WO2010074188A1

WO2010074188A1 - Light diffusion plate, surface light source device, and liquid crystal display device

Info

Publication number: WO2010074188A1
Application number: PCT/JP2009/071513
Authority: WO
Inventors: 濱松豊博; 井山浩暢
Original assignee: 住友化学株式会社
Priority date: 2008-12-22
Filing date: 2009-12-17
Publication date: 2010-07-01
Also published as: TW201037366A; JP2010250273A

Abstract

Disclosed is a light diffusion plate (3) which is formed from a propylene resin having a tacticity of not less than 95%. The light diffusion plate (3)is used in a surface light source device (1) which comprises a light source (2) that is arranged on the back side of the light diffusion plate (3).

Description

Light diffusing plate, surface light source device, and liquid crystal display device

The present invention relates to a light diffusing plate having excellent heat resistance and capable of suppressing thermal deformation, and a surface light source device and a liquid crystal display device configured using the light diffusing plate.

As a liquid crystal display device, for example, a configuration in which a surface light source device is disposed as a backlight on the back side of a liquid crystal panel (image display unit) including a liquid crystal cell is known. As the surface light source device for the backlight, a surface light source device having a configuration in which a plurality of light sources are disposed in a lamp box (housing) and a light diffusion plate is disposed on the front side of these light sources is known. (Refer to Unexamined-Japanese-Patent No. 2004-170937 (patent document 1)).
As the light diffusing plate, those made of acrylic resin or polycarbonate resin are often used.
As the light diffusing plate used in the surface light source device as described above, it is required to be lighter, hard to break, not to be deformed by heat from the light source, moisture, etc., acrylic resin or polycarbonate The above-mentioned conventional light diffusing plate made of a resin cannot satisfy all of the required characteristics.
As a result of diligent research, the present applicant has found that if a propylene resin is used as a constituent resin, it is possible to provide a light diffusing plate that is lighter, has sufficient strength, and is not easily deformed by heat or moisture (Japanese Patent Laid-Open No. 2008-2008). -83660 (see Patent Document 2)).

In recent years, with an increase in size and thickness of a backlight unit and an increase in brightness of a backlight, a light diffusing plate used for the backlight is required to have a further excellent heat resistance.
According to the study by the present inventors, when a very severe heat resistance test (85 ° C. × 50% RH, 60 hours) was performed on a light diffusion plate made of propylene resin, it was found that slight deformation could occur. It was.
An object of this invention is to provide the light diffusing plate which is excellent in intensity | strength and heat resistance, and can suppress a thermal deformation also on severe thermal conditions.
In order to achieve the above object, the present invention provides the following means.
[1] A light diffusion plate made of propylene resin having a tacticity of 95% or more.
[2] A light diffusing plate comprising a resin composition containing 100 parts by mass of a propylene resin having a tacticity of 95% or more and 0.01 part by mass to 2.0 parts by mass of a nucleating agent.
[3] The propylene resin has a melt flow rate of 0.5 g / 10 min to 30 g / 10 min measured under the conditions of a test temperature: 230 ° C. and a test load: 3.8 kg in accordance with JIS K7210-1999. 3. The light diffusing plate according to 1 or 2 above.
[4] A surface light source device comprising the light diffusing plate according to any one of items 1 to 3 and a plurality of light sources arranged on a back side of the light diffusing plate.
[5] The light diffusing plate according to any one of items 1 to 3, a plurality of light sources arranged on the back side of the light diffusing plate, a liquid crystal panel arranged on the front side of the light diffusing plate, A liquid crystal display device comprising:
The light diffusing plate according to the invention of [1] contains a propylene resin having a tacticity of 95% or more, and therefore has high strength and excellent heat resistance. Deformation can be suppressed. That is, by improving both strength and heat resistance, thermal deformation is suppressed even under severe thermal conditions. Therefore, the obtained light diffusing plate can cope with an increase in the size, thickness and brightness of the surface light source device.
The light diffusion plate according to the invention of [2] is composed of a resin composition containing 100 parts by mass of a propylene resin having a tacticity of 95% or more and 0.01 part by mass to 2.0 parts by mass of a nucleating agent. It has high strength and excellent heat resistance, can suppress thermal deformation even under severe heat conditions, and can obtain a light diffusing plate with a good appearance by containing a specific amount of a nucleating agent. Therefore, the obtained light diffusing plate can cope with an increase in size, thickness and brightness of the surface light source device.
In the invention of [3], since the melt flow rate of the propylene resin constituting the light diffusing plate is 0.5 to 30 g / 10 min, there is an advantage that it is easy to mold and the productivity can be further improved.
In the invention of [4], a light diffusing plate that can suppress thermal deformation even under severe thermal conditions is used, so that a high-quality surface light source device excellent in durability is provided.
In the invention of [5], a light diffusing plate that can suppress thermal deformation even under severe thermal conditions is used, so that a high-quality liquid crystal display device excellent in durability is provided.

