JP2006188577A - Biaxially oriented film for optical use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxially oriented film for optical use imparting a good color, containing extremely reduced amount of fine particles in the film without using antimony (Sb) or germanium (Ge) as a catalyst. <P>SOLUTION: The biaxially oriented film for optical use comprises an aromatic polyester substantially free from metal elements of density ≥5.0 and the film has color b value of from -0.5 to 2.0 obtained by transmitted light measurement, and containing ≤195 particles/mm<SP>2</SP>of fine particles with particle diameter of 1-10 μm measured by a dark field microscopic method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a biaxially stretched film for optics, and more particularly, to a biaxially stretched film for optics that is made of polyester and exhibits an excellent hue.

  Polyester is widely used in films because of its excellent mechanical, physical and chemical performance. In recent years, the preservation of the global environment has become an important issue, and there is a demand for films with low environmental impact. As for polyester, a film containing no Sb or Ge element is desirable from the viewpoint of reducing environmental load.

Japanese Patent Publication No. 48-2229 Japanese Patent Publication No. 47-26597 International Publication No. 01/00706 Pamphlet International Publication No. 03/008479 Pamphlet International Publication No. 03/027166 Pamphlet Japanese Patent Laid-Open No. 11-158257

  However, when a polyester that does not use antimony (Sb) or germanium (Ge) as a catalyst is used as a raw material, usually only a film having a poor hue can be obtained. An object of the present invention is to provide a biaxially stretched film for optics that exhibits a good hue and has a very small amount of fine particles in the film even though Sb or Ge is not used as a catalyst.

That is, the present invention comprises an aromatic polyester that does not substantially contain a metal element having a specific gravity of 5.0 or more, and has a color b ^* value of -0.5 to 2.0 by transmitted light measurement, measured by dark field microscopy. It is a biaxially stretched film for optics, characterized in that the number of fine particles having a particle diameter of 1 to 10 μm caused by the catalyst present in the film is 195 particles / mm ² or less.

  According to the present invention, there is provided an optically biaxially stretched film that exhibits a good hue and has a very small amount of fine particles in the film even though antimony (Sb) or germanium (Ge) is not used as a catalyst. be able to.

The present invention will be described in detail below.
[Aromatic polyester]
The aromatic polyester in the present invention is a polyester obtained by a polycondensation reaction between an aromatic dicarboxylic acid component typified by terephthalic acid, naphthalenedicarboxylic acid, or an ester-forming derivative thereof, and a glycol component. This polyester may be a copolyester, and as a copolymer component, a component other than an aromatic dicarboxylic acid component and a glycol component, for example, an aliphatic dicarboxylic acid component, an aromatic dihydroxy compound, and an oxycarboxylic acid component are copolymerized. May be.

  The aromatic polyester is preferably a polyester selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polytetramethylene terephthalate, polytetramethylene naphthalate, Among these, a polyester having polyethylene terephthalate as a main constituent is particularly preferable. The “main constituent component” means that 80 mol% or more of all repeating units of the polyester is an aromatic polyester.

[Metal elements having a specific gravity of 5.0 or more]
The metal element having a specific gravity of 5.0 or more in the present invention is a metal element derived from a metal compound contained in a catalyst, a metal color adjuster, a matting agent or the like contained in the polyester. Specific examples include antimony, germanium, manganese, cobalt, cerium, tin, zinc, lead, and cadmium. On the other hand, for example, titanium, aluminum, calcium, magnesium, sodium, and potassium do not correspond to metals having a specific gravity of 5.0 or more.

  In the present invention, substantially not containing a metal element means that the content of the metal element is 10 ppm or less, preferably 7 ppm by weight or less, more preferably 5 ppm by weight or less. When it exceeds 10 ppm, there is a disadvantage in that the handling property and the environmental load in film formation are large. For example, in the case of an antimony element, when it exceeds 10 ppm, it becomes a foreign substance at the time of yarn production or film formation, and adheres to the periphery of the die or die, which adversely affects long-term continuous formability. In the case of lead, tin, and cadmium elements, if it exceeds 10 ppm, the metal elements themselves are toxic and the environmental load increases. In the case of germanium, since it is expensive per se, if the content exceeds 10 ppm, the price of the resulting polyester composition increases, which is not preferable.

