JP2010113969A - Light guide plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide plate excellent in transferring property and heat resistance and reduced in color unevenness regardless of its extremely thin thickness of ≥150 in the ratio (L/T)of its width to its thickness in a light incident direction. <P>SOLUTION: The light guide plate is formed by molding a cyclic olefin resin composition satisfying a light transmittance T<SB>420</SB>of ≥75% at the wavelength of 420 nm and a light transmittance T<SB>750</SB>of ≥87% at the wavelength of 750 nm at the optical path length of 50 mm. The melt viscosity measured at 260°C and 1216/sec in shear rate based on ISO 11443 preferably ranges from 45 Pa s to 85 Pa s. Preferably, the cyclic olefin resin composition having a glass transition point of ≥100°C is used. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light guide plate formed by molding a cyclic olefin-based resin composition, and a method for improving transferability of the fine unevenness in a molded body having a surface with fine unevenness such as a light guide plate.

  Conventionally, an optical molded body such as a light guide plate and an optical lens is manufactured by injection molding a thermoplastic resin. Further, as a thermoplastic resin for producing such an optical molded body, norbornene-based addition polymer or norbornene-based ring-opening polymer hydride, which is excellent in transparency, molding processability, mechanical strength, etc., is used. ing.

  Generally, in order to obtain a good molded article, it is considered important to use a resin excellent in melt fluidity at the time of molding. If the melt flowability of the thermoplastic resin is poor, it will not be possible to obtain a good molded product even if the processing conditions during molding (for example, temperature, pressure, etc.) are changed, or the shape of the molded product obtained will be There may be inconveniences such as restrictions.

  For example, Patent Document 1 discloses an injection-molded article made of a thermoplastic saturated norbornene resin having a specific number average molecular weight, having a thin portion with a thickness of 700 μm or less over 25 mm along the flow direction from the gate. Although proposed, the thermoplastic saturated norbornene-based resin used has poor fluidity and poor transferability, so that a good molded product may not be obtained.

  As a conventional technique for producing a molded body using a resin having excellent melt fluidity at the time of molding, for example, Patent Document 2 discloses high transparency, excellent moldability, and mechanical strength and heat resistance. A norbornene-based addition polymer having a melt flow rate (hereinafter sometimes referred to as “MFR”) at 280 ° C. and a load of 2.16 kg of 60 to 200 g / 10 min is disclosed as a polymer having both.

  Patent Document 3 discloses that a polymer having high transparency, excellent moldability, and having both mechanical strength and heat resistance has an MFR of 50 to 300 g / 10 min at 280 ° C. and a load of 2.16 kg. A norbornene-based ring-opening polymer hydride is disclosed.

  However, in the case of producing a thin molded product having a further reduced thickness by injection molding, only the MFR of the norbornene-based addition polymer or norbornene-based ring-opening polymer hydride to be used is adjusted as described in the above document. However, it has been pointed out that the obtained injection-molded product is inferior in heat resistance, and even if it has excellent heat resistance, cracks may occur at the time of mold release, which is a problem. In general, in the case of producing an injection-molded article using a thermoplastic resin, it is necessary to increase the MFR value (that is, increase the fluidity) in order to ensure high transferability. The molecular weight of the resin must be lowered. However, if the molecular weight of the thermoplastic resin used is too small, the bending strength of the injection-molded product is insufficient, and the molded product is easily cracked at the time of mold release.

Therefore, a technique for obtaining a thin injection-molded body having excellent transferability, heat resistance, and strength characteristics (no crack at the time of mold release and no crack at the stress test) is disclosed (Patent Document 4). ).
JP-A-5-47034 JP 2000-169558 A JP 2000-219725 A JP 2006-124657 A

  According to the invention described in Patent Document 4, a molded body having excellent transferability, heat resistance, and strength characteristics is obtained. However, in recent years, there has been a demand for further reduction in thickness. Specifically, in the light guide plate, a light guide plate having a ratio (L / T) of the width and thickness in the light incident direction of 150 or more is required.