FIG. 1 is a schematic view showing an embodiment of a liquid crystal display device according to the present invention.
FIG. 2 is a cross-sectional view showing an example of the concavo-convex shape formed on the surface of the light diffusion plate.
FIG. 3 is a cross-sectional view showing another example of the uneven shape formed on the surface of the light diffusion plate.
FIG. 4 is a perspective view showing another example of a substantially semicircular convex portion.
FIG. 5 is a cross-sectional view showing still another example of the uneven shape formed on the surface of the light diffusion plate.
FIG. 6 is a perspective view showing the substantially triangular convex portion of FIG.
FIG. 7 is a perspective view showing another example of the substantially triangular convex portion.

An embodiment of a liquid crystal display device according to the present invention is shown in FIG. In FIG. 1, (30) is a liquid crystal display device, (11) is a liquid crystal cell, (12) and (13) are polarizing plates, and (1) is a surface light source device (backlight). Polarizing plates (12) and (13) are respectively arranged on the upper and lower sides of the liquid crystal cell (11), and a liquid crystal panel (20) as an image display unit is constituted by these constituent members (11), (12) and (13). Yes. In addition, as the liquid crystal cell (11), those capable of displaying a color image are preferably used.
The said surface light source device (1) is arrange | positioned at the lower surface side (back side) of the polarizing plate (13) below the said liquid crystal panel (20). That is, this liquid crystal display device (30) is a direct liquid crystal display device.
The surface light source device (1) is a thin box-shaped lamp box (5) having a rectangular shape in plan view and having an upper surface side (front surface side) opened, and the lamp box (5) spaced apart from each other. And a light diffusion plate (3) disposed on the upper side (front side) of the plurality of light sources (2). The said light diffusing plate (3) is mounted and fixed with respect to the said lamp box (5) so that the open surface may be block | closed. A light reflecting layer (not shown) is provided on the inner surface of the lamp box (5). Although it does not specifically limit as said light source (2), For example, in addition to linear light sources, such as a cold-cathode tube, a hot cathode tube, and EEFL (external electrode fluorescent lamp), dot-like, such as light emitting diodes (LED) A light source or the like is used.
The light diffusing plate (3) is made of a propylene resin having a tacticity of 95% or more. In this embodiment, the light diffusing plate (3) is made of a resin composition in which light diffusing particles and / or a nucleating agent are dispersed in a propylene resin having a tacticity of 95% or more.
Since the light diffusing plate (3) according to the above configuration uses propylene resin as a constituent resin, it is lightweight, excellent in mechanical strength and hard to break, and excellent in heat resistance and moisture resistance due to heat and moisture. Difficult to deform. In addition, since propylene resin having a tacticity of 95% or more is used, the light diffusion plate (3) has high mechanical strength and excellent heat resistance, and therefore under severe heat conditions. Can suppress thermal deformation of the light diffusion plate (3). That is, by improving both the mechanical strength and heat resistance of the light diffusing plate (3), the thermal deformation of the light diffusing plate (3) is suppressed by these synergistic effects even under severe heat conditions. Therefore, even if the surface light source device (1) is increased in size, thickness, and brightness, thermal deformation of the light diffusing plate (3) is suppressed, and the surface light source device (1) is of high quality.
In the present invention, as the propylene resin constituting the light diffusion plate (3), one having a tacticity of 95% or more is used. By using a propylene resin having a tacticity of 95% or more, both the strength and heat resistance of the light diffusion plate (3) can be improved, and the heat of the light diffusion plate (3) can be improved even under severe heat conditions. Deformation can be suppressed. Among them, it is preferable to use a propylene resin having a tacticity of 96% or more, and it is particularly preferable to use a propylene resin having a tacticity of 97% or more.
The tacticity means triad isotacticity (mm triad fraction) (unit:%) measured by ¹³ C-NMR. The larger this value (%), the better the stereoregularity of the methyl group arrangement of the propylene resin (ie, the higher the isotacticity). For example, in the case of 100% mm triad fraction, It shows that it is an isotactic polypropylene with methyl groups attached to the same side (the same configuration with respect to the polymer backbone of all methyl groups). Note that syndiotactic polypropylene in which the steric configurations of adjacent methyl groups are all reversed has a triad isotacticity (mm triad fraction) of 0%.
