JP2017097217A - Optical film and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent reduction in an emission light quantity of an image display panel using a self-luminous element while sufficiently maintaining an antireflection function of an antireflection film constituted by a circularly polarizing plate.SOLUTION: An optical film includes reflection layers 10R, 10G, 10B made of a cholesteric liquid crystal on a substrate 15 made of a film material. The reflection layers 10R, 10G, 10B made of a cholesteric liquid crystal have a birefringence Δn of 0.04 or more and 0.11 or less.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an optical film disposed on a panel surface of an image display panel using self-luminous elements such as organic EL elements.

  Conventionally, an antireflection film made of a circularly polarizing plate made by laminating a linearly polarizing plate and a quarter-wave plate is arranged on the panel surface (viewer side) of an image display panel, and reflection of external light is reduced by this antireflection film. A method has been proposed. This antireflection film converts extraneous light directed to the panel surface of the image display panel into linearly polarized light by a linear polarizing plate and then converts it into circularly polarized light by a quarter wavelength plate. Although the extraneous light by the circularly polarized light is reflected on the surface of the image display panel or the like, the rotation direction of the polarization plane is reversed during the reflection. As a result, this reflected light is converted into linearly polarized light in the direction shielded by the linear polarizing plate by the quarter wavelength plate, contrary to the arrival time, and then shielded by the subsequent linear polarizing plate. Outgoing emission is significantly suppressed.

  However, in an image display panel using a self-luminous element such as an organic EL element, the light emitted from each pixel is natural light. Therefore, when an antireflection film is provided by this circularly polarizing plate, linearly polarized light provided on the antireflection film is provided. The amount of emitted light is reduced to approximately ½ due to the light shielding by the plate, thereby reducing the luminance of the display screen. For this reason, Patent Documents 1 and 2 disclose a configuration in which a reflection layer made of cholesteric liquid crystal is provided between the image display panel and the antireflection film to increase the amount of emitted light. In other words, the reflective layer made of cholesteric liquid crystal has an optical characteristic of selectively reflecting incident light in accordance with the polarization plane (so-called polarization plane selective reflection characteristic), and is an antireflection film out of the light emitted from each pixel. It selectively reflects the circularly polarized light component in the light shielding direction and selectively transmits the circularly polarized light component in the direction that transmits the antireflection film. As a result, the circularly polarized light component reflected by the reflective layer is reflected on the panel surface or the like of the image display panel, and the rotation direction of the polarization surface is reversed. As a result, the circularly polarized component is transmitted through the reflective layer and shielded by the antireflection film. As a result, the luminance of the display screen can be prevented from being lowered.

  However, when preventing a decrease in brightness by the reflective layer made of cholesteric liquid crystal, the extraneous light component that is converted to circularly polarized light by the antireflective film and reflected by the panel surface of the image display panel is also reflected by the optical film made of cholesteric liquid crystal. Then, the light is reflected again on the panel surface, and the emission is promoted. Thereby, in this case, there is a problem that the antireflection function of the extraneous light is impaired.

JP 2001-357879 A JP 2004-030955 A

  The present invention has been made in view of such a situation, while preventing a decrease in the amount of emitted light for an image display panel with a self-luminous element while sufficiently ensuring an antireflection function for an antireflection film with a circularly polarizing plate, For the purpose.

  The present inventor has conducted extensive research to solve the above problems, and reduced the birefringence Δn of the reflective layer by the cholesteric liquid crystal, and reduces the half width of the reflectance in the circularly polarized light component reflected by the reflective layer, This led to the completion of the present invention.

  Specifically, the present invention provides the following.

(1) Provided with a reflective layer made of cholesteric liquid crystal on a substrate made of film material,
The reflective layer of the cholesteric liquid crystal is
An optical film having a birefringence Δn of 0.04 to 0.11.

  According to (1), the half-value width of the reflectance can be reduced to a size corresponding to the half-value width of the emitted light from the pixel of the corresponding self-luminous element, whereby the emitted light from each pixel can be obtained. Can sufficiently reduce the loss and prevent a decrease in the amount of emitted light, and for extraneous light, the amount of reflected light is reduced to sufficiently ensure the antireflection function of the antireflection film by the circularly polarizing plate. be able to.

  (2) In (1), the liquid crystal material of the reflective layer is an optical film that is a liquid crystal material having reverse dispersion wavelength characteristics.

(3) In (1),
The liquid crystal material of the reflective layer is an optical film that is a liquid crystal material having at least a cyclohexane structure in the molecular structure.

  According to (2) or (3), a more specific configuration prevents a decrease in the amount of emitted light for an image display panel using a self-luminous element while sufficiently ensuring an antireflection function in an antireflection film using a circularly polarizing plate. be able to.

(4) In the optical film disposed on the panel surface of the image display panel in which the pixels by the self-light-emitting elements whose emission light is at least in the red wavelength band, the green wavelength band, and the blue wavelength band are arranged in a matrix shape,
A linear polarizing plate that emits incident external light by linearly polarized light;
A quarter-wave plate for emitting linearly polarized external light incident from the linearly polarizing plate as circularly polarized light;
Circularly polarized external light incident from the ¼ wavelength plate is transmitted and circularly polarized light whose polarization plane is opposite to the circularly polarized external light incident from the ¼ wavelength plate. And a reflective layer that reflects circularly polarized light in a specific wavelength band,
The specific wavelength band is
The absolute difference between the center wavelength of the specific wavelength band and the center wavelength of the light emitted from the pixel is 30 nm or less,
The optical film whose difference absolute value of the half value width of the said specific wavelength band and the half value width of the emitted light from the said pixel is 30 nm or less.

