JP2008197223A - Optical element, polarizing plate, retardation plate, lighting system and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element which is used for displaying an image having a similar color balance when the image is observed head-on and obliquely and is excellent in handling property or the like. <P>SOLUTION: The optical element has a transparent base material and a selective reflection layer formed on the transparent base material and is used in a system equipped with a light source. The transparent base material consists of a laminate which has at least one layer A formed from a methacrylic resin A which has ≥120°C Vicat softening point and contains ≥70 wt.% methyl methacrylate unit, and at least one layer B formed from a resin composition which contains a methacrylic resin B containing ≥70 wt.% methyl methacrylate unit and elastic body particles and has 95-115°C Vicat softening point and ≥15% tensile fracture strain, and in which the layer B is the outermost layer. The optical element is characterized in that the lower limit λ<SB>L</SB>of a wavelength range of the reflected light when the optical element reflects the light of 0° incident angle is made longer than the wavelength λ<SB>R1</SB>of the light which is emitted from the light source and shows the maximum luminous intensity in the wavelength range of 600-700 nm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical element, a polarizing plate, a retardation plate, an illumination device, and a liquid crystal display device. Specifically, an optical element, a polarizing plate, excellent in high-temperature and high-humidity resistance and handling properties, and used for displaying an image having the same color balance in front and oblique observation, The present invention relates to a retardation plate, an illumination device, and a liquid crystal display device.

  The liquid crystal display device includes a light source, two dichroic polarizers, and a liquid crystal cell disposed between the dichroic polarizers. Light from a light source such as a cold cathode tube, a hot cathode tube, LED (light emitting diode), EL (electroluminescence), blue light (wavelength 410 to 470 nm), green light (wavelength 520 to 580 nm), and red light ( (Wavelength 600 to 660 nm) is balanced and emits white light. The light is converted into linearly polarized light by the first dichroic polarizer. The linearly polarized light is converted into linearly polarized light with the phase unchanged or inverted depending on the difference in voltage application or no voltage application in the liquid crystal cell. When the polarization transmission axis of the first dichroic polarizer and the polarization transmission axis of the second dichroic polarizer (also referred to as analyzer) are perpendicular, the linearly polarized light whose phase is inverted in the liquid crystal cell is The linearly polarized light that is transmitted through the second dichroic polarizer and whose phase is unchanged in the liquid crystal cell cannot pass through the second dichroic polarizer. In general, even if the phase can be inverted with respect to light incident from an incident angle of 0 degrees (that is, the phase is delayed by a half wavelength), the phase delay is exactly halved for light incident from an oblique direction. 1 wavelength cannot be obtained, resulting in distortion. The degree of distortion varies depending on the wavelength. As a result, the color image when viewed from the front is different from the color image when viewed from an oblique direction.

  Also, reflective polarizers may be used to improve brightness. In the reflective polarizer, the selective reflection band of light incident from an oblique direction is shifted to the short wavelength side as compared with the selective reflection band of light incident from the front. Even with a reflective polarizer that can reflect the entire visible light region with respect to light incident from the front, long wavelength light (red light) may not be reflected with respect to light incident from an oblique direction. For this reason, in general, in a liquid crystal display device, the color image when viewed from the front is different from the color image when viewed from an oblique direction.

In order to eliminate the difference in hue depending on the observation angle, Patent Document 1 includes a cholesteric liquid crystal layer having a selective reflection band at wavelengths λ ₁ to λ ₂ (λ ₁ <λ ₂ ) with respect to normal incident light. It has been proposed to arrange a collimator in the backlight system that satisfies λ ₀ <λ ₁ with respect to the maximum wavelength λ ₀ of the emission spectrum of the light source used in combination. The collimator described in Patent Document 1 has a function of aligning light traveling at various angles with only light traveling in the vertical direction. Therefore, light rays incident from an oblique direction are reflected by this collimator and are not transmitted.

  Further, in Patent Document 2, it has a transmission characteristic with respect to incident light in the visible light region in the normal direction, has a reflection wavelength band in the infrared region, and has a reflection wavelength as the incident angle with respect to the normal direction increases. It has been proposed to arrange an infrared reflecting layer (B) whose band changes to the short wavelength side in an illumination device. Patent Document 2 discloses an infrared reflective layer (B) having a transmittance of light of 10% or less at a wavelength of 710 nm, 640 nm, or 610 nm at an incident angle of 45 degrees. That is, in the infrared reflection layer (B), the red light incident obliquely is almost completely reflected or absorbed by the infrared reflection layer (B).

JP 2002-169026 A (US Publication 2002/0036735) JP 2004-309618 A

  By the way, a polarizing plate consists of a dichroic polarizer and the protective film laminated | stacked on the both surfaces. As the dichroic polarizer, a uniaxially oriented polyvinyl alcohol film in which iodine and / or a dichroic dye is adsorbed is generally used. As a protective film, a cellulose ester film such as a triacetyl cellulose (hereinafter referred to as TAC) film is generally used because of its excellent flatness, light transmittance, optical isotropy, and the like.

However, the TAC film has a high moisture permeability and a large dimensional change due to humidity. Therefore, when used as a protective film, the durability of the polarizing plate is impaired, and the usage environment of the polarizing plate is limited.
For example, under the condition of high temperature and high humidity, the polarizer is decolored by the moisture transmitted through the TAC film, and the polarization characteristics are greatly deteriorated. Moreover, when the polarizing plate is enlarged, a phenomenon in which the polarization characteristics at the periphery of the polarizing plate are deteriorated due to the change in the dimensions of the polarizer and the TAC film due to humidity is observed.
Therefore, when exposed to severe conditions of high temperature and high humidity, such as for automobiles, or for large screen applications such as large-scale television, a protective film with higher resistance to high temperature and high humidity is required.

  In addition, for the polarizing plate protective film disposed on the outermost surface of the display, scratch resistance is also an important characteristic. Conventionally, the scratch resistance is improved by forming a hard coat layer made of an ultraviolet curable resin or a thermosetting resin on the surface of the TAC film. However, even when such a hard coat layer is formed, the underlying cellulose film itself is soft and plastically deformed, so that sufficient scratch resistance cannot be realized.

  As a means for improving moisture permeability and scratch resistance, it has been proposed to use a polymethyl methacrylate (PMMA) resin film as a protective film. Since PMMA resin film has a high light transmittance and is excellent in optical isotropy, it is often found in various literatures that it can be used as a protective film. In addition, the PMMA resin film has a moisture permeability as low as about 1/100 as compared with the TAC film, and has excellent scratch resistance.

However, the PMMA resin film as a protective film has two drawbacks.
The first point is that it is inferior in mechanical strength, very brittle, and easy to tear. Since it breaks easily, a polarizing plate cannot be produced by a rational manufacturing process of roll-to-roll.
The second point is that the heat resistance is low. Under the durability test conditions of the polarizing plate, the temperature is 90 ° C./95% RH under severe temperature and humidity. Under such a high temperature condition, the mechanical strength of the PMMA resin is remarkably lowered and the polarizer cannot be supported.

  Patent Document 3 discloses a heat-resistant acrylic resin composition in which acrylic rubber particles having a multilayer structure are mixed in a copolymer composed of methyl methacrylate units and N-cyclohexylmaleimide units. It is reported that the resin composition is excellent in heat resistance and improved in mechanical strength by the action of acrylic rubber particles, and is suitable for processing into a film. However, when acrylic rubber particles are added, scratch resistance and heat resistance under high humidity conditions tend to be reduced.

  Patent Document 4 discloses that a biaxially stretched film made of a copolymer of methyl methacrylate and N-alkylmaleimide, maleic anhydride, etc. improves mechanical strength, and has excellent durability and heat resistance. It is disclosed that it becomes a board protective film. However, stretching may cause optical anisotropy and may impair display display quality. Moreover, since the molecular orientation produced by stretching is relaxed under high temperature conditions, the heat resistance of the film tends to decrease.

  Patent Document 5 discloses an acrylic resin film in which a soft layer (flexural modulus 1500 MPa or less) and a hard layer (flexural modulus 1600 MPa or more) are laminated. It is disclosed that by using this film, the mechanical strength can be improved while maintaining high scratch resistance. For the soft layer having a flexural modulus of 1500 MPa or less, a methacrylate resin blended with rubber particles is used. Examples of the methacrylate resin include a single or copolymer of methacrylate, a copolymer of methacrylate and acrylate, and the like.

Japanese Patent Laid-Open No. 5-98113 Japanese Patent Laid-Open No. 5-288929 JP-A-2002-292808

An object of the present invention is to provide an optical element, a polarizing plate, a retardation plate, an illumination device, and a liquid crystal display device that are used to display an image having the same color balance in front and oblique observations. .
An object of the present invention is an optical element suitable for a polarizing plate protective film, a polarizing plate, a retardation plate, a lighting device, and a liquid crystal display, which has excellent optical performance, high temperature and humidity resistance, and handling properties, and has a sufficient surface hardness. To provide an apparatus.

The present inventor can obtain an image in which blue, green and red are well balanced when the liquid crystal display device disclosed in the above-mentioned patent document is observed from the front. I noticed that sometimes the images look bluish. And this reason came to be thought that it is because the collimator or infrared reflection layer (B) used in the above-mentioned patent documents 1 and 2 blocks too much red light incident obliquely.
In addition, as a result of examining the laminated film proposed in Patent Document 3, the present inventors have confirmed that the heat resistance is reduced under high humidity conditions. Therefore, the inventors estimated that the cause is that the Vicat softening point is lower than 95 ° C. because the film has a very soft layer having a flexural modulus of 1500 MPa or less.

Therefore, the present inventors formed a selective reflection layer on a laminate including a layer A of methacrylic resin having a specific Vicat softening point and the like, and a layer B of a resin composition containing elastic particles and methacrylic resin. An optical element having a band that reflects light having an incident angle of 0 degrees in a wavelength band (λ _{L to} λ _H ) longer than the wavelength λ _{R1 of} light that exhibits the maximum emission intensity in the wavelength range of 600 nm to 700 nm of the light source. When equipped with an illuminating device for a liquid crystal display device, it is possible to display an image with the same color balance in front and oblique observation, excellent high-temperature and high-humidity resistance, handling properties, and sufficient surface hardness. I found it. Based on these findings, the present inventors have further studied and completed the present invention.

Thus, the present invention includes the following.
(1) An optical element for use in an apparatus having a light source, which has a transparent base material and a selective reflection layer formed on the transparent base material,
The transparent substrate has a Vicat softening point of 120 ° C. or higher and a layer A formed of a methacrylic resin A containing a methyl methacrylate unit of 70% by weight or more;
It was formed of a resin composition containing methacrylic resin B containing 70% by weight or more of methyl methacrylate units and elastic particles, having a Vicat softening point of 95 ° C. to 115 ° C. and a tensile fracture strain of 15% or more. Layer B,
Each has at least one layer,
Layer B consists of a laminate that is at least one outermost layer,
An optical element in which a lower limit λ _L of a wavelength band for reflecting a light beam having an incident angle of 0 degrees is longer than a wavelength λ _{R1 of} light that exhibits a maximum emission intensity in a wavelength band of 600 nm to 700 nm among light emitted from a light source.

(2) The optical element according to claim 1, wherein the transparent substrate is a laminate having an average thickness of less than 100 μm, wherein the layer B is laminated on both sides of the layer A.

