Liquid crystal display protection plate, and curved liquid crystal display protection plate and method for manufacturing the same

Abstract

The present invention provides a liquid crystal display protection plate capable of suppressing the degradation of visibility such as color unevenness, blackout, and coloring when a liquid crystal display protection plate on a liquid crystal screen is observed through a polarizing filter. The liquid crystal display protection plate (1) includes a resin plate (16) in which base material layers (22) are laminated on both surfaces of a phase difference adjustment layer (21). The phase difference adjustment layer contains a transparent thermoplastic resin (A) having an absolute value of a photoelastic coefficient of 10.0×10-12 / Pa or less and an absolute value of an orientation birefringence of 10.0×10-4-100.0×10-4. The base material layers each contain a transparent thermoplastic resin (B) having an absolute value of a photoelastic coefficient of 10.0×10-12 / Pa or less and having an absolute value of an orientation birefringence of less than 10.0×10-4. The Tg of the phase difference adjustment layer is higher than the Tg of the base material layer. The total thickness of the base material layers is larger than the thickness of the phase difference adjustment layer. The Re value of the resin plate is 50-330 nm.

Description

Technical Field

[0001] The present invention relates to a liquid crystal display protection plate, a curved liquid crystal display protection plate, and a method for manufacturing the same.

Background Art

[0002] In a liquid crystal display and a touch panel display in which a liquid crystal display and a touch panel are combined, a protection plate may be provided on the front side thereof to prevent the surface from being damaged. In this specification, this protection plate is referred to as a "liquid crystal display protection plate". The liquid crystal display protection plate includes a resin plate made of at least one layer of a thermoplastic resin layer and a cured film formed on at least one surface of the resin plate as required.

[0003] Patent Document 1 discloses a scratch-resistant resin plate including a methacrylic resin plate and a cured film formed on at least one surface thereof, which is suitable as a display window protection plate for a portable information terminal (Claims 1, 2, 7, Paragraph 0010, etc.). Patent Document 2 discloses a polycarbonate-based resin laminate for a liquid crystal display cover including a laminate in which a methacrylic resin layer is laminated on one surface of a polycarbonate-based resin layer and a cured film formed on the methacrylic resin layer of this laminate (Claims 1, Paragraph 0008, etc.).

[0004] The liquid crystal display protection plate is installed on the front side (viewer side) of the liquid crystal display, and the viewer views the screen of the liquid crystal display through this protection plate. Here, since the liquid crystal display protection plate hardly changes the polarization property of the light emitted from the liquid crystal display, when viewing the screen through a polarization filter such as polarized sunglasses, depending on the angle formed by the polarization axis of the emitted light and the transmission axis of the polarization filter, the screen may become dark and the visibility of the image may decrease (blackout phenomenon).

[0005] Therefore, a liquid crystal display protection plate that can suppress a decrease in the 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 discloses a liquid crystal display protection plate made of a scratch-resistant resin plate having a cured film formed on at least one surface of the resin plate, and having an in-plane retardation value (also referred to as "Re value") of 85 to 300 nm (Claim 1).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0007] In recent years, in applications such as in-vehicle car navigation systems and display audio, displays with shape processing such as curved surface processing have been developed from the viewpoints of design and visibility. For a display having a curved surface, a liquid crystal display protection plate with a curved surface adapted to the shape is used. A liquid crystal display protection plate with a curved surface can be manufactured by forming a cured film on a flat resin plate obtained by extrusion molding or the like, if necessary, and then performing thermoforming such as press molding, vacuum molding, and pressure air molding. The resin plate included in the liquid crystal display protection plate preferably has an Re value within a suitable range and a small variation in the Re value both before and after thermoforming.

[0008] Patent Document 4 aims to provide a resin laminate (resin plate) that is excellent in thermoformability or printability at low temperatures and suppresses the occurrence of coloring and color unevenness after thermoforming. Patent Document 4 discloses a resin laminate in which an acrylic resin layer is laminated on at least one surface of a polycarbonate resin layer by coextrusion molding, the heat shrinkage rate in the width direction is -10 to 0%, the heat shrinkage rate in the extrusion direction is 0 to 10%, and the Re value is 1500 nm or less (Claim 1). In Patent Document 4, the polycarbonate resin has a terminal structure derived from a specific monohydric phenol, thereby lowering the glass transition temperature of the polycarbonate resin and enabling thermoformability at low temperatures (Paragraph 0018). The resin laminate described in Patent Document 4 preferably further has a hard coat layer on the acrylic resin layer (Claim 7).

[0009] In Patent Documents 3 and 4, the resin plate is preferably a laminate in which a methacrylic resin layer is laminated on at least one surface of a polycarbonate resin layer (Claim 6 of Patent Document 3, Paragraph 0096 of Patent Document 4). In these laminates, for example, by adjusting the molding conditions according to the thickness of the resin plate, the birefringence of the polycarbonate resin layer can be adjusted, and the Re value of the liquid crystal display protection plate can be adjusted within a suitable range (Paragraph 0036 of Patent Document 3, etc.).

[0010] An image diagram showing the relationship between stress and birefringence, and the relationship between orientation birefringence, stress birefringence, and photoelastic coefficient is shown in FIG. 7. The polycarbonate resin used in Patent Documents 3 and 4 has an extremely large absolute value of the photoelastic coefficient of 90×10 -12 / Pa, and the Re value changes with a slight stress. Therefore, when using a polycarbonate resin, it is difficult to obtain an optically uniform liquid crystal display protection plate. For example, when observing a liquid crystal display protection plate on a liquid crystal screen through a polarizing filter, color unevenness may be observed due to variations 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.

[0011] The methacrylic resin used in Patent Document 1 has a small absolute value of photoelastic coefficient of 3.2×10 -12 / Pa, and the Re value hardly changes with stress. Therefore, when using a methacrylic resin, an optically uniform liquid crystal display protection plate can be obtained. However, since the absolute value of the orientation birefringence of the methacrylic resin is as small as 4.0×10 -4 , although it depends on the thickness, the Re value of the obtained liquid crystal display protection plate tends to be as small as about 20 nm. Therefore, when observing the liquid crystal display protection plate on the liquid crystal screen through a polarizing filter, depending on the angle formed by the polarization axis of the emitted light and the transmission axis of the polarizing filter, a blackout may occur where the screen becomes completely dark, and the visibility of the image may decrease.

[0012] Also, generally, when the Re value of the liquid crystal display protection plate is larger than the suitable range, when viewed through a polarizing filter, the difference in the light transmittance of each wavelength in the visible light region becomes large, and various colors may be seen, which may reduce the visibility (coloring phenomenon).

[0013] The present invention has been made in view of the above circumstances, and in both before and after thermoforming, the in-plane retardation value (Re value) is within a suitable range, the variation in the in-plane retardation value (Re value) is small, and when observing the liquid crystal display protection plate on the liquid crystal screen through a polarizing filter, it is possible to suppress a decrease in visibility such as color unevenness, blackout, and coloring. An object is to provide a liquid crystal display protection plate.

Means for Solving the Problems

[0014] The present invention provides a liquid crystal display protection plate, a liquid crystal display protection plate with a curved surface, and a method for manufacturing the same, as described in the following [1] to

[13] . [1] It includes a flat resin plate in which a base material layer is laminated on both sides of a retardation adjustment layer, The retardation adjustment layer has an absolute value of photoelastic coefficient (C A ) of 10.0×10 -12is 10 / 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 uniaxially stretched at a rate of 3 mm / min at a temperature 10 °C higher than the glass transition temperature with a draw ratio of 100%, and the orientation birefringence (Δn A ) whose absolute value is obtained by measuring the retardation value in the plane of the central portion of the test piece is 10.0×10 -4 ~100.0×10 -4 . The transparent thermoplastic resin (A) is included, The base material layer has an absolute value of the photoelastic coefficient (C B ) 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 uniaxially stretched at a rate of 3 mm / min at a temperature 10 °C higher than the glass transition temperature with a draw ratio of 100%, and the orientation birefringence (Δn B ) whose absolute value is obtained by measuring the retardation value in the plane of the central portion of the test piece is less than 10.0×10 -4 . The transparent thermoplastic resin (B) is included, When the glass transition temperature of the retardation adjustment layer is Tg A and the glass transition temperature of the base material layer is Tg B , Tg A >Tg B , When the thickness of the retardation adjustment layer is T A and the total thickness of the base material layer is T B , T A <T B , A liquid crystal display protection plate, wherein the in-plane retardation value (Re value) of the flat resin plate is 50 to 330 nm.

[0015] [2] The liquid crystal display protection plate according to [1], wherein the flat resin plate has a standard deviation of the in-plane retardation value (Re value) within a range of 17 cm in width and 22 cm in length of 15.0 nm or less. [3] The liquid crystal display protection plate according to [1] or [2], wherein when the flat resin plate is heated to a temperature of Tg B or higher and Tg A or lower, the absolute value of the change rate of the in-plane retardation value (Re value) after heating with respect to that before heating is 50% or less. [4] The flat resin plate has a Tg B or higher Tg A When heated to a temperature of or lower, the standard deviation of the in-plane retardation value (Re value) within a range of 17 cm in width and 22 cm in length is 25.0 nm or less, the liquid crystal display protection plate according to any one of [1] to [3].

[0016] [5] The transparent thermoplastic resin (A) contains an aromatic vinyl monomer unit, Let the content of the aromatic vinyl monomer unit in the transparent thermoplastic resin (A) be V [mass%], and the thickness of the retardation adjustment layer be T A [mm], the liquid crystal display protection plate according to any one of [1] to [4], which satisfies the following formula (1). 6.0 ≦ V × T A ≦ 30.0 ··· (1) [6] The liquid crystal display protection plate according to any one of [1] to [5], provided with a cured film on at least one outermost surface. [7] The liquid crystal display protection plate according to any one of [1] to [6], wherein the flat resin plate is an extruded plate.

[0017] [8] Including a resin plate having a curved surface, with a substrate layer laminated on both sides of the retardation adjustment layer, The retardation adjustment layer has an absolute value of the photoelastic coefficient (C A ) of 10.0 × 10 -12 / Pa or less, and a test piece with a width of 20 mm, a length of 40 mm, and a thickness of 1 mm is uniaxially stretched at a rate of 3 mm / min with a 100% elongation rate at a temperature 10 °C higher than the glass transition temperature, and the in-plane retardation value of the central portion of the test piece is measured to obtain the absolute value of the orientation birefringence (Δn A ) of 10.0 × 10 -4 ~100.0 × 10 -4 , and includes a transparent thermoplastic resin (A), The substrate layer has an absolute value of the photoelastic coefficient (C B ) of 10.0 × 10 -12It is below / Pa, and a test piece with a width of 20 mm, a length of 40 mm, and a thickness of 1 mm is uniaxially stretched at a rate of 3 mm / min at a temperature 10 °C higher than the glass transition temperature with an elongation rate of 100%, and the in-plane retardation value of the central part of the test piece is measured to obtain the orientation birefringence (Δn B ) whose absolute value is less than 10.0×10 -4 . It contains a transparent thermoplastic resin (B), Let the glass transition temperature of the retardation adjustment layer be Tg A , and let the glass transition temperature of the base material layer be Tg B . When A Tg B >, Let the thickness of the retardation adjustment layer be T A , and let the total thickness of the base material layer be T B . When A T B >, A liquid crystal display protection plate with a curved surface, wherein the in-plane retardation value of the resin plate having the curved surface is 50 to 330 nm.

