JP2019132913A - Laminate, display, and inspection method - Google Patents

Abstract

To provide a laminate that has a functional layer having birefringence laminated on a base material having in-plane birefringence, the laminate allowing measurement of a phase difference value and crossed Nicol inspection.SOLUTION: A laminate has a functional layer having birefringence laminated on a base material having in-plane birefringence, and when the degree of orientation of the base material is X, and a change in ellipticity measured only in the functional layer and a change in ellipticity measured in the laminate is Y%, X/Y is 1 or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laminate, a display device, and an inspection method.

In image display devices such as liquid crystal display devices (LCD) and organic electroluminescence display devices (OLED), circularly polarizing plates are used for the purpose of improving display characteristics and preventing reflection. In a circularly polarizing plate, typically, a polarizer and a retardation layer (typically a quarter-wave layer) form an angle of 45 ° between an absorption axis of the polarizer and a slow axis of the retardation phase. Thus, they are laminated.
The circularly polarizing plate is formed by forming a functional layer on a base material, laminating it with a polarizer, and removing the base material when a functional layer such as a quarter wavelength layer is produced by transfer. Yes.
For example, Patent Document 1 describes that a quarter wavelength layer is formed as a transfer layer from a transfer film.

JP, 2006-206217, A

When a base material having birefringence in the surface is used as the base material, there is a problem that a retardation value or a crossed Nicols test cannot be performed on a laminate with a birefringence functional layer such as a quarter wavelength layer. there were.
Further, in the display device, when a film made of triacetyl cellulose (TAC) is used as the transparent base material of the functional layer having birefringence, there is a problem that TAC has high hydrophilicity and water absorption.
The present invention has been made in view of such circumstances, and in a laminate in which a functional layer having birefringence and a substrate having birefringence in a plane are laminated, measurement of a retardation value, An object of the present invention is to provide a laminate capable of crossed Nicols inspection. The present invention also provides a laminate having excellent performance as a liquid crystal display when a substrate having birefringence is used as a transparent substrate of a functional layer having birefringence in a liquid crystal display device. It is the purpose. Furthermore, an object of this invention is to provide the display apparatus using the said laminated body, and the inspection method using the said laminated body.

As a result of intensive studies to solve the above-mentioned problems, the present inventors measured only the functional layer in a laminate in which a functional layer having birefringence and a substrate having birefringence in the plane were laminated. The above problem can be solved by setting the ratio (X / Y) of the degree of orientation (X) of the base material to the ellipticity and the change rate (Y%) of the ellipticity measured with the laminate. I found out.
The present invention has been completed based on such findings.

The present invention relates to the following [1] to [10].
[1] A laminate in which a functional layer having birefringence and a substrate having birefringence in a plane are laminated, the degree of orientation of the substrate is X, the ellipticity measured only by the functional layer, and the laminate A laminate characterized in that X / Y is 1 or more, where Y is the rate of change of the ellipticity measured in (1).
[2] The functional layer is a ¼ wavelength layer that imparts a phase difference of ¼ wavelength to the transmitted light, or a ½ wavelength layer that imparts a phase difference of ½ wavelength to the transmitted light. The laminate according to [1].
[3] The laminate according to [1] or [2], wherein the functional layer is a functional layer containing a liquid crystal polymer.
[4] The laminate according to any one of [1] to [3], wherein the base material is made of polyester.
[5] The laminate according to any one of [1] to [4], wherein the base material is made of polyethylene terephthalate or polyethylene naphthalate.
[6] The laminate according to any one of [1] to [5], wherein the standard deviation of the in-plane ellipticity change is 2.5% or less.
[7] The laminate according to any one of [1] to [6], wherein the retardation of the substrate is 3,000 nm or more.
[8] A display device comprising the laminate according to any one of [1] to [7] and a polarizer.
[9] A testing method comprising evaluating the uniformity of a functional layer using the laminate according to any one of [1] to [7].
[10] Evaluation is performed by appearance evaluation using transmitted light, and the transmitted light is light that has passed through a polarizer, a laminate, and an analyzer from a light source, and the polarizer is provided with a functional layer of a substrate. The inspection method according to [9], wherein the light source is provided on a surface opposite to the formed surface and the light source is a white LED.

  According to the present invention, in a laminate in which a functional layer having birefringence and a substrate having birefringence in a plane are laminated, a laminate capable of measuring a retardation value and performing crossed Nicols inspection is provided. be able to. Further, according to the present invention, in a liquid crystal display device, when a base material having birefringence is used as a transparent base material of a functional layer having birefringence, a laminate having excellent performance as a liquid crystal display is provided. be able to. Furthermore, according to this invention, the display apparatus using the said laminated body and the test | inspection method using the said laminated body can be provided.

FIG. 1 is a cross-sectional view showing an embodiment of the configuration of the laminate of the present invention. 2A is a cross-sectional view showing the relationship between the polarizer and the λ / 4 layer in the liquid crystal display device of the present invention, and FIG. 2B shows the polarizer and λ / in the conventional liquid crystal display device. It is sectional drawing which shows the relationship with 4 layers. FIG. 3 is an explanatory view showing an embodiment of the inspection method of the present invention.