  In order to manufacture such a thin light guide plate, the technique described in Patent Document 4 is not sufficient. For this reason, a suitable material for manufacturing a thin light guide plate as required in recent years is required. However, as described above, increasing the fluidity of the material in order to improve the transferability decreases the heat resistance. It tends to end up. Furthermore, as described above, research to obtain a light guide plate that is excellent in transferability, heat resistance, etc. and does not cause color unevenness has been actively conducted, and it is extremely difficult to dramatically improve the performance. It has not been realized.

  The present invention has been made to solve the above-described problems, and an object of the present invention is an extremely thin light guide plate having a ratio (L / T) of the width and thickness in the incident direction of light of 150 or more. However, an object of the present invention is to provide a light guide plate that is excellent in transferability, heat resistance, and the like and does not cause color unevenness.

  The present inventors have intensively studied to solve the above problems. As a result, it has been found that a cyclic olefin resin composition in which the light transmittance in the visible light region measured by increasing the optical path length is higher than a specific value and the melt viscosity is higher than a specific value can solve the above problems. The invention has been completed. More specifically, the present invention provides the following.

(1) A light guide plate formed by molding a cyclic olefin-based resin composition that satisfies an optical path length of 50 mm, a light transmittance T ₄₂₀ at a wavelength of 420 nm of 75% or more, and a light transmittance T ₇₅₀ at a wavelength of 750 nm of 87% or more.

  (2) The cyclic olefin resin composition has a melt viscosity of 45 Pa · s to 85 Pa · s measured at 260 ° C. and a shear rate of 1216 / sec in accordance with ISO 11443. The light-guide plate as described in (1) whose glass transition point of the cyclic olefin resin contained is 100 degreeC or more.

  (3) The light guide plate according to (1) or (2), wherein the ratio (L / T) of the width (L) in the light incident direction to the thickness (T) is 150 or more.

（式中、Ｒ’^１〜Ｒ’^８は、それぞれ同一でも異なっていてもよく、水素原子、ハロゲン原子、及び、炭化水素基からなる群より選ばれるものであり、Ｒ’^５とＲ’^６、Ｒ’^７とＲ’^８は、一体化して２価の炭化水素基を形成してもよく、Ｒ’^５又はＲ’^６と、Ｒ’^７又はＲ’^８とは、互いに環を形成していてもよい。） (4) The light guide plate according to any one of (1) to (3), wherein the cyclic olefin-based resin composition contains a polymer containing a repeating unit represented by the following general formula (II) as a cyclic olefin resin.

(In the formula, R ′ ^{1 to} R ′ ⁸ may be the same or different and are selected from the group consisting of a hydrogen atom, a halogen atom, and a hydrocarbon group, and R ′ ⁵ and R ′ ^6. , R ′ ⁷ and R ′ ⁸ may be combined to form a divalent hydrocarbon group, and R ′ ⁵ or R ′ ⁶ and R ′ ⁷ or R ′ ⁸ form a ring with each other. May be.)

  (5) The light guide plate according to any one of (1) to (4), wherein the cyclic olefin-based resin composition contains a copolymer of norbornene and ethylene.

  According to the present invention, it is possible to obtain a thin light guide plate which is excellent in transferability, heat resistance and the like and does not cause color unevenness.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. . In addition, although description may be abbreviate | omitted suitably about the location where description overlaps, the summary of invention is not limited.

The light guide plate of the present invention is characterized in that the light transmittance T ₄₂₀ having a wavelength of ₄₂₀ nm and the light transmittance T ₇₅₀ having a wavelength of 750 nm, which are measured by increasing the optical path length, are set to specific values. In addition, when trying to improve the fluidity of the resin, the physical properties such as heat resistance tend to decrease, but by using a cyclic olefin resin composition suitable for the present invention described later, heat resistance and the like can be improved. While maintaining the physical properties necessary for a sufficiently equipped light guide plate, the fluidity can be sufficiently enhanced, and as a result, a very excellent light guide plate can be obtained.

<Cyclic olefin resin composition>
[Cyclic olefin resin]
The cyclic olefin resin is not particularly limited as long as it contains a cyclic olefin component as a copolymerization component and is a polyolefin resin containing the cyclic olefin component in the main chain. For example,
(A1) Cyclic olefin addition polymer or hydrogenated product thereof,
(A2) an addition copolymer of a cyclic olefin and an α-olefin or a hydrogenated product thereof,
(A3) A ring-opening (co) polymer of a cyclic olefin or a hydrogenated product thereof.