[0018] [9] The liquid crystal display protection plate with a curved surface according to [8], wherein the standard deviation of the in-plane retardation value within the range of a width of 17 cm and a length of 22 cm of the resin plate having the curved surface is 25.0 nm or less.

[10] The transparent thermoplastic resin (A) contains an aromatic vinyl monomer unit, Let the content of the aromatic vinyl monomer unit in the transparent thermoplastic resin (A) be V [mass%], and let the thickness of the retardation adjustment layer be T A [mm]. The liquid crystal display protection plate with a curved surface according to [8] or [9] that satisfies the following formula (1). 6.0 ≦ V × T A ≦ 30.0 ··· (1)

[11] The liquid crystal display protection plate with a curved surface according to any one of [8] to

[10] , having a cured film on at least one outermost surface.

[12] The liquid crystal display protection plate with a curved surface according to any one of [8] to

[11] , wherein the resin plate having the curved surface is a thermoformed plate obtained by thermoforming a flat resin plate.

[0019] Step of forming a flat resin plate with the substrate layers laminated on both sides of the retardation adjustment layer; heating the flat resin plate to a temperature of Tg B or higher and Tg A or lower, and thermoforming it into a shape with a curved surface, the method for manufacturing a liquid crystal display protection plate with a curved surface according to any one of [8] to

[12] .

Advantages of the Invention

[0020] According to the present invention, in both before and after thermoforming, the in-plane retardation value (Re value) is within a suitable range, the variation of the in-plane retardation value (Re value) is small, and it is possible to provide a liquid crystal display protection plate that suppresses a decrease in visibility such as color unevenness, blackout, and coloring when observing the liquid crystal display protection plate on the liquid crystal screen through a polarizing filter.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0022] Generally, for a thin film formed body, depending on the thickness, the terms "film", "sheet", or "plate" are used, but there is no clear distinction among them. The "resin plate" referred to in this specification shall include "resin film" and "resin sheet". In this specification, the glass transition temperature of a general material is represented by "Tg".

[0023] [Liquid Crystal Display Protective 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 base material layer is laminated on both sides of a retardation adjustment layer. The flat resin plate is preferably an extruded plate. By thermoforming the above liquid crystal display protective plate of the present invention, a liquid crystal display protective plate with a curved surface can be manufactured. 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 base material layer is laminated on both sides of a retardation adjustment layer, and further includes a cured film as required. 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 outermost surface as required.

[0024] In the liquid crystal display protective plate and the liquid crystal display protective plate with a curved surface of the present invention, the retardation adjustment layer contains a transparent thermoplastic resin (A) having specific optical properties, and the base material layer contains a transparent thermoplastic resin (B) having specific optical properties. When the glass transition temperature of the retardation adjustment layer is Tg A (°C) and the glass transition temperature of the base material layer is Tg B (°C), Tg A >Tg B is satisfied. When the thickness of the retardation adjustment layer is T A and the total thickness of the base material layer is T B , T A <T B is satisfied.

[0025] The in-plane retardation value (also referred to as the "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 the range of 17 cm in width and 22 cm in length of 15.0 nm or less. The flat resin plate has a Tg B Tg or higher A When heated to a temperature below, the absolute value of the change rate of the Re value after heating with respect to before heating is preferably 50% or less. The flat resin plate has a Tg B Tg or higher A When heated to a temperature below, 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 the range of 17 cm in width and 22 cm in length of 25.0 nm or less.

[0026] FIG. 1 and FIG. 2 are schematic cross-sectional views of the liquid crystal display protection plates according to the first and second embodiments of the present invention. In the figures, reference numerals 1 and 2 denote the liquid crystal display protection plates, reference numeral 16 denotes the flat resin plate, reference numeral 21 denotes the retardation adjustment layer, reference numeral 22 denotes the base material layer, and reference numeral 31 denotes the cured film, respectively. The liquid crystal display protection plate 1 of the first embodiment is composed of a flat resin plate 16 having a three-layer structure in which base material layers 22 are laminated on both sides of the retardation adjustment layer 21. The liquid crystal display protection plate 2 of the second embodiment is formed with a cured film 31 on at least one surface of a flat resin plate 16 having a three-layer structure in which base material layers 22 are laminated on both sides of the retardation adjustment layer 21. In the example shown in FIG. 2, cured films 31 are formed on both sides of the flat resin plate 16. The configuration of the liquid crystal display protection plate is not limited to the illustrated example, and design changes can be made as appropriate without departing from the spirit of the present invention. As shown in FIGS. 1 and 2, a flat liquid crystal display protection plate can be thermoformed to produce a liquid crystal display protection plate with a curved surface.

[0027] In a flat resin plate and a resin plate having a curved surface, the retardation adjustment layer has an absolute value of photoelastic coefficient (C A ) of 10.0×10 -12 / Pa or less, and a test piece with a width of 20 mm, a length of 40 mm, and a thickness of 1 mm is uniaxially stretched at a rate of 3 mm / min at a temperature 10 °C higher than the glass transition temperature with a 100% elongation rate, and the in-plane retardation value at the central portion of the uniaxially stretched test piece is measured and obtained. The absolute value of the orientation birefringence (Δn A ) is 10.0×10 -4 ~100.0×10 -4 . It contains a transparent thermoplastic resin (A).

[0028] "Retardation" is the phase difference between the light in the direction of the molecular main chain and the light in the direction perpendicular to it. Generally, a polymer can obtain an arbitrary shape by being heated and melt-molded, but it is known that retardation occurs due to the stress generated during the heating and cooling processes and the orientation of molecules. In this specification, unless otherwise specified, "retardation" refers to the in-plane retardation.

[0029] Generally, the Re value of a resin plate is represented by the following formula (i). [Re value of resin plate] = [Birefringence (ΔN)] × [Thickness (d)] ··· (i) Birefringence (ΔN) is represented by the following formula (ii). [Birefringence] = [Stress birefringence] + [Orientation birefringence] ··· (ii) Stress birefringence and orientation birefringence are represented by the following formulas (iii) and (iv), respectively. [Stress birefringence] = [Photoelastic coefficient (C)] × [Stress] ··· (iii) [Orientation birefringence] = [Intrinsic birefringence] × [Orientation degree] ··· (iv) In formula (iv), the orientation degree is a value in the range of 0 to 1.0. An image diagram showing the relationship between stress and birefringence, and the relationship between orientation birefringence, stress birefringence, and photoelastic coefficient is shown in Fig. 7.

[0030] 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 the orientation birefringence schematically shown in FIG. 7. In the liquid crystal display protection plate and the curved liquid crystal display protection plate of the present invention, by including a retardation adjustment layer containing the transparent thermoplastic resin (A) having the above specific optical properties, when observing the liquid crystal display protection plate on the liquid crystal screen through a polarizing filter, it is possible to suppress a decrease in visibility such as color unevenness and blackout.

[0031] In this specification, the "Re value of the resin plate" is the average value of the Re values of about 110,000 birefringence pixels within a measurement range of 17 cm in width and 22 cm in length, unless otherwise specified. The "standard deviation of the Re value of the resin plate" is the standard deviation of the Re values of about 110,000 birefringence pixels within a measurement range of 17 cm in width and 22 cm in length, unless otherwise specified. The average value and the standard deviation of the Re value can be measured, for example, using a retardation measuring instrument "WPA-100-L" manufactured by Photonic Lattice Co., Ltd. by the method described in the section of [Examples] below.

[0032] 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, particularly preferably 90 to 150 nm, and most preferably 100 to 140 nm. When the Re value is less than the above lower limit value, when observing the liquid crystal display protection plate on the liquid crystal screen through a polarizing filter, blackout may occur regardless of the relationship between the polarization axis of the emitted light and the transmission axis of the polarizing filter. When the Re value exceeds the above upper limit value, when visually recognized through a polarizing filter, the difference in the light transmittance of each wavelength in the visible light region becomes large, and various colors may be seen, resulting in a possible decrease in visibility (colored phenomenon).

[0033] For the standard deviation of the Re value of a flat resin plate and a resin plate having a curved surface, the smaller it is, the less variation in the Re value, which is preferable. If the standard deviation of the Re value is sufficiently small, when observing a liquid crystal display protection plate on a liquid crystal screen through a polarizing filter, color unevenness caused by variation in the Re value is suppressed and visibility is improved. The standard deviation of the Re value of the flat resin plate is preferably 15 nm or less, more preferably 10 nm or less, still more preferably 7 nm or less, particularly preferably 5 nm or less, and most preferably 4 nm or less. 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.

[0034] 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 higher and Tg A or lower, more preferably Tg B or higher and Tg A lower. When the flat resin plate is heated to a temperature of Tg B or higher and Tg A or lower, the absolute value of the change rate of the Re value after heating with respect to the Re value before heating is preferably 50% or less, more preferably 45% or less, still more preferably 40% or less, particularly preferably 35% or less, and most preferably 30% or less. The change rate of the Re value after heating with respect to the Re value before heating is represented by the following formula. [Change rate of Re value after heating with respect to Re value before heating](%) = ([Re value after heating] - [Re value before heating]) / [Re value before heating] × 100

[0035] When the flat resin plate is heated to a temperature of Tg B or higher and Tg A or lower, the standard deviation of the Re value within a 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, particularly preferably 15.0 nm or less, and most preferably 10.0 nm or less.

[0036] The overall thickness (d) of the flat resin plate and the resin plate having a curved surface is not particularly limited, preferably 0.2 to 4.5 mm, more preferably 0.3 to 4.0 mm, and particularly preferably 0.4 to 3.0 mm. If it is too thin, the rigidity of the liquid crystal display protection plate may be insufficient, and if it is too thick, it may prevent the weight reduction of the liquid crystal display or the touch panel display including the same.

[0037] (Retardation adjustment layer) The flat resin plate and the resin plate having a curved surface include a retardation adjustment layer. The retardation adjustment layer is a layer that mainly determines the Re value of the liquid crystal display protection plate and contains a transparent thermoplastic resin (A) having specific optical properties.

[0038] <Transparent thermoplastic resin (A)> The absolute value of the photoelastic coefficient (C A ) of the transparent thermoplastic resin (A) is 10.0×10 -12 / Pa or less, preferably 8.0×10 -12 / Pa or less, more preferably 6.0×10 -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 (C A ) is below the above upper limit value, stress birefringence due to residual stress generated during molding processes such as extrusion molding is small (see Fig. 7), and the standard deviation of the Re value of the liquid crystal display protection plate can be reduced. As a result, when observing the liquid crystal display protection plate on the liquid crystal screen through a polarizing filter, color unevenness caused by variations in the Re value is suppressed, and visibility is improved.

