JP7405165B2 - Manufacturing method of liquid crystal panel, polarizing plate and liquid crystal display device - Google Patents

Description

The present invention relates to a method for manufacturing a liquid crystal panel used in a thin liquid crystal display device. More specifically, the present invention relates to a method for producing a liquid crystal panel that does not cause coloring or iridescence and can be made thinner even when a polyester film is used as a protective film for a polarizing plate of a liquid crystal display. Furthermore, the present invention relates to a polarizing plate used in a method for manufacturing a liquid crystal panel, and a liquid crystal display device using the polarizing plate.

A polarizing plate is used in a liquid crystal display device, and a polyester film having an in-plane retardation of 3000 to 30000 nm has been proposed as a polarizer protective film for a polarizing plate (see, for example, patent documents). However, in order to provide sufficient in-plane retardation to a polyester film, it is necessary to make the film thick, which is disadvantageous in making liquid crystal display devices thinner in recent years.
On the other hand, polarizer protective films with low in-plane retardation such as triacetyl cellulose (TAC) and acrylic do not cause problems with coloration or iridescence due to retardation, but when the film is made thinner, the moisture permeability There are problems such as deterioration of the polarizer and dimensional stability due to an increase in the amount of water, dimensional stability due to moisture absorption in the manufacturing process, and lack of mechanical strength.In the case of acrylic, there are problems such as easy breakage and poor handling.
Polarizing plates compatible with thin liquid crystal display devices include polarizing plates with a protective film on only one side (Japanese Unexamined Patent Publication No. 10-186133), and polarizing plates with a dichroic organic dye coated on the base film that serves as the protective film. JP 2013-156665, JP 2015-16502) have been proposed, but these protective films such as TAC and acrylic have the above-mentioned problems.

Japanese Patent Application Publication No. 2012-256057

The present invention has been made against the background of such problems of the prior art. That is, the purpose of the present invention is to use polyester, which has excellent moisture permeability, dimensional stability, and mechanical strength even though it is thin, as a polarizer protective film, while also achieving excellent visibility (suppression of iridescence) and high productivity. An object of the present invention is to provide a method for manufacturing a liquid crystal panel used in a liquid crystal display device that can be made thinner. Another object of the present invention is to provide a polarizing plate used in the method for manufacturing the liquid crystal panel, and a liquid crystal display device using the polarizing plate.

The present inventor has completed the present invention as a result of intensive studies to achieve the above object.
That is, a typical present invention is as follows.
Item 1.
a step of cutting a long light source side polarizing plate into a predetermined size;
A method for manufacturing a liquid crystal panel, comprising: cutting a long viewing-side polarizing plate into a predetermined size; and bonding a light source-side polarizing plate and a viewing-side polarizing plate to a liquid crystal cell,
A method for producing a liquid crystal panel in which either or both of the elongated light source side polarizing plate and the elongated viewing side polarizing plate have the following characteristics (1) to (3).
(1) A polarizer is provided on a polyester base film, and the angle between the fast axis of the polyester base film and the transmission axis direction of the polarizer is 10 degrees or less,
(2) The refractive index of the polyester base film in the fast axis direction is 1.53 to 1.62, and (3) The thickness of the polyester base film is 90 μm or less.
Item 2. The method for manufacturing a liquid crystal panel according to Item 1, wherein the fast axis of the polyester base film is substantially perpendicular to the longitudinal direction of the polyester base film.
Item 3.
Item 3. The method for manufacturing a liquid crystal panel according to item 1 or 2, wherein the polyester base film has a retardation of 1,500 to 10,000 nm.
Item 4.
Item 4. The method for manufacturing a liquid crystal panel according to any one of Items 1 to 3, wherein the viewing side polarizing plate has a polyester base film having a retardation of 2000 to 5000 nm.
Item 5.
Item 5. The method for manufacturing a liquid crystal panel according to any one of Items 1 to 4, wherein the viewing side polarizing plate has a polyester base film having a thickness of 20 to 60 μm.
Item 6.
Item 6. The method for manufacturing a liquid crystal panel according to any one of Items 1 to 5, wherein the light source side polarizing plate has a polyester base film having a thickness of 30 to 90 μm.
Section 7.
Item 7. The method for manufacturing a liquid crystal panel according to any one of Items 1 to 6, comprising only a coating layer between the polarizer and the liquid crystal cell.
Section 8.
A polarizing plate comprising a polarizer and a polyester base film having the following characteristics as a polarizer protective film on at least one of the polarizers.
(1) The angle between the fast axis of the polyester base film and the transmission axis direction of the polarizer is 10 degrees or less,
(2) the polyester base film has a refractive index in the fast axis direction of 1.53 to 1.62, and
(3) Item 9: The thickness of the polyester base film is 90 μm or less.
Item 9. The polarizing plate according to Item 8, wherein the polarizing plate is elongated, and the fast axis of the polyester base film is substantially perpendicular to the longitudinal direction of the polyester base film.
Item 10.
A liquid crystal display device comprising a backlight light source, a liquid crystal cell, and a polarizing plate on the viewing side and the light source side of the liquid crystal cell, wherein at least one of the viewing side polarizing plate and the light source side polarizing plate is the polarizing plate according to claim 8. or a liquid crystal display device cut from the elongated polarizing plate according to claim 9.

According to the present invention, a polyester having excellent moisture permeability, dimensional stability, and mechanical strength is used as a polarizer protective film even though it is thin, and has excellent visibility (suppression of iridescence) and high productivity. A method for manufacturing a liquid crystal panel used in a liquid crystal display device that can be made thinner can be provided. Further, according to the present invention, it is possible to provide a polarizing plate used in the method for manufacturing the liquid crystal panel, and a liquid crystal display device using the polarizing plate.

First, the polarizing plate used in the present invention will be explained.
The polarizing plate has a polarizer in which a dichroic dye is oriented on a polyester base film, and the transmission axis direction of the polarizer is approximately parallel to the fast axis direction of the polyester base film. Note that hereinafter, the polyester base film may be simply referred to as a base film.

(Polyester base film)
The refractive index (nx) of the polyester base film in the fast axis direction is preferably adjusted to a low value in the range of 1.53 or more and 1.62 or less. Thereby, it is possible to suppress iridescence even when the thickness of the polyester base film is reduced. The details of the mechanism that suppresses iridescence are unknown, but reflection at the interface between the air layer and the base film in the direction of the polarizer's transmission axis may be suppressed, or the polarizer's dichroic dye may contain aromatic molecules within its molecules. This seems to be because, in the case of a dye having a ring, the orientation direction of the aromatic rings of the dichroic dye is close to the orientation direction of the aromatic rings of the base film, and reflection at this interface is suppressed. If the refractive index exceeds 1.62, rainbow-like color spots may occur when observed from an oblique direction. Preferably it is 1.61 or less, more preferably 1.60 or less, still more preferably 1.59 or less, even more preferably 1.58 or less.

On the other hand, the lower limit of the refractive index is 1.53. If the refractive index is less than 1.53, the crystallization of the base film will be insufficient, and the properties obtained by stretching, such as dimensional stability, mechanical strength, and chemical resistance, will become insufficient, which is not preferable. Preferably it is 1.54 or more, more preferably 1.55 or more, still more preferably 1.56 or more, even more preferably 1.57 or more.

In the polarizing plate, it is preferable that the transmission axis of the polarizer and the fast axis (perpendicular to the slow axis) of the base film are substantially parallel. Here, "substantially parallel" means that the angle between the transmission axis of the polarizer and the fast axis of the base film is preferably 10 degrees or less, more preferably 7 degrees or less, still more preferably 5 degrees or less, and even more preferably means 3° or less, more preferably 2° or less, particularly preferably 1° or less. The directions of the fast axis and the slow axis can be determined by measuring with a molecular orientation meter (for example, MOA-6004 type molecular orientation meter manufactured by Oji Scientific Instruments Co., Ltd.).

The difference between the refractive index (nx) in the fast axis direction and the refractive index (ny) in the slow axis direction of the base film is preferably 0.05 to 0.2. If it is less than 0.05, it may be difficult to bring the refractive index of the base film in the fast axis direction within a specified range. If it exceeds 0.2, the base film may be easily torn in the slow axis direction, making handling difficult. The lower limit of the difference between the refractive index in the fast axis direction and the refractive index in the slow axis direction is more preferably 0.06, further preferably 0.07, and particularly preferably 0.08. The upper limit of the difference between the refractive index in the fast axis direction and the refractive index in the slow axis direction is more preferably 0.17, even more preferably 0.15, and particularly preferably 0.13.

