JP5286644B2 - Polyester resin and polyester film containing the same - Google Patents

Description

  The present invention relates to a polyester resin having a low photoelastic coefficient and a refractive index and excellent in optical isotropy, and particularly relates to an optical polyester film excellent in optical isotropy and light reflectivity.

  A film in which polymers having different refractive indexes are alternately laminated can efficiently reflect light having a specific wavelength, and is used as an optical filter or a reflector. A film excellent in optical isotropy is used as a retardation film or the like in a liquid crystal display or the like.

  For example, in Patent Document 1, a light-reflective film in which a copolymerized polyester is laminated on polyethylene naphthalate resin (hereinafter PEN), and in Patent Document 2, a light-reflective fiber in which nylon or acrylic is laminated on a polyester resin is disclosed in Patent Document 3. Proposes a multilayer optical film in which PEN and copolymerized polyester are laminated, and Patent Document 4 proposes a photographic film made of PEN copolymerized polyester having excellent transparency.

However, the polyesters described in Patent Documents 1 and 3 are inferior in workability because polyesters having different Tg are laminated, and the polymer combination in Patent Document 2 is diverted to a laminated film because the adhesiveness between the polymers is inferior. In addition, the polyesters described in Patent Documents 1, 3, and 4 have a large photoelastic coefficient and cannot be used for liquid crystal displays and the like.
JP 2000-141567 A (2nd term) WO98 / 46815 pamphlet (2-5) Japanese National Patent Publication No. 9-506837 (paragraphs 2-6) Japanese Patent Application Laid-Open No. 6-295014 (paragraph 2)

  An object of the present invention is to solve the above-described conventional problems, and to provide a polyester resin having a low photoelastic coefficient and exhibiting excellent light reflectivity when used as a laminated film, and a polyester film containing the same.

Polyesters object of the present invention, comprising at least 5 to 80 mol% of an alicyclic dicarboxylic acid component relative to the total dicarboxylic acid component and 5 to 80 mol% relative to the total glycolic Ingredient spiroglycol and spiro glycol components mentioned above It is a resin and is achieved by a polyester resin that satisfies the following formulas (1) and (2).

65 ° C. ≦ Glass transition temperature by differential scanning calorimetry ≦ 90 ° C. (1)
1.500 ≦ refractive index at sodium D line ≦ 1.570 (2)

  According to the present invention, a polyester film having a low photoelastic coefficient suitable for a liquid crystal display can be obtained, and a laminated polyester film excellent in light reflectivity can be obtained.

Polyester resin of the present invention is a polyester resin containing 5 to 80 mol% of 5 to 80 mol% and spiro glycol component relative to the total glycolic Ingredient at least alicyclic dicarboxylic acid component relative to the total dicarboxylic acid components, The glass transition temperature (hereinafter referred to as T g) is in the range of 65 to 90 ° C., and the refractive index at the sodium D line is 1. 5 0 to 1. It has a range of 5 7 0.

  When the Tg is less than 65 ° C., the optical properties are likely to change with time due to insufficient heat resistance, and the difference in Tg between the laminated resins becomes large when laminated with polyethylene terephthalate (hereinafter referred to as PET). Film formation stability is impaired. When a laminated film is used, it is preferable to match the Tg of the polyester resin of the present invention with the Tg of the laminated polymer, and the difference between the Tg (Tg1) of the laminated polymer and the Tg (Tg2) of the polyester resin of the present invention (| Tg1−Tg2). |) Is preferably within 10 ° C, more preferably within 5 ° C.

  When Tg exceeds 90 ° C., the Tg difference becomes too large when laminating PET or the like, so that film-forming stability is impaired, and it becomes difficult to lower the refractive index of the polyester resin. Therefore, the Tg of the polyester resin of the present invention is preferably in the range of 70 to 85 ° C, more preferably in the range of 75 to 85 ° C.

  With respect to the refractive index of the polyester resin of the present invention, it was difficult for the polyester resin to be less than 1.500, and when it exceeded 1.570, the difference in refractive index with the laminated polymer was small, and thus obtained. The light reflectivity of the laminated film is reduced. The refractive index of the polyester resin of the present invention is preferably in the range of 1.510 to 1.560. In addition, the refractive index in this invention points out the refractive index measured using the sodium D line | wire on 23 degreeC conditions.

To provide the characteristics, the polyester resin comprises from 5 to 80 mol% of 5 to 80 mol% and spiro glycol component relative to the total glycolic Ingredient at least alicyclic dicarboxylic acid component relative to the total dicarboxylic acid component It is necessary. The aromatic ring contained in the polyester resin has the effect of increasing Tg, but at the same time has the effect of increasing the refractive index and increasing the photoelastic coefficient.
When the photoelastic coefficient is large, the phase difference changes greatly when a stress is applied to the film, so that it is not suitable for a film for liquid crystal display applications.
Therefore, in the polyester resin of the present invention, the refractive index and the photoelastic coefficient are reduced by substituting this aromatic ring component with an alicyclic dicarboxylic acid component or an alicyclic diol. Examples of the alicyclic dicarboxylic acid component in the present invention include a cyclohexane dicarboxylic acid component and a decalin dicarboxylic acid component. In particular, a cyclohexanedicarboxylic acid component is preferable from the viewpoint of availability and polymerization reactivity. As the cyclohexanedicarboxylic acid component, cyclohexanedicarboxylic acid or an ester thereof can be used as a raw material.