[0039] The absolute value of the orientation birefringence (Δn A ) of the transparent thermoplastic resin (A) is 10.0×10 -4 ~100.0×10 -4 and preferably 20.0×10 -4 ~90.0×10 -4 more preferably 30.0×10 -4 ~70.0×10 -4, particularly preferably 35.0×10 -4 ~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 protection 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. In this specification, unless otherwise specified, "orientation birefringence" shall be measured by the method described in the section of [Examples] below.

[0040] The transparent thermoplastic resin (A) is not particularly limited as long as it is a transparent thermoplastic resin that satisfies the range of the photoelastic coefficient (C A ) and the orientation birefringence (Δn A ). In one aspect, the transparent thermoplastic resin (A) can contain one or more aromatic vinyl monomer units. The aromatic vinyl monomer is not particularly limited, and examples thereof include styrene (St); nuclear alkyl-substituted styrenes such as 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-ethylstyrene, and 4-tert-butylstyrene; α-alkyl-substituted styrenes such as α-methylstyrene and 4-methyl-α-methylstyrene. Among them, styrene (St) is preferable from the viewpoint of availability.

[0041] Let the content of the aromatic vinyl monomer unit in the transparent thermoplastic resin (A) be V [mass%], and the thickness of the retardation layer be T A [mm]. The product of these (V×T A ) preferably satisfies the following formula (1). 6.0≦V×T A ≦30.0···(1) The transparent thermoplastic resin (A) has a small absolute value of the photoelastic coefficient (C A ), and the stress birefringence is almost zero. When the transparent thermoplastic resin (A) contains an aromatic vinyl monomer unit such as a styrene (St) unit, the orientation birefringence (Δn A) tends to depend on the content V [mass%] of the aromatic vinyl monomer unit in the transparent thermoplastic resin (A). Therefore, V × T A is strongly correlated with the Re value of the liquid crystal display protective plate. V × T A When satisfies the above formula (1), the Re value of the liquid crystal display protective plate can be controlled within an appropriate range.

[0042] In addition to the aromatic vinyl monomer unit, the transparent thermoplastic resin (A) may be a copolymer having methacrylic acid ester units such as methyl methacrylate (MMA) units; acid anhydride units such as maleic anhydride units; and other monomer units such as acrylonitrile units. Specific examples of the transparent thermoplastic resin (A) containing an aromatic vinyl monomer unit include methacrylic acid ester-styrene copolymer (MS resin); styrene-maleic anhydride copolymer (SMA resin); styrene-methacrylic acid ester-maleic anhydride copolymer (SMM resin); α-methylstyrene-maleic anhydride-methacrylic acid ester copolymer (αStMM resin); acrylonitrile-styrene copolymer (AS resin); acrylic imide resin, and the like. These can be used alone or in combination of two or more.

[0043] The following products are listed as commercially available products of the above resins. MS resin: "Toyolac MS" manufactured by Toyo Styrene, etc., SMA resin: "Plexiglas FT15" manufactured by Daicel-Evonik, "XIBOND", "XIRAN" manufactured by Polyscope, etc., SMM resin: "Resifai" manufactured by Denka, etc., AS resin: "Lytac-A" manufactured by Nippon A&L, etc., Acrylic imide resin: "Pleximid" manufactured by Daicel-Evonik, etc.

[0044] The transparent thermoplastic resin (A) has a photoelastic coefficient (C defined in the present invention A ) and orientation birefringence (Δn AAs long as it satisfies the range of (), a resin containing no aromatic vinyl monomer units may be used. Examples of the transparent thermoplastic resin (A) containing no aromatic vinyl monomer units include modified methacrylic resins containing at least one unit selected from methacrylic ester units such as methyl methacrylate units, glutarimide units, N-substituted or unsubstituted maleimide units, and lactone ring units. These can be used alone or in combination of two or more.

[0045] The transparent thermoplastic resin (A) is a resin containing aromatic vinyl monomer units that satisfy the range of the photoelastic coefficient (C A ) and the orientation birefringence (Δn A ), or a mixture of a resin containing no aromatic vinyl monomer units (such as a modified methacrylic resin) that satisfies the range of the photoelastic coefficient (C A ) and the orientation birefringence (Δn A ) defined in the present invention.

[0046] In the present invention, general methacrylic resins (unmodified methacrylic resins) and polycarbonate resins other than the above do not satisfy the photoelastic coefficient and / or the orientation birefringence within the defined range of the present invention and are not included in the transparent thermoplastic resin (A). The absolute value of the photoelastic coefficient of the polycarbonate resin is as large as 90×10 -12 / Pa, and the Re value changes with a slight stress. Therefore, when using a polycarbonate resin, it is difficult to obtain an optically uniform liquid crystal display protection plate. For example, when observing a liquid crystal display protection plate on a liquid crystal screen through a polarizing filter, color unevenness may be observed due to variations in the Re value. In particular, before thermoforming and after thermoforming, the change in the Re value of the resin plate is large, and the variation in the Re value of the resin plate tends to increase. The thermoforming process includes, for example, a process of heating the resin plate, a process of pressing a mold against the heated resin plate, a process of cooling the resin plate in the mold, and a process 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-based resin with a large absolute value of the photoelastic coefficient, significant retardation unevenness is caused by the residual stress generated in the cooling process of thermoforming, and the variation in the Re value of the resin plate tends to increase. The methacrylic resin has a small absolute value of the photoelastic coefficient of 3.2×10 -12 / Pa, and the Re value hardly changes with stress. Therefore, when using a methacrylic resin, an optically uniform liquid crystal display protection plate can be obtained. However, since the absolute value of the orientation birefringence of the methacrylic resin is 4.0×10 -4 is small, depending on the thickness, the Re value of the obtained liquid crystal display protection plate tends to be as small as about 20 nm. Therefore, when observing the liquid crystal display protection plate on the liquid crystal screen through a polarizing filter, depending on the angle formed by the polarization axis of the emitted light and the transmission axis of the polarizing filter, blackout may occur where the screen becomes completely dark, and the visibility of the image may decrease.

[0047] The thickness (T A ) of the retardation adjustment layer is not particularly limited, preferably 0.05 to 3.0 mm, more preferably 0.05 to 0.5 mm, particularly preferably 0.1 to 0.3 mm, and most preferably 0.1 to 0.2 mm.

[0048] The retardation adjustment layer can contain, in a small amount, one or more other polymers whose photoelastic coefficient and / or orientation birefringence are outside the defined range of the transparent thermoplastic resin (A). The type of other polymers is not particularly limited, and examples include general non-modified methacrylic resins, polycarbonate resins, polyolefins such as polyethylene and polypropylene, polyamides, polyphenylene sulfides, polyether ether ketones, polyesters, polysulfones, polyphenylene oxides, polyimides, polyetherimides, and other thermoplastic resins such as polyacetals; thermosetting resins such as phenol resins, melamine resins, silicone resins, and epoxy resins, etc. A general non-modified methacrylic resin is, for example, a resin composed of one or more methacrylic acid ester units. It is preferable that the content of the transparent thermoplastic resin (A) in the retardation adjustment layer is higher, preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 98% by mass or more. The content of other polymers in the retardation adjustment layer is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 2% by mass or less.

[0049] The retardation adjustment layer can contain various additives as needed. Examples of additives include colorants, antioxidants, heat degradation inhibitors, ultraviolet absorbers, light stabilizers, lubricants, mold release agents, polymer processing aids, antistatic agents, flame retardants, light diffusing agents, matting agents, rubber components such as core-shell particles and block copolymers (impact resistance modifiers), and phosphors, etc. The content of the additives can be appropriately set within a range that does not impair the effects of the present invention. With respect to 100 parts by mass of the constituent resin of the retardation adjustment layer, for example, the content of the antioxidant is preferably 0.01 to 1 part by mass, the content of the ultraviolet absorber is preferably 0.01 to 3 parts by mass, the content of the light stabilizer 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 adding other polymers and / or additives to the retardation adjustment layer, the addition timing can be either during the polymerization of the transparent thermoplastic resin (A) or after the polymerization.

[0050] The retardation adjustment layer may be a resin layer composed of a resin composition containing a transparent thermoplastic resin (A) and a known rubber component (impact modifier). Examples of the rubber component include core-shell structured multilayer polymer particles, rubber-like polymers having a salami structure, and block polymers. The rubber component can contain diene monomer units, alkyl acrylate monomer units, and the like. From the viewpoint of the transparency of the retardation adjustment 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.

[0051] The glass transition temperature (TgA) of the retardation adjustment layer is not particularly limited as long as TgA > TgB is satisfied. Preferably it is 90 to 170 °C, more preferably 100 to 160 °C, particularly preferably 110 to 155 °C, and most preferably 130 to 155 °C. Note that the "glass transition temperature (TgA) of the retardation adjustment layer" is the glass transition temperature of all the constituent materials of the retardation adjustment layer composed of one or more transparent thermoplastic resins (A) and, if necessary, one or more optional components.

[0052] Tg A and Tg B The difference (Tg A -Tg B ) is preferably 5 to 70 °C, more preferably 10 to 50 °C, particularly preferably 15 to 45 °C, and most preferably 20 to 40 °C. If Tg A -Tg B is within the above range, as will be described in detail below, it is possible to suppress the change in the Re value of the resin plate, thermoform the resin plate well, and further suppress the deformation of the obtained curved liquid crystal display protection plate.

[0053] In the present invention, thermoforming can preferably be performed at a temperature of Tg B or higher and Tg A or lower. Tg B +10 °C to Tg BIt is more preferable to perform thermoforming at a temperature of +30°C. Within this temperature range, the resin plate can be well thermoformed into a desired shape, and the residual stress generated in the cooling process of thermoforming can be suppressed to a small level. In this case, the change in the Re value can be suppressed, and the deformation of the obtained liquid crystal display protection plate with a curved surface can be suppressed. For example, when a reliability test (such as 1000 hours at 105°C or 72 hours at 85°C and 85% RH) for an in-vehicle display is performed on the liquid crystal display protection plate with a curved surface, the deformation due to the release of residual stress is suppressed, which is preferable.

[0054] Tg B +10°C to Tg B Within the range of +30°C and below Tg A It is particularly preferable to perform thermoforming at a temperature below Tg. A If it is at a temperature below Tg, since the stress and orientation of the retardation adjustment layer are not released, the change in the Re value and the deformation of the liquid crystal display protection plate with a curved surface are effectively suppressed, which is preferable. Tg B When thermoforming is performed at a temperature below +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 forming time is lengthened, etc., the resin plate can be thermoformed into a desired shape, but a large forming stress is generated in the resin plate. When a reliability test for an in-vehicle display is performed on the liquid crystal display protection plate with a curved surface obtained under this condition, a large residual stress is released, and there is a risk of significant deformation.

[0055] (Base material layer) The flat resin plate and the resin plate having a curved surface are laminated on both sides of the above-mentioned retardation adjustment layer and include a base material layer having a glass transition temperature (Tg) lower than that of the retardation adjustment layer. The base material layer can increase the overall thickness (d) of the resin plate and improve the rigidity of the resin plate.

