JP2015173066A - Backlight device, liquid crystal display device and laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure sufficient sharp directivity with a simple structure, in a structure using a reflection type polarization plate to improve utilization efficiency of emission light from a primary light source.SOLUTION: In a backlight device 2, after directivity of emission light from the emission surface of a light guide plate 12 is corrected by a prism sheet 14 having a downward projected shape, the emission light is supplied to a liquid crystal display panel 3 through a reflection type polarization plate 16. The backlight device is provided with a 1/4 wavelength plate 15 provided between the prism sheet 14 and the reflection type polarization plate 16, between the prism sheet 14 and the light guide plate, or between the light guide plate and a reflection sheet arranged on an opposite surface to the prism sheet 14 of the light guide plate.

Description

  The present invention relates to a backlight device, a liquid crystal display device, and a laminate, for example, an edge light that emits light emitted from a primary light source from the edge (end face) of the light guide plate to the light guide plate and propagates from the output surface while propagating internally. The present invention relates to a type backlight device and a liquid crystal display device using the edge light type backlight device.

  Conventionally, in a liquid crystal display device, illumination light is supplied to a liquid crystal display panel from an edge-light type backlight device or the like to display a desired image. In the edge light type backlight device, a primary light source is constituted by a rod-like light source such as a cold cathode ray tube or a point light source such as a light emitting diode, and the light emitted from the primary light source is transmitted from the end face (edge) of the light guide plate to the light guide plate. Incident and propagates internally. The light guide plate is provided with a device for irregularly reflecting and diffusing the emitted light of the primary light source that propagates in this way, so that the emitted light of the primary light source is gradually emitted from the emitting surface while internally propagating. . In the edge light type backlight device, the directivity of the emitted light from the light guide plate is corrected by the prism sheet in the front direction of the emitting surface and supplied to the liquid crystal display panel. Thus, in the edge light type backlight device, the surface light source used for illumination of the liquid crystal display panel is configured by using the emitted light of the primary light source by the rod-like light source and the point light source.

  With regard to such an edge light type backlight device, Patent Documents 1 and 2 disclose that the directivity of outgoing light is sharp in the front direction by repeatedly providing a convex strip or the like having a pentagonal cross section on the outgoing surface of the light guide plate. A method of improving directivity and improving the utilization efficiency of outgoing light has been proposed.

  In Patent Document 3, instead of a linear polarizing plate, a so-called reflective polarizing plate is arranged to reflect the emitted light component of the backlight device that has been absorbed by the linear polarizing plate and re-apply to the light guide plate. An incident configuration is disclosed. According to this configuration, the re-entered outgoing light can be reused, and the usage efficiency of the outgoing light can be improved.

  In Patent Document 4, in a backlight device having a configuration in which a prism sheet having an upward convex shape is disposed on the light exit surface of a light guide plate, a quarter-wave plate, a reflective polarization plate is provided between the prism sheet and the liquid crystal display panel. The structure which arrange | positions a board sequentially is disclosed. In this configuration, the polarization component reflected by the reflective polarizing plate is converted into circularly polarized light by the quarter-wave plate and re-enters the light guide plate, and is re-entered and reflected inside the light guide plate. As a result, when the direction of the circularly polarized light is reversed, as a result, when the light is again emitted from the light guide plate and incident on the reflective polarizing plate, the linearly polarized light is transmitted through the reflective polarizing plate to be reflected into the reflective polarizing plate. Incident. Thereby, in the case of this configuration, the polarized light component reflected by the reflective polarizing plate is positively converted into the polarized light component that passes through the reflective polarizing plate, thereby further improving the light utilization efficiency.