(3) The said optical element whose average transmittance | permeability of light with a wavelength of 600 nm-700 nm at an incident angle of 60 degrees is 40% or more and 80% or less.
(4) The average transmittance of light having a wavelength of 600 nm to 700 nm at an incident angle of 0 degree is 60% or more,
The optical element described above, wherein an average transmittance of light having a wavelength of 600 nm to 700 nm at an incident angle of 0 degrees is larger than an average transmittance of light having a wavelength of 600 nm to 700 nm at an incident angle of 60 degrees.
(5) The said optical element whose average transmittance | permeability of light with a wavelength of 600 nm-700 nm in the incident angle of 60 degree | times is 50% or more and 80% or less.

(6) The optical element described above, wherein the selective reflection layer includes a resin layer having cholesteric regularity.
(7) The selective reflection layer includes a resin layer having cholesteric regularity,
The above optical element, wherein the chiral pitch of the resin layer is 400 nm or more, and the maximum reflectance in the selective reflection band at an incident angle of 0 degree is 10% or more and 40% or less.
(8) When the light having the wavelength exhibiting the maximum reflectance in the selective reflection band at the incident angle of 0 degrees is incident at the incident angle of 60 degrees, the reflectance is 50% or more and 90% of the maximum reflectance at the incident angle of 0 degrees. The above-mentioned optical element which is the following.
(9) The optical element described above, wherein an average reflectance of light having a wavelength of 600 nm to 700 nm at an incident angle of 60 degrees is 20% or more and 60% or less.

(10) A polarizing plate in which the optical element and a linear polarizer are laminated.
(11) A retardation plate in which the optical element and a retardation element are laminated.
(12) A lighting device in which a light reflecting element, a light source, a light diffusing element, and the optical element are arranged in this order.
(13) A polarized light illumination device in which a light reflecting element, a light source, a light diffusing element, and the polarizing plate are arranged in this order.
(14) A liquid crystal display device in which a light reflecting element, a light source, a light diffusing element, the optical element, a linear polarizer, a liquid crystal panel, and an analyzer are arranged in this order.
(15) The liquid crystal display device as described above, wherein the light source is selected from a cold cathode tube, a hot cathode tube, a light emitting diode, and electroluminescence.

  Conventional liquid crystal display devices are often reddish when observed obliquely. This is because the amount of red light when viewed from an oblique angle is relatively higher than the amount of blue and green light when compared to the light amount balance of blue, green and red when viewed from the front. On the other hand, if the transmittance of light having a wavelength of 710 nm, 640 nm, or 610 nm incident from an oblique angle is set to 10% or less as in Patent Documents 1 and 2, the light quantity balance of blue, green, and red when viewed from the front is reduced. As a result, the amount of red light when observed from an oblique direction is relatively low compared to the amounts of blue and green light. As a result, when the liquid crystal display device is observed obliquely, it tends to be bluish or reddish or dark.

  In the optical element of the present invention, the color balance of blue, green and red when observed from an oblique direction can be adjusted to the same balance as the balance of blue, green and red when observed from the front. As a result, when observed from an oblique direction, the color reproduction range can be widened without redness or bluishness.

  An optical element according to an embodiment of the present invention includes a cholesteric resin layer having a selective reflection layer having a chiral pitch of 400 nm or more, and a maximum reflectance in a selective reflection band at an incident angle of 0 degree is 10% or more and 40% or less. . Since the selective reflection band of the cholesteric resin layer shifts to the short wavelength side when the incident angle increases, when the optical element of the present invention is installed in a device having a light source, the color balance of blue, green and red when observed from an oblique direction is increased. It can be adjusted to a balance similar to the balance of blue, green and red when observed from the front. As a result, when observed from an oblique direction, the color reproduction range can be widened without being reddish or bluish.

  In addition, the optical element of the present invention is flexible and excellent in flexibility, and does not cause visual defects such as interference fringes on the display screen, and further, does not cause visual defects due to light leakage, color unevenness, coloring, etc. near the frame of the display screen. A liquid crystal display device can be provided. The optical element of the present invention is excellent in high-temperature and high-humidity resistance and handling properties, and has a sufficient surface hardness. Furthermore, since the surface hardness is high, it has excellent scratch resistance.

The figure which shows an example of the emission spectrum of a light source. The figure for demonstrating a selective reflection zone | band. The figure which shows an example of the optical element (circularly polarized light reflecting plate) of this invention. 1 is a diagram showing a configuration of an example of a liquid crystal display device of the present invention.

Explanation of symbols

1: Transparent substrate 2: Alignment film 3: Cholesteric resin layer 11: Polarizer Y (analyzer)
12: Liquid crystal cell 13: Polarizer X
17: Optical element of the present invention (circularly polarizing reflector)
18: Light diffuser 19: Cold cathode tube 20: Reflector

The optical element of the present invention has a layer A formed of a methacrylic resin A having a Vicat softening point of 120 ° C. or higher and containing 70% by weight or more of a methyl methacrylate unit,
It was formed of a resin composition containing methacrylic resin B containing 70% by weight or more of methyl methacrylate units and elastic particles, having a Vicat softening point of 95 ° C. to 115 ° C. and a tensile fracture strain of 15% or more. Layer B,
Each has at least one layer,
A transparent substrate made of a laminate in which layer B is at least one outermost surface layer;
A selective reflection layer formed on the transparent substrate,
An optical element having a lower limit λ _L of a wavelength band for reflecting a light beam having an incident angle of 0 ° is longer than a wavelength λ _{R1 of} light that exhibits a maximum emission intensity in a wavelength band of 600 nm to 700 nm among light emitted from a light source.
The optical element of the present invention is a member used with a light source, and is disposed on the light emission side of the light source.

The optical element of the present invention has a wavelength band for reflecting light (hereinafter sometimes referred to as a selective reflection band). The solid line 30 in FIG. 2 shows the wavelength dependence of the reflectance at an incident angle of 0 degree. The selective reflection band is a portion where the reflectance is larger than the other portions in a specific wavelength region (a wavelength region between λ _L and λ _H ) as indicated by a solid line 30. In FIG. 2, the reflectance changes clearly at the boundary between the selective reflection band and the non-selective reflection band, and the graph has a rectangular or trapezoidal shape, but the reflectance changes slowly, for example, the graph is a parabola. A gentle mountain shape such as Here, the lower limit λ _L and the upper limit λ _H of the selective reflection band are the shortest and the longest, respectively, among the wavelengths showing the reflectance that is ½ times the maximum reflectance in the selective reflection band.

FIG. 1 shows an example of an emission spectrum of a light source (cold cathode tube) used in a liquid crystal display device. λ _R1 is the wavelength of light that exhibits the maximum emission intensity in the wavelength band of 600 nm to 700 nm in the light emitted from the light source.
The wavelength range of the band for reflecting the light beam (selective reflection band) varies depending on the incident angle. In the present invention, the lower limit wavelength λ _{L of the} band for reflecting the light beam having the incident angle of 0 degrees is longer than the wavelength λ _R1 .

Furthermore, in the optical element of the present invention, it is preferable that λ _L is longer than the wavelength λ _{R2 of} light that exhibits the maximum emission intensity in the wavelength band of 630 to 700 nm in the light emitted from the light source. By making λ _L have a longer wavelength, the color balance when viewed from the front can be improved, or the value of the area ratio of the color reproduction range to the chromaticity range can be increased.

In FIG. 1, since λ _R1 is about 610 nm, λ _L is preferably set to a wavelength longer than 610 nm. The selective reflection band λ _L shown by the solid line 30 in FIG. 2 is about 680 nm. The width of the selective reflection band (difference between λ _H and λ _L ) is preferably 50 nm or more, particularly preferably 80 nm or more.

  The maximum reflectance of the selective reflection band at an incident angle of 0 degree is preferably 10% to 40%, more preferably 15% to 35%. When the maximum reflectance is in the above range, when the display screen of the liquid crystal display device is observed obliquely, an image having the same color balance as that observed from the front can be obtained. When the maximum reflectance is low, the image tends to be reddish when observed from an oblique direction. When the maximum reflectance is high, the image tends to be bluish when observed from an oblique direction.

  In the optical element of the present invention, the reflectance when the light having the wavelength exhibiting the maximum reflectance in the selective reflection band at the incident angle of 0 degrees is incident at the incident angle of 60 degrees is preferably the maximum reflectance at the incident angle of 0 degrees. Is from 50% to 90%, more preferably from 60% to 85%.

  In the optical element of the present invention, the average transmittance of light having a wavelength of 600 nm to 700 nm at an incident angle of 0 degree is preferably 60% or more, more preferably 70% or more. Furthermore, it is preferable that the average transmittance of light having a wavelength of 600 nm to 700 nm at an incident angle of 0 ° is larger than the average transmittance of light having a wavelength of 600 nm to 700 nm at an incident angle of 60 ° described later. Specifically, the average transmittance of light having a wavelength of 600 nm to 700 nm at an incident angle of 60 degrees is preferably 94% or less of the average transmittance of light having a wavelength of 600 nm to 700 nm at an incident angle of 0 degrees.

  The light transmittance of blue light and green light at an incident angle of 0 degree can be appropriately selected in consideration of the light quantity balance with respect to red light. The average transmittance of blue light (wavelength 400 nm to 500 nm) and green light (wavelength 500 nm to 600 nm) at an incident angle of 0 degree is preferably 60% or more, more preferably 70% or more. In the present specification, the average transmittance is an arithmetic average value of transmittance measured at a wavelength interval of 10 nm.

The selective reflection band is preferably shifted to the short wavelength side as the incident angle of light increases. Specifically, the selective reflection band preferably includes the wavelength λ _R1 or λ _R2 at an incident angle of 60 degrees. As the incident angle increases, the selective reflection band shifts to the short wavelength side. Thereby, the average transmittance of light having a wavelength of 600 nm to 700 nm at an incident angle of 60 degrees can be lowered.

A broken line 31 in FIG. 2 shows an example of the selective reflection band at an incident angle of 60 degrees. In FIG. 2, the lower limit of the selective reflection band is about 610 nm.
In the optical element of the present invention, the average transmittance of light having a wavelength of 600 nm to 700 nm at an incident angle of 60 degrees is preferably 40% to 80%, more preferably 50% to 80%. When the light transmittance is less than the above range, the display image when observed obliquely tends to be bluish. When the light transmittance exceeds the above range, the display image when observed from an oblique angle tends to be reddish.

In the optical element of the present invention, the average transmittance of blue light (wavelength 400 nm to 500 nm) and green light (wavelength 500 nm to 600 nm) at an incident angle of 60 degrees is preferably 60% or more, more preferably 70% or more.
Further, the average transmittance of light having a wavelength of 600 nm to 700 nm at an incident angle of 60 degrees may be smaller than the average transmittance of blue light (wavelength of 400 nm to 500 nm) and green light (wavelength of 500 to 600 nm) at an incident angle of 60 degrees. More specifically, it is preferably 5 to 30% smaller than the average transmittance of blue light (wavelength 400 to 500 nm) and green light (wavelength 500 nm to 600 nm) at an incident angle of 60 degrees.

  In the optical element of the present invention, the average reflectance of light having a wavelength of 600 nm to 700 nm at an incident angle of 60 degrees is preferably 20% to 60%, more preferably 25% to 50%.

(Transparent substrate)
The transparent substrate constituting the optical element of the present invention comprises a laminate having at least one layer A and one layer B, with the layer B being the outermost layer. The transparent substrate has an overall thickness of less than 100 μm.

