JPWO2006046481A1 - Method for producing methacrylic resin extrusion plate for optics - Google Patents

Abstract

A mixture of a regular methacrylic resin polymer having an apparent density of 0.63 g / ml to 0.78 g / ml and an amorphous methacrylic resin polymer having an apparent density of 0.55 g / ml to 0.63 g / ml. And a methacrylic resin extrusion raw material having an apparent density of 0.80 g / ml or more of the mixture, wherein the plate thickness accuracy in the width direction is controlled within ± 1.0% of the average plate thickness Methacrylic resin extrusion plate, used in office automation equipment such as personal computers and word processors, various displays for displaying image signals, for example, display devices used for panel monitors, television monitors, etc. and lighting devices for indoor and outdoor spaces A methacrylic resin extrusion plate for a light guide plate suitable for a display device or a signboard is provided.

Description

  The present invention relates to a display device or a signboard used for an office automation device such as a personal computer or a word processor, a display device for displaying various image signals, for example, a panel monitor, a television monitor, and a surface light source device for indoor and outdoor spaces. It is related with the manufacturing method of the methacrylic resin extrusion board for light-guide plates suitable for etc.

  Transparent thermoplastic resins, and in particular methacrylic resins, have been used for many lighting applications because of their excellent light transmission and mechanical properties. In recent years, however, they have been used as backs for display devices equipped with lighting lamps. It has come to be used as a light guide plate for light. Two types of backlights are commonly used: 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. Currently, the edge light method is used. Has become the mainstream. In recent years, there has been a strong demand for higher brightness, larger size, and thinner display devices, and development has continued under the concept of brighter, larger, and thinner products. In particular, there is a strong demand for the development of a high-luminance surface emitting device using an edge light system.

  For this reason, with respect to the light guide plate used in the light source device, there is a strong demand for a light guide plate that efficiently emits incident light of light incident from a light source lamp disposed on the side surface to the output surface. .

However, in the normal extrusion plate, the variation in the thickness in the extrusion direction is small, but the variation in the thickness in the width direction is large, so that the light incident from the light source lamp arranged in the light source device is irregularly emitted and the luminance uniformity Inferior to this, high brightness cannot be obtained.
A plurality of technical disclosures have been made so far regarding the method of increasing the brightness using the light guide plate. For example, a method for 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 for increasing the brightness by using it is disclosed (for example, see Patent Document 2), but the process is complicated.

Japanese Patent Publication No.39-1194 JP-A-4-145485

  However, other than the technology using the methacrylic resin containing these complicated fine particles, the present situation is that the level that can sufficiently meet the demands associated with the increase in size and thickness of the display device such as luminance and luminance unevenness has not been reached. .

  An object of the present invention is to provide a methacrylic resin for a light guide plate suitable for display devices used for various monitors for displaying image signals, for example, display devices used for panel monitors, television monitors, etc., and illumination devices for indoor and outdoor spaces, signboards, etc. The object is to provide an extruded plate and a method for producing the same.

As a result of intensive studies to solve the above problems, the present inventors mixed a methacrylic resin extruded raw material having an indefinite shape with a methacrylic resin extruded raw material having a fixed shape at a specific ratio, and obtained an extruded methacrylic resin plate. It has been found that the use of the light guide plate can increase the luminance and reduce the luminance unevenness, thereby completing the present invention.
That is, the present invention
[1] A regular methacrylic resin polymer having an apparent density of 0.63 g / ml to 0.78 g / ml and an amorphous methacrylic resin polymer having an apparent density of 0.55 g / ml to 0.63 g / ml have an apparent density of 0. The resulting mixture was extruded to give a plate thickness of 2.0 to 15.0 mm, and the plate thickness accuracy in the width direction was ± 1. A method for producing a methacrylic resin extruded plate for a light guide plate that is within 0%,
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 described in 1 or 2 above,
It is.

  The present invention will be specifically described below.

