Patent Application
20240385477
The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2023-080818 filed on May 16, 2023, the contents of which are incorporated herein by reference in their entirety.
The present disclosure relates to display devices and optical films.
Conventional display devices typically display desired images on their display screen when lighted while making their display screen appear black when unlighted. Considerations have been made to improve the designability of such display devices by making the display screen, when unlighted, harmonizable with the surrounding components and the enclosure, for example, and thereby making the display screen less noticeable.
The display screen is made less noticeable when unlighted by, for example, placing on a front surface side of the display panel a semi-transparent component transmitting part of light, such as a screen or a decorative film (e.g., JP 2001-331132 A, JP 6696014 B).
JP 2001-331132 A discloses a display device including a display fitted in an attached portion and emitting a display light to an outside during lighting; a screen covering a front face of the display having a large number of minute holes capable of transmitting the display light, wherein a surface of the screen has the same color and pattern as those of the attached portion on a periphery of the display.
JP 6696014 B discloses a display device with a decorative sheet including: a display device having a display surface; and a decorative sheet that is provided to face the display surface. The decorative sheet includes a picture pattern portion and a plurality of transmitting portions that are portions in which the picture pattern portion is not formed, wherein an aperture ratio is 5% or more and 50% or less, and each of the transmitting portions is formed such that a distance between the transmitting portions adjacent to each other is 40 μm or more and 140 μm or less. The display device is a dot matrix liquid crystal display, and a pitch of each of the transmitting portions is larger than a pitch of a pixel on the display surface.
When a display device is unlighted, a semi-transparent component placed on the viewer side of the display panel reflects part of ambient light so that the viewer sees the color and pattern of the semi-transparent component. The studies made by the present inventors found that when an air layer is present between the semi-transparent component and the display panel, part of ambient light transmitted through the semi-transparent component undergoes interface reflection in the interfaces with the air. Since interface reflection causes incident light to be reflected with almost no change in color, the color of the interface-reflected light includes the complementary color of the color of the semi-transparent component and the complementary color of the pattern of the semi-transparent component. Thus, when light reflected by the semi-transparent component and the interface-reflected light are mixed, the semi-transparent component sometimes appears not in a vivid color but whitish.
In a conventional technique disclosed in JP 2001-331132 A, for example, the smoke plate 23 is placed in the back surface side of the screen 20 (see
The studies made by the present inventors also revealed that the whitish appearance during reflective display does not matter when a semi-transparent component having a silverish reflective surface is used which almost uniformly reflects light with any wavelength falling in the visible spectrum, whereas the whitish appearance matters when a colored semi-transparent component is used which reflects light with a specific wavelength. A display device or an optical film including a colored semi-transparent component thus leaves room for improvement to provide both vivid reflective display and high-luminance transmissive display.
In response to the above issues, an object of the present invention is to provide a display device and an optical film which are capable of providing vivid reflective display without a decrease in luminance.
The present invention can provide a display device and an optical film that are capable of providing vivid reflective display without a decrease in luminance.
Hereinafter, the present invention is described in more detail based on embodiments with reference to the drawings. The present invention is not limited to the following embodiments. In the following description, components having the same or similar functions in different drawings are commonly provided with the same reference sign so as to appropriately avoid repetition of description. The structures in the present invention may be combined as appropriate without departing from the gist of the present invention.
Herein, the expression that two directions are orthogonal to each other means that the angle formed between the two directions falls preferably within the range of 90°±3°, more preferably within the range of 90°±1°, still more preferably within the range of 90° 0.5°. The expression that two directions are parallel to each other means that the angle formed between the two directions falls preferably within the range of 0°±3°, more preferably within the range of 0°±1°, still more preferably within the range of 0°±0.5°.
Herein, the “viewer side” means the surface to be observed by the viewer and is also referred to as the “front surface side”. The “back surface side” means the surface opposite to the viewer side.
One embodiment of the present invention is directed to a display device including: an optical film; and a display panel placed closer to a back surface side than the optical film is, the optical film including a colored semi-transparent component and a first linear polarizer or louver film being placed closer to the back surface side than the colored semi-transparent component is and being integrated with the colored semi-transparent component, the louver film including a light absorptive part and a light transmissive part arranged in a pattern, the semi-transparent component being configured to transmit part of light incident from the back surface side and reflect part of light incident from a viewer side opposite to the back surface side.
A smoke layer is placed closer to the back surface side than an optical film is in a conventional device in order to reduce or prevent interface reflection. A smoke layer is, for example, a layer with a low transmittance formed on a surface of a transparent substrate by a technique such as solid printing. An example thereof is a smoke layer with a transmittance of 50% or lower. A typical smoke layer absorbs part of incident light and has a constant absorptivity independent of the polarization state of the incident light and the angle of incidence of the incident light. The present embodiment can provide vivid reflective display by employing, instead of the smoke layer, the first linear polarizer placed closer to the back surface side than the colored semi-transparent component is. In the display device according to the present embodiment, preferably, the optical film 110A includes no smoke layer in its region overlapping the display region of a display panel 100.
