JP4397757B2 - Optical element, condensing backlight system, and liquid crystal display device - Google Patents

Description

  The present invention relates to an optical element using a polarizing element. The present invention also relates to a condensing backlight system using the optical element, and further to a liquid crystal display device using the same.

  Attempts have long been made to condense or collimate a diffuse light source using an optical film having a flat surface, or to control the transmittance only in a specific direction. As a typical example, there is a method of combining a bright line light source and a band pass filter (for example, Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, Patent Document 5, Patent Document 6, Patent Document 7, (See Patent Document 8, Patent Document 9, etc.). In addition, a light source that emits bright lines, such as CRT and electroluminescence, and a method of concentrating and collimating light by arranging a bandpass filter on a display device have been proposed (for example, Patent Document 10, Patent Document 11, Patent). (Refer to Literature 12, Patent Literature 13, Patent Literature 14 and the like).

  Further, a method combining polarization and phase difference has been proposed (see Patent Document 15). Other optical elements comprising a reflective polarizer, an optical rotatory plate, and a reflective polarizer have been proposed (see Patent Document 16, Patent Document 17, and Patent Document 18). Moreover, what uses the hologram material is proposed (refer patent document 19).

  However, in the method using the bright line spectrum as an optical film for imparting directivity to the diffused light source, the precision relating to the wavelength matching between the light source type and the bandpass filter is high, and the production is difficult. On the other hand, it is not a big problem with monochromatic light, but when it corresponds to the three primary colors, the color will be felt if the transmittance change of each color does not change at the same ratio depending on the incident angle. Therefore, the combination of the bright line light source and the bandpass filter requires precise matching between the light source wavelength and the bandpass filter, and the technical difficulty is high.

  For example, in Patent Document 13 and Patent Document 14, a reflection plate obtained by combining a left circular polarization separation plate and a right circular polarization separation plate, or a reflection obtained by arranging a half-wave plate between circular polarization separation plates in the same direction. Condensing light in the front direction using a plate. However, in this system, it is necessary to form a layer corresponding to each wavelength of the light source, and three sets of layers are necessary for colorization. This was complicated and expensive.

  In addition, when using polarized light and a phase difference, if the angle at which the light can be emitted is narrowed, a secondary transmission region tends to appear at a larger incident angle.

  In general, the optical path length increases when obliquely entering the phase difference plate, and the optical path length difference tends to increase as the optical path length increases. By combining this characteristic with a polarizer, a polarizing element having an angle dependency in transmittance as in Patent Document 15 can be manufactured. Such a polarizing element can change the transmittance according to the incident angle. For example, according to such a polarizing element, it is possible to increase the transmittance in the front direction and reduce the transmittance of oblique incident light.

  Furthermore, between the optical elements that separate circularly polarized light in the same direction, if a layer that does not have a phase difference in the front and gives a phase difference of ½ wavelength in the oblique direction is inserted, the oblique direction is totally reflected. Light is transmitted only in the direction (see Patent Document 20). However, in this method, if a condition for total reflection at a specific angle is set, there remains a problem that a region that transmits again at a larger incident angle occurs. As the incident angle increases, the optical path length increases and the phase difference received increases. For this reason, it has the property of transmitting again at an incident angle that receives a phase difference of 3/4 wavelength. For this reason, when the transmission characteristic only to the front face is narrowed down, a transmission component in an oblique direction is generated and a failure occurs.

  Patent Document 17, Patent Document 18, and Patent Document 19 are all about the problem of productivity reduction and area yield deterioration caused by laminating the reflective polarizer laminates for transflective reflector applications by shifting the angles. Can be produced by roll-to-roll by using an optical rotator to improve productivity. In such a general combination of a reflective polarizer, an optical rotatory plate, and a reflective polarizer, the angle dependency of the transmittance did not occur. In addition, it is difficult to control and manufacture a phase difference plate whose optical rotation characteristics change depending on the incident angle with a general optical material such as quartz or sucrose, or a laminated body of phase difference plates. there were. The TN liquid crystal layer functions as an optical rotatory plate, but it also functions as an optical rotator of approximately 90 ° in the oblique incident direction as in the front direction, and there is no particular phenomenon that the optical rotation angle changes depending on the incident angle. .

  On the other hand, most of the hologram materials are expensive, soft and have poor mechanical properties, and there is a problem in long-term durability.

As described above, the conventional optical element has problems such as difficulty in fabrication, difficulty in obtaining the desired optical characteristics, and poor reliability.
JP-A-6-235900 Japanese Patent Laid-Open No. 2-158289 Japanese Patent Laid-Open No. 10-321025 US Pat. No. 6,307,604 German Patent Application Publication No. 3836955 German Patent Application No. 42222028 European Patent Application Publication No. 578302 US Patent Application Publication No. 2002/34009 International Publication No. 02/25687 Pamphlet JP-T-2001-521643 Special table 2001-516066 gazette US Patent Application Publication No. 2002/036735 JP 2002-90535 A Japanese Patent Laid-Open No. 2002-258048 Japanese Patent No. 2561483 US Pat. No. 4,984,872 US Patent Application Publication No. 2003/63236 International Publication No. 03/27731 Pamphlet International Publication No. 03/27756 Pamphlet Japanese Patent Laid-Open No. 10-321025

  An object of the present invention is to provide an optical element that can condense and collimate incident light from a light source, and can suppress transmission of light in an arbitrary direction.

  Another object of the present invention is to provide a condensing backlight system using the optical element, and further to provide a liquid crystal display device.

  As a result of intensive studies to solve the above problems, the present inventors have found the following optical elements and have completed the present invention. That is, the present invention is as follows.

And emits the polarized light separating incoming Shako, a polarizing element is formed by a cholesteric liquid crystal (A),
An optical element in which a linearly polarized light reflective polarizer (B) that transmits one of orthogonal linearly polarized light and selectively reflects the other is laminated,
The polarizing element (A) is formed of a cholesteric liquid crystal layer having a reflection bandwidth of 200 nm or more and a pitch length changing.
The outgoing light with respect to the incident light in the normal direction has a distortion rate of 0.5 or more,
The outgoing light with respect to the incident light that is inclined by 60 ° or more from the normal direction has a distortion rate of 0.2 or less,
An optical element characterized in that the linearly polarized light component of outgoing light increases as the incident angle increases.

The linearly polarized light component of the emitted light that increases as the incident angle increases in the polarizing element (A) has a polarization axis of linearly polarized light in a direction substantially orthogonal to the normal direction of the polarizing element surface. the optical element of the upper Symbol characterized by.

The linearly polarized light component of the emitted light that increases as the incident angle increases in the polarizing element (A) has a polarization axis of linearly polarized light in a direction substantially parallel to the normal direction of the polarizing element surface. the optical element of the upper Symbol characterized by.

Polarizing element (A) has an upper SL have shifted Kano optical element, characterized in that substantially reflects non-transparent component of the incident light.

Upper SL have shifted Kano optical element thickness of the polarizing element (A) is characterized in that at 2μm or more.

Straight line polarized reflection type polarizer (B) is, on SL have shifted Kano optical element characterized in that it is a grid-type polarizer.

Straight line polarized reflection type polarizer (B) is, on SL have shifted Kano optical element, characterized in that two or more two or more layers of a multilayer thin film laminate having a refractive index difference.

The optical element of the upper Symbol the multi layer thin film laminate characterized in that it is a vapor deposition film.

Straight line polarized reflection type polarizer (B) is, on SL have shifted Kano optical element, characterized in that two or more two or more layers of a multilayer thin film laminate having a birefringence.

The optical element of the upper Symbol the multi layer thin film stack is characterized in that is obtained by stretching the two or more two or more layers of the resin laminate having birefringence.

Optical element characterized by being stacked to sandwich half-wave plate (C) between the polarizing element (A), the linearly polarized reflection type polarizer (B) in the above have shifted Kano optical element .

1/2-wavelength plate (C) is, upper Symbol optical element which is a wide-band wavelength plate that functions substantially as a half-wave plate in the entire visible light region.

The half- wave plate (C) has an X-axis direction in which the in-plane refractive index is maximum, a Y-axis direction perpendicular to the X-axis, nx, ny, and thickness d (nm). )
A front retardation value at each wavelength in the light source wavelength band (420~650nm): (nx-ny ) × d is, the optical elements of the upper SL, characterized in that at 1/2-wavelength ± 10%.

1/2-wavelength plate (C) is to control the retardation in the thickness direction, the upper SL have shifted Kano optical element, characterized in that is obtained by reducing the phase difference change with respect to the angle change.

The half- wave plate (C) has an in-plane refractive index in the X-axis direction, a direction perpendicular to the X-axis as a Y-axis, and a film thickness direction as a Z-axis. Is nx, ny, nz,
Nz = (nx-nz) / Nz coefficient expressed by (nx-ny) is -2.5 <optics above SL which is a Nz ≦ 1.

Characterized on the outside of the straight line polarized reflection type polarizer (B), the polarization transmission axis of the linearly polarized light reflection polarizer (B), that the polarizing plate is arranged so that the polarization axis direction of the polarizing plate are aligned above Symbol have shifted Kano optical element to.

Each layer, upper SL have shifted Kano optical element characterized by being laminated with transparent adhesive or pressure-sensitive adhesive.

Condensing backlight system, characterized in that the Kano optical element displacement have above formed by arranging at least a light source.

Upper Symbol condensing backlight system characterized by having a primary condensing means for condensing within ± 60 degrees from the law line direction.

Upper Symbol condensing backlight system, wherein the primary focusing means is a micro prism sheet array disposed on the light source.

To Kano condensing backlight system deviations have the liquid crystal display apparatus characterized by comprising placing at least a liquid crystal cell.

A liquid crystal display device, wherein a diffusion plate having no backscattering and depolarization is laminated on the liquid crystal cell viewing side on the liquid crystal display device.

  The optical element of the present invention includes a polarizing element (A) formed of cholesteric liquid crystal that emits polarized light by separating incident light, and a straight line that transmits one of orthogonal linearly polarized light and selectively reflects the other. A polarization reflection type polarizer (B) is disposed. An example of a sectional view of the optical element (X) of the present invention is shown in FIG. In the optical element of the present invention, the polarizing element (A) and the linearly polarized light reflecting polarizer (B) are disposed with a half-wave plate (C) interposed therebetween. An example of a cross-sectional view of the optical element (Y) of the present invention is shown in FIG.

  The optical elements (X) and (Y) of the present invention utilize a unique phenomenon of the polarizing element (A). That is, in the optical elements (X) and (Y) of the present invention, when the incident angle is increased to a certain extent, the emitted light is linearly polarized, and even if the incident angle is further increased, the polarization axis direction of the linearly polarized light does not change, Utilizing the unique property of the polarizing element (A) that keeps the polarization state constant, combining this with a linearly polarized reflective polarizer (B) and further a half-wave plate (C) The incident light is controlled to be in a predetermined direction, and the secondary transmission component is suppressed.

  In any of the polarizing elements (A), the outgoing light with respect to the incident light in the normal direction has a distortion rate of 0.5 or more, and circularly polarized light is emitted at an incident angle close to the normal incident light or the normal incident light. Since the ratio of circularly polarized light increases as the distortion rate of outgoing light with respect to incident light in the normal direction increases, it is preferably 0.7 or higher, and more preferably 0.9 or higher. On the other hand, the outgoing light with respect to the incident light inclined at an angle of 60 ° or more from the normal direction has a distortion rate of 0.2 or less, and linearly polarized light is emitted at a deep incident angle. Since the ratio of linearly polarized light increases as the distortion rate of the outgoing light with respect to the incident light incident with an inclination of 60 ° or more from the normal direction, it is preferably 0.2 or less, more preferably 0.1 or less. Thus, the polarizing element (A) of the present invention has a feature that the linearly polarized light component of the emitted light increases as the incident angle increases.

  As the polarizing element (A), the linearly polarized light component of the emitted light that increases as the incident angle increases has a linearly polarized light polarization axis substantially perpendicular to the normal direction of the polarizing element surface. it can. FIG. 1A shows that the outgoing light (e) transmitted through the polarizing element (A1) which is an optical surface (x-axis-y-axis plane) has different polarization components depending on the incident angle of the incident light (i). FIG. FIG. 1B is a conceptual diagram when the emitted light (e) is viewed from the z-axis direction. Note that, as shown in FIG. 3, (i) linearly polarized light, (ii) natural light, (iii) circularly polarized light, and (iv) elliptically polarized light.

  Emission light (e1): Emission light with respect to the incident light (i1) in the z-axis direction (normal direction) with respect to the polarizing element (A1), and is circularly polarized light.

  Outgoing light (e2), (e4): outgoing light with respect to incident light (i2), (i4) obliquely incident on the polarizing element (A1), and elliptically polarized light. The outgoing light (e2) is elliptically polarized light that exists on a plane including the z axis and the y axis and has an axis orthogonal to the plane. The outgoing light (e4) is elliptically polarized light that exists on a plane including the z-axis and the x-axis and has an axis orthogonal to the plane.