The methacrylic resin used in the present invention can be obtained by copolymerizing at least 70% by weight of methyl methacrylate or ethyl methacrylate with a monomer having copolymerizability with these. As monomers having copolymerizability with these, methacrylates such as butyl methacrylate, ethyl methacrylate, methyl methacrylate, propyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, 2-ethylhexyl methacrylate, and acrylic acid Examples include, but are not limited to, acrylic acid esters such as methyl, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, and 2-ethylhexyl acrylate, and unsaturated acids such as methacrylic acid and acrylic acid. It is not something.
The regular-shaped methacrylic resin extrusion raw material used in the present invention refers to a spherical, cylindrical or flat methacrylic resin obtained by a polymerization reaction. The amorphous methacrylic resin extrusion raw material refers to a methacrylic resin obtained by mechanically pulverizing a methacrylic resin molding once molded into a plate shape.

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 composed of methyl methacrylate or ethyl methacrylate and another monomer. After suspending the homogeneously dissolved product in an aqueous medium containing a dispersion stabilizer, it is maintained at a predetermined polymerization temperature for a certain period of time to complete the polymerization, and the resulting turbid polymer is filtered, washed with water and dried. Is obtained.
As a polymerization initiator used in suspension polymerization, a known radical polymerization initiator for polymerization of a vinyl monomer may be used. For example, azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl-2,2′-azobisisobutyrate, t-butylperoxypivalate, t-butylper Examples thereof include oxy 2-ethyl hexaate, cumyl peroxy 2-ethyl hexanoate, benzoyl peroxide, lauroyl peroxide and the like. The amount of these radical polymerization initiators used is usually preferably in the range of 0.01 to 2.0 parts by weight with respect to 100 parts by weight of the monomer or monomer mixture.
The chain transfer agent used in suspension polymerization may be a well-known one used for polymerization of methyl methacrylate. Examples thereof include t-butyl mercaptan, n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan and the like. The amount of these chain transfer agents used is usually preferably in the range of 0.01 to 2.0 parts by weight with respect to 100 parts by weight of the monomer or monomer mixture.
The dispersion stabilizer used in suspension polymerization is not particularly limited, but is a poorly water-soluble inorganic compound such as calcium phosphate, calcium carbonate, aluminum hydroxide, polyvinyl alcohol, polyethylene oxide, nonionic polymer compound of cellulose derivative, Examples include anionic polymer compounds such as polyacrylic acid and salts thereof, polymethacrylic acid and salts thereof, and copolymers of methacrylic acid esters and methacrylic acid and salts thereof. The amount of these dispersion stabilizers used is preferably in the range of 0.01 to 5.0 parts by weight with respect to 100 parts by weight of water.
Examples of water used in suspension polymerization include pure water, ion exchange water, and deionized water. Although the usage-amount of water is not specifically limited, The range of 100-250 weight part is preferable with respect to 100 weight part of monomers or monomer mixtures.
The polymerization temperature for suspension polymerization is not particularly limited, but is about 60 to 120 ° C., which is a temperature suitable for the polymerization initiator to be 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, and a baffle is generally attached to the vessel. Is.
Further, if necessary, a release agent, a colorant, an ultraviolet absorber, an antioxidant, a light diffusing agent, a plasticizer and the like may be suspended and polymerized.
After completion of the suspension polymerization, a spherical methacrylic resin polymer can be obtained by washing, dehydrating and drying by a known method.

