WO2006046481A1

WO2006046481A1 - Optical methacrylic resin extrusion plate manufacturing method

Info

Publication number: WO2006046481A1
Application number: PCT/JP2005/019390
Authority: WO
Inventors: Shunji Kamiya; Yoshikazu Tsuruta
Original assignee: Asahi Kasei Chemicals Corporation
Priority date: 2004-10-28
Filing date: 2005-10-21
Publication date: 2006-05-04
Also published as: JP4717008B2; KR100857501B1; TWI275477B; TW200628287A; CN101035665A; CN101035665B; KR20070043815A; JPWO2006046481A1

Abstract

There is provided a methacrylic resin extrusion plate formed by a mixture having an apparent density of 0.80 g/ml or above prepared by mixing methacrylic resin polymer of a definite shape having an apparent density of 0.63 g/ml to 0.78 g/ml and methacrylic resin polymer of an indefinite shape having an apparent density of 0.55 g/ml to 0.63 g/ml. The plate thickness accuracy in the width direction is controlled to be within ± 1.0% of the average plate thickness. The methacrylic resin extrusion plate for a light guide plate is preferably used for office automation devices such as a personal computer and a word processor, display devices used for various monitors displaying an image signal such as a panel monitor and a television monitor, display devices used for indoor or outdoor illumination devices and sign boards.

Description

Specification

Method for producing methacrylic resin extrusion plate for optics

Technical field

The present invention is used for office automation equipment such as personal computers and word processors, various monitors for displaying image signals, for example, display devices used for panel monitors, television monitors and the like, and surface light source devices for indoor and outdoor spaces. The present invention relates to a method for producing a methacrylic resin extruded plate for a light guide plate suitable for a display device or a signboard.

Background art

[0002] Transparent thermoplastic resin, and in particular, methallyl resin, in particular, has been used for many lighting applications because of its excellent light transmission and mechanical properties. It has come to be used as a light guide plate for backlights of display devices. There are two commonly used backlight systems: the so-called direct type, in which the light guide plate is sandwiched between the light source and the liquid crystal unit, and the edge light method in which the light source is attached to the edge of the light guide plate. The method has become mainstream. In recent years, development has continued under the concept of brighter, larger and thinner products, where the demand for higher brightness, larger size, and thinner display devices is stronger. In particular, there is a strong demand for the development of high-intensity surface emitting devices using the edge light method.

[0003] For this reason, the light guide plate used in the light source device also has a great demand for a light guide plate that efficiently emits incident light of light incident from the light source lamp disposed on the side surface to the output surface. It is getting stronger.

[0004] However, in a normal extruded plate, although the thickness variation in the extrusion direction is small, the light incident from the light source lamp disposed in the light source device in which the thickness variation in the width direction is large is irregularly emitted. However, the brightness uniformity is inferior and high brightness cannot be obtained.

A number of technical disclosures have been made so far regarding the method of increasing the brightness using the light guide plate. For example, a method of obtaining a uniform light emitting surface by dispersing and diffusing light diffusing particles in a light guide plate (see, for example, Patent Document 1), and a light scattering plastic material including fine particles having different refractive indexes in a light guide. A method of increasing the brightness by using it is disclosed. (For example, see Patent Document 2), the process is complicated.

[0005] Patent Document 1: Japanese Patent Publication No. 39-1194

Patent Document 2: JP-A-4-145485

Disclosure of the invention

Problems to be solved by the invention

[0006] However, in addition to the technology using methacrylic resin containing these complicated fine particles, the level can sufficiently meet the demands associated with the increase in size and thickness of display devices, such as brightness and luminance spots. It is the current situation that has been reached.

[0007] An object of the present invention is suitable for various monitors that display image signals, for example, display devices used for panel monitors, television monitors and the like, and display devices and signboards used for indoor and outdoor lighting devices. An object is to provide a methacrylic resin extruded plate for a light guide plate and a method for producing the same.

