WO2010074312A1

WO2010074312A1 - Light diffusion plate

Info

Publication number: WO2010074312A1
Application number: PCT/JP2009/071850
Authority: WO
Inventors: 濱松豊博; 井山浩暢
Original assignee: 住友化学株式会社
Priority date: 2008-12-25
Filing date: 2009-12-22
Publication date: 2010-07-01
Also published as: TW201035113A; JP2011008216A

Abstract

Disclosed is a light diffusion plate (3) which is formed from a resin composition containing 100 parts by mass of a propylene resin and 0.03-10 parts by mass of a hindered amine light stabilizer having a specific chemical structure. 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 diffusion plate

The present invention relates to a light diffusing plate in which discoloration is prevented and bleed-out is suppressed, and a surface light source device and a liquid crystal display device having excellent durability that are 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)).
As a light diffusing plate used in a backlight, it is desired that the color of the light diffusing plate is less discolored under light and heat from a light source or the like and in various other environments.
In order to suppress such discoloration, for example, a benzotriazole-based ultraviolet absorber such as Adeka Stab LA-31 manufactured by ADEKA is included in a styrene resin-based light diffusion plate (Japanese Patent Application Laid-Open No. 2007-264598). (See Patent Document 3).

However, according to the study by the present inventors, for example, when a benzotriazole ultraviolet absorber such as ADEKA STAB LA-31 manufactured by ADEKA is included in a light diffusion plate made of propylene resin, the ultraviolet absorber is immediately Turned out to bleed out. When the ultraviolet absorber bleeds out, the transparency of the light diffusing plate is lowered and a good image cannot be obtained.
It has also been found that when a benzotriazole ultraviolet absorber such as Adeka Stab LA-31 manufactured by ADEKA is included in a light diffusion plate made of propylene resin, a sufficient discoloration preventing effect cannot be obtained.
Therefore, it is desired to develop a light diffusion plate made of propylene resin that can obtain a sufficient discoloration preventing effect and can suppress bleed out.
The present invention has been made in view of such a technical background, and provides a light diffusing plate in which discoloration is prevented and bleeding out is suppressed under an environment such as light or heat from a light source and its use. For the purpose.
In order to achieve the above object, the present invention provides the following means.
[1] 100 parts by mass of propylene resin, a first hindered amine light stabilizer represented by the following formula (I), a second hindered amine light stabilizer represented by the following formula (II), and the following formula (XI) A light diffusing plate comprising a resin composition containing 0.03 parts by mass to 10 parts by mass of one or more light stabilizers selected from the group consisting of third hindered amine light stabilizers.

(Wherein R ¹¹ and R ¹² each independently represents a hydrogen atom, a linear alkyl group having 1 to 24 carbon atoms or a branched alkyl group having 3 to 24 carbon atoms, and n represents 1 to It is an integer of 100.)

(In the formula, R ²¹ represents a substituent represented by the following formula (V).)

(In the formula, R ⁵² represents a butyl group, and R ⁵³ represents a substituent represented by the following formula (VI).)

(In the formula, R ⁶⁴ represents a hydrogen atom, a linear alkyl group having 1 to 12 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, a linear alkoxyl group having 1 to 12 carbon atoms, or carbon. Represents a branched alkoxyl group having 3 to 12 atoms.)

(In the formula, R ¹⁰¹ and R ¹⁰² each independently represent a hydrogen atom, a linear alkyl group having 1 to 24 carbon atoms, or a branched alkyl group having 3 to 24 carbon atoms.)
[2] The resin composition further includes a first ultraviolet absorber represented by the following formula (III) and a second ultraviolet absorber represented by the following formula (IV) with respect to 100 parts by mass of the propylene resin. 2. The light diffusing plate according to item 1 above, containing 0.03 to 10 parts by mass of one or more ultraviolet absorbers selected from the group consisting of:

(Wherein R ³¹ , R ³² and R ³³ each independently represents a hydrogen atom, a methyl group, a tert-butyl group, a tert-octyl group, —O (CH ₂ ) ₇ CH ₃ or the following formula (VII): And X represents a hydrogen atom or a chlorine atom.)

(In the formula, R ⁴¹ , R ⁴² , R ⁴³ and R ⁴⁴ are each independently represented by a hydrogen atom, a cyano group, a phenyl group, —COOCH ₃ , —COOC ₂ H ₅ , and the following formula (VIII): A substituent, a substituent represented by the following formula (IX) or a substituent represented by the following formula (X) is represented.)

