Liquid crystal display protection plate, and liquid crystal display protection plate with curved surface and manufacturing method thereof

Abstract

The present invention provides a liquid crystal display protection plate that can suppress the reduction of visibility such as color unevenness, blackening and coloring when the liquid crystal display protection plate located on a liquid crystal screen is observed through a polarizing filter. The liquid crystal display protection plate (1) includes a resin plate (16) having a base material layer (22) laminated on both sides of a phase difference adjustment layer (21). The phase difference adjustment layer includes a photoelastic coefficient having an absolute value of 10.0×10 ‑12 / Pa or less and the absolute value of the orientation birefringence is 10.0×10 ‑4 ~100.0×10 ‑4 The base layer includes a transparent thermoplastic resin (A) having an absolute value of a photoelastic coefficient of 10.0×10 ‑12 / Pa or less and the absolute value of the orientation birefringence is less than 10.0×10 ‑4 The phase difference adjustment layer has a Tg higher than that of the substrate layer. The total thickness of the substrate layer is greater than that of the phase difference adjustment layer. The Re value of the resin plate is 50 to 330 nm.

Description

Technical Field

[0001] The invention relates to a liquid crystal display protection plate, a liquid crystal display protection plate with a curved surface and a manufacturing method thereof. Background Art

[0002] In a liquid crystal display and a touch panel display obtained by combining a liquid crystal display and a touch panel, a protective plate may be provided on the front side thereof to prevent scratches on the surface, etc. In this specification, the protective plate is referred to as a "liquid crystal display protective plate".

[0003] The liquid crystal display protection plate includes a resin plate composed of at least one thermoplastic resin layer and a cured coating film formed on at least one surface of the resin plate as needed.

[0004] Patent Document 1 discloses a scratch-resistant resin plate suitable for a display window protection plate of a portable information terminal, comprising a methacrylic resin plate and a cured coating formed on at least one surface thereof (claims 1, 2, 7, paragraph 0010, etc.). Patent Document 2 discloses a polycarbonate resin laminate for a liquid crystal display cover, comprising a laminate having a methacrylic resin layer laminated on one surface of a polycarbonate resin layer and a cured coating formed on the methacrylic resin layer of the laminate (claim 1, paragraph 0008, etc.).

[0005] The LCD protection plate is provided on the front side (viewer side) of the LCD, and the viewer views the LCD screen through the protection plate. Here, since the LCD protection plate hardly changes the polarization of the light emitted from the LCD, when the screen is viewed through a polarizing filter such as polarized sunglasses, the screen may become darker and the image visibility may decrease (blackening phenomenon) depending on the angle between the polarization axis of the emitted light and the transmission axis of the polarizing filter.

[0006] Therefore, a liquid crystal display protection plate capable of suppressing the reduction in the visibility of an image when the screen of a liquid crystal display is viewed through a polarizing filter is being studied. For example, Patent Document 3 discloses a liquid crystal display protection plate comprising a scratch-resistant resin plate having a cured coating 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).

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2004-299199

[0010] Patent Document 2: Japanese Patent Application Publication No. 2006-103169

[0011] Patent Document 3: Japanese Patent Application Publication No. 2010-085978

[0012] Patent Document 4: Japanese Patent Application Publication No. 2018-103518 Summary of the invention

[0013] Problems to be solved by the invention

[0014] In recent years, displays with curved surface processing and other shape processing are being developed for applications such as in-vehicle car navigation systems and display audio from the perspective of design and visibility. In displays having curved surfaces, a curved liquid crystal display protection plate that matches the shape of the curved surface is used. For a flat resin plate obtained by extrusion molding, a cured coating is formed as required, and then hot forming such as press molding, vacuum molding and pressure molding is performed, thereby manufacturing a curved liquid crystal display protection plate. The resin plate contained in the liquid crystal display protection plate has an Re value within an appropriate range in both the two stages before and after hot forming, and preferably the deviation of the Re value is small.

[0015] Patent Document 4 aims to provide a resin laminate (resin sheet) which is excellent in thermoformability or printability at low temperatures and in which coloration and color unevenness after thermoforming are suppressed.

[0016] 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 co-extrusion 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 less than 1500nm (Claim 1).

[0017] Patent Document 4 discloses that the polycarbonate resin has a terminal structure derived from a specific monohydric phenol, thereby lowering the glass transition temperature of the polycarbonate resin and achieving thermoformability at low temperatures (Paragraph 0018).

[0018] The resin laminate described in Patent Document 4 preferably further has a hard coat layer on the acrylic resin layer (claim 7).

[0019] In Patent Documents 3 and 4, the resin plate is preferably a laminated plate in which a methacrylic resin layer is laminated on at least one surface of a polycarbonate resin layer (claim 6 of Patent Document 3, paragraph 0096 of Patent Document 4). In these laminated plates, 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 protective plate can be adjusted to an appropriate range (paragraph 0036 of Patent Document 3, etc.).

[0020] The graphs showing the relationship between stress and birefringence and the relationship between orientation birefringence, stress birefringence and photoelastic coefficient are shown in Figure 7 .

[0021] The absolute value of the photoelastic coefficient of the polycarbonate resin used in Patent Documents 3 and 4 is 90×10 -12 / Pa, which is very large, and the Re value changes due to slight stress. Therefore, when using polycarbonate resins, it is difficult to obtain an optically uniform LCD protection plate. For example, when observing the LCD protection plate located on the LCD screen through a polarizing filter, it is possible to observe color unevenness due to the deviation of the Re value. Especially after thermoforming, due to the residual stress generated in the cooling process of thermoforming, there is a tendency for the deviation of the Re value of the resin plate to become larger.

[0022] The absolute value of the photoelastic coefficient of the methacrylic resin used in Patent Document 1 is as small as 3.2×10 -12 / Pa, Re value is unlikely to change due to stress. Therefore, when using methacrylic resin, an optically uniform LCD protective plate can be obtained. However, since the absolute value of the orientation birefringence of methacrylic resin is as small as 4.0×10 -4 Therefore, although it also depends on the thickness, the Re value of the obtained LCD protective plate tends to decrease to about 20nm. Therefore, when the LCD protective plate located on the LCD screen is observed through a polarizing filter, the screen may become dark and the visibility of the image may be reduced depending on the angle between the polarization axis of the outgoing light and the transmission axis of the polarizing filter.

[0023] In addition, generally speaking, when the Re value of the LCD protective plate is larger than the appropriate range, when viewing through a polarizing filter, the difference in light transmittance of each wavelength in the visible light region becomes larger, and various colors may be seen, thereby reducing visibility (coloration phenomenon).

[0024] The present invention has been completed in view of the above-mentioned situation, and its purpose is to provide a liquid crystal display protection plate, in which the in-plane retardation value (Re value) is within an appropriate range in both the two stages before and after thermoforming, and the deviation of the in-plane retardation value (Re value) is small, which can suppress the reduction in visibility such as color unevenness, blackening and coloring when observing the liquid crystal display protection plate located on the liquid crystal screen through a polarizing filter.

[0025] Methods used to solve problems

[0026] The present invention provides the following liquid crystal display protection plates [1] to

[13] , and liquid crystal display protection plates with curved surfaces and methods for manufacturing the same.

[0027] [1] A liquid crystal display protective plate comprising a flat resin plate on which a base material layer is laminated on both sides of a phase difference adjustment layer,

[0028] The phase difference adjustment layer includes a photoelastic coefficient (C A ) has an absolute value of 10.0×10 -12 / Pa or less and the orientation birefringence (Δn A ) has an absolute value of 10.0×10 -4 ~100.0×10 -4 The transparent thermoplastic resin (A), the oriented birefringence (Δn A ) is obtained by uniaxially stretching a test piece having a width of 20 mm, a length of 40 mm and a thickness of 1 mm at a temperature 10° C. higher than the glass transition temperature at a rate of 3 mm / min at a stretching ratio of 100% and measuring the in-plane retardation value of the central portion of the test piece,

[0029] The substrate layer includes a photoelastic coefficient (C B ) has an absolute value of 10.0×10 -12 / Pa or less and the orientation birefringence (Δn B ) is less than 10.0×10 -4 The transparent thermoplastic resin (B), the oriented birefringence (Δn B ) is obtained by uniaxially stretching a test piece having a width of 20 mm, a length of 40 mm and a thickness of 1 mm at a temperature 10° C. higher than the glass transition temperature at a rate of 3 mm / min at a stretching ratio of 100% and measuring the in-plane retardation value of the central portion of the test piece,

[0030] When the glass transition temperature of the phase difference adjustment layer is set to Tg A The glass transition temperature of the substrate layer is set to Tg B When Tg A >Tg B ,

[0031] When the thickness of the phase difference adjustment layer is set to T A The total thickness of the above-mentioned substrate layer is set as T B When T A <T B ,

[0032] The in-plane retardation value (Re value) of the flat resin plate is 50 to 330 nm.

[0033] [2] The liquid crystal display protection plate according to [1], wherein the standard deviation of the in-plane retardation value (Re value) of the flat resin plate within a range of a width of 17 cm and a length of 22 cm is 15.0 nm or less.

[0034] [3] The protective plate for a liquid crystal display as described in [1] or [2], wherein the flat resin plate is heated to a temperature of Tg B Above and Tg A At a temperature of 100 Å or less, the absolute value of the rate of change of the in-plane retardation value (Re value) after heating relative to that before heating is 50% or less.

[0035] [4] The protective plate for a liquid crystal display as described in any one of [1] to [3], wherein the flat resin plate is heated to a temperature of Tg B Above and Tg A At a temperature of 1000 nm or less, the standard deviation of the in-plane retardation value (Re value) within a range of 17 cm in width and 22 cm in length was 25.0 nm or less.

[0036] [5] The liquid crystal display protection plate according to any one of [1] to [4], wherein

[0037] The transparent thermoplastic resin (A) contains an aromatic vinyl monomer unit,

[0038] When the content of the aromatic vinyl monomer unit in the transparent thermoplastic resin (A) is V [mass %], and the thickness of the phase difference adjustment layer is T A [mm], the following formula (1) is satisfied:

[0039] 6.0≤V×T A ≤30.0…(1).

[0040] [6] The liquid crystal display protection plate according to any one of [1] to [5], comprising a cured coating film on at least one outermost surface.

[0041] [7] The liquid crystal display protection plate according to any one of [1] to [6], wherein the flat resin plate is an extrusion-molded plate.