Means for solving the problem

[0008] As a result of intensive studies to solve the above-mentioned problems, the present inventors mixed a metataryl resin extruded material having an irregular shape with a metataryl resin extruded material having a fixed shape at a specific ratio, and then extrusion molding. By using the methacrylic resin plate used as a light guide plate, it was found that the brightness was increased and the brightness unevenness was reduced, and the present invention was completed.

That is, the present invention

[1] The apparent density between the apparent density methacrylic resin having an apparent density of 0.63 gZml to 0.78 gZml and the amorphous methacrylic resin polymer having an apparent density of 0.55 gZml to 0.63 gZml is at least 0.80 gZml. The resulting mixture is extruded, and the thickness is 2.0-15. Omm, and the thickness accuracy in the width direction is within ± 1.0% of the average thickness. Method for producing a methacrylic resin extruded plate for

[2] The light guide plate according to claim 1, wherein the plate thickness is 3.5 to 8.5 mm, and the plate thickness accuracy in the width direction is within ± 0.5% of the average plate thickness. For producing methacrylic resin extruded plate for

[3] A methacrylic resin extruded plate for a light guide plate produced by the method described in 1 or 2 above. [0009] The present invention will be specifically described below.

[0010] The methacrylic resin used in the present invention is methyl methacrylate! The / soot can be obtained by copolymerizing 70% by weight or more of methacrylic acid methacrylate and a monomer having copolymerizability with these. Monomers that are copolymerizable with these include butyl methacrylate, ethyl methacrylate, methyl methacrylate, propyl methacrylate, cyclohexyl methacrylate, methacrylate methacrylate, 2-ethylhexyl methacrylate, etc. Methacrylic acid esters, Methyl acrylate, Ethyl acrylate, Butyl acrylate, Acrylic acid cyclohexyl, Acrylic acid ester, Acrylic acid ester such as 2-Ethylhexyl acrylate, Methacrylic acid, Acrylic The power of unsaturated acids such as acids is not limited to these.

The regular-shaped methacrylic resin extruded raw material used in the present invention is a spherical, cylindrical or flat methacrylic resin obtained by a polymerization reaction. The unshaped metataryl resin extrusion raw material is methacrylic resin obtained by mechanically crushing a methacrylic resin molding once formed into a plate shape.

[0011] The spherical methacrylic resin is obtained by a suspension polymerization method. The suspension polymerization method will be described.

First, a polymerization initiator and a chain transfer agent are uniformly dissolved in a monomer mixture consisting of methyl methacrylate or ethyl methacrylate and another monomer. The homogeneously dissolved product is suspended in an aqueous medium containing a dispersion stabilizer and then held at a predetermined polymerization temperature for a certain period of time to complete the polymerization. The resulting turbid polymer is filtered, washed with water and dried. Is obtained. The polymerization initiator used in suspension polymerization may be a radical polymerization initiator known for polymerization of vinyl monomers. For example, azobisisobutyrate-tolyl, 2,2 'azobis (2,4 dimethylvale-tolyl), dimethyl-2,2, -azobisisobutyrate, tert-butylperoxypivalate, tert-butylperoxy 2- Examples include ethyl hexaate, cumyl paroxy 2-ethyl hexanoate, benzoyl peroxide, lauroyl peroxide, and the like. These radical polymerization initiators are preferably used in an amount of usually 0.01 to 2.0 parts by weight per 100 parts by weight of the monomer or monomer mixture. The chain transfer agent used in the suspension polymerization may be a well-known one used for polymerization of methyl methacrylate. For example, t-butyl mercaptan, n-butyl mercaptan, Examples thereof include n-octyl mercaptan and n-dodecyl mercaptan. The amount of these chain transfer agents used is usually preferably in the range of 0.01 to 2.0 parts by weight per 100 parts by weight of the monomer or monomer mixture.