The average particle diameter of the spherical methacrylic resin 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 at 0.2 mm or more, and a polymer having an average particle diameter of 0.5 mm or less can be stably produced. Moreover, when the apparent density is in the range of 0.70 g / ml to 0.78 g / ml, good plate thickness accuracy can be obtained.
Next, a columnar or flat methacrylic resin polymer, which is an important component of the present invention, will be described. Cylindrical methacrylic resin polymer is a spherical methacrylic resin polymer obtained by the above suspension polymerization, supplied to an extruder with a vent, extruded at a temperature of 220 to 260 ° C. and a vent vacuum pressure of 1.3 to 8 kPa in a strand form from a die. It can be extruded, water cooled and cut with a strand cutter. Alternatively, a melted methacrylic resin polymer obtained by a known solution polymerization method or bulk polymerization method is extruded into a strand shape from an extrusion die, cooled with water, and cut with a strand cutter. The flat methacrylic resin polymer can be extruded from an extruder with a vent in the same manner as in the production of the cylindrical methacrylic resin polymer, 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 of the distillation column and inside the distillation column. preferable. Specifically, aromatic compounds such as toluene, xylene, ethylbenzene and diethylbenzene, aliphatic compounds such as octane and decane, alicyclic compounds such as decalin, esters such as butyl acetate and pentyl acetate, 1,1, And halogen compounds such as 2,2-tetrachloroethane. In particular, alkylbenzene, and among them, toluene, xylene, and ethylbenzene, have an appropriate boiling point, and are preferable because they have less burden on deaeration and do not adversely affect polymerization. The amount of the solvent varies depending on the boiling point of the solvent, but 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. For example, di-t-butyl peroxide, dicumyl peroxide, methyl ethyl ketone peroxide, -T-butyl perphthalate, di-t-butyl perbenzoate, t-butyl peracetate, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 1,1-bis (t-butyl Peroxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, di-t-amyl peroxide, benzoyl peroxide, cumene hydroperoxide, lauryl peroxide, azobis Isobutanol diacetate, 1,1′-azobiscyclohexanecarbonitrile, 2-phenylazo 2 , 4-dimethyl-4-methoxyvaleronitrile, 2-cyano-2,2-propylazoformaside, 2,2′-azobisisobutyronitrile and the like. 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.
Further, mercaptans are mainly used as the molecular weight regulator used in this case. Examples of mercaptans include n-butyl mercaptan, isobutyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, sec-dodecyl mercaptan, t-butyl mercaptan, phenyl mercaptan, thiocresol, thioglycolic acid and its ester, and ethylenethio. A glycol etc. can be mentioned. The amount of these molecular weight regulators 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 uniformly stirred by 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 120 to 160 ° C. so that it is substantially constant within the range of 40 to 70%. The polymerization reaction is carried out at temperature. 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 preheater is reduced, and the transport of the polymerization solution is facilitated. 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. Moreover, it is preferable because the thermal decomposition resistance does not decrease.
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 liquid is superheated to a temperature of 200 to 290 ° C. with a preheater or the like, has a sufficient space at the top, and has a temperature of 200 to 250 ° C., 2.7 to 13 kPa, and a devolatilization tank under vacuum. And the polymerized product is taken out.
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 polymer can be extruded from an extruder in the same manner as in the production of the cylindrical methacrylic resin polymer, and then cut with an underwater cutter.

  Furthermore, if necessary, a mold release agent, a colorant, an ultraviolet absorber, an antioxidant, a light diffusing agent, a plasticizer, etc. may be added before cutting using a feed pump from the side of the extruder. .

  The shape of the columnar polymer, which is an important component of the present invention, is defined by the major axis (a1), minor axis (b1), and length (L) of the cross section. The major axis (a1) and the minor axis (b1) are both 2.00 to 4.000 mm, (b1) / (a1) = 0.66 to 1.00, and the length (L) is 2.00 to 400. 5.000 mm. It is preferable that the thickness is within this range because good thickness accuracy can be obtained.

  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). The major axis (a2) and minor axis (b2) are both 2.00 to 4.000 mm, (b2) / (a2) = 0.66 to 1.00, and the thickness (T) is 1.000. 3.000 mm. It is preferable that the thickness is within this range because good thickness accuracy can be obtained.

  Further, good plate thickness accuracy can be obtained when the apparent density of the columnar or flat methacrylic resin polymer is in the range of 0.63 g / ml to 0.70 g / ml.

