JP2008197224A - 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 contains a thermoplastic resin and an ultraviolet absorbent unevenly distributed in the central part in the thickness direction and has <100 μm average thickness. 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 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, the present invention relates to an optical element, a polarizing plate, a retardation plate, an illuminating device, and a liquid crystal display device used for displaying an image having the same color balance in front and oblique observations.

  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 which 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 degree (that is, the phase is delayed by one 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. Therefore, 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, the polarizing plate used for a liquid crystal display device etc. is a laminated body which consists of a dichroic polarizer and a protective film. As the dichroic polarizer constituting the polarizing plate, a film obtained by adsorbing iodine or a dichroic dye on a film obtained by forming a film of polyvinyl alcohol by a solution casting method and stretching in a boric acid solution is usually used. ing.

  A triacetyl cellulose (TAC) film is widely used as a protective film constituting the polarizing plate. However, the triacetyl cellulose film has insufficient heat resistance and moisture resistance, and when used for a long time in a high temperature or high humidity atmosphere, the degree of polarization is significantly reduced, the polarizer and the protective film are separated, TAC Transparency may decrease due to hydrolysis. As a result, the performance of the polarizing plate is degraded, and when used in a liquid crystal display (LCD), the image quality is degraded.

Patent Document 3 proposes a polarizing plate in which a laminated film made of a norbornene-based resin is laminated on a polarizer as a protective film. This protective film is composed of a three-layer laminate in which surface layers are laminated on both sides of the intermediate layer, and at least the intermediate layer contains an ultraviolet absorber, and the concentration of the ultraviolet absorber in the intermediate layer is higher than that of both surface layers. Is set. According to Patent Document 3, it is possible to protect a liquid crystal or a polarizer from ultraviolet rays by imparting an ultraviolet absorptivity to the norbornene-based resin, and by reducing the concentration of the ultraviolet absorber in one or both surface layers, It is said that molding without roll contamination becomes possible at the time of molding.
Japanese Patent Laid-Open No. 2002-249600

  In addition, display devices, particularly liquid crystal display devices, are used as information display means for various electronic devices such as televisions, personal computers, portable information terminals, and mobile phones. In many cases, various stresses are applied to the surface of the display device due to unexpected mechanical external force or exposure to sunlight for a long time. In a display device including a conventional polarizing plate with a protective layer laminated, a large number of scratches are caused on the display surface with use, resulting in a situation where visibility and appearance are impaired.

  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. . Specifically, an object is to provide an optical element, a polarizing plate, a retardation plate, an illumination device, and a liquid crystal display device in which characteristics such as transmittance appropriately change according to an incident angle. Another object of the present invention is to provide an optical element that is excellent in visibility, weather resistance, ultraviolet light transmission preventing effect, adhesion between the polarizer and the protective layer, and can maintain a high degree of polarization even under high temperature and high humidity. is there.

  When the liquid crystal display device disclosed in the above-mentioned patent document is observed from the front, the present inventors can obtain an image in which blue, green and red are well balanced. I noticed that the image was bluish when displayed. 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.

Therefore, the present inventor has obtained a band having a wavelength longer than the wavelength λ _{R1 of} light, which is obtained by forming a selective reflection layer on a transparent substrate, and exhibits the maximum emission intensity in the wavelength range of 600 nm to 700 nm of the light source. An optical element having a band that reflects light having an incident angle of 0 degrees in (λ _{L to} λ _H ) is provided in an illumination device of a liquid crystal display device, and an image having the same color balance in front and oblique observations. It was found that can be displayed. Based on these findings, the present inventor further studied, and when the transparent base material used is one in which the ultraviolet absorber is unevenly distributed in the central portion in the thickness direction and the average thickness is less than 100 μm, It has been found that a liquid crystal display device excellent in weather resistance can be obtained, and the present invention has been completed.

Thus, the present invention includes the following.
(1) An optical element for use in an apparatus including a light source, having a transparent base material and a selective reflection layer formed on the transparent base material,
The transparent base material comprises a thermoplastic resin, the ultraviolet absorber is unevenly distributed in the central portion in the thickness direction, and the average thickness is less than 100 μm,
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 transparent substrate is
An intermediate layer 1 comprising an ultraviolet absorber and a thermoplastic resin;
Glass transition temperature (Tg) laminated on one surface of the intermediate layer 1 is a surface layer 2 made of an acrylic resin having a temperature of 100 ° C. or higher, and glass transition temperature (Tg) laminated on the other surface of the intermediate layer 1 ) Surface layer 3 made of acrylic resin at 100 ° C. or higher
Said optical element which consists of a laminated body which has.
(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, 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 optical element, 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.
(6) The optical element, 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 optical element, 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.
(8) The reflectance 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 is 50% to 90% of the maximum reflectance at the incident angle of 0 degrees. The optical element.
(9) The optical element, 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, 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.

  The optical element according to the preferred embodiment of the present invention transmits light having a wavelength of 600 nm to 700 nm incident at an incident angle of 60 degrees in the range of 40% to 80%. The color balance of blue, green and red when observed 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.

  The optical element of one embodiment of the present invention has a cholesteric resin layer having a chiral pitch of 400 nm or more, and has a maximum reflectance in the selective reflection band at an incident angle of 0 degree of 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.