In addition, as a cyclic olefin resin containing a cyclic olefin component used in the present invention as a copolymerization component,
(A4) A resin obtained by grafting and / or copolymerizing an unsaturated compound having a polar group to the resins (a1) to (a3).

  Examples of the polar group include a carboxyl group, an acid anhydride group, an epoxy group, an amide group, an ester group, and a hydroxyl group. Examples of the unsaturated compound having a polar group include (meth) acrylic acid and maleic acid. Acid, maleic anhydride, itaconic anhydride, glycidyl (meth) acrylate, alkyl (meth) acrylate (carbon number 1-10) ester, maleic acid alkyl (carbon number 1-10) ester, (meth) acrylamide, (meta ) 2-hydroxyethyl acrylate.

  In the present invention, the cyclic olefin-based resins (a1) to (a4) containing the cyclic olefin component as a copolymerization component may be used alone or in combination of two or more.

  Moreover, as the cyclic olefin-based resin containing the cyclic olefin component used in the present invention as a copolymerization component, a commercially available resin can be used. Examples of commercially available cyclic olefin-based resins include TOPAS (registered trademark) (manufactured by TOPAS Advanced Polymers), Apel (registered trademark) (manufactured by Mitsui Chemicals), Zeonex (registered trademark) (manufactured by ZEON Corporation), Examples include ZEONOR (registered trademark) (manufactured by ZEON Corporation), ARTON (registered trademark) (manufactured by JSR Corporation), and the like.

（式中、Ｒ^１〜Ｒ^１２は、それぞれ同一でも異なっていてもよく、水素原子、ハロゲン原子、及び、炭化水素基からなる群より選ばれるものであり、Ｒ^９とＲ^１０、Ｒ^１１とＲ^１２は、一体化して２価の炭化水素基を形成してもよく、Ｒ^９又はＲ^１０と、Ｒ^１１又はＲ^１２とは、互いに環を形成していてもよい。また、ｎは、０又は正の整数を示し、ｎが２以上の場合には、Ｒ^５〜Ｒ^８は、それぞれの繰り返し単位の中で、それぞれ同一でも異なっていてもよい。） The addition copolymer of (a2) cyclic olefin and α-olefin preferably used in the composition of the present invention is not particularly limited. Particularly preferred examples include a copolymer containing [1] an α-olefin component having 2 to 20 carbon atoms and [2] a cyclic olefin component represented by the following general formula (I).

(In the formula, R ^{1 to} R ¹² may be the same or different and are selected from the group consisting of a hydrogen atom, a halogen atom, and a hydrocarbon group, and R ⁹ , R ¹⁰ , R ^11, and R ¹² may be integrated to form a divalent hydrocarbon group, and R ⁹ or R ¹⁰ and R ¹¹ or R ¹² may form a ring with each other, and n is When 0 or a positive integer is represented and n is 2 or more, R ^{5 to} R ⁸ may be the same or different in each repeating unit.

R ^{1 to} R ¹² in the general formula (I) may be the same or different and are selected from the group consisting of a hydrogen atom, a halogen atom, and a hydrocarbon group.

Specific examples of R ^{1 to} R ⁸ include, for example, a hydrogen atom; a halogen atom such as fluorine, chlorine and bromine; a lower alkyl group such as a methyl group, an ethyl group, a propyl group and a butyl group. May be different from each other, may be partially different, or all may be the same.

Specific examples of R ^{9 to} R ¹² include, for example, hydrogen atom; halogen atom such as fluorine, chlorine, bromine; methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, hexyl group, stearyl. Alkyl group such as cyclohexyl group; cycloalkyl group such as cyclohexyl group; substituted or unsubstituted aromatic hydrocarbon group such as phenyl group, tolyl group, ethylphenyl group, isopropylphenyl group, naphthyl group, anthryl group; benzyl group, phenethyl And an aralkyl group in which an aryl group is substituted with an alkyl group, and the like. These may be different from each other, may be partially different, or all may be the same.