In the display device according to the present embodiment, the display panel 100 preferably includes a second linear polarizer 51 placed closer to the viewer side, and the transmission axis of the first linear polarizer 112 and the transmission axis of the second linear polarizer 51 are preferably parallel to each other. With this configuration, the display device can more favorably provide bright transmissive display without a decrease in luminance.
The present embodiment can effectively provide vivid reflective display when, as shown in
As shown in
The semi-transparent component is a component that transmits part of light incident from the back surface side and reflects part of light incident from the front surface side (viewer side) opposite to the back surface side. Also, the semi-transparent component is a colored semi-transparent component. The term “colored” means being chromatic colored and excludes achromatic colors such as white and black as well as silver. The “chromatic color” herein refers to a color with different transmittance values for lights in the visible range (400 to 700 nm), such as a color with transmittance values that differ by 30% or more in the range of 400 to 700 nm.
As described above, when being a colored semi-transparent component which is not of an achromatic color or silver, the semi-transparent component is susceptible to influence of interface reflection between the optical film and the display panel. Thus, when the configuration of the present embodiment is applied to a display device including a colored semi-transparent component, whitish appearance during reflective display can be effectively reduced or prevented, so that vivid reflective display can be achieved. The whitish appearance means appearing more in an achromatic color.
The transmittance of the semi-transparent component for light incident from the back surface side may be 50% or higher. When the transmittance of the semi-transparent component is lower than 50%, the luminance of the display device may decrease to make the display image difficult to see in a bright environment. The transmittance of the semi-transparent component is more preferably 70% or higher. The upper limit of the transmittance of the semi-transparent component is, for example, 90%. The transmittance of the semi-transparent component will suffice as long as it is 50% or higher in the region overlapping the display region of the display panel 100.
Herein, the transmittance refers to the total light transmittance and is measured by a method in conformity with JIS K 7361-1. The total light transmittance can be measured, for example, with a device such as a haze meter NDH2000 available form Nippon Denshoku Industries Co., Ltd.
The reflectance of the semi-transparent component for light incident from the viewer side falls within the range of about 3% to about 50%. A reflectance of lower than 3% is ineffective because it causes the color and the pattern to be almost unperceivable. A reflectance of 50% or higher means that the transmittance is lower than 50%, which is not preferred since the displayed image is difficult to see in a bright environment in some cases. The transmittance means the visible light transmittance, and the reflectance means the visible light reflectance.
The semi-transparent component in a plan view may be placed on the entire optical film or may be placed on part of the optical film such that a specific pattern or the like can be expressed. Non-limiting examples of the specific pattern include geometric patterns with designability, wood grain patterns, specific character strings, and company logos. During reflective display, the specific pattern is perceived by the viewer. At least part of the semi-transparent component is chromatic colored, and the semi-transparent component may entirely be colored or may partly include a region of an achromatic color.
Examples of the semi-transparent component include metal thin films, dielectric multilayer films, films containing a pigment that reflects light, and printed layers printed with a pigment that reflects light.
Examples of the metal thin films include those formed using a metal such as aluminum, silver, titanium, or tungsten by metal deposition or sputtering, for example. Most common metal thin films are of an achromatic color, and can be colored by being laminated with a color pigment layer. Examples of such a metal thin film on which a color pigment layer is adsorbed include color anodized aluminum sheets. The thickness of the metal thin film is, for example, from 30 nm to 100 nm. Color anodizing includes, for example, electrolytically treating the surface of aluminum to form an oxide coating and coloring the oxide coating through impregnation with a colorant.
Specifically, a method may be used including forming an aluminum thin film, for example, to a thickness of 100 nm in the “SHARP” letter portion shown in
The films containing a pigment that reflects light (hereinafter, also referred to as a reflective pigment) may be, for example, films obtained by kneading a reflective pigment into a binder resin. The printed layers printed with a reflective pigment may be obtained by, for example, printing on the surface of the transparent base 113 by a printing method such as gravure printing, screen printing, or inkjet printing. When the letters “SHARP” shown in
The reflective pigment is a pigment that reflects ambient light with specific wavelengths to the viewer side and that causes the viewer to perceive the specific colors corresponding to the wavelengths of light to be reflected. The specific wavelengths are those of light in the visible spectrum (380 nm to 780 nm). The semi-transparent component may contain reflective pigments of multiple colors to cause the viewer to perceive the desired color through additive color mixing of lights reflected by the reflective pigments of multiple colors. When printing is performed with a reflective pigment(s), the resulting printed layer can transmit at least part of light incident from the display panel without the micropores formed in its printing base as in JP 2001-331132 A and JP 6696014 B since there are gaps between the particles of the pigment.
