JP2022025963A - Liquid crystal display protection plate, liquid crystal display protection plate having curved surface and method for manufacturing the same - Google Patents

Abstract

To provide a liquid crystal display protection plate capable of suppressing the reduction of visibility when observing the liquid crystal display protection plate on a liquid crystal screen through a polarizing filter.SOLUTION: A liquid crystal display protection plate includes a resin plate including a retardation control layer laminated on at least one surface of a base material layer. The retardation control layer having an acid anhydride unit, an imide unit or a lactone ring unit in a main chain includes a transparent thermoplastic resin (A) having a Tg of 135-180°C, a photoelastic coefficient absolute value of 10.0×10-12/Pa or less and an orientation birefringence absolute value of 10.0×10-4-100.0×10-4; the base material layer includes a transparent thermoplastic resin (B) having a photoelastic coefficient absolute value of 10.0×10-12/Pa or less and an orientation birefringence absolute value of less than 10.0×10-4; the Tg of the retardation control layer is higher than that of the base material layer; the thickness of the base material layer is larger than the total thickness of the retardation control layer; and the Re value of the resin plate is 50-330 nm.SELECTED DRAWING: Figure 1

Description

The present invention relates to a liquid crystal display protective plate, a liquid crystal display protective plate with a curved surface, and a method for manufacturing the same.

In a liquid crystal display or a touch panel display in which a liquid crystal display and a touch panel are combined, a protective plate may be provided on the front side thereof in order to prevent scratches on the surface. In the present specification, this protective plate is referred to as a "liquid crystal display protective plate".
The liquid crystal display protective plate includes a resin plate composed of at least one thermoplastic resin layer and, if necessary, a cured film formed on at least one surface of the resin plate.

Patent Document 1 discloses a scratch-resistant resin plate that includes a methacrylic resin plate and a cured film formed on at least one of the surfaces thereof and is suitable as a display window protection plate for a portable information terminal (scratch-resistant resin plate). Claims 1, 2, 7, paragraph 0010, etc.). Patent Document 2 describes a polycarbonate system for a liquid crystal display cover including a laminated board in which a methacrylic resin layer is laminated on one surface of a polycarbonate resin layer and a cured film formed on the methacrylic resin layer of the laminated board. A resin laminate is disclosed (claim 1, paragraph 0008, etc.).
The methacrylic resin used in Patent Document 1 is a general methacrylic resin (non-denatured methacrylic resin) having no ring structure unit.

The liquid crystal display protective plate is installed on the front side (viewer side) of the liquid crystal display, and the viewer sees the screen of the liquid crystal display through this protective plate. Here, since the liquid crystal display protective plate hardly changes the polarization property of the emitted light from the liquid crystal display, when the screen is viewed through a polarizing filter such as polarized sunglasses, the angle formed by the polarization axis of the emitted light and the transmission axis of the polarizing filter is formed. In some cases, the screen becomes dark and the visibility of the image is reduced (blackout phenomenon).

Therefore, a liquid crystal display protective plate capable of suppressing a decrease in visibility of an image when viewing the screen of a liquid crystal display through a polarizing filter has been studied. For example, Patent Document 3 comprises a scratch-resistant resin plate having a cured film formed on at least one surface of the resin plate, and has an in-plane retardation value (also referred to as “Re value”) of 85 to 300 nm. A liquid crystal display protective plate is disclosed (claim 1).

Japanese Unexamined Patent Publication No. 2004-299199 Japanese Unexamined Patent Publication No. 2006-103169 Japanese Unexamined Patent Publication No. 2010-0857978 Japanese Unexamined Patent Publication No. 2018-103518

In recent years, in applications such as in-vehicle car navigation systems and display audio, displays having been subjected to shape processing such as curved surface processing have been developed from the viewpoint of design and visibility. For a display having a curved surface, a liquid crystal display protective plate with a curved surface matching the shape is used. A cured film is formed on a flat resin plate obtained by extrusion molding, if necessary, and then thermoforming such as press molding, vacuum forming, and pressure molding is performed to obtain a curved liquid crystal display protective plate. Can be manufactured. It is preferable that the resin plate included in the liquid crystal display protective plate has a Re value within a preferable range both before and after thermoforming, and the variation in the Re value is small.

It is an object of Patent Document 4 to provide a resin laminate (resin plate) which is excellent in thermoformability or printability at a low temperature and suppresses coloring and color unevenness after thermoforming.
In Patent Document 4, an acrylic resin layer is laminated on at least one surface of a polycarbonate resin layer by coextrusion molding, and the heat shrinkage rate in the width direction is -10 to 0%, and the heat shrinkage rate in the extrusion direction is A resin laminate having a Re value of 0 to 10% and a Re value of 1500 nm or less is disclosed (claim 1).
In Patent Document 4, the polycarbonate-based resin has a terminal structure derived from a specific monovalent phenol, so that the glass transition temperature of the polycarbonate-based resin is lowered and thermoformability at a low temperature is possible (paragraph 0018). ..
The resin laminate described in Patent Document 4 preferably has a hard coat layer on the acrylic resin layer (claim 7).

In Patent Documents 3 and 4, the resin plate is preferably a laminated plate in which a methacrylic resin layer is laminated on at least one surface of a polycarbonate-based resin layer (claim 6 of Patent Document 3, paragraph 0090 of Patent Document 4). ). In these laminated plates, for example, the birefringence of the polycarbonate-based resin layer can be adjusted by adjusting the molding conditions according to the thickness of the resin plate, and the Re value of the liquid crystal display protective plate can be adjusted within a suitable range. Yes (paragraph 0036 of Patent Document 3, etc.).

FIG. 7 shows an image diagram showing the relationship between stress and birefringence, and the relationship between orientation birefringence, stress birefringence, and photoelastic coefficient.
The polycarbonate-based resin used in Patent Documents 3 and 4 has a very large absolute value of photoelastic coefficient of 90 × ^10-12 / Pa, and the Re value changes with a slight stress. Therefore, when a polycarbonate resin is used, it is difficult to obtain an optically uniform liquid crystal display protective plate. For example, when observing the liquid crystal display protective plate on the liquid crystal screen through a polarizing filter, color unevenness may be observed due to the variation in the Re value. In particular, after thermoforming, the variation in the Re value of the resin plate tends to increase due to the residual stress generated in the cooling process of thermoforming.

The general methacrylic resin (non-denatured methacrylic resin) used in Patent Document 1 which does not have a ring structure unit has a small absolute value of photoelastic coefficient of 3.2 × ^10-12 / Pa. , Re value does not change easily due to stress. Therefore, when a general methacrylic resin having no ring structure unit is used, an optically uniform liquid crystal display protective plate can be obtained. However, since the absolute value of the orientation birefringence of a general methacrylic resin having no ring structure unit is as small as 4.0 × 10 ^-4 , the Re value of the obtained liquid crystal display protective plate depends on the thickness. Tends to be as small as about 20 nm. Therefore, when observing the liquid crystal display protection plate on the liquid crystal screen through the polarizing filter, blackout occurs in which the screen becomes pitch black depending on the angle between the polarizing axis of the emitted light and the transmission axis of the polarizing filter, and the image is visually recognized. There is a risk of deterioration of sex.

Further, in general, when the Re value of the liquid crystal display protection plate is larger than a suitable range, the difference in light transmittance of each wavelength in the visible light region becomes large when visually recognized through a polarizing filter, and various colors can be seen. Visibility may be reduced (colored phenomenon).

The present invention has been made in view of the above circumstances, and the in-plane retardation value (Re value) is within a suitable range both before and after thermoforming, the variation is small, and the liquid crystal filter is used. It is an object of the present invention to provide a liquid crystal display protective plate capable of suppressing deterioration of visibility such as color unevenness, blackout, and coloring when observing the liquid crystal display protective plate on the liquid crystal screen.

The present invention provides the following [1] to [14], a liquid crystal display protective plate, a curved liquid crystal display protective plate, and a method for manufacturing the same.
[1] A flat resin plate having a phase difference adjusting layer laminated on at least one surface of the base material layer is included.
The phase difference adjusting layer has at least one ring structure unit selected from the group consisting of an acid anhydride unit, an imide unit including a ring structure, and a lactone ring unit in the main chain, and has a glass transition temperature (Tg _A0 ). ) Is 135 to 180 ° C., the absolute value of the photoelastic coefficient ( _CA ) is 10.0 × ^10-12 / Pa or less, and the test piece having a width of 20 mm, a length of 40 mm, and a thickness of 1 mm is subjected to a glass transition temperature. Absolute value of orientation double refraction (Δn _A ) obtained by uniaxially stretching at a rate of 3 mm / min at a higher temperature of 10 ° C. and measuring the in-plane retardation value of the central portion of the test piece. Contains the transparent thermoplastic resin (A) of 10.0 × 10 ^-4 to 100.0 × 10 ^-4 .
The base material layer has a photoelastic coefficient ( _CB ) of 10.0 × ^10-12 / Pa or less, and a test piece having a width of 20 mm, a length of 40 mm, and a thickness of 1 mm is placed at 10 ° C. above the glass transition temperature. The absolute value of the orientation birefringence (Δn _B ) obtained by uniaxially stretching at a high temperature of 3 mm / min at a stretching rate of 100% and measuring the in-plane retardation value of the central portion of the test piece is 10. Containing transparent thermoplastic resin (B) less than 0 × 10 ^-4 ,
When the glass transition temperature of the retardation adjusting layer is Tg _A (° C.) and the glass transition temperature of the substrate layer is Tg _B (° C.), Tg _A > Tg _B.
When the total thickness of the retardation adjusting layer is _TA and the thickness of the base material layer is _TB , _TA < _TB .
A liquid crystal display protective plate having an in-plane retardation value of 50 to 330 nm of the flat resin plate.

[2] The transparent thermoplastic resin (A) is a copolymer having 30 to 99% by mass of the ring structure unit and 70 to 1% by mass of a vinyl-based monomer unit, and is a liquid crystal display protective plate of [1]. ..
[3] The liquid crystal display protective plate of [1] or [2], wherein the transparent thermoplastic resin (A) is a methacrylic resin having the ring structure unit and the methyl methacrylate unit.
[4] The liquid crystal display protective plate according to any one of [1] to [3], wherein Tg _A -Tg _B is 20 ° C. or higher.

[5] The liquid crystal display protective plate according to any one of [1] to [4], wherein the flat resin plate has a standard deviation of a retardation value in a plane within a range of 17 cm in width and 22 cm in length of 15.0 nm or less. ..
[6] When the flat resin plate is heated to a temperature of Tg _B or more and Tg _A or less, the absolute value of the rate of change of the in-plane retardation value after heating with respect to before heating is 50% or less [1]. A liquid crystal display protective plate according to any one of [5].
[7] When the flat resin plate is heated to a temperature of Tg _B or more and Tg _A or less, the standard deviation of the in-plane retardation value within the range of width 17 cm and length 22 cm is 25.0 nm or less. [1] ]-[6] Liquid crystal display protective plate.

