JP2008242350A - Optical element, polarizing plate, retardation plate, illumination device, and liquid crystal display device - Google Patents

Abstract

[PROBLEMS] To display an image having few optical defects and having the same color balance in front and oblique observation, and is excellent in high-temperature and high-humidity resistance, weather resistance, and handling properties, and has sufficient surface hardness. An optical element is provided.
A transparent substrate comprising a thermoplastic resin, wherein the ultraviolet absorber is unevenly distributed in the center in the thickness direction, and has an average thickness of less than 100 μm; and a selection formed on the transparent substrate An optical element having a layer having a reflection band or a selective absorption band, which has a transmittance T _{B, N} in the front direction at a wavelength of 440 nm, an average value T _{B, 60} of transmittance in a polar angle of 60 degrees direction at a wavelength of 440 nm, and a wavelength Frontal transmittance T _{G, N} at 530 nm _, average value T _{G, 60} of transmittance at a polar angle of 60 degrees in a wavelength of 530 nm, frontal transmittance T _{R, N at} a wavelength of 620 nm, and polar angle at a wavelength of 620 nm The average value T _{R, 60} of the transmittance in the direction of 60 degrees is the expression [1]: (T _{B, 60} / T _{B, N} )> (T _{G, 60} / T _{G, N} ) ≈ (T _{R, 60} / T _{R, N} ) An optical element that satisfies the relationship.
[Selection figure] None

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, it has excellent weather resistance, high temperature and humidity resistance, and handling properties, and has sufficient surface hardness, which is used to display images with few optical defects and the same color balance in front and oblique observations. The present invention relates to an optical element, a polarizing plate, a retardation plate, an illuminating device, and a liquid crystal display device.

  The liquid crystal display device includes a light source, two dichroic polarizers, and a liquid crystal cell disposed between the dichroic polarizers. Light from a light source such as a cold cathode tube, a hot cathode tube, LED (light emitting diode), EL (electroluminescence), blue light (wavelength 410 to 470 nm), green light (wavelength 520 to 580 nm), and red light ( (Wavelength 600 to 660 nm) is balanced and emits white light. The light is converted into linearly polarized light by the first dichroic polarizer. The linearly polarized light is converted into linearly polarized light with the phase unchanged or inverted depending on the difference in voltage application or no voltage application in the liquid crystal cell. When the polarization transmission axis of the first dichroic polarizer and the polarization transmission axis of the second dichroic polarizer (also referred to as analyzer) are perpendicular, the linearly polarized light whose phase is inverted in the liquid crystal cell is The linearly polarized light 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, in Patent Document 1, a cholesteric liquid crystal layer having a selective reflection band at wavelengths λ1 to λ2 (λ1 <λ2) with respect to normal incident light is combined and used. It has been proposed that a collimator satisfying λ0 <λ1 with respect to the maximum wavelength λ0 of the emission spectrum of the light source to be arranged in the backlight system. The collimator described in Patent Document 1 has a function of aligning light traveling at various angles with only light traveling in the vertical direction. Therefore, light rays incident from an oblique direction are reflected by this collimator and are not transmitted.

  Further, in Patent Document 2, it has a transmission characteristic with respect to incident light in the visible light region in the normal direction, has a reflection wavelength band in the infrared region, and has a reflection wavelength as the incident angle with respect to the normal direction increases. It has been proposed to arrange an infrared reflecting layer (B) whose band changes to the short wavelength side in an illumination device. Patent Document 2 discloses an infrared reflective layer (B) having a transmittance of light of 10% or less at a wavelength of 710 nm, 640 nm, or 610 nm at an incident angle of 45 degrees. That is, in the infrared reflection layer (B), 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 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 extrusion molding by reducing the concentration of the ultraviolet absorber on one or both surface layers. It is said that it is possible to form without roll contamination.
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. Various stresses are applied to the components used for the display surface of the display device, such as unexpected mechanical external force, exposure to sunlight or light emitted from the backlight for a long time, or heat. Is often added. In a display device having a polarizing plate with a conventional protective layer laminated, a number of scratches are attached to the display surface as it is used, and the visibility and appearance are impaired. The effect of this scratch is close to that of the light source. A member arranged at a position is larger, and is liable to lead to luminance unevenness and luminance defects (optical defects).

An object of the present invention is to provide an optical element, a polarizing plate, a retardation plate, an illuminating device, and a liquid crystal display device that are used to display an image having few optical defects and having a similar color balance in front and oblique observations. It is to provide. 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.
In addition, the object of the present invention is an optical element, a polarizing plate, a retardation plate, which is excellent in visibility, weather resistance, ultraviolet light transmission preventing effect, and adhesiveness with a polarizer, and can maintain a high degree of polarization even under high temperature and high humidity. An object is to provide an illumination device and a liquid crystal display device.

