CN-115561939-B - Liquid crystal display device having a light shielding layer

Abstract

Provided is a liquid crystal display device which can be switched between a transparent state and a scattering state, can suppress a decrease in transmittance in the transparent state, and can suppress a decrease in luminance in the center portion of a panel in the scattering state. A liquid crystal display device includes, in order from an observation surface side toward a back surface side, a first liquid crystal panel including a polymer dispersed liquid crystal including a polymer network and a liquid crystal component, a light source for irradiating light from an oblique direction to a main surface of the back surface side of the first liquid crystal panel, and a second liquid crystal panel.

Inventors

• MURATA KOJI
• HASEBA YASUHIRO
• Hanawa Kazutaka
• NAKAMURA KIMIAKI
• HONDA MARIKO
• Kimi Mitsuko
• HASEGAWA TADASHI
• SHIMADA NOBUJI

Assignees

• 夏普显示科技株式会社

Dates

Publication Date

20260505

Application Date

20220701

Priority Date

20210702

Claims (14)

1. 1. A liquid crystal display device is characterized in that, The device is provided with: A first liquid crystal panel, a light source and a second liquid crystal panel, The first liquid crystal panel includes a polymer dispersed liquid crystal including a polymer network and a liquid crystal component, The light source irradiates light from an oblique direction to a main surface of the first liquid crystal panel on the back side, A back side light source is provided between the light source and the second liquid crystal panel, The back-side light source irradiates light from an oblique direction to a back-side main surface of the first liquid crystal panel.
2. 2. The liquid crystal display device according to claim 1, wherein, The first liquid crystal panel displays images in a field sequential color mode, The light source includes a plurality of light emitting elements that emit light of different colors from each other.
3. 3. The liquid crystal display device according to claim 1, wherein, The first liquid crystal panel further includes a thin film transistor.
4. 4. The liquid crystal display device according to claim 1, wherein, When the length of the long side of the first liquid crystal panel is 2a cm, The distance between the first liquid crystal panel and the second liquid crystal panel is a cm or less.
5. 5. The liquid crystal display device according to claim 1, wherein, When the length of the long side of the first liquid crystal panel is 2a [ cm ], the distance between the first liquid crystal panel and the light source is h11[ cm ], and the incident angle of light from the light source to the main surface on the back surface side of the first liquid crystal panel is θ11[ ° ], the following (formula 1-1) is satisfied: H11 is 1 or less and { a/(tan. Theta.11) }) is 1 to 1.
6. 6. The liquid crystal display device according to claim 1, wherein, The light source is a first light source and is provided corresponding to one end edge portion of a pair of end edge portions of the first liquid crystal panel which are opposite to each other, A second light source is provided between the first liquid crystal panel and the second liquid crystal panel, the second light source being provided in correspondence with the other end portion of the pair of end portions, The second light source irradiates light from an oblique direction to a main surface of the first liquid crystal panel on the back side, The incident angle of the light from the first light source to the main surface on the back surface side of the first liquid crystal panel is the same as the incident angle of the light from the second light source to the main surface on the back surface side of the first liquid crystal panel.
7. 7. The liquid crystal display device according to claim 1, wherein, The following (formula 1-1) and (formula 2-1) are satisfied when the length of the long side of the first liquid crystal panel is 2a [ cm ], the distance between the first liquid crystal panel and the light source is h11[ cm ], the incident angle of light from the light source to the main surface on the back side of the first liquid crystal panel is θ11[ ° ], and the incident angle of light from the back side light source to the main surface on the back side of the first liquid crystal panel is θ21[ ° ]. H11 is 1 or less and { a/(tan. Theta.11) } (1-1) Θ11- θ21>10 ° (formula 2-1).
8. 8. The liquid crystal display device according to claim 1, wherein, The back side light source is a first back side light source and is provided corresponding to one end edge portion of a pair of end edge portions of the first liquid crystal panel facing each other, A second back side light source is provided between the light source and the second liquid crystal panel, the second back side light source being provided in correspondence with the other end edge portion of the pair of end edge portions, The second back side light source irradiates light from an oblique direction to a main surface of the back side of the first liquid crystal panel, The incident angle of the light from the first back-side light source to the back-side main surface of the first liquid crystal panel is the same as the incident angle of the light from the second back-side light source to the back-side main surface of the first liquid crystal panel.
9. 9. The liquid crystal display device according to any one of claims 1 to 8, wherein, The first liquid crystal panel further includes a first support substrate disposed on the back surface side of the polymer dispersed liquid crystal, and a second support substrate disposed on the observation surface side of the polymer dispersed liquid crystal.
10. 10. The liquid crystal display device according to claim 9, wherein, The first liquid crystal panel further includes an alignment film disposed between at least one of the first support substrate and the polymer dispersed liquid crystal and between the second support substrate and the polymer dispersed liquid crystal, The alignment film is a horizontal alignment film in which the liquid crystal component is aligned parallel to the surface of the alignment film.
11. 11. The liquid crystal display device according to claim 10, wherein, The liquid crystal component has positive dielectric anisotropy.
12. 12. The liquid crystal display device according to claim 9, wherein, The first liquid crystal panel further includes a transparent resin plate provided on the back surface side of the first support substrate.
13. 13. The liquid crystal display device according to claim 9, wherein, The first liquid crystal panel further includes an anisotropic light diffusion film on at least one of a back surface side of the first support substrate and a viewing surface side of the second support substrate, and the anisotropic light diffusion film has a function of transmitting light when viewed from the front surface and scattering light when viewed obliquely.
14. 14. The liquid crystal display device according to any one of claims 1 to 8, 10 to 13, wherein, The second liquid crystal panel includes, in order from the back surface side toward the observation surface side, a third support substrate, a liquid crystal layer, a fourth support substrate, and an anisotropic light reflection film having a function of transmitting light when viewed from the front surface and reflecting light when viewed obliquely.