[8] A resin plate having a curved surface in which a phase difference adjusting layer is laminated on at least one surface of a base material layer is included.
The phase difference adjusting layer has at least one ring structure unit selected from the group consisting of an acid anhydride unit, an imide unit including a ring structure, and a lactone ring unit in the main chain, and has a glass transition temperature (Tg _A0 ). ) Is 135 to 180 ° C., the absolute value of the photoelastic coefficient ( _CA ) is 10.0 × ^10-12 / Pa or less, and the test piece having a width of 20 mm, a length of 40 mm, and a thickness of 1 mm is subjected to a glass transition temperature. Absolute value of orientation double refraction (Δn _A ) obtained by uniaxially stretching at a rate of 3 mm / min at a higher temperature of 10 ° C. and measuring the in-plane retardation value of the central portion of the test piece. Contains the transparent thermoplastic resin (A) of 10.0 × 10 ^-4 to 100.0 × 10 ^-4 .
The base material layer has a photoelastic coefficient ( _CB ) of 10.0 × ^10-12 / Pa or less, and a test piece having a width of 20 mm, a length of 40 mm, and a thickness of 1 mm is placed at 10 ° C. above the glass transition temperature. The absolute value of the orientation birefringence (Δn _B ) obtained by uniaxially stretching at a high temperature of 3 mm / min at a stretching rate of 100% and measuring the in-plane retardation value of the central portion of the test piece is 10. Containing transparent thermoplastic resin (B) less than 0 × 10 ^-4 ,
When the glass transition temperature of the retardation adjusting layer is Tg _A (° C.) and the glass transition temperature of the substrate layer is Tg _B (° C.), Tg _A > Tg _B.
When the total thickness of the retardation adjusting layer is _TA and the thickness of the base material layer is _TB , _TA < _TB .
A liquid crystal display protective plate with a curved surface, wherein the in-plane retardation value of the resin plate having a curved surface is 50 to 330 nm.

[9] The transparent thermoplastic resin (A) is a copolymer having 30 to 99% by mass of the ring structure unit and 70 to 1% by mass of a vinyl-based monomer unit, and is a liquid crystal display with a curved surface according to [8]. Protective plate.
[10] The transparent thermoplastic resin (A) is a liquid crystal display protective plate with a curved surface according to [8] or [9], which is a methacrylic resin having the ring structure unit and the methyl methacrylate unit.
[11] A liquid crystal display protective plate with a curved surface according to any one of [8] to [10], wherein Tg _A -Tg _B is 20 ° C. or higher.
[12] The resin plate having the curved surface has a curved surface according to any one of [8] to [11], wherein the standard deviation of the in-plane retardation value within the range of 17 cm in width and 22 cm in length is 25.0 nm or less. Liquid crystal display protection plate.

[13] The liquid crystal display protective plate according to any one of [1] to [7] or the liquid crystal display protective plate with a curved surface according to any one of [8] to [12], which has a cured film on at least one outermost surface.

[14] A step of forming a flat resin plate in which the phase difference adjusting layer is laminated on at least one surface of the base material layer.
The method for manufacturing a liquid crystal display protective plate with a curved surface according to any one of [8] to [12], which comprises a step of heating the flat resin plate to a temperature of Tg _B or more and Tg _A or less and thermoforming into a shape having a curved surface. ..

According to the present invention, the in-plane retardation value (Re value) is within a suitable range both before and after thermoforming, the variation is small, and the liquid crystal display on the liquid crystal screen is protected through a polarizing filter. It is possible to provide a liquid crystal display protective plate capable of suppressing deterioration of visibility such as color unevenness, blackout, and coloring when observing the plate.

It is a schematic sectional view of the liquid crystal display protection plate of 1st Embodiment which concerns on this invention. It is a schematic cross-sectional view of the liquid crystal display protection plate of the 2nd Embodiment which concerns on this invention. It is a schematic cross-sectional view of the liquid crystal display protection plate containing a cured film of one Embodiment which concerns on this invention. It is a schematic diagram of the manufacturing apparatus of the extruded plate of one Embodiment which concerns on this invention. It is a schematic perspective view of the resin type used in the section of [Example]. It is a schematic cross-sectional view for demonstrating the evaluation method of the molding ratio in the section of [Example]. It is an image diagram which shows the relationship between stress and birefringence, and the relationship between orientation birefringence, stress birefringence, and photoelastic coefficient.

Generally, for thin film moldings, the terms "film", "sheet", or "plate" are used, depending on the thickness, but there is no clear distinction between them. The "resin plate" referred to in the present specification shall include a "resin film" and a "resin sheet".
In the present specification, the glass transition temperature of a general material is represented by "Tg".

[Liquid crystal display protection plate]
The present invention relates to a liquid crystal display protective plate. The liquid crystal display protective plate can be suitably used for protecting a liquid crystal display and a touch panel display in which a liquid crystal display and a touch panel are combined.
The liquid crystal display protective plate of the present invention includes a flat resin plate in which a phase difference adjusting layer is laminated on at least one surface of a base material layer. The flat resin plate is preferably an extruded plate.
The liquid crystal display protective plate of the present invention described above can be thermally molded to manufacture a liquid crystal display protective plate with a curved surface.
The liquid crystal display protective plate with a curved surface of the present invention includes a resin plate having a curved surface in which a phase difference adjusting layer is laminated on at least one surface of a base material layer. The resin plate having a curved surface is a thermoformed plate obtained by thermoforming a flat resin plate.
The liquid crystal display protective plate and the liquid crystal display protective plate with a curved surface of the present invention can have a cured film on at least one of the outermost surfaces, if necessary.
The liquid crystal display protective plate having a cured film is also referred to as a "cured film-containing liquid crystal display protective plate".

In the liquid crystal display protective plate and the liquid crystal display protective plate with a curved surface of the present invention, the phase difference adjusting layer contains a transparent thermoplastic resin (A) having specific optical characteristics, and the base material layer is transparent having specific optical characteristics. Contains the thermoplastic resin (B).
The transparent thermoplastic resin (A) is a resin having at least one ring structure unit selected from the group consisting of an acid anhydride unit, an imide unit including a ring structure, and a lactone ring unit in the main chain. The glass transition temperature (Tg _A0 ) of the transparent thermoplastic resin (A) is 135 to 180 ° C.
When the glass transition temperature of the phase difference adjusting layer is Tg _A (° C.) and the glass transition temperature of the substrate layer is Tg _B (° C.), Tg _A > Tg _B.
When the total thickness of the phase difference adjusting layer is _TA and the thickness of the base material layer is _TB , _TA < _TB .

The in-plane retardation value (also referred to as “Re value”) of the flat resin plate and the resin plate having a curved surface is 50 to 330 nm.
The flat resin plate preferably has a standard deviation of the Re value within a range of 17 cm in width and 22 cm in length of 15.0 nm or less.
When the flat resin plate is heated to a temperature of Tg _B or more and Tg _A or less, the absolute value of the rate of change of the Re value after heating with respect to that before heating is preferably 50% or less.
When the flat resin plate is heated to a temperature of Tg _B or more and Tg _A or less, the standard deviation of the Re value within the range of 17 cm in width and 22 cm in length is preferably 25.0 nm or less.
The resin plate having a curved surface preferably has a standard deviation of the Re value within a range of 17 cm in width and 22 cm in length of 25.0 nm or less.

1 and 2 are schematic cross-sectional views of the liquid crystal display protective plate of the first and second embodiments according to the present invention. FIG. 3 is a schematic cross-sectional view of a liquid crystal display protective plate containing a cured film according to an embodiment of the present invention. In the figure, reference numerals 1 and 2 are liquid crystal display protective plates, reference numeral 3 is a cured film-containing liquid crystal display protective plate, reference numerals 16A and 16B are flat resin plates, reference numeral 21 is a retardation adjustment layer, reference numeral 22 is a substrate layer, and reference numeral 31 Indicates a cured film, respectively.
The liquid crystal display protective plate 1 of the first embodiment is composed of a flat resin plate 16A having a two-layer structure in which a retardation adjusting layer 21 is laminated on one side of a base material layer 22.
The liquid crystal display protective plate 2 of the second embodiment is composed of a flat resin plate 16B having a three-layer structure in which the phase difference adjusting layer 21 is laminated on both surfaces of the base material layer 22.
The cured film-containing liquid crystal display protective plate 3 has a cured film 31 formed on at least one surface of a flat resin plate 16B having a three-layer structure in which retardation adjusting layers 21 are laminated on both sides of a base material layer 22. .. In the example shown in FIG. 3, the cured film 31 is formed on both surfaces of the flat resin plate 16B.
The configuration of the liquid crystal display protective plate is not limited to the illustrated example, and the design can be appropriately changed as long as the gist of the present invention is not deviated.
A flat liquid crystal display protective plate as shown in FIGS. 1 to 3 can be thermoformed to manufacture a curved liquid crystal display protective plate.

In the flat resin plate and the resin plate having a curved surface, the phase difference adjusting layer has an absolute value of the photoelastic coefficient ( _CA ) of 10.0 × ^10-12 / Pa or less, and has a width of 20 mm, a length of 40 mm, and a thickness of 1 mm. The test piece was uniaxially stretched at a rate of 3 mm / min at a temperature 10 ° C. higher than the glass transition temperature at a stretching rate of 100%, and the in-plane retardation value of the central portion of the test piece after uniaxial stretching was measured and obtained. It contains a transparent thermoplastic resin (A) having an absolute value of the orientation birefringence (Δn _A ) of 10.0 × 10 ^-4 to 100.0 × 10 ^-4 .

"Ritalization" is the phase difference between the light in the direction of the main chain of the molecule and the light in the direction perpendicular to it. Generally, a polymer can be obtained by heating and melting to obtain an arbitrary shape, but it is known that retardation occurs due to stress generated in the process of heating and cooling and orientation of molecules. In addition, in this specification, "retamination" means in-plane retardation unless otherwise specified.

Generally, the Re value of the resin plate is represented by the following formula (i).
[Re value of resin plate] = [birefringence (ΔN)] × [thickness (d)] ... (i)
Birefringence (ΔN) is expressed by the following equation (ii).
[Birerefringence] = [Stress birefringence] + [Orientation birefringence] ... (ii)
The stress birefringence and the orientation birefringence are represented by the following equations (iii) and (iv), respectively.
[Stress birefringence] = [photoelastic coefficient (C)] × [stress] ... (iii)
[Orientation birefringence] = [Inherent birefringence] x [Orientation degree] ... (iv)
In equation (iv), the degree of orientation is a value in the range of 0 to 1.0.
FIG. 7 shows an image diagram showing the relationship between stress and birefringence, and the relationship between orientation birefringence, stress birefringence, and photoelastic coefficient.

In the present invention, the optical properties of the transparent thermoplastic resin (A) and the transparent thermoplastic resin (B) are specified by the photoelastic coefficient and orientation birefringence shown in FIG. 7 as a model.
The liquid crystal display protective plate and the liquid crystal display protective plate with a curved surface of the present invention include a phase difference adjusting layer containing the transparent thermoplastic resin (A) having the above-mentioned specific optical characteristics, so that the liquid crystal on the liquid crystal screen is passed through a polarizing filter. It is possible to suppress deterioration of visibility such as color unevenness and blackout when observing the display protective plate.

In the present specification, the "Re value of the resin plate" is an average value of the Re values of about 110,000 birefringent pixels within the measurement range of 17 cm in width and 22 cm in length, unless otherwise specified. Unless otherwise specified, the "standard deviation of the Re value of the resin plate" is the standard deviation of the Re value of about 110,000 birefringent pixels within the measurement range of 17 cm in width and 22 cm in length.
The average value and standard deviation of the Re value can be measured, for example, by using a retardation measuring instrument "WPA-100-L" manufactured by Photonic Lattice Co., Ltd., by the method described in the section [Example] below.

The Re value of the flat resin plate and the resin plate having a curved surface is 50 to 330 nm, preferably 70 to 250 nm, more preferably 80 to 200 nm, and particularly preferably 90 to 150 nm. If the Re value is less than the above lower limit, blackout may occur when observing the liquid crystal display protection plate on the liquid crystal screen through the polarizing filter, regardless of the relationship between the polarization axis of the emitted light and the transmission axis of the polarization filter. There is. When the Re value exceeds the above upper limit value, when visually recognized through a polarizing filter, the difference in light transmittance of each wavelength in the visible light region becomes large, and various colors may be seen and the visibility may be deteriorated (coloring phenomenon). ..