Specific examples of the case where R ⁹ and R ¹⁰ or R ¹¹ and R ¹² are integrated to form a divalent hydrocarbon group include, for example, alkylidene groups such as an ethylidene group, a propylidene group, and an isopropylidene group. Can be mentioned.

When R ⁹ or R ¹⁰ and R ¹¹ or R ¹² form a ring with each other, the formed ring may be monocyclic or polycyclic, or may be a polycyclic ring having a bridge. , A ring having a double bond, or a ring composed of a combination of these rings may be used. Moreover, these rings may have a substituent such as a methyl group.

  Specific examples of the cyclic olefin component represented by the general formula (I) include those similar to those described in JP-A-2007-302722.

  Further preferred cyclic olefin-based resins are those containing a cyclic olefin component represented by the following general formula (II) as a polymerization component, and examples include (b1) to (b3).

（式中、Ｒ’^１〜Ｒ’^８は、それぞれ同一でも異なっていてもよく、水素原子、ハロゲン原子、及び、炭化水素基からなる群より選ばれるものであり、Ｒ’^５とＲ’^６、Ｒ’^７とＲ’^８は、一体化して２価の炭化水素基を形成してもよく、Ｒ’^５又はＲ’^６と、Ｒ’^７又はＲ’^８とは、互いに環を形成していてもよい。）

(In the formula, R ′ ^{1 to} R ′ ⁸ may be the same or different and are selected from the group consisting of a hydrogen atom, a halogen atom, and a hydrocarbon group, and R ′ ⁵ and R ′ ^6. , R ′ ⁷ and R ′ ⁸ may be combined to form a divalent hydrocarbon group, and R ′ ⁵ or R ′ ⁶ and R ′ ⁷ or R ′ ⁸ form a ring with each other. May be.)

(B1) Cyclic olefin addition polymer or hydrogenated product thereof,
(B2) Addition copolymer of cyclic olefin and α-olefin or hydrogenated product thereof,
(B3) Ring-opening (co) polymers of cyclic olefins or hydrogenated products thereof.

In addition, as a cyclic olefin resin containing a particularly preferred cyclic olefin component used in the present invention as a copolymerization component,
(B4) A resin obtained by grafting and / or copolymerizing an unsaturated compound having a polar group to the resins (b1) to (b3).

  Examples of the polar group include the same polar groups listed in paragraph 0025 above.

  In the present invention, the cyclic olefin resins (b1) to (b4) containing the above particularly preferred cyclic olefin component as a copolymerization component may be used alone or in combination of two or more. Among the particularly preferred cyclic olefin resins used in the present invention, the cyclic olefin resin (b2) is particularly preferred. This is because it is easy to adjust the melt viscosity of the cyclic olefin-based resin composition to the above range by adjusting the content of the repeating unit derived from the α-olefin and the content of the repeating unit derived from the cyclic olefin. .

  Moreover, as the cyclic olefin-based resin containing a particularly preferable cyclic olefin component used in the present invention as a copolymerization component, a commercially available resin can be used. Examples of the commercially available cyclic olefin resins include TOPAS (registered trademark) (manufactured by TOPAS Advanced Polymers).

  The (b2) addition copolymer of cyclic olefin and α-olefin that is particularly preferably used is not particularly limited. Particularly preferred examples include a copolymer comprising [1] a cyclic olefin component represented by the above general formula (II) and [2] an α-olefin component having 2 to 20 carbon atoms.

[[1] Cyclic olefin component represented by general formula (II)]
In the addition polymer of the cyclic olefin component preferably used in the present invention and another copolymer component such as ethylene, the cyclic olefin component represented by the general formula (II) serving as the copolymer component will be described.

R ′ ^{1 to} R ′ ⁸ in the general formula (II) may be the same or different, and are selected from the group consisting of a hydrogen atom, a halogen atom, and a hydrocarbon group.

Specific examples of R ′ ^{1 to} R ′ ⁴ include a hydrogen atom; a halogen atom such as fluorine, chlorine and bromine; a lower alkyl group such as a methyl group, an ethyl group, a propyl group and a butyl group. These may be different from each other, may be partially different, or all may be the same.