In the following description, the description of “A to B” representing a numerical range represents a numerical range including end points. That is, it represents “A or more and B or less” (when A <B) or “A or less and B or more” (when A> B). Moreover, in the following description, the combination of a preferable aspect is a more preferable aspect.
Embodiments of the present invention will be described below.
[Laminate]
The laminate of the present invention is a laminate in which a functional layer having birefringence and a substrate having birefringence in a plane are laminated, and the degree of orientation of the substrate is X, and the ellipticity measured only with the functional layer When the rate of change in ellipticity measured with the laminate is Y%, X / Y is 1 or more.
The laminate of the present invention is a substrate having in-plane birefringence by setting the ratio (X / Y) of the degree of orientation (X) of the substrate to the change rate (Y%) of the ellipticity to 1 or more. Even if is laminated, it is possible to evaluate a functional layer having birefringence. In addition, by using the laminate of the present invention for a display device, a transparent substrate having higher hydrophobicity can be adopted instead of the conventionally used TAC, and the problem of water absorption is solved.

<Ellipticity>
In the laminate of the present invention, when the ellipticity measured with only the functional layer is A and the ellipticity measured with the laminate is B, the change rate C of the ellipticity is expressed by the following equation (1).
C (%) = | B−A | ÷ A × 100 (1)
Here, the ellipticity is a value measured at a wavelength of 550 nm in the center of the sample under the conditions of a temperature of 23 ± 5 ° C. and a humidity of 50 ± 10%, and is measured by the following measurement method.
Specifically, a polarizer is provided on the surface of the substrate opposite to the surface having the functional layer, and light having a wavelength of 550 nm from the light source is vertically incident from the polarizer side. On the other hand, an analyzer (polarizer) and a light-receiving part (light-receiving element) are provided in this order on the surface opposite to the surface having the base material of the functional layer, and the change in the light amount when the polarizer is rotated once is detected. Measure the ellipticity with.
The measurement of the ellipticity may be performed using a known measuring device and is not particularly limited. For example, the RETS series manufactured by Otsuka Electronics Co., Ltd. is exemplified.

In the laminate of the present invention, the preferred range of the rate of change in ellipticity is preferably 5% or less, more preferably 4% or less, still more preferably 3% or less, although it depends on the orientation degree of the substrate to be laminated. More preferably, it is 2% or less, More preferably, it is 1% or less.
In order to make the change rate (C) of the ellipticity within the above preferable range, the absorption axis of the polarizer provided on the surface of the substrate opposite to the surface on which the functional layer is provided, It is preferable that the optical axis direction (slow axis direction) of the substrate having refraction be parallel or orthogonal.
The angle formed between the absorption axis of the polarizer and the optical axis direction of the substrate having birefringence in the plane is preferably 0 ° ± 5 °, more preferably 0 ° ± 3 °, and still more preferably 0 ° ± 2 °. More preferably, it is 0 ° ± 1 °, and most preferably 0 °.
The angle formed between the absorption axis of the polarizing plate and the optical axis direction of the substrate having birefringence in the plane is preferably 90 ° ± 5 °, more preferably 90 ° ± 3 °, and still more preferably 90 ° ±. 2 °, more preferably 90 ± 1 °, and most preferably 90 °.

In the present invention, it is preferable that the standard deviation of the in-plane ellipticity change is 2.5% or less. The standard deviation is calculated by measuring the ellipticity measured only with the functional layer and the change in ellipticity measured with the laminate at 16 points in the plane of the substrate. Specifically, in a laminate of 10 × 10 cm, the ellipticity is measured at 16 points, which are intersections when lines are provided at intervals of 2 cm vertically and horizontally, and the change from the ellipticity measured only by the functional layer is measured. Calculate the standard deviation. (Alternative: More specifically, for the laminate to be measured, the ellipticity at 16 points, which is the intersection when four lines are provided vertically and horizontally so as to be divided into 5 equal parts vertically and horizontally, respectively. And calculate the change from the ellipticity measured only in the functional layer, and obtain the standard deviation.)
When the standard deviation is 2.5% or less, the in-plane uniformity is excellent, and the laminate can be suitably used for appearance inspection. A display device is also preferable because the uniformity of display within the surface is improved. The standard deviation is more preferably 2% or less, still more preferably 1.5% or less, still more preferably 1.0% or less, and still more preferably 0.5% or less.
The average value obtained by measuring the change in ellipticity at 16 points in the plane is preferably 5% or less, more preferably 4% or less, still more preferably 3% or less, still more preferably 2% or less, and particularly preferably. 1% or less.

<Functional layer having birefringence>
The laminate of the present invention has a functional layer having birefringence. The functional layer having birefringence may have birefringence in the plane or birefringence in the depth direction, and is not particularly limited.
Here, when the functional layer having birefringence has in-plane birefringence, the measurement angle is set to 0 ° and the measurement wavelength is 590 nm, the in-plane phase difference is measured, and the in-plane phase difference is 20 nm or more. Is defined as having in-plane birefringence. A known measuring device may be used as the measuring device and is not particularly limited. For example, KOBRA-WR manufactured by Oji Scientific Instruments Co., Ltd. or RETS-100 manufactured by Otsuka Electronics Co., Ltd. is used, and the temperature is 25 ± 5 ° C. and the humidity. Measure at the center of the sample at 50 ± 10%.
When the functional layer having birefringence has birefringence in the depth direction, the measurement wavelength is set to 590 nm, the phase difference between the measurement angles of 0 ° and 40 ° is measured, and the thickness direction phase difference is calculated. Those having a thickness direction retardation of 20 nm or more are defined as having birefringence in the thickness direction. As a measuring device, a known measuring device may be used, and is not particularly limited. For example, using KOBRA-WR manufactured by Oji Scientific Instruments Co., Ltd., under conditions of a temperature of 25 ± 5 ° C. and a humidity of 50 ± 10%, Measure at the center of the sample.