Further, the base film preferably has retardation (Re, hereinafter simply referred to as retardation means in-plane retardation) of 1500 to 10000 nm. A preferable lower limit of retardation is 2000 nm, a second preferable lower limit is 2500 nm, a more preferable lower limit is 3000 nm, an even more preferable lower limit is 3500 nm, and an even more preferable lower limit is 4000 nm. Depending on the type of backlight source, if the retardation is too low, rainbow spots may appear. A preferable upper limit is 8000 nm, a more preferable upper limit is 7000 nm, an even more preferable upper limit is 6000 nm, an especially preferable upper limit is 5500 nm, and a most preferable upper limit is 5000 nm. A base film having a retardation higher than this will have a large thickness, making it unsuitable for use in thin liquid crystal display devices.

Among these, in the case of a polarizing plate on the light source side, the lower limit of the in-plane retardation of the base film is preferably 2500 nm, more preferably 3000 nm, even more preferably 3500 nm, and especially A preferable lower limit is 4000 nm. The upper limit is as described above.
In the case of the polarizing plate on the viewing side, the upper limit of the in-plane retardation of the base film is preferably 6000 nm, more preferably 5500 nm, still more preferably 5000 nm. The lower limit is as described above.

Note that in-plane retardation can be determined by measuring the refractive index and thickness in two orthogonal axes on the base film, or by using a commercially available automatic birefringence measurement device such as KOBRA-21ADH (Oji Scientific Instruments Co., Ltd.). It can also be found using Note that the refractive index can be determined using an Abbe refractometer (measurement wavelength: 589 nm).

The ratio (Re/Rth) of the in-plane retardation to the thickness direction retardation (Rth) of the base film is preferably 0.2 or more, more preferably 0.5 or more, and even more preferably 0.6 or more. . The larger the ratio (Re/Rth) between the retardation and the retardation in the thickness direction, the more isotropic the action of birefringence becomes, and the more likely it is that rainbow-like color spots are less likely to occur depending on the viewing angle. In a completely uniaxial (uniaxially symmetric) film, the ratio of the above in-plane retardation to the thickness direction retardation (Re/Rth) is 2.0, so the ratio of the above retardation to the thickness direction retardation (Re/Rth) is 2.0. ) is preferably 2.0. Note that the thickness direction retardation means the average of the retardations obtained by multiplying the two birefringences ΔNxz and ΔNyz by the film thickness d when the film is viewed from a cross section in the thickness direction.

The thickness of the base film is preferably in the range of 15 to 90 μm. More preferably, it is in the range of 20 to 80 μm. Even with a film having a thickness of less than 15 μm, it is theoretically possible to obtain a retardation of 1500 nm or more. However, in that case, the anisotropy of the mechanical properties of the film becomes significant, making it more likely to tear or tear, and its practicality as an industrial material is significantly reduced. The lower limit of the thickness is more preferably 20 μm, still more preferably 25 μm, particularly preferably 30 μm, and most preferably 35 μm. On the other hand, if the upper limit of the thickness of the polyester base film exceeds 90 μm, this is not preferable as it does not suit the purpose of making the film thinner. The upper limit of the thickness is more preferably 80 μm, still more preferably 70 μm, particularly preferably 60 μm, and most preferably 50 μm.

Among these, in the case of a polarizing plate on the light source side, the lower limit of the thickness of the base film is preferably 30 μm, more preferably 35 μm, and still more preferably 40 μm. The upper limit is as described above.
In the case of the polarizing plate on the viewing side, the upper limit of the thickness of the base film is preferably 60 μm, more preferably 50 μm, and still more preferably 45 μm. The lower limit is as described above.

The polyester used for the base film can be polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), but may also contain other copolymer components. These resins have excellent transparency as well as excellent thermal and mechanical properties, and retardation can be easily controlled by stretching. In particular, polyethylene terephthalate has a large intrinsic birefringence, and by stretching the film, the refractive index in the fast axis (perpendicular to the slow axis direction) direction can be kept low, and even if the film is thin, it is relatively easy to do so. It is the most suitable material because it provides a large retardation.

Further, for the purpose of suppressing deterioration of the dichroic dye used in the polarizer, it is desirable that the polyester base film has a light transmittance of 20% or less at a wavelength of 380 nm. The light transmittance at 380 nm is more preferably 15% or less, further preferably 10% or less, particularly preferably 5% or less. When the light transmittance is 20% or less, deterioration of the optically functional dye due to ultraviolet rays can be suppressed. Note that the transmittance is measured in a direction perpendicular to the plane of the film, and can be measured using a spectrophotometer (for example, Hitachi U-3500 model).

In order to make the transmittance of the base film at a wavelength of 380 nm 20% or less, it is desirable to adjust the type and concentration of the ultraviolet absorber and the thickness of the film as appropriate. The ultraviolet absorber used in the present invention is a known substance. Examples of the ultraviolet absorber include organic ultraviolet absorbers and inorganic ultraviolet absorbers, and organic ultraviolet absorbers are preferred from the viewpoint of transparency. Examples of organic ultraviolet absorbers include benzotriazole-based, benzophenone-based, cyclic iminoester-based, and combinations thereof, but are not particularly limited as long as the absorbance is within the above-mentioned range. However, from the viewpoint of durability, benzotriazole type and cyclic imino ester type are particularly preferable. When two or more types of ultraviolet absorbers are used together, ultraviolet rays of different wavelengths can be absorbed at the same time, so that the ultraviolet absorption effect can be further improved.

In addition to the ultraviolet absorber, it is also a preferable embodiment to include various additives other than the catalyst within a range that does not impede the effects of the present invention. Examples of additives include inorganic particles, heat-resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, light stabilizers, flame retardants, heat stabilizers, antioxidants, and antigelation agents. , surfactants, etc. Furthermore, in order to achieve high transparency, it is also preferable that the polyester base film contains substantially no particles. "Substantially no particles" means, for example, in the case of inorganic particles, the content is 50 ppm or less, preferably 10 ppm or less, particularly preferably below the detection limit when the inorganic element is quantified by fluorescent X-ray analysis. means.

The base film preferably has an Nz coefficient expressed by |ny-nz|/|ny-nx| of 2.5 or less. The Nz coefficient can be determined as follows. The orientation axis direction of the film was determined using a molecular orientation meter (Oji Scientific Instruments Co., Ltd., MOA-6004 type molecular orientation meter), and the biaxial refractive index (ny, nx, However, ny>nx) and the refractive index in the thickness direction (nz) are determined using an Abbe refractometer (manufactured by Atago Corporation, NAR-4T, measurement wavelength 589 nm). The Nz coefficient can be determined by substituting nx, ny, and nz thus obtained into the formula expressed as |ny-nz|/|ny-nx|. Note that nz is the refractive index in the direction perpendicular to the surface of the polyester base film.

If the Nz coefficient of the base film exceeds 2.5, rainbow spots may occur depending on the angle when the liquid crystal display device is observed from an oblique direction. The Nz coefficient is more preferably 2.4 or less, still more preferably 2.3 or less. The lower limit value of the Nz coefficient is 1.20. This is because it is difficult to obtain a film of less than 1.20 in terms of manufacturing technology. In order to maintain the mechanical strength of the film, the lower limit of the Nz coefficient is preferably 1.30 or more, more preferably 1.40 or more, even more preferably 1.45 or more, and even more preferably 1.50 or more. It is.

It is preferable that the degree of plane orientation of the base film expressed by (nx+ny)/2-nz is equal to or less than a specific value. Here, the values of nx, ny, and nz are determined in the same manner as the Nz coefficient. The degree of plane orientation of the polyester base film is preferably 0.150 or less, more preferably 0.140 or less, still more preferably 0.135 or less. When the degree of plane orientation exceeds 0.150, rainbow spots may be observed depending on the angle when the liquid crystal display device is observed from an oblique direction. If the degree of plane orientation is less than 0.080, the film thickness may vary and the retardation value may become non-uniform within the film plane.