  The inventor can obtain an image in which blue, green and red are well balanced when the liquid crystal display device disclosed in the above-mentioned patent document is observed from the front. I noticed that sometimes the images look bluish. And it came to mind that this 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, between the liquid crystal panel and the light source having a wavelength showing the emission intensity peak in each wavelength region of blue light, green light, and red light,
A layer having a selective reflection band or a selective absorption band is formed on a transparent base material in which a specific ultraviolet absorber is unevenly distributed in the central portion in the thickness direction and the average thickness is less than 100 μm, from the front direction. Slightly shows selective reflection or selective absorption only for the blue light peak wavelength, and does not show selective reflection or selective absorption for the green light peak wavelength and red light peak wavelength from the front direction. An optical element that does not show selective reflection or selective absorption with respect to the peak wavelength of blue light, the peak wavelength of green light, and the peak wavelength of red light, or a specific ultraviolet absorber is unevenly distributed in the center in the thickness direction and has an average thickness A layer having a selective reflection band or a selective absorption band is formed on a transparent substrate having a thickness of less than 100 μm, and the blue light peak wavelength and the green light peak from the front direction are formed. An optical element that does not exhibit selective reflection or selective absorption with respect to the peak wavelength of long and red light, but exhibits some selective reflection or selective absorption with respect to the peak wavelength of green light and the peak wavelength of red light from an oblique direction, When the display device is equipped with an illuminating device, it has been found that a liquid crystal display device having excellent weather resistance can be obtained because an image with the same color balance can be displayed in front and oblique observation.
The present invention has been further studied and completed based on these findings.

Thus, the present invention includes the following.
(1) A transparent base material comprising a thermoplastic resin, in which the ultraviolet absorber is unevenly distributed in the center in the thickness direction, and has an average thickness of less than 100 μm; and selective reflection formed on the transparent base material A layer having a band or a selective absorption band,
Transmittance T _{B, N} in the front direction of wavelength 440 nm, average value T _{B, 60} of transmittance in the polar angle 60 degrees direction of wavelength 440 nm, transmittance T _{G, N} in the front direction of wavelength 530 nm, polar angle of wavelength 530 nm The average value T _{G, 60} of the transmittance in the direction of 60 degrees, the transmittance T _{R, N} in the front direction at a wavelength of 620 nm, and the average value T _{R, 60} of the transmittance in the polar angle 60 degrees direction at a wavelength of 620 nm are expressed by the formula [1 ]: (T _{B, 60} / T _{B, N} )> (T _{G, 60} / T _{G, N} ) ≈ (T _{R, 60} / T _{R, N} )
An optical element that satisfies the above relationship.

(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 above optical element having at least one selective reflection band or selective absorption band in a wavelength range of 350 nm to 500 nm in the front direction.
(4) The above optical element having at least one selective reflection band or selective absorption band in a wavelength range of 450 nm to 700 nm in a polar angle direction of 60 degrees.
(5) The optical element described above, wherein the layer having a selective reflection band or a selective absorption band includes a resin layer having cholesteric regularity.

(6) A polarizing plate in which the optical element and a linear polarizer are laminated.
(7) A retardation plate in which the optical element and a retardation element are laminated.
(8) 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.
(9) 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.
(10) 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.
(11) The liquid crystal display device as described above, wherein the light source is selected from a cold cathode tube, a hot cathode tube, a light emitting diode, and electroluminescence.

  Conventional liquid crystal display devices are often reddish when observed obliquely. This is because the amount of red light when viewed from an oblique angle is relatively higher than the amount of blue and green light when compared to the light amount balance of blue, green and red when viewed from the front. On the other hand, if the transmittance of light having a wavelength of 710 nm, 640 nm, or 610 nm incident obliquely is reduced to 10% or less as in Patent Documents 1 and 2, the light quantity balance of blue, green, and red when observed 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 of the present invention is relatively less likely to transmit blue light at a polar angle of 0 degrees (front direction) compared to green light and red light. In an oblique direction (for example, a polar angle of 60 degrees), blue light, green light, and red light are transmitted to substantially the same degree. Further, the optical element of the present invention transmits blue light, green light, and red light at substantially the same degree at a polar angle of 0 degrees (front direction), and green light and red light at an oblique direction (for example, polar angle of 60 degrees). Is relatively difficult to transmit compared to blue light. The optical element of the present invention having such transmission characteristics has a color when any of the color coordinates (x, y) when white light is transmitted obliquely transmits white light at a polar angle of 0 degrees. It becomes smaller than the coordinates (x _N , y _N ). When this optical element is combined with a liquid crystal panel, the shift in color coordinates due to the viewing angle cancels out, so the color balance of blue, green, and red when viewed from an oblique angle is blue, green, and red when viewed from the front. Can be adjusted to the same balance. As a result, when observed from an oblique direction, it is not yellowish or bluish, and the color reproduction range can be widened.
Moreover, the optical element of the present invention is excellent in visibility, weather resistance, ultraviolet light transmission preventing effect, and adhesion to a polarizer, and can maintain a high degree of polarization even under high temperature and high humidity.

