CN105531610B

CN105531610B - Liquid crystal display device, polarizer and polaroid protective film

Info

Publication number: CN105531610B
Application number: CN201480050003.4A
Authority: CN
Inventors: 藤田敦史; 村田浩一; 向山幸伸; 佐佐木靖
Original assignee: Toyobo Co Ltd
Current assignee: Toyobo Co Ltd
Priority date: 2013-09-10
Filing date: 2014-09-05
Publication date: 2019-09-03
Anticipated expiration: 2034-09-05
Also published as: JP2018185535A; KR20210116714A; KR20160053955A; KR102491441B1; JPWO2015037527A1; CN105531610A; TWI675226B; JP2024045417A; WO2015037527A1; JP2022105524A; TW201531748A; JP2020115211A; KR20230015521A

Abstract

The present invention provides a kind of polaroid protective film formed by polyester film, is able to suppress light leakage when configuring 2 polarizers under crossed nicols environment.A kind of polaroid protective film formed by polyester film, wherein the absolute value of the gradient relative to film conveying direction or the percent thermal shrinkage of width direction is 15 degree or less.

Description

Liquid crystal display device, polarizer and polaroid protective film

Technical field

The present invention relates to polaroid protective films used in the polarizer in liquid crystal display device.

Background technique

Polarizer used in liquid crystal display device (LCD) is usually to be hold to make iodine to poly- by 2 polaroid protective films The composition for the polarizing film that vinyl alcohol (PVA) etc. has dyed, as polaroid protective film, usually using cellulose triacetate (TAC) Film.In recent years, require polarizer thin layer with the slimming of LCD.However, the TAC as protective film is thinned thus When the thickness of film, it may occur that enough mechanical strengths can not be obtained, and the problem of penetrability deterioration.In addition, TAC film is very Valuableness needs cheap substitution raw material strongly.

Therefore, it in order to keep polarizer thin layer, proposes and substitutes TAC film using polyester film, so that as polarizing film Protective film is able to maintain the method (Patent Documents 1 to 3) of high-durability thickness is thin.

Polyester film excellent in te pins of durability compared with TAC film, but different from TAC film, due to birefringence, When being used as polaroid protective film, there are problems that causing image quality to reduce because of optical distortion.That is, the polyester with birefringence Film due to defined optical anisotropy (retardation), when being used as polaroid protective film, if from oblique sight It examines, then can generate rainbow shape color spot, image quality reduces.Therefore, in Patent Documents 1 to 3, make using by using copolyester Reduce the countermeasure of retardation for polyester.

In addition, disclosed in Patent Document 4 be, as back light and then used by using white light-emitting diode Oriented polyester films with certain retardation can solve the uneven color of rainbow shape as polaroid protective film.

It is disclosed in Patent Document 5 to be, polaroid protective film due to when manufacturing polarizer or the polarizer that makes with Compound process of liquid crystal cells etc. is by a large amount of heat treatment procedure, therefore, in order to good dimensional stability, it is specific and Speech, the shrinking percentage of the polyester film after unrestricted heat treatment in preferably 120 DEG C × 30 minutes are in the direction film MD, the direction TD 5% or less.

Existing technical literature

Patent document

Patent document 1: Japanese Unexamined Patent Publication 2002-116320 bulletin

Patent document 2: Japanese Unexamined Patent Publication 2004-219620 bulletin

Patent document 3: Japanese Unexamined Patent Publication 2004-205773 bulletin

Patent document 4:WO2011-162198

Patent document 5: Japanese Unexamined Patent Publication 2010-277028 bulletin

Summary of the invention

Problems to be solved by the invention

As described above, the polyester film for being used as polaroid protective film is based on various viewpoints and improvement has been repeated, but this There are also further rooms for improvement for the discoveries such as inventor.That is, there are following new issues for the inventors of the present invention's discovery: will use at present The polyester film improved is as the polarizer of polaroid protective film and another polarizer to become crossed nicols Relationship when being configured, it some times happens that a small amount of light leakage, visuality deteriorates.Therefore, problem of the present invention is that, providing can Inhibit the polaroid protective film of above-mentioned a small amount of light leakage formed by polyester film.

The solution to the problem

The inventors of the present invention are concentrated on studies in order to solve the above problems, as a result, it has been found that, by so that polyester film Percent thermal shrinkage become maximum direction, with angle (i.e. percent thermal shrinkage formed by the conveying direction of its polyester film or width direction Be maximum direction relative to film conveying direction or the gradient in thin-film width direction) absolute value be 15 degree of modes below It is controlled, the above subject can be solved.Based on above-mentioned opinion, further research, is provided with following inventions for representative repeatedly.

1st

A kind of polaroid protective film, is formed by polyester film, and film conveying direction or width direction and the heat of film are received The absolute value that shrinkage becomes angle formed by maximum direction is 15 degree or less.

2nd

The polaroid protective film according to the 1st, wherein the retardation of polyester film is 4000~30000nm, Nz system Number is 1.7 or less.

3rd

According to polaroid protective film described in the 1st or the 2nd, wherein the planar orientation degree of polyester film is 0.13 or less.

4th

A kind of polarizer, it includes the composition that the two sides in polarizing film are laminated with polaroid protective film,

At least unilateral polaroid protective film is polaroid protective film described in the 1st~any one of the 3rd.

5th

A kind of polarizer, be laminated with the 1st~any one of the 3rd in the unilateral side of polarizing film described in polarizing film protect Cuticula.

6th

A kind of liquid crystal display device with back light, 2 polarizers and is configured between 2 polarizers Liquid crystal cells, wherein

The back light is the white light source with continuous luminous spectrum,

The polarizer is to be laminated with the composition of polaroid protective film in the two sides of polarizing film,

It is configured at least one of the polaroid protective film of the polarizer of incident light side and is configured at the polarisation of emergent light side At least one of the polaroid protective film of plate is polaroid protective film described in the 1st~any one of the 3rd.

7th

The liquid crystal display device according to the 6th, wherein the incident light side of the polarizer for being configured at incident light side Polaroid protective film and the polaroid protective film of emergent light side of the polarizer for being configured at emergent light side be the 1st~the Polaroid protective film described in any one of 3.

8th

The back light is the white light source with continuous luminous spectrum,

The polarizer is polarizer described in the 5th.

The effect of invention

According to the present invention, when being configured 2 polarizers with the relationship of crossed nicols, can inhibit to occur in the past A small amount of light leakage.In addition, according to a kind of preferred embodiment, it is possible to provide a kind of liquid crystal display device, be not only adapted to slimming, And rainbow spot will not be generated, but also can reduce the deterioration of the visuality as caused by the light leakage, there is excellent visuality.

Detailed description of the invention

Fig. 1 shows be 0 degree with the conveying direction of film and carry out 360 degree of measurements with percent thermal shrinkage of 5 degree of intervals to film Result example.In the example, it is about 15 degree that percent thermal shrinkage, which becomes maximum angle,.

Fig. 2 is in order to by finding out heat with the percent thermal shrinkage of 5 degree of measuring spaces, with precision more than 1 degree of interval or 1 degree of interval Shrinking percentage become maximum angle and using angle as X-axis, percent thermal shrinkage be Y-axis mark and draw figure.

Fig. 3 shows schematically the interval of fixture utilized in the method 1 of the gradient for reducing percent thermal shrinkage.

Fig. 4 indicate reduce percent thermal shrinkage gradient method 4 in utilizable stenter length direction distance with The relationship of tenter temperatures.

Specific embodiment

1. polaroid protective film

Polaroid protective film of the invention is polyester film, and percent thermal shrinkage becomes conveying of the maximum direction relative to film The absolute value of the gradient (the hereinafter referred to as gradient of percent thermal shrinkage) of direction or width direction is preferably 15 degree or less.It is aforementioned The absolute value of the gradient of percent thermal shrinkage is preferably 12 degree or less, more preferably 10 degree or less, be even more preferably 8 degree with Under, further preferably 6 degree or less, be particularly preferably 4 degree or less, most preferably 2 degree or less.Due to the gradient of percent thermal shrinkage Absolute value it is smaller the more preferred, therefore lower limit be 0 degree.

The exact mechanism of the above-mentioned a small amount of light leakage of generation is still not clear, but can consider as follows.Under normal conditions, in liquid crystal In showing device, 2 polarizers are configured in a manner of becoming the relationship of crossed nicols.By 2 polarizers with crossed nicols When relationship is configured, it is generally the case that light will not pass through 2 polarizers.It is contemplated, however, that when polaroid protective film is because of warm When handling and shrinking, polarizing film is also shunk slightly therewith or warpage, as a result the relationship of complete crossed nicols be destroyed and Light leakage occurs.It is maximum direction relative to film conveying direction in the percent thermal shrinkage of polaroid protective film according to this principle Or thin-film width direction in it is oblique when, light leakage becomes significant.It should be noted that polaroid protective film conveying direction is usually and partially The polarizing axis of vibration piece is parallel or vertical.

Disclosed in Patent Document 5 be by the percent thermal shrinkage in the direction MD, the direction TD is that 5% polyester film below is formed Polaroid protective film.However, shown by above-mentioned mechanism it is small even if the percent thermal shrinkage in the direction MD and the percent thermal shrinkage in the direction TD, When percent thermal shrinkage becomes maximum direction and tilts relative to film conveying direction or thin-film width direction, can also occur aforementioned inclined The problem of light leaks out.