<Methacrylic resin>
Layer A and layer B are layers containing a methacrylic resin. The methacrylic resin used in the present invention contains methyl methacrylate units in an amount of 70% by weight or more, preferably 70 to 98% by weight, more preferably 70 to 95% by weight, and particularly preferably 75 to 95% by weight. When the methacrylic resin is not a homopolymer of methyl methacrylate, the content of monomer units copolymerizable therewith is 30% by weight or less, preferably 2-30% by weight, more preferably 5-30% by weight, particularly preferably 5 to 25% by weight. The methacrylic resin is obtained by polymerizing methyl methacrylate and a monomer copolymerizable with methyl methacrylate according to a conventional method.

Examples of the copolymerizable monomer include N-alkylmaleimide; maleic anhydride; a methacrylic acid ester compound having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in the ester moiety; and aromatic vinyl such as styrene and α-methylstyrene. Examples thereof include compounds having one aliphatic carbon-carbon double bond in the molecule, such as compounds; alkyl acrylates such as methyl acrylate and ethyl acrylate; The aromatic vinyl compound can increase the copolymerization reactivity of methyl methacrylate with N-alkylmaleimide or maleic anhydride. Moreover, the thermal decomposition of resin at high temperature can be suppressed by copolymerizing alkyl acrylate.
The layer A and the layer B can be formed by controlling the type and use ratio of the monomer copolymerizable with methyl methacrylate and using other compounding agents.

Layer A constituting the transparent substrate is a layer formed of methacrylic resin A having a Vicat softening point of 120 ° C. or higher and containing 70% by weight or more of methyl methacrylate units.
Layer B contains methacrylic resin B containing 70% by weight or more of methyl methacrylate units and elastic particles having a number average particle diameter of 2.0 μm or less, and has a Vicat softening point of 95 ° C. to 115 ° C., and has a tensile fracture strain. Is a layer formed of a resin composition having 15% or more.
In the present invention, Vicat softening point and tensile breaking strain are values measured under the conditions employed in the examples. Furthermore, in the optical element of the present invention, at least one outermost surface layer is the layer B.

The methacrylic resin A constituting the layer A has a Vicat softening point of 120 ° C. or higher, preferably 120 to 150 ° C.
As the methacrylic resin A giving such a Vicat softening point, in addition to the methyl methacrylate unit, the N-alkylmaleimide unit, the maleic anhydride unit, and the ester moiety have an alicyclic hydrocarbon group having 5 to 22 carbon atoms. A suitable example includes 2 to 30% by weight, preferably 5 to 20% by weight, of any one or more of the methacrylic acid ester compound units. If the proportion of units other than methyl methacrylate units is less than 2% by weight, the effect of improving heat resistance tends to decrease, and if it exceeds 30% by weight, moldability tends to be impaired. Of course, methacrylic resin A has N-alkylmaleimide units, maleic anhydride units, and alicyclic hydrocarbon groups having 5 to 22 carbon atoms in the ester portion as long as the Vicat softening point is within the specified range. You may have units other than an ester compound unit.

  Among the N-alkylmaleimide units, those in which the alkyl moiety is a methyl group or a branched or cyclic alkyl group having 3 to 7 carbon atoms such as methyl, isopropyl, t-butyl, cyclohexyl and the like are particularly preferable. When the alkyl moiety is a normal alkyl group such as ethyl, n-propyl, n-butyl, etc., the heat resistance improving effect tends to be small. Further, in the case of N-substituted with an aromatic group, the obtained copolymer is colored yellow, and the light transmittance tends to decrease.

You may copolymerize the methacrylic acid ester compound unit which has a C5-C22 alicyclic hydrocarbon group in an ester part. Examples of the alicyclic hydrocarbon group having 5 to 22 carbon atoms include cyclopentyl, cyclohexyl, norbornyl, tricyclo [5.2.1.0 ^2,6 ] dec-8-yl and the like.

  The resin composition constituting the layer B has a Vicat softening point of 95 ° C. to 115 ° C. and a tensile fracture strain of 15% or more. This resin composition is a mixture of methacrylic resin B with elastic particles.

<Elastic particles>
The elastic particles used in the present invention are particles made of a rubber-like elastic body. Examples of the rubber-like elastic body include an acrylate-based rubber-like polymer, a rubber-like polymer containing butadiene as a main component, and an ethylene-vinyl acetate copolymer. Examples of the acrylic ester rubbery polymer include those containing butyl acrylate, 2-ethylhexyl acrylate, or the like as a main component. Of these, acrylate polymers based on butyl acrylate and rubbery polymers based on butadiene are preferred. The elastic particles may be formed by laminating two kinds of polymers, and typical examples thereof include an alkyl acrylate such as butyl acrylate, a grafted rubber elastic component of styrene, and polymethyl. Examples thereof include elastic particles in which a hard resin layer made of a copolymer of methacrylate and / or methyl methacrylate and an alkyl acrylate forms a core-shell structure.

  The elastic particles used in the present invention preferably have a number average particle diameter in a state dispersed in a methacrylic resin of 2.0 μm or less, more preferably 0.1 to 1.0 μm, particularly preferably 0.1 to 0.00. 5 μm. Even if the primary particle diameter of the elastic particles is small, if the number average particle diameter of the secondary particles formed by agglomeration or the like is large, the transparent substrate has too high haze (cloudiness) and the light transmittance is low. Therefore, it tends to be unsuitable for the viewing side. Moreover, when the number average particle size becomes too small, the flexibility tends to decrease.

In the present invention, the refractive index n _a of the wavelength 380nm~780nm of elastic particles (lambda) is between the refractive index n _b (λ) at a wavelength 380nm~780nm methacrylic resin as a matrix, | n _a (lambda ) −n _b (λ) | ≦ 0.05 is preferably satisfied. In particular, it is more preferable that | n _a (λ) −n _b (λ) | ≦ 0.045. Incidentally, n _a (lambda) and n _b (lambda) is the average value of the principal refractive index at a wavelength lambda. When the value of | n _a (λ) −n _b (λ) | exceeds the above value, transparency tends to decrease due to interface reflection caused by a difference in refractive index at the interface.

  As the elastic particles used in the present invention, a resin composition using acrylic rubber particles having a multilayer structure is particularly suitable. When acrylic rubber particles having a multilayer structure are used, the tensile breaking strain can be easily increased to 15% or more without lowering the Vicat softening point more than necessary. The acrylic rubber particles having a multilayer structure can be produced by a known method (for example, JP-A-57-200412).

  The addition amount of the elastic particles is preferably 20 to 60% by weight of the total amount of the resin composition. If the amount of the elastic particles is too small, the effect of improving the tensile fracture strain tends to decrease. Conversely, if the amount is too large, the Vicat softening point tends to decrease, and the heat resistance as a film tends to decrease.

  As the methacrylic resin B, those containing no units other than methyl methacrylate units and those containing alkyl acrylate units other than methyl methacrylate units are suitable. Furthermore, an aromatic vinyl compound unit can also be included as needed.

  Resin compositions containing methacrylic resin B and multilayered acrylic rubber particles are commercially available as impact-resistant PMMA resins such as “Delpet SR” (product name, manufactured by Asahi Kasei Chemicals Corporation).

  The transparent substrate may have other resin layers in addition to the layer A and the layer B. Examples of the resin constituting the other resin layer include methacrylic resins, polystyrene resins, acrylonitrile-styrene copolymers, methyl methacrylate-styrene copolymers other than those described above. Moreover, you may use the resin composition which knead | mixed 2 or more types chosen from these.

  Layer A, layer B, and other resin layers may contain other additives as necessary. Additives include: antioxidants such as phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants; UV absorption such as benzotriazole UV absorbers, benzoate UV absorbers, benzophenone UV absorbers Agents; Light stabilizers such as hindered amine light stabilizers; Colorants such as dyes and pigments; Lubricants such as esters of aliphatic alcohols, esters of polyfunctional alcohols, fatty acid amides, inorganic particles; Triester plasticizers, phthalic acid Examples thereof include plasticizers such as ester plasticizers and fatty acid-basic acid ester plasticizers.

Although the transparent base material used for this invention is not limited by the manufacturing method, What was obtained by the melt coextrusion molding method using T die from the point which is excellent in productivity and thickness precision is preferable.
In the melt coextrusion molding method using a T-die, the methacrylic resin A, the resin composition, and other constituent resin layers that are formed as necessary are melted in separate extruders to obtain a molten state. After laminating, a transparent substrate having a laminated structure can be created at a stretch by extruding the sheet from a T-die and pulling the sheet with a cooling roll.

  At this time, the surface roughness of the transparent substrate increases as the ratio (Tt / Tr) between the sheet thickness Tt immediately after being pushed out from the T-die and the sheet thickness Tr after being taken out by the cooling roll increases. . In order to change the values of Tt and Tr, it is necessary to change the gap between the slits of the T die and the rotation speed of the cooling roll, but these also affect other qualities such as uneven thickness of the transparent substrate. There are limits to give. Generally, it is preferable to adjust Tt / Tr between 5 and 40.

  In a transparent base material, it laminates | stacks so that the layer B may become the outermost surface layer, but it is preferable not to contact the cooling roll with the layer B which became the outermost surface layer at the time of transparent base material manufacture. That is, it is preferable that the surface on the side opposite to the layer B that is the outermost surface layer is in contact with the cooling roll. When the cooling roll is brought into contact with the layer B immediately after the coextrusion molding, the surface protrusion formed by the elastic particles may be crushed and the surface roughness may be reduced. In addition, a method of sandwiching a sheet extruded from a T-die between two parallel metal rolls is also generally used, but even with such a method, surface protrusions are crushed and the surface roughness is reduced. . The outermost surface layer on which the layer B is disposed is preferably brought into contact with another roll after the temperature of the layer B is cooled below the glass transition point of the resin. When layer B is formed on both sides of layer A, only one layer B can be brought into contact with the cooling roll, but the other layer B is preferably not brought into contact with the cooling roll in order to be the outermost surface layer.

The transparent substrate can be produced by preparing films constituting each layer by a conventionally known molding method and bonding them together with an adhesive.
Adhesives include acrylic adhesives, urethane adhesives, polyester adhesives, polyvinyl alcohol adhesives, polyolefin adhesives, modified polyolefin adhesives, polyvinyl alkyl ether adhesives, rubber adhesives, ethylene -Vinyl acetate adhesive, vinyl chloride-vinyl acetate adhesive, SEBS (styrene-ethylene-butylene-styrene copolymer) adhesive, SIS (styrene-isoprene-styrene block copolymer) adhesive, ethylene -Ethylene-based adhesives such as styrene copolymer, acrylic acid ester-based adhesives such as ethylene- (meth) methyl acrylate copolymer, ethylene- (meth) ethyl acrylate copolymer, and the like. Of these, those that maintain a predetermined elasticity after bonding are more preferable, and examples of such adhesives include SEBS adhesives, SIS adhesives, and ethylene-vinyl acetate adhesives.
The average thickness of the layer made of this adhesive is usually 0.01 to 30 μm, preferably 0.1 to 15 μm.

In the present invention, the thickness of the entire transparent substrate is preferably 100 μm or less. If the thickness of the entire transparent substrate is greater than 100 μm, the flexibility tends to decrease.
The transparent base material preferably has a total thickness of layer A of 30 μm or more and a total thickness of layer B of 10% or more of the total thickness of the transparent base material, preferably 30% or more. Is more preferable. When the total thickness of the layer A is thinner than 30 μm, the heat resistance tends to decrease. On the other hand, if the total thickness of the layer B is less than 10% of the total thickness of the transparent substrate, the flexibility and impact resistance tend to decrease. Further, the thickness of each layer A and layer B is preferably 1 μm or more from the viewpoint of the balance between productivity and optical characteristics.