The figure which shows an example of the emission spectrum of a light source (four wavelength cold cathode tube). The figure which shows an example of the emission spectrum of another light source (RGB light emitting diode). The figure which shows an example of the wavelength distribution of the transmittance | permeability of the optical filter of a 1st embodiment. The figure which shows an example of the optical element (circularly polarized light reflecting plate) of this invention. It is a figure which shows the chromaticity coordinate (x, y) of the light which permeate | transmitted the optical filter and liquid crystal panel of Example 3. FIG. It is a figure which shows distribution of linear distance (DELTA) xy between the front direction chromaticity coordinate of the light which permeate | transmitted the optical filter of Example 3, and the liquid crystal panel, and diagonal direction chromaticity coordinate. It is a figure which shows the chromaticity coordinate (x, y) of the light which permeate | transmitted the optical filter and liquid crystal panel of Example 4. FIG. It is a figure which shows distribution of linear distance (DELTA) xy between the front direction chromaticity coordinate of the light which permeate | transmitted the optical filter of Example 4, and the liquid crystal panel, and diagonal direction chromaticity coordinate. It is a figure which shows the chromaticity coordinate (x, y) of the light which permeate | transmitted the isotropic film of the comparative example 3, and the liquid crystal panel. It is a figure which shows distribution of linear distance (DELTA) xy between the isotropic film of the comparative example 3, and the front direction chromaticity coordinate of the light which permeate | transmitted the liquid crystal panel, and diagonal direction chromaticity coordinate.

Explanation of symbols

1: Transparent base material 2: Alignment film 3: Cholesteric resin layer

The optical element of the present invention has a transmittance T _{B, N} in the front direction at a wavelength of 440 nm, an average value T _{B, 60} of a transmittance in the polar angle of 60 degrees direction at a wavelength of 440 nm, and a transmittance T _{G in} the front direction at a wavelength of 530 nm _{. N} , the average value T _{G, 60} of the transmittance of the wavelength 530 nm in the polar angle 60 degrees direction, the transmittance T _{R, N of} the wavelength 620 nm in the front direction, and the average value T of the transmittance of the wavelength 620 nm in the polar angle 60 degrees direction _{R, 60} is the formula [1]: (T _{B, 60} / T _{B, N} )> (T _{G, 60} / T _{G, N} ) ≈ (T _{R, 60} / T _{R, N} )
A selective reflection band or a selective absorption band satisfying the above relationship.

  The selective reflection band or the selective absorption band is a band in which the transmittance is smaller than other parts in a specific wavelength range. More specifically, the selective reflection band or the selective absorption band is a band having a characteristic in which the transmittance is lower by 5% or more due to the internal structure of the optical element in addition to the decrease in the transmittance due to the interface reflection on the surface of the optical element. It is. In order to measure selective reflection characteristics or selective absorption characteristics excluding interface reflection, for example, the optical element is placed in a liquid medium close to the average refractive index of the optical element, and a measurement light beam is incident thereon to perform spectroscopy. It can be determined by measuring the transmitted light intensity (assumed as intensity A), measuring the spectral transmission intensity (intensity B) of only the medium in the same manner, and dividing the intensity A by the intensity B.

The solid line N in FIG. 3 shows the wavelength dependence of the transmittance at a polar angle of 0 degrees. The selective reflection band or the selective absorption band is a part where the transmittance is smaller than the other part in the specific wavelength region as indicated by the solid line N. In FIG. 3, the selective reflection band or selective absorption band forms a gentle valley like a parabola, but may form a rectangular or trapezoidal valley.
The wavelength range of the selective reflection band or the selective absorption band varies depending on the polar angle. The broken line A in FIG. 3 is the transmittance when observed from an oblique direction. When observed from an oblique direction, the selective reflection band or selective absorption band shifts to the short wavelength side as compared to the front direction.
The optical element of the present invention uses this phenomenon to change the transmittance in the front direction and the oblique direction for each wavelength as described above.

