WO2021095794A1 - Liquid crystal display protective plate - Google Patents

Abstract

The present invention provides a liquid crystal display protective plate with which it is possible to suppress a reduction in visibility due to rainbow uneveness, blackout, coloring, etc., when said liquid crystal display protective plate on a liquid crystal screen is viewed through a polarization filter. A liquid crystal display protective plate (1) according to the present invention comprises a resin plate (16X) including a phase difference adjustment layer (21) containing a transparent thermoplastic resin (A), which has a photoelastic coefficient (C_A) with an absolute value of no more than 10.0×10^-12∕Pa and an orientation birefringence (Δn_A) with an absolute value of 10.0×10^-4 to 100.0×10^-4, as found by uniaxially drawing a 20 mm wide, 40 mm long and 1 mm thick test piece to an elongation degree of 100% at a speed of 3 mm/minute and a temperature 10°C higher than the glass transition temperature thereof, and then measuring the in-plane retardation value of the center section of said test piece, wherein the in-plane retardation value is 50 to 330 nm.

Description

Liquid crystal display protection plate

The present invention relates to a liquid crystal display protective plate.

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

For example, Patent Document 1 discloses a scratch-resistant resin plate that includes a methacrylic resin plate and a cured film formed on at least one of the surfaces thereof and is suitable as a display window protective plate for a portable information terminal. (Claims 1, 2, 7, paragraph 0010, etc.). Patent Document 2 describes a polycarbonate system for a liquid crystal display cover, which includes a laminated plate in which a methacrylic resin layer is laminated on one surface of a polycarbonate resin layer, and a cured film formed on the methacrylic resin layer of the laminated plate. A resin laminate is disclosed (claim 1, paragraph 0008, etc.).

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

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

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

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

FIG. 6 shows an image diagram showing the relationship between stress and birefringence, and the relationship between orientation birefringence, stress birefringence, and photoelastic coefficient.
The polycarbonate resin used in Patent Document 3 has a ^{very large absolute value of photoelastic coefficient of 90 × 10-12} / Pa, and the Re value changes with a slight stress. Therefore, when a polycarbonate resin is used, it is difficult to obtain an optically uniform liquid crystal display protective plate. For example, when observing the liquid crystal display protective plate on the liquid crystal screen through a polarizing filter, rainbow unevenness may be observed due to the variation in the Re value.

On the other hand, the methacrylic resin used in Patent Document 1 has a ^{small absolute value of photoelastic coefficient of 3.2 × 10-12} / Pa, and the Re value is unlikely to change due to stress. Therefore, when a methacrylic resin is used, an optically uniform liquid crystal display protective plate can be obtained. However, since the absolute value of the orientation birefringence of the methacrylic resin is as ^{small as 4.0 × 10 -4} , the Re value of the obtained liquid crystal display protective plate tends to be as small as about 20 nm, although it depends on the thickness. Therefore, when observing the liquid crystal display protective plate on the liquid crystal screen through the polarizing filter, blackout occurs in which the screen becomes pitch black depending on the angle between the polarizing axis of the emitted light and the transmission axis of the polarizing filter, and the image is visually recognized. There is a risk of reduced sex.

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

The present invention has been made in view of the above circumstances, and suppresses deterioration of visibility such as rainbow unevenness, blackout, and coloring when observing the liquid crystal display protective plate on the liquid crystal screen through a polarizing filter. It is an object of the present invention to provide a liquid crystal display protective plate capable of providing a protective plate.

The present invention provides the following liquid crystal display protective plates [1] to [6].
_{[1] A} test piece having an absolute value of photoelastic coefficient (CA) of 10.0 × ^10-12 / Pa or less and a width of 20 mm, a length of 40 mm, and a thickness of 1 mm is 10 ° C. higher than the glass transition temperature. The absolute value of _{orientation birefringence (Δn A} ) obtained by uniaxially stretching at a rate of 3 mm / min at a temperature of 3 mm / min and measuring the in-plane retardation value of the central portion of the test piece is 10.0. A resin plate having a phase difference adjusting layer containing a transparent thermoplastic resin (A) of × 10 ^-4 to 100.0 × 10 ^{-4 is included.}
A liquid crystal display protective plate having an in-plane retardation value of 50 to 330 nm.

[2] The liquid crystal display protective plate of [1], wherein the standard deviation of the in-plane retardation value within the range of 17 cm in width and 22 cm in length is 15.0 nm or less.
[3] The transparent thermoplastic resin (A) contains an aromatic vinyl monomer unit and contains.
Transparent thermoplastic resin content of the aromatic vinyl monomer units in (A) and V [wt%], when the thickness of the phase difference adjusting layer was T _{A [mm],} the following formula (1) The liquid crystal display protective plate of [1] or [2] that satisfies the above conditions.
_{6.0 ≦ V × T A ≦ 30.0} ··· (1)

[4] the resin plate further when the absolute value of photoelastic coefficient _{(C B)} is 10.0 × ¹⁰ -12 / Pa or less, and the width 20 mm, length 40 mm, a test piece having a thickness of 1 mm, the glass _{Orientation birefringence (Δn B} ) obtained by uniaxially stretching at a rate of 3 mm / min at a temperature 10 ° C. higher than the transition temperature at a stretching rate of 100% and measuring the in-plane retardation value of the central portion of the test piece. The liquid crystal display protective plate according to any one of [1] to [3], which has a base material layer containing a transparent thermoplastic resin (B) having an absolute value of ^{less than 10.0 × 10 -4.}
[5] The liquid crystal display protective plate according to any one of [1] to [4], further comprising a cured film on at least one surface of the resin plate.
[6] The liquid crystal display protective plate according to any one of [1] to [5], wherein the resin plate is an extruded plate.