In the present invention, the surface roughness (Ra) of the layer B which is the outermost surface layer is preferably 8 to 30 nm, more preferably 10 to 20 nm. If the surface roughness is too small, the slipperiness of the transparent substrate is deteriorated and the operability tends to be lowered. For example, when a transparent base material is transported by roll-to-roll, the transparent base material sticks to the transport roll, and wrinkles or breaks. Moreover, when winding a transparent base material as a roll, it rubs between transparent base materials, a damage | wound is carried out, the air escape between transparent base materials is not fully performed, and the shape of a winding roll may deteriorate.
On the other hand, if the surface roughness is too large, the transparency of the transparent substrate tends to decrease due to light scattering on the surface.

  The surface roughness of the outermost surface layer on which the layer B is arranged can be set to a value within the above range by controlling the amount of elastic particles contained in the layer B and the method for producing the transparent substrate. Generally, the surface roughness increases as the amount of the elastic particles added increases.

  The transparent substrate is preferably a laminate in which functional layers such as a hard coat layer, an antireflection layer, an antifouling layer and an antiglare layer are further laminated. As each functional layer, a normal functional layer employed in manufacturing a display element may be selected, and a laminating method may follow a conventional method.

(Hard coat layer)
The hard coat layer is a layer having a function of increasing the surface hardness, and preferably exhibits a hardness of “H” or more in a pencil hardness test (a test plate is a glass plate) shown in JIS K5600-5-4. The transparent substrate provided with such a hard coat layer preferably has a pencil hardness of 4H or higher. The material for forming the hard coat layer (hard coat material) is preferably a material that is cured by heat or light. For example, organic hard such as organic silicone, melamine, epoxy, acrylic, urethane acrylate, etc. Coating materials; inorganic hard coat materials such as silicon dioxide; and the like. Among these, urethane acrylate-based and polyfunctional acrylate-based hard coat materials are preferable from the viewpoint of good adhesive strength and excellent productivity.

  The hard coat layer contains various fillers for the purpose of adjusting the refractive index, improving the flexural modulus, stabilizing the volume shrinkage, and improving heat resistance, antistatic properties, and antiglare properties, as desired. it can. Further, the hard coat layer can contain additives such as an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, a leveling agent, and an antifoaming agent.

(Antireflection layer)
The antireflection layer is a layer for preventing the transfer of external light, and is laminated on the surface of the transparent substrate (surface exposed to the outside) directly or via another layer such as a hard coat layer. The transparent substrate provided with the antireflection layer preferably has an incident angle of 5 °, a reflectance at a wavelength of 430 nm to 700 nm of 2.0% or less, and a reflectance at a wavelength of 550 nm of 1.0% or less. Is preferred.

  The thickness of the antireflection layer is preferably 0.01 μm to 1 μm, more preferably 0.02 μm to 0.5 μm. The antireflection layer has a refractive index smaller than the refractive index of a layer (such as a protective layer or a hard coat layer) on which the antireflection layer is laminated, specifically a low refractive index of 1.30 to 1.45. Examples thereof include those composed of a refractive index layer; those obtained by alternately laminating a plurality of low refractive index layers of a thin film made of an inorganic compound and high refractive index layers of a thin film made of an inorganic compound.

  The material for forming the low refractive index layer is not particularly limited as long as it has a low refractive index. Examples thereof include a resin material such as an ultraviolet curable acrylic resin, a hybrid material in which inorganic fine particles such as colloidal silica are dispersed in the resin, and a sol-gel material using a metal alkoxide such as tetraethoxysilane. The material for forming these low refractive index layers may be a polymerized polymer, or may be a monomer or oligomer serving as a precursor. Moreover, it is preferable that each material contains the compound containing a fluorine group, in order to provide antifouling property.

As the sol-gel material, a sol-gel material containing a fluorine group is preferably used. Examples of the sol-gel material containing a fluorine group include perfluoroalkylalkoxysilane. Perfluoroalkylalkoxysilane is, for example, CF ₃ (CF ₂ ) _n CH ₂ CH ₂ Si (OR) ₃ (wherein R represents an alkyl group having 1 to 5 carbon atoms, and n is 0 to 12). A compound represented by an integer). Specifically, as perfluoroalkylalkoxysilane, trifluoropropyltrimethoxysilane, trifluoropropyltriethoxysilane, tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, heptadecafluorodecyltrimethoxysilane , And heptadecafluorodecyltriethoxysilane. Among these, the compound whose said n is 2-6 is preferable.

  The low refractive index layer can be made of a cured product of a thermosetting fluorine-containing compound or an ionizing radiation curable fluorine-containing compound. The cured product preferably has a dynamic friction coefficient of 0.03 to 0.15, and a contact angle with water of 90 to 120 degrees. Examples of the curable fluorine-containing compound include a perfluoroalkyl group-containing silane compound (for example, (heptadecafluoro-1,1,2,2-tetradecyl) triethoxysilane) and the like, and a fluorine-containing polymer having a crosslinkable functional group. Can be mentioned.

  The fluorine-containing polymer having a crosslinkable functional group is obtained by copolymerizing a fluorine-containing monomer and a monomer having a crosslinkable functional group, or by copolymerizing a fluorine-containing monomer and a monomer having a functional group, and then in the polymer. It can be obtained by adding a compound having a crosslinkable functional group to the functional group.

  Fluoroolefins such as fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoro-2,2-dimethyl-1,3-dioxole; biscoat 6FM (Osaka Organic) Chemical), M-2020 (manufactured by Daikin), (meth) acrylic acid partial or fully fluorinated alkyl ester derivatives, fully or partially fluorinated vinyl ethers, and the like.

  Monomers having a crosslinkable functional group or compounds having a crosslinkable functional group include monomers having a glycidyl group such as glycidyl acrylate and glycidyl methacrylate; monomers having a carboxyl group such as acrylic acid and methacrylic acid; hydroxyalkyl acrylate and hydroxyalkyl Monomers having a hydroxyl group such as methacrylate; methylol acrylate, methylol methacrylate; monomers having a vinyl group such as allyl acrylate and allyl methacrylate; monomers having an amino group; monomers having a sulfonic acid group;

  As a material for forming the low refractive index layer, a material containing a sol in which fine particles such as silica, alumina, titania, zirconia, magnesium fluoride and the like are dispersed in an alcohol solvent is used because it can improve scratch resistance. Can do. From the viewpoint of antireflection properties, the fine particles preferably have a lower refractive index. Such fine particles may have voids, and silica hollow fine particles are particularly preferable. The average particle size of the hollow fine particles is preferably 5 nm to 2,000 nm, and more preferably 20 nm to 100 nm. Here, the average particle diameter is a number average particle diameter obtained by observation with a transmission electron microscope.

(Anti-fouling layer)
The antifouling layer is a layer that can impart water repellency, oil repellency, sweat resistance, antifouling properties, and the like. As a material used for forming the antifouling layer, a fluorine-containing organic compound is suitable. Examples of the fluorine-containing organic compound include fluorocarbon, perfluorosilane, and polymer compounds thereof. As a method for forming the antifouling layer, a physical vapor deposition method such as vapor deposition or sputtering, a chemical vapor deposition method, a wet coating method, or the like can be used depending on the material to be formed. The average thickness of the antifouling layer is preferably 1 nm to 50 nm, more preferably 3 nm to 35 nm.
Further, the transparent substrate may be provided with other layers such as a gas barrier layer, a transparent antistatic layer, a primer layer, an electromagnetic shielding layer, and an undercoat layer.

When the functional layer as described above is formed, it is preferable to perform chemical treatment on the surface to be formed. Examples of the chemical treatment include corona discharge treatment, sputtering treatment, low-pressure UV irradiation treatment, and plasma treatment. In addition to the chemical treatment, the transparent substrate may be subjected to mechanical treatment such as etching, sandblasting, embossing roll, etc. for the purpose of enhancing adhesion with the functional layer and imparting antiglare properties.
There is no particular limitation on the method for forming these functional layers, and a general method may be employed for forming each functional layer.

The transparent substrate used in the present invention preferably has an absolute value of the photoelastic coefficient of 30 × 10 ⁻¹³ cm ² / dyn or less, more preferably 10 × 10 ⁻¹³ cm ² / dyn or less. More preferably, it is 5 × 10 ⁻¹³ cm ² / dyn or less. When the photoelastic coefficient is larger than the above numerical value, the transparent substrate tends to develop a phase difference due to external stress, and tends to deteriorate optical performance.

Transparent substrate used in the present invention, the in-plane direction retardation Re (Re = d × (n x -n y value is defined by); n _x is a refractive index of in-plane slow axis, n _y Is the refractive index in the direction perpendicular to the slow axis in the plane; d is the average thickness of the film, and retardation Rth in the thickness direction (Rth = d × ([ _nx + _ny ] / 2− _nz) ) Is preferably a value having a small absolute value of _nz (refractive index in the thickness direction). Specifically, the in-plane retardation Re of the transparent substrate is preferably 10 nm or less at a wavelength of 550 nm, more preferably 5 nm or less, particularly preferably 3 nm or less, and 2 nm or less. Most preferably. The retardation Rth in the thickness direction of the transparent substrate is preferably −10 nm to +10 nm, more preferably −5 nm to +5 nm, at a wavelength of 550 nm.

The transparent substrate used in the present invention preferably has a moisture permeability of 10 g · m ⁻² day ⁻¹ or more and 200 g · m ⁻² day ⁻¹ or less. By setting the moisture permeability to the above-mentioned preferable range, when the transparent substrate is used as a protective layer for the polarizer, the adhesion with the polarizer is improved. The moisture permeability can be measured by the cup method described in JIS Z 0208 under the test conditions for 24 hours in an environment of 40 ° C. and 92% RH.

(Selective reflective layer)
The selective reflection layer constituting the optical element of the present invention is not particularly limited as long as the optical element can exhibit the above optical characteristics (light transmittance and light reflectance with respect to the incident angle).
As the selective reflection layer, for example, a multilayer thin film (for example, a cold filter) in which inorganic oxides having different refractive indexes are alternately deposited; a thin film in which resin thin films having different refractive indexes are laminated; a multilayer film of resins having different refractive indexes; Infrared reflective film obtained by biaxial stretching; Infrared reflective film obtained by uniaxial stretching of two types of resin films having different refractive indexes, and laminated by orthogonality; Resin layer having cholesteric regularity A circularly polarized light reflecting plate having a selective reflection band in the infrared region; a layered right and left twisted product of the circularly polarized light reflecting plate; a circle including a resin layer having cholesteric regularity in the same twisted direction A laminate in which two polarizing reflectors are laminated via a half-wave plate; a grid polarizer or the like.

  An optical element according to an embodiment of the present invention includes a resin layer having a cholesteric regularity in a selective reflection layer (hereinafter sometimes referred to as a cholesteric resin layer), and the chiral pitch of the resin layer is 400 nm or more, and The maximum reflectance in the selective reflection band at an incident angle of 0 degree is 10% or more and 40% or less.