  According to (4), the center wavelength and the half-value width of the reflection band in the reflection layer can be set to a size corresponding to the emitted light from the corresponding pixel. Thereby, about the emitted light from each pixel, a loss can fully be reduced and the fall of emitted light quantity can be prevented. Moreover, about extraneous light, the light quantity of reflected light can be reduced and the antireflection function can fully be ensured about the antireflection film by a circularly-polarizing plate.

(5) In (4), the reflective layer comprises:
An optical film which is a plurality of reflective layers respectively corresponding to the red wavelength band, the green wavelength band, and the blue wavelength band.

  According to (5), with a more specific configuration, it is possible to sufficiently reduce a decrease in the amount of emitted light for an image display panel using a self-luminous element while sufficiently ensuring an antireflection function in an antireflection film using a circularly polarizing plate. it can.

(6) In (4) or (5),
The reflective layer is
An optical film which is a reflective layer of cholesteric liquid crystal having a birefringence Δn of 0.04 or more and 0.11 or less.

  According to (6), a more specific configuration of the reflective layer prevents a decrease in the amount of emitted light for the image display panel using the self-luminous element while sufficiently ensuring the antireflection function of the antireflection film using the circularly polarizing plate. be able to.

(7) In (6),
The liquid crystal material of the reflective layer is an optical film which is a liquid crystal material having reverse dispersion wavelength characteristics.

(8) In (6),
The liquid crystal material of the reflective layer is an optical film that is a liquid crystal material having at least a cyclohexane structure in the molecular structure.

  According to (7) or (8), an image display panel using a self-luminous element while sufficiently ensuring an antireflection function in an antireflection film using a circularly polarizing plate is obtained with a more specific configuration relating to the liquid crystal material forming the reflective layer. A decrease in the amount of emitted light can be prevented.

  (9) In any one of (4), (5), (6), (7), and (8), antireflection is achieved by antireflection by laminating at least two layers of a low refractive index layer and a high refractive index layer. An optical film on which films are laminated.

  According to (9), it is possible to prevent reflection more reliably.

  (10) On the panel surface of the image display panel in which the pixels of the self-light-emitting elements whose emitted light is at least in the red wavelength band, the green wavelength band, and the blue wavelength band are arranged in a matrix, (1), (2), ( The image display apparatus which has arrange | positioned the optical film in any one of 3).

  (11) An image display device in which the optical film according to any one of (4), (5), (6), (7), (8), and (9) is disposed on the panel surface of the image display panel.

  According to (10) or (11), it is possible to prevent a decrease in the amount of light emitted from the image display panel using the self-luminous element while sufficiently ensuring the antireflection function of the antireflection film using the circularly polarizing plate.

  ADVANTAGE OF THE INVENTION According to this invention, the fall of emitted light quantity can be prevented about the image display panel by a self-light-emitting element, ensuring the antireflection function in the antireflection film by a circularly-polarizing plate fully.

It is sectional drawing which shows the image display apparatus which concerns on 1st Embodiment of this invention. It is a figure where it uses for description of the antireflection film which concerns on the image display apparatus of FIG. FIG. 4 is a diagram for explaining the continuation of FIG. 3. It is sectional drawing which shows the optical film applied to the image display apparatus of FIG. It is a graph which shows the measurement result of an Example and a comparative example.

[First Embodiment]
FIG. 1 is a sectional view showing an image display apparatus according to the first embodiment of the present invention. In this image display device 1, an optical film 3 is adhered and held on a panel surface (viewer side surface) of an image display panel 2 by a pressure-sensitive adhesive layer 4 made of a pressure-sensitive adhesive or the like. Here, the image display panel 2 is an image display panel using self-luminous elements. More specifically, the image display panel 2 is an image display panel using organic EL elements, and emits light in a red wavelength band, a green wavelength band, and a blue wavelength band related to color image display. It is formed by arranging red, green, and blue pixels, which emit outgoing light of natural light in the wavelength band and blue wavelength band, in a matrix.

  The optical film 3 is an antireflection film for preventing reflection of extraneous light by the function of a circularly polarizing plate. After the separator film (not shown) is peeled to expose the adhesive layer 4, the adhesive layer 4 displays an image. The panel 2 is stuck and held on the panel surface. Instead of the pressure-sensitive adhesive layer 4 made of a pressure-sensitive adhesive, the optical film 3 may be arranged with various adhesives such as an ultraviolet curable resin and pressure-sensitive adhesives.

  In this embodiment, the image display device 1 has an antireflection film for preventing reflection by a fine uneven shape on the surface on the side opposite to the image display panel 2 of the optical film 3, or at least a refractive index of 1.20 or more. An antireflection film (which is a so-called AR film) 11 for preventing reflection is provided by laminating two layers of a low refractive index layer having a refractive index of 40 or less and a high refractive index layer having a refractive index of 1.60 to 2.00. As a result, it is configured to further prevent reflection. In addition, in this antireflection film 11, you may abbreviate | omit as needed.