Specific examples of R ′ ^{5 to} R ′ ⁸ include, for example, a hydrogen atom; a halogen atom such as fluorine, chlorine, bromine; a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and a hexyl group. An alkyl group such as a stearyl group; a cycloalkyl group such as a cyclohexyl group; a substituted or unsubstituted aromatic hydrocarbon group such as a phenyl group, a tolyl group, an ethylphenyl group, an isopropylphenyl group, a naphthyl group, and an anthryl group; a benzyl group , Phenethyl group, and other aralkyl groups in which an alkyl group is substituted with an aryl group. These may be different, may be partially different, or all may be the same. .

Specific examples of the case where R ′ ⁵ and R ′ ⁶ , or R ′ ⁷ and R ′ ⁸ are integrated to form a divalent hydrocarbon group include, for example, an ethylidene group, a propylidene group, an isopropylidene group, etc. Examples include alkylidene groups.

When R ′ ⁵ or R ′ ⁶ and R ′ ⁷ or R ′ ⁸ form a ring, the formed ring may be monocyclic or polycyclic, and may be a polycyclic ring having a bridge. It may be a ring having a double bond, or may be a ring composed of a combination of these rings. Moreover, these rings may have a substituent such as a methyl group.

  Specific examples of the cyclic olefin component represented by the general formula (II) include bicyclo [2.2.1] hept-2-ene (common name: norbornene), 5-methyl-bicyclo [2.2.1] hepta. 2-ene, 5,5-dimethyl-bicyclo [2.2.1] hept-2-ene, 5-ethyl-bicyclo [2.2.1] hept-2-ene, 5-butyl-bicyclo [2 2.1] hept-2-ene, 5-ethylidene-bicyclo [2.2.1] hept-2-ene, 5-hexyl-bicyclo [2.2.1] hept-2-ene, 5-octyl -Bicyclo [2.2.1] hept-2-ene, 5-octadecyl-bicyclo [2.2.1] hept-2-ene, 5-methylidene-bicyclo [2.2.1] hept-2-ene 5-vinyl-bicyclo [2.2.1] hept-2-ene 5-propenyl - bicyclo [2.2.1] or a cyclic olefin of 2 rings such as hept-2-ene.

  These cyclic olefin components may be used singly or in combination of two or more. Among the specific examples described in the above publications, the use of bicyclo [2.2.1] hept-2-ene (common name: norbornene) alone provides a resin that easily balances fluidity and optical properties. This is preferable.

[[2] α-olefin component having 2 to 20 carbon atoms]
The C2-C20 alpha-olefin used as the copolymerization component of the addition polymer of the cyclic olefin component preferably used for this invention and other copolymerization components, such as ethylene, is not specifically limited. For example, the thing similar to Unexamined-Japanese-Patent No. 2007-302722 can be mentioned. These α-olefin components may be used alone or in combination of two or more.

  [1] The polymerization method of the cyclic olefin component represented by the general formula (II) and [2] the α-olefin component having 2 to 20 carbon atoms and the hydrogenation method of the obtained polymer are particularly limited. Instead, it can be carried out according to known polymerization methods. It may be random copolymerization or block copolymerization.

[Other copolymer components]
The (b2) addition copolymer of cyclic olefin and α-olefin, which is particularly preferably used in the composition of the present invention, comprises the above-mentioned [1] cyclic olefin component represented by the general formula (II) and [2] carbon number 2 In addition to the α-olefin component of ˜20, other copolymerizable unsaturated monomer components may be contained as necessary within the range not impairing the object of the present invention.

  The unsaturated monomer that may be optionally copolymerized is not particularly limited, and examples thereof include hydrocarbon monomers containing two or more carbon-carbon double bonds in one molecule. Can be mentioned. Specific examples of the hydrocarbon-based monomer having two or more carbon-carbon double bonds in one molecule include those similar to those described in JP-A-2007-302722.

  The polymerization catalyst used is not particularly limited, and can be obtained by a known method using a conventionally known catalyst such as a Ziegler-Natta, metathesis, or metallocene catalyst. The addition copolymer of cyclic olefin and α-olefin or the hydrogenated product thereof preferably used in the present invention is preferably produced using a metallocene catalyst or a Ziegler-Natta catalyst.