[0056] In the above lamination structure, the following effects can be obtained. A flat resin plate with a retardation adjustment layer on its surface at Tg B Tg or higher AWhen thermoforming at the following temperatures, there is a risk of cracking in the retardation adjustment layer. Especially when the retardation adjustment layer contains brittle resins such as SMA resin and SMM resin, cracks are likely to occur in the retardation adjustment layer during thermoforming at the above temperatures. In a flat resin plate with substrate layers formed on both sides of the retardation adjustment layer, even when the retardation adjustment layer contains brittle resins such as SMA resin and SMM resin, Tg B Tg or higher A When thermoforming at temperatures below this, cracking of the retardation adjustment layer can be effectively suppressed. In the heating process of thermoforming, the temperature of the surface rises first and then the temperature of the interior rises. In a laminated structure with substrate layers formed on both sides of the retardation adjustment layer, the temperature of the retardation adjustment layer inside rises less easily than the substrate layer on the surface. Therefore, the change in the Re value after thermoforming compared to before thermoforming can be effectively suppressed more than when heating a flat resin plate with a retardation adjustment layer on the surface.

[0057] The substrate layer is preferably a resin layer that does not affect the Re value of the liquid crystal display protection plate, and is preferably a resin layer containing a transparent thermoplastic resin (B) with a sufficiently small photoelastic coefficient and orientation birefringence. The composition and thickness of the substrate layers laminated on both sides of the retardation adjustment layer may be the same or different as long as each substrate layer is a resin layer containing the transparent thermoplastic resin (B) having the above optical properties.

[0058] <Transparent thermoplastic resin (B)> The absolute value of the photoelastic coefficient (C B ) of the transparent thermoplastic resin (B) is preferably smaller, preferably 10.0×10 -12 / Pa or less, more preferably 8.0×10 -12 / Pa or less, still more preferably 6.0×10 -12 / Pa or less, particularly preferably 5.0×10 -12 / Pa or less, most preferably 4.0×10 -12 / Pa or less. The photoelastic coefficient (C BWhen the absolute value of () is equal to or less than the above upper limit value, stress birefringence due to residual stress generated during molding processes such as extrusion molding is sufficiently small (see Fig. 7), and the standard deviation of the Re value of the resin plate can be reduced. As a result, when observing the liquid crystal display protection plate on the liquid crystal screen through the polarizing filter, color unevenness due to variations in the Re value is suppressed, and visibility is improved.

[0059] The orientation birefringence (Δn of the transparent thermoplastic resin (B) B ) absolute value of is preferably small, preferably 10.0×10 -4 or less, more preferably 8.0×10 -4 or less, even more preferably 6.0×10 -4 or less, particularly preferably 4.0×10 -4 or less, most preferably 2.0×10 -4 or less. When the absolute value of the orientation birefringence (Δn of the transparent thermoplastic resin (B) B ) is equal to or less than the above upper limit value, the influence on the Re value of the resin plate is sufficiently small (see Fig. 7), and the Re value of the resin plate can be well controlled within an appropriate range.

[0060] The transparent thermoplastic resin (B) is not particularly limited as long as it is a transparent thermoplastic resin that satisfies the ranges of the photoelastic coefficient (C B ) and the orientation birefringence (Δn B ). Specific examples include general non-modified methacrylic resins (PM), modified methacrylic resins modified with glutarimide units, N-substituted or unsubstituted maleimide units, lactone ring units, etc., and cycloolefin polymers (COP). The transparent thermoplastic resin (B) can be used alone or in combination of two or more.

[0061] The methacrylic resin (PM) is a homopolymer or copolymer containing structural units derived from one or more methacrylic acid esters. From the viewpoint of transparency, the content of the methacrylic acid ester monomer unit in the methacrylic resin (PM) is preferably 50% by mass or more, more preferably 80% by mass or more, particularly preferably 90% by mass or more, and may be 100% by mass.

[0062] 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 aliphatic hydrocarbon esters of methacrylic acid; polycyclic aliphatic hydrocarbon esters of methacrylic acid, and the like. From the viewpoint of transparency, the methacrylic resin (PM) preferably contains 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 90% by mass or more, and may be 100% by mass.

[0063] The methacrylic resin (PM) may contain structural units derived from one or more other monomers other than methacrylic acid esters. Examples of other monomers include acrylic acid esters such as methyl acrylate (MA), ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate; styrenes; acrylonitrile, methacrylonitrile; maleic anhydride, phenyl maleimide, cyclohexyl maleimide; and the like. Among them, MA is preferable from the viewpoint of transparency. For example, a copolymer of MMA and MA is excellent in transparency and 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.

[0064] The methacrylic resin (PM) is preferably obtained by polymerizing one or more methacrylic acid esters containing MMA and, if necessary, other monomers. When using a plurality of types of monomers, usually, a plurality of types of monomers are mixed to prepare a monomer mixture, and then polymerization is carried out. The polymerization method is not particularly limited, and from the viewpoint of productivity, radical polymerization methods such as bulk polymerization, suspension polymerization, solution polymerization, and emulsion polymerization are preferable.

[0065] The photoelastic coefficient (C defined in the present invention B) and the orientation birefringence (Δn B ), as long as it satisfies the range, as the transparent thermoplastic resin (B), resins of the types exemplified as the transparent thermoplastic resin (A) (specifically, MS resin, SMA resin, SMM resin, AS resin, modified methacrylic resin, etc.) may be used. Depending on the monomer composition or the modification rate, resins of the types exemplified as the transparent thermoplastic resin (A) may be usable as the transparent thermoplastic resin (B).

[0066] Polycarbonate resins have a photoelastic coefficient and an orientation birefringence outside the specified range of the present invention and are not included in the transparent thermoplastic resin (B). Polycarbonate resins have an absolute value of the photoelastic coefficient of 90×10 -12 / Pa, which is very large, and the Re value changes with a slight stress. Therefore, when using polycarbonate resins, it is difficult to obtain an optically uniform liquid crystal display protection plate. For example, when observing a liquid crystal display protection plate on a liquid crystal screen through a polarizing filter, color unevenness may be observed due to variations in the Re value. In particular, before and after thermoforming, the change in the Re value of the resin plate is large, and the variation in the Re value of the resin plate tends to increase.

[0067] 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 substrate layer is not particularly limited as long as Tg A >Tg B is satisfied. Preferably it is 80 to 160°C, more preferably 100 to 150°C, particularly preferably 110 to 140°C, and most preferably 110 to 130°C. Note that the "glass transition temperature (Tg B ) of the substrate layer" is the glass transition temperature of all the constituent materials of the substrate layer composed of one or more transparent thermoplastic resins (B) and, if necessary, one or more optional components.

[0068] Let the total thickness of the base material layers laminated on both sides of the phase difference adjustment layer be T. B In the liquid crystal display protection plate of the present invention, the total thickness (T B ) of the base material layers is designed to be larger than the thickness (T A ) of the phase difference adjustment layer. That is, in the liquid crystal display protection plate of the present invention, T A < T B is satisfied. The total thickness (T B ) of the base material layers is not particularly limited as long as T A < T B is satisfied, and it is appropriately designed according to the desired thickness and rigidity of the liquid crystal display protection plate. T B is preferably 0.05 to 4.0 mm, more preferably 0.5 to 3.0 mm, particularly preferably 1.0 to 3.0 mm, and most preferably 1.5 to 2.5 mm.

[0069] In the present invention, T B / T A > 1, preferably T B / T A ≧ 1.2, more preferably T B / T A ≧ 1.5, still more preferably T B / T A ≧ 2.0, particularly preferably T B / T A ≧ 5.0, and most preferably T B / T A ≧ 7.0. When T A and T B are in the above relationship, the ratio of the total thickness (T B ) of the base material layers to the total thickness (d) of the resin plate is sufficiently large, and molding can be performed at a temperature suitable for the base material layer during thermoforming such as curved surface forming, which is preferable. When the thickness (T B ) of the phase difference adjustment layer is larger than the total thickness (T A ) of the base material layers, it is difficult to achieve the desired molding rate (shaping rate) in thermoforming at a temperature near the glass transition temperature (Tg B ) of the base material layer. In this case, the glass transition temperature (Tg A)It is necessary to perform thermoforming at an extremely high temperature. Under these temperature conditions, the degree of orientation of the retardation adjustment layer decreases, the Re value decreases, and there is a risk of blackout when observing the liquid crystal display protection plate on the liquid crystal screen through a polarizing filter. T A <T B If so, it is preferable to perform the forming at a temperature suitable for the base material layer during thermoforming.

[0070] The base material layer can contain, in a small amount, one or more other polymers whose photoelastic coefficient and / or orientation birefringence are outside the definition as the transparent thermoplastic resin (B). The type of the other polymer is not particularly limited, and examples include polycarbonate resins, polyolefins such as polyethylene and polypropylene, polyamides, polyphenylene sulfides, polyether ether ketones, polyesters, polysulfones, polyphenylene oxides, polyimides, polyetherimides, and other thermoplastic resins such as polyacetals; thermosetting 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 higher, 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.

[0071] The base material layer can contain various additives as needed. Examples of the types of additives and the preferred addition amounts are the same as those of the additives that can be used in the retardation adjustment layer. When adding another polymer and / or an additive to the base material layer, the addition timing can be either during the polymerization of the transparent thermoplastic resin (B) or after the polymerization.

[0072] The base material layer may be a resin layer composed of a resin composition containing the transparent thermoplastic resin (B) and a known rubber component (impact modifier). Examples of the rubber component are the same as those of the rubber components that can be used in the retardation adjustment layer. From the viewpoint of the transparency of the base material layer, the difference between the refractive index of the rubber component and the refractive index of the transparent thermoplastic resin (B) which is the main component is preferably smaller.

[0073] (Another resin layer) The flat resin plate and the resin plate having a curved surface may have other resin layers other than the retardation adjustment layer and the base material layer. Examples of the laminated structure of the resin plate include a three-layer structure of a base material layer - retardation adjustment layer - base material layer; a four-layer structure of a base material layer - retardation adjustment layer - base material layer - other resin layer; a four-layer structure of a base material layer - retardation adjustment layer - other resin layer - base material layer, etc.

[0074] (Hard coat film) The liquid crystal display protection plate and the liquid crystal display protection plate with a curved surface of the present invention can have a hard coat film on at least one outermost surface as needed. When the liquid crystal display protection plate with a curved surface has a hard coat film on at least one outermost surface, the timing of forming the hard coat film may be before or after the curved surface processing. Curved surface processing may be performed after forming a hard coat film on at least one surface of the flat liquid crystal display protection plate, or the flat liquid crystal display protection plate may be curved and a hard coat film may be formed on at least one surface of the obtained liquid crystal display protection plate with a curved surface. The hard coat film can function as an abrasion-resistant layer (hard coat layer) or a low-reflectivity layer for improving visibility. The hard coat film can be formed by a known method. Examples of the material of the hard coat film include inorganic, organic, organic-inorganic, and silicone-based materials. From the perspective of productivity, organic and organic-inorganic materials are preferred.