Examples of the reflective pigment include metallic pigments. The metallic pigments may reflect light having specific wavelengths and absorb light having wavelengths other than the specific wavelengths. Examples of the metallic pigments include metallic strips coated with a pigment, and the pigment may be coated with a polymer such as an acrylic resin. Examples of the metallic pigments include “FRIEND COLOR®” available from Toyo Aluminium K.K. Pearl pigments using optical interference can also be used. Representative examples thereof include “Effect pigment” available from Merck KGaA.
The metallic strips are preferably those that reflect visible light, and examples include aluminum, nickel, titanium, stainless steel, and alloys of any of these metals.
The pigment used to coat the metallic strips may be an organic pigment or an inorganic pigment, but is preferably an organic pigment. Examples of the organic pigment include phthalocyanine, halogenated phthalocyanine, quinacridone, diketopyrrolopyrrole, isoindolinone, azomethine metal complexes, indanthrone, perylene, perynone, anthraquinone, dioxazine, benzoimidazolone, condensed azo, triphenylmethane, quinophthalone, and anthrapyrimidine. Examples of the inorganic pigment include titanium oxide, iron oxide, carbon black, and bismuth vanadate.
Other modes of the semi-transparent component include those obtained by, as described in JP 2001-331132 A and JP 6696014 B, forming a specific pattern on a screen with multiple micropores or a decorative film with transmissive parts.
The first linear polarizer 112 is a linear polarizer that converts incident light to linearly polarized light and is a component that changes the polarization state and/or direction of incident light. The first linear polarizer 112, which can more effectively reduce or prevent interface reflection, is preferably an absorptive linear polarizer that absorbs light polarized in a specific direction and transmits light vibrating in a direction orthogonal to the specific direction.
The first linear polarizer may be a linear polarizer that includes a polarizing film including dichroic molecules and a pair of protective films between which the polarizing film including dichroic molecules is held. Examples of the first linear polarizer include “TEG1465DU” available from Nitto Denko Corporation.
Examples of the polarizing film including dichroic molecules include polyvinyl alcohol (PVA)-based films on which dyeing treatment with iodine and stretching treatment (e.g., uniaxial stretching) have been performed.
The protective films can be those usually used in the field of linear polarizers. Examples thereof include cellulose-based resin films such as triacetyl cellulose (TAC)-based resin films, polyester-based resin films, polyvinyl alcohol-based resin films, polycarbonate-based resin films, polyamide-based resin films, polyimide-based resin films, polyethersulfone-based resin films, polysulfone-based resin films, polystyrene-based resin films, polynorbornene-based resin films, polyolefin-based resin films, (meth)acrylic resin films, and acetate-based resin films. The protective films are preferably transparent films with, for example, a transmittance of 90% or higher.
The first linear polarizer is a coating-type polarizing layer including dichroic molecules. The coating-type polarizing layer including dichroic molecules may be formed on the semi-transparent component. Examples of the coating-type polarizing layer including dichroic molecules include those obtained by coating with a composition including a lyotropic liquid crystalline compound and dichroic dye molecules. Examples of the dichroic dye molecules include dichroic dye molecules having an azo group. The coating-type polarizing layer may be one disclosed in any of JP 2010-250025 A, JP 4622434 B, JP 2568882 B, and JP 3492693 B.
When the first linear polarizer is a polarizer including the polarizing film held between the protective films, the optical film 110A may warp depending on the pressure from attaching the first linear polarizer to the transparent base 113 and the difference in coefficient of linear expansion between the transparent base 113 and the protective films. Use of a coating-type polarizing layer as the first linear polarizer can reduce or prevent warpage of the optical film 110A.
The coating-type polarizing layer including the dichroic molecules may be directly applied to the surface of the semi-transparent component. In this case, the coating-type polarizing layer including dichroic molecules and the semi-transparent component are in contact with each other. Also, an alignment film may be formed on the surface of the semi-transparent component and a coating-type polarizing layer may be formed on the surface of the alignment film. The alignment film can be one usually used in the field of liquid crystal panels.
As shown in
The transparent base 113 is suitably a component that transmits light, and may be used as a base of the semi-transparent component 111. The transparent base 113 preferably has a high transmittance in order to maintain the luminance of the display device high. For example, the transmittance is preferably 90% or higher. To reduce or prevent blurriness of the displayed image, the transparent base 113 preferably has a haze of 10% or lower. The haze can be measured by a method in conformity with JIS K 7136, for example, with a device such as a turbidity meter “Haze Meter NDH2000” available form Nippon Denshoku Industries Co., Ltd.