In addition, patent document 5 also discloses, for the position at film both ends, reduce slow axis and the film side TD in pellicular front To angulation and its deviation, to prevent the gamut (color shift) and color spot of liquid crystal display.However, in pellicular front The direction of slow axis may not be parallel with the inclination of percent thermal shrinkage, therefore, even the film that slow axis is controlled in pellicular front, also can The problem of aforementioned polarisation leaks out occurs.

Polyester film used in polaroid protective film of the invention can be obtained by arbitrary polyester resin.To polyester The type of resin is not particularly limited, and arbitrary polyester resin obtained from being condensed dicarboxylic acids and glycol can be used.

It as the dicarboxylic acid component being able to use in the manufacture of polyester resin, such as can enumerate: terephthalic acid (TPA), isophthalic two Formic acid, phthalic acid, 2,5- naphthalenedicarboxylic acid, 2,6- naphthalenedicarboxylic acid, 1,4- naphthalenedicarboxylic acid, 1,5- naphthalenedicarboxylic acid, diphenyl carboxylic Acid, diphenoxyethanedicarboxylic acid, diphenyl sulfone carboxylic acid, anthracene dioctyl phthalate, 1,3- cyclopentane dicarboxylic acid, 1,3- hexamethylene dicarboxyl Acid, 1,4- cyclohexane dicarboxylic acid, hexahydro terephthalic acid, hexahydro M-phthalic acid, malonic acid, dimethyl malonic acid, succinic acid, 3,3- diethyl succinic acid, glutaric acid, 2,2- dimethylated pentanedioic acid, adipic acid, 2- methyl adipic acid, trimethyladipic acid, heptan Diacid, azelaic acid, dimeric dibasic acid, decanedioic acid, suberic acid, dodecanedicarboxylic acid etc..

It as the diol component being able to use in the manufacture of polyester resin, such as can enumerate: ethylene glycol, propylene glycol, six Asias Methyl glycol, neopentyl glycol, 1,2- cyclohexanedimethanol, 1,4 cyclohexane dimethanol, decamethylene glycol, 1,3- propylene glycol, Bis- (4- hydroxy phenyl) propane of 1,4- butanediol, 1,5- pentanediol, 1,6-HD, 2,2-, bis- (4- hydroxy phenyl) sulfones etc..

The dicarboxylic acid component and diol component for constituting polyester resin can be used any one kind or two or more.It is poly- as constituting The suitable polyester resin of ester film, such as can enumerate: polyethylene terephthalate, polypropylene terephthalate, Polybutylene terephthalate (PBT), polyethylene naphthalate etc. can more preferably be enumerated: polyethylene terephthalate Ester, polyethylene naphthalate, these polyester resin can also further contain other copolymer compositions.These resins it is transparent Property is excellent, and thermal characteristics, mechanical property are also excellent, can easily control retardation by stretch process.In particular, poly- pair Ethylene terephthalate can relatively easily obtain big delay due to intrinsic birefringent big the thickness of film is thin Amount, therefore be optimum raw material.

(percent thermal shrinkage)

The percent thermal shrinkage of polyester film is preferably 5% or less in all directions.Heat on all directions of polyester film Shrinking percentage can be operated as follows and is measured.

Polyester film is cut into the square shape of one side 21cm, is placed 2 hours or more in 23 DEG C, the atmosphere of 65%RH. On the polyester film, describe the circle of diameter 80mm centered on its center, using two dimensional image analyzer (for example, The QUICK IMAGE of MITUTOYO manufacture), using the conveying direction of film as 0 degree, with 5 degree of measuring space diameters.Here, will Film conveying direction is as 0 degree, in stenter from upper surface when film, will rotate clockwise what (right-hand rotation) setting was positive Angle will rotate (left-hand rotation) counterclockwise and set the angle being negative.If be measured in the range of~85 degree of -90 degree, so that it may To measure comprehensive diameter.

Then, polyester film is carried out to heat treatment 30 minutes at 85 DEG C, in water, then wiping is attached to film table The moisture in face, carries out air-dried, then places 2 hours or more in 23 DEG C, the atmosphere of 65%RH.Then, as described above with 5 Spend measuring space diameter of a circle.Diameter before heat treatment is set as L₀, the equidirectional diameter after heat treatment be set as L, according to The percent thermal shrinkage of all directions is found out according to following formula.

Percent thermal shrinkage (%)=((L₀-L)/L₀)×100

If carrying out percent thermal shrinkage obtained from 360 degree of measurements with graphical representation with 5 degree of intervals, such as such as Fig. 1 institute Show.In Fig. 1, show that the percent thermal shrinkage at round center is 0%, with elongated at a distance from round center, percent thermal shrinkage becomes larger.Separately Outside, circumference indicates for film conveying direction to be set as 0 degree of angle.Thus, 90 degree are parallel with thin-film width direction.

For the percent thermal shrinkage found out by above-mentioned measuring method, maximum value is preferably 5% or less, is more preferably 3% or less, it is even more preferably 1% or less, is most preferably 0.5% or less.The lower limit of percent thermal shrinkage is not particularly limited, For example, 0.01% or more.

(gradient of percent thermal shrinkage)

As described above, percent thermal shrinkage is measured with 5 degree of intervals, percent thermal shrinkage become maximum direction according to following step, It is found out with 1 degree of precision.That is, as shown in Fig. 2, horizontal axis being set as 0 degree of angle as film conveying direction, works as the longitudinal axis Make the percent thermal shrinkage in the angle to mark and draw the measurement result of the percent thermal shrinkage (knot of the percent thermal shrinkage of -90~85 degree of ranges of degree Fruit).At this moment, also (percent thermal shrinkage of -90 degree corresponds to 90 degree of heat for interpolation -180 degree~-95 degree and 90 degree~175 degree of value Shrinking percentage, 0 degree of percent thermal shrinkage corresponds to-percent thermal shrinkage of 180 degree).Then, the curve of approximation for connecting each plot point is drawn, Become maximum direction with 1 degree of reading percent thermal shrinkage of precision, is defined as α.It should be noted that -90 degree≤α≤90 degree.

When percent thermal shrinkage becomes range of the maximum direction α in -45~45 degree of degree, which is set as percent thermal shrinkage Gradient.In addition, being interpreted as when percent thermal shrinkage becomes maximum direction α below 45 degree or more and -45 degree by thin-film width side To favouring benchmark, rather than film conveying direction, by α -90 spend (when α be 45 degree or more), 90 degree of+α (α be -45 spend below When) it is set as the gradient of percent thermal shrinkage.When the difference of the maxima and minima of percent thermal shrinkage is 0.1% or less, Suo Youfang To percent thermal shrinkage it is roughly equal, therefore the gradient of percent thermal shrinkage is considered as 0 degree there is no gradient by percent thermal shrinkage.

(light leakage evaluation method)

Light leakage is to configure 2 polarizers with the relationship of crossed nicols, and measurement penetrates its 550nm~600nm wave The maximum transmission of long light.The measurement that arbitrary spectrophotometer carries out the transmitance of light can be used.The maximum measured Transmitance is preferably 0.02% or less, more preferably 0.015% or less.

In the following, retardation and Nz coefficient and planar orientation degree to polyester film carry out from the viewpoint of inhibiting rainbow spot Explanation.

(retardation)

Polyester film used in polaroid protective film preferably has the retardation of 4000~30000nm.If retardation is 4000nm or more, then issuable rainbow spot when can inhibit the liquid crystal display device from oblique, it can be ensured that it is good can Depending on property.The preferred retardation of polyester film is 4500nm or more, more preferably 5000nm or more, further preferably 6000nm Above, it is still more preferably 8000nm or more, is more preferably 10000nm or more.Here, so-called 4000~30000nm is Refer to comprising 4000nm as lower limit value, comprising 30000nm as upper limit value, but is also contemplated within the range not included.

The upper limit of the retardation of polyester film is not particularly limited, for example, 30000nm.This is because, even if using Polyester film with the retardation more than it, being substantially also unable to get further improves visual effect, along with prolonging The rising measured late, the thickness of film also become relatively thicker, and the operability as industrial materials is likely to decrease.

The value of the retardation of oriented polyester films can be found out by following steps.Using molecularly oriented meter (for example, prince The manufacture of measuring instrument Co., Ltd., MOA-6004 type molecularly oriented meter) find out the orientation axis direction of film.To measure wavelength 589nm is orientated the refraction of the refractive index (ny) of axis direction and orthogonal with orientation axis direction direction in pellicular front to measure Rate (nx).The absolute value (| ny-nx |) for finding out the specific refractivity (anisotropy) of these biaxially orienteds, by it multiplied by film Thickness can find out the value of retardation.KOBRA-21ADH (prince's measuring instrument strain formula meeting can be used for example in the retardation of film Society) etc. commercially available automatic double refraction detection device be measured.In addition, Abbe refractometer can be used for example in the refractive index of film The commercially available analyzers such as meter (ATAGO CO., LTD, manufacture, NAR-4T) are measured.

(Nz coefficient)

Polyester film used in polaroid protective film is on the basis of the range of above-mentioned retardation, preferably | ny-nz |/| Ny-nx | shown in Nz coefficient be 1.7 or less.Nz coefficient can be found out as follows.Use molecularly oriented meter (prince's measuring instrument strain The manufacture of formula commercial firm, MOA-6004 type molecularly oriented meter) the orientation axis direction that finds out film, pass through Abbe refractomecer (ATAGO CO., LTD, manufacture, NAR-4T, measurement wavelength 589nm) find out the refraction for being orientated the twin shaft of axis direction and orthogonal to that direction The refractive index (nz) of rate (ny, nx, wherein, ny > nx) and thickness direction.Thus nx, ny, nz for finding out are substituted into | ny-nz |/| ny-nx | shown in formula, Nz coefficient can be found out.