It is preferable that the standard deviation of the Re value of the flat resin plate and the resin plate having a curved surface is small because the variation of the Re value is small. If the standard deviation of the Re value is sufficiently small, when the liquid crystal display protective plate on the liquid crystal screen is observed through the polarizing filter, the color unevenness caused by the variation of the Re value is suppressed and the visibility is improved.
The standard deviation of the Re value of the flat resin plate is preferably 15.0 nm or less, more preferably 10.0 nm or less, still more preferably 7.0 nm or less, particularly preferably 5.0 nm or less, and most preferably 4.0 nm or less. be.
The standard deviation of the Re value of the resin plate having a curved surface is preferably 25.0 nm or less, more preferably 20.0 nm or less, particularly preferably 15.0 nm or less, and most preferably 10.0 nm or less.

It is preferable that the Re value and the standard deviation of the Re value of the flat resin plate do not change significantly by thermoforming. In the present invention, the thermoforming temperature is preferably Tg _B or more and Tg _A or less, and more preferably Tg _B or more and less than Tg _A.
When the flat resin plate is heated to a temperature of Tg _B or more and Tg _A or less, the absolute value of the rate of change of the Re value after heating with respect to that before heating is preferably 50% or less, more preferably 45% or less, still more preferably. It is 40% or less, particularly preferably 35% or less, and most preferably 30% or less.
The rate of change of the Re value after heating with respect to that before heating is expressed by the following formula.
[Rate of change of Re value after heating] (%) = [([Re value after heating]-[Re value before heating]) / [Re value before heating]] × 100

When the flat resin plate is heated to a temperature of Tg _B or more and Tg _A or less, the standard deviation of the Re value within the range of 17 cm in width and 22 cm in length is preferably 25.0 nm or less, more preferably 20.0 nm or less. It is particularly preferably 15.0 nm or less, and most preferably 10.0 nm or less.

The total thickness (d) of the flat resin plate and the resin plate having a curved surface is not particularly limited, and is preferably 0.2 to 6.0 mm, more preferably 0.3 to 4.0 mm, and particularly preferably 0.4 to. It is 3.0 mm. If it is too thin, the rigidity of the liquid crystal display protective plate may be insufficient, and if it is too thick, it may hinder the weight reduction of the liquid crystal display or the touch panel display including the liquid crystal display.

(Phase difference adjustment layer)
The flat resin plate and the resin plate having a curved surface include a phase difference adjusting layer. The phase difference adjusting layer is a layer that mainly determines the Re value of the liquid crystal display protective plate, and contains a transparent thermoplastic resin (A) having specific optical characteristics.

<Transparent thermoplastic resin (A)>
The absolute value of the photoelastic coefficient (CA) of the transparent thermoplastic resin ( _A ) is 10.0 × ^10-12 / Pa or less, preferably 8.0 × ^10-12 / Pa or less, more preferably 6. It is 0.0 × ^10-12 / Pa or less, particularly preferably 5.0 × ^10-12 / Pa or less, and most preferably 4.0 × ^10-12 / Pa or less. When the absolute value of the photoelastic coefficient ( _CA ) is not more than the above upper limit value, the stress birefringence due to the residual stress generated during the molding process such as extrusion molding is small (see FIG. 7), and the liquid crystal display protective plate. The standard deviation of the Re value of can be reduced. As a result, when the liquid crystal display protective plate on the liquid crystal screen is observed through the polarizing filter, the color unevenness caused by the variation of the Re value is suppressed, and the visibility is improved.

The absolute value of the orientation double refraction (Δn _A ) of the transparent thermoplastic resin (A) is 10.0 × 10 ^-4 to 100.0 × 10 ^-4 , preferably 20.0 × 10 ^-4 to 90. It is 0 × 10 ^-4 , more preferably 30.0 × 10 ^-4 to 70.0 × 10 ^-4 , and particularly preferably 35.0 × 10 ^-4 to 60.0 × 10 ^-4 . When the absolute value of the orientation birefringence (Δn _A ) of the transparent thermoplastic resin (A) is within the above range, the Re value of the liquid crystal display protective plate can be controlled within an appropriate range.
Since the orientation birefringence depends on the degree of orientation of the polymer, it is affected by manufacturing conditions such as molding conditions and stretching conditions. Unless otherwise specified in the present specification, "orientation birefringence" shall be measured by the method described in the section [Example] below.

In the present invention, the transparent thermoplastic resin (A) is a resin having at least one ring structure unit selected from the group consisting of an acid anhydride unit, an imide unit containing a ring structure, and a lactone ring unit in the main chain. be. The transparent thermoplastic resin (A) can be used alone or in combination of two or more.
When a resin having at least one of the above ring structure units in the main chain is used as the transparent thermoplastic resin (A), the glass transition temperature (Tg _A0 ) of the transparent thermoplastic resin (A) is increased to Tg _A >. It is easy to realize Tg _B. Further, the orientation birefringence of the phase difference adjusting layer can be increased without changing the photoelastic coefficient so much.

As the transparent thermoplastic resin (A), a copolymer containing 30 to 99% by mass of a ring structure unit and 70 to 1% by mass of one or more vinyl-based monomer units is preferable.
The content of the ring structure unit in the transparent thermoplastic resin (A) is more preferably 50 to 95% by mass, and particularly preferably 60 to 90% by mass. When the content of the ring structure unit in the transparent thermoplastic resin (A) is 30% by mass or more, the glass transition temperature (Tg _A0 ) of the transparent thermoplastic resin (A) is effectively increased, and the orientation birefringence is improved. It can be effectively increased. When the content of the vinyl-based monomer unit in the transparent thermoplastic resin (A) is 1% by mass or more, the toughness of the liquid crystal display protective plate can be enhanced.
The glass transition temperature (Tg _A0 ) of the transparent thermoplastic resin (A) is 135 to 180 ° C., preferably 140 to 170 ° C., and more preferably 145 to 160 ° C.

The vinyl-based monomer is not particularly limited, and known ones can be used. For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate. Butyl, (meth) s-butyl acrylate, t-butyl (meth) acrylate, amyl (meth) acrylate, i-amyl (meth) acrylate, n-hexyl (meth) acrylate, (meth) acrylic 2-Ethylhexyl acid, pentadecyl (meth) acrylate, dodecyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-2-ethyl acrylate Hydroxyethyl, 2-ethoxyethyl (meth) acrylate, glycidyl (meth) acrylate, allyl (meth) acrylate, cyclohexyl (meth) acrylate, norbornenyl (meth) acrylate, and isobonyl (meth) acrylate. (Meta) acrylic acid esters such as; unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid, and itaconic acid; olefins such as ethylene, propylene, 1-butene, isobutylene, and 1-octene; butadiene, isoprene, etc. And conjugated diene such as Milsen; styrene (St), 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-ethylstyrene, 4-tert-butylstyrene, α-methylstyrene, 4-methyl-α- Aromatic vinyl compounds such as methylstyrene; (meth) acrylamide, (meth) acrylonitrile; vinyl acetate, vinylpyridine, vinyl ketone, vinyl chloride, vinylidene chloride, vinylidene fluoride and the like can be mentioned.
In the present specification, (meth) acrylic is a general term for acrylic and methacrylic, and (meth) acrylonitrile is a general term for acrylonitrile and methacrylic nitrile.

As the transparent thermoplastic resin (A), a modified methacrylic resin having one or more of the above ring structure units, a methyl methacrylate (MMA) unit, and, if necessary, one or more other units is preferable.
The method for producing the above-mentioned modified methacrylic resin is not particularly limited, and a known method can be applied. As a production method, a method of copolymerizing a plurality of types of monomers including a monomer having a ring structure, methyl methacrylate (MMA), and other monomers as necessary by a known method, and known methods. Examples thereof include a method of producing a methacrylic resin containing an MMA unit and having no ring structure unit, and then introducing a ring structure into the main chain to form a ring structure unit.
Examples of the polymerization method include a suspension polymerization method, a (continuous) massive polymerization method, a solution polymerization method, a radical polymerization method such as an emulsion polymerization method; and an anion polymerization method.

<Resin with acid anhydride unit>
Examples of the acid anhydride unit include a maleic anhydride unit and a glutaric anhydride unit.

As the maleic anhydride unit, the unit represented by the following formula (1) is preferable.

In formula (1), R ¹¹ and R ¹² are independently hydrogen atoms or organic groups having 1 to 20 carbon atoms. The organic group is not particularly limited as long as it has 1 to 20 carbon atoms, and is, for example, a linear element or a branched alkyl group, a linear element or a branched alkylene group, an aryl group, -OCOCH ₃ groups, and -CN. The group etc. can be mentioned. The organic group may contain a hetero atom such as an oxygen atom.
The organic group preferably has 1 to 10 carbon atoms, and more preferably 1 to 5 carbon atoms.
Particularly preferably, both R ¹¹ and R ¹² are hydrogen atoms. When both R ¹¹ and R ¹² are hydrogen atoms, a copolymer component such as styrene is usually used from the viewpoint of ease of production and adjustment of natural birefringence.

The method for producing the transparent thermoplastic resin (A) having a maleic anhydride unit is not particularly limited, and a known method can be used.
Examples of the transparent thermoplastic resin (A) having a maleic acid anhydride unit include a styrene-maleic acid anhydride copolymer (SMA resin); a styrene-methacrylate ester-maleic acid anhydride copolymer (SMM resin); α. -Methylstyrene-maleic acid anhydride-methacrylate copolymer (αStMM resin) and the like can be mentioned.
Examples of commercially available transparent thermoplastic resins having a maleic anhydride unit include the following products.
SMA resin: Daicel-Evonik's "Plexiglas", Polyscoppe's "XIBOND", "XIRAN", etc.
SMM resin: Denka's "Regisphi" etc.

As the glutaric anhydride unit, a unit represented by the following formula (2) is preferable. As the transparent thermoplastic resin (A), a methacrylic acid resin having a glutaric acid anhydride unit and a methyl methacrylate (MMA) unit can be used, and this methacrylic acid resin is a "glutaric acid anhydride-modified methacrylic acid resin". Alternatively, it is also referred to as "glutaric acid anhydride-modified PMMA".

In the above formula (2), R ²¹ and R ²² are independently hydrogen atoms or alkyl groups having 1 to 5 carbon atoms, preferably methyl groups.

The method for producing a methacrylic resin having a glutaric anhydride unit (glutaric acid anhydride-modified methacrylic resin) is not particularly limited, and a known method can be used. After copolymerizing the unsaturated carboxylic acid monomer and the unsaturated carboxylic acid alkyl ester monomer, the obtained copolymer is heated in the presence of a catalyst as necessary, and dealcoholized and / or dehydrated. A method of carrying out an intramolecular cyclization reaction is preferable.

<Resin having an imide unit including a ring structure>
Examples of the imide unit containing a ring structure include a glutarimide unit, an N-substituted or unsubstituted maleimide unit, and the like, and a glutarimide unit is preferable.
As the glutarimide unit, a unit represented by the following formula (3) is preferable. As the transparent thermoplastic resin (A), a methacrylic resin containing a glutarimide unit and a methyl methacrylate (MMA) unit can be used, and the methacrylic resin is "glutarimide-modified methacrylic resin" or "glutarimide". Also called "modified PMMA".

In the above formula (3), R ³¹ and R ³² are independently hydrogen atoms or methyl groups, preferably methyl groups. R ³³ is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an organic group having 6 to 15 carbon atoms including an aromatic ring, preferably a hydrogen atom or a methyl group. , N-Butyl group, cyclohexyl group, or benzyl group, more preferably a methyl group.

The method for producing a methacrylic resin having a glutarimide unit (glutarimide-modified methacrylic resin) is not particularly limited, and a known method can be used.
Commercially available products of glutarimide-modified methacrylic resin include the following products.
Daicel-Evonik's "Pleximid".