  In addition, although alicyclic components, such as a cyclohexane dicarboxylic acid component, exist, such as a cis type and a trans type, it is preferable in this invention that a cis type ratio is 90-50 mol%. If the transformer ratio is high, the photoelastic coefficient tends to increase, so that it tends to be poor.

  As the alicyclic glycol in the present invention, a spiroglycol component and an isosorbide component are preferable, and a spiroglycol component is particularly preferable from the viewpoint of the color tone of the obtained polyester. Here, spiroglycol refers to 3,9-bis (2-hydroxy-1,1-dimethylethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane.

  In the present invention, for example, in the case of PET, Tg decreases when the terephthalic acid component (aromatic ring component) is substituted with cyclohexanedicarboxylic acid or the like. Then, Tg rises by substituting alicyclic glycol components, such as a spiro glycol component and an isosorbide component, with an ethylene glycol component, and as a result, Tg of this invention is realizable. The effect of increasing Tg is significant in spiroglycol components and isosorbide components.

  The polyester resin of the present invention preferably has an intrinsic viscosity in the range of 0.65 to 1.0. When the intrinsic viscosity is less than 0.65, the polyester resin becomes brittle, which is not preferable. When the intrinsic viscosity exceeds 1.0, the melt viscosity becomes high, so that accurate lamination becomes difficult.

  In the polyester resin of the present invention, the number of moles of aromatic rings contained in 1 kg of the polyester resin is preferably 4.8 moles or less in order to reduce the refractive index and the photoelastic coefficient. When it exceeds 4.8 mol, the refractive index and the photoelastic coefficient tend to increase, which is not preferable. The number of moles of aromatic rings in the present invention is based on the number of moles of benzene rings. The definition in the present invention will be described using PET and PEN as examples.

  In the case of PET, since the molecular weight of the basic repeating unit is 192, the number of basic repeating units per kg of the polymer is 5.2. Since 1 mol of the terephthalic acid component (corresponding to one benzene ring) is contained in the basic repeating unit, the number of moles of aromatic ring of PET is calculated to be 5.2. On the other hand, in the case of PEN, the molecular weight of the basic repeating unit is 242 and the number of basic repeating units per kg of polymer is 4.1. Although 1 mole of naphthalene dicarboxylic acid component is contained in the basic repeating unit, since the naphthalene ring corresponds to 2 benzene rings, the number of moles of aromatic ring of PEN is calculated as 8.2 moles.

Polyester resin of the present invention includes 5 to 80 mol% of 5 to 80 mol% and spiro glycol component relative to the total glycolic Ingredient at least alicyclic dicarboxylic acid component relative to the total dicarboxylic acid components, other dicarboxylic acid As a component, it is preferable to contain 20-95 mol% of at least 1 sort (s) of dicarboxylic acid components selected from a 2, 6- naphthalene dicarboxylic acid component, a terephthalic acid component, and an isophthalic acid component with respect to all the dicarboxylic acid components. Moreover, about a glycol component, it is preferable to contain 20-95 mol% of ethylene glycol components as a glycol component. When the above-mentioned aromatic dicarboxylic acid component is less than 20 mol%, it becomes difficult to make Tg 65 ° C. or higher, for example, when laminating with PET or PEN, the interlaminar adhesion with these resins deteriorates. come. Similarly, when the ethylene glycol component is less than 20 mol%, interlayer adhesion with these resins deteriorates when laminated with PET or PEN. On the other hand, when the aromatic dicarboxylic acid component exceeds 95 mol%, it is difficult to reduce the refractive index and the photoelastic coefficient. When the ethylene glycol component exceeds 95 mol%, the Tg may be 65 ° C. or higher. It becomes difficult.

In the polyester resin of the present invention, the content of the alicyclic dicarboxylic acid component and the spiroglycol needs to be in the range of 5 to 80 mol%, more preferably 8 to 50 mol%, respectively from the above description.

  The polyester resin of the present invention is preferably amorphous and is substantially amorphous in the above-described copolymerization range. The term “amorphous” in the present invention means that the heat of fusion is 4 J / g or less in DSC measurement. Such an amorphous polyester resin is preferable because its optical properties hardly change during film production.

  On the other hand, such an amorphous polyester resin tends to be heat-sealed by drying and easily form a lump. Then, the lump formation by drying can be suppressed by containing 5 to 50 weight% of crystalline polyester resins. Such a crystalline polyester resin preferably has a heat of crystal melting of 4 J / g or more in differential scanning calorimetry.

  As a method of including the crystalline polyester, melt kneading by a vent type extruder is preferable. That is, it is a method in which crystalline polyester and the polyester resin of the present invention are melt-kneaded with a vent type extruder to obtain pellets. Examples of the crystalline polyester include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and copolymers thereof, and polyethylene terephthalate is most preferable.

  The aromatic dicarboxylic acid component contained in the polyester resin of the present invention is at least selected from the above-mentioned types, but a terephthalic acid component and an isophthalic acid component are preferable from the viewpoint of refractive index and photoelastic coefficient, and these are used at the same time. It doesn't matter. In particular, the terephthalic acid component is preferably used mainly from the viewpoint of adhesion to other polyester resins. As other dicarboxylic acid components, conventionally known ones may be copolymerized as long as the characteristics allow, and the same applies to glycol components. Examples of such components include aliphatic dicarboxylic acids such as adipic acid and sebacic acid and esters thereof, aromatic dicarboxylic acids such as 4,4′-bisphenylenedicarboxylic acid, 5-sodiumsulfoisophthalic acid, diphenic acid, and the like. Examples thereof include glycol components such as esters, diethylene glycol, butanediol, propanediol, polyethylene glycol, and polytetramethylene glycol. Further, inorganic particles, organic particles, dyes, pigments, antistatic agents, antioxidants, waxes and the like may be contained.