Description

Liquid crystal display device having a light shielding layer Technical Field The following disclosure relates to a liquid crystal display device. Background A typical display method of a liquid crystal display device is to apply a voltage to a liquid crystal composition enclosed between a pair of substrates, and to change the alignment state of liquid crystal molecules in the liquid crystal composition according to the applied voltage, thereby controlling the light transmission amount. Such a liquid crystal display device is used in a wide range of fields, while exhibiting characteristics such as thin, light weight, and low power consumption. In recent years, as one of driving methods of a liquid crystal display device for displaying a color image, development of a field sequential color (FSC: field Sequential Color) method has been advanced. The normal FSC method is a method in which a display period (1 frame period) of 1 screen is divided into 3 subfields, each of red (R), green (G), and blue (B) LEDs (LIGHT EMITTING diodes) as light sources of backlight light is sequentially switched, an image signal of a color corresponding to the color of the light of each LED is sequentially supplied to a liquid crystal panel in synchronization with the switching, and the transmission state is controlled to perform additive color mixing on the retina of the eye of an observer. According to the FSC method, a color display can be performed without forming a plurality of subpixels in1 pixel, and thus, a high resolution can be realized. Further, since light from the LEDs is directly used, it is not necessary to form a color filter having a high absorptance in each pixel, and the light use efficiency of each LED is improved. In recent years, a see-through display capable of displaying the back surface of a see-through liquid crystal display device has been attracting attention. As a liquid crystal display device used as a see-through display, a liquid crystal display device using a polymer dispersed liquid crystal (PDLC: polymer Dispersed Liquid Crystal) has been developed. PDLCs are polymers in which a liquid crystal component is dispersed in a polymer network, and the alignment state of the liquid crystal component is changed by application of a voltage, so that the transparent state and the scattering state can be switched by utilizing the refractive index difference between the liquid crystal component and the polymer network. As a technology related to the FSC type see-through display, for example, patent document 1 discloses a liquid crystal display device that includes 2 liquid crystal panels and that is capable of performing color display without providing a color filter by driving a light source in the FSC type. Patent document 2 discloses a liquid crystal display device in which light irradiated from a light source is made incident on a light modulation layer disposed between a pair of transparent substrates by FSC driving. Prior art literature Patent literature Patent document 1 International publication No. 2015/053023 Japanese patent application laid-open No. 2016-85452 Disclosure of Invention Problems to be solved by the invention In the liquid crystal display device of patent document 1, since transparent display or color display is realized by combining a polarizing plate and FSC driving, the transmittance in transmissive display is insufficient (for example, about 25%). Further, in patent document 2, since light is guided from a light source driven by FSC disposed along a side of a liquid crystal panel into a light modulation layer (for example, a polymer dispersed liquid crystal), light from the side is greatly attenuated as it goes toward a central portion of the liquid crystal panel due to light loss such as diffraction or scattering by a thin film transistor or the polymer dispersed liquid crystal in the liquid crystal panel, and in the case where the liquid crystal panel is enlarged, sufficient brightness may not be obtained in the central portion of the panel. Therefore, the size of the liquid crystal panel is limited, and it is difficult to increase the size of the liquid crystal panel. The present invention has been made in view of the above-described situation, and an object of the present invention is to provide a liquid crystal display device capable of switching between a transparent state and a scattering state, suppressing a decrease in transmittance in the transparent state, and suppressing a decrease in luminance in a central portion of a panel in the scattering state. Solution for solving the problem (1) An embodiment of the present invention is a liquid crystal display device including, in order from a viewing surface side toward a back surface side, a first liquid crystal panel including a polymer dispersed liquid crystal including a polymer network and a liquid crystal component, a light source for applying light to a main surface of the back surface side of the first liquid crystal pan