The optical element of the present invention only needs to have a selective reflection band or a selective absorption band that satisfies the formula [1]. The value of (T _{G, 60} / T _{G, N} ) and the value of (T _{R, 60} / T _{R, N} ) need to be approximately equal. Based on the value of (T _{G, 60} / T _{G, N} ), the value of (T _{R, 60} / T _{R, N} ) is usually within 5%, preferably within 3%. The value of (T _{B, 60} / T _{B, N} ) needs to be larger than the value of (T _{G, 60} / T _{G, N} ). Based on the value of (T _{G, 60} / T _{G, N} ) or (T _{R, 60} / T _{R, N} ), the value of (T _{B, 60} / T _{B, N} ) is usually 10% or more, Preferably it is 20% or more larger.

  There are at least two embodiments having such a selective reflection band or selective absorption band. In the first embodiment, blue light is relatively difficult to transmit compared with green light and red light at a polar angle of 0 degrees (front direction), and blue light, green light, and red light at a polar angle of 60 degrees. In the second embodiment, blue light, green light, and red light are transmitted at approximately the same angle at a polar angle of 0 degrees (front direction). At 60 degrees, green light and red light are relatively less transmitted than blue light.

(First embodiment)
In the optical element of the first embodiment, blue light is relatively less transmitted at a polar angle of 0 degrees (front direction) than green light and red light, and blue light, green light, and The red light is transmitted through almost the same level.
That is, the optical element of the first embodiment has a selective reflection band or a selective absorption band in the wavelength range of blue light when observed from the front direction, and this selective reflection band or selective absorption band is observed at a polar angle of 60 degrees. In this case, the wavelength region shifts to the short wavelength side, and the transmittance of blue light becomes substantially the same as the transmittance of green light and red light.

  As shown in FIG. 1 or FIG. 2, the light source used in the liquid crystal display device emits light in the wavelength range of blue light 410 to 470 nm, the wavelength range of green light 520 to 580 nm, and the wavelength range of red light 600 to 660 nm. Has an intensity peak. FIG. 1 shows an emission spectrum of a 4-wavelength CCFL (cold cathode tube), and FIG. 2 shows an emission spectrum of an RGB light emitting diode (LED).

The optical element of the first embodiment may have a selective reflection band or a selective absorption band in the entire range of wavelengths of 350 nm to 500 nm, more preferably wavelengths of 410 to 470 nm, when observed from the front direction. You may make it have a selective reflection band or a selective absorption band only in the partial range of the said wavelength range.
At this time, it is preferable that the wavelength showing the peak of the emission intensity is included in the selective reflection band or the selective absorption band.

In the optical element of the first embodiment, the transmittance T _{B, N in} the front direction at a wavelength of 440 nm is usually 50 to 80%, preferably 60 to 70%, and the transmittance in the polar angle of 60 degrees direction at a wavelength of 440 nm. The average value T _{B, 60} is usually 80% or more, the transmittance T _{G, N in} the front direction at a wavelength of 530 nm is usually 80% or more, and the average value of the transmittance in the polar angle 60 degree direction at a wavelength of 530 nm _{TG, 60} is usually 80% or more, the transmittance T _{R, N in} the front direction at a wavelength of 620 nm is usually 80% or more, and the average value T _R of the transmittance in the polar angle 60 ° direction at a wavelength of 620 nm ₆₀ is usually 80% or more.

(Second embodiment)
The optical element of the second embodiment transmits blue light, green light, and red light at approximately the same degree at a polar angle of 0 degrees (front direction), and the green light and red light are relative to blue light at a polar angle of 60 degrees. It is difficult to penetrate.
That is, the optical element of the second embodiment has a selective reflection band or a selective absorption band in the wavelength range of green light and red light, respectively, when observed from a direction with a polar angle of 60 degrees. When the band is observed at a polar angle of 0 degree, the wavelength band shifts to the longer wavelength side, and the transmittances of green light and red light become substantially the same as the transmittance of blue light.

As shown in FIG. 1 or FIG. 2, the light source used in the liquid crystal display device emits light in the wavelength range of blue light 410 to 470 nm, the wavelength range of green light 520 to 580 nm, and the wavelength range of red light 600 to 660 nm. Has an intensity peak.
The optical element of the second embodiment may have a selective reflection band or a selective absorption band over the entire wavelength range of green light to red light (wavelength 450 to 700 nm) in observation from a direction with a polar angle of 60 degrees. However, it is preferable to have a selective reflection band or a selective absorption band respectively in the wavelength ranges corresponding to the wavelengths showing the emission intensity peaks in the green light wavelength region and the red light wavelength region.
Moreover, it is preferable that it has a selective reflection band or a selective absorption band in the range of wavelengths 520 nm to 600 nm and wavelengths 620 nm to 900 nm, respectively, in the front direction.