[0042] [8] A curved liquid crystal display protective plate comprising a resin plate having a curved surface and a base material layer laminated on both sides of a phase difference adjustment layer,

[0043] The phase difference adjustment layer includes a photoelastic coefficient (C A ) has an absolute value of 10.0×10 -12 / Pa or less and the orientation birefringence (Δn A ) has an absolute value of 10.0×10 -4 ~100.0×10 -4 The transparent thermoplastic resin (A), the oriented birefringence (Δn A) is obtained by uniaxially stretching a test piece having a width of 20 mm, a length of 40 mm and a thickness of 1 mm at a temperature 10° C. higher than the glass transition temperature at a rate of 3 mm / min at a stretching ratio of 100% and measuring the in-plane retardation value of the central portion of the test piece,

[0044] The substrate layer includes a photoelastic coefficient (C B ) has an absolute value of 10.0×10 -12 / Pa or less and the orientation birefringence (Δn B ) is less than 10.0×10 -4 The transparent thermoplastic resin (B), the oriented birefringence (Δn B ) is obtained by uniaxially stretching a test piece having a width of 20 mm, a length of 40 mm and a thickness of 1 mm at a temperature 10° C. higher than the glass transition temperature at a rate of 3 mm / min at a stretching ratio of 100% and measuring the in-plane retardation value of the central portion of the test piece,

[0045] When the glass transition temperature of the phase difference adjustment layer is set to Tg A The glass transition temperature of the substrate layer is set to Tg B When Tg A >Tg B ,

[0046] When the thickness of the phase difference adjustment layer is set to T A The total thickness of the above-mentioned substrate layer is set as T B When T A <T B ,

[0047] The in-plane retardation value of the resin plate having the curved surface is 50 to 330 nm.

[0048] [9] The curved liquid crystal display protection plate as described in [8], wherein the standard deviation of the in-plane retardation value of the curved resin plate within the range of 17 cm in width and 22 cm in length is less than 25.0 nm.

[0049]

[10] The curved liquid crystal display protection plate as described in [8] or [9], wherein:

[0050] The transparent thermoplastic resin (A) contains an aromatic vinyl monomer unit,

[0051] When the content of the aromatic vinyl monomer unit in the transparent thermoplastic resin (A) is V [mass %], and the thickness of the phase difference adjustment layer is T A [mm], the following formula (1) is satisfied:

[0052] 6.0≤V×TA ≤30.0…(1).

[0053]

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

[10] , wherein a cured coating is provided on at least one outermost surface.

[0054]

[12] The curved liquid crystal display protective plate 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.

[0055]

[13] The method for manufacturing a protective plate for a liquid crystal display with a curved surface according to any one of [8] to

[12] , comprising:

[0056] a step of forming a flat resin plate having the base material layer laminated on both sides of the phase difference adjustment layer; and

[0057] The flat resin plate is heated to Tg B Above and Tg A The process of heat forming the steel sheet into a curved shape at a temperature below 0.1°C.

[0058] Effects of the Invention

[0059] According to the present invention, a liquid crystal display protective plate can be provided, wherein the in-plane retardation value (Re value) is within an appropriate range and the deviation of the in-plane retardation value (Re value) is small in both the two stages before and after thermoforming, and the reduction in visibility such as color unevenness, blackening and coloring when the liquid crystal display protective plate located on the liquid crystal screen is observed through a polarizing filter can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 This is a schematic cross-sectional view of a liquid crystal display protection plate according to a first embodiment of the present invention.

[0061] Figure 2 This is a schematic cross-sectional view of a liquid crystal display protection plate according to a second embodiment of the present invention.

[0062] Figure 3 This is a schematic diagram of an apparatus for producing an extrusion-molded plate according to one embodiment of the present invention.

[0063] Figure 4 This is a schematic cross-sectional view of a liquid crystal display protection plate for a comparative example.

[0064] Figure 5 This is a schematic perspective view of a resin mold used in the [Example].

[0065] Figure 6 This is a diagram for explaining how to calculate the forming rate.

[0066] Figure 7 It is a graphic diagram showing the relationship between stress and birefringence and the relationship between orientation birefringence, stress birefringence and photoelastic coefficient. DETAILED DESCRIPTION

[0067] Generally, for a thin film formed body, the terms "film", "sheet" or "plate" are used depending on the thickness, but there is no clear distinction between them. The "resin plate" described in this specification includes "resin film" and "resin sheet".

[0068] In this specification, the glass transition temperature of a general material is represented by "Tg".

[0069] [LCD display protection plate]

[0070] The present invention relates to a liquid crystal display protection plate, which can be suitably used for protecting a liquid crystal display and a touch panel display obtained by combining a liquid crystal display and a touch panel.

[0071] The liquid crystal display protective plate of the present invention comprises a flat resin plate having a base material layer laminated on both sides of a phase difference adjustment layer, and the flat resin plate is preferably an extrusion-molded plate.

[0072] The above-mentioned liquid crystal display protection plate of the present invention can be thermoformed to manufacture a liquid crystal display protection plate with a curved surface.

[0073] The curved surface LCD protective plate of the present invention comprises a resin plate having a curved surface with a base material layer laminated on both sides of a phase difference adjustment layer, and further comprises a cured coating film as required. The resin plate having a curved surface is a thermoformed plate obtained by thermoforming a flat resin plate.

[0074] The LCD protection plate and the curved LCD protection plate of the present invention may include a cured coating on at least one of the outermost surfaces as required.

[0075] In the LCD protective plate and the curved LCD protective plate of the present invention, the phase difference adjustment layer comprises a transparent thermoplastic resin (A) having specific optical properties, and the substrate layer comprises a transparent thermoplastic resin (B) having specific optical properties. A (°C), the glass transition temperature of the substrate layer is defined as Tg B (℃), Tg A >Tg B When the thickness of the phase difference adjustment layer is set to T A , the total thickness of the substrate layer is set to T B When T A <T B .

[0076] The in-plane retardation value (also referred to as "Re value") of the flat resin plate and the resin plate having a curved surface is 50 to 330 nm.

[0077] The standard deviation of the Re value of the flat resin plate within a range of 17 cm in width and 22 cm in length is preferably 15.0 nm or less.

[0078] The flat resin plate is heated to Tg B Above and Tg A At a temperature of 0.5 Å or less, the absolute value of the rate of change of the Re value after heating relative to that before heating is preferably 50% or less.

[0079] The flat resin plate is heated to Tg B Above and Tg A At a temperature of 1000 Å or less, the standard deviation of the Re value in a range of 17 cm in width and 22 cm in length is preferably 25.0 nm or less.

[0080] The resin plate having a curved surface preferably has a standard deviation of Re value of 25.0 nm or less within a range of 17 cm in width and 22 cm in length.

[0081] Figure 1 , Figure 2 Schematic cross-sectional views of the first and second embodiments of the liquid crystal display protection plates of the present invention. In the figure, symbols 1 and 2 represent the liquid crystal display protection plates, symbol 16 represents the flat resin plate, symbol 21 represents the phase difference adjustment layer, symbol 22 represents the substrate layer, and symbol 31 represents the cured coating.

[0082] 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 a base material layer 22 is laminated on both surfaces of a phase difference adjustment layer 21 .

[0083] The LCD protection plate 2 of the second embodiment is a LCD protection plate having a three-layer structure in which a base material layer 22 is laminated on both sides of a phase difference adjustment layer 21, and a cured coating 31 is formed on at least one surface of a flat resin plate 16. Figure 2 In the example shown, cured films 31 are formed on both surfaces of the flat resin plate 16 .

[0084] The structure of the liquid crystal display protection plate is not limited to the illustrated example, and appropriate design changes can be made without departing from the gist of the present invention.

[0085] Can be Figure 1 , Figure 2 The flat LCD protection plate shown is thermoformed to produce a curved LCD protection plate.

[0086] In the flat resin plate and the resin plate having a curved surface, the phase difference adjustment layer includes a photoelastic coefficient (CA ) has an absolute value of 10.0×10 -12 / Pa or less and the orientation birefringence (Δn A ) has an absolute value of 10.0×10 -4 ~100.0×10 -4 The transparent thermoplastic resin (A), the oriented birefringence (Δn A ) is obtained by uniaxially stretching a test piece having a width of 20 mm, a length of 40 mm and a thickness of 1 mm at a temperature 10°C higher than the glass transition temperature at a speed of 3 mm / min at a stretching ratio of 100% and measuring the in-plane retardation value of the central part of the test piece after uniaxial stretching.

[0087] "Delay" refers to the phase difference between light in the direction of the main chain of the molecule and light in the direction perpendicular to it. Generally, polymers can be formed into any shape by heating and melting, but it is known that delay occurs due to stress generated during heating and cooling and the orientation of molecules. It should be noted that in this specification, unless otherwise specified, "delay" means delay in the plane.

[0088] Generally, the Re value of a resin plate is represented by the following formula (i).

[0089] [Re value of resin plate] = [birefringence (ΔN)] × [thickness (d)] (i)

[0090] The birefringence (ΔN) is represented by the following formula (ii).

[0091] [Birefringence] = [stress birefringence] + [orientation birefringence] (ii)

[0092] The stress birefringence and the orientation birefringence are represented by the following formulas (iii) and (iv), respectively.

[0093] [Stress birefringence] = [Photoelastic coefficient (C)] × [Stress] (iii)

[0094] [Orientation birefringence] = [intrinsic birefringence] × [degree of orientation] (iv)

[0095] In formula (iv), the degree of orientation is a value in the range of 0 to 1.0.

[0096] The graphs showing the relationship between stress and birefringence and the relationship between orientation birefringence, stress birefringence and photoelastic coefficient are shown in Figure 7 .

[0097] In the present invention, using Figure 7 The optical properties of the transparent thermoplastic resin (A) and the transparent thermoplastic resin (B) are determined by the photoelastic coefficient and the orientation birefringence schematically shown in FIG.

[0098] In the liquid crystal display protection plate and the curved liquid crystal display protection plate of the present invention, by including a phase difference adjustment layer containing the above-mentioned transparent thermoplastic resin (A) with specific optical properties, it is possible to suppress the reduction in visibility such as color unevenness and blackening when observing the liquid crystal display protection plate located on the liquid crystal screen through a polarizing filter.

[0099] In this specification, unless otherwise specified, the "Re value of the resin plate" is the average value of the Re values ​​of the birefringent pixels of about 110,000 points within the 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 the birefringent pixels of about 110,000 points within the measurement range of 17 cm in width and 22 cm in length.

[0100] The average value and standard deviation of the Re value can be measured, for example, using a retardation measuring device "WPA-100-L" manufactured by Photonic Lattice Corporation by the method described in the section "Examples" to be described later.

[0101] 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.

[0102] When the Re value is less than the above lower limit, when the LCD protection plate on the LCD screen is observed through a polarizing filter, it may turn black regardless of the relationship between the polarization axis of the outgoing light and the transmission axis of the polarizing filter. When the Re value is greater than the above upper limit, when viewing through a polarizing filter, the difference in light transmittance of each wavelength in the visible light region becomes large, and various colors may be seen, thereby reducing visibility (coloration phenomenon).

[0103] When the standard deviation of the Re value of the flat resin plate and the resin plate having a curved surface is small, the deviation of the Re value is small, which is preferred. If the standard deviation of the Re value is sufficiently small, when the liquid crystal display protection plate located on the liquid crystal screen is observed through a polarizing filter, color unevenness caused by the deviation of the Re value is suppressed, and visibility is improved.

[0104] The standard deviation of the Re value of the flat resin plate is preferably 15 nm or less, more preferably 10 nm or less, further preferably 7 nm or less, particularly preferably 5 nm or less, and most preferably 4 nm or less.

[0105] 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.

[0106] The Re value and the standard deviation of the Re value of the flat resin plate are preferably not greatly changed by thermoforming. In the present invention, the thermoforming temperature is preferably Tg B Above and Tg A Below, more preferably Tg B Above and below Tg A temperature.