As the functional layer, any optical functional layer can be used as long as it has birefringence. As a functional layer, a quarter wavelength layer (hereinafter also referred to as a λ / 4 layer) that imparts a phase difference of ¼ wavelength to transmitted light, and a phase difference of ½ wavelength is imparted to transmitted light. A ½ wavelength layer (hereinafter also referred to as λ / 2 layer) is preferably exemplified.
The functional layer is preferably a functional layer containing a liquid crystal polymer as will be described later.

[Λ / 4 layer]
Hereinafter, the λ / 4 layer will be described as a functional layer, but the same applies to the λ / 2 layer except that the orientation angle is changed.
FIG. 1 is a cross-sectional view showing an embodiment of the configuration of the laminate 10 of the present invention. In the present invention, the λ / 4 layer 16 forms the alignment film 14 on the substrate 12, and forms the λ / 4 layer 16 on the alignment film 14 that imparts a quarter-wave phase difference to the transmitted light. . Here, the λ / 4 layer 16 is preferably made of a liquid crystal material cured in a state of being aligned by the alignment regulating force of the alignment film 14, and the liquid crystal material is more preferably a liquid crystal polymer. That is, the functional layer is preferably a functional layer containing a liquid crystal polymer.
When a substrate having birefringence in the plane is used as the substrate 12, the laminate of the present invention is obtained, but the laminate of the present invention is not limited to this, and a λ / 4 layer prepared in advance is used. In addition, it includes a mode in which the film is formed on a substrate having birefringence in the surface by transfer.

  Examples of the liquid crystal material include Japanese Patent Application Publication No. 2010-522289, Japanese Unexamined Patent Application Publication No. 2006-243470, Japanese Unexamined Patent Application Publication No. 2007-243470, Japanese Unexamined Patent Application Publication No. 2009-75494, Japanese Unexamined Patent Application Publication No. 2009-62508, and Japanese Unexamined Patent Application Publication No. 2009-. Application of liquid crystal compounds described in JP-A No. 179563, JP-A 2009-242717, JP-A 2009-242718, JP-A 4222360, JP-A 41866981, JP-A 2015-230347, etc. can do.

When the base material 12 is a base material having birefringence in the plane, the alignment film 14 is a λ / 4 layer in a direction of 45 degrees obliquely with respect to the slow axis of the base material having birefringence in the plane. It is preferable that 16 liquid crystal materials are prepared so as to be aligned. Further, the alignment film may be arranged at an angle of 15 degrees, 75 degrees, etc. with respect to the slow axis of the substrate having birefringence in the plane.
The alignment film 14 may be made of a photo-alignment film, may be made by a rubbing process, may be made by a fine line-shaped uneven shape by a shaping process, and various configurations can be widely applied. it can. Alternatively, the alignment film 14 may be omitted by forming the λ / 4 layer 16 by applying a photo-alignment technique with a photo-alignment liquid crystal polymer having a photo-alignment function.

<Base material having birefringence in plane>
The substrate having birefringence in the plane (hereinafter, also simply referred to as “substrate”) is preferably a transparent substrate, and preferably has a transmittance in the visible light region of 80% or more, 84% The above is more preferable. In addition, the said transmittance | permeability can be measured by JISK7361-1: 1997 (the test method of the total light transmittance of a plastic-transparent material).
The substrate having birefringence in the plane is not particularly limited, and examples thereof include, but are not limited to, substrates made of polycarbonate, olefin polymer, acrylic, polyester, and the like. Among these, the base material is preferably a polyester base material made of polyester from the viewpoints of cost, mechanical strength, and high retardation as will be described later.

Although it does not specifically limit as a material which comprises the said polyester base material, From the viewpoint of obtaining the desired orientation degree and retardation mentioned later, from an aromatic dibasic acid or its ester-forming derivative, and diol or its ester-forming derivative. A linear saturated polyester to be synthesized is preferred. Specific examples of such polyester include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), and polyethylene-2,6-naphthalate.
The polyester used for the polyester substrate may be a copolymer of these polyesters. The polyester is mainly used (for example, a component of 80 mol% or more), and a small proportion (for example, 20 mol% or less). It may be blended with these types of resins. Polyethylene terephthalate (PET) or polyethylene naphthalate (PEN, polyethylene-2,6-naphthalate) is particularly preferred as the polyester because of its excellent balance of mechanical properties and optical properties. In particular, it is preferably made of polyethylene terephthalate (PET). This is because polyethylene terephthalate is highly versatile and easily available. In the present invention, even a highly versatile film such as PET can be used as a base material for a functional phase such as a retardation layer. Further, in a liquid crystal display device, it can also be used as a protective layer for a polarizer. it can.
Furthermore, PET is excellent in transparency, heat or mechanical properties, can control the retardation by stretching, has a large intrinsic birefringence, and can obtain a large retardation relatively easily even when the film thickness is small.