  The amorphous methacrylic resin polymer, which is an important component of the present invention, is obtained by mechanically molding a material obtained by molding the methacrylic resin polymer obtained from the suspension polymerization, solution polymerization, and bulk polymerization into a plate shape by a melt extrusion method or the like. It is obtained by crushing. 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 holes in the screen. A screen having a diameter of about 8 to 12 mmφ is usually used, and an irregular-shaped methacrylic resin polymer that has passed through this screen is used in the present invention.

  When the apparent density of the amorphous methacrylic resin polymer is in the range of 0.55 g / ml to 0.63 g / ml, good plate thickness accuracy can be obtained.

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

  The preferred mixing ratio of each polymer varies depending on the size of the polymer, but in the case of the polymer particle size of the examples of the present application, the amorphous methacrylic resin polymer with respect to 100 parts by weight of the regular methacrylic resin polymer. Is 5 to 380 parts by weight, preferably 10 to 330 parts by weight, and more preferably 10 to 230 parts by weight. Further, the ratio of the spherical, cylindrical and / or flat methacrylic resin polymer in the regular-shaped methacrylic resin polymer is such that the cylindrical and / or flat methacrylic resin polymer 0 with respect to 100 parts by weight of the spherical methacrylic resin polymer. -400 parts by weight, preferably 0-250 parts by weight, more preferably 0-150 parts by weight.

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

  The plate thickness accuracy is the difference between the average value of the plate thickness measured at intervals of 50 mm in a plate having a width of 1000 mm and the maximum and minimum values of the measurement points. When the plate thickness is 2.0 to 15.0 mm, the plate thickness accuracy is within ± 1.0% of the average plate thickness, preferably within ± 0.5%.

  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 methacrylic resin extruded plate of the present invention has the effect of maximizing the luminous efficiency of light incident from the light source lamp and reducing luminance spots.

The present invention will be described based on examples.
(Method for measuring the average particle diameter of spherical methacrylic resin polymer)
An electromagnetic shaking sieving meter (electromagnetic vibration AS200 DISIT manufactured by Mitamura Riken Kogyo Co., Ltd.) was used. Place 100 g of sample on top of sieve of 7 stages with nominal size 500-425-355-300-250-150-150, shake for 10 minutes with sieve shaker, and then spherical methacrylic resin on each sieve The polymer was weighed, a cumulative residual distribution curve was written, the median diameter was determined, and the average particle diameter was obtained. For a polymer having a small average particle size, the measurement was performed using a seven-stage sieve having a nominal size of 300-250-180-125-100-63-63.
(Measurement method of major axis, minor axis and length of cylindrical methacrylic resin polymer)
Using an outer micrometer (MDC-25M manufactured by Mitutoyo Corporation), the major axis, minor axis, and length of 200 samples were measured to 0.001 mm, and the average value was obtained.
(Measurement method of major axis, minor axis, length of flat methacrylic resin polymer)
Using an outer micrometer (MDC-25M manufactured by Mitutoyo Corporation), the major axis, minor axis, and thickness of 200 samples were measured to 0.001 mm, and the average value was obtained.
(Apparent density)
It measured according to JISK7365.
(Measurement of thickness of methacrylic resin extrusion plate)
Measurement was performed up to 0.001 mm using a 19-point outside micrometer (MDC-25M manufactured by Mitutoyo Corporation) at intervals of 50 mm on the plate having a width of 1000 mm shown in FIG. The average value of each measurement point was obtained, 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 was “plate thickness accuracy-A”, and the plate thickness accuracy of the minimum thickness was “plate thickness accuracy-B”.
Sheet thickness accuracy-A (%) = (maximum value-average value) / average value × 100 (1)
Sheet thickness accuracy-B (%) = (minimum value-average value) / average value x 100 (2)