  Outgoing light (e3), (e5): outgoing light with respect to incident light (i3), (i5) obliquely incident on the polarizing element (A1) at a large angle, and linearly polarized light. The outgoing light (e3) is linearly polarized light that exists on a plane including the z-axis and the y-axis and has an axis orthogonal to the plane. The outgoing light (e5) is linearly polarized light that exists on a plane including the z-axis and the x-axis and has an axis orthogonal to the plane. Thus, the outgoing lights (e3) and (e5), which are linearly polarized light, have their polarization axes substantially perpendicular to the z-axis, that is, parallel to the optical surface (x-axis-y-axis plane). Yes.

  In the polarizing element (A), the linearly polarized light component of the emitted light that increases as the incident angle increases has a polarization axis of linearly polarized light in a direction substantially parallel to the normal direction of the polarizing element surface. Can be illustrated. FIG. 2A shows that the outgoing light (e) transmitted through the polarizing element (A2) which is an optical surface (x-axis-y-axis plane) has different polarization components depending on the incident angle of the incident light (i). FIG. FIG. 2B is a conceptual diagram when the emitted light (e) is viewed from the z-axis direction.

  Emission light (e41): Emission light with respect to the incident light (i41) in the z-axis direction (normal direction) with respect to the polarizing element (A2), and is circularly polarized light.

  Emission light (e42), (e44): Emission light with respect to incident light (i42), (i44) obliquely incident on the polarizing element (A2), and is elliptically polarized light. The outgoing light (e42) is elliptically polarized light that exists on a plane including the z-axis and the y-axis and has an axis parallel to the plane. The outgoing light (e44) is elliptically polarized light that exists on a plane including the z-axis and the x-axis and has an axis parallel to the plane.

  Outgoing light (e43), (e45): outgoing light with respect to incident light (i43), (i45) obliquely incident on the polarizing element (A2) at a large angle, and linearly polarized light. The outgoing light (e43) is linearly polarized light that exists on a plane including the z-axis and the y-axis and has an axis parallel to the plane. The outgoing light (e45) is linearly polarized light that exists on a plane including the z-axis and the x-axis and has an axis parallel to the plane. Thus, the outgoing lights (e43) and (e45) that are linearly polarized light have their polarization axes substantially parallel to the z axis, that is, orthogonal to the optical surface (x axis-y axis plane). Yes.

  The polarizing element (A) is formed of a cholesteric liquid crystal layer. The reflection bandwidth of the polarizing element is preferably 200 nm or more. Conventionally, a cholesteric liquid crystal layer is supposed to transmit / reflect circularly polarized light regardless of the incident angle. See FIG. In fact, until now, in the single-pitch narrow-band cholesteric liquid crystal layer (a1), the emitted light has been circularly polarized regardless of the incident angle of the incident light. In the present invention, a cholesteric liquid crystal layer having a broadband selective reflection wavelength band finds out and utilizes a phenomenon in which linearly polarized light is transmitted when the incident angle of incident light is large as described above. That is, this phenomenon is not obtained in a single pitch cholesteric liquid crystal layer having a selective reflection function only at a specific wavelength, but is obtained only in a cholesteric liquid crystal layer in which the pitch length is changed over a wide band.

  In the past, when a cholesteric liquid crystal layer having a large birefringence was oriented thickly to several tens of μm by Takezoe (Jpn. J. Appl. Phys., 22, 1080 (1983)) It has been reported that incident light having a large angle is totally reflected and cannot be transmitted. See FIG. However, this document does not describe that incident light having a large incident angle is linearly polarized.

  The polarizing element (A) having the above phenomenon can be obtained, for example, by stacking cholesteric liquid crystal layers having different center wavelengths to form a cholesteric liquid crystal layer having a selective reflection wavelength band covering the entire visible light region. See FIG. FIG. 6 shows a case where three layers of R (red wavelength region), G (green wavelength region), and B (blue wavelength region) are stacked. In addition, a cholesteric liquid crystal layer having a wider band by changing the twist pitch length in the thickness direction can be used. See FIG. Thus, the polarizing element having the above phenomenon may be a laminated product of cholesteric liquid crystal layers having a plurality of different selective reflection wavelength bands as shown in FIG. 6, and the pitch length is continuous in the thickness direction as shown in FIG. Any of the changing cholesteric liquid crystal layers can be used, and both have the same effect.

  The reason why the above phenomenon occurs is not clear. If the light is simply separated by the Brewster angle at the interface of the liquid crystal layer, linearly polarized light should be generated for a specific wavelength even in a single pitch cholesteric liquid crystal layer. Further, since there is no difference between the cholesteric liquid crystal layer laminate and the cholesteric liquid crystal layer whose pitch length continuously changes in the thickness direction, it is clear that there is no reflection effect due to the lamination interface. Therefore, it can be considered that the above phenomenon is that the cholesteric liquid crystal layer having a different wavelength band imparts a phase difference to the circularly polarized light separated when transmitted through the cholesteric liquid crystal layer and linearly polarized.

  In order for the above phenomenon to function effectively, a sufficiently wide selective reflection bandwidth is required, preferably 200 nm or more, more preferably 300 nm or more, and even more preferably 400 nm or more. Specifically, in order to cover the visible light region, it is necessary to cover the range of 400 to 600 nm. Since the selective reflection wavelength shifts to the short wavelength side according to the incident angle, the extended selective reflection wavelength band should be extended to the long wavelength side to cover the visible light range regardless of the incident angle. However, it is not limited to this.

  In order for the phenomenon of the polarizing element of the present invention to function effectively, the cholesteric liquid crystal layer is preferably sufficiently thick. In general, in the case of a cholesteric liquid crystal layer having a single pitch length, sufficient selective reflection can be obtained if the thickness is about several pitches (2 to 3 times the selective reflection center wavelength). If the selective reflection center wavelength is in the range of 400 to 600 nm, considering the refractive index of the cholesteric liquid crystal, it functions as a polarizing element if the thickness is about 1 to 1.5 μm. Since the cholesteric liquid crystal layer used in the polarizing element of the present invention has a reflection band in a wide band, the thickness is preferably 2 μm or more. The thickness is desirably 4 μm or more, more desirably 6 μm or more.

  In order to obtain the polarizing element (A), it is also preferable to use a broadband cholesteric liquid crystal whose selective reflection band covers the visible light range. This is because the broadband cholesteric liquid crystal layer has a large thickness and can effectively impart a phase difference.

  In the polarizing element (A), circularly polarized light is obtained from incident light in the front direction (normal direction), and linearly polarized light is emitted from incident light at a deep incident angle in a direction perpendicular to or parallel to the normal line. Therefore, if the selective reflection wavelength band is sufficiently extended to the long wavelength side, the reflectance in the visible light region does not change, and it can be visually recognized as a specular reflector having no color tone change.

  On the other hand, the linearly polarized light reflecting polarizer (B) transmits one of orthogonal linearly polarized light and selectively reflects the other. FIG. 8A shows that the outgoing light (e) transmitted through the linearly polarized light reflecting polarizer (B) that is the optical surface (x-axis-y-axis plane) is the same regardless of the incident angle of the incident light (i). It is a conceptual diagram which shows emitting the linearly polarized light of a direction. FIG. 8B is a conceptual diagram when the emitted light (e) is viewed from the z-axis direction. In FIG. 8, incident light (i) is not shown. Moreover, the linearly polarized light orthogonal to the outgoing light (e) is reflected.

  As shown in FIG. 11, the optical element (X) of the present invention is laminated in the order of the polarizing element (A) and the linearly polarized reflective polarizer (B), and the incident light is transmitted in this order. . FIG. 9 shows the outgoing light transmitted in the order of the polarizing element (A) and the linearly polarized reflective polarizer (B). FIG. 9 shows a case where the polarizing element (A1) is used as the polarizing element (A).

  Emission light (e21): Present on the z-axis. The circularly polarized light (e1) vertically transmitted through the polarizing element (A1) is transmitted through the linearly polarized light reflecting polarizer (B) to become linearly polarized light. Half of the circularly polarized light (e1) is transmitted and half is reflected.

  Emission light (e22): Present on a plane including the z-axis and the y-axis. The axis of elliptically polarized light (e2) that has passed through the polarizing element (A1) and the transmission axis of the linearly polarized light reflecting polarizer (B) are in a parallel relationship, and most of them are transmitted as linearly polarized light.

  Emission light (e23): exists on a plane including the z-axis and the y-axis. The axis of the linearly polarized light (e3) transmitted through the polarizing element (A1) and the transmission axis of the linearly polarized light reflective polarizer (B) are in the same direction and transmit linearly polarized light.

  Emission light (e24): Present on a plane including the z-axis and the x-axis. The axis of elliptically polarized light (e4) transmitted through the polarizing element (A1) and the transmission axis of the linearly polarized light reflection type polarizer (B) are orthogonal, and most of the light is reflected and some linearly polarized light is transmitted.

  Emission light (e25): Present on a plane including the z-axis and the x-axis. The axis of the linearly polarized light (e5) that has passed through the polarizing element (A1) and the transmission axis of the linearly polarized light reflective polarizer (B) are orthogonal, and all are reflected and no light is transmitted.

  9 illustrates the case where the polarizing element (A1) is used as the polarizing element (A). However, when the polarizing element (A2) is used as the polarizing element (A), the x-axis and the y-axis in FIG. It is possible to obtain outgoing light having a composition in which the relationship with is reversed.

  As described above, the light incident on the optical element (X) in the vertical direction becomes circularly polarized light by the polarizing element (A), and transmits only the light that matches the linearly polarized light transmission axis of the linearly polarized light reflecting polarizer (B). Anything that doesn't match is reflected. On the other hand, in the oblique direction, the state of the emitted light varies depending on the direction. In FIG. 1B, since the linearly polarized light transmission axes of the polarizing element (A1) and the linearly polarized light reflecting polarizer (B) coincide with each other in the x-axis direction, the incident light passes through the optical element (X). On the other hand, in the y-axis direction, since the linearly polarized light transmission axes of the polarizing element (A1) and the linearly polarized light reflecting polarizer (B) are orthogonal, the incident light does not pass through the optical element (X) and is totally reflected. Is done. Thus, in the front, the original light amount is 50% by the polarizing element (A1), and the light is half that by the linearly polarized light reflecting polarizer (B). However, if the polarization degree of the polarizing element (A1) and the linearly polarized light reflection type polarizer (B) is sufficiently high, there is little absorption loss and the efficiency is high if the reflected light is re-reflected by a backlight installed below. The optical element is dependent on the transmittance angle. The optical element (X) of the present invention is a transmittance angle-dependent optical element having a small absorption loss due to a polarization separation function by selective reflection using a cholesteric liquid crystal.

  Since the optical element (X) can obtain linearly polarized light as outgoing light, it has a function of improving luminance and condensing light by arranging it on the light source side of the liquid crystal display device. Further, since there is essentially no absorption loss, all light rays having an angle not incident on the liquid crystal display device are reflected to the light source side and recycled. This is because the light emitted from the light source in the oblique direction has an exit only in the front direction and is substantially condensed.

  The optical element (X) of the present invention is capable of concentrating light in a necessary direction including the front surface by reflecting light only in an arbitrary direction with respect to the light collecting characteristic. Specifically, in a notebook computer or the like that is essential for a liquid crystal display, no light is required in the vertical direction of the panel, and only light in the horizontal direction is required. Therefore, the optical element (X) of the present invention is preferably used. it can.

  On the other hand, as shown in FIG. 12, the optical element (Y) of the present invention is laminated in the order of a polarizing element (A), a half-wave plate (C), and a linearly polarized light reflecting polarizer (B). Incident light passes through the optical element (Y) in this order. The case where the polarizing element (A1) is used as the polarizing element (A) for the outgoing light transmitted in the order of the polarizing element (A) and the half-wave plate (C) will be described.

  In addition, in FIG. 15, the conceptual diagram in which polarization changes with a wavelength plate is shown. F: fast axis, S: slow axis. Reference numerals 15-1 and 15-2 denote conversion from linearly polarized light to circularly polarized light using a quarter wave plate. Reference numerals 15-3 and 15-4 denote conversion from circularly polarized light to linearly polarized light using a quarter wave plate. Reference numerals 15-5 and 15-6 indicate axial or rotational conversion using a half-wave plate.

  The light emitted from the polarizing element (A1) is as shown in FIG. When the outgoing light that has passed through the polarizing element (A1) passes through the half-wave plate (C), the circularly polarized light in the front direction (normal direction) becomes circularly polarized light whose rotational direction is reversed, as shown in FIG. The polarization direction of the linearly polarized light transmitted in the oblique direction is rotated by 90 degrees (see FIGS. 15-5 and 6).