Even if the retardation of polyester film is 4000nm~30000nm, when Nz coefficient is more than 1.7, the two of a pair of of polarizer Used in person polyester film as polaroid protective film in the case where (for example, being configured at the incident light of the polarizer of incident light side The polaroid protective film of side and the polaroid protective film of the emergent light side for the polarizer for being configured at emergent light side are polyester film Situation), from oblique when liquid crystal display device, rainbow spot still can be generated because of angle sometimes.It is generated from the above-mentioned rainbow spot of inhibition From the perspective of, Nz coefficient is more preferably 1.65 or less, further preferably 1.63 or less.The lower limit value of Nz coefficient is 1.2.This It is due to obtaining the film less than 1.2 in manufacturing technology and being difficult.In addition, the mechanical strength in order to keep film, Nz system Several lower limit values is preferably 1.3 or more, more preferably 1.4 or more, further preferably 1.45 or more.

(surface orientation coefficient)

By the delay magnitude of polyester film and the control of Nz coefficient on the basis of above-mentioned particular range, by by (nx+ Ny surface orientation coefficient shown in)/2-nz is set as particular value and uses in the two of a pair of of polarizer hereinafter, can more reliably eliminate Rainbow spot when polyester film is as polaroid protective film.Here, the value of nx, ny and nz can pass through method same as Nz coefficient To find out.The planar orientation degree of oriented polyester films is preferably 0.13 or less, is more preferably 0.125 or less, is more preferably 0.12 or less.By the way that planar orientation degree is set as 0.13 hereinafter, from oblique when liquid crystal display device, can completely eliminate because of angle The rainbow spot spent and observed.Planar orientation degree is preferably 0.08 or more, more preferably 0.1 or more.It is thin when planar orientation degree is less than 0.08 Film thickness changes, and the value of retardation becomes uneven sometimes in pellicular front.

(retardation ratio)

For polyester film, the ratio between retardation (Re) and thickness direction retardation amount (Rth) (Re/Rth) be preferably 0.2 with Upper, more preferably 0.5 or more, further preferably 0.6 or more.This is because, above-mentioned retardation and thickness direction retardation amount The ratio between (Rth) (Re/Rth) is bigger, and birefringent effect more increases isotropism, by rainbow shape color spot caused by viewing angle It becomes difficult to generate.For complete 1 axis (1 axial symmetry) film, above-mentioned retardation and thickness direction retardation amount it Become 2 than (Re/Rth).It is vertical with differently- oriented directivity with close to complete 1 axis (1 axial symmetry) film however, as described later The mechanical strength in straight direction is substantially reduced.Therefore, the upper limit of the ratio between retardation and the retardation of thickness direction (Re/Rth) is excellent It is selected as 1.2 or less, more preferably 1 or less.Occurred to completely inhibit by rainbow shape color spot caused by viewing angle, it is above-mentioned to prolong The ratio between amount and the retardation of thickness direction (Re/Rth) are not necessarily 2 late, are sufficient for 1.2 or less.In addition, even if above-mentioned Ratio is 1.0 hereinafter, also can sufficiently meet field angle characteristic required by liquid crystal display device (left and right 180 degree, upper and lower 120 Degree left and right).

(uneven thickness)

In order to inhibit polyester film retardation variation, the uneven thickness of preferred film is small.From this viewpoint, polyester The uneven thickness of film is preferably 5% or less, is more preferably 4.5% or less, is still more preferably 4% or less, especially Preferably 3% or less.The uneven thickness of film can be measured by following steps.From film roll along the direction TD with 40mm wide Degree cuts film.For the sample cut, the continuous thickness gauge of contact (the submitting speed: 1.5m/ points of ANRITSU manufacture is utilized Clock, sampling period: 100ms) continuously measure the direction TD thickness, find out average value, maximum value, minimum value.Uneven thickness is Pass through the absolute value for the value that the following formula is calculated.

Uneven thickness=((maximum value of measurement result)-(minimum value of measurement result))/(average value of measurement result) × 100 (%)

(film thickness)

The thickness of polyester film is not particularly limited, usually 15~300 μm, preferably 15~200 μm.Film thickness When less than 15 μm, the anisotropy of the mechanical characteristic of film becomes obviously, and fracture, breakage etc. occur sometimes.Particularly preferred thickness The lower limit of degree is 25 μm.On the other hand, when the upper limit of the thickness of polaroid protective film is more than 300 μm, the thickness of polarizer becomes It is blocked up without preferred.From the viewpoint of the practicability as polaroid protective film, the upper limit of thickness is preferably 200 μm.Especially The upper limit of preferred thickness and general TAC film are 100 μm of equal extent.

(light transmittance)

From the viewpoint of the deterioration for inhibiting the optical functionals pigments such as iodine pigment contained in polarizing film, it is generally desirable to, The light transmittance of the wavelength 380nm of polyester film is 20% or less.The light transmittance of 380nm is more preferably 15% or less, is further excellent It is selected as 10% or less, particularly preferably 5% or less.If aforementioned light transmittance be 20% hereinafter, if can inhibit optical functional Pigment goes bad because of caused by ultraviolet light.Light transmittance is the value measured relative to the plane of film with vertical process, be can be used Spectrophotometer (for example, spectrophotometer V-7100 of Japan Spectroscopy Corporation's manufacture) is measured.

By suitably adjusting the type of the ultraviolet absorbing agent of compounding, concentration and the thickness of film, orientation can be made poly- The light transmittance of the wavelength 380nm of ester film controls below 20%.For ultraviolet absorbing agent used in the present invention, Ke Yishi When select well known ultraviolet absorbing agent come using.As specific ultraviolet absorbing agent, the suction of organic ultraviolet light can be enumerated Agent and inorganic UV absorber are received, from the viewpoint of the transparency, preferred organic ultraviolet absorbing agent.

It as organic ultraviolet absorbing agent, can enumerate: benzotriazole, benzophenone and cyclic imide base ester Class etc. and their arbitrary combination, are not particularly limited.From the viewpoint of durability, particularly preferred benzotriazole, Or cyclic imide base ester class.When ultraviolet absorbing agent of more than two kinds is applied in combination, since respective wavelength can be absorbed simultaneously Ultraviolet light, therefore can further improve ultraviolet radiation absorption effect.

As benzophenone ultraviolet absorbent, Benzotriazole Ultraviolet Stabilizer and vinyl cyanide ultraviolet light Absorbent, such as can enumerate: 2- [2 '-hydroxyls -5 '-(methacryloxymethyl) phenyl] -2H- benzotriazole, 2- [2 ' - Hydroxyl -5 '-(methacryloxyethyl) phenyl] -2H- benzotriazole, 2- [2 '-hydroxyls -5 '-(methacryloxy third Base) phenyl] -2H- benzotriazole, 2,2 '-dihydroxy -4,4 '-dimethoxy-benzophenone, 2,2 ', 4,4 '-tetrahydroxy hexichol first Ketone, 2,4- di-t-butyl -6- (5- chlorobenzotriazole -2- base) phenol, 2- (2 '-hydroxyls -3 '-tert-butyl -5 '-aminomethyl phenyl) - 5- chlorobenzotriazole, 2- (5- chlorine (2H)-benzotriazole -2- base) -4- methyl -6- (tert-butyl) phenol, 2,2 '-di-2-ethylhexylphosphine oxides (4- (1,1,3,3- tetramethyl butyl) -6- (2H- benzotriazole -2- base) phenol etc..It is inhaled as cyclic imide base ester class ultraviolet light Receive agent, such as can enumerate: 2,2 '-(Isosorbide-5-Nitraes-phenylene) bis- (4H-3,1- benzoxazin-4-ones), 2- methyl -3,1- benzo are disliked Piperazine -4- ketone, 2- butyl -3,1- benzoxazin-4-one, 2- phenyl -3,1- benzoxazin-4-one etc..These ultraviolet absorbing agents It can be used only a kind, two or more can also be applied in combination.

When being compounded ultraviolet absorbing agent in polyester film, oriented polyester films are made to 3 layers or more of multilayered structure, Addition ultraviolet absorbing agent is preferred in layer (i.e. middle layer) other than the outermost layer of film.

(other ingredients etc.)

Other than ultraviolet absorbing agent, containing each in the range for not interfering effect of the invention, oriented polyester films Kind additive is also preferred mode.It as additive, such as can enumerate: inorganic particle, heat resistance polymeric particles, alkali metal Compound, alkaline earth metal compound, phosphorus compound, antistatic agent, photostabilizer, fire retardant, heat stabilizer, antioxidant, anticol Solidifying agent, surfactant etc..In addition, in order to play high transparency, it is also preferred that being substantially free of particle in polyester film." essence It is upper to be free of particle " refer to: in the case where being, for example, inorganic particle, when being quantified using x-ray fluorescence analysis to inorganic elements For 50ppm or less, preferably 10ppm or less, particularly preferably detectable limit content below.