[0107] The flat resin plate is heated to Tg B Above and Tg A At temperatures below 300°, the absolute value of the rate of change of the Re value after heating relative to that before heating is preferably 50% or less, more preferably 45% or less, further preferably 40% or less, particularly preferably 35% or less, and most preferably 30% or less.

[0108] The change rate of the Re value after heating relative to that before heating is expressed by the following formula.

[0109] [Rate of change of Re value after heating relative to before heating] (%) = ([Re value after heating] - [Re value before heating]) / [Re value before heating] × 100

[0110] The flat resin plate is heated to Tg B Above and Tg A At a temperature of 1000 Å or less, 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.

[0111] The thickness (d) of the flat resin plate and the resin plate with a curved surface as a whole is not particularly limited, and is 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 become insufficient, and if it is too thick, it may hinder the lightweighting of the liquid crystal display or the touch panel display containing it.

[0112] (Phase difference adjustment layer)

[0113] The flat resin plate and the resin plate having a curved surface include a phase difference adjustment layer. The phase difference adjustment layer is a layer that mainly determines the Re value of the liquid crystal display protective plate, and includes a transparent thermoplastic resin (A) having specific optical properties.

[0114] <Transparent thermoplastic resin (A)>

[0115] The photoelastic coefficient (C A ) has an absolute value of 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 photoelastic coefficient (C A ) is less than the upper limit, the stress birefringence caused by the residual stress generated during the extrusion molding process is small (refer to Figure 7 ), the standard deviation of the Re value of the LCD protective plate can be reduced. As a result, when the LCD protective plate located on the LCD screen is observed through a polarizing filter, color unevenness caused by the deviation of the Re value is suppressed, and visibility is improved.

[0116] Orientation birefringence (Δn A ) has an absolute value of 10.0×10 -4 ~100.0×10 -4 , 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 orientation birefringence (Δn A ) is within the above range, the Re value of the liquid crystal display protection plate can be controlled to be within an appropriate range.

[0117] Orientation birefringence depends on the degree of orientation of the polymer and is therefore affected by production conditions such as molding conditions and stretching conditions. In this specification, "orientation birefringence" is measured by the method described in the section [Examples] below unless otherwise specified.

[0118] The transparent thermoplastic resin (A) may be any resin satisfying the photoelastic coefficient (C A ) and orientation birefringence (Δn A ) is not particularly limited.

[0119] In one embodiment, the transparent thermoplastic resin (A) may contain one or more aromatic vinyl monomer units. The aromatic vinyl monomer is not particularly limited, and examples thereof include: styrene (St); core 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, etc. Among them, styrene (St) is preferred from the viewpoint of availability.

[0120] The content of the aromatic vinyl monomer unit in the transparent thermoplastic resin (A) is V [mass %], and the thickness of the phase difference adjustment layer is T A [mm]. Their product (V×T A ) preferably satisfies the following formula (1).

[0121] 6.0≤V×T A ≤30.0…(1)

[0122] The photoelastic coefficient (C A ) is small, and the stress birefringence is almost zero. When the transparent thermoplastic resin (A) contains aromatic vinyl monomer units such as styrene (St) units, the orientation birefringence (Δn A ) has a tendency to depend on the content V [mass %] of the aromatic vinyl monomer unit in the transparent thermoplastic resin (A). Therefore, V×T A It is strongly related to the Re value of the LCD protection plate. A When the above formula (1) is satisfied, the Re value of the liquid crystal display protective plate can be controlled within an appropriate range.

[0123] The transparent thermoplastic resin (A) may be a copolymer having, in addition to the aromatic vinyl monomer unit, other monomer units such as a methacrylate unit such as a methyl methacrylate (MMA) unit, an acid anhydride unit such as a maleic anhydride unit, and an acrylonitrile unit.

[0124] Specific examples of the transparent thermoplastic resin (A) containing an aromatic vinyl monomer unit include: methacrylate-styrene copolymer (MS resin); styrene-maleic anhydride copolymer (SMA resin); styrene-methacrylate-maleic anhydride copolymer (SMM resin); α-methylstyrene-maleic anhydride-methacrylate copolymer (αStMM resin); acrylonitrile-styrene copolymer (AS resin); acrylimide resin, etc. These can be used alone or in combination.

[0125] Examples of commercially available products of the above resin include the following.

[0126] MS resin: "Toyo MS" manufactured by Toyo Styrene, etc.

[0127] SMA resin: "Plexiglas FT15" manufactured by Daicel-Evonik, "XIBOND" and "XIRAN" manufactured by Polyscope, etc.

[0128] SMM resin: "レジスファイ" manufactured by デンカ, etc.,

[0129] AS resin: "Rakutenko-A" manufactured by Japan's Elastrol, etc.,

[0130] Acrylimide resin: "Pleximid" manufactured by Daicel-Evonik, etc.

[0131] The transparent thermoplastic resin (A) may satisfy the photoelastic coefficient (C A ) and orientation birefringence (Δn A ), it may be a resin that does not contain an aromatic vinyl monomer unit. As the transparent thermoplastic resin (A) that does not contain an aromatic vinyl monomer unit, there may be mentioned a modified methacrylic resin containing a methacrylate unit such as a methyl methacrylate unit and at least one unit selected from a glutarimide unit, an N-substituted or unsubstituted maleimide unit, and a lactone ring unit. These may be used alone or in combination.

[0132] The transparent thermoplastic resin (A) may include a material satisfying the photoelastic coefficient (C A ) and orientation birefringence (Δn A ) range and the resin does not contain the photoelastic coefficient (C A ) and orientation birefringence (Δn A ) in the range of 1: 1 to 5: 1. A mixture of resins (modified methacrylic resins, etc.) containing aromatic vinyl monomer units in the range of 1: 1 to 5: 1.

[0133] In the present invention, the photoelastic coefficient and / or orientation birefringence of general methacrylic resins (unmodified methacrylic resins) and polycarbonate resins other than the above are outside the specified range of the present invention and are not included in the transparent thermoplastic resin (A).

[0134] The absolute value of the photoelastic coefficient of polycarbonate resin is 90×10 -12 / Pa, which is very large, and the Re value changes due to a slight stress. Therefore, when using polycarbonate resins, it is difficult to obtain an optically uniform LCD protection plate. For example, when observing the LCD protection plate on the LCD screen through a polarizing filter, color unevenness may be observed due to the deviation of the Re value.

[0135] In particular, there is a tendency that the Re value of the resin plate changes greatly after thermoforming, and the deviation of the Re value of the resin plate becomes larger than that before thermoforming. The thermoforming process, for example, includes a process of heating the resin plate, a process of pressing the mold onto the heated resin plate, a process of cooling the resin plate in the mold, and a process of removing the cooled resin plate from the mold. In the cooling process, strain (residual stress) is generated in the resin plate. In a resin plate using a polycarbonate resin having a large absolute value of the photoelastic coefficient, there is a tendency that the deviation of the Re value of the resin plate becomes larger due to significant delay unevenness caused by the residual stress generated in the cooling process of thermoforming.

[0136] The absolute value of the photoelastic coefficient of methacrylic resin is as small as 3.2×10 -12 / Pa, Re value is unlikely to change due to stress. Therefore, when using methacrylic resin, an optically uniform LCD protective plate can be obtained. However, since the absolute value of the orientation birefringence of methacrylic resin is as small as 4.0×10 -4 Therefore, although it also depends on the thickness, the Re value of the obtained LCD protective plate tends to decrease to about 20nm. Therefore, when the LCD protective plate located on the LCD screen is observed through a polarizing filter, the screen may become dark and the visibility of the image may be reduced depending on the angle between the polarization axis of the outgoing light and the transmission axis of the polarizing filter.

[0137] The thickness of the phase difference adjustment layer (T A ) is not particularly limited, but is 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.

[0138] The phase difference adjustment layer may contain a small amount of one or more other polymers whose photoelastic coefficient and / or orientation birefringence are outside the provisions of the transparent thermoplastic resin (A). There is no particular limitation on the type of other polymers, and examples thereof include: general non-modified methacrylic resins, polycarbonate resins, polyolefins such as polyethylene and polypropylene, polyamides, polyphenylene sulfide, polyetheretherketone, polyester, polysulfone, polyphenylene ether, polyimide, polyetherimide, polyacetal and other thermoplastic resins; phenolic resins, melamine resins, silicone resins, epoxy resins and other thermosetting resins; and the like.

[0139] Typical non-modified methacrylic resins include, for example, resins containing one or more methacrylate units.

[0140] The content of the transparent thermoplastic resin (A) in the phase difference adjustment layer is preferably high, 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 phase difference adjustment layer is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 2% by mass or less.

[0141] The phase difference adjustment layer may contain various additives as needed. As additives, colorants, antioxidants, thermal degradation inhibitors, ultraviolet absorbers, light stabilizers, lubricants, release agents, polymer processing aids, antistatic agents, flame retardants, light diffusers, matting agents, core-shell particles and block copolymers and other rubber components (impact resistance modifiers) and phosphors can be listed. The content of additives can be appropriately set within the range that does not impair the effect of the present invention. Relative to 100 parts by mass of the constituent resin of the phase difference 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 0.01 to 3 parts by mass, the content of the light stabilizer is 0.01 to 3 parts by mass, and the content of the lubricant is 0.01 to 3 parts by mass.

[0142] When other polymers and / or additives are added to the phase difference adjusting layer, the timing of addition may be during the polymerization of the transparent thermoplastic resin (A) or after the polymerization.

[0143] The phase difference adjustment layer can be a resin layer composed of a resin composition comprising a transparent thermoplastic resin (A) and a known rubber component (impact resistance modifier). As the rubber component, multilayer polymer particles of a core-shell structure, rubber-like polymers and block polymers having a salami structure can be listed. The rubber component can include diene monomer units and alkyl acrylate monomer units, etc. From the perspective of the transparency of the phase difference adjustment layer, it is preferred 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.

[0144] The glass transition temperature (Tg A ) As long as Tg is met A >Tg B The temperature is not particularly limited, but is preferably 90 to 170°C, more preferably 100 to 160°C, particularly preferably 110 to 155°C, and most preferably 130 to 155°C.

[0145] It should be noted that the glass transition temperature (Tg A )" is the glass transition temperature of all the constituent materials of the phase difference adjusting layer including one or more transparent thermoplastic resins (A) and, if necessary, one or more optional components.

[0146] Tg A With TgB 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 When the content is within the above range, the change in the Re value of the resin plate can be suppressed as described below, the resin plate can be thermally formed satisfactorily, and deformation of the obtained curved liquid crystal display protective plate can be suppressed.

[0147] In the present invention, it is preferred that the B Above and Tg A Thermoforming is performed at the following temperatures.

[0148] More preferably, at Tg B +10℃~Tg B Thermoforming is performed at a temperature of +30°C. If within this temperature range, the resin plate can be well thermoformed into the desired shape, and the residual stress generated in the cooling process of the thermoforming can be suppressed to a small value. In this case, the change in Re value can be suppressed, and the deformation of the resulting curved LCD protection plate can be suppressed. For example, in the case of a reliability test of a vehicle-mounted display on a curved LCD protection plate (for example, 1000 hours at 105°C or 72 hours at 85°C 85% RH), the deformation caused by the release of residual stress is suppressed, which is preferred.