The tacticity (mm triad fraction) is measured as follows. That is, the propylene resin to be measured is dissolved by heating in a mixed solvent of orthodichlorobenzene / orthodichlorobenzene-d4, and ¹³ C-NMR of this solution is measured. In the ¹³ C-NMR spectrum obtained by measurement, “mm”, “mr”, and “rr” peaks are identified.
(Mm peak intensity) ÷ {(mm peak intensity) + (mr peak intensity) + (rr peak intensity)} × 100
The value (%) calculated by the above formula is tacticity (mm triad fraction).
When the propylene resin to be measured contains an ethylene unit, in order to eliminate the influence of the methyl group of the propylene unit adjacent to ethylene, the Sαγ peak intensity observed at 37.9 ppm is used, and “mm ”And“ mr ”are corrected.
The light diffusing plate (3) is preferably composed of a resin composition containing 100 parts by mass of a propylene resin having a tacticity of 95% or more and 0.01 parts by mass to 2.0 parts by mass of a nucleating agent. When the content of the nucleating agent is 0.01 parts by mass or more, appearance of white spots and the like on the surface can be suppressed, and a light diffusing plate having a good appearance can be obtained, and 2.0 parts by mass or less. Therefore, it is possible to suppress a decrease in optical characteristics and an increase in cost due to poor dispersion of the nucleating agent. The content of the nucleating agent is more preferably 0.02 to 1.5 parts by mass, and 0.03 to 1.0 parts by mass with respect to 100 parts by mass of propylene resin having a tacticity of 95% or more. Part is particularly preferred.
The nucleating agent is not particularly limited, and examples thereof include sorbitol nucleating agents, organophosphate nucleating agents, carboxylic acid metal salt nucleating agents, and rosin nucleating agents. It is done.
Examples of the sorbitol nucleating agent include dibenzylidene sorbitol, 1,3: 2,4-di (methylbenzylidene) sorbitol, 1,3: 2,4-di (ethylbenzylidene) sorbitol, 1,3: 2, 4-di (butylbenzylidene) sorbitol, 1,3: 2,4-di (methoxybenzylidene) sorbitol, 1,3: 2,4-di (ethoxybenzylidene) sorbitol, 1,3-chlorobenzylidene-2,4- Examples thereof include methylbenzylidene sorbitol, mono (methyl) dibenzylidene sorbitol, 1,3: 2,4-bis-O- (3,4-dimethylbenzylidene) -D-sorbitol, "Millad 3988" sold by Milliken, sold by Mitsui Chemicals "NC-4", and the like "Gel All-MD," which is available from New Japan Chemical Company.
Examples of the organic phosphate nucleating agent include sodium bis (4-t-butylphenyl) phosphate, lithium bis (4-t-butylphenyl) phosphate, and bis (4-t-butylphenyl). Aluminum phosphate, 2,2′-methylene-bis (4,6-di-t-butylphenyl) phosphate sodium salt, 2,2′-methylene-bis (4,6-di-t-butylphenyl) Lithium phosphate, 2,2′-methylene-bis (4,6-di-t-butylphenyl) aluminum phosphate, 2,2′-methylidene-bis (4,6-di-t-butylphenyl) Calcium phosphate, 2,2′-ethylidene-bis (4,6-di-t-butylphenyl) phosphate sodium salt, 2,2′-ethylidene-bis (4,6-di-t-butylphenyl) phosphate Lithium salt, 2,2'-eth Examples thereof include aluminum salt of redene-bis (4,6-di-t-butylphenyl) phosphate, calcium salt of bis- (4-t-butylphenyl) phosphate, and commercially available products such as those sold by ADEKA “ADK STAB NA-11”, “ADK STAB NA-21”, “ADK STAB NA-27”, “ADK STAB NA-71”, and the like.
Examples of the carboxylic acid metal salt nucleating agent include aluminum benzoate, potassium benzoate, sodium benzoate, lithium benzoate, aluminum di-para-t-butylbenzoate, titanium di-para-t-butylbenzoate. , Chromium di-para-t-butylbenzoate, aluminum hydroxy-di-t-butylbenzoate, aluminum-p-butylbenzoate, sodium β-naphthoate, aluminum adipate, sodium sebacate, potassium sebacate, sebacic acid Aluminum and the like are listed, and examples of commercially available products include “AL-PTBBA” sold by Japan Chemtech.
Examples of the rosin nucleating agent include rosin acid metal salts. Examples of rosin acid metal salts include sodium rosin acid salt, potassium rosin acid salt, magnesium rosin acid salt, and the like. Examples thereof include “Pine Crystal KM-1300”, “Pine Crystal KM-1500”, and “Pine Crystal KR-50M” sold by Arakawa Chemical Industries.
Moreover, as a propylene resin which comprises the said light diffusing plate (3), based on JISK7210-1999, the melt flow rate (MFR) measured on condition of test temperature: 230 degreeC and test load: 3.8kg is. It is preferable to use a propylene resin having a weight of 0.5 g / 10 min to 30 g / 10 min. When the MFR is 0.5 g / 10 min or more, the amount of extrusion per unit time during extrusion molding can be increased, and when the MFR is 30 g / 10 min or less, molding becomes easy. Among these, it is particularly preferable to use a propylene resin having a melt flow rate of 1.0 g / 10 min to 10 g / 10 min.
The propylene resin may be a homopolypropylene obtained by polymerizing propylene alone, or may be a copolymer of propylene and a copolymerizable component that can be copolymerized therewith. The content of propylene units in the propylene resin is preferably 75% by mass or more in that sufficient rigidity is obtained. The copolymer component is not particularly limited, and examples thereof include α-olefins such as ethylene and 1-butene.