According to the present invention, a liquid crystal display protective plate capable of suppressing deterioration of visibility such as rainbow unevenness, blackout, and coloring when observing the liquid crystal display protective plate on the liquid crystal screen through a polarizing filter is provided. Can be provided.

It is a schematic cross-sectional view of the liquid crystal display protection plate of 1st Embodiment which concerns on this invention. It is a schematic cross-sectional view of the liquid crystal display protection plate of the 2nd Embodiment which concerns on this invention. It is a schematic cross-sectional view of the liquid crystal display protection plate of the 3rd Embodiment which concerns on this invention. It is a schematic diagram of the manufacturing apparatus of the extrusion-molded plate of one Embodiment which concerns on this invention. It is a histogram which shows the distribution of the Re value of the liquid crystal display protection plate obtained in Example 7. It is a histogram which shows the distribution of the Re value of the liquid crystal display protection plate obtained in the comparative example 6. It is an image diagram which shows the relationship between stress and birefringence, and the relationship between orientation birefringence, stress birefringence, and photoelastic coefficient.

Generally, for thin film molded products, the terms "film", "sheet", or "plate" are used depending on the thickness, but there is no clear distinction between them. The "resin plate" referred to in the present specification shall include a "resin film" and a "resin sheet".

[Liquid crystal display protection plate]
The present invention relates to a liquid crystal display protective plate. The liquid crystal display protective plate can be suitably used for protecting the liquid crystal display and the touch panel display in which the liquid crystal display and the touch panel are combined.
The liquid crystal display protective plate of the present invention includes a retardation adjusting layer, more preferably a base material layer and / or a cured film. The liquid crystal display protective plate of the present invention preferably includes a phase difference adjusting layer, a resin plate including a base material layer if necessary, and a cured film formed on at least one surface of the resin plate. The resin plate is preferably an extruded plate.

1 to 3 are schematic cross-sectional views of the liquid crystal display protective plate of the first to third embodiments according to the present invention. In the figure, reference numerals 1 to 3 indicate a liquid crystal display protective plate, reference numerals 16X and 16Y indicate a resin plate, reference numeral 21 indicates a retardation adjusting layer, reference numeral 22 indicates a base material layer, and reference numeral 31 indicates a cured film.
The liquid crystal display protective plate 1 of the first embodiment is made of a resin plate 16X having a single layer structure including only the phase difference adjusting layer 21.
The liquid crystal display protective plate 2 of the second embodiment is made of a resin plate 16Y having a two-layer structure including a retardation adjusting layer 21 and a base material layer 22.
The liquid crystal display protective plate 3 of the third embodiment has a cured coating 31 formed on at least one surface of a resin plate 16Y having a two-layer structure composed of a retardation adjusting layer 21 and a base material layer 22. In the example shown in FIG. 3, the cured coating 31 is formed on both sides of the resin plate 16Y.
The configuration of the liquid crystal display protective plate is not limited to the illustrated example, and the design can be appropriately changed as long as the gist of the present invention is not deviated.

In the present invention, the phase difference adjusting layer when the absolute value of photoelastic coefficient _{(C A)} is 10.0 × ¹⁰ -12 / Pa or less, a width 20 mm, length 40 mm, a test piece having a thickness of 1 mm, the glass transition Uniaxial stretching at a rate of 3 mm / min at a temperature 10 ° C. higher than the temperature (Tg) at a stretching rate of 100%, and the in-plane retardation value (also referred to as "Re value") of the central portion of the test piece after uniaxial stretching. Includes a transparent thermoplastic resin (A) having an absolute value of orientation double refraction (Δn _A ) of 10.0 × 10 ^-4 to 100.0 × 10 ^-4.

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

Generally, the Re value of the resin plate is represented by the following formula (i).
[Re value of resin plate] = [birefringence (ΔN)] × [thickness (d)] ... (i)
Birefringence (ΔN) is represented by the following equation (ii).
[Brefringence] = [Stress birefringence] + [Orientation birefringence] ... (ii)
The stress birefringence and the orientation birefringence are represented by the following equations (iii) and (iv), respectively.
[Stress birefringence] = [photoelastic coefficient (C)] × [stress] ... (iii)
[Orientation birefringence] = [Inherent birefringence] x [Orientation degree] ... (iv)
In equation (iv), the degree of orientation is a value in the range of 0 to 1.0.
FIG. 6 shows an image diagram showing the relationship between stress and birefringence, and the relationship between orientation birefringence, stress birefringence, and photoelastic coefficient.

In the present invention, the optical characteristics of the transparent thermoplastic resin (A) and the transparent thermoplastic resin (B) described later are specified by the photoelastic coefficient and orientation birefringence shown in FIG.
When the liquid crystal display protective plate of the present invention includes the phase difference adjusting layer containing the transparent thermoplastic resin (A) having the above-mentioned specific optical characteristics, the liquid crystal display protective plate on the liquid crystal screen is observed through a polarizing filter. However, it is possible to suppress deterioration of visibility such as uneven rainbow and blackout.