  However, in the configuration disclosed in Patent Document 4, in order to supply the light emitted from the prism sheet to the liquid crystal display panel with a sufficient peak light amount and sharp directivity, there is a problem that the configuration of the prism sheet becomes complicated. There are still insufficient problems. In other words, when a prism sheet is configured simply by repeating triangular ridges, the apex angle of the ridges is controlled to ensure the desired directivity, but in this case, the peak light intensity is maximized. It is difficult to sufficiently suppress the sidelobe light at the holding vertex angle. As a result, after all, it is necessary to devise the cross-sectional shape of the ridges, or to provide a partial light shielding portion as disclosed in Patent Document 4.

JP-A-8-254606 Japanese Patent Laid-Open No. 9-5505 JP 2000-227518 A JP 2013-47794 A

  The present invention has been made in view of such a situation, and in a configuration for improving the utilization efficiency of light emitted from a primary light source by using a reflective polarizing plate, sufficiently sharp directivity is ensured by a simple configuration. As a result, an object is to provide a liquid crystal display device with high efficiency and high contrast.

  The present inventor has intensively studied to solve the above-mentioned problems, and has arrived at the idea that a prism sheet having a downward convex shape, a quarter-wave plate, and a reflective polarizing plate are sequentially arranged on the light exit surface of the light guide plate. The present invention has been completed.

    Specifically, the present invention provides the following.

(1) In a backlight device for supplying directivity to the liquid crystal display panel via a reflective polarizing plate after correcting the directivity of the emitted light from the exit surface of the light guide plate by a prism sheet having a downward convex shape,
Between the prism sheet and the reflective polarizing plate, between the prism sheet and the light guide plate, or between the light guide plate and the reflective sheet disposed on the surface opposite to the prism sheet of the light guide plate, A backlight device provided with a quarter-wave plate.

  According to (1), by using a prism sheet having a downwardly convex shape, it is possible to ensure sufficiently sharp directivity with a simple configuration as compared with the case of using an upwardly convex prism sheet, As a result, a liquid crystal display device with high efficiency and high contrast can be provided.

(2) In (1), the prism sheet is
The retardation value Re of the substrate is 20 nm or less.

  According to (2), since the optical anisotropy of the prism sheet base material can be sufficiently suppressed in practice, the polarized light component reflected by the reflective polarizing plate is efficiently transmitted through the reflective polarizing plate. Can be converted into components.

  (3) In (1) or (2), the prism sheet and the quarter-wave plate are integrated.

  (4) In (1) or (2), the quarter-wave plate and the reflective polarizing plate are integrated.

  (5) In (1) or (2), the prism sheet, the quarter-wave plate, and the reflective polarizing plate are integrated.

  (6) In (1) or (2), the quarter-wave plate and the reflection sheet are integrated.

  According to (3), (4), (5) and (6), the air interface can be reduced and the efficiency can be further improved.

  (7) A liquid crystal display device in which a liquid crystal display panel is laminated on the backlight device according to any one of (1), (2), (3), (4), (5), and (6).

  According to (7), a sufficiently sharp directivity can be secured with a simple configuration, and as a result, a liquid crystal display device with high efficiency and high contrast can be provided.

  (8) A laminate in which a quarter-wave plate is integrally provided on the other surface of the prism sheet in which protrusions are repeatedly formed on one surface of the transparent substrate.

  (9) A laminate in which a quarter-wave plate is integrally provided on a reflective polarizing plate.

  (10) A laminate in which a quarter-wave plate and a reflective polarizing plate are sequentially and integrally provided on the other surface of a prism sheet formed by repeatedly forming protrusions on one surface of a transparent substrate.

  (11) A laminate in which a quarter-wave plate is integrally provided on the reflection sheet.

  According to (8), (9), (10), and (11), the directivity of the emitted light from the exit surface of the light guide plate is corrected by the prism sheet having the downward convex shape, and then passed through the reflective polarizing plate. When applied to a backlight device supplied to a liquid crystal display panel, the air interface can be reduced and the efficiency can be further improved.

(12) In (8) or (10),
The prism sheet is
The retardation value Re of the substrate is 20 nm or less.

  According to (12), the optical anisotropy of the base material of the prism sheet can be sufficiently suppressed practically, so that the polarized component reflected by the reflective polarizing plate is efficiently transmitted through the reflective polarizing plate. Can be converted into components.