The dispersion stabilizer used in the suspension polymerization is not particularly limited. However, it is a poorly water-soluble inorganic compound such as calcium phosphate, calcium carbonate, and aluminum hydroxide, polybutal alcohol, polyethylene oxide, and cellulose derivative. -On-based polymer compounds, polyacrylic acid and its salts, polymethacrylic acid and its salts, copolymer of methacrylic acid ester and methacrylic acid and its salts, etc. . The amount of these dispersion stabilizers used is preferably in the range of 0.01 to 5.0 parts by weight per 100 parts by weight of water.

Examples of water used in the suspension polymerization include pure water, ion exchange water, and deionized water. The amount of water used is not particularly limited, but is preferably in the range of 100 to 250 parts by weight per 100 parts by weight of the monomer or monomer mixture! /.

The polymerization temperature for suspension polymerization is not particularly limited, but is about 60 to 120 ° C and is suitable for the polymerization initiator used. As a polymerization apparatus, a polymerization vessel equipped with a well-known stirring blade, for example, a turbine blade, a fiddler blade, a propeller blade, a blue margin blade, or the like, is used, and the vessel is provided with a kaffle. Is common.

Furthermore, if necessary, a release agent, a colorant, an ultraviolet absorber, an antioxidant, a light diffusing agent, a plasticizer, etc. may be suspended and polymerized.

After the completion of the suspension polymerization, the spherical methacrylate resin can be obtained by washing, dehydrating and drying by a known method.

The average particle size of the spherical methallyl succinic polymer, which is an important constituent of the present invention, is 0.2 to 0.5 mm, preferably 0.25 to 0.39 mm. Good plate thickness accuracy can be obtained when the thickness is 0.2 mm or more, and a polymer having an average particle diameter of 0.5 mm or less can be stably produced. Further, when the apparent density is in the range of 0.70 g / ml to 0.78 g / ml, good thickness accuracy can be obtained.

Next, a columnar or flat methacrylic resin, which is an important constituent element of the present invention, will be described. Cylindrical methacrylic resin is a spherical polymer obtained by suspension polymerization. Tacryl resin can be supplied to an extruder equipped with a vent, extruded at a temperature of 220 to 260 ° C and vented vacuum pressure of 1.3 to 8 kPa in a strand from an extrusion die, water cooled, and cut with a strand cutter. Alternatively, a molten methacrylic resin polymer obtained by a known solution polymerization method or bulk polymerization method can be extruded into a strand shape from an extrusion die, cooled with water, and cut with a strand cutter. The flat methacrylic resin can be extruded from an extruder with a vent in the same manner as in the production of the cylindrical methacrylic resin, and then cut with an underwater cutter.

Examples of the solution polymerization method and the bulk polymerization method include the following methods. The solvent in the solution polymerization method has a higher boiling point than the methyl methacrylate monomer, the methyl methacrylate monomer, and the monomer copolymerizable with methyl methacrylate at the bottom and inside of the distillation column. Is preferred. Specifically, aromatic compounds such as toluene, xylene, ethylbenzene, and jetylbenzene, aliphatic compounds such as octane and decane, alicyclic compounds such as decalin, esters such as butyl acetate and pentyl acetate, 1, And halogen compounds such as 1, 2, 2-tetrachloroethane. Especially alkylbenzene, and moreover toluene

Xylene and ethylbenzene are preferable because they have an appropriate boiling point, are less degassed, and have no adverse effect on polymerization. The amount of the solvent varies depending on the boiling point of the solvent. The amount of the solvent is 30% by weight or less, preferably 20% by weight or less, based on the weight of the entire mixture at the time of polymerization. If no solvent is used during polymerization, bulk polymerization occurs.

The polymerization initiator used in the solution polymerization method and bulk polymerization method is one that decomposes actively at the polymerization temperature to generate radicals. Ketone peroxide, di-t-butyl perphthalate, di-t-butyl perbenzoate, t-butyl peracetate, 2,5-dimethyl-2,5-di (tert-butylberoxy) hexane, 1,1-bis (t-butylperoxy) — 3, 3, 5 Trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, di-t-amyl peroxide, benzoyl peroxide, cumene hydride peroxide, lauryl baroxide, azobisisobutanol di Acetate, 1, 1'-azobiscyclohexanecarbo nitrile, 2 phenyl 2, 4, dimethyl mono 4-methoxyvalero- Lil, 2 Shiano 2, 2-propyl § zone Holm § Sid, 2, 2, over § zone bis isobutyronitrile port - be mentioned tolyl I can do it. The amount of these polymerization initiators used is preferably 0.001 to 0.03% by weight based on the weight of the total reaction mixture.