  The polyester resin of the present invention preferably contains an element selected from an alkali metal, an alkaline earth metal, Zn, Co, and Mn as a metal component. By containing these metal elements, electrostatic applicability when forming a film of the polyester resin is improved. In the case of an alkali metal, Na is easy to color the polyester resin yellow, and K is good. In alkaline earth metals, Ca tends to form foreign matter, and Mg is preferable. Of Zn, Co, and Mn, Mn is preferable from the viewpoint of foreign matter and color tone. Among these, Mg and Mn are preferable from the viewpoint of the transparency of the resin, and Mn is particularly preferable.

  The metal compound described above may also serve as a transesterification reaction catalyst. In particular, a manganese compound is preferable because of its strong activity in transesterification. The metal compound is preferably soluble in polyester, and is preferably a hydroxide, chloride or acetate, and particularly preferably acetate.

  When these metal compounds are contained in the polyester resin, it is preferable to use a phosphorus compound in combination. Although it does not specifically limit about a phosphorus compound, For example, a phosphoric acid type, a phosphorous acid type, a phosphonic acid type, a phosphinic acid type compound etc. can be mentioned, Among these, these ester compounds are preferable from a viewpoint of foreign material formation suppression.

  Furthermore, the polyester composition of the present invention preferably contains a heat stabilizer, and particularly preferably contains 0.01 to 2.0% by weight of a heat stabilizer containing trivalent phosphorus. When the content of the heat stabilizer is less than 0.01% by weight, the effect of improving the heat resistance is small. When the content of the heat stabilizer exceeds 2.0% by weight, no significant improvement in the effect is seen, which is economically wasteful. It is.

  As the heat-resistant stabilizer containing trivalent phosphorus, a commercially available heat-resistant stabilizer can be applied. For example, tris (2,4-di-tert-butylphenyl) phosphite, bis [2,4-bis (1,1-Dimethylethyl) -6-methylphenyl] ethyl ester phosphorous acid, tetrakis (2,4-di-tert-butylphenyl) [1,1-biphenyl] -4,4′-diylbisphospho Knight, bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite, bis (2,4-dicumylphenyl) pentaerythritol diphosphite, bis (2,6-di-tert-butyl-4) -Methylphenyl) pentaerythritol-di-phosphite and the like can be mentioned, but not limited thereto.

  In the polyester resin of the present invention, a titanium compound, a germanium compound, or an antimony compound can be used as a polymerization catalyst. Among these, a germanium compound and an antimony compound having a good color tone of the obtained polyester are preferable.

  The polyester film of the present invention contains the above-described polyester resin, has a small photoelastic coefficient and refractive index, and can be suitably used for liquid crystal display applications.

  The laminated polyester film of the present invention exhibits excellent light reflectivity by being laminated with polyester resins having different refractive indexes. The laminated polyester film of the present invention is a polyester film containing at least one layer of the polyester resin of the present invention, but in order to obtain excellent light reflectivity, the polyester resin of the present invention and PET can be laminated alternately. preferable. Since the polyester resin of the present invention has a lower refractive index than PET and is amorphous, the refractive index hardly changes even when the film is stretched. Therefore, light is efficiently reflected at the interface between the polyester resin layer and the PET layer of the present invention.

    Of course, a higher light reflectance is preferable, but 90% is preferable as a light reflective film. In order to obtain excellent light reflectivity, the total number of laminated layers is preferably 250 or more.

  The method for obtaining such a laminated film is realized by feeding the polymers fed from different flow paths into a multilayer laminating apparatus using two or more extruders. Examples of the multilayer laminating apparatus include a multi-manifold die, a feed block, a static mixer, and the like. In particular, it is preferable to use a multi-manifold die or a feed block in view of the accuracy of the laminated thickness. The polymer laminated in this manner is extruded from the die into a sheet shape and cooled by a cooling drum or the like to obtain an unstretched sheet. In order to obtain an unstretched sheet with good thickness unevenness and surface condition, it is preferable to use an electrostatic application method.

  The resulting unstretched sheet can then be uniaxially or biaxially stretched. In biaxial stretching, simultaneous biaxial stretching and sequential biaxial stretching can be performed.

  Next, the polyester resin and film production method of the present invention will be described in detail.

  The polyester resin of the present invention is a method of synthesizing a low polymer by esterifying a dicarboxylic acid and a diol, and then synthesizing the low polymer by a transcondensation reaction between the dicarboxylic acid ester and the diol. Then, a method of subjecting this to condensation polymerization can be used. Since spiroglycol is easily decomposed by an acid component, when it is used, it is preferably polymerized by a transesterification reaction in order to avoid the decomposition.