  The optical film 3 is formed by laminating a linear polarizing plate 7, a quarter-wave plate 8, a positive C plate 9, and a reflective layer 10 on a base material 6 made of a transparent film material. Here, although various transparent film materials applicable to this type of optical film can be widely applied to the base material 6, in this embodiment, a transparent film material made of TAC (triacetyl cellulose) is applied. A hard coat layer 6A is provided on the side surface.

  The linearly polarizing plate 7 is a so-called sheet polarizer type polarizer that absorbs a linearly polarized light component in a direction orthogonal to the transmission axis direction. After impregnating polyvinyl alcohol (PVA) with iodine or the like, the linearly polarized light is stretched and linearly polarized. An optical functional layer 7A having an optical function as a plate is produced. The linearly polarizing plate 7 is arranged such that the optical functional layer 7A is directly held by the base material 6, but the optical functional layer 7A is sandwiched by the base material 6 made of a transparent film material such as TAC. You may make it hold | maintain. Moreover, you may arrange | position the base material by the transparent film material by TAC etc. separately on the image display panel 2 side surface of the optical functional layer 7A.

  The quarter-wave plate 8 includes a half-wave retardation layer 8A that imparts a half-wave phase difference to the transmitted light, and a quarter-wave retardation that imparts a quarter-wave phase difference to the transmitted light. The layer is composed of a laminate with the layer 8B, and the half-wave retardation layer 8A and the quarter-wave retardation layer 8B are each made of a cured liquid crystal material. The quarter wavelength plate 8 has a slow axis direction of the half wavelength retardation layer 8 </ b> A and a quarter wavelength retardation layer 8 </ b> B in a clockwise direction and a counterclockwise direction with respect to the transmission axis direction of the linear polarizing plate 7. It arrange | positions so that it may make an angle of 15 degree | times and 75 degree | times to a direction, respectively, and, thereby, it is comprised so that it may function by the wavelength characteristic of reverse dispersion with respect to the transmitted light of the linearly-polarizing plate 7.

  The positive C plate 9 is provided for the purpose of improving the viewing angle characteristic by bringing the characteristic seen from the oblique direction closer to the characteristic seen from the front direction on the display screen of the image display device 1.

  The half-wave retardation layer 8A, the quarter-wave retardation layer 8B, and the positive C plate 9 are respectively formed on the half-wave retardation layer 8A, 1 / 4 wavelength retardation layer 8B and positive C plate 9 are sequentially transferred to the linear polarizing plate 7 by the transfer method, or are each prepared as a half wavelength retardation layer 8A and a quarter wavelength retardation produced on a transfer film. After the layer 8B and the positive C plate 9 are laminated by the transfer method, a laminate of the half-wave retardation layer 8A, the quarter-wave retardation layer 8B, and the positive C plate 9 is manufactured, and then the laminate is transferred. Is transferred to a linearly polarizing plate. In addition, after laminating a partial configuration related to the laminated body of the ½ wavelength phase difference layer 8A, the ¼ wavelength phase difference layer 8B, and the positive C plate 9 by the transfer method, this partial configuration is made using the transfer method. You may make it laminate | stack a laminated body and the remaining member on the linearly-polarizing plate 7 one by one.

  The quarter-wave plate 8 may be manufactured as a single layer by a retardation layer made of a liquid crystal material having reverse wavelength dispersion, or may be manufactured using an optical film having reverse wavelength dispersion. Specifically, Teijin's Pure Ace having reverse wavelength dispersibility, or Japanese translations of PCT publication No. 2010-522892, JP-A 2006-243470, JP-A 2007-243470, JP-A 2009-75494, JP-A-2009-62508, JP-A-2009-179563, JP-A-2009-242717, JP-A-2009-242718, JP-A-422223, JP-A-41866981 A liquid crystal compound can be illustrated.

  Since the spiral axis of the cholesteric liquid crystal is substantially perpendicular to the substrate, the hue changes when observed from an oblique direction. Therefore, the quarter-wave plate 8 can alleviate the color change from the diagonal characteristic of the cholesteric liquid crystal by designing the phase difference value.

  Specifically, the quarter-wave plate 8 has wavelength dispersion of reverse wavelength dispersion, and the front phase difference is preferably 130 nm to 150 nm at the measurement wavelength 550 nm, and more preferably 135 nm to 145 nm. . The slow axis is designed to be 45 degrees or 135 degrees with respect to the absorption axis of the polarizing plate. At this time, in order to provide an external light antireflection function, the thickness of the positive C plate in the thickness direction Rth (C), Rth (A) of the thickness direction of the quarter wavelength plate, at a measurement wavelength of 590 nm, | Rth (A) + Rth (C) | ≦ 30 nm is preferable, and | Rth (A) + Rth (C) | ≦ 20 nm is more preferable. The wavelength dispersion of the reverse wavelength dispersion is preferably such that Re (450) / Re (550) is 0.83 to 0.92, where Re (λ) is the phase difference value of the measurement wavelength λ, and 0.85 to 0 More preferred is .89. Re (650) / Re (550) is preferably from 1.00 to 1.18, and more preferably from 1.02 to 1.10.