A predetermined in-plane retardation can be imparted to the base film by stretching it. The stretching may be uniaxial or biaxial stretching as long as the properties are obtained.

The base film is prepared as a long film. The fast axis of the base film may be in the longitudinal direction of the base film or in a direction perpendicular to the longitudinal direction, but in the present invention, the fast axis of the base film is parallel to the longitudinal direction of the base film. A preferred configuration is approximately vertical. "Substantially perpendicular" means that the angle between the longitudinal direction of the base film and the 90 degree direction (i.e. the width direction of the base film) and the fast axis of the base film is preferably 10 degrees or less, more preferably This means 7° or less, more preferably 5° or less, even more preferably 3° or less, even more preferably 2° or less, particularly preferably 1° or less.

A general polarizer made of stretched polyvinyl alcohol (PVA) with iodine adsorbed has a transmission axis perpendicular to the longitudinal direction, so the fast axis of the base film is also abbreviated to the longitudinal direction of the base film. By holding it vertically, roll-to-roll lamination is possible. In addition, when the fast axis of the base film is set in the longitudinal direction of the base film, the molecules of the base film are perpendicular to the longitudinal direction, and the process of bonding with a polarizer and bonding with a liquid crystal cell When a strong tension or bending force is applied to the film, it is easy to break and it becomes difficult to maintain stable production.The breakage becomes especially noticeable when the base film is made thin.Furthermore, when the polarizer is made thin, However, by making the fast axis of the base film substantially perpendicular to the longitudinal direction of the base film, these problems are less likely to occur.

In order to make the fast axis of the base film substantially perpendicular to the longitudinal direction of the base film, the elongated base film is stretched in the longitudinal direction when manufactured. A method of stretching in the longitudinal direction will be specifically explained by taking as an example a method of stretching between rolls having different speeds.

The unstretched original fabric obtained by extruding molten PET onto a cooling roll is guided to a low-speed roll and then to a high-speed roll, thereby being stretched between the low-speed roll and the high-speed roll. It is preferable that the low-speed roll heats the film with a plurality of heating rolls as preheating. An infrared heater may be provided between the low speed roll and the high speed roll to heat the film.
The stretching temperature is preferably 80 to 130°C, particularly preferably 90 to 120°C. The stretching ratio is preferably 3.0 times to 7.5 times, more preferably 3.5 times to 7.0 times, still more preferably 4.0 times to 7.0 times. The stretching may be performed in multiple stages of two or three or more stages.

The stretched film is then heat treated. The heat treatment temperature is preferably 100 to 250°C, particularly preferably 180 to 245°C. The heat treatment may be performed using a roll or may be performed using hot air in equipment such as a dryer.
Further, relaxation treatment may be performed in the heat treatment step. The relaxation treatment is preferably 0.5 to 10%, more preferably 1 to 7%, even more preferably 2 to 5%. By performing the relaxation treatment, the thermal shrinkage rate of the base film can be reduced. The relaxation process can be performed using a speed difference between the rolls.

Note that, before stretching in the longitudinal direction, a weak stretching of 1.05 to 2.8 times may be applied in the transverse direction in a tenter.
Although the stretching method using rolls has been described above, the unstretched original fabric may be introduced into a tenter and stretched in the longitudinal direction using a simultaneous biaxial stretching machine.

The heat shrinkage rate of the base film is preferably 5% or less in all directions. The heat shrinkage rate in all directions of the base film is measured as follows.

The base film is cut out into a square shape of 21 cm on each side and left in an atmosphere of 23° C. and 65% RH for 2 hours or more. Draw a circle with a diameter of 80 mm centered at the center on this base film, and use a two-dimensional image measuring machine (for example, QUICK IMAGE manufactured by MITUTOYO) to measure the diameter at 5 degree intervals with the film running direction as 0 degree. Measure. Here, assuming that the film flow direction is 0 degrees, when the film is viewed from above inside the tenter, clockwise (rightward) rotation is a positive angle, and counterclockwise (counterclockwise) rotation is a negative angle. If you measure in the range of -90 degrees to 85 degrees, you can measure the diameter in all directions.

Next, the base film is heat-treated in water at 85° C. for 30 minutes, the moisture adhering to the film surface is wiped off, air-dried, and then left in an atmosphere of 23° C. and 65% RH for 2 hours or more. Thereafter, measure the diameter of the circle at 5 degree intervals in the same manner as above. Let Lo be the diameter before heat treatment, and L be the diameter in the same direction after heat treatment, and calculate the heat shrinkage rate in each direction according to the formula below.

Heat shrinkage rate (%) = ((Lo- L) / Lo) x 100

The maximum value of the thermal contraction rate determined by the above measurement method is preferably 5% or less, more preferably 3% or less, even more preferably 1% or less, and most preferably 0.7% or less. . The lower limit of the heat shrinkage rate is not particularly limited, but is, for example, 0.01% or more.

In order to reduce the heat shrinkage rate, a method of annealing the base film off-line can be mentioned. In-line methods include methods such as narrowing the clip width during heat treatment to relax the clip, or heating and annealing while relaxing the clip after opening and before winding.

(Easy adhesive layer)
The base film may be provided with an easily adhesive layer (easily adhesive layer P1) in order to improve the adhesion with the alignment layer and the polarizer.
As the resin used for the easily bonding layer, polyester resin, polyurethane resin, polycarbonate resin, acrylic resin, etc. are used, and polyester resin, polyester polyurethane resin, polycarbonate polyurethane resin, and acrylic resin are preferable. The easily adhesive layer is preferably crosslinked. Examples of the crosslinking agent include isocyanate compounds, melamine compounds, epoxy resins, and oxazoline compounds.

The easily adhesive layer can be provided by coating the base film as a water-based paint containing these resins and, if necessary, adding a crosslinking agent, particles, etc., and drying the coating. Examples of the particles include those used for the above-mentioned base material.
Although the easily bonding layer may be provided offline on the stretched base material, it is preferably provided in-line during the film forming process. When provided in-line, after applying an easy-adhesion coating liquid before stretching with rolls, the film is led to a dryer and dried by heating, and then stretched with rolls. In the case of stretching in a tenter using a simultaneous biaxial stretching machine or in the case of roll stretching and heating in a dryer, drying may be performed in the heating step during stretching after coating the adhesive coating liquid.
The coating amount of the easily adhesive layer is preferably 0.01 to 1.0 g/m ² , more preferably 0.03 to 0.5 g/m ² .

(Functional layer)
It is also a preferable form that a functional layer such as a hard coat layer, an antireflection layer, a low reflection layer, an antiglare layer, and an antistatic layer is provided on the side of the base film opposite to the polarizer.
When providing a functional layer, an easily adhesive layer (easily adhesive layer P2) may be provided between the functional layer and the base material. For the easily bonding layer P2, the resins, crosslinking agents, etc. mentioned for the above-mentioned easily bonding layer P1 are suitably used. Further, the easily bonding layer P1 and the easily bonding layer P2 may have the same composition or different compositions.

It is preferable that the easily adhesive layer P2 is also provided in-line. Although the easily adhesive layer P1 and the easily adhesive layer P2 may be coated and dried one after another, it is also preferable to coat both sides at the same time.

Note that in the following description, the term "base film" includes not only those without an easily bonding layer but also those with one. Similarly, those provided with a functional layer are also included in the base film.

(polarizer)
The polarizer used in the present invention can be used without limitation, such as a film made of PVA adsorbed with a dichroic dye such as iodine, or a film obtained by coating a liquid crystal compound and a dichroic dye. . Among these, one in which iodine is adsorbed to PVA is preferable. Polarizers made of PVA with iodine adsorbed are generally produced by immersing an unstretched film of PVA in a bath containing iodine and then uniaxially stretching it, or by immersing a uniaxially stretched film in a bath containing iodine and then Obtained by crosslinking in a boric acid bath.

The thickness of the polarizer is preferably 1 to 30 μm, more preferably 1.5 to 20 μm. More preferably, it is 2 to 15 μm. If it is less than 1 μm, it may not be possible to exhibit sufficient polarization characteristics or it may be too thin to handle. If it exceeds 30 μm, it does not meet the purpose of thinning.

