve as a diffusing agent. have.

The light diffusion sheet may have a yellowing occurrence time of 6 hours or more, preferably 7 hours or more, and more preferably 8 hours or more, as measured in accordance with ISO 13468-1. The light-diffusion sheet satisfying the above range does not cause color distortion even when the backlight is used for a long time, and can serve as an excellent light-diffusing plate.

According to another embodiment of the present invention, it is possible to provide a light-diffusion sheet prepared including the above-described light-diffusion beads and polymethyl methacrylate resin. The light-diffusion sheet may include 1 to 50 parts by weight, specifically, 10 to 30 parts by weight of the light-diffusing beads based on 100 parts by weight of the polymethacrylate resin.

The weight average molecular weight of the polymethyl methacrylate resin may be 20,000 to 300,000 g/mol, specifically, 50,000 to 200,000 g/mol, but is not limited thereto.

The light-diffusion sheet according to an embodiment of the present invention is a mixture of a light-diffusion bead prepared using a specific dispersion stabilizer and a methyl methacrylate monomer prepared in an embodiment of the present invention and a methyl methacrylate resin of the same series In the case of manufacturing this, remarkably improved light transmittance and low haze can be obtained, which can be suitable for long-time use of backlights for liquid crystal displays, lighting devices, signboards, or glass showcase lighting devices.

According to another embodiment of the present invention, it is possible to provide a master batch chip (Master Batch Chip) manufactured using the above-described light diffusion beads.

Hereinafter, a preferred embodiment and a method for measuring physical properties of the light-diffusion bead of the present invention and a light-diffusion sheet manufactured using the same will be described in detail.

How to measure physical properties

1) Measure average particle size (Mode) and particle size distribution (SPAN)

The average particle diameter (mode) and particle size distribution (SPAN) of the light-diffusion beads prepared in Examples and Comparative Examples were measured using the Melbourne Mastersizer 2000S instrument.

2) Light Transmission (LT) and Yellow Index (YI)

Light transmittance and yellowness were measured for the light diffusion sheets prepared in Examples and Comparative Examples according to ASTM D1003.

3) haze

It was measured using a haze transmittance meter (HR-100, Murakami Color Research Laboratory) according to ISO 14782.

4) Matte property of the specimen

- Matte emotional evaluation

When observed with the naked eye, if the particle distribution of the specimen was uniform and rough to the touch, the matte property was evaluated as "good", if the particle distribution looked uneven and smooth, it was evaluated as "poor", and if it was moderate, it was evaluated as "medium".

- Surface roughness evaluation

The optical profiler system used to measure the surface roughness was measured with Nano View NV-2700 (Manufacturer: Nanosystem Korea), and the analysis conditions were scan with an objective lens 20x x eyepiece 1x (F.O.V: 318um x 238um) The range was measured at +- 20um.

5) Thermal properties

-Glass transition temperature: It was measured in the range of 25~250℃ at a rate of 5℃ per minute using a DSC (Differential scanning calorimeter, TA DSC 2010) device.

- Temperature at which 2% weight loss occurs (2% Td): Thermogravimetric analysis (Thermal

Gravimetric Analysis) was used to measure the weight loss according to temperature by increasing the temperature from 25°C to 500°C at 10°C per minute.

6) Yellowing resistance

10 g of a diffusion sheet dried in a convection oven at 150° C., 200° C., and 230° C. was weighed into an aluminum dish and sampled every 30 minutes for a total of 10 hours to measure the degree of yellowing. The degree of yellowing can be measured using Hunter LAB's Color quest XE to measure the yellowness, L*, a*, b* values of the sample according to ISO 13468-1. The yellowing resistance is indicated by the yellowing time compared to the existing sample.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples. However, the following examples and comparative examples are merely examples for explaining the present invention in more detail, and the present invention is not limited by the following examples and comparative examples.

[Production Example 1]

<Production of dispersion stabilizer>

In a three-neck flask with a condenser, 24.2 g of methyl methacrylate and 15.9 g of potassium hydroxide (KOH, purity 85%) were put together with 2,000 g of water and reacted in a nitrogen atmosphere at room temperature for 1 hour. 180 g of 2-sulfoethyl methacrylate potassium salt and 700 g of water are additionally added thereto, and 45 g of methyl methacrylate, 2,2'-azobis(2-amidinopropane)dihydrochloride (2,2'-Azobis) (2-amidinopropane) dihydrochloride) 0.3 g was added and polymerization was started at 50 °C. When the reaction temperature reached 60° C., 4.5 g of methyl methacrylate monomer was dividedly added 6 times at intervals of every 6 minutes from 15 minutes onwards. After reacting at the same temperature for a total of 6 hours, it was cooled to obtain a 5 wt% polymer aqueous solution.