  According to the present invention, it is possible to secure sufficiently sharp directivity with a simple configuration in a configuration in which the use efficiency of light emitted from a primary light source is improved using a reflective polarizing plate.

1 is a cross-sectional view showing a liquid crystal display device according to a first embodiment of the present invention. 3 is a chart for explaining a backlight device according to the liquid crystal display device of FIG. 1. It is sectional drawing which shows the liquid crystal display device which concerns on 2nd Embodiment of this invention. It is a figure where it uses for description of the backlight apparatus which concerns on the liquid crystal display device of FIG. It is a figure which shows the directivity which concerns on a different direction from FIG. It is a figure which shows the directivity which concerns on a different direction from FIG.4 and FIG.5. It is a figure which shows the liquid crystal display device which concerns on 3rd Embodiment of this invention. It is a figure which shows the liquid crystal display device which concerns on 4th Embodiment of this invention. It is a figure which shows the liquid crystal display device which concerns on 5th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a cross-sectional view showing a schematic configuration of the liquid crystal display device according to the first embodiment of the present invention. The liquid crystal display device 1 is configured by laminating a backlight device 2 and a liquid crystal display panel 3. Here, in the liquid crystal display panel 3, a liquid crystal cell 6 is configured by sandwiching the liquid crystal 5 between glass plates 4A and 4B formed by forming transparent electrodes, and linear polarizing plates 7A and 7A are formed on the entrance surface and the exit surface of the liquid crystal cell 6, respectively. 7B is arranged. Thereby, the liquid crystal display panel 3 emits the illumination light supplied from the backlight device 2 with the light intensity modulated in accordance with the driving of the transparent electrode, and displays a desired image. Note that a variety of configurations such as a TN (Twisted Nematic) method, a VA (Virtual Alignment) method, and an IPS (In-Place-Switching) can be widely applied to the liquid crystal display panel.

  The backlight device 2 is a so-called edge light type backlight device, and a primary light source (in this embodiment, a rod-shaped light source using a cold cathode ray tube) 11 is an end surface of a light guide plate 12 (hereinafter referred to as an incident surface). The light emitted from the primary light source 11 is incident on the light guide plate 12 from the incident surface. As a result, the backlight device 2 emits light emitted from the primary light source 11 from the light emission surface of the light guide plate 12 while propagating through the light guide plate 12.

  In the backlight device 2, the reflection sheet 13 is disposed on the back surface (the side opposite to the liquid crystal display panel 3) of the light guide plate 12, and the internal propagation light of the light guide plate 12 leaks from the back surface of the light guide plate 12 by the reflection sheet 13. Is incident again on the light guide plate 12 to improve the light use efficiency. Reflective sheets can be widely applied to film materials obtained by vapor-depositing highly reflective metal materials such as silver on various film materials, sheet materials made of white resin material, regular reflection members, irregular reflection members, etc. In order to maintain high properties, a highly reflective and regular reflection member is preferable.

  In the backlight device 2, a downward convex prism sheet 14, a quarter wavelength plate 15, and a reflective polarizing plate 16 are sequentially arranged on the light exit surface of the light guide plate 12. Here, the internally propagating light emitted from the exit surface of the light guide plate 12 is propagated from the entrance surface toward the surface opposite to the entrance surface, and the component below the critical angle is emitted from the exit surface. The light is emitted with directivity inclined obliquely to the internal propagation direction.

  The prism sheet 14 corrects the directivity of the emitted light emitted from the light guide plate 12 in the front direction of the emission surface by the directivity inclined obliquely in the internal propagation direction. The reflection-type polarizing plate 16 transmits the polarized light component transmitted through the linear polarizing plate 7A of the liquid crystal display panel 3 with respect to the outgoing light from the prism sheet 14 that is transmitted through the quarter-wave plate 15 and is orthogonal thereto. The polarized light component absorbed by the linearly polarizing plate 7A is reflected. The ¼ wavelength plate 15 converts the linearly polarized light into circularly polarized light by giving a phase difference corresponding to ¼ wavelength to the polarization component of the linearly polarized light reflected by the reflective polarizing plate 16, and emits it. This improves the light utilization efficiency.