[0149] It is particularly preferred that the B +10℃~Tg B +30℃ and below Tg A If the temperature is less than Tg A At a temperature of , the stress and orientation of the phase difference adjustment layer will not be released, thereby effectively suppressing the change in Re value and the deformation of the curved liquid crystal display protection plate, thereby being preferred.

[0150] Below Tg B When thermoforming is performed at a temperature of +10°C, it is difficult to thermoform the resin plate into the desired shape. If a large load is applied or the molding time is extended within this temperature range, thermoforming into the desired shape is possible, but a large molding stress is generated in the resin plate. When the curved LCD protection plate obtained under this condition is subjected to a reliability test for an in-vehicle display, the large residual stress is released and there is a possibility of significant deformation.

[0151] (Base material layer)

[0152] The flat resin plate and the curved resin plate include a substrate layer laminated on both sides of the phase difference adjustment layer and having a glass transition temperature (Tg) lower than that of the phase difference adjustment layer. The substrate layer can increase the thickness (d) of the entire resin plate and improve the rigidity of the resin plate.

[0153] In the above-mentioned stacked structure, the following effects can be obtained.

[0154] In Tg B Above and Tg A When a flat resin plate having a phase difference adjustment layer on the surface is thermoformed at a temperature below 100°C, cracks may be generated in the phase difference adjustment layer. In particular, when the phase difference adjustment layer includes a brittle resin such as an SMA resin and an SMM resin, cracks are easily generated in the phase difference adjustment layer when thermoforming is performed at the above temperature.

[0155] In a flat resin plate having a base material layer formed on both sides of a phase difference adjustment layer, even when the phase difference adjustment layer includes a brittle resin such as an SMA resin or an SMM resin, the phase difference adjustment layer has a brittle resin layer at Tg B Above and Tg A When the thermal forming is performed at a temperature below 100 Å, cracking of the phase difference adjusting layer can be effectively suppressed.

[0156] In the heating process of thermoforming, the temperature of the surface rises first, and then the temperature of the inside rises. In a laminated structure in which a base material layer is formed on both sides of the phase difference adjustment layer, the temperature of the phase difference adjustment layer located inside is difficult to rise compared to the base material layer located on the surface. Therefore, compared with heating a flat resin plate having a phase difference adjustment layer on the surface, the change in the Re value after thermoforming relative to that before thermoforming can be effectively suppressed.

[0157] The substrate layer is preferably a resin layer that does not affect the Re value of the liquid crystal display protective plate, and is preferably a resin layer containing a transparent thermoplastic resin (B) having a sufficiently small photoelastic coefficient and orientation birefringence. As long as each substrate layer is a resin layer containing a transparent thermoplastic resin (B) having the above-mentioned optical properties, the composition and thickness of the substrate layers stacked on both sides of the phase difference adjustment layer may be the same or different.

[0158] <Transparent thermoplastic resin (B)>

[0159] The photoelastic coefficient (C B ) is preferably as small as possible, preferably 10.0×10 -12 / Pa or less, more 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 photoelastic coefficient (C B ) is below the upper limit, the stress birefringence caused by the residual stress generated during the molding process such as extrusion molding is sufficiently small (refer to Figure 7 ), the standard deviation of the Re value of the resin plate can be reduced. As a result, when the LCD protection plate located on the LCD screen is observed through a polarizing filter, color unevenness caused by the deviation of the Re value is suppressed, and visibility is improved.

[0160] Oriented birefringence (Δn B ) is preferably small, preferably less than 10.0×10 -4 , more preferably 8.0×10 -4 Below, more preferably 6.0×10 -4 Below, particularly preferably 4.0×10 -4 Below, the most preferred is 2.0×10 -4 When the orientation birefringence (Δn B ) is below the upper limit, the influence on the Re value of the resin plate is sufficiently small (refer to Figure 7 ), the Re value of the resin plate can be well controlled within an appropriate range.

[0161] The transparent thermoplastic resin (B) may be any resin satisfying the photoelastic coefficient (C B ) and orientation birefringence (Δn B ) is not particularly limited. Specific examples include general unmodified methacrylic resins (PM), modified methacrylic resins modified with glutarimide units, N-substituted or unsubstituted maleimide units, lactone ring units, and cycloolefin polymers (COP). The transparent thermoplastic resin (B) can be used alone or in combination.

[0162] The methacrylic resin (PM) is a homopolymer or copolymer containing structural units derived from one or more methacrylic esters. From the viewpoint of transparency, the content of the methacrylic ester monomer 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 also be 100% by mass.

[0163] Preferred methacrylates include, for example, methyl methacrylate (MMA), ethyl methacrylate, butyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, monocyclic aliphatic hydrocarbon methacrylate, polycyclic aliphatic hydrocarbon methacrylate, etc. From the viewpoint of transparency, the methacrylic resin (PM) preferably contains MMA units, and the content of the 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.

[0164] Methacrylic resin (PM) may contain structural units derived from one or more other monomers other than methacrylate. As other monomers, acrylates such as methyl acrylate (MA), ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate can be listed; styrenes; acrylonitrile, methacrylonitrile; maleic anhydride, phenylmaleimide, cyclohexylmaleimide; etc. Among them, MA is preferred from the viewpoint of transparency. For example, the copolymer of MMA and MA has excellent transparency and is therefore preferred. The content of MMA in the copolymer is preferably 80% by mass or more, more preferably 85% by mass or more, particularly preferably 90% by mass or more, and can be 100% by mass.

[0165] Methacrylic resin (PM) is preferably obtained by polymerizing one or more methacrylates including MMA and other monomers as needed. When multiple monomers are used, polymerization is usually performed after preparing a monomer mixture by mixing multiple monomers. There is no particular restriction on the polymerization method, but from the viewpoint of productivity, free radical polymerization methods such as bulk polymerization, suspension polymerization, solution polymerization and emulsion polymerization are preferred.

[0166] As long as the photoelastic coefficient (C B ) and orientation birefringence (Δn B ), as the transparent thermoplastic resin (B), the types of resins exemplified as the transparent thermoplastic resin (A) (specifically, MS resin, SMA resin, SMM resin, AS resin, and modified methacrylic resin, etc.) can be used. Depending on the monomer composition or the modification rate, the types of resins exemplified as the transparent thermoplastic resin (A) may be used as the transparent thermoplastic resin (B).

[0167] The photoelastic coefficient and orientation birefringence of the polycarbonate-based resin are outside the prescribed ranges of the present invention and are not included in the transparent thermoplastic resin (B).

[0168] The absolute value of the photoelastic coefficient of polycarbonate resin is 90×10 -12 / Pa, is very large, and the Re value changes due to slight stress. Therefore, when using polycarbonate resins, it is difficult to obtain an optically uniform LCD protection plate. For example, when observing the LCD protection plate located on the LCD screen through a polarizing filter, it is possible to observe color unevenness due to the deviation of the Re value. In particular, after thermoforming, there is a tendency that the Re value of the resin plate changes greatly and the deviation of the Re value of the resin plate becomes larger than before thermoforming.

[0169] As described above, when the glass transition temperature of the phase difference adjustment layer is set to Tg A (℃), the glass transition temperature of the substrate layer is Tg B (℃), Tg A >Tg B .

[0170] The glass transition temperature (Tg B ) As long as Tg is met A >Tg B The temperature is preferably 80 to 160°C, more preferably 100 to 150°C, particularly preferably 110 to 140°C, and most preferably 110 to 130°C.

[0171] It should be noted that the glass transition temperature (Tg B )" is the glass transition temperature of all constituent materials of the substrate layer including one or more transparent thermoplastic resins (B) and, if necessary, one or more optional components.

[0172] The total thickness of the base material layers laminated on both sides of the phase difference adjustment layer is defined as T. B In the liquid crystal display protection plate of the present invention, the total thickness of the substrate layer (T B ) is designed to be thicker than the thickness of the phase difference adjustment layer (T A That is, the liquid crystal display protection plate of the present invention satisfies T A <T B The total thickness of the substrate layer (T B ) As long as T A <T B There is no particular limitation and the thickness and rigidity of the LCD protective plate can be appropriately designed. B It 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.

[0173] In the present invention, T B / T A>1, preferably T B / T A ≥1.2, preferably T B / T A ≥1.5, preferably T B / T A ≥2.0, particularly preferably T B / T A ≥5.0, most preferably T B / T A ≥7.0.

[0174] If T A and T B In the above relationship, the total thickness of the substrate layer (T B ) relative to the overall thickness (d) of the resin sheet is sufficiently large so that it can be formed at a temperature suitable for the substrate layer during thermal forming such as curved surface forming, which is preferred.

[0175] The thickness of the phase difference adjustment layer (T A ) is greater than the total thickness of the substrate layer (T B ) is large, the glass transition temperature (Tg B ) is difficult to achieve the desired forming rate (shaping rate). In this case, it is necessary to heat the phase difference adjustment layer at a temperature higher than the glass transition temperature (Tg A ) temperature. Under this temperature condition, the orientation degree of the phase difference adjustment layer decreases, the Re value decreases, and when the LCD protection plate located on the LCD screen is observed through a polarizing filter, it may turn black. If T A <T B , it is preferred that the forming can be performed at a temperature suitable for the base material layer during thermoforming.

[0176] The substrate layer may contain a small amount of one or more other polymers having photoelastic coefficients and / or orientation birefringence other than those specified for the transparent thermoplastic resin (B). The types of other polymers are not particularly limited, and examples thereof include polycarbonate resins, polyolefins such as polyethylene and polypropylene, polyamides, polyphenylene sulfide, polyetheretherketone, polyester, polysulfone, polyphenylene ether, polyimide, polyetherimide, and other thermoplastic resins such as polyacetal; and thermosetting resins such as phenolic resins, melamine resins, silicone resins, and epoxy resins.

[0177] The content of the transparent thermoplastic resin (B) in the substrate layer is preferably high, 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 substrate layer is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 2% by mass or less.

[0178] The base material layer may contain various additives as required. Examples of the types of additives and preferred addition amounts are the same as those of the additives that can be used in the phase difference adjustment layer.

[0179] When other polymers and / or additives are added to the base material layer, the timing of addition may be during the polymerization of the transparent thermoplastic resin (B) or after the polymerization.

[0180] The substrate layer may be a resin layer composed of a resin composition comprising a transparent thermoplastic resin (B) and a known rubber component (impact resistance modifier). The rubber component is exemplified by the same rubber component that can be used in the phase difference adjustment layer. From the perspective of the transparency of the substrate layer, it is preferred that the difference between the refractive index of the rubber component and the refractive index of the transparent thermoplastic resin (B) as the main component is smaller.

[0181] (Other resin layers)

[0182] The flat resin plate and the resin plate with a curved surface may have other resin layers other than the phase difference adjustment layer and the substrate layer. Examples of the laminated structure of the resin plate include: a three-layer structure of substrate layer-phase difference adjustment layer-substrate layer; a four-layer structure of substrate layer-phase difference adjustment layer-substrate layer-other resin layers; a four-layer structure of substrate layer-phase difference adjustment layer-other resin layers-substrate layer, etc.