[0075] The inorganic hard coat film can be formed, for example, by depositing an inorganic material such as metal oxides such as SiO2, Al2O3, TiO2, and ZrO2 by vapor deposition such as vacuum evaporation and sputtering. The organic hard coat film can be formed, for example, by applying a paint containing a resin such as a melamine-based resin, an alkyd-based resin, a urethane-based resin, and an acrylic-based resin and heating and curing it, or by applying a paint containing a polyfunctional acrylic-based resin and curing it with ultraviolet light. The organic-inorganic cured film can be formed, for example, by applying an ultraviolet curable hard coat paint containing inorganic ultrafine particles such as silica ultrafine particles having a photopolymerizable functional group introduced on the surface and a curable organic component, and subjecting the curable organic component and the photopolymerizable functional group of the inorganic ultrafine particles to a polymerization reaction by ultraviolet irradiation. In this method, a network crosslinked coating film in which the inorganic ultrafine particles are dispersed in the organic matrix in a state of being chemically bonded to the organic matrix can be obtained. The silicone-based cured film can be formed, for example, by polycondensing partial hydrolyzates such as carbon functional alkoxysilane, alkyltrialkoxysilane, and tetraalkoxysilane, or materials obtained by blending colloidal silica therewith. In the above method, examples of the coating method of the material include dip coating, various roll coatings such as gravure roll coating, flow coating, rod coating, blade coating, spray coating, die coating, and bar coating.

[0076] The thickness of the scratch-resistant (hard coat) 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, there is a risk of cracking due to bending during the manufacturing process. The thickness of the low-reflectivity cured film (low-reflectivity 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.

[0077] In addition, the liquid crystal display protection plate and the curved liquid crystal display protection plate of the present invention can optionally have known surface treatment layers such as an antiglare layer, an antireflection layer, and an antifingerprint layer on the surface.

[0078] [Manufacturing method of liquid crystal display protection plate] The manufacturing method of the flat liquid crystal display protection plate of the present invention includes a step (1) of forming a flat extruded resin plate in which a base material layer having a relatively low glass transition temperature (Tg) is laminated on both sides of the retardation adjustment layer. The manufacturing method of a flat liquid crystal display protection plate with a cured film includes the above step (1) and a step (2) of forming a cured film on at least one surface of the obtained extruded resin plate.

[0079] (Step (1)) The flat liquid crystal display protection plate is preferably formed by co-extrusion molding. Hereinafter, the manufacturing method of a flat extruded resin plate by the co-extrusion molding method will be described. FIG. 3 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 form from a T-die 11 having a wide discharge port in the form of a desired laminated structure. Examples of the lamination method include a feed block method of laminating before flowing into the T-die and a multi-manifold method of laminating inside the T-die. From the viewpoint of enhancing the interfacial smoothness between layers, the multi-manifold method is preferable. The molten thermoplastic resin laminate co-extruded from the T-die 11 is pressurized and cooled using the first to third cooling rolls 12 to 14. The flat extruded 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. In addition, the configuration of the manufacturing apparatus can be appropriately designed and changed within a range not departing from the gist of the present invention.

[0080] In step (1), let the temperature of the entire resin on the third cooling roll 14 be TX. FIG. 3 schematically shows the measurement range of TX in the section of [Example]. The temperature of the resin on the manufacturing line can be measured by a known method. For example, as TX, the surface temperature of the resin on the third cooling roll 14 can be measured using a non-contact thermometer such as an infrared radiation thermometer.

[0081] In the present invention, molding is performed so that the Re value of the flat extruded resin plate is 50 to 330 nm. Preferably, molding is performed such that the standard deviation of the Re value within the range of a width of 17 cm and a length of 22 cm of the flat extruded resin plate is 25.0 nm or less. In order to control the Re value, it is necessary to control the molecular orientation. The molecular orientation is generated, for example, by the stress during molding near the glass transition temperature of the polymer. By optimizing the manufacturing conditions in the process of extrusion molding, the molecular orientation can be controlled, and thereby, the Re value after extrusion molding of the liquid crystal display protection plate can be optimized.

[0082] (Step (2)) In step (2), an inorganic or organic cured film is formed on at least one surface of the flat liquid crystal display protection plate obtained in step (1) or the flat liquid crystal display protection plate thermoformed in step (3) described later by a known method. Since the method for forming the cured film has been described above, it is omitted here.

[0083] (Other steps) The method for manufacturing a flat liquid crystal display protection plate and a flat liquid crystal display protection plate with a cured film may have other steps other than the above, as necessary. For example, between step (1) and step (2), for the purpose of improving the adhesion of the cured film to the flat liquid crystal display protection plate, a primer treatment is performed on the surface of the flat liquid crystal display protection plate obtained in step (1) where the cured film is to be formed. ; Steps such as surface roughening treatments such as sandblasting treatment and solvent treatment; surface treatments such as surface oxidation treatments such as corona discharge treatment, chromic acid treatment, ozone irradiation treatment, and ultraviolet irradiation treatment may be added.

[0084] [Method for manufacturing a liquid crystal display protection plate with a curved surface] The method for manufacturing a liquid crystal display protection plate with a curved surface of the present invention is a step (1) of molding a flat liquid crystal display protection plate in which a base material layer having a relatively low glass transition temperature (Tg) is laminated on both sides of a retardation adjustment layer, and a flat liquid crystal display protection plate at Tg B Tg or higher AIt has a step (3) of heating to the following temperature (TY) and thermoforming into a shape having a curved surface. The method for manufacturing a liquid crystal display protection plate with a curved surface according to the present invention can have, between step (1) and step (3), a step (2) of forming a cured film on at least one surface of a flat liquid crystal display protection plate, if necessary. In this case, in step (3), the flat liquid crystal display protection plate with a cured film is thermoformed. Steps (1) and (2) have been described in the section [Method for manufacturing a liquid crystal display protection plate], so they are omitted here.

[0085] (Step (3)) Shape processing such as curved surface processing on a flat liquid crystal display protection plate or a flat liquid crystal display protection plate with a cured film can be performed by known thermoforming such as press forming, vacuum forming, and pressure air forming. In the present invention, a flat liquid crystal display protection plate having a base material layer formed on both surfaces of the retardation adjustment layer is preferably thermoformed at a temperature lower than Tg B super Tg A and lower than TX. In step (3), the thermoforming temperature is TY. TX > TY, and it is preferable that Tg B < TY < Tg A is satisfied.

[0086] In the present invention, it is preferable to perform thermoforming at a temperature of Tg B or higher and Tg A or lower (TY). More preferably, thermoforming is performed at a temperature lower than super Tg B super Tg A and particularly preferably, thermoforming is performed at a temperature of Tg B + 10°C to Tg B + 30°C. Within the above temperature range, a flat liquid crystal display protection plate can be well thermoformed into a desired shape, and the residual stress generated in the cooling process of thermoforming can be suppressed to a small level. In this case, the change in the Re value can be suppressed, and the deformation of the liquid crystal display protection plate with a curved surface obtained after thermoforming can be suppressed. For example, when a reliability test (for example, 1000 hours at 105 °C or 72 hours at 85 °C and 85% RH) of an in-vehicle display is performed on a liquid crystal display protection plate with a curved surface, the deformation due to the release of residual stress is suppressed, which is preferable.

[0087] Tg B +10 °C to Tg B Within the range of +30 °C and, Tg A It is most preferable to perform thermoforming at a temperature lower than. Tg A If it is at a temperature lower than, since the stress and orientation of the retardation adjustment layer are not released, the change in the Re value and the deformation of the liquid crystal display protection plate with a curved surface are effectively suppressed, which is preferable. Tg B When thermoforming is performed at a temperature lower than Tg + 10 °C, it is difficult to thermoform the extruded resin plate into a desired shape. Even in this temperature range, if a large load is applied or the forming time is lengthened, etc., it is possible to thermoform into a desired shape, but a large forming stress is generated in the resin plate. When a reliability test of an in-vehicle display is performed on the liquid crystal display protection plate with a curved surface obtained under this condition, a large residual stress is released and there is a risk of large deformation.

[0088] Generally, if thermoforming is performed at a temperature lower than the Tg of the constituent resin of the retardation adjustment layer of the extruded resin plate, it is considered that the decrease in the Re value can be suppressed. However, when the inventors variously studied the thermoforming conditions, it was found that even when thermoforming was performed at a temperature lower than the Tg of the constituent resin of the retardation adjustment layer of the extruded resin plate, if the thermoforming temperature was higher than the temperature for controlling the orientation of the extruded resin plate in the extrusion molding process, the orientation of the resin was relaxed and the Re value might decrease significantly. And the Tg of the constituent resin of the retardation adjustment layer A However, when the inventors variously studied the thermoforming conditions, it was found that even when thermoforming was performed at a temperature lower than the Tg of the constituent resin of the retardation adjustment layer of the extruded resin plate, if the thermoforming temperature was higher than the temperature for controlling the orientation of the extruded resin plate in the extrusion molding process, the orientation of the resin was relaxed and the Re value might decrease significantly. And the Tg of the constituent resin of the retardation adjustment layer A It was found that even when thermoforming was performed at a temperature lower than the Tg of the constituent resin of the retardation adjustment layer of the extruded resin plate, if the thermoforming temperature was higher than the temperature for controlling the orientation of the extruded resin plate in the extrusion molding process, the orientation of the resin was relaxed and the Re value might decrease significantly. And the Tg of the constituent resin of the retardation adjustment layer AWhen a curved liquid crystal display protection plate that is thermoformed at a temperature lower than the temperature for controlling the orientation of the extruded resin plate in the extrusion molding process and higher than the temperature of the extruded resin plate in the extrusion molding process is observed through a polarizing filter, depending on the angle formed between the polarization axis of the emitted light and the transmission axis of the polarizing filter, a blackout occurs where the screen becomes completely dark, and the visibility of the image may decrease.

[0089] As a result of investigations by the present inventors, it was found that the orientation of the retardation adjustment layer that contributes to the magnitude of the Re value is formed up to the third cooling roll when, for example, a resin plate with an overall thickness of 3 mm is extrusion molded under the condition of a second cooling roll speed of 0.75 m / min. That is, in the present invention, TX is synonymous with "the temperature at which the orientation of the retardation adjustment layer that contributes to the magnitude of the Re value is fixed during cooling in the extrusion molding process". Therefore, the temperature (TX) of the entire resin on the third cooling roll can be used as the lower limit value of "the temperature for controlling the orientation of the extruded resin plate in the extrusion molding process". When thermoforming is performed below TX, the resin temperature in the thermoforming process does not reach the resin temperature on the third cooling roll and the resin temperature upstream of the third cooling roll. Under this condition, in the thermoforming process, relaxation of the resin orientation is suppressed, a decrease in the Re value is effectively suppressed, and a decrease in visibility when observing the liquid crystal display protection plate on the liquid crystal screen through a polarizing filter can be effectively suppressed. When co-extrusion is performed under the condition that the second cooling roll speed exceeds 0.75 m / min, the orientation of the retardation adjustment layer may be formed between the third cooling roll and the take-up roll. Also, when the overall thickness of the extruded resin plate to be molded is made thicker than 3 mm, the orientation of the retardation adjustment layer may be formed between the third cooling roll and the take-up roll.

