JPS58142314A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a medium enabling repeated erasing and rewriting by utilizing the phase transition of a guest-host liq. crystal consisting of a liq. crystal causing smectic-nematic phase transition as a host material and a dichromatic dye as a guest material. CONSTITUTION:Transparent electrodes 3, 4 and transparent substrates 5, 6 are made of ''NESA '' glass, and the glass is rubbed so as to orient the major axes of liq. crystal molecules in a guest-host liq. crystal material layer 1 parallel to the substrates. A ''Myler '' film having 8-16mum thickness is used as a spacer 2, a smectic-nematic liq. crystal represented by structural formulaI is used as the host of the liq. crystal material 1, and a dichromatic dye represented by structural formula II is used as the guest. A light-purple pit with a deep-purple background can be recorded by applying >=5V DC voltage between the electrodes and by irradiating >=30mW Ar laser light for 2 msec, and the pit can be erased by irradiating laser light without applying an electric field.

Description

Detailed Description of the Invention This invention relates to an optical recording medium, more specifically, a rewritable optical recording utilizing the optical recording function of a dust host liquid crystal having a phase transition between a smectic phase and a nematic phase. It is related to the medium for use.

In recent years, in the field of information processing, with the rapid increase in the amount and variety of information, conventional magnetic memory as a general recording method is becoming insufficient and has a tendency to be unable to respond to the above diversity. It is in. Therefore, as an alternative to the conventional recording method, an optical recording method using a layered optical recording medium is being considered.

An example of a medium used in such an optical recording method is a thin metal film or a metal-containing polymer material, but since this is a writing method in which the recorded portion of the medium is bath-melted and evaporated using a radar beam to form a hole, it is not possible to erase or rewrite the recording. is impossible.

On the other hand, as an example of this rewritable optical recording medium.

A medium that combines thermoplastic and photoconductor is known, but the number of rewrites is limited to 100 at most.
Anything less than that is simply not enough. As described above, the reality is that conventional optical recording media have many problems and drawbacks, such as many of them being unrewritable or insufficient.

In order to solve these drawbacks, the present inventors conducted numerous experiments and researches, and as a result, we decided to utilize the optical recording function of a dust host liquid crystal that has a reversible phase transition between a smectic phase and a nematic phase ( We have realized a medium that can be repeatedly erased and rewritten and has significantly improved optical recording properties.
], the invention will be specifically described below with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the optical recording medium of the present invention, in which l represents a dust host liquid crystal material layer.

2 is space? , 3 and 4 are transparent electrodes, and 5 and 6 are transparent substrates, respectively.

For the transparent electrodes 3, 4 and transparent substrates 5, 6, for example, Nesa F9 glass is used, and the Nesa glass is subjected to a 2-pin process in order to align the long axes of the liquid crystal molecules parallel to the substrates. ? 2 has a film thickness of 81am to 16Jm
r (smectic range 21.1 to 33
．． 5°C, nematic range 33.5-41.5°C),
A dichroic dye was used as the dust material. Then, a direct current voltage of 5V or more is applied between the electrodes to the zero-order optical recording medium having the total amount of dust material of about aVt-, and an Al-Nrede beam (λg=514.5nm) is applied between the electrodes.

It was possible to write minute bits with an output of 30 mW or more and an irradiation time of 2 m8). In this case, with the dichroic dye used above, the unrecorded area shows deep purple and the recorded bits show light purple, and the ratio of the light transmittance is 1:2 or more for the unrecorded area (g) of the recorded bits at 550 nm light. So 6 nine, and said record beep) a2! It is stable regardless of whether or not voltage is applied to the transparent electrode at temperatures between S and 30°C, and recording pits on the sides can be erased by irradiating the recorded bits with radar light without applying voltage. is rarely possible. Furthermore, it was confirmed that all recorded bits were erased by heating the entire medium, and that this example had sufficient performance to withstand erasing and rewriting approximately 500 times or more.

- The function of the above-mentioned dust host liquid crystal material layer in this invention can be explained as follows. The host material used is a liquid crystal that exhibits a reversible phase transition, from a smectic phase at room temperature to a nematic phase at high temperatures. In this nematic phase, the liquid crystal molecules easily align in the direction of the dipole moment due to an external electric field, but in the smectic phase, the orientation does not change easily due to an external electric field; The substrate is pretreated so that the 4-moment without RA is oriented parallel to the substrate.

Next, the dust material is a dye having dichroism, which is oriented in accordance with the orientation of the host liquid crystal, and whose light absorption characteristics change depending on the orientation direction.

Here, Fig. 2 (a) to (d) respectively show the status of (a) before writing, (a) record writing, (6) record retention and reading, and (d) record erasing for this recording medium. There are nine things. In the figure, the dust host liquid crystal material layer is shown separately as a dust material 1& and a host material 1b.