  In the case of the transesterification method, for example, dimethyl terephthalate, dimethyl cyclohexanedicarboxylate, ethylene glycol, and spiro glycol as raw materials are charged into a reaction can so as to have a predetermined polymer composition. In this case, if ethylene glycol is added by 1.7 to 2.3 mole times the total dicarboxylic acid component, the reactivity is improved. After melting these at about 150 ° C., magnesium acetate and antimony trioxide are added as a transesterification reaction and a polymerization catalyst, respectively. At 150 ° C., these monomer components become a homogeneous molten liquid. Next, methanol is distilled while raising the temperature in the reaction vessel to 235 ° C., and the ester exchange reaction is carried out. After the transesterification is thus completed, a transesterification catalyst deactivator such as trimethyl phosphoric acid is added.

  When the addition of the catalyst is completed, the reaction product is charged into the polymerization apparatus, and the internal pressure of the apparatus is reduced from normal pressure to 133 Pa or lower while the internal temperature is slowly raised to 285 ° C. As the polymerization reaction proceeds, the viscosity of the reaction product increases. When the predetermined stirring torque is reached, the reaction is terminated, and the polyester is discharged from the polymerization apparatus into a water tank. The discharged polyester is quenched in a water tank and made into chips with a cutter.

  Although a polyester resin can be obtained in this way, the above is an example, and the monomer, catalyst and polymerization conditions are not limited thereto.

  Next, the production of the polyester film will be described.

  As the film forming method, a T-die method with good thickness unevenness can be preferably used.

  For melt extrusion of the polyester resin, an extruder type melt extrusion apparatus equipped with a single screw or a twin screw extruder can be used. A laminated film can be produced by using two or more extruders, laminating a molten polyester with a multi-manifold die or a feed block, and extruding the laminated polyester.

  The cast method is to measure the melted polyester resin with a gear pump and then discharge it from the T-die die. Then, on the cooled drum, the electrostatic application method, air chamber method, air knife method, press roll, which are well-known close contact means It is preferable to obtain an unstretched film by tightly cooling and solidifying to a cooling medium such as a drum by a method or the like and then rapidly cooling to room temperature. In particular, the electrostatic application method is particularly preferably used to obtain flatness and uniform thickness.

  The obtained unstretched film can be further uniaxially or biaxially stretched.

  The biaxial stretching method is not particularly limited, and methods such as a sequential biaxial stretching method and a simultaneous biaxial stretching method can be used.

    When stretching by sequential biaxial stretching, the obtained unstretched film is heated to contact on a roll group heated to (glass transition temperature Tg-30 ° C.) or more and (glass transition temperature Tg + 50 ° C.) or less of the polyester resin. The film is stretched 1.1 to 4.0 times in the longitudinal direction, and once cooled, the end of the film is bitten by a tenter clip, and the width of the polyester resin (glass transition temperature Tg + 5 ° C.) or more is increased. The glass resin is stretched 1.1 to 4.0 times in a temperature atmosphere of (glass transition temperature Tg + 50 ° C.) to obtain a biaxially oriented polyester resin film.

  When the biaxially oriented film after stretching is further heat-treated at a temperature in the range of Tg + 50 ° C. to Tg + 150 ° C., the dimensional stability is improved.

  The polyester film thus obtained has a low photoelastic coefficient and is suitable as a liquid crystal display film. Moreover, the film which laminated | stacked PET etc. alternately is excellent in light reflectivity, and is suitable for a reflector use.

  The present invention will be described more specifically with reference to the following examples.

In addition, the measuring method of a physical property and the evaluation method of an effect were performed in accordance with the following method.
(1) Thermal properties of polyester (glass transition point, heat of crystal melting)
About 10 mg of the sample to be measured was weighed, sealed with an aluminum pan and pan cover, and measured with a differential scanning calorimeter (DSC7 model, manufactured by Perkin Elmer). In the measurement, the temperature was raised from 20 ° C. to 285 ° C. at a rate of 16 ° C./min in a nitrogen atmosphere, then rapidly cooled with liquid nitrogen, and again from 20 ° C. to 285 ° C. at a rate of 16 ° C./min. Raise the temperature. The glass transition point was measured in the second temperature raising process.

The amount of heat of crystal melting was calculated from the area of the crystal melting peak appearing in the second temperature raising process.
(2) Refractive index of polyester A polyester resin is melt-extruded to obtain an unstretched sheet having a thickness of 100 μm.
Subsequently, the refractive index was measured with an “Abbe refractometer NAR-4T” manufactured by Atago Co., Ltd. under a temperature condition of 23 ° C. using sodium D line as a light source.
(3) Intrinsic viscosity Intrinsic viscosity was measured at 25 ° C using orthochlorophenol as a solvent.
(4) Photoelastic coefficient (× 10 ⁻¹² Pa ⁻¹ )
A sample having a short side of 1 cm and a long side of 7 cm was cut out. The thickness of this sample is d (μm). Using this sample, TRANSDUCER U3C1-5K manufactured by Shimadzu Corporation, the checker was placed 1 cm above and below, and a tension (F) of 1 kg / mm ² (9.81 × 10 ⁶ Pa) was applied in the long side direction. . In this state, the phase difference R (nm) was measured using a polarizing microscope 5892 manufactured by Nikon Corporation. Sodium D line (589 nm) was used as a light source. These numerical values were applied to photoelastic coefficient = R / (d × F) to calculate the photoelastic coefficient.