The transparent base 113 can be, for example, a glass plate or a resin plate such as an acrylic plate or a polycarbonate plate. The transparent base 113 may have a flat surface or a curved surface.
When being placed closer to the viewer side than the semi-transparent component 111 is as shown in
The hard coat layer is preferably one with high transparency and high scratch resistance. Examples include coating layers such as acrylic resin layers and epoxy resin layers. The transmittance of the hard coat layer is preferably 90% or higher, for example.
As shown in
The display panel 100 preferably includes the second linear polarizer 51 placed closer to the viewer side. The second linear polarizer 51 can be a linear polarizer similar to the first linear polarizer 112. The second linear polarizer 51 may be a linear polarizer that includes a polarizing film including dichroic molecules and a pair of protective films between which the polarizing film including dichroic molecules is held.
The display panel 100 may be any display panel that provides transmissive display by emitting display light to the viewer side, and may be a liquid crystal panel or a self-luminous panel such as a light emitting diode (LED) panel including LEDs.
The following shows a case where the display panel 100 is a liquid crystal panel. As shown in
The third linear polarizer 52 can be a linear polarizer similar to the first linear polarizer 112. The second and third linear polarizers 51 and 52 can be known polarizers such as “TEG1465DU” available from Nitto Denko Corporation.
Although not shown, the second linear polarizer 51 may be attached by a transparent adhesive to the surface of the TFT substrate 10 opposite to the liquid crystal layer 30, and the third linear polarizer 52 may be attached by a transparent adhesive to the surface of the CF substrate 20 opposite to the liquid crystal layer 30.
Examples of the liquid crystal panel include those including a first substrate, a second substrate, and a liquid crystal layer held between the first and second substrates. The first substrate may be the TFT substrate 10 including switching elements such as thin film transistors (TFTs), and the second substrate may be a color filter (CF) substrate 20 including color filters. The TFT substrate 10 and the CF substrate 20 are attached to each other by a sealant 40 and the liquid crystal layer 30 is sealed between the substrates.
Although not shown, an example of the configuration of the TFT substrate 10 is one including, on a supporting substrate, gate lines and source lines crossing the gate lines, TFTs placed at or near the intersections of the gate lines and the source lines, and pixel electrodes electrically connected to the TFTs. Each region surrounded by gate lines and source lines is a pixel.
The pixel electrodes and the later-described counter electrode may be transparent electrodes, and can be made of, for example, a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or tin oxide (SnO), or an alloy of any of these materials.
The color filter substrate 20, for example, may include on a supporting substrate 21 a color filter layer 22 and a black matrix 23. The color filter layer 22 may include red, green, and blue color filters. Each color filter overlaps a pixel of the TFT substrate. The desired color can be expressed by mixing colors while controlling the amounts of lights transmitted through the color filters of different colors.
The black matrix 23 in a plan view may be placed to partition the color filters. The color filters and the black matrix are not limited and may each be one known in the field of liquid crystal panels.
The supporting substrates used in the TFT substrate 10 and the CF substrate 20 are preferably transparent substrates, such as glass substrates or plastic substrates.
The display mode of the liquid crystal panel may be the vertical electric field mode or the transverse electric field mode. Examples of the vertical electric field mode include the vertical alignment (VA) mode where with no voltage applied, the liquid crystal molecules in the liquid crystal layer are aligned substantially perpendicularly to the substrate surfaces. Examples of the transverse electric field mode include the fringe field switching (FFS) mode and the in-plane-switching (IPS) mode where with no voltage applied, the liquid crystal molecules in the liquid crystal layer are aligned substantially horizontally to the substrate surfaces. The state with no voltage applied incudes cases where voltage lower than the threshold for the liquid crystal molecules is applied to the liquid crystal layer.
The expression “substantially horizontally” means that the tilt angle is 0° or greater and 10° or smaller, preferably 0° or greater and 5° or smaller, more preferably 0° or greater and 2° or smaller. The expression “substantially perpendicularly” means that the tilt angle is 830 or greater and 90° or smaller, preferably 850 or greater and 90° or smaller, more preferably 87.5° or greater and 88.0° or smaller.
The liquid crystal layer 30 controls the amount of light transmitted therethrough using its liquid crystal molecules whose alignment changes according to the electric field generated inside the liquid crystal layer 30 in response to the voltage applied between the pixel electrode and the counter electrode. In the vertical electric field mode, the counter electrode is placed in the TFT substrate while in the transverse electric field mode, the counter electrode is placed in the CF substrate.
The anisotropy of dielectric constant (Δε), defined by the following formula (L), of the liquid crystal molecules may be positive or negative.