[Hue]
The biaxially stretched film for optics of the present invention has a color b ^* value in the range of -0.5 to 2.0 as measured by transmitted light. If the color b ^* value is less than −0.5, the blueness of the image of the display device tends to be too strong, and if it exceeds 2.0, the image of the display device tends to have a yellowish tone. The hue is a numerical value in the L ^* a ^* b ^* color system.

In the present invention, in order to obtain the above-described hue, the polyester preferably contains a color adjusting agent per film weight, preferably 0.1 to 10 ppm, more preferably 0.3 ppm to 9 ppm, and particularly preferably 0.5 to 8 ppm. This color adjuster has a maximum absorption wavelength of 540 to 600 nm, preferably 545 to 595 nm, more preferably 540 to 595 nm, measured in a chloroform solution state with a color adjuster concentration of 20 mg / L and an optical path length of 1 cm. The color adjusting agent is 550 to 590 nm, and the ratio of the absorbance at each wavelength to the absorbance at the maximum absorption wavelength satisfies all of the following formulas (1) to (4).
0.00 ≦ A ₄₀₀ / A _max ≦ 0.20 (1)
0.10 ≦ A ₅₀₀ / A _max ≦ 0.70 (2)
0.55 ≦ A ₆₀₀ / A _max ≦ 1.00 (3)
0.00 ≦ A ₇₀₀ / A _max ≦ 0.05 (4)
(Wherein, A ₄₀₀ , A ₅₀₀ , A ₆₀₀ , A ₇₀₀ are the absorbance in the visible light absorption spectrum at 400 nm, 500 nm, 600 nm, and 700 nm, respectively, and A _max is the absorbance in the visible light absorption spectrum at the maximum absorption wavelength. .)

This color adjusting agent preferably further satisfies any or all of the following formulas (6) to (9).
0.00 ≦ A ₄₀₀ / A _max ≦ 0.15 (6)
0.30 ≦ A ₅₀₀ / A _max ≦ 0.60 (7)
0.60 ≦ A ₆₀₀ / A _max ≦ 0.95 (8)
0.00 ≦ A ₇₀₀ / A _max ≦ 0.03 (9)

  If the color adjusting agent is less than 0.1 ppm, the resulting film has an unfavorable yellowish tint, and if it exceeds 10 ppm, the lightness is weakened and the appearance is darkened, which is not preferred as an optically biaxially stretched film.

  If the maximum absorption wavelength at 380 to 780 nm measured in a chloroform solution state with a color adjusting agent concentration of 20 mg / L and an optical path length of 1 cm is less than 540 nm, the redness of the film becomes strong. A taste becomes strong and it is not preferable as a biaxially stretched film for optics, and if any one of the conditions of the formulas (1) to (4) is not satisfied, the coloring of the film is large and not preferable.

  The color adjusting agent is an organic polyaromatic ring dye or pigment. Specifically, as described later, a blue color adjusting agent, a purple color adjusting agent, a red color adjusting agent, and an orange color adjusting agent can be exemplified. These may be used alone or in combination of two or more.

As the color adjusting agent, a blue color adjusting agent and a purple color adjusting agent are preferably used in combination. In this case, the weight ratio of the blue color adjusting agent to the purple color adjusting agent is preferably in the range of 90:10 to 40:60, and in the range of 80:20 to 50:50. When the weight ratio of the blue color adjusting agent exceeds 90, the color a ^* value of the obtained film becomes small and green, and when the weight ratio of the blue color adjusting agent is less than 40, the color a ^* value increases and the red color is increased. Presented unfavorably.