(Creation of polarizing plate)
A polarizing plate is obtained by laminating a polarizer on a base film. As for the lamination method, if the polarizer is made by adsorbing iodine on PVA, it is preferable to manufacture the polarizer by laminating the base film and the polarizer together. As the adhesive for bonding, conventionally used adhesives can be used without limitation. Among these, preferred examples include PVA-based water-based adhesives and UV-curable adhesives, with UV-curable adhesives being particularly preferred.

A polarizer made of PVA with iodine adsorbed may be used as a single polarizer film, but there is a method of transferring the polarizer to a polyester base film using a base laminated polarizer laminated with a supporting base material. is also a preferred method. This base material laminated polarizer is easy to handle because it has a supporting base material even if the thickness of the polarizer is 10 μm or less, and thin polarizers of 8 μm or less or 6 μm or less can be easily laminated to a polyester base film. can be done.
This technique has been introduced in many publications such as JP-A No. 2001-350021 and JP-A No. 2009-93074.

To give a specific example, first, PVA is applied to a thermoplastic resin supporting base material that is unstretched or uniaxially stretched perpendicular to the longitudinal direction, and then PVA is applied to the thermoplastic resin supporting base material coated with PVA. The laminate is stretched in the longitudinal direction 2 to 20 times, preferably 3 to 15 times. The stretching temperature is preferably 80 to 180°C, more preferably 100 to 160°C. Subsequently, the stretched laminate is immersed in a bath containing a dichroic dye to adsorb the dichroic dye. Examples of dichroic dyes include iodine and organic dyes. When using iodine, an aqueous solution of iodine and potassium iodide is preferred. Subsequently, it is immersed in an aqueous solution of boric acid for treatment, washed with water, and then dried. Note that stretching by 1.5 to 3 times may be performed as preliminary stretching before adsorption of the dichroic dye. Note that the above is just an example, and the dichroic dye may be adsorbed before stretching, or the dichroic dye may be treated with boric acid before the dichroic dye is adsorbed. Stretching may also be carried out in a bath containing a dichroic dye or in a bath containing an aqueous boric acid solution. Further, these steps may be divided into multiple steps and performed in combination.

As the supporting base material of the thermoplastic resin, polyesters such as polyethylene terephthalate, polyolefins such as polypropylene and polyethylene, polyamides, polyurethanes, etc. are used. The supporting base material made of thermoplastic resin may be subjected to an adhesion-facilitating treatment or a peel-facilitating treatment.

A polarizing plate is obtained by bonding the polarizer surface of a base laminated polarizer to a polyester base film using an adhesive, and then peeling off the supporting base material.

The thus obtained laminate of a polyester base film and a polarizer can be used as a polarizing plate.
It is also a preferable form to separately provide a protective layer or a retardation layer on the opposite side of the polarizer to the polyester base film.

Examples of the protective layer include resin films such as triacetylcellulose, acrylic, and cyclic polyolefin, and these can be bonded together with an adhesive. Moreover, a protective layer can also be provided by coating. The protective layer formed by coating can be made of various materials such as acrylic, polyester, and polyurethane. Moreover, a photocuring type, a thermosetting type, etc. can be selected as appropriate.

Examples of retardation layers include those made by stretching and aligning resin films such as triacetylcellulose, acrylic, and cyclic polyolefin, and those made by coating liquid crystal compounds on these base materials, and these can be bonded together with an adhesive. I can do it.

Moreover, a coating type retardation layer can also be provided on the polarizer. What is a coated retardation layer? The retardation layer itself is a retardation layer formed by coating, and does not stand alone as an independent layer. Methods for providing a retardation layer include coating a retardation compound on a polarizer, and separately providing a retardation layer on a releasable base material and transferring it onto the polarizer. Can be mentioned. The retardation layer is preferably a retardation layer made of a liquid crystal compound. The liquid crystal compound may be a rod-shaped liquid crystal compound, a plate-shaped liquid crystal compound, or the like depending on the purpose, and may be in the form of a polymer or have a reactive functional group. In the method of coating a retardation compound on a polarizer, the polarizer is subjected to a rubbing treatment, or a separate alignment layer is provided on the polarizer to provide alignment control power, and then the liquid crystal compound is coated. is preferred. For the alignment layer, polyvinyl alcohol and its derivatives, polyimide and its derivatives, acrylic resin, polysiloxane derivatives, etc. are preferably used, and the alignment layer is subjected to a rubbing treatment.

The alignment layer may be a photoalignment layer. A photo-alignment layer is an alignment film in which a coating liquid containing a polymer or monomer having a photo-reactive group and a solvent is applied to a base film, and an alignment control force is imparted by irradiating the base film with polarized light, preferably polarized ultraviolet rays. It refers to
Specific examples of the resin for the photo-alignment layer include polyimide, polyamide, (meth)acrylic, polyester, etc., which have a photoreactive group capable of causing a photodimerization reaction, such as a cinnamoyl group and a chalcone group.

Specific orientation layers include, for example, JP-A No. 2006-285197, JP-A No. 2007-76839, JP-A No. 2007-138138, JP-A No. 2007-94071, JP-A No. 2007-121721, JP 2007-140465, JP 2007-156439, JP 2007-133184, JP 2009-109831, JP 2002-229039, JP 2002-265541, JP Orientation layer described in JP 2002-317013, JP 2003-520878, JP 2004-529220, JP 2013-33248, JP 2015-7702, JP 2015-129210 can be mentioned.

In addition, as a method for providing a retardation layer on a polarizer, there is a method in which a coated retardation layer is separately provided on a releasable base material and transferred onto the polarizer. This is a preferable method in that it is not affected by the solvent used in the preparation.
The method of providing a coated retardation layer on a releasable base material is to perform a rubbing treatment on the releasable base material, or to provide an alignment layer as described above to provide orientation control power. It is preferable to apply the liquid crystal compound using the following steps. After the transfer-type retardation layer thus obtained is bonded to a polarizer using an adhesive or a pressure-sensitive adhesive, the releasable base material is peeled off.
As examples of these methods and retardation layers, reference may be made to JP-A No. 2008-149577, JP-A No. 2002-303722, WO2006/100830, JP-A No. 2015-64418, and the like.

Note that these retardation layers can be selected to have suitable characteristics depending on the type of liquid crystal cell.

When bonding a polarizing plate to a liquid crystal cell, an adhesive is generally used.
As the adhesive layer, rubber-based, acrylic-based, urethane-based, olefin-based, silicone-based, and other adhesives can be used without limitation, with acrylic adhesives being preferred. The adhesive may be applied to the target object, for example, the polarizer side of a polarizing plate, but the release film on one side of an optical transparent adhesive (release film/adhesive layer/release film) that does not require a substrate may be used. A method in which the film is peeled off and then bonded to the polarizer surface is preferred. As the adhesive, an ultraviolet curable adhesive, a urethane adhesive, or an epoxy adhesive is preferably used.

In the present invention, it is a preferred embodiment that only a coating layer exists between the polarizer and the liquid crystal cell. This means that there is no independent film between the polarizer and the liquid crystal cell. Specifically, only any combination of an adhesive layer, a pressure-sensitive adhesive layer, a protective coat layer, and a coated retardation layer is present between the polarizer and the liquid crystal cell. With such a configuration, the liquid crystal display device can be made thinner.

Specific preferred examples of lamination between a polarizer and a liquid crystal cell include the following.
Polarizer / adhesive layer / liquid crystal cell polarizer / protective coat layer / adhesive layer / liquid crystal cell polarizer / coated retardation layer / adhesive layer / liquid crystal cell polarizer / adhesive layer / coated retardation Layer / Adhesive layer / Liquid crystal cell polarizer / Protective coat layer / Coated retardation layer / Adhesive layer / Liquid crystal cell polarizer / Protective coat layer / Adhesive layer / Coated retardation layer / Adhesive layer / Liquid Crystal Cell Note that the adhesive layer described above may be an adhesive layer.

In addition, in this specification, the term "polarizing plate" refers not only to a laminate of a polyester base film and a polarizer, but also to a laminate in which an adhesive layer, an adhesive layer, a protective layer, and a retardation layer are laminated on a polarizer. Sometimes.

In the present invention, a long polarizing plate is prepared. Preferably, the elongated polarizing plate is wound into a roll. From the viewpoint of productivity, the length of the elongated polarizing plate is preferably 100 m or more, more preferably 300 m or more, particularly preferably 500 m or more. The upper limit of the length is not particularly limited as long as it can be handled, but realistically it is preferably 10,000 m or less.