(Measurement method of brightness of light guide plate and brightness spots)
In accordance with the light source device shown in FIG. 2, a cold cathode tube of 3 mmφ (manufactured by Harrison Electric Co., Ltd.) is installed as a light source on both end faces on the side of the light guide plate with a length of 319 mm, and Ray White 75 (manufactured by Kimoto) is used as the light reflecting sheet. Two light diffusion sheets D121 (manufactured by Tsujiden) were placed on the top of the light guide plate. The cold cathode tube was charged with a voltage of 12 V from a DC voltage stabilizer and turned on for 20 minutes, and then a luminance meter (CA-1000: manufactured by Minolta) installed at a position 1 m away from the light emitting surface, the entire light emitting surface was 19 × 19 = The luminance of each of the measurement points divided by 361 was measured. Next, the average luminance was calculated from the obtained 361 measured values. Further, the uniformity was calculated as an evaluation index of luminance spots from the obtained 361 measured values by the following formula (3).
Luminance uniformity (%) = minimum luminance value / maximum luminance value × 100 (3)

(Production of spherical methacrylic 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, 0.65 of aluminum hydroxide The parts by weight were 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 substantially complete the polymerization reaction. Next, the polymerization reaction liquid is cooled to 50 ° C., diluted sulfuric acid is added, washed and dehydrated and dried, and a spherical methacrylic resin polymer (polymer-) of 1.0 g / 10 min of melt flow rate (ISO-1139-Cond 13) is obtained. A) was obtained. The average particle diameter of the polymer-A was 0.39 mm, and the apparent density was 0.76 g / ml.
(Production of cylindrical methacrylic resin polymer (polymer-B))
1,1-bis (t-butylperoxy) -3,3,5-trimethyl was added to a monomer mixture consisting of 79.9% by weight methyl methacrylate, 5.1% by weight methyl acrylate, and 15% by weight ethylbenzene. 150 ppm of cyclohexane and 300 ppm of n-octyl mercaptan
In addition, polymerization is continuously carried out in a completely mixed polymerization reactor until the polymerization temperature is 155 ° C., the residence time is 2.0 hours, and the polymerization conversion is 53%. The polymerization liquid was continuously taken out from the polymerization reactor, and then heated to 260 ° C. with a heating plate, and cast and dropped through the space between the heating plates. The devolatilization tank was maintained at 2.7 kPa and 230 ° C., and the polymer, unreacted monomer and solvent were separated. 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 (ISO 1139 Cond 13). ) A cylindrical methacrylic resin polymer (polymer-B) of 1.0 g / 10 min was obtained. The major axis (a1), minor axis (b1), and length (L) of Polymer-B are (a1) 2.773 mm, (b1) 2.689 mm, (L) 3.105 mm, (b1) / ( a1) 0.97 and the apparent density was 0.67 g / ml.
(Manufacture of flat methacrylic resin polymer (Polymer-C))
Instead of extruding into a strand from a die in the production process of polymer-B, and then cooling with water and then cutting with a cutter, it is cut by an under water cut method in which it is extruded and cut into water from a die, and melt flow rate (ISO-1139-Cond13) 1 A flat methacrylic resin polymer (Polymer-C) of 0.0 g / 10 min was obtained. The major axis (a2), minor axis (b2), and thickness (T) of Polymer-D are (a2) 3.178 mm, (b2) 3.089 mm, (T) 1.505 mm, (b2) / ( a2) 0.97, the apparent density was 0.68 g / ml.
(Production of amorphous methacrylic resin polymer (Polymer-D))
150 mmφ single screw extruder having a T-die for sheet (die temperature: 250 ° C.) using polymer-A (cylinder temperature: 200 ° C.-210 ° C.-210 ° C.-260 ° C.-260 ° C.-240 ° C. from the feed side)) And an extruded sheet molding machine comprising a temperature-controlled three polishing roll (roll temperature: 80 ° C.) and a take-up device, extruded at an extrusion rate of 600 kg / hr 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 using a pulverizer (U10-30120XLFX type) (screen: 10 mmφ) manufactured by Horai Co., Ltd. to obtain an amorphous methacrylic resin polymer (Polymer-D). The apparent density of the polymer-D was 0.60 g / ml.