  The blue color adjusting agent is generally described as “Blue” among commercially available color adjusting agents. Specifically, the maximum absorption wavelength in the visible light spectrum in the solution is about 580 to 620 nm. It is what. CISolvent Blue 11, CISolvent Blue 25, CISolventBlue 35, CISolvent Blue 36, CISolventBlue 45 (Telasol Blue RLS), CISolventBlue 55, CISolvent Blue 63, CISolventBlue 78, CISolvent Examples include Blue 83, CISolventBlue 87, and CISolvent Blue 94.

  The purple color adjusting agent is described as “Violet” among commercially available color adjusting agents. Specifically, the maximum absorption wavelength in the visible light absorption spectrum in the solution is about 560 to 580 nm. It is what. C.I.Solvent Violet 8, C.I.Solvent Violet 13, C.I.Solvent Violet 14, C.I.Solvent Violet 21, C.I.Solvent Violet 27, C.I.Solvent Violet 28, C.I.SolventViolet 36 are illustrated as purple color adjusting agents.

  The red color adjusting agent is described as “Red” among commercially available color adjusting agents. Specifically, the maximum absorption wavelength in the visible light absorption spectrum in the solution is about 480 to 520 nm. It is what. CISolvent Red 24, CISolvent Red 25, CISolventRed 27, CISolvent Red 30, CISolventRed 49, CISolvent Red 52, CISolventRed 100, CISolvent Red 109, CISolventRed 111, CISolvent Examples include Red 121, CISolventRed 135, CISolvent Red 168, and CISolventRed 179.

  The orange-based color adjusting agent is represented by “Orange” among commercially available color adjusting agents. C.I. Solvent Orange 60 is exemplified as the orange color adjusting agent.

[Fine particles]
The biaxially stretched film for optics of the present invention has 195 particles / mm ² or less of fine particles having a particle diameter of 1 to 10 μm caused by the catalyst present in the film as measured by dark field microscopy. If the number of fine particles exceeds 195 particles / mm ² , the transparency of the film deteriorates due to light scattering by the particles, and the image becomes blurred when used for an optical biaxially stretched film.

  In the present invention, the titanium metal element present in the polyester is preferably 2 to 15 mmol%, more preferably 3 to 10 mmol%, based on the total dicarboxylic acid component constituting the polyester. If the titanium metal element is less than 2 mmol%, the polycondensation reaction of the polyester does not proceed sufficiently, and if it exceeds 15 mmol%, the hue of the resulting film is yellowish and the heat resistance is lowered, which is not preferable.

And it is preferable that the molar ratio of a titanium metal element and a phosphorus element satisfy | fills following Numerical formula (5).
1 ≦ P / Ti ≦ 15 (5)
(In the formula, P represents the concentration (mmol%) of the phosphorus element contained in the polyester, and Ti represents the concentration (mmol%) of the titanium metal element soluble in the polyester contained in the polyester.)

  If the P / Ti is less than 1, the resulting film has a yellow hue, and if it exceeds 15, the polycondensation reaction of the polyester becomes slow, which is not preferable. The range of P / Ti is more preferably 2-10.

  Titanium metal elements soluble in polymers do not include inorganic titanium compounds such as titanium oxide, but are contained as impurities in organic titanium compounds usually used as catalysts and titanium oxides used as matting agents. An organic titanium compound.

  The intrinsic viscosity of the polyester is preferably 0.40 to 1.00. The intrinsic viscosity is a value calculated from a numerical value measured at a measurement temperature of 35 ° C. using orthochlorophenol as a solvent.

[Production method of polyester]
The aromatic polyester in the present invention can be produced by a generally known production method. For example, first, a dicarboxylic acid component such as terephthalic acid is directly esterified with a glycol component such as ethylene glycol, or a lower alkyl ester of a dicarboxylic acid component such as dimethyl terephthalate is transesterified with a glycol component such as ethylene glycol. To produce a glycol ester of dicarboxylic acid and / or a low polymer thereof. Then, the reaction product is heated under reduced pressure in the presence of a polymerization catalyst and subjected to a polycondensation reaction until a predetermined degree of polymerization is obtained, whereby a desired aromatic polyester is produced.