In the present specification, the "Re value of the liquid crystal display protective plate" is an average value of the Re values of about 110,000 birefringent pixels within the measurement range of 17 cm in width and 22 cm in length, unless otherwise specified. Unless otherwise specified, the "standard deviation of the Re value of the liquid crystal display protective plate" is the standard deviation of the Re value of about 110,000 birefringent pixels within the measurement range of 17 cm in width and 22 cm in length.

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

The smaller the standard deviation of the Re value of the liquid crystal display protective plate is, the less the variation of the Re value is, which is preferable. The standard deviation of the Re value is preferably 15 nm or less, more preferably 10 nm or less, still more preferably 7 nm or less, particularly preferably 5 nm or less, and most preferably 4 nm or less. When the standard deviation of the Re value is not more than the above upper limit value, when observing the liquid crystal display protective plate on the liquid crystal screen through the polarizing filter, rainbow unevenness due to the variation of the Re value is suppressed and the visibility is improved.

The average value and standard deviation of the Re value of the liquid crystal display protective plate are measured, for example, by using the retardation measuring device "WPA-100-L" manufactured by Photonic Lattice Co., Ltd. and the method described in the section [Example] below. be able to.

The overall thickness (d) of the liquid crystal display protective plate is not particularly limited, and is preferably 0.2 to 6.0 mm, more preferably 0.3 to 5.0 mm, and particularly preferably 0.4 to 3.0 mm. .. If it is too thin, the rigidity of the liquid crystal display protective plate may be insufficient, and if it is too thick, it may hinder the weight reduction of the liquid crystal display or the touch panel display including the liquid crystal display.

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

<Transparent thermoplastic resin (A)>
The absolute value of the photoelastic coefficient of the transparent thermoplastic resin _{(A) (C} A) is a 10.0 × ¹⁰ -12 / Pa or less, preferably 8.0 × ¹⁰ -12 / Pa or less, more preferably 6 It ^{is 0.0 × 10-12} / Pa or less, particularly preferably 5.0 × ^10-12 / Pa or less, and most preferably 4.0 × ^10-12 / Pa or less. If the absolute value of photoelastic coefficient (C _A) is at more than the above upper limit, small stress birefringence due to the residual stress generated during molding of the extrusion molding (see FIG. 6.), Liquid crystal display protective plate The standard deviation of the Re value of can be reduced. As a result, when the liquid crystal display protective plate on the liquid crystal screen is observed through the polarizing filter, rainbow unevenness due to the variation of the Re value is suppressed, and the visibility is improved.

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

Transparent thermoplastic resin (A), if a transparent thermoplastic resin which satisfies the range of photoelastic coefficient specified in the present invention (C _A) and orientation birefringence ([Delta] n _A), is not particularly limited.
In one aspect, the transparent thermoplastic resin (A) can contain one or more aromatic vinyl monomer units. The aromatic vinyl monomer is not particularly limited, and styrene (St); nuclear alkyl substitutions such as 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-ethylstyrene, and 4-tert-butylstyrene. Styrene; α-methylstyrene, α-alkyl substituted styrene such as 4-methyl-α-methylstyrene and the like can be mentioned. Of these, styrene (St) is preferable from the viewpoint of availability.

The content of the aromatic vinyl monomer units in the transparent thermoplastic resin (A) and V [wt%], the thickness of the phase difference adjusting layer and T _{A [mm].} These product (V × _{T A)} preferably satisfies the following formula (1).
_{6.0 ≦ V × T A ≦ 30.0} ··· (1)
Transparent thermoplastic resin (A), the absolute value of photoelastic coefficient (C _A) is small, the stress birefringence is substantially zero. When the transparent thermoplastic resin (A) contains an aromatic vinyl monomer unit such as a styrene (St) unit, the orientation compound refraction (Δn _A ) is an aromatic vinyl monomer unit in the transparent thermoplastic resin (A). Tends to depend on the content V [mass%] of. Therefore, V × T _A is strongly correlated with Re value of the liquid crystal display protection panel. If V × T _A satisfies the above formula (1), it is possible to control the Re value of the liquid crystal display protective plate to a suitable range.

The transparent thermoplastic resin (A) includes, in addition to the aromatic vinyl monomer unit, a methacrylic acid ester unit such as a methyl methacrylate (MMA) unit; an acid anhydride unit such as a maleic anhydride unit; an acrylonitrile unit and the like. It may be a copolymer having a monomer unit of.
Specific examples of the transparent thermoplastic resin (A) containing an aromatic vinyl monomer unit include methacrylic acid ester-styrene copolymer (MS resin); styrene-maleic anhydride copolymer (SMA resin); styrene-. Examples thereof include a methacrylic acid ester-maleic anhydride copolymer (SMM resin); an acrylonitrile-styrene copolymer (AS resin). These can be used alone or in combination of two or more.
The content V [mass%] of the aromatic vinyl monomer unit in the transparent thermoplastic resin (A) is not particularly limited, and is preferably 10 to 90% by mass, more preferably 20 to 80% by mass.

Transparent thermoplastic resin (A), as long as it satisfies the range of photoelastic coefficient specified in the present invention (C _A) and orientation birefringence ([Delta] n _A), a resin containing no aromatic vinyl monomer unit There may be. The transparent thermoplastic resin (A) containing no aromatic vinyl monomer unit includes a methacrylic acid ester unit such as a methyl methacrylate unit, a glutarimide unit, an N-substituted or unsubstituted mylemid unit, and a lactone ring unit. Modified methacrylic resins containing at least one unit of choice. These can be used alone or in combination of two or more.