  Emission light (e11): Present on the z-axis. This corresponds to the outgoing light (e1) transmitted vertically through the polarizing element (A1). Due to the phase difference of the half-wave plate (C), the outgoing light (e1) is circularly polarized light whose rotational direction is reversed.

  Outgoing light (e12): The outgoing light (e2) receives the phase difference of the half-wave plate (C), and the shaft angle is rotated by 90 degrees. The outgoing light (e12) is elliptically polarized light having an axis parallel to the plane including the z axis and the y axis.

  Outgoing light (e13): The outgoing light (e3) receives the phase difference of the half-wave plate (C), and the shaft angle is rotated 90 degrees. The outgoing light (e13) is linearly polarized light having an axis parallel to the plane including the z axis and the y axis.

  Outgoing light (e14): The outgoing light (e4) receives the phase difference of the half-wave plate (C), and the shaft angle is rotated by 90 degrees. The outgoing light (e14) is elliptically polarized light having an axis parallel to the plane including the z axis and the x axis.

  Outgoing light (e15): The outgoing light (e5) receives the phase difference of the half-wave plate (C), and the shaft angle is rotated by 90 degrees. The outgoing light (e15) is linearly polarized light having an axis parallel to the plane including the z axis and the x axis.

  The outgoing light transmitted through the polarizing element (A) and the half-wave plate (C) shown in FIG. 10 has the same polarization axis as that of the outgoing light transmitted through the polarizing element (A2) shown in FIG. Thus, circularly polarized light and elliptically polarized light having opposite rotation directions are obtained. Therefore, by laminating the linearly polarized light reflection type polarizer (B) on the optical element (X), it is possible to obtain emitted light similar to that obtained when the polarizing element (A2) is used as the polarizing element (A). it can. That is, in the oblique direction, the linearly polarized light transmission axis of the polarizing element (A) and the linearly polarized light reflecting polarizer (B) is orthogonal to the direction described in the optical element (X). The light is totally reflected without passing through the optical element (Y). This orientation can be controlled by the arrangement of the stretching axis of the half-wave plate (C) and the polarization transmission axis of the linearly polarized light reflecting polarizer (B). As described above, the optical element (Y) has an effect that the direction in which the emitted light is condensed can be arbitrarily controlled in addition to the effect of the optical element (X) by using the half-wave plate (C). Have.

  Specifically, when the angle between the transmission axis of the linearly polarized light reflective polarizer (B) and the extension axis of the half-wave plate (C) is (θ), when θ = 0 °, The axis for condensing is the reflection axis direction of the linearly polarized light reflection type polarizer (B). When θ = 45 °, the focusing axis is the transmission axis of the linearly polarized light reflecting polarizer (B). When 0 ° <θ <90 °, the condensing axis is an angle between the reflection axis of the linearly polarized reflective polarizer (B) and the transmission axis of the linearly polarized reflective polarizer (B).

  When applied to a general liquid crystal display for a notebook personal computer, the polarization transmission axis of the linearly polarized light reflection type polarizer (B) needs to be arranged at 45 ° with respect to the horizontal direction of the liquid crystal display. If θ = 22.5 ° is suitable for this, light in the vertical direction of the display is efficiently reflected.

  Generally, by installing a prism sheet on a surface light source, light in all directions can be collected in the front direction. Conventionally, a prism sheet is used by laminating a vertical prism sheet for converging light in the horizontal (left and right) direction on the front and a horizontal prism sheet for condensing light in the vertical (vertical) direction on the front. There were many. According to the present invention, the prism sheet can be removed or only one sheet can be obtained.

  By using the present invention, it is possible to easily obtain characteristics that could not be obtained by conventional optical elements. When the optical element according to the present invention is used, it is possible to obtain an optical element having a high transmittance in the front direction, a good oblique shielding effect, and no absorption loss in combination with the selective reflection characteristics of cholesteric liquid crystal. Stable performance can be easily obtained without requiring secondary transmission in an oblique direction and precise adjustment of wavelength characteristics.

  Further, unlike the conventional lens sheet and prism sheet, the optical element of the present invention does not require an air interface and can be used by being laminated with a polarizing plate or the like as a laminated integrated product, which is advantageous in terms of handling. It has a great effect on thinning. Because it does not have a regular structure that is visible like a prism structure, moiré is unlikely to occur, and the use of diffuser plates that reduce the total light transmittance and lower haze (generally the total light transmittance is improved) Has the advantage that it can be easily performed. Of course, there is no problem when used in combination with a prism sheet or the like. For example, it is preferable to use a combination in which condensing to a steep front is performed by a prism sheet, and a secondary transmission peak appearing at a large emission angle by the prism sheet is shielded by the optical element of the present invention.

  Further, in a conventional backlight device using only a prism sheet, the direction of the outgoing light peak tends to be biased away from the light source cold cathode tube. This is because a large number of light beams emitted obliquely from the light guide plate are emitted away from the light source cold cathode tube, and it is difficult to position the peak intensity in the vertical direction of the screen. On the other hand, when the optical element according to the present invention is used, the emission peak can be easily matched in the front direction.

  A viewing angle widening system can be constructed by combining a condensing backlight source using these optical elements and a diffuser plate that has little backscattering and does not cause depolarization.

  A condensing backlight system using the optical element thus obtained can easily obtain a light source having a higher degree of parallelism than conventional ones. In addition, since collimated light with reflected polarized light that has essentially no absorption loss can be obtained, the reflected non-parallel light component returns to the backlight side, and only the parallel light component is extracted by scattering reflection or the like. The recycling is repeated, and a substantially high transmittance and high light utilization efficiency can be obtained.

  As described above, the polarizing element (A) of the present invention can be formed of a cholesteric liquid crystal layer having a reflection bandwidth of 200 nm or more. The cholesteric liquid crystal layer can be formed by stacking cholesteric liquid crystal layers having a plurality of different selective reflection wavelength bands. Further, a cholesteric liquid crystal layer whose pitch length continuously changes in the thickness direction can be used. In order to control the emitted light as shown in the polarizing element (A1) in FIG. 1 or the polarizing element (A2) in FIG. 2 (control the direction of the polarization axis of the obliquely emitted light), an appropriate cholesteric liquid crystal layer is selected. And do it.

  The difference in the axial direction of the linearly polarized light of obliquely transmitted light such as the polarizing element (A1) and the polarizing element (A2) can be arbitrarily produced depending on the stacking order of the cholesteric liquid crystal layers and the production method. In the case of a polarization splitting element with a general Brewster angle, the transmitted light in the oblique direction is uniquely defined, and only those having a linearly polarized light axis in a direction substantially parallel to the normal of the optical surface can be obtained. Absent. The selective reflection wavelength band of the polarizing element (A) preferably includes at least 550 nm.

(Laminated cholesteric liquid crystal layer)
In the case where the polarizing element is a laminate of cholesteric liquid crystal layers having a plurality of different selective reflection wavelength bands, each cholesteric liquid crystal layer appropriately includes a plurality of cholesteric liquid crystal layers so that the reflection bandwidth of the laminate is 200 nm or more. Select and stack.

  A suitable cholesteric liquid crystal layer may be used without any particular limitation. For example, a liquid crystal polymer exhibiting cholesteric liquid crystallinity at high temperature, a polymerizable liquid crystal obtained by polymerizing a liquid crystal monomer and, if necessary, a chiral agent and an alignment aid by irradiation with ionizing radiation such as an electron beam or ultraviolet light or heat, or a liquid crystal polymer thereof A mixture etc. are mention | raise | lifted. The liquid crystallinity may be either lyotropic or thermotropic, but is preferably a thermotropic liquid crystal from the viewpoint of ease of control and ease of formation of a monodomain.

The cholesteric liquid crystal layer can be formed by a method according to a conventional alignment process. For example, rayon is formed by forming a film of polyimide, polyvinyl alcohol, polyester, polyarylate, polyamide imide, polyether imide, etc. on a support substrate having a birefringence retardation as small as possible such as triacetyl cellulose or amorphous polyolefin. An alignment film rubbed with a cloth or the like, an obliquely deposited layer of SiO _2, a substrate using a stretched substrate surface property such as polyethylene terephthalate or polyethylene naphthalate as an alignment film, or the substrate surface is rubbed with a cloth A substrate that has been processed with a fine polishing agent typified by Bengala and formed fine irregularities with fine alignment regulating force on the surface, or an alignment that generates liquid crystal regulating force by light irradiation such as azobenzene compound on the substrate film Liquid crystal polymer on a suitable alignment film consisting of a substrate on which a film is formed, etc. Expand and heat to a temperature above the glass transition temperature and below the isotropic phase transition temperature, then cool to below the glass transition temperature in a state where the liquid crystal polymer molecules are in the planar orientation to form a solidified layer in which the orientation is fixed And how to do it. Further, the structure may be fixed by irradiation of energy such as ultraviolet rays or ion beams at the stage where the alignment state is formed.

  The liquid crystal polymer film is formed by, for example, thinning a solution of a liquid crystal polymer in a solvent by spin coating, roll coating, flow coating, printing, dip coating, casting film formation, bar coating, or gravure printing. It can be carried out by a method of developing a layer and drying it as necessary. Examples of the solvent include chlorinated solvents such as methylene chloride, trichloroethylene, and tetrachloroethane; ketone solvents such as acetone, methyl ethyl ketone, and cyclohexanone; aromatic solvents such as toluene; cyclic alkanes such as cycloheptane; or N -Methyl pyrrolidone, tetrahydrofuran, etc. can be used suitably.

  In addition, a heating melt of a liquid crystal polymer, preferably a heating melt exhibiting an isotropic phase, is developed according to the above, and a thin layer is further developed and solidified while maintaining the melting temperature as necessary. can do. This method is a method that does not use a solvent. Therefore, the liquid crystal polymer can be developed even by a method that provides good hygiene in the working environment.

  In developing the liquid crystal polymer or the like, a method of superimposing a cholesteric liquid crystal layer through an alignment film may be employed as necessary for the purpose of reducing the thickness. The cholesteric liquid crystal layer thus obtained can be used without being peeled off from the support substrate / alignment substrate used at the time of film formation and transferred to another optical material.

  Cholesteric liquid crystal layer stacking methods include the method of laminating a plurality of individually produced cholesteric liquid crystal layers with an adhesive or adhesive, the method of crimping after swelling or dissolving the surface with a solvent, etc., heat, ultrasonic waves, etc. The crimping method is given while adding. Moreover, after producing a cholesteric liquid crystal layer, methods, such as overlaying the cholesteric liquid crystal layer which has another selective reflection center wavelength on this layer, can be used.

(Cholesteric liquid crystal layer whose pitch length changes continuously in the thickness direction)
For the cholesteric liquid crystal layer whose pitch length is continuously changed in the thickness direction, there is a method of irradiating the composition with an ionizing radiation such as an electron beam or an ultraviolet ray by the following method using a composition containing the same liquid crystal monomer. For example, a method using a difference in polymerization rate due to a difference in ultraviolet transmittance in the thickness direction (Japanese Patent Laid-Open No. 2000-95883), a method of forming a concentration difference in the thickness direction by extraction with a solvent (Japanese Patent No. 3062150) And a method of performing the second polymerization by changing the temperature after the first polymerization (US Pat. No. 6,057,008) and the like.

  In addition, a step of applying a liquid crystal mixture containing a polymerizable mesogenic compound (a) and a polymerizable chiral agent (b) to an alignment substrate, and a state in which the liquid crystal mixture is in contact with a gas containing oxygen from the substrate side A method of performing a polymerization and curing step by irradiating with ultraviolet rays, and increasing the difference in polymerization rate in the thickness direction due to inhibition of oxygen polymerization by irradiating ultraviolet rays from the substrate side (Japanese Patent Laid-Open No. 2000-139953) is preferably used. It is done.

  Regarding the method described in JP-A-2000-13953, a cholesteric liquid crystal layer having a wider reflection wavelength band can be obtained by the following method.

For example, in the ultraviolet polymerization step, the liquid crystal mixture is in contact with a gas containing oxygen at an ultraviolet irradiation intensity of 20 to 200 mW / cm ² at a temperature of 20 ° C. or higher for 0.2 to 5 seconds. The step (1) of irradiating ultraviolet rays from the alignment substrate side, the step (2) of heating the liquid crystal layer at 70 to 120 ° C. for 2 seconds or more in a state where the liquid crystal layer is in contact with the gas containing oxygen, and then In the state in which the liquid crystal layer is in contact with a gas containing oxygen, the step of irradiating with ultraviolet rays from the alignment substrate side at a temperature of 20 ° C. or higher and lower than the step (1) for 10 seconds or more. (3) Next, there is a method performed by the step (4) of irradiating ultraviolet rays in the absence of oxygen (Japanese Patent Application No. 2003-93963).