  The polymerization catalyst used in the production of the aromatic polyester is preferably a titanium compound and / or an aluminum compound. As the titanium compound, a general titanium compound, for example, titanium acetate or tetra-n-butoxy titanium can be used as a polyester polycondensation catalyst. Preferably, a compound represented by the following general formula (I) is used. Or a product obtained by reacting a compound represented by the following general formula (I) with an aromatic polyvalent carboxylic acid represented by the following general formula (II) or an anhydride thereof, or in the following general formula (III) The compound represented is used.

（式中、Ｒ^１、Ｒ^２、Ｒ^３およびＲ^４はそれぞれ同一若しくは異なって、アルキル基またはフェニル基を示し、ｍは１〜４の整数を示し、かつｍが２、３または４の場合、２個、３個または４個のＲ^２およびＲ^３は、それぞれ同一であっても異なっていてもどちらでもよい。）

(Wherein R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents an alkyl group or a phenyl group, m represents an integer of 1 to 4, and m is 2, 3 or 4) 2, 3 or 4 R ² and R ³ may be the same or different from each other.)

（式中、ｑは２〜４の整数を表わす。）

(In the formula, q represents an integer of 2 to 4.)

（式中、Ｘは炭素数１〜２０のアルキル基、アルコキシ基、または炭素数６〜２０のアリール基、アリールオキシ基である。）

(In the formula, X represents an alkyl group having 1 to 20 carbon atoms, an alkoxy group, or an aryl group or aryloxy group having 6 to 20 carbon atoms.)

  As the aluminum compound, aluminum acetylacetonate is preferable because it is stable and easy to handle. These titanium compounds and aluminum compounds may be used alone or in combination of two or more, but it is particularly preferable to use the titanium compound alone.

  Among these, the most preferred embodiment uses the compound represented by the above general formula (I), the compound represented by the general formula (I) and the aromatic polyvalent carboxylic acid represented by the above general formula (II) or an anhydride thereof. Or a mode in which a compound represented by the above general formula (III) is used alone.

  As tetraalkoxide titanium and / or tetraphenoxide titanium represented by the general formula (I), R may be an alkyl group and / or a phenyl group. Examples include tetraisopropoxy titanium, tetra-n-propoxy titanium, tetra-n-butoxy titanium, tetraethoxy titanium, and tetraphenoxy titanium.

  In addition, the aromatic polyvalent carboxylic acid represented by the general formula (II) to be reacted with the titanium compound or the anhydride thereof includes phthalic acid, trimellitic acid, hemimellitic acid, pyromellitic acid or an anhydride thereof. Illustrated.

  When the titanium compound and the aromatic polyvalent carboxylic acid or its anhydride are reacted, the aromatic polyvalent carboxylic acid or a part of its anhydride is dissolved in a solvent, and the titanium compound is dropped into this, What is necessary is just to make it react for 30 minutes or more at the temperature of 0-200 degreeC.

  In addition, the compound represented by general formula (III) is a compound represented by general formula (I) and monoalkylphosphonic acid, monoarylphosphonic acid, monoalkylphosphate, monoarylphosphate in the range of 70 to 150 ° C. It can be obtained by reacting.

  As described above, a phosphorus compound is added to the polyester composition in order to keep the titanium metal element and phosphorus element soluble in the polyester in a preferred molar ratio. As the phosphorus compound, phosphoric acid, phosphorous acid, phosphonic acid, phosphinic acid, or alkyl, aryl ester or phosphonoacetate compounds thereof are preferably used.

  The addition method of the phosphorus compound into the polyester composition may be any time after the ester exchange reaction or the esterification reaction is substantially completed, but usually immediately after the esterification reaction or the ester exchange reaction is completed. It is preferable to add and then polycondensate.