In addition, mercabtans are mainly used as the molecular weight regulator used in this case. Examples of the mercaptans include n-butyl mercaptan, isobutyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, sec-dodecyl mercaptan, t-butyl mercaptan, felt mercaptan, tiocresol, thioglycolic acid and the like. Examples thereof include esters and ethylenethioglycol. The amount of these molecular weight modifiers used is preferably 0.01 to 0.5% by weight based on the weight of the total reaction mixture.

The polymerization reactor uses a device that is stirred uniformly with a stirring blade such as a double helical ribbon or pitched paddle type. In the polymerization, the monomer or monomer solution is continuously supplied to the polymerization reactor, and the polymerization conversion rate of the monomer is substantially constant within a range of 0 to 70%. The polymerization reaction is carried out at a temperature of 160 ° C. The polymerization conversion rate is preferably 40% or more, and the load of the devolatilization process due to the volatile components is reduced. On the other hand, if it is 70% or less, for example, the piping pressure loss between the polymerization reactor and the pre-heater is reduced, so that the polymerization liquid can be easily transported. When the polymerization temperature is 120 ° C or higher, the polymerization rate is practical. When the polymerization temperature is 160 ° C or lower, the polymerization rate is appropriate, and the polymerization conversion rate can be easily adjusted. Further, it is preferable since the heat decomposability is not lowered.

The polymerization solution obtained by such a polymerization reaction is devolatilized and the polymer is taken out. As the devolatilizer, an extruder with a multistage vent, a devolatilization tank, or the like is used. Preferably, the polymerization solution is superheated to a temperature of 200 to 290 ° C with a pre-heater or the like, has a sufficient space at the top, and 200 to 250 ° C, a temperature of 2.7 to 13 kPa, under vacuum Feed to the devolatilization tank and take out the polymer.

This polymer is continuously transferred to an extruder in a molten state, extruded through a die from a die into a strand, cooled with water, and cut with a strand cutter to obtain a cylindrical polymer. The flat methacrylic resin can be extruded from an extruder in the same manner as in the production of the cylindrical methacrylic resin, and then cut with an underwater cutter. Furthermore, if necessary, before cutting, a release agent, a colorant, an ultraviolet absorber, an antioxidant, a light diffusing agent, a plasticizer, and the like are added using a feed pump from the side portion of the extruder. That's right.

[0014] The shape of the columnar polymer, which is an important component of the present invention, is defined by the major axis (al), minor axis (b 1), and length (L) of the cross section. The major axis (al) and minor axis (bl) are both 2.000-4. OOOmm, (bl) Z (al) = 0.66 ~: L 00, and the length (L) is 2.000 ~ 5. OOOmm. It is preferable that the thickness is within this range because good thickness accuracy can be obtained.

[0015] The shape of the flat polymer, which is an important component of the present invention, is defined by the major axis (a2), minor axis (b2), and thickness (T). Both the major axis (a2) and minor axis (b2) are 2. 000-4. OOOmm, (b2) / (a2) = 0.66 ~: L.00, and the thickness (T) is 1.000. ~ 3. OOOmm. By making it within this range, it is preferable because good thickness accuracy can be obtained.

[0016] Further, the apparent density of the columnar or flat methacrylic rosin polymer is from 0.63 gZml to 0.6.

When it is within the range of 70 gZml, good thickness accuracy can be obtained.