Further, in the ultraviolet polymerization step, the liquid crystal mixture is in contact with a gas containing oxygen, at a temperature of 20 ° C. or higher, an ultraviolet irradiation intensity of 1 to 200 mW / cm ² and a range of 0.2 to 30 seconds. Step (1) of irradiating ultraviolet rays from the alignment substrate side three times or more while lowering the ultraviolet irradiation intensity and lengthening the ultraviolet irradiation time each time the number of times of ultraviolet irradiation increases, and then in the absence of oxygen Then, there is a method performed by the step (2) of irradiating with ultraviolet rays (Japanese Patent Application No. 2003-94307).

Further, the ultraviolet polymerization step is carried out for 0.2 to 5 seconds at an ultraviolet irradiation intensity of 20 to 200 mW / cm ² at a temperature of 20 ° C. or higher in a state where the liquid crystal mixture is in contact with a gas containing oxygen. Step (1) of irradiating ultraviolet rays from the alignment substrate side, and then in a state where the liquid crystal layer is in contact with a gas containing oxygen, until it reaches a temperature higher than Step (1) and 60 ° C. or higher, A step (2) of irradiating with ultraviolet rays from the alignment substrate side for 10 seconds or more at a temperature rising rate of 2 ° C./second or lower with an ultraviolet irradiation intensity lower than that in step (1), and then irradiating with ultraviolet rays in the absence of oxygen. An example is a method performed in the step (3) (Japanese Patent Application No. 2003-94605).

  Furthermore, the following method can be used. In the following method, a cholesteric liquid crystal layer having a wide reflection wavelength band and good heat resistance can be obtained. For example, there is a method in which a liquid crystal mixture containing a polymerizable mesogenic compound (a), a polymerizable chiral agent (b) and a photopolymerization initiator (c) is subjected to ultraviolet polymerization between two substrates (Japanese Patent Application 2003). No. 4346, Japanese Patent Application No. 2003-4101). Further, there is a method in which a polymerizable ultraviolet absorber (d) is further added to the liquid crystal mixture and ultraviolet polymerization is carried out between two substrates (Japanese Patent Application No. 2003-4298). Also, a method of applying a liquid crystal mixture containing a polymerizable mesogenic compound (a), a polymerizable chiral agent (b), and a photopolymerization initiator (c) on an alignment substrate and subjecting it to ultraviolet polymerization in an inert gas atmosphere (Japanese Patent Application No. 2003-4406).

The ultraviolet polymerization step is performed for 0.1 to 5 seconds at a temperature of 70 ° C. or higher and an ultraviolet irradiation intensity of 10 to 200 mW / cm ^{2 in} a state where the liquid crystal mixture is in contact with a gas containing oxygen. , Ultraviolet ray irradiation (1), and then a step (2) of heat treatment at 70 ° C. or higher for 0.1 to 5 seconds in a state where the liquid crystal layer is in contact with a gas containing oxygen, After step (1) and step (2), the step can be performed by step (3) in which ultraviolet rays are irradiated in the absence of oxygen. Preferably, the step (1) and the step (2) are repeated a plurality of times, and then the step (3) of ultraviolet irradiation is performed (Japanese Patent Application No. 2004-71158).

Further, in the ultraviolet polymerization step, the liquid crystal mixture is in contact with a gas containing oxygen at an ultraviolet irradiation intensity of 10 to 200 mW / cm ² at a temperature of 70 ° C. or higher for 0.01 to 5 seconds. , Ultraviolet irradiation step (1), and then the step (2) of heat-treating at 70 ° C. or more for a time exceeding 5 seconds in a state where the liquid crystal layer is in contact with a gas containing oxygen. After step 1) and step (2), it can be carried out by having step (3) of irradiating with ultraviolet rays in the absence of oxygen. Preferably, the step (1) and the step (2) are repeated a plurality of times, and then the step (3) of ultraviolet irradiation is performed (Japanese Patent Application No. 2004-168666).

  In addition, as a manufacturing method of a polarizing element (A2), the method of the said Japanese Patent Application No. 2003-93963 is preferable.

  The polymerizable mesogenic compound (a), polymerizable chiral agent (b) and the like that form the cholesteric liquid crystal layer will be described below. These materials are cholesteric liquid crystal layers whose pitch length is continuously changed in the thickness direction, and cholesteric to form a laminate. Any liquid crystal layer can be used.

  As the polymerizable mesogenic compound (a), those having at least one polymerizable functional group and having a mesogenic group composed of a cyclic unit or the like are preferably used. Examples of the polymerizable functional group include an acryloyl group, a methacryloyl group, an epoxy group, and a vinyl ether group. Among these, an acryloyl group and a methacryloyl group are preferable. Further, by using a compound having two or more polymerizable functional groups, a crosslinked structure can be introduced to improve durability. Examples of the cyclic unit serving as a mesogenic group include biphenyl, phenylbenzoate, phenylcyclohexane, azoxybenzene, azomethine, azobenzene, phenylpyrimidine, diphenylacetylene, diphenylbenzoate, and bicyclohexane. Cyclohexylbenzene, terphenyl and the like. In addition, the terminal of these cyclic units may have substituents, such as a cyano group, an alkyl group, an alkoxy group, a halogen group, for example. The mesogenic group may be bonded via a spacer portion that imparts flexibility. Examples of the spacer portion include a polymethylene chain and a polyoxymethylene chain. The number of repeating structural units forming the spacer portion is appropriately determined depending on the chemical structure of the mesogenic portion, but the repeating unit of the polymethylene chain is 0 to 20, preferably 2 to 12, and the repeating unit of the polyoxymethylene chain is 0 to 0. 10, preferably 1-3.

The molar extinction coefficient of the polymerizable mesogenic compound (a) is 0.1 to 500 dm ³ mol ⁻¹ cm ⁻¹ @ 365 nm, 10 to 30000 dm ³ mol ⁻¹ cm ⁻¹ @ 334 nm, and 1000 to 100,000 dm ^3. it is preferable that the mol ^-1 cm ^-1 @ 314nm. Those having the molar extinction coefficient have ultraviolet absorbing ability. Molar extinction coefficient is ^{0.1~50dm 3 mol -1 cm -1 @ 365nm} , a ^{50~10000dm 3 mol -1 cm -1 @ 334nm} , is 10000~50000dm ³ mol ^-1 cm ^-1 @ 314nm More preferred. Molar extinction coefficient is ^{0.1~10dm 3 mol -1 cm -1 @ 365nm} , a ^{1000~4000dm 3 mol -1 cm -1 @ 334nm} , at 30000~40000dm ³ mol ^-1 cm ^-1 @ 314nm More preferably. Molar extinction coefficient of ^{0.1dm 3 mol -1 cm -1 @ 365nm} , 10dm 3 mol -1 cm -1 @ 334nm, 1000dm 3 mol -1 cm -1 @ without stick 314nm smaller than sufficient polymerization rate difference It is difficult to increase the bandwidth. On the other ^{hand, 500dm 3 mol -1 cm -1 @} 365nm, 30000dm 3 mol -1 cm -1 @ 334nm, 100000dm 3 mol -1 cm -1 @ If 314nm greater than the polymerization curing to not proceed completely does not end There is. The molar extinction coefficient is a value measured from the absorbance at 365 nm, 334 nm, and 314 nm obtained by measuring the spectrophotometric spectrum of each material.

  The polymerizable mesogenic compound (a) having one polymerizable functional group is, for example, a general formula of the following chemical formula 1:

(In the formula, R _{1 to} R ₁₂ may be the same or different and represent —F, —H, —CH ₃ , —C ₂ H ₅ or —OCH ₃ , and R ₁₃ represents —H or —CH ₃ . X ₁ is represented by the general formula (2):
— (CH ₂ CH ₂ O) _a — (CH ₂ ) _b — (O) _c —, and X ₂ represents —CN or —F. In the general formula (2), a is an integer of 0 to 3, b is an integer of 0 to 12, c is 0 or 1, and when a = 1 to 3, b = 0 and c = 0. Yes, when a = 0, b = 1 to 12, and c = 0 to 1. ).

  Examples of the polymerizable chiral agent (b) include LC756 manufactured by BASF.

  The amount of the polymerizable chiral agent (b) is preferably about 1 to 20 parts by weight, preferably 3 to 7 parts by weight based on 100 parts by weight of the total of the polymerizable mesogenic compound (a) and the polymerizable chiral agent (b). The part is more suitable. The helical twisting force (HTP) is controlled by the ratio of the polymerizable mesogenic compound (a) and the polymerizable chiral agent (b). By setting the ratio within the above range, the reflection band can be selected so that the reflection spectrum of the obtained cholesteric liquid crystal film can cover the long wavelength region.

  The liquid crystal mixture usually contains a photopolymerization initiator (c). Various kinds of photopolymerization initiators (c) can be used without particular limitation. Examples thereof include Irgacure 184, Irgacure 907, Irgacure 369, Irgacure 651 and the like manufactured by Ciba Specialty Chemicals. The blending amount of the photopolymerization initiator is preferably about 0.01 to 10 parts by weight with respect to 100 parts by weight of the total of the polymerizable mesogenic compound (a) and the polymerizable chiral agent (b), and 0.05 to 5 parts by weight. The part is more suitable.

  As the polymerizable ultraviolet absorber (d), a compound having at least one polymerizable functional group and having an ultraviolet absorbing function can be used without any particular limitation. Specific examples of the polymerizable ultraviolet absorber (d) include RUVA-93 manufactured by Otsuka Chemical Co., and UVA935LH manufactured by BASF. The blending amount of the polymerizable ultraviolet absorber (d) is preferably about 0.01 to 10 parts by weight with respect to a total of 100 parts by weight of the polymerizable mesogenic compound (a) and the polymerizable chiral agent (b). 5 parts by weight is more preferred.

  In order to widen the bandwidth of the resulting cholesteric liquid crystal film, the mixture can be mixed with an ultraviolet absorber to increase the UV exposure intensity difference in the thickness direction. Further, the same effect can be obtained by using a photoreaction initiator having a large molar extinction coefficient.

  The mixture can be used as a solution. Solvents used in preparing the solution are usually halogenated hydrocarbons such as chloroform, dichloromethane, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, phenols such as phenol and parachlorophenol, benzene, toluene, Aromatic hydrocarbons such as xylene, methoxybenzene, 1,2-dimethoxybenzene, others, acetone, methyl ethyl ketone, ethyl acetate, tert-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene bricol monomethyl ether, diethylene glycol Dimethyl ether, ethyl cellosolve, butyl cellosolve, 2-pyrrolidone, N-methyl-2-pyrrolidone, pyridine, triethylamine, te Rahidorofuran, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, can be used acetonitrile, butyronitrile, carbon disulfide, cyclopentanone, cyclohexanone and the like. The solvent to be used is not particularly limited, but methyl ethyl ketone, cyclohexanone, cyclopentanone and the like are preferable. Although the concentration of the solution depends on the solubility of the thermotropic liquid crystalline compound and the final film thickness of the cholesteric liquid crystal film, it cannot be generally stated, but it is usually preferably about 3 to 50% by weight.

  It should be noted that the exemplified alignment substrate can also be used when a cholesteric liquid crystal layer whose pitch length continuously changes in the thickness direction is produced. A similar method can be adopted as the orientation method.

(Linear polarization reflection type polarizer (B))
Examples of the linearly polarized light reflective polarizer (B) include a grid-type polarizer, a multilayer thin film laminate of two or more layers made of two or more materials having a difference in refractive index, and a deposited multilayer thin film having different refractive indexes used for a beam splitter, etc. , Two or more birefringent layer multilayer thin film laminates made of two or more materials having birefringence, two or more resin laminates using two or more resins having birefringence, stretched linearly polarized light For example, it may be separated by reflecting / transmitting in an orthogonal axial direction.

  For example, phase difference expression such as polyethylene naphthalate, polyethylene terephthalate, materials that generate phase difference by stretching such as polycarbonate, acrylic resin typified by polymethyl methacrylate, norbornene resin typified by JSR Arton, etc. A resin obtained by uniaxially stretching a small amount of resin alternately as a multilayer laminate can be used. Specific examples of the linearly polarized light reflective polarizer (B) include 3M DBEF, Nitto Denko PCF, and the like.

  The selective reflection wavelength bandwidth of the linearly polarized light reflection type polarizer (B) is preferably 200 nm or more, more preferably 300 nm or more, and further preferably 400 nm or more, like the polarizing element (A). Specifically, in order to cover the visible light region, it is preferable to cover the range of 400 to 600 nm. To cover the visible light range regardless of the incident angle, the selective reflection wavelength band shifts to the short wavelength side according to the incident angle, so it is desirable to set the extended selective reflection wavelength band mainly to the long wavelength side. Is not limited.

  In addition, the polarizing element (A) and the linearly polarized reflection type polarizer (B) have a selective reflection wavelength band of at least 550 nm, preferably 100 nm or more, more preferably 200 nm or more, and more preferably 300 nm or more. preferable.