[0183] (Curing film)

[0184] The LCD protection plate and the curved LCD protection plate of the present invention may include a cured coating on at least one of the outermost surfaces as required.

[0185] When at least one outermost surface of the curved LCD protection plate is provided with a cured film, the cured film may be formed before or after the curved surface processing. The curved surface processing may be performed after the cured film is formed on at least one surface of the flat LCD protection plate, or the flat LCD protection plate may be curved and the cured film may be formed on at least one surface of the resulting curved LCD protection plate.

[0186] The cured film can function as an abrasion-resistant layer (hard coat layer) or a low-reflection layer for improving visibility. The cured film can be formed by a known method.

[0187] Examples of the material of the cured film include inorganic, organic, organic-inorganic, and silicone-based materials. From the viewpoint of productivity, organic and organic-inorganic materials are preferred.

[0188] The inorganic cured film can be formed, for example, by forming an inorganic material such as metal oxides such as SiO 2 , Al 2 O 3 , TiO 2 , and ZrO 2 into a film by vapor phase film formation such as vacuum evaporation and sputtering.

[0189] The organic cured film can be formed, for example, by applying a coating material containing a resin such as melamine resin, alkyd resin, polyurethane resin, and acrylic resin and curing it by heating, or by applying a coating material containing a multifunctional acrylic resin and curing it by ultraviolet light.

[0190] The organic-inorganic cured coating can be formed by, for example, applying an ultraviolet-curable hard coating containing inorganic ultrafine particles such as ultrafine silica particles into which photopolymerizable functional groups are introduced and a curable organic component on the surface, and using ultraviolet irradiation to cause the curable organic component to polymerize with the photopolymerizable functional groups of the inorganic ultrafine particles. In this method, a mesh-like cross-linked coating can be obtained in which the inorganic ultrafine particles are dispersed in an organic matrix in a state of chemical bonding with the organic matrix.

[0191] The silicone-based cured film can be formed, for example, by polycondensing partial hydrolyzates of carbon-functional alkoxysilane, alkyltrialkoxysilane, tetraalkoxysilane, or the like, or materials containing colloidal silica blended therein.

[0192] Among the above methods, examples of the material coating method include dip coating, various roll coatings such as gravure roll coating, flow coating, rod coating, knife coating, spray coating, die coating, and bar coating.

[0193] The thickness of the scratch-resistant (hard-coated) cured film (scratch-resistant layer, hard-coating layer) is preferably 2 to 30 μm, more preferably 5 to 20 μm. When it is too thin, the surface hardness becomes insufficient, and when it is too thick, cracks may be generated due to bending in 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. Whether it is too thin or too thick, the low-reflectivity performance may become insufficient.

[0194] In addition, the LCD protection plate and the curved LCD protection plate of the present invention may have a known surface treatment layer such as an anti-glare layer, an anti-reflection layer, and an anti-fingerprint layer on the surface as needed.

[0195] [Method for manufacturing liquid crystal display protective plate]

[0196] The method for producing a flat liquid crystal display protective plate of the present invention comprises 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 surfaces of a retardation adjustment layer.

[0197] The method for producing a flat liquid crystal display protective plate with a cured film comprises the above step (1) and a step (2) of forming a cured film on at least one surface of the obtained extruded resin plate.

[0198] (Process (1))

[0199] The flat liquid crystal display protection plate is preferably formed by co-extrusion molding.

[0200] Hereinafter, a method for producing a flat extruded resin sheet by the co-extrusion molding method will be described.

[0201] exist Figure 3 , as one embodiment, a schematic diagram of an extrusion molding device including a T-die 11, first to third cooling rolls 12 to 14, and a pair of take-off rolls 15 is shown.

[0202] The constituent resins of each layer are melt-kneaded using an extruder, and co-extruded in a plate-like form from a T-die 11 having a wide discharge port in the form of a desired laminated structure.

[0203] Examples of the lamination method include a feed block method of laminating before flowing into a T-die and a multi-manifold method of laminating inside a T-die. From the viewpoint of improving the smoothness of the interface between layers, the multi-manifold method is preferred.

[0204] The molten thermoplastic resin laminate coextruded from the T-die 11 is pressurized and cooled by first to third cooling rollers 12 to 14. The flat extruded resin sheet 16 obtained after pressurization and cooling is taken away by a pair of take-off rollers 15. The number of cooling rollers can be appropriately designed.

[0205] It should be noted that the configuration of the production apparatus may be appropriately modified in design without departing from the spirit of the present invention.

[0206] In step (1), the temperature of the entire resin on the third cooling roller 14 is TX. Figure 3 The measurement range of TX in the [Example] section is schematically shown.

[0207] The temperature of the resin on the production line can be measured by a known method. For example, as TX, the surface temperature of the resin on the third cooling roller 14 can be measured using a non-contact thermometer such as an infrared radiation thermometer.

[0208] In the present invention, the extruded resin sheet is molded so that the Re value of the flat extruded resin sheet is 50 to 330 nm.

[0209] It is preferred that the extruded resin sheet be molded 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 a flat extruded resin sheet is 25.0 nm or less.

[0210] In order to control the Re value, it is necessary to control the orientation of the molecules. The orientation of the molecules is caused by the stress during molding near the glass transition temperature of the polymer, for example. By optimizing the manufacturing conditions during the extrusion molding process to control the orientation of the molecules, the Re value of the LCD protection plate after extrusion molding can be optimized.

[0211] (Process (2))

[0212] In step (2), an inorganic or organic cured film is formed on at least one surface of the flat LCD protective plate obtained in step (1) or the LCD protective plate after thermal forming in step (3) described later by a known method. The method for forming the cured film has been described above, so it is omitted here.

[0213] (Other processes)

[0214] The method for producing a flat LCD protection plate and a flat LCD protection plate with a cured coating film may include other steps than those described above as necessary.

[0215] For example, between step (1) and step (2), in order to improve the adhesion of the cured film to the flat liquid crystal display protection plate, a step of performing surface treatment on the surface of the flat liquid crystal display protection plate obtained in step (1) on which the cured film is formed can be added. The surface treatment includes: primer treatment; surface roughening treatment such as sandblasting and solvent treatment; surface oxidation treatment such as corona discharge treatment, chromic acid treatment, ozone irradiation treatment and ultraviolet irradiation treatment.

[0216] [Manufacturing method of a curved liquid crystal display protective plate]

[0217] The method for manufacturing a curved liquid crystal display protection plate of the present invention comprises the steps of: forming a flat liquid crystal display protection plate having a substrate layer having a relatively low glass transition temperature (Tg) laminated on both sides of a phase difference adjustment layer; and heating the flat liquid crystal display protection plate to a temperature of Tg. B Above and Tg A The step (3) of hot forming into a shape having a curved surface is performed at the following temperature (TY).

[0218] In the method for manufacturing a curved LCD protective plate of the present invention, between step (1) and step (3), a step (2) of forming a cured coating on at least one surface of a flat LCD protective plate may be included as needed. In this case, in step (3), the flat LCD protective plate with the cured coating is thermoformed.

[0219] Steps (1) and (2) have been described in the section [Method for producing a liquid crystal display protective plate] and are therefore omitted here.

[0220] (Process (3))

[0221] Shape processing such as curved surface processing of a flat LCD protective plate or a flat LCD protective plate with a cured film can be performed by known thermal forming such as press forming, vacuum forming, and pressure forming.

[0222] In the present invention, it is preferred that the B And less than Tg A The flat liquid crystal display protection plate having the base material layer formed on both sides of the phase difference adjustment layer is thermally formed at a temperature lower than TX.

[0223] In step (3), the hot forming temperature is set to TY. Preferably, TX>TY, Tg B <TY<Tg A .

[0224] In the present invention, it is preferred that B Above and Tg A Thermoforming is performed at a temperature (TY) below 100°C, preferably at a temperature above Tg B And less than Tg A Thermoforming is carried out at a temperature of Tg, particularly preferably at B +10℃~Tg B Thermoforming is carried out at a temperature of +30°C.

[0225] If it is within the above temperature range, the flat LCD protection plate can be well thermoformed into the desired shape, and the residual stress generated in the cooling process of thermoforming can be suppressed to a small value. In this case, the change in Re value can be suppressed, and the deformation of the curved LCD protection plate obtained after thermoforming can be suppressed. For example, in the case of a reliable test of a vehicle-mounted display on a curved LCD protection plate (for example, 1000 hours at 105°C or 72 hours at 85°C 85% RH), the deformation caused by the release of residual stress is suppressed, which is preferred.

[0226] Most preferably, Tg B +10℃~Tg B+30℃ and below Tg A If the temperature is less than Tg A At a temperature of , the stress and orientation of the phase difference adjustment layer will not be released, thereby effectively suppressing the change in Re value and the deformation of the curved liquid crystal display protection plate, thereby being preferred.

[0227] Below Tg B When thermoforming is performed at a temperature of +10°C, it is difficult to thermoform the extruded resin sheet into the desired shape. If a large load is applied or the molding time is extended within this temperature range, thermoforming into the desired shape is possible, but a large molding stress is generated in the resin sheet. When the curved LCD protection sheet obtained under this condition is subjected to a reliability test for an in-vehicle display, the large residual stress is released and there is a possibility of significant deformation.

[0228] It is generally believed that if the Tg of the constituent resin of the phase difference adjustment layer of the extruded resin sheet is A The reduction in Re value can be suppressed by performing thermoforming at a lower temperature. However, the inventors have conducted various studies on thermoforming conditions and found that even if the Tg of the constituent resin of the phase difference adjustment layer of the extruded resin sheet is lower than A When thermoforming is performed at a low temperature, if the thermoforming temperature is higher than the temperature for controlling the orientation of the extruded resin sheet in the extrusion molding process, the orientation of the resin is relaxed and the Re value is sometimes greatly reduced. In addition, it is known that when the Tg of the constituent resin of the phase difference adjustment layer is observed through a polarizing filter, the Re value is reduced. A When a curved liquid crystal display protective plate is thermoformed at a temperature that is low and higher than the temperature for controlling the orientation of the extruded resin plate in the extrusion molding process, the screen may become dark and the visibility of the image may be reduced depending on the angle between the polarization axis of the emitted light and the transmission axis of the polarizing filter.

[0229] As a result of the research conducted by the inventors, it is known that, for example, when a resin plate with an overall thickness of 3 mm is extruded under the condition that the speed of the second cooling roller is 0.75 m / min, the orientation of the phase difference adjustment layer that contributes to the size of the Re value is formed before the third cooling roller. That is, in the present invention, TX has the same meaning as "the temperature at which the orientation of the phase difference adjustment layer that contributes to the size of the Re value is fixed during cooling in the extrusion molding process". Therefore, as the lower limit of "the temperature for controlling the orientation of the extruded resin plate in the extrusion molding process", the temperature of the entire resin on the third cooling roller (TX) can be used. In the case of thermoforming at less than TX, the resin temperature in the thermoforming process will not reach the resin temperature on the third cooling roller and the resin temperature on the upstream side of the third cooling roller. Under this condition, in the thermoforming process, the relaxation of the orientation of the resin can be suppressed, the reduction of the Re value can be effectively suppressed, and the reduction in visibility when observing the liquid crystal display protection plate located on the liquid crystal screen through a polarizing filter can be effectively suppressed. It should be noted that in the case of co-extrusion under the condition that the speed of the second cooling roller is greater than 0.75 m / min, the orientation of the phase difference adjustment layer may be formed between the third cooling roller and the withdrawal roller. In addition, when the entire thickness of the molded extruded resin sheet is made thicker than 3 mm, there is a possibility that the orientation of the phase difference adjusting layer is formed between the third cooling roll and the take-off roll.