  When the quarter-wave plate 8 is composed of two layers of the half-wave retardation layer 8A and the quarter-wave retardation layer 8B having positive dispersion wavelength characteristics, the retardation of the half-wave retardation layer 8A The front phase difference is preferably 220 nm to 290 nm and more preferably 230 nm to 275 nm at a measurement wavelength of 550 nm. The phase difference of the quarter-wave retardation layer 8B is preferably from 100 nm to 150 nm, more preferably from 110 nm to 140 nm, with the front phase difference at a measurement wavelength of 550 nm. It is preferable to apply the same material to the half-wave retardation layer 8A and the quarter-wave retardation layer 8B. The combination of the slow axes of the half-wave retardation layer 8A and the quarter-wave retardation layer 8B is set to 15 ° ± 5 ° and 75 ° ± 5 ° with respect to the absorption axis of the polarizing plate, respectively. It is preferable. The wavelength dispersion is preferably such that Re (450) / Re (550) is 1.01 to 1.17, and 1.05 to 1.13, where Re (λ) is the phase difference value of the measurement wavelength λ. It is more preferable. Re (650) / Re (550) is preferably 0.90 to 0.99, and more preferably 0.93 to 0.97. At this time, in order to provide an external light reflection preventing function, the thickness direction retardation Rth of the positive C plate is preferably −140 nm to −40 nm at a measurement wavelength of 590 nm.

  In addition, here, the transfer method, for example, when forming a desired layer on a base material, does not form this layer directly on the base material, but can be peeled once on a releasable support. After the layers are laminated to produce a transfer body (transfer film), the layer formed on the support is finally laminated on the substrate (transferred layer) according to the process, demand, etc. In this method, a desired layer is formed on the base material by bonding and laminating on the base material and then peeling off and removing the support.

  When the linearly polarizing plate 7, the quarter wavelength plate 8 and the positive C plate 9 are arranged on the panel surface of the image display panel 2 as described above, the external light L1 due to natural light is converted into the linearly polarizing plate 7 as shown in FIG. Is converted into linearly polarized light by the ¼ wavelength plate 8 and then converted into circularly polarized light. In FIG. 2, the natural light and the circularly polarized light are indicated by arrows. The external light L1 due to the circularly polarized light is reflected by the panel surface of the image display panel 2 and the rotation direction of the polarization surface is reversed. As a result, the light is transmitted through the quarter wavelength plate 8 and shielded by the linear polarizing plate 7. The light is converted into linearly polarized light in the direction and shielded by the subsequent linearly polarizing plate 7, and as a result, the emission to the outside is remarkably suppressed and antireflection is achieved.

  However, when the linear polarizing plate 7, the quarter wavelength plate 8, and the positive C plate 9 are simply arranged on the panel surface of the image display panel 2, the red wavelength band emitted from the red, green, and blue pixels. In the case of the emitted light LR, LG, LB in the green wavelength band and the blue wavelength band, the image display panel 2 is an image display panel by an organic EL element which is a self-luminous element, and is emitted from each pixel by natural light. As a result, the light is shielded by the linearly polarizing plate 7 and about half of the light quantity is absorbed. As a result, the quantity of emitted light is significantly reduced.

  Therefore, in this embodiment, the reflective layer 10 is provided, and the wavelength bands of the red, green, and blue outgoing lights LR, LG, and LB emitted from the red, green, and blue pixels, and the linear polarizing plate 7 The circularly polarized light component corresponding to the linearly polarized light component that is shielded by the light is selectively reflected toward the image display panel 2, thereby preventing a decrease in the amount of emitted light.

  That is, in this case, as shown in FIG. 3, the emitted light LR, LG, LB from each of the red, green, and blue pixels is a natural light, so that two types of circularly polarized light whose rotation directions are opposite to each other are synthesized. The light is emitted from the image display panel 2 by light, and one circularly polarized light component L2 of the two types of circularly polarized light is the reflective layer 10, the positive C plate 9, the quarter wavelength plate 8, the linearly polarizing plate. 7 is transmitted through. The remaining one type of circularly polarized light component L3 is selectively reflected by the reflective layer 10 and then reflected by the panel surface of the image display panel 2 to reverse the rotation direction of the polarization surface. The light passes through the C plate 9, the quarter wavelength plate 8, and the linear polarizing plate 7 and is emitted. In this case, the light emitted from each pixel is simply compared with the case where the linear polarizing plate 7, the quarter wavelength plate 8, and the positive C plate 9 are simply arranged on the panel surface of the image display panel 2. The light is emitted remarkably efficiently, and a decrease in the amount of emitted light can be prevented.

  On the other hand, the extraneous light L1 is converted into linearly polarized light by the linearly polarizing plate 7, and then converted into circularly polarized light by the quarter wavelength plate 8, and reflected by the panel surface of the image display panel 2 to rotate the polarization surface. The direction is reversed and enters the reflective layer 10. Here, the light emitted from the image display panel 2 is light emitted from each pixel in a limited wavelength band of red, green, and blue, whereas external light incident on the reflective layer 10 in this way. L1 is incident light in a wide wavelength band including these red, green, and blue wavelength bands. As a result, the extraneous light L1 reflected from the panel surface of the image display panel 2 is selectively reflected by the reflection layer 10 in the wavelength band component L1B corresponding to the emitted light LR, LG, LB from the red, green, and blue pixels. Although reflected, most of the remaining components pass through the reflective layer 10 and enter the quarter-wave plate 8 where they are converted to linearly polarized light and blocked by the linearly polarizing plate 7. Thereby, a sufficient antireflection function can be ensured.