Δε=(dielectric constant in long axis direction)−(dielectric constant in short axis direction) (L)
Although not shown, alignment films controlling the alignment azimuth of the liquid crystal molecules with no voltage applied may be placed, one between the TFT substrate 10 and the liquid crystal layer 30 and one between the CF substrate 20 and the liquid crystal layer 30. The alignment film can be made of a material commonly used in the field of liquid crystal panels, such as a polymer having a polyimide, polyamic acid, or polysiloxane main chain structure.
The display device according to Embodiment 1 may further include a backlight 200 closer to the back surface side than the display panel 100 is. The backlight 200 can be a known one and may be, for example, an edge-lit backlight including light sources on the end surfaces of a light guide plate or a direct-lit backlight including light sources on its surface and increasing the uniformity of light using a diffuser, for example.
The display device according to Embodiment 1 may further include an enclosure 300 that houses the display panel 100 and the optical film 110A. Double-sided tape 301 may be placed on the back surface side surface of the optical film 110A overlapping the frame region to fix the optical film 110A to the enclosure 300. The enclosure 300 may include inside, for example, a circuit substrate (not shown) on which drive circuits that drive the display panel 100 and the backlight 200 are formed. The enclosure 300 may be any enclosure that can house the display panel 100 and the optical film 110A and may be made of a metal or resin. The shape of the enclosure 300 is not limited to the shape shown in
The following shows the display method of the display device according to Embodiment 1 with reference to
In
The display device 1-A according to Embodiment 1 can provide reflective display and transmissive display. Herein, reflective display means a display method that uses reflection of light (ambient light) incident on the display device from the viewer side to cause the viewer to perceive the color and pattern of the colored semi-transparent component. Herein, transmissive display means a display method that causes light (display light) emitted from the display panel side to be transmitted through the front plate to the viewer side, thus causing the viewer to perceive an image or the like displayed on the display panel.
As shown in
Next, reflective display is described. As shown in
The transmittance of the semi-transparent component 111 varies depending on the pattern formed on the semi-transparent component 111, but is about 60% to about 80%, for example. The transmittance of the semi-transparent component 111 can be measured, for example, with spectrophotometer CM-5 available from Konica Minolta Japan, Inc.
As described above, the display device 1-A includes no smoke layer and includes the first linear polarizer 112 being placed closer to the back surface side than the semi-transparent component 111 is and being integrated with the semi-transparent component 111. When the transmission axis of the first linear polarizer 112 and the transmission axis of the second linear polarizer 51 in the display panel 100 are parallel to each other, a high luminance can be achieved more effectively during transmissive display. Also, about 50% of interface-reflected light from ambient light reflected in the interface between the optical film 110A and the air layer is absorbed by the first linear polarizer 112. In this manner, the display device 1-A can achieve both bright transmissive display and vivid reflective display.
Hereinafter, the display method of a display device 1001 according to Comparative Embodiment 1 is described with reference to
As shown in
Next, reflective display is described. Light L5 reflected by the semi-transparent component 111 is similar to that in the case of the display device 1-A, and description thereof is thus omitted. Description of light L6, which results from absorption of ambient light L4 by the internal components of the display panel 100, is also omitted. As shown in
The following Table 1 shows the luminance during transmissive display and the proportion of light emitted toward the viewer to the interface-reflected light, measured on the display device 1-A according to Embodiment 1 and the display device 1001 according to Comparative Embodiment 1.
As shown in Table 1, during transmissive display, the display device 1001 according to Comparative Embodiment 1 with the optical film including no polarizer can achieve brightness equivalent to that achieved by the display device 1-A according to Embodiment 1. During reflective display, however, the display device 1001 according to Comparative Embodiment 1, which has a higher proportion of light emitted toward the viewer to the interface-reflected light than the display device 1-A, causes the color and pattern of the semi-transparent component 111 to appear whitish, not vivid.
Hereinafter, the display method of a display device 1002 according to Comparative Embodiment 2 is described with reference to
The smoke layer 400 can be formed by coating the back surface side surface of the front surface plate with a resin composition obtained by mixing a transparent resin with a black pigment, for example. The transmittance B of the smoke layer 400 can be adjusted by changing the amount of the black pigment added, and is 70% or lower, for example.
As shown in
Next, reflective display is described. Light L5 reflected by the semi-transparent component 111 is similar to that in the case of the display device 1-A, and description thereof is thus omitted. Description of light L6, which results from absorption of ambient light L4 by the internal components of the display panel 100, is also omitted. As shown in
The following Table 2 shows the luminance during transmissive display and the proportion of light emitted toward the viewer to the interface-reflected light, measured on the display device 1-A according to Embodiment 1, the display device 1001 according to Comparative Embodiment 1, and the display device 1002 according to Comparative Embodiment 2.