(1/2 wavelength plate (C))
As the half-wave plate (C), for example, polyethylene naphthalate, polyethylene terephthalate, polycarbonate, norbornene resin represented by JSR Arton, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene and other polyolefins, polyarylate, Those obtained by uniaxially stretching a resin film such as polyamide, those obtained by improving the viewing angle characteristics by biaxially stretching, or those in which the nematic alignment state of the rod-like liquid crystal is fixed can be used.

  The half-wave plate (C) is preferably a broadband wave plate having a phase difference characteristic that functions as a substantially half-wave plate in the entire visible light region in order to align the optical characteristics of each color and suppress coloring. . This is because if the change in the retardation value for each wavelength is too large, a difference occurs in the polarization characteristics for each wavelength, which affects the shielding performance for each wavelength and is colored and visually recognized. In this half-wave plate (C), the direction in which the in-plane refractive index is maximum is the X axis, the direction perpendicular to the X axis is the Y axis, and the refractive indexes in the respective axial directions are nx, ny, and thickness d ( nm), the front phase difference value at each wavelength in the light source wavelength band (420 to 650 nm): (nx−ny) × d is preferably within ½ wavelength ± 10%. The variation of the phase difference value within the light source wavelength band is preferably small, desirably within ± 7%, and more desirably within ± 5%.

  Such a half-wave plate (C) can give a phase difference equivalent to a half-wave regardless of the wavelength of incident light by controlling different wavelength lamination characteristics by different axis lamination of different kinds of retardation plates or molecular design.

  A wider functioning wavelength band is better, but at least when the emission center wavelength of the light source is a cold cathode tube, blue is located at about 435 nm, green is at 545 nm, and red is at around 610 nm. Since light is emitted with a value width, it is desirable that the characteristics of the half-wave plate (C) function within a range of at least about 420 nm to 650 nm. Polyvinyl alcohol is representative as a material of a retardation plate having such characteristics, and as a material designed for molecular use for optics, a norbornene-based resin film represented by JSR Arton or Nippon Zeon Zeonore, Examples include Teijin Pure Ace WR.

  The half-wave plate (C) more preferably functions as a half-wave plate for obliquely incident light. Generally, a phenomenon occurs in which the phase difference value changes due to an increase in the optical path length of the half-wave plate with respect to an obliquely incident light beam, and deviates from the originally obtained phase difference value. In order to prevent this, it is preferable to use a half-wave plate (C) in which the retardation in the thickness direction is controlled and the change in retardation with respect to the change in angle is reduced. As a result, a phase difference equivalent to that of the vertically incident light can be imparted to the obliquely incident light.

  In general, an Nz coefficient is used as a control coefficient for the retardation value in the thickness direction. The Nz coefficient is defined by taking the direction in which the in-plane refractive index is maximum as the X axis, the direction perpendicular to the X axis as the Y axis, and the thickness direction of the film as the Z axis, and the refractive indexes in the respective axial directions as nx, ny, nz. , Nz = (nx−nz) / (nx−ny). In order to give a phase difference value equivalent to that of the normal incident light to the incident light from the oblique direction, −2.5 <Nz ≦ 1 is preferable. More preferably, −2 <Nz ≦ 0.5. A typical example of the retardation plate that has been controlled in the thickness direction is a NRZ film manufactured by Nitto Denko. Note that the method as shown in Patent Document 17 cannot prevent the secondary transmission in the oblique direction. This is because it is impossible to achieve both the development of the phase difference in the oblique direction and the suppression of the increase in the phase difference in the oblique direction. This is the advantage of the present invention.

  The half-wave plate (C) may be composed of a single retardation plate, and two or more retardation plates can be laminated and used so as to have a desired retardation. The thickness of the half-wave plate (C) is usually preferably from 0.5 to 200 μm, particularly preferably from 1 to 100 μm.

(Lamination of each layer)
The optical element of the present invention can be used not only in the optical path but also in a bonded state. This is because the air interface is not required because the transmittance is controlled not by the surface shape but by the polarization characteristics of the optical element.

  The layers are preferably laminated using an adhesive or a pressure-sensitive adhesive from the viewpoint of workability and light utilization efficiency. In that case, the adhesive or pressure-sensitive adhesive is transparent, has no absorption in the visible light region, and the refractive index is desirably as close as possible to the refractive index of each layer from the viewpoint of suppressing surface reflection. From this viewpoint, for example, an acrylic pressure-sensitive adhesive can be preferably used. Each layer is separately formed into a monodomain in the form of an alignment film, etc., and sequentially laminated by a method such as transfer to a translucent substrate, an alignment film or the like for alignment without providing an adhesive layer, etc. It is also possible to form the layers as appropriate and to form each layer directly in sequence.

  In each layer and (viscous) adhesive layer, particles are added to adjust the degree of diffusion as necessary to give isotropic scattering, UV absorbers, antioxidants, leveling during film formation A surfactant or the like can be appropriately added for the purpose of imparting property.

(Condensing backlight system)
It is desirable to dispose a diffuse reflector on the light source (on the side opposite to the liquid crystal cell arrangement surface). The main component of the light beam reflected by the collimating film is an oblique incident component, and is regularly reflected by the collimating film and returned to the backlight direction. Here, when the regular reflection property of the reflector on the back side is high, the reflection angle is preserved, and the light cannot be emitted in the front direction and becomes lost light. Accordingly, it is desirable to dispose a diffuse reflector in order to increase the scattering reflection component in the front direction without preserving the reflection angle of the reflected return beam.

  The light condensing characteristic according to the present invention can control light condensing in the front direction even with a diffusing surface light source such as a direct type backlight or an inorganic / organic EL element.

  It is desirable to install an appropriate diffusion plate (D) between the optical elements (X) and (Y) of the present invention and the backlight source (L). This is because the light reuse efficiency is increased by scattering the incident and reflected light rays in the vicinity of the backlight light guide and scattering a part thereof in the vertical incident direction. The diffusion plate can be obtained by a method such as embedding fine particles having different refractive indexes in a resin in addition to a surface irregularity shape. This diffusion plate may be sandwiched between the optical elements (X) and (Y) and the backlight, or may be bonded to the optical elements (X) and (Y).

  When the liquid crystal cell (LC) bonded with the optical elements (X) and (Y) is disposed close to the backlight, there is a possibility that Newton's ring may occur in the gap between the film surface and the backlight. By arranging a diffusion plate having surface irregularities on the light guide plate side surface of the elements (X) and (Y), generation of Newton rings can be suppressed. Moreover, you may form the layer which served as the uneven | corrugated structure and the light-diffusion structure in the surface itself of optical element (X) in this invention, (Y).

(Liquid crystal display device)
The optical elements (X) and (Y) are suitably applied to a liquid crystal display device in which polarizing plates (P) are disposed on both sides of a liquid crystal cell (LC), and the optical elements (X) and (Y) are It is applied to the polarizing plate (P) side of the light source side surface of the liquid crystal cell. In FIGS. 13 and 14, a polarizing plate (P) is laminated on a linearly polarized light reflecting polarizer (B). The optical elements (X) and (Y) are arranged so that the polarizing element (A) is on the light source side.

  16 to 19 illustrate liquid crystal display devices. 16 to 19 illustrate the case where the optical element (Y) is used. A reflector (RF) is also shown along with the light source (L). FIG. 16 shows a case where a direct type backlight (L) is used as the light source (L). FIG. 17 shows a case where a sidelight type light source (L) is used for the light guide plate (S). FIG. 18 shows a case where a planar light source (L) is used. FIG. 19 shows a case where a prism sheet (Z) is used.

  By laminating a diffusion plate that does not have backscattering and depolarization on the liquid crystal cell viewing side on the liquid crystal display device combined with the above-mentioned collimated backlight, light with good display characteristics near the front is diffused. The viewing angle can be enlarged by obtaining uniform and good display characteristics within the entire viewing angle.

  The viewing angle widening film used here is a diffusion plate that does not substantially have backscattering. The diffusion plate can be provided as a diffusion adhesive material. The location is on the viewing side of the liquid crystal display device, but it can be used either above or below the polarizing plate. However, it is desirable to provide a layer as close to the cell as possible, such as between the polarizing plate and the liquid crystal cell, in order to prevent the deterioration of the contrast due to the influence of the blur of the pixel or the like or the slight remaining backscattering. In this case, a film that does not substantially eliminate polarized light is desirable. For example, a fine particle dispersion type diffusion plate as disclosed in JP-A Nos. 2000-347006 and 2000-347007 is preferably used.

  When the viewing angle widening film is located outside the polarizing plate, the collimated light beam is transmitted from the liquid crystal layer to the polarizing plate, so that in the case of the TN liquid crystal cell, it is not necessary to use a viewing angle compensating retardation plate. In the case of an STN liquid crystal cell, it is only necessary to use a retardation film in which only the front characteristics are well compensated. In this case, since the viewing angle widening film has an air surface, it is possible to adopt a type based on a refraction effect due to the surface shape.

  On the other hand, when a viewing angle widening film is inserted between the polarizing plate and the liquid crystal layer, it becomes a diffused light at the stage where it passes through the polarizing plate. In the case of a TN liquid crystal, it is necessary to compensate for the viewing angle characteristics of the polarizer itself. In this case, it is necessary to insert a retardation plate for compensating the viewing angle characteristics of the polarizer between the polarizer and the viewing angle widening film. In the case of STN liquid crystal, it is necessary to insert a phase difference plate for compensating the viewing angle characteristics of the polarizer in addition to the front phase difference compensation of STN liquid crystal.

  In the case of a viewing angle widening film having a regular structure inside, such as a conventional microlens array film or hologram film, a microlens included in a black matrix of a liquid crystal display device or a conventional parallel light conversion system of a backlight Moire was likely to occur due to interference with a fine structure such as an array / prism array / louver / micromirror array. However, the collimated film in the present invention has no regular structure in the plane, and there is no regular modulation of the emitted light, so there is no need to consider compatibility with the viewing angle widening film and the arrangement order. Accordingly, the viewing angle widening film is not particularly limited as long as it does not cause interference / moire with the pixel black matrix of the liquid crystal display device, and the options are wide.

  In the present invention, it is a light scattering plate as described in JP-A-2000-347006 and JP-A-2000-347007, which has substantially no backscattering as a viewing angle widening film and does not cancel polarization. A haze of 80% to 90% is preferably used. In addition, a hologram sheet, a microprism array, a microlens array, or the like can be used as long as it does not form interference / moire with the pixel black matrix of the liquid crystal display device even if it has a regular structure inside. Such primary condensing means is preferably one that condenses within ± 60 degrees from the normal direction, and further condenses within ± 50 degrees.

(Other materials)
Note that the liquid crystal display device is manufactured by appropriately using various optical layers and the like according to a conventional method.

  In general, a polarizing plate having a protective film on one side or both sides of a polarizer is generally used.

  The polarizer is not particularly limited, and various types can be used. Examples of the polarizer include hydrophilic polymer films such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene / vinyl acetate copolymer partially saponified film, and two colors such as iodine and dichroic dye. Examples thereof include polyene-based oriented films such as those obtained by adsorbing volatile substances and uniaxially stretched, polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Among these, a polarizer composed of a polyvinyl alcohol film and a dichroic material such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm.

  A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching it can be produced, for example, by dyeing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution such as potassium iodide which may contain boric acid, zinc sulfate, zinc chloride and the like. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface and anti-blocking agent by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven dyeing by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, or may be performed while dyeing, or may be performed with dyeing after iodine. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

  As a material for forming the transparent protective film provided on one side or both sides of the polarizer, a material excellent in transparency, mechanical strength, thermal stability, moisture shielding property, isotropy and the like is preferable. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, styrene such as polystyrene and acrylonitrile / styrene copolymer (AS resin) -Based polymer, polycarbonate-based polymer and the like. Polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Polymer blends and the like are also examples of polymers that form the transparent protective film. The transparent protective film can also be formed as a cured layer of thermosetting or ultraviolet curable resin such as acrylic, urethane, acrylurethane, epoxy, and silicone.

  Moreover, the polymer film described in JP-A-2001-343529 (WO01 / 37007), for example, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain, and (B) a substitution in the side chain And / or a resin composition containing a thermoplastic resin having unsubstituted phenyl and a nitrile group. A specific example is a film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the film, a film made of a mixed extruded product of the resin composition or the like can be used.

  Although the thickness of a protective film can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and handleability, and thin layer property. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable.

  Moreover, it is preferable that a protective film has as little color as possible. Therefore, Rth = [(nx + ny) / 2−nz] · d (where nx and ny are the main refractive index in the plane of the film, nz is the refractive index in the film thickness direction, and d is the film thickness). A protective film having a retardation value in the film thickness direction of −90 nm to +75 nm is preferably used. By using a film having a thickness direction retardation value (Rth) of −90 nm to +75 nm, the coloring (optical coloring) of the polarizing plate caused by the protective film can be almost eliminated. The thickness direction retardation value (Rth) is more preferably −80 nm to +60 nm, and particularly preferably −70 nm to +45 nm.