  The light guide plate 12 is made in a substantially plate shape using a transparent resin such as acrylic, and is disclosed in Japanese Patent Application Laid-Open Nos. 8-254606 and 9-5505 on the exit surface. The protrusions with a pentagonal cross section are repeatedly formed on the exit surface so as to extend almost perpendicular to the entrance surface and perpendicular to the extension direction, and the reflective surface facing the exit surface is substantially parallel to the entrance surface. The slope with the action of raising the light guide from the entrance surface in the normal direction of the exit surface has been repeatedly produced in the direction perpendicular to the extension direction, and due to the sharp directivity with suppressed sidelobe light It is configured to emit internally propagating light. In this ridge, it may be produced integrally with the main body part by injection molding or extrusion molding related to the production of the light guide plate, and the transparent plate-like member is formed by a molding process using an ultraviolet curable resin or the like. You may make it produce.

  Thus, when the downward convex prism sheet 14, the quarter wavelength plate 15, and the reflective polarizing plate 16 are sequentially arranged on the light exit surface of the light guide plate 12, a prism sheet having a simple configuration is used. Thus, light can be supplied to the liquid crystal display panel 3 with a sufficient peak light amount and with a sharp directivity. As a result, a liquid crystal display device with high efficiency and high contrast can be provided.

  That is, when using an upward convex prism sheet, a slope on the primary light source side (hereinafter referred to as a light source side slope) and a slope on the opposite side (hereinafter referred to as a reverse slope) The light emitted from the light guide plate is incident through the prism sheet. However, since the incident light on these two slopes has a directivity inclined obliquely in the internal propagation direction, only the light incident on the opposite slope is emitted with the directivity in the front direction of the exit surface, and is incident on the light source side slope. With respect to the incident light, directivity cannot be set in a desired direction, and as a result, the incident light on the light source side slope increases the sidelobe light. As a result, when an upwardly convex prism sheet is used, it is necessary to shield the light source side slope so that light emitted from the light guide plate does not enter, and the configuration becomes complicated. Also, with respect to the transmitted light on the reverse side slope, the inclination that maximizes the peak light amount in the front direction is different from the inclination that can most suppress the light amount of the sidelobe light. I need it.

  On the other hand, in the downward convex prism sheet, the light emitted from the light guide plate is transmitted through the light source side inclined surface and incident on the prism sheet, and then reflected by the reverse side inclined surface to be directed in the front direction of the output surface. By being corrected, it is possible to emit light from the light guide plate with sharp directivity in the front direction without providing any light shielding portion.

  When a quarter wave plate and a reflective polarizing plate are applied to such a backlight device using an upwardly convex prism sheet (the configuration of Patent Document 4), the light guide plate reflected by the reflective polarizing plate is returned to. Even the light is shielded by the light shielding part provided on the prism sheet, and the light quantity loss due to the light shielding part is further increased.

  On the other hand, when the downward convex prism sheet is used in combination with the quarter wavelength plate and the reflective polarizing plate as in this embodiment, the return light to the light guide plate reflected by the reflective polarizing plate is also used. Thus, the influence of the light shielding portion can be effectively avoided, and the light use efficiency can be improved as compared with the case of the upward convex prism sheet.

  In this embodiment, as described above, a projection is provided on the exit surface of the light guide plate so that the directivity is sharp, and a reflective polarizing plate is used in combination with such a light guide plate. In this case, the polarized light component reflected by the reflective polarizing plate passes through the ridges of the light guide plate many times until it passes through the reflective polarizing plate and is emitted to the liquid crystal display panel. . As a result, the incident light to the liquid crystal display panel becomes light having a spread in a direction perpendicular to the extending direction of the ridges.