In the optical element of the second embodiment, the transmittance T _{B, N in} the front direction at a wavelength of 440 nm is usually 80% or more, and the average value T _{B, 60} of the transmittance in the polar angle 60 degrees direction at a wavelength of 440 nm is Usually, the transmittance T _{G, N in} the front direction at a wavelength of 530 nm is 80% or more, and the average value T _{G, 60} of the transmittance in the polar angle 60 ° direction at a wavelength of 530 nm is usually 50%. The transmittance T _{R, N in} the front direction at a wavelength of 620 nm is usually 80% or more and the average value T _R of the transmittance in the polar angle direction of 60 degrees at a wavelength of 620 nm. _{, 60} is usually 50 to 80%, preferably 60 to 70%.

  The optical element of the present invention has a transparent substrate and a layer having a selective reflection band or a selective absorption band formed on the transparent substrate.

(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. In other words, in the present invention, a UV absorber that is distributed more in the center in the thickness direction than in the vicinity of the surface of the transparent substrate is employed. The state of distribution of the ultraviolet absorber can be confirmed by measuring the transmittance of the ultraviolet region of the substrate fragment with a microspectroscope. In addition, the absence of an ultraviolet absorber on the surface of the transparent substrate can be confirmed by taking a reflection spectrum of the surface by infrared reflection absorption spectroscopy. 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 the (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 mm, L100 mm, t0.1 mm) and a 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 by adjusting the thickness and the composition of the material constituting the transparent substrate.

  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 the alicyclic olefin polymer 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. Described hydrogenated polymers; thermoplastic dicyclopentadiene-based ring-opening polymers described in JP-A No. 11-124429 (WO 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 content of a resin component (oligomer component) having a molecular weight of 2,000 or less in the thermoplastic resin is 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 K 0115.
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. All use of a double-flight type single screw extruder is required. 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 by bonding three films using an adhesive other than the above-described coextrusion 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.

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

(Hard coat layer)
The hard coat layer is a layer having a function of increasing the surface hardness, and preferably exhibits a hardness of “H” or higher in a pencil hardness test (a test plate is a glass plate) shown in JIS K 5600-5-4. The transparent substrate provided with such a hard coat layer preferably has a pencil hardness of 4H or higher.
The material for forming the hard coat layer (hard coat material) is preferably a material that is cured by heat or light. For example, organic hard such as organic silicone, melamine, epoxy, acrylic, urethane acrylate, etc. Coating materials; inorganic hard coat materials such as silicon dioxide; and the like. Among these, urethane acrylate-based and polyfunctional acrylate-based hard coat materials are preferable from the viewpoint of good adhesive strength and excellent productivity.

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

  In addition, the transparent substrate used in the present invention is preferably subjected to surface treatment in advance. By performing the surface treatment, the adhesion between the transparent substrate and the alignment film described later can be enhanced. Examples of the surface treatment include glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment, and flame treatment. It is also preferable to provide an adhesive layer (undercoat layer) on the transparent substrate in order to improve the adhesion between the transparent substrate and the alignment film.

[Layer with selective reflection band or selective absorption band]
The layer having a selective reflection band or selective absorption band constituting the optical element of the present invention is particularly limited as long as the optical element can exhibit a selective reflection band or selective absorption band satisfying the relationship of the above formula [1]. Not.

  As a layer having a selective reflection band or a selective absorption band, 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; Infrared reflective film obtained by biaxial stretching of multilayer films of different resins; Infrared reflective film obtained by uniaxial stretching of two types of resin films having different refractive indexes, and laminated by orthogonalizing them; A circularly polarizing reflector including a resin layer having cholesteric regularity having a selective reflection band in the infrared region; a right-twisted product and a left-twisted product of the circularly polarizing reflector being laminated; cholesteric regularity in the same twisting direction A laminate of two circularly polarized light reflectors including a resin layer with a half-wave plate; a grid polarizer or the like.

  In an optical element according to a preferred embodiment of the present invention, a layer having a selective reflection band or a selective absorption band includes a resin layer having cholesteric regularity (hereinafter sometimes referred to as a cholesteric resin layer).

FIG. 4 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 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 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. 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 composed of a para-substituted cyclic compound or the like with a polyacrylate, polymethacrylate, polysiloxane, polymalonate, etc. in a polymer main chain, directly or through a spacer portion composed of a conjugated atomic group ( 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). 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 chemical formula [1].
R ¹ -B ¹ -A ¹ -B ³ -MB ⁴ -A ² -B ² -R ² [1]
In addition, A ¹ and A ² in the chemical formula [1] are spacer groups as will be described later, but this spacer group is omitted and B ¹ and B ³ or B ⁴ and B ² are directly bonded. Also good.

In the chemical formula [1], R ¹ and R ² represent a polymerizable group. Specific examples of the polymerizable groups R ¹ and R ² include (r-1) to (r-15) shown in Chemical Formula 1, but are not limited thereto.

B ¹ , B ² , B ³ and B ⁴ each independently represents a single bond or a divalent linking group. Also, B ^3, at least one of B ⁴ is preferably a -O-CO-O-.