Transparent thermoplastic resin (A) is a resin containing an aromatic vinyl monomer unit satisfying the range of photoelastic coefficient (C _A) and orientation birefringence ([Delta] n _A) specified in the present invention, defined in the present invention or it may be a mixture of a photoelastic coefficient (C _a) and does not contain an aromatic vinyl monomer unit satisfying the range of orientation birefringence ([Delta] n _a) resin (modified methacrylic resin).

In the present invention, general methacrylic resins (non-modified methacrylic resins) and polycarbonate resins other than the above have a photoelastic coefficient and / or orientation birefringence outside the specified range of the present invention, and are transparent thermoplastic resins. Not included in (A).
The polycarbonate resin has a very large absolute value of the photoelastic coefficient of 90 × ^10-12 / Pa, and the Re value changes with a slight stress. Therefore, when a polycarbonate resin is used, it is difficult to obtain an optically uniform liquid crystal display protective plate. For example, when observing the liquid crystal display protective plate on the liquid crystal screen through a polarizing filter, rainbow unevenness may be observed due to the variation in the Re value.
The absolute value of the photoelastic coefficient of the methacrylic resin is as ^{small as 3.2 × 10-12} / Pa, and the Re value is unlikely to change due to stress. Therefore, when a methacrylic resin is used, an optically uniform liquid crystal display protective plate can be obtained. However, since the absolute value of the orientation birefringence of the methacrylic resin is as ^{small as 4.0 × 10 -4} , the Re value of the obtained liquid crystal display protective plate tends to be as small as about 20 nm, although it depends on the thickness. Therefore, when observing the liquid crystal display protective plate on the liquid crystal screen through the polarizing filter, blackout occurs in which the screen becomes pitch black depending on the angle between the polarizing axis of the emitted light and the transmission axis of the polarizing filter, and the image is visually recognized. There is a risk of reduced sex.

The thickness of the phase difference adjusting layer (T _A) is not particularly limited, the transparent thermoplastic resin (A) may contain aromatic vinyl monomer unit is preferably designed so as to satisfy the above equation (1). The lower limit of T _A is preferably 0.05 mm, more preferably 0.075 mm, more preferably 0.10 mm, particularly preferably 0.15 mm, most preferably 0.20 mm. The upper limit value of T _A is preferably 3.0 mm, more preferably 1.0 mm, more preferably 0.50 mm, particularly preferably 0.40 mm, most preferably 0.30 mm.

The retardation adjusting layer may contain, in a small amount, one or more other polymers whose photoelastic coefficient and / or orientation birefringence is out of the scope of the transparent thermoplastic resin (A). The types of other polymers are not particularly limited, and are generally non-modified methacrylic resins, polycarbonate resins, polyolefins such as polyethylene and polypropylene, polyamides, polyphenylene sulfides, polyether ether ketones, polyesters, polysulfones, and polyphenylene oxides. , Polyethylene, polyetherimide, and other thermoplastic resins such as polyacetal; thermocurable resins such as phenolic resin, melamine resin, silicone resin, and epoxy resin.
A general non-modified methacrylic resin is, for example, a resin composed of one or more kinds of methacrylic acid ester units.
The content of the transparent thermoplastic resin (A) in the retardation adjusting layer is preferably large, preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 98% by mass or more. The content of the other polymer in the retardation adjusting layer is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 2% by mass or less.

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

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

(Base layer)
The resin plate included in the liquid crystal display protective plate of the present invention may include a base material layer, if necessary, in accordance with the phase difference adjusting layer. The base material layer can be laminated on the phase difference adjusting layer for the purpose of increasing the overall thickness (d) of the liquid crystal display protective plate and improving the rigidity of the liquid crystal display protective plate. The base material layer is preferably a resin layer that does not affect the Re value of the liquid crystal display protective plate, and is a resin layer containing a transparent thermoplastic resin (B) having a sufficiently small photoelastic coefficient and orientation birefringence. Is preferable.

<Transparent thermoplastic resin (B)>
Absolute value smaller are preferred photoelastic coefficient of the transparent thermoplastic resin _{(B) (C} B), preferably 10.0 × ¹⁰ -12 / Pa or less, more preferably 8.0 × ¹⁰ -12 / Pa or less It is more preferably 6.0 × ^10-12 / Pa or less, particularly preferably 5.0 × ^10-12 / Pa or less, and most preferably 4.0 × ^10-12 / Pa or less. If the absolute value of photoelastic coefficient (C _B) is less than the above upper limit, sufficiently stress birefringence due to the residual stress generated during molding of the extrusion molding small (see FIG. 6.), Liquid crystal display The standard deviation of the Re value of the protective plate can be reduced. As a result, when the liquid crystal display protective plate on the liquid crystal screen is observed through the polarizing filter, rainbow unevenness due to the variation of the Re value is suppressed, and the visibility is improved.

_{The orientation birefringence (Δn B} ) of the transparent thermoplastic resin (B) is preferably small, preferably ^{less than 10.0 × 10 -4} , more preferably 8.0 × 10 ^-4 or less, still more preferably 6.0. It is × 10 ^-4 or less, particularly preferably 4.0 × 10 ^-4 or less, and most preferably 2.0 × 10 ^-4 or less. When the absolute value of the orientation birefringence (Δn _B ) of the transparent thermoplastic resin (B) is not more than the above upper limit value, the influence on the Re value of the liquid crystal display protective plate is sufficiently small (see FIG. 6). , The Re value of the liquid crystal display protective plate can be satisfactorily controlled within an appropriate range.