  However, when a quarter wavelength plate is provided as in this embodiment, the polarized light component reflected by the reflective polarizing plate can be positively converted into the polarized light component that passes through the reflective polarizing plate. The number of times of passing through the ridge can be reduced, and as a result, spreading in a direction perpendicular to the extending direction of the ridge can be suppressed.

[Prism sheet and 1/4 phase difference plate]
In this embodiment, the prism sheet 14 has a convex strip 14 </ b> B having a triangular cross-section extending along the incident surface of the light guide plate 12 on the base material 14 </ b> A made of a transparent film material by a shaping process using an ultraviolet curable resin. , Repeatedly produced in a direction orthogonal to the extending direction of the ridges 14B. Instead of using an ultraviolet curable resin, a thermosetting resin or the like may be used, and further, the substrate 14A may be directly pressed by a mold. In the prism sheet 14, a material having an in-plane retardation value Re of 20 nm or less, more preferably a material having a retardation value Re of 10 nm or less, such as acrylic, is applied to the base material 14A. The light reflected by the reflective polarizing plate and transmitted through the prism sheet 14 is prevented from changing greatly in phase difference, thereby preventing a decrease in light utilization efficiency.

  In this embodiment, the quarter-wave plate 15 is manufactured integrally with the prism sheet 14, thereby effectively avoiding loss due to the interface with the air between the prism sheet 14 and improving the light utilization efficiency. Let

  In addition, about this integration, when the quarter wavelength plate 15 is produced integrally with the prism sheet 14 by the transfer method, after the retardation layer according to the quarter wavelength plate 15 is produced on the base material 14A, the ridge 14B is produced. In the case of manufacturing the method, various methods of integration can be applied, for example, in the case where the ridge 14B is manufactured on the base material 14A and then the retardation layer related to the quarter wavelength plate 15 is manufactured.

  Here, in the transfer method, for example, when a desired layer is formed on a base material, the layer is not directly formed on the base material, but can be peeled once on a releasable support. After forming the transfer body by laminating the layers, the layer formed on the support is finally placed on the substrate (transfer base material) on which the layer is to be laminated according to the process, demand, etc. In this method, a desired layer is formed on the substrate by bonding and laminating, and then peeling and removing the support. In the case of this transfer method, an alignment film is prepared on a support made of various film materials, and then the alignment regulating force of the alignment film is applied by applying a coating liquid relating to the retardation layer, drying and irradiating ultraviolet rays. Thus, the liquid crystal material related to the retardation layer is solidified in an aligned state, thereby producing a retardation layer. Subsequently, the retardation layer is attached to the base material 14A with an adhesive layer such as an ultraviolet curable resin layer, and then the support is peeled off. When producing by the transfer method, the ridge 14B may be produced in advance on the base material 14A, or the ridge 14B may be produced after producing the retardation layer.

  In addition, after forming the retardation layer related to the quarter wavelength plate 15 on the base material 14A, when preparing the ridge 14B, after forming the alignment film on the base material 14A, the coating liquid related to the retardation layer is applied. The phase difference layer is prepared by irradiating with ultraviolet rays after being worked and dried, and then the ridges 14B are prepared by a forming process.

  After producing the ridges 14B on the base material 14A, when producing the retardation layer according to the quarter-wave plate 15, after producing the ridges on the base material by a shaping process, an orientation film is produced on the base material 14A. Then, the retardation layer is prepared by coating and drying the coating liquid relating to the retardation layer and irradiating with ultraviolet rays.

  In addition, the alignment film according to the retardation layer can be prepared by applying a photo-alignment film, by a fine line-shaped uneven shape forming process, or by a surface rubbing process. Can be widely applied.