<Resin having a lactone ring unit>
From the viewpoint of ease of manufacture, production yield, structural stability, etc., the lactone ring unit is preferably a 4- to 8-membered ring, more preferably a 5- to 6-membered ring, and particularly preferably a 6-membered ring. be able to. Of these, the 6-membered ring unit represented by the following formula (4) is particularly preferable.
As the transparent thermoplastic resin (A), a methacrylic resin containing a lactone ring unit and a methyl methacrylate (MMA) unit can be used, and the methacrylic resin is a "lactone ring-modified methacrylic resin" or a "lactone ring". Also called "modified PMMA".

In the above formula (4), R ⁴¹ , R ⁴² , and R ⁴³ are each independently a hydrogen atom or an organic group having 1 to 20 carbon atoms. The organic group is not particularly limited as long as it has 1 to 20 carbon atoms, and is, for example, a linear element or a branched alkyl group, a linear element or a branched alkylene group, an aryl group, -OCOCH ₃ groups, and -CN. The group etc. can be mentioned. The organic group may contain a hetero atom such as an oxygen atom.
The organic group preferably has 1 to 10 carbon atoms, and more preferably 1 to 5 carbon atoms.
Particularly preferably, R ⁴² is a methyl group and R ⁴¹ and R ⁴³ are hydrogen atoms.

The method for producing a methacrylic resin having a lactone ring unit (lactone ring-modified methacrylic resin) is not particularly limited, and a known method can be used. A method of performing a lactone cyclization condensation step of obtaining a polymer having a hydroxyl group and an ester group in the molecular chain by the polymerization step and heat-treating the obtained polymer to introduce a lactone ring structure into the polymer is preferable.
Commercially available products of the lactone ring-modified methacrylic resin include the following products.
"Acriview" manufactured by Nippon Shokubai Co., Ltd., etc.

<Characteristics of phase difference adjustment layer>
The general methacrylic resin (non-modified methacrylic resin) and polycarbonate resin having no ring structure unit have a photoelastic coefficient and / or orientation birefringence of the transparent thermoplastic resin (A) used in the present invention. It is out of the specified range.
The polycarbonate resin has a very large absolute value of the photoelastic coefficient of 90 × ^10-12 / Pa, and the Re value changes with a slight stress. Therefore, when a polycarbonate resin is used, it is difficult to obtain an optically uniform liquid crystal display protective plate. For example, when observing the liquid crystal display protective plate on the liquid crystal screen through a polarizing filter, color unevenness may be observed due to the variation in the Re value.
In particular, after thermoforming, the change in the Re value of the resin plate is large compared to before thermoforming, and the variation in the Re value of the resin plate tends to be large. The thermoforming step includes, for example, a step of heating the resin plate, a step of pressing the mold against the heated resin plate, a step of cooling the resin plate in the mold, and a step of taking out the cooled resin plate from the mold. In the cooling process, strain (residual stress) is generated in the resin plate. In a resin plate using a polycarbonate resin having a large absolute value of the photoelastic coefficient, remarkable retardation unevenness occurs due to residual stress generated in the cooling process of thermoforming, and the variation in the Re value of the resin plate tends to be large.

A general methacrylic resin (non-denatured methacrylic resin) having no ring structure unit has a small absolute value of photoelastic coefficient of 3.2 × ^10-12 / Pa, and the Re value does not easily change due to stress. .. Therefore, when a general methacrylic resin having no ring structure unit is used, an optically uniform liquid crystal display protective plate can be obtained. However, since the absolute value of the orientation birefringence of a general methacrylic resin having no ring structure unit is as small as 4.0 × 10 ^-4 , the Re value of the obtained liquid crystal display protective plate depends on the thickness. Tends to be as small as about 20 nm. Therefore, when observing the liquid crystal display protection plate on the liquid crystal screen through the polarizing filter, blackout occurs in which the screen becomes pitch black depending on the angle between the polarizing axis of the emitted light and the transmission axis of the polarizing filter, and the image is visually recognized. There is a risk of deterioration of sex.

The total thickness ( _TA ) of the phase difference adjusting layer is not particularly limited, and is preferably 0.025 to 1.0 mm, more preferably 0.05 to 0.5 mm, particularly preferably 0.05 to 0.4 mm, and most preferably. It is preferably 0.05 to 0.3 mm.

The phase difference adjusting layer is other than the transparent thermoplastic resin (A) having at least one ring structure unit selected from the group consisting of an acid anhydride unit, an imide unit including a ring structure, and a lactone ring unit in the main chain. It can contain one or more other polymers in small amounts. The photoelastic coefficient and orientation birefringence of the other polymer may be within or outside the specification of the transparent thermoplastic resin (A).
The types of other polymers are not particularly limited, and are general methacrylic resins (non-modified methacrylic resins) having no ring structure unit, polycarbonate resins, polyolefins such as polyethylene and polypropylene, polyamides, and polyphenylene sulfides. , Polyether ether ketones, polyesters, polysulfones, polyphenylene oxides, polyimides, polyetherimides, and other thermoplastic resins such as polyacetal; thermocurable resins such as phenolic resins, melamine resins, silicone resins, and epoxy resins. Be done.
Examples of general non-denatured methacrylic acid resins include resins obtained by copolymerizing MMA with a small amount of methyl acrylate.
The content of the transparent thermoplastic resin (A) in the retardation adjusting layer is preferably large, preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 98% by mass or more. The content of the other polymer in the retardation adjusting layer is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 2% by mass or less.

The phase difference adjusting layer can contain various additives, if necessary. Additives include colorants, antioxidants, thermal degradation inhibitors, UV absorbers, light stabilizers, lubricants, mold release agents, polymer processing aids, antistatic agents, flame retardants, light diffusing agents, and matting agents. Examples thereof include rubber components (impact resistance modifiers) such as agents, core-shell particles and block copolymers, and phosphors. The content of the additive can be appropriately set as long as the effect of the present invention is not impaired. For example, the content of the antioxidant is 0.01 to 1 part by mass, the content of the ultraviolet absorber is 0.01 to 3 parts by mass, and the light stabilizer is 100 parts by mass with respect to 100 parts by mass of the constituent resin of the retardation adjusting layer. The content is preferably 0.01 to 3 parts by mass, and the content of the lubricant is preferably 0.01 to 3 parts by mass.
When another polymer and / or an additive is added to the retardation adjusting layer, the timing of addition may be during or after the polymerization of the transparent thermoplastic resin (A).

The phase difference adjusting layer may be a resin layer made of a resin composition containing a transparent thermoplastic resin (A) and a known rubber component (impact resistance modifier). Examples of the rubber component include multi-layer polymer particles having a core-shell structure, a rubber-like polymer having a salami structure, and a block polymer. The rubber component may contain a diene-based monomer unit, an alkyl acrylate-based monomer unit, and the like. From the viewpoint of the transparency of the phase difference adjusting layer, it is preferable that the difference between the refractive index of the rubber component and the refractive index of the transparent thermoplastic resin (A) as the main component is smaller.

The glass transition temperature (Tg _A ) of the phase difference adjusting layer is not particularly limited as long as Tg _A > Tg _B is satisfied. It is preferably 135 to 180 ° C, more preferably 140 to 170 ° C, particularly preferably 145 to 165 ° C, and most preferably 145 to 160 ° C.
The "glass transition temperature (Tg _A ) of the phase difference adjusting layer" is the entire constituent material of the phase difference adjusting layer composed of one or more kinds of transparent thermoplastic resin (A) and, if necessary, one or more kinds of arbitrary components. The glass transition temperature of.

The difference between Tg _A and Tg _B (Tg _A − Tg _B ) is preferably 20 ° C. or higher, more preferably 25 ° C. or higher, still more preferably 30 ° C. or higher, particularly preferably 35 ° C. or higher, and most preferably 40 ° C. or higher. Is.
When Tg _A − Tg _B is 20 ° C. or higher, the resin plate can be satisfactorily thermoformed while suppressing the change in the Re value of the resin plate, as described in detail below, and the obtained curved surface is further formed. It is possible to suppress the deformation of the liquid crystal display protective plate.

In the present invention, thermoforming can be preferably performed at a temperature of Tg _B or more and Tg _A or less.
It is more preferable to perform thermoforming at a temperature of Tg _B + 10 ° C to Tg _B + 30 ° C. Within this temperature range, the resin plate can be satisfactorily thermoformed into a desired shape, and the residual stress generated in the thermoforming cooling step can be suppressed to a small value. In this case, the change in the Re value can be suppressed, and the deformation of the obtained curved liquid crystal display protective plate can be suppressed. For example, when a reliability test of an in-vehicle display (for example, 1000 hours at 105 ° C. or 72 hours at 85 ° C. 85% RH) is carried out on a curved liquid crystal display protective plate, deformation due to release of residual stress is suppressed, which is preferable.

It is particularly preferable to perform thermoforming within the range of Tg _B + 10 ° C. to Tg _B + 30 ° C. and at a temperature lower than Tg _A. When the temperature is lower than Tg _A , the stress and orientation of the retardation adjustment layer are not released, so that the change in the Re value and the deformation of the curved liquid crystal display protective plate are effectively suppressed, which is preferable.
When thermoformed at a temperature of Tg _B + 10 ° C., it is difficult to thermoform the resin plate into a desired shape. Even in this temperature range, if a large load is applied or the molding time is lengthened, thermoforming can be performed into a desired shape, but a large molding stress is generated in the resin plate. When a reliability test of an in-vehicle display is carried out on a curved liquid crystal display protective plate obtained under these conditions, a large residual stress is released and there is a risk of large deformation.

(Base layer)
The flat resin plate and the resin plate having a curved surface include a base material layer having a lower glass transition temperature (Tg) than the retardation adjusting layer. The base material layer can increase the overall thickness (d) of the resin plate and improve the rigidity of the resin plate.
The base material layer is preferably a resin layer that does not affect the Re value of the liquid crystal display protective plate, and is a resin layer containing a transparent thermoplastic resin (B) having a sufficiently small photoelastic coefficient and orientation birefringence. Is preferable.

<Transparent thermoplastic resin (B)>
The absolute value of the photoelastic coefficient (CB) of the transparent thermoplastic resin ( _B ) is preferably as small as possible, preferably 10.0 × ^10-12 / Pa or less, and more preferably 8.0 × ^10-12 / Pa or less. It is more preferably 6.0 × ^10-12 / Pa or less, particularly preferably 5.0 × ^10-12 / Pa or less, and most preferably 4.0 × ^10-12 / Pa or less. When the absolute value of the photoelastic coefficient ( _CB ) is not more than the above upper limit value, the stress birefringence due to the residual stress generated during the molding process such as extrusion molding is sufficiently small (see FIG. 7), and the resin plate. The standard deviation of the Re value of can be reduced. As a result, when the liquid crystal display protective plate on the liquid crystal screen is observed through the polarizing filter, the color unevenness caused by the variation of the Re value is suppressed, and the visibility is improved.

The orientation birefringence (Δn _B ) of the transparent thermoplastic resin (B) is preferably small, preferably less than 10.0 × 10 ^-4 , more preferably 8.0 × 10 ^-4 or less, still more preferably 6.0. It is × 10 ^-4 or less, particularly preferably 4.0 × 10 ^-4 or less, and most preferably 2.0 × 10 ^-4 or less. When the absolute value of the orientation birefringence (Δn _B ) of the transparent thermoplastic resin (B) is not more than the above upper limit value, the influence on the Re value of the resin plate is sufficiently small (see FIG. 7), and the resin. The Re value of the plate can be well controlled within an appropriate range.

The transparent thermoplastic resin ( _{B) is not particularly limited as long as it is a transparent thermoplastic resin that satisfies the range of the photoelastic coefficient (CB) and the orientation birefringence (Δn B )} specified in the present invention. Specific examples include general non-denatured methacrylic resin (PM), cycloolefin polymer (COP) and the like. Depending on the monomer composition or the modification rate, the type of resin exemplified as the transparent thermoplastic resin (A) (specifically, SMA resin, SMM resin, modified methacrylic resin, etc.) is the transparent thermoplastic resin (B). May be used as. For example, by adjusting the content of the ring structure unit contained in the main chain to a low value, the absolute value of the photoelastic coefficient ( _CB ) is 10.0 × ^10-12 / Pa or less, and the orientation birefringence (Δn _B ). It can be designed so that the absolute value of is less than 10.0 × 10 ^-4 and Tg _A > Tg _B.
The transparent thermoplastic resin (B) can be used alone or in combination of two or more.