(Wherein R ¹⁰⁵ and R ¹⁰⁶ each represent —COOC ₂ H ₅ )
[3] The resin composition according to item 1 above, further comprising 0.03 to 10 parts by mass of a first ultraviolet absorber represented by the following formula (III) with respect to 100 parts by mass of the propylene resin. Light diffusing plate.

[4] 100 parts by mass of propylene resin, a first hindered amine light stabilizer represented by the following formula (I), a second hindered amine light stabilizer represented by the following formula (II), and the following formula (XI) ) And a resin composition containing 0.03 to 10 parts by mass of one or more light stabilizers selected from the group consisting of third hindered amine light stabilizers. The resin composition absorbs ultraviolet rays. A light diffusing plate that does not contain an agent.

(In the formula, R ¹⁰¹ and R ¹⁰² each independently represent a hydrogen atom, a linear alkyl group having 1 to 24 carbon atoms, or a branched alkyl group having 3 to 24 carbon atoms.)
[5] A surface light source device comprising the light diffusing plate according to any one of items 1 to 4 and a plurality of light sources arranged on the back side of the light diffusing plate.
[6] The light diffusing plate according to any one of 1 to 4 above, 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:
In the invention of [1], since propylene resin is used as the constituent resin, it is lightweight, excellent in mechanical strength and hardly broken, and excellent in heat resistance and moisture resistance, and is not easily deformed by heat or moisture. A resin containing 0.03 to 10 parts by mass of one or more light stabilizers selected from the group consisting of the first, second and third hindered amine light stabilizers with respect to 100 parts by mass of propylene resin Since it consists of a composition, discoloration is prevented in a certain environment, such as light from a light source and heat, and bleed-out is also suppressed.
In the invention of [2], since propylene resin is used as the constituent resin, it is lightweight, excellent in mechanical strength and hardly broken, and excellent in heat resistance and moisture resistance and hardly deformed by heat or moisture. Further, 0.03 to 10 parts by mass of one or more light stabilizers selected from the group consisting of the first, second and third hindered amine light stabilizers are contained with respect to 100 parts by mass of the propylene resin. Therefore, discoloration is prevented in an environment with light from the light source, heat, and the like, and bleeding out is also suppressed. Furthermore, since it contains 0.03 to 10 parts by mass of one or more ultraviolet absorbers selected from the group consisting of the first and second ultraviolet absorbers with respect to 100 parts by mass of propylene resin, the effect of preventing discoloration is obtained. Furthermore, the bleed-out is also suppressed.
In the invention of [3], since propylene resin is used as the constituent resin, it is lightweight, excellent in mechanical strength and hardly broken, and excellent in heat resistance and moisture resistance and hardly deformed by heat or moisture. Further, 0.03 to 10 parts by mass of one or more light stabilizers selected from the group consisting of the first, second and third hindered amine light stabilizers are contained with respect to 100 parts by mass of the propylene resin. Therefore, discoloration is prevented in an environment with light from the light source, heat, and the like, and bleeding out is also suppressed. Further, since 0.03 to 10 parts by mass of the first ultraviolet absorber is contained with respect to 100 parts by mass of the propylene resin, the effect of preventing discoloration is further enhanced and bleeding out is also suppressed.
In the invention of [4], since propylene resin is used as the constituent resin, it is lightweight, excellent in mechanical strength and hardly broken, and excellent in heat resistance and moisture resistance, and is not easily deformed by heat or moisture. Further, containing 0.03 parts by mass to 10 parts by mass of one or more light stabilizers selected from the group consisting of the first, second and third hindered amine light stabilizers with respect to 100 parts by mass of the propylene resin, And since it does not contain an ultraviolet absorber, discoloration is prevented in an environment such as light or heat from the light source, and bleeding out is also suppressed.
In the invention of [5], since a light diffusing plate that prevents discoloration and suppresses bleed out is used, a high-quality surface light source device having excellent durability is provided.
In the invention of [6], since the light diffusing plate that is prevented from being discolored and suppressed from bleeding out is used, 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 diffusion plate (3) includes 100 parts by mass of a propylene resin, a first hindered amine light stabilizer represented by the formula (I), a second hindered amine light stabilizer represented by the formula (II), and the It consists of a resin composition containing 0.03 to 10 parts by mass of one or more light stabilizers (HALS) selected from the group consisting of third hindered amine light stabilizers represented by the formula (XI). The light stabilizer may be one selected from the group consisting of the first, second and third hindered amine light stabilizers, or two or more selected from the group.