  FIG. 2 is a chart showing the evaluation results of the backlight device. In FIG. 2, in Comparative Example 1, a prism sheet having a downwardly convex shape made of an acrylic base material is disposed on a light guide plate (which is the above-described light guide plate) in which convex stripes having a pentagonal cross section are arranged on the exit surface. A reflective polarizing plate is provided without providing a / 4 retardation plate. Example 1 is the backlight device according to the above-described embodiment using the above-described light guide plate in which ridges having a pentagonal cross section are arranged on the exit surface. Comparative Example 2 is a case where the fast axis direction of the quarter retardation plate is set to the transmission axis direction of the reflective polarizing plate in the backlight device according to Example 1. In Comparative Examples 3, 4, and 5, in the configurations of Comparative Example 1, Example, and Comparative Example 2, respectively, instead of the acrylic material, a matte-treated PET (Polyethylene terephthalate) material is applied to the prism sheet base material. It is. Moreover, the comparative example 6 and Example 2 are the structures which provided the protruding item | line of the cross-sectional triangle shape by 90 degrees of apex angles instead of the protruding item | line of a pentagonal cross section in the structure of the comparative example 1 and the example, respectively. .

  In these configurations shown in FIG. 2, the quarter-wave plate is integrated with the reflective polarizing plate instead of the prism sheet. Moreover, what was called a silver vapor deposition film which is the film material which vapor-deposited silver was applied to the reflection sheet. The retardation value Re of the base material of the prism sheet was 18 nm.

  In FIG. 2, the peak luminance indicates each measured value as a relative value with the measured peak luminance value of Comparative Example 1 as 100%, together with the measured value by actual measurement. The light guide direction at the half-width angle is a direction (internal propagation direction) from the incident surface to a surface opposite to the incident surface, and the light guide vertical direction is a direction orthogonal to the light guide direction.

  In FIG. 2, a quarter wavelength plate is provided by comparison between Comparative Examples 1 and 2 and Example 1, comparison between Comparative Examples 3 and 5 and Comparative Example 4, and comparison between Comparative Example 6 and Example 2. Thus, it can be seen that the amount of outgoing light in the front direction increases (peak luminance) by converting the antireflective article light of the reflective polarizing plate into circularly polarized light. Further, by comparing Comparative Examples 3 to 5 with Comparative Example 1, Example 1 and Comparative Example 2, the retardation value Re of the prism sheet can be reduced, the amount of light in the front direction can be increased, and the directivity can be sharpened. I understand.

  In this embodiment, a downwardly convex prism sheet, a quarter-wave plate, and a reflective polarizing plate are sequentially provided on the output surface of the light guide plate, so that the output light from the primary light source can be obtained using the reflective polarizing plate. In the configuration for improving the utilization efficiency, a sufficiently sharp directivity can be secured with a simple configuration, and as a result, a liquid crystal display device with high efficiency and high contrast can be provided.

  Further, by integrating the prism sheet and the quarter wavelength plate, the loss due to the air interface can be reduced and the amount of emitted light can be further increased.

[Second Embodiment]
FIG. 3 is a diagram showing a liquid crystal display device according to the second embodiment of the present invention in comparison with FIG. The liquid crystal display device 21 of this embodiment is configured in the same manner as the liquid crystal display device 1 of the first embodiment, except that a backlight device 22 is disposed instead of the backlight device 2. The backlight device 22 is configured in the same manner as the backlight device 2 except that the quarter-wave plate 15 is disposed integrally with the reflective polarizing plate 16 instead of the prism sheet 14.

  Here, for this integration, a quarter-wave plate 15 may be provided integrally with the reflective polarizing plate 16 by a transfer method, and the retardation element related to the quarter-wave plate 15 is provided on the reflective polarizing plate 16. Further, the quarter wavelength plate 15 may be attached to the reflective polarizing plate 16 by adhesion with an ultraviolet curable resin or the like.