(adhesive layer)

In the present invention, in order to improve the cementability with polarizing film, preferably having in at least single side of polyester film will gather At least one kind of in ester resin, polyurethane resin or polyacrylics makees adhesive layer as main component.Here, " main Ingredient " refers to the ingredient in the solid component for constituting adhesive layer for 50 mass % or more.It is used to form the coating of adhesive layer Liquid preferably comprises at least 1 in water-soluble or water dispersible copolymer polyester resin, acrylic resin and polyurethane resin The aqueous coating fluid of kind.It as above-mentioned coating fluid, such as can enumerate: Japanese Patent No. No. 3567927 bulletins, Japanese Patent No. No. 3589232 bulletins, No. 3589233 bulletins of Japanese Patent No., Japanese Patent No. No. 3900191 bulletins, Japanese Patent No. Water solubility disclosed in No. 4150982 bulletins etc. or water dispersible copolymer polyester resin solution, acrylic resin solution and Polyurethane resin solution etc..

Adhesive layer can obtain by the following method: above-mentioned coating fluid is coated on non-stretched film or longitudinal single shaft It is dry at 100~150 DEG C after the single or double of oriented film, it is further transversely stretched and is obtained.Final is easy The coating weight of adhesive layer is preferably controlled to 0.05~0.2g/m².If coating weight is lower than 0.05g/m², then sometimes with obtain it is inclined The cementability of vibration piece becomes inadequate.On the other hand, if coating weight is more than 0.2g/m², then resistance to blocking can reduce sometimes.? When adhesive layer is arranged in the two sides of polyester film, the coating weight of the adhesive layer on two sides can be the same or different, can be each From independently being set within the above range.

Particle is added in adhesive layer preferred to easy slip is assigned.The average grain diameter of particle is preferably 2 μm or less. If the average grain diameter of fruit granule is more than 2 μm, then particle is easy to fall off from coating.As the particle contained in adhesive layer, example Can such as enumerate: titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, aluminium oxide, talcum, kaolin, clay, calcium phosphate, The inorganic particles such as mica, hectorite, zirconium oxide, tungsten oxide, lithium fluoride, calcirm-fluoride；Phenylethylene, acrylic compounds, melamine Organic polymers species particle such as amine, benzocarbamidine amine, organic silicon etc..These particles can be separately added to adhesive layer In, two or more can also be combined and be added.

The average grain diameter of particle can obtain by the following method: shoot particle with scanning electron microscope (SEM) Photo, the multiplying power for being 2~5mm with the size of 1 the smallest particle, the maximum gauge for measuring 300~500 particles is (farthest 2 points between distance), calculate its average value and obtain.

Coating fluid can be used well known method and be coated.Such as can enumerate: reverse roll coating method, gravure coating process, Engagement rubbing method, roller brush method, spraying coating method, air knife coating method, bar rubbing method, tubular type scraper method etc..These methods can To carry out alone or in combination.

For polyester film, in order to keep it good with the cementability of polarizing film, sided corona treatment also can be implemented, at coating Reason, flame treatment etc..

(functional layer)

On the face for being opposite side with the face for configuring polarizing film of polyester film, reflective in order to prevent, inhibition dazzle, inhibition Damage etc., and various functions layers are set, i.e. selected from by hard conating, antiglare layer, anti-reflection layer, low reflection on oriented polyester surface The functional layer of one or more of the group of layer, anti-low reflection layer, antireflection antiglare layer and antistatic layer composition is also preferred side Formula.When various functions layers are arranged, oriented polyester films preferably have adhesive layer on its surface.At this point, from inhibiting by reflecting From the perspective of the interference that light generates, preferably the refractive index of adhesive layer is adjusted thin to the refractive index of functional layer and oriented polyester Near the geometrical mean of the refractive index of film.The adjustment of the refractive index of adhesive layer can use well known method, such as can be with By making to be easy to carry out adjustment in binder resin containing titanium, zirconium, other metallicses.

(manufacturing method of polyester film)

The polyester film used as polaroid protective film can be manufactured according to the manufacturing method of normal polyester film.Example Such as the following methods can be used: polyester resin is melted, make the No yield point polyester of extrusion molding sheet in glass transition temperature It at a temperature of above, after being longitudinally stretched using the speed difference of roller, is transversely stretched through stenter, implements heat treatment. It can may be biaxially oriented film for single axle drawn membrane.

(gradient for reducing percent thermal shrinkage)

For percent thermal shrinkage is become maximum direction relative to the exhausted of the gradient of film conveying direction or width direction Value is controlled and is not particularly limited in 15 degree of the following method, but preferably pays attention to following aspect.That is, the heat treatment in stenter There is the shrinkage stress for the adjoint stretching for not being thermally fixed removal and with cooling thermal stress in the cooling section after process.Separately Outside, the film relative to end is limited by fixture, and the film of central portion, which compares, to be stretched, therefore, thin in cooling section There are biased for the distribution of film conveying direction and the stress of width direction.It becomes the main original for generating the gradient of percent thermal shrinkage Cause.According to such case, following example reduces the specific method of the gradient of percent thermal shrinkage.

(method 1 for reducing the gradient of percent thermal shrinkage)

In cooling section after heat fixation, grip separation is reduced in film conveying direction, stenter cooling zone can be made Between film conveying direction stress it is uniform, so as to reduce the gradient of percent thermal shrinkage.Thus, it is heat-shrinked to reduce The temperature band of the gradient of rate, preferably appropriate adjustment diminution grip separation.Due to due to film forms, thin film fabrication condition is different Difference, therefore be not particularly limited, but when the temperature is excessively high, relative to conveying direction, left end (film viewed from above When) the gradient of percent thermal shrinkage of film become larger (right-hand end becomes larger in negative direction) in positive direction.In addition, too low in temperature When, since the thermal shrinking quantity of film is too small, flatness is bad, and it is not preferable.In this way, by the way that the temperature for reducing grip separation is set It is scheduled on optimum range, the stress of the conveying direction in the cooling section of stenter can be made to become uniformly, so as to reduce percent thermal shrinkage Gradient.

It is also critically important in the relaxation rate that film conveying direction reduces grip separation in order to reduce the gradient of percent thermal shrinkage. Due to being not particularly limited because that film forms, thin film fabrication condition is different is different, relaxation rate is preferably 0.01~3%, More preferably 0.05~1.5%.When relaxation rate is excessively high, film is not shunk completely, and flatness is bad, and it is not preferable.In addition, When relaxation rate is too low, the effect for reducing the gradient of percent thermal shrinkage is lower.Here so-called relaxation rate can be used such as Fig. 3 institute The distance between centers of the fixture shown, is calculated by following formula.

Relaxation rate=(((distance between the fixture before relaxation)-(distance between the fixture after relaxation))/(between the fixture before relaxation Distance)) × 100 (%)

When the percent thermal shrinkage of width direction is excessively high, there is the gradient bigger tendency of percent thermal shrinkage.Therefore, it more preferably adjusts Whole stenter guide rail pattern (rail patten), and appropriate adjustment thin-film width direction reduce grip separation relaxation rate and Temperature.In this way, by the way that optimum range and root will be set in the temperature band and relaxation rate of film conveying direction diminution grip separation According to appropriate adjustment stenter guide rail pattern is needed so that the shrinking percentage of width direction will not become excessive, stenter cooling zone can be made Between the stress of conveying direction become uniformly, the gradient of percent thermal shrinkage can be reduced.

(method 2 for reducing the gradient of percent thermal shrinkage)

Cooling section after heat fixation separates film end from fixture, and release is limited by fixture bring, can be made The stress of the width direction in the cooling section of stenter becomes uniform.In addition, by by the tension adjustment of rolling step to Appropriate, Can make the stress of the conveying direction in the cooling section of stenter becomes uniform.As a result, by making stenter cool down the conveying in section The stress in direction becomes uniformly, so as to reduce the gradient of percent thermal shrinkage.

For film end to be not particularly limited from the method that fixture separates, currently known method is used.Tool It for body, can enumerate: the method that film is cut off from fixture and the method for decontroling fixture.By film from the side that fixture is cut off Method is arbitrary, such as can enumerate the cutting using cutter or the fusing using laser.Above method combination can also be come real It applies.When film is cut off from fixture, it is generally desirable to, it is carried out at film both ends close to the position of fixture.

It is desirable that film temperature when film end is separated from fixture is 50 DEG C~300 DEG C.Relative to the molten of film Point Tm, film temperature is higher, is more difficult to maintain the flatness of film, in addition, the glass transition temperature Tg relative to film, thin When film temperature is too low, the gradient of percent thermal shrinkage becomes difficult to reduce.Thus, it is desirable that being higher than (glass transition temperature Tg-20 DEG C), separate lower than cutting off film from fixture at a temperature of (Tm-10 DEG C of fusing point).Here film temperature is to utilize spoke Penetrate the measured value that thermometer obtains.

When film end is separated from fixture, the preferred tension of appropriate adjustment rolling step.Tension appropriate is because of film Composition, thickness and thin film fabrication condition are different and different, therefore are not particularly limited, preferably 0.01~3kg/mm², it is more excellent It is selected as 0.1~2kg/mm².When tension is excessively high, relative to conveying direction, the gradient of the percent thermal shrinkage of the film of left end exists Positive direction becomes larger (right-hand end becomes larger in negative direction).In addition, when tension is too low, relative to conveying direction, left end it is thin The gradient of the percent thermal shrinkage of film becomes larger (right-hand end becomes larger in positive direction) in negative direction.Wherein, above-mentioned tendency is to convey The case where evaluating angle on the basis of direction is positive and negative in opposite tendency by the case where benchmark of width direction.

When the percent thermal shrinkage of width direction is excessively high, the gradient of percent thermal shrinkage becomes larger.It is therefore preferable that adjusting film end Guide rail pattern before fixture separation, adjustment reduces the relaxation rate and temperature of grip separation in thin-film width direction as described above. In this way, the stress of the conveying direction in the cooling section of stenter can be made to become uniformly by the way that tension is set in proper range, thus The gradient of percent thermal shrinkage can be reduced.