[0017] The amorphous metataryl rosin polymer, which is an important constituent of the present invention, is formed into a plate shape by melt extrusion or the like from the above-mentioned suspension polymerization, solution polymerization, or bulk polymerization. It is obtained by mechanically grinding the material. As the pulverizer, an impact pulverizer such as an impact crusher, a hammer crusher or a shear pulverizer such as a cutter mill can be used. In particular, the cutter mill is preferable because the size of the pulverized product can be adjusted depending on the size of the screen holes. A screen having a diameter of about 8 to 12πιπιφ is usually used, and an irregularly-shaped methallyl rosin polymer that has passed through this screen is used in the present invention.

[0018] When the apparent density of the irregular-shaped methallyl rosin polymer is in the range of 0.55 gZml to 0.63 gZml, good plate thickness accuracy can be obtained.

In the present invention, the regular-shaped methacrylic resin and the irregular-shaped methacrylic resin polymer are mixed and used as a raw material for extruding methallyl resin. It is important that the mixing ratio of the regular-shaped methacrylic resin and the irregular-shaped methacrylic resin polymer is mixed so that the apparent density of the mixture is 0.80 gZml or more. When the apparent density of the mixture is 0.80 gZml or more, the extrusion stability is excellent, and an extruded plate with good thickness accuracy can be obtained.

[0020] The preferred mixing ratio of each polymer varies depending on the size of the polymer. In the case of the polymer particle size of the example, the amorphous methacrylic resin is 5 to 380 parts by weight, preferably 10 to 330 parts by weight, with respect to 100 parts by weight of the regular methacrylic resin. The amount is preferably 10 to 230 parts by weight. In addition, the proportion of the spherical, cylindrical, Z or flat methallyl slag polymer in the regular-shaped methacrylic slag polymer is cylindrical, Z or flat methacrylic slag relative to 100 parts by weight of the spherical methallyl succinic polymer. The fat polymer is 0 to 400 parts by weight, preferably 0 to 250 parts by weight, and more preferably 0 to 150 parts by weight.

[0021] The extruded plate of the present invention can be produced by a usual melt extrusion method. For example, a mixture of the regular shape methacrylic resin and the irregular shape methacrylic resin polymer of the present invention is melted at 220 to 300 ° C., then extruded into a plate shape through a T-die, the surface is finished with a polishing roll, cooled, and then cut. A plate-like body can be obtained.

[0022] The plate thickness accuracy is the difference between the average value of the plate thickness measured at intervals of 50 mm and the maximum and minimum values of the measurement points for a plate having a width of 1000 mm. When the plate thickness is 2.0 to 15. Omm, the plate thickness accuracy is within ± 1.0% of the average plate thickness, preferably within ± 0.5%.

[0023] Further, when the plate thickness is 3.5 to 8.5 mm, the plate thickness accuracy is within ± 0.5% of the average plate thickness.

The invention's effect

[0024] The metathalyl resin extruded plate of the present invention has the effect of maximally improving the light emission efficiency of light that has also entered the light source lamp force and reducing luminance spots.

BEST MODE FOR CARRYING OUT THE INVENTION

[0025] The present invention will be described based on examples.

(Measuring method of average particle diameter of spherical metataryl rosin polymer)

An electromagnetic shaking sieving meter (electromagnetic vibration AS200 DISIT manufactured by Mitamura Riken Kogyo Co., Ltd.) was used. Sample lOOg is placed on top of the 7-stage sieve of the size 500-425-355-300-250-150-150, and shaken with a sieve shaker for 10 minutes, then spherical on each sieve. The metataryl rosin polymer was weighed, a cumulative residual distribution curve was written, the median diameter was determined, and the average particle diameter was obtained. For polymers with a small average particle size, measurements were made using a seven-stage sieve with a nominal size of 300-250-180-125-100-63-63.

(Measurement method of major axis, minor axis, length of cylindrical methacrylic resin) Using an outer micrometer (MDC-25M manufactured by Mitutoyo Corporation), the major axis, minor axis, and length of 200 samples were measured up to 0.00 lmm, and the average value was determined.