  Since the optical element of the present invention has the above characteristics and is excellent in weather resistance against light such as ultraviolet rays, it can provide a liquid crystal display device in which image quality is unlikely to deteriorate.

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. FIG. 6 illustrates a structure 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 comprises a transparent base material comprising a thermoplastic resin, the ultraviolet absorber is unevenly distributed in the central portion in the thickness direction, and the average thickness is less than 100 μm, and the transparent base material. A selective reflection layer formed,
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)
As for the transparent base material which comprises the optical element of this invention, the ultraviolet absorber is unevenly distributed in the thickness direction center part. The transparent base material has an overall average thickness of less than 100 μm.
The material which comprises a transparent base material will not be specifically limited if it is an optically transparent thermoplastic resin. Transparent thermoplastic resins include alicyclic structure-containing polymer resins, chain olefin polymers such as polyethylene and polypropylene, triacetyl cellulose, polyvinyl alcohol, polyimide, polyarylate, polyester, polycarbonate, polysulfone, polyethersulfone, Amorphous polyolefin, a modified acrylic polymer, an epoxy resin, etc. are mentioned. These can be used alone or in combination of two or more. Among these, acrylic resins are preferable from the viewpoints of transparency, low hygroscopicity, dimensional stability, lightness, and the like.

A suitable transparent substrate used in the present invention is a laminate of the surface layer 2, the intermediate layer 1, and the surface layer 3.
Of the surface layer 2, the intermediate layer 1, and the surface layer 3, at least one layer is preferably formed of a material containing a resin having a tensile modulus of elasticity of 3.0 GPa or more. The rigidity of the transparent substrate is improved by using a resin having a tensile modulus of 3.0 GPa or more.
The intermediate layer 1 is a layer made of an ultraviolet absorber and a thermoplastic resin.
The surface layer 2 is a layer that is laminated on one surface of the intermediate layer 1 and is made of an acrylic resin having a glass transition temperature (Tg) of 100 ° C. or higher.
The surface layer 3 is a layer that is laminated on the other surface of the intermediate layer 1 and is made of an acrylic resin having a glass transition temperature (Tg) of 100 ° C. or higher.

The acrylic resin used for the surface layer 2 and the surface layer 3 is an acrylic resin having a glass transition temperature (Tg) of 100 ° C. or higher. A more preferable range of the glass transition temperature (Tg) of the acrylic resin is 100 ° C to 170 ° C, and a more preferable range is 100 ° C to 140 ° C. When the glass transition temperature of the acrylic resin is smaller than the above range, the surface hardness tends to be insufficient.
The acrylic resin used for the surface layer 2 and the acrylic resin used for the surface layer 3 may be the same resin or different resins.

  As said acrylic resin, the polymer resin which has a (meth) acrylic acid ester as a main component is used preferably. This polymer resin may be a homopolymer or copolymer consisting only of (meth) acrylic acid ester, and is a copolymer of (meth) acrylic acid ester and a monomer copolymerizable therewith. May be. In addition, (meth) acrylic acid means acrylic acid and / or methacrylic acid. Similarly, (meth) acrylic acid ester means acrylic acid ester and / or methacrylic acid ester.

  The (meth) acrylic acid ester used as the main component of the acrylic resin is preferably a structure derived from (meth) acrylic acid, an alkanol having 1 to 15 carbon atoms, and a cycloalkanol. More preferably, it is a structure derived from an alkanol having 1 to 8 carbon atoms. When there are too many carbon numbers, the elongation at the time of the fracture | rupture of the brittle film obtained will become large too much.

  Specific examples of the (meth) acrylic acid ester include methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, sec-butyl acrylate. , T-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, n-decyl acrylate, n-dodecyl acrylate; methyl methacrylate, ethyl methacrylate, methacryl N-propyl acid, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, sec-butyl methacrylate, t-butyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, methacrylic acid 2 -Ethylhexyl, methacrylic acid n- Sill, and the like methacrylic acid n- dodecyl.

  Moreover, these (meth) acrylic acid esters may have an arbitrary substituent such as a hydroxyl group or a halogen atom. Examples of the (meth) acrylic acid ester having such a substituent include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-methacrylic acid 2- Examples include hydroxypropyl, 4-hydroxybutyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, glycidyl methacrylate, and the like. These (meth) acrylic acid esters may be used alone or in combination of two or more.

  The acrylic resin used in the present invention has a (meth) acrylic acid ester content of preferably 50% by weight or more, more preferably 85% by weight or more, and particularly preferably 90% by weight or more.

  The monomer copolymerizable with the (meth) acrylic acid ester is not particularly limited, but α, β-ethylenically unsaturated carboxylic acid ester monomers other than the (meth) acrylic acid ester described above, α, β-ethylenically unsaturated carboxylic acid monomer, alkenyl aromatic monomer, conjugated diene monomer, non-conjugated diene monomer, vinyl cyanide monomer, unsaturated carboxylic acid amide monomer, Examples thereof include carboxylic acid unsaturated alcohol esters and olefin monomers.

  Specific examples of the α, β-ethylenically unsaturated carboxylic acid ester monomer other than the (meth) acrylic acid ester described above include dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, dimethyl itaconate, etc. Can be mentioned.

  The α, β-ethylenically unsaturated carboxylic acid monomer may be any of monocarboxylic acid, polyvalent carboxylic acid, partial ester of polyvalent carboxylic acid, and polyvalent carboxylic acid anhydride. Examples include acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, monoethyl maleate, mono n-butyl fumarate, maleic anhydride, itaconic anhydride and the like.