  Examples of the metathesis catalyst include molybdenum or tungsten-based metathesis catalysts (for example, described in JP-A Nos. 58-127728 and 58-129003) as a catalyst for ring-opening polymerization of cycloolefin. In addition, the polymer obtained by the metathesis catalyst uses an inorganic carrier-supported transition metal catalyst or the like, and 90% or more of the main chain double bond and 98% or more of the carbon-carbon double bond in the side chain aromatic ring are hydrogenated. It is preferable to add.

[Other resins, etc.]
The cyclic olefin resin composition used in the present invention may contain two or more different cyclic olefin resins. In particular, by blending a cyclic olefin resin having a very low melt viscosity, the melt viscosity measured at 260 ° C. and a shear rate of 1216 / sec in accordance with ISO 11443 of the cyclic olefin resin composition is 45 Pa · s. It becomes easy to adjust to a preferable range of 85 Pa · s.

  You may make the cyclic olefin resin composition used for this invention contain other resin in the range which does not impair the effect of this invention.

  The cyclic olefin-based resin composition used in the present invention includes a nucleating agent, a pigment such as carbon black and an inorganic calcined pigment, an antioxidant, a stabilizer, a plasticizer, a lubricant, and a mold release agent as long as the effects of the invention are not impaired. In addition, a composition imparted with desired characteristics by adding an additive such as a flame retardant is also included.

[Physical properties of cyclic olefin resin]
The cyclic olefin resin glass transition point is preferably 100 ° C. or higher. By setting the glass transition point in the above range, a light guide plate having high heat resistance can be obtained. A more preferable glass transition point is 120 ° C. or higher. In addition, the glass transition point (Tg) employ | adopts the value measured by DSC method (method of JISK7121) on the temperature increase rate of 10 degree-C / min conditions.

<Physical Properties of Cyclic Olefin Resin Composition>
The fluidity of the resin composition of the present invention can reflect the melt viscosity under a condition under a constant piston flow shear rate as an index. Although obtained in units of Pa · s, the lower the numerical value, the better the fluidity at the time of melting, and the better the fluidity at the time of molding. In general, melt flow rate (MFR) is used as an index of fluidity, but MFR is measured under a constant load, and the shear rate of the piston varies depending on the resin. On the other hand, the melt viscosity measurement index under a constant piston flow is considered to be an index closer to the actual flow characteristics considering that actual injection molding is performed with a constant piston flow. In the present invention, the melt viscosity under such a constant shear rate condition is used as an index of fluidity.

  The cyclic olefin resin composition used in the present invention preferably has a melt viscosity of 45 Pa · s to 85 Pa · s measured at 260 ° C. and a shear rate of 1216 / sec in accordance with ISO11443. More preferably, it is 45 Pa · s to 60 Pa · s. When the melt viscosity of the cyclic olefin-based resin composition is less than 45 Pa · s, the mechanical strength as the light guide plate is lowered, which is not preferable. When the melt viscosity exceeds 85 Pa · s, the fluidity is deteriorated and the transfer property is excellent. It tends to be difficult to obtain a light plate.

<Light guide plate>
The light guide plate of the present invention is obtained by molding the cyclic olefin-based resin composition. The molding method is not particularly limited, but is preferably injection molding. This is because it is easy to give fine irregularities to the light guide plate.

  The light guide plate of the present invention uses a cyclic olefin resin composition having an optical path length of 50 mm and a light transmittance measured at a wavelength of 420 nm of 75% or more and a light transmittance measured at a wavelength of 750 nm of 87% or more. Color unevenness of the emitted light is reduced on the surface of the light guide plate, the luminance is increased, and a liquid crystal display element having a good color tone can be obtained.

  The size of the light guide plate is not particularly limited, but the present invention is characterized by having excellent transferability, heat resistance, etc. even with a very thin light guide plate. As described above, using a cyclic olefin resin composition having a melt viscosity of 45 Pa · s to 85 Pa · s measured at 260 ° C. and a shear rate of 1216 / sec in accordance with ISO 11443, and a glass transition point of 100 ° C. or higher. This is because the light guide plate is produced. “Very thin” means that the light guide plate can be easily obtained even when the ratio (L / T) of the width (L) in the light incident direction to the thickness (T) is 150 or more, for example. Can do. Moreover, if said especially preferable cyclic olefin resin composition is used, even if it is a light guide plate whose L / T is 200 or more, a high quality light guide plate can be obtained easily.

