JPH0548060A - Solid-state image sensor element - Google Patents

Abstract

PURPOSE:To improve the light utilization efficiency in black-and-white mode by attaining the color filter function by a G-H type liquid crystal so as to eliminate the formation of color filter and simultaneously to use a color camera even in black-and-white mode. CONSTITUTION:A G-H liquid crystal cell composed of a transparent electrode substrates 7a and 7b and the G-H liquid crystal that is composed of bicolor dye as a guest and a smectic (SP) liquid crystal 11 as a host is mounted on the element having a photoelectric conversion area 2, charge transfer area 3, charge transfer electrode area 4 and light shield film 5 with a flattening film 6 in between. Then the G-H liquid crystal is allowed to selectively transmit a colored light or non-colored light depending on the presence or absence of voltage charged on the electrode of the substrates 7a and 7b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image sensor,
In particular, it relates to a solid-state image sensor capable of color imaging.

[0002]

2. Description of the Related Art FIG. 4 is a sectional view of a conventional solid-state image pickup device used in a single-plate color camera. In the figure, 1
Is a semiconductor substrate, 2 is a photoelectric conversion region, 3 is a charge transfer region,
Reference numeral 4 is a charge transfer electrode made of polysilicon, 5 is a light-shielding film having an opening on the photoelectric conversion region 2, 6a and 6b are flattening films made of a transparent polymer material, and 10 is an effective aperture ratio of the solid-state imaging device. Therefore, a microlens formed on each photoelectric conversion region 2, 12 is a red lens, a green lens on the photoelectric conversion region 2,
This is a color filter layer in which filters of respective colors of blue are regularly arranged.

[0003]

As described above, in the single plate type color camera, it is indispensable to use the solid-state image pickup device having the color filter layer for identifying the color of the light incident on the photoelectric conversion region. Thus, in order to form a color filter, a gelatin pattern forming step, a dyeing step,
Since the steps such as the protective film forming step must be repeated a plurality of times, the device becomes very expensive. Further, in the three-plate color camera, it is necessary to separate each color using a dichroic mirror, but since the dichroic mirror itself is expensive, it is difficult to reduce the cost of the color camera.

By the way, a color camera may be operated in a monochrome mode, but in that case, a conventional solid-state image pickup device requires a signal synthesizing circuit, which makes the circuit complicated and It was difficult to faithfully reproduce the original information.

Further, since the color filter transmits only light of a specific wavelength, 1/3 to 2 of the incident light is used.
/ 3 does not contribute to photoelectric conversion. Therefore, when the color camera is operated in the monochrome mode, the light utilization efficiency is extremely reduced.

[0006]

In the solid-state image pickup device of the present invention, the color filter function in the prior art is achieved by the GH liquid crystal having the guest-host (GH) electro-optical effect. .

In this G.H type liquid crystal, for example, light is absorbed and the transmitted light is colored when no voltage is applied,
In addition, liquid crystal molecules and dye molecules are arranged so that light is not absorbed and transmitted light is not colored when a voltage is applied. As a result, the solid-state image pickup device can function as a color device when no voltage is applied, and can function as a monochrome device when a voltage is applied.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a sectional view showing a first embodiment of the present invention. In the figure, 1 is a semiconductor substrate, 2 is a photoelectric conversion region, 3 is a charge transfer region, 4 is a charge transfer electrode made of polysilicon, 5 is a light-shielding film having an opening on the photoelectric conversion region, and 6a and 6b are transparent. Flattening film made of molecular material, 7
a and 7b are transparent electrode substrates each having a conductive film made of ITO, tin oxide or the like formed on the surface, 8 is a dichroic dye dissolved as a guest, Δε> 0 (Δε is the dielectric anisotropy nematic liquid crystals) (N _P LCD), 9 polarizer, 10 is a microlens.

The N _P liquid crystal 8 is processed so that the director thereof is parallel to the transparent electrode substrate, and has a homogeneous alignment. The dichroic dye used as the guest dye is a material having anisotropy in absorption of visible light in the major axis direction and the minor axis direction of the molecule. A dichroic dye is used. As the dichroic dye, various kinds of commonly used merocyanine-based, styryl-based, azo-based, anthraquinone-based, tetrazine-based dyes and the like can be used.

FIG. 2A is a schematic diagram showing a state of incident light in a state where no voltage is applied between the transparent electrode substrates in the embodiment of FIG. In this state, since the vibration direction of the white linearly polarized light that has passed through the polarizer 9 and the light absorption axis of the p-type dichroic dye coincide with each other, light absorption occurs, the transmitted light is colored, and the solid-state imaging device is used as a color device. Function.

FIG. 2B is a schematic diagram showing a state of incident light in a state where a voltage is applied between the transparent electrode substrates in the above embodiment. In this state, the vibration direction of the white linearly polarized light passing through the polarizer and the light absorption axis of the dye are orthogonal to each other, so that light absorption does not occur and the transmitted light is not colored, and the solid-state imaging device functions as a monochrome device.

FIG. 3 is a sectional view showing a second embodiment of the present invention. In the figure, portions common to those of the embodiment of FIG. 1 are designated by the same reference numerals, and a duplicate description will be omitted. In this embodiment, using the smectic liquid crystal (S _P LCD) 11 as a host liquid crystal for G · H type liquid crystal. Since the smectic liquid crystal itself has a polarization effect, the polarizer, which was indispensable in the first embodiment, is not required in this embodiment, which facilitates the manufacture and significantly improves the light utilization efficiency. Particularly, when the image pickup device is used in the monochrome mode, almost 100% of the incident light can be introduced into the photoelectric conversion region.

The preferred embodiment has been described above.
The present invention is not limited to these examples, and various modifications can be made. For example, the liquid crystal is a cholesteric liquid crystal (C _P LCD) can be used, also, the liquid crystal polymer - can be used as a liquid crystal composite film (polymer dispersed liquid crystal). Further, it is possible to use a liquid crystal having Δε <0 (N _N liquid crystal or the like), or to use an n-type dichroic dye instead of the p-type dichroic dye.

The dye pattern may be a mosaic pattern as in the conventional color filter layer, but may be a stripe pattern. When a three-plate color camera is constructed, a chip having a uniform pattern formed on the entire surface can be used.

[0015]

As described above, since the solid-state image pickup device of the present invention achieves the color filter function by the G.H type liquid crystal cell, according to the present invention, it is a complicated process to manufacture. It is possible to construct a solid-state color camera without using a color filter layer that requires the above, and without using an expensive dichroic mirror.

Further, in order to use the color camera in the black and white mode, it is only necessary to allow colorless light to pass through the G / H type liquid crystal, and a complicated signal synthesizing circuit becomes unnecessary. Further, since the monochrome signal is not obtained by combining the color signals, the original image can be faithfully reproduced. Further, in the black and white mode, when the polarizer is not used, the light is not absorbed before entering the photoelectric conversion region, so that the light utilization efficiency is significantly improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining a usage state of the first embodiment of the present invention.

FIG. 3 is a sectional view showing a second embodiment of the present invention.

FIG. 4 is a sectional view of a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate 2 ... Photoelectric conversion area 3 ... Charge transfer area 4 ... Charge transfer electrode 5 ... Light-shielding film 6a, 6b ... Flattening film 7a, 7b ... Transparent electrode substrate 8 ... N _P liquid crystal 9 ... Polarizer 10 ... Microlens 11 ... _SP liquid crystal 12 ... Color filter layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04N 9/07 A 8943-5C

Claims (1)

[Claims] 1. A solid-state imaging device in which a guest-host type liquid crystal cell is mounted on a photoelectric conversion device.