[0090] In the present invention, it is preferable to thermoform a flat liquid crystal display protection plate having a substrate layer formed on both sides of the retardation adjustment layer at a temperature below Tg B below Tg A and below TX. In this case, even when the retardation adjustment layer contains a brittle resin such as SMA resin and SMM resin, cracking of the retardation adjustment layer can be effectively suppressed. In the heating process of thermoforming, the temperature of the interior rises after the temperature of the surface has risen first. In a laminated structure in which the substrate layers are formed on both surfaces of the retardation adjustment layer, it is difficult for the temperature of the retardation adjustment layer inside to rise compared to the substrate layer on the surface. Therefore, it is possible to effectively suppress the change in the Re value after thermoforming compared to before thermoforming, rather than heating a flat liquid crystal display protection plate having a retardation adjustment layer on the surface.

[0091] In the present invention, in step (1), molding is performed so that the Re value of the flat extruded resin plate becomes 50 to 330 nm. In step (1), preferably, molding is performed so that the standard deviation of the Re value within the range of a width of 17 cm and a length of 22 cm of the flat liquid crystal display protection plate becomes 25.0 nm or less. The absolute value of the change rate of the Re value after thermoforming with respect to before thermoforming is 50% or less, preferably 40% or less, more preferably 30% or less, particularly preferably 25% or less, and most preferably 20% or less. The change rate of the Re value after thermoforming with respect to before thermoforming is represented by the following formula. [Change rate of Re value after thermoforming with respect to before thermoforming][%]=100×([Re value after thermoforming]−[Re value before thermoforming]) / [Re value before thermoforming]

[0092] The standard deviation of the Re value within the range of a width of 17 cm and a length of 22 cm of the curved surface liquid crystal display protection plate of the present invention obtained after thermoforming 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.

[0093] The lower limit value of the radius of curvature of the curved surface included in the curved surface liquid crystal display protection plate of the present invention obtained after thermoforming is 50 mm, preferably 75 mm, more preferably 100 mm, particularly preferably 200 mm, and most preferably 300 mm. The upper limit value is 1000 mm, preferably 800 mm, more preferably 600 mm, particularly preferably 500 mm, and most preferably 400 mm. In the present invention, even when thermoforming is performed, the change in the Re value of the resin plate is suppressed. Therefore, the Re value is within a suitable range, the variation in the Re value is small, and a liquid crystal display protection plate with a curved surface can be stably manufactured.

[0094] As described above, according to the present invention, in both before and after thermoforming, the Re value is within a suitable range, the variation in the Re value is small, and it is possible to provide a liquid crystal display protection plate that suppresses a decrease in visibility such as color unevenness, blackout, and coloring when observing the liquid crystal display protection plate on the liquid crystal screen through a polarizing filter.

[0095] [Use] The liquid crystal display protection plate and the liquid crystal display protection plate with a curved surface of the present invention are suitable as protection plates for liquid crystal displays or touch panel displays used in, for example, ATMs of financial institutions such as banks; vending machines; televisions; portable information terminals (PDAs) such as mobile phones (including smartphones), personal computers, tablet personal computers, digital audio players, portable game machines, copy machines, fax machines, and digital information devices such as car navigation systems. The liquid crystal display protection plate and the liquid crystal display protection plate with a curved surface of the present invention are suitable as protection plates for in-vehicle liquid crystal displays, for example. [Examples]

[0096] 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. (Glass transition temperature (Tg) of the 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 apparatus. After performing nitrogen substitution for 30 minutes or more, in a nitrogen gas stream of 10 ml / min, the temperature was once raised from 25°C to 200°C at a rate of 20°C / min, held for 10 minutes, and cooled to 25°C (primary scan). Next, the temperature was raised to 200°C at a rate of 10°C / min (secondary scan), and from the results obtained in the secondary scan, the glass transition temperature (Tg) was calculated by the midpoint method. In the case where multiple Tg data are obtained in a resin composition containing two or more resins, the value derived from the resin of the main component was adopted as the Tg data.

[0097] (Photoelastic coefficient of the transparent thermoplastic resin) The transparent thermoplastic resin was press-molded to obtain a resin plate with a thickness of 1.0 mm. From the central part of the obtained resin plate, a test piece with a width of 15 mm and a length of 80 mm was cut out. Both ends in the longitudinal direction of this test piece were gripped with a pair of chucks. The distance between the chucks was set to 70 mm. Using the “X-axis Articulated Stage” manufactured by Oji Scientific Instruments Co., Ltd., tension was applied to the test piece. The tension was increased stepwise from 0 N to 30 N in increments of 10 N. The tension was monitored by a “Sensor Separate Type Digital Force Gauge ZTS-DPU-100N” manufactured by Imada Co., Ltd. For each stage of tension application conditions from 0 N to 100 N, the following measurements were carried out. The phase difference value [nm] at the central part of the test piece in the state where tension was applied was measured using the “KOBRA-WR” manufactured by Oji Scientific 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 measurement part was measured. The cross-sectional area (S) [m 2 (= 15 [mm] × d [mm] × 10 -6 ) and the stress [Pa] (= tension [N] / S [m 2 ) and the birefringence (= phase difference value [nm] × 10 -6 / d [mm]) were calculated respectively. The stress was plotted on the horizontal axis and the birefringence on the vertical axis, and the slope of the straight line obtained by the least squares method was determined as the photoelastic coefficient.

[0098] (Birefringence of Oriented Transparent Thermoplastic Resin) A transparent thermoplastic resin was press-molded to obtain a resin plate with a thickness of 1.0 mm. A test piece with a width of 20 mm and a length of 50 mm was cut out from the central part of the obtained resin plate and set in an autograph with a heating chamber (manufactured by SHIMADZU). The distance between the chucks was set to 20 mm. After holding at a temperature 10 °C higher than the glass transition temperature (Tg) for 3 minutes, it was uniaxially stretched at a rate of 3 mm / min. The elongation rate was set to 100%. Under these conditions, the distance between the chucks after stretching was 40 mm. The stretched test piece was removed from the above device, cooled to 23 °C, then the thickness (d) was measured, and the Re value of the central part was measured using "KOBRA-WR" manufactured by Oji Scientific Instruments Co., Ltd. under the condition of a measurement wavelength of 589.5 nm. The value of the birefringence was calculated by dividing the obtained Re value by the thickness (d) of the test piece.

[0099] (Average Value and Standard Deviation of Re Value of Liquid Crystal Display Protective Plate) For test pieces of the liquid crystal display protective plate before curved surface forming (width 21 cm, length 30 cm) and test pieces of the liquid crystal display protective plate after curved surface forming (width 17 cm, length 22 cm), the average value and standard deviation of the Re value were measured as follows. The standard lens (FUJINON HF12.5HA-1B) was attached to "WPA-100-L" manufactured by Photonic Lattice Co., Ltd. The height of the lens was adjusted so that the measurement range was 17 cm in width and 22 cm in length. The Re values of about 110,000 birefringence pixels were measured, and the average value and standard deviation were obtained. Based on the following formula, the change rate of the average value of the Re value after curved surface forming with respect to before curved surface forming was obtained. [Change Rate of Re Value After Heating with Respect to Before Heating](%) = ([Re Value After Heating] - [Re Value Before Heating]) / [Re Value Before Heating] × 100

[0100] (Thickness of Each Layer) The thickness of each layer was measured using a "Universal Projector (V-12B)" manufactured by Nikon Instech Co., Ltd.

[0101] (Color Non-uniformity) A test piece of the liquid crystal display protection plate was placed on the liquid crystal display so that the transmission axis of the polarizer on the viewing 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 this, and the polarizing film was rotated at various angles, and the appearance at the angle where the color unevenness caused by the variation in the Re value was the strongest was visually evaluated in the following 3 levels. A (Good): There is no color unevenness, and the visibility of the liquid crystal display is not reduced. B (Fair): There is a little color unevenness, and the visibility of the liquid crystal display is slightly reduced. C (Poor): There is significant color unevenness, and the visibility of the liquid crystal display is greatly reduced.

[0102] (Blackout) A test piece of the liquid crystal display protection plate was placed on the liquid crystal display so that the transmission axis of the polarizer on the viewing 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 this, and the polarizing film was rotated at various angles, and the appearance at the angle where the transmitted light intensity of the liquid crystal display was the smallest was visually evaluated in the following 3 levels. A (Good): The transmitted light intensity is sufficiently high, and characters and the like displayed on the liquid crystal display can be clearly seen. B (Fair): 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 (Poor): The transmitted light intensity is almost zero, and characters and the like displayed on the liquid crystal display cannot be seen.

[0103] (Colored) A test piece of the liquid crystal display protection plate was placed on the liquid crystal display so that the transmission axis of the polarizer on the viewing 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 this, and the polarizing film was rotated at various angles, and the appearance at the angle where the coloring of the liquid crystal display was the largest was visually evaluated in the following 3 levels. A (Good): There is no significant coloring, and the visibility of the liquid crystal display is not reduced. B (Acceptable): There is coloration, and the visibility of the liquid crystal display slightly decreases. C (Defective): There is significant coloration, and the visibility of the liquid crystal display decreases.

[0104] (Crack) The liquid crystal display protection plate after curved surface forming was visually observed and evaluated in the following two steps. A (Good): There is no crack in the retardation adjustment layer, and the visibility of the liquid crystal display does not decrease. C (Defective): A crack occurs in the retardation adjustment layer, and the visibility of the liquid crystal display decreases.

[0105] (Forming Rate of Curved Surface Liquid Crystal Display Protection Plate) With Curved Surface liquid crystal For the test piece (width 17 cm, length 22 cm) of the display protection plate with a curved surface, the forming rate was measured as follows. Referring to Figure 6, it will be described. The upper figure in Figure 6 is a schematic cross-sectional view of the resin mold (male mold and female mold) used for forming the liquid crystal display protection plate with a curved surface, which is the yz cross-sectional view of Figure 5. The lower figure in Figure 6 is a schematic cross-sectional view of the liquid crystal display protection plate with a curved surface corresponding to the upper figure in Figure 6. In the figure, reference numeral 26 is the liquid crystal display protection plate with a curved surface, and reference numeral M is the resin mold. The liquid crystal display protection plate 26 with a curved surface was placed on a flat surface plate with the convex curved surface S1 side facing upward. In that state, the height L1 from the surface plate to the center of the concave curved surface S2 was measured. On the other hand, the height L2 of the convex curved surface MS1 of the male mold of the resin mold M used for forming the liquid crystal display protection plate 26 with a curved surface was measured. Based on the following formula, the forming rate was obtained. Forming Rate [%] = (L1 / L2) × 100

[0106] [Materials] The materials used are as follows. (MS1) According to the production method of copolymer (A) described in the [Examples] section of Japanese Patent Application Laid-Open No. 2003-231785, MS resin (copolymer of methyl methacrylate (MMA) and styrene (St)) was polymerized. Tg = 109 °C, content of aromatic vinyl monomer unit = 35% by mass.

[0107] <SMM resin> (SMM1) Denka Co., Ltd. "Resifar R200", Tg = 135 °C, styrene-maleic anhydride-MMA copolymer. Content of aromatic vinyl monomer unit = 56% by mass.

[0108] <Acrylic imide resin> (PMMI1) Daicel-Evonik "Pleximid TT50", Tg = 155 °C. Content of aromatic vinyl monomer unit = 0% by mass.