  Specific examples of the alkenyl aromatic monomer include styrene, α-methylstyrene, methyl α-methylstyrene, vinyl toluene and divinylbenzene.

  Specific examples of the conjugated diene monomer include 1,3-butadiene, 2-methyl-1,3-butadiene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, and 2-chloro-1. , 3-butadiene, cyclopentadiene and the like. Specific examples of the non-conjugated diene monomer include 1,4-hexadiene, dicyclopentadiene, and ethylidene norbornene.

  Specific examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile and the like.

Specific examples of the α, β-ethylenically unsaturated carboxylic acid amide monomer include acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, N, N-dimethylacrylamide and the like.
Specific examples of the carboxylic acid unsaturated alcohol ester monomer include vinyl acetate.
Specific examples of the olefin monomer include ethylene, propylene, butene, pentene and the like.

  As the monomer copolymerizable with (meth) acrylic acid ester, one type may be used alone, or two or more types may be used in combination. As a monomer copolymerizable with (meth) acrylic acid ester, an alkenyl aromatic monomer is preferable, and styrene is particularly preferable.

  In the acrylic resin used in the present invention, the content of the monomer copolymerizable with (meth) acrylic acid ester is 50% by weight or less, preferably 15% by weight or less, more preferably 10% by weight or less. .

  Preferable specific examples of the acrylic resin used in the present invention include methyl methacrylate / methyl acrylate / butyl acrylate / styrene copolymer, methyl methacrylate / methyl acrylate copolymer, methyl methacrylate / styrene / acrylic. Examples thereof include butyl acid copolymer. One type of acrylic resin may be used alone, or two or more types may be used in combination. In the present invention, among these, a polymethacrylate resin is preferable, and among them, a polymethyl methacrylate resin is more preferable.

  Although the molecular weight of acrylic resin is not specifically limited, Usually, it is 50,000-500,000 in a weight average molecular weight. When the molecular weight is within this range, a homogeneous film can be easily produced by the melt casting method.

  The acrylic resin used in the present invention preferably has an elongation at break in the tensile test in the range of 10 to 180%, and more preferably in the range of 50 to 170%. When the elongation at break is within the above range, the bristle film has good dregs. When two or more kinds of acrylic resins are used in combination, the elongation at break of the mixture is preferably within the above range. The elongation at break is a value obtained under the conditions of test piece type 1B (W10, L100, t0.1 mm) and speed of 5 mm / min according to JIS K 7127.

  As for a transparent base material, each thickness of the surface layer 2 and the surface layer 3 becomes like this. Preferably it is 10 micrometers or more, More preferably, it is 20-60 micrometers. When the thickness of each surface layer is within the above range, surface pencil hardness and flexibility can be sufficiently imparted.

  The surface hardness of at least one of the surface layer 2 and the surface layer 3 is preferably a pencil hardness of 1H or more for the purpose of the present invention. The pencil hardness can be adjusted depending on the thickness and composition.

  Examples of the thermoplastic resin constituting the intermediate layer 1 include polycarbonate resin, polyethersulfone resin, polyethylene terephthalate resin, polyimide resin, polymethyl methacrylate resin, polysulfone resin, polyarylate resin, polyethylene resin, polystyrene resin, and polyvinyl chloride. Examples include resins, cellulose diacetate, cellulose triacetate, and alicyclic olefin polymers. Of these, acrylic resins are preferred.

  Examples of alicyclic olefin polymers include cyclic olefin random multi-component copolymers described in JP-A No. 05-310845 and US Pat. No. 5,179,171; JP-A No. 05-97978 and US Pat. No. 5,202,388. Examples of the hydrogenated polymers described include thermoplastic dicyclopentadiene ring-opening polymers described in JP-A No. 11-124429 (International Publication No. 99/20676) and hydrogenated products thereof.

  The thermoplastic resin constituting the intermediate layer 1 has a weight average molecular weight (Mw) of usually 5,000 to 100,000, preferably 8,000 to 80,000, more preferably 10,000 to 50,000. . When the weight average molecular weight is in such a range, the mechanical strength and molding processability of the transparent substrate are highly balanced, which is preferable.

The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the thermoplastic resin is not particularly limited, but is usually 1.0 to 10.0, preferably 1.0 to 4.0, more preferably 1. The range is from 2 to 3.5.
The weight average molecular weight and number average molecular weight are converted to standard polyisoprene measured by gel permeation chromatography (hereinafter abbreviated as “GPC”) using cyclohexane (toluene when the resin is not dissolved) as a solvent. Is the value of

  The thermoplastic resin has a resin component (that is, an oligomer component) having a molecular weight of 2,000 or less, usually 5% by weight or less, preferably 3% by weight or less, more preferably 2% by weight or less. When the amount of the oligomer component is large, when the laminate is produced, fine irregularities are generated in each of the intermediate layer 1, the surface layer 2 and the surface layer 3, or unevenness in thickness occurs in each layer, resulting in poor surface accuracy. There is a possibility.

  In order to reduce the amount of oligomer components, the selection of polymerization catalyst and hydrogenation catalyst; reaction conditions such as polymerization reaction and hydrogenation reaction; temperature conditions in the process of pelletizing resin as a molding material; That's fine. The amount of the oligomer component can be measured by gel permeation chromatography using cyclohexane (toluene if the resin does not dissolve).