  The color adjusting agent can be added at any stage of the aromatic polyester production process, and is preferably added until the completion of the polymerization reaction, particularly preferably after completion of the esterification reaction or transesterification reaction.

[Film Production Method]
The biaxially stretched film for optics of the present invention can be produced using a conventionally known melt film forming method.
For example, the dried polyester composition is melted in the range of 270 ° C. to 300 ° C., extruded into a sheet, and cooled with a cooling drum to obtain an unstretched film. Next, the unstretched film can be produced by stretching in a biaxial direction, heat setting, and heat relaxation treatment if necessary. At this time, the surface properties, density, and heat shrinkage properties of the film vary depending on the stretching conditions and other manufacturing conditions, and accordingly, the conditions are appropriately selected as necessary to form a film.

Hereinafter, the present invention will be described more specifically with reference to examples. In addition, the numerical value in an Example was measured with the following method.
(A) Intrinsic viscosity A dilute solution obtained by dissolving a film sample in orthochlorophenol at 100 ° C for 60 minutes was determined from a value measured at 35 ° C using an Ubbelohde viscometer.

(I) Diethylene glycol content The film sample was decomposed using hydrazine hydrate (hydrated hydrazine), and the content of diethylene glycol in the decomposition product was measured using gas chromatography ("HP6850" manufactured by Hewlett-Packard Company). did.

(C) Color b ^* value by transmitted light measurement of film According to JIS-Z8722 and 8729 standards, the color b * value of the transmitted light of the film is determined using a color meter (Nippon Denshoku Industries Co., Ltd., SZ-Σ90). It was measured.

(D) Metal element content with a specific gravity of 5.0 or more Film samples are mixed with ammonium sulfate, sulfuric acid, nitric acid and perchloric acid, wet-decomposed at about 300 ° C for 9 hours, diluted with distilled water, and made by Rigaku ICP. Qualitative analysis was performed using an analyzer (JY170 ULTRACE), and the presence or absence of a metal element having a specific gravity of 5.0 or more was confirmed. About the metal element with which existence of 1 weight ppm or more was confirmed, the element content was shown.

(E) Content of titanium, aluminum, antimony, manganese and phosphorus soluble in polyester The amount of titanium element, aluminum element, antimony element, manganese element and phosphorus element soluble in polyester in the polymer is a granular polymer sample. After being melted by heating on an aluminum plate, a test molded body having a flat surface was prepared with a compression press and determined using a fluorescent X-ray apparatus (type 3270E manufactured by Rigaku Corporation). However, regarding the amount of titanium element in the polyester composition to which titanium oxide was added as a matting agent, the sample was dissolved in orthochlorophenol and then extracted with 0.5 N hydrochloric acid. The extract was quantified using a Hitachi Z-8100 atomic absorption spectrophotometer. Here, when dispersion of titanium oxide was confirmed in the extract after extraction with 0.5N hydrochloric acid, the titanium oxide particles were settled with a centrifuge, and only the supernatant was recovered by the gradient method. went. By these operations, even if the polyester composition contains titanium oxide, the titanium element soluble in the polyester can be quantified.

(F) Haze Melt extrusion from a melt extruder into a sheet on a rotary cooling drum, followed by rapid cooling and solidification to create an unstretched film (sheet) having a thickness of 500 μm, and a turbidimeter (HDH-1001DP) manufactured by Nippon Denshoku Industries Co. ).

(G) Fine particles After treating the surface of the film with methyl ethyl ketone and removing the slippery layer, using a microscope (Nikon Microphoto-FX), a transmission dark field measurement method, light source 10 scale, 100 times I took a picture. In the obtained photograph, the number of particles observed to have a diameter of 1 to 10 μm was counted with an image analyzer.