First, FIG. 2(a) shows a smectic phase, in which the dipole moment is oriented parallel to the substrate. As shown in the figure, the recording/writing section is irradiated with a laser beam 7, and the transparent electrode 3 is
．． When a voltage 8 is applied between 4 and 4, the recording/writing portion is heated by the Raded light irradiation, undergoes a phase transition from a smectic phase to a nematic phase, and the dipole moment is directly aligned to the substrate due to the voltage 8.

In this way, if a voltage of 8 is applied and then cooled to a smectic phase, the orientation of the recording/writing area will be maintained even without voltage application, and due to the action of the dust material, the light absorption characteristics of the recording/writing area will be different from that of the unwritten area. It becomes different. If the transmittance in the writing area increases, like the dichroic dye in the above example, the readout light 9 is applied to it as in (1), and the transmitted light 1O is used for recording. Furthermore, as in (d) above, in order to erase records, the entire medium must be heated without applying a voltage, or the writing section must be exposed to radar light without applying a voltage. All you have to do is heat it by irradiation.

The liquid crystal as the host material in the present invention has a smectic phase that is sufficiently stable and stable near room temperature, and further exhibits a nematic phase in a sufficiently wide temperature range above that, and
Since it is desirable to have a large dipole moment, a specific example is a mixed liquid crystal containing the above-mentioned real components.

As a dust material that can be used in this invention, the size of -94 used in the example is I6.
ψ's cry ψ
G Han-1-F4 wm
−Φ Low −
(to) so-to 8
0 8A fable h ψ g
Examples include ψ, c13HN N, and the like. All of these dyes have a large dichroic ratio, and it is desirable to use them alone or in the form of a mixture.

As is clear from the above description, the present invention utilizes the phase transition between the smectic phase and the nematic phase as a recording method and performs this by heating by Raded light irradiation, so that extremely minute recording is possible. The voltage application during this recording is necessary only during writing, and is unnecessary for any of the recording holding, reading, and erasing in the smectic phase. Furthermore, as mentioned above, the use of phase transition significantly improves the repeatability of repetitive erasing and rewriting, and since it does not utilize so-called hysteresis, no temperature bias is required and operation control is easy. On the other hand, since the above-mentioned dichroic dye is used as a dust material, it has extremely advantageous features such as being able to use the difference in spread transmittance, reflectance, etc. during readout, and eliminating the need for any polarizing plate etc. has. Therefore, it becomes possible to write and erase with a highly repetitive, highly repetitive laser beam, which is particularly required for the above-mentioned type of recording method.
It can be used as a high-density optical recording medium in place of conventional magnetic recording.

[Brief explanation of drawings]

1st @ is a sectional view showing one embodiment of the present invention, and 2nd figure (&)
~(Year is an explanatory diagram of the operating raw salt of the same example. 1...Dust host liquid crystal, 1a...Dust material, 1
b...Host material, 3.4...Transparent electrode, 5.6.
...Transparent substrate, 7...Writing radar light, 9...Reading light, 10...Transmitted light. 71 Figure 1 Procedural Amendment June 15, 1980 Haruki Shimada, Commissioner of the Japan Patent Office, 1, Indication of the case 1984 Tatami Permission Request No. jt811! ! II
f2, Invention No. 04 optical recording medium 3, relationship with the case of the person making the amendment Patent Applicant (029) Oki Electric Industry Co., Ltd. 4, Agent 5, Date of amendment order ) (64) (1) Amend the claims as shown in the attached sheet. (2) "Formula 5" on page 17 of the specification is corrected as follows. (3) In the specification page 25, line 7, before “3.4...” “2.
...Add a spacer. (4) Claims characterized by "8...applied voltage" before "9..." in line 8 on page 25 (1) A liquid crystal having a phase transition between a smectic phase and a nematic phase is used as a host material. , a dust host liquid crystal using a dichroic dye as a dust material is interposed and held between substrates having electrodes,
An optical recording medium characterized in that molecules of the liquid crystal are oriented parallel to the substrate surface, and recording and erasing are performed using a laser beam. (2) ICa as a liquid crystal host material with phase transition
Claim No. (1) using at least one of Htv-○(ycN)
Optical recording medium described in Section 2. (3) At least one of the following materials as a dichroic dye:
The optical recording medium according to claim (1), using:

Claims (1)

[Scope of Claims] (1) A dust host liquid crystal containing a liquid crystal having a phase transition between a smectic phase and a nematic phase as a host material and a dichroic dye as a dust material is interposed and held between substrates having electrodes,
The liquid crystal molecules are used as a liquid crystal host material having a planar (2) phase transition on the substrate surface. Claim No. (1) using at least one of the following:
Optical recording medium described in Section 2. (3) At least one of the following materials as a dichroic dye:
The optical recording medium according to claim (1), using: Oh! -yuto N m w v＞
tHt-m v-IF
4 v-1v-1-φ ■
0 - Bay
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