[0109] <SMA-containing resin> (SMA1) Polyscope "XIRAN", Tg = 152 °C, styrene-maleic anhydride copolymer. Content of aromatic vinyl monomer unit = 77% by mass. (SMA2) SMA resin (SMA1) / methacrylic resin (PMMA1) (mass ratio) = 82 / 18, Tg = 145 °C, styrene-maleic anhydride copolymer alloy resin. Content of aromatic vinyl monomer unit = 63% by mass.

[0110] <Methacrylic resin> (PMMA1) Copolymer of methyl methacrylate (MMA) and methyl acrylate (MA), "Parapet EH" manufactured by Kuraray Co., Ltd., Tg = 110 °C. (PMMA2) Copolymer of methyl methacrylate (MMA) and methyl acrylate (MA), "Parapet HR-S" manufactured by Kuraray Co., Ltd., Tg = 119 °C. (PMMA3) Copolymer of methyl methacrylate (MMA) and methyl acrylate (MA), Tg = 85 °C.

[0111] <Polycarbonate resin> (PC1) Manufactured by Sumitomo Chemical Polycarbonate Co., Ltd., "SD Polycarbonate 300 Series", Tg = 150°C.

[0112] [Examples 1 to 4, Comparative Examples 1 and 2] (Manufacture of liquid crystal display protection plate) Using a 50 mmφ single-screw extruder (manufactured by Toshiba Machine Co., Ltd.), the resin for the base material layer (transparent thermoplastic resin (B) or comparative resin) was melt-extruded. Using a 30 mmφ single-screw extruder (manufactured by Toshiba Machine Co., Ltd.), the resin for the retardation adjustment layer (transparent thermoplastic resin (A) or comparative resin) was melt-extruded. These resins in a molten state were laminated through a multi-manifold die, and a three-layer thermoplastic resin laminate in which the base material layer was laminated on both sides of the retardation adjustment layer was co-extruded from a T-die. This thermoplastic resin laminate was sandwiched between a first cooling roll and a second cooling roll adjacent to each other, wound around the second cooling roll, sandwiched between the second cooling roll and a third cooling roll, and wound around the third cooling roll for cooling. The flat resin plate obtained after cooling was taken up by a pair of take-up rolls. In this way, a liquid crystal display protection plate (reference drawing: Figure 1) composed of a flat resin plate having a three-layer structure in which the base material layer was laminated on both sides of the retardation adjustment layer was obtained. From the central part of the obtained liquid crystal display protection plate, a test piece having a width of 21 cm and a length of 30 cm was cut out so that the extrusion molding direction (resin flow direction) was the long side direction. Using this test piece, the evaluation of the liquid crystal display protection plate before curved surface molding was carried out.

[0113] (Curved surface molding) From the central part of the above test piece, a test piece for curved surface molding having a width of 17 cm and a length of 22 cm was cut out so that the extrusion molding direction (resin flow direction) was the long side direction. The following procedure was performed on this test piece for curved surface molding. A resin mold manufactured by SSI Co., Ltd., "Chemical Wood Prolab65" was prepared. As shown in Figure 5, the resin mold M was composed of a combination of a female mold FM (illustrated lower mold) and a male mold MM (illustrated upper mold), and the overall shape was a rectangular parallelepiped shape with a width (dimension in the illustrated x direction) of 200 mm × a length (dimension in the illustrated y direction) of 250 mm × a height (dimension in the illustrated z direction) of 35 mm. A concave curved surface is formed on the upper surface of the female mold FM, and a convex curved surface that joins with the concave curved surface of the female mold FM is formed on the lower surface of the male mold MM. The height of the female mold FM was 15 - 25 mm, and the height of the male mold MM was 20 - 10 mm. The cross-sectional shape parallel to the y-z plane of the concave curved surface of the female mold FM and the convex curved surface of the male mold MM was uniform regardless of the position in the x direction shown in the figure, and was an arc shape with a radius of curvature of 300 mm.

[0114] 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 forming was placed on the PTFE sheet, and it was held for 6 - 7 minutes until the temperature of the test piece reached the forming temperature described in Table 3 (for example, 130°C in Example 1). Next, the PTFE sheet and the test piece for curved surface forming placed on it were taken out of the oven. Next, using a non-contact thermometer ("PT-S80" manufactured by Optel Co., Ltd.), the temperature of the test piece immediately before being sandwiched between the female mold FM and the male mold MM was measured, and it was confirmed that it was the forming temperature described in Table 3 (for example, 130°C in Example 1). Next, the test piece for curved surface forming at the above-mentioned forming temperature was placed on the female mold FM at room temperature (20 - 25°C), the male mold MM at room temperature (20 - 25°C) was placed on it, and a load of 3 kg was applied from above. Next, it was cooled over 1 - 2 minutes until the temperature of the test piece became near room temperature. The test piece after cooling was taken out of the resin mold M, and using this test piece, the evaluation of the liquid crystal display protection plate (liquid crystal display protection plate with a curved surface) after curved surface forming was carried out.

[0115] For each example, the type and physical properties of the resin used, the thickness of the retardation adjustment layer, the total thickness of the base material layer, the thermoforming temperature, and the evaluation results of the liquid crystal display protection plate before and after curved surface forming are shown in Tables 1 - 3. In each example of Tables 1 - 3, the conditions not described in the table were regarded as common conditions.

[0116] [Comparative Examples 3 - 5] A liquid crystal display protection plate made of a three-layer flat resin plate (reference drawing: Figure 4) was manufactured in the same manner as in Examples 1 to 4, except that coextrusion molding was performed such that a retardation adjustment layer was laminated on both sides of the base material layer, and then curved surface forming was carried out. In Figure 4, reference numeral 101 indicates a comparative liquid crystal display protection plate, reference numeral 116 indicates a comparative resin plate, reference numeral 121 indicates a retardation adjustment layer, and reference numeral 122 indicates a base material layer, respectively. Similar to Examples 1 to 4, evaluation of the liquid crystal display protection plate before and after curved surface forming was carried out. For each example, the type and physical properties of the resin used, the thickness of the retardation adjustment layer, the total thickness of the base material layer, the thermoforming temperature, and the evaluation results of the liquid crystal display protection plate before and after curved surface forming are shown in Tables 1 to 3.

[0117] [Examples 4-1 to 4-8] (Manufacture of Liquid Crystal Display Protection Plate) A flat liquid crystal display protection plate was manufactured in the same method and lamination structure as in Example 4. However, in each example, the extrusion amount and the rotation speeds of the first to third cooling rolls were adjusted so that the temperature (TX) of the entire resin on the third cooling roll became the temperature described in Table 5. As TX, the surface temperature of the resin on the third cooling roll was measured using an infrared radiation thermometer. Figure 3 schematically shows the measurement range of TX. In the above manner, flat liquid crystal display protection plates (S1-1) to (S1-5) (reference drawing: Figure 1) having a three-layer structure in which a base material layer was laminated on both sides of the retardation adjustment layer were obtained. The thicknesses of the two base material layers were made the same. The lamination structure, the type and physical properties of the resin used, the total thickness of the retardation adjustment layer, the total thickness of the base material layer, and the overall thickness are shown in Table 4. From the central part of the obtained liquid crystal display protection plate, a test piece having a width of 17 cm and a length of 22 cm was cut out such that the extrusion molding direction (resin flow direction) was the long side direction. Using this test piece, evaluation of the flat liquid crystal display protection plate before thermoforming was carried out.

[0118] (Manufacture of Liquid Crystal Display Protection Plate with Curved Surface) For the above test piece (width 17 cm, length 22 cm) cut out from a flat extruded resin sheet, using the same resin mold M as in Example 4 (refer to Fig. 5), thermoforming was carried out in the same manner as in Example 4. A polytetrafluoroethylene (PTFE) sheet (300 mm × 300 mm × 12 mm) was placed in an oven, and the inside of the oven was heated to 170 °C. In this state, the test piece was placed on the PTFE sheet and held for 6 - 7 minutes until the temperature of the test piece reached the forming temperature (TY) shown in Table 5 (for example, 140 °C in Example 4-1). Next, the test piece at the above forming temperature was placed on a female mold FM at room temperature (20 - 25 °C), and a male mold MM at room temperature (20 - 25 °C) was placed on it, and a load of 3 kg was applied from above. Then, it was cooled over 1 - 2 minutes until the temperature of the test piece was near room temperature. The cooled test piece was taken out from the resin mold M, and using this test piece, the evaluation of the liquid crystal display protection plate with a curved surface was carried out.

[0119] For each example, the glass transition temperature (Tg) of the resin used, the temperature (TX) of the entire resin on the third cooling roll in the extrusion molding process, the thermoforming temperature (TY), and the relationships between these temperatures are shown in Table 5. In each example of Table 5, the conditions not described in the table were taken as common conditions. For each example, the evaluation results of the flat extruded resin sheet before thermoforming and the liquid crystal display protection plate with a curved surface are shown in Table 6.

[0120]

Table 1

[0121]

Table 2

[0122]

Table 3

[0123]

Table 4

[0124]

Table 5

[0125]

Table 6

[0126] [Summary of Results] In Examples 1 to 4, a liquid crystal display protection plate made of a flat resin plate in which a base material layer was laminated on both sides of a retardation adjustment layer was manufactured. In these examples, the retardation adjustment layer was a layer containing a transparent thermoplastic resin (A) whose absolute value of photoelastic coefficient (C A ) was 10.0×10 -12 / Pa or less and whose absolute value of orientation birefringence (Δn A ) was 10.0×10 -4 to 100.0×10 -4 . The base material layer was a layer containing a transparent thermoplastic resin (B) whose absolute value of photoelastic coefficient (C B ) was 10.0×10 -12 / Pa or less and whose absolute value of orientation birefringence (Δn B ) was less than 10.0×10 -4 . When the glass transition temperature of the retardation adjustment layer was Tg A and the glass transition temperature of the base material layer was Tg B , Tg A >Tg B .

[0127] For all of the liquid crystal display protection plates before curved surface forming obtained in Examples 1 to 4, the average value of the Re value within the range of width 17 cm and length 22 cm was 50 to 330 nm, and the standard deviation of the Re value within the range of width 17 cm and length 22 cm was 15.0 nm or less. In these examples, when the liquid crystal display protection plate obtained was used to observe the liquid crystal display protection plate on the liquid crystal screen through a polarizing filter, color unevenness, coloring, and blackout were effectively suppressed.

[0128] In Examples 1 to 4, the obtained liquid crystal display protection plate was thermoformed at a temperature of Tg B or higher Tg A or lower (Tg B or higher Tg A less than) to produce a liquid crystal display protection plate with a curved surface. For all the liquid crystal display protection plates with curved surfaces obtained in Examples 1 to 4, the average value of the Re value within the range of a width of 17 cm and a length of 22 cm was 50 to 330 nm, and the standard deviation of the Re value within the range of a width of 17 cm and a length of 22 cm was 15.0 nm or less. In these examples, the absolute value of the change rate of the average value of the Re value after thermoforming with respect to that before thermoforming was 50% or less. In these examples, when observing the liquid crystal display protection plate on the liquid crystal screen through a polarizing filter using the obtained liquid crystal display protection plate with a curved surface, color unevenness, coloring, and blackout were effectively suppressed.