  In addition, in the case of the transfer method, after preparing an alignment film on a support made of various film materials, the coating liquid for the retardation layer is applied, dried and irradiated with ultraviolet rays to align the alignment film. The liquid crystal material related to the retardation layer is solidified in a state where the retardation layer is aligned by the regulating force, thereby producing the retardation layer on the support. Subsequently, the retardation layer is attached to the reflective polarizing plate 16 with an adhesive layer such as an ultraviolet curable resin layer, and then the support is peeled off. In addition, when integrating by a transfer method, the reflection type polarizing plate 16 may be prepared in advance as described above, and the retardation layer related to the quarter wavelength plate may be transferred. After transferring the phase difference layer to the base material related to the reflective polarizing plate 16, the reflective polarizing plate 16 may be produced.

  4, 5, and 6 are characteristic curve diagrams showing directivities in the internal propagation direction, the direction that forms an angle of 45 degrees with the internal propagation direction, and the direction that is orthogonal to the internal propagation direction. 4 to 6, the symbol L <b> 1 is a measurement result of Example 1, and the symbol L <b> 2 is a configuration in which the reflective polarizing plate and the quarter retardation plate are separated from each other in the configuration of Example 1. The symbol L3 is the measurement result of Comparative Example 1.

  4 to 6, it can be seen that the amount of emitted light in the front direction is increased even if the air interface is reduced by integrating the quarter-wave plate with the reflective polarizing plate.

[Third Embodiment]
FIG. 7 is a diagram showing a liquid crystal display device according to a third embodiment of the present invention in comparison with FIG. The liquid crystal display device 31 of this embodiment is configured in the same manner as the liquid crystal display device 1 of the first embodiment, except that a backlight device 32 is disposed instead of the backlight device 2. The backlight device 32 is configured in the same manner as the backlight device 2 except that the reflective polarizing plate 16 is integrated and arranged in addition to the prism sheet 14 and the quarter-wave plate 15.

  Here, in integrating the prism sheet 14, the quarter-wave plate 15, and the reflective polarizing plate 16, the prism sheet 14 and the quarter-wave plate 15 are first formed in the same manner as described above for the first embodiment. After the integration, the reflective polarizing plate 16 may be integrated with an adhesive such as an ultraviolet curable resin, and the quarter wavelength plate 15 and the reflective polarizing plate 16 are the same as described above for the second embodiment. Then, the prism sheet 14 may be integrated with an adhesive such as an ultraviolet curable resin.

  According to this embodiment, after the reflection type polarizing plate is further integrated, the loss due to the air interface can be further reduced, and the light emitted from the light guide plate can be provided to the liquid crystal display panel more efficiently. .

[Fourth Embodiment]
FIG. 8 is a diagram showing a liquid crystal display device according to a fourth embodiment of the present invention in comparison with FIG. The liquid crystal display device 41 of this embodiment is configured in the same manner as the liquid crystal display device 1 of the first embodiment, except that a backlight device 42 is disposed instead of the backlight device 2. The backlight device 42 is configured in the same manner as the backlight device 2 except that a quarter-wave plate 45 is disposed separately from the prism sheet 14 on the light guide plate 12 side of the prism sheet 14.

  Here, the quarter-wave plate 45 is configured by forming an alignment film on a transparent film material, and then forming a retardation layer. By setting the thickness of the retardation layer, the quarter-wave plate 45 has a directivity inclined obliquely. 12 is configured to give a phase difference of ¼ wavelength to the light emitted from the light guide plate 12 emitted from the light guide 12.

  Thereby, in this embodiment, the polarization component reflected by the reflective polarizing plate is converted into circularly polarized light after passing through the prism sheet. Even if the polarization component reflected by the reflective polarizing plate is converted to circularly polarized light after passing through the prism sheet as in this embodiment, the same effect as in the first embodiment can be obtained.

[Fifth Embodiment]
FIG. 9 is a diagram showing a liquid crystal display device according to a fifth embodiment of the present invention in comparison with FIG. The liquid crystal display device 51 of this embodiment is configured in the same manner as the liquid crystal display device 1 of the first embodiment, except that a backlight device 52 is disposed instead of the backlight device 2. The backlight device 52 is configured in the same manner as the backlight device 2 except that the quarter wavelength plate 50 is disposed integrally with the reflection sheet 13 on the light guide plate 12 side of the reflection sheet 13.