  However, even when the reflection layer 10 reflects only the wavelength bands corresponding to the light beams LR, LG, and LB emitted from the red, green, and blue pixels, the partial component L1B of the extraneous light is reflected in the reflection layer. 10, and the reflected component is reflected by the panel surface of the image display panel 2, and then is sequentially transmitted through the reflective layer 10, the positive C plate 9, the quarter wavelength plate 8, and the linear polarizing plate 7 to be emitted. Thus, it was found that the antireflection function could not be sufficiently secured.

  Therefore, in this embodiment, the wavelength band used for reflection by the reflection layer 10 is narrowed, and reflection of extraneous light on the reflection layer 10 is further reduced, thereby further ensuring an antireflection function.

  Here, in this embodiment, the reflective layer 10 (FIG. 1) is a straight line that is shielded by the linear polarizing plate 7 in the red wavelength band of the emitted light LR from the red pixel of the image display panel 2 from the image display panel 2 side. Corresponding to the linearly polarized light component shielded by the linearly polarizing plate 7 for the green wavelength band of the red light reflecting layer 10R that selectively reflects the circularly polarized light component corresponding to the polarized light component and the output light LG from the green pixel of the image display panel 2 The circularly polarized light component corresponding to the linearly polarized light component shielded by the linearly polarizing plate 7 with respect to the blue wavelength band of the light LB emitted from the blue pixel of the image display panel 2 and the green reflective layer 10G that selectively reflects the circularly polarized light component Are sequentially provided.

  Here, these reflective layers 10R, 10G, and 10B are formed of a liquid crystal layer made of a polymerizable liquid crystal material made of cholesteric liquid crystal. Here, the liquid crystal layer made of cholesteric liquid crystal exhibits unique optical characteristics based on a helical molecular arrangement, and light incident in parallel to the helical axis has a wavelength corresponding to the pitch of the cholesteric helix, depending on the direction of rotation of the helix. The selective reflection characteristic according to the polarization plane, which selectively reflects the circularly polarized light component in the rotational direction and transmits the circularly polarized light component in the other rotational direction, is shown. The central wavelength λ of selective reflection by this cholesteric liquid crystal layer is represented by n · p, and the wavelength band (half width) Δλ of this selective reflection is represented by Δn · p. Here, p is the helical pitch of the cholesteric liquid crystal layer, and n is the average refractive index of the liquid crystal. Since Δλ = Δn / n · λ, Δλ depends on Δn / n. Since the liquid crystal average refractive index n does not change greatly, Δλ is set by controlling the substantial Δn. Δn is the birefringence of the liquid crystal layer, and is represented by the difference in refractive index (ne-no) in the direction parallel to and perpendicular to the major axis of the liquid crystal molecules. In addition, the specific calculation method of (DELTA) n in this invention measures the retardation (Re) in 550 nm which expresses when the liquid crystal material to be used is homogeneously aligned and fixed without adding a chiral agent first. For this measurement, for example, KOBRA-WR manufactured by Oji Scientific Instruments can be used. Next, the sample thickness (d) of the produced homogeneous orientation is measured, and Δn is calculated from the relational expression Re = Δn · d.

  Here, when the reflection bandwidth in the reflection layers 10R, 10G, and 10B becomes narrower with respect to the wavelength bands of the emission lights LR, LG, and LB from each pixel, the loss of the emission light from each pixel in the reflection layers 10R, 10G, and 10B. On the contrary, if the reflection bandwidths in the reflective layers 10R, 10G, and 10B are increased with respect to the wavelength bands of the emitted light LR, LG, and LB, a sufficient antireflection function can be secured. Disappear. Further, if the center wavelength of the reflection band in the reflective layers 10R, 10G, and 10B is deviated from the center wavelength of the emitted light LR, LG, and LB of each pixel, the loss of the emitted light from each pixel increases. Become.

  Therefore, in this embodiment, the reflection bands in the reflection layers 10R, 10G, and 10B with respect to the center wavelengths of the emitted light LR, LG, and LB in the red wavelength band, the green wavelength band, and the blue wavelength band emitted from the image display panel 2. And the half-value widths of the emitted light beams LR, LG, and LB in the red wavelength band, the green wavelength band, and the blue wavelength band are half the reflection bands in the reflective layers 10R, 10G, and 10B. It is set so as to substantially coincide with the value width Δn.

  More specifically, the center wavelength of the emitted light LR, LG, and LB in the red wavelength band, the green wavelength band, and the blue wavelength band emitted from the image display panel 2 and the reflection bands in the corresponding reflective layers 10R, 10G, and 10B. Although the absolute value of the difference from the center wavelength is set to 30 nm or less, the absolute value is preferably set to 20 nm or less, and more preferably, the absolute value is set to 10 nm or less. Here, the center wavelengths of the emitted lights LR, LG, and LB are center wavelengths having a half width defined by the peak light amounts of the emitted lights LR, LG, and LB. The center wavelength of the reflection band is the center wavelength of the half-value width related to the reflectance, and the half-value width related to the reflectance is a wavelength bandwidth indicating a reflectance that is ½ of the peak value of the reflectance.

  Further, the absolute value of the difference between the half-value width of the emitted light LR, LG, LB in the red wavelength band, the green wavelength band, and the blue wavelength band and the half-value width of the reflectance in the corresponding reflective layers 10R, 10G, 10B Is set to 30 nm or less, preferably the absolute value is set to 20 nm or less, more preferably the absolute value is set to 10 nm or less.