Transparent thermoplastic resin (B), if a transparent thermoplastic resin which satisfies the range of photoelastic coefficient specified in the present invention (C _B) and orientation birefringence ([Delta] n _B), are not particularly limited. Specific examples include a general non-modified methacrylic resin (PM), a modified methacrylic resin modified with a glutarimide unit, an N-substituted or unsubstituted mylemid unit, a lactone ring unit, and a cycloolefin polymer (COP). ) Etc. can be mentioned. The transparent thermoplastic resin (B) can be used alone or in combination of two or more.

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

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

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

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

As long as it satisfies the range of photoelastic coefficient specified in the present invention (C _B) and orientation birefringence (Δn _B), as a transparent thermoplastic resin (B), illustrated type as the transparent thermoplastic resin (A) Resins (specifically, MS resin, SMA resin, SMM resin, AS resin, modified methacrylic resin, etc.) may be used. Depending on the monomer composition or the modification rate, the type of resin exemplified as the transparent thermoplastic resin (A) may be used as the transparent thermoplastic resin (B).

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

The thickness of the substrate layer (T _B) is not particularly limited, and is appropriately designed in accordance with the desired thickness and rigidity of the liquid crystal display protection panel. The lower limit of T _B is preferably 0.05 mm, more preferably 0.5 mm, more preferably 1.0 mm, particularly preferably 2.0 mm, most preferably 3.0 mm. The upper limit of T _B is preferably 6.0 mm, more preferably 5.0 mm, more preferably 4.0 mm, particularly preferably 3.0 mm, most preferably 2.0 mm.

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

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

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

(Other resin layer)
The resin plate included in the liquid crystal display protective plate of the present invention may have a phase difference adjusting layer and, if necessary, a resin layer other than the base material layer. The laminated structure of the resin plate includes a two-layer structure of a retardation adjusting layer-a base material layer; a three-layer structure of a base material layer-a retardation adjusting layer-another resin layer; another resin layer-a base material layer-a phase difference. Examples thereof include a three-layer structure of the adjusting layer.

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

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

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

In addition, the liquid crystal display protective plate 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, if necessary.

[Manufacturing method of liquid crystal display protective plate]
The method for manufacturing a liquid crystal display protective plate of the present invention includes a step (X) of preparing a resin plate having a single-layer structure or a laminated structure, which includes a retardation adjusting layer and, if necessary, a base material layer.
The method for producing a liquid crystal display protective plate of the present invention further includes a step (Y) of forming a cured film on at least one surface of the obtained resin plate, if necessary.

(Step (X))
A resin plate having a single-layer structure or a laminated structure including a retardation adjusting layer can be molded by a known method such as a cast molding method, an injection molding method, or an extrusion molding method. Above all, the extrusion molding method is preferable. In the case of a laminated structure, a coextrusion molding method is preferable.

Hereinafter, a method for manufacturing a resin plate by an extrusion molding method will be described.
One or more kinds of transparent thermoplastic resin (A), another polymer if necessary, and other additives if necessary are put into an extruder, melt-kneaded, and the obtained molten resin is T. A resin plate having a single-layer structure consisting of only a phase difference adjusting layer can be formed by extruding from a die in a plate-like form, pressurizing and cooling using a plurality of cooling rolls, and taking over by a take-up roll.

FIG. 4 shows a schematic view of an extrusion molding apparatus including a T-die 11, first to third cooling rolls 12 to 14, and a pair of take-up rolls 15 as an embodiment. The molten resin plate extruded from the T-die 11 is pressurized and cooled by using a plurality of cooling rolls 12 to 14. The pressurized and cooled resin plate 16 is picked up by a pair of picking rolls 15. The number of cooling rolls can be appropriately designed. The above extrusion, cooling, and pick-up steps are carried out continuously.

In the case of a laminated structure, the resin raw materials of each layer in the molten state are laminated by a feed block method in which the resin raw materials are laminated before the inflow of the T die or a multi-manifold method in which the resin raw materials are laminated inside the T die, and then extruded from the T die in a plate shape. It can be molded by pressurizing and cooling with a plurality of cooling rolls and taking over with a take-up roll.

In the present invention, the resin plate is molded so that the Re value of the resin plate is 50 to 330 nm.
In order to control the Re value, it is necessary to control the orientation of the molecule. The orientation of the molecules is generated, for example, by the stress during molding near the glass transition temperature of the polymer. By optimizing the production conditions in the process of extrusion molding, the orientation of the molecules can be controlled, whereby the Re value after extrusion molding of the resin plate can be optimized.

(Step (Y))
In the step (Y), an inorganic or organic cured film is formed on at least one surface of the resin plate obtained in the step (X) by a known method. Since the method for forming the cured film has been described above, it is omitted here.

(Other processes)
The method for manufacturing a liquid crystal display protective plate of the present invention may have steps other than the above steps (X) and (Y), if necessary.
For example, with respect to the surface of the resin plate obtained in step (X) on which the cured film is formed, for the purpose of improving the adhesion of the cured film to the resin plate between the steps (X) and (Y). , Primer treatment, sandblasting, and surface unevenness treatment such as solvent treatment; even if a step of performing surface treatment such as corona discharge treatment, chromium acid treatment, ozone irradiation treatment, and surface oxidation treatment such as ultraviolet irradiation treatment is added. Good.