As shown in Table 2, during transmissive display, the display device 1002 according to Comparative Embodiment 2 with the optical film including the smoke layer instead of the polarizer has a lower luminance than the display device 1-A. During reflective display, however, the display device 1002 according to Comparative Embodiment 2 has a lower proportion of light emitted toward the viewer to the interface-reflected light than the display device 1001 according to Comparative Embodiment 1, and thus achieves more vivid reflective display than the display device 1001 according to Comparative Embodiment 1.
The first λ/4 waveplate may be any waveplate that provides a phase difference of a quarter of a wavelength to incident light having a wavelength A. The first λ/4 waveplate, for example, is a phase difference plate that provides an in-plane phase difference of a quarter of a wavelength (precisely, 137.5 nm), preferably an in-plane phase difference of 120 nm or more and 150 nm or less, to light with a wavelength of 550 nm.
The first λ/4 waveplate may have a fast axis and a slow axis orthogonal to the fast axis. The transmission axis of the first linear polarizer and the slow axis of the first λ/4 waveplate may form an angle of substantially 45°. Herein, an angle of substantially 45° is an angle falling preferably within the range of 45°±3°, more preferably within the range of 45°±1°, still more preferably within the range of 45°±0.5°.
Hereinbelow, the display method of the display device 1-B according to Embodiment 2 is described with reference to
As shown in
Next, reflective display is described. Light L5 reflected by the semi-transparent component 111 is similar to that in the case of the display device 1-A, and description thereof is thus omitted. Description of light L6, which results from absorption of ambient light L4 by the internal components of the display panel 100, is also omitted. As shown in
The following Table 3 shows the luminance during transmissive display and the proportion of light emitted toward the viewer to the interface-reflected light, measured on the display device 1-A according to Embodiment 1 and the display device 1-B.
As shown in Table 3, the display device 1-B, with the optical film further including the λ/4 waveplate closer to the back surface side than the first linear polarizer is, has a lower luminance during transmissive display than the display device 1-A is. Still, since the interface-reflected light during reflective display is not emitted toward the viewer, the display device 1-B can provide very vivid reflective display.
Hereinbelow, the display method of the display device 1-C according to Embodiment 3 is described with reference to
As shown in
Next, reflective display is described. Light L5 reflected by the semi-transparent component 111 is similar to that in the case of the display device 1-A, and description thereof is thus omitted. Description of light L6, which results from absorption of ambient light L4 by the internal components of the display panel 100, is also omitted. As shown in
The following Table 4 shows the luminance during transmissive display and the proportion of light emitted toward the viewer to the interface-reflected light, measured on the display device 1-A according to Embodiment 1 and the display device 1-C according to Embodiment 3.
As shown in Table 4, the display device 1-C with the optical film further including the λ/4 waveplate placed closer to the back surface side than the first linear polarizer is and with the display panel including the λ/4 waveplate placed closer to the viewer side can provide very vivid reflective display since the luminance during transmissive display is as high as that of the display device 1-A and the interface-reflected light is not emitted toward the viewer during reflective display.
When the circular polarizer (combination of the first linear polarizer 112 and the first λ/4 waveplate 114) is placed closer to the viewer side than the display panel is, the transmittance can be suitably modulated. Thus, when the display panel is a liquid crystal panel, the display mode is more preferably a vertical electric field mode such as the VA mode than a transverse electric field mode such as the IPS mode.
When the circular polarizer (combination of the first linear polarizer 112 and the first λ/4 waveplate 114) is placed closer to the viewer side than the display panel is, the internal reflectance of the display panel can be reduced. Thus, when the display panel is a self-luminous panel such as an OLED panel which has a higher internal reflectance than a liquid crystal panel, vivid reflective display can be more effectively provided. The present embodiment is suitable particularly for cases where a self-luminous panel is used in a bright environment such as an outdoor environment.
The self-luminous panel is a panel that includes a light emitting element inside and can emit light by itself, thus being capable of emitting light toward the viewer without any external light source such as a backlight. The self-luminous panel can be a known one, such as an organic light emitting diode (OLED) panel including OLEDs.
The configuration of the light emitting diode is not limited, and may be, for example, a stack of a cathode, a light emitting layer, and an anode arranged in the stated order. When the light emitting element is an OLED, the light emitting layer may include a fluorescent material, a phosphorescent material, or another material as the light emitting material. An electron transport layer may be placed between the cathode and the light emitting layer. A hole transport layer may be placed between the light emitting layer and the anode.
Light emitting elements such as OLEDs may be arranged, for example, in a matrix pattern in the TFT substrate. In this case, light emitting elements may be placed for the respective TFTs arranged at or near the intersections of the gate lines and the source lines (in the respective pixels). The region in which the light emitting elements are placed defines the display region. The light emitting elements may include red light emitting elements, green light emitting elements, and blue light emitting elements.