A ¹ and A ² 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), No. 2367670), acyloin ether (US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin compound (US Pat. No. 2,722,512), a combination of triarylimidazole dimer and p-aminophenyl ketone ( U.S. Pat. No. 3,549,367), acridine and phenazine compounds (JP-A-60-105667, U.S. 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 No. 98/00428, etc. Although it can be used as appropriate, a material having a large HTP, which 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, and a die coating method 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 this circularly polarized light is reflected is the selective reflection band.
As shown in FIG. 4, white light incident on the cholesteric resin layer of the circularly polarized light reflector at an incident angle θ1 is refracted at the surface of the cholesteric resin layer and passes through the cholesteric resin layer at a refraction angle θ2, corresponding to the wavelength λ. One circularly polarized light is reflected at the reflection angle θ2 by the cholesteric resin layer (the layer denoted by P2 in FIG. 4) having the pitch length P, and refracted at the surface of the cholesteric resin layer and emitted at the emission angle θ1. 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 [3].
λ _c = n × P × cos θ 2 Formula [2]
_{n o × P × cosθ2 ≦ λ} ≦ n e × P × cosθ2 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.
In order to provide a selective reflection band when observed from the front direction at a wavelength of 350 to 500 nm, the pitch length is preferably adjusted to 200 to 360 nm, more preferably 220 to 330 nm.
The pitch length is preferably adjusted to 260 to 500 nm, more preferably 280 to 470 nm in order to provide a selective reflection band at a wavelength of 450 to 700 nm when observed from the direction of a polar angle of 60 degrees.
In order to provide a selective reflection band at a wavelength of 520 to 600 nm when observed from the front direction, the pitch length is preferably adjusted to 300 to 430 nm, more preferably 320 to 400 nm.

In order to provide a selective reflection band when observed from the front direction at a wavelength of 620 to 900 nm, the pitch length is preferably adjusted to 360 to 640 nm, more preferably 380 to 600 nm.
Note that the pitch length is the distance in the chiral axis direction until the angle of the molecular axis gradually shifts in the chiral structure as it advances along the plane and then returns to the original molecular axis direction again.
Further, the reflectance increases according 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, 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.
In a liquid crystal display device, the polarization transmission axes of a pair of linear polarizers (hereinafter, the pair of linear polarizers may be referred to separately as a linear polarizer X and a linear polarizer Y (analyzer)), The liquid crystal cells are arranged so as to be parallel or perpendicular to each other. 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, a light reflecting element, a light source, a light diffusing element, and a 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, or the polarizing plate, the retardation plate, the illumination device, or the polarization illumination device. In particular, the light source, the optical element of the present invention, the linear polarizer X, the liquid crystal cell, and the linear polarizer Y are preferably arranged in this order. In addition, reflective elements, light guide plates, light diffusing elements, prism sheets, reflective polarizers, quarter wavelength plates, half wavelength plates, viewing angle compensation films, antireflection films, antiglare films, etc. are arranged. May be.

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

  In the liquid crystal display device of the present invention, the white light emitted from the light source passes through the optical element of the present invention and then passes through the liquid crystal panel so that an image can be visually recognized. In the optical element, the chromaticity coordinates of the transmitted light in the oblique direction are converted into light that is relatively blue or green as compared to the chromaticity coordinates of the transmitted light in the front direction. In the liquid crystal panel, since the chromaticity coordinate of the transmitted light in the oblique direction is converted to light that is relatively red or yellow as compared to the chromaticity coordinate of the transmitted light in the front direction, the light transmitted through the optical element is converted to the liquid crystal panel. When the light is transmitted, it becomes white light in which blue, green, and red are balanced in both the front direction and the oblique direction.

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

(Transparent substrate A)
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 supplied to 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. and an extruder gear pump speed of 18 rpm.

  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 10 μm mesh disc filter with a mesh opening, and the molten resin is injected at a temperature of the extruder outlet pump of 260 ° C. and a speed of the extruder gear pump of 18 rpm. The other surface of the multi-manifold die having a slip surface roughness Ra of 0.1 μm was supplied.

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. Substrate A was obtained by coextrusion molding. When discharging from the die, both sides of the die and the back side of the die are made of SUS enclosure, the distance from the die to the enclosure member is 100 to 200 mm, and the distance from the sheet-like laminate to the enclosure member is 250 to Covered to be between 300 mm. Also, edge pinning was adopted as a method of casting the molten film to a cooling roll with an air gap amount of 50 mm.
The depth of the linear concave portion or the height of the linear convex portion of the transparent substrate A was 20 nm or less and the width was in the range of 800 nm or more. The physical properties of the transparent substrate A are shown in Table 1.