A 150 mmφ single screw extruder (cylinder temperature: feed side) having a T-die for a sheet (die temperature: 250 ° C.) of a mixture of polymer-A 100 parts by weight and polymer-D 50 parts by weight (apparent density 0.83 g / ml) 200 ° C.−210 ° C.−210 ° C.−260 ° C.−260 ° C.−240 ° C.)) and a temperature-controlled three polishing roll (roll temperature: 80 ° C.) and an extrusion sheet molding machine comprising a take-up device. Extrusion was performed at an amount of 600 kg / hr to obtain a methacrylic resin extruded plate (extruded plate-A) having a width of 1000 mm and a thickness of 6 mm. Table 1 shows the result of measuring the thickness measurement points shown in FIG.
Next, the obtained 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 out plate was polished using a precision polishing machine (PLA-BEAUTY: manufactured by Megaro Technica Co., Ltd.). Further, buffing is performed to finish the mirror surface. Next, using a printing screen with a 15 inch size dot gradation and using Matte Medium SR931 (manufactured by 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.

Extruded plate-B was obtained in the same manner as in Example 1 except that the blend amount of Polymer-D used in Example 1 was 100 parts by weight (apparent density 0.88 g / ml). The thickness measurement, brightness, and brightness spots were measured in the same manner as in Example 1, and the results are shown in Table-1.
<Comparative Example 1>
Extruded plate-C was obtained in the same manner as in Example 1 except that the blend amount of Polymer-D used in Example 1 was 400 parts by weight (apparent density 0.75 g / ml). The thickness measurement, brightness, and brightness spots were measured in the same manner as in Example 1, and the results are shown in Table-1.
<Comparative Examples 2 and 3>
Polymer-A (apparent density 0.76 g / ml) and polymer-D (apparent density 0.60 g / ml) used in Example 1 were each extruded in the same manner as in Example 1, and extruded plate-D. And extruded plate-E was obtained. The thickness measurement, brightness, and brightness spots were measured in the same manner as in Example 1, and the results are shown in Table-1.

  The same as Example 1 except that the polymer (A 50 parts by weight) and the polymer (B 50 parts by weight) were used instead of the polymer (A 100 parts by weight) used in Example 1 (apparent density 0.88 g / ml). Extruded plate-F was thus obtained. The thickness measurement, brightness, and brightness spots were measured in the same manner as in Example 1, and the results are shown in Table-1.

  Extruded plate-G was obtained in the same manner as in Example 1 except that the mixture (polymer apparently 0.87 g / ml) was used instead of polymer-B used in Example 3. The thickness measurement, brightness, and brightness spots were measured in the same manner as in Example 1, and the results are shown in Table-1.

A methacrylic resin extruded plate (extruded plate-H) having a thickness of 8 mm was molded using the extruded raw material of Example 1, and the thickness measurement, luminance, and luminance unevenness were measured in the same manner as in Example 1. Table 1 shows the results. Shown in
(Summary of results)
Both the brightness | luminance of Example 1-5 and the brightness spot expressed the performance outstanding compared with Comparative Examples 1-3.

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

The thickness measurement point in this invention is shown. An example of the luminance evaluation method in the edge light type liquid crystal light source device using the light guide plate of the present invention is shown.

Explanation of symbols

A: Light source (cold cathode tube)
B: Lamp house C: Light guide plate D: Light reflection sheet E: Light diffusion sheet

Claims (3)

  A regular methacrylic resin polymer having an apparent density of 0.63 g / ml to 0.78 g / ml and an amorphous methacrylic resin polymer having an apparent density of 0.55 g / ml to 0.63 g / ml have an apparent density of 0.80 g / ml. Mix so as to be more than ml, and extrude the resulting mixture, the plate thickness is 2.0-15.0 mm, the plate thickness accuracy in the width direction is within ± 1.0% of the average plate thickness A method for producing a methacrylic resin extruded plate for a light guide plate.   The methacrylic resin for a 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. Extruded plate manufacturing method. A methacrylic resin extruded plate for a light guide plate produced by the method according to claim 1 or 2.

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