  The intermediate layer 1 contains an ultraviolet absorber. The ultraviolet absorber may be contained only in the intermediate layer 1 or may be contained in the surface layer 2 and / or the surface layer 3. When it is also contained in the surface layer 2 and / or the surface layer 3, it is important that the content of the ultraviolet absorber in the surface layer 2 and / or the surface layer 3 is considerably less than the content in the intermediate layer 1. .

  The ultraviolet absorber used in the present invention is not particularly limited. For example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone UV absorbers, benzotriazole UV absorbers, acrylonitrile UV absorbers, triazine compounds, nickel complex compounds, inorganic powders, etc. A well-known thing is mentioned. Among these, 2,2′-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2′-hydroxy- 3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2,4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol, 2,2'- Dihydroxy-4,4′-dimethoxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone and the like are preferable. Among these, 2,2'-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol) is particularly preferable.

  As a method of forming the intermediate layer 1 (in some cases, the surface layers 2 and 3) containing the ultraviolet absorber, a method of blending an ultraviolet absorber with a thermoplastic resin and forming the mixture; A method of forming using a master batch of a thermoplastic resin contained in a high concentration and a thermoplastic resin not containing an ultraviolet absorber; a method of directly supplying the molten resin at the time of melt extrusion molding of the intermediate layer 1, etc. Any method may be adopted.

  The amount of the ultraviolet absorber contained in the intermediate layer 1 is preferably 0.5 to 5 parts by weight, more preferably 1.0 to 5 parts by weight with respect to 100 parts by weight of the thermoplastic resin constituting the intermediate layer 1. When the content of the ultraviolet absorber is within the above range, it is possible to efficiently block ultraviolet rays without deteriorating the color tone of the polarizing plate, and to prevent a decrease in the degree of polarization during long-term use. When the content of the ultraviolet absorber in the intermediate layer 1 is less than 0.5 parts by weight, the light transmittance at wavelengths of 370 nm and 380 nm increases, and the degree of polarization of the polarizing plate tends to decrease.

  Further, it is desirable that the concentration variation of the ultraviolet absorber contained in the intermediate layer 1 is 0.1% or less over the entire surface. This is because if the variation in the concentration of the ultraviolet absorber is suppressed within this range, the deterioration due to ultraviolet rays occurs uniformly, and color tone unevenness when mounted on a liquid crystal display device is less likely to occur. If the variation in the concentration of the UV absorber in the intermediate layer 1 exceeds 0.1% over the entire surface, uneven color tone can be clearly seen and the color tone tends to be poor. Further, after long-term use, deterioration due to ultraviolet rays becomes non-uniform, and the color tone tends to become worse.

The variation in the concentration of the ultraviolet absorber in the intermediate layer 1 is measured by the following procedure.
First, the ultraviolet transmittance of the laminate is measured with a spectrophotometer. Next, the thickness of the laminate is measured with a contact-type thickness meter. Next, the cross section of the measurement part is observed with an optical microscope, the ratio of the thickness of the surface layer and the intermediate layer 1 is determined, and the thickness of the intermediate layer 1 is determined. And the density | concentration of a ultraviolet absorber is computed from following formula (A) from a ultraviolet-ray transmittance and thickness.
C = −log ₁₀ (0.01T) / K / L (A)
In the formula (A), C is the concentration (% by weight) of the ultraviolet absorber, T is the light transmittance (%), K is the extinction coefficient (−), and L is the thickness (μm) of the laminate.

The above operation is performed at regular intervals in the longitudinal direction and the lateral direction of the laminate, and an arithmetic average value of these measured values is taken, and this is defined as an average concentration C _ave . Then, the maximum value of the measured density C is C _max and the minimum value is C _{min and} is calculated from the following equation.
Concentration variation (%) = (C _ave −C _min ) / C _ave × 100, or
The larger of (C _max -C _ave ) / C _ave × 100

  As means for reducing the variation in the concentration of the ultraviolet absorber in the intermediate layer 1 to 0.1% or less over the entire surface, (1) a dried thermoplastic resin and an ultraviolet absorber are mixed. Next, the mixture is put into a hopper connected to an extruder, and supplied to a single screw extruder for melt extrusion; (2) A thermoplastic resin is put into a hopper with a dryer. In addition, an ultraviolet absorber is introduced from another inlet. A method in which the thermoplastic resin and the ultraviolet absorber are supplied to a twin-screw extruder while being metered with a feeder and melt-extruded.

  The thickness of the intermediate layer 1 is preferably 10 to 40 μm. When the thickness of the intermediate layer 1 is less than 10 μm, the interface between the layers tends to be rough, and the surface state such as flatness and smoothness tends to deteriorate. On the other hand, when the thickness of the intermediate layer 1 exceeds 40 μm, the entire polarizing plate becomes thick when used as a polarizing plate protective film.

  The thickness of the intermediate layer 1 is determined by measuring the total thickness using a commercially available contact-type thickness meter, cutting the thickness measurement portion and observing the cross section with an optical microscope, and measuring the thickness of the intermediate layer 1 and the surface layer. The thickness ratio is obtained, and the thickness of the intermediate layer 1 is calculated from the ratio. The above operation was performed at regular intervals in the horizontal direction and the vertical direction of the laminate, and average values and variations were obtained.