The case where the photoelastic coefficient was less than 100 was regarded as acceptable.
(5) Reflectivity A spectrophotometer (U-3410 Spectrophotometer) manufactured by Hitachi, Ltd. was fitted with a φ60 integrating sphere 130-0632 (Hitachi Ltd.) and a 10 ° inclined spacer, and the peak value of reflectivity was measured. The band parameter was set to 2 / servo, the gain was set to 3, and the range from 187 nm to 2600 nm was set to 120 nm / min. Measured at a detection speed of. In order to standardize the reflectance, an attached BaSO ₄ plate was used as a standard reflecting plate. In this evaluation method, since the relative reflectance is obtained, the reflectance may be 100% or more.
(6) Peelability The test was conducted according to JIS K5600 (2002). The film was regarded as a hard substrate, and 25 lattice patterns were cut at intervals of 2 mm. Further, a tape cut to a length of about 75 mm was adhered to the lattice portion, and the tape was peeled off at an angle close to 60 ° in a time of 0.5 to 1.0 seconds. Here, Sekisui's cello tape (registered trademark) no. 252 (width 18 mm) was used. The evaluation result was expressed by the number of lattices in which one lattice was completely separated. When the thickness of the test film was less than 100 μm, a sample in which the test film was firmly bonded to the biaxially stretched PET film (Toray “Lumirror” T60) having a thickness of 100 μm with an adhesive was used for the peel test. . At this time, a test was performed by cutting a grid in the surface of the test sample so as not to penetrate the test sample. The number of peeling was 4 or less.

Example 1
(Synthesis of polyester)
67.6 parts by weight of dimethyl terephthalate, 17.4 parts by weight of dimethyl 1,4-cyclohexanedicarboxylate having a cis / trans ratio of 72/28, 54 parts by weight of ethylene glycol, 20 parts by weight of spiroglycol, acetic acid 0.04 part by weight of manganese tetrahydrate and 0.02 part by weight of antimony trioxide were weighed and charged into a transesterification reactor. The contents were dissolved at 150 ° C. and stirred.

  While stirring, methanol was distilled while slowly raising the temperature of the reaction contents to 235 ° C. After distillation of a predetermined amount of methanol, an ethylene glycol solution containing 0.02 part by weight of trimethyl phosphoric acid and bis (2,6-di-tert-butyl-4-methylphenyl) penta manufactured by Asahi Denka Kogyo Co., Ltd. 0.05 parts by weight of erythritol di-phosphite) was added. After adding trimethyl phosphoric acid, the mixture was stirred for 10 minutes to complete the transesterification reaction. Thereafter, the transesterification reaction product was transferred to a polymerization apparatus.

  Next, the content of the polymerization apparatus was stirred and the pressure was reduced and the temperature was raised, and polymerization was carried out while distilling ethylene glycol. The reduced pressure was reduced from normal pressure to 133 Pa or less over 90 minutes, and the temperature was raised from 235 ° C. to 285 ° C. over 90 minutes.

  When the stirring torque of the polymerization apparatus reached a predetermined value, the inside of the polymerization apparatus was returned to normal pressure with nitrogen gas, the valve at the bottom of the polymerization apparatus was opened, and a gut-shaped polymer was discharged into the water tank. The polyester gut cooled in the water tank was cut with a cutter to obtain chips.

  In this way, polyester A was obtained. The obtained polyester A had an intrinsic viscosity of 0.78.

  Similarly, a PET resin was polymerized in the same manner as described above except that 100 parts by weight of dimethyl terephthalate and 64 parts by weight of ethylene glycol were used. The obtained PET resin had an intrinsic viscosity of 0.65, a Tg of 80 ° C., and no crystal melting heat peak was observed. .

(Formation of single-layer biaxially stretched film)
Although the polyester chip was vacuum-dried, a lump was seen in a part thereof, which was broken and then supplied to the extruder. The polyester supplied to the extruder was melted at 280 ° C., filtered through a metal nonwoven fabric filter, and then extruded from a T die as a molten sheet. The molten sheet was cooled and solidified on a specular drum whose surface temperature was controlled at 25 ° C. by an electrostatic application method (electrodes used a tungsten wire having a diameter of 0.15 mm) to form an unstretched sheet. The photoelastic coefficient was measured using the unstretched sheet.

The photoelastic coefficient was 85 × 10 ⁻¹² Pa ⁻¹ .

(Formation of laminated polyester film)
The polyester A and the PET resin were each vacuum dried and then supplied to two extruders.

  Polyester A and PET resin were each melted at 280 ° C. with an extruder, passed through a gear pump and a filter, and then merged in a 101-layer feed block. At this time, both surface layers of the laminated film were made to be PET resin layers, and the laminated thickness was alternately laminated so that the polyester A layer / PET resin layer was ½. That is, the polyester A layer was laminated alternately so that 50 layers and the PET layer were 51 layers.

  The 101-layer laminate thus obtained was supplied to a die, extruded into a sheet, and rapidly cooled and solidified on a casting drum maintained at a surface temperature of 25 ° C. by electrostatic application (DC voltage 8 kV). .

  The obtained cast film was led to a roll type longitudinal stretching machine, heated by a group of rolls heated to 90 ° C., and stretched 3 times in the longitudinal direction between rolls having different peripheral speeds. The film that had been stretched in the machine direction was then led to a tenter-type transverse stretcher. The film was preheated with hot air at 100 ° C. in a tenter and stretched 3.3 times in the transverse direction. The stretched film was directly heat treated with hot air at 200 ° C. in a tenter. In this way, a film having a thickness of 50 μm could be obtained. The properties of the obtained film are shown in Table 1. Since the polyester resin of the present invention has a photoelastic coefficient of less than 100 and a low refractive index, it has excellent light reflectivity when used as a laminated film.