  As the protective film, a cellulose polymer such as triacetyl cellulose is preferable from the viewpoints of polarization characteristics and durability. A triacetyl cellulose film is particularly preferable. In addition, when providing a protective film in the both sides of a polarizer, the protective film which consists of the same polymer material may be used by the front and back, and the protective film which consists of a different polymer material etc. may be used. The polarizer and the protective film are usually in close contact with each other through an aqueous adhesive or the like. Examples of the water-based adhesive include an isocyanate-based adhesive, a polyvinyl alcohol-based adhesive, a gelatin-based adhesive, a vinyl-based latex, a water-based polyurethane, and a water-based polyester.

  The surface of the transparent protective film to which the polarizer is not adhered may be subjected to a hard coat layer, an antireflection treatment, an antisticking treatment, or a treatment for diffusion or antiglare.

  The hard coat treatment is applied for the purpose of preventing scratches on the surface of the polarizing plate. For example, a transparent protective film with a cured film excellent in hardness, sliding properties, etc. by an appropriate ultraviolet curable resin such as acrylic or silicone is used. It can be formed by a method of adding to the surface of the film. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.

  Anti-glare treatment is applied for the purpose of preventing external light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, roughening by sandblasting or embossing. It can be formed by imparting a fine concavo-convex structure to the surface of the transparent protective film by an appropriate method such as a method or a compounding method of transparent fine particles. Examples of the fine particles to be included in the formation of the surface fine concavo-convex structure include a conductive material made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, or the like having an average particle diameter of 0.5 to 50 μm. Transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, etc. may be used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  The antireflection layer, antisticking layer, diffusion layer, antiglare layer, and the like can be provided on the transparent protective film itself, or can be provided separately from the transparent protective film as an optical layer.

  A retardation plate is laminated on a polarizing plate as a viewing angle compensation film and used as a wide viewing angle polarizing plate. The viewing angle compensation film is a film for widening the viewing angle so that an image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction rather than perpendicular to the screen. As the retardation plate, an appropriate quarter-wave plate or half-wave plate is used according to the purpose of use. As these materials, materials whose phase difference is controlled using the same material as that of the half-wave plate (C) can be used.

  As such a viewing angle compensation retardation plate, a birefringent film that has been biaxially stretched or stretched in two orthogonal directions, a bidirectionally stretched film such as a tilted orientation film, and the like are used. Examples of the inclined alignment film include a film obtained by bonding a heat shrink film to a polymer film and stretching or / and shrinking the polymer film under the action of the contraction force by heating, and a film obtained by obliquely aligning a liquid crystal polymer. Can be mentioned. The viewing angle compensation film can be appropriately combined for the purpose of preventing coloring or the like due to a change in viewing angle based on a phase difference caused by a liquid crystal cell or increasing the viewing angle for good viewing.

  In addition, from the viewpoint of achieving a wide viewing angle with good visibility, an optically compensated phase difference in which an optically anisotropic layer composed of a liquid crystal polymer alignment layer, particularly a discotic liquid crystal polymer gradient alignment layer, is supported by a triacetylcellulose film. A plate can be preferably used.

  In addition to the above, the optical layer laminated in practical use is not particularly limited. For example, one or more optical layers that may be used for forming a liquid crystal display device such as a reflective plate or a transflective plate are used. Can do. In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a reflecting plate or a semi-transmissive reflecting plate is further laminated on an elliptical polarizing plate or a circular polarizing plate can be given.

  A reflective polarizing plate is a polarizing plate provided with a reflective layer, and is used to form a liquid crystal display device or the like that reflects incident light from the viewing side (display side). Such a light source can be omitted, and the liquid crystal display device can be easily thinned. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is attached to one surface of the polarizing plate via a transparent protective layer or the like as necessary.

  Specific examples of the reflective polarizing plate include those in which a reflective layer is formed by attaching a foil or vapor-deposited film made of a reflective metal such as aluminum on one surface of a protective film matted as necessary. In addition, the protective film may include fine particles having a surface fine concavo-convex structure and a reflective layer having a fine concavo-convex structure thereon. The reflective layer having the fine concavo-convex structure has an advantage that incident light is diffused by irregular reflection to prevent directivity and glaring appearance and to suppress unevenness in brightness and darkness. Moreover, the protective film containing fine particles also has an advantage that incident light and its reflected light are diffused when passing through it and light and dark unevenness can be further suppressed. The reflective layer with a fine concavo-convex structure reflecting the surface fine concavo-convex structure of the protective film is transparently protected by an appropriate method such as a vapor deposition method such as a vacuum deposition method, an ion plating method, a sputtering method, or a plating method. It can be performed by a method of attaching directly to the surface of the layer.

  The reflective plate can be used as a reflective sheet in which a reflective layer is provided on an appropriate film according to the transparent film, instead of the method of directly imparting to the protective film of the polarizing plate. Since the reflective layer is usually made of metal, the usage form in which the reflective surface is covered with a protective film, a polarizing plate or the like is used to prevent a decrease in reflectance due to oxidation, and thus the long-term sustainability of the initial reflectance. More preferable is the point of avoiding the additional attachment of the protective layer.

  The semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror that reflects and transmits light with the reflective layer. A transflective polarizing plate is usually provided on the back side of a liquid crystal cell, and displays an image by reflecting incident light from the viewing side (display side) when a liquid crystal display device is used in a relatively bright atmosphere. In a relatively dark atmosphere, a liquid crystal display device or the like that displays an image using a built-in light source such as a backlight built in the back side of the transflective polarizing plate can be formed. In other words, the transflective polarizing plate is useful for forming a liquid crystal display device of a type that can save energy of using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source even in a relatively dark atmosphere. It is.

  Further, the polarizing plate may be formed by laminating a polarizing plate and two or three or more optical layers, like the above-described polarization separation type polarizing plate. Therefore, a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above-mentioned reflective polarizing plate or transflective polarizing plate and a retardation plate are combined may be used.

  The elliptical polarizing plate and the reflective elliptical polarizing plate are obtained by laminating a polarizing plate or a reflective polarizing plate and a retardation plate in an appropriate combination. Such an elliptical polarizing plate can be formed by sequentially laminating them in the manufacturing process of the liquid crystal display device so as to be a combination of a (reflective) polarizing plate and a retardation plate. An optical film such as an elliptically polarizing plate has an advantage that it can improve the production efficiency of a liquid crystal display device and the like because of excellent quality stability and lamination workability.

  The optical element of the present invention can be provided with an adhesive layer or an adhesive layer. The pressure-sensitive adhesive layer can be used for adhering to a liquid crystal cell and also used for laminating optical layers. When adhering the optical films, their optical axes can be set at an appropriate arrangement angle in accordance with the target retardation characteristics.

  It does not restrict | limit especially as an adhesive agent or an adhesive. For example, acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyvinyl ether, vinyl acetate / vinyl chloride copolymer, modified polyolefin, epoxy-based, fluorine-based, natural rubber, synthetic rubber and other rubber-based polymers Can be appropriately selected and used. In particular, those excellent in optical transparency, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties and excellent in weather resistance, heat resistance and the like can be preferably used.

  The adhesive or pressure-sensitive adhesive can contain a crosslinking agent according to the base polymer. Examples of adhesives include natural and synthetic resins, in particular, tackifier resins, glass fibers, glass beads, metal powders, other inorganic powders, fillers, pigments, colorants, and antioxidants. An additive such as an agent may be contained. Further, it may be an adhesive layer containing fine particles and exhibiting light diffusibility.

  The adhesive and the pressure-sensitive adhesive are usually used as an adhesive solution having a solid content concentration of about 10 to 50% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent. As the solvent, an organic solvent such as toluene or ethyl acetate or a solvent such as water can be appropriately selected and used.

  The pressure-sensitive adhesive layer and the adhesive layer can be provided on one side or both sides of a polarizing plate or an optical film as an overlapping layer of different compositions or types. The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is generally 1 to 500 μm, preferably 5 to 200 μm, particularly preferably 10 to 100 μm.

  For the exposed surface such as the adhesive layer, a separator is temporarily attached and covered for the purpose of preventing contamination until it is put to practical use. Thereby, it can prevent contacting an adhesion layer in the usual handling state. As the separator, except for the above thickness conditions, for example, a suitable thin leaf body such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foam sheet, metal foil, laminate thereof, and the like, silicone type or Appropriate ones according to the prior art, such as those coated with an appropriate release agent such as a long mirror alkyl type, fluorine type or molybdenum sulfide, can be used.

  In the present invention, each layer such as the optical element and the adhesive layer is made of an ultraviolet absorber such as a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex compound. What gave the ultraviolet absorptivity by systems, such as a processing system, may be used.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples. Each measurement is as follows.

  (Reflection wavelength band): The reflection spectrum was measured with a spectrophotometer (manufactured by Otsuka Electronics Co., Ltd., instantaneous multi-photometry system, MCPD-2000), and a reflection wavelength band having half the maximum reflectance was obtained.

  (Distortion rate): In order to evaluate the distortion rate of the polarizing element, the transmission spectrum of the sample was measured with an instantaneous multiphotometer (MCPD-2000 manufactured by Otsuka Electronics Co., Ltd.). When natural light is projected and the sample is installed perpendicularly to the projected light (measurement of outgoing light from the front), and when the sample is installed at an angle of 60 ° from the vertical direction (measurement of 60 ° outgoing light) About each, the state of the light which permeate | transmitted them was measured with the polarizing plate arrange | positioned at the output side, and the transmission spectrum when a polarizing plate was rotated 10 degree | times was measured. As the polarizing plate, a Sigma-Optical Gram Thompson prism polarizer was used (extinction ratio of 0.00001 or less). The distortion rate was obtained from the following calculation formula. Strain rate = minimum transmittance / maximum transmittance.

  (Phase difference): The retardation of the wave plate is determined by taking the direction in which the in-plane refractive index is maximum as the X axis, the direction perpendicular to the X axis as the Y axis, and the thickness direction of the film as the Z axis. The refractive indexes nx, ny, and nz at 550 nm were measured with an automatic birefringence measuring device (manufactured by Oji Scientific Instruments, automatic birefringence meter KOBRA21ADH), where the refractive indexes were nx, ny, and nz. From the thickness d (nm), the front phase difference: (nx−ny) × d was calculated. Further, the Nz coefficient was calculated.

  A light table KLV7000 made by Hakuba was used as the light source device (diffuse light source). Other measuring instruments are haze measurement (manufactured by Murakami Color, Haze Meter HM150), spectral characteristics of transmission and reflection (Hitachi, spectrophotometer U4100), polarizing plate characteristics (manufactured by Murakami Color, DOT3), luminance measurement (manufactured by Topcon , Luminance meter BM7), luminance and color tone angle distribution measuring instrument (ELDIM, Ez-Contrast), and ultraviolet irradiator (USHIO, UVC321AM1).

Example 1
(Polarizing element (A))
Five kinds of cholesteric liquid crystal polymers having selective reflection center wavelengths of 460 nm, 510 nm, 580 nm, 660 nm, and 800 nm were prepared based on the specification of European Patent Application No. 0837544.

  The cholesteric liquid crystal polymer has the following chemical formula 2:

A polymerizable nematic liquid crystal monomer A represented by the formula:

The polymerizable chiral agent B represented by the following ratio (weight ratio)
Selective reflection center wavelength: monomer A / chiral agent B (combination ratio): selective reflection wavelength band (nm)
460 nm: 9.2 / 1: 430 to 490 nm
510 nm: 10.7 / 1: 480 to 550 nm
580 nm: 12.8 / 1: 540 to 620 nm
660 nm: 14.9 / 1: 620 to 810 nm
800 nm: 17/1: 700 to 900 nm
It was produced by polymerizing the liquid crystal mixture blended in 1.

  Each of the liquid crystal mixtures was made into a 33 wt% solution dissolved in tetrahydrofuran, and then purged with nitrogen in an environment of 60 ° C. to obtain a reaction initiator (azobisisobutyronitrile, 0.5 wt% based on the mixture). ) Was added for polymerization treatment. The resulting polymer was purified by reprecipitation separation with diethyl ether.

  The cholesteric liquid crystal polymer was dissolved in methylene chloride to prepare a 10% by weight solution. The solution was applied to the alignment substrate with a wire bar so that the thickness upon drying was about 1.5 μm. A 75 μm thick polyethylene terephthalate (PET) film was used as the alignment substrate, and a polyimide alignment film was applied to the surface of about 0.1 μm and rubbed with a rayon rubbing cloth. After coating, it was dried at 140 ° C. for 15 minutes. After this heat treatment, the liquid crystal was cooled and fixed at room temperature to obtain a thin film.

  Each color was overcoated on the obtained liquid crystal thin film through the same process, and the layers were sequentially laminated from the long wavelength side to the short wavelength side. As a result, an approximately 8 μm-thick cholesteric liquid crystal laminate in which each liquid crystal layer was laminated in order from the short wavelength side was obtained. The obtained cholesteric liquid crystal laminate was peeled off from the PET substrate. The obtained cholesteric liquid crystal laminate had a selective reflection function at 430 nm to 900 nm. This was made into the polarizing element (A1-1).