[Example 1]

<Production of light-diffusion beads>

3000 g of distilled water was put into a 5 liter reactor, 40 g of a dispersion stabilizer of the 5% aqueous solution of Preparation Example 1, and 15 g of sodium sulfate as a dispersion aid were added and dissolved. 1000 g of methyl methacrylate, 20 g of ethylene glycol dimethacrylate as a crosslinking agent, 4.0 g of n-octyl mercaptan as a chain transfer agent, and 2.0 g of benzoyl peroxide as an initiator were added, and the monomer mixture was dispersed in the aqueous phase while stirring at 500 rpm. The mixture was polymerized at 80° C. for 1 hour and 20 minutes, then heated to 105° C. to conduct additional polymerization for 30 minutes, and then cooled to 30° C. The cross-linked polymer particles obtained by the polymerization reaction were repeatedly washed with distilled water and dehydrated, and then dried.

[Example 2]

As shown in Table 1 below, except that the polymerization temperature was changed during the preparation of the light-diffusion beads, it was prepared in the same manner as in Example 1, and the physical properties were measured and shown in Table 2 below.

[Examples 3 to 4]

As shown in Table 1 below, except that the polymerization temperature and the composition of the reactants were changed during the preparation of the light-diffusion beads, it was prepared in the same manner as in Example 1, and the physical properties were measured and shown in Table 2 below.

[Comparative Examples 1 to 4]

As shown in Table 1 below, except that the composition of the monomer and the type of dispersion stabilizer were changed during the preparation of the light-diffusion beads, it was prepared in the same manner as in Example 1, and the physical properties were measured and shown in Table 2 below.

<Manufacturing of light diffusion sheet>

After mixing 80 wt% of a polymethyl methacrylate product (LG MMA, IH830L) and 20 wt% of the light-diffusion beads prepared in Examples 1 to 4 and Comparative Examples 1 to 4 using a tumbler, light diffusion through an extruder A resin composition pellet was obtained, and after drying the pellet, a sheet-shaped specimen having width, length and thickness of 70 mm x 75 mm x 2.5 mm was prepared by an injection machine. The physical properties were measured and shown in Table 2 below.

Unit (g) Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 monomer MMA 1000 1000 1000 1000 1000 500 500 700 ST - - - - - 500 500 300 crosslinking agent 20 20 40 80 20 20 20 20 dispersion stabilizer type Preparation Example 1 Preparation Example 1 Preparation Example 1 Preparation Example 1 5 wt% PVA 5 wt% PVA Preparation Example 1 Copolymer of methacrylic acid and methacrylic ester content 40 40 40 40 40 40 40 40 dispersion aid 15 15 15 15 15 15 15 15 polymerization temperature 80 75 75 70 80 80 80 80 initiator 2 2 2 2 2 2 2 2 chain transfer agent 4 4 4 4 4 4 4 4

In Table 1, MMA means a methyl methacrylate monomer, ST means a styrene monomer, and PVA means polyvinylalcohol.

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 light diffusion bead Average particle diameter (㎛) 59.5 53.7 45.8 58.9 340 200 65.1 150 particle size distribution 1.84 1.8 1.37 1.28 10 9 3.5 9 particle diameter ratio 1.08 1.07 1.05 1.02 1.32 1.30 1.25 1.21 Tg(℃) 124 125 125 131 105 95 112 106 2% Td(℃) 290 292 287 290 195 250 250 250 light diffusing sheet Light transmittance (%) 90 90.5 90.7 90.2 88 75 77 71 Haze (%) 36 38 55 44 80 85 90 70 Yellowness (%) 0.01 0.04 0.05 0.1 1.1 1.4 1.4 1.3 Yellowing resistance (hr) 8 8 10 8 3 2 2 3 matte middle Good Good middle error error error error

As shown in Table 2, in Examples 1 to 4, by using the dispersion stabilizer according to the present invention, the production of crosslinked polymer particles having a small size is easily and uniformly formed, the particle size distribution is uniform, and the average particle diameter is 30 to It was found that there is a characteristic of 60 μm.

However, in Comparative Examples 1 and 2 using a generally widely used dispersant, it can be seen that the particle size is relatively large and the particle size distribution is also wide, which is difficult to disperse during extrusion with general polymethyl methacrylate resin during processing. There may be problems, and there is a risk that the beauty and uniformity of the final light-diffusing lighting device may be deteriorated. When this was applied as a light-diffusion sheet, it was confirmed that the yellowness was high and the matte property when touched by hand was also clearly deteriorated. In addition, comparing Example 1 with Comparative Example 3, as shown in Example 1, when Preparation Example 1, which is a dispersion stabilizer of the present invention, and MMA as a monomer are used alone, light transmittance and yellowing resistance are excellent, and low haze and yellow color It could be confirmed that there is a diagram. In Comparative Example 3, Preparation Example 1 was used in the same manner, but it was confirmed that haze increased and yellowing resistance decreased when ST monomer was mixed.