The propylene resin preferably has a propylene unit content of 75 to 100% by mass, an ethylene unit content of 0 to 15% by mass, and a 1-butene unit content of 0 to 25% by mass. The propylene resin is more preferably composed of a propylene unit content of 95 to 100% by mass, an ethylene unit content of 0 to 5% by mass, and a 1-butene unit content of 0 to 5% by mass. Further, the propylene resin includes a propylene unit content of 99 to 100% by mass, an ethylene unit content of 0 to 1% by mass, and a 1-butene unit content of 0 to 1% by mass (including homopolypropylene). Is most preferred.
The light diffusing particle (light diffusing agent) is not particularly limited as long as it is a particle having a refractive index different from that of the propylene resin and can diffuse light transmitted through a light diffusing plate containing the particle. For example, it may be inorganic particles such as glass particles, glass fibers, silica particles, aluminum hydroxide particles, calcium carbonate particles, barium sulfate particles, titanium oxide particles, talc, styrene polymer particles, acrylic polymers. Organic particles such as particles and siloxane polymer particles may be used.
As the light diffusing particles, those having a volume average particle diameter in the range of 0.5 μm to 25 μm are usually used. Among these, a preferable lower limit value of the volume average particle diameter is 0.7 μm, and a preferable upper limit value of the volume average particle diameter is 20 μm, and a particularly preferable upper limit value is 10 μm. The volume average particle size (D ₅₀ ) is determined by measuring the particle size and volume of all particles, integrating the volume sequentially from the smallest particle size, and the integrated volume is 50% of the total volume of all particles. The particle diameter of the resulting particles.
The content of the light diffusing particles in the light diffusing plate (3) is preferably set in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of the propylene resin. When the content is 0.01 parts by mass or more, the light diffusion effect can be sufficiently obtained, and when the content is 20 parts by mass or less, sufficient mechanical strength can be secured.
The propylene resin or the resin composition constituting the light diffusion plate (3) is optionally provided with an ultraviolet absorber, a heat stabilizer, an antioxidant, a weathering agent, a light stabilizer, a fluorescent whitening agent, and a processing stabilizer. Such additives may be included.
The light diffusing plate (3) of this invention can be manufactured as follows, for example. Extrusion method for extrusion molding, injection molding method for injection molding, hot press for hot pressing, a resin composition in which light diffusing particles and / or nucleating agents are dispersed in propylene resin having a tacticity of 95% or more It can be produced by a known molding method such as a method. The said manufacturing method is only what showed the example, and the light diffusing plate (3) of this invention is not limited to what was manufactured with such a manufacturing method.
The thickness of the light diffusing plate (3) is usually set in the range of 0.1 mm to 3 mm, preferably 0.5 mm to 3 mm.
The size of the light diffusing plate (3) is not particularly limited, and is appropriately set according to the size of the target surface light source device (1) or liquid crystal display device (30), for example. However, among them, it is particularly suitable as a light diffusing plate designed to have a size of 20 type (length 30 cm, width 40 cm) or more.
The surface (one side or both sides) of the light diffusing plate (3) according to the present invention may be a flat surface as shown in FIG. 1 or may have an irregular shape such as a prism shape.
In FIG. 2, an example of the uneven | corrugated shape formed in the surface (one side or both surfaces) (6b) of the light diffusing plate (3) of this invention is shown. In FIG. 2, a concavo-convex shape in which the cross-sectional shape is a triangular convex portion (V-shaped groove) is adopted. In the example of FIG. 2, adjacent triangular convex portions (71) are formed in a continuous manner without any interval (in other words, adjacent V-shaped grooves (72) are formed in a continuous shape). However, the configuration is not particularly limited to such a configuration, and adjacent triangular convex portions may be configured to be discontinuous with an interval (d ₁ ). The pitch interval (P ₁ ) of the triangular protrusions (71) is preferably in the range of 30 μm to 500 μm. The height (H ₁ ) of the triangular convex portion (71) is preferably in the range of 30 μm to 500 μm. The spacing distance (d ₁ : not shown) between the adjacent triangular protrusions (71) is preferably in the range of 1 μm to 10 μm. Further, the apex angle (θ) of the apex of the triangular convex portion (71) is preferably 10 to 100 °, and more preferably 10 to 90 °.