  The cholesteric regularity is such that the molecular axes are arranged in a certain direction on one plane, but the direction of the molecular axes is slightly shifted on the next plane, and the angle is further shifted on the next plane. In this structure, the angle of the molecular axis is shifted (twisted) one after another in the normal direction of the plane. Such a structure in which the direction of the molecular axis is twisted is called a chiral structure. The normal line (chiral axis) of the plane is preferably substantially parallel to the thickness direction of the cholesteric resin layer. The thickness of the cholesteric resin layer is preferably 1 μm to 10 μm, particularly preferably 1 μm to 5 μm.

  The cholesteric resin layer used in the present invention has a chiral pitch of preferably 400 nm or more, more preferably 430 nm or more. The chiral pitch is the distance in the chiral axis direction in which the angle gradually shifts as the direction of the molecular axis advances along the plane in the chiral structure and then returns to the original molecular axis direction again.

  Among these, the circularly polarizing reflector including a resin layer having cholesteric regularity is relatively easy to adjust the selective reflection band. Therefore, a circularly polarizing reflector including a resin layer having cholesteric regularity will be described.

FIG. 3 is a view showing the structure of an example of the optical element (circularly polarizing reflector) of the present invention.
This circularly polarized light reflector can be obtained by forming an alignment film 2 on a sheet-like transparent substrate 1 and further forming a resin layer (reflection selective layer) 3 having cholesteric regularity thereon.

<Alignment film>
The alignment film is formed on the surface of the transparent substrate in order to regulate the orientation of the resin layer having cholesteric regularity in one direction in the plane. The alignment film contains, for example, a polymer such as polyimide, polyvinyl alcohol, polyester, polyarylate, polyamideimide, or polyetherimide. The alignment film can be obtained by laminating a solution (composition for alignment film) containing such a polymer into a film, drying, and rubbing in one direction.

Examples of the method of laminating the film include spin coating, roll coating, flow coating, printing, dip coating, casting film forming, bar coating, die coating, and gravure printing.
The rubbing method is not particularly limited, and examples thereof include a method of rubbing the alignment film in a fixed direction with a roll made of a synthetic fiber such as nylon or a natural fiber such as cotton or a felt. In order to remove fine powder (foreign matter) generated during rubbing and to clean the surface of the alignment film, it is preferable to clean the formed alignment film with isopropyl alcohol or the like.
In addition to the rubbing method, a method of irradiating the surface of the alignment film with polarized ultraviolet light can also provide the alignment film with a function of regulating the alignment of the resin layer having cholesteric regularity in one direction in the plane.
The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 1 μm.

<Cholesteric resin layer>
The circularly polarized light reflector includes a resin layer having cholesteric regularity. The cholesteric regularity is such that the molecular axes are aligned in a certain direction on one plane, but the direction of the molecular axis is slightly shifted in the next plane, and the angle is further shifted in the next plane. In this structure, the angle of the molecular axis is shifted (twisted) one after another in the normal direction of the plane. Such a structure in which the direction of the molecular axis is twisted is called a chiral structure. The normal line (chiral axis) of the plane is preferably substantially parallel to the thickness direction of the cholesteric resin layer. The thickness of the cholesteric resin layer is preferably 1 μm to 10 μm, particularly preferably 1 μm to 5 μm.

<Material for forming cholesteric resin layer (1): liquid crystal polymer>
As a material for forming the cholesteric resin layer, first, a liquid crystal polymer is exemplified.
In general, a substance is in one of three states (phases): gas, liquid, and solid, depending on conditions such as temperature and pressure. Liquid crystals are described as “in the middle of liquid and solid”. In general, the liquid crystal substance is a solid at a low temperature and a transparent liquid at a high temperature like other substances, but becomes a turbid liquid at an intermediate temperature range. This state is a liquid crystal state. The liquid crystal material exhibiting such a state has a long rod-like or disk-like portion in its molecular structure. In the liquid crystal state, this part is in a “solid state”, that is, a state in which it is regularly arranged, and the other part is in a “liquid state”, that is, in a state where it can maintain a fluid free position. . The liquid crystal molecules are optically arranged in such a "solid state" where the portions are regularly arranged according to the ambient conditions such as electric field and temperature, or the arrangement state changes or becomes even more discrete. Characteristics change. The liquid crystal material is liquid and fluid in the liquid crystal state, but exhibits the same characteristics as crystals because the molecules are arranged with a certain regularity. In other words, it is “a liquid but a crystal character”. The liquid crystal polymer is a polymer having such liquid crystal properties. A cholesteric resin layer can be obtained by laminating this liquid crystal polymer on the alignment film.

As this liquid crystal polymer, there is a polymer having a mesogenic structure. A mesogen is a conjugated linear atomic group that imparts liquid crystal alignment.
As a polymer having a mesogenic structure, a mesogenic group composed of a para-substituted cyclic compound or the like is bonded to a polymer main chain such as polyester, polyamide, polycarbonate, and polyesterimide directly or via a spacer portion that imparts flexibility. Having a structure; low molecular weight crystalline compound comprising a para-substituted cyclic compound or the like, directly or via a spacer portion comprising a conjugated atomic group in the polymer main chain of polyacrylate, polymethacrylate, polysiloxane, polymalonate, etc. Those having a structure in which a mesogenic part) is bonded.
Examples of the spacer part include a polymethylene chain and a polyoxymethylene chain. The number of carbon atoms contained in the structural unit forming the spacer portion is appropriately determined depending on the chemical structure of the mesogen portion. In general, in the case of a polymethylene chain, the number of carbon atoms is 1-20, preferably 2-12, and in the case of a polyoxymethylene chain, the number of carbon atoms is 1-10, preferably 1-3. is there.

  Other examples of the liquid crystal polymer include a nematic liquid crystal polymer containing a low molecular chiral agent; a liquid crystal polymer incorporating a chiral component; a mixture of a nematic liquid crystal polymer and a cholesteric liquid crystal polymer. The liquid crystal polymer having a chiral component introduced therein is a liquid crystal polymer that itself functions as a chiral agent. In the mixture of the nematic liquid crystal polymer and the cholesteric liquid crystal polymer, the pitch of the chiral structure of the nematic liquid crystal polymer can be adjusted by changing the mixing ratio thereof.

  In addition, para-substituted cyclics that impart nematic orientation such as azomethine, azo, azoxy, ester, biphenyl, phenylcyclohexane, and para-substituted aromatic units such as bicyclohexane and para-substituted cyclohexyl units. Cholesteric regularity imparted by a method of introducing an appropriate chiral component or a low molecular chiral agent composed of a compound having an asymmetric carbon into a compound having a compound (Japanese Patent Laid-Open No. 55-21479, US) (See Japanese Patent No. 5332522 and the like). Examples of the terminal substituent at the para position in the para-substituted cyclic compound include a cyano group, an alkyl group, and an alkoxyl group.

  The liquid crystal polymer is not limited by its production method. The liquid crystal polymer can be obtained, for example, by subjecting a monomer having a mesogenic structure to radical polymerization, cationic polymerization, or anionic polymerization. A monomer having a mesogenic structure can be obtained, for example, by introducing a mesogenic group into a vinyl monomer such as an acrylic ester or a methacrylic ester directly or via a spacer portion by a known method. In addition, the liquid crystal polymer can be obtained by adding a vinyl-substituted mesogenic monomer via the Si-H bond of polyoxymethylsilylene in the presence of a platinum catalyst; and a phase transfer catalyst via a functional group imparted to the main chain polymer. By introducing a mesogenic group by the esterification reaction used; a monomer having a mesogenic group introduced into a part of malonic acid via a spacer part and a diol, if necessary, may be subjected to a polycondensation reaction.

(Chiral agent introduced or contained in liquid crystal polymer)
As the chiral agent to be introduced or contained in the liquid crystal polymer, conventionally known ones can be used. Examples thereof include a chiral monomer described in JP-A-6-281814, a chiral agent described in JP-A-8-209127, and a photoreactive chiral compound described in JP-A-2003-131187.
Further, as the chiral agent, in order to avoid an unintended change of the phase transition temperature due to the addition of the chiral agent, a chiral agent that exhibits liquid crystallinity is preferable. Further, from the viewpoint of economy, a material having a large HTP (= 1 / P · c), which is an index representing the efficiency of twisting the liquid crystal polymer, is preferable. Here, P represents the pitch length of the chiral structure, and c represents the concentration of the chiral agent. The pitch length of the chiral structure is a distance in the chiral axis direction until the angle of the molecular axis in the chiral structure gradually shifts as it advances along the plane and then returns to the original molecular axis direction again.

<Material for Forming Cholesteric Resin Layer (2): Polymerizable Composition>
Suitable materials for forming the cholesteric resin layer include a polymerizable composition containing a polymerizable liquid crystal compound, preferably a polymerizable composition containing a polymerizable liquid crystal compound, a polymerization initiator, and a chiral agent. Examples of a method for forming a cholesteric resin layer using this material include a coating liquid in which a polymerizable liquid crystal compound, a polymerization initiator, a chiral agent, and a surfactant, an alignment regulator, and the like are dissolved in a solvent as necessary. There is a method of laminating a film on a substrate, drying it, and polymerizing the dried film.

(Polymerizable liquid crystal compound contained in the polymerizable composition)
As the polymerizable liquid crystal compound, a rod-like liquid crystal compound is preferably used.
Examples of the rod-like liquid crystal compound include a compound represented by the formula (1).
R1-B1-A1-B3-M-B4-A2-B2-R2 Formula (1)
In addition, although A1 and A2 in Formula (1) are spacer groups so that it may mention later, B1 and B3 or B4 and B2 may couple | bond together directly, omitting this spacer group.

  In formula (1), R1 and R2 represent a polymerizable group. Specific examples of R1 and R2 that are polymerizable groups include (r-1) to (r-15) shown in Chemical Formula 1, but are not limited thereto.

  B1, B2, B3 and B4 each independently represent a single bond or a divalent linking group. Moreover, it is preferable that at least one of B3 and B4 is —O—CO—O—.

  A1 and A2 represent a spacer group having 1 to 20 carbon atoms. Examples of the spacer group include a polymethylene group and a polyoxymethylene group. The number of carbon atoms contained in the structural unit forming the spacer group is appropriately determined depending on the chemical structure of the mesogenic group. In general, in the case of a polymethylene group, the number of carbon atoms is 1-20, preferably 2-12, and in the case of a polyoxymethylene group, the number of carbon atoms is 1-10, preferably 1-3.

  M represents a mesogenic group. The material for forming the mesogen group M is not particularly limited, but azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines Alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used.

(Polymerization initiator contained in the polymerizable composition)
The polymerization initiator includes a thermal polymerization initiator and a photopolymerization initiator, and a photopolymerization initiator is preferred because the polymerization reaction is fast.
As photopolymerization initiators, polynuclear quinone compounds (US Pat. Nos. 3,046,127 and 2,951,758), oxadiazole compounds (US Pat. No. 4,212,970), α-carbonyl compounds (US Pat. No. 2,367,661, US Pat. No. 2,367,670) ), Acyloin ether (US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin compound (US Pat. No. 2,722,512), combination of triarylimidazole dimer and p-aminophenyl ketone (US Pat. No. 3,549,367) , Acridine and phenazine compounds (Japanese Patent Laid-Open No. 60-105667, US Pat. No. 4,239,850).

The amount of the polymerization initiator is preferably 1 to 10 parts by weight and more preferably 1 to 5 parts by weight with respect to 100 parts by weight of the polymerizable liquid crystal compound. When a photopolymerization initiator is used, it is preferable to use ultraviolet rays as irradiation light. The irradiation energy is preferably from ^{0.1mJ / cm 2 ~50J / cm 2} , further preferably ^{0.1mJ / cm 2 ~800mJ / cm 2} .
The irradiation method of ultraviolet rays is not particularly limited. Further, the amount of ultraviolet irradiation until the polymerization conversion rate reaches 100% is appropriately selected depending on the kind of the polymerizable liquid crystal compound.