  In the present invention, the substrate has in-plane birefringence. Here, the measurement angle is set to 0 ° and the measurement wavelength is 590 nm, the in-plane phase difference is measured, and those having an in-plane phase difference of 20 nm or more are defined as having in-plane birefringence. A known measuring device may be used as the measuring device and is not particularly limited. For example, KOBRA-WR, PAM-UHR100, KOBRA-HBPR / SPC manufactured by Oji Scientific Instruments Co., Ltd., RETS-100 manufactured by Otsuka Electronics Co., Ltd. Use and measure at the center of the sample under conditions of temperature 25 ± 5 ° C. and humidity 50 ± 10%.

The substrate preferably has a retardation of 3,000 nm or more. When the retardation is 3,000 nm or more, the occurrence of rainbow unevenness due to the substrate is suppressed, which is more suitable for visual inspection. The upper limit of the retardation of the substrate is not particularly limited, but is preferably 30,000 nm or less from the viewpoint of thinning, the handling property as a transfer substrate, and the cost. The retardation of the base material is more preferably 5,000 to 25,000 nm, and still more preferably 7,000 to 20,000 nm.
Moreover, since the influence of the change of the retardation by a wavelength becomes small by using a base material with large retardation, it is more suitable for the inspection of the uniformity of a display apparatus and a functional layer.

The retardation is defined by the following formula based on the refractive index (nx) in the slow axis direction, the refractive index (ny) in the fast axis direction, and the thickness (d) of the base material in the plane of the base material. Is represented by
Retardation (Re) = (nx−ny) × d
The retardation can be measured (measurement angle 0 °, measurement wavelength 590 nm) by, for example, KOBRA-WR, PAM-UHR100, KOBRA-HBPR / SPC manufactured by Oji Scientific Instruments.
Further, using two polarizing plates, the orientation axis direction (principal axis direction) of the base material is obtained, and the refractive indexes (nx, ny) of two axes orthogonal to the orientation axis direction are obtained as Abbe refractometers. (NAT-4T, manufactured by Atago Co., Ltd.) may be used. Here, an axis showing a larger refractive index is defined as a slow axis. The thickness d (nm) of the substrate is measured using an electric micrometer (manufactured by Anritsu Co., Ltd.), and the unit is converted to nm. Retardation can also be calculated from the product of the refractive index difference (nx−ny) and the thickness d (nm) of the film.
The retardation is measured at the center of the base material under the conditions of a temperature of 25 ± 5 ° C. and a humidity of 50 ± 10 ° C.

Hereinafter, the case where the base material is a polyester base material, in particular, a PET base material will be mainly described.
In the present invention, when the substrate is a PET substrate made from PET, the refractive index difference (nx−ny) (hereinafter also referred to as Δn) is preferably 0.05 or more. It is preferable that Δn is 0.05 or more because the film thickness necessary for obtaining the retardation value described above can be reduced. On the other hand, the Δn is preferably 0.25 or less. When it is 0.25 or less, it is not necessary to stretch the PET base material excessively, and it is preferable because the PET base material is prevented from being torn and torn and is excellent in practicality as an industrial material.
From the above viewpoint, Δn is more preferably 0.07 or more, and more preferably 0.20 or less, and still more preferably 0.20 or less, from the viewpoint of durability in the heat and humidity resistance test. When the durability in the heat and humidity resistance test is excellent, it is particularly suitable as a base material when the functional layer is a transfer material.
The refractive index (nx) in the slow axis direction is preferably 1.66 or more, more preferably 1.68 or more, and is preferably 1.78 or less, more preferably 1.73 or less. The refractive index (ny) in the fast axis direction is preferably 1.55 or more, more preferably 1.57 or more, and preferably 1.65 or less, more preferably 1.62 or less.

Moreover, when the said polyester base material is a PEN base material which uses polyethylene naphthalate (PEN) as a raw material, said (DELTA) n becomes like this. Preferably it is 0.05 or more. It is preferable that Δn is 0.05 or more because the film thickness necessary for obtaining the retardation value described above can be reduced. On the other hand, the Δn is preferably 0.30 or less. The above Δn is preferably 0.30 or less because the PEN base material is prevented from tearing and tearing, and is excellent in practicality as an industrial material. In the case of the PEN substrate, Δn is more preferably 0.07 or more, more preferably 0.27 or less, and still more preferably 0.25 or less.
The refractive index (nx) in the slow axis direction in the case of the PEN substrate is preferably 1.70 or more, more preferably 1.72 or more, and preferably 1.90 or less, more preferably Is 1.88 or less. Further, the refractive index (ny) in the fast axis direction in the case of the PEN base material is preferably 1.55 or more, more preferably 1.57 or more, and preferably 1.75 or less, more preferably Is 1.73 or less.