[0230] In the present invention, it is preferred that the B And less than Tg A The flat LCD protection plate having the substrate layer formed on both sides of the phase difference adjustment layer is thermoformed at a temperature lower than TX. In this case, even if the phase difference adjustment layer includes a brittle resin such as SMA resin and SMM resin, cracks in the phase difference adjustment layer can be effectively suppressed.

[0231] In the heating process of thermoforming, the temperature of the surface rises first, and then the temperature of the inside rises. In a laminated structure in which a base material layer is formed on both sides of the phase difference adjustment layer, the temperature of the phase difference adjustment layer located inside is less likely to rise than the base material layer located on the surface. Therefore, compared with heating a flat LCD protective plate having a phase difference adjustment layer on the surface, the change in the Re value after thermoforming relative to that before thermoforming can be effectively suppressed.

[0232] In the present invention, in step (1), the flat extruded resin plate is molded so that the Re value is 50 to 330 nm. In step (1), the flat liquid crystal display protective plate is preferably molded so that the standard deviation of the Re value within the range of 17 cm in width and 22 cm in length is 25.0 nm or less.

[0233] The absolute value of the change rate of Re value after hot forming relative to that before hot forming is 50% or less, preferably 40% or less, more preferably 30% or less, particularly preferably 25% or less, and most preferably 20% or less.

[0234] The change rate of the Re value after hot forming relative to that before hot forming is expressed by the following formula.

[0235] [Rate of change of Re value after thermoforming relative to before thermoforming] [%] = 100 × ([Re value after thermoforming] - [Re value before thermoforming]) / [Re value before thermoforming]

[0236] The standard deviation of the Re value within the range of 17 cm in width and 22 cm in length of the curved 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.

[0237] The lower limit of the radius of curvature of the curved surface contained in the curved 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 is 1000 mm, preferably 800 mm, more preferably 600 mm, particularly preferably 500 mm, and most preferably 400 mm.

[0238] In the present invention, even when thermoforming is performed, the change in the Re value of the resin plate can be suppressed, so that the Re value is within an appropriate range, and a curved liquid crystal display protection plate with a small variation in the Re value can be stably manufactured.

[0239] As described above, according to the present invention, a liquid crystal display protective plate can be provided, wherein the Re value is within an appropriate range and the deviation of the Re value is small in both the two stages before and after thermoforming, and the reduction in visibility such as color unevenness, blackening and coloring when the liquid crystal display protective plate is observed on a liquid crystal screen through a polarizing filter can be suppressed.

[0240] [use]

[0241] The liquid crystal display protection plate and the curved liquid crystal display protection plate of the present invention are suitable as protection plates for liquid crystal displays or touch panel displays used in digital information devices such as ATMs, vending machines, televisions, mobile phones (including smart phones), personal computers, tablet computers and other portable information terminals (PDAs), digital audio players, portable game consoles, copiers, fax machines and car navigation systems of financial institutions such as banks.

[0242] The liquid crystal display protection plate and the curved liquid crystal display protection plate of the present invention are suitable as a protection plate for a liquid crystal display for vehicle use, for example.

[0243] Example

[0244] Examples of the present invention and comparative examples are described.

[0245] [Evaluation items and evaluation methods]

[0246] The evaluation items and evaluation methods are as follows.

[0247] (Glass transition temperature (Tg) of transparent thermoplastic resin)

[0248] The glass transition temperature (Tg) of the transparent thermoplastic resin is measured using a differential scanning calorimeter ("DSC-50", manufactured by Rigaku Corporation). 10 mg of the transparent thermoplastic resin is placed in an aluminum pan and placed in the above-mentioned apparatus. Perform nitrogen replacement for more than 30 minutes, and then in a nitrogen gas flow of 10 ml / min, first increase the temperature from 25°C to 200°C at a rate of 20°C / min, maintain for 10 minutes, and cool to 25°C (first scan). Next, increase the temperature to 200°C at a rate of 10°C / min (second scan), and calculate the glass transition temperature (Tg) using the midpoint method based on the results obtained in the second scan. It should be noted that when multiple Tg data are obtained in a resin composition containing two or more resins, the value of the resin from the main component is used as the Tg data.

[0249] (Photoelastic coefficient of transparent thermoplastic resin)

[0250] A transparent thermoplastic resin was pressed to obtain a 1.0 mm thick resin plate. A test piece with a width of 15 mm and a length of 80 mm was cut from the central portion of the obtained resin plate. The two ends of the test piece in the longitudinal direction were clamped by a pair of chucks. The distance between the chucks was set to 70 mm.

[0251] Tension was applied to the test piece using an "X-axis dovetail slide" manufactured by Oji Instruments Co., Ltd. The tension was increased in steps of 10 N from 0 N to 30 N. The tension was monitored using a "separate sensor digital force gauge ZTS-DPU-100N" manufactured by IMONDA Co., Ltd.

[0252] The following measurements were performed for the tension applying conditions at each stage from 0 N to 100 N.

[0253] The phase difference value [nm] of the central part of the test piece under tension was measured using "KOBRA-WR" manufactured by Oji Instruments at a measurement wavelength of 589.5nm. The test piece was then removed from a pair of chucks and the thickness (d [mm]) of the phase difference measurement portion was measured. The cross-sectional area (S) [m 2 ](=15[mm]×d[mm]×10 -6 ), stress [Pa] (= tension [N] / S [m 2 ]), birefringence (= phase difference value [nm] × 10 -6 / d[mm]). A graph was plotted with stress on the horizontal axis and birefringence on the vertical axis, and the slope of the straight line obtained by the least square method was determined as the photoelastic coefficient.

[0254] (Orientation Birefringence of Transparent Thermoplastic Resins)

[0255] A transparent thermoplastic resin is pressed 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 is cut out from the central part of the obtained resin plate and set in an Autograph (manufactured by SHIMADZU) with a heating chamber. The distance between the chucks is set to 20 mm. It is kept at a temperature 10°C higher than the glass transition temperature (Tg) for 3 minutes, and then uniaxially stretched at a speed of 3 mm / min. The stretching rate is set to 100%. Under this condition, the distance between the chucks after stretching is 40 mm. The stretched test piece is removed from the above-mentioned device, cooled to 23°C, and the thickness (d) is measured. The Re value of the central part is measured using "KOBRA-WR" manufactured by Prince Measuring Instruments Co., Ltd. under the condition of a measuring wavelength of 589.5 nm. The obtained Re value is divided by the thickness (d) of the test piece to calculate the value of oriented birefringence.

[0256] (Average and standard deviation of Re values ​​of LCD protection plates)

[0257] The average value and standard deviation of Re values ​​of the test pieces of the LCD protective plate before curved surface forming (width 21 cm, length 30 cm) and after curved surface forming (width 17 cm, length 22 cm) were measured as follows.

[0258] A standard lens (FUJINON HF12.5HA-1B) was mounted on the "WPA-100-L" manufactured by Photonic Lattice. The height of the lens was adjusted so that the measurement range was 17 cm in width and 22 cm in length. The Re values ​​of approximately 110,000 birefringent pixels were measured, and the average value and standard deviation were calculated.

[0259] The change rate of the average value of the Re value after the curved surface forming relative to that before the curved surface forming was determined by the following formula.

[0260] [Rate of change of Re value after heating relative to before heating] (%) = ([Re value after heating] - [Re value before heating]) / [Re value before heating] × 100

[0261] (Thickness of each layer)

[0262] The thickness of each layer was measured using a "Universal Projector (V-12B)" manufactured by Nicon Instruments.

[0263] (Uneven color)

[0264] The test piece of the LCD protective plate was placed on the LCD so that the transmission axis of the polarizer on the viewing side of the LCD was perpendicular to the extrusion molding direction of the resin plate. In addition, a polarizing film was placed on it, and the polarizing film was rotated to various angles. The visual performance at the angle where the color unevenness caused by the deviation of the Re value was the strongest was visually evaluated in the following three stages.

[0265] A (good): There is no color unevenness at all, and the visibility of the liquid crystal display is not reduced.

[0266] B (pass): Color unevenness is small, and visibility on the LCD display is slightly reduced.

[0267] C (poor): There is significant color unevenness, and the visibility of the liquid crystal display is greatly reduced.

[0268] (Turns to black)

[0269] The test piece of the LCD protective plate was placed on the LCD so that the transmission axis of the polarizer on the viewing side of the LCD was perpendicular to the extrusion molding direction of the resin plate. In addition, a polarizing film was placed on it, and the polarizing film was rotated to various angles. The visual performance of the LCD at the angle with the minimum transmitted light intensity was visually evaluated in the following three stages.

[0270] A (good): The transmitted light intensity is sufficiently high, and characters and the like displayed on the liquid crystal display can be clearly recognized.

[0271] B (pass): The transmitted light intensity is slightly low, and the visibility of characters etc. displayed on the liquid crystal display is slightly reduced.

[0272] C (poor): The intensity of transmitted light is almost zero, and the characters and the like displayed on the liquid crystal display cannot be recognized.

[0273] (coloring)

[0274] The test piece of the LCD protective plate was placed on the LCD so that the transmission axis of the polarizer on the viewing side of the LCD was perpendicular to the extrusion molding direction of the resin plate. A polarizing film was further placed on it, and the polarizing film was rotated to various angles. The visual performance of the LCD at the angle where the coloring was the largest was visually evaluated in the following three stages.

[0275] A (good): There is no significant coloring, and the visibility of the liquid crystal display is not reduced.

[0276] B (pass): There is coloration, and the visibility of the liquid crystal display is slightly reduced.

[0277] C (poor): There is significant coloring, and visibility on a liquid crystal display is reduced.

[0278] (crack)

[0279] The liquid crystal display protective plate after curved surface molding was visually observed and evaluated in the following two stages.

[0280] A (good): There are no cracks in the phase difference adjustment layer, and the visibility of the liquid crystal display does not decrease.

[0281] C (poor): Cracks were generated in the phase difference adjustment layer, and the visibility of the liquid crystal display was reduced.

[0282] (Forming rate of curved LCD protection plate)

[0283] The molding rate was measured for the test piece (width 17 cm, length 22 cm) with a curved liquid crystal display protection plate in the following manner. Figure 6 Provide explanation. Figure 6 The above figure is a schematic cross-sectional view of a resin mold (male mold and female mold) used in forming a curved liquid crystal display protection plate. Figure 5 yz cross-section diagram. Figure 6 The following figure is with Figure 6 The above figure corresponds to a schematic cross-sectional view of a curved LCD protection plate. In the figure, symbol 26 is a curved LCD protection plate, and symbol M is a resin mold.