As described above, according to the present invention, it is possible to suppress deterioration of visibility such as rainbow unevenness, blackout, and coloring when observing the liquid crystal display protective plate on the liquid crystal screen through a polarizing filter. A liquid crystal display protective plate can be provided.

[Use]
The liquid crystal display protective plate of the present invention is, for example, an ATM of a financial institution such as a bank; a vending machine; a television; a mobile information terminal (PDA) such as a mobile phone (including a smartphone), a personal computer, a tablet-type personal computer, or a digital audio. It is suitable as a protective plate for a liquid crystal display or a touch panel display used in digital information devices such as players, portable game machines, copying machines, fax machines, and car navigation systems.
The liquid crystal display protective plate of the present invention is suitable as, for example, a protective plate for an in-vehicle liquid crystal display.

Examples and comparative examples according to the present invention will be described.
[Evaluation items and evaluation methods]
The evaluation items and evaluation methods are as follows.
(Content of aromatic vinyl monomer unit in transparent thermoplastic resin (A))
The content (V mass%) of the aromatic vinyl monomer unit in the MS resin or SMM resin was determined by ¹ H-NMR method using a nuclear magnetic resonance apparatus (“GX-270” manufactured by JEOL Ltd.). ..

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

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

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

(Average value and standard deviation of Re value of liquid crystal display protection plate)
A test piece having a width of 21 cm and a length of 30 cm was cut out from the central portion of the extruded plate so that the extrusion direction (resin flow direction) was the long side direction. A standard lens (FUJINON HF12.5HA-1B) was attached to "WPA-100-L" manufactured by Photonic Lattice Co., Ltd. The height of the lens was adjusted so that the measurement range was 17 cm in width and 22 cm in length. Then, the Re value of the number of birefringent pixels of about 110,000 points was measured, and the average value and the standard deviation were obtained.

(Thickness of each layer)
When the liquid crystal display protective plate had a single-layer structure, the thickness was measured using a "coolant proof micrometer" manufactured by Mitutoyo Co., Ltd. When the liquid crystal display protective plate had a laminated structure, the thickness of each layer was measured using a "universal projector (V-12B)" manufactured by Nikon Instec Co., Ltd.

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

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

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

[material]
The materials used are as follows.
<MS resin>
Polymerize MS resin (copolymer of methyl methacrylate (MMA) and styrene (St)) according to the method for producing a copolymer (A) described in the section of [Example] of JP-A-2003-231785. did. The following three types of MS resins were produced by changing the mass ratio of MMA and St charged in the autoclave.
(MS-1) Tg = 116 ° C., content of aromatic vinyl monomer unit V = 10% by mass,
(MS-2) Tg = 109 ° C., content of aromatic vinyl monomer unit V = 35% by mass,
(MS-3) Tg = 100 ° C., content of aromatic vinyl monomer unit V = 90% by mass.

<SMA resin>
(SMA-1) Copolymer of styrene (St) and maleic anhydride (MAH), "XIRAN SO23110" manufactured by Polyscape Co., Ltd., Tg = 152 ° C., content of aromatic vinyl monomer unit V = 75 mass %.
(SMA-2)
-Alloy, which is a mixture of the above SMA resin (SMA-1) and the methacrylic resin (PMMA-2) described later at a mass ratio of 86:14, Tg = 145 ° C., and the content of aromatic vinyl monomer unit V = 64. 5% by mass.

<Methacrylic resin>
(PMMA-1) Copolymer of methyl methacrylate (MMA) and methyl acrylate (MA) (MMA / MA (mass ratio) = 98.9: 1.1), "Parapet HR-S" manufactured by Kuraray Co., Ltd. , Tg = 119 ° C., content of aromatic vinyl monomer unit V = 0% by mass.
(PMMA-2) Homopolymer of methyl methacrylate (MMA), "Parapet HM" manufactured by Kuraray Co., Ltd., Tg = 120 ° C., content of aromatic vinyl monomer unit V = 0% by mass.

<Polycarbonate resin>
(PC-1) "SD Polycarbonate 300 Series" manufactured by Sumika Polycarbonate Limited, Tg = 150 ° C., content of aromatic vinyl monomer unit V = 0% by mass.

[Examples 1 to 6, Comparative Examples 1 to 4]
A resin for the phase difference adjusting layer (transparent thermoplastic resin (A) or comparative resin) was melt-extruded using a 50 mmφ single-screw extruder (manufactured by Toshiba Machine Co., Ltd.). The molten resin is discharged from the T-die in a plate shape, sandwiched between the first cooling roll and the second cooling roll adjacent to each other, wound around the second cooling roll, and the second cooling roll and the third cooling roll. It was cooled by sandwiching it between the two and winding it around a third cooling roll. The resin plate obtained after cooling was taken up by a pair of taking-up rolls. In this way, a liquid crystal display protective plate having a single-layer structure composed of only a phase difference adjusting layer was obtained. For each example, the type and characteristics of the resins used, the thickness of the phase difference adjusting layer _{(T A), V × T} A, and the evaluation results of the liquid crystal display protection panel, shown in Table 1 and Table 2.