FIG. 3 shows another example of the uneven shape formed on the surface (one side or both sides) (6b) of the light diffusion plate (3). In FIG. 3, an uneven shape including a substantially semicircular convex portion (81) having a substantially semicircular cross-sectional shape is employed. In the example of FIG. 3, adjacent semi-circular protrusions (81) are formed in a discontinuous manner with an interval (d ₂ ), but are not particularly limited to such a configuration. The matching semi-circular convex portions (81) may be formed continuously (that is, d ₂ = 0) without any interval. The pitch interval (P ₂ ) of the substantially semicircular protrusions (81) is preferably in the range of 30 μm to 500 μm. The height (H ₂ ) of the substantially semicircular protrusion (81) is preferably in the range of 30 μm to 500 μm. In addition, the spacing (d ₂ ) between the adjacent substantially semicircular convex portions (81) is preferably in the range of 1 μm to 10 μm. Note that the substantially semicircular convex portion (81) includes not only those having a semicircular cross-sectional shape as shown in FIG. 3, but also a cylindrical body such as a cylindrical lens (82) shown in FIG. It may be in the shape of any arc of the cross section when cut by a plane that is parallel to the central axis and does not include the central axis. Alternatively, the cross section may be a semi-elliptical arc or a semi-elliptical arc. It may be a part of a flat curved shape or the like.
Further, the uneven shape formed on the surface (one side or both sides) (6b) of the light diffusing plate (3) may be a shape provided with a substantially semicircular concave groove in which the substantially semicircular convex portion is inverted. Good. The substantially semi-circular groove includes those having a semicircular cross-sectional shape, and also, for example, a cylindrical body, such as a cylindrical lens, cut along a plane that is parallel to the central axis and does not include the central axis. In this case, the cross section may have any arc shape, or the cross section may have a semi-elliptical arc shape, a flat curved shape that is a part of the semi-elliptical arc shape, or the like.
In FIG. 5, the further another example of the uneven | corrugated shape formed in the surface (one side or both sides) (6b) of a light diffusing plate (3) is shown. In FIG. 5, the uneven | corrugated shape containing the substantially triangular convex part (91) whose cross-sectional shape is a substantially triangular shape is employ | adopted. The left and right hypotenuses in the cross-sectional shape of the substantially triangular convex portion (91) are both straight at the tip side and curved at the base end side (bottom side) (curved bulging sideways at the center). That is, the left and right slopes of the substantially triangular convex portion (91) are composed of a straight portion (92) on the distal end side and a curved portion (93) on the proximal end side. In the example of FIG. 5, the adjacent substantially triangular protrusions (91) are formed in a discontinuous manner with an interval (d ₃ ), but are not particularly limited to such a configuration and are adjacent to each other. The substantially triangular convex portions (91) may be configured continuously (i.e., d ₃ = 0) without any interval. The pitch interval (P ₃ ) of the substantially triangular convex portions (91) is preferably in the range of 30 μm to 500 μm. The height (H ₃ ) of the substantially triangular convex portion (91) is preferably in the range of 30 μm to 500 μm. Further, it is preferable that the spacing (d ₃ ) between the adjacent substantially triangular convex portions (91) is in the range of 1 μm to 10 μm. The apex angle (α) of the substantially triangular convex portion (91) is preferably 10 ° to 100 °, and more preferably 10 ° to 90 °. The curve of the curved portion (93) may be, for example, an arc-shaped part or an elliptical arc-shaped part. As the arc-shaped part, for example, a cylindrical lens having a circular arc shape in a cross section when the cylindrical body is cut by a plane that is parallel to the central axis and does not include the central axis, etc. Is mentioned. In the above-described embodiment (FIGS. 5 and 6), the substantially triangular convex portion (91) is a slope formed by connecting the proximal-side curved portion (93) to the distal-side straight portion (92). However, the present invention is not particularly limited to such a configuration. For example, as shown in FIG. 7, a slope having only a curved portion (93) without a straight portion is provided. A configuration may be adopted.
The pitch interval (P ₁ ) (P ₂ ) (P ₃ ) of the concavo-convex convex portions does not necessarily have to be constant over the entire light diffusing plate (3), and the convex portions adjacent to each other partially or entirely. (71) (81) (91) may be different. Further, the height (H ₁ ) (H ₂ ) (H ₃ ) of the concavo-convex convex portions does not necessarily have to be constant over the entire light diffusion plate (3), and is partially or entirely adjacent. You may differ between convex parts (71) (81) (91). Similarly, the apex angle (θ) (α) and the interval (d ₁ ) (d ₂ ) (d ₃ ) of the concavo-convex shape do not necessarily have to be constant throughout the light diffusion plate (3). Alternatively, the protrusions (71) (81) (91) which are adjacent to each other may be different.
The light diffusing plate (3), the surface light source device (1), and the liquid crystal display device (30) according to the present invention are not particularly limited to those of the above-described embodiment, and the spirit is within the scope of the claims. Any design changes are allowed as long as they do not deviate from.