(Measurement method of major axis, minor axis and length of flat methacrylic resin)

Using an outer micrometer (MDC-25M manufactured by Mitutoyo Corporation), the major axis, minor axis, and thickness of 200 samples were measured up to 0.001 mm, and the average value was obtained.

(Apparent density)

Measured according to JIS K 7365.

(Measurement of thickness of methacrylic resin extruded plate)

Using a 1000 mm wide plate shown in Fig. 1, measurements were made up to 0.00 lmm using a 19 point outside micrometer (MDC-25M manufactured by Mitutoyo Corporation) at 50 mm intervals. The average value of each measurement point was determined, and the plate thickness accuracy was calculated from the average value and the maximum value and minimum value of each measurement point. The plate thickness accuracy of the maximum thickness is “plate thickness accuracy A”, and the plate thickness accuracy of the minimum thickness is “plate thickness accuracy B”.

Thickness accuracy—A (%) = (Maximum value—Average value) Z Average value X 100 (1)

Sheet thickness accuracy B (%) = (Minimum value average value) Z Average value X 100 (2)

[0026] (Measurement method of brightness of light guide plate, brightness spot)

In accordance with the light source device shown in Fig. 2, a cold cathode tube of 3mmφ (made by Harrison Electric Co., Ltd.) is installed as a light source on both end faces of the light guide plate at the length of 319mm, and Ray White 75 (made by Kimoto) is used as a light reflecting sheet. And two light diffusion sheets D121 (made by Gidden) were placed on the top of the light guide plate. The cold cathode tube was charged with a voltage of 12V from a DC voltage stabilizer and lit for 20 minutes after being lit for 20 minutes. The luminance meter (CA-1000: manufactured by Minolta) installed at a position distant from the light emitting surface vertically 19 X horizontal The luminance of each of the measurement points divided into 19 = 361 was measured. Next, the average luminance was calculated from the 361 measured values obtained in the above. Also, the uniformity was calculated from the obtained 361 measured values as an evaluation index of luminance spots by the following formula (3).

Luminance uniformity (%) = Minimum luminance value Z Maximum luminance value X 100 (3)

[0027] (Production of Spherical Metataryl Resin Polymer (Polymer—A))

95.0 parts by weight of methyl methacrylate, 5.0 parts by weight of methyl acrylate, 0.15 parts by weight of lauroyl peroxide, 0.25 parts by weight of n-octyl mercaptan, 130 parts by weight of deionized water, 00.65 parts by weight of aluminum was put into a 200-liter polymerization machine and mixed with stirring. Suspension polymerization was carried out at a reaction temperature of 80 ° C for 150 minutes, followed by aging at 100 ° C for 60 minutes to complete the polymerization reaction. Next, the polymerization reaction solution was cooled to 50 ° C, diluted sulfuric acid was added, washed and dehydrated and dried, and melt flow rate (ISO-1139—Condl3) l. OgZlO-containing spherical methacrylic resin (polymer) — I got A). Polymer-A had an average particle size of 0.39 mm and an apparent density of 0.76 gZml.

(Manufacture of cylindrical methacrylic resin (polymer B))

1,1-bis (t-butylperoxy) -3,3,5-trimethyl in a monomer mixture consisting of 79.9% by weight methyl methacrylate, 5.1% by weight methyl acrylate, and 15% by weight ethylbenzen 150 ppm of cyclohexane and 300 ppm of n-octyl mercaptan are added, and polymerization is continuously carried out to a polymerization temperature of 155 ° C, a residence time of 2.0 hours, and a polymerization conversion rate of 53% in a fully mixed polymerization reactor. The polymerization solution was continuously taken out from the polymerization reactor, then heated to 260 ° C with a heating plate, and cast and dropped through the space between the heating plates. A devolatilization tank, maintained at 2.7 kPa, 230 ° C, separated the polymer from unreacted monomers and solvent. The polymer is continuously transferred to the extruder in a molten state, extruded through the extruder into a strand from a die, water-cooled (water temperature: 60 ° C bath), cut with a strand cutter, and melt flow rate ( I SO 1139 Condi 3) 1. A 10-minute cylindrical methacrylic resin (polymer B) was obtained. The major axis (al), minor axis (bl), and length (L) of polymer—B are (al) 2. 773mm, (bl) 2. 689mm, (L) 3. 105mm, (bl) / ( al) It was 0.97 and the apparent density was 0.67 gZml.