[Examples 7 to 8, Comparative Examples 5 to 6]
A resin for the base material layer (transparent thermoplastic resin (B) or comparative resin) was melt-extruded using a 50 mmφ single-screw extruder (manufactured by Toshiba Machine Co., Ltd.). A resin for the phase difference adjusting layer (transparent thermoplastic resin (A) or comparative resin) was melt-extruded using a 30 mmφ single-screw extruder (manufactured by Toshiba Machine Co., Ltd.). These melted resins were laminated via a multi-manifold type die, and a thermoplastic resin laminate having a two-kind two-layer structure was co-extruded from the T-die. A resin having a two-layer structure of two types in a molten state is discharged from a T-die, sandwiched between the first cooling roll and the second cooling roll adjacent to each other, wound around the second cooling roll, and the second cooling roll and the third. It was cooled by sandwiching it with a cooling roll and winding it around a third cooling roll. The resin plate obtained after cooling was taken up by a pair of taking-up rolls. In this way, a liquid crystal display protective plate having a two-kind two-layer structure composed of a phase difference adjusting layer and a base material layer was obtained. For each example, the type and characteristics of the resins used, the thickness of each layer, V × T _A, and the evaluation results of the liquid crystal display protection panel, shown in Table 1 and Table 2.

[Examples 9 to 12]
A resin for the base material layer (transparent thermoplastic resin (B) was melt-extruded using a 50 mmφ single-screw extruder (manufactured by Toshiba Machine Co., Ltd.). A 30 mmφ single-screw extruder (manufactured by Toshiba Machine Co., Ltd.) was used. , The resin for the phase difference adjusting layer (transparent thermoplastic resin (A)) was melt-extruded. These resins in the molten state were laminated via a multi-manifold type die, and the phase difference was formed from the T die to both sides of the base material layer. A thermoplastic resin laminate having a two-kind three-layer structure in which adjustment layers are laminated was co-extruded. A molten two-kind three-layer resin was discharged from a T-die, and adjacent first cooling rolls and second cooling were performed. The resin plate obtained after cooling was cooled by being sandwiched between the rolls, wrapped around the second cooling roll, sandwiched between the second cooling roll and the third cooling roll, and wrapped around the third cooling roll. It was taken up by a pair of take-up rolls. In this way, a liquid crystal display protective plate having a two-kind three-layer structure in which phase difference adjusting layers were laminated on both sides of the base material layer was obtained. types and characteristics, the thickness of each layer, V × T _a, and the evaluation results of the liquid crystal display protection panel, shown in Table 1 and Table 2.

[Summary of results]
In Examples 1-6, and the absolute value of the photoelastic coefficient _{(C A)} is 10.0 × ¹⁰ -12 / Pa or less, and the absolute value of the orientation birefringence ([Delta] n _A) is 10.0 × 10 ^- A single-layer liquid crystal display protective plate having only a phase difference adjusting layer made of a transparent thermoplastic resin (A) of ⁴ to 100.0 × 10 ^{-4 was manufactured.}
In Examples 7 and 8 when the absolute value of photoelastic coefficient _{(C A)} is 10.0 × ¹⁰ -12 / Pa or less, and the absolute value of the orientation birefringence ([Delta] n _A) is 10.0 × 10 ^- and ⁴ ~ 100.0 × ^{10 -4} in a transparent thermoplastic resin (a) phase difference adjusting layer formed of an absolute value of photoelastic coefficient _{(C B)} is not more than 10.0 × ¹⁰ -12 / Pa, Further, a liquid crystal display protective plate having a laminated structure with a base material layer made of a transparent thermoplastic resin (B) having an absolute value of orientation birefringence (Δn _B ^{) of less than 10.0 × 10 -4 was manufactured.}

The liquid crystal display protective plates obtained in Examples 1 to 8 have an average Re value of 50 to 330 nm in the range of 17 cm in width and 22 cm in length, and Re in the range of 17 cm in width and 22 cm in length. The standard deviation of the values was 15.0 nm or less.
In each of Examples 1 to 8, when the liquid crystal display protective plate on the liquid crystal screen was observed through the polarizing filter, rainbow unevenness, coloring, and blackout were effectively suppressed. In particular, the V × _{T A} value from 6.0 to 30.0 in an exemplary 1 to 3 and 6 to 8, exemplary values of V × _{T A} is outside the range of 6.0 to 30.0 Example Better results were obtained than 4 and 5. Incidentally, V × of _T value of _A is outside the range of 6.0 to 30.0 Examples 4 and 5, the blackout in Re value is less Example 4 B rating higher embodiments Re value 5 Then the coloring was B rating

In Example 7, a PMMA base material layer was added to the configuration of Example 1. In Example 8, a PMMA substrate layer was added to the configuration of Example 6. In Example 7, as compared with Example 1, the overall thickness (d) could be increased without significantly changing the average value and standard deviation of the Re value of the liquid crystal display protective plate. Similarly, in Example 8, the overall thickness (d) could be increased without significantly changing the average value and standard deviation of the Re value of the liquid crystal display protective plate as compared with Example 6. In Examples 7 and 8, a liquid crystal display protective plate suitable as a protective plate for a touch panel display, which has high rigidity and is less likely to be deformed, was obtained.