Since the light diffusion 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. A resin containing 0.03 to 10 parts by mass of one or more light stabilizers selected from the group consisting of the first, second and third hindered amine light stabilizers with respect to 100 parts by mass of propylene resin Since it consists of a composition, discoloration is prevented in a certain environment, such as light from a light source and heat, and bleed-out is also suppressed. Therefore, the surface light source device (1) has excellent durability and high quality. The content of the specific light stabilizer is preferably 0.05 to 5 parts by mass with respect to 100 parts by mass of the propylene resin, and further 0.10 parts by mass with respect to 100 parts by mass of the propylene resin. It is particularly preferably 2 to 2 parts by mass.
In this invention, the said light diffusing plate (3) is 0.03 mass part of 1 or more types of light stabilizers chosen from the group which consists of said 1st, 2nd and 3 with respect to 100 mass parts of propylene resin. It is preferably composed of a resin composition containing 0.03 parts by mass to 10 parts by mass of one or more kinds of ultraviolet absorbers selected from the group consisting of 10 parts by mass and the first and second ultraviolet absorbers. In this case, in addition to the hindered amine light stabilizer (HALS), a specific ultraviolet absorber is contained in a specific amount, so that the effect of preventing discoloration can be further enhanced while suppressing bleed out. The content of the specific light stabilizer is preferably 0.05 to 5 parts by mass with respect to 100 parts by mass of the propylene resin, and further 0.10 parts by mass with respect to 100 parts by mass of the propylene resin. It is particularly preferably 2 to 2 parts by mass. Further, the content of the specific ultraviolet absorber is preferably 0.05 parts by mass to 5 parts by mass with respect to 100 parts by mass of the propylene resin, and further 0.10 parts by mass with respect to 100 parts by mass of the propylene resin. It is particularly preferably 2 to 2 parts by mass. Moreover, as the specific ultraviolet absorber, it is preferable to use a first ultraviolet absorber represented by the general formula (III) (one kind or two or more kinds) may be used. In this case, compared with the case where the said 2nd ultraviolet absorber is used, the outstanding discoloration prevention effect can be maintained over a long period of time.
Alternatively, the light diffusing plate (3) contains 0.03 of one or more light stabilizers selected from the group consisting of the first, second, and third hindered amine light stabilizers with respect to 100 parts by mass of the propylene resin. The resin composition is preferably contained in an amount of 10 to 10 parts by mass, and the resin composition preferably contains no ultraviolet absorber (UVA). In this case, bleed out is further suppressed. Even in a configuration in which this ultraviolet absorber (UVA) is not contained, it is preferable to contain 0.05 to 5 parts by mass of the specific light stabilizer with respect to 100 parts by mass of the propylene resin. It is particularly preferable to contain 0.10 to 2 parts by mass of the specific light stabilizer with respect to parts by mass.
Although it does not specifically limit as a 1st hindered amine light stabilizer represented by the said general formula (I), For example, Tinuvin 622LD (made by Ciba Japan) etc. are mentioned. Tinuvin 622LD has the formula (I), wherein R ¹¹ is a hydrogen atom and R ¹² is a methyl group.
Although it does not specifically limit as a 2nd hindered amine light stabilizer represented by the said general formula (II), For example, Kimasorb 119FL (made by Ciba Japan) etc. are mentioned. The Kimasorb 119FL includes 90% by mass of a second hindered amine light stabilizer represented by the formula (II), and a first hindered amine light in which R ¹¹ is a hydrogen atom and R ¹² is a methyl group in the formula (I). It is a mixture with 10% by weight of stabilizer.
In addition, used in the examples, Tinuvin XT850FF (manufactured by Ciba Japan) and Tinuvin XT855FF (manufactured by Ciba Japan) are the first hindered amine light stabilizer represented by formula (I) and formula (XI). It is at least one light stabilizer selected from the group consisting of the third hindered amine light stabilizers represented.
Although it does not specifically limit as a 1st ultraviolet absorber represented by the said general formula (III), For example, Tinuvin 234 (made by Ciba Japan), Tinuvin 328 (made by Ciba Japan), SEESORB703 (Manufactured by Sipro Kasei Co., Ltd.), SEESORB 707 (manufactured by Sipro Kasei Co., Ltd.) and the like.
In the formula (III), the tinuvin 234 is a substituent in which R ³¹ is represented by the formula (VII), R ³² is a hydrogen atom, R ³³ is a substituent represented by the formula (VII), and X is a hydrogen atom. is there.
In the tinuvin 328, in formula (III), R ³¹ is a tert-octyl group, R ³² is a hydrogen atom, R ³³ is a tert-octyl group, and X is a hydrogen atom.
In the SEESORB 703, in the formula (III), R ³¹ is a tert-butyl group, R ³² is a hydrogen atom, R ³³ is a methyl group, and X is a chlorine atom.
The SEESORB707, in Formula ^{(III), R 31} is a hydrogen ^{atom, R 32} is -O _(CH ₂₎ 7 CH ₃ ^{group, R 33} is a hydrogen atom, X is a hydrogen atom.