The light-diffusion sheets of Examples 1 to 4 used the light-diffusion beads using the MMA monomer and the dispersion stabilizer of the present invention, and were mixed with the polymethyl methacrylate resin of the same series as the light-diffusion beads of the present invention. It has light transmittance and low haze, so it is suitable for use in backlights for liquid crystal displays, lighting devices, signboards, or glass showcase lighting devices.

As described above, the present invention has been described with reference to specific matters and limited examples and drawings, but these are only provided to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments, and the present invention is not limited to the above embodiments. Various modifications and variations are possible from these descriptions by those of ordinary skill in the art.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and not only the claims to be described later, but also all those with equivalent or equivalent modifications to the claims will be said to belong to the scope of the spirit of the present invention. .

Claims (14)

A light-diffusion bead polymerized including a monomer, a crosslinking agent and a dispersion stabilizer, comprising:
As the monomer, methyl methacrylate monomer is used alone,
The dispersion stabilizer is prepared by polymerizing a mixture for a dispersion stabilizer including the following Chemical Formulas 1 and 2 and an alkyl (meth)acrylate-based monomer,
The light diffusion beads have an average particle diameter of 10 to 100 μm, and a particle size distribution of 1 to 3.
[Formula 1]

(In Formula 1, R ₁ is hydrogen or C1 to C3 alkyl, n is an integer selected from 1 to 3, and M is any one selected from lithium, sodium, potassium and ammonium salts.)
[Formula 2]

(In Formula 2, R ₂ is hydrogen or C1 to C3 alkyl, and M is any one selected from lithium, sodium, potassium and ammonium salts.) The method of claim 1,
The particle diameter ratio (major axis/minor axis) of the light-diffusion bead is in the range of 1.0 to 1.2. The method of claim 1,
The light-diffusion beads are light-diffusion beads comprising 0.001 to 10 parts by weight of a dispersion stabilizer based on 100 parts by weight of a methyl (meth)acrylate-based monomer. The method of claim 1,
The light-diffusion beads are light-diffusion beads comprising 0.1 to 10 parts by weight of a crosslinking agent based on 100 parts by weight of a methyl (meth)acrylate-based monomer. The method of claim 1,
The glass transition temperature (Tg) of the light-diffusion bead is 120 ℃ or more, the temperature at which a 2% weight loss occurs (2% Td) is 285 ℃ or more of the light-diffusing bead. (a) stirring a reaction mixture in which a monomer, a crosslinking agent, and a dispersion stabilizer are added to water at room temperature;
(b) raising the reaction temperature to perform a polymerization reaction;
includes,
The monomer is a methyl (meth) acrylate-based monomer is used alone,
The dispersion stabilizer is prepared by polymerizing a mixture for a dispersion stabilizer including the following Chemical Formulas 1 and 2 and an alkyl (meth)acrylate-based monomer,
The average particle diameter of the light-diffusion beads is 10 to 100 μm, and the particle size distribution is 1 to 3.
[Formula 1]

(In Formula 1, R ₁ is hydrogen or C1 to C3 alkyl, n is an integer selected from 1 to 3, and M is any one selected from lithium, sodium, potassium and ammonium salts.)
[Formula 2]

(In Formula 2, R ₂ is hydrogen or C1 to C3 alkyl, and M is any one selected from lithium, sodium, potassium and ammonium salts.) A light-diffusion sheet manufactured including the light-diffusion bead of any one of claims 1 to 5. 8. The method of claim 7,
The light-diffusing sheet has a light transmittance of 80% or more, and a yellowness (YI) of 0.01 to 1, measured according to ASTM D1003. 8. The method of claim 7,
The light diffusing sheet is a light diffusing sheet having a haze measured according to ISO 14782 of 60 or less. 8. The method of claim 7,
The light-diffusing sheet is a light-diffusing sheet having a yellowing occurrence time of 6 hours or more, measured in accordance with ISO 13468-1. 8. The method of claim 7,
The light-diffusion sheet is a light-diffusion sheet manufactured by further comprising a polymethyl methacrylate resin. 12. The method of claim 11,
The light-diffusing sheet is a light-diffusing sheet comprising 1 to 50 parts by weight of light-diffusion beads based on 100 parts by weight of the polymethacrylate resin. 12. The method of claim 11,
The weight average molecular weight of the polymethyl methacrylate resin is a light diffusion sheet of 20,000 to 300,000 g / mol. A master batch chip manufactured including the light diffusion beads of any one of claims 1 to 5 selected from the group consisting of (Mater Batch Chip).