The methacrylic resin (PM) is a homopolymer or a copolymer having one or more methacrylic acid ester units. From the viewpoint of transparency, the content of the methacrylic acid ester monomer unit in the methacrylic acid resin (PM) is preferably 50% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more. , 100% by mass.

Preferred methacrylic acid esters include, for example, methyl methacrylate (MMA), ethyl methacrylate, butyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate; monocyclic fatty acid methacrylate. Hydrocarbic acid ester; Examples thereof include methacrylic acid polycyclic aliphatic hydrocarbon ester. From the viewpoint of transparency, the methacrylic resin (PM) preferably has MMA units, and the content of MMA units in the methacrylic resin (PM) is preferably 50% by mass or more, more preferably 80% by mass or more. Particularly preferably, it is 90% by mass or more, and may be 100% by mass.

The methacrylic resin (PM) may contain one or more other monomer units other than the methacrylic acid ester. Other monomers include methyl acrylate (MA), ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate and the like. Acrylic acid esters; styrenes; (meth) acrylonitrile and the like. Above all, MA is preferable from the viewpoint of transparency. For example, a copolymer of MMA and MA has excellent transparency and is preferable. The content of MMA in this copolymer is preferably 80% by mass or more, more preferably 85% by mass or more, particularly preferably 90% by mass or more, and may be 100% by mass.

The methacrylic resin (PM) is preferably obtained by polymerizing one or more methacrylic acid esters containing MMA and, if necessary, other monomers. When a plurality of types of monomers are used, usually, a plurality of types of monomers are mixed to prepare a monomer mixture, and then polymerization is performed. The polymerization method is not particularly limited, and from the viewpoint of productivity, a radical polymerization method such as a bulk polymerization method, a suspension polymerization method, a solution polymerization method, and an emulsion polymerization method is preferable.

The polycarbonate-based resin is not included in the transparent thermoplastic resin (B) because the photoelastic coefficient and the orientation birefringence are outside the specified range of the present invention.
The polycarbonate resin has a very large absolute value of the photoelastic coefficient of 90 × ^10-12 / Pa, and the Re value changes with a slight stress. Therefore, when a polycarbonate resin is used, it is difficult to obtain an optically uniform liquid crystal display protective plate. For example, when observing the liquid crystal display protective plate on the liquid crystal screen through a polarizing filter, color unevenness may be observed due to the variation in the Re value. In particular, after thermoforming, the change in the Re value of the resin plate is large compared to before thermoforming, and the variation in the Re value of the resin plate tends to be large.

As described above, when the glass transition temperature of the retardation adjustment layer is Tg _A (° C) and the glass transition temperature of the substrate layer is Tg _B (° C), Tg _A > Tg _B.
The glass transition temperature (Tg _B ) of the base material layer is not particularly limited as long as Tg _A > Tg _B is satisfied. It is preferably 70 to 160 ° C, more preferably 100 to 150 ° C, particularly preferably 110 to 140 ° C, and most preferably 110 to 130 ° C.
The "glass transition temperature (Tg _B ) of the base material layer" is the glass of all the constituent materials of the base material layer composed of one or more kinds of transparent thermoplastic resins (B) and, if necessary, one or more kinds of arbitrary components. The transition temperature.

Let _TB be the thickness of the base material layer. In the liquid crystal display protective plate of the present invention, the thickness ( _TB ) of the base material layer is designed to be larger than the total thickness ( _TA ) of the phase difference adjusting layer. That is, the liquid crystal display protective plate of the present invention satisfies _TA < _TB . The thickness ( _TB ) of the base material layer is not particularly limited as long as _TA < _TB is satisfied, and is appropriately designed according to the desired thickness and rigidity of the liquid crystal display protective plate. _TB is preferably 0.05 to 5.0 mm, more preferably 0.5 to 4.0 mm, particularly preferably 1.0 to 3.0 mm, and most preferably 1.5 to 2.5 mm.

In the present invention, TB / T _A > 1, preferably _TB / T _A ≥ 1.2, more preferably _TB / T _A ≥ 1.5, and even more preferably _TB / T _{A ≥} 2. 0, particularly preferably _TB / _TA ≧ 5.0, most preferably _TB / _TA ≧ 7.0.
If _TA and _TB have the above relationship, the ratio of the thickness ( _TB ) of the base material layer to the total thickness (d) of the resin plate is sufficiently large, and it is suitable for the base material layer during thermoforming such as curved surface molding. Molding can be performed at a different temperature, which is preferable.

When the total thickness ( _TA ) of the phase difference adjusting layer is larger than the thickness of the base material layer ( _TB ), the desired molding rate (calculation) is obtained by thermoforming at a temperature near the glass transition temperature (Tg _B ) of the base material layer. Form rate) is difficult to achieve. In this case, it is necessary to thermoform the retardation adjustment layer above the glass transition temperature (Tg _A ). Under this temperature condition, the degree of orientation of the phase difference adjusting layer is lowered, the Re value is lowered, and blackout may occur when the liquid crystal display protective plate on the liquid crystal screen is observed through the polarizing filter. When _TA < _TB , molding can be performed at a temperature suitable for the base material layer during thermoforming, which is preferable.

The base material layer may contain, in a small amount, one or more other polymers whose photoelastic coefficient and / or orientation birefringence is out of the scope of the transparent thermoplastic resin (B). The type of other polymer is not particularly limited, and is not particularly limited, such as polycarbonate resin, polyolefin such as polyethylene and polypropylene, polyamide, polyphenylene sulfide, polyether ether ketone, polyester, polysulfone, polyphenylene oxide, polyimide, polyetherimide, and polyacetal. Other thermoplastic resins include thermocurable resins such as phenolic resins, melamine resins, silicone resins, and epoxy resins.
The content of the transparent thermoplastic resin (B) in the base material layer is preferably large, preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 98% by mass or more. The content of the other polymer in the base material layer is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 2% by mass or less.

The base material layer can contain various additives, if necessary. Examples of the types of additives and preferable addition amounts are the same as those of additives that can be used for the phase difference adjusting layer.
When another polymer and / or an additive is added to the base material layer, the timing of addition may be during or after the polymerization of the transparent thermoplastic resin (B).

The base material layer may be a resin layer made of a resin composition containing a transparent thermoplastic resin (B) and a known rubber component (impact resistance modifier). Examples of the rubber component are the same as those of the rubber component that can be used for the phase difference adjusting layer. From the viewpoint of the transparency of the base material layer, it is preferable that the difference between the refractive index of the rubber component and the refractive index of the transparent thermoplastic resin (B) as the main component is smaller.

(Other resin layer)
The flat resin plate and the resin plate having a curved surface may have a resin layer other than the retardation adjusting layer and the base material layer. The laminated structure of the resin plate includes a two-layer structure of a retardation adjustment layer-a base material layer; a three-layer structure of a retardation adjustment layer-a base material layer-a retardation adjustment layer; Three-layer structure of resin layer; three-layer structure of other resin layer-phase difference adjustment layer-base material layer; four-layer structure of phase difference adjustment layer-base material layer-phase difference adjustment layer-other resin layer; phase difference Examples thereof include a four-layer structure of an adjusting layer-a base material layer-another resin layer-a retardation adjusting layer.

(Hardened film)
The liquid crystal display protective plate and the liquid crystal display protective plate with a curved surface of the present invention can have a cured film formed on at least one of the outermost surfaces, if necessary.
The cured film can function as a scratch resistant layer (hard coat layer) or a low reflective layer for the effect of improving visibility. The cured film can be formed by a known method.
Examples of the material of the cured film include inorganic, organic, organic-inorganic, and silicone-based materials, and organic-based and organic-inorganic-based materials are preferable from the viewpoint of productivity.

The inorganic cured film is formed by forming an inorganic material such as a metal oxide such as SiO ₂ , Al ₂ O ₃ , TIO ₂ , and ZrO ₂ by vapor deposition such as vacuum deposition and sputtering. be able to.
For the organic cured film, for example, a paint containing a resin such as a melamine resin, an alkyd resin, a urethane resin, and an acrylic resin is applied and heat-cured, or a paint containing a polyfunctional acrylic resin is applied. It can be formed by curing with ultraviolet rays.
For example, the organic-inorganic cured film is coated with an ultraviolet curable hard coat paint containing inorganic ultrafine particles such as silica ultrafine particles having a photopolymerization-reactive functional group introduced on the surface and a curable organic component, and is irradiated with ultraviolet rays. It can be formed by polymerizing a curable organic component and a photopolymerization-reactive functional group of inorganic ultrafine particles. In this method, a network-like crosslinked coating film in which the inorganic ultrafine particles are chemically bonded to the organic matrix and dispersed in the organic matrix can be obtained.
The silicone-based cured film can be formed, for example, by polycondensing a partially hydrolyzed product such as carbon functional alkoxysilane, alkyltrialkoxysilane, and tetraalkoxysilane, or a material containing colloidal silica.
In the above method, examples of the material coating method include various roll coats such as dip coats and gravure roll coats, flow coats, rod coats, blade coats, spray coats, die coats, and bar coats.

When laminating thermosetting coating materials, the resin plate can be exposed to higher temperatures than when other types of coating materials are used. If the curing temperature is insufficient, the curing reaction of the coating material may not proceed sufficiently, and the surface hardness of the cured coating or the adhesion to the resin plate may decrease. Even if the curing temperature is insufficient, if the curing time is lengthened, it may be sufficiently cured, but this is not preferable in terms of productivity. A sufficiently high curing temperature is required for the curing reaction to proceed satisfactorily, but when the curing temperature is higher than the glass transition temperature (Tg) of the underlying layer of the cured film, the underlying layer is thermally expanded. Since the coating material is cured, there is a possibility that the liquid crystal display protective plate may be wrinkled and / or the cured coating may be cracked.

The resin plate included in the liquid crystal display protective plate of the present invention has a structure in which a phase difference adjusting layer having a relatively high glass transition temperature (Tg) is laminated on at least one surface of a base material layer. In the present invention, a cured film can be formed on a retardation adjusting layer having a relatively high glass transition temperature (Tg) and excellent heat resistance. Therefore, the curing temperature is set within a temperature condition in which the retardation adjusting layer, which is the underlayer of the cured coating, does not thermally expand, that is, a temperature condition equal to or lower than the glass transition temperature (Tg) of the retardation adjusting layer, which is the underlayer of the cured coating. It can be set to a sufficiently high temperature at which the curing reaction proceeds well. When a thermosetting coating material is used, the curing temperature is preferably Tg _B or more and Tg _A or less, and more preferably Tg _B or more and less than Tg _A.

The present invention is particularly useful when forming a cured coating using a thermosetting coating material. According to the present invention, even when a cured film is formed using a thermosetting film material that requires a relatively high curing temperature, the surface hardness of the cured film and the adhesion to the resin plate are good, and the liquid crystal display A liquid crystal display protective plate containing a cured film without wrinkles and / or cracking of the cured film can be stably manufactured with good productivity.

The thickness of the scratch resistant (hard coat property) cured film (scratch resistant layer, hard coat layer) is preferably 2 to 30 μm, more preferably 5 to 20 μm. If it is too thin, the surface hardness will be insufficient, and if it is too thick, cracks may occur due to bending during the manufacturing process. The thickness of the low-reflection cured film (low-reflection layer) is preferably 80 to 200 nm, more preferably 100 to 150 nm. If it is too thin or too thick, the low reflection performance may be insufficient.