Examples of the antireflective layer include resin layers including a low-refractive index material and moth-eye films. The moth-eye films are films that can reduce or prevent reflection by continuously changing the incident light reflectance. Examples thereof include those having nanoscale fine irregularities on the surface of a film such as a transparent film regularly at intervals shorter than the wavelength of visible light. The antireflective layer can be, for example, MOSMITE available from Mitsubishi Chemical Corporation.
The display device can provide transmissive display as long as at least the second linear polarizer 51 in a plan view overlaps the display region of the display panel 100. The frame region, having no involvement in transmissive display, may therefore include regions not overlapping the second linear polarizer 51 in a plan view. The regions included in the frame region and not overlapping the second linear polarizer 51 may be seen through during reflective display or may reflect ambient light to cause stray light. Placing the light blocking components 302 in these regions overlapping the frame region in a plan view can reduce or prevent occurrence of the see-through regions and occurrence of stray light to make reflective display vivid. The light blocking components 302 are preferably not placed in any region overlapping the display region in a plan view.
The light blocking components 302 may be made of the same material as the black matrix 23, and may be formed using a material such as a black pigment by printing such as screen printing. Black tape may also be used.
When the first linear polarizer is a polarizer in which a polarizing film is held between protective films, the optical film 110D may warp depending on the pressure applied to attach the first linear polarizer 112 to the transparent base 113 and/or the difference in coefficient of linear expansion between the transparent base 113 and the protective films 112b. In Embodiment 6, the transparent film 116 whose coefficient of linear expansion is of the same level as that of the protective films 112b is attached to the viewer side surface of the optical film 110D, so that warpage of the optical film 110D can be reduced or prevented.
In the display device 1-F, the difference in coefficient of linear expansion between the transparent film 116 and one of the protective films 112b is 30×10−6/K or less. This configuration can effectively reduce or prevent warpage of the optical film 110D. The difference in coefficient of linear expansion between the transparent film 116 and one of the protective films 112b is more preferably 50×10−6/K or less.
The polarizing film 112a including dichroic molecules and the protective films 112b may be ones similar to those used in Embodiment 1.
Examples of the transparent film 116 include those mentioned as examples of the protective films, including cellulose-based resin films such as triacetyl cellulose (TAC)-based resin films, polyester-based resin films, polyvinyl alcohol-based resin films, polycarbonate-based resin films, polyamide-based resin films, polyimide-based resin films, polyethersulfone-based resin films, polysulfone-based resin films, polystyrene-based resin films, polynorbornene-based resin films, polyolefin-based resin films, (meth)acrylic resin films, acetate-based resin films, and polyethylene terephthalate (PET) films. The transparent film 116 preferably has a transmittance of 90% or higher.
In Embodiment 6, the transparent film 116 is one having a difference in coefficient of linear expansion from the protective films 112b of 30×10−6/K or less, and may be a film made of the same material as or a different material from that of the protective films 112b. For example, when the protective films 112b are TAC films, the transparent film 116 may be a TAC film or a different film such as a polyethylene terephthalate (PET) film.
The thicknesses of the transparent film 116 and the protective films 112b may each be, for example, 50 μm to 200 μm. To reduce or prevent warpage of the optical film 110D, the thickness of the transparent film 116 and the thickness of each protective film 112b are preferably equal to each other, and the difference in thickness between the transparent film 116 and the protective films 112b is preferably 50 μm or less, for example.
When the transparent base 113 and each protective film 112b of the first linear polarizer 112 are attached to each other by an adhesive layer and the transparent base 113 and the transparent film 116 are attached to each other by another adhesive layer, for reduction or prevention of warpage of the optical film 110D, the thicknesses of the two adhesive layers are preferably equal to each other and may be from 5 μm to 50 μm, for example.
The louver film is a component that absorbs light incident thereon from a specific direction and is often used to prevent reflection of the screen on the windshield of a car. The louver film typically has a property of absorbing incident light from the top and bottom directions and transmitting light from the other directions. The louver film is often incorporated into a backlight, and the louver film in the present embodiment may be one used in the field of backlights. Use of a louver film instead of a first linear polarizer also enables provision of vivid reflective display. When the present embodiment is applied to a display device whose backlight originally includes a louver film, the luminance during transmissive display does not change. Since there is less need to strictly set the axes of the louver film than in the case of linear polarizers, the flexibility of design of the display device can be enhanced.
The louver film includes patterned light absorptive parts and light transmissive parts.
In a plan view, the light absorptive parts 117b may be parallel to one another. The intervals of the light absorptive parts 117b can be adjusted or the angle of the light absorptive parts 117b to the direction normal to the optical film can be adjusted to adjust the viewing angle characteristics.