  The variation in the thickness of the intermediate layer 1 is preferably 1 μm or less over the entire surface. When the thickness variation of the intermediate layer 1 is 1 μm or less over the entire surface, the color tone variation is reduced. In addition, since the color tone change after long-term use is uniform, color tone unevenness after long-term use does not occur.

The variation in the thickness of the intermediate layer 1 is as follows, where the arithmetic average value of the measured values measured above is the reference thickness T _ave , the maximum value of the measured thickness T is T _max , and the minimum value is T _min . It is calculated from the formula of
Thickness variation (μm) = T _ave −T _min , and
The larger of T _max -T _ave .

  In the present invention, the surface layer 2 and / or the surface layer 3 may also contain an ultraviolet absorber, but the content in that case is preferably 100 parts by weight of the acrylic resin constituting the surface layer. 0.5 parts by weight or less. More specifically, the content is determined in consideration of the content of the ultraviolet absorber in the intermediate layer 1 so as to ensure the necessary ultraviolet transmission preventing performance as the entire transparent substrate.

  In the present invention, any of the surface layers 2 and 3 and the intermediate layer 1 of the transparent substrate may contain other compounding agents other than the ultraviolet absorber. Other compounding agents are not particularly limited, but inorganic fine particles; stabilizers such as antioxidants, heat stabilizers and near infrared absorbers; resin modifiers such as lubricants and plasticizers; coloring dyes and pigments Agents; antistatic agents and the like. These compounding agents can be used alone or in combination of two or more, and the compounding amount is appropriately selected within a range not impairing the object of the present invention.

  The transparent substrate preferably has a light transmittance at a wavelength of 380 nm of 4% or less, and more preferably 3% or less. The transparent substrate preferably has a light transmittance of 1% or less at a wavelength of 370 nm, more preferably 0.5% or less. Further, the transparent substrate preferably has a light transmittance of 85% or more at a wavelength of 420 to 780 nm, more preferably 90% or more.

When the light transmittance of the transparent substrate at a wavelength of 380 nm or a wavelength of 370 nm exceeds the above range, the polarizer changes due to ultraviolet rays, and the degree of polarization tends to decrease. When the light transmittance at a wavelength of 420 to 780 nm is less than the above range, the luminance tends to decrease particularly when used for a long period of time when mounted on a display device such as a liquid crystal display device.
The light transmittance can be measured using a spectrophotometer according to JIS K0115.
The thickness of the transparent substrate is preferably 30 μm to 80 μm.

  The method for obtaining the transparent substrate is not particularly limited, but preferably a coextrusion method such as a coextrusion T-die method, a coextrusion inflation method, a coextrusion lamination method, a film lamination molding method such as dry lamination, and the intermediate layer 1 A known method such as a coating molding method in which the resin film constituting the surface layer is coated on the constituting film can be appropriately used. Among these, the coextrusion molding method is preferable from the viewpoint of production efficiency and not leaving volatile components such as a solvent in the film.

  Among the coextrusion molding methods, the coextrusion T-die method is preferable. Further, examples of the coextrusion T-die method include a feed block method and a multi-manifold method, but the multi-manifold method is more preferable in that variation in the thickness of the intermediate layer 1 can be reduced.

  When the co-extrusion T-die method is employed as a method for obtaining a transparent substrate, the melting temperature of the thermoplastic resin in the extruder having a T-die is 80 to 180 ° C. than the glass transition temperature (Tg) of this thermoplastic resin. It is preferable to set the temperature higher, more preferably 100 to 150 ° C. higher than the glass transition temperature. If the melting temperature in the extruder is excessively low, the flowability of the thermoplastic resin may be insufficient. Conversely, if the melting temperature is excessively high, the resin may be deteriorated.

  In order to make the thickness variation of the intermediate layer 1 1 μm or less over the entire surface, (1) a polymer filter having an opening of 20 μm or less is provided in the extruder; (2) the gear pump is rotated at 5 rpm or more; (3) (4) The air gap is 200 mm or less; (5) Edge pinning is performed when the film is cast on a cooling roll; (6) A twin-screw extruder or screw as an extruder. Use a double-flight type single-screw extruder; Unless even one of the above (1) to (6) is implemented, it is difficult to make the thickness variation of the intermediate layer 1 within ± 1 μm on the entire surface.

  What is necessary is just to select extrusion temperature suitably according to the thermoplastic resin to be used. The temperature inside the extruder is preferably Tg to (Tg + 100) ° C., the outlet of the extruder is (Tg + 50) to (Tg + 170) ° C., and the die temperature is preferably (Tg + 50) ° C. to (Tg + 170) ° C. Here, Tg is the glass transition temperature of the extruded resin.

  When the melt extrusion method is used as a method for obtaining the transparent substrate, the sheet-like molten resin extruded from the opening of the die is brought into close contact with the cooling drum. The method for bringing the molten resin into close contact with the cooling drum is not particularly limited, and examples thereof include an air knife method, a vacuum box method, and an electrostatic contact method.

  The number of cooling drums is not particularly limited, but is usually two or more. Examples of the arrangement method of the cooling drum include, but are not limited to, a linear type, a Z type, and an L type. Further, the way of passing the molten resin extruded from the opening of the die through the cooling drum is not particularly limited.