In addition, the liquid crystal display protective plate and the liquid crystal display protective plate with a curved surface of the present invention have known surface treatments such as an anti-glare (anti-glare) layer, an anti-reflection (anti-reflection) layer, and an anti-fingerprint layer on the surface thereof, if necessary. Can have layers.

[Manufacturing method of liquid crystal display protection plate]
The method for manufacturing a liquid crystal display protective plate of the present invention includes a step (X) of forming a flat resin plate in which a retardation adjusting layer is laminated on at least one surface of a base material layer, and is further obtained if necessary. It is possible to have a step (Y) of forming a cured film on at least one surface of the flat resin plate.

(Process (X))
The flat resin plate having the laminated structure can be molded by a known method such as a cast molding method, an injection molding method, or an extrusion molding method. Above all, the coextrusion molding method is preferable.
Hereinafter, a method for manufacturing a flat resin plate by a coextrusion molding method will be described.
FIG. 4 shows a schematic diagram of an extrusion molding apparatus including a T-die 11, first to third cooling rolls 12 to 14, and a pair of take-up rolls 15 as an embodiment.
The constituent resins of each layer are melt-kneaded using an extruder and co-extruded in a plate-like form from a T-die 11 having a wide discharge port in the form of a desired laminated structure.
Examples of the laminating method include a feed block method of laminating before the inflow of the T-die, a multi-manifold method of laminating inside the T-die, and the like. The multi-manifold method is preferable from the viewpoint of improving the interfacial smoothness between layers.
The molten thermoplastic resin laminate co-extruded from the T-die 11 is pressurized and cooled using a plurality of cooling rolls 12-14. The flat resin plate 16 obtained after pressurization and cooling is taken up by a pair of take-up rolls 15. The number of cooling rolls can be appropriately designed. The configuration of the manufacturing apparatus can be appropriately redesigned as long as it does not deviate from the gist of the present invention.

In the present invention, molding is performed so that the Re value of the flat resin plate is 50 to 330 nm.
More preferably, molding is performed so that the standard deviation of the Re value within the range of the flat resin plate having a width of 17 cm and a length of 22 cm is 15.0 nm or less.
In order to control the Re value, it is necessary to control the orientation of the molecule. The orientation of the molecules is generated, for example, by the stress during molding near the glass transition temperature of the polymer. By optimizing the production conditions in the process of extrusion molding, the orientation of the molecules can be controlled, whereby the Re value after extrusion molding of the resin plate can be optimized.

(Step (Y))
In the step (Y), an inorganic or organic cured film is formed on at least one surface of the flat resin plate obtained in the step (X) by a known method. The cured film is preferably formed on a retardation adjusting layer having a relatively high glass transition temperature (Tg).
As described above, the present invention is particularly useful when forming a cured film using a thermosetting film material. When a thermosetting material is used, it is preferable to apply the thermosetting material on a flat resin plate and heat it at a temperature of Tg _B or more and Tg _A or less to form a cured film. In this case, the curing temperature is set within a temperature condition in which the retardation adjusting layer, which is the underlayer of the cured coating, does not thermally expand, that is, a temperature condition lower than the glass transition temperature (Tg) of the retardation adjusting layer, which is the underlayer of the cured coating. It can be set to a sufficiently high temperature at which the curing reaction proceeds well. Therefore, the surface hardness of the cured film and the adhesion to the resin plate are good, and the liquid crystal display protective plate containing the cured film without wrinkles and / or cracking of the cured film can be stably manufactured with good productivity. can.

(Other processes)
The method for manufacturing a liquid crystal display protective plate of the present invention may have steps other than the above steps (X) and (Y), if necessary.
For example, between the step (X) and the step (Y), for the purpose of improving the adhesion of the cured film to the flat resin plate, on the surface of the flat resin plate obtained in the step (X) to form the cured film. On the other hand, surface unevenness treatment such as primer treatment, sandblast treatment, and solvent treatment; surface treatment such as corona discharge treatment, chromium acid treatment, ozone irradiation treatment, and surface oxidation treatment such as ultraviolet irradiation treatment has been added. You may.

[Manufacturing method of LCD protective plate with curved surface]
The method for manufacturing a curved liquid crystal display protective plate of the present invention is as follows.
A step (X) of forming a flat resin plate in which a phase difference adjusting layer is laminated on at least one surface of a base material layer, and
It has a step (Z) of heating a flat resin plate to a temperature of Tg _B or more and Tg _A or less and thermoforming it into a shape having a curved surface.
The method for manufacturing a curved liquid crystal display protective plate of the present invention is a step (Y) of forming a cured film on at least one surface of a flat resin plate, if necessary, between steps (X) and step (Z). ) Can have. In this case, in step (Z), a flat resin plate with a cured film is thermoformed.
The steps (X) and (Y) have been described in the section [Manufacturing method of liquid crystal display protective plate], and are omitted here.
In step (Z), shape processing such as curved surface processing on a flat resin plate or a flat resin plate with a cured film can be performed by known thermoforming such as press molding, vacuum forming, and pressure forming.

In the present invention, in the step (X), molding is performed so that the Re value of the flat resin plate is 50 to 330 nm. In the step (X), molding is preferably performed so that the standard deviation of the Re value within the range of the width 17 cm and the length 22 cm of the flat resin plate is 15.0 nm or less.
When the flat resin plate is heated to a temperature of Tg _B or more and Tg _A or less, the absolute value of the rate of change of the Re value after heating with respect to that before heating is preferably 50% or less, more preferably 45% or less, still more preferably. It is 40% or less, particularly preferably 35% or less, and most preferably 30% or less.
When the flat resin plate is heated to a temperature of Tg _B or more and Tg _A or less, the standard deviation of the Re value within the range of 17 cm in width and 22 cm in length is preferably 25.0 nm or less, more preferably 20.0 nm or less. It is particularly preferably 15.0 nm or less, and most preferably 10.0 nm or less.
In the present invention, since the change in the Re value of the resin plate is suppressed even if thermoforming is performed, the curved liquid crystal display protective plate having a Re value within a suitable range and a small variation in the Re value can be stably obtained. Can be manufactured to.

As described above, according to the present invention, the Re value is within a suitable range both before and after thermoforming, the variation is small, and the liquid crystal display protective plate on the liquid crystal screen through the polarizing filter. It is possible to provide a liquid crystal display protective plate capable of suppressing deterioration of visibility such as color unevenness, blackout, and coloring when observing.

[Use]
The liquid crystal display protection plate and the liquid crystal display protection plate with a curved surface of the present invention are, for example, ATMs of financial institutions such as banks; vending machines; televisions; mobile information of mobile phones (including smartphones), personal computers, tablet-type personal computers, etc. It is suitable as a protective plate for a liquid crystal display or a touch panel display used in digital information devices such as terminals (PDAs), digital audio players, portable game machines, copy machines, fax machines, and car navigation systems.
The liquid crystal display protective plate and the curved liquid crystal display protective plate of the present invention are suitable as, for example, a protective plate for an in-vehicle liquid crystal display.

Examples and comparative examples according to the present invention will be described.
[Evaluation items and evaluation methods]
The evaluation items and evaluation methods are as follows.
(Copolymerization composition of glutarimide-modified methacrylic resin)
The copolymerization composition of the glutarimide-modified methacrylic resin was determined by ¹ H-NMR method using a nuclear magnetic resonance apparatus (“400YH” manufactured by JEOL Ltd.). TMS (tetramethylsilane) was used as the internal standard substance.
A sample solution was prepared by dissolving 0.04 g of the resin in 0.55 ml of deuterated chloroform, and ^{1 1} H-NMR spectrum was measured under the condition of 64 times of integration in a room temperature environment, and the following two peaks were identified. ..
Peak derived from N-methyl group of glutarimide (δ = around 3.0ppm),
Peak derived from the ester of methyl methacrylate (δ = around 3.6 ppm).
The molar ratio of the ring structure unit and the MMA unit in the sample was obtained from the integral ratio of the above two peaks, and this was converted into a mass ratio to obtain the copolymer composition (contents of the ring structure unit and the MMA unit).

(Copolymerization composition of lactone ring-modified methacrylic resin)
The copolymer composition (contents of ring structure unit and MMA unit) of the lactone ring-modified methacrylic resin was determined according to the method described in the section of [Example] of International Publication No. 2016/185722.

(Glass transition temperature (Tg) of transparent thermoplastic resin)
The glass transition temperature (Tg) of the transparent thermoplastic resin was measured using a differential scanning calorimeter (“DSC-50”, manufactured by Rigaku Corporation). 10 mg of the transparent thermoplastic resin was placed in an aluminum pan and set in the above device. After performing nitrogen substitution for 30 minutes or more, the temperature was once raised from 25 ° C. to 200 ° C. at a rate of 20 ° C./min in a nitrogen stream of 10 ml / min, held for 10 minutes, and cooled to 25 ° C. (primary scan). ). Then, the temperature was raised to 200 ° C. at a rate of 10 ° C./min (secondary scanning), and the glass transition temperature (Tg) was calculated by the midpoint method from the results obtained by the secondary scanning. When a plurality of Tg data can be obtained in a resin composition containing two or more kinds of resins, the value derived from the resin as the main component was adopted as the Tg data.

(Photoelastic coefficient of transparent thermoplastic resin)
The transparent thermoplastic resin was press-molded to obtain a resin plate having a thickness of 1.0 mm. A test piece having a width of 15 mm and a length of 80 mm was cut out from the central portion of the obtained resin plate. Both ends of the test piece in the longitudinal direction were gripped by a pair of chucks. The distance between the chucks was 70 mm.
Tension was applied to the test piece using an "X-axis dovetail stage" manufactured by Oji Measuring Instruments Co., Ltd. The tension was gradually increased by 10N from 0N to 30N. The tension was monitored by "Sensor Separate Type Digital Force Gauge ZTS-DPU-100N" manufactured by Imada.
The following measurements were carried out for the tension application conditions at each stage from 0N to 100N.
The phase difference value [nm] of the central portion of the test piece under tension was measured using "KOBRA-WR" manufactured by Oji Measuring Instruments Co., Ltd. under the condition of a measurement wavelength of 589.5 nm. After that, the test piece was removed from the pair of chucks, and the thickness (d [mm]) of the phase difference measuring portion was measured. Cross-sectional area (S) [m ² ] (= 15 [mm] x d [mm] x ^10-6 ) of test piece, stress [Pa] (= tension [N] / S [m ² ]), birefringence ( = Phase difference value [nm] × ^10-6 / d [mm]) was calculated respectively. Stress was plotted on the horizontal axis and birefringence was plotted on the vertical axis, and the slope of the straight line obtained by the minimum self-squared method was obtained as the photoelastic coefficient.

(Orientation birefringence of transparent thermoplastic resin)
The transparent thermoplastic resin was press-molded to obtain a resin plate having a thickness of 1.0 mm. A test piece having a width of 20 mm and a length of 50 mm was cut out from the central portion of the obtained resin plate and set in an autograph with a heating chamber (manufactured by SHIMADZU). The distance between the chucks was 20 mm. After holding for 3 minutes at a temperature 10 ° C. higher than the glass transition temperature (Tg), uniaxial stretching was performed at a rate of 3 mm / min. The draw ratio was 100%. Under this condition, the distance between chucks after stretching is 40 mm. After removing the stretched test piece from the above apparatus and cooling it to 23 ° C., the thickness (d) is measured, and the Re value in the central portion is measured using "KOBRA-WR" manufactured by Oji Measuring Instruments Co., Ltd. at a measurement wavelength of 589. It was measured under the condition of 5 nm. The value of the orientation birefringence was calculated by dividing the obtained Re value by the thickness (d) of the test piece.