The method for obtaining the polyester base material is not particularly limited as long as the above-described retardation is satisfied. For example, the polyester, such as PET, as a material is melted and extruded into a sheet to form glass. The method of heat-processing after transverse stretching using a tenter etc. at the temperature more than transition temperature is mentioned.
The transverse stretching temperature is preferably 80 to 130 ° C, more preferably 90 to 120 ° C. The transverse draw ratio is preferably 2.5 to 6.0 times, more preferably 3.0 to 5.5 times. When the transverse draw ratio is 6.0 times or less, the resulting polyester layer is excellent in transparency, and when the draw ratio is 2.5 times or more, the necessary draw tension is obtained, and the resulting polyester layer has a plurality of layers. Since refraction becomes large and desired retardation is obtained, it is preferable.
The polyester layer may be subjected to transverse stretching of the unstretched polyester under the above conditions using a biaxial stretching test apparatus and then stretched in the flow direction with respect to the transverse stretching (hereinafter also referred to as longitudinal stretching). . In this case, the longitudinal stretching preferably has a stretching ratio of 2 times or less. It is preferable that the stretching ratio of the longitudinal stretching is 2 times or less because a desired Δn is easily achieved.
Moreover, as processing temperature at the said heat processing, Preferably it is 80-250 degreeC, More preferably, it is 100-220 degreeC.

  Examples of the method for controlling the retardation of the polyester substrate produced by the above-described method to 3,000 nm or more include a method of appropriately setting the draw ratio, the drawing temperature, and the film thickness of the produced polyester substrate. Specifically, for example, the higher the stretching ratio, the lower the stretching temperature, and the thicker the film, the easier it is to obtain high retardation. The lower the stretching ratio, the higher the stretching temperature, and the film thickness. The thinner, the easier it is to obtain low retardation.

In the present invention, the degree of orientation of the substrate is preferably 2.0 or more. When the degree of orientation is 2.0 or more, when the degree of orientation of the substrate is X, the ellipticity measured only by the functional layer, and the rate of change of the ellipticity measured by the laminate is Y%, X / Y is It becomes easy to set it to 1 or more. Moreover, a desired retardation value can be obtained with a thinner film thickness. The degree of orientation is more preferably 3.0 or more, still more preferably 4.0 or more, and still more preferably 5.0 or more.
The degree of orientation, when the maximum value of the surface orientation parameter Y of the base material _{Y max,} the minimum value was _{Y min,} which is a value represented by Y max _{/ Y min.} The surface orientation parameter Y is an absorption intensity (I) at 1,340 cm ⁻¹ on the one-time reflection spectrum of the FTIR-S polarization ATR method measured by rotating the polyester substrate surface in-plane every 10 ° as an orientation parameter. ₁₃₄₀ ) and the absorption intensity (I ₁₄₁₀ ) at 1,410 cm ⁻¹ [I ₁₃₄₀ / I ₁₄₁₀ ]. More specifically, it can be determined by the method described in the examples.

In the present invention, when the degree of orientation of the substrate is X, the ellipticity measured only by the functional layer, and the change rate of the ellipticity measured by the laminate is Y%, X / Y is 1 or more. By setting X / Y to 1 or more, it is possible to provide a laminate capable of measuring a retardation value and performing crossed Nicols inspection. In addition, a stacked body having excellent performance as a liquid crystal display device can be provided.
X / Y is preferably 1.5 or more, more preferably 2 or more, still more preferably 2.5 or more, still more preferably 3 or more, and still more preferably 5 or more. X / Y is not particularly limited, but is preferably 50 or less from the viewpoint of ease of production.

  The thickness of the substrate is preferably 20 μm or more, more preferably 50 μm or more, preferably 500 μm or less, more preferably 300 μm or less, and further preferably 150 μm or less. When the thickness of the substrate is 20 μm or more, it becomes easy to achieve a desired degree of orientation and retardation, and cracks, tears, etc. derived from the anisotropy of mechanical properties are suppressed, making it practical as an industrial material. Since it is excellent, it is preferable. Moreover, it is preferable for it to be 500 μm or less because the substrate has flexibility and is excellent in practicality as an industrial material.

  In the present invention, the substrate is subjected to surface treatment such as primer coating, saponification treatment, glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment, and flame treatment without departing from the spirit of the present invention. May be.