(Transparent substrate B)
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 base material B 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. Table 1 shows the physical properties of the transparent substrate B.
In addition, the various conditions at the time of film manufacture are the same as the conditions of the transparent base material A.

(Transparent substrate C)
A polymethyl methacrylate resin (PMMA2) containing an ultraviolet absorber was subjected to single layer extrusion molding to obtain a film-like transparent substrate C having a width of 600 mm and a thickness of 80 μm. The physical properties of the transparent substrate C are shown in Table 1.
In addition, the various conditions at the time of film manufacture are the same as the conditions of the transparent base material A.

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

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

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

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

Example 1
Plasma treatment was performed on both surfaces of the transparent substrate A so that the wetting index was 56 dyne / cm. A solution comprising 5 parts by weight of polyvinyl alcohol and 95 parts by weight of water was applied to the surface of the transparent substrate A on the resin 1 layer side 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 A to obtain an alignment film having an average thickness of 0.1 μm.

Nematic liquid crystal compound (BASF, trade name “LC242”) 100 parts by weight, chiral agent (BASF, trade name “LC756”) 6.05 parts, photopolymerization initiator (Ciba Specialty Chemicals) , Trade name "Irgacure 907") 3.28 parts by weight and surfactant (trade name "KH-40", manufactured by Seimi Chemical Co., Ltd.) 0.23 parts by weight are dissolved in 164 parts by weight of methyl ethyl ketone, and polyfluoro having a pore size of 2 µm A coating solution was prepared by filtering using an ethylene CD / X syringe filter.
On the alignment film, the coating solution was applied to a dry thickness of 1 μm and dried at 100 ° C. for 5 minutes. Subsequently, ultraviolet rays were irradiated at 500 mJ / cm ² to form a cholesteric resin layer, thereby obtaining an optical element F1. The evaluation results of the optical element F1 are shown in Table 2.

Example 2
Plasma treatment was performed on both surfaces of the transparent substrate A so that the wetting index was 56 dyne / cm. A solution comprising 5 parts by weight of polyvinyl alcohol and 95 parts by weight of water was applied to the surface of the transparent substrate A on the resin 1 layer side 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 A to obtain an alignment film having an average thickness of 0.1 μm.

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

On the alignment film, the coating solution was applied to a dry thickness of 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, thereby obtaining an optical element F2. The evaluation results of the optical element F2 are shown in Table 2.

Comparative Example 1
Transparent substrate B was used as optical element F3. The evaluation results of the optical element F3 are shown in Table 2.

Comparative Example 2
An optical element F4 was obtained in the same manner as in Example 1 except that the transparent substrate A was changed to the transparent substrate C. The evaluation results of the optical element F4 are shown in Table 2.

(Transmittance of optical element)
The collimated white light having the emission spectrum shown in FIG. 1 is incident on the optical element at polar angles of 0 degrees and 60 degrees, and the light transmittance is measured by a spectroscope (trade name “S-2600” manufactured by Soma Optical Co., Ltd.). Measured with

(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

(Bright spot)
Cut the circularly polarized light reflector into a square with a side of 20 cm, place the circularly polarized light reflector on the backlight so that the cholesteric resin layer is on the backlight side, and five observers visually observe the luminescent spots (optical defects). ) Was confirmed.
○: One or less persons judged to have bright spots ×: Two or more persons judged to have bright spots

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

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

Example 3
(Creating a polarizer)
The polyvinyl alcohol film was uniaxially stretched 2.5 times, immersed in an aqueous solution at 30 ° C. containing 0.2 g / L of iodine and 60 g / L of potassium iodide, and then 70 g / L of boric acid and potassium iodide. It was immersed in an aqueous solution containing 30 g / L and simultaneously uniaxially stretched 6.0 times and held for 5 minutes. Finally, it was dried at room temperature for 24 hours, with an average thickness of 30 μm, and a degree of polarization. 99.95% of the polarizer P was obtained.

(Creation of incident side polarizing plate X)
A polyvinyl alcohol-based adhesive is applied to both surfaces of the polarizer P, a surface on which the cholesteric resin layer of the optical element F1 is not formed is superimposed on one surface of the polarizer P, and a transparent group is formed on the other surface of the polarizer P. The material A was overlapped, and the incident side polarizing plate X having a selective reflection band was obtained by a roll-to-roll method.

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

  The incident-side polarizing plate X is overlaid on one surface of a liquid crystal cell in VA (vertical alignment) mode with the transparent substrate A side facing the liquid crystal cell side, and the outgoing-side polarizing plate Y is overlaid on the other surface of the liquid crystal cell. A liquid crystal panel was obtained. The polarization transmission axis of the incident side polarizing plate X and the polarization transmission axis of the output side polarizing plate Y were set to be in a perpendicular relationship.