Next, specific examples of the present invention will be described, but the present invention is not particularly limited to these examples.
<Example 1>
After dry blending 100 parts by mass of propylene resin (“W101” manufactured by Sumitomo Chemical Co., Ltd.) and 0.3 part by mass of a phosphate ester nucleating agent (“ADEKA STAB NA11” manufactured by ADEKA), the mixture was supplied to an extruder and 200 A light diffusion plate (thickness 1.5 mm, width 250 mm) was obtained by melt-kneading at ~ 250 ° C and extruding at a die temperature of 250 to 260 ° C via a multi-manifold die.
The tacticity of the propylene resin (“W101” manufactured by Sumitomo Chemical Co., Ltd.) measured by the following measurement method was 97.98%. Moreover, the melt flow rate (MFR) measured by the following measuring method about the said propylene resin (Sumitomo Chemical Co., Ltd. "W101") was 24.6 g / 10min.
<Example 2>
A light diffusing plate was obtained in the same manner as in Example 1 except that “E111G” manufactured by Prime Polymer Co., Ltd. was used instead of “W101” manufactured by Sumitomo Chemical Co., Ltd. as the propylene resin.
The tacticity of the propylene resin (“E111G” manufactured by Prime Polymer Co., Ltd.) measured by the following measurement method was 97.67%. Moreover, the melt flow rate (MFR) measured by the following measuring method about the said propylene resin ("E111G" by Prime Polymer Co., Ltd.) was 1.6 g / 10min.
<Example 3>
A light diffusing plate was obtained in the same manner as in Example 1 except that “F113G” manufactured by Prime Polymer Co., Ltd. was used instead of “W101” manufactured by Sumitomo Chemical Co., Ltd. as the propylene resin.
The tacticity of the propylene resin ("F113G" manufactured by Prime Polymer Co., Ltd.) measured by the following measurement method was 97.97%. Moreover, the melt flow rate (MFR) measured with the following measuring method about the said propylene resin ("F113G" by Prime Polymer Co., Ltd.) was 8.4 g / 10min.
<Comparative Example 1>
A light diffusing plate was obtained in the same manner as in Example 1 except that “FSX20L8” manufactured by Sumitomo Chemical Co., Ltd. was used instead of “W101” manufactured by Sumitomo Chemical Co., Ltd. as the propylene resin.
The tacticity of the propylene resin (“FSX20L8” manufactured by Sumitomo Chemical Co., Ltd.) measured by the following measurement method was 93.54%. Moreover, the melt flow rate (MFR) measured by the following measuring method about the said propylene resin (Sumitomo Chemical Co., Ltd. "FSX20L8") was 4.8 g / 10min.
<Measurement method of tacticity of propylene resin>
300 mg of propylene resin to be measured (resin alone, ie, containing no nucleating agent) was dissolved by heating in 3 mL of a mixed solvent of orthodichlorobenzene / orthodichlorobenzene-d4 (80% by volume / 20% by volume). The ¹³ C-NMR is measured using a Bruker NMR measuring apparatus (AVANCE 600). In the obtained ¹³ C-NMR spectrum, with reference to tetramethylsilane, the peak observed at 21.14 to 22.10 ppm was identified as “mm”, and the peak observed at 20.46 to 21.14 ppm was It was identified as “mr”, and the peak observed at 19.75 to 20.40 ppm was identified as “rr”.
(Mm peak intensity) ÷ {(mm peak intensity) + (mr peak intensity) + (rr peak intensity)} × 100
The value (%) calculated by the above formula is tacticity (mm triad fraction).
When the propylene resin to be measured contains an ethylene unit, in order to eliminate the influence of the methyl group of the propylene unit adjacent to ethylene, the Sαγ peak intensity observed at 37.9 ppm is used, and “mm ”And“ mr ”integrated intensities were corrected.
<Measurement method of melt flow rate of propylene resin>
Based on JIS K7210-1999, the melt flow rate (MFR) of the propylene resin was measured under the conditions of a test temperature: 230 ° C. and a test load: 3.8 kg.