[Display device]
As described above with reference to FIG. 1, the laminate of the present invention may be a laminate formed when a functional layer such as a retardation layer is produced. You may use especially for a liquid crystal display device.
A liquid crystal display device is generally composed of a liquid crystal cell in which a transparent electrode, a liquid crystal layer, a color filter and the like are sandwiched between glass plates, and two polarizing plates provided on both sides thereof. It has the structure which has a child and the protective film arrange | positioned at the upper and lower sides.
Hereinafter, a description will be given with reference to the drawings. FIG. 2B shows the relationship between the polarizer 134 and the λ / 4 layer 138 in the conventional liquid crystal display device 130. Protection films 132 and 136 are disposed above and below the polarizer 134. In FIG. 2B, the λ / 4 layer 138 is provided for sunglasses and for preventing coloring.
Conventionally, as a protective film for the polarizer 134, a TAC film made of triacetyl cellulose (TAC) having no in-plane birefringence has been used. The TAC film is excellent in that it does not have birefringence in the plane, but since it is hydrophilic and has water absorption, moisture in the air, There has been a problem that the TAC film, which is a protective film, absorbs water or absorbs moisture due to wetness or the like, thereby degrading the polarizer. Therefore, a protective film with low moisture permeability is required for the protective film on the viewer side of the polarizer.
FIG. 2A shows the relationship between the polarizer 24 and the λ / 4 layer 28 in the liquid crystal display device 20 of the present invention. In the liquid crystal display device 20 of the present invention, instead of the protective film 136, a base material having birefringence in the plane is used as the protective film 26, and the ellipticity measured only with the λ / 4 layer 28, and λ / When the change rate of the ellipticity measured by the laminate of the four layers 28 and the protective film 26 is Y% and the orientation degree of the substrate is X, X / Y is 1 or more. By making the base material which has birefringence in a plane into the protective film 26, the material selectivity of a protective film improves and it can be set as a low moisture-permeable protective film. In addition, as a base material which has birefringence in the said surface, the base material mentioned above is used and a preferable aspect is also the same.
Although the case where the λ / 4 layer is used as the functional layer has been described as an example, the present invention is not limited to this, and the present invention is similarly applied to a display device using the λ / 2 layer. .

  Further, the display device of the present invention is not limited to the above-described embodiment, and a polarizer may be provided on the functional layer side of the laminate. That is, as described above, not only the functional layer having birefringence / the layer structure of the substrate / polarizer / display element having birefringence in the plane, but also the substrate / birefringence having birefringence in the plane. It may be a layer structure of functional layer / polarizer / display element.

[Inspection method]
The inspection method of the present invention is characterized by evaluating the uniformity of the functional layer using the laminate of the present invention.
The inspection method of the present invention will be described with reference to FIG. In FIG. 3, light from the light source enters the polarizer 32 perpendicularly, passes through the polarizer 32, the base material 34 having birefringence in the plane, and the functional layer 36 having birefringence in this order, and as necessary. The light passes through a polarizer 38, which is an analyzer, and is sent to a light receiving unit (not shown).
In FIG. 3, the arrow described in the polarizer 32 represents the absorption axis of the polarizer, and the arrow described in the base material 34 having birefringence in the plane represents the slow axis and is described in the polarizer 38. The arrow made represents the absorption axis of the polarizer. Also, in FIG. 3, a λ / 4 layer is exemplarily described as the functional layer 36 having birefringence, and an arrow of the functional layer 36 indicates that a phase difference (45 °) is given. In FIG. 3, the absorption axes of the polarizer 32 and the polarizer 38 are arranged so as to be orthogonal to each other.
Here, the ellipticity obtained by measuring the absorption axis of the polarizer 32 and the slow axis of the base material 34 having birefringence in the plane with only the functional layer 36, and the laminate (the base material 34 and the functional layer 36 The phase difference of the functional layer 36 is measured by laminating so that X / Y is 1 or more, where Y is the rate of change in ellipticity measured in the laminate) and X is the orientation degree of the substrate. It becomes possible.
Further, by observing the transmitted light from the functional layer 36 with the polarizer 38 provided, an appearance inspection of the uniformity of the functional layer 36 can be performed.
In FIG. 3, it is described that the absorption axis of the polarizer 32 and the slow axis of the base material 34 having birefringence in the plane are parallel, but the above-mentioned X / Y is 1 or more. The range may have an angle. Further, the absorption axis of the polarizer 32 and the slow axis of the base material 34 having birefringence in the plane may be arranged so as to form an angle of 90 °, and the range in which X / Y is equal to or larger than that. The angle may be from 90 °.
Although not shown in FIG. 3, an alignment layer may be further provided between the base material 34 having birefringence in the plane and the functional layer 36.

In the inspection method of the present invention, the light source is not particularly limited, but as a light source for appearance inspection, a cold cathode fluorescent tube (also referred to as CCFL), a hot cathode fluorescent tube, white Any of LEDs (white light-emitting diodes) and the like may be used, but a white LED is preferable because it has a continuous and broad emission spectrum and the generation of rainbow unevenness is further suppressed.
Here, the white LED is an element that emits white by combining a phosphor with a phosphor type, that is, a light emitting diode that emits blue light or ultraviolet light using a compound semiconductor, and in particular, a compound semiconductor is used. A white LED composed of a light emitting element in which a blue light emitting diode and an yttrium / aluminum / garnet yellow phosphor are combined has a continuous and broad emission spectrum and is excellent in luminous efficiency, and thus is suitable as a light source.