(Chiral agent contained in the polymerizable composition)
As the chiral agent to be contained in the polymerizable composition, those described in JP-A No. 2003-66214, JP-A No. 2003-313187, US Pat. No. 6,468,444, WO 98/00428, and the like are appropriately used. However, a large HTP that is an index representing the efficiency of twisting the liquid crystal compound is preferable from the viewpoint of economy. HTP is represented by the formula: HTP = 1 / P · c. Here, P represents the pitch length of the chiral structure, and c represents the concentration of the chiral agent. In order to avoid an unintended change in the phase transition temperature due to the addition of the chiral agent, it is preferable to use a chiral agent that exhibits liquid crystallinity.

(Other compounding agents included in the polymerizable composition)
A surfactant can be used to adjust the surface tension of the coating solution and the film of the coating solution before polymerization. Particularly preferred is a nonionic surfactant, and an oligomer having a molecular weight of about several thousand is preferred. Examples of such a surfactant include KH-40 manufactured by Seimi Chemical Co., Ltd.

  The alignment modifier contained in the polymerizable composition is for controlling the alignment state of the air-side surface of the cholesteric resin layer formed on the substrate, and may also serve as the surfactant. Depending on the orientation state, resins are appropriately used. As such a resin, polyvinyl alcohol, polyvinyl butyral, or a modified product thereof is used, but not limited thereto.

  As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of the organic solvent include ketones, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, and ethers. In particular, ketones are preferable in consideration of environmental load. Two or more organic solvents may be used in combination.

  In order to laminate the coating liquid into a film, a known method such as an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, a die coating method, or the like can be performed.

  The cholesteric resin layer used in the present invention is preferably a non-liquid crystalline resin layer. This is because the cholesteric regularity does not change depending on the ambient temperature, electric field, or the like when it is non-liquid crystalline. The non-liquid crystalline cholesteric resin layer can be obtained by selecting a polymerizable composition containing a polymerizable liquid crystal compound having two or more polymerizable groups and polymerizing it. By the polymerizable liquid crystal compound having two or more polymerizable groups, a relatively rigid cross-linked structure is introduced into the cholesteric resin, and a resin that does not produce liquid crystallinity is obtained.

When light is incident on the resin layer having cholesteric regularity, only the left-handed or right-handed circularly polarized light in the specific wavelength region is reflected. Light other than the reflected circularly polarized light is transmitted. The specific wavelength region where the circularly polarized light is reflected is called a selective reflection band.
As shown in FIG. 3, the white light incident on the cholesteric resin layer of the circularly polarized light reflector at an incident angle θ ₁ is refracted at the surface of the cholesteric resin layer and passes through the cholesteric resin layer at a refractive angle θ ₂ , and has a wavelength λ One circularly polarized light is reflected at a reflection angle θ ₂ by a cholesteric resin layer (a layer denoted as P2 in FIG. 3) having a pitch length P corresponding to, and is refracted at the surface of the cholesteric resin layer to be emitted at an emission angle θ ₁ . To do. Refraction is performed according to Snell's law.

When the helical axis 4 representing the rotation axis when the molecular axis is twisted in the chiral structure and the normal line of the cholesteric resin layer are parallel, the pitch length P of the chiral structure and the wavelength λ of the circularly polarized light to be reflected are (2) and formula (3).
λ _c = n × P × cos θ ₂ formula (2)
_{n o × P × cosθ 2 ≦} λ ≦ n e × P × cosθ 2 Equation (3)
Wherein, n _o represents the minor axis direction of the refractive index of the rod-like liquid crystal compound, n _e represents the refractive index of the long axis of the rod-like liquid crystal _{compound, n = (n e + n} o) / 2, P is chiral structure Represents the pitch length.

That is, the center wavelength λ _c of the selective reflection band depends on the pitch length P of the chiral structure in the cholesteric resin layer. By changing the pitch length of this chiral structure, the selected wavelength band can be changed. Further, the reflectance is proportional to the number of stacked chiral structures. In order to adjust the reflectance, the number of layers of the chiral structure, that is, the thickness is adjusted. Since the width of the selective reflection band is dependent on the difference between n _o and n _e, selects the manufacturing easy suitable liquid crystal compounds.

A polarizing plate can be obtained by laminating the optical element of the present invention with a linear polarizer. Moreover, a phase difference plate can be obtained by laminating the optical element of the present invention with a phase difference element. By laminating with a linear polarizer and a retardation element, an air layer between the elements is eliminated, and unnecessary reflection and interference at the interface can be reduced. In addition, a cholesteric resin layer can be directly laminated | stacked on a linear polarizer or a phase difference element by using a linear polarizer or a phase difference element instead of the transparent base material which laminates | stacks the said cholesteric resin layer.
In addition, an illumination device, a polarized illumination device, and a liquid crystal display device can be obtained by combining the optical element of the present invention with another optical element.

  The linear polarizer transmits one of two linearly polarized lights that intersect at right angles. For example, a hydrophilic polymer film such as a polyvinyl alcohol film or an ethylene vinyl acetate partially saponified film adsorbed a dichroic substance such as iodine or a dichroic dye and uniaxially stretched, the hydrophilic polymer film Examples include uniaxially stretched and dichroic substances adsorbed, and polyene oriented films such as polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Other examples include a polarizer having a function of separating polarized light such as grid polarizer and multilayer polarizer into reflected light and transmitted light. Of these, a polarizer containing polyvinyl alcohol is preferred.

The degree of polarization of the linear polarizer used in the present invention is not particularly limited, but is preferably 98% or more, more preferably 99% or more. The average thickness of the linear polarizer is preferably 5 μm to 80 μm.
The polarization transmission axes of a pair of linear polarizers (hereinafter, the pair of linear polarizers may be referred to as linear polarizer X and linear polarizer Y (analyzer) separately) are parallel or perpendicular to each other. In this manner, the liquid crystal cells are arranged therebetween. The linear polarizer may change its polarization performance due to moisture absorption. In order to prevent this, a protective film is usually bonded to both sides of the linear polarizer X or the analyzer. The protective film bonded to the analyzer may be provided with an antireflection layer, an antifouling layer, an antiglare layer, and the like.

  The phase difference element is an element that can change the phase of light. For example, what stretched and orientated the polymer film is mentioned. The retardation element can be used as the protective film bonded to a linear polarizer.

  In the illumination device of the present invention, a light reflecting element, a light source, a light diffusing element, and an optical element of the present invention are arranged in this order. In the polarized illumination device of the present invention, the light reflecting element, the light source, the light diffusing element, and the polarizing plate of the present invention are arranged in this order. The polarizing plate is preferably arranged so that the optical element of the present invention is closer to the light diffusing element than the linear polarizer. In addition, a prism sheet, a reflective polarizer, a quarter wavelength plate, a half wavelength plate, a viewing angle compensation film, an antireflection film, an antiglare film, and the like may be disposed.

  The light reflecting element is an element that can reflect light. Specifically, a reflecting plate provided with a reflective metal film or a white film can be used. The light source used in the present invention only needs to emit white light, and is selected from a cold cathode tube, a hot cathode tube, a light emitting diode, and electroluminescence. The light diffusing element is an element that scatters light into diffused light to eliminate the in-plane distribution of luminance. Specifically, a light diffusing material such as silicone beads dispersed in a transparent substrate (sometimes referred to as a light diffusing plate), or a light diffusing material applied to the surface of a transparent substrate (referred to as a light diffusing sheet) In some cases).

  The liquid crystal display device of the present invention includes the optical element of the present invention. Furthermore, the polarizing plate, the retardation plate, the illumination device, or the polarization illumination device is provided. In particular, the light source, the optical element of the present invention, the linear polarizer X, the liquid crystal cell, and the linear polarizer Y are preferably arranged in this order. In addition, reflective elements, light guide plates, light diffusing elements, prism sheets, reflective polarizers, quarter wavelength plates, half wavelength plates, viewing angle compensation films, antireflection films, antiglare films, etc. are arranged. May be.

A liquid crystal cell is filled with a liquid crystal substance between two glass substrates provided with transparent electrodes facing each other with a gap of several μm, and a voltage is applied to this electrode to change the alignment state of the liquid crystal and pass through this. The amount of light to be controlled is controlled.
The liquid crystal cell is classified according to a method (operation mode) for changing the alignment state of the liquid crystal substance. For example, a TN (Twisted Nematic) type liquid crystal cell, a STN (Super Twisted Nematic) type liquid crystal cell, or a HAN (Hybrid Alignment Nematic) type. Liquid crystal cells, IPS (In Plane Switching) type liquid crystal cells, VA (Vertical Alignment) type liquid crystal cells, MVA (Multi-domain Vertical Alignment type liquid crystal cells, OCB (Optical Compensated Bend) type liquid crystal cells, etc.

FIG. 4 is a diagram showing a configuration of an example of the liquid crystal display device of the present invention. As shown in FIG. 4, the reflecting plate 20, the cold cathode tube 19, the light diffusing plate 18, the circularly polarizing reflecting plate 17, the linear polarizer X, the liquid crystal cell 12, and the linear polarizer Y are arranged in this order. When the light from the light source is incident on the circularly polarized light reflector with an incident angle of 0 degree, the selective reflection band of the optical element is in the infrared region, so that each of blue, green, and red light is transmitted as it is. As the incident angle increases, the selective reflection band shifts to the short wavelength side, and the red light is partially reflected, and the light transmittance of the red light decreases.
At an incident angle of 60 degrees, the average transmittance of light having a wavelength of 600 nm to 700 nm is adjusted to 40% or more and 80% or less. Further, the average reflectance of light having a wavelength of 600 nm to 700 nm is adjusted.
As a result, the balance of the red light with respect to the blue light and the green light is adjusted, and an image with the same color balance can be displayed in the front and oblique observation.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not restrict | limited to the following Example. Parts and% are based on weight unless otherwise specified.

<Resin 1>
A mixture having 100 parts by weight of methyl methacrylate (hereinafter referred to as MMA), 15 parts by weight of N-cyclohexylmaleimide, 15 parts by weight of styrene, 0.05 part by weight of azo-t-butane, and 200 parts by weight of toluene was prepared. Thereafter, the mixture was charged into the polymerization tank while being filtered through a polytetrafluoroethylene filter having a pore diameter of 0.05 μm. In the polymerization tank, solution polymerization was performed at 130 ° C. under nitrogen pressure for 16 hours, and then gradually heated, and finally held at 180 ° C. for 16 hours to decompose the polymerization initiator. The temperature was further raised and maintained at 230 ° C. for 1 hour, and then subjected to a demonomer step under nitrogen pressure to remove unreacted monomers and the like to obtain Resin 1.

The Vicat softening point of Resin 1 was 128 ° C. and the flexural modulus was 3300 MPa.
Moreover, the ratio (weight ratio) of each structural unit of the resin 1 was MMA / N-cyclohexylmaleimide / styrene = 77/11/12 as a result of measurement by ¹ H-NMR spectrum.
The tensile fracture strain of Resin 1 was 5%. In the present invention, the tensile fracture strain of the resin is a test piece prepared in accordance with JIS K 6717-2. When the sample breaks without yielding, tensile fracture strain, when breaking after yielding, The measured value of the nominal strain at the time of tensile fracture was taken as the tensile fracture strain.