The width of the long polarizing plate is prepared according to the size of the liquid crystal cell. Liquid crystal display devices are often rectangular. When the transmission axis of the polarizing plate is arranged perpendicularly or parallel to the long side of the liquid crystal cell, it is preferable to prepare a long polarizing plate with different widths on the light source side and the viewing side. In this case, each width is set to match the long side and short side of the target liquid crystal cell. Further, when the transmission axis of the polarizing plate is installed at an angle of about 45 degrees with respect to the liquid crystal cell, it is preferable to prepare elongated polarizing plates with the same width on the light source side and the viewing side.
It is preferable to prepare in advance a long polyester base film with slits wider than the intended width of the polarizing plate, and after laminating the polarizer and other layers, slit it to a predetermined width.

(Manufacture of liquid crystal panels)
A liquid crystal panel is manufactured by bonding a liquid crystal cell and a polarizing plate.

The method for manufacturing a liquid crystal panel involves cutting a long light source side polarizing plate into a predetermined size, cutting a long viewing side polarizing plate into a predetermined size, and attaching a light source to a liquid crystal cell. This includes a step of bonding the side polarizing plate and the viewing side polarizing plate. The order of these steps does not matter. That is, a long polarizing plate may be cut into a predetermined size and then bonded to the liquid crystal cell, or a long polarizing plate may be bonded to the liquid crystal cell first and then cut into a predetermined size. Alternatively, cutting and bonding may be performed almost simultaneously.
It is preferable that either or both of the elongated light source side polarizing plate and the polarizing plate satisfy the following requirements (1) to (3).
(1) A polarizer is provided on a polyester base film, and the angle between the fast axis (perpendicular to the slow axis) of the polyester base film and the transmission axis direction of the polarizer is 10 degrees or less,
(2) The polyester base film has a refractive index of 1.53 to 1.62 in the fast axis direction, and (3) the polyester base film has a thickness of 90 μm or less.
Note that the elongated light source side polarizing plate and the elongated viewing side polarizing plate may be the same or different.

When using a set of polarizing plates that satisfy characteristics (1) to (3) above as both the light source side polarizing plate and the viewing side polarizing plate, the thickness of the base film of the light source side polarizing plate is the same as that of the viewing side polarizing plate. The thickness is preferably the same as or thicker than the base film.

If only one elongated polarizing plate satisfies the requirements (1) to (3) above, the other polarizing plate may be a known polarizing plate, for example.
The other polarizing plate has a polarizer on a polyester base film, and the angle between the fast axis (perpendicular to the slow axis) of the polyester base film and the transmission axis direction of the polarizer is 80°. It is also preferable that the angle is between 90 degrees and further satisfies the conditions (2) and (3) above. In this case, it is preferable that the fast axis of the polyester base film is substantially parallel to the longitudinal direction of the polyester base film. Such a polarizing plate can be obtained by using a polyester base film used as a protective film that is stretched mainly in the width direction.

The process of cutting out a sheet polarizing plate from a long polarizing plate and bonding it to a liquid crystal cell includes the following method.
(1) A step of cutting a long polarizing plate in advance and preparing a plurality of sheet polarizing plates, and a step of bonding these to a liquid crystal cell.
(2) In a series of bonding processes, the polarizing plate is unwound from a long polarizing plate wound into a roll, cut to the required length each time, and the cut polarizing plate is attached to the liquid crystal cell. match.
(3) In a series of bonding steps, the polarizing plate is unwound from a long polarizing plate wound into a roll, and cut to the required length while being bonded to the liquid crystal cell.
(4) In a series of bonding processes, after unwinding the polarizing plate from the long polarizing plate wound into a roll and bonding it to the liquid crystal cell, the polarizing plate is attached to a length that almost matches the liquid crystal cell. cut.

Note that in these steps, as described above, it is preferable to use a polarizing plate provided with an adhesive layer in advance, but an adhesive layer may be laminated during the bonding process. Further, an adhesive layer may be provided on the liquid crystal cell side.

When laminating a polarizing plate on a liquid crystal cell, it is preferable to laminate the polarizer so that the polyester base film is on the opposite side of the liquid crystal cell, starting from the polarizer. That is, it is preferable to laminate such that the polyester base film is disposed on the viewing side of the polarizer of the viewing side polarizing plate and/or on the light source side of the polarizer of the light source side polarizing plate.

(liquid crystal cell)
A liquid crystal cell has a liquid crystal compound placed between substrates such as glass on which a liquid crystal driving circuit is provided. As the liquid crystal cell, NT type, VA type, IPS type, etc. can be used without particular limitation. There are also types called in-cell type (touch sensor circuit is installed on the liquid crystal side of the board) and on-cell type (touch sensor circuit is installed outside the board), which have a touch sensor function in the liquid crystal cell. It's okay. In-cell type and on-cell type are particularly preferable liquid crystal cells because they allow the display device to be made thinner if a touch sensor function is provided.
Note that in this specification, when a liquid crystal cell has a touch sensor function, the component including the component having the touch sensor function is referred to as a liquid crystal cell. In addition, the color filter on the glass substrate of the liquid crystal cell is also called a liquid crystal cell.

(Liquid crystal display device)
The liquid crystal panel thus obtained is housed in a housing together with a backlight source to form a liquid crystal display device. Further, a touch panel may be laminated on the liquid crystal panel. Further, a protective body such as glass, a resin sheet, or a resin film may be provided on the surface of the liquid crystal display device. Furthermore, a shatterproof film may be provided in case glass used in a liquid crystal cell or the like breaks.

(backlight light source)
The backlight light source is not particularly limited. Typical light sources include a combination of a blue light emitting diode and a yellow phosphor, a combination of a blue light emitting diode, a green phosphor and a red phosphor, an organic EL light source, a quantum dot light source, and a KSF phosphor ( _K2SiF ). _Examples include white light emitting diodes using Mn ⁴⁺ ). Among these, suitable light sources include a combination of a blue light emitting diode and a yellow phosphor, an organic EL light source, and a quantum dot light source.
The light source can be installed in a direct type, which is installed directly below the liquid crystal panel, or a side edge type, which is installed on the lower side of the liquid crystal panel. Depending on the type of light source, a light guide plate, a diffusion film, a lens film, etc. are used.

The display device of the present invention is particularly useful not only for general televisions, video display systems, and computer displays, but also for smartphones, tablet terminals, ATMs, car navigation systems, instruments in automobiles, monitors replacing mirrors, signboards, etc. It is.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples, and may be implemented with appropriate changes within the scope of the spirit of the present invention. Both are possible and are within the technical scope of the present invention.
The evaluation method of physical properties in Examples is as follows.

(1) Refractive index of polyester base film
Using a molecular orientation meter (Oji Scientific Instruments Co., Ltd., MOA-6004 type molecular orientation meter), determine the slow axis direction of the film, and place it in a 4 cm x 2 cm square so that the slow axis direction is parallel to the long side. A rectangle was cut out and used as a sample for measurement. For this sample, the refractive index of two orthogonal axes (refractive index in the slow axis direction: ny, fast axis (refractive index in the direction perpendicular to the slow axis direction): nx), and the refractive index in the thickness direction ( nz) was determined using an Abbe refractometer (manufactured by Atago, NAR-4T, measurement wavelength: 589 nm).

(2) Retardation (Re)
Retardation is a parameter defined as the product (△Nxy×d) of the anisotropy of the refractive index of two perpendicular axes on the film (△Nxy=|nx−ny|) and the film thickness d (nm). It is a measure of optical isotropy and anisotropy. The biaxial refractive index anisotropy (△Nxy) is determined by the method (1) above, and the absolute value of the biaxial refractive index difference (|nx−ny|) is calculated as the refractive index anisotropy (△Nxy). Nxy). The thickness d (nm) of the film was measured using an electric micrometer (Millitron 1245D, manufactured by Finereuf Co., Ltd.), and the unit was converted into nm. Retardation (Re) was determined from the product (ΔNxy×d) of the refractive index anisotropy (ΔNxy) and the film thickness d (nm).