Examples 2 , 3, 5-7, Reference Example 4
A polyester was polymerized in the same manner as in Example 1 except that the amount ratio of dimethyl terephthalate, dimethyl 1,4-cyclohexanedicarboxylate, ethylene glycol, and spiroglycol was changed. No crystal melting heat peak was observed from the obtained polyester resin. Furthermore, using the PET resin polymerized in Example 1, a laminated film was obtained under the same conditions.

The results are shown in Table 1. Examples 2 and 3 showed satisfactory characteristics because they were within the scope of the present invention although some unevenness occurred when biaxially stretching the laminated film because Tg was different from PET by 10 ° C. or more. Reference Example 4 also showed satisfactory characteristics, but the photoelastic modulus slightly increased due to the large number of moles of aromatic rings. Further, Example 5 showed excellent light reflectivity because the refractive index was sufficiently low. However, since the amount of the copolymerization component was increased, the compatibility with PET was lowered and the delamination property was weakened. In Example 6, the intrinsic viscosity was 0.65, a slight unevenness was observed in the lamination property during film formation, and the reflectance was not large relative to the refractive index. In Example 7, since the intrinsic viscosity was as high as 0.95, a slight unevenness was observed in the lamination property during film formation, and the reflectance was not large for the refractive index.

Example 8
A polyester film was obtained in the same manner as in Example 1 except that dimethyl 1,4-cyclohexanedicarboxylate having a cis / trans ratio of dimethyl 1,4-cyclohexanedicarboxylate of 15/85 was used. The results are shown in Table 1. Since the trans ratio of dimethyl 1,4-cyclohexanedicarboxylate was higher than that in Example 1, the photoelastic coefficient was higher than that in Example 1. In addition, a crystal melting heat peak of the polyester resin was not observed.

Example 9
66.4 parts by weight of dimethyl terephthalate, 29 parts by weight of dimethyl decalin dicarboxylate, 57 parts by weight of ethylene glycol, 7 parts by weight of spiroglycol, 0.04 parts by weight of manganese acetate tetrahydrate, 0% of antimony trioxide .02 parts by weight were weighed and charged into a transesterification reactor. The contents were dissolved at 150 ° C. and stirred.

  While stirring, methanol was distilled while slowly raising the temperature of the reaction contents to 235 ° C. After distillation of a predetermined amount of methanol, an ethylene glycol solution containing 0.02 part by weight of trimethyl phosphoric acid and bis (2,6-di-tert-butyl-4-methylphenyl) penta manufactured by Asahi Denka Kogyo Co., Ltd. 0.05 parts by weight of erythritol di-phosphite) was added. After adding trimethyl phosphoric acid, the mixture was stirred for 10 minutes to complete the transesterification reaction. Thereafter, the transesterification reaction product was transferred to a polymerization apparatus.

  Next, the content of the polymerization apparatus was stirred and the pressure was reduced and the temperature was raised, and polymerization was carried out while distilling ethylene glycol. The reduced pressure was reduced from normal pressure to 133 Pa or less over 90 minutes, and the temperature was raised from 235 ° C. to 285 ° C. over 90 minutes.

  When the stirring torque of the polymerization apparatus reached a predetermined value, the inside of the polymerization apparatus was returned to normal pressure with nitrogen gas, the valve at the bottom of the polymerization apparatus was opened, and a gut-shaped polymer was discharged into the water tank. The polyester gut cooled in the water tank was cut with a cutter to obtain chips.

  In this way, polyester I was obtained. The crystal melting heat peak of polyester I was not observed. Using the obtained polyester I, a polyester film was obtained in the same manner as in Example 1. The results are shown in Table 1. When the decalin dicarboxylic acid component was used, the photoelastic coefficient could be made smaller than that of the polyester resin of Example 2 using the cyclohexane dicarboxylic acid component.

Reference Example 10
77 parts by weight of dimethyl terephthalate, 20 parts by weight of dimethyl 1,4-cyclohexanedicarboxylate having a cis / trans ratio of 72/28, 62 parts by weight of ethylene glycol, 7.3 parts by weight of isosorbide, and manganese acetate tetrahydrate 0.04 parts by weight of salt and 0.02 parts by weight of antimony trioxide were weighed and charged into a transesterification reactor. The contents were dissolved at 150 ° C. and stirred.

  While stirring, methanol was distilled while slowly raising the temperature of the reaction contents to 235 ° C. After distillation of a predetermined amount of methanol, an ethylene glycol solution containing 0.02 part by weight of trimethyl phosphoric acid and bis (2,6-di-tert-butyl-4-methylphenyl) penta manufactured by Asahi Denka Kogyo Co., Ltd. 0.05 parts by weight of erythritol di-phosphite) was added. After adding trimethyl phosphoric acid, the mixture was stirred for 10 minutes to complete the transesterification reaction. Thereafter, the transesterification reaction product was transferred to a polymerization apparatus.

  Next, the content of the polymerization apparatus was stirred and the pressure was reduced and the temperature was raised, and polymerization was carried out while distilling ethylene glycol. The reduced pressure was reduced from normal pressure to 133 Pa or less over 90 minutes, and the temperature was raised from 235 ° C. to 285 ° C. over 90 minutes.