  Here, the quarter-wave plate 50 is configured by forming an alignment film on a transparent film material, and then preparing a retardation layer, and by setting the thickness of the retardation layer, the light guide plate has a diagonally inclined directivity. 12 is configured to give a phase difference of ¼ wavelength to the outgoing light emitted to the reflection sheet side.

  Thereby, in this embodiment, the polarization component reflected by the reflective polarizing plate is converted into circularly polarized light after passing through the prism sheet and the light guide plate. Even if the polarization component reflected by the reflective polarizing plate is converted to circularly polarized light after passing through the light guide plate as in this embodiment, the same effect as in the first embodiment can be obtained.

[Sixth Embodiment]
In this embodiment, in the first to fourth embodiments described above, a + C plate is disposed on the light guide plate side of the quarter wavelength plate, and viewing angle characteristics are improved by this + C plate. Here, the + C plate may be provided integrally with the quarter wavelength plate, or may be provided integrally with another member on the light guide plate side.

  Even when a + C plate is further provided as in this embodiment, the same effect as in the above-described embodiment can be obtained.

Other Embodiment
The specific configuration suitable for the implementation of the present invention has been described in detail above, but the present invention can be variously modified and further combined with the configuration of the above-described embodiment without departing from the spirit of the present invention. it can.

  That is, in the above-described first embodiment, the case where the prism sheet and the quarter-wave plate are integrated has been described. However, the present invention is not limited to this, and when a practically sufficient characteristic can be secured, a separate body Alternatively, the reflective polarizing plate and the quarter wavelength plate may be integrated.

1, 21, 31, 41 Liquid crystal display device 2, 22, 32, 42 Backlight device 3 Liquid crystal display panel 4A, 4B Glass plate 5 Liquid crystal 6 Liquid crystal cell 7A, 7B Linear polarizing plate 11 Primary light source 12 Light guide plate 13 Reflective sheet 14 Prism sheet 15, 45 1/4 wavelength plate 16 Reflective polarizing plate

Claims (12)

In the backlight device for supplying the liquid crystal display panel via the reflective polarizing plate after correcting the directivity of the outgoing light from the outgoing surface of the light guide plate by the prism sheet having a downward convex shape,
Between the prism sheet and the reflective polarizing plate, between the prism sheet and the light guide plate, or between the light guide plate and the reflective sheet disposed on the surface opposite to the prism sheet of the light guide plate, A backlight device provided with a quarter-wave plate. The prism sheet is
The backlight device according to claim 1, wherein the retardation value Re of the substrate is 20 nm or less. The backlight device according to claim 1, wherein the prism sheet and the quarter-wave plate are integrated. The backlight device according to claim 1, wherein the quarter-wave plate and the reflective polarizing plate are integrated. The backlight device according to claim 1, wherein the prism sheet, the quarter-wave plate, and the reflective polarizing plate are integrated. The quarter wave plate and the reflection sheet were integrated.
The backlight device according to claim 1 or 2. A liquid crystal display device in which a liquid crystal display panel is laminated on the backlight device according to claim 1, claim 2, claim 3, claim 4, claim 5, or claim 6. A laminated body in which a quarter-wave plate is integrally provided on the other surface of a prism sheet formed by repeatedly forming protrusions on one surface of a transparent substrate. A laminated body in which a quarter-wave plate is integrally provided on a reflective polarizing plate. A laminate in which an 11/4 wavelength plate and a reflective polarizing plate are sequentially and integrally provided on the other surface of a prism sheet formed by repeatedly producing protrusions on one surface of a transparent substrate. A laminated body in which a quarter wave plate is integrally provided on a reflection sheet. The prism sheet is
The laminate according to claim 8 or 10, wherein the substrate has a retardation value Re of 20 nm or less.

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