(3) Thickness direction retardation (Rth)
Thickness direction retardation refers to the two birefringences △Nxz (=|nx-nz|) and △Nyz (=|ny-nz|) when viewed from the cross section in the film thickness direction. This is a parameter that indicates the average retardation obtained by multiplying the The thickness direction retardation (Rth ) was sought.

(4) Transmission axis direction of polarizer Rotate the sample polarizing plate with a known extinction axis (direction perpendicular to the transmission axis direction), and the extinction axis direction in the state where the amount of transmitted light is the least is determined. The direction parallel to the extinction axis of the known polarizing plate was defined as the transmission axis direction of the sample.

(5) Angle between the fast axis of the polyester base film and the direction of the transmission axis of the polarizer Remove the polarizer from the sample polarizing plate with a cloth impregnated with solvent, and adjust the direction of the fast axis according to (1). and the angle with the transmission axis direction of the polarizer determined in (4) was determined.

(6) Nz coefficient The value obtained by |ny-nz|/|ny-nx| was defined as the Nz coefficient. However, the values of ny and nx were selected so that ny>nx.

(7) Degree of plane orientation (ΔP)
The value obtained by (nx+ny)/2-nz was defined as the plane orientation degree (ΔP).

(8) Light transmittance at a wavelength of 380 nm Using a spectrophotometer (manufactured by Hitachi, Model U-3500), the light transmittance of each film in the wavelength range of 300 to 500 nm was measured using an air layer as a standard. The transmittance was determined.

(9) Heat shrinkage rate
The polyester film cut out from the slit roll was cut into a square shape of 21 cm on each side, and left in an atmosphere of 23° C. and 65% RH for 2 hours or more. A circle with a diameter of 80 mm centered on the center of this polyester film was drawn, and the diameter was measured at 5-degree intervals using a two-dimensional image measuring machine (QUICK IMAGE, manufactured by MITUTOYO) with the flow direction of the film set at 0 degrees. Here, the film flow direction was set to 0 degrees, and clockwise (rightward) rotation on the upper surface of the film was set as a positive angle, and counterclockwise (counterclockwise) rotation was set as a negative angle. Since the diameter was measured, measurements were taken in the range of -90 degrees to 85 degrees in all directions. Next, this polyester film was heat-treated in water at 85° C. for 30 minutes, the water adhering to the film surface was wiped off, air-dried, and then left in an atmosphere of 23° C. and 65% RH for 2 hours or more. Thereafter, the diameter of the circle was measured at 5 degree intervals in the same manner as above. The diameter before heat treatment is Lo, and the diameter in the same direction after heat treatment is L, and the heat shrinkage rate in each direction was determined according to the following formula.

Heat shrinkage rate (%) = ((Lo- L) / Lo) x 100

(10) Maximum value of heat shrinkage rate
The maximum value of the heat shrinkage rates measured in all directions at 5 degree intervals was defined as the maximum heat shrinkage rate.

(11) Rainbow spot observation
The liquid crystal display devices obtained in each example were visually observed in a dark place from the front and diagonally, and the presence or absence of iridescence was determined as follows. Here, the diagonal direction means a range of 30 degrees to 60 degrees from the normal direction of the screen of the liquid crystal display device.

○: No iridescence observed at all
△: Slight rainbow spots are observed.
×: Rainbow spots are observed

<Manufacture of polyester resin for base film>
(Production Example 1-Polyester X)
When the temperature of the esterification reactor was raised to 200°C, 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were charged, and while stirring, 0.017 parts by mass of antimony trioxide as a catalyst was added. 0.064 parts by mass of magnesium acetate tetrahydrate and 0.16 parts by mass of triethylamine were charged. Next, the pressure and temperature were raised to carry out a pressure esterification reaction under the conditions of a gauge pressure of 0.34 MPa and 240° C., and then the esterification reactor was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. Furthermore, the temperature was raised to 260° C. over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. Then, 15 minutes later, a dispersion treatment was performed using a high-pressure dispersion machine, and after 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reactor, and a polycondensation reaction was performed at 280° C. under reduced pressure.

After the polycondensation reaction is complete, it is filtered using a Naslon filter with a 95% cut diameter of 5 μm, extruded into a strand from a nozzle, and cooled and solidified using cooling water that has been previously filtered (pore size: 1 μm or less). , cut into pellets. The obtained polyethylene terephthalate resin (X) had an intrinsic viscosity of 0.62 dl/g, and contained substantially no inert particles or internally precipitated particles. (Hereafter abbreviated as PET(X).)

(Production Example 2-Polyester Y)
10 parts by mass of dried UV absorber (2,2'-(1,4-phenylene)bis(4H-3,1-benzoxazinone-4-one), particle-free PET(X) (intrinsic viscosity (0.62 dl/g) was mixed and used a kneading extruder to obtain a polyethylene terephthalate resin (Y) containing an ultraviolet absorber (hereinafter abbreviated as PET (Y)).

<Production of easy adhesive layer component>
(Polymerization of urethane resin D-1)
Urethane resin D-1 containing an aliphatic polycarbonate polyol as a constituent component was produced by the following procedure. Into a four-neck flask equipped with a stirrer, a Dimroth condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 43.75 parts by mass of 4,4-diphenylmethane diisocyanate, 12.85 parts by mass of dimethylolbutanoic acid, and several parts by mass were added. 153.41 parts by mass of polyhexamethylene carbonate diol having an average molecular weight of 2000, 0.03 parts by mass of dibutyltin dilaurate, and 84.00 parts by mass of acetone as a solvent were added, and the mixture was stirred at 75°C for 3 hours under a nitrogen atmosphere to form a reaction solution. It was confirmed that the amount of amine equivalent reached the predetermined value. Next, the temperature of this reaction solution was lowered to 40° C., and then 8.77 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring, the temperature was adjusted to 25°C, and while stirring and mixing at 2000 min-1, a polyurethane prepolymer solution was added and water-dispersed. . Thereafter, acetone and part of the water were removed under reduced pressure to prepare an aqueous dispersion (Dw-1) of a water-soluble polyurethane resin with a solid content of 35%. The resulting polyurethane resin (D-1) containing the aliphatic polycarbonate polyol as a constituent had a glass transition temperature of -30°C.

(Polymerization of oxazoline crosslinking agent E-1)
A mixture of 58 parts by mass of ion-exchanged water and 58 parts by mass of isopropanol as an aqueous medium and a polymerization initiator (2,2 4 parts by mass of '-azobis(2-amidinopropane) dihydrochloride) were added. Meanwhile, in a dropping funnel, 16 parts by mass of 2-isopropenyl-2-oxazoline as a polymerizable unsaturated monomer having an oxazoline group, methoxypolyethylene glycol acrylate (average number of added moles of ethylene glycol, 9 moles, Shin Nakamura Chemical A mixture of 32 parts by weight of methyl methacrylate and 32 parts by weight of methyl methacrylate was added thereto, and the mixture was added dropwise at 70° C. for 1 hour under a nitrogen atmosphere. After completion of the dropwise addition, the reaction solution was stirred for 9 hours and cooled to obtain a water-soluble resin (Ew-1) having an oxazoline group with a solid content concentration of 40% by mass.

(Preparation of coating liquid for easy adhesion layer)
A coating solution for an easily adhesive layer was prepared by mixing the following coating materials.
Water 55.62% by mass
Isopropanol 30.00% by mass
Aqueous dispersion of polyurethane resin (Dw-1) 11.29% by mass
Oxazoline crosslinking agent aqueous solution (Ew-1) 2.26% by mass
Particles 0.71% by mass
(Silica sol with an average particle size of 40 nm, solid content concentration 40% by mass)
Particles 0.07% by mass
(Silica sol with average particle size of 450 nm, solid content concentration 40% by mass)
Surfactant 0.05% by mass
(Silicon-based, solid content concentration 10% by mass)

<Manufacture of base film 1>
After drying 90 parts by mass of particle-free PET (X) resin pellets and 10 parts by mass of PET (Y) resin pellets containing an ultraviolet absorber as raw materials for the base film intermediate layer at 135° C. for 6 hours under reduced pressure (1 Torr). , was supplied to extruder 2 (for intermediate layer II), and PET (X) was dried by a conventional method and supplied to extruder 1 (for outer layer I and outer layer III), and melted at 285 ° C. . These two types of polymers are each filtered using a stainless steel sintered filter medium (nominal filtration accuracy: 95% of particles cut out at 10 μm), laminated in a two-type and three-layer confluence block, and extruded in a sheet form from a nozzle. An unstretched film was produced by winding the film around a casting drum with a surface temperature of 30° C. and cooling and solidifying it using an electrostatic casting method. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thicknesses of layer I, layer II, and layer III was 10:80:10.