<Creation of multilayer structure acrylic rubber particle A>
Into a reactor equipped with a stirrer and a condenser, 6860 ml of distilled water and 20 g of sodium dioctylsulfosuccinate as an emulsifier were added, and the temperature was raised to 75 ° C. in a nitrogen atmosphere while stirring, so that there was no influence of oxygen. An emulsifier-containing distilled water was obtained.
In this distilled water containing an emulsifier, a mixed solution comprising MMA 220 g, n-butyl acrylate 33 g, allyl methacrylate (hereinafter referred to as ALMA) 0.8 g and diisopropylbenzene hydroperoxide (hereinafter referred to as PBP) 0.2 g. In addition, it was held at 80 ° C. for 15 minutes to polymerize the first layer.

  Next, a mixed liquid consisting of 1270 g of n-butyl acrylate, 320 g of styrene, 20 g of diethylene glycol acrylate, 13.0 g of ALMA and 1.6 g of PBP was continuously added for 1 hour in the reaction liquid after the completion of the first layer polymerization. The solution was added dropwise, and after completion of the addition, the reaction was further allowed to proceed for 40 minutes to polymerize the second layer.

Next, as a polymerization for the third layer, a mixed solution comprising 340 g of MMA, 2.0 g of n-butyl acrylate, 0.3 g of PBP and 0.1 g of n-octyl mercaptan in the reaction solution after the reaction of the second layer is completed. Then, a mixed solution consisting of 340 g of MMA, 2.0 g of n-butyl acrylate, 0.3 g of PBP and 1.0 g of n-octyl mercaptan was added. Thereafter, the temperature was raised to 95 ° C. and held for 30 minutes to obtain a latex of multilayer structure acrylic rubber particles. A small amount of latex was sampled and the average particle size was determined by the absorbance method and found to be 200 nm.
The obtained latex was put into a 0.5% aluminum chloride aqueous solution to agglomerate the polymer, washed with warm water 5 times, and dried to obtain multilayer acrylic rubber particles A.

<Resin 2>
After mixing 80 parts by weight of PMMA resin “Delpet 80NH” (product name, manufactured by Asahi Kasei Chemicals; methyl methacrylate / methyl acrylate copolymer) with 20 parts by weight of multilayer acrylic rubber particles A, a twin screw extruder was used. And melt kneaded at 260 ° C. to obtain Resin 2.
Resin 2 had a Vicat softening point of 102 ° C. and a flexural modulus of 2500 MPa.
The tensile fracture strain of Resin 2 was 20%.

<Resin 3>
After mixing 20 parts by weight of the above resin 1 and 80 parts by weight of the multilayer acrylic rubber particles A, a resin 3 was obtained by melt-kneading at 260 ° C. using a twin screw extruder.
Resin 3 had a Vicat softening point of 90 ° C. and a flexural modulus of 1500 MPa.
The tensile fracture strain of Resin 3 was 55%.

<Transparent substrate 1>
Using a two-layer, two-layer multi-layer coextrusion apparatus, resin 1 and resin 2 are formed into a sheet shape from a T-die having a width of 700 mm and a slit gap of 1 mm at extrusion rates of 20 kg / hr and 20 kg / hr, respectively. Then, the sheet was cooled while being pulled with a metal roll at 100 ° C. at a speed of about 10 m / min, to obtain a laminated film 1 in which resin 1 layer 40 μm thickness-resin 2 layer 40 μm thickness was laminated. The resin 1 layer was in contact with the metal roll surface, and the resin 2 layer was discharged so as not to contact the metal roll. The thickness of the sheet immediately after being discharged from the T-shaped die is about 1 mm, and the sheet discharged from the T-shaped die is finally stretched 10 times or more. The physical properties of the transparent substrate 1 are shown in Table 1.

<Transparent substrate 2>
Using a single layer extrusion apparatus, resin 1 was discharged in a sheet form from a T-shaped die having a width of 700 mm and a slit gap of 1 mm at an extrusion rate of 40 kg / hr, and the sheet was discharged with a metal roll at 100 ° C. to 10 m / Cooling while taking up at a speed of about minutes, a transparent substrate 2 having a thickness of 80 μm was obtained. The physical properties of the transparent substrate 2 are shown in Table 1.

<Transparent substrate 3>
Using a single layer extrusion apparatus, the resin 3 was discharged in the form of a sheet from a T-type die having a width of 700 mm and a slit gap of 1 mm at an extrusion rate of 40 kg / hr, and the sheet was discharged with a metal roll at 100 ° C. to 10 m / Cooling while taking up at a speed of about minutes, a transparent substrate 3 having a thickness of 80 μm was obtained. The physical properties of the transparent substrate 3 are shown in Table 1.

<Transparent substrate 4>
The transparent substrate 4 was a triacetyl cellulose film “KC8UX2M” (product name, manufactured by Konica Minolta, thickness 80 μm; tensile fracture strain 25%; indicated as “TAC” in the table). The physical properties of the transparent substrate 4 are shown in Table 1.

（透明基材の透湿度）
４０℃、９２％ＲＨの環境下に２４時間放置する試験条件で、ＪＩＳ Ｚ ０２０８に記載のカップ法に準じた方法で測定した。透湿度の単位はｇ・ｍ^-2・ｄａｙ^-1である。

(Moisture permeability of transparent substrate)
The measurement was performed by a method according to the cup method described in JIS Z 0208 under the test conditions of leaving for 24 hours in an environment of 40 ° C. and 92% RH. The unit of moisture permeability is g · m ⁻² · day ⁻¹ .

(Re and Rth of transparent substrate)
High-speed spectroscopic ellipsometer [J. A. Using Woollam, M-2000U], Re and Rth values at a wavelength of 550 nm were determined.

(Photoelastic coefficient of transparent substrate)
While applying a load to the transparent substrate in the range of 50 to 150 g, the retardation in the film plane is measured, and this is divided by the thickness of the film to obtain a birefringence value Δn. Δn was obtained while changing the load, a load-Δn curve was created, and the slope was taken as the photoelastic coefficient.

(Surface roughness of transparent substrate)
The average roughness (Ra) was measured using a color 3D laser microscope (manufactured by Keyence Corporation, product name “VK-9500”) in accordance with JIS B 0601: 2001.

Example 1
Plasma treatment was performed on both surfaces of the transparent substrate 1 so that the wetting index was 56 dyne / cm. A composition for alignment film consisting of 5 parts of polyvinyl alcohol and 95 parts of water was applied to one side (A layer (resin 1) side) of the transparent substrate 1 and dried to form a film. Next, the film was rubbed with a felt roll in a direction parallel to the longitudinal direction of the transparent substrate 1 to obtain an alignment film having an average thickness of 0.1 μm.

  Nematic liquid crystal compound (BASF, trade name “LC242”) 100 parts, chiral agent (BASF, trade name “LC756”) 3.60 parts, photopolymerization initiator (Ciba Specialty Chemicals, product) (Name “Irgacure 907”) 3.21 parts and surfactant (trade name “KH-40”, manufactured by Seimi Chemical Co., Ltd.) 0.11 parts were dissolved in 160 parts of methyl ethyl ketone, and a CD / polyethylene made of polyfluoroethylene having a pore diameter of 2 μm. A liquid crystal coating solution was prepared by filtering using an X syringe filter.

On the alignment film, a liquid crystal coating solution was applied so that the dry thickness was 1.85 μm, and dried at 100 ° C. for 5 minutes. Subsequently, ultraviolet rays were irradiated at 150 mJ / cm ² to form a cholesteric resin layer, and a circularly polarized light reflecting plate was obtained.
The collimated white light having the emission spectrum shown in FIG. 1 is incident on the circularly polarizing plate at an incident angle of 0 degree, and the light transmittance is measured by a spectroscope (trade name “S-2600” manufactured by Soma Optical Co., Ltd.). Measured with The selective reflection band at an incident angle of 0 degree was a wavelength of 700 to 820 nm, and the average transmittance of light having a wavelength of 600 nm to 700 nm at an incident angle of 0 degree was 89%.
Next, collimated white light (light having a wavelength λ _R1 having a maximum emission intensity in the wavelength band of 600 nm to 700 nm having a wavelength λ _R1 of 630 nm) was incident at an incident angle of 60 degrees, and the light transmittance was measured in the same manner. The average transmittance of light having a wavelength of 600 nm to 700 nm at an incident angle of 60 degrees was 71%. Other physical properties are shown in Table 2.

(Flexibility of circularly polarized light reflector)
A circularly polarized light reflector was punched into 1 cm × 5 cm to obtain a film piece. The obtained film piece was wound around a 3 mmφ steel rod, and it was tested whether or not the wound film piece was broken at the bar. A total of 10 film pieces were tested, and the flexibility was expressed by the following index according to the number of broken film pieces.
○: No broken film pieces △: One broken film piece ×: Two or more broken film pieces

(Evaluation of curling property of circularly polarized light reflector)
The circularly polarized light reflector was cut into a size of 10 cm × 10 cm, placed on a horizontal plate, the curled state was observed, and the curl property was evaluated according to the following criteria.
A: No curling is observed and good. B: Almost inconspicuous but slightly curled.
X: Curl is clearly recognized and there is a problem in practical use.

(Creating a polarizer)
The polyvinyl alcohol film was uniaxially stretched 2.5 times, immersed in an aqueous solution at 30 ° C. containing 0.2 g / L of iodine and 60 g / L of potassium iodide, and then 70 g / L of boric acid and potassium iodide. It was immersed in an aqueous solution containing 30 g / L and simultaneously uniaxially stretched 6.0 times and held for 5 minutes. Finally, it was dried at room temperature for 24 hours, with an average thickness of 30 μm, and a degree of polarization. 99.95% of the polarizer P was obtained.

(Creation of incident side polarizing plate X)
A polyvinyl alcohol-based adhesive is applied to both sides of the polarizer P, and the surface (the B layer (resin 2) side) where the cholesteric resin layer of the circularly polarizing reflector is not formed is superimposed on one surface of the polarizer P The B layer (resin 2) side of the transparent substrate 1 was overlapped on the other surface of the child P, and bonded by a roll-to-roll method to obtain an incident side polarizing plate X having a circularly polarized light reflection function.

(Creation of output side polarizing plate Y)
Applying 25 mL / m ² of a 1.5 mol / L isopropyl alcohol solution of potassium hydroxide to one side of a 80 μm thick triacetyl cellulose film (“KC8UX2M” (product name, manufactured by Konica Minolta)) Dry at 25 ° C. for 5 seconds. Next, the film was washed with running water for 10 seconds, and finally the surface of the film was dried by blowing air at 25 ° C. to obtain a protective film in which only one surface of the triacetylcellulose film was saponified.
A polyvinyl alcohol-based adhesive was applied to both sides of the polarizer P, the surfaces on which the saponification treatment of the protective film was applied were overlapped on both sides of the polarizer P, and bonded to each other by a roll-to-roll method to obtain an output-side polarizing plate Y. .

  The incident side polarizing plate X and the outgoing side polarizing plate Y were incorporated into a liquid crystal display device having the configuration shown in FIG. The evaluation results of the liquid crystal display device are shown in Table 3.

(Chromaticity change)
The liquid crystal display device was visually observed from an angle of 0 to 80 degrees in the left-right direction, and evaluated according to the following criteria: ○: Almost no change in chromaticity was observed in the range of 0 to 80 degrees in the left-right direction.
X: Reddish at 60 degrees or more in the left-right direction.