  In the present invention, the degree of adhesion of the extruded sheet-like thermoplastic resin to the cooling drum varies depending on the temperature of the cooling drum. When the temperature of the cooling drum is raised, the adhesion is improved. However, if the temperature is raised too much, the sheet-like thermoplastic resin may not be peeled off from the cooling drum, and there is a possibility that a problem of winding around the drum may occur. Therefore, the cooling drum temperature is preferably (Tg + 30) ° C. or lower, more preferably (Tg−5) ° C. to (Tg−45) ° C., where Tg is the glass transition temperature of the thermoplastic resin extruded from the die. . By doing so, problems such as slipping and scratches can be prevented.

  In addition, in the method for producing a transparent substrate, it is important to reduce the content of residual solvent. As a means for that purpose, (1) reduce the residual solvent of the thermoplastic resin itself; (2) Examples thereof include pre-drying a thermoplastic resin used before molding. The preliminary drying is performed with a hot air dryer or the like, for example, in the form of pellets or the like. The drying temperature is preferably 100 ° C. or more, and the drying time is preferably 2 hours or more. By performing preliminary drying, the residual solvent in the transparent base material can be reduced, and foaming of the extruded thermoplastic resin can be prevented.

  As a method for producing a transparent substrate, it is also possible to produce three transparent films by using an adhesive in addition to the aforementioned extrusion method. 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. Among these, those that maintain a predetermined elasticity after curing are more preferable, and examples of such adhesives include SEBS adhesives, SIS adhesives, and ethylene-vinyl acetate adhesives.

  By laminating surface layers on both sides of the intermediate layer 1 using such an adhesive that maintains elasticity, the flexibility of the transparent substrate can be improved, and the transparent substrate is punched to a size suitable for the product. The cutting characteristics at the time are good. Moreover, since this adhesive bond layer acts as a stress buffer layer that relieves stress generated when an external force is applied to the transparent substrate, the protective properties of the polarizer can be further improved.

  The average thickness of the adhesive layer is usually 0.01 to 30 μm, preferably 0.1 to 15 μm.

  On the outer surface of the transparent substrate of the present invention, that is, the surface of the surface layer 2 and / or the surface layer 3 made of an acrylic resin, irregularly formed linear recesses and linear protrusions are substantially formed. The surface is preferably a flat surface. The fact that it is not substantially formed means that even if a linear recess or a linear protrusion is formed, a linear recess having a depth of less than 50 nm or a width of more than 500 nm, and a height of less than 50 nm or a width of 500 nm. It is a larger linear convex part. More preferably, it is a linear concave portion having a depth of less than 30 nm or a width of 700 nm, and a linear convex portion having a height of less than 30 nm or a width of greater than 700 nm. By adopting such a configuration, it is possible to prevent the occurrence of light interference and light leakage based on the light refraction at the linear concave portions or the linear convex portions, and the optical performance can be improved. In addition, irregularly occurring means that it is formed with an unintended size, shape, or the like at an unintended position.

  The depth of the linear concave portion described above, the height of the linear convex portion, and the width thereof can be obtained by the following method. Light is applied to the transparent substrate, the transmitted light is projected onto the screen, and the portion of the light that appears on the screen has light stripes or dark stripes (the depth of the linear concave portion and the height of the linear convex portion are Cut out at 30 mm square. The surface of the cut film piece is observed using a three-dimensional surface structure analysis microscope (field region 5 mm × 7 mm), converted into a three-dimensional image, and a cross-sectional profile in the MD direction is obtained from the three-dimensional image. The cross-sectional profile is obtained at 1 mm intervals in the visual field region.

  In this cross-sectional profile, an average line is drawn, the length from the average line to the bottom of the linear recess is the linear recess depth, or the length from the average line to the top of the linear protrusion is the linear protrusion height. It becomes. The distance between the intersection of the average line and the profile is the width. The maximum values are obtained from the measured values of the linear concave portion depth and the linear convex portion height, respectively, and the width of the linear concave portion or the linear convex portion showing the maximum value is obtained. The maximum value of the linear recess depth and the height of the linear convex portion obtained from the above, the width of the linear concave portion and the width of the linear convex portion showing the maximum value, the depth of the linear concave portion of the film Let the height of the linear protrusions and their widths.

  Furthermore, the transparent substrate used in the present invention may have a functional layer such as a hard coat layer, an antireflection layer, or an antifouling layer formed on the outer surface of the transparent substrate.

(Hard coat layer)
The hard coat layer is preferably formed of a heat or photo-curing material that exhibits a hardness of “1H” or higher in a pencil hardness test (test plate is a glass plate) shown in JIS K5600-5-4. The pencil hardness of the transparent substrate provided with the hard coat layer is preferably 4H or more. When the surface layer of the transparent substrate is composed of an acrylic resin, it becomes easy to adjust the pencil strength of the surface to 4H or more by the hard coat layer.

  Examples of the hard coat layer material include organic hard coat materials such as organic silicone, melamine, epoxy, acrylic, and urethane acrylate; and inorganic hard coat materials such as silicon dioxide. Of these, urethane acrylate-based and polyfunctional acrylate-based hard coat materials are preferably used from the viewpoint of good adhesive strength and excellent productivity.

This hard coat layer has a refractive index n _H between the refractive index n _L of the low refractive index layer laminated thereon, n _H ≧ 1.53, and n _H ^1/2 −0.2 <. It is preferable to have a relationship of n _L <n _H ^1/2 +0.2 in order to develop the antireflection function.