[0129] Among Examples 1 to 4, in Examples 1, 2, and 4 where V×T A was in the range of 6.0 to 30.0, the average value of the Re value was in a particularly preferable range both before and after the curved surface processing.

[0130] In Examples 4-1 to 4-8, the values of TX and TY were determined so as to satisfy the condition of thermoforming at a temperature (TY) less than Tg B super Tg A and less than TX, and a flat liquid crystal display protection plate and a liquid crystal display protection plate with a curved surface were manufactured. For all the flat liquid crystal display protection plates obtained in these examples, the average value of the Re value was 50 to 330 nm, and the standard deviation of the Re value was 25.0 nm or less (15.0 nm or less, 10.0 nm or less). For all the liquid crystal display protection plates with curved surfaces obtained in these examples, the average value of the Re value was 50 to 330 nm, and the standard deviation of the Re value was 25.0 nm or less (15.0 nm or less, 10.0 nm or less). In these examples, the absolute value of the change rate of the Re value after thermoforming with respect to that before thermoforming was 50% or less (20% or less). The thermoforming temperature (TY) is the Tg of the retardation adjustment layer resinA Since the temperature was lower than that of TX, it is considered that the orientation of the resin in the retardation adjusting layer was hardly disturbed during the thermoforming process, and the Re value was almost maintained. In these examples, when the curved LCD protective plate on the LCD screen was observed through a polarizing filter, blackout, coloring, and color unevenness were effectively suppressed. From the results of Examples 4-1 to 4-8, TX>TY and Tg B <TY<Tg A It was found that it is more preferable to perform curved surface processing under the condition that satisfies the following:

[0131] In Comparative Example 1, Tg A <Tg B and Tg A and Tg B A curved LCD protective plate was manufactured by thermoforming at a temperature higher than 100° C. In this comparative example, the absolute value of the rate of change of the average Re value after thermoforming to that before thermoforming was more than 50%. The curved LCD protective plate obtained in this comparative example had a low Re value, and when the LCD protective plate on the LCD screen was observed through a polarizing filter, a noticeable blackout was observed.

[0132] In Comparative Example 2, the resin for the retardation adjustment layer was a resin having a photoelastic coefficient (C A ) and orientation birefringence (Δn A The liquid crystal display protection plate obtained in this comparative example before curved molding had a large standard deviation of Re (large variation in Re value), and when the liquid crystal display protection plate placed on the liquid crystal screen was observed through a polarizing filter, noticeable color unevenness was observed. In this comparative example, Tg B More than Tg AA curved LCD protective plate was manufactured by thermoforming at the following temperature. In this comparative example, the absolute value of the rate of change of the average Re value after thermoforming relative to before thermoforming was more than 50%, and the standard deviation of the Re value after thermoforming was more than 25.0 nm. The curved LCD protective plate obtained in this comparative example had a large standard deviation of the Re value (large variation in the Re value), and when the LCD protective plate on the LCD screen was observed through a polarizing filter, noticeable color unevenness was observed.

[0133] In Comparative Example 3, a liquid crystal display protective plate was manufactured from a resin plate in which retardation adjustment layers were laminated on both sides of a base layer. B More than Tg A The curved LCD protective plate was manufactured by thermoforming at the following temperature. In this comparative example, the absolute value of the rate of change of the average Re value after thermoforming to that before thermoforming was 50% or less. However, the retardation adjustment layer on the surface was bent at a temperature lower than the Tg of the retardation adjustment layer, so that the retardation adjustment layer cracked.

[0134] In Comparative Examples 4 and 5, a liquid crystal display protective plate was manufactured from a resin plate in which retardation adjustment layers were laminated on both sides of a base layer. B ) and orientation birefringence (Δn B The polycarbonate resin used was one for which the Tg A <Tg B The liquid crystal display protection plates obtained in these comparative examples before curved molding had a large standard deviation in the Re value (large variation in the Re value), and when the liquid crystal display protection plate placed on the liquid crystal screen was observed through a polarizing filter, noticeable color unevenness was observed. In these comparative examples, Tg A and Tg BThe curved LCD protective plate was produced by thermoforming at a temperature higher than 100° C. The absolute value of the rate of change of the average Re value after thermoforming relative 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 LCD protective plates obtained in these comparative examples had a large standard deviation of the Re value (large variation in the Re value), and when the LCD protective plate on the LCD screen was observed through a polarizing filter, noticeable color unevenness was observed.

[0135] The present invention is not limited to the above-described embodiment and examples, and appropriate design changes are possible without departing from the spirit of the present invention.

[0136] This application claims priority based on Japanese Patent Application No. 2020-077644, filed on April 24, 2020, and Japanese Patent Application No. 2020-216445, filed on December 25, 2020, the disclosures of which are incorporated herein in their entirety. [Explanation of symbols]

[0137] 1, 2 LCD display protection plate 11 T-die 12~14 Cooling roll 15 Take-off roll 16 Flat resin plate 21 Phase difference adjustment layer 22 Base material layer 31 Hardened coating

Claims

1. A flat resin plate having substrate layers laminated on both sides of a retardation adjustment layer, The retardation adjustment layer has an absolute value of photoelastic coefficient (C Ａ ), which is 10.0 × 10 －１２ / Pa or less, and a test piece with a width of 20 mm, a length of 40 mm, and a thickness of 1 mm is uniaxially stretched at a rate of 3 mm / min at a temperature 10 °C higher than the glass transition temperature with an elongation rate of 100%, and the in-plane retardation value of the central portion of the test piece is measured to obtain the absolute value of the orientation birefringence (Δn Ａ ), which is 10.0 × 10 －４ to 100.0 × 10 －４ and contains a transparent thermoplastic resin (A). The base material layer has an absolute value of the photoelastic coefficient (C Ｂ ) of 10.0 × 10 －１２ / Pa or less, and a test piece with a width of 20 mm, a length of 40 mm, and a thickness of 1 mm is uniaxially stretched at a rate of 3 mm / min at a temperature 10°C higher than the glass transition temperature with an elongation rate of 100%, and the in-plane retardation value of the central portion of the test piece is measured to obtain the absolute value of the orientation birefringence (Δn Ｂ ) of less than 10.0 × 10 －４ and contains a transparent thermoplastic resin (B). Let the glass transition temperature of the retardation layer be Tg Ａ and the glass transition temperature of the base layer be Tg Ｂ . When this is the case, Tg Ａ > Tg Ｂ and Let the thickness of the retardation adjustment layer be T Ａ and the total thickness of the base material layer be T Ｂ When this is the case, T Ａ <T Ｂ and A liquid crystal display protection plate, wherein the in-plane retardation value of the flat resin plate is 50 to 330 nm.

2. The liquid crystal display protection plate according to claim 1, wherein the flat resin plate has a standard deviation of the in-plane retardation value within a range of 17 cm in width and 22 cm in length of 15.0 nm or less.

3. The flat resin plate has a Tg Ｂ of 80°C or higher Ａ When heated to a temperature of 120°C or lower, the absolute value of the change rate of the in-plane retardation value after heating with respect to that before heating is 50% or less. The liquid crystal display protection plate according to claim 1 or 2.

4. The flat resin plate has a Tg Ｂ or higher Tg Ａ When heated to a temperature of or lower, the standard deviation of the in-plane retardation value within a range of 17 cm in width and 22 cm in length is 25.0 nm or less. The liquid crystal display protection plate according to any one of claims 1 to 3.

5. The transparent thermoplastic resin (A) contains an aromatic vinyl monomer unit, Let the content of the aromatic vinyl monomer unit in the transparent thermoplastic resin (A) be V [mass%], and let the thickness of the retardation layer be T Ａ The liquid crystal display protection plate according to any one of claims 1 to 4, which satisfies the following formula (1) when [mm]. 6.0 ≤ V × T Ａ ≤ 30.0... (1)

6. The liquid crystal display protection plate according to any one of claims 1 to 5, having a cured film on at least one outermost surface.

7. The liquid crystal display protection plate according to any one of claims 1 to 6, wherein the flat resin plate is an extruded plate.

8. A resin plate having a curved surface, having substrate layers laminated on both sides of a retardation adjustment layer, The retardation adjustment layer has an absolute value of photoelastic coefficient (C Ａ ), which is 10.0×10 －１２ / Pa or less, and a test piece with a width of 20 mm, a length of 40 mm, and a thickness of 1 mm is uniaxially stretched at a rate of 3 mm / min at a temperature 10°C higher than the glass transition temperature with an elongation ratio of 100%, and the in-plane retardation value of the central portion of the test piece is measured to obtain the absolute value of the orientation birefringence (Δn Ａ ), which is 10.0×10 －４ to 100.0×10 －４ , and contains a transparent thermoplastic resin (A). The base material layer has an absolute value of photoelastic coefficient (C Ｂ ) of 10.0 × 10 －１２ / Pa or less, and a test piece with a width of 20 mm, a length of 40 mm, and a thickness of 1 mm is uniaxially stretched at a rate of 3 mm / min at a temperature 10 °C higher than the glass transition temperature with an elongation rate of 100%, and the in-plane retardation value of the central portion of the test piece is measured to obtain the absolute value of the orientation birefringence (Δn Ｂ ) of less than 10.0 × 10 －４ and contains a transparent thermoplastic resin (B). Let the glass transition temperature of the retardation layer be Tg Ａ and the glass transition temperature of the base material layer be Tg Ｂ . When this is the case, Tg Ａ > Tg Ｂ and Let the thickness of the retardation adjustment layer be T Ａ and the total thickness of the base material layer be T Ｂ When this is the case, T Ａ < T Ｂ and A liquid crystal display protection plate with a curved surface, wherein the in-plane retardation value of the resin plate having the curved surface is 50 to 330 nm.

9. The liquid crystal display protection plate with a curved surface according to claim 8, wherein the resin plate having the curved surface has a standard deviation of the in-plane retardation value within a range of 17 cm in width and 22 cm in length of 25.0 nm or less.

10. The transparent thermoplastic resin (A) contains an aromatic vinyl monomer unit, When the content of the aromatic vinyl monomer unit in the transparent thermoplastic resin (A) is V [mass%] and the thickness of the retardation layer is T Ａ The curved liquid crystal display protection plate according to claim 8 or 9, which satisfies the following formula (1), where the unit of T is [mm]. 6.0 ≤ V × T Ａ ≤ 30.0... (1)

11. The liquid crystal display protection plate with a curved surface according to any one of claims 8 to 10, having a cured film on at least one outermost surface.

12. The liquid crystal display protection plate with a curved surface according to any one of claims 8 to 11, wherein the resin plate having the curved surface is a thermoformed plate obtained by thermoforming a flat resin plate.

13. A step of forming a flat resin plate having the substrate layers laminated on both sides of the retardation adjustment layer, heating the flat resin plate to a temperature of Tg Ｂ or higher and Tg Ａ or lower, and thermoforming it into a shape having a curved surface, the method for manufacturing a liquid crystal display protection plate with a curved surface according to any one of claims 8 to 12.

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