(Uneven color of display device)
The liquid crystal display device was displayed in white, and the color unevenness was visually observed at an incident angle of 60 degrees and evaluated according to the following criteria.
○: Uneven color is not visible ×: Uneven color is conspicuous

(Frame failure)
The liquid crystal display device was left in a constant temperature bath at a temperature of 60 ° C. and a humidity of 90% for 500 hours. The liquid crystal display device is displayed in black and the screen is visually observed.
○: No light leakage is observed over the entire surface.
X: Light leakage is observed at the end.

Comparative Example 1
The light transmittance of the transparent substrate 1 was measured in the same manner as the light transmittance of the circularly polarized light reflector of Example 1. The selective reflection band was not confirmed, and the average transmittance of light having a wavelength of 600 nm to 700 nm was 90% when collimated white light was incident at an incident angle of 0 degree. When the collimated white light was incident at an incident angle of 60 degrees, the average transmittance of light having a wavelength of 600 nm to 700 nm was 82%. Other physical properties are shown in Table 2.
4 except that the transparent substrate 1 was used in place of the circularly polarized light reflector used in Example 1, and the evaluation was incorporated into a liquid crystal display device having the configuration shown in FIG. It was reddish at 60 degrees or more in the left-right direction. The evaluation results of the liquid crystal display device are shown in Table 3.

Example 2
Plasma treatment was performed on both surfaces of the transparent substrate 1 so that the wetting index was 56 dyne / cm. A composition for alignment film consisting of 5 parts of polyvinyl alcohol and 95 parts of water was applied to one side (A layer (resin 1) side) of the transparent substrate 1 and dried to form a film. Next, the film was rubbed with a felt roll in a direction parallel to the longitudinal direction of the transparent substrate 1 to obtain an alignment film having an average thickness of 0.1 μm.

  Nematic liquid crystal compound (BASF, trade name “LC242”) 100 parts, chiral agent (BASF, trade name “LC756”) 3.46 parts, photopolymerization initiator (Ciba Specialty Chemicals, product) (Name “Irgacure 907”) 3.21 parts and surfactant (trade name “KH-40”, manufactured by Seimi Chemical Co., Ltd.) 0.11 parts were dissolved in 160 parts of methyl ethyl ketone, and a CD / polyethylene made of polyfluoroethylene having a pore diameter of 2 μm. A liquid crystal coating solution was prepared by filtering using an X syringe filter.

On the alignment film, the liquid crystal coating solution was applied so that the dry thickness was 1.88 μm, and dried at 100 ° C. for 5 minutes. Subsequently, ultraviolet rays were irradiated at 150 mJ / cm ² to form a cholesteric resin layer, and a circularly polarized light reflecting plate was obtained.
When the cross section of the circularly polarized light reflector was observed with an SEM, the helical pitch of the cholesteric resin layer was 470 nm. Other physical properties are shown in Table 2.

The collimated white light having the emission spectrum shown in FIG. 1 is incident on this circularly polarized light reflector at an incident angle of 0 degree, and the light reflectance is measured with a spectroscope (product name “S-2600” manufactured by Soma Optics). It was measured. The selective reflection band was from 690 nm to 850 nm, and the maximum reflectance was 24% at a wavelength of 760 nm.
Next, collimated white light was incident at an incident angle of 60 degrees, and the light reflectance was measured in the same manner. The reflectance at a wavelength of 760 nm was 20%, and the reflectance at a wavelength of 760 nm at an incident angle of 0 degrees was 83%. The average reflectance of light having a wavelength of 600 nm to 700 nm at an incident angle of 60 degrees was 29%.

  The circularly polarized light reflector was incorporated into a liquid crystal display device having the structure shown in FIG. Almost no change in chromaticity was observed in the range of 0 to 80 degrees on the left and right. The characteristics of the liquid crystal display device are shown in Table 3.

Comparative Example 2
Plasma treatment was performed on both surfaces of the transparent substrate 1 so that the wetting index was 56 dyne / cm. A composition for alignment film comprising 5 parts of polyvinyl alcohol and 95 parts of water was applied to one side (A layer (resin 1) side) of the transparent substrate 1 and dried to form a film. Next, the film was rubbed with a felt roll in a direction parallel to the longitudinal direction of the transparent substrate 1 to obtain an alignment film having an average thickness of 0.1 μm.

  Nematic liquid crystal compound (BASF, trade name “LC242”) 100 parts, chiral agent (BASF, trade name “LC756”) 4.98 parts, photopolymerization initiator (Ciba Specialty Chemicals, product) (Name "Irgacure 907") 3.24 parts and 0.12 parts of a surfactant (trade name "KH-40" manufactured by Seimi Chemical Co., Ltd.) are dissolved in 162 parts of methyl ethyl ketone, and a CD / polyethylene made of polyfluoroethylene having a pore diameter of 2 μm is used. A liquid crystal coating solution was prepared by filtering using an X syringe filter.

On the alignment film, a liquid crystal coating solution was applied so that the dry thickness was 1.50 μm, and dried at 100 ° C. for 5 minutes. Subsequently, ultraviolet rays were irradiated at 150 mJ / cm ² to form a cholesteric resin layer, and a circularly polarized light reflecting plate was obtained.
When the cross section of the circularly polarized light reflector was observed with an SEM, the helical pitch of the cholesteric resin layer was 365 nm. Other physical properties are shown in Table 2.

  Further, the light reflectance was measured in the same manner as in Example 2. The selective reflection band was from 530 nm to 630 nm, and the maximum reflectance was 28% at a wavelength of 555 nm. When collimated white light was incident at an incident angle of 60 degrees, the reflectance at a wavelength of 555 nm was 12%, and 43% of the reflectance at a wavelength of 555 nm at an incident angle of 0 degrees. The average reflectance of light having a wavelength of 600 nm to 700 nm at an incident angle of 60 degrees was 18%.

  Instead of the circularly polarized light reflecting plate used in Example 2, the circularly polarized light reflecting plate was used, and the liquid crystal display device having the configuration shown in FIG. Yellowish green was exhibited at 60 degrees or more in the left-right direction. The characteristics of the liquid crystal display device are shown in Table 3.

Comparative Example 3
A circularly polarized light reflector was obtained in the same manner as in Example 1 except that the transparent substrate 1 was replaced with the transparent substrate 2. The collimated white light having the emission spectrum shown in FIG. 1 is incident on the circularly polarizing plate at an incident angle of 0 degree, and the light transmittance is measured by a spectroscope (trade name “S-2600” manufactured by Soma Optical Co., Ltd.). Measured with The selective reflection band at an incident angle of 0 degree was a wavelength of 700 to 820 nm. Table 2 shows the physical properties of the circularly polarizing plate, and Table 3 shows the characteristics of the liquid crystal display device.

Comparative Example 4
A circularly polarized light reflector was obtained in the same manner as in Example 1 except that the transparent substrate 1 was replaced with the transparent substrate 3. The collimated white light having the emission spectrum shown in FIG. 1 is incident on the circularly polarizing plate at an incident angle of 0 degree, and the light transmittance is measured by a spectroscope (trade name “S-2600” manufactured by Soma Optical Co., Ltd.). Measured with The selective reflection band at an incident angle of 0 degree was a wavelength of 700 to 820 nm. The physical properties of the transparent substrate 3 are shown in Table 1. Table 2 shows the physical properties of the circularly polarizing plate, and Table 3 shows the characteristics of the liquid crystal display device.

Comparative Example 5
A circularly polarized light reflecting plate was obtained in the same manner as in Example 1 except that the transparent substrate 1 was replaced with a TAC film (transparent substrate 4). The collimated white light having the emission spectrum shown in FIG. 1 is incident on the circularly polarizing plate at an incident angle of 0 degree, and the light transmittance is measured by a spectroscope (trade name “S-2600” manufactured by Soma Optical Co., Ltd.). Measured with The selective reflection band at an incident angle of 0 degree was a wavelength of 700 to 820 nm. The physical properties of the transparent substrate 4 are shown in Table 1. Table 2 shows the physical properties of the circularly polarizing plate, and Table 3 shows the characteristics of the liquid crystal display device.

Claims (15)

An optical element for use in an apparatus equipped with a light source, comprising a transparent substrate and a selective reflection layer formed on the transparent substrate,
The transparent substrate has a Vicat softening point of 120 ° C. or higher and a layer A formed of a methacrylic resin A containing a methyl methacrylate unit of 70% by weight or more;
It was formed of a resin composition containing methacrylic resin B containing 70% by weight or more of methyl methacrylate units and elastic particles, having a Vicat softening point of 95 ° C. to 115 ° C. and a tensile fracture strain of 15% or more. Layer B,
Each has at least one layer,
Layer B consists of a laminate that is at least one outermost layer,
An optical element in which a lower limit λ _L of a wavelength band for reflecting a light beam having an incident angle of 0 degrees is longer than a wavelength λ _{R1 of} light that exhibits a maximum emission intensity in a wavelength band of 600 nm to 700 nm among light emitted from a light source.   The optical element according to claim 1, wherein the transparent substrate is a laminate having an average thickness of less than 100 μm, wherein the layer B is laminated on both surfaces of the layer A.   The optical element according to claim 1, wherein an average transmittance of light having a wavelength of 600 nm to 700 nm at an incident angle of 60 degrees is 40% or more and 80% or less. The average transmittance of light having a wavelength of 600 nm to 700 nm at an incident angle of 0 degree is 60% or more,
2. The optical element according to claim 1, wherein an average transmittance of light having a wavelength of 600 nm to 700 nm at an incident angle of 0 degrees is larger than an average transmittance of light having a wavelength of from 600 nm to 700 nm at an incident angle of 60 degrees.   The optical element according to claim 1, wherein an average transmittance of light having a wavelength of 600 nm to 700 nm at an incident angle of 60 degrees is 50% or more and 80% or less.   The optical element according to claim 1, wherein the selective reflection layer includes a resin layer having cholesteric regularity. The selective reflection layer includes a resin layer having cholesteric regularity,
2. The optical element according to claim 1, wherein the chiral pitch of the resin layer is 400 nm or more, and the maximum reflectance in a selective reflection band at an incident angle of 0 degree is 10% or more and 40% or less.   When light having a wavelength exhibiting the maximum reflectance in the selective reflection band at an incident angle of 0 degrees is incident at an incident angle of 60 degrees, the reflectance is 50% or more and 90% or less of the maximum reflectance at the incident angle of 0 degrees. The optical element according to claim 1.   The optical element according to claim 1, wherein an average reflectance of light having a wavelength of 600 nm to 700 nm at an incident angle of 60 degrees is 20% or more and 60% or less.   A polarizing plate in which the optical element according to claim 1 and a linear polarizer are laminated.   A retardation plate in which the optical element according to claim 1 and a retardation element are laminated.   A lighting device in which a light reflecting element, a light source, a light diffusing element, and the optical element according to claim 1 are arranged in this order.   A polarized light illumination device in which a light reflection element, a light source, a light diffusion element, and the polarizing plate according to claim 10 are arranged in this order.   A liquid crystal display device in which a light reflecting element, a light source, a light diffusing element, the optical element according to claim 1, a linear polarizer, a liquid crystal panel, and an analyzer are arranged in this order.   The liquid crystal display device according to claim 14, wherein the light source is selected from a cold cathode tube, a hot cathode tube, a light emitting diode, and electroluminescence.

Images