  This hard coat layer contains various fillers for the purpose of adjusting the refractive index, improving the flexural modulus, stabilizing the volume shrinkage, improving heat resistance, antistatic properties, antiglare properties, etc., as desired. You may squeeze it. Furthermore, various additives such as an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, a leveling agent, and an antifoaming agent can be blended.

(Antireflection layer)
The antireflection layer is a layer for preventing the transfer of external light. The transparent base material on which such an antireflection layer is laminated may have a reflectance at an incident angle of 5 ° and 430 to 700 nm of 2.0% or less and a reflectance at 550 nm of 1.0% or less. preferable. The thickness of the antireflection layer is preferably 0.01 μm to 1 μm, more preferably 0.02 μm to 0.5 μm. As such an antireflection layer, for example, a layer in which a low refractive index layer having a refractive index smaller than that of the hard coat layer, preferably a refractive index of 1.30 to 1.45, is laminated, or a low layer made of an inorganic compound. Examples thereof include those obtained by repeatedly laminating a refractive index layer and a high refractive index layer made of an inorganic compound.

  The material for forming the low refractive index layer is not particularly limited as long as the refractive index is lower than that of the transparent substrate or the hard coat layer. For example, a resin material such as an ultraviolet curable acrylic resin, or a colloid in the resin. Examples thereof include hybrid materials in which inorganic fine particles such as silica are dispersed and sol-gel materials using metal alkoxides such as tetraethoxysilane. The material for forming the exemplified low refractive index layer may be a polymerized polymer, or a monomer or oligomer serving as a precursor. Moreover, it is preferable that each material contains the compound containing the fluorine group for providing antifouling property to the surface.

Examples of the sol-gel material containing a fluorine group include perfluoroalkylalkoxysilane. As perfluoroalkyl alkoxysilane, for example, general formula: CF ₃ (CF ₂ ) _n CH ₂ CH ₂ Si (OR) ₃ (wherein R represents an alkyl group having 1 to 5 carbon atoms, n is And an integer of 0 to 12). Specifically, for example, trifluoropropyltrimethoxysilane, trifluoropropyltriethoxysilane, tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, heptadecafluorodecyltrimethoxysilane, heptadecafluorodecyltri And ethoxysilane. Among these, the compound wherein n is 2 to 6 is preferable.

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

  The thickness of the low refractive index layer is not particularly limited, but is usually 0.05 to 0.3 μm, particularly preferably 0.1 to 0.3 μm.

(Anti-fouling layer)
In order to improve the antifouling property of the low refractive index layer, an antifouling layer may be further provided on the low refractive index layer (observation side). The antifouling layer is a layer that can impart water repellency, oil repellency, sweat resistance, antifouling properties and the like to the surface. 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, or a polymer compound 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 to 50 nm, more preferably 3 to 35 nm.

  In addition to these layers, other layers such as an antiglare layer, a gas barrier layer, a transparent antistatic layer, a primer layer, an electromagnetic shielding layer, and an undercoat layer may be provided on the transparent substrate.

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 of the present invention has been subjected to mechanical treatment by etching, sandblasting, embossing roll, etc. for the purpose of enhancing adhesion with the functional layer and imparting antiglare properties. Also good.
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 adjusting the moisture permeability to the above-mentioned preferable range, when the optical element of the present invention is used as a protective layer for the polarizer, 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 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.

  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 mesogenic 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.
Pasted

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.

(Transparent substrate 1)
Double flight type uniaxial extrusion with polymethylmethacrylate resin (tensile modulus 3.3 GPa, glass transition temperature Tg = 110 ° C .; hereinafter sometimes referred to as “PMMA1”) provided with a leaf disk-shaped polymer filter with an opening of 10 μm The molten resin was fed into one of the multi-manifold dies having a die slip surface roughness Ra of 0.1 μm at an extruder outlet temperature of 260 ° C.

  At the same time, 2% by weight of an ultraviolet absorber is added to polymethyl methacrylate resin (tensile elastic modulus 2.5 GPa, glass transition temperature Tg = 100 ° C.), and this ultraviolet absorber-containing polymethyl methacrylate resin (hereinafter referred to as “PMMA2”). Is introduced into a double flight type single screw extruder equipped with a leaf disk-shaped polymer filter with an opening of 10 μm, and the molten resin is melted at an extruder outlet temperature of 260 ° C. and the surface roughness Ra of the die slip is 0.1 μm. To the other of the multi-manifold dies.

  Then, each of the molten polymethyl methacrylate resin (PMMA1) and the UV-absorbing polymethyl methacrylate resin (PMMA2) is discharged from the multi-manifold die at 260 ° C., and cast to a cooling roll adjusted to 130 ° C., Thereafter, the film is passed through a cooling roll whose temperature is adjusted to 50 ° C., and consists of a three-layer structure of PMMA1 layer (15 μm) -PMMA2 layer (50 μm) -PMMA1 layer (15 μm), and is a film-like transparent film having a width of 600 mm and a thickness of 80 μm The substrate 1 was obtained by coextrusion molding. The depth of the linear concave portion or the height of the linear convex portion of the transparent substrate 1 was 20 nm or less and the width was in the range of 800 nm or more.