[0284] The curved LCD protection plate 26 is placed on a flat platform with the convex surface S1 side as the upper side. In this state, the height L1 from the platform to the center of the concave surface S2 is measured. On the other hand, the height L2 of the convex surface MS1 of the male mold of the resin mold M used for molding the curved LCD protection plate 26 is measured. The molding rate is calculated according to the following formula.

[0285] Forming rate [%] = (L1 / L2) × 100

[0286] [Material]

[0287] The materials used are described below.

[0288]

[0289] (MS1) MS resin (copolymer of methyl methacrylate (MMA) and styrene (St)) was polymerized according to the method for producing copolymer (A) described in [Examples] of JP-A-2003-231785. Tg = 109°C, content of aromatic vinyl monomer units = 35% by mass.

[0290] <SMM resin>

[0291] (SMM1) "Regisphi R200" manufactured by Denka Corporation, Tg = 135°C, styrene-maleic anhydride-MMA copolymer. Aromatic vinyl monomer unit content = 56% by mass.

[0292] <Acrylimide resin>

[0293] (PMMI1) Pleximid TT50 from Daicel-Evonik, Tg = 155° C. Aromatic vinyl monomer unit content = 0% by mass.

[0294] <Resins containing SMA>

[0295] (SMA1) "XIRAN" from Polyscope, Tg = 152°C, styrene-maleic anhydride copolymer. Aromatic vinyl monomer unit content = 77% by mass.

[0296] (SMA2) SMA resin (SMA1) / methacrylic resin (PMMA1) (mass ratio) = 82 / 18, Tg = 145°C, styrene-maleic anhydride copolymer alloy resin. Aromatic vinyl monomer unit content = 63% by mass.

[0297] <Methacrylic resin>

[0298] (PMMA1) A copolymer of methyl methacrylate (MMA) and methyl acrylate (MA), “Parapette EH” manufactured by Kuraray Co., Ltd., Tg=110°C.

[0299] (PMMA2) A copolymer of methyl methacrylate (MMA) and methyl acrylate (MA), “Parapet HR-S” manufactured by Kuraray Co., Ltd., Tg=119°C.

[0300] (PMMA3) Copolymer of methyl methacrylate (MMA) and methyl acrylate (MA), Tg = 85°C.

[0301] <Polycarbonate resin>

[0302] (PC1) "SD Polycarbonate 300 Series" manufactured by Sumika Polycarbonate Co., Ltd., Tg = 150°C.

[0303] [Examples 1 to 4, Comparative Examples 1 and 2]

[0304] (Manufacture of LCD protection panels)

[0305] Using a 50mmφ single-screw extruder (manufactured by Toshiba Machine Co., Ltd.), the resin for the substrate layer (transparent thermoplastic resin (B) or comparative resin) is melt-extruded. Using a 30mmφ single-screw extruder (manufactured by Toshiba Machine Co., Ltd.), the resin for the phase difference adjustment layer (transparent thermoplastic resin (A) or comparative resin) is melt-extruded. These resins in a molten state are stacked through a multi-manifold die, and a thermoplastic resin stack having a three-layer structure in which the substrate layer is stacked on both sides of the phase difference adjustment layer is co-extruded from a T-die. The thermoplastic resin stack is sandwiched between the first cooling roller and the second cooling roller adjacent to each other, wound onto the second cooling roller, sandwiched between the second cooling roller and the third cooling roller, and wound onto the third cooling roller, thereby cooling. The flat resin plate obtained after cooling is taken away by a pair of take-away rollers. In this way, a liquid crystal display protective plate consisting of a flat resin plate having a three-layer structure in which the substrate layer is stacked on both sides of the phase difference adjustment layer is obtained (refer to the accompanying drawings: Figure 1 ).

[0306] A test piece 21 cm wide and 30 cm long was cut out from the center of the obtained LCD protective plate so that the extrusion molding direction (resin flow direction) became the longitudinal direction. The test piece was used to evaluate the LCD protective plate before curved molding.

[0307] (Surface forming)

[0308] A curved surface molding test piece having a width of 17 cm and a length of 22 cm was cut out from the center of the test piece so that the extrusion molding direction (resin flow direction) became the longitudinal direction. The test piece was subjected to curved surface molding in the following manner.

[0309] A resin mold made of "Chemical Wood Prolab 65" manufactured by SSI Co., Ltd. was prepared. Figure 5 As shown, the resin mold M is composed of a combination of a female mold FM (the lower mold shown in the figure) and a male mold MM (the upper mold shown in the figure), and the overall shape is a rectangular parallelepiped with a width (dimension in the x direction shown in the figure) of 200 mm × a length (dimension in the y direction shown in the figure) of 250 mm × a height (dimension in the z direction shown in the figure) of 35 mm.

[0310] A concave surface is formed on the upper surface of the female mold FM, and a convex surface is formed on the lower surface of the male mold MM to engage with the concave surface of the female mold FM. The height of the female mold FM is 15 to 25 mm, and the height of the male mold MM is 20 to 10 mm. The cross-sectional shape of the concave surface of the female mold FM and the convex surface of the male mold MM parallel to the yz plane is uniform regardless of the position in the x direction shown in the figure, and is an arc shape with a curvature radius of 300 mm.

[0311] A polytetrafluoroethylene (PTFE) sheet (300 mm × 300 mm × 12 mm) was placed in an oven, and the oven was heated to 170°C. In this state, a curved surface forming test piece was placed on the PTFE sheet and kept for 6 to 7 minutes until the temperature of the test piece reached the forming temperature recorded in Table 3 (for example, 130°C in Example 1). Then, the PTFE sheet and the curved surface forming test piece placed thereon were taken out of the oven. Next, a non-contact thermometer (PT-S80 manufactured by Optex Co., Ltd.) was used to measure the temperature of the test piece just before being sandwiched by the female mold FM and the male mold MM, and it was confirmed to be the forming temperature recorded in Table 3 (for example, 130°C in Example 1). Next, the curved surface forming test piece of the above-mentioned forming temperature was placed on the female mold FM at room temperature (20 to 25°C), and the male mold MM at room temperature (20 to 25°C) was placed thereon, and a load of 3 kg was applied thereto. Then, the test piece is cooled for 1 to 2 minutes until the temperature of the test piece reaches near room temperature. The cooled test piece is taken out from the resin mold M, and the curved surface-molded liquid crystal display protection plate (curved liquid crystal display protection plate) is evaluated using the test piece.

[0312] For each example, the type and physical properties of the resin used, the thickness of the phase difference adjustment layer, the total thickness of the substrate layer, the thermoforming temperature, and the evaluation results of the liquid crystal display protective plate before and after the curved surface forming are shown in Tables 1 to 3. In each example of Tables 1 to 3, the conditions not described in the table are common conditions.

[0313] [Comparative Examples 3 to 5]

[0314] A liquid crystal display protection plate composed of a three-layer flat resin plate was manufactured in the same manner as in Examples 1 to 4 except that the phase difference adjustment layer was laminated on both sides of the substrate layer for co-extrusion molding (see the attached drawings: Figure 4 ), implement surface forming. Figure 4 In the figure, reference numeral 101 denotes a comparative LCD protective plate, reference numeral 116 denotes a comparative resin plate, reference numeral 121 denotes a phase difference adjustment layer, and reference numeral 122 denotes a substrate layer. The evaluation of the LCD protective plate before and after curved surface forming was carried out in the same manner as in Examples 1 to 4.

[0315] Tables 1 to 3 show the type and properties of the resin used, the thickness of the phase difference adjustment layer, the total thickness of the base layer, the thermoforming temperature, and the evaluation results of the liquid crystal display protective plate before and after curved surface forming for each example.

[0316] [Examples 4-1 to 4-8]

[0317] (Manufacture of LCD protection panels)

[0318] A flat LCD protective plate was manufactured by the same method and laminated structure as in Example 4. However, in each example, the extrusion amount and the rotation speed of the first to third cooling rollers were adjusted so that the temperature (TX) of the entire resin on the third cooling roller was the temperature described in Table 5. As TX, the surface temperature of the resin on the third cooling roller was measured using an infrared radiation thermometer. Figure 3 The measurement range of TX is schematically shown in FIG.

[0319] In the above manner, flat liquid crystal display protection plates (S1-1) to (S1-5) having a three-layer structure in which a base material layer is laminated on both sides of a phase difference adjustment layer are obtained (see the attached drawings: Figure 1 ). The thickness of the two substrate layers is the same.

[0320] Table 4 shows the laminated structure, the types and physical properties of the resins used, the total thickness of the phase difference adjustment layers, the total thickness of the base material layers, and the total thickness.

[0321] A test piece 17 cm wide and 22 cm long was cut out from the center of the obtained LCD protective plate so that the extrusion molding direction (resin flow direction) became the longitudinal direction. The flat LCD protective plate before thermoforming was evaluated using the test piece.

[0322] (Manufacturing of protective plates for curved liquid crystal displays)

[0323] The test piece (width 17 cm, length 22 cm) cut out from a flat extruded resin plate was prepared using the same resin mold M as in Example 4 (refer to Figure 5 ), and hot forming is carried out by the same method as in Example 4.

[0324] Place a polytetrafluoroethylene (PTFE) sheet (300mm×300mm×12mm) in an oven, and heat the oven to 170°C. In this state, place a test piece on the PTFE sheet and keep it for 6 to 7 minutes until the temperature of the test piece reaches the forming temperature (TY) recorded in Table 5 (for example, 140°C in Example 4-1). Next, place the test piece at the above forming temperature on a female mold FM at room temperature (20 to 25°C), place a male mold MM at room temperature (20 to 25°C) thereon, and apply a load of 3kg thereto. Next, cool it down for 1 to 2 minutes until the temperature of the test piece reaches near room temperature. Take out the cooled test piece from the resin mold M, and use the test piece to evaluate the curved liquid crystal display protective plate.

[0325] 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 temperature relationship therebetween are shown in Table 5. In each example in Table 5, the conditions not described in the table are common conditions.

[0326] Table 6 shows the evaluation results of the flat extruded resin plate and the curved liquid crystal display protective plate before thermoforming for each example.

[0327]

[0328]

[0329]

[0330]

[0331]

[0332]

[0333] [Results Summary]

[0334] In Examples 1 to 4, a liquid crystal display protection plate composed of a flat resin plate having a base material layer laminated on both sides of a phase difference adjustment layer was manufactured. In these examples, the phase difference adjustment layer is a layer having a photoelastic coefficient (C A ) has an absolute value of 10.0×10 -12 / Pa or less and the orientation birefringence (Δn A ) has an absolute value of 10.0×10 -4 ~100.0×10 -4 The substrate layer is a layer of a transparent thermoplastic resin (A). B ) has an absolute value of 10.0×10 -12 / Pa or less and the orientation birefringence (ΔnB ) is less than 10.0×10 -4 When the glass transition temperature of the phase difference adjustment layer is set to Tg A , the glass transition temperature of the substrate layer is set to Tg B When Tg A >Tg B .

[0335] In the LCD protection plates before curved surface forming obtained in Examples 1 to 4, the average value of Re value within the range of 17 cm in width and 22 cm in length was 50 to 330 nm, and the standard deviation of Re value within the range of 17 cm in width and 22 cm in length was 15.0 nm or less. In these examples, when the obtained LCD protection plates were used and the LCD protection plates on the LCD screen were observed through a polarizing filter, color unevenness, coloring, and blackening were effectively suppressed.