  More specifically, in this type of image display panel, the emitted light LR, LG, LB in the red wavelength band, the green wavelength band, and the blue wavelength band generally has center wavelengths of 624 nm, 525 nm, and 458 nm, respectively. The full width at half maximum is about 40 nm, 30 nm, and 20 nm. Thus, the reflective layers 10R, 10G, and 10B are applied with a liquid crystal layer having a birefringence Δn satisfying 0.04 ≦ Δn ≦ 0.11, so that the reflective layers 10R, 10G, and 10B satisfy the above conditions. Can be produced.

  Here, the reflective layers 10R, 10G, and 10B are prepared by applying a coating liquid relating to cholesteric liquid crystal and then drying and curing. The composition according to the coating liquid contains a liquid crystal material and a chiral agent having a turning property with respect to the liquid crystal material. Further, the composition may contain a leveling agent, a polymerization initiator, an additive and the like. Here, in the liquid crystal material satisfying the condition of the birefringence Δn, a liquid crystal material exhibiting reverse dispersion wavelength characteristics can be applied, or a liquid crystal material having a cyclohexane structure can be applied.

  Here, examples of the liquid crystal material having such reverse dispersion include, for example, JP-T-2010-522289, JP-A-2006-243470, JP-A-2007-243470, JP-A-2009-75494, Liquid crystals described in Japanese Unexamined Patent Application Publication No. 2009-62508, Japanese Unexamined Patent Application Publication No. 2009-179563, Japanese Unexamined Patent Application Publication No. 2009-242717, Japanese Unexamined Patent Application Publication No. 2009-242718, Japanese Patent No. 4222360, Japanese Patent No. 41868981, and the like. A compound can be illustrated.

  Examples of the liquid crystal material having a cyclohexane structure include Japanese Patent Application Laid-Open Nos. 2001-163833, 2007-91612, 2007-917996, 2006-241403, 2006-200608, 2006-37005, and 2006-2006. A material prepared by adding a polymerizable group such as an acrylate group to a molecular terminal of a liquid crystal material described in 8928 or a material described in JP-A-2008-274204 can be applied.

  As the chiral agent, Palio Color LC756 manufactured by BASF can be applied. In the cholesteric liquid crystal layer, the ratio between the chiral agent and the liquid crystal material can be varied to adjust the helical pitch p of the cholesteric liquid crystal layer, thereby adjusting the center wavelength and the half width.

  In this embodiment, the reflective layer 10 is formed by applying a laminate of reflective layers 10R, 10G, and 10B from a corresponding transfer film by a transfer method, a base material 6, a linearly polarizing plate 7, a quarter-wave plate 8, and a positive C plate 9. It is formed by transferring to a laminate.

[Transfer film]
FIG. 4 is a view showing a transfer film that is an optical film used for transfer of the reflective layer 10. The transfer film 17 is formed by sequentially forming the orientation layer 16 and the reflective layers 10R, 10G, and 10B on the base material 15, and the base material 6, the linearly polarizing plate 7, and 1/4 by an adhesive layer made of an ultraviolet curable resin or the like. After being bonded to the laminate of the wave plate 8 and the positive C plate 9, the substrate 15 is peeled integrally with the alignment layer 16 to produce the optical film 3.

  Here, although the transparent film material by PET (polyethylene terephthalate) resin is applied to the base material 15, this type of material such as a TAC (Triacetylcellulose) film material, a COP (Cyclo Olefin Polymer) film material, etc. is used instead of the PET film material. Various transparent film materials applied to the film material can be widely applied.

  The alignment layer 16 is composed of a photo-alignment layer to which alignment ability is imparted by a photo-alignment technique. More specifically, the alignment layer 16 is constituted by a photo-alignment layer using, for example, a light-dimerization type material. However, the alignment layer 16 is not limited to the light-dimerization-type material, and various photo-alignment layer materials can be widely applied. Can do. The light dimerization type material is described in “M. Schadt, K. Schmitt, V. Kozinkov and V. Chigrinov: Jpn. J. Appl. Phys., 31, 2155 (1992)”, “M. Schadt, 1992”. H. Seiberle and A. Schuster: Nature, 381, 212 (1996). The alignment layer 16 is produced by applying an application liquid related to the alignment layer 16 and drying it, and then irradiating with ultraviolet rays by linearly polarized light. The alignment layer 16 may be produced by a fine line-shaped uneven shape forming process, or a rubbing process such as a polyimide film formed on the surface of the substrate 15 or a direct rubbing process on the surface of the substrate 15. Thus, a fine line-shaped uneven shape may be produced as the alignment layer 16.

  The reflective layer 10R is manufactured by applying a coating liquid made of a liquid crystal material that satisfies the above-described conditions of the center wavelength and the half-width for the red wavelength band, and then drying and curing. Here, the cholesteric liquid crystal layer thus produced exhibits an alignment regulating force on its surface. Thereby, in this embodiment, after coating the coating liquid by the liquid crystal material which satisfies the conditions of the center wavelength and the half-width described above for the green wavelength band, the reflective layer 10G according to the green wavelength band is dried and cured. Is produced. Subsequently, similarly, after applying a coating liquid made of a liquid crystal material that satisfies the above-described conditions of the center wavelength and half-width for the blue wavelength band, drying and curing are performed to produce the reflective layer 10B for the blue wavelength band. The

  Note that the order of the red reflective layer 10R, the green reflective layer 10G, and the blue reflective layer 10B may be changed as necessary.