(Transparent substrate 2)
Polymethylmethacrylate resin (glass transition temperature Tg = 110 ° C .; hereinafter sometimes referred to as “PMMA1”) is introduced into a double flight type single screw extruder having a leaf disk-shaped polymer filter having an opening of 10 μm. At an outlet temperature of 260 ° C., the molten resin was supplied to one of the multi-manifold dies having a die slip surface roughness Ra of 0.1 μm.

  At the same time, a polycarbonate resin (tensile elastic modulus 2.2 GPa, UV absorber-free, water absorption 0.2%, sometimes referred to as “PC”) and a leaf disk-shaped polymer filter with an opening of 10 μm is installed. It was introduced into a flight type single screw extruder, and the molten resin was supplied to the other of the multi-manifold dies having a die slip surface roughness Ra of 0.1 μm at an extruder outlet temperature of 260 ° C.

  Then, molten polymethyl methacrylate resin (PMMA1), polycarbonate resin (PC), and ethylene-vinyl acetate copolymer as an adhesive layer forming material are each discharged from a multi-manifold die at 260 ° C., and the temperature is adjusted to 130 ° C. The PMMA1 layer (20 μm) -adhesive layer (4 μm) -PC layer (32 μm) -adhesive layer (4 μm) -PMMA1 layer ( A film-like transparent substrate 2 having a width of 600 mm and a thickness of 80 μm, having a three-layer structure of 20 μm), was obtained by coextrusion molding.

(Tensile modulus)
A thermoplastic resin is formed into a single layer to obtain a film having a thickness of 100 μm, a 1 cm × 25 cm test piece is cut out, and a tensile tester (Tensilon UTM-10T-PL, manufactured by Toyo Baldwin Co., Ltd.) is used based on ASTM D882. It was measured under the conditions of a tensile speed of 25 mm / min. The same measurement is performed 5 times, and the arithmetic average value is set as the representative value of the tensile elastic modulus.

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 an alignment film comprising 5 parts of polyvinyl alcohol and 95 parts of water was applied to one 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 0.11 part of a surfactant (trade name "KH-40" manufactured by Seimi Chemical Co., Ltd.) were dissolved in 160 parts of methyl ethyl ketone, and a polyfluoroethylene CD / 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 1.
The circularly polarized light reflection plate was incorporated in a liquid crystal display device having the configuration shown in FIG. 4, and the change in chromaticity depending on the observation angle was visually evaluated. Almost no change in chromaticity was observed in the range of 0 to 80 degrees on the left and right.

Comparative Example 1
The light transmittance of the transparent substrate 1 was measured in the same manner as in 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 1.
Instead of the circularly polarized light reflector used in Example 1, the transparent substrate 1 was used and incorporated in the liquid crystal display device having the configuration shown in FIG. 4 in the same manner as in Example 1, and the chromaticity change due to the observation angle was visually evaluated. It was reddish at 60 degrees or more in the left-right direction.

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 composed of 5 parts of polyvinyl alcohol and 95 parts of water was applied to one 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 1.

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 reflection plate was incorporated in a liquid crystal display device having the configuration shown in FIG. 4, and the change in chromaticity depending on the observation angle was visually evaluated. Almost no change in chromaticity was observed in the range of 0 to 80 degrees on the left and right.

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 composed of 5 parts of polyvinyl alcohol and 95 parts of water was applied to one 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 surfactant (trade name “KH-40”, manufactured by Seimi Chemical Co., Ltd.) were dissolved in 162 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 1.50 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 1.

  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%.

  In place of the circularly polarized light reflector used in Example 2, the circularly polarized light reflector is used and incorporated in the liquid crystal display device having the configuration shown in FIG. did. Yellowish green was exhibited at 60 degrees or more in the left-right direction.

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. Then, the circularly polarized light reflecting plate was incorporated in a liquid crystal display device having the configuration shown in FIG. 4, and the chromaticity change depending on the observation angle was visually evaluated. Almost no change in chromaticity was observed in the range of 0 to 80 degrees on the left and right, but ΔYI was large by irradiation with an arc lamp.

(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.

(Weatherability)
Using a sunshine weather meter (S-80, manufactured by Suga Test Instruments Co., Ltd.), the circularly polarized light reflector was exposed for 200 hours under the conditions of a sunshine carbon arc lamp and a relative humidity of 60%. The change (ΔYI) was measured using a color difference meter (manufactured by Suga Test Instruments Co., Ltd.) and evaluated with the following indices.
○: ΔYI is less than 2 ×: ΔYI is 2 or more

Claims (15)

An optical element for use in an apparatus having a light source, comprising a transparent substrate and a selective reflection layer formed on the transparent substrate,
The transparent base material comprises a thermoplastic resin, the ultraviolet absorber is unevenly distributed in the central portion in the thickness direction, and the average thickness is less than 100 μm,
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. Transparent substrate
An intermediate layer 1 comprising an ultraviolet absorber and a thermoplastic resin;
Glass transition temperature (Tg) laminated on one surface of the intermediate layer 1 is a surface layer 2 made of an acrylic resin having a temperature of 100 ° C. or higher, and glass transition temperature (Tg) laminated on the other surface of the intermediate layer 1 ) Surface layer 3 made of acrylic resin at 100 ° C. or higher
The optical element according to claim 1, comprising a laminate having   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 reflecting element, a light source, a light diffusing 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.

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