(method 3 for reducing the gradient of percent thermal shrinkage)

According to idea same as method 2 is reduced, by making the film temperature of tenter outlet be higher than predetermined temperature (i.e. glass Tg-20 DEG C of glass transition temperature) and it is lower than predetermined temperature (Tm-70 DEG C of fusing point), the gradient of percent thermal shrinkage can be reduced.This When, since effect is controlled by room temperature, it is therefore desirable that control room temperature.

(method 4 for reducing the gradient of percent thermal shrinkage)

It is set by adjusting the temperature of the cooling process after stenter heat fixation, the inclination of percent thermal shrinkage can also be reduced Degree.For example, it is preferable that heat-fixing temperature~tenter outlet temperature is set along stenter length direction as shown in Figure 4 It is fixed at -15/X~-100/X (DEG C/m).Here, X indicates tenter outlet width (m).Thus, for example, wide in tenter outlet When degree is 2m, preferably in the every advance 1m of stenter length direction, the range with -7.5 DEG C~-50 DEG C declines temperature.By The temperature of every tenter outlet width is indicated in above-mentioned temperature, therefore, the hereinafter referred to as temperature setting of per unit width.

In addition, it is preferred that tenter outlet temperature, which is typically set at Tg or less,.The temperature of per unit width is set in length Degree direction be -100/X (DEG C/m) below when, the gradient of percent thermal shrinkage is more than 15 degree, and it is not preferable, for -15/X (DEG C/m) with When upper, although the gradient of percent thermal shrinkage can be reduced sufficiently, tenter apparatus investment is excessive, and it is not preferable.

(method 5 for reducing the gradient of percent thermal shrinkage)

Even there are the film of the gradient of percent thermal shrinkage, by disposably volume to winding carry out such as 80 DEG C~ 120 DEG C, 10 seconds~90 minutes offline annealings, can also reduce the gradient of percent thermal shrinkage.In offline annealing, Substantially ensure that temperature, the time of annealing to be adjusted are preferred.In addition, currently known in tenter outlet~volume It is also ideal that online annealing processing is carried out between coiling.At this point, substantially ensuring annealing in the same manner as above-mentioned offline annealing The temperature of processing, time are preferably, in terms of heat treatment efficiency, maintenance flatness, more preferably to use pneumatic roller (air can roll)。

For above-mentioned reduction method 1~5, any method can individually be implemented, implementation can also be combined.By above-mentioned Method can make the gradient of percent thermal shrinkage become 15 degree or less.

For polyester film, longitudinal stretching, after stretching horizontally is being carried out, by heat treatment procedure, is cutting both sides edge And mill volume (mill roll) is formed, it is split as needed, to become segmentation volume.So-called both sides edge refers to: by film The length of entire width be set as 100%, from film both ends preferably 1%~10% range, more preferably 1%~ 5% range.It should be noted that so-called both ends here, with the film two before the cutting that illustrates for above-mentioned reduction method 2 It holds identical.Wherein, the region that mill volume is carried out to the two sides that 3 wait timesharing, especially has the absolute value of the gradient of percent thermal shrinkage to become larger Tendency, therefore, it is preferred that the absolute value of the gradient of the percent thermal shrinkage in the region, which is controlled at 15 degree or less,.

For the oriented polyester films with above-mentioned specific retardation and Nz coefficient, when can be film-made by adjusting Condition (for example, thickness etc. of stretching ratio, draft temperature, film) and obtain.For example, stretching ratio is higher, draft temperature is got over Low, the thickness of film is thicker, is more easy to get high latency amount.On the other hand, stretching ratio is lower, and draft temperature is higher, film Thickness it is thinner, be more easy to get low latency amount.

As specific film forming condition, for example, longitudinal drawing temperature and transverse drawing temperature be preferably 80~145 DEG C, More preferably 90~140 DEG C.Longitudinal stretching multiplying power is preferably 1.0~3.5 times, more preferably 1.0 times~3.0 times.In addition, laterally Stretching ratio is preferably 2.5~6.0 times, more preferably 3.0~5.5 times.

In order to by retardation control in above-mentioned specific range, preferably control longitudinal stretching multiplying power and cross directional stretch multiplying power Ratio.If the difference of stretching ratio in length and breadth is too small, it is difficult to improve retardation, it is not preferable.In addition, for improving retardation For, draft temperature is set to lower be also preferred.The temperature of subsequent heat treatment is preferably 100~250 DEG C, is more preferably 180~245 DEG C.

In order to make Nz coefficient become above-mentioned specific value, the ratio of longitudinal stretching multiplying power and cross directional stretch multiplying power is preferably controlled Rate is preferably made single axle drawn membrane.In addition, in order to reduce Nz coefficient, in order to improve the molecular weight of polymer, reduce crystallinity And it is also preferred for adding copolymer composition.It in turn, can be by appropriate in order to control the Nz coefficient of film in specific range Set total stretching ratio, draft temperature and carry out.For example, total stretching ratio is lower, draft temperature is higher, more available low Nz Coefficient.

In order to make planar orientation degree become above-mentioned particular value, total stretching ratio is preferably controlled.If total stretching ratio is excessively high, Planar orientation degree becomes excessively high, and it is not preferable.In addition, control draft temperature is also preferred for reducing planar orientation degree.It is logical The difference for increasing longitudinal stretching multiplying power and cross directional stretch multiplying power is crossed, low total stretching ratio is set, sets high draft temperature, it can be with Nz coefficient, planar orientation degree is set to become particular value or less.

Since draft temperature and stretching ratio generate large effect to the uneven thickness of film, from uneven thickness From the perspective of, it is also preferred that the optimization of condition is filmed.Longitudinal stretching multiplying power is reduced especially for retardation is improved When, longitudinal thickness unevenness is deteriorated sometimes.A certain specific range presence due to longitudinal thickness unevenness in stretching ratio can become Excessively poor region, therefore, it is desirable that setting film forming condition in the case where deviateing the range.

Ultraviolet absorbing agent can combine well known method to the compounding of oriented polyester films to implement.For example, can lead to Following methods etc. are crossed to be compounded: using mixing extruder, dried ultraviolet absorbing agent being mixed to come in advance with polymer raw material Masterbatch is first made, mixes the defined masterbatch with polymer raw material in forming thin film.

For the ultraviolet absorbing agent concentration of above-mentioned masterbatch, in order to be uniformly dispersed ultraviolet absorbing agent and economically into Row compounding, is preferably set to the concentration of 5~30 mass %.Condition as production masterbatch is, it is preferable to use mixing extruder, squeezes out Temperature was squeezed out more than the fusing point of polyester raw material and at 290 DEG C of temperature below with 1~15 minute.It is ultraviolet at 290 DEG C or more The weightlessness of light absorbers is big, increases in addition, the viscosity of masterbatch reduces.In 1 minute extrusion below, ultraviolet absorbing agent it is equal Even mixing becomes difficult.At this point it is possible to which stabilizer, color tone adjustment agents, antistatic agent is added as needed.

For being compounded ultraviolet absorbing agent in the middle layer of the oriented polyester films of the multilayered structure more than tool haves three layers, It can be implemented by gimmick below.Well known melting stacking extrusion is supplied separately to by the pellet of polyester as outer layer Machine, as middle layer with will the masterbatch containing ultraviolet absorbing agent and polyester pellet mix, dry in defined ratio after, confession Well known melting stacking extruder is awarded, squeezes out slabbing from the die head of slit-shaped, solidification is allowed to cool on casting roll and is come Make non-stretched film.That is, using 2 or more extruders, 3 layers of manifold or interflow block (such as with square merging part Collaborate block), the film layer for constituting two outer layers, the film layer for constituting middle layer are laminated, 3 layers of piece is squeezed out from tube head, with casting Roller is cooled down to make non-stretched film.

In order to remove the foreign matter for leading to contain in optics bad point, raw material polyester, preferably in the system of oriented polyester films During making, high-precision filtration is carried out in melting extrusion.The filtering of filter material used in the high-precision filtration of molten resin Particle size (exhibits initial filtration efficiency 95%) is preferably 15 μm or less.If the filtering particle size of filter material is more than 15 μm, remove 20 μm or more foreign matters are easy to become inadequate.

1. polarizer

Polarizer is the clamping of 2 polaroid protective films by the polarizing film of the formation such as polyvinyl alcohol film with iodine staining Two sides composition, at least one of aforementioned 2 polaroid protective films are preferably that the absolute value of gradient of percent thermal shrinkage exists The polyester film of particular range.In addition, in one embodiment, polarizer is preferably laminated on a face of polarizing film The composition of polaroid protective film.Polarizing film and polaroid protective film are laminated via bonding agent, it is generally the case that with 70 DEG C~ 120 DEG C of range carries out heat treatment in 10 minutes~60 minutes or so and obtains polarizer.

(configuration of polaroid protective film)

In liquid crystal display device, above-mentioned specific polyester film is protected preferably as two polarizing films of a pair of of polarizer Film uses.It is so-called a pair of polarizer refer to, relative to liquid crystal configurations in the polarizer of incident light side and relative to liquid crystal configurations in The combination of the polarizer of emergent light side.That is, the polyester film is preferred for the polarizer of incident light side and the polarisation of emergent light side The polarizer of both plates.As long as the polyester film is layered at least one face for constituting the polarizing film of each polarizer.