  When the stirring torque of the polymerization apparatus reached a predetermined value, the inside of the polymerization apparatus was returned to normal pressure with nitrogen gas, the valve at the bottom of the polymerization apparatus was opened, and a gut-shaped polymer was discharged into the water tank. The polyester gut cooled in the water tank was cut with a cutter to obtain chips.

  In this way, polyester J was obtained. From the obtained polyester J, no crystal melting heat peak was observed. A polyester film was obtained by the same method as in Example 1 using the obtained polyester J. The results are shown in Table 1. When isosorbide was used, the Tg was more likely to increase than when spiroglycol was used, but the decrease in refractive index was small.

Example 11
A laminated polyester film was formed in the same manner except that the polyester A and the PET resin used in Example 1 were used and the total number of laminated layers was 251 layers. The thickness of the obtained laminated polyester film was 50 μm. The results are shown in Table 1. Since the number of stacked layers was increased from 101 to 251 in Example 1, the number of light reflecting layers increased and excellent light reflectivity was exhibited.

Example 12
A multilayer laminate film was obtained in the same manner as in Example 1 except that bis (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol-di-phosphite) manufactured by Asahi Denka Kogyo Co., Ltd. was not used. It was.

  Since the heat resistance is lower than that of Example 1, the melt viscosity is likely to change during film formation, and some unevenness is observed in the lamination property during film formation, and the light reflectance is lower than that of Example 1. .

Example 13
Exactly the same as Example 1 except that the amount of bis (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol-di-phosphite) manufactured by Asahi Denka Kogyo Co., Ltd. was 0.01 parts by weight. Similarly, a multilayer laminated film was obtained.

  Since the heat resistance is lower than that of Example 1, the melt viscosity is likely to change during film formation, and some unevenness is observed in the lamination property during film formation, and the light reflectance is lower than that of Example 1. .

Example 14
56.1 parts by weight of dimethyl terephthalate, 24.8 parts by weight of dimethyl 1,4-cyclohexanedicarboxylate having a cis / trans ratio of 72/28, 52 parts by weight of ethylene glycol, and 25.1 parts by weight of spiroglycol Then, 0.04 part by weight of manganese acetate tetrahydrate and 0.02 part by weight of antimony trioxide were weighed and charged into a transesterification reactor. The contents were dissolved at 150 ° C. and stirred.

  While stirring, methanol was distilled while slowly raising the temperature of the reaction contents to 235 ° C. After distillation of a predetermined amount of methanol, an ethylene glycol solution containing 0.02 part by weight of trimethyl phosphoric acid and bis (2,6-di-tert-butyl-4-methylphenyl) penta manufactured by Asahi Denka Kogyo Co., Ltd. 0.05 parts by weight of erythritol di-phosphite) was added. After adding trimethyl phosphoric acid, the mixture was stirred for 10 minutes to complete the transesterification reaction. Thereafter, the transesterification reaction product was transferred to a polymerization apparatus.

  Next, the content of the polymerization apparatus was stirred and the pressure was reduced and the temperature was raised, and polymerization was carried out while distilling ethylene glycol. The reduced pressure was reduced from normal pressure to 133 Pa or less over 90 minutes, and the temperature was raised from 235 ° C. to 285 ° C. over 90 minutes.

  When the stirring torque of the polymerization apparatus reached a predetermined value, the inside of the polymerization apparatus was returned to normal pressure with nitrogen gas, the valve at the bottom of the polymerization apparatus was opened, and a gut-shaped polymer was discharged into the water tank. The polyester gut cooled in the water tank was cut with a cutter to obtain chips.

  In this way, polyester K was obtained. The properties of polyester K are shown in Table 1.

  Next, 75 parts by weight of polyester K and 25 parts by weight of the polyethylene terephthalate chip obtained in Example 1 were mixed and kneaded by a vent type twin screw extruder having an L / D of 42 to obtain a kneaded chip L. .

  A film was obtained in the same manner as in Example 1 except that the polyester L was used in place of the polyester A in Example 1. Polyester L was able to form a film smoothly without forming a lump by heat fusion even in vacuum drying.

  The properties of the obtained film are shown in Table 1.

Example 15
95 parts by weight of the polyester A of Example 1 and 5 parts by weight of the polyethylene terephthalate chip of Example 1 were kneaded with the vent type biaxial kneader of Example 14, and this polyester was used in place of the polyester A. A film was obtained as in Example 1.

  The polyester had less chip fusion in vacuum drying than in Example 1, but a lump was present, and an operation for breaking it was necessary.

Example 16
34.1 parts by weight of dimethyl terephthalate, 35.2 parts by weight of dimethyl 1,4-cyclohexanedicarboxylate having a cis / trans ratio of 72/28, 44 parts by weight of ethylene glycol, and 39.5 parts by weight of spiroglycol Then, 0.04 part by weight of manganese acetate tetrahydrate and 0.02 part by weight of antimony trioxide were weighed and charged into a transesterification reactor. The contents were dissolved at 150 ° C. and stirred.