Although it does not specifically limit as a 2nd ultraviolet absorber represented by the said formula (IV), For example, SEESORB501 (made by Sipro Kasei), SEESORB502 (made by Sipro Kasei), PR25 (made by Clariant) , B-CAP (manufactured by Clariant) and the like.
The SEESORB501, in Formula ^{(IV), R 41} is a phenyl ^{group, R 42} is a phenyl ^{group, R 43} is a cyano ^{group, R 44} is -COOC ₂ H ₅ group.
The SEESORB 502 is a substituent represented by the formula (IV), wherein R ⁴¹ is a phenyl group, R ⁴² is a phenyl group, R ⁴³ is a cyano group, and R ⁴⁴ is a formula (IX).
The PR25, in Formula ^(IV), ₃ groups ^{R 41} is ^{-COOCH, R 42} is -COOCH ₃ ^{group, the substituents R 43} is represented by formula ^(VIII), is ^{R 44} is hydrogen atom.
In the formula (IV), R ⁴¹ is a substituent represented by the formula (X), R ⁴² is a hydrogen atom, R ⁴³ , R ⁴⁴ , R ¹⁰⁵ , and R ¹⁰⁶ are all —COOC ₂ H in the formula (IV). _Five groups.
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.
It is preferable that light diffusing particles and / or nucleating agents are further blended with the propylene resin constituting the light diffusing plate (3).
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 diameter (D ₅₀ ) is determined by measuring the particle diameter and volume of all the particles, and sequentially integrating the volumes from the smallest particle diameter, and the integrated volume is 50% with respect to the total volume of all the 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.
Further, the nucleating agent is not particularly limited. For example, sorbitol nucleating agent, organophosphate nucleating agent, metal salt nucleating agent of carboxylic acid, rosin nucleating agent, etc. Can be used.
The content of the nucleating agent in the light diffusing plate (3) is preferably in the range of 0.01 to 1.0 part by mass with respect to 100 parts by mass of the propylene resin. Appearance of white spots or the like on the surface is suppressed by being 0.01 parts by mass or more, and a light diffusing plate having a good appearance can be obtained, and dispersion of the nucleating agent is 1.0 parts by mass or less. It is possible to suppress a decrease in optical characteristics and an increase in cost due to defects.
You may make the resin composition which comprises the said light diffusing plate (3) contain additives, such as a heat stabilizer, antioxidant, a weathering agent, a fluorescent whitening agent, and a processing stabilizer, as needed.
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 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 light diffusing plate (3) of this invention can be manufactured as follows, for example. The resin composition having the above composition can be produced by a known molding method such as an extrusion molding method for extrusion molding, an injection molding method for injection molding, or a hot pressing method for hot pressing. 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 light diffusing plate (3) may be flat on both sides as shown in FIG. 1, or at least one side may be a surface on which irregularities such as a lenticular lens, a Fresnel lens, and a prism lens are formed. Alternatively, at least one surface may be a matte surface.
In the case of using the matte surface, the ten-point average roughness (Rz) of the surface is preferably set to 1 μm to 100 μm, and thereby the surface (matte surface) of the light diffusion plate (3) is set. The occurrence of scratches can be sufficiently suppressed.
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.
Moreover, as a method of forming irregularities on the surface of the light diffusing plate (3), for example, if the light diffusing plate is produced by extrusion molding, resin particles insoluble in the resin constituting the surface side layer are used. Examples thereof include a method of containing and extrusion molding, a method of transferring a concavo-convex to the surface of an extruded plate (light diffusion plate) by bringing a transfer roll having a concavo-convex shape on the surface thereof into contact immediately after extrusion. Moreover, when manufacturing a light-diffusion board by injection molding or a hot press, the method etc. which transfer an unevenness | corrugation using the metal mold | die with which the uneven | corrugated shape was provided to the molding surface are mentioned.
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 thereof 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>
99.1 parts by mass of propylene resin ("FSX20L8" manufactured by Sumitomo Chemical Co., Ltd.), 0.5 parts by mass of Tinuvin XT850FF (Ciba Japan Co., Ltd.), 0.2 parts by mass of Sumizer GP (manufactured by Sumitomo Chemical Co., Ltd., thermal stabilizer), After dry blending 0.2 part by weight of ADK STAB NA11 (manufactured by ADEKA, phosphate ester nucleating agent), it is supplied to an extruder with a screw diameter of 40 mm and melt-kneaded at 210-250 ° C., via a multi-manifold die Then, a light diffusion plate (thickness 1.5 mm, width 250 mm) was obtained by extrusion at a die temperature of 250 to 260 ° C.
<Examples 2 to 9, Comparative Examples 1 to 5>
A light diffusing plate was obtained in the same manner as in Example 1 except that the materials shown in Tables 1 to 3 were used in the ratios shown in Tables 1 to 3, respectively.
In the table, “LA31” is an ultraviolet absorber made by ADEKA, and “Irgaphos 168” is a heat stabilizer made by Ciba Japan.