(Manufacture of flat methacrylic resin (polymer C))

In the production process of polymer B, instead of extruding into a strand from a die and then cooling with water and then cutting with a cutter, it is cut with an underwater cut method that extrudes and cuts into water from a die, and melt flowlay HISO-1139—Condl3) l. A flat methacrylic resin (polymer C) with OgZ of 10 minutes was obtained. Polymer — D major axis (a2), minor axis (b2), thickness (T) are (a2) 3. 178mm, (b2) 3. 089mm, (T) l. 505mm, (b2) / (a2) 0.97, apparent density 0.668 g / ml.

(Manufacture of amorphous metataryl rosin polymer (Polymer D))

Polymer — 150mm φ single screw extrusion with A and T die for sheet (die temperature: 250 ° C) Machine (cylinder temperature: 200 ° C -210 ° C -210 ° C -260 ° C -260 ° C -240 ° C) from the feed side) and three poly cinder rolls (roll temperature: 80 ° C) ) And an extrusion sheet forming machine comprising a take-up device, and extruded with a extrusion amount of 600 kgZhr to obtain a methacrylic resin extruded plate having a width of 1000 mm and a thickness of 6 mm. Next, this extruded plate was pulverized by using a pulverizer (U10-30120XLFX type) (screen: 10 mmφ) manufactured by Horai Co., Ltd. to obtain an irregular-shaped metataryl rosin polymer (polymer D). The apparent density of Polymer-D was 0.60 gZml. Example 1

[0028] 150 mm φ single screw extruder (cylinder temperature) with T die (die temperature: 250 ° C) for sheet (mixture of 100 parts by weight of polymer A and 50 parts by weight of polymer D (apparent density 0.83 g / ml)) Degree: 200 ° C -210 ° C -210 ° C -260 ° C -260 ° C -240 ° C))) and 3 poly cinder rolls (roll temperature: 80 ° C) A methacrylic resin extruded plate (extruded plate-A) having a width of 1000 mm and a thickness of 6 mm was obtained by extrusion using an extrusion sheet molding machine having a removing device strength and an extrusion amount of 600 kgZhr. Table 1 shows the results of measuring the thickness measurement points shown in Fig. 1 and calculating the plate thickness accuracy.

Next, the resulting extruded plate was cut into a size of 241 mm in width and 319 mm in length using a circular saw, and the cut surface of the cut plate was cut using a precision polishing machine (PLA—Beauty: manufactured by Megalotech-Power Co., Ltd.). Polish and then puffed to give a mirror finish. Next, using a printing screen having a 15-inch size dot gradation and using Mattmedium SR931 (Mino Group) as ink, screen printing was performed on one side of the light guide plate to obtain a light guide plate. Table 1 shows the measurement results of luminance and luminance spots.

Example 2

[0029] A mixture in which the blending amount of the polymer D used in Example 1 was 100 parts by weight (apparent density 0.

Extruded plate B was obtained in the same manner as in Example 1 except that the amount was 88 g / ml). As in Example 1, thickness measurement, brightness, and brightness spots were measured, and the results are shown in Table 1.

Extruded plate C was obtained in the same manner as in Example 1 except that the mixture (polymer apparently used in Example 1) had a blending amount of 400 parts by weight (apparent density 0.75 g / ml). As in Example 1, thickness measurement, brightness, and brightness spots were measured, and the results are shown in Table 1. <Comparative Examples 2, 3>

Polymer A (apparent density 0.76 gZml) and polymer D (apparent density 0.60 gZml) used in Example 1 were each extruded in the same manner as in Example 1 and extruded plate D and extruded plate E Obtained. As in Example 1, thickness measurement, luminance, and luminance spots were measured, and the results are shown in Table 1.