(H) Preparation of catalyst and color adjusting agent)
(1) Synthesis of Titanium Catalyst A Add 1/2 mole of tetrabutoxytitanium to trimellitic anhydride in ethylene glycol solution (0.2% by weight) with respect to trimellitic anhydride and keep at 80 ° C. under normal pressure in air. And reacted for 60 minutes. Thereafter, it was cooled to room temperature, and the produced catalyst was recrystallized with 10 times the amount of acetone. The precipitate was filtered through filter paper and dried at 100 ° C. for 2 hours to obtain the target compound. This is designated as titanium catalyst A.

(2) Visible light absorption spectrum measurement of the color adjusting agent, color adjusting agent preparation The color adjusting agent shown in Table 1 is made into a chloroform solution having a concentration of 20 mg / L at room temperature, and is filled in a quartz cell having an optical path length of 1 cm. Filled with chloroform alone, a visible light absorption spectrum in the visible light region of 380 to 780 nm was measured using a Hitachi spectrophotometer U-3010. When mixing two color adjusting agents, the total concentration was 20 mg / L. The ratio of the absorbance at each wavelength of 400, 500, 600, and 700 nm to the maximum absorption wavelength and the absorbance at that wavelength was measured. Further, the thermal weight reduction start temperature of the powder color matching agent was measured. The results are shown in Table 1. In addition, when these color adjusting agents are added in the polyester production process in Examples and Comparative Examples, they are dissolved or dispersed at a temperature of 100 ° C. to a concentration of 0.1% by weight with respect to the glycol solution used as a raw material. Prepared.

[Example 1]
-Manufacture of polyester composition chip In a mixture of 100 parts of dimethyl terephthalate and 70 parts of ethylene glycol, 0.016 part of titanium catalyst A prepared in Reference Example 1 was charged into a SUS container capable of pressure reaction. The ester exchange reaction was performed while increasing the pressure from 140 ° C. to 240 ° C. under a pressure of 0.07 MPa, and then 0.023 part of triethylphosphonoacetate was added to complete the ester exchange reaction.

  Thereafter, 0.2 part of a 0.1 wt% ethylene glycol solution of the color adjusting agent A shown in Table 1 was added to the reaction product, transferred to a polymerization vessel, heated to 290 ° C., and heated under a high vacuum of 30 Pa or less. A condensation reaction was performed to obtain a polyester composition having an intrinsic viscosity of 0.63 and a diethylene glycol content of 1.3% by weight. Furthermore, it was made into a chip according to a conventional method. The results are shown in Table 2.

・ Adjustment of easy-slip coating solution Ratio of 65% by weight of the following polyester resin (I), 20% of the crosslinking agent (B), 10% by weight of spherical particles (C), and 5% by weight of wetting agent (D) Then, an aqueous coating solution having a total concentration of these components of 8% was prepared by dispersing the mixture.

(I) Polyester resin:
A polyester resin having an acid component of 70 mol% of 2,6-naphthalenedicarboxylic acid / 25 mol% of isophthalic acid / 5 mol% of 5-sodium sulfoisophthalic acid and a glycol component of 90 mol% of ethylene glycol / 10 mol% of diethylene glycol.
(B) Crosslinking agent:
Consists of 25 mol% methyl methacrylate, 30 mol% 2-isopropenyl-2-oxazoline, 10 mol% polyethylene oxide methacrylate / 35% acrylamide.
(C) Spherical particles:
Spherical cross-linked acrylic particles (particle size 100 nm).
(D) Wetting agent:
Polyoxyethylene lauryl ether.