In Comparative Examples 1 and 2 when the absolute value of photoelastic coefficient _{(C A)} is 10.0 × ¹⁰ -12 / Pa or less, and the absolute value of the orientation birefringence ([Delta] n _A) is 10.0 × 10 ^- A single-layer liquid crystal display protective plate having a phase difference adjusting layer made of a transparent thermoplastic resin (A) having a ^{size of 4} to 100.0 × 10 ^{-4 was manufactured.} However, in these comparative examples, outside the scope of V × _{T A} value from 6.0 to 30.0 average value of Re of the obtained liquid crystal display protective plate is out of the range of 50 ~ 330 nm .. Among these comparative examples, in Comparative Example 1 having a low Re value, the blackout was evaluated as C, and in Comparative Example 2 having a high Re value, the colored product was evaluated as C.

In Comparative Examples 3 and 4, the photoelastic coefficient (C _A) and / or orientation birefringence ([Delta] n _A) is a liquid crystal display protective plate having a single layer structure of the phase difference adjusting layer formed of a comparative resin is defined outside of the present invention Manufactured. In Comparative Example 3 using a methacrylic resin, the obtained liquid crystal display protective plate had a small Re value of less than 50 nm, and blackout occurred when the liquid crystal display protective plate on the liquid crystal screen was observed through a polarizing filter. It was. In Comparative Example 4 using the polycarbonate-based resin, rainbow unevenness occurred when the liquid crystal display protective plate on the liquid crystal screen was observed through the polarizing filter.

In Comparative Example 5 when the absolute value of photoelastic coefficient _{(C A)} is 10.0 × ¹⁰ -12 / Pa or less, and the absolute value of the orientation birefringence ([Delta] n _A) is 10.0 × ^{10 -4} ~ a phase difference adjusting layer consisting of 100.0 × ^{10 -4} in a transparent thermoplastic resin (a), the a photoelastic coefficient _{(C B)} and orientation birefringence ([Delta] n _B) is comparative resin is outside the preferred range A liquid crystal display protective plate having a laminated structure with a base material layer was manufactured.
In Comparative Example 6, a phase difference adjusting layer orientation birefringence ([Delta] n _A) is made of comparative resin is defined outside of the present invention, the photoelastic coefficient (C _B) and orientation birefringence ([Delta] n _B) is a preferable range A liquid crystal display protective plate having a laminated structure with a base material layer made of an outer comparative resin was manufactured.
The liquid crystal display protective plate obtained in these comparative examples has a large standard deviation of the Re value (large variation in the Re value), and when the liquid crystal display protective plate on the liquid crystal screen is observed through a polarizing filter, rainbow unevenness occurs. occured.

As an example, FIGS. 5A and 5B show the distribution of Re values of the liquid crystal display protective plates obtained in Example 7 and Comparative Example 6. It is shown that the Re value of the liquid crystal display protective plate obtained in Example 7 has a small variation, whereas the Re value of the liquid crystal display protective plate obtained in Comparative Example 6 has a large variation.

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

This application claims priority based on Japanese Application Japanese Patent Application No. 2019-207044 filed on November 15, 2019, and incorporates all of its disclosures herein.

1 to 3 Liquid crystal display protection plate 11 T die 12 to 14 Cooling roll 15 Take- up roll 16, 16X, 16Y Resin plate 21 Phase difference adjustment layer 22 Base material layer 31 Hardened film

Claims (6)

1. _A test piece having an absolute value of photoelastic coefficient (CA ^{) of 10.0 × 10-12} / Pa or less and a width of 20 mm, a length of 40 mm, and a thickness of 1 mm is 3 mm at a temperature 10 ° C higher than the glass transition temperature. The absolute value of the _{orientation birefringence (Δn A} ) obtained by uniaxially stretching at a stretching rate of 100% at a rate of / min and measuring the in-plane retardation value of the central portion of the test piece ^{is 10.0 × 10 −.} A resin plate having a phase difference adjusting layer containing a transparent thermoplastic resin (A) of ⁴ to 100.0 × 10 ^{-4 is included.}
   A liquid crystal display protective plate having an in-plane retardation value of 50 to 330 nm.
2. The liquid crystal display protective plate according to claim 1, wherein the standard deviation of the in-plane retardation value within the range of 17 cm in width and 22 cm in length is 15.0 nm or less.
3. The transparent thermoplastic resin (A) contains an aromatic vinyl monomer unit and contains.
   Transparent thermoplastic resin content of the aromatic vinyl monomer units in (A) and V [wt%], when the thickness of the phase difference adjusting layer was T _{A [mm],} the following formula (1) The liquid crystal display protective plate according to claim 1 or 2, which satisfies the above conditions.
   _{6.0 ≦ V × T A ≦ 30.0} ··· (1)
4. The resin plate further when the absolute value of photoelastic coefficient _{(C B)} is 10.0 × ¹⁰ -12 / Pa or less, and the width 20 mm, length 40 mm, a test piece having a thickness of 1 mm, than the glass transition temperature The absolute value of _{orientation birefringence (Δn B} ) obtained by uniaxially stretching at a high temperature of 10 ° C. at a rate of 3 mm / min at a stretching rate of 100% and measuring the in-plane retardation value of the central portion of the test piece is The liquid crystal display protective plate according to any one of claims 1 to 3, which has a base material layer containing a transparent thermoplastic resin (B) having a size of less than 10.0 × 10 ^-4.
5. The liquid crystal display protective plate according to any one of claims 1 to 4, further comprising a cured film on at least one surface of the resin plate.
6. The liquid crystal display protective plate according to any one of claims 1 to 5, wherein the resin plate is an extruded plate.

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