Example 3

[0030] The polymer used in Example 1 was replaced with Example 1 except that the polymer (A50 parts by weight) and the polymer (B50 parts by weight) were used instead of A100 parts by weight. In the same manner, Extruded Plate-F was obtained. As in Example 1, thickness measurement, luminance, and luminance spots were measured, and the results are shown in Table 1.

Example 4

[0031] Extruded plate-G was obtained in the same manner as in Example 1, except that the mixture was changed to a mixture using the polymer C instead of the polymer B used in Example 3 (apparent density 0.87 gZml). As in Example 1, thickness measurement, luminance, and luminance spots were measured, and the results are shown in Table 1.

Example 5

[0032] Using the extruded raw material of Example 1, a methacrylic resin extruded plate (extruded plate H) having a thickness of 8 mm was formed, and in the same manner as in Example 1, thickness measurement, luminance, and luminance unevenness were measured. The results are shown in Table 1

(Summary of results)

The brightness | luminance of Example 1-5 and the brightness spot expressed the performance outstanding compared with Comparative Examples 1-3.

[0033] [Table 1]

Polymer (parts by weight) Extruded plate Average plate Max plate JS plate S accuracy-A Minimum plate thickness Accuracy-B Average brightness Brightness uniformity

ABCD 5, mm) (mm) (%) imm) 《%) (cd / m ² ) (%) Implemented 1 100 0 0 50 6, 030 6.045 + 0.25 6.010 -0.33 2935 82 Implemented 2 100 0 0 100 Extrusion plate B 6.015 6, 036 +0.35 5.997 -0.30 2928 81 Comparative example 1 100 0 0 400 Extrusion plate G 6.008 6.084 +1.26 5.930 —1.30 2795 72 Comparative example 2 100 0 0 0 Extrusion plate D 6.006 6.078 +1.20 5.927 -1.32 2790 73 Comparative example 3 0 0 0 100 Extrusion plate E 6.000 + 2. 17 5.890 -1.83 2680 70 Example 3 50 50 0 50 Extrusion plate F 6.001 6.019 +0.30 S.982 to 0.32 2928 83 Example 4 50 0 50 50 Extruded plate G 5.997 6.020 +0.38 5.977 -0.33 2920 81 Example 5 100 0 0 50 Extruded plate H 8.010 8.032 +0.27 7.995 —0. 19 2950 "ο

Industrial applicability

[0034] The light guide plate of the present invention is used in office automation equipment such as personal computers and word processors, various monitors for displaying image signals, for example, display devices used for panel monitors, television monitors and the like, and lighting devices for indoor and outdoor spaces. It can be suitably used for display devices and signboards.

Brief Description of Drawings

[0035] [Fig. 1] Shows thickness measurement points in the present invention.

FIG. 2 shows an example of a luminance evaluation method in an edge light type liquid crystal light source device using the light guide plate of the present invention.

Explanation of symbols

[0036] A: Light source (cold cathode tube)

B: Lamp house

C: Light guide plate

D: Light reflection sheet

E: Light diffusion sheet

Claims

The scope of the claims

[1] Apparent density between 0.663 gZml to 0.78 gZml of fixed-form methacrylic resin and apparent density between 0.55 gZml to 0.63 gZml of amorphous methacrylic resin polymer with an apparent density of at least 0.80 g / ml The resulting mixture is extruded to obtain a sheet thickness of 2.0 to 15. Omm, and the sheet thickness accuracy in the width direction is within ± 1.0% of the average sheet thickness. A method for producing a metathalyl resin extruded plate for optical plates.

[2] The light guide plate according to claim 1, wherein the plate thickness is 3.5 to 8.5 mm, and the plate thickness accuracy in the width direction is within ± 0.5% of the average plate thickness. For producing a methacrylic resin extruded plate.

[3] A methacrylic resin extruded plate for a light guide plate produced by the method according to claim 1 or claim 2.