  From the incident side polarizing plate X side, white light having the emission spectrum shown in FIG. 1 is incident on the liquid crystal panel, the liquid crystal panel is in a white display state, the chromaticity of the transmitted light is measured, and the CIE ) Chromaticity coordinates were determined based on the color system (JIS Z 8701) established in 1931, and the distribution according to the observation angle was determined.

The results are shown in FIG. 5 and FIG. FIG. 5 shows chromaticity coordinates (x, y). The white circle is the chromaticity when the polar angle is 0 degree. There is little shift of chromaticity coordinates depending on the observation angle, and a small distribution is formed around the white circles. FIG. 6 shows the linear distance (Δxy) between the chromaticity coordinates (x _N , y _N ) in the front direction and the chromaticity coordinates (x _θ , y _θ ) in the oblique direction. It can be seen that (Δxy) does not increase as much as the difference even when the observation angle increases.
Table 3 shows the evaluation results of chromaticity change, color unevenness, and frame failure.

Example 4
A liquid crystal panel was obtained in the same manner as in Example 3 except that the optical element F1 was replaced with the optical element F2.
The results of the chromaticity distribution according to the observation angle are shown in FIGS. FIG. 7 shows chromaticity coordinates (x, y). The white circle is the chromaticity when the polar angle is 0 degree. There is little shift of chromaticity coordinates depending on the viewing angle, and the distribution is small and small. FIG. 8 shows the linear distance (Δxy) between the chromaticity coordinates (x _N , y _N ) in the front direction and the chromaticity coordinates (x _θ , y _θ ) in the diagonal direction. It can be seen that (Δxy) does not increase as much as the difference even when the observation angle increases.
Table 3 shows the evaluation results of chromaticity change, color unevenness, and frame failure.

Comparative Example 3
(Creation of incident side polarizing plate Z)
A polyvinyl alcohol-based adhesive is applied to both sides of the polarizer P, the optical element F3 is overlapped on both sides of the polarizer P, and the incident side polarizing plate Z having no selective reflection band and no selective absorption band is bonded by a roll-to-roll method. Obtained.
A liquid crystal panel was obtained in the same manner as in Example 3 except that the incident side polarizing plate X was changed to the incident side polarizing plate Z.

The results of the chromaticity distribution according to the observation angle are shown in FIGS. FIG. 9 shows chromaticity coordinates (x, y). The white circles in FIG. 9 are chromaticity coordinates with a polar angle of 0 degrees. It can be seen that as the observation angle increases, the chromaticity is distributed in the upper right direction. FIG. 10 shows the linear distance (Δxy) between the chromaticity coordinates (x _N , y _N ) in the front direction and the chromaticity coordinates (x _θ , y _θ ) in the oblique direction. It can be seen that (Δxy) increases as the polar angle increases.
Table 3 shows the evaluation results of chromaticity change, color unevenness, and frame failure.

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

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

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

  As shown in Tables 2 and 3, the liquid crystal display devices of Examples 3 and 4 manufactured according to the present invention have no chromaticity change, uneven color, and no frame failure. On the other hand, the liquid crystal display device of Comparative Example 3 has color unevenness, a frame failure, and poor display image visibility.

Claims (11)

A transparent substrate comprising a thermoplastic resin, wherein the UV absorber is unevenly distributed in the center in the thickness direction, and has an average thickness of less than 100 μm; and a selective reflection band or a selection formed on the transparent substrate Having a layer with an absorption band;
Transmittance T _{B, N} in the front direction at a wavelength of 440 nm, average value T _{B, 60} of transmittance in a polar angle of 60 degrees direction at a wavelength of 440 nm, transmittance T _{G, N} in the front direction at a wavelength of 530 nm, polar angle at a wavelength of 530 nm The average value T _{G, 60} of the transmittance in the direction of 60 degrees, the transmittance T _{R, N} in the front direction at a wavelength of 620 nm, and the average value T _{R, 60} of the transmittance in the polar angle 60 degrees direction at a wavelength of 620 nm are expressed by the formula [1 ]: (T _{B, 60} / T _{B, N} )> (T _{G, 60} / T _{G, N} ) ≈ (T _{R, 60} / T _{R, N} )
An optical element that satisfies the above relationship. 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 the optical element has at least one selective reflection band or selective absorption band in a wavelength range of 350 nm to 500 nm in the front direction.   The optical element according to claim 1, wherein the optical element has at least one selective reflection band or selective absorption band in a wavelength range of 450 nm to 700 nm in a polar angle direction of 60 degrees.   The optical element according to claim 1, wherein the layer having a selective reflection band or a selective absorption band includes a resin layer having cholesteric regularity.   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 6 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 10, 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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