  The polarizing element (A1-1) had a distortion rate in the front direction of about 0.55 and a distortion rate in the 60 ° inclination direction of about 0.05. Outgoing light transmitted through the polarizing element (A1-1) is linearly polarized light with a large incident angle, and the linearly polarized light is polarized in a direction substantially orthogonal to the normal direction (front) of the polarizing element surface. Had an axis.

(Linear polarization reflection type polarizer (B))
DBEF manufactured by 3M was used.

(Optical element (X))
As shown in FIG. 11, in the order of the polarizing element (A1-1) and the linearly polarized reflective polarizer (B), Nitto Denko's acrylic adhesive (NO.7): laminated using a thickness of 20 μm, An optical element (X1) was obtained.

(Characteristic evaluation)
The optical element (X1) was placed on the diffusion light source with the polarizing element (A1-1) on the lower side, and the emitted light was measured. The results are shown in FIG. The linearly polarized light reflection type polarizer (B) has a condensing characteristic in the reflection axis direction. The half-width of light collection is ± 32 °, and transmission at a deep angle is suppressed.

Example 2
(1/2 wavelength plate (C))
A polycarbonate retardation film (TR film) manufactured by Nitto Denko was used. The front retardation value was 270 nm, Nz = about 1.0, the thickness was 35 μm, the retardation value at 430 nm was about + 8%, and the retardation value at 650 nm was about −5%.

(Optical element (X))
The same polarizing element (A1-1) and linearly polarized light reflecting polarizer (B) as those in Example 1 were used. As shown in FIG. 12, Nitto Denko's acrylic adhesive (NO.7) in the order of the polarizing element (A1-1), the half-wave plate (C), and the linearly polarized reflective polarizer (B): Lamination was performed using a thickness of 20 μm to obtain an optical element (Y1). At this time, the angle between the polarization transmission axis of the linearly polarized light reflection type polarizer (B) and the slow axis of the half-wave plate (C) was set to 22.5 °.

(Characteristic evaluation)
The optical element (Y1) was placed on the diffusion light source, and the emitted light was measured. The results are shown in FIG. The 45 ° azimuth with respect to the polarization transmission axis of the linearly polarized light reflection type polarizer (B) was narrowed down to about ± 40 ° half-value width. At this time, the transmission axis direction of the linearly polarized light reflection type polarizer (B) was shifted by 45 degrees from the x-axis, and the azimuth angle for total reflection could be shifted by 45 degrees from Example 1.

Example 3
As shown in FIG. 14, a polarizing plate (P) is arranged on the side of the linearly polarized light reflective polarizer (B) of the optical element (Y1) obtained in Example 2 so that the axial angles are parallel to each other. Acrylic pressure-sensitive adhesive material (NO. 7) manufactured: Affixed using a thickness of 20 μm. As the polarizing plate (P), NPF-TEG1465DU manufactured by Nitto Denko was used.

(Characteristic evaluation)
The said optical element (Y1) with a polarizing plate (P) was arrange | positioned on a diffusion light source, and emitted light measurement was performed. The results are shown in FIG. It can be seen that, even in the state with a polarizing plate, the intensity of outgoing light is high in the front direction as in Example 2 described above and functions as an optical element shielded in the oblique direction.

Example 4
From the Sharp TFT liquid crystal display device (model number LQ10D362 / 10.4 / TFT), the lower polarizing plate was peeled off and the optical element (Y1) with the polarizing plate (P) obtained in Example 3 was used. The polarizing plates (P) were bonded together in the direction in which the polarization axis directions coincided. Further, the two prism sheets arranged between the backlight light guide and the liquid crystal cell were removed. The outline is as shown in FIG.

(Characteristic evaluation)
The emitted light of the liquid crystal display device was measured. The results are shown in FIG. It can be seen that, even in the state with the liquid crystal display device, the intensity of the emitted light is high in the front direction and functions as an optical element shielded in the oblique direction, as in the third embodiment.

Example 5
In Example 4, a liquid crystal display device similar to that of Example 4 was obtained except that the two prism sheets were not removed. The outline is as shown in FIG.

(Characteristic evaluation)
The emitted light of the liquid crystal display device was measured. The results are shown in FIG. It can be seen that even in the state with the prism sheet, the intensity of the emitted light is high in the front direction and functions as an optical element that is shielded in the oblique direction, as in the fourth embodiment.

Example 6
(Polarizing element (A))

In a solution in which 96 parts by weight of a photopolymerizable mesogen compound (polymerizable nematic liquid crystal monomer) represented by formula (4), 4 parts by weight of a polymerizable chiral agent (LC756 manufactured by BASF) and a solvent (methyl ethyl ketone) were prepared and mixed, Then, a coating liquid (solid content: 20% by weight) containing 5% by weight of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Irgacure 184) was prepared. The coating solution was cast on a stretched PET film (orientated substrate) and dried at 80 ° C. for 2 minutes, and then the other PET substrate was laminated. Subsequently, ultraviolet rays were irradiated at 3 mW / cm ² for 5 minutes while heating at 120 ° C. to obtain a cholesteric liquid crystal layer. The other substrate was transferred to one PET substrate surface using an isocyanate-based adhesive, and one PET substrate was removed. The obtained cholesteric liquid crystal layer had a thickness of 9 μm and a selective reflection band of 430 nm to 860 nm.

  The pitch length was measured by a cross-sectional TEM photograph. The cholesteric pitch was changed continuously in the thickness direction. This was designated as a polarizing element (A1-2).

  The polarizing element (A1-2) had a distortion rate in the front direction of about 0.99 and a distortion rate in the 60 ° inclination direction of about 0.10. Outgoing light transmitted through the polarizing element (A1-2) is outgoing light having a large incident angle is linearly polarized light, and the linearly polarized light is polarized in a direction substantially orthogonal to the normal direction (front face) of the polarizing element surface. Had an axis.

(Optical element (X))
In Example 1, an optical element (X2) was obtained in the same manner as in Example 1 except that the polarizing element (A1-2) was used instead of the polarizing element (A1-1).

(Characteristic evaluation)
The optical element (X2) was placed on the diffusion light source, and the emitted light was measured. The result was almost the same as in Example 1.

Example 7
(Polarizing element (A))
In a solution in which 96 parts by weight of a photopolymerizable mesogen compound (polymerizable nematic liquid crystal monomer) represented by the above chemical formula 4 and 4 parts by weight of a polymerizable chiral agent (LC756 manufactured by BASF) and a solvent (cyclopentanone) were prepared and mixed, A coating liquid (solid content 30 wt%) was prepared by adding 0.5 wt% of a photopolymerization initiator (Ciba Specialty Chemicals, Irgacure 907) to the solid content. The coating solution was cast on a stretched PET film (alignment substrate) using a wire bar so that the thickness after drying was 7 μm, and the solvent was dried at 100 ° C. for 2 minutes. The obtained film was subjected to first UV irradiation at 40 mW / cm ² for 1.2 seconds in an air atmosphere at 40 ° C. from the PET side. Subsequently, the second UV irradiation was performed at 4 mW / cm ² for 60 seconds while the temperature was increased to 90 ° C. at a temperature increase rate of 3 ° C./second in an air atmosphere. Next, 3rd UV irradiation was performed at 60 mW / cm ² for 10 seconds from the PET side under a nitrogen atmosphere, thereby obtaining a cholesteric liquid crystal layer having a selective reflection band of 425 to 900 nm.

  The pitch length was measured by a cross-sectional TEM photograph. The cholesteric pitch was changed continuously in the thickness direction. This was designated as a polarizing element (A1-3).

  The polarizing element (A1-3) had a distortion rate in the front direction of about 0.99 and a distortion rate in the 60 ° inclination direction of about 0.04. Outgoing light transmitted through the polarizing element (A1-3) is outgoing light having a large incident angle is linearly polarized light, and the linearly polarized light is polarized in a direction substantially orthogonal to the normal direction (front face) of the polarizing element surface. Had an axis.

(Optical element (X))
In Example 1, an optical element (X3) was obtained in the same manner as in Example 1 except that the polarizing element (A1-3) was used instead of the polarizing element (A1-1).

(Characteristic evaluation)
The optical element (X3) was placed on the diffusion light source, and the emitted light was measured. The result was almost the same as in Example 1.

Example 8
(Polarizing element (A))
96 parts by weight of a photopolymerizable mesogen compound (polymerizable nematic liquid crystal monomer) represented by the above chemical formula 4 and 4 parts by weight of a polymerizable chiral agent (LC756 manufactured by BASF) and a solvent (cyclopentanone) have a selective reflection center wavelength of 550 nm. A coating liquid (solid content 30% by weight) is prepared by adding 3% by weight of a photopolymerization initiator (Ciba Specialty Chemicals Co., Ltd., Irgacure 907) to the solid content adjusted and blended. did. The coating solution was cast on a stretched PET film (alignment substrate) using a wire bar so that the thickness after drying was 6 μm, and the solvent was dried at 100 ° C. for 2 minutes. The obtained film was subjected to first UV irradiation at 50 mW / cm ² for 1 second in an air atmosphere at 40 ° C. from the PET side. Thereafter, heating was performed at 90 ° C. for 1 minute without UV irradiation (the selective reflection band at this time was 420 to 650 nm). Next, the second UV irradiation was performed at 90 m in an air atmosphere at 5 mW / cm ² for 60 seconds (the selective reflection band at this time was 420 to 900 nm). Next, a cholesteric liquid crystal layer having a selective reflection band of 425 to 900 nm was obtained by performing third UV irradiation at 80 mW / cm ² for 30 seconds from the PET side in a nitrogen atmosphere.

  The pitch length was measured by a cross-sectional TEM photograph. The cholesteric pitch was changed continuously in the thickness direction. This was made into the polarizing element (A1-4).

  The polarizing element (A1-4) had a distortion rate in the front direction of about 0.99 and a distortion rate in the 60 ° inclination direction of about 0.04. Outgoing light transmitted through the polarizing element (A1-4) is linearly polarized light with a large incident angle, and the linearly polarized light is polarized in a direction substantially orthogonal to the normal direction (front face) of the polarizing element surface. Had an axis.

(Optical element (X))
In Example 1, an optical element (X4) was obtained in the same manner as in Example 1 except that the polarizing element (A1-4) was used instead of the polarizing element (A1-1).

(Characteristic evaluation)
The optical element (X4) was placed on the diffusion light source, and the emitted light was measured. The result was almost the same as in Example 1.

Example 9
(Polarizing element (A))
Seven kinds of cholesteric liquid crystal polymers having selective reflection center wavelengths of 410 nm, 460 nm, 510 nm, 580 nm, 660 nm, 750 nm, and 850 nm were prepared based on the specification of European Patent Application No. 0837544.

The cholesteric liquid crystal polymer is the following ratio (weight ratio) of the polymerizable nematic liquid crystal monomer A and the polymerizable chiral agent B used in Example 1.
Selective reflection center wavelength: monomer A / chiral agent B (combination ratio): selective reflection wavelength band (nm)
410 nm: 8.5 / 1: 380 to 440 nm
460 nm: 9.2 / 1: 430 to 490 nm
510 nm: 10.7 / 1: 480 to 550 nm
580 nm: 12.8 / 1: 540 to 620 nm
660 nm: 14.9 / 1: 620 to 810 nm
800 nm: 17/1: 700 to 900 nm
850 nm: 20/1: 800 to 1000 nm
It was produced by polymerizing the liquid crystal mixture blended in 1.

  Each of the liquid crystal mixtures was made into a 33 wt% solution dissolved in tetrahydrofuran, and then purged with nitrogen in an environment of 60 ° C. to obtain a reaction initiator (azobisisobutyronitrile, 0.5 wt% based on the mixture). ) Was added for polymerization treatment. The resulting polymer was purified by reprecipitation separation with diethyl ether.

  The cholesteric liquid crystal polymer was dissolved in methylene chloride to prepare a 10% by weight solution. The solution was applied to the alignment substrate with a wire bar so that the thickness upon drying was about 1.5 μm. A 75 μm thick polyethylene terephthalate (PET) film was used as the alignment substrate, and a polyimide alignment film was applied to the surface of about 0.1 μm and rubbed with a rayon rubbing cloth. After coating, it was dried at 140 ° C. for 15 minutes. After this heat treatment, the liquid crystal was cooled and fixed at room temperature to obtain a thin film.

  Each color was overcoated on the obtained liquid crystal thin film through the same process, and the layers were sequentially laminated from the long wavelength side to the short wavelength side. As a result, a laminate of about 8 μm thick cholesteric liquid crystal in which each liquid crystal layer was laminated in order from the short wavelength side was obtained. The obtained cholesteric liquid crystal laminate was peeled off from the PET substrate. The obtained cholesteric liquid crystal laminate had a selective reflection function at 380 nm to 1000 nm. This was made into the polarizing element (A2-1).