Polyester film formation Polyethylene terephthalate resin pellets were dried under reduced pressure at 140 ° C. for 6 hours, then supplied to an extruder, and the polyester resin melted at about 285 ° C. was placed on a rotating cooling drum by electrostatic printing. Then, it was extruded into a sheet shape by means of an air knife method or the like to obtain an unstretched sheet with as little thickness unevenness as possible. Subsequently, the obtained sheet was heated to 100 ° C. and stretched 3.2 times in the longitudinal direction (longitudinal direction) to obtain a uniaxially oriented film. Then, the said coating liquid was apply | coated on both surfaces of the uniaxially oriented film by the reverse roller method. Further, after stretching 3.8 times in the transverse direction (width direction) in a zone heated to 160 ° C., heat treatment is performed in a heat treatment zone at 230 ° C. to obtain a 125 μm thick biaxially oriented laminated polyester film. It was. The thickness of the easy-slip layer formed on both surfaces of the film was 80 nm, respectively. The results are shown in Table 3.

[Comparative Example 1]
A mixture of 100 parts by weight of dimethyl terephthalate and 70 parts by weight of ethylene glycol was charged with 0.032 parts by weight of manganese acetate tetrahydrate in a reactor equipped with a stirrer, a rectifying column and a methanol distillation condenser, and 140 ° C. The ester exchange reaction was carried out while distilling out the methanol produced as a result of the reaction while gradually raising the temperature to 240 ° C. Thereafter, 0.02 part by weight of trimethyl phosphate was added to complete the transesterification reaction. Subsequently, the obtained reaction product was transferred to a reaction vessel equipped with a stirrer, a nitrogen inlet, a vacuum port, and a distillation device, 0.045 parts by weight of antimony trioxide was added, and the temperature was raised to 290 ° C., 30 Pa A polycondensation reaction was performed under the following high vacuum to obtain a polyester composition. Molding evaluation was performed in the same manner as in Example 1. The results are shown in Table 3.

  The biaxially stretched optical film of the present invention can be used as a base film for an antireflection film, a touch screen, or a diffusion plate, and can be used as a component of a display device such as an LCD, CRT, PDP, or EL. .

Claims (4)

It consists of an aromatic polyester that does not substantially contain a metal element with a specific gravity of 5.0 or more, and has a color b ^* value of -0.5 to 2.0 by transmitted light measurement, present in a film measured by dark field microscopy. A biaxially stretched film for optics, characterized in that the number of fine particles having a particle diameter of 1 to 10 μm caused by the catalyst is 195 particles / mm ² or less. The maximum absorption wavelength at a wavelength of 380 to 780 nm measured in a chloroform solution state with a color adjusting agent concentration of 20 mg / L and an optical path length of 1 cm is 540 to 600 nm, and the ratio of the absorbance at each wavelength to the absorbance at the maximum absorption wavelength is The biaxially stretched film for optics according to claim 1, comprising 0.1 to 10 ppm of a color adjusting agent satisfying all of the following formulas (1) to (4) per film weight.
0.00 ≦ A ₄₀₀ / A _max ≦ 0.20 (1)
0.10 ≦ A ₅₀₀ / A _max ≦ 0.70 (2)
0.55 ≦ A ₆₀₀ / A _max ≦ 1.00 (3)
0.00 ≦ A ₇₀₀ / A _max ≦ 0.05 (4)
(Wherein, A ₄₀₀ , A ₅₀₀ , A ₆₀₀ , A ₇₀₀ are the absorbance in the visible light absorption spectrum at 400 nm, 500 nm, 600 nm, and 700 nm, respectively, and A _max is the absorbance in the visible light absorption spectrum at the maximum absorption wavelength. .) The titanium metal element present in the polyester is in the range of 2 to 15 mmol% with respect to all dicarboxylic acid components constituting the polyester, and the molar ratio of the titanium metal element and the phosphorus element satisfies the following formula (5). The biaxially stretched film for optics according to claim 1.
1 ≦ P / Ti ≦ 15 (5)
(In the formula, P represents the concentration (mmol%) of the phosphorus element contained in the polyester, and Ti represents the concentration (mmol%) of the titanium metal element soluble in the polyester contained in the polyester.)   The biaxially stretched film for optics according to claim 2, wherein a blue color adjusting agent and a purple color adjusting agent are used in combination in a weight ratio of 90:10 to 40:60 as the color adjusting agent.