(Average value and standard deviation of Re value of liquid crystal display protection plate)
The average Re values of the liquid crystal display protective plate test piece (width 21 cm, length 30 cm) before curved surface molding and the liquid crystal display protective plate test piece (width 17 cm, length 22 cm) after curved surface molding are as follows. Values and standard deviations were measured.
A standard lens (FUJINON HF12.5HA-1B) was attached to "WPA-100-L" manufactured by Photonic Lattice. The height of the lens was adjusted so that the measurement range was 17 cm in width and 22 cm in length. The Re value of the number of birefringent pixels of about 110,000 points was measured, and the average value and the standard deviation were obtained.
Based on the following formula, the rate of change of the average Re value after the curved surface was formed with respect to that before the curved surface was formed.
[Rate of change of Re value after heating] (%) = [([Re value after heating]-[Re value before heating]) / [Re value before heating]] × 100

(Thickness of each layer)
The thickness of each layer was measured using a "universal projector (V-12B)" manufactured by Nikon Instec.

(Color unevenness)
A test piece of the liquid crystal display protective plate was placed on the liquid crystal display so that the transmission axis of the polarizing element on the visual side of the liquid crystal display and the extrusion molding direction of the resin plate were perpendicular to each other. Further, a polarizing film was placed on the polarizing film, the polarizing film was rotated at various angles, and the appearance at the angle at which the color unevenness due to the variation in the Re value became the strongest was visually evaluated in the following three stages.
A (good): There is no color unevenness, and the visibility of the liquid crystal display does not deteriorate.
B (possible): There is some color unevenness, and the visibility of the liquid crystal display is slightly reduced.
C (defective): There is remarkable color unevenness, and the visibility of the liquid crystal display is greatly reduced.

(Blackout)
A test piece of the liquid crystal display protective plate was placed on the liquid crystal display so that the transmission axis of the polarizing element on the visual side of the liquid crystal display and the extrusion molding direction of the resin plate were perpendicular to each other. Further, a polarizing film was placed on the polarizing film, the polarizing film was rotated at various angles, and the appearance at the angle at which the transmitted light intensity of the liquid crystal display was minimized was visually evaluated in the following three stages.
A (good): The transmitted light intensity is sufficiently high, and the characters and the like displayed on the liquid crystal display can be clearly seen.
B (possible): The transmitted light intensity is slightly low, and the visibility of characters and the like displayed on the liquid crystal display is slightly reduced.
C (defective): The transmitted light intensity is almost zero, and the characters and the like displayed on the liquid crystal display cannot be visually recognized.

(Colored)
A test piece of the liquid crystal display protective plate was placed on the liquid crystal display so that the transmission axis of the polarizing element on the visual side of the liquid crystal display and the extrusion molding direction of the resin plate were perpendicular to each other. Further, a polarizing film was placed on the polarizing film, the polarizing film was rotated at various angles, and the appearance at the angle at which the coloring of the liquid crystal display was maximized was visually evaluated in the following three stages.
A (good): There is no noticeable coloring, and the visibility of the liquid crystal display does not deteriorate.
B (possible): There is coloring, and the visibility of the liquid crystal display is slightly reduced.
C (defective): There is remarkable coloring, and the visibility of the liquid crystal display is deteriorated.

(Molding rate)
For the liquid crystal display protective plate after curved surface molding, the molding rate was calculated as follows. This will be described with reference to FIG. FIG. 6 is a schematic cross-sectional view. In FIG. 6, the curvature of the liquid crystal display protective plate is exaggerated.
The liquid crystal display protective plate P after forming the curved surface was placed on the surface plate T so that the convex side was on the upper side. The separation distance D (mm) between the uppermost portion of the liquid crystal display protective plate P and the surface plate T was measured using a feeler gauge, and the molding ratio was determined based on the following formula. In the resin mold used for the evaluation, the molding rate is 100% when D = 5 mm.
[Molding rate] (%) = [D / 5] x 100

[material]
The materials used are as follows.
<Transparent thermoplastic resin (A) having a ring structure unit>
(PMMI1) Glutarimide-modified methacrylic resin, "PLEXIMID TT50" manufactured by Daicel Evonik, Tg = 155 ° C., ring structure unit content 86% by mass, methyl methacrylate (MMA) unit content 14% by mass.
(PMMI2) Glutarimide-modified methacrylic resin, Tg = 125 ° C., ring structure unit content 15% by mass, methyl methacrylate (MMA) unit content 85% by mass. PMMI2 was synthesized according to the production method described in the section of [Example 1] of JP-A-2008-134490.

(PMML1) Lactone ring-modified methacrylic resin, Tg = 149 ° C., ring structure unit content 65% by mass, methyl methacrylate (MMA) unit content 35% by mass. It was synthesized according to the production method described in the section [Example 1] of International Publication No. 2016/185722.
(PMML2) Lactone ring-modified methacrylic resin, Tg = 132 ° C., ring structure unit content 28% by mass, methyl methacrylate (MMA) unit content 72% by mass. It was synthesized according to the production method described in the section [Example 1] of International Publication No. 2016/185722.

<Non-denatured methacrylic resin having no ring structure unit>
(PMMA1) A polymer obtained by copolymerizing a small amount of methyl acrylate (MA) with methyl methacrylate (MMA), "Parapet HR" manufactured by Kuraray Co., Ltd., Tg = 119 ° C., and a ring structure unit content of 0% by mass.

<Polycarbonate resin>
(PC1) "SD Polycarbonate 300 Series" manufactured by Sumika Polycarbonate Limited, Tg = 150 ° C.

[Examples 1 and 2, Comparative Examples 1 and 5]
(Manufacturing of LCD protective plate)
A resin for the base material layer (transparent thermoplastic resin (B) or comparative resin) was melt-extruded using a 50 mmφ single-screw extruder (manufactured by Toshiba Machine Co., Ltd.). A resin for the phase difference adjusting layer (transparent thermoplastic resin (A) or comparative resin) was melt-extruded using a 30 mmφ single-screw extruder (manufactured by Toshiba Machine Co., Ltd.). These melted resins were laminated via a multi-manifold type die, and a three-layered thermoplastic resin laminate in which phase difference adjusting layers were laminated on both sides of the base material layer was co-extruded from the T-die. This thermoplastic resin laminate is sandwiched between the first cooling roll and the second cooling roll adjacent to each other, wound around the second cooling roll, sandwiched between the second cooling roll and the third cooling roll, and the third It was cooled by wrapping it around a cooling roll. The flat resin plate obtained after cooling was taken up by a pair of taking-up rolls. In this way, a liquid crystal display protective plate (reference drawing: FIG. 2) made of a flat resin plate having a three-layer structure in which phase difference adjusting layers are laminated on both sides of the base material layer was obtained.
A test piece having a width of 21 cm and a length of 30 cm was cut out from the central portion of the obtained liquid crystal display protective plate so that the extrusion molding direction (resin flow direction) was the long side direction. Using this test piece, the liquid crystal display protective plate before curved surface molding was evaluated.

Tables 1 and 2 show the types and physical properties of the resin used, the total thickness of the retardation adjustment layer, the thickness of the base material layer, and the evaluation results of the liquid crystal display protective plate before curved surface forming for each example. In each example of Table 1, the conditions not shown in the table were set as common conditions.

(Curved surface molding)
A curved surface forming test piece having a width of 17 cm and a length of 22 cm was cut out from the central portion of the test piece so that the extrusion molding direction (resin flow direction) was the long side direction. A curved surface was formed on this test piece as follows.
A resin mold manufactured by using "Chemical Wood Prolab 65" manufactured by SSI was prepared.
The resin mold consists of a combination of a female mold (lower mold in the figure) and a male mold (upper mold in the figure) as shown in FIG. It had a rectangular parallelepiped shape (dimensions in the direction) 250 mm × height (dimensions in the z direction in the figure) 35 mm.
A concave curved surface is formed on the upper surface of the female mold, and a convex curved surface that joins the concave curved surface of the female mold is formed on the lower surface of the male mold. It was 15 mm.
The cross-sectional shapes of the female concave curved surface and the male convex curved surface parallel to the yz plane were uniform regardless of the position in the x direction shown in the figure, and were arcuate with a radius of curvature of 600 mm. In the drawing, the curvature is exaggerated and shown.

A polytetrafluoroethylene (PTFE) sheet (300 mm × 300 mm × 12 mm) was placed in the oven, and the inside of the oven was heated to 170 ° C. In this state, a test piece for curved surface molding is placed on a PTFE sheet, and the temperature of the test piece is the molding temperature shown in Table 3 (for example, using a non-contact thermometer (“PT-S80” manufactured by Optex)). In Example 1, it was held for 6 to 7 minutes until it reached 133 ° C.). Then, the PTFE sheet and the curved surface forming test piece placed on the PTFE sheet were taken out from the oven. Next, a test piece for curved surface molding at the above molding temperature is placed on a female mold at room temperature (20 to 25 ° C.), a male mold at room temperature (20 to 25 ° C.) is placed on the test piece, and 3 kg from above. Loaded. Then, the test piece was cooled to near room temperature over 1 to 2 minutes. The cooled test piece was taken out from the resin mold, and the liquid crystal display protective plate (liquid crystal display protective plate with curved surface) after curved surface molding was evaluated using this test piece.
For each example, Table 3 shows the thermoforming temperature and the evaluation results of the liquid crystal display protective plate after the curved surface molding. In each example of Table 3, the conditions not shown in the table were set as common conditions.
For Comparative Example 1, curved surface molding was performed by changing the thermoforming temperature. In Comparative Example 1, an example in which the thermoforming temperature was 123 ° C. and Comparative Example 1-1 were used, and an example in which the thermoforming temperature was 140 ° C. and Comparative Example 1-2.

[Summary of results]
In Examples 1 and 2, a liquid crystal display protective plate made of a flat resin plate in which retardation adjusting layers are laminated on both sides of a base material layer was manufactured. In these examples, as the material of the retardation adjusting layer, the main chain has a ring structure unit (specifically, a glutarimide unit or a lactone ring unit), and the glass transition temperature (Tg _A0 ) is 135 to 180 ° C. A modified methacrylic resin was used. A non-modified methacrylic resin was used as the material of the base material layer. The phase difference adjusting layer has an absolute value of photoelastic coefficient ( _CA ) of 10.0 × ^10-12 / Pa or less, and an absolute value of orientation birefringence (Δn _A ) of 10.0 × 10 ^-4 to 100. It was 0.0 × 10 ^-4 . The base layer has an absolute value of photoelastic coefficient ( _CB ) of 10.0 × ^10-12 / Pa or less and an absolute value of orientation birefringence (Δn _B ) of less than 10.0 × 10 ^-4 . rice field. When the glass transition temperature of the phase difference adjusting layer was Tg _A and the glass transition temperature of the substrate layer was Tg _B , Tg _A > Tg _B. When the total thickness of the phase difference adjusting layer was _TA and the thickness of the base material layer was _TB , _TA < _TB .

In each of the flat liquid crystal display protective plates before curved surface forming obtained in Examples 1 and 2, the average value of the Re value was 50 to 330 nm, and the standard deviation of the Re value was 15.0 nm or less. In these examples, when the obtained liquid crystal display protective plate was used and the liquid crystal display protective plate on the liquid crystal screen was observed through a polarizing filter, color unevenness, coloring, and blackout were effectively suppressed.

In Examples 1 and 2, the obtained flat liquid crystal display protective plate was thermoformed at a temperature of Tg _B or more and Tg _A or less (Tg _B or more and less than Tg _A ) to produce a curved liquid crystal display protective plate. In each of the curved liquid crystal display protective plates obtained in Examples 1 and 2, the average value of the Re value was 50 to 330 nm, and the standard deviation of the Re value was 15.0 nm or less. In these examples, the absolute value of the rate of change of the average Re value after thermoforming with respect to that before thermoforming was 50% or less. In these examples, when the obtained liquid crystal display protective plate with a curved surface was used and the liquid crystal display protective plate on the liquid crystal screen was observed through a polarizing filter, color unevenness, coloring, and blackout were effectively suppressed. ..