Next, a coating solution for easy adhesion was applied to both sides of this unstretched PET film by a reverse roll method so that the coating amount after drying was 0.08 g/m ² , and then it was put into a dryer and dried at 80°C for 20 minutes. Dry for seconds.

The obtained unstretched film was then heated to 105°C using a heated roll group and an infrared heater, and then stretched 4.0 times in the running direction using a roll group with a difference in circumferential speed, and then heated with hot air at a temperature of 125°C. zone and stretched 1.0 times in the width direction. Next, the film was processed at a temperature of 225° C. for 30 seconds while maintaining the stretched width in the width direction.

Thereafter, both ends of the film cooled to 130° C. were cut with a shear blade and then wound up to obtain a uniaxially oriented PET film having a film thickness of 60 μm. The center portion of the obtained film was slit to a width of 30 cm to obtain a film roll with a length of about 500 m. It was confirmed that the fast axis of the obtained film roll was within a range of 90±0.5 degrees with respect to the longitudinal direction of the film over the entire width.
The various characteristics of the above-mentioned base film are sampled at three points in the width direction (three points at the center and at both ends) and are average values. The heat shrinkage rate was measured by sampling one point in the center.

<Manufacture of base films 2 to 4>
Films were formed in the same manner as Base Film 1 except that the line speed was changed and the thickness of the unstretched film was changed to obtain films with different film thicknesses. The obtained film rolls (base films 2 to 4), which are slit to a width of 30 cm in the same way as base film 1, have fast axes in the range of 90 ± 0.5 degrees with respect to the longitudinal direction of the film over the entire width. It was confirmed.

<Manufacture of base film 5>
An unstretched film (coated with an easy-adhesive layer) prepared in the same manner as base film 1 was introduced into a simultaneous biaxial stretching machine, and while the edges of the film were held with clips, it was placed in a hot air zone at a temperature of 125°C. The film was stretched 6.5 times in the running direction and 2.2 times in the width direction. Next, the film was processed at a temperature of 225° C. for 30 seconds while maintaining the stretched width in the width direction.
Thereafter, both ends of the film cooled to 130° C. were cut with a shear blade and then wound up to obtain a biaxially oriented PET film with a film thickness of 40 μm. The center portion of the obtained film was slit to a width of 30 cm to obtain a film roll with a length of about 500 m. It was confirmed that the fast axis of the obtained film roll was within a range of 90±0.5 degrees with respect to the longitudinal direction of the film over the entire width.

<Manufacture of base films 6 and 7>
A biaxially oriented PET film with a film thickness of about 40 μm was obtained in the same manner as base film 5 except that the thickness of the unstretched film was changed and stretched 6.0 times in the running direction and 2.2 times in the width direction. . The center part of the obtained film was slit into a width of 30 cm to form a film roll with a length of about 500 m, which was used as the base film 6, and the obtained film was slit into a width of 30 cm from the right end to form a film roll with a length of 500 m. This was used as the base film 7. It was confirmed that the fast axis of the film roll of the base film 6 was within a range of 90±0.5 degrees with respect to the longitudinal direction of the film over the entire width. It was confirmed that the fast axis of the film roll of the base film 7 was within a range of 90±3 degrees with respect to the longitudinal direction of the film over the entire width.

<Manufacture of base film 8>
A biaxially oriented PET film with a film thickness of about 40 μm was obtained in the same manner as base film 5 except that the thickness of the unstretched film was changed and stretched 4.5 times in the running direction and 2.4 times in the width direction. . The center portion of the obtained film was slit to a width of 30 cm to obtain a film roll with a length of about 500 m. It was confirmed that the fast axis of the obtained film roll was within a range of 90±1 degrees with respect to the longitudinal direction of the film over the entire width.

<Manufacture of base material laminated polarizer 1>
An unstretched film with a thickness of 100 μm is prepared using polyester was formed.
The obtained laminate was stretched and wound up twice in the longitudinal direction between rolls having different circumferential speeds at 120°C. Next, the obtained laminate was treated with a 4% boric acid aqueous solution for 30 seconds, and then immersed in a mixed aqueous solution of iodine (0.2%) and potassium iodide (1%) for 60 seconds for dyeing. Then, it was treated with a mixed aqueous solution of potassium iodide (3%) and boric acid (3%) for 30 seconds.
Furthermore, this laminate was uniaxially stretched in the longitudinal direction in a mixed aqueous solution of boric acid (4%) and potassium iodide (5%) at 72°C, then washed with a 4% aqueous potassium iodide solution, and the aqueous solution was stretched with an air knife. After removing it, dry it in an oven at 80°C, slit both ends and roll it up to form a base laminated polarizer 1 (a polarizer laminated on a thermoplastic resin base material made of polyester) with a width of 30 cm and a length of 1000 m. obtained something. The total stretching ratio was 6.5 times, and the thickness of the polarizer was 5 μm. The thickness was determined by embedding the base laminated polarizer in epoxy resin, cutting out a section, and observing it with an optical microscope.

<Manufacture of base material laminated polarizers 2 and 3>
A base material lamination polarizer 2 with a polarizer thickness of 3.5 μm and a base material lamination with a polarizer thickness of 8.0 μm were performed in the same manner as base material lamination polarizer 1 except that the coating thickness of the polyvinyl alcohol aqueous solution was changed. Polarizer 3 was obtained.

<Manufacture of single layer polarizer 1>
A polyvinyl alcohol resin film with a degree of saponification of 99.9% was introduced into rolls having different circumferential speeds, and uniaxially stretched three times at 100°C. The obtained stretched polyvinyl alcohol stretched film was dyed in a mixed aqueous solution of potassium iodide (0.3%) and iodine (0.05%), and then dyed in a 10% aqueous solution of boric acid at 72°C. It was uniaxially stretched twice. Thereafter, it was washed with ion-exchanged water, further immersed in a 6% potassium iodide aqueous solution, the aqueous solution was removed with an air knife, and then dried at 45° C. to obtain a polarizer. The thickness of the polarizer was 18 μm.

<Creation of polarizing plate 1>
After coating the base film 1 with an ultraviolet curable acrylic adhesive, the polarizer surfaces of the base laminated polarizer 1 are bonded together, and ultraviolet rays are irradiated from the base laminated polarizer side to bond the polyester base film. The base material laminated polarizer 1 was laminated and wound up into a roll. Next, while unrolling from the roll, peel off the thermoplastic resin base material of the base laminated polarizer, and release film (light release liner, heavy release liner) on both sides of the acrylic adhesive layer (no base material). The light release liner of a commercially available optical transparent adhesive sheet (manufactured by Nitto Denko Corporation) laminated with the adhesive layer is peeled off, and the light release liner is pasted on the polarizer surface, and the adhesive layer is laminated and rolled into a long length of polarized light. Board 1 was obtained.

<Creation of polarizing plates 2 to 8>
Long polarizing plates 2 to 8 were obtained in the same manner as in the preparation of polarizing plate 1 except that the base films 2 to 8 were changed.

<Creation of polarizing plates 9, 10, 11>
Elongated polarizing plates 9, 10, and 11 were obtained in the same manner as in the preparation of polarizing plate 4, except that the base laminated polarizers were changed to 2, 3, and single-layer polarizer 1.

<Creation of polarizing plates 12 and 13>
(Formation of antireflection layer)
A coating solution for forming a medium refractive index layer having the following composition is applied to one side of the base film 5 using a bar coater, dried at 70°C for 1 minute, and then irradiated with ultraviolet rays of 400 mJ/cm2 using a high-pressure mercury lamp and dried. A medium refractive index layer with a film thickness of 5 μm was obtained. Next, on the formed medium refractive index layer, a coating liquid for forming a high refractive index layer having the following composition is formed using a bar coater in the same manner as for the medium refractive index layer, and further on top of that, the coating liquid for forming a high refractive index layer having the following composition is applied. A coating solution for forming a low refractive index layer was formed in the same manner as the medium refractive index layer. Thereafter, a polarizing layer was provided on the opposite side in the same manner as for base film 1. A long polarizing plate 12 having an antireflection layer laminated thereon was obtained. Similarly, a long polarizing plate 13 was obtained from the base film 6.