[0336] In Examples 1 to 4, at Tg B Above and Tg A Below (Tg B Above and below Tg A ) to form a liquid crystal display protection plate with a curved surface.

[0337] In the curved liquid crystal display protection plates obtained in Examples 1 to 4, the average value of Re value within the range of 17 cm in width and 22 cm in length was 50 to 330 nm, and the standard deviation of Re value within the range of 17 cm in width and 22 cm in length was 15.0 nm or less. In these Examples, the absolute value of the change rate of the average value of Re value after thermoforming relative to that before thermoforming was 50% or less.

[0338] In these examples, the obtained curved LCD protection plate was used, and when the LCD protection plate on the LCD screen was observed through a polarizing filter, color unevenness, coloring, and darkening were effectively suppressed.

[0339] In Examples 1 to 4, V×T A In Examples 1, 2, and 4, which are within the range of 6.0 to 30.0, the average value of the Re value at both stages before and after the curved surface processing is within a particularly preferred range.

[0340] In Examples 4-1 to 4-8, in order to satisfy the requirement of B And less than Tg A The values ​​of TX and TY are determined by thermoforming at a temperature (TY) lower than TX, and a flat LCD protection plate and a curved LCD protection plate are manufactured.

[0341] In the flat liquid crystal display protection plates obtained in these Examples, the average 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).

[0342] In the curved liquid crystal display protection plates obtained in these embodiments, the average value of Re value is 50 to 330 nm, and the standard deviation of Re value is 25.0 nm or less (15.0 nm or less, 10.0 nm or less). In these embodiments, the absolute value of the change rate of Re value after thermoforming relative to that before thermoforming is 50% or less (20% or less).

[0343] Thermoforming temperature (TY) is higher than the Tg of the phase difference adjustment layer resin. A Since the temperature is lower than TX, it is considered that the orientation of the phase difference adjustment layer resin is hardly destroyed in the thermal forming process and the Re value is basically maintained.

[0344] In these embodiments, when the curved LCD protection plate on the LCD screen is observed through a polarizing filter, darkening, coloring, and color unevenness are effectively suppressed.

[0345] From the results of Examples 4-1 to 4-8, it is more preferable to satisfy TX>TY and Tg B <TY<Tg A Surface processing is carried out under the conditions of.

[0346] In Comparative Example 1, Tg A <Tg B , above Tg A and Tg B The curved LCD protection plate was manufactured by thermoforming at a temperature of . In this comparative example, the absolute value of the change rate of the average value of Re value after thermoforming relative to that before thermoforming was greater than 50%. The curved LCD protection plate obtained in this comparative example had a low Re value, and when the LCD protection plate on the LCD screen was observed through a polarizing filter, it was significantly blackened.

[0347] In Comparative Example 2, as the resin of the phase difference adjustment layer, a photoelastic coefficient (C A ) and orientation birefringence (Δn A ) is a polycarbonate resin outside the provisions of the present invention. The standard deviation of the Re value of the liquid crystal display protection plate before curved surface molding obtained in this comparative example is large (the deviation of the Re value is large), and when the liquid crystal display protection plate located on the liquid crystal screen is observed through a polarizing filter, color unevenness is significantly observed.

[0348] In this comparative example, at Tg BAbove and Tg A Thermoforming was performed at the following temperature to manufacture a curved LCD protective plate. In this comparative example, the absolute value of the rate of change of the average value of the Re value after thermoforming relative to that before thermoforming was greater than 50%, and the standard deviation of the Re value after thermoforming was greater than 25.0 nm. The standard deviation of the Re value of the curved LCD protective plate obtained in this comparative example was large (the deviation of the Re value was large), and when the LCD protective plate located on the LCD screen was observed through a polarizing filter, color unevenness was significantly observed.

[0349] In Comparative Example 3, a liquid crystal display protective plate consisting of a resin plate having a phase difference adjustment layer laminated on both sides of a substrate layer was manufactured. B Above and Tg A Thermoforming was performed at a temperature below 100°C to manufacture a curved liquid crystal display protective plate. In this comparative example, the absolute value of the rate of change of the average value of Re value after thermoforming relative to that before thermoforming was 50% or less. However, since the phase difference adjustment layer located on the surface was bent at a temperature lower than the Tg of the phase difference adjustment layer, cracks were generated in the phase difference adjustment layer.

[0350] In Comparative Examples 4 and 5, a liquid crystal display protection plate was manufactured, which was composed of a resin plate having a phase difference adjustment layer laminated on both sides of a substrate layer. As the resin of the substrate layer, a photoelastic coefficient (C B ) and orientation birefringence (Δn B ) is a polycarbonate resin outside the scope of the present invention. Tg A <Tg B The standard deviation of the Re value of the LCD protective plate before curved surface forming obtained in these comparative examples is large (the deviation of the Re value is large), and when the LCD protective plate located on the LCD screen is observed through a polarizing filter, color unevenness is significantly observed.

[0351] In these comparative examples, A and Tg B Thermoforming was performed at a high temperature to produce a curved LCD protection plate. The absolute value of the rate of change of the average Re value after thermoforming relative to that before thermoforming was greater than 50%, and the standard deviation of the Re value after thermoforming was greater than 25.0 nm. The standard deviation of the Re value of the curved LCD protection plate obtained in these comparative examples was large (the deviation of the Re value was large), and when the LCD protection plate located on the LCD screen was observed through a polarizing filter, color unevenness was significantly observed.

[0352] The present invention is not limited to the above-described embodiments and examples, and appropriate design changes may be made without departing from the gist of the present invention.

[0353] 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.

[0354] Explanation of symbols

[0355] 1.2 LCD display protection plate

[0356] 11 T-die head

[0357] 12~14 cooling rollers

[0358] 15 Take-off Roller

[0359] 16 Flat resin sheet

[0360] 21 Phase difference adjustment layer

[0361] 22 Base material layer

[0362] 31 Curing film

Claims

1. A liquid crystal display protective plate comprising a flat resin plate having a base material layer laminated on both sides of a phase difference adjustment layer, The phase difference adjustment layer includes a photoelastic coefficient (C A ) has an absolute value of 10.0×10 -12 / Pa or less and the orientation birefringence (Δn A ) has an absolute value of 10.0×10 -4 ~100.0×10 -4 The transparent thermoplastic resin (A), the oriented birefringence (Δn A ) is obtained by uniaxially stretching a test piece having a width of 20 mm, a length of 40 mm and a thickness of 1 mm at a temperature 10° C. higher than the glass transition temperature at a rate of 3 mm / min at a stretching ratio of 100% and measuring the in-plane retardation value of the central portion of the test piece, The substrate layer comprises a photoelastic coefficient (C B ) has an absolute value of 10.0×10 -12 / Pa or less and the orientation birefringence (Δn B ) is less than 10.0×10 -4 The transparent thermoplastic resin (B), the oriented birefringence (Δn B ) is obtained by uniaxially stretching a test piece having a width of 20 mm, a length of 40 mm and a thickness of 1 mm at a temperature 10° C. higher than the glass transition temperature at a rate of 3 mm / min at a stretching ratio of 100% and measuring the in-plane retardation value of the central portion of the test piece, When the glass transition temperature of the phase difference adjustment layer is set to Tg A , the glass transition temperature of the substrate layer is set to Tg B When Tg A >Tg B , When the thickness of the phase difference adjustment layer is set to T A , the total thickness of the substrate layer is set to T B When T A <T B , 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 standard deviation of the in-plane retardation value of the flat resin plate within the range of a width of 17 cm and a length of 22 cm was 15.0 nm or less.

3. The liquid crystal display protection plate according to claim 1 or 2, wherein: The flat resin plate is heated to Tg B Above and Tg A At a temperature of 100 Å or less, the absolute value of the rate of change of the in-plane retardation value after heating relative to that before heating is 50% or less.

4. The liquid crystal display protection plate according to claim 1 or 2, wherein: The flat resin plate is heated to Tg B Above and Tg A At a temperature of 1000 Å or less, the standard deviation of the in-plane retardation value within a range of 17 cm in width and 22 cm in length was 25.0 nm or less.

5. The liquid crystal display protection plate according to claim 1 or 2, wherein: 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 phase difference adjustment layer is T A [mm], the following formula (1) is satisfied: 6.0≤V×T A ≤30.0…(1)。 6. The liquid crystal display protection plate according to claim 1 or 2, wherein: A cured film is provided on at least one outermost surface.

7. The liquid crystal display protection plate according to claim 1 or 2, wherein: The flat resin plate is an extrusion-molded plate.

8. A curved liquid crystal display protective plate, comprising a resin plate having a curved surface and a base material layer laminated on both sides of a phase difference adjustment layer, The phase difference adjustment layer includes a photoelastic coefficient (C A ) has an absolute value of 10.0×10 -12 / Pa or less and the orientation birefringence (Δn A ) has an absolute value of 10.0×10 -4 ~100.0×10 -4 The transparent thermoplastic resin (A), the oriented birefringence (Δn A ) is obtained by uniaxially stretching a test piece having a width of 20 mm, a length of 40 mm and a thickness of 1 mm at a temperature 10° C. higher than the glass transition temperature at a rate of 3 mm / min at a stretching ratio of 100% and measuring the in-plane retardation value of the central portion of the test piece, The substrate layer comprises a photoelastic coefficient (C B ) has an absolute value of 10.0×10 -12 / Pa or less and the orientation birefringence (Δn B ) is less than 10.0×10 -4 The transparent thermoplastic resin (B), the oriented birefringence (Δn B ) is obtained by uniaxially stretching a test piece having a width of 20 mm, a length of 40 mm and a thickness of 1 mm at a temperature 10° C. higher than the glass transition temperature at a rate of 3 mm / min at a stretching ratio of 100% and measuring the in-plane retardation value of the central portion of the test piece, When the glass transition temperature of the phase difference adjustment layer is set to Tg A , the glass transition temperature of the substrate layer is set to Tg B When Tg A >Tg B , When the thickness of the phase difference adjustment layer is set to T A , the total thickness of the substrate layer is set to T B When T A <T B , The resin plate having a curved surface has an in-plane retardation value of 50 to 330 nm.

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

10. The curved liquid crystal display protection plate according to claim 8 or 9, wherein: 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 phase difference adjustment layer is T A [mm], the following formula (1) is satisfied: 6.0≤V×T A ≤30.0…(1)。 11. The curved liquid crystal display protection plate according to claim 8 or 9, wherein: A cured film is provided on at least one outermost surface.

12. The curved liquid crystal display protection plate according to claim 8 or 9, wherein: The resin plate having a curved surface is a thermoformed plate obtained by thermoforming a flat resin plate.

13. The method for manufacturing a protective plate for a liquid crystal display with a curved surface according to claim 8 or 9, comprising: a step of forming a flat resin plate having the base material layer laminated on both sides of the phase difference adjustment layer; and The flat resin plate is heated to Tg B Above and Tg A The process of heat forming the steel sheet into a curved shape at a temperature below 0.1°C.

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