In a suitable embodiment, which can be used as the incident light side of the polarizer of incident light side Polaroid protective film uses, and the polaroid protective film of the emergent light side of the polarizer as emergent light side uses.Only in structure When the oriented polyester films are laminated on a face at the polarizing film of polarizer, arbitrary polarizing film can be used on another face Protective film (such as TAC film etc.) is not provided with polaroid protective film.Using the polyester film as being configured at incident light side Liquid crystal cell side (the i.e. incident light of the polaroid protective film of the liquid crystal cell side of polarizer and the polarizer for being configured at emergent light side Side) polaroid protective film when, have a possibility that polarized light property for changing liquid crystal cells, therefore, the polarizing films of these positions is protected Cuticula it is preferable to use other than the polyester film polaroid protective film (such as with TAC film, acrylic film, drop ice Piece alkenes film is film free of birefringence as representative).The absolute value of the gradient of these films further preferably percent thermal shrinkage Small person.

2. liquid crystal display device

Under normal conditions, the composition of liquid crystal display device are as follows: towards display image from the side opposed with back light Side (visible side or emergent light side), successively have rear module, liquid crystal cells and front module.Rear module and previous groups Part usually by transparent substrate, be formed in the transparent conductive film of its liquid crystal cells side surface and be configured at the polarizer structure of its opposite side At.Here, for polarizer, in component below, it is configured at the side opposed with back light, in front in component, It is configured at the side (visible side or emergent light side) of display image.

(back light)

Liquid crystal display device includes at least back light, 2 polarizers and the liquid crystal cells being configured between 2 polarizers As member of formation.Liquid crystal display device of the invention can also suitably have other member of formation in addition to these, example Such as colour filter, lens blooming, diffusion sheet, antireflection film.

The composition of backlight can be in a manner of the sidelight using light guide plate, reflecting plate etc. as member of formation, or under straight Type mode.Back light is preferably the white light source with the luminescent spectrum of continuous wide scope.Here, so-called continuous wide model The luminescent spectrum enclosed refers to, at least the wavelength region of 450nm~650nm, preferably visible light region in the intensity of light become The luminescent spectrum that zero wavelength is not present.As the white light source of the luminescent spectrum with such continuous wide scope, such as White LED can be enumerated, but not limited to this.

The White LED being able to use in the present invention includes: fluorophor mode, will use the sending for having compound semiconductor The light emitting diode and fluorophor of blue light or ultraviolet light combine and issue the element of white；Organic Light Emitting Diode (Organic Light emitting diode:OLED) etc..It as fluorophor, such as can enumerate: yttrium-aluminium-garnet system yellow fluorescence Body, terbium aluminium garnet system yellow fluorophor etc..In White LED, the blue-light-emitting comprising compound semiconductor will be used The white light-emitting diode for the light-emitting component that diode and yttrium-aluminium-garnet system yellow fluorophor are composed has continuous And the luminescent spectrum of wide scope, and luminous efficiency is also excellent, is suitable as back light of the invention therefore.White LED Small power consumption, therefore be also beneficial to energy-saving using its liquid crystal display device of the invention.

As fluorescent tubes such as the widely used cold-cathode tube of back light, thermionic-cathode tubes there is luminescent spectrum to exist all the time Specific wavelength has the discontinuous luminescent spectrum at peak.Therefore, it is difficult to the effect for the rainbow spot that is inhibited, therefore not preferably as this The light source of the liquid crystal display device of invention.

Embodiment

In the following, the present invention is further illustrated referring to embodiment, but the present invention is not limited by following embodiments, it can also Implemented with being suitably changed in the range of can meet purport of the invention, these embodiments are all contained in of the invention In technical scope.

Physical property in embodiment evaluation method is as follows described.

(1) percent thermal shrinkage and its gradient

The polyester film cut out from each cut-out portion of segmentation volume is cut into the square shape of one side 21cm, in 23 DEG C, 65% It is placed 2 hours or more in the atmosphere of RH.The circle for describing the diameter 80mm centered on the center of the polyester film, uses two dimension Determining image instrument (the QUICK IMAGE of MITUTOYO manufacture) is straight with 5 degree of measuring spaces using the conveying direction of film as 0 degree Diameter.Here, using film conveying direction as 0 degree, (right-hand rotation) will be rotated clockwise in film upper surface and sets the angle being positive, it will Rotation (left-hand rotation) sets the angle being negative counterclockwise.In order to measure diameter, with the measurement of the range of -90~85 degree of degree, to all Direction is measured.Then, which is carried out to heat treatment 30 minutes at 85 DEG C, in water, then wiping attachment It in the moisture of film surface, carries out air-dried, is then placed 2 hours or more in 23 DEG C, the atmosphere of 65%RH.Then, with it is above-mentioned Similarly with 5 degree of measuring space diameter of a circles.Diameter before heat treatment is set as L₀, the equidirectional diameter after heat treatment sets It is set to L, the percent thermal shrinkage of all directions is found out according to following formula.

Percent thermal shrinkage (%)=((L₀-L)/L₀)×100

(maximum value of percent thermal shrinkage)

It is set as maximum percent thermal shrinkage for maximum value is become in the directive percent thermal shrinkage of institute.For each segmentation volume (L, C, R), 3 point samplings (central, both ends) is carried out at 3 points in thin-film width direction, is similarly evaluated, 3 maximum heats are received The average value of shrinkage is recorded in table 1 as the maximum value of percent thermal shrinkage.It should be noted that in current embodiment, any point 3 points of the maximum percent thermal shrinkage in the center and both ends of cutting volume is 5% or less.

(reading in the maximum direction (α) of percent thermal shrinkage)

According to acquiring directive percent thermal shrinkage as a result, it is as described below measurement percent thermal shrinkage gradient.Such as Fig. 2 institute Show, measured value (- 90 degree~85 marked and drawed using horizontal axis as angle, with the longitudinal axis is the percent thermal shrinkage corresponding to the angle Degree), the degree of interpolation -180 degree~-95,90 degree~175 degree of value (- 90 percent thermal shrinkages spent corresponding to 90 degree of percent thermal shrinkage, 0 degree Percent thermal shrinkage correspond to the-percent thermal shrinkage of 180 degree).Then, the curve of approximation of connection plot point is drawn, is read with 1 degree of precision Percent thermal shrinkage becomes maximum direction, is defined as α.Wherein, -90 degree≤α≤90 degree.

(gradient of percent thermal shrinkage)

When percent thermal shrinkage becomes range of the maximum direction α in -45~45 degree of degree, which is set as percent thermal shrinkage Gradient.In addition, being interpreted as when percent thermal shrinkage becomes maximum direction α below 45 degree or more and -45 degree by thin-film width Direction favours benchmark, rather than film conveying direction, by α -90 spend (when α be 45 degree or more), 90 degree of+α (α be -45 spend below When) it is set as the gradient of percent thermal shrinkage.For each segmentation roll up (L, C, R), thin-film width direction carry out 3 point samplings (center, 3 points of both ends), it is carried out similarly the above measurement, is received the average value of the absolute value of the gradient of 3 percent thermal shrinkages as heat The gradient of shrinkage is recorded in table 1.It should be noted that in current embodiment, 3 points of the percent thermal shrinkage in center and both ends The absolute value of gradient be 15 degree or less.

(2) light leakage evaluation method

In the unilateral side of the polarizing film formed by PVA film, it is bonded triacetate cellulose film (Fujifilm Corporation manufacture, 80 μm of thickness), it is bonded the polyester film made of aftermentioned method on the other surface.Make when fitting With bonding agent, and the heat treatment of 85 DEG C, 30 minutes is carried out in an oven, to manufacture polarizer.It should be noted that with inclined The orthogonal mode of main axis of orientation of the polarizing axis and polyester film of vibration piece is pasted.By obtained 2 polarizers It is configured to crossed nicols.At this moment, 2 polarizers are configured in such a way that each polyester film is in the outside of polarizing film.So Afterwards, the spectrophotometer V7100 manufactured using Japan Spectroscopy Corporation, measurement penetrate 550~600nm of 2 polarizers Wavelength light maximum transmission rate.For measurement result, evaluated as described below.

Zero: maximum transmission rate is 0.02% or less

×: maximum transmission rate is 0.02% or more

(3) retardation (Re)

Retardation refer to the anisotropy (△ Nxy=| nx-ny |) of the refractive index with the orthogonal twin shaft on film with it is thin Parameter defined in the product (△ Nxy × d) of film thickness d (nm) is to show optical isotropism and anisotropic scale. The anisotropy (△ Nxy) of the refractive index of twin shaft can be found out by the following method.Use molecularly oriented meter (prince's measuring instrument strain The manufacture of formula commercial firm, MOA-6004 type molecularly oriented meter) the orientation axis direction of film is found out, become the side of long side to be orientated axis direction Formula cuts out the rectangle of 4cm × 2cm, as test sample.For the sample, using Abbe refractomecer (ATAGO CO., LTD, manufacture, NAR-4T, measurement wavelength 589nm) measure the refractive index (nx, ny) of orthogonal twin shaft and the refraction of thickness direction Rate (Nz), the anisotropy (△ Nxy) by the absolute value of the specific refractivity of aforementioned twin shaft (| nx-ny |) as refractive index.It is thin The thickness d (nm) of film is measured using electric micrometer (Feinpruf GmbH manufacture, Millitron1245D), and unit is changed It is counted as nm.Retardation is found out according to the product (△ Nxy × d) of the anisotropy (△ Nxy) of refractive index and the thickness d (nm) of film (Re)。

(4) Nz coefficient

Will be by | ny-nz |/| ny-nx | obtained value is used as Nz coefficient.Wherein, selected in a manner of ny > nx ny and The value of nx.