Coating liquid for forming medium refractive index layer (refractive index 1.52)
Dipentaerythritol hexaacrylate 70 parts by weight 1,6-bis(3-acryloyloxy-2-hydroxypropyloxy)hexane
30 parts by weight Photopolymerization initiator 4 parts by weight (manufactured by Ciba Specialty Chemicals Co., Ltd., Irgacure 184)
Isopropanol 100 parts by weight

Coating liquid for forming high refractive index layer (refractive index 1.64)
ITO fine particles (average particle size 0.07 μm) 85 parts by weight Tetramethylolmethane triacrylate 15 parts by weight Photoinitiator (KAYACURE BMS, manufactured by Nippon Kayaku) 5 parts by weight Butyl alcohol 900 parts by weight

Coating liquid for forming a low refractive index layer (refractive index 1.42)
1,10-diacryloyloxy-2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorodecane 70 parts by weight dipentaerythritol Hexaacrylate 10 parts by weight Silica gel fine particles (XBA-ST, manufactured by Nissan Chemical) 60 parts by weight Photoinitiator (KAYACURE BMS, manufactured by Nippon Kayaku) 5 parts by weight

<Creation of sheet polarizing plates 14 to 18 with different angles>
The polyester base film 5 and the base laminated polarizer 1 are cut out to a size of 30 cm x 30 cm, and after coating the base film 5 with an acrylic adhesive, the polarizer surfaces of the base laminated polarizer 1 are bonded together, After curing by irradiating ultraviolet rays from the base laminated polarizer side, the thermoplastic resin base material was peeled off. Subsequently, the light release liner of a commercially available optical transparent adhesive sheet was peeled off and bonded to the polarizer surface. By changing the lamination angle of the polyester base film 5 and the base laminated polarizer 1, sheet polarizing plates 14 to 18 were obtained. Note that the unlaminated parts that occur when changing the angle have been deleted.

<Examples 1 to 12, Comparative Example 1>
(Creation of liquid crystal panel and liquid crystal display device 1)
A commercially available 10-inch liquid crystal display device (IPS type, light source: blue LED + yellow phosphor edge light source) was prepared by removing the polarizing plates on the light source side and viewing side. On the other hand, the polarizing plate 4 as a long polarizing plate on the light source side is a polarizing plate wound into a roll with a length of 500 m, which is slit to match the length of the long side of the liquid crystal cell. The plate was unrolled and cut to match the length of the short side of the liquid crystal cell to prepare a single sheet light source side polarizing plate.
Furthermore, as a long polarizing plate on the viewing side, the polarizing plate listed in Table 2 was slit to match the length of the short side of the liquid crystal cell, and the polarizing plate was wound into a roll with a length of 500 m. The roll-shaped polarizing plate was unwound and cut to match the length of the long side of the liquid crystal cell to obtain a single-sheet viewing-side polarizing plate.
The heavy release liner of each sheet-shaped polarizing plate was peeled off and bonded to a liquid crystal cell to create a liquid crystal panel, and this liquid crystal cell was attached to the original liquid crystal display device. The results are shown in Table 2.

<Examples 13 to 16>
(Creation of liquid crystal panel and liquid crystal display device 2)
The procedure was the same as above except that only the polarizing plate on the light source side was replaced. Note that, as the viewing side polarizing plate, a polarizing plate used on the viewing side of a commercially available liquid crystal display device was used as it was. The results are shown in Table 3.

<Examples 17 to 19>
(Creation of liquid crystal panel and liquid crystal display device 3)
The procedure was the same as above except that only the polarizing plate on the viewing side was replaced. Note that, as the light source side polarizing plate, the polarizing plate used on the light source side of a commercially available liquid crystal display device was used as it was. The results are shown in Table 3.

In addition, in the above implementation, no troubles due to breakage of the polyester base film and the elongated polarizing plate occurred.

<Reference examples 1 to 5>
(Creation of liquid crystal panel and liquid crystal display device 4)
The appropriate range of the angle between the fast axis of the polyester base film and the transmission axis direction of the polarizer was confirmed by the following method.
The single leaf polarizing plates 14 to 18 are arranged so that the transmission axis direction of the polarizer is parallel to the short side of the liquid crystal cell and matches the length of the short side, and the absorption axis direction of the polarizer matches the length of the long side of the liquid crystal cell. I cut it out like this. The same procedure as in Example 1 was carried out except that this cut out polarizing plate was used as the viewing side polarizing plate. The results are shown in Table 4.

In the method of manufacturing a liquid crystal panel for a liquid crystal display device of the present invention, since polyester is used as the base film of the polarizing plate used, even if the base film is thin, (1) it has excellent mechanical properties and has good hygroscopic elongation; (2) It is possible to manufacture an excellent liquid crystal panel in terms of: (2) excellent moisture absorption resistance, moisture permeability resistance, and excellent polarizer protection effect;
Furthermore, in the case of a rolled-up long polarizing plate, the orientation direction of the base film is the longitudinal direction, so it is less likely to break when creating the polarizing plate or when pasting the liquid crystal cell, resulting in excellent productivity. . In addition, a polarizing plate with a protective film on only one side does not have the above problems and is easy to use, making it possible to significantly reduce the thickness of the liquid crystal panel.

Claims (7)

a step of cutting a long light source side polarizing plate into a predetermined size;
A method for manufacturing a liquid crystal panel, comprising: cutting a long viewing-side polarizing plate into a predetermined size; and bonding a light source-side polarizing plate and a viewing-side polarizing plate to a liquid crystal cell,
Either or both of the elongated light source side polarizing plate and the elongated viewing side polarizing plate have a polarizer on a polyester base film, and further include the following (1) to (7). A method for manufacturing a liquid crystal panel having characteristics.
(1) The angle between the fast axis of the polyester base film and the transmission axis direction of the polarizer is 10 degrees or less.
(2) The polyester base film has a refractive index of 1.53 to 1.62 in the fast axis direction.
(3) The thickness of the polyester base film is 60 μm or less.
(4) The polyester base film has an Nz coefficient of 1.85 to 2.5.
(5) The angle between the longitudinal direction and 90 degrees of the polyester base film and the fast axis of the polyester base film is 10 degrees or less.
(6) Re/Rth of the polyester base film is 0.6 or more and 0.74 or less.
(7) The difference between the refractive index (nx) in the fast axis direction and the refractive index (ny) in the slow axis direction of the polyester base film is 0.080 to 0.150. 2. The method for manufacturing a liquid crystal panel according to claim 1, wherein the polarizer is a film made of PVA adsorbed with a dichroic dye, and has a thickness of 1 to 20 μm. 3. The method for manufacturing a liquid crystal panel according to claim 1, wherein the degree of plane orientation of the polyester base film is 0.128 to 0.15. 4. The method for manufacturing a liquid crystal panel according to claim 1, wherein only a coating layer is provided between the polarizer and the liquid crystal cell. 5. The method for manufacturing a liquid crystal panel according to claim 4, further comprising a coated retardation layer between the polarizer and the liquid crystal cell. A long polarizing plate comprising a polarizer and a polyester base film having the following characteristics as a polarizer protective film on at least one of the polarizers.
(1) The angle between the fast axis of the polyester base film and the transmission axis direction of the polarizer is 10 degrees or less.
(2) The polyester base film has a refractive index of 1.53 to 1.62 in the fast axis direction.
(3) The thickness of the polyester base film is 60 μm or less.
(4) The polyester base film has an Nz coefficient of 1.85 to 2.5.
(5) The angle between the longitudinal direction and 90 degrees of the polyester base film and the fast axis of the polyester base film is 10 degrees or less.
(6) Re/Rth of the polyester base film is 0.6 or more and 0.74 or less.
(7) The difference between the refractive index (nx) in the fast axis direction and the refractive index (ny) in the slow axis direction of the polyester base film is 0.080 to 0.150. 7. The elongated polarizing plate according to claim 6, wherein the polarizer is a film made of PVA adsorbed with a dichroic dye, and has a thickness of 1 to 20 μm.