  The light guide plate of the present invention is characterized by excellent transferability. As described above, excellent transferability is easily realized by using a particularly preferable cyclic olefin resin composition. “Excellent transferability” means that the transfer rate measured by the method described in the examples is 95% or more. A more preferable transfer rate is 97% or more, and such a high transfer rate can be easily realized by the light guide plate of the present invention because the particularly preferable cyclic olefin resin composition has high fluidity.

It is preferable that the brightness | luminance of the light-guide plate measured by the method as described in an Example is 4500 cd / m < ² > or more.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these Examples.

<Material>
Cyclic olefin resin 1 (resin 1): TOPAS 5013L-10 (manufactured by Polyplastics)
Cyclic olefin resin 2 (resin 2): TOPAS 6013S-04 (manufactured by Polyplastics)
Cyclic olefin resin 3 (Resin 3): ZEONOR 1060R (manufactured by Nippon Zeon Co., Ltd.)
Cyclic olefin resin 4 (resin 4): ZEONOR 1420 (manufactured by Nippon Zeon Co., Ltd.)
Cyclic olefin resin 5 (Resin 5): TOPAS TM (manufactured by Polyplastics)

  Table 1 shows the melt viscosity, glass transition point, and content of the cyclic olefin component of the cyclic olefin resin compositions used in Examples and Comparative Examples shown below.

  The melt viscosity of the cyclic olefin-based resin compositions of Examples and Comparative Examples is a melt viscosity at 260 ° C. and a shear rate of 1216 / sec, and the measurement is performed using a capillary die having a diameter (D) of 1 mm and a length (L) of 20 mm. The method was performed in accordance with ISO11443.

  The glass transition point (Tg) was measured by a DSC method (method described in JIS K7121) at a temperature rising rate of 10 ° C./min.

Using TOPAS5013L-10 (resin 1), a two-screw extruder was melt-extruded at set temperatures of 260 ° C. and 300 ° C., respectively, to produce two types of pellets. These pellets are referred to as Resin 6 and Resin 7.
Resin 6: 260 ° C. extruded product of TOPAS 5013L-10 Resin 7: 300 ° C. extruded product of TOPAS 5013L-10

<Examples 1 to 4, Comparative Examples 1 and 2>
Screen size 3inch, width 38.9mm, length 72.0mm, thickness 0.3mm (The thickness on the anti-gate side was changed by changing the die cavity top. The thickness on the anti-gate side is called the product thickness), The light guide plates of Examples and Comparative Examples were manufactured under the molding conditions shown in Table 2 using a mold having an optical element of a light plate having a V-cut prism. The shape of the light guide plate is shown in FIG.

[Measurement of transfer rate]
The transfer rate was measured by using a laser microscope (manufactured by Keyence Co., Ltd.), and measuring the height of the convex portion at the substantially central portion of the gate side, the non-gate side, and the central measurement location shown in FIG. When 100% was transferred, the transfer rate was 3.25 μm, so the transfer rate was determined and the results are shown in Table 5. In addition, the height of a convex part used the average of 5 times measurement.

[Measurement of brightness]
A backlight unit having the structure shown in Table 3 was created using the molded light guide plate described above. Further, three LEDs in Table 4 were attached to the side edges as shown in FIG. A current of 20 mA was passed to turn on three LEDs, and the luminance of the light guide plate was measured. For the luminance measurement, using a BM-7 type luminance meter manufactured by Topcon Corporation, as shown in FIG. 2, three central portions of the surface of the light guide plate divided into nine parts were measured. Table 5 shows the measurement values averaged after five measurements.

The light guide plates of Examples 1 to 4 have a high transfer rate and high luminance, and were confirmed to be excellent as a light guide plate. Particularly, in Examples 1 and 4, the transfer rate was 96% or more and the luminance was 4500 cd / m ² or more, and it was confirmed that the light guide plate was particularly excellent.