Each light diffusion plate obtained as described above was evaluated according to the following evaluation method. The evaluation results are shown in Tables 1 to 3.
<Durability evaluation method>
Each light diffusion plate is subjected to the following mercury lamp irradiation test, high-temperature and high-humidity test, high-temperature test, and low-temperature test, the surface state of the light diffusion plate after the test is visually observed, and powder is adhered to the surface (that is, bleeding) "No"), and "Good" indicates that the surface condition was good and similar to the initial state before the test (ie, no bleed out). Further, the yellowness YI of the light diffusing plate before the above test was measured by the following YI measurement method, which was designated as “initial YI”, and the yellowness YI of the light diffusing plate after the above test was measured. YI ”, and the change amount ΔYI was obtained by the following calculation formula.
ΔYI = (YI after test) − (initial YI)
(250 hours mercury lamp irradiation test)
The light diffusion plate was irradiated with a mercury lamp for 250 hours under the condition of 75 ° C.
(250 hours high temperature and high humidity test)
The light diffusion plate was placed for 250 hours under high temperature and high humidity conditions of 60 ° C. and 90% RH.
(250 hour high temperature test)
The light diffusing plate was placed under a high temperature condition of 80 ° C. for 250 hours.
(250 hour low temperature test)
The light diffusing plate was placed for 250 hours under a low temperature condition of −40 ° C.
(500 hours mercury lamp irradiation test)
The light diffusion plate was irradiated with a mercury lamp for 500 hours under the condition of 75 ° C.
(500 hours high temperature and high humidity test)
The light diffusion plate was placed for 500 hours under high temperature and high humidity conditions of 60 ° C. and 90% RH.
(500 hours high temperature test)
The light diffusing plate was placed under high temperature conditions of 80 ° C. for 500 hours.
(500 hours low temperature test)
The light diffusing plate was placed for 500 hours under a low temperature condition of −40 ° C.
[Yellowness YI measurement method]
Using a spectrophotometer equipped with an integrating sphere (“UV-4000” manufactured by Hitachi, Ltd.), the spectral transmittance in the wavelength range of 380 to 780 nm of the light diffusion plate was measured, and based on this, the yellowness YI was calculated. .
As is apparent from Tables 1 to 3, the light diffusing plates of Examples 1 to 9 of the present invention sufficiently suppress discoloration even after a mercury lamp irradiation test, a high temperature and high humidity test, a high temperature test, and a low temperature test for 500 hours. And no bleed-out occurred.
In the light diffusing plates of Examples 1 and 2, the addition amount of the hindered amine light stabilizer with respect to 100 parts by mass of the propylene resin is a small addition amount in the range of 0.1 parts by mass to 2.0 parts by mass. In the light diffusion plate of No. 5, the addition amount of the hindered amine light stabilizer and the ultraviolet absorber with respect to 100 parts by mass of the propylene resin is a small addition amount ranging from 0.1 parts by mass to 2.0 parts by mass. The light diffusing plates of Examples 1 to 5 have such a small addition amount (low cost), ΔYI is smaller than 5 and the discoloration is sufficiently suppressed, mercury lamp irradiation test, high temperature and high humidity Even if a test, a high temperature test, and a low temperature test are performed for 500 hours, bleed-out does not occur, which is particularly preferable.
In contrast, in Comparative Examples 1 to 5 that deviated from the specified range of the present invention, bleeding out occurred in 250 hours when the mercury lamp irradiation test, the high temperature and high humidity test, the high temperature test, and the low temperature test were performed.