The light transmissive parts 117a may be made of a transparent resin, such as a polystyrene-based resin, polyolefin-based resin, polyvinyl chloride-based resin, polyurethane-based resin, polyester-based resin, polyamide-based resin, urethane resin, fluororesin, or silicone resin.
The light absorptive parts 117b may be made of a resin containing a colorant. Examples of the colorant include common organic or inorganic pigments, such as carbon black, tin oxide, titanium oxide, yellow iron oxide, disazo yellow, and phthalocyanine blue. The resin used for the light absorptive parts 117b may be the same as the transparent resin used for the light transmissive parts 117a.
In Embodiment 8, the linear polarizer can be the first linear polarizer mentioned as an example in Embodiment 1, or may be a linear polarizer including a polarizing film including dichroic molecules or a coating-type polarizing layer including dichroic molecules. The louver film can be the one mentioned as an example in Embodiment 7.
The louver film typically controls the emission direction without changing the polarization state of incident light. Yet, the resin of the light transmissive parts, for example, may more or less introduce a phase difference, so that when a laminate of the first linear polarizer and the louver film is used, as shown in
Another embodiment of the present invention is directed to an optical film including a colored semi-transparent component and a first linear polarizer or louver film being placed closer to the back surface side than the semi-transparent component is and being integrated with the semi-transparent component, the lover film including light absorptive parts and light transmissive parts arranged in a pattern, the semi-transparent component being configured to transmit part of light incident from the back surface side and reflect part of light incident from the viewer side. The optical film can be used as a component of a display device. When the optical film is used as a component of a display device, the colored semi-transparent component may be placed closer to the viewer side than the first linear polarizer is and a display panel may be placed closer to the back surface side than the first linear polarizer is.
In the present embodiment, the optical film includes the first linear polarizer, not the smoke layer, being placed closer to the back surface side than the colored semi-transparent component is. Thus, when a display panel is placed to face the first linear polarizer side of the optical film, vivid reflective display and bright transmissive display can be achieved.
The optical film 110A, as shown in
The semi-transparent component is a component transmitting part of light incident from the back surface side and reflecting part of light incident from the viewer side opposite to the back surface side, and is a colored semi-transparent component. The semi-transparent component has a transmittance of preferably 50% or higher, more preferably 70% or higher, for light incident from the back surface side. The upper limit of the transmittance of the semi-transparent component is, for example, 90%.
Examples of the semi-transparent component include metal thin films, films containing a pigment that reflects light, and print layers printed with a pigment that reflects light.
The first linear polarizer 112 is preferably an absorptive linear polarizer. The first linear polarizer may be the linear polarizer described above including the polarizing film including dichroic molecules and a pair of protective films between which the polarizing film including dichroic molecules is held, or the coating-type polarizing layer including dichroic molecules. The coating-type polarizing layer including dichroic molecules may be formed on the semi-transparent component.
When the first linear polarizer 112 and the first λ/4 waveplate 114 are laminated, the laminate can function as a circular polarizer to convert incident light to circularly polarized light. Thus, when a display panel is placed to face the first linear polarizer side of the optical film, the interface-reflected light is not emitted toward the viewer during reflective display, so that very vivid reflective display can be provided.
The transmission axis of the first linear polarizer and the slow axis of the first λ/4 waveplate preferably form an angle of substantially 45°.
With the antireflective layer, the optical film can more effectively reduce or prevent emission of the interface-reflected light reflected in the air layer between the optical film and the display device toward the viewer when a display panel is placed to face the first linear polarizer side of the optical film.
In addition, the optical film 110D further includes the transparent film 116 on the surface opposite to the surface on which the first linear polarizer 112 is placed, and the difference in coefficient of linear expansion between the transparent film 116 and one of the protective films 112b is 30×10−6/K or less. When the transparent film 116 whose coefficient of linear expansion is of the same level as that of the protective films is attached to the viewer side surface of the optical film 110D, warpage of the optical film 110D can be reduced or prevented.
Use of the louver film instead of the first linear polarizer also enables provision of both bright transmissive display and vivid reflective display when a display panel is placed closer to the back surface side than the optical film is.
The louver film 117 may include in a plan view the light transmissive parts 117a alternately with the light absorptive parts 117b.
Use of the optical film 110F including the semi-transparent component 111, the louver film 117, and the first linear polarizer 112 in the stated order enables provision of both bright transmissive display and more vivid reflective display when a display panel is placed to face the first linear polarizer side of the optical film.
The linear polarizer may be one similar to the first linear polarizer mentioned as an example in Embodiment 1, and may be a linear polarizer including a polarizing film including dichroic molecules or a coating-type polarizing layer including dichroic molecules, for example.
The display devices and the optical films according to the embodiments, for example, may be used as an instrument panel of a vehicle to display instruments such as a speedometer, or may be used as a control panel of a home electrical appliance.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-080818 | May 2023 | JP | national |