EXAMPLES Hereinafter, although this invention is demonstrated in detail with reference to an Example and a comparative example, this invention is not limited to these Examples at all.
[Example 1]
<Method for producing laminate>
As a substrate having birefringence in the plane, a biaxially stretched polyester substrate having a width of 1 m and a length of 2000 m having the following characteristics was prepared.
Thickness: 60 μm
Degree of orientation: 5.5 (standard deviation of in-plane ellipticity change: 0.23)
Retardation (Re) of wavelength 590 nm: 5400
nx (590 nm) = 1.70
ny (590 nm) = 1.61
Δn (590 nm) = 0.09
A coating liquid for forming an alignment layer containing a photodimerization reaction type photo-alignment material (trade name: ROP-103, manufactured by Lorick) as the photo-alignment material is applied to the raw material and dried to obtain an alignment layer having a thickness of 0.1 μm. A layer forming layer was formed. Furthermore, the substrate was attached with a long alignment film having an alignment layer by irradiating polarized ultraviolet rays (polarization axis being 45 degrees with respect to the film transport direction) through a wire grid.
A liquid crystal compound dissolved in a solvent (licrive (registered trademark) RMS03-013C (trade name) manufactured by Merck & Co., Inc.) was applied onto the substrate with the alignment film, dried (liquid crystal alignment), and cooled to near room temperature. A retardation layer (λ / 4 layer), which is a liquid crystal layer having a thickness of 1 μm, was formed by curing with ultraviolet rays to obtain a biaxially stretched polyester substrate with retardation.

<Measurement of orientation>
The degree of orientation of the polyester substrate used in the examples and comparative examples was determined by the following method using UVIR FTS600 (manufactured by Bio-Rad, FT-IR) at a temperature of 23 ° C. ± 5 ° C. and a humidity of 50 ± 10%. Measured with
The orientation degree of the polyester substrate was defined by the orientation parameter Z, and the orientation parameter Z was measured by an infrared absorption spectrum analysis in a single reflection of the FTIR-S polarized ATR method.
That is, the measurement surface of the polyester base material is set in a one-time reflection ATR accessory device, the spectrum of one-time reflection is measured, and after the baseline is optimized, the absorption intensity (I ₁₃₄₀ ) at _1,340 cm ⁻¹ and 1, The absorption intensity (I ₁₄₁₀ ) at 410 cm ⁻¹ is quantified. Here, the absorption band of 1340 cm ⁻¹ is ωCH ₂ pitch vibration, which indicates the presence of the trans isomer, and its intensity quantitatively indicates the concentration of the trans isomer, that is, the state of strong orientation in which the polyester molecules are stretched. Is. The absorption band of 1410 cm ⁻¹ is C = C stretching vibration, and the absorption intensity in in-plane rotation is constant, so that the absorption intensity is normalized as a reference band. Further, the orientation parameter Z is represented by the following formula, and the orientation distribution is measured in the same manner in the range of 0 ° to 170 ° by in-plane rotation every 10 ° starting from the orientation axis direction of the biaxially stretched polyester film. To do. The direction of the orientation axis of the polyester substrate is set so that the polarizing plate i and the polarizing plate ii are in a crossed Nicol state on the light source, and the polyester substrate is further installed between the polarizing plates i and ii. The direction parallel to the absorption axis of the polarizing plate ii when the brightness was lowest when the polyester substrate was rotated was taken as the orientation direction of the polyester film.
Z = I ₁₃₄₀ / I ₁₄₁₀
The maximum value among the 18 orientation parameters Y thus measured was Z _max , the minimum value was Z _min , and Z _max / Z _min was the degree of orientation (X) of the polyester substrate.

<Measurement of change in ellipticity and standard deviation of change in ellipticity>
Adhesive glass was bonded to the retardation layer side of the biaxially stretched polyester substrate with retardation produced in Example 1, and the functional layer (λ / 4 layer) was transferred to glass to produce a sample. Using the RETS-100 made by Otsuka Electronics Co., Ltd., a sample with only the functional layer (λ / 4 layer), the angle formed by the absorption axis of the polarizer and the slow axis of the functional layer (λ / 4 layer) is 45 degrees. The ellipticity was measured after installation.
In addition, the standard deviation is an ellipse obtained by measuring the ellipticity at 16 points, which is an intersection when a 10 × 10 cm laminate is used as a sample, and lines are provided at intervals of 2 cm vertically and horizontally, and measured only by the functional layer. The change from the rate was calculated, and the standard deviation was obtained.

<Appearance evaluation of functional layer uniformity>
The appearance evaluation of the uniformity of the functional layer was performed as follows.
A polarizer, a substrate having birefringence in the plane, a functional layer (λ / 4 layer), and an analyzer are installed in the order shown in FIG. 3, and the absorption axis and the slow axis are set at the angles described in Examples / Comparative Examples. installed.
Two people who can observe the functional layer without Nizimura, some Nijimura can be seen, but one point that can observe the functional layer, 0 points that Nijimura is strong and cannot observe the functional layer, 20 people will evaluate The average score was calculated.
The evaluation criteria are as follows.
◎: Average point is 1.5 points or more ○: Average point is 1.0 point or more and less than 1.5 points ×: Average point is less than 1.0 point

[Examples 2 to 4, 6 to 10, and Comparative Examples 1 to 3]
<Preparation of substrate A having birefringence in the plane>
The polyethylene terephthalate material was melted at 290 ° C., extruded through a film-forming die, into a sheet form, closely adhered onto a water-cooled and cooled rotating quenching drum, and cooled to produce an unstretched film. This unstretched film is preheated at 120 ° C. for 1 minute in a biaxial stretching test apparatus, and then stretched at 120 ° C. to a stretch ratio of 4.5 times, and then the stretch direction is a stretch ratio in the direction of 90 degrees. Stretching was performed at 1.5 times to obtain a biaxially stretched polyester base material having the following characteristics.
Thickness: 60 μm
Degree of orientation: 5.5 (standard deviation of in-plane ellipticity change: 0.23)
Retardation (Re) of wavelength 590 nm: 5400
nx (590 nm) = 1.70
ny (590 nm) = 1.61
Δn (590 nm) = 0.09