(5) planar orientation degree (△ P)

Planar orientation degree (△ P) will be used as by the obtained value of (nx+ny)/2-nz.

(6) thickness direction retardation amount (Rth)

2 when thickness direction retardation amount refers to from film thickness directional profile birefringent △ Nxz (=| nx-nz |), △ Nyz (=| ny-nz |) is respectively multiplied by the parameter of the average value of display delay amount obtained from film thickness d.Using with prolong The same method of the measurement measured late finds out nx, ny, nz and film thickness d (nm), calculates (△ Nxz × d) and (△ Nyz × d) Average value finds out thickness direction retardation amount (Rth).

(7) rainbow spot is observed

Unilateral in the polarizing film formed by PVA and iodine attaches the polyester film made of aftermentioned method, so that polarizing film Polarizing axis and the orientation main shaft of polyester film become vertical, in the one side attaching TAC film (Fujifilm of its opposite side Corporation manufacture, 80 μm of thickness), to make polarizer.Obtained polarizer is each respectively at two sides to clip liquid crystal 1, each polarizer configured in a manner of the relationship of crossed nicols, to make liquid crystal display device.Before each polarizer Polyester film is stated to be configured as the mode with liquid crystal opposite side (compared with distant positions).The light source of liquid crystal display device uses white LED is as light source (day sub- chemical, NSPW500CS), and the White LED is by blue LED and yttrium-aluminium-garnet class The light-emitting component that yellow fluorophor combines is constituted.From the front of this liquid crystal display device and oblique progress visually, For being determined as follows whether there is or not the generation of rainbow spot.

A: it is generated without rainbow spot from either direction.

A ': when from oblique, extremely light rainbow spot is observed according to angle.

B: when from oblique, light rainbow spot is observed according to angle.

C: when from oblique, rainbow spot can be observed.

D: from positive direction and it is oblique from when, rainbow spot can be observed.

(8) tearing strength

Manufactured Elmendorf tear tester is made using Toyo Seiki, according to JIS P-8116, is measured each thin The tearing strength of film.Direction is torn to carry out in a manner of parallel with the orientation major axes orientation of film, is determined as follows.It needs Illustrate, being orientated the measurement of major axes orientation, (prince's measuring instrument Co., Ltd. manufactures, MOA-6004 type point with molecularly oriented meter Son orientation meter) it measures.

Zero: tearing strength is 50mN or more

×: tearing strength is lower than 50mN

(Production Example 1- polyester A)

So that reaction kettle of the esterification is heated up, when reaching 200 DEG C, puts into 86.4 mass parts of terephthalic acid (TPA) and ethylene glycol 64.6 Mass parts, while stirring investment as 0.017 mass parts of antimony trioxide of catalyst, 0.064 mass parts of magnesium acetate 4 hydrate, 0.16 mass parts of triethylamine.Then, pressurization heating is carried out, it is anti-that pressurization esterification is carried out under conditions of gauge pressure 0.34MPa, 240 DEG C Reaction kettle of the esterification is restored to normal pressure, adds 0.014 mass parts of phosphoric acid by Ying Hou.In turn, 260 DEG C were warming up to 15 minutes, addition 0.012 mass parts of trimethyl phosphate.Then, over the course of 15 mins, decentralized processing is carried out with high pressure dispersing machine, after 15 minutes, will To esterification reaction product be transferred to batch condensation polymerization reactor, 280 DEG C, decompression under carry out polycondensation reaction.

After polycondensation reaction, carried out with stainless steel fibre (NASLON) filter processed that 95% retention diameter is 5 μm Filtration treatment is extruded into strand form from nozzle, is carried out using the cooling water for having carried out filtration treatment (aperture is 1 μm or less) in advance Cooling, solidification, is cut into partical.Obtained pet resin (A) (hereinafter referred to as PET (A).) spy Property viscosity be 0.62dl/g, and be substantially free of non-active particles and internal particle be precipitated.

(Production Example 2- polyester B)

By the dried ultraviolet absorbing agent of the 10 mass parts (bis- (4H-3,1- benzoxazine -4- of 2,2 '-(1,4- phenylenes) Ketone), 90 mass parts without particle PET (A) (inherent viscosity 0.62dl/g) mix, using mixing extruder, contained The pet resin (B) (hereinafter referred to as PET (B)) of ultraviolet absorbing agent.

(preparation of the modified coating fluid of Production Example 3- cementability)

Carry out ester exchange reaction and polycondensation reaction using usual way, prepare as dicarboxylic acid component (relative to Dicarboxylic acid component is whole) 46 moles of % of terephthalic acid (TPA), 46 moles of % of M-phthalic acid and 5-sodium sulfo isophthalate 8 rub You are %, (relative to glycol component entirety) 50 moles of % of 50 moles of % of ethylene glycol and neopentyl glycol as glycol component Composition water dispersible alkali containing Sulfonic acid metal copolymer polyester resin.Then, by 51.4 mass parts of water, 38 mass of isopropanol After part, 5 mass parts of normal-butyl cellosolve, the mixing of 0.06 mass parts of nonionic class surfactant, heating stirring is carried out, reaches 77 After DEG C, 5 mass parts of copolymer polyester resin of above-mentioned water dispersible alkali containing Sulfonic acid metal are added, continue stirring until without resin Agglomeration after, aqueous resin dispersion liquid is cooled to room temperature, the uniform water dispersible for obtaining 5.0 mass % of solid component concentration is total Poly- polyester resin liquid.In turn, by condensate silica dioxide granule (Fuji Silysia chemical Ltd. manufacture, Sylysia 310) it after 3 mass parts are distributed in 50 mass parts water, is added in the above-mentioned water dispersible copolymer polyester resin liquid of 99.46 mass parts 20 mass parts of water are added in 0.54 mass parts of aqueous dispersions of Sylysia 310 while stirring, to obtain the modified coating of cementability Liquid.

(polaroid protective film 1)

As base film middle layer raw material by without particle 90 mass parts of PET (A) resin granular material with contain it is ultraviolet After 10 mass parts of PET (B) resin granular material of light absorbers are dried under reduced pressure (1Torr) 6 hours at 135 DEG C, supply to extruder 2 (II layers of middle layer use), in addition, by PET (A) using usual way it is dry after, be respectively fed to extruder 1 (I layer of outer layer with Outer layer III use), and dissolved at 285 DEG C.This 2 kinds of polymer are used to the filter material (nominal filter fineness of stainless steel sintered body respectively 10 μm of particles 95% retain) filtering, it is laminated in 2 kind of 3 laminated stream block, after squeezing out slabbing by tube head, is applied using electrostatic Casting method is cooled and solidified on 30 DEG C of surface temperature of casting drum, makes non-stretched film.At this point, adjusting each extrusion The discharge rate of machine so that I layers, II layers, the ratio between III layers of thickness be 10:80:10.

Then, the modified coating fluid of above-mentioned cementability is coated on the two sides of the non-stretched PET film by reverse roll method, so that Coating weight after drying becomes 0.08g/m², then 20 seconds dry at 80 DEG C.

The non-stretched film for being formed with the coating layer is guided to tentering stretching-machine, clamps the end of film with fixture on one side Portion guides on one side to 125 DEG C of temperature of hot wind area, stretches 4.0 times in the width direction.Then, it is keeping stretching in the width direction Width in the state of, handled with 225 DEG C, 30 seconds of temperature, then, will be cooled to 130 DEG C of film from both ends The position for playing 2% is cut off with cutter, with 0.5kg/mm²Tension winding, cut remove both sides edge, thus obtain by film thickness The mill volume that the uniaxial orientation PET film of about 50 μm of degree is formed.The mill is rolled up and carries out 3 equal parts, obtains 3 segmentation volumes (L, C, R).It needs It is noted that the segmentation volume for being located at the left side relative to film conveying direction is set as L, is set as positioned at the segmentation volume on the right R, center is set as C.

(polaroid protective film 2)

By changing the thickness of non-stretched film, making thickness is about 100 μm, in addition to this, same as polaroid protective film 1 Operation obtains 3 formed by uniaxial orientation PET film segmentation volumes (L, C, R).

(polaroid protective film 3)

Unused cutter is cut after heat fixation, in addition to this, is equally operated, is obtained by list with polaroid protective film 1 Axis is orientated 3 segmentations that PET film is formed and rolls up (L, C, R).

(polaroid protective film 4)

It is not drawn using heated roller group and infrared heater by what is made by method same as polaroid protective film 1 Stretch film heating to 105 DEG C, then with after there is the roller group of difference to stretch 2 times along direction of travel, according to polarizing film The same method of protective film 1 stretches 4.0 times in the width direction, then, will be cooled to 140 DEG C of film from both ends 2% Position cut off with cutter, with 0.65kg/mm²Tension winding, adjust the thickness of non-stretched film, thus obtain by film thickness (L, C, R) is rolled up in 3 segmentations that the Biaxially oriented PET film of about 50 μm of degree is formed.

(polaroid protective film 5)

As the method for separating film from fixture, the method for being changed to decontrol fixture by the method cut with cutter is removed Except this, is equally operated with polaroid protective film 1, obtain 3 formed by uniaxial orientation PET film segmentation volumes (L, C, R).