〔Example〕
FIG. 5 is a chart showing the measurement results of Examples and Comparative Examples of the present invention. In FIG. 5, the reference example is a characteristic of only the image display panel 2, and the half width B, the half width G, and the half width R are the half widths of the emitted light from the blue pixel, the green pixel, and the red pixel, respectively. , 20 nm, 30 nm, and 40 nm, respectively.

  In Comparative Example 1, reflective layers 10R, 10G, and 10B made of cholesteric liquid crystal layers were prepared using a liquid crystal material (molecular structure A) having a normal positive wavelength dispersion characteristic, and a positive C plate, a 1/2 wavelength retardation layer And a quarter-wave plate by laminating a quarter-wave retardation layer and a linear polarizing plate, and further laminated with an antireflection film 11 and arranged on the panel surface of the image display panel according to the reference example. Here, this cholesteric liquid crystal layer had a birefringence Δn of 0.15, and a half-value width B, a half-value width G, and a half-value width R were 60 nm, 70 nm, and 80 nm, respectively.

  The comparative example 2 is a configuration in which the reflective layer 10 is omitted from the configuration of the comparative example 1. In the example of FIG. 5, the emitted light amount (brightness improvement rate) of the example and the comparative example is shown by the magnification with respect to the emitted light amount of the comparative example 2 on the basis of the emitted light amount of the comparative example 2. Thereby, the emitted light quantity of the comparative example 1 was 1.67 times of the comparative example 2. In Comparative Example 2, although the luminance improvement rate is increased as compared with Comparative Example 1 by providing the reflective layer 10, it can be seen that the external light reflectance is increased.

  The molecular structure A is Palio Color LC242 manufactured by BASF, and the reflective layers 10R, 10G, and 10B are 4.3 parts by weight, 5.1 parts by weight, 5 parts by weight, respectively, with respect to 100 parts by weight of the above compound. .9 parts by weight was added with methyl ethyl ketone at a solid content of 25%. Further, 4% of the initiator Irgacure 907 was added to each solution and dissolved again. After coating with PET # 8 on the PET substrate, After drying for 1 minute in a 90 degree oven, it produced by UV hardening.

  Examples 1 to 3 are examples in which the reflective layers 10R, 10G, and 10B of the cholesteric liquid crystal layer were prepared from the liquid crystal materials having molecular structures 1, 2, and 3 each having a cyclohexane structure, and Example 4 was a wavelength of reverse dispersion. This is an example in which the reflective layers 10R, 10G, and 10B of the cholesteric liquid crystal layer are produced from the reverse dispersion liquid crystals 1 to 3 having characteristics.

More specifically, the molecular structures 1, 2, and 3 are as follows.

  Reflective layers 10R, 10G, and 10B are obtained by adding LC756 to 4.3 parts by weight, 5.1 parts by weight, and 5.9 parts by weight, respectively, with respect to 100 parts by weight of the above compounds (molecular structures 1 to 3). Is dissolved in methyl ethyl ketone at a solid content of 25%, and 4% of the initiator Irgacure 907 is added to each solution and dissolved again. After coating on PET substrate with Miyabar # 8, 1 minute in a 90 degree oven. After drying, it was prepared by UV curing.

  Moreover, in the reverse dispersion liquid crystal 1, a material obtained by blending a mixture of the compound (1), RM (1), and RM (3) described in JP-T-2010-528992 with a blending ratio of 5: 3: 2 has a molecular structure. Reflective layers 10R, 10G, and 10B were produced in the same manner as in Examples 1 to 3, except that the compounds according to Examples 1 to 3 were used instead of the compound.

  In Example 1, the birefringence Δn was 0.10, and the half width B, the half width G, and the half width R were 35 nm, 45 nm, and 55 nm. In Example 2, the birefringence Δn was 0.11, and the half width B, the half width G, and the half width R were 40 nm, 50 nm, and 60 nm, respectively. In Example 3, the birefringence Δn was 0.09, and the half width B, the half width G, and the half width R were 30 nm, 40 nm, and 50 nm, respectively. In these Examples 1 to 3, the external light reflectance can be reduced as compared with Comparative Example 1, and a luminance improvement rate substantially equal to that of Comparative Example 1 can be obtained.

  In Example 4, the birefringence Δn was 0.05, and the half width B, the half width G, and the half width R were 20 m, 30 nm, and 40 nm, respectively. In the same manner as in Examples 1 to 3, Example 4 can reduce the external light reflectance as compared with Comparative Example 1, and can obtain a luminance improvement rate substantially equivalent to that of Comparative Example 1.

[Other Embodiments]
As mentioned above, although the specific structure suitable for implementation of this invention was explained in full detail, this invention can change the structure of the above-mentioned embodiment variously in the range which does not deviate from the meaning of this invention.

  That is, in the above-mentioned embodiment, the case where the laminated structure of the reflective layers 10R, 10G, and 10B is formed on the alignment layer by sequentially applying and curing the coating liquid has been described. Instead of coating the reflective layer coating solution directly on the reflective layer and curing it, after preparing the corresponding alignment layers, the coating solution is coated and cured to produce the reflective layer. Then, a laminated structure of the reflective layers 10R, 10G, and 10B may be formed. In addition, an orientation layer and a reflective layer are produced on a substrate made of a transparent film material to produce three types of optical films made of a transfer film, and the reflective layers are sequentially transferred using this transfer film, whereby the reflective layers 10R, 10G, A laminated structure of 10B may be formed.