<Preparation of base material B having in-plane birefringence>
The stretch ratio of the base material A having birefringence in the plane was changed to obtain a base material B having birefringence in the plane.
Thickness: 90μm
Orientation degree: 3.8
Retardation (Re) at a wavelength of 590 nm: 5400 (standard deviation of in-plane ellipticity change: 1.24)
nx (590 nm) = 1.68
ny (590 nm) = 1.62
Δn (590 nm) = 0.06

<Preparation of substrate C having birefringence in the plane>
The stretch ratio of the base material A having birefringence in the plane was changed to obtain a base material C having birefringence in the plane.
Thickness: 180μm
Orientation degree: 2.2
Retardation (Re) at a wavelength of 590 nm: 5400 (standard deviation of in-plane ellipticity change: 2.12)
nx (590 nm) = 1.66
ny (590 nm) = 1.63
Δn (590 nm) = 0.03

<Preparation of functional layer (λ / 4 layer)>
An alignment layer forming coating solution containing a photodimerization reaction type photo-alignment material (trade name: ROP-103, manufactured by Lorick) as a photo-alignment material is applied onto an isotropic glass substrate by a spin coater. Then, it was dried to form an alignment layer forming layer having a thickness of 0.1 μm. Furthermore, the alignment layer was obtained by irradiating polarized ultraviolet rays through a wire grid.
Next, liquid crystal dissolved in a solvent (manufactured by Merck & Co., Inc., licensee (registered trademark) RMS03-013C (trade name)) is applied with a spin coater, dried in an oven (liquid crystal alignment), and then cooled to near room temperature. Then, it was cured with ultraviolet rays to obtain a retardation layer (λ / 4 layer) which is a liquid crystal layer having a thickness of 1 μm.

A base material having birefringence in the plane and a functional layer (produced on isotropic glass) are separately produced, and the angle is set as described in Table 1 and Table 2, and the change in ellipticity, and The standard deviation of the change in ellipticity was measured.
In addition to the above test, in the same manner as in Example 1, with respect to each substrate, the angle formed by the polarizer absorption axis and the substrate slow axis is the angle described in Table 1 or Table 2, Similar results were obtained when a retardation layer (λ / 4 layer) was provided by coating.
The results are shown in Tables 1 and 2 below.

[Example 5]
Table 1 below shows the results of an appearance inspection performed in the same manner as in Example 1 except that the light source used for the appearance inspection was changed from white LED to CCFL.

As shown in Table 1 and Table 2, in a laminate in which a functional layer having birefringence and a base material having birefringence in a plane are laminated, the ellipticity measured only by the functional layer and measured by the laminate When the ratio (X / Y) of the degree of orientation (X) of the substrate to the change rate (Y%) of the ellipticity is 1 or more, it became possible to inspect the uniformity of the functional layer by visual inspection. . The inspection was particularly suitable when a white LED was used as the light source.
On the other hand, as shown in Comparative Example 1, when X / Y was less than 1, visual inspection could not be performed.

  10: laminate of the present invention, 12: substrate, 14: alignment film, 16: λ / 4 layer, 20: liquid crystal display device of the present invention, 22: protective film, 24: polarizer, 26: protective film, 28 : Λ / 4 layer, 32: polarizer, 34: base material, 36: functional layer, 38: polarizer, 130: conventional liquid crystal display device, 132: protective film, 134: polarizer, 136: protective film, 138 : Λ / 4 layer

Claims (10)

It is a laminate in which a functional layer having birefringence and a substrate having birefringence in a plane are laminated,
The orientation degree of the substrate is X,
When the ellipticity measured only in the functional layer and the change rate of the ellipticity measured in the laminate are Y%,
A laminate having X / Y of 1 or more.   The functional layer is a ¼ wavelength layer that imparts a phase difference of ¼ wavelength to transmitted light, or a ½ wavelength layer that imparts a phase difference of ½ wavelength to transmitted light. 1. The laminate according to 1.   The laminate according to claim 1, wherein the functional layer is a functional layer containing a liquid crystal polymer.   The laminated body in any one of Claims 1-3 in which the said base material consists of polyester.   The laminate according to any one of claims 1 to 4, wherein the substrate is made of polyethylene terephthalate or polyethylene naphthalate.   The laminate according to any one of claims 1 to 5, wherein the standard deviation of the in-plane ellipticity change is 2.5% or less.   The laminated body in any one of Claims 1-6 whose retardation of the said base material is 3,000 nm or more. It has the laminate according to any one of claims 1 to 7 and a polarizer,
Display device.   The inspection method characterized by evaluating the uniformity of a functional layer using the laminated body in any one of Claims 1-7.   Evaluation is performed by appearance evaluation using transmitted light, and the transmitted light is light that has passed through a polarizer, a laminate, and an analyzer from a light source, and the polarizer is a surface on which a functional layer of a base material is provided. The inspection method according to claim 9, wherein the light source is a white LED.