<Example 5, Comparative Examples 3 and 4>
The screen size is 12.1 inch (width 270.0 mm, length 187.4 mm), the thickness is 0.5 mm, the shape of the optical element of the light guide plate is changed to a dot-shaped prism mold, and the molding conditions are listed in Table 6. A light guide plate was produced in the same manner as in Example 1 except that the conditions were changed.

  The transferability of the light guide plates of Example 5 and Comparative Example 3 was measured in the same manner as Example 1 and the like. The measurement results are shown in Table 7.

  In Example 5, the transfer rate was 98% or more, and a good light guide plate was obtained.

<Examples 6 and 7, Comparative Example 4>
[Molding sample for light transmittance measurement]
As the material, the above-described resin 1, resin 6, and resin 7 were used. An electric molding machine with a clamping force of 75 t (Sumitomo Heavy Industries, Ltd.) was used as a mold, using a rod-shaped test piece with a side gate having a 6 mm square of 50 mm length and a 4 mm square cross section at the center in the length direction. Molding was performed at a cylinder temperature of 280 ° C., a mold temperature of 120 ° C., and an injection speed of 1 m / min. Note that the die surface at the sample end face is polished to a surface roughness of 5 nm.

[Light transmittance measurement]
Using a spectrophotometer V570 manufactured by JASCO Corporation, set up a black metal piece with a φ4 hole on the light incident side of the sample installation in order to narrow down the measurement light. Went. Thereafter, the sample was set so that the hole of φ4 was at the center of the sample end face, and the light transmittance (T420 and T750) at wavelengths of 420 nm and 750 nm was measured at an optical path length of 50 mm. The obtained light transmittance is shown in Table 8.

[Color unevenness observation]
In the same manner as in Example 1, a light guide plate was produced, and a backlight unit was produced and an LED was installed. The light was turned on with a current of 10 mA, and color unevenness was observed visually with the light emitted from the light guide plate. Table 8 shows the observation results of color unevenness.

In Examples 6 and 7 having _T420 of 75% or more and _T750 of 87% or more, a good light guide plate having no color unevenness was obtained.

  As described above, the light transmittance at a wavelength of 420 nm is 75% or more, the light transmittance at a wavelength of 750 nm is 85% or more, and a melt viscosity measured at 260 ° C. and a shear rate of 1216 / sec in accordance with ISO 11443 is 45 Pa · By using a cyclic olefin resin composition having a glass transition temperature of 100 ° C. or higher at s to 85 Pa · s, a thin light guide plate excellent in transferability, heat resistance and the like and having little color unevenness can be obtained.

(A) It is a front view of the light guide plate of an Example, (b) It is a side view of the light guide plate of an Example. It is a figure which shows the measurement location of transcription | transfer property and a brightness | luminance.

Claims (5)

A light guide plate formed by molding a cyclic olefin-based resin composition having an optical path length of 50 mm, a light transmittance T ₄₂₀ at a wavelength of 420 nm of 75% or more and a light transmittance T ₇₅₀ at a wavelength of 750 nm of 87% or more. The cyclic olefin resin composition has a melt viscosity of 45 Pa · s to 85 Pa · s measured at 260 ° C. and a shear rate of 1216 / sec in accordance with ISO11443.
The light guide plate according to claim 1, wherein the cyclic olefin resin contained in the cyclic olefin resin composition has a glass transition point of 100 ° C. or higher.   The light guide plate according to claim 1 or 2, wherein a ratio (L / T) of a width (L) in a light incident direction to a thickness (T) is 150 or more. The light guide plate according to any one of claims 1 to 3, wherein the cyclic olefin-based resin composition contains a polymer containing a repeating unit represented by the following general formula (II) as a cyclic olefin resin.

(In the formula, R ′ ^{1 to} R ′ ⁸ may be the same or different and are selected from the group consisting of a hydrogen atom, a halogen atom, and a hydrocarbon group, and R ′ ⁵ and R ′ ^6. , R ′ ⁷ and R ′ ⁸ may be combined to form a divalent hydrocarbon group, and R ′ ⁵ or R ′ ⁶ and R ′ ⁷ or R ′ ⁸ form a ring with each other. May be.) The light guide plate according to claim 1, wherein the cyclic olefin-based resin composition contains a copolymer of norbornene and ethylene.

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