  While stirring, methanol was distilled while slowly raising the temperature of the reaction contents to 235 ° C. After distillation of a predetermined amount of methanol, an ethylene glycol solution containing 0.02 part by weight of trimethyl phosphoric acid and bis (2,6-di-tert-butyl-4-methylphenyl) penta manufactured by Asahi Denka Kogyo Co., Ltd. 0.05 parts by weight of erythritol di-phosphite) was added. After adding trimethyl phosphoric acid, the mixture was stirred for 10 minutes to complete the transesterification reaction. Thereafter, the transesterification reaction product was transferred to a polymerization apparatus.

  Next, the content of the polymerization apparatus was stirred and the pressure was reduced and the temperature was raised, and polymerization was carried out while distilling ethylene glycol. The reduced pressure was reduced from normal pressure to 133 Pa or less over 90 minutes, and the temperature was raised from 235 ° C. to 285 ° C. over 90 minutes.

  When the stirring torque of the polymerization apparatus reached a predetermined value, the inside of the polymerization apparatus was returned to normal pressure with nitrogen gas, the valve at the bottom of the polymerization apparatus was opened, and a gut-shaped polymer was discharged into the water tank. The polyester gut cooled in the water tank was cut with a cutter to obtain chips.

  In this way, polyester M was obtained. The properties of polyester M are shown in Table 1.

  Next, 50 parts by weight of polyester M and 50 parts by weight of the polyethylene terephthalate chip obtained in Example 1 were mixed and kneaded in a vent type twin-screw extruder having an L / D of 42 to obtain a kneaded chip L. .

  A film was obtained in the same manner as in Example 1 except that Polyester M was used in place of Polyester A in Example 1. Polyester M was able to form a film smoothly without forming a lump due to heat fusion even in vacuum drying.

  The properties of the obtained film are shown in Table 1.

Example 17
A polyester film was obtained in the same manner as in Example 1 except that dimethyl 1,4-cyclohexanedicarboxylate having a cis / trans ratio of dimethyl 1,4-cyclohexanedicarboxylate of 50/50 was used. The results are shown in Table 1. Since the trans ratio of dimethyl 1,4-cyclohexanedicarboxylate was higher than that in Example 1, the photoelastic coefficient was higher than that in Example 1. A crystal melting peak of the polymer was not observed.

Comparative Example 1
Polyester K containing 15 mol% of an isophthalic acid component was polymerized in the same manner as in the polymerization of the PET resin of Example 1, except that 15 parts by weight of dimethyl isophthalate and 85 parts by weight of dimethyl terephthalate were used. A laminated film was obtained using polyester K instead of polyester A in Example 1. Although a result is shown in Table 1, since neither an alicyclic dicarboxylic acid component nor an alicyclic diol component was contained, the photoelastic coefficient was large and the reflectance of the laminated film was also small.

Comparative Example 2 to Comparative Example 4
Various polyesters were polymerized by polarizing the quantity ratio and type of the polyester raw material. Using these polyesters, a film laminated with PET was obtained in the same manner as in Example 1. The results are shown in Table 1. In Comparative Examples 2 and 3 containing only either the alicyclic dicarboxylic acid component or the alicyclic diol component, the photoelastic coefficient or the glass transition point cannot satisfy the scope of the present invention, and the laminateability and peelability are low. It was inferior.

Claims (12)

At least an alicyclic dicarboxylic acid component relative to the total dicarboxylic acid component of 5 to 80 mol% and spiro glycol component relative to the total glycolic Ingredient is a polyester resin containing 5 to 80 mol%, the following formula (1), ( A polyester resin satisfying 2).
65 ° C. ≦ Glass transition temperature by differential scanning calorimetry ≦ 90 ° C. (1)
1.500 ≦ refractive index at sodium D line ≦ 1.570 (2)   The polyester resin according to claim 1, wherein the alicyclic dicarboxylic acid component is a cyclohexanedicarboxylic acid component.   The polyester resin according to claim 1 or 2, wherein the intrinsic viscosity is in a range of 0.65 to 1.0. The polyester resin according to any one of claims 1 to 3, wherein the number of moles of aromatic rings contained in the polyester repeating unit is 4.8 moles or less in terms of 1 kg of the polyester resin. 5. The composition according to claim 1, wherein 20 to 95 mol% of at least one dicarboxylic acid component selected from 2,6-naphthalenedicarboxylic acid component, terephthalic acid component and isophthalic acid component is contained with respect to the total dicarboxylic acid component. The polyester resin according to item. The ethylene glycol component is contained as a glycol component in an amount of 20 to 95 mol%.
The polyester resin according to any one of 5. Heat stabilizer resin composition obtained by adding 0.01 to 2.0% by weight relative to the polyester composition containing a trivalent phosphorus in the polyester resin according to any one of 請 Motomeko 1-6. The polyester resin according to any one of claims 1 to 6 , or the polyester resin composition (A) according to claim 7 , and a polyester resin (B) having a heat of crystal melting by differential scanning calorimetry of 4 J / g or more. And a polyester resin composition containing 5 to 50% by weight based on the polyester resin composition from which the polyester resin (B) is obtained . The polyester film containing the polyester resin of any one of Claims 1-6 , or the polyester resin composition of Claim 7 or 8 . A laminated polyester film comprising at least one layer of the polyester resin according to any one of claims 1 to 6 , or the polyester resin composition according to claim 7 or 8 . A laminated polyester film in which the polyester resin according to any one of claims 1 to 6 , or the polyester resin composition according to claim 7 or 8 and a polyethylene terephthalate resin are alternately laminated.   The laminated polyester film according to claim 11, wherein the light reflectance is 90% or more.