  In the above-described embodiment, the case where the reflective layer is transferred to the antireflection film by the circularly polarizing plate including the positive C plate by the transfer method and then disposed on the panel surface of the image display panel is described. Is not limited to this, an optical film formed by arranging a reflective layer on a substrate made of a transparent film material is sequentially placed on the panel surface of the image display panel, and then an antireflection film made of a circularly polarizing plate is placed. Widely applied to various forms, such as when an optical film provided with a reflective layer is laminated with an antireflective film made of a circularly polarizing plate without using a method, and then placed on the panel surface of an image display panel. Can do.

  In the above-described embodiment, the birefringence Δn is set for each of the three reflective layers corresponding to the respective pixels whose emitted light is in the red wavelength band, the green wavelength band, and the blue wavelength band, and further, the center wavelength and the half width are set. Although the case of setting is described, the present invention is not limited to this, and it is not always necessary to set all three reflective layers so as to satisfy the above-mentioned conditions. Only a part of these three reflective layers is described above. You may set so that conditions may be satisfied.

  In the above-described embodiment, the case where the three reflection layers 10R, 10G, and 10B that selectively reflect the emitted light in the red wavelength band, the green wavelength band, and the blue wavelength band are stacked is described. Without limitation, only two layers or only one of these three reflective layers may be provided as necessary. Further, the driving conditions for each pixel may be set so as to correspond to the laminated structure of the reflective layers. Thus, for example, if the reflective layer 10B is provided only for the blue wavelength band, the driving condition for only the blue pixel can be relaxed, and thereby the driving condition for the organic EL element related to the blue pixel can be relaxed. it can. Here, in the organic EL element, the efficiency is lowered on the short wavelength side, so that the driving condition on the short wavelength side is severer than that on the long wavelength side, but the reflective layer 10B is provided only in the blue wavelength band in this way. Thus, if the conditions for driving the blue pixels can be relaxed, the reliability of the organic EL panel and the reliability of the image display device using the organic EL panel can be further improved.

DESCRIPTION OF SYMBOLS 1 Image display apparatus 2 Image display panel 3 Optical film 4 Adhesive layer 6 Base material 6A Hard coat layer 7 Linearly polarizing plate 7A Optical functional layer 8 1/4 wavelength plate 8A 1/4 wavelength phase difference layer 8B 1/8 wavelength Retardation layer 9 Positive C plate 10, 10R, 10G, 10B Reflective layer 11 Antireflection film 15 Base material 16 Orientation layer 17 Transfer film

Claims (11)

On the base material made of film material, equipped with a reflective layer made of cholesteric liquid crystal,
The reflective layer of the cholesteric liquid crystal is
An optical film having a birefringence Δn of 0.04 to 0.11. The optical film according to claim 1, wherein the liquid crystal material of the reflective layer is a liquid crystal material having wavelength characteristics of reverse dispersion. The optical film according to claim 1, wherein the liquid crystal material of the reflective layer is a liquid crystal material having a molecular structure having at least a cyclohexane structure. In the optical film disposed on the panel surface of the image display panel in which the pixels by the self-light-emitting elements whose emission light is at least in the red wavelength band, the green wavelength band, and the blue wavelength band are arranged in a matrix,
A linear polarizing plate that emits incident external light by linearly polarized light;
A quarter-wave plate for emitting linearly polarized external light incident from the linearly polarizing plate as circularly polarized light;
Circularly polarized external light incident from the ¼ wavelength plate is transmitted and circularly polarized light whose polarization plane is opposite to the circularly polarized external light incident from the ¼ wavelength plate. And a reflective layer that reflects circularly polarized light in a specific wavelength band,
The specific wavelength band is
The absolute difference between the center wavelength of the specific wavelength band and the center wavelength of the light emitted from the pixel is 30 nm or less,
An optical film in which an absolute difference between the half-value width of the specific wavelength band and the half-value width of light emitted from the pixel is 30 nm or less. The reflective layer is
The optical film according to claim 4, which is a plurality of reflective layers respectively corresponding to the red wavelength band, the green wavelength band, and the blue wavelength band. The reflective layer is
The optical film according to claim 4, wherein the birefringence Δn is a reflective layer made of a cholesteric liquid crystal having a birefringence Δn of 0.04 or more and 0.11 or less. The optical film according to claim 6, wherein the liquid crystal material of the reflective layer is a liquid crystal material having reverse dispersion wavelength characteristics. The optical film according to claim 6, wherein the liquid crystal material of the reflective layer is a liquid crystal material having at least a cyclohexane structure in a molecular structure. An antireflection film for antireflection is laminated by laminating at least two layers of a low refractive index layer and a high refractive index layer. Any one of claims 4, 5, 6, 7, and 8. The optical film described in 1. The panel surface of an image display panel in which pixels of self-luminous elements having at least emitted light in a red wavelength band, a green wavelength band, and a blue wavelength band are arranged in a matrix form. An image display device in which any one of the optical films is disposed. The image display apparatus which has arrange | positioned the optical film in any one of Claim 4, Claim 5, Claim 7, Claim 8, Claim 9 on the panel surface of the said image display panel.

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