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

100 parts by mass of propylene resin, a first hindered amine light stabilizer represented by the following formula (I), a second hindered amine light stabilizer represented by the following formula (II), and the following formula (XI) A light diffusing plate comprising a resin composition containing 0.03 to 10 parts by mass of one or more light stabilizers selected from the group consisting of third hindered amine light stabilizers.

(Wherein R 11 and R 12 each independently represents a hydrogen atom, a linear alkyl group having 1 to 24 carbon atoms or a branched alkyl group having 3 to 24 carbon atoms, and n represents 1 to It is an integer of 100.)

(In the formula, R 21 represents a substituent represented by the following formula (V).)

(In the formula, R 52 represents a butyl group, and R 53 represents a substituent represented by the following formula (VI).)

(In the formula, R 64 represents a hydrogen atom, a linear alkyl group having 1 to 12 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, a linear alkoxyl group having 1 to 12 carbon atoms, or carbon. Represents a branched alkoxyl group having 3 to 12 atoms.)

(In the formula, R 101 and R 102 each independently represent a hydrogen atom, a linear alkyl group having 1 to 24 carbon atoms, or a branched alkyl group having 3 to 24 carbon atoms.)
The resin composition further comprises a first ultraviolet absorber represented by the following formula (III) and a second ultraviolet absorber represented by the following formula (IV) with respect to 100 parts by mass of the propylene resin. The light diffusing plate according to claim 1, comprising 0.03 parts by mass to 10 parts by mass of at least one ultraviolet absorber selected from the above.

(Wherein R 31 , R 32 and R 33 each independently represents a hydrogen atom, a methyl group, a tert-butyl group, a tert-octyl group, —O (CH 2 ) 7 CH 3 or the following formula (VII): And X represents a hydrogen atom or a chlorine atom.)

(In the formula, R 41 , R 42 , R 43 and R 44 are each independently represented by a hydrogen atom, a cyano group, a phenyl group, —COOCH 3 , —COOC 2 H 5 , and the following formula (VIII): A substituent, a substituent represented by the following formula (IX) or a substituent represented by the following formula (X) is represented.)

(Wherein R 105 and R 106 each represent —COOC 2 H 5 )
The light according to claim 1, wherein the resin composition further contains 0.03 to 10 parts by mass of a first ultraviolet absorber represented by the following formula (III) with respect to 100 parts by mass of the propylene resin. Diffusion plate.

(Wherein R 31 , R 32 and R 33 each independently represents a hydrogen atom, a methyl group, a tert-butyl group, a tert-octyl group, —O (CH 2 ) 7 CH 3 or the following formula (VII): And X represents a hydrogen atom or a chlorine atom.)
100 parts by mass of propylene resin, a first hindered amine light stabilizer represented by the following formula (I), a second hindered amine light stabilizer represented by the following formula (II), and the following formula (XI) A resin composition containing 0.03 parts by mass to 10 parts by mass of one or more light stabilizers selected from the group consisting of third hindered amine light stabilizers, and the resin composition contains an ultraviolet absorber A light diffusing plate that does not.

(Wherein R 11 and R 12 each independently represents a hydrogen atom, a linear alkyl group having 1 to 24 carbon atoms or a branched alkyl group having 3 to 24 carbon atoms, and n represents 1 to It is an integer of 100.)

(In the formula, R 21 represents a substituent represented by the following formula (V).)

(In the formula, R 52 represents a butyl group, and R 53 represents a substituent represented by the following formula (VI).)

(In the formula, R 64 represents a hydrogen atom, a linear alkyl group having 1 to 12 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, a linear alkoxyl group having 1 to 12 carbon atoms, or carbon. Represents a branched alkoxyl group having 3 to 12 atoms.)

(In the formula, R 101 and R 102 each independently represent a hydrogen atom, a linear alkyl group having 1 to 24 carbon atoms, or a branched alkyl group having 3 to 24 carbon atoms.)
A surface light source device comprising: the light diffusing plate according to any one of claims 1 to 4; and a plurality of light sources arranged on a back side of the light diffusing plate.
5. A light diffusing plate according to claim 1, 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.