Each light diffusion plate obtained as described above was evaluated according to the following evaluation method. The evaluation results are shown in Table 1.
<Bending elastic modulus measurement method>
Based on JIS K7203-1995, the bending elastic modulus (MPa) of the light diffusing plate was measured.
<Load deflection temperature evaluation method>
Based on J1S K7207-1995, the deflection temperature under load (° C.) of the light diffusion plate was measured at a load of 0.45 MPa.
As is clear from the table, the light diffusing plates of Examples 1 to 3 of the present invention have a large bending elastic modulus and an excellent strength, and also have a high load deflection temperature and an excellent heat resistance. Therefore, thermal deformation can be suppressed even under severe thermal conditions.
On the other hand, the light diffusion plate of Comparative Example 1 has a low bending elastic modulus and a low deflection temperature under load, and it is difficult to prevent thermal deformation under severe thermal conditions.

The light diffusing plate of the present invention is suitably used as a light diffusing plate for a surface light source device, but is not particularly limited to such applications. The surface light source device of the present invention is preferably used as a backlight for a liquid crystal display device, but is not particularly limited to such applications.

DESCRIPTION OF SYMBOLS 1 ... Surface light source device 2 ... Light source 3 ... Light diffusing plate 20 ... Liquid crystal panel 30 ... Liquid crystal display device

Claims

A light diffusion plate made of propylene resin with a tacticity of 95% or more.
A light diffusing plate comprising a resin composition containing 100 parts by mass of a propylene resin having a tacticity of 95% or more and 0.01 parts by mass to 2.0 parts by mass of a nucleating agent.
The propylene resin has a melt flow rate of 0.5 g / 10 min to 30 g / 10 min measured under conditions of a test temperature: 230 ° C. and a test load: 3.8 kg in accordance with JIS K7210-1999. 3. The light diffusing plate according to 1 or 2.
A surface light source device comprising: the light diffusing plate according to any one of claims 1 to 3; and a plurality of light sources arranged on a back side of the light diffusing plate.
A light diffusing plate according to any one of claims 1 to 3, a plurality of light sources arranged on the back side of the light diffusing plate, and a liquid crystal panel arranged on the front side of the light diffusing plate. Liquid crystal display device.