In Comparative Example 1, a resin having a ring structure unit in the main chain was used as the material of the retardation adjustment layer, but this resin has a ring structure unit content of less than 30% by mass and a glass transition temperature (Tg). _A0 ) was less than 135 ° C., and the absolute value of orientation birefringence (Δn _A ) was less than 10.0 × 10 ^-4 .
In the flat liquid crystal display protective plate obtained in Comparative Example 1, blackout was noticeably observed when the liquid crystal display protective plate on the liquid crystal screen was observed through the polarizing filter.
In Comparative Example 1-1, the obtained flat liquid crystal display protective plate was thermoformed at a temperature of Tg _B or more and Tg _A or less (Tg _B or more and less than Tg _A ) to produce a curved liquid crystal display protective plate. Since the forming temperature was too close to Tg _B , the forming rate was low and curved surface forming could not be performed satisfactorily. The obtained curved liquid crystal display protective plate had a low Re value, and when the liquid crystal display protective plate on the liquid crystal screen was observed through a polarizing filter, blackout was noticeably observed.
In Comparative Example 1-2, the obtained flat liquid crystal display protective plate was thermoformed at a temperature exceeding Tg _A to produce a curved liquid crystal display protective plate. In the obtained liquid crystal display protective plate with a curved surface, the absolute value of the rate of change of the average Re value after thermoforming with respect to that before thermoforming was more than 50%. The curved liquid crystal display protective plate obtained in this comparative example had a low Re value, and when the liquid crystal display protective plate on the liquid crystal screen was observed through a polarizing filter, color unevenness and blackout were noticeably observed.

In Comparative Example 2, the same resin as in Example 1 was used as the material for the retardation adjusting layer and the base material layer, but _TA > _TB . In this comparative example, the obtained flat liquid crystal display protective plate was thermoformed at a temperature of Tg _B or more and Tg _A or less (Tg _B or more and less than Tg _A ) to produce a curved liquid crystal display protective plate. Under the condition of _TA > _TB , thermoforming could not be performed at a temperature of Tg _B or more and Tg _A or less (Tg _B or more and less than Tg _A ), and the molding rate was remarkably low.

In Comparative Example 3, a resin having a ring structure unit in the main chain was used as the material of the retardation adjustment layer, but this resin has a ring structure unit content of less than 30% by mass and a glass transition temperature (Tg). _A0 ) was less than 135 ° C., and the absolute value of orientation birefringence (Δn _A ) was less than 10.0 × 10 ^-4 .
In Comparative Example 3, the obtained flat liquid crystal display protective plate was thermoformed at a temperature of Tg _B or more and Tg _A or less (Tg _B or more and less than Tg _A ) to produce a curved liquid crystal display protective plate. Since the forming temperature was too close to Tg _B , the forming rate was low and curved surface forming could not be performed satisfactorily. The obtained curved liquid crystal display protective plate had a low Re value, and when the liquid crystal display protective plate on the liquid crystal screen was observed through a polarizing filter, blackout was noticeably observed.

In Comparative Example 4, as the resin of the phase difference adjusting layer, a polycarbonate resin having a photoelastic coefficient (CA) and orientation birefringence (Δn _A ) outside the _scope of the present invention was used. The flat liquid crystal display protective plate before curved surface forming obtained in this comparative example has a Re value larger than a suitable range, a large standard deviation of the Re value (large variation in the Re value), and is displayed on the liquid crystal screen through a polarizing filter. When observing the liquid crystal display protective plate in the above, color unevenness and coloring were remarkably observed.
In Comparative Example 4, a flat liquid crystal display protective plate was thermoformed at a temperature of Tg _B or more and Tg _A or less (Tg _B or more and less than Tg _A ) to manufacture a curved liquid crystal display protective plate. In this comparative example, the absolute value of the rate of change of the average Re value after thermoforming with respect to that before thermoforming was more than 50%. In the liquid crystal display protective plate with a curved surface obtained in this comparative example, color unevenness was remarkably observed when the liquid crystal display protective plate on the liquid crystal screen was observed through a polarizing filter.

In Comparative Example 5, a general non-denatured methacrylic resin having no ring structure unit was used as the material of the retardation adjusting layer. This resin had a glass transition temperature (Tg _A0 ) of less than 135 ° C. and an absolute value of orientation birefringence (Δn _A ) of less than 10.0 × 10 ^-4 . As the material of the base material layer, a polycarbonate resin having a photoelastic coefficient ( _{CB) and orientation birefringence (Δn B )} outside the specifications of the present invention was used. Tg _A <Tg _B. The obtained flat liquid crystal display protective plate before forming the curved surface has a large standard deviation of the Re value (large variation in the Re value), and when the liquid crystal display protective plate on the liquid crystal screen is observed through the polarizing filter, the color is large. The unevenness was noticeable.
In Comparative Example 5, a liquid crystal display protective plate with a curved surface was manufactured by thermoforming at a temperature higher than Tg _A and Tg _B. The absolute value of the rate of change of the average Re value after thermoforming with respect to that before thermoforming was more than 50%, and the standard deviation of the Re value after thermoforming was more than 25.0 nm. The curved liquid crystal display protective plate obtained in this comparative example has a large standard deviation of the Re value (large variation in the Re value), and when the liquid crystal display protective plate on the liquid crystal screen is observed through the polarizing filter, the color unevenness is large. Was noticeably seen.

The present invention is not limited to the above embodiments and examples, and the design can be appropriately changed as long as the gist of the present invention is not deviated.

1, 2 Liquid crystal display protective plate 3 Liquid crystal display protective plate containing cured film 11 T-die 12-14 Cooling roll 15 Take-up roll 16A, 16B Flat resin plate 21 Phase difference adjustment layer 22 Base material layer 31 Cured film

Claims (14)

A flat resin plate in which a phase difference adjusting layer is laminated on at least one surface of a base material layer is included.
The phase difference adjusting layer has at least one ring structure unit selected from the group consisting of an acid anhydride unit, an imide unit including a ring structure, and a lactone ring unit in the main chain, and has a glass transition temperature (Tg _A0 ). ) Is 135 to 180 ° C., the absolute value of the photoelastic coefficient ( _CA ) is 10.0 × ^10-12 / Pa or less, and the test piece having a width of 20 mm, a length of 40 mm, and a thickness of 1 mm is subjected to a glass transition temperature. Absolute value of orientation double refraction (Δn _A ) obtained by uniaxially stretching at a rate of 3 mm / min at a higher temperature of 10 ° C. and measuring the in-plane retardation value of the central portion of the test piece. Contains the transparent thermoplastic resin (A) of 10.0 × 10 ^-4 to 100.0 × 10 ^-4 .
The base material layer has a photoelastic coefficient ( _CB ) of 10.0 × ^10-12 / Pa or less, and a test piece having a width of 20 mm, a length of 40 mm, and a thickness of 1 mm is placed at 10 ° C. above the glass transition temperature. The absolute value of the orientation birefringence (Δn _B ) obtained by uniaxially stretching at a high temperature of 3 mm / min at a stretching rate of 100% and measuring the in-plane retardation value of the central portion of the test piece is 10. Containing transparent thermoplastic resin (B) less than 0 × 10 ^-4 ,
When the glass transition temperature of the retardation adjusting layer is Tg _A (° C.) and the glass transition temperature of the substrate layer is Tg _B (° C.), Tg _A > Tg _B.
When the total thickness of the retardation adjusting layer is _TA and the thickness of the base material layer is _TB , _TA < _TB .
A liquid crystal display protective plate having an in-plane retardation value of 50 to 330 nm of the flat resin plate. The liquid crystal display protective plate according to claim 1, wherein the transparent thermoplastic resin (A) is a copolymer having the ring structure unit of 30 to 99% by mass and the vinyl-based monomer unit of 70 to 1% by mass. The liquid crystal display protective plate according to claim 1 or 2, wherein the transparent thermoplastic resin (A) is a methacrylic resin having the ring structure unit and the methyl methacrylate unit. The liquid crystal display protective plate according to any one of claims 1 to 3, wherein Tg _A -Tg _B is 20 ° C. or higher. The liquid crystal display protective plate according to any one of claims 1 to 4, wherein the flat resin plate has a standard deviation of a retardation value in a plane within a range of 17 cm in width and 22 cm in length of 15.0 nm or less. Claims 1 to 5, wherein the flat resin plate has an absolute value of the rate of change of the in-plane retardation value after heating with respect to before heating when heated to a temperature of Tg _B or more and Tg _A or less. The liquid crystal display protective plate according to any one of the items. Claims 1 to 6 indicate that when the flat resin plate is heated to a temperature of Tg _B or more and Tg _A or less, the standard deviation of the in-plane retardation value within the range of 17 cm in width and 22 cm in length is 25.0 nm or less. The liquid crystal display protective plate according to any one of the above items. A resin plate having a curved surface in which a phase difference adjusting layer is laminated on at least one surface of a base material layer is included.
The phase difference adjusting layer has at least one ring structure unit selected from the group consisting of an acid anhydride unit, an imide unit including a ring structure, and a lactone ring unit in the main chain, and has a glass transition temperature (Tg _A0 ). ) Is 135 to 180 ° C., the absolute value of the photoelastic coefficient ( _CA ) is 10.0 × ^10-12 / Pa or less, and the test piece having a width of 20 mm, a length of 40 mm, and a thickness of 1 mm is subjected to a glass transition temperature. Absolute value of orientation double refraction (Δn _A ) obtained by uniaxially stretching at a rate of 3 mm / min at a higher temperature of 10 ° C. and measuring the in-plane retardation value of the central portion of the test piece. Contains the transparent thermoplastic resin (A) of 10.0 × 10 ^-4 to 100.0 × 10 ^-4 .
The base material layer has a photoelastic coefficient ( _CB ) of 10.0 × ^10-12 / Pa or less, and a test piece having a width of 20 mm, a length of 40 mm, and a thickness of 1 mm is placed at 10 ° C. above the glass transition temperature. The absolute value of the orientation birefringence (Δn _B ) obtained by uniaxially stretching at a high temperature of 3 mm / min at a stretching rate of 100% and measuring the in-plane retardation value of the central portion of the test piece is 10. Containing transparent thermoplastic resin (B) less than 0 × 10 ^-4 ,
When the glass transition temperature of the retardation adjustment layer is Tg _A (° C.) and the glass transition temperature of the substrate layer is Tg _B (° C.), Tg _A > Tg _B.
When the total thickness of the retardation adjusting layer is _TA and the thickness of the base material layer is _TB , _TA < _TB .
A liquid crystal display protective plate with a curved surface, wherein the in-plane retardation value of the resin plate having a curved surface is 50 to 330 nm. The curved liquid crystal display protection according to claim 8, wherein the transparent thermoplastic resin (A) is a copolymer having the ring structure unit of 30 to 99% by mass and the vinyl-based monomer unit of 70 to 1% by mass. Board. The curved liquid crystal display protective plate according to claim 8 or 9, wherein the transparent thermoplastic resin (A) is a methacrylic resin having the ring structure unit and the methyl methacrylate unit. The liquid crystal display protective plate with a curved surface according to any one of claims 8 to 10, wherein Tg _A -Tg _B is 20 ° C. or higher. The liquid crystal display with a curved surface according to any one of claims 8 to 11, wherein the resin plate having a curved surface has a standard deviation of a retardation value in a plane within a range of 17 cm in width and 22 cm in length of 25.0 nm or less. Display protection plate. The liquid crystal display protective plate according to any one of claims 1 to 7, or the liquid crystal display protective plate with a curved surface according to any one of claims 8 to 12, which has a cured film on at least one outermost surface. A step of forming a flat resin plate in which the phase difference adjusting layer is laminated on at least one surface of the base material layer, and
The curved liquid crystal display protective plate according to any one of claims 8 to 12, further comprising a step of heating the flat resin plate to a temperature of Tg _B or more and Tg _A or less and thermoforming into a shape having a curved surface. Production method.

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