  The polarizing element (A2-1) had a distortion rate in the front direction of about 0.95, a distortion rate in the 30 ° inclination direction of about 0.25, and a distortion rate in the 60 ° inclination direction of about 0.10. It was. Outgoing light transmitted through the polarizing element (A2-1) is linearly polarized light with a large incident angle, and the linearly polarized light is polarized in a direction substantially parallel to the normal direction (front) of the polarizing element surface. Had an axis.

(Linear polarization reflection type polarizer (B))
DBEF manufactured by 3M was used.

(Optical element (X))
As shown in FIG. 11, in the order of the polarizing element (A2-1) and the linearly polarized reflective polarizer (B), Nitto Denko's acrylic adhesive (NO.7): laminated using a thickness of 20 μm, An optical element (X2) was obtained.

(Characteristic evaluation)
The optical element (X2) was placed on the diffusion light source with the polarizing element (A2-1) on the lower side, and the emitted light was measured. The results are shown in FIG. The linearly polarized light reflection type polarizer (B) has a condensing characteristic in the reflection axis direction. The half-width of the light collection is ± 39 °, and transmission at a deep angle is suppressed.

Comparative Example 1
The polarizing element (A-1) used in Example 1 was disposed on the diffusion light source, and the emitted light was measured. The results are shown in FIG. It was not condensed in the vertical and horizontal directions.

Comparative Example 2
An optical element was obtained in which the retardation layer was bonded to the polarizing element (A-1) used in Example 1, and the polarizing element (A-1) was bonded to the optical rotator. Nitto Denko's acrylic adhesive NO. 7 (thickness 25 μm), and the polarization transmission axes of the linearly polarized light reflective polarizers (B) were approximately parallel.

  The retardation layer was produced as follows. Liquid crystal monomer (BASF, LC242), chiral agent (BASF, LC756), and polymerization initiator (Ciba Specialty Chemicals, Irgacure 907) are LC242 / LC756 / so that the selective reflection center wavelength is 200 nm. Irgacure 907 was dissolved at a weight ratio of 88/11/3 in a solvent (methyl ethyl ketone) so as to be a 20 wt% solution.

  Using a wire bar coater, apply to a PET substrate (Toray Lumirror 75 μm thickness) with a dry thickness of 6 μm, heat at 80 ° C. for 2 minutes to remove the solvent and dry, once to the isotropic transition temperature of this liquid crystal monomer Then, the solvent was dried and then gradually cooled to form a layer having a uniform orientation. The obtained film was irradiated with UV to fix the orientation state and obtain a C plate layer. When the phase difference of the C plate was measured, the phase difference when measured by tilting it by 2 ° and 30 ° in the front direction with respect to light having a wavelength of 550 nm was 165 nm.

  This optical element was placed on a diffusing light source, and the emitted light was measured. The results are shown in FIG. The light was collected in all directions, and the half width was 35 °. However, light leakage due to radiation could be confirmed near 60 °. Also, visually, the angle through which the light was lost was colored red.

Comparative Example 3
Two prism sheets arranged between the backlight light guide and the liquid crystal cell without peeling off the lower polarizing plate of Sharp TFT liquid crystal display device (model number LQ10D362 / 10.4 / TFT) used in Example 5 The emitted light was measured for the removed one. The results are shown in FIG. In the state with the liquid crystal display device, the front luminance is low and the effectiveness of condensing can be seen.

Comparative Example 4
The following samples were prepared according to the examples of the pamphlet of International Publication No. 03/27756. An optical rotator was bonded to the linearly polarized light reflective polarizer (B) used in Example 1, and further a linearly polarized reflective polarizer (B) was bonded to the optical rotator. Nitto Denko's acrylic adhesive NO. 7 (thickness 25 μm), and the polarization transmission axes of the linearly polarized light reflective polarizers (B) were approximately parallel.

  The above optical rotator was produced as follows. A liquid crystal monomer (manufactured by BASF, LC242), a chiral agent (manufactured by BASF, LC756), and a polymerization initiator (manufactured by Ciba Specialty Chemicals, Irgacure 369) are LC242 / LC756 / Irgacure 369 = 96.4 / 0.1 / It dissolved in the solvent (methyl ethyl ketone) so that it might become a 20 weight% solution by the weight ratio of 3.5. Using a wire bar coater, it was applied to a PET substrate (Toray Lumirror 75 μm thick), heated at 80 ° C. for 2 minutes to remove the solvent, dried, and polymerized and cured in an ultraviolet irradiator under a nitrogen gas purge environment. The thickness of the obtained liquid crystal cured product was about 6 μm. The optical rotation power of this sample was about 85 °.

  The polarizing element obtained by laminating the linearly polarized light reflecting polarizer (B), the optical rotator, and the linearly polarized light reflecting polarizer (B) had a selective reflection function at 380 to 1100 nm. The optical rotator had a distortion rate of 0.01 or less in the front direction and a distortion rate of 0.01 or less in the 60 ° tilt direction, and no specific incidence angle dependency was generated with respect to the transmittance. The polarizing element exhibited substantially the same performance as a polarizing element in which DBEF was bonded to DBEF at an axial angle of about 85 °.

It is a conceptual diagram which shows the polarization-axis direction of the emitted light which permeate | transmitted the polarizing element (A1). It is a conceptual diagram which shows the polarization axis direction of the emitted light at the time of seeing FIG. 1 (A) from the normal line direction of a polarizing element (A1). It is a conceptual diagram which shows the polarization-axis direction of the emitted light which permeate | transmitted the polarizing element (A2). It is a conceptual diagram which shows the polarization axis direction of the emitted light at the time of seeing FIG. 2 (A) from the normal line direction of a polarizing element (A2). It is a conceptual diagram explaining a polarization component etc. It is a conceptual diagram which shows the polarization separation by the conventional cholesteric liquid crystal layer. It is a conceptual diagram which shows the polarization separation by the conventional cholesteric liquid crystal layer. It is a conceptual diagram which shows the polarization separation by a polarizing element (A). It is a conceptual diagram which shows the polarization separation by a polarizing element (A). It is a conceptual diagram which shows the polarization axis direction of the emitted light which permeate | transmitted only the linearly polarized light reflection type polarizer (B). It is a conceptual diagram which shows the polarization axis direction of the emitted light at the time of seeing FIG. 8 (A) from the normal line direction of a linearly polarized light reflection type polarizer (B). It is a conceptual diagram which shows the polarization axis direction of the emitted light which permeate | transmitted the polarizing element (A1) and then the linearly polarized light reflection type polarizer (B). It is a conceptual diagram which shows the polarization axis direction of the emitted light which permeate | transmitted the polarizing element (A1) and then the 1/2 wavelength plate (C). It is an example of sectional drawing of the optical element (X) of this invention. It is an example of sectional drawing of the optical element (Y) of this invention. It is an example of sectional drawing at the time of laminating | stacking a polarizing plate (P) on the optical element (X) of this invention. It is an example of sectional drawing at the time of laminating | stacking a polarizing plate (P) on the optical element (Y) of this invention. It is a conceptual diagram which shows conversion of the polarization seed | species by a wavelength plate. It is an example of sectional drawing of the liquid crystal display device using the optical element (Y) of this invention. It is an example of sectional drawing of the liquid crystal display device using the optical element (Y) of this invention. It is an example of sectional drawing of the liquid crystal display device using the optical element (Y) of this invention. It is an example of sectional drawing of the liquid crystal display device using the optical element (Y) of this invention. It is a figure showing the transmitted light intensity angle distribution of the optical element (X1) of Example 1. FIG. It is a figure showing the transmitted light intensity angle distribution of the optical element (Y1) of Example 2. FIG. It is a figure showing the transmitted light intensity angle distribution of the optical element (Y1) with a polarizing plate (P) of Example 3. FIG. It is a figure showing the transmitted light intensity angle distribution of the liquid crystal display device of Example 4. It is a figure showing the transmitted light intensity angle distribution of the liquid crystal display device of Example 5. It is a figure showing the transmitted light intensity angle distribution of the optical element (X2) of Example 9. FIG. It is a figure showing the transmitted light intensity angle distribution of the polarizing element (A-1) of the comparative example 1. It is a figure showing the transmitted light intensity angle distribution of the optical element of the comparative example 2. It is a figure showing the transmitted light intensity angle distribution of the liquid crystal display device of the comparative example 3.

Explanation of symbols

A Polarizing element i Incident light e Outgoing light B Linearly polarized reflective polarizer C Half wave plate X Optical element Y Optical element P Polarizer D Diffusion plate L Light source LC Liquid crystal cell

Claims (22)

You emit incident light by the polarization separation polarizing element and (A),
An optical element in which a linearly polarized light reflective polarizer (B) that transmits one of orthogonal linearly polarized light and selectively reflects the other is laminated,
The polarizing element (A) is formed of a cholesteric liquid crystal layer having a reflection bandwidth of 200 nm or more and a pitch length changing.
The outgoing light with respect to the incident light in the normal direction has a distortion rate of 0.5 or more,
The outgoing light with respect to the incident light that is inclined by 60 ° or more from the normal direction has a distortion rate of 0.2 or less,
An optical element characterized in that the linearly polarized light component of outgoing light increases as the incident angle increases.   The linearly polarized light component of the emitted light that increases as the incident angle increases in the polarizing element (A) has a polarization axis of linearly polarized light in a direction substantially perpendicular to the normal direction of the polarizing element surface. The optical element according to claim 1.   The linearly polarized light component of the emitted light that increases as the incident angle increases in the polarizing element (A) has a polarization axis of linearly polarized light in a direction substantially parallel to the normal direction of the polarizing element surface. The optical element according to claim 1.   The optical element according to claim 1, wherein the polarizing element (A) substantially reflects a non-transmission component of incident light.   The optical element according to claim 1, wherein the polarizing element (A) has a thickness of 2 μm or more. Linearly polarized reflection type polarizer (B) The optical element according to any one of claims 1 to 5, characterized in that a grid polarizer. The optical element according to any one of claims 1 to 5 , wherein the linearly polarized light reflection type polarizer (B) is a multilayer thin film laminate of two or more layers having a refractive index difference. The optical element according to claim 7, wherein the multilayer thin film laminate is a vapor-deposited thin film. The optical element according to any one of claims 1 to 5 , wherein the linearly polarized light reflection type polarizer (B) is a multilayer thin film laminate of two or more layers having birefringence. The optical element according to claim 9, wherein the multilayer thin film laminate is obtained by stretching two or more types of resin laminates having birefringence. It has laminated | stacked on both sides of the 1/2 wavelength plate (C) between the polarizing element (A) in the optical element in any one of Claims 1-10 , and a linearly polarized light reflection type polarizer (B). An optical element characterized by the above. 12. The optical element according to claim 11, wherein the half-wave plate (C) is a broadband wavelength plate that functions as a substantially half-wave plate in the entire visible light range. In the half-wave plate (C), the direction in which the in-plane refractive index is maximum is the X axis, the direction perpendicular to the X axis is the Y axis, the refractive indexes in the respective axial directions are nx, ny, and thickness d (nm). )
13. The optical element according to claim 12 , wherein a front phase difference value (nx-ny) × d at each wavelength in the light source wavelength band (420 to 650 nm) is within ½ wavelength ± 10%. The optical element according to any one of claims 11 to 13 , wherein the half-wave plate (C) controls the phase difference in the thickness direction to reduce the phase difference change with respect to the angle change. In the half-wave plate (C), the direction in which the in-plane refractive index is the maximum is the X axis, the direction perpendicular to the X axis is the Y axis, and the thickness direction of the film is the Z axis. Is nx, ny, nz,
The optical element according to claim 14 , wherein an Nz coefficient represented by Nz = (nx−nz) / (nx−ny) is −2.5 <Nz ≦ 1. The polarizing plate is arranged outside the linearly polarized light reflecting polarizer (B) so that the polarization transmission axis of the linearly polarized light reflecting polarizer (B) is aligned with the polarizing axis direction of the polarizing plate. The optical element according to any one of claims 1 to 15 . The optical element according to any one of claims 1 to 16, characterized in that each layer was laminated with a translucent adhesive or a pressure-sensitive adhesive. The optical element according to any one of claims 1 to 17 condensing backlight system characterized by comprising placing at least a light source. 19. The condensing backlight system according to claim 18, further comprising primary condensing means for condensing within ± 60 degrees from the normal direction. 20. The condensing backlight system according to claim 19, wherein the primary condensing means is a microprism sheet array disposed on the light source. 21. A liquid crystal display device, wherein at least a liquid crystal cell is disposed in the concentrating backlight system according to any one of claims 18 to 20 . 22. A liquid crystal display device according to claim 21, wherein a diffusion plate having no backscattering and depolarization is laminated on the liquid crystal cell viewing side.

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