(polaroid protective film 6)

By method same as polaroid protective film 1,1.0 times are stretched along direction of travel, stretches 3.5 in the width direction Times, obtain 3 segmentations formed by about 75 μm of film thickness of uniaxial orientation PET film volume (L, C, R).

(polaroid protective film 7)

With method same as polaroid protective film 1, changes the thickness of non-stretched film, cross directional stretch multiplying power is set as 3.8 times, draft temperature be set as 135 DEG C, obtain 3 segmentations formed by about 100 μm of thickness of uniaxial orientation PET film volume (L、C、R)。

(polaroid protective film 8)

With method same as polaroid protective film 1, by cross directional stretch multiplying power is set as 3.8 times, draft temperature is set as 135 DEG C, obtain 3 segmentations formed by about 50 μm of thickness of uniaxial orientation PET film volume (L, C, R).

(polaroid protective film 9)

Unused cutter is cut after heat fixation, in addition to this, is equally operated, is obtained by list with polaroid protective film 8 Axis is orientated 3 segmentations that PET film is formed and rolls up (L, C, R).

(polaroid protective film 10)

With method same as polaroid protective film 1, by cross directional stretch multiplying power is set as 4.2 times, draft temperature is set as 135 DEG C, obtain 3 segmentations formed by about 50 μm of thickness of uniaxial orientation PET film volume (L, C, R).

(polaroid protective film 11)

Winding tension after being cut off with cutter is set as 0.2kg/mm², in addition to this, same as polaroid protective film 10 Operation obtains 3 formed by uniaxial orientation PET film segmentation volumes (L, C, R).

(polaroid protective film 12)

Unused cutter is cut after heat fixation, in addition to this, is equally operated, is obtained by list with polaroid protective film 10 Axis is orientated 3 segmentations that PET film is formed and rolls up (L, C, R).

(polaroid protective film 13)

By method same as polaroid protective film 4,1.8 times are stretched along direction of travel, stretches 2.0 in the width direction Times, in addition, the winding tension after being cut off with cutter is set as 0.2kg/mm², obtain being taken by about 275 μm of film thickness of twin shaft (L, C, R) is rolled up in 3 segmentations formed to PET film.

(polaroid protective film 14)

It will be guided using the non-stretched film of method same as polaroid protective film 1 production to tentering stretching-machine, one side The end of film is clamped with fixture, is guided on one side to 125 DEG C of temperature of hot wind area, is stretched 3.5 times in the width direction.Then, exist In the state of keeping the width stretched in the width direction, handled with 225 DEG C, 30 seconds of temperature, in 90 DEG C~70 DEG C of temperature It spends section and reduces 0.2% grip separation in conveying direction, obtain being formed by about 75 μm of film thickness of uniaxial orientation PET film (L, C, R) is rolled up in 3 segmentations.

(polaroid protective film 15)

It will be guided using the non-stretched film of method same as polaroid protective film 1 production to tentering stretching-machine, one side The end of film is clamped with fixture, is guided on one side to 125 DEG C of temperature of hot wind area, is stretched 3.5 times in the width direction.Then, exist In the state of keeping the width stretched in the width direction, handled with 225 DEG C, 30 seconds of temperature, in 90 DEG C~70 DEG C of temperature It spends section and reduces 0.1% grip separation in conveying direction, obtain being formed by about 75 μm of film thickness of uniaxial orientation PET film (L, C, R) is rolled up in 3 segmentations.

(polaroid protective film 16)

It will be guided using the non-stretched film of method same as polaroid protective film 1 production to tentering stretching-machine, one side The end of film is clamped with fixture, is guided on one side to 125 DEG C of temperature of hot wind area, is stretched 3.5 times in the width direction.Then, exist In the state of keeping the width stretched in the width direction, handled with 225 DEG C, 30 seconds of temperature, in 110 DEG C~70 DEG C of temperature It spends section and reduces 0.2% grip separation in conveying direction, obtain being formed by about 75 μm of film thickness of uniaxial orientation PET film (L, C, R) is rolled up in 3 segmentations.

(polaroid protective film 17)

It will be guided using the non-stretched film of method same as polaroid protective film 1 production to tentering stretching-machine, one side The end of film is clamped with fixture, is guided on one side to 125 DEG C of temperature of hot wind area, is stretched 3.5 times in the width direction.Then, exist In the state of keeping the width stretched in the width direction, handled with 225 DEG C, 30 seconds of temperature, at 150 DEG C~100 DEG C Temperature range reduces 0.4% grip separation in conveying direction, obtains being formed by about 75 μm of film thickness of uniaxial orientation PET film 3 segmentations roll up (L, C, R).

(polaroid protective film 18)

It will be guided using the non-stretched film of method same as polaroid protective film 1 production to tentering stretching-machine, one side The end of film is clamped with fixture, is guided on one side to 125 DEG C of temperature of hot wind area, is stretched 3.5 times in the width direction.Then, exist In the state of keeping the width stretched in the width direction, handled with 225 DEG C, 30 seconds of temperature, with per unit width -55 DEG C/temperature of m is set for cooling down, obtain 3 segmentations formed by about 75 μm of film thickness of uniaxial orientation PET film volume (L、C、R)。

(polaroid protective film 19)

It will be guided using the non-stretched film of method same as polaroid protective film 1 production to tentering stretching-machine, one side The end of film is clamped with fixture, is guided on one side to 125 DEG C of temperature of hot wind area, is stretched 3.5 times in the width direction.Then, exist In the state of keeping the width stretched in the width direction, handled with 225 DEG C, 30 seconds of temperature, with per unit width -35 DEG C/temperature of m is set for cooling down, obtain 3 segmentations formed by about 75 μm of film thickness of uniaxial orientation PET film volume (L、C、R)。

(polaroid protective film 20)

It will be guided using the non-stretched film of method same as polaroid protective film 1 production to tentering stretching-machine, one side The end of film is clamped with fixture, is guided on one side to 125 DEG C of temperature of hot wind area, is stretched 3.5 times in the width direction.Then, exist In the state of keeping the width stretched in the width direction, handled with 225 DEG C, 30 seconds of temperature, with per unit width -120 DEG C/temperature of m is set for cooling down, obtain 3 segmentations formed by about 75 μm of film thickness of uniaxial orientation PET film volume (L、C、R)。

For polaroid protective film 1~20, by the absolute value of the gradient of percent thermal shrinkage, percent thermal shrinkage maximum value, with And the result of light leakage evaluation is shown in table 1.

[table 1]

In table 1, so-called " film " refers to above-mentioned polaroid protective film.

In addition, for the liquid crystal display device for using polaroid protective film 1~20 to make as described above, by rainbow spot observe with And the result of measurement tearing strength is shown in following table 2.

[table 2]

According to shown in table 1 as a result, display if the absolute value of the gradient of percent thermal shrinkage be 15 degree hereinafter, if can press down Make a small amount of light leakage when 2 polarizers configure in a manner of in the relationship of crossed nicols.In addition, polaroid protective film 1~20 The maximum value of percent thermal shrinkage is respectively less than 1%.

As a result, the retardation for being shown in oriented polyester films is 4000 or more and its Nz coefficient is according to shown in table 2 When 1.7 or less, rainbow spot is inhibited to generate with can dramatically.In addition, show on the basis of the condition, by by oriented polyester films Planar orientation degree control 0.13 hereinafter, can more effectively inhibit rainbow spot generate.

Industrial availability

According to the present invention it is possible to provide the polaroid protective film formed by polyester film, by 2 polarizers to submit When the mode of the relationship of fork prism configures, the generation of a small amount of light leakage can inhibit, and be suitable for obtaining having excellent visual liquid Crystal device.Thus, industrial availability of the invention is very high.

Claims

1. a kind of polaroid protective film, for for the polarizing axis of polarizing film it is parallel with the conveying direction of polaroid protective film or The polaroid protective film that vertical mode is laminated, the polaroid protective film are formed by polyester film, and percent thermal shrinkage becomes maximum Direction is relative to film conveying direction or the absolute value of the gradient of width direction for 15 degree hereinafter, the planar orientation degree of polyester film For 0.13 or less, percent thermal shrinkage maximum value less than 1%.

2. polaroid protective film according to claim 1, wherein the retardation of polyester film is 4000~30000nm, Nz Coefficient is 1.7 or less.

3. polaroid protective film according to claim 1 or 2, wherein the planar orientation degree of polyester film be 0.08 or more and 0.13 or less.

4. a kind of polarizer, it includes the composition that the two sides in polarizing film are laminated with polaroid protective film,

At least unilateral polaroid protective film is polaroid protective film described in any one of claims 1 to 3.

5. a kind of polarizer is laminated with the protection of polarizing film described in any one of claims 1 to 3 in the unilateral side of polarizing film Film.

6. a kind of liquid crystal display device, with back light, 2 polarizers and the liquid being configured between 2 polarizers Brilliant unit, wherein

The back light is the white light source with continuous luminous spectrum,

It is configured at least one of the polaroid protective film of the polarizer of incident light side and is configured at the polarizer of emergent light side At least one of polaroid protective film is polaroid protective film described in any one of claims 1 to 3.

7. liquid crystal display device according to claim 6, wherein the incident light of the polarizer for being configured at incident light side The polaroid protective film of the emergent light side of the polaroid protective film of side and the polarizer for being configured at emergent light side is wanted for right Polaroid protective film described in asking any one of 1~3.

8. a kind of liquid crystal display device, with back light, 2 polarizers and the liquid being configured between 2 polarizers Brilliant unit, wherein

The back light is the white light source with continuous luminous